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microwave oven inverter P.S. revisited
finally came across an article by VK3HZ that describes how to make a
microwave oven inverter PS work, as a stand alone supply. the link is: www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu |
microwave oven inverter P.S. revisited
On Aug 27, 12:40*pm, raypsi wrote:
finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie |
microwave oven inverter P.S. revisited
On Aug 28, 4:02*pm, wrote:
On Aug 27, 12:40*pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie |
microwave oven inverter P.S. revisited
On Aug 28, 8:39*pm, wrote:
On Aug 28, 4:02*pm, wrote: On Aug 27, 12:40*pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu |
microwave oven inverter P.S. revisited
On Sep 1, 7:48*pm, raypsi wrote:
On Aug 28, 8:39*pm, wrote: On Aug 28, 4:02*pm, wrote: On Aug 27, 12:40*pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose *that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage. .. But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu- Hide quoted text - - Show quoted text - Thats pretty much my idea. In radars something very similar to develop 6KV to charge the PFN. If you could analyze the circuit where the current sample is picked off the AC mains that would tell us a lot about what would be needed to develop the proper feedback signal off of the switching transformer. Unfortunately I am without power supply at the moment. Well I have one but my wife has forbid me to touch it. That is her primary cooking device As Dave idicated the rectifiers for the output of the pwer supply are configured as a doubler and it could be configured as a bridge if you wanted lower voltage. I am thinking maybe( a lot of supposig here) this thing may be configured from 1500 to nearly 5kv by using a combination af feedback adjustment and rectifier configuration. I agree with about the caps, I emailed Dave and he pretty much agrees with my idea at least in theory but he has dropped the project at least for now. didnt you say you had a source for these power supplies. Anyone who gets this to work would surely have some serious ham radio bragging rights. Jimmie |
microwave oven inverter P.S. revisited
On Sep 1, 9:57*pm, wrote:
On Sep 1, 7:48*pm, raypsi wrote: On Aug 28, 8:39*pm, wrote: On Aug 28, 4:02*pm, wrote: On Aug 27, 12:40*pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies.. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose *that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage. . But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu- Hide quoted text - - Show quoted text - Thats pretty much my idea. In radars something very similar to develop 6KV to charge the PFN. If you could analyze the circuit where the current sample is picked off the AC mains that would tell us a lot about what would be needed to develop the proper feedback signal off of the switching transformer. Unfortunately I am without power supply at the moment. Well I have one but my wife has forbid me to touch it. That is her primary cooking device As Dave idicated the rectifiers for the output of the pwer supply are configured as a doubler and it could be configured as a bridge if you wanted lower voltage. I am thinking maybe( a lot of supposig here) this thing may be configured from 1500 to nearly 5kv by using a combination af feedback adjustment and rectifier configuration. I agree with about the caps, I emailed Dave and he pretty much agrees with my idea at least in theory but he has dropped the project at least for now. didnt you say you had a source for these power supplies. Anyone who gets this to work would surely have some serious ham radio bragging rights. Jimmie- Hide quoted text - - Show quoted text - I have found some better schematics on the inverter. It looks like modifying the power supply for amateur QRO is very plausable. Where could I post them so anyone who wanted them would have access? Jimme |
microwave oven inverter P.S. revisited
On Sep 6, 3:18 pm, wrote:
On Sep 1, 9:57 pm, wrote: On Sep 1, 7:48 pm, raypsi wrote: On Aug 28, 8:39 pm, wrote: On Aug 28, 4:02 pm, wrote: On Aug 27, 12:40 pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage. . But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu- Hide quoted text - - Show quoted text - Thats pretty much my idea. In radars something very similar to develop 6KV to charge the PFN. If you could analyze the circuit where the current sample is picked off the AC mains that would tell us a lot about what would be needed to develop the proper feedback signal off of the switching transformer. Unfortunately I am without power supply at the moment. Well I have one but my wife has forbid me to touch it. That is her primary cooking device As Dave idicated the rectifiers for the output of the pwer supply are configured as a doubler and it could be configured as a bridge if you wanted lower voltage. I am thinking maybe( a lot of supposig here) this thing may be configured from 1500 to nearly 5kv by using a combination af feedback adjustment and rectifier configuration. I agree with about the caps, I emailed Dave and he pretty much agrees with my idea at least in theory but he has dropped the project at least for now. didnt you say you had a source for these power supplies. Anyone who gets this to work would surely have some serious ham radio bragging rights. Jimmie- Hide quoted text - - Show quoted text - I have found some better schematics on the inverter. It looks like modifying the power supply for amateur QRO is very plausable. Where could I post them so anyone who wanted them would have access? Jimme Do you have windows movie maker you could put it on youtube.com if there in some pix file extension like jgp or gif. I had a single pix that I put in movie maker with intro caption. Then downloaded it to youtube. A 15 sec single frame video with intro caption. Thanks for bringing it up, that jarred my grey matter. I can post a video to you tube Now to figure out how to get that power supply to copy on my scanner. 73 n8zu |
microwave oven inverter P.S. revisited
On Sep 6, 7:57*pm, raypsi wrote:
On Sep 6, 3:18 pm, wrote: On Sep 1, 9:57 pm, wrote: On Sep 1, 7:48 pm, raypsi wrote: On Aug 28, 8:39 pm, wrote: On Aug 28, 4:02 pm, wrote: On Aug 27, 12:40 pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose *that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage. . But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle.. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu- Hide quoted text - - Show quoted text - Thats pretty much my idea. In radars something very similar to develop 6KV to charge the PFN. If you could analyze the circuit where the current sample is picked off the AC mains that would tell us a lot about what would be needed to develop the proper feedback signal off of the switching transformer. Unfortunately I am without power supply at the moment. Well I have one but my wife has forbid me to touch it. That is her primary cooking device As Dave idicated the rectifiers for the output of the pwer supply are configured as a doubler and it could be configured as a bridge if you wanted lower voltage. I am thinking maybe( a lot of supposig here) this thing may be configured from 1500 to nearly 5kv by using a combination af feedback adjustment and rectifier configuration. I agree with about the caps, I emailed Dave and he pretty much agrees with my idea at least in theory but he has dropped the project at least for now. didnt you say you had a source for these power supplies. Anyone who gets this to work would surely have some serious ham radio bragging rights. Jimmie- Hide quoted text - - Show quoted text - I have found some better schematics on the inverter. It looks like modifying the power supply for amateur QRO is very plausable. Where could I post them so anyone who wanted them would have access? Jimme Do you have windows movie maker you could put it on youtube.com if there in some pix file extension like jgp or gif. I had a single pix that I put in movie maker with intro caption. Then downloaded it to youtube. A 15 sec single frame video with intro caption. Thanks for bringing it up, that jarred my grey matter. I can post a video to you tube Now to figure out how to get that power supply to copy on my scanner. 73 n8zu- Hide quoted text - - Show quoted text - I guess you downloaded David Smiths diagram. Mine has much more detail. Give me an email address and I will get it to you. David Smiths address in the article is good and he wants a dialog with anyone interested in this project. I think the 3 of us need to get together and compare notes and draw in as many other people into this project as we can. I have about given up on finding another microwave at the thrift store that uses an inverter. I guess I will just bite the bulllet and buy one. I have a few experiments I want to do. Jimmie |
microwave oven inverter P.S. revisited
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microwave oven inverter P.S. revisited
On Sep 7, 1:52*am, msg wrote:
wrote: snip I have found some better schematics on the inverter. It looks like modifying the power supply for amateur QRO is very plausable. Where could I post them so anyone who wanted them would have access? Please email me at 'msg _at_ cybertheque _dot_ org; I'd be happy to put any data you have into a web page. *I have been pondering building a HV SMPS for years based on PC PSU parts and have been following threads in this N.G. on the oven PSU with interest. Michael Its in the mail. I think if you had transformer from a microwave oven that a circuit based on a PC power supply would be doable. The panasonic uwave uses IGBTs instead of FETS or bipolars the way the PC power supplies do. I think the use of IGBTs is a good idea given the voltages and currents. The uwave inverte also operates at 30Khz with the PC operates at about 12Khz. Jimmie Jimmie |
microwave oven inverter P.S. revisited
I'm fairly sure is a zero voltage switching converter with active voltage clamp. The series inductor and the 4uF capacitor form a harmonic filter. The resonant switching circuit is the capacitor in series with the upper switch, the primary inductance of the transformer and the capacitor in parallel with the transformer. So it can be devolved into a single switch feed forward converter function from the lower switch and resonant energy recovery by the upper switch... which results in a quasi push-pull output. Search patents by E. Miyata in USPTO for more details. Considering it's purpose, I'd expect this design's output power is probably in the neighborhood of 750W. Don't confuse this with the name plate rating. Of course the designer didn't consider ICAS service so YMMV. |
microwave oven inverter P.S. revisited
Search patents by E. Miyata in USPTO for more details. I had a nagging feeling that I'd disremembered the circuit Miyata developed and tried to look it up. Must be an IEEE paper since there's no patent in his name that I can find. But these patents may help: 6936803 and 6884977 This paper seems to describe a circuit close to that oven converter. http://yakimov.homeftp.net/banditko/...ticles%20from% 20ieeexplore/01217760.pdf |
microwave oven inverter P.S. revisited
It would be interesting to know the phasing of the transformer windings. Since it's voltage fed and there is no output inductor I would have guessed it was a ZVS flyback supply with active recovery of the leakage inductance energy. A flyback is a constant power output topology by nature, so it's a natural for powering a magnetron. But the waveform in the pdf concering the oven looks like a forward converter. Maybe it's the result of the active clamp? I've designed flyback converters with outputs of a couple KW for TWT tubes but they were hard switched with multiple rectified outputs on the transformer stacked series to reduce the voltage stress. At low output voltages a flyback is unsuitable for much power because of the high peak current developed in the rectifiers and switches. Sorry to babble on about this but I found the oven circuit fascinating. The white goods guys are very clever. I hope you can get it working as a power supply for your amplifier. |
microwave oven inverter P.S. revisited
On Sep 7, 10:18*pm, Grumpy The Mule wrote:
It would be interesting to know the phasing of the transformer windings. Since it's voltage fed and there is no output inductor I would have guessed it was a ZVS flyback supply with active recovery of the leakage inductance energy. *A flyback is a constant power output topology by nature, so it's a natural for powering a magnetron. *But the waveform in the pdf concering the oven looks like a forward converter. *Maybe it's the result of the active clamp? I've designed flyback converters with outputs of a couple KW for TWT tubes but they were hard switched with multiple rectified outputs on the transformer stacked series to reduce the voltage stress. *At low output voltages a flyback is unsuitable for much power because of the high peak current developed in the rectifiers and switches. Sorry to babble on about this but I found the oven circuit fascinating. *The white goods guys are very clever. I hope you can get it working as a power supply for your amplifier. I have my doubts about using it as is too, but I think there is a lot to learn here. For example I hae never used IGBTs before and already I hae begun to learn. This may also be a chance for me to learn to design a transformer that will work at 30Khz. I was thinking of using push-pull driver on the primay of the transformer instead of the flyback circuit. Something similar to a PC power supply. The Panasonic power supply is definately designed for constant current. The input current is monitored through a current transformer and this applied to the contol circuit so that a decrease in input current results in a greater output voltage through pulse width modulation. The plan is to take this feedback from a coil on the output transformer instead of the current transformer and apply it to the control circuit. I am hoping this will turn the constant current power supply into a voltage regulated power supply. Also the output rectifiers use a voltage doubler. My plan is to change this to a full wave bridge, I think David mentioned this too. I may not get full legal power out of it but maybe I can power a couple of 4cx250s. That wouldnt be bad for a $50 power supply. Jimmie |
microwave oven inverter P.S. revisited
If it's a flyback then push-pull drive won't provide enough voltage. In a flyback the E*T products of each half cycle have to be equal or the transformer saturates. You see a flyback transformer isn't really a transformer. It's a coupled inductor. The switch charges the core then the core discharges into the secondary. Current doesn't flow in both primary and secondary at the same time. So the output voltage isn't a function of the turns ratio but of the ratio of switch's on and off times. A flyback with voltage feedback control regulates the output voltage regardless of the turns ratio. Other considerations demand more turns for high output voltages, mainly the secondary voltage is reflected to the primary and added to the input bus increasing voltage stress on the switch. The primary turns are determined by the factors effecting core saturation. All this leads me back around to thinking it's a single ended forward converter with resonant reset into the seconday. Even if it is some form of ZVS flyback it may be possible to convert the oven power supply to a voltage regulated converter with either a voltage divider on the output or a voltage sensing winding with fewer turns. Because the volts per turn in the secondaries are fixed by the control this works well. If the sense winding has 100 times fewer turns the voltage developed by it will be 100 times less. There are some errors due to imperfect coupling between the windings and the rectifiers Vf but these can be tweaked out enough to get the regulation down about 3% with some reasonable minimim load maintained. There is another topology called a fly-forward that transfers energy during both the off and on times of the switch to the secondary. It's bascially a single ended forward converter that resets the magnetizing energy into the secondary in flyback mode. I'm convinced the oven uses resonant switching though so I doubt that's being used here. The reason for the very small input filter capacitor is power factor. With the small filter capacitor the line current follows the envelop of the switch current. If the duty cycle is constant over a half cycle then the current waveform is determined by the line voltage and then you have nice haversines of current drawn from the line. If the voltage control circuit response is fast, then the current will be distorted. With a larger input filter capacitor the current will look like the typical uncorrected SMPS with a capacitor input and draw huge current spikes at the peak of the line as the capacitor is charged. Then you must draw less power from the line to account for the low power factor. The input rectifier might have to be beefed up as well and more agressive inrush limiting would be needed too. I hope it's a forward converter then the transformer would be very handy. I may have to start snagging ovens from the curb side on trash day. I have a bucket full of 4CX250B (really, a bucket full) waiting for a home. And yes, IGBT's rock. |
microwave oven inverter P.S. revisited
On Sep 8, 1:13 am, Grumpy The Mule wrote:
If it's a flyback then push-pull drive won't provide enough voltage. In a flyback the E*T products of each half cycle have to be equal or the transformer saturates. You see a flyback transformer isn't really a transformer. It's a coupled inductor. The switch charges the core then the core discharges into the secondary. Current doesn't flow in both primary and secondary at the same time. So the output voltage isn't a function of the turns ratio but of the ratio of switch's on and off times. A flyback with voltage feedback control regulates the output voltage regardless of the turns ratio. Other considerations demand more turns for high output voltages, mainly the secondary voltage is reflected to the primary and added to the input bus increasing voltage stress on the switch. The primary turns are determined by the factors effecting core saturation. All this leads me back around to thinking it's a single ended forward converter with resonant reset into the seconday. Even if it is some form of ZVS flyback it may be possible to convert the oven power supply to a voltage regulated converter with either a voltage divider on the output or a voltage sensing winding with fewer turns. Because the volts per turn in the secondaries are fixed by the control this works well. If the sense winding has 100 times fewer turns the voltage developed by it will be 100 times less. There are some errors due to imperfect coupling between the windings and the rectifiers Vf but these can be tweaked out enough to get the regulation down about 3% with some reasonable minimim load maintained. There is another topology called a fly-forward that transfers energy during both the off and on times of the switch to the secondary. It's bascially a single ended forward converter that resets the magnetizing energy into the secondary in flyback mode. I'm convinced the oven uses resonant switching though so I doubt that's being used here. The reason for the very small input filter capacitor is power factor. With the small filter capacitor the line current follows the envelop of the switch current. If the duty cycle is constant over a half cycle then the current waveform is determined by the line voltage and then you have nice haversines of current drawn from the line. If the voltage control circuit response is fast, then the current will be distorted. With a larger input filter capacitor the current will look like the typical uncorrected SMPS with a capacitor input and draw huge current spikes at the peak of the line as the capacitor is charged. Then you must draw less power from the line to account for the low power factor. The input rectifier might have to be beefed up as well and more agressive inrush limiting would be needed too. I hope it's a forward converter then the transformer would be very handy. I may have to start snagging ovens from the curb side on trash day. I have a bucket full of 4CX250B (really, a bucket full) waiting for a home. And yes, IGBT's rock. I agree it's not a flyback. I don't think it's resonant converter because you looky at VK3HZ's data on loading it, the duty cycle would take it way out of resonant. As for power factor with lots of input capacitor filtering, a double pi AC filter with toroids would smooth the fawk out of any huge SMPS input capacitor filter. When I put a triple pi toroid on the AC line to my 500 watt SMPS computer tower, what a big difference, knocked out all kinds of harmonics and spikes. And reduce my electric bill. Is that like stealing from the electric co? 73 n8zu |
microwave oven inverter P.S. revisited
raypsi wrote:
snip I agree it's not a flyback. I don't think it's resonant converter because you looky at VK3HZ's data on loading it, the duty cycle would take it way out of resonant. Thanks to jimmie for the PDF service manual; inspection of the schematics shows differences between the block diagram (which seems to show a resonant configuration) and the inverter detail schematic (which shows a voltage doubler configuration). There are also mistakes in wiring runs (circuit box outlines confused as wires and having cross-connect dots misplaced, etc.). After accounting for these, the above assumptions seem correct. A quick web search for inverter microwave ovens seems to yield only Panasonic models, and the cheapest in my area is $158.00 at Walmart. To me, this isn't really cost-effective, and they are too new to be found in the alley. I intend to continue to explore utilizing PC PSU parts to build an HV supply. Michael |
microwave oven inverter P.S. revisited
On Sep 8, 11:08*am, msg wrote:
raypsi wrote: snip I agree it's not a flyback. I don't think it's resonant converter because you looky at VK3HZ's data on loading it, the duty cycle would take it way out of resonant. Thanks to jimmie for the PDF service manual; inspection of the schematics shows differences between the block diagram (which seems to show a resonant configuration) and the inverter detail schematic (which shows a voltage doubler configuration). There are also mistakes in wiring runs (circuit box outlines confused as wires and having cross-connect dots misplaced, etc.). After accounting for these, the above assumptions seem correct. A quick web search for inverter microwave ovens seems to yield only Panasonic models, and the cheapest in my area is $158.00 at Walmart. *To me, this isn't really cost-effective, and they are too new to be found in the alley. *I intend to continue to explore utilizing PC PSU parts to build an HV supply. Michael The part can be bought as a spare for about $40 or $50 dollars. I have found a couple of them at Goodwill. I would have be tearing into it but our 20 year old microwave finally bit the dust so my wife put claim on this one. I have also seen them setting on the curb on trash day. On was on my way out and thought I would pick it up on my way back in. Didnt work out. Since I started looking for them it seems there are two common reasons people get rid of old microwaves. One is to have the latest , greatest model and the other is because the digital display quits working. Any sort of failure out of warranty usually means a trip to the curb. THESE MUST BE OPERATED UNDER LOAD OR THEY WILL SMOKE. At least that is what happend to mine. Jimmie |
microwave oven inverter P.S. revisited
raypsi wrote: snip I agree it's not a flyback. I don't think it's resonant converter because you looky at VK3HZ's data on loading it, the duty cycle would take it way out of resonant. I'm sorry, I should have been more precise in my use of terms. It's zero voltage switching or ZVS which is resonant transition. The resonance is much higher than the swicthing frequency and it isn't effected by the changes in duty cycle. Although it does steal some on-time Sometimes it's called quasi-resonant and there's a variant called ZCS or zero current switching. It's not a resonant converter like series or parallel resonant converters where the output is controlled by shifting the frequency. |
microwave oven inverter P.S. revisited
THESE MUST BE OPERATED UNDER LOAD OR THEY WILL SMOKE. At least that is what happend to mine. Jimmie Oh, sorry to hear that. Yeah, it's a bad idea to operate any switch mode power supply without a minimum load unless the min. load is built-in or the thing is so inefficent that its own losses make up the minimum load. The output diodes probably didn't like that... just my guess. I found some interesting stuff on the panasonic inverter. On the fusor chat they claim it's 85% efficient and good for 1200W. The efficiency seems right, the 1200W seems... optimistic. Also this, instructions on getting the inverter to play. http://www.fusor.net/board/view.php?...er&key=1162079 046 |
microwave oven inverter P.S. revisited
Oh!
I forgot to mention soft-switching, that's the most common catch-all term. |
microwave oven inverter P.S. revisited
On Sep 8, 7:13*pm, Grumpy The Mule wrote:
THESE MUST BE OPERATED UNDER LOAD OR THEY WILL SMOKE. At least that is what happend to mine. Jimmie Oh, sorry to hear that. *Yeah, it's a bad idea to operate any switch mode power supply without a minimum load unless the min. load is built-in or the thing is so inefficent that its own losses make up the minimum load. The output diodes probably didn't like that... just my guess. I found some interesting stuff on the panasonic inverter. On the fusor chat they claim it's 85% efficient and good for 1200W. *The efficiency seems right, the 1200W seems... optimistic. Also this, instructions on getting the inverter to play.http://www.fusor.net/board/view.php?..._hvpower&key=1... 046 * Hey mule: Your url got cropped. The inverter PS I have can be fooled into thinking it has a load. There is a current sense I found and a voltage sense both on the primary side. It's a piece of cake opto coupling a signal back to those sense inputs. they are both straight voltage dividers with Vrefs. And the current sense uses a 50K ohm trim pot for adjustment. They use a 100meg bleeder for a load. And the filament which is at least 150 watts, loads the supply too. I suspect my 120VAC inverter will work off of 240VAC And if you take out the filament circuit that gives yoiu an extra 150 watts. I suspect I can gits 1500 watts from my 1300 watt interer PS, with input filtering of the DC off the mains. But the final report wont happen until i gits the feedback circuit wired. That will prevent it from trying to produce 1300 watts into no load. With no load it will try to up the voltage to produce more current. Which it can't produce more current so it keeps increasing the voltage untill it lets out the smoke, When it hits 3000 volts I will fool the sense circuits: a voltage divider for the current sense and another divider for the voltage sense, into seeing 1300 watts. Another trick is to run the mains off a variac starting at 10 VAC very slow. Also supply seperate power to the PWM IC circuit, Just to see how far it will go, and not get it to go into run away. I see the power trouble how can you gits 1300 watts out of that little bitty core? That's what they used to say about silicone diodes when they used to replace a 5U4 tube. They used to tell me how can a little piece of wire with a bead on it replace a tube as big as your fist no freaking way. I also made a living selling 2.5 amp 1000 piv diodes. I mean the primary of this thing uses litz wire that looks like 10AWG wire about 13 turns around the core and they using 4 strands of 28 AWG to run the filament The HV secondary measures only 6.8 ohms DC. 73 OM n8zu |
microwave oven inverter P.S. revisited
Ok, this should work. http://tinyurl.com/6at4zu I mean the primary of this thing uses litz wire that looks like 10AWG wire about 13 turns around the core and they using 4 strands of 28 AWG to run the filament The HV secondary measures only 6.8 ohms DC. I'm glad you mentioned that. If the core is ferrite and it's gapped, then the litz makes sense to reduce eddy current losses from the fringing field sprayed out of the gap. A gapped core would also most likely mean it is a flyback. It really is amazing the power density SMPS can achieve. Though the overload capacity available from big hunks of iron and copper isn't to be discounted lightly. I had to pick up a 10KW autotransformer today. I don't know how much it weighed but I'd guess 130lbs, or there about. The two transformers in the 10KW SMPS are maybe four pounds total. |
microwave oven inverter P.S. revisited
On Sep 9, 7:50 pm, Grumpy The Mule wrote:
Ok, this should work. http://tinyurl.com/6at4zu I mean the primary of this thing uses litz wire that looks like 10AWG wire about 13 turns around the core and they using 4 strands of 28 AWG to run the filament The HV secondary measures only 6.8 ohms DC. I'm glad you mentioned that. If the core is ferrite and it's gapped, then the litz makes sense to reduce eddy current losses from the fringing field sprayed out of the gap. A gapped core would also most likely mean it is a flyback. It really is amazing the power density SMPS can achieve. Though the overload capacity available from big hunks of iron and copper isn't to be discounted lightly. I had to pick up a 10KW autotransformer today. I don't know how much it weighed but I'd guess 130lbs, or there about. The two transformers in the 10KW SMPS are maybe four pounds total. Hey mule Exactly right it is a gapped core. Once I git's a scope on I'll see. But the voltage doubler they using is full wave doubler. Which means they taking the positive and negative waves to get 4000 or so volts DC Now the positive half they use a .0082 mfd for a filter and the negative half they use a .0056 mfd filter both at 3000wvdc. .. They use a damper diode that looks like a varistor, and a hold down cap is .032 mfd at 500V across the primary. The power into the primary is filter by an LC just to prevent the RF getting back into the mains/bridge diodes pack. 73 OM n8zu |
microwave oven inverter P.S. revisited
Exactly right it is a gapped core. Once I git's a scope on I'll see. But the voltage doubler they using is full wave doubler. Which means they taking the positive and negative waves to get 4000 or so volts DC Now the positive half they use a .0082 mfd for a filter and the negative half they use a .0056 mfd filter both at 3000wvdc. my guess is the quasi-push pull output is due to the leakage energy recovery circuit. HV flyback transformers usually have very high leakage inductance (the part of the magnetizng inductance not coupled to the secondary is leakage inductance) because distance between windings is a major cause of poor coupling and you need distance for isolation. The leakage energy sloshes about in the primary causing all sorts of mischief. This circuit recovers it and dumps it back into the primary. It's unusual since the leakage energy is usually dumped back into the bulk storage capacitor on the primary side if it's recovered by a clamp winding or active clamp circuit. A soft switching topology often uses the leakage inductance to reduce transistion losses in the switch. Sometimes a discrete inductor is added in series with the transformer primary to add to it. Another bonus for the lousy coupling of the HV flyback transformer... no discrete inductor needed. I think of this as electronic ju-jitsu. The energy per half cycle (on the secondary) won't be equal so juggling the capacitor values helps equalize the voltage stress. Eh! I might be completely wrong. Simulating it would be the thing but it's too much like work work and I'd need the transformer parameters. At least that's how I think it works... Please let me know when you've scoped the waveforms. |
microwave oven inverter P.S. revisited
On Sep 10, 8:05*pm, Grumpy The Mule wrote:
Exactly right it is a gapped core. Once I git's a scope on I'll see. But the voltage doubler they using is full wave doubler. Which means they taking the positive and negative waves *to get 4000 or so volts DC Now the positive half they use a .0082 mfd for a filter and the negative half they use a .0056 mfd filter both at 3000wvdc. my guess is the quasi-push pull output is due to the leakage energy recovery circuit. *HV flyback transformers usually have very high leakage inductance (the part of the magnetizng inductance not coupled to the secondary is leakage inductance) because distance between windings is a major cause of poor coupling and you need distance for isolation. * The leakage energy sloshes about in the primary causing all sorts of mischief. *This circuit recovers it and dumps it back into the primary. It's unusual since the leakage energy is usually dumped back into the bulk storage capacitor on the primary side if it's recovered by a clamp winding or active clamp circuit. * A soft switching topology often uses the leakage inductance to reduce transistion losses in *the switch. *Sometimes a discrete inductor is added in series with the transformer primary to add to it. *Another bonus for the lousy coupling of the HV flyback transformer... no discrete inductor needed. *I think of this as electronic ju-jitsu. The energy per half cycle (on the secondary) won't be equal so juggling the capacitor values helps equalize the voltage stress. Eh! *I might be completely wrong. *Simulating it would be the thing but it's too much like work work and I'd need the transformer parameters. At least that's how I think it works... Please let me know when you've scoped the waveforms. The schematic I sent to msg actually refers to it as a flyback circuit. I am guessing one of the IGBTs is being used as a damper. Jimmie Jimmie |
microwave oven inverter P.S. revisited
On Sep 10, 8:05*pm, Grumpy The Mule wrote:
my guess is the quasi-push pull output is due to the leakage energy recovery circuit. *HV flyback transformers usually have very high leakage inductance (the part of the magnetizng inductance not coupled to the secondary is leakage inductance) because distance between windings is a major cause of poor coupling and you need distance for isolation. * Exactly right I was in a hurry to get off to work and cut out the part about the Damper diode and hold down capacitor. So yeah the diode which looks like a varistor and may very well be a varistor, is the push pull switch shorting out the induced trailing edge energy of the IGBT. They use a .032 mfd across the primary along with the damper. So the damper is switching on after the IGBT turned is off. At least that's how I think it works... Please let me know when you've scoped the waveforms. Hopefully on the day 911, I get this powered up with low voltage. . VK3HZ waveforms were at 50 hz trace sweep frequency so you couldn't see the 30khz waveform. 73 OM n8zu |
microwave oven inverter P.S. revisited
On Sep 1, 7:48*pm, raypsi wrote:
On Aug 28, 8:39*pm, wrote: On Aug 28, 4:02*pm, wrote: On Aug 27, 12:40*pm, raypsi wrote: finally came across an article by VK3HZ that describes how to make a microwave oven inverter PS work, as a stand alone supply. the link is:www.users.bigpond.net.au/dwsmith/hv_inverter.pdf It's only regulated from the primary side. And you can make it put out anything from 2000 to 4000 VDC. but at 1300 watts. So all I have to do is load down the primary to fake out the regulator into seeing 1300 watts, Or run class A. The output or the input still has to be filtered There's an opto coupler that has to see a 110hz square wave, according to VK3HZ, that'll keep the supply running full tilt as long as there is power supplied to the inverter. 73 n8zu If the circuit can be driven from 555 osc perhaps the pulse width can be controlled from a feedback voltage taken off the output of the power supply. I am thinking adding a small winding to the transformer rectifying and filtering it and supplying this back to control the pulse width of your osc. JImmie- Hide quoted text - - Show quoted text - I was the OP of the origonal thread about the inverter power supplies. I was actually more interested in learning about the design of the power supplies so I could possibly build one from scratch. With the right information this may be easier to do than to modify one from a microwave oven. I am very grateful for the information. I have a couple of the Panasonic power supplies unfortunately they dont work but maybe I can repair them now that I have a schematic. Information on the transformer would be a good thing to have as I am sure it could be optimized for the desired output voltage and current needed for an amateur amplifier. With the current transformer on the front end I am guessing this may be the feedback path for regulation. That is to say the power supply is being controlled by the amount of current that is being drawn on the input side of the power supply. If this is the case maybe this input can be taken of the out put of the power supply and then the supply could be voltage regulated instead of being power regulated. Jimmie- Hide quoted text - - Show quoted text - Hey Jimmie I suppose *that you could use the duty cycle feature of this supply to control the output but I'd need a bank of 450WVDC caps to supply filtering. So say the power of the amp drops: the supply will compensate by increasing the voltage But with feedback I could drop the duty cycle thru the opto coupled input. Thus causing a drop in voltage which the filter would handle. By running the inverter at another lower duty cycle I can control the output voltage. I would suggest at least a bank of 16, 450WVDC for a little head room. Plus that would take out the 120 cycle ripple. 73 n8zu- Hide quoted text - - Show quoted text - The mains rectifier could use some filtering too. Im thinking using the caps out of some old PC power supplies Jimmie |
microwave oven inverter P.S. revisited
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microwave oven inverter P.S. revisited
On Sep 12, 10:54*am, Grumpy The Mule wrote:
wrote : The mains rectifier could use some filtering too. Im thinking using the caps out of some old PC power supplies Jimmie Lots of good parts in a PC power supply... Use the NTC inrush limiter resistors from the old PC supply too so the caps don't pound the snot out of the on-off switch and line recifier. Yeah, I was planning on using pretty much the whole input section to the PC power supply. The one I am looking at I think I can cut out the whole circuit with a coping saw and mount it on some standoffs. This would put the rectifiers and caps on a seperate little chassis and I wont have to shoehorn in the 'lytics on to the inverter board. I was noticing that the schematic for the 120VAC uwave inverters is pretty much the same as the 240VAC inverter. I was expecting mains input to be different. What I was expecting was a voltage doubler on the 120VAC board since the 240VAC board used a bridge. This would mean that the inverter section is designed to run off of anything from 150VDC to 300VDC . I need to take a closer look at just what are the differences in the 120 and 240 inverters. Jimmie Jimmie |
microwave oven inverter P.S. revisited
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microwave oven inverter P.S. revisited
On Sep 12, 9:49*pm, Grumpy The Mule wrote:
wrote : Yeah, I was planning on using pretty much the whole input section to the PC power supply. The one I am looking at I think I can cut out the whole circuit with a coping saw and mount it on some standoffs. This would put the rectifiers and caps on a seperate little chassis and I wont have to shoehorn in the 'lytics on to the inverter board. I was noticing that the schematic for the 120VAC uwave inverters is pretty much the same as the 240VAC inverter. I was expecting mains input to be different. What I was expecting was a voltage doubler on the 120VAC board since the 240VAC board used a bridge. This would mean that the inverter section is designed to run off of anything from 150VDC to 300VDC . I need to take a closer look at just what are the differences in the 120 and 240 inverters. Jimmie Jimmie Frankenstein style construction. *Hopefully you'll be tempted to shout "IT'S ALIVE!" but without the arcs and sparks. A 2:1 input range is a piece of cake for a flyback. *An 8:1 range isn't unheard of in commodity products. *Not being strictly bounded by the transformer (coupled inductor) turns ratio can be handy! There need not be any differences in the power components. The control parameters important to operation of the oven might need adjustment though. That said, optimization for each range could save a few coins. Make a million ovens or two and it adds up.- Hide quoted text - - Show quoted text - I went through the parts list for each power supply and their are some different part #s for the 120vac compared to the 240vac unit and the wiring is a little different. Grumpy, did you want a detailed schematic or did I already give you one? Send me an email and I will get one to you. There are part#s for everything. Maybe you could order just the transformer if you wanted. Jimmie |
microwave oven inverter P.S. revisited
Thanks for the schematic Jimmie.
The description of the inverter circuit translated by google says it's both variable frequency pulse and width modulated er... I think. This Could be critical conduction control. I couldn't find any mention of the flyback topology but my Portuguese consists of only a dozen or so words that I learned while living on the east coast and five of those are unseemly. ------------------------------------------------------------- This Power Supply Reversing receives the 120v or 220v 60Hz AC and provides the entry for the 4000 Vdc the magnetron tube, before performing the same function made by the processor and high-capacitor and diode, high. .. The entry of tension AC120V or 220V 60Hz is retificada immediately to a voltage DC. .. Voltage DC This will feed a device IGBT switching required. This device will chavear On and off for 20 to 40 kHz PWM (Pulse Wide Modulation) the sign of the microprocessor in the DPC. .. This microprocessor commands the processor high voltage to amplify and until 2000Vac 3Vac about by the processor. .. Then a circuit of half wave rectifier folder, which consists of a diode and high voltage capacitors, generate 4000V required for the magnetron. .. The output of the magnetron is always monitored by the current output of the processor internally reverse the circuit. |
microwave oven inverter P.S. revisited
On Sep 14, 5:56*pm, Grumpy The Mule wrote:
Thanks for the schematic Jimmie. The description of the inverter circuit translated by google says it's both variable frequency pulse and width modulated er... I think. *This Could be critical conduction control. I couldn't find any mention of the flyback topology but my Portuguese consists of only a dozen or so words that I learned while living on the east coast and five of those are unseemly. ------------------------------------------------------------- This Power Supply Reversing receives the 120v or 220v 60Hz AC and provides the entry for the 4000 Vdc the magnetron tube, before performing the same function made by the processor and high-capacitor and diode, high. . The entry of tension AC120V or 220V 60Hz is retificada immediately to a voltage DC. . Voltage DC This will feed a device IGBT switching required. This device will chavear On and off for 20 to 40 kHz PWM (Pulse Wide Modulation) the sign of the microprocessor in the DPC. . This microprocessor commands the processor high voltage to amplify and until 2000Vac 3Vac about by the processor. . Then a circuit of half wave rectifier folder, which consists of a diode and high voltage capacitors, generate 4000V required for the magnetron. . The output of the magnetron is always monitored by the current output of the processor internally reverse the circuit. This thing seems to be regulated primarily by the input CURRENT which would be the same as power and David Smith said in his discription. I think the answer to using it as a power supply is to turn it into a VOLTAGE regulated power supply by taking a voltage sample off of the HV transformer, possible by adding a couple of turns coil to the transformer, and replacing the input from the current transformer with this one. Naturally the inpit to IINDO may have to be suitably modified also. I cant remember now where I saw it refered to as a.flyback circuit but it said "FLYBACK" no trouble with translation. I will look for it tonight. Jimmie |
microwave oven inverter P.S. revisited
On Sep 15, 12:57*am, wrote:
On Sep 14, 5:56*pm, Grumpy The Mule wrote: Thanks for the schematic Jimmie. The description of the inverter circuit translated by google says it's both variable frequency pulse and width modulated er... I think. *This Could be critical conduction control. I couldn't find any mention of the flyback topology but my Portuguese consists of only a dozen or so words that I learned while living on the east coast and five of those are unseemly. ------------------------------------------------------------- This Power Supply Reversing receives the 120v or 220v 60Hz AC and provides the entry for the 4000 Vdc the magnetron tube, before performing the same function made by the processor and high-capacitor and diode, high. . The entry of tension AC120V or 220V 60Hz is retificada immediately to a voltage DC. . Voltage DC This will feed a device IGBT switching required. This device will chavear On and off for 20 to 40 kHz PWM (Pulse Wide Modulation) the sign of the microprocessor in the DPC. . This microprocessor commands the processor high voltage to amplify and until 2000Vac 3Vac about by the processor. . Then a circuit of half wave rectifier folder, which consists of a diode and high voltage capacitors, generate 4000V required for the magnetron. . The output of the magnetron is always monitored by the current output of the processor internally reverse the circuit. This thing seems to be regulated primarily by the input CURRENT which would be the same as power and David Smith said in his discription. I think the answer to using it as a power supply is to turn it into a VOLTAGE regulated power supply by taking a voltage sample off of the HV transformer, possible by adding a couple of turns coil to the transformer, and replacing the input from the current transformer with this one. Naturally the inpit to IINDO may have to be suitably modified also. I cant remember now where I saw it refered to as a.flyback circuit but it said "FLYBACK" no trouble with translation. I will look for it tonight. Jimmie- Hide quoted text - - Show quoted text - While brows varios inverter circuits I began to wonder how difficult would it be to convert a pulse width modulated power supply into a power supply /AM modulator. Could this be as simple as appling audio on the feedback path between the output and the PWM circuit. Just an idle thought. Jimmie |
microwave oven inverter P.S. revisited
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microwave oven inverter P.S. revisited
On Sep 15, 12:57*pm, Highland Ham wrote:
wrote: snip This thing seems to be regulated primarily by the input CURRENT which would be the same as power and David Smith said in his discription. I think the answer to using it as a power supply is to turn it into a VOLTAGE regulated power supply by taking a voltage sample off of the HV transformer, possible by adding a couple of turns coil to the transformer, and replacing the input from the current transformer with this one. Naturally the inpit to IINDO may have to be suitably modified also. ========================================== You might consider taking a voltage sample by 'tapping' a low DC voltage fraction from the HV output ,putting that into an opamp with adjustable output. You can see how this is done in an article *in QEX-July.August 1999 ,pages 50-55. 'A regulated 2400 V power supply ' by VE6AXW Frank *GM0CSZ / KN6WH Thanks Frank, but I dont have QEX or access Jimmie |
microwave oven inverter P.S. revisited
steve H wrote:
wrote: On Sep 15, 12:57 pm, Highland Ham wrote: wrote: snip This thing seems to be regulated primarily by the input CURRENT which would be the same as power and David Smith said in his discription. I think the answer to using it as a power supply is to turn it into a VOLTAGE regulated power supply by taking a voltage sample off of the HV transformer, possible by adding a couple of turns coil to the transformer, and replacing the input from the current transformer with this one. Naturally the inpit to IINDO may have to be suitably modified also. ========================================== You might consider taking a voltage sample by 'tapping' a low DC voltage fraction from the HV output ,putting that into an opamp with adjustable output. You can see how this is done in an article in QEX-July.August 1999 ,pages 50-55. 'A regulated 2400 V power supply ' by VE6AXW Frank GM0CSZ / KN6WH ============================================== Thanks Frank, but I dont have QEX or access Jimmie ====================================== http://www.realhamradio.com/hvreg.pdf for a schematic. hth Steve H ================================= Indeed ,that's the one. Tnx Steve for the interesting URL Frank GM0CSZ / KN6WH |
microwave oven inverter P.S. revisited
On Sep 15, 3:03*pm, Highland Ham wrote:
steve H wrote: wrote: On Sep 15, 12:57 pm, Highland Ham wrote: wrote: snip This thing seems to be regulated primarily by the input CURRENT which would be the same as power and David Smith said in his discription. I think the answer to using it as a power supply is to turn it into a VOLTAGE regulated power supply by taking a voltage sample off of the HV transformer, possible by adding a couple of turns coil to the transformer, and replacing the input from the current transformer with this one. Naturally the inpit to IINDO may have to be suitably modified also. ========================================== You might consider taking a voltage sample by 'tapping' a low DC voltage fraction from the HV output ,putting that into an opamp with adjustable output. You can see how this is done in an article *in QEX-July.August 1999 ,pages 50-55. 'A regulated 2400 V power supply ' by VE6AXW Frank *GM0CSZ / KN6WH ============================================== Thanks Frank, but I dont have QEX or access Jimmie ======================================http://www.realhamradio.com/hvreg.pdf for a schematic. hth Steve H ================================= Indeed ,that's the one. *Tnx Steve for the interesting URL Frank * GM0CSZ / KN6WH- Hide quoted text - - Show quoted text - Is there any more info on the circuit besides the schematic? This looks like something I could build and I probably already have most of the parts. I see it uses SCRs for switching. I guess there is no problem with latchup. I built a 400Hz inverter one time and it seemed to work for a while until one day it latched up on me and smoked. I had been using it to power some selsyn motors. Someone plugged a soldering iron into the inverter and I think it was a little too much load. I guess that is what I get for not labeling my outlets. Jimmie |
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