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Old 22nd February 2012, 06:07 AM   #1
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Default About my pwm sine inverter

Hello

I never succed with PIC programing, so I've assembled a schematic of a simple version pwm sine inverter.

Anyones can look at my schematic and tell me if it would work ok ?

Thank you

Bye

Gaetan
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File Type: gif inverter sine - sg3524.gif (42.5 KB, 284 views)

Last edited by gaetan8888; 22nd February 2012 at 06:23 AM.
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Old 22nd February 2012, 04:58 PM   #2
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Hello

No reply to my question ?

Thank

Bye

Gaetan
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Old 22nd February 2012, 05:52 PM   #3
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The circuit doesn´t work. You must provide some method to remove gate charge of power mosfet´s, must use SG3525 which is push pull output (Totem Pole). In your way both mosfet will be on in the second clock pulse, then they will explode.

I´m working in the same idea like your, but in other way. Mine is as follows: HCF4060 oscillating with remote control 450KHz resonator. On Q13 obtain a 55.5Hz, low pass filter (1/2 TL082) gives quasi senoidal waveform. Q4 gives 3.5KHz, integrating it (2/2 TL082) gives triangular. Comparator (TS3702) between them gives PWM easy signal. HCF4049/4050 generates 180deg out of phase gate mosfet signals. A 12+12/315VCA gives 220VRMS quasi senoidal PWM. It is currently under design, but it is working.

No alarms, no protection, only a 15Amp fuse.

Best regards.
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Old 22nd February 2012, 09:00 PM   #4
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Hello

I've put a 1k resistor (from gate to ground), to remove gate charge of power mosfet´s.

Is it ok ?

Here's my new schematic.

Thank

Bye

Gaetan
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File Type: gif inverter sine - sg3524- ver 2.gif (44.6 KB, 246 views)
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Old 23rd February 2012, 02:16 AM   #5
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Hello

I have few SG3524 but no SG3525, that why I use a SG3524 in my schematic.

Is the SG3525 would do a much better job ?

I would need to redone the schematic to use the SG3525.

Bye

Gaetan

Last edited by gaetan8888; 23rd February 2012 at 02:43 AM.
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Old 23rd February 2012, 11:59 AM   #6
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I don´t like passive turning off. In the case you won´t use SG3525, put a complementary pair of NPN and PNP devices of the quickliest velocity and current at your hand, before the pull down resistor. I can suggest 2SD1207 and 2SA1315. Or a more specific MOSFET driver.
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Old 23rd February 2012, 02:45 PM   #7
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Hello

I can't find any SG3525 here around, so I've redone my SG3524 schematic for a better turning off of the mosfets, as you suggested.

Is it better in my ver.3 schematic ?

I know that I won't get a very good sine at the transformer output, but maby adding a negative feedback from the transformer output to the SG3524 input will do a better sine, wich side of the transformer output I use for a nfb ?

Thank you

Bye

Gaetan
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File Type: gif inverter sine - sg3524- ver 3.gif (70.1 KB, 205 views)

Last edited by gaetan8888; 23rd February 2012 at 03:11 PM.
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Old 23rd February 2012, 03:52 PM   #8
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Now the circuit is better, but still will not work. The 1K resistors must be moved to the base of the transistors, because the PNP device will be not properly biased at turn off, since 3524 is open emitter/collector.. And, you can increment the value to 10K to drain less current from inside transistors, 1K means 12mA at 12V and such a current is not dangerous, but not necessary.

At the output of the transformer, if the load is a resistance of R ohms, the current will be R times scaled the same voltage waveform. But if it is inductive, the CURRENT will approximate to a senoidal one, but voltage always will be still a PWM. So, if you want to BFW the output, you must integer (Say, low pass filter at a cutoff frequency several times (5 to 10) lower the PWM frequency) the output to recover the senoidal wave, and a servo (Like an Op amp) substracting the sample above mentioned from that of the XR2206 generated. But XR2206 is a bit expensive to this function, why not to use a single opamp in wien bridge?

Good luck.
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Old 23rd February 2012, 09:07 PM   #9
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Hello

Here the new circuit with 10k at the base of the bjt transistors.

Is it ok ?

Thank you

Bye

Gaetan
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File Type: gif inverter sine - sg3524- ver 4.gif (71.1 KB, 185 views)
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Old 23rd February 2012, 10:10 PM   #10
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How do you intend to get a sinewave output? You also need feedback for the output to regulate the output.
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