Synchronous Rectification

mgm2000ro · 25th May 2010, 08:43 PM

Hello, this method from synchronous rectification is good ?

Sch3mat1c · 26th May 2010, 01:07 AM

No, this is better.
http://myweb.msoe.edu/williamstm/Ima...409_Schem2.png
http://myweb.msoe.edu/williamstm/Ima...409_Schem3.png

mgm2000ro · 26th May 2010, 01:12 PM

Hello and thank you for the schematics.
I've looked at them and from what I can tell the differences are the mosfter polarity and the
direct command of the mosfets from the totempole, with a ground common to the PWM integrated circuit.

The reversed polarity of the mosfets works in my case but I can't use a common ground, that's why
I went with a GDT command.

To me they look mostly identical, please correct me if I'm wrong.

Sch3mat1c · 27th May 2010, 04:49 AM

The two sets of rectifier transistors have to be on simultaneously, while the inverter transistors are off. A GDT cannot provide this action.

Tim

mgm2000ro · 27th May 2010, 05:27 AM

I'm confused, do you mean whit GDT i have no power to turn off large input capacitance of rectifier mosfet? I can add an pnp transistor to turn off rectifier mosfet.
What is your opinion?

Sch3mat1c · 28th May 2010, 09:50 PM

No.

The required waveform is fundamentally different.

This is the inverter waveform (top), and drain waveform at the rectifier, with gate drive disconnected.

Both rectifier transistors must be turned on during dead time (shown here at +12V).

Tim

orfeus · 29th May 2010, 05:47 AM

I suggest you the LTC3722. It's expensive but it gives much more design flexibility. It can be cooperate with a second stage controller to make various modifications. The problem is that you will have to deal with full bridge rectification. Download and the software. It will help you.

26th May 2010, 01:07 AM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	No, this is better. http://myweb.msoe.edu/williamstm/Ima...409_Schem2.png http://myweb.msoe.edu/williamstm/Ima...409_Schem3.png __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

27th May 2010, 04:49 AM	#4
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	The two sets of rectifier transistors have to be on simultaneously, while the inverter transistors are off. A GDT cannot provide this action. Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

28th May 2010, 09:50 PM	#6
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	No. The required waveform is fundamentally different. This is the inverter waveform (top), and drain waveform at the rectifier, with gate drive disconnected. Both rectifier transistors must be turned on during dead time (shown here at +12V). Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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26th May 2010, 01:12 PM	#3
mgm2000ro diyAudio Member Join Date: Nov 2004 Location: Bucharest	Hello and thank you for the schematics. I've looked at them and from what I can tell the differences are the mosfter polarity and the direct command of the mosfets from the totempole, with a ground common to the PWM integrated circuit. The reversed polarity of the mosfets works in my case but I can't use a common ground, that's why I went with a GDT command. To me they look mostly identical, please correct me if I'm wrong.

29th May 2010, 05:47 AM	#7
orfeus diyAudio Member Join Date: Jan 2008	I suggest you the LTC3722. It's expensive but it gives much more design flexibility. It can be cooperate with a second stage controller to make various modifications. The problem is that you will have to deal with full bridge rectification. Download and the software. It will help you.

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