Conversion of +/-37v Amplifier SMPS +/-75vdc ?? PLEASE HELP

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Hello Everyone,
Can any body help me iam new to Electronics,
i have build 400rms amplifier, which requires +/-75 to operate

i want to build smps for my amplifier but does not find such a circuit for that,
the circuit i have of smps has a ouptup of +/-37vdc but i want 75v
please help me and tell me about the changes in the given circuit daigram to generate my desire output voltage!!

*amplifier circuit "ampli1.jpg"
*SMPS circuit "switcher1.jpg"


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  • switcher1.JPG
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Joined 2007
Paid Member
I doubt its going to be that easy.

Altering the series chain of zeners to give 150 volts instead of the current 74 volts would appear to be the way this design works. The caps on the SMPS would need altering to >80 volt types.

The biggest problems would be with the output transformer and the parallel FET's. Both would need uprating massively and the transformer redesigned. Have you any idea how much a 12 to 150 volts SMPS would draw from the 12 volt supply when asked to deliver 400 watts to a load ?

Put it this way, a typical car battery would be flat within an hour.
iam building this smps for home use, i have 12v 30amp power supply
i found a site which calculates a transformer winding in such smps but the main problem that i have been facing is the resistance connect to optocoupler and 2 resistance connect across pin 2 and 16, what will the new values of these resistance for the generation of 150v??
Joined 2007
Paid Member
12v at 30 amps wont power an SMPS to produce 400 wrms from an amp. Yes, it will produce a lot of power but not that much. The SMPS is not 100% efficient, neither is the amp.

The opto coupler resistor shouldn't be any different to what is there now because the zeners will only conduct when the 150 volt point has been reached. The 10k divider of R2/3 I'm pretty sure will affect the output voltage but I wouldn't like to suggest whether any changes are needed. The zener chain is the deciding factor in maintaining the output at the chosen value.

Don't under estimate anything like this... it almost certainly wont be as easy as you think.
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