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g4wim_tim · 14th May 2021, 8:59 pm

Hi Steve,

I built practically the same design in the mid 80's and its still working well even now.

Mine was a little different and rated to a conservative 50 amps at 13.8V 100% duty cycle.

It uses six 50amp motorola darlingtons each on thier own heatsink and all driven from the the 723 output directly, but the 723 is powered sepearately from a PSU voltage a few volts higher than the main high current power supply.

Doing this makes it easier to drive the series pass devices closer to saturation without having an excessively high voltage across them.

The design as drawn has to have enough raw volts to take into the account the 723 and series pass devices voltage drop plus head room resulting in a larger than necessary drop across the series pass devices.

Mine also has two 50 amp bridge rectifiers and 200,000uF of smoothing to reduce raw ripple voltage again to minimize power loss / heat in the series pass devices.

Building a big high current power supply takes some doing !

73 Tim

14th May 2021, 8:59 pm	#13
g4wim_tim Pentode Join Date: Nov 2018 Location: Freckleton, Lancashire, UK. Posts: 232	Re: Big DC power supply Hi Steve, I built practically the same design in the mid 80's and its still working well even now. Mine was a little different and rated to a conservative 50 amps at 13.8V 100% duty cycle. It uses six 50amp motorola darlingtons each on thier own heatsink and all driven from the the 723 output directly, but the 723 is powered sepearately from a PSU voltage a few volts higher than the main high current power supply. Doing this makes it easier to drive the series pass devices closer to saturation without having an excessively high voltage across them. The design as drawn has to have enough raw volts to take into the account the 723 and series pass devices voltage drop plus head room resulting in a larger than necessary drop across the series pass devices. Mine also has two 50 amp bridge rectifiers and 200,000uF of smoothing to reduce raw ripple voltage again to minimize power loss / heat in the series pass devices. Building a big high current power supply takes some doing ! 73 Tim __________________ Building and tinkering for over 50 years, from 807's to digital amateur TV.