[Radio Wrangler]

OK, thats definitely a later supply.

There are three switchers and the main controller chip gets rectified mains directly. No R/C startup circuit,

Q5 is a little ancillary switcher running off rectified mains (labelled B+ to keep the Americans comfortable) It's a flyback converter. Notice that there is a thyristor crowbar on its output.

The rectified mains does NOT feed a reservoir, the voltage is allowed to drop between half cycles. If there had been a reservoir, it would have held the voltage, the rectifiers would drop out over a lot of the half cycle and the mains current would drop to zero.

Q3 and Q10 with an inductor and a diode make a boost converter and this drives the real reservoir. While the mains voltage is low the boost converter boosts it to take some power. The controller chip looks at the mains voltage and massages the current the booster takes to sinusoidally follow the sinusoidal mains... so the power supply pretends to take current just like a resistive load. This is called power factor correction. It's now required on many higher power things. You'll find it in some Linn hifi amps, my TIG welder in the garage has it. It gives the alternators wherever the mains comes from a less damaging experience.

Q1 Q25 T1 are the main power converter, turning the PFC boost voltage into all the outputs. T1 is where mains isolation happens.

A protection chip monitors the main outputs and if something is wrong shuts down the main control chip via an opto isolator.


Overall, this supply is a bit more comprehensive and a bit better protected than most computer supplies.

David