Where did the power go in my Half-Bridge SMPS ?

[walker1]

I have been working on modifying Half-Bridge PC supplies, and so far no problems with that.

However, I find it strange, I need something like 230W from the 230V AC mains, if my total output load is only 140W DC.
I have used a true power meter on the AC, so Voltage-Current phase should not be the problem.

The heat build-up in the supply may be something like 10-20W, but where do the remaining 70-80W go ?

If I look at the +/- 160V DC going into the transformer primary, everything seems to fit.

Is there some sort of a form factor when peak rectifying AC to DC involved here ?

 

[electricuwe]

Unless you have a supply employing an PFC (Power Factor Controller)most of excessive "power" consumption will be caused by distroted input current. To avoid mixing up power and apparent power (voltage (RMS)*current(RMS)) the 230W should be correctly labeled 230 VA.

 

[walker1]

Right !

I have just been through an analysis of a simple rectifier circuit by using a spice program.

Iin RMS was 1.2A AC sugesting something like 270 W.
However, by averaging V*I over an entire period I only
got 150 W, which corresponded nicely with 145 W drawn by the resistive load.
(5W lost in rectifiers, simulated wire resistance etc.)

In other words:
Do not always believe what you meassure.
At least not if AC and a rectifier is involved