The latest PC power supplies have very high efficiency, also at low loads, I did read LLC circuits are used fro the European models to achieve this. So I googled a bit and found this interesting paper:
A bit different topology, but makes a lot of sense.
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Hello Jan,
I like the half or full bridge zero voltage crossing circuits, switching losses are really low and you don't have to switch very fast. They are my workhorses when I need AC power at LF to MF. I didn't know they call them LLC circuits.
Same technology is used in ballasts for fluorescent tubes (inclusive CFL). I am planning to build a self-oscillating Zero Voltage Switching inverter with 1200V IGBT where both IGBTs are at input ground level (that gives about 750V peak voltage across the switch, but less ripple current with respect to a half bridge solution). All directly fed from rectified mains.
There are also limitations (as mentioned in the paper). The control range is limited and to get less power, you need higher frequency. Wide input voltage range is also difficult. To remain high efficiency at low load, you should use on/off control (burst mode) in the DC to AC converter. This saves you from core losses (that are also present under light load).
Best regards,
Wim PA3DJS
The author of your article shows a poor understanding of LLC resonant converters. In very few cases can the resonant components be composed solely of parasitics. The aim of this and LCL topologies is solely to include unavoidable parasitics in useful energy transfer or reduced-loss switching.
As magnetics used in small low profile designs tend to be unavoidably leaky, and their wound components tend to be photo-plotted, predictable parasitic component generation becomes more easily available, if teir design is repeated slavishly.
RL
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