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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Richie, this design is not very well known and I haven't seen it used comercially. It's because it works best for driving highly inductive loads which are uncommon in normal voltage supplies, such as capacitor charging or Jacob's ladder experiments and everywhere you need current limited power supply.
When you short circuit the transformer's output, the capacitor Cr resonates with leakage inductance of the transformer (or external inductance) and the transistors only "kick" the LC so it keeps oscillating, switching very little current. They switch only real input power (ideally) and the reactive power is circulating in the tank circuit. It is also zero voltage switching, further decreasing switching losses.
The waveforms are basically sine in the LC tank, "fullwave rectified sinewave" voltage on the dc choke and more or less constant current through the choke (at given output load).
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
If you re-draw the circuit with the L1 and L1' inductors moved to either side of the bridge-leg's mid-point and the devices connected directly to the DC bus, then you should be able to use a single centre tapped winding. It also closely resembles a standard inductive turn-on snubber shown in Fig 10 (c) on p.5 here:
There may be equations in this paper that will help you with sizing the inductors and also for calculating peak voltage across the devices, since they are no longer clamped to be within the DC bus rails.
As far as I remember, the peak off-state voltage across any switch is equal to the DC bus voltage plus a contribution due to L x di/dt developed across each inductor.
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CF parallel resonant inverter: choke design
and everywhere you need current limited power supply. 
