The attached LTspice simulation and schematic show an improved version of the special PFC circuit, but the voltage and/or current waveforms are too peaky in this converter…
Also, the transformer is suffering enormous voltage spikes. I believe that this needs a energy recycling snubber to be used with it….so has Dr Cuk not given us enough information to implement his fantastic converter with? Perhaps he is understandably only divulging the basic detail? –not enough to achieve implementation?
The circuit is a resonant circuit, and L3 is the resonant inductor, and C1 is the resonant capacitor. I thought that the LC resonant frequency would need to be roughly at the switching frequency but that gives poor performance….the power throughput cannot be made high enough that way.
If C1 is too low Faradic value then C1 has too high voltage across it. If L3 has too low value then the peak current is too high. If L3 is too high Henry-ic value, then the current throughput goes down and you can’t get the power throughput.
The transformer primary would need a heavy snubber, and this would be very dissipative, unless some kind of energy recycling snubber was implemented. The problem is, where would you recycle the energy too?….since there is no storage capacitor on the primary side, and recycling to the secondary needs another isolation transformer.
The circuit would obviously need a controller to control it…but there is no “primary ground” to use to ground such a controller to. Therefore, an output of an isolated SMPS would need to be used to “ground” the controller to. Then the sensed current and output voltage signals would need to be referred to this isolated ground. The necessary fast current sense in the power FET loop will be difficult, because this will have to be transferred across an isolation barrier to the control chip, and this will be difficult. A hall sensor would have to be used, but they have poor bandwidth which would mess things up.
Does anyone know how to set the component values for this converter? The only advantage of this modified cuk converter appears to be that you can dispense with the mains diode bridge. But in exchange, one needs to have a lot of extra housekeeping circuitry to manage the control of this converter. This seems unwise, since a mains rectifier bridge only cost about 30p, and only dissipate about 1.5% of the total power budget.