Parallel versus Series Resonance Converter Topology - Pros/cons

Jan 04, 2006 2 Replies
K

Hi



I'm working on a resonance converter and have read a little bit on the subject thus far. Most recommend using a series resonance topology, but I cannot seem to find the excact reason why the parallel resonance converter is disregarded.



The block diagram is a follows:



formatting link
\\tmp\\parallel_resonance_conv.jpg



In this parallel resonance converter the OSC is adjusted to exactly the resonance frequency. Offcourse this will let the voltage envelope continue to rise on the LC circuit, but that is taken care of by the optocoupler which will shut down the driver when the voltage is to high on the output



So in essence the converter is operating burst like on the resonance point



In this converter the current is cycled between the L and C in the LC circuit, so there is little current in the driver. On the contrary the series converter has large current in the drive.



But what is the drawbacks to an parallel LC circuit like this versus a standard series LC resonance converter? Something that I'm missing?



Thanks



Klaus



Vote
Twitter Facebook LinkedIn
T

Transistors are most efficient switching quick and solid. A capacitor is like a train hitting a brick wall. Series resonant has an inductor in series, so the switching harmonics are handled softly. Peak currents are low and the world sleeps soundly.

If you must have a parallel resonant tank, you can feed it with a series inductor (check my website for a related project), but the behavior is a bit more complicated (showing both series and parallel resonant behavior).

Tim

-- Deep Fryer: a very philosophical monk. Website:

formatting link

Vote
Twitter Facebook LinkedIn
F

There isn't any - it depends on what one needs the converter to do. In general, parallel resonant converters tend to be current-fed i.e. large inductor on the input, so they regulate slower. The Mapham Inverter is the classic version. Other kinds work on dumping energy into the parallel tank and regulate by changing the dump frequency - Philips did a "Parallel Resonant Power Supply?" PRPS application note.

If your reason for wanting a resonant converter is getting a clean sinusoidal output voltage then the large parallel capacitor on the output helps a good deal. Often those converters are running at a *fixed* frequency and the output voltage is controlled by adjusting the Inductor part of the L/C resonator (For large setups, such as an UPS, the "inductor" is a full-bridge feeding a constant current DC/DC converter - the current sets the "Inductance"). Cancelling part of the flux by transformer action can work too.

Vote
Twitter Facebook LinkedIn

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required