does anybody know a buck (buck/boost) controller chip capable for very low speed (like 2kHz to 30 kHz)? I know that is totally not state of the art but power IGBT are slooow. I find millions of 500kHz, MHz chips and think I need the expertise of someone knowing the market. Sync operation or capability for multiphases might be nice. If the controller shortens pulses - there are minimum switch on/switch off times. So a hysteretic controller might be problematic?
Any advice is much appreciated.
Many controller chips still have external timing capacitor. I have run a UC3843 with external capacitor cut for 1700Hz switching. Not hard to do.
piglet
There's always TL494 and whatnot. They're not going away any time soon.
/Do/ take the time to willfully ignore the applications in the datasheet that show voltage mode control -- this isn't the 70s, we can afford better.
You can do current-mode control, average mode being the easiest. Use an external op-amp, or op-reference so to speak (TL431 etc.), to regulate voltage. Use that to control current, and regulate current with a shunt resistor or current sensor, and an internal op-amp (just strap the other internal amp to a disabled state).
I suppose you'll want a bootstrap or isolated gate driver, for whatever voltage range you're doing. They're out there, no problem, just go shopping.
There are also IGBT integrated modules with all the outputs you need for, say, buck or motor control, and gate drivers (though you may need to add DC-DC supplies for them). They're usually on the slow side, but that's fine for your application.
Tim
Same here. I used one for current-controlled switching at 100Hz. Works. Can be sync'd. Though these are from the days when electricity was "free" and just came out of the wall outlet. So a little amplification is necessary to reduce the 1V current shunt drop.
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