Hysteretic control of power converters: Part I. Basics

[@HaykDingchyan]

Dear Prof. , enjoying your explanation a lot. Please make a video how to use the hysteretic control for the multi-phase buck converters.

[@sambenyaakov]

Thanks. Will try.

[@pigrew]

Thanks! I hope part 2 can talk about the advantages/disadvantages of hysteretic control... i.e.: Why should I choose this strategy for a design? Does it provide stability guarantees?

[@al3ko1985]

Hi Nathan - I think you've got a good point here. Though I would argue that part 2 should focus on an outer voltage loop with an inner current loop as mentioned by Sam in the beginning of his video. Combined voltage/current control is a popular choice in DC/DC converter control. So benchmarking (voltage/current) hysteresis control with conventional (voltage/current) PWM control could be a part 3 to finalize the topic "Hysteresis control". Or perhaps there is no difference at all? Either way, thanks to Sam for his motivation and time to prepare these educational and informative videos. Highly appreciated. Cheers,

[@sambenyaakov]

Will try to include as much as I cab. Thanks guys for encouragement.

[@sanatghosh9278]

sir, your all video helpful for ours. thank you.

[@sambenyaakov]

Thanks

[@Dr.Wiryajati]

Thanks!, nice and clear, many thanks

[@sambenyaakov]

Thanks

[@KratosGhostofSparta-pp1cr]

Hi sir. Could you please make the next parts? Thank you so much.

[@sambenyaakov]

Oops, forgot all about this. Will try.Thanks.

[@markomiljanov1597]

Could it stabilize the loop when ceramic capacitors are used (at the sw. frequency capacitor is still capacitor, not a resistance)?

[@sambenyaakov]

No so, usually ESR prevails. If not, the system will be stable but higher ripple and lower frequency.

[@Metalloys]

Thank you professor. Do you think Hysteretic controllers are suitable for large power converters (~2-3kW) 220AC to 400DC (with CM control loop inside an outer voltage control loop with no compensation network, just Bang-bang) ?

[@sambenyaakov]

The other way around will be better. Inner hysteresis and outer with compensation.

[@Metalloys]

@@sambenyaakov Thank you Professor. Yes, this is what I meant (inner hyst.). My question was that the outer (voltage) is WITHOUT compensation, just a LPF in the voltage feedback ?

[@ebarbie5016]

I did some PLECS based simulations and noticed an interesting phenomenon: If I set the cap's ESR to zero, the switching frequency expression no longer holds, neither the triangular shape of the output voltage ripple. It becomes a sinusoidal ripple 180 deg out of phase with respect to the switching frequency. The switching frequency value appears to be random. Is this expected behavior or a simulation setup bug? Thanks

[@markomiljanov1597]

Of course, it becomes unstable.

[@ebarbie5016]

​@@markomiljanov1597 it is still stable, as the reference voltage is perfectly tracked.

[@sambenyaakov]

It is usually stable but ripple will go high, frequency normally down and over and under shoots larger.

[@bob760214]

Excuse me, what's the feature between constant on-time and hysteretic control

[@sambenyaakov]

Constant on time needs a modulator and phase compensation and I think does not keep the ripple constant.

[@qqqqqq6686]

could it be that ESR is higher than total Capacitor impedance? In other way yes it is clear as |Z|=sqrt((R^2+(Xl-Xc)^2)), was that not mistake or am I too tired now :) Theoretically this could be only in resonance point when L compensate C in 100%.

[@sambenyaakov]

Zc=1/wC

[@qqqqqq6686]

@@sambenyaakov I do not get it. The real Cap Impedance; Zc conist of serial connected ESR plus ESL and plus C, so how could the ESR be bigger than Zc, only in resonance for my understanding

[@sambenyaakov]

The total Z= 1/(jwC) + jwL + ESR so at high frequency 1/(jwC) could be smaller than ESR. C is not the whole device only the capacitance portion!

[@qqqqqq6686]

@@sambenyaakov now I see. thank you.

[@yogiranjit]

sir, plz add part 2 and further of this video. plz plzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz add. mainly for boost converter.

[@sambenyaakov]

Thanks. I meant to, but then I went astray. Will try to go back to it.

[@ats89117]

This is the way most women control thermostats! Many also drive this way, alternating between the accelerator and the brakes...

[@sambenyaakov]

Please let's arrest chauvinism