Hi Kelly, thanks for your answer. Actually I'm using the configuration with the jumpers "up/up" (158V max) for ease of measuring. With the jumpers "down/down" (500V max) the ripple is very similar, not so much better. In my application I want to drive the piezo actuator in consecutive stable positions. So I'm going to generate the setpoint (voltage reference...) with a PWM signal with a given duty-cycle. Adjusting the duty-cycle the microcontroller can control the elongation of the piezo element. The piezo element is attached to a thin layer of glass (part of an adaptive lens) which is bent to obtain a variable focusing power of the lens. To be able to do that, I need a very stable output from 0 to 500V. Is it possible with this kind of circuit or i can only optimize it in a small range of output voltage? After carefully reading the datasheet I'm now thinking that this behaviour is caused by the hysteretic control strategy...am I right? PS: With "50Vpp with only about 20V setpoint" I mean that with a PWM input signal which should produce a 20Vdc output (according to it's duty-cycle), I get that horrible sawtooth-like waveform with 50Vpp of amplitude. I need almost constant or negligible ripple across the full 0-500V voltage range.
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