el00
Member level 5
Hello
I have designed a pcb board for class D evaluation. I am generating PWM modulated signal through a bench signal generator, and I have only the final stage of the class D: from the signal generator I go to an inverter (to generate complementary PWM for H and L), dead time generation, half bridge and low pass filter. PWM is modulated at ~300kHz with a rail of 100V.
Everything is working as expected, I get a very clean output on a resistive load, for now I am using 25ohm but I will go lower, later on.
But... problems arose when I tried to measure efficiency. I am using current probes (clamps), one on the power rail and the other on the output (this is redundant as I measure voltage). Probes are battery powered. However, the high frequency noise irradiated into the probes from the switching frequency is so high that I cannot even see a 1-2A signal on the scope coming from the probes. I have partially solved by putting a filter between the probe and the oscilloscope, but it is still not acceptable.
What is your experience in measuring class D efficiency? Is there any advice that I should be aware of?
Thank you
I have designed a pcb board for class D evaluation. I am generating PWM modulated signal through a bench signal generator, and I have only the final stage of the class D: from the signal generator I go to an inverter (to generate complementary PWM for H and L), dead time generation, half bridge and low pass filter. PWM is modulated at ~300kHz with a rail of 100V.
Everything is working as expected, I get a very clean output on a resistive load, for now I am using 25ohm but I will go lower, later on.
But... problems arose when I tried to measure efficiency. I am using current probes (clamps), one on the power rail and the other on the output (this is redundant as I measure voltage). Probes are battery powered. However, the high frequency noise irradiated into the probes from the switching frequency is so high that I cannot even see a 1-2A signal on the scope coming from the probes. I have partially solved by putting a filter between the probe and the oscilloscope, but it is still not acceptable.
What is your experience in measuring class D efficiency? Is there any advice that I should be aware of?
Thank you