[SOLVED] Measuring the Audio Susceptibility of a Boost Converter that draws 10A DC input

[kanmaedexandzelbladex]

Hello Everyone,

I'm planning to measure the audio susceptibility (vo(s)/vi(s)) of my Boost Converter but it's drawing 10A DC current at its input for a full-load output. The 10A DC current has small ripple around 0.6A peak-to-peak. If I put a signal generator on top (in series) with my input DC voltage it will get damaged and the signal generator has a 1A fuse so it cannot be used in this application. I am thinking of some way of doing the measurement by sort of isolating the signal generator? Could this be done in a simple way like with a transformer and some few components without the need for a construction of some amplifier?

The image attached here I found from **broken link removed** seems to show how to measure input impedance of power supplies without the putting the input AC voltage in series with the DC input. I don't have any Network Analyzers and so I'm planning to do the measurement manually by looking at the oscilloscope.I'm also not sure how the measurement circuit should be designed. The resistor I think is for biasing the transistor to work as a switch?

Thanks

 

[mtwieg]

That's a fine technique for doing it. The FET is not switching, it's biased in its saturation region so it will act like a linearly controlled voltage source. It will probably dissipate a large amount of power at 10A, so make sure it is a large device with a good heatsink.

Also to do the measurement you only want to look at the component of the waveforms at your excitation frequency, so you will probably need a good digital scope which can perform trace averaging to reject the switching frequency ripple.

 

[kanmaedexandzelbladex]

Thank you very much!