Example for PWM-induced inductor / capacitor buzzing

A reply of sorts to the latest podcast of 'The Amphour' ( #127 - http://theamphour.com/the-amp-hour-12... ).

Scenario: The left board contains LEDs (of course) and a step-down constant current driver. The right board is just a PWM-driven switch. Initially the switch is fully on and the LED driver can do it's thing undisturbed. As the duty-cycle of the MOSFET gets smaller, the LED driver shifts to higher peak currents to compensate, so the average current and LED brightness stays the same. Overall efficiency goes down, noise level increases to unbearable levels. You wouldn't want to have something like that in any device. The PWM frequency of the 'disturbing' switch is pretty low.

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