Smooth OFF to ON switch...via PWM

[treez]

Hello, i periodically need to switch a fet on which delivers 400mA current from the secondary of a current transformer.

The primary contains a 50KHz sinusoidal current (2A9 Average), which is produced by a highly resonant LC tank circuit.

Because of the resonant nature, i cannot simply and suddenly switch the switch from OFF to ON (because it would excite resonances in the resonant system)......but instead i must PWM the switch ON/OFF/ON...etc until its ON all the time....so i must gradually increase the dutcy cycle from 0 to 100%, until its ON all the time.

I need the gradual switching interval to be 5ms.

Do you know of a way of doing this?

 

[FvM]

It's surely possible, but is it necessary? The secondary of a current transformer would be switched between low impedance loads respectively a short only. So the generated transient on the primary can't be large. Or the peak power dissipated by the transistor would be sufficient low to allow it's operation in linear mode for 5 ms.