ClassE PWM question.

[DMOD]

Ok, tried to re-register on ClassE formum since I have new email, but no joy.

This is regarding the U400 PWM circuit on the PWM Generator schematic.

Assume I have a 110V 4 Amp DC supply and 5 F260N's for about 350 Watts carrier.

The R409 pot sets the carrier level. So how low a carrier level can be set. 10% of max, 20% of max?

I would like to use a 5 volt logic level to the gate of a 2N7000 mosfet, with a series resistor in it's drain, to switch in "Tune" and other power setting levels at the VSCLAMP or pin 9 junction.

Phil- AC0OB

[W4NEQ]

If you hear back from Steve, please let him know I've been trying to contact him too ...

[KF1Z]

You don't need 5 260n's for that low power... :-)

250 watts of carrier for every 260n / diode pair.

So you only need 2 of them for 350 watt carrier.


With that pot, you can go to 0 pwm output


Bruce
kf1z

[DMOD]

You don't need 5 260n's for that low power... :-)

250 watts of carrier for every 260n / diode pair.

So you only need 2 of them for 350 watt carrier.


With that pot, you can go to 0 pwm output

Right, understand the rule of thumb. I would probably use 2 - 260n's for margin's.

Thanks, but I don't want to use the pot. I want to parallel up to three control fet circuits controlled by logic levels to set power.

If I don't have the ability to control the supply voltage and hence control output power in that fashion, I want to control output power by controlling the PW which is controlled by bias on the VSCLAMP, pin 9.   

I simply wanted to know if I can still modulate linearly as the Pulse Width's get more narrow.