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Title: ClassE PWM question. Post by: DMOD on June 20, 2012, 04:37:29 PM 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 Title: Re: ClassE PWM question. Post by: W4NEQ on June 21, 2012, 07:45:32 AM If you hear back from Steve, please let him know I've been trying to contact him too ...
Title: Re: ClassE PWM question. Post by: KF1Z on June 21, 2012, 08:09:43 AM 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 Title: Re: ClassE PWM question. Post by: DMOD on June 21, 2012, 03:51:14 PM Quote 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. |