First, thanks to SgtWookie for his advice regarding posting my problem/project. Much appreciated as I'm a newbie around here.
I'm trying to construct a circuit to drive a 12 volt automotive cooling fan. Hence I plan to use a P-Channel mosfet as a high side switch, driven by a suitable PWM circuit (I need to do this because the fan motor has a chassis earth to negative)
I have tried a 555 based PWM circuit (as attached but driving a p-channel mosfet, high side, a schottky for D2 and a 47ohm gate resistor), but the mosfet overheats - due, I suspect, to slow switching. I also tried a totem pole drive circuit, connected directly to the 555 output, but the high current from the 555 fried the totem transistors.
I came across SgtWookies "Simple PWM Circuit" and was wondering if I could use this to drive the mosfet - perhaps even via a dedicated driver chip (I can easily source a TC4428A for this purpose)
(original circuit at http://forum.allaboutcircuits.com/showthread.php?t=9016)
Any help would be appreciated
Zebbo
I'm trying to construct a circuit to drive a 12 volt automotive cooling fan. Hence I plan to use a P-Channel mosfet as a high side switch, driven by a suitable PWM circuit (I need to do this because the fan motor has a chassis earth to negative)
I have tried a 555 based PWM circuit (as attached but driving a p-channel mosfet, high side, a schottky for D2 and a 47ohm gate resistor), but the mosfet overheats - due, I suspect, to slow switching. I also tried a totem pole drive circuit, connected directly to the 555 output, but the high current from the 555 fried the totem transistors.
I came across SgtWookies "Simple PWM Circuit" and was wondering if I could use this to drive the mosfet - perhaps even via a dedicated driver chip (I can easily source a TC4428A for this purpose)
(original circuit at http://forum.allaboutcircuits.com/showthread.php?t=9016)
Any help would be appreciated
Zebbo
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