FET Switching regulator

Claim 1

A drive circuit for a system using pulse width modulation of a least one field effect transistor which has a source, a gate and a drain, in which the system includes a modulator coupled via said drive circuit to an input between the gate and source, the modulator providing repetitive cycles with variable on and off intervals indicated by discrete on and off levels at a modulator output, said transistor having a gate capacitance which is the internal gate-to-source capacitance; wherein said drive circuit comprises first and second transformers each having a primary and a secondary winding, the secondary winding of the first transformer having one terminal coupled to said gate and another terminal coupled to said source, with a diode in series directly between said one terminal and the gate, said diode being the only significant circuit element connected between said one terminal and the gate, so that an on-drive pulse applied via the first transformer charges said gate capacitance to bias said field effect transistor on, the charge being held by the diode; a switching device having an output connected directly between said gate and said source and an input connected to the secondary winding of the second transformer, so that an off-drive pulse applied via the second transformer turns on said switching device to thereby discharge said gate capacitance to bias the field effect transistor off: transformer drive means coupled between said modulator output and said first and second transformer primary winding, including on-control means operative in response to a transition to said on level to apply a very short pulse to the primary winding of the first transformer to provide said on-drive pulse, and including off-control means operative in response to a transition to said off level to apply a very short pulse to the primary winding of the second transformer to provide said off-drive pulse, said very short pulses being substantially less than one microsecond.