High efficiency bias circuit for high frequency inductively loaded power switching transistor

Claim 2

A power switching circuit comprising: a transistor switch including a collector, an emitter and a base; a second transistor having a first conductivity type and connected to couple a turn-on bias voltage to the base of the transistor switch; a third transistor having a second conductivity type opposite the first conductivity type and including a collector emitter path connected to couple the base of the transistor switch to ground potential and operative as a low impedance current path to bias the transistor switch nonconducting; logic means for applying a common bias signal to base electrodes at the second and third transistors so that the second and third transistors are always in opposite conductivity modes; first and second diodes connected in series coupling the emitter of the transistor switch to ground, and providing sufficient voltage drop so that a voltage drop across the first and second diodes exceeds a voltage drop across the collector emitter path of the third transistor when it is conducting; and an anti-saturation diode coupling the base electrode of the second and third transistors to the collector of the transistor switch.

Claim 3

A power switching circuit comprising: a transistor switch including a collector, an emitter and a base; means for controlling a conductivity state of the transistor switch including; second and third transistors of opposite conductivity type to one another and having their emitter electrodes joined in common to the base of the transistor switch; drive control means coupled to control a conductivity state of the second and third transistors in opposite modes of conductivity including a binary logic circuit coupled to apply bilevel signals in common to base electrodes of the second and third transistors, the third transistor coupling a bias voltage to bias the transistor switch conductive and the second transistor coupling a ground reference to bias the transistor switch nonconductive; at least first and second diodes coupling the emitter of the transistor switch to the ground reference and operative for maintaining the emitter at the transistor switch at a slightly higher voltage than a voltage drop across a collector emitter path at the second transistor when it is conducting; and a feedback path including an anti-saturation diode coupling a base electrode at the second and third transistors to the collector of the transistor switch.

Claim 4

A power switching circuit comprising: a transistor switch including a collector, an emitter and a base; means for controlling a conductivity state of the transistor switch including; second and third transistors of opposite conductivity type to one another and having their emitter electrodes joined in common to the base of the transistor switch; drive control means coupled to control a conductivity state of the second and third transistors in opposite modes of conductivity including a binary logic circuit coupled to apply bilevel signals in common to base electrodes of the second and third transistors, the third transistor coupling a bias voltage to bias the transistor switch conductive and the second transistor coupling a ground reference to bias the transistor switch nonconductive; at least first and second diodes coupling the emitter of the transistor switch to the ground reference and operative for maintaining the emitter at the transistor switch at a slightly higher voltage than a voltage drop across a collector emitter path at the second transistor when it is conducting; and a feedback path including an anti-saturation diode coupling a base electrode at the second and third transistors to the collector of the transistor switch.

Claim 5

A power switch as defined in claim 2 wherein recovery time of the first and second diodes is slow relative to a switching speed at the transistor switch.