US 4,399,500 A · Multimode base drive circuit for power switching transistor

Abstract

A base drive circuit for a power switching transistor in a power inverter circuit utilizes a center tapped current transformer winding to regeneratively couple the collector current of the power switching transistor to its base drive electrode. A first segment of the center tapped transformer winding is coupled via a control transistor to provide proportional base drive to the power transistors when it is biased into conduction. This forward drive mode continues until the control transistor is biased nonconducting, at which point, the second segment of the center tapped transformer winding is connected to the base drive electrode to provide a reverse drive current to the power transistor base to provide rapid turn-off and reset the transformer. A supplemental drive path coupled to a converter power source via a diode to the control transistor operates to supply additional drive current therethrough to the power transistor at the turn-on transition in order to eliminate the quasi-saturation region that normally exists in a regeneratively driven power switching transistor at turn-on.

Claims10

Dependent claims

A multimode base drive circuit for a power switching transistor comprising;

a regenerative feedback circuit coupling a main conduction path electrode of the power switching transistor to its drive electrode and including a control transistor to complete a circuit path in the feedback circuit and enable regeneration, and
a supplemental drive path including a unidirectional conducting device and coupling a power source in series with the main conduction path electrode of the power transistor to the control transistor whereby drive signals supplied by the regenerative feedback path at a switching transition of the power switching transistor from nonconduction to conduction are supplemented by adding a drive current signal through the supplemental drive path in response to a collector-emitter voltage of the power switching transistor when in a conduction state.

A base drive circuit for a switching transistor in a power conversion circuit comprising;

a regenerative feedback circuit including a current transformer having a sensing winding for sensing main power path current in the switching transistor and a first drive winding for supplying forward base drive current to the switching transistor proportional to the main power path current and a second drive winding for supplying a reverse base drive current to the switching transistor proportional to the remaining main power path current,
a supplemental drive current path for coupling main power path current via a diode to the switching transistor for supplementing drive current at turn-on and operative so that the diode is reverse biased after the switching transistor is in hard saturation to remove said supplemental drive current, and
a clamping means for coupling and limiting a reverse voltage generated by the second drive winding in order to enhance the fall of collector current at turn-off of the switching transistor.

A transistor drive circuit in a power inverter circuit including an input terminal, an output terminal, and a power switching transistor interconnecting the input and output terminal,

the transistor drive circuit for biasing the power switching transistor into a conductive state including a current transformer having a current sensing winding connected in series with a main power path of the power switching transistor and a forward bias winding coupled to a control electrode of the power switching transistor and operative for supplying drive current thereto proportional to current in the current sensing winding to bias the power switching transistor conducting, and a supplemental drive circuit including a diode and interconnecting the input terminal to the control electrode and operative for supplying additional base drive current directly from a power source at the input terminal to the control electrode at a start of conduction of the power switching transistor to drive it into hard saturation and the diode responsive to attainment of hard saturation to become back biased and terminate the supplemental drive current, and
the current transformer including a reverse bias winding coupled via a hot carrier diode to a control electrode of the power switching transistor and operative for supplying reverse drive current thereto proportional to current in the current sensing winding to bias the power switching transistor nonconducting, the hot carrier diode being forward biased by a reverse voltage in the transformer at the end of a conduction interval and coupling reverse drive to the control electrode.

Dependencies are inferred from the claim text.

Multimode base drive circuit for power switching transistor

Life of this patent

Multimode base drive circuit for power switching transistor

Life of this patent

Abstract

Claims10