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Low Energy Base Driver for PWM Full-Bridge Converter Switching Regulator

IP.com Disclosure Number: IPCOM000042908D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Hitchcock, LJ: AUTHOR [+2]

Abstract

Pulse circuit 1 (Fig. 1) is added to a known proportional base ve drive circuitry 2-2' of a known pulse_width modulated (PWM) push-pull fullbridge converter switching regulator (SR) 3. Circuitry 2-2' in coaction with circuit 1 provides a low energy base drive for the power transistors Q3-Q6 of SR 3. During each half-cycle, in response to the output of circuit 1, circuitry 2-2' provides to the bases of the appropriate series-connected pair of power transistors Q3/Q6 or Q4/Q5, as the case might be, a short duration high base drive current at the beginning (i.e., at turn-on) of the turn-on period, and for the substantial remainder of the turn-on period, provides a low base drive current.

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Low Energy Base Driver for PWM Full-Bridge Converter Switching Regulator

Pulse circuit 1 (Fig. 1) is added to a known proportional base

ve drive circuitry 2-2' of a known pulse_width modulated (PWM) push-pull fullbridge converter switching regulator (SR) 3. Circuitry 2-2' in coaction with circuit 1 provides a low energy base drive for the power transistors Q3-Q6 of SR 3. During each half-cycle, in response to the output of circuit 1, circuitry 2-2' provides to the bases of the appropriate series-connected pair of power transistors Q3/Q6 or Q4/Q5, as the case might be, a short duration high base drive current at the beginning (i.e., at turn-on) of the turn-on period, and for the substantial remainder of the turn-on period, provides a low base drive current. As a result, at the beginning of the turn-on period, the particular pair of power transistors are turned-on faster by the high base current thereby minimizing turn-on losses, but at the end (i.e., at turn-off) of the turn-on period when the base drive current is low, the transistors are more easily turned-off, thereby minimizing turn-off losses. Circuitry 2-2' has two identical circuits 2 and 2' which coact to control Q3 and Q6 of one branch of bridge converter 3 and Q4 and Q5 of the other branch, in a push-pull manner, their respective inputs B1 and B2 being cross-coupled for this purpose. Inputs B1 and B2 of circuits 2 and 2', respectively, respond to input pulses PWM1, which causes Q3 and Q6 to turn ON. Inputs B2 and B1 of circuits 2 and 2', respectively, respond to input pulses PWM2, which cause Q4 and Q5 to turn ON. Inputs C of circuits 2 and 2' are commonly connected to the output of pulse circuit 1. The alternating pulse-width modulating pulses PWM1 and PWM2 (Fig. 2) are derived, for example, from an external synchronized source (not shown). In accordance with well-known principles, a portion of the primary current of power transformer T2 is fed back to the particular pair of ON power transistors by the transformer action of feedback winding 4 of driver transformer T1 and thus resulting in alternate proportional base drive currents being fed to Q3/Q6 and to Q4/Q5, respectively, from circuits 2 and 2', respectively. In operation, just prior to t1 (Fig. 2), driver transistors Q1-Q2 of driver circuit 2 and their counterparts (not shown) of driver circuit 2' are in their ON states. Under these conditions, PWM1 and PWM2 are at t...