Browse Prior Art Database

Switching Power Converter Drive System

IP.com Disclosure Number: IPCOM000100913D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Lin, KM: AUTHOR

Abstract

A compound switch consisting of a bipolar transistor and a MOSFET are controlled to switch the primary current of a power converter at high frequency with constant turn-off time.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 83% of the total text.

Switching Power Converter Drive System

       A compound switch consisting of a bipolar transistor and
a MOSFET are controlled to switch the primary current of a power
converter at high frequency with constant turn-off time.

      The figure shows the present embodiment in which the disclosed
drive system is incorporated into a known power converter. It is seen
that the supply voltage is rectified by a bridge rectifier and
supplied to the primary winding of converter transformer TX2. It is
further seen that transister Q11 and MOSFET Q12 together form a
switch which is controllable to interrupt TX2 primary winding
current.

      When power is turned on, capacitor C1, in series with high
resistor R1 across 300 volts, is charged to provide control circuit
bias. Until the charge on C1 reaches 13 volts, the voltage of point
P1 is zero, insuring that MOSFET Q12 is off and no TX2 primary coil
current flows. When the charge on C1 exceeds 13 volts, current flows
to the base of transistor Q1 through two paths: one through R2 and
Z1, the other through transistor Q3, R3 and C2. This current
saturates Q1 and turns off transistors Q7 and Q8. At this time
transistors Q2, Q4 and Q5 turn on, charging capacitor C3, causing the
point P1 voltage to go high, turning Q12, on permitting the flow of
TX2 primary coil current.

      The current of TX2 and the power supply output voltage are
sensed by a differential amplifier circuit including transformer TX1
and transistors Q13 a...