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Transistor Switching Regulator Start Circuit

IP.com Disclosure Number: IPCOM000073964D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Moorman, WA: AUTHOR

Abstract

This starting circuit is utilized for a transistor switching regulator to substitute temporarily for the normal supply for the transistor control and drive circuit.

This text was extracted from a PDF file.
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This is the abbreviated version, containing approximately 68% of the total text.

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Transistor Switching Regulator Start Circuit

This starting circuit is utilized for a transistor switching regulator to substitute temporarily for the normal supply for the transistor control and drive circuit.

After start-up, the control and drive is powered from a rectifier and filter circuit driven by a transformer which is energized through the switching transistor.

When AC line voltage is applied to the input, a rectified and filtered voltage is produced at V1. Current 10 charges C1 and C2 through R1 and D3. When the voltage on C1 and C2 reaches the Zener voltage of D1, Q1 turns on which in turn causes Q2 to turn on thus holding Q1 on in a latching fashion. Current now flows from C1 through Q1 and R6 causing V2 to increase to the Zener voltage of D2. This causes the Darlington connected emitter-follower transistors Q3 and Q4 to conduct by the power of C2, thereby producing a regulated output voltage V3. This completes the initial start-up power connection 12 for the control and drive circuits 14 of the switching transistor 16.

Control and drive circuit 14 now starts switching 16 on and off, drawing current through the primary of T1. After the first few cycles, the voltage produced in secondary 1, rectified by D4, takes over to supply output current 12. The start circuit continues to supply current 12 to circuit 14 until low-pass L-C filter 18 can respond and provide steady state current 20 to 14.

Shortly after 20 is established, C1 completes its discharge to...