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Voltage Regulator With Voltage Level Detect Circuit

IP.com Disclosure Number: IPCOM000084092D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Belcher, PN: AUTHOR [+3]

Abstract

The figure shows a voltage-regulator circuit which also incorporates a voltage level detect circuit. The voltage-regulator portion comprises the current source I (generated by conventional means); transistors TX1, TX2, and TX3; resistors R1, R2, R3, R4, and R5; diodes D1, D2, D3, and D4; zener diode Z1; and capacitor C1.

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Voltage Regulator With Voltage Level Detect Circuit

The figure shows a voltage-regulator circuit which also incorporates a voltage level detect circuit. The voltage-regulator portion comprises the current source I (generated by conventional means); transistors TX1, TX2, and TX3; resistors R1, R2, R3, R4, and R5; diodes D1, D2, D3, and D4; zener diode Z1; and capacitor C1.

The basic regulator loop is formed by TX1, TX2, Z1, D1, D2, R4, and R5. Transistor TX2 controls the output voltage by controlling the base current of the series pass device TX1. Negative feedback through Z1, D1, D2, and R4 regulates the output voltage to a value determined by Z1, D1, D2, R4, R5, and the V(be) characteristic of TX2. The emitter current of TX1 is limited by R1, TX3, R2, R3, D3, and D4. Capacitor C1 improves the transient response.

The level detect function operates as follows: When the output voltage V(out) of the regulator is well below its regulated value (as at initial power on) the voltage at point X is near ground and the level detect output is at a down level. As V(out) rises and approaches its regulated value, the diode stack (Z1, DQ, and D2) begins to conduct and the voltage at point X rises. When the voltage at point X reaches a predetermined threshold level, the level detect output switches to an uplevel.

Unlike conventional level detection circuits, this circuit operates by sensing the activity of the regulator loop when it is near its regulating state, instead of sensi...