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Constant Voltage Power Supply

IP.com Disclosure Number: IPCOM000075332D
Original Publication Date: 1971-Sep-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Chang, AW: AUTHOR

Abstract

This power supply circuit provides an output voltage V0 directly proportional to changes in the main power supply V2. The output voltage V0 is employed to drive current source transistor and resistor combinations such as TX1-R and TX2-R, Fig. 2. The power supply V2 is also connected to the current source transistors TX1 and TX2. Accordingly, these transistors will be driven by constant current despite voltage variations in V2, because V0 is also changing a proportional amount, and thus, the base-to-emitter voltage across transistors TX1 and TX2 remains constant.

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Constant Voltage Power Supply

This power supply circuit provides an output voltage V0 directly proportional to changes in the main power supply V2. The output voltage V0 is employed to drive current source transistor and resistor combinations such as TX1-R and TX2-R, Fig. 2. The power supply V2 is also connected to the current source transistors TX1 and TX2. Accordingly, these transistors will be driven by constant current despite voltage variations in V2, because V0 is also changing a proportional amount, and thus, the base-to-emitter voltage across transistors TX1 and TX2 remains constant.

At ambient temperature, transistor TX3 is conducting lightly, and the forward voltage drop characteristics of diodes D1, D2 and D3 provide a constant voltage differential between output voltage V0 and the main power supply V2, i.e., the voltage across the diodes D1, D2, D3 in combination with the voltage divider comprising resistors R1, R2 and R3 provide a predetermined voltage at the base of transistor TX5. Transistor TX3 and transistor TX5 form a differential amplifier.

The circuit also provides temperature compensation in that the voltage V TOTAL, which equals V0-V2, will shrink or decrease due to a decrease in the base-to-emitter voltage drops as the temperature rises. Additionally, by properly selecting the values of resistors R5 and R6, the output V TOTAL is temperature compensated by the conduction of transistor TX4. When the base voltage at transistor TX5 is dropping,...