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TIME DEPENDENT CURRENT LIMITING

IP.com Disclosure Number: IPCOM000024194D
Original Publication Date: 1979-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 103K

Publishing Venue

Xerox Disclosure Journal

Abstract

An improvement to a regulated power supply is disclosed whereby the addition of an RC circuit slows overload reaction of the power supply and therefore enables use of lighter power supplies for circuits with short-term high loads.

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XEROX DISCLOSURE JOURNAL

TIME DEPENDENT CURRENT LIMITING Proposed Carlo Infante Classification

U.S. C1. 323/9 Int. C1. G05f 1/10

- PRIOR ART

- -

FIG. I

Volume 4 Number 6 November/December 1979 759

[This page contains 1 picture or other non-text object]

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TIME DEPENDENT CURRENT LIMITING (Cont'd)

An improvement to a regulated power supply is disclosed whereby the addition of an RC circuit slows overload reaction of the power supply and therefore enables use of lighter power supplies for circuits with short-term high loads.

With reference to the prior art of Figure 1, the unregulated voltage source 10 typically comprises a transformer 11, a rectifier bridge 12 and a capacitor 13. Transistor 14 is a power transistor often designated as a pass transistor. Amplifier 15 is a high-gain amplifier. An accurate reference voltage -VvF is applied to terminal 16. Transistor 17 is a small-signal PNP transistor. oltage shifting circuitry 18 is connected between transistors 14 and 17. During normal operation, transistor 17 is off and does not have any effect. Resistor 19 is the voltage dropping resistor. The regulated output voltage is available across terminals 20 and


21.

During normal operation, any deviation from the correct output voltage is sensed by amplifier 15 and fed to transistor 14 in order to correct the value of the output voltage. If excessive current is drawn, this will result in a voltage appearing across resistor 19, thereby turning on transistor 17, which will limit the output current by decreasing the output voltage across terminals 20 and 21. Some loads encountered in practice, such as motors, printer mechanisms, etc., are not static but are time dependent. In other words, the current drawn is not continuous but is pulsed, and the d...