Browse Prior Art Database

REVERSE D.C. SWITCHING CIRCUIT

IP.com Disclosure Number: IPCOM000005943D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2001-Nov-19
Document File: 1 page(s) / 42K

Publishing Venue

Motorola

Related People

Harshad Parikh: AUTHOR [+2]

Abstract

In many instances the polarity of a D.C. supply can be inadvertently reversed while connecting it to an electronic circuit, which can cause damage to the circuit. The switching circuit illustrated below is utilized to connect a DC. supply to an electronic circuit with the correct polarity.

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m M-ROLA

Technical Developments October 1990

REVERSE D.C. SWITCHING CIRCUIT

by Harshad Rarikh and Swee Min Liew

   In many instances the polarity of a D.C. supply can be inadvertently reversed while connecting it to an electronic circuit, which can cause damage to the circuit. The switching circuit illustrated below is utilized to connect a DC. supply to an electronic circuit with the correct polarity.

   If the switching circuit is connected, i.e., the positive D.C. supply terminal to the V, terminal, the transistor Cl, will not turn on and, thus, relay the K, does not switch. Therefore, the positive D.C. supply terminal is connected directly to the V, terminal of the electronic circuit and the negative D.C. supply terminal is connected to the circuit ground.

   When someone inadvertently reverses the polarity of the D.C. supply, transistor 0, will be turned on and the 2-pole relay K, is activated. Relay K, will switch from position A to position B. Thus, the positive DC. supply terminal will be correctly connected to the V, terminal of the electronic circuit and the negative D.C. supply terminal will be correctly connected to the electronic circuit ground. This circuit can be applied to any D.C. operated product, provided that the
D.C. is greater than the 0.7 volts required to turn on transistor Cl,. Also, relay K, must be chosen for the correct operating voltage.

0 Motorola, Inc. 1990 6

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