Browse Prior Art Database

DUAL OUTPUT ISOLATED DC POWER SUPPLY

IP.com Disclosure Number: IPCOM000005748D
Original Publication Date: 1988-Oct-01
Included in the Prior Art Database: 2001-Nov-01
Document File: 1 page(s) / 57K

Publishing Venue

Motorola

Related People

Anthony Mazzarisi: AUTHOR

Abstract

A dual output DC isolated power supply is provided which provides two low power output DC voltages usable for FET biasing. This is accomplished with a minimum number of parts, and regulation of the DC output voltages is achieved with only a single i!ener diode.

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MOTOROLA Technical Developments Volume a October 1988

DUAL OUTPUT ISOLATED DC POWER SUPPLY

by Anthony Mazzarisi

   A dual output DC isolated power supply is provided which provides two low power output DC voltages usable for FET biasing. This is accomplished with a minimum number of parts, and regulation of the DC output voltages is achieved with only a single i!ener diode.

   The present dual output DC bias supply essentially utilizes what appears to be similar to an "Armstrong oscillator" to generate a dual output switching power supply. Transistor Ql acts as a device which controls the amount of current flowing through the primary coil of transistor Tl.

   Upon power-up, pins 7 and 9 of Tl are charged with a positive voltage. This voltage across Cl permits cur- rent to flow through C2. This generates a current flow through C2 and Dl which biases the base of Ql. As the base of Ql is positively biased, Qi turns on enabling current to flow through the primary coil of Tl, pins 8-9. A current will be generated at the secondary in response thereto. However, because D2 and D3 are reverse- biased, continuous current flow will be inhibited preventing any voltage to be generated at the dual outputs of the present circuit.

   When C2 charges up, the bias on Ql is removed and Qi turns off. As current ceases to flow through the collector of Qi when it is disabled, a "flyback" voltage is generated across the primary coil (pins 9-8) and cur- rent flows from pin 9 to pin 8 (the coil...