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Power Supply with Optical Isolator

IP.com Disclosure Number: IPCOM000076638D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Bowen, AJ: AUTHOR [+3]

Abstract

A feedback error signal from a transformer secondary winding is coupled to a control circuit for the primary winding with electrical isolation by a light-emitting diode and a responsive phototransistor.

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Power Supply with Optical Isolator

A feedback error signal from a transformer secondary winding is coupled to a control circuit for the primary winding with electrical isolation by a light-emitting diode and a responsive phototransistor.

The AC input, rectified and filtered by 10, is applied to primary winding 15 of transformer 20. The load voltage VL, taken from secondary winding 25 and rectified and filtered by 30, is compared by comparator 50 with a stable reference voltage provided by winding 35, rectifier and filter 40, and reference 45. The output of 50 drives light-emitting diode 55. Phototransistor 60 is responsive to the light emitted by 55 and provides a current drive for transimpedance amplifier
65. The current of 55 ranges from I1 to I2 during the regulation cycle and the voltage output from 65 ranges from V1 to V2.

The signal from 65 and a linear ramp generated by 70 are applied to modulator 75. The ripple DC voltage across primary winding 15 is modulated as the modulated pulse from 75 switches power transistor 80.

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