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Isolated Feedback For Switching Regulator

IP.com Disclosure Number: IPCOM000049693D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Kapur, KN: AUTHOR

Abstract

Optoelectronic coupler 10 provides feedforward control derived from the input AC line vantage for a switching regulator power supply.

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Isolated Feedback For Switching Regulator

Optoelectronic coupler 10 provides feedforward control derived from the input AC line vantage for a switching regulator power supply.

Power stage 11 is configured as a transformer-coupled switching regulator. The switching device or devices 12, as the case might be, are connected to the input winding N1 of transformer T1. The output winding N2 provides a DC regulated output voltage Vo at output terminals 13 via rectifier and filter circuit 14. Terminals 13 are also connected to the sense inputs 15 of the control stage and driver stage of driver/ control circuit 16 that drives and controls the on/off cycle associated with the power switch(es) of circuit 12 with its control signal Vc.

The optoisolator, i.e., optoelectronic coupler 10, isolates feedback voltage Vfb from the unregulated AC input line voltage that is applied to input terminal 17, which is connected to the inputs of bias supply 18 and rectifier and filter circuit
19. More particularly, the bulk DC voltage Vbu of circuit 19, which is applied across inputs 12a and 12b of circuit 12, is also applied across inputs 1Oa and 1Ob of isolator 10, which in turn references it with the output voltage Vbi of supply 18. The feedback signal Vfb at the output of isolator 10 is thus proportional to the bulk voltage Vbu as referenced to the bias voltage Vbi. Voltage Vbf is fed to the control stage of circuit 16 to stabilize operation of the feedforward control loop 20. For examp...