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Inverted Synchronization Technique for Switched Mode Power Supplies

IP.com Disclosure Number: IPCOM000037954D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Johnson, WM: AUTHOR

Abstract

Disclosed is a technique to prevent noise that is created from the switching action of a switched mode power supply from interfering with the proper operation of other switched mode supplies that are located in close proximity.

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Inverted Synchronization Technique for Switched Mode Power Supplies

Disclosed is a technique to prevent noise that is created from the switching action of a switched mode power supply from interfering with the proper operation of other switched mode supplies that are located in close proximity.

When two switching power supplies are placed in close proximity or are interconnected by some means, the noise generated by one supply will frequently interfere with the switching action of the second supply. The noise is generated by the fast transition of switching currents that flow through parasitic inductances in the circuit. This noise is often induced into the control circuit of the other switching supply and may cause a premature change in the state of its pulse width modulator. this effect may adversely effect regulation of the supplies and most often will cause audible noise to be emitted.

Two switched mode power supplies are shown in Figure I. The switches in each supply are enabled at the beginning of the ramp waveforms and are disabled when the ramp waveforms cross the error signals, es1 and es2, from the amplifiers. The pulse width modulator ramp in each supply is enabled only when its synchronization signal is in the low state. If both supplies have a maximum duty cycle of 0.5 and the synchronization signal from Power Supply 1 is inverted and applied to Power Supply 2, the ramp waveforms are never active at the same time. When the switch of Power Supply 1 ch...