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Capacitor Coupled Inverter Regulator

IP.com Disclosure Number: IPCOM000080353D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 35K

Publishing Venue

IBM

Related People

Hellwarth, GA: AUTHOR [+2]

Abstract

High-frequency switching of a power regulator is accomplished with minimum switching noise by capacitively coupling the power source into a transformer primary, the size of the capacitor being selected to advantageously resonate with the transformer leakage inductance. The circuit is particularly useful for powering low-level analog circuits that might be rendered inaccurate, by the switching noise of high-frequency switching regulators.

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Capacitor Coupled Inverter Regulator

High-frequency switching of a power regulator is accomplished with minimum switching noise by capacitively coupling the power source into a transformer primary, the size of the capacitor being selected to advantageously resonate with the transformer leakage inductance. The circuit is particularly useful for powering low-level analog circuits that might be rendered inaccurate, by the switching noise of high-frequency switching regulators.

Fundamentally, the circuit shown converts DC power from source 10 into AC and then reconverts it to DC, so that the DC voltage has a controlled or regulated value when applied to load circuit 11. Switches 12 and 13 are power switches such as silicon-controlled rectifiers (SCRs), which are alternately gated into conduction by means not shown. When switch 12 is closed, capacitor 14 charges towards voltage source V, the charging current flowing through primary 15 of transformer 16. Current from secondary winding 17 charges filter capacitor 18 through rectifier diode 19.

Assuming switch 12 is a SCR and the initial conduction gate has been removed, the dropping of current through 12 to zero causes switch 12 to open. After a time delay, switch 13 is closed so that capacitor 14 discharges through 15 towards zero voltage. The resulting current in secondary winding 20 and rectifier diode 21 continues charging filter capacitor 18 and supplying DC power to load
11. When current from discharging capacitor 14 drops to zero, switch 13 opens thus completing one cycle. Diodes 22 and 23 are included for transient suppression.

Each current pulse is shaped into a half-sine by a series resonant circuit, composed of capacitor 14 and the leakage inductance of transformer 16. The Q of this resonant circuit is less than one, and this low Q causes the resonant frequency to differ from the high-Q case by a...