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Switching Regulator Having Ripple Compensation by Current Insertion in Transformer Primary

IP.com Disclosure Number: IPCOM000085056D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hoffman, HS: AUTHOR

Abstract

Normal switching regulator feedback does not operate at switching frequency. The smoothing at this frequency is taken care of by the filter. Clamping is usually used to keep reactive energy from being dissipated in the main switches. However, such clamping is usually dissipative. In this switching regulator, the ripple current, e.g., from the clamping circuit, is fed in a controlled manner with a gain circuit to nearly cancel the ripple.

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Switching Regulator Having Ripple Compensation by Current Insertion in Transformer Primary

Normal switching regulator feedback does not operate at switching frequency. The smoothing at this frequency is taken care of by the filter. Clamping is usually used to keep reactive energy from being dissipated in the main switches. However, such clamping is usually dissipative. In this switching regulator, the ripple current, e.g., from the clamping circuit, is fed in a controlled manner with a gain circuit to nearly cancel the ripple.

In the circuit shown, current flowing in inductor L of a preregulator stage, not shown, flows through either primary 10 of transformer T1 or primary 12 of transformer T2, which time share the conduction. When a switch 14 or 16 is turned off, leakage energy and magnetizing energy flow into the snubbing circuit around that switch.

When the voltage on the snubbing capacitor becomes equivalent to the clamp capacitor C1 voltage, the conduction switches to the clamp winding 18 or
20. Both T1 and T2 do this in turn, thereby accomplishing the charging of capacitor C1. The discharge of C1 is through diode D1 to node N. Thus, C1 can return its energy to the source, providing rough ripple compensation.

To provide better ripple compensation, transistor Q1 is interposed between diode D1 and N so as to control the returned current amplitude as a function of time, based on a signal coupled back to transistor Q1 from T1, T2 output via current transformer T...