Compaq Computer Corporation, Inc.

Compaq Information Technologies Group, L.p.

Robert Wolf

Raoji A Patel

Raymond A Pelletier

Raoji Patel

A regulated power supply in which square wave output of a switching rectifier is applied to a filter comprises a series inductor and a parallel capacitor. This filter lacks a series resistor. The ramp signal is developed across a second capacitor in series with a first resistor, and in parallel with the rectifier output. An amplifier adds the ramp signal to a signal representing the error in the DC output voltage of the power supply, producing an output that is fed to a control circuit. The control circuit in response generates a voltage control signal that controls the switching of the rectifier.

Unique method of reducing losses in circuits using V2 PWM control

A method of preventing current hogging in parallel connected transformers, and an apparatus for efficiently implementing the method are presented. Current hogging occurs when synchronous power converter transformers operate in a low output current mode. Low output current demands are typically meet by adjusting the duty cycle of the transformer to a low level. This results in the catch FET maintaining a low resistance path to ground for long time periods and allows a stronger one of the parallel power converter transformers to sink current to ground through a weaker transformer. The method consists of using a current sensor to detect low or negative output currents, and then driving the transistor providing the path to ground to an off state. A preferred embodiment of an apparatus to prevent current hogging includes a current sense inductor placed in series with the primary side of the power converter connected to an operational amplifier having an input reference voltage selected to provide an output when the current sense inductor records less than a certain positive voltage. The op amp turns on a driver to force off a transistor which normally conducts to ground when the duty cycle is in an off state.

Growing community of inventors

Nashua, NH, United States of America

Robert Wolf