Browse Prior Art Database

Variable Frequency Oscillator for Switching Regulator Control

IP.com Disclosure Number: IPCOM000088264D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Ellis, JJ: AUTHOR

Abstract

Switching regulators operate by pulse width control of a switch, such as a transistor, by which an input bulk voltage is connected to an output circuit, such as a rectifier-filter combination. A signal which is fed back from, or otherwise tracks, the output is utilized to control the duty cycle or ratio of on to off of the switch to effect transfer of energy at a rate which will produce the desired output level. Bias voltage for operation of the circuits may be taken from the output, as well.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Variable Frequency Oscillator for Switching Regulator Control

Switching regulators operate by pulse width control of a switch, such as a transistor, by which an input bulk voltage is connected to an output circuit, such as a rectifier-filter combination. A signal which is fed back from, or otherwise tracks, the output is utilized to control the duty cycle or ratio of on to off of the switch to effect transfer of energy at a rate which will produce the desired output level. Bias voltage for operation of the circuits may be taken from the output, as well.

During start-up operations, some ramp-up technique is usually employed so that the filter capacitor will be charged gradually, without overburdening the circuits. Also, some start-up bias is usually provided, which is not as well regulated as the final bias.

This oscillator is adapted for use as the basic clock in such a system. It provides a desired ramp-up of frequency during start-up operations and is substantially independent of the value of the bias voltage.

In the schematic of Fig. 1, a timing capacitor C is provided which is charged through R1 by a current source Is in parallel with another current supply through R2 from Vb. Is is itself a function of Vb and the feedback or control voltage Vs, as shown in Fig. 2. A discharge circuit for C is provided through R1 and Q.

A control 10 is operative to compare the voltage across C with upper and lower limits alpha Vb and beta Vb. alpha Vb and beta Vb are provided by...