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Buck Converter With Switch Referenced to Ground

IP.com Disclosure Number: IPCOM000052965D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 2 page(s) / 25K

Publishing Venue

IBM

Related People

Driscoll, CD: AUTHOR [+2]

Abstract

This article describes a stepdown DC-to-DC (or buck) converter in which the switching transistor is referenced to ground.

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Buck Converter With Switch Referenced to Ground

This article describes a stepdown DC-to-DC (or buck) converter in which the switching transistor is referenced to ground.

In a conventional buck converter, the switch transistor is not referenced to ground, making it difficult to provide proper transistor drive voltages. Different approaches have been used in an effort to overcome drive problems. In a ``level shifting'' approach, a control circuit which is referenced to ground is used to drive a high voltage PNP transistor which, in turn, drives the switch transistor in the buck converter. The drawbacks to this approach are the high power dissipation levels, the requirement for an expensive high voltage PNP transistor, and the difficulty of achieving negative off drive.

In a ``transformer drive'' approach in a conventional buck converter, a pulse transformer is used to drive the base of the switch transistor. For large variations of bulk voltage, the required ratio may make it difficult or impossible to reset the transformer each cycle. Also, pulse transformers tend to be expensive.

In the buck converter disclosed in the drawing, the control circuit and the switch transistor are both referenced to ground while the output voltage Vo is referenced to the bulk voltage Vb. When the switch transistor Q1 is driven on by control 10, current is supplied to load 12 while capacitor 14 charges and energy is stored in inductor 16. When Q1 is on, diode 18 is backbiased. When swi...