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Flyback Transformer Overshoot Compensation

IP.com Disclosure Number: IPCOM000080341D
Original Publication Date: 1973-Dec-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Gerbitz, CG: AUTHOR [+2]

Abstract

A rectified output circuit of a flyback transformer circuit frequently is subject to a surge at the beginning of the power delivery pulse. This surge can be compensated by use of a high-voltage diode as the rectifier diode in the circuit.

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Flyback Transformer Overshoot Compensation

A rectified output circuit of a flyback transformer circuit frequently is subject to a surge at the beginning of the power delivery pulse. This surge can be compensated by use of a high-voltage diode as the rectifier diode in the circuit.

Fig. 1 shows a typical secondary circuit in a flyback transformer coupled power supply. Fig. 2 shows the waveform which appears across the terminals XY of the transformer secondary. The initial surge 10 in the output pulse across XY provides an undesired nonlinearity in the output circuit.

The effective resistance of a low-voltage diode typically rises with time asymptotically to its equilibrium value. However, high-voltage diodes typically have a fast rise in their effective resistance, overshooting the equilibrium value and returning asymptotically to it, as shown in Fig. 3. Such a high-voltage diode 12 is used in the circuit of Fig. 1. In that figure, diode 12 is shown schematically to consist of a pure diode 14 and a series resistor R(t) which varies in time, in accordance with Fig. 3. Thus, the initial overshoot 10 of voltage is compensated by the initial overshoot 16 of diode resistance R(t), so that a desired square-wave output ZY, as show in Fig. 4, is achieved.

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