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Induction Heating Power Inverter

IP.com Disclosure Number: IPCOM000089676D
Original Publication Date: 1977-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Diel, SA: AUTHOR

Abstract

This simple circuit converts a direct current voltage source to a source of high frequency power suitable for induction heating applications.

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Induction Heating Power Inverter

This simple circuit converts a direct current voltage source to a source of high frequency power suitable for induction heating applications.

Assume that the silicon-controlled rectifier (SCR) (S) is "off", and that the capacitor charging current I has already been established. When this current flows, the voltage drop across the inductor L1 is zero, and the charge in and the voltage across capacitor C1 steadily increases.

When the voltage across C1 reaches a certain level V1, the voltage- controlled pulse generator (VCPG) fires the SCR. The voltage across the SCR rapidly drops to a low value, effectively connecting C1 across the inductor L1. Then one complete cycle of a sinusoidal current flows in L1. The SCR conducts the current during the first half of the cycle, and the diode D conducts the reverse current during the second half of the cycle. Energy is transferred from L1 to the load to be heated during this cycle. Hot all energy is transferred, however, and the remaining energy is returned to C1. The voltage across the capacitor at the end of the cycle is V2, which is less than at the beginning, depending on how much energy was transferred during the cycle.

The SCR is "commutated", that is "turned off", during reverse current flow when diode D is conducting. The SCR is thus provided with the necessary recovery current and reverse bias to enable it to regain its forward voltage blocking capability. At the end of the cycle, the voltage across the SCR quickly rises to the partially discharged capacitor voltage V2, and the voltage across the inductor L1 drops to zero, and a new cycle begins.

The c...