Research on simple and efficient series-resonant inverter

A novel power modulation method for resonant inverter and a simple and practical analog frequency auto-tracing circuit are proposed. The power modulation method when is compared with the pulse density modulation method exhibits the following advantages: simple implementation in analog or digital control; reduction of the inverter cost. Compared with the conventional frequency auto-tracing circuit, the proposed frequency auto-tracing circuit has the advantages as follow: the output voltage sensor is not needed, which reduces the cost of induction heating applications and EMI noise; the compensating effect of the phase compensating circuit has no relationship with output current magnitude. The disadvantage of the power modulation method is that the current of induction heating coil is not continuous in low power. In this paper, the principle of circuit is analyzed in detail. Practical engineering application results show that the time division power modulation method and the frequency auto-tracing circuit have the advantages of simple realization, high reliability, low cost and great engineering application value.