LLC Resonant Induction Heating Power Supply With Three-regulation Power Control

Induction heating power has been widely applied in metal melting, heat treatment,welding and other industrial production. Compared to the traditional flame heatingand heat effect of electric, induction heating has many advantages such as highlyefficient, material and energy saving, environmentally friendly, safely and so on. Inrecent years, due to the continuous innovation of the power semiconductor and powercontrol technology, induction heating power supply gradually develops towards highpower capacity, high frequency and intelligent control. The power supply powercontrol has been an important standard to measure the quality of the Induction heatingpower, and on this basis, the control system is achieved digitization and simplicity.According to electrostatic coupling theory， the topology and the circuitcharacteristics of the resonant LLC load are systematically analyzed in this paper. Aspecific scheme which can configure the resonant parameters of the LLC tank isproposed. And it systematically describes how to select the proper type of inverter inactual production by means of calculating and deducing the impedance of two invertercircuit loads and mathematical formulas of the power.The practical advantages and disadvantages of various power adjustment schemesin actual production in recent years are studied. On the basis of the traditional voltageand current dual closed-loop power control, a three-regulation power control schemeinvolving voltage current plus inverter angle is proposed, which not only meets thepower load matching, but also ensures a constant output power. Therefore the inputpower factor of induction heating power supply and power control accuracy aregreatly improved.