Rapid and precise high frequency inverter initialization process for induction heating systems

A method for minimizing initialization time in a high-frequency inverter for controlling heat distribution within a workpiece in induction heating applications, comprising:

• initiating a power supply having a DC output and operably connected to the high-frequency inverter into an idle state wherein the power supply outputs an idle DC power level;
• placing the workpiece within an induction coil operably connected to the high-frequency inverter, the induction coil configured to receive a high-frequency AC output from an inverter power stage of the high-frequency inverter and filtered through a resonant tank section of the high-frequency inverter to inductively heat the workpiece;
• selecting an initial inverter frequency of a high-frequency AC output, the initial inverter frequency comprising an expected resonant frequency for a combination of the workpiece and a topology of a resonant circuit defined by the resonant tank section, the induction coil, and the workpiece;
• increasing the DC output produced by the power supply to an initial DC power level;
• sending an enable signal from the power supply to a phase locked loop controller disposed in the high-frequency inverter, whereupon the phase locked loop controller executes a frequency regulating algorithm comprising:
• (a) receiving one or more feedback signals from the resonant tank section of the high-frequency inverter, wherein the resonant circuit is defined by the resonant tank section in combination with the induction coil and the workpiece comprises a resonant frequency;
• (b) comparing a phase of the one or more feedback signals to a phase of the high-frequency AC output;
• (c) sending firing signals comprising timing waveforms to an inverter power stage disposed within the high-frequency inverter to adjust a phase and a frequency of the high-frequency AC output;
• (d) repeating each of steps (a) through (c) until the frequency of the high-frequency AC output is equivalent to the resonant frequency of the resonant circuit;
• and
• (e) sending a synchronization signal to the power supply;
• increasing the initial DC power level to a target DC power level upon receipt of the synchronization signal;
• maintaining the target DC power level for a heat treatment period;
• decreasing the target DC power level to the idle DC power level;
• and
• removing the workpiece from the induction coil.