Bus Voltage Frequency and Phase Estimation Method for Induction Heating Appliances

Induction heating cooking appliances are powered by a single-phase utility AC grid whose first stage is a full-bridge rectifier with a capacitive filter that generates a DC voltage VB that feeds up the inverter that supplies the AC current to the heating coil. Information about the frequency and phase angle of the input voltage
$v_{\mathrm{B}}$
is required to compute important operational parameters of the resonant converter as well as to comply with harmonic emissions standards. This paper presents a digital circuit that provides real-time information about the frequency and phase of the full-wave rectified voltage of a half-bridge series-resonant inverter for induction-heated cooking appliances. The proposed technique and its digital implementation are detailed. Since induction cooktops market is global, the proposed method must work with the different standards of mains frequency and voltage amplitude that there are in different countries. Simulations are performed to confirm the validity of the proposed technique and, finally, the digital circuit is implemented in a system-on-chip (SoC), and the technique is experimentally verified in a prototype.