HF induction heater for different size containers - uses load detection for container suspended by induction heating coil for controlling voltage supply of latter

摘要

The HF induction heater has a coil (50) supplied from the mains via a rectifier (30) in response to a drive control signal. The mains voltage is fed to a step-down transformer (140), in turn coupled to a rectifier (150) associated with a zero transition detector (170). The delayed output of the detector is fed to an AND logic (190) together with a switching signal provided by a comparator (90). The comparator compares the output of a difference amplifier (80), for an input current detector signal and an output power setting, with a reference voltage. A second comparator (200) or an integrator (100) compares the output of the AND logic (190) with a reference signal, to provide the drive control signal. ADVANTAGE - Allows accurate detection of container size to be heated by induction heating device