Control circuit for induction heating cooking ring - includes two modulation modes for low and high range operation

摘要

The control system moderates the current applied in order to vary the power output. The power is modulated in two separate modes. The power is varied between a minimum and an intermediate setting by modulating repeated wave trains of variable length and constant period. The period is at least long enough to avoid "flicker" type perturbations of the supply. The period of the wave trains may for example, be 2 seconds, in which case the intermediate powr is 1 kw. For variation of the power between the intermediate and maximum settings, the power is modulated in a second mode. The high frequency alternating voltage is cut, only allowing current to pass for a certain fraction of each period. Change from the first mode to the second may be made automatically.