This paper introduces four steps of frequency sweep circuit debugging for induction furnace inverter

1. Maximum sweep range:

When P11 is used to limit the highest sweep frequency of inverter, observe the waveform frequency of u19.4 with an oscilloscope. When P11 is adjusted, the frequency range of u19.4 should be 50 ~ 450hz

2. Set sweep range:

Adjust P11 so that the frequency of u19.4 is about 350Hz, and the output voltage of P11 (u17.2) is about 8V

3. Observe the sweep beat

Turn on the sweep switch and slightly turn the power adjusting potentiometer. When the low frequency light L15 flashes, observe the waveform of u18.9 with an oscilloscope, as shown in the figure below. The waveform cycle is 0.5 ~ 1s, which is the sweep beat

4. Observe the inversion pulse

The oscillograph is connected to the gate of MOS transistor. The inverting pulse is single pulse, the pulse width is about 40 μ s, and the pulse amplitude is generally 3 ~ 6V.

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