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As shown in the figure, PWM is used to control the current of the electromagnet through a drive and chopper circuit, but the current has been unstable.

Hardware design
novembre 20, 2020 by Bibi 1001

Use about 3.3v, about 30Khz, and a PWM wave input with a duty ratio of about 0.7 to control the electromagnet current through the drive circuit and the chopper circuit, but the current keeps changing, and the voltage output from the HO pin of the drive circuit is always The increase is because there is a problem with the circuit principle or the component parameters are wrong. After finishing the design, urgently, please help, thank you!

QQ截图20180504170547.png

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Dagan postato su November 20, 2020

Did the host add freewheeling diodes to both ends of the electromagnet?

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  • Bibi

    Bibi postato su November 20, 2020

    When the two MOSFETs are turned off, the two diodes D5 and D7 are used as freewheeling diodes to power the electromagnet. Is my understanding correct?

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Dagan postato su November 20, 2020

The negative pole of the DC power supply you use is not grounded, so can the measurement be accurate?

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  • Bibi

    Bibi postato su November 20, 2020

    Under normal circumstances, is the current on the load in the middle of the H-bridge chopper circuit constant? Is the voltage of the load a PWM waveform or is it a constant voltage?

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Dagan postato su November 20, 2020

This problem has not been specifically tested, if the frequency is high, it should be approximately constant.

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