Design of DC chopper speed regulation system composed of IGBT

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design content

Speed ​​control system plan determination

Since the adjustable DC power supply capacity is not large, the single-phase AC power supply, single-phase rectifier transformer step-down, diode bridge rectifier, and capacitor filtering can be used to obtain the chopper input DC power supply, which can be obtained by IGBT chopping. Adjust the DC power supply.

The IGBT is a field-controlled input device with low input power. The CW494 integrated pulse width controller not only provides the required chopping frequency and pulse width, but also has a maximum output current of 250mA. Therefore, the circuit can be simplified without driving the amplifier circuit, thus simplifying the circuit. The internal circuit block diagram of the CW494 is shown below.

The CW494 has two internal amplifiers for easy voltage feedback. If proportional integral adjustment is used, and the feedback resistance and capacitance parameters are properly selected, the voltage static accuracy can be calculated without calculation, and the dynamic accuracy calculation can also be omitted.

To achieve current limiting protection, current cutoff feedback can be used. Due to the small load power, the resistor can be sampled, and the relay can be added. When the overcurrent is serious, the main circuit power can be cut off.

The system block diagram is shown below.

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