Drive control device for motor
View Patent ↗A drive control device for a motor includes an input terminal, an output terminal, an inverter circuit, a first switch unit, a capacitor, a diode, a rectifier circuit, a photo coupler, a second switch unit, and a voltage detector. The inverter circuit converts a direct current voltage into an alternating current voltage, and outputs the alternating current voltage to the output terminal. The first switch unit shorts the output terminal based on a control signal. The capacitor is connected to the input terminal, and is charged by a direct current voltage. The diode is connected between the input terminal and the capacitor. The diode limits a direction where a charge current for charging the capacitor flows. The rectifier circuit rectifies an induced voltage, which is generated in the motor, and outputs a rectified voltage. The photo coupler converts the rectified voltage into an optical signal, and thereafter, converts the optical signal into a converted signal. The second switch unit outputs the control signal based on the converted signal. The voltage detector detects whether the direct current voltage is input to the input terminal, and determines whether to negate the control signal.
1. A drive control device for a motor, the drive control device serving to control drive of the motor, the drive control device comprising:
an input terminal that receives a direct current voltage;
an output terminal that outputs an alternating current voltage to the motor;
an inverter circuit that converts the direct current voltage into the alternating current voltage, and outputs the alternating current voltage to the output terminal;
a first switch unit that shorts the output terminal based on a control signal;
a capacitor that is connected to the input terminal, and is charged with the direct current voltage;
a diode that is connected between the input terminal and the capacitor, and limits a direction where a charge current for charging the capacitor flows;
a rectifier circuit that rectifies an induced voltage generated in the motor, and outputs a rectified voltage;
a photo coupler that converts the rectified voltage into an optical signal, and thereafter, converts the optical signal into a converted signal;
a second switch unit that outputs the control signal based on the converted signal, the second switch unit including a second switch unit input terminal connected to the capacitor and a second switch unit output terminal that outputs the control signal; and
a voltage detector that detects whether the direct current voltage is input to the input terminal, and determines whether to negate the control signal,
wherein
the second switch unit
outputs a voltage of the second switch unit input terminal as the control signal to the second switch unit output terminal when not receiving the converted signal, and
does not output the control signal to the second switch unit output terminal when receiving the converted signal, and
the voltage detector negates the control signal when detecting that the direct current voltage is input to the input terminal.
2. The drive control device for a motor according to claim 1 , further comprising a plurality of the output terminals in which phases of the alternating current voltage are different from one another,
wherein
the first switch unit includes a first transistor having a control terminal that receives the control signal, and
the first switch unit is connected between the plurality of the output terminals.
3. The drive control device for a motor according to claim 2 , wherein
the direct current voltage is supplied from a voltage source,
the voltage detector includes
a first resistor and a second resistor, which are connected in series between a positive terminal and a negative terminal of the voltage source in this order; and
a second transistor connected between the control terminal of the first switch unit and the negative terminal of the voltage source, and
the second transistor includes a control terminal connected to a connecting node between the first resistor and the second resistor.
4. The drive control device for a motor according to claim 2 , wherein
the second switch unit includes
a third transistor connected between the second switch unit input terminal and the second switch unit output terminal; and
a third resistor connected between the second switch unit input terminal and a control terminal of the third transistor,
the second switch unit input terminal is connected to a connecting node between the capacitor and the diode,
the second switch unit output terminal is connected to the control terminal of the first switch unit,
the control terminal of the third transistor is connected to an output of the photo coupler, and
the third transistor is turned ON or OFF based on the converted signal.
5. The drive control device for a motor according to claim 1 , further comprising a voltage divider that divides the rectified voltage coming from the rectifier circuit and outputs a divided voltage to the photo coupler.
6. The drive control device for a motor according to claim 1 , wherein
the second switch unit
outputs the control signal by setting a state between the second switch unit input terminal and the second switch unit output terminal into a conductive state when the converted signal is in an OFF state, and
sets the state between the second switch unit input terminal and the second switch unit output terminal into a cut-off state when the converted signal is in an ON state.
7. The drive control device for a motor according to claim 1 , wherein
the voltage detector includes a voltage detector output terminal connected to the second switch unit output terminal, and
the second switch unit is configured such that an output impedance of the second switch unit is higher than an output impedance of the voltage detector when the converted signal is in an ON state and input of the direct current voltage to the input terminal is detected.