JP4854634B2 - Inverter device - Google Patents

Description

  The present invention relates to an inverter device that performs additional operation control of an induction motor or the like.

  This conventional inverter device incorporates an inverter circuit, receives DC power supply from a driving power source supplied to a load, converts it into AC power of a predetermined frequency by the inverter circuit, and supplies the AC power to the load. The frequency of the output power is controlled by a control signal input to the inverter circuit. When the control signal is direct current, the frequency of the output power is controlled by the level of the voltage of the control signal.

As a control signal, a pulse signal output from a microcomputer or the like is smoothed by a capacitor, converted into a DC voltage, and input to an inverter circuit (see, for example, Patent Document 1). That is, when the duty ratio of the pulse signal increases, the voltage of the control signal increases. Conversely, when the duty ratio decreases, the voltage of the control signal decreases.
JP 2005-198387 A (paragraph 0022)

  In the conventional inverter device, when the supply of power is stopped or during a power failure, the supply of drive power is stopped and the output of a pulse signal for generating a control signal is also stopped. However, even if the output of the pulse signal is stopped, the electric charge is stored in the smoothing capacitor, so that the voltage of the control signal does not decrease for a while. On the other hand, the voltage of the driving power supply decreases at a faster rate.

  A plurality of transistors are provided at the output stage of the inverter circuit. Since these transistors are provided for switching, they are set to operate in a saturation region. However, when the voltage of the driving power supply decreases, the operating state of the transistor changes from the saturation region to the active region, the electric resistance increases rapidly, and the amount of heat generated in the transistor increases. Therefore, there is a risk that these transistors will be destroyed by overheating.

  Then, this invention makes it a subject to provide the inverter apparatus which the transistor of an inverter circuit does not carry out an overheat destruction at the time of an operation stop or a power failure in view of said problem.

  In order to solve the above problems, an inverter device according to the present invention inputs a control signal obtained by smoothing a pulse signal output from a microcomputer with a capacitor to an inverter circuit, and outputs the inverter circuit according to the voltage of the control signal. In the inverter device that changes the voltage, the charge stored in the capacitor is discharged before the drive power supply voltage supplied to the inverter circuit drops below a predetermined voltage, and the input of the control signal to the inverter circuit is stopped. Discharging means is provided.

  When the voltage of the driving power supply falls below a predetermined voltage, there is a risk that the operating state of the transistor provided in the final stage of the inverter circuit will transition to the active state. Therefore, before that, by discharging the charge of the capacitor, the voltage of the control signal is made zero so that the inverter circuit does not operate.

  In addition to stopping the operation of the inverter device, there is a problem of overheating destruction of the transistor even at the time of unexpected power failure. Therefore, the AC commercial power source is used as a power source, and a voltage drop detecting means for detecting that the voltage of the AC commercial power source has decreased to a predetermined voltage is provided, and the capacitor is discharged when the voltage of the AC commercial power source decreases to the predetermined voltage. It was configured as follows.

  As is clear from the above description, the present invention discharges the capacitor that smooths the control signal before the voltage of the driving power supply supplied to the inverter circuit falls below a predetermined voltage, and the voltage of the control signal It is possible to stop the operation of the inverter circuit by setting the zero to zero and prevent the transistor of the inverter circuit from being overheated.

  Referring to FIG. 1, reference numeral 1 denotes an inverter device according to the present invention. An inverter IC 2 that is an inverter circuit is built in the inverter device 1. An induction motor 11 as a load is connected to the inverter IC2. Further, a DC 15V power source 21 is connected to the inverter IC2 as a driving power source. The DC power supplied from the 15V power source 21 is converted into AC power by the inverter IC2 and supplied to the induction motor 11. .

  The frequency of the AC power supplied to the induction motor 11 is configured to be controlled by the voltage level of the DC control signal generated by the control signal generator 3. The control signal generator 3 is provided with a phototransistor of the photocoupler PC1. A light emitting diode of the photocoupler PC1 is connected to the microcomputer 4 in a pair with the phototransistor.

  When the microcomputer 4 increases the rotation speed of the induction motor 11, that is, when the frequency of the AC power output from the inverter IC 2 to the induction motor 11 is increased, it is sent from the microcomputer 4 to the control signal generator 3 via the photocoupler 1. Increase the duty ratio of the pulse signal. Then, the pulse signal is smoothed by the capacitor 31 and input to the inverter IC.

  The microcomputer 4 is connected to other light emitting diodes of the photocoupler PC2. The phototransistor on the other side of the photocoupler PC2 stops the 15V power supply 21 when not in use in order to reduce standby power for energy saving. In the present invention, the phototransistor on the other side of the photocoupler PC2 is connected so as to drop the base of the transistor TR1 to the ground. Therefore, in a state where the inverter IC2 is operated, the microcomputer 4 always turns on the phototransistor of the photocoupler PC2 and keeps the transistor TR1 in the off state.

  The inverter device 1 uses a commercial 100V power source 6 as a power source. When the voltage of the 100V power source 6 is equal to or higher than a predetermined voltage, a pulse signal having the same frequency as the frequency of the 100V power source 6 is passed through the photocoupler PC3. Are input to the microcomputer 4. On the other hand, when the voltage of the 100V power supply 6 falls below a predetermined voltage due to a power failure or the like, the pulse signal is not input to the microcomputer 4, so that the microcomputer 4 can detect a voltage drop of the 100V power supply 6 due to a power failure or the like.

  With the above circuit configuration, for example, when stopping the operation of the inverter device 1, if a stop button (not shown) is operated, the microcomputer 4 detects that the stop operation has been performed, and stops the output of the pulse signal from the photocoupler 1. To do. As a result, charging of the capacitor 31 is stopped.

  In the present invention, the phototransistor of the photocoupler 2 is further turned off simultaneously. Then, the base potential of the transistor TR1 rises and the transistor TR1 is turned on. Therefore, the electric charge stored in the capacitor 31 is discharged from the resistor 5 through the transistor TR1. Due to this discharge, the voltage of the control signal input to the inverter IC2 instantaneously becomes zero, and the operation of the inverter IC2 can be stopped before the final stage transistor of the inverter IC2 transitions to the active region.

  In addition, when the microcomputer 4 detects the occurrence of a power failure even when the 100V power supply 6 has a power failure instead of the stop operation, the charge of the capacitor 31 is discharged and the operation of the inverter IC2 is immediately stopped as described above.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention.

The circuit diagram which shows the structure of one embodiment of this invention

Explanation of symbols

1 Inverter device 3 Control signal generator

Claims (2)

  A control signal obtained by smoothing the pulse signal output from the microcomputer with a capacitor is input to the inverter circuit, and in the inverter device that changes the output of the inverter circuit according to the voltage of the control signal, the drive supplied to the inverter circuit An inverter device comprising discharge means for discharging the electric charge stored in the capacitor before the power supply voltage for use drops below a predetermined voltage and stopping input of a control signal to the inverter circuit.   An AC commercial power source is used as a power source, and a voltage drop detecting means for detecting that the voltage of the AC commercial power source has dropped to a predetermined voltage is provided, and the capacitor is discharged when the voltage of the AC commercial power source drops to a predetermined voltage. The inverter device according to claim 1.

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