JPH06178567A - Motor driving circuit with dynamic brake circuit - Google Patents

Abstract

PURPOSE:To facilitate the downsizing and to brake a motor even at power off. CONSTITUTION:This is a motor driving circuit which drives a motor through drive lines DL1 and DL2 from a DC power source by the inverter circuit consisting of a plurality of transistors Tr11, Tr12, Tr21, and Tr22 and diodes D11, D12, D21, and D22 connected to respective transistors Tr11, Tr12, Tr21, and Tr22 and applies the brake to the motor M by a dynamic brake circuit during power-off. The dynamic brake circuit has a thyristor, where an anode is connected to the line on the positive side of a DC power source and a cathode to the drive lines DL1 and DL2, a resistor which connects the anode of the thyristor with a gate, and an optical MOSFET being the switching element, which is connected between the cathode of the thyristor and the gate and breaks the electric contact between the cathode and the gate connected when the DC power is off and turns on the thyristor with the voltage induced by the rotation of the motor M so as to apply the brake to the motor.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a synchronous motor and a D
The present invention relates to a motor drive circuit including a dynamic brake circuit that drives a C servomotor by a servo drive circuit and connects the generated output of the driven motor to a heavy load to perform dynamic braking.

[0002]

2. Description of the Related Art Conventionally, some dynamic brake circuits of this type use a relay or use a photocoupler and a transistor to connect a power generation output of a motor to a heavy load. FIG. 4 is a circuit diagram showing a conventional example of a dynamic brake circuit using a relay. In this conventional example, power is supplied to the inverter circuit +
The power supply line is connected to one end of the contact B of the relay RY, the other end of the relay RY is connected to the anodes of the two diodes BD1 and BD2 in common, and the two diodes BD1 and BD are connected.
The two cathodes are connected to the motor drive lines DL1 and D, respectively.
It is connected to L2. Therefore, when the power is turned off and the relay RY is turned on, the diode D1 of the inverter circuit, which is a full bridge circuit with the two diodes, is turned on.
With the combination of 1, D12, D21 and D22, the two drive lines DL1 and DL2 of the motor are in the same state as if they were short-circuited. As a result, the four transistors Tr1
The motor M is dynamically braked in a state where all of 1, Tr12, Tr21, Tr22 are off. However, the relay used in this case has to pass a large current and requires a power relay having a large shape. In order to solve this, as shown in FIG. 5, a thyristor and a pulse transformer for driving the thyristor have been proposed instead of the relay RY. Further, a method has been proposed in which drive lines, that is, motor terminals are connected to each other via a photocoupler in order to brake the motor (Japanese Patent Laid-Open No. 61-251493). In the case of this proposal, the drive power supply for the inverter circuit must drive the photocoupler.

[0003]

In the conventional dynamic brake circuit described above, in the case of using a relay, a power relay must be used, and there is a problem that the size cannot be reduced. In the case of using a coupler, there is no driving power supply when the power is off, so there is a problem that the brake is not applied. In view of the above problems, it is an object of the present invention to provide a motor drive circuit including a dynamic brake circuit that can be easily downsized without using a relay and can apply a brake even when the power is off.

[0004]

A motor drive circuit according to the present invention comprises an inverter circuit including a plurality of transistors connected between DC power supply lines and a diode connected to each transistor, and a DC power supply via a drive line. To supply current to drive the motor, and when the power is off, the motor drive circuit applies a brake to the motor by a dynamic brake circuit connected between the positive side line of the DC power supply line and the drive line. The circuit is connected between the thyristor whose anode is connected to the positive side line of the DC power supply line and whose cathode is connected to the drive line, a bias resistor which connects the anode and gate of the thyristor, and the cathode and gate of the thyristor. And the connected cathode and gate when the DC power supply is on. However, when the DC power supply is off, the connected cathode and gate are made non-conductive, and the voltage generated by the rotation of the motor and rectified by the diode and supplied to the thyristor is biased. And a switching element for supplying a voltage to the gate of the thyristor via the switch to turn on the thyristor and brake the motor.

The switching element is an optical MOSF.
ET is preferable, and when the motor is a DC servomotor driven via two drive lines, the dynamic brake circuit is provided between the positive side line and each drive line. Even when the motors are AC servo motors that are connected to each other and are driven via three drive lines, the dynamic brake circuit is connected between the positive electrode side line and each drive line. Is preferred.

[0006]

When the DC power is normally supplied, the switching element is on, so the thyristor is off, and the dynamic brake circuit has no effect. When the supply of DC power is stopped, the switching element is turned off, and the cathode and gate of the thyristor are opened. In this case, an optical MOSFET is preferable as the switching element in terms of withstand voltage. On the other hand, the voltage generated by the rotation of the motor and rectified by the diode of the inverter circuit is supplied to the thyristor. Since this voltage is also applied to the gate of the thyristor via the resistor, the thyristor turns on, short-circuits the drive lines together with the diode, loads the motor, and brakes the motor.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of a motor drive circuit of the present invention. 2 is a circuit diagram showing the dynamic brake circuit of FIG. 1 in detail, and FIG. 3 is the optical MOS of FIG.
It is a circuit diagram which shows FET in detail. The inverter circuit is
The transistors Tr11, 12 and the transistors Tr21, 22 connected in series are configured to be connected in parallel between the + power supply line and the − power supply line. The connection point between the transistors Tr11 and 12 and the transistors Tr21 and Tr21
The connection points of 2 are respectively the drive lines DL of the motor M.
1 and DL2. Also, the transistor Tr
Diodes D11, D12, D21 and D22 are respectively provided between the emitters and collectors of 11, 12, 21, and 22.
Are connected.

The dynamic brake circuit is composed of brake circuits BS1 and BS2 connected between the + power supply line and the drive drive lines DL1 and DL2, respectively. In each of the brake circuits BS1 and BS2, the anode A is connected to the + power supply line and the cathode K is connected to the drive line, a resistor RR connecting the gate G of the thyristor SS and the anode A, the gate G and the cathode. The light source M, which is a switching element that short-circuits the gate G and the cathode K of the thyristor SS when power is supplied to the capacitor CC that connects the capacitor K and the power line.
It is composed of an OSFET. The optical MOSFET is
It is composed of switching transistors Tr01 and Tr02 connected in series between the gate G and the cathode K, and light emitting elements EL01 and EL02 for driving the switching transistors Tr01 and Tr02, and has a + power supply terminal PT and a −power supply terminal. While the + and-power supplies are applied to NT and the switching power supply, respectively, the switching transistor T
r01 and Tr02 short-circuit the gate G and the cathode K. + Power supply terminal PT and-power supply terminal NT
The power applied to and is supplied when the inverter circuit is supplied with power, and is not supplied when the inverter circuit is not supplied with power. However, the + power supply terminal PT and the −power supply terminal NT are separate circuits separated from the power supply line of the inverter circuit, and are not affected by the induced voltage of the motor M.

Next, the operation of the embodiment shown in FIGS. 1 to 3 will be described. When the power is supplied to the power line of the inverter circuit and the motor M is driven, the light M
Power is also supplied to the terminals PT and NT of the OSFET, and the light M
Since the OSFET is turned on and the gate and cathode of the thyristor SS are short-circuited, the thyristor SS is turned off. Therefore, the dynamic brake circuit does not work,
The motor M continues to be driven normally. At that time, it is assumed that the power supply is stopped for some reason. Since the motor M tries to rotate by inertia, the diodes D11 and D1
2, D21 and D22 generate a regenerative voltage between the + power supply line and the drive line. On the other hand, the optical MOSFET is turned off and the gate G of the thyristor SS and the cathode K are turned off. At this time, since the voltage is supplied between the anode A and the cathode K of the thyristor SS, the gate G of the thyristor SS is also biased via the resistor RR, the thyristor SS is turned on, and as long as an induced voltage exists, That is, the motor M is loaded as long as the motor M rotates. When the motor M stops, the induced voltage also disappears, so that the thyristor SS also turns off and returns to the initial state.

That is, in this embodiment, the power source for turning on the thyristor SS when the power source is off is the thyristor S.
The induced voltage itself applied to S is used. For this reason, a high voltage is applied between the + power supply line and the drive line, but there is no problem because some optical MOSFETs have high withstand voltage characteristics (for example, 600V), unlike photocouplers. Although an optical MOSFET is used as a switching element in this embodiment, it is obvious that an element other than the optical MOSFET can be used as a switching element as long as it has a high breakdown voltage.

[0011]

As described above, according to the present invention, since the dynamic brake circuit is composed of the combination of the thyristor and the optical MOSFET, the size can be easily reduced, and the dynamic brake circuit can be used as a motor when the power is off. By short-circuiting the drive line of the motor by using the induced voltage, there is an effect that the motor can be braked even when the power is off.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a motor drive circuit of the present invention.

FIG. 2 is a circuit diagram showing the dynamic brake circuit of FIG. 1 in detail.

FIG. 3 is a circuit diagram showing the optical MOSFET of FIG. 2 in detail.

FIG. 4 is a circuit diagram showing a conventional example using a relay.

FIG. 5 is a circuit diagram showing a conventional example using a thyristor.

[Explanation of symbols]

Tr11, Tr12, Tr21, Tr22 Transistor D11, D12, D21, D22 Diode BS1, BS2 Brake circuit DL1, DL2 Drive line SS Thyristor RR Resistor CC Capacitor PT + Power supply terminal NT-Power supply terminal EL01, EL02 Light emitting element Tr01, Tr02 Switching transistor

Claims (4)

[Claims] 1. An inverter circuit composed of a plurality of transistors connected between DC power supply lines and a diode connected to each transistor, supplies a current from a DC power supply through a drive line to drive a motor, and a power supply. In a motor drive circuit that applies a brake to a motor by a dynamic brake circuit connected between a positive side line of a DC power supply line and a drive line when off, the dynamic brake circuit has an anode connected to a positive side line of the DC power supply line. , A cathode whose cathode is connected to the drive line, a bias resistor which connects the anode and gate of the thyristor, and a cathode which is connected between the cathode and gate of the thyristor and is connected when the DC power supply is on. Conducts electrical connection with the gate, but turns off the DC power supply. When it is off, the connected cathode and gate are made non-conducting, and the voltage generated by the rotation of the motor and rectified by the diode and supplied to the thyristor is also supplied to the thyristor gate via the bias resistor. A motor drive circuit comprising: a switching element that is turned on to brake the motor. 2. The switching element is an optical MOSFE
The motor drive circuit according to claim 1, wherein T is T. 3. The motor is a DC servomotor driven via two drive lines, and the dynamic brake circuit is connected between the positive electrode side line and each drive line, respectively. The motor drive circuit according to item 1 or 2. 4. The motor is an AC servomotor driven via three drive lines, and the dynamic brake circuit is connected between the positive side line and each drive line. The motor drive circuit according to item 1 or 2.