JPH02294295A - Motor driving device - Google Patents

Abstract

PURPOSE:To permit the protection of a voltage control type switching element even when the same element is short-circuited by a load by a method wherein a potential difference between both terminals of the voltage control type switching element is detected. CONSTITUTION:A drive circuit 12 puts the transistor Tr1 of a voltage control type switching element ON/OFF by an input signal -D1 while a potential difference detecting circuit 13 detects a voltage between the emitter and the collector of the transistor Tr1 of the same switching element. A drive voltage control circuit 14 reduces the drive voltage of the transistor Tr1 of the voltage control type switching element to a predetermined voltage when the detecting voltage Vi of the potential difference detecting circuit 13 has become higher than a predetermined level. When the operating time of a drive voltage limiting circuit 14 has become longer than a predetermined time, an alarm signal outputting circuit 15 outputs an alarm signal AL1. According to this method, the current of the voltage control type switching element Tr1 may be limited and the same switching element may be protected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field in Icheon] The present invention relates to a motor drive device, and more particularly to a motor drive device having a voltage-controlled switching element.

[Prior Art] Conventionally, as shown in FIG. 3, this type of motor drive device controls power by connecting a direct power source DC, a capacitor C, a coil L, and a direct current source DC in parallel. a plurality of pairs of voltage-controlled switching elements Trl to Tr4 for
A drive circuit 12 that turns on/off the flywheel diodes D1 to D4, the voltage-controlled switching elements Trl to Tr4, and the voltage-controlled switching element Tri''=
It consists of a current detection circuit 5 that detects the current flowing through the Tr 4, an instantaneous current over alarm signal output circuit 6 that generates an alarm ALM when the flowing current exceeds a predetermined value even if it is vague, and a reference power source 7. was.

[Problems to be Solved by the Invention] The above-described conventional motor drive device detects when an excessive current flows through the voltage-controlled switching elements Tri to Tr4, outputs an instantaneous current over alarm signal ALM, and operates manually. By turning off the signals D1 to D4, the voltage controlled switching elements Tri to Tr4 are protected. If you try to drive the motor M in a situation where A-B is short-circuited due to insulation deterioration of the motor M or incorrect connection between the motor drive device and the motor M, the voltage-controlled switching elements Trl to Tr4 will short-circuit the load. The currents of the voltage-controlled switching elements Tri to Tr4 are large currents that are limited only by line impedance. In this state, this conventional motor drive device turns off the voltage-controlled switching elements Tri to Tr4, so the voltage-controlled switching elements Trl to T
There is a drawback that a voltage higher than the breakdown voltage of the voltage-controlled switching elements Tri to Tr4 is applied to both ends of r4, which causes damage to the voltage-controlled switching elements Tri to Tr4.

An object of the present invention is to provide a motor drive device that protects a voltage-controlled switching element even when the voltage-controlled switching element is short-circuited to a load due to insulation deterioration or incorrect connection of the motor.

[Means for Solving the Problems] A motor drive device of the present invention includes a potential difference detection circuit that detects a potential difference between both ends of a voltage-controlled switching element, and when this potential difference becomes higher than a predetermined level, the voltage-controlled switching element is activated. a drive voltage limiting circuit that reduces the drive voltage of the drive voltage, and an alarm signal output circuit that detects the operating time of the drive voltage limiting circuit and outputs an alarm signal when the operating time becomes longer than a predetermined time. have.

[Function] Therefore, even if the voltage-controlled switching element is short-circuited to the load due to deterioration of the motor insulation or incorrect connection, the voltage-controlled switching element can be protected.

[Example] Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a motor drive device showing one embodiment of the present invention, and FIG. 2 is a detailed circuit diagram of the control circuit 1 shown in FIG.

The output of the DC power supply DC is smoothed by a capacitor C, and voltage-controlled switching elements Tri, Tr2, Tr3,
It is connected to a bridge circuit composed of Tr4. Voltage controlled switching elements Tri, Tr2, Tr3, Tr4
controls the output power of motor M. Diode Di
, D2, D3, and D4 are flywheel diodes for flowing reactive current due to the inductance of the motor M. The control circuit 1 is a drive circuit for turning on/off the voltage-controlled switching element Tri. Control circuit 2 for voltage-controlled switching elements Tr2, Tr3, and Tr4,
3.4 is the same as the control circuit 1.

Next, the control circuit 1 will be explained. The drive circuit 12 turns on/off the voltage-controlled switching element Tri based on the input signal D1. The potential difference detection circuit 13 detects the emitter-collector voltage of the voltage-controlled switching element Tri. When the detected voltage Vi of the potential difference detection circuit 13 becomes higher than a predetermined level, the tribe voltage limiting circuit 14 reduces the drive voltage of the voltage-controlled switching element Trl to a predetermined voltage. This makes it possible to limit the current of the voltage-controlled switching element Tri. The alarm signal output circuit 15 outputs an alarm signal ALI when the operating time of the drive voltage limiting circuit 14 becomes longer than a predetermined time.

Next, a detailed explanation will be given with reference to FIG.

First, the drive circuit 12 will be explained. The input signal D1 is insulated by a photocoupler +21 connected to resistors 120 and 122, and input to the base of a transistor 124.

The collector of transistor 124 is connected to the bases of resistor 123, transistor 125, and transistor +26. Emitter of transistor 125 and transistor 1
The emitter of 2B is connected via a resistor 129 to the base of a voltage-controlled switching element Trl. A power supply 127 is connected between the collector of transistor +25 and the emitter of voltage-controlled switching element Trl.
A power supply 128 is connected between the collector of 26 and the emitter of the voltage-controlled switching element Tri. Now, when the photocoupler 12+ is turned on by the input signal D1, the transistor 124 is turned off, the transistor 125 is turned on, and the transistor 126 is turned off.

As a result, the positive voltage of the power supply 127 is applied between the emitter and base of the voltage-controlled switching element Tri.
The voltage controlled switching element Trl is turned on. next,
When the human power signal D1 changes and the photocoupler 121 turns off, the transistor 124 turns on and the transistor 1
25 is turned off, and transistor 126 is turned on. As a result, the negative voltage of the power supply 128 is applied between the emitter and base of the voltage-controlled switching element Tri, and the voltage-controlled switching element Tri is turned off. in this way,
From the input signal Kt, the voltage controlled switching element Tri
can be turned on/off.

Next, the potential difference detection circuit 13 will be explained.

The collector of the voltage-controlled switching element Trl is connected to the resistor 132, and the collector of the voltage-controlled switching element Tr+
The emitter of is connected to a resistor 133 through a power supply 128. Since the resistor +32 and the resistor 133 are connected in series, a voltage proportional to the emitter-collector voltage of the voltage-controlled switching element Tri is applied to the resistor 13.
3 is obtained as a detection voltage Vi. Dai Saiichi Do 1
31 is when the voltage controlled switching element Trl is off;
This is to make the detection voltage Vi almost zero. The capacitor 134 is provided to prevent the detection voltage from being erroneously output during the period from when the ON signal is input to the voltage-controlled switching element Trl until the pressure-controlled switching element Tr+ is actually turned on. be. The comparator 142 compares the detection voltage Vi with the reference voltage +41, and when the former is larger than the latter, the voltage is applied to the transistor 144 via the resistor 143.
Turn on. The collector of the transistor 144 is the resistor 14
5 to the base of the voltage-controlled switching element Trl.

Next, the drive voltage limiting circuit 14 will be explained.

Now, if the voltage-controlled switching element Tri is short-circuited to the load, both ends of the voltage-controlled switching element Trl will be
The voltage of the DC power supply DC is applied, the detection voltage Vi becomes larger than the reference voltage 141, the output of the comparator 142 becomes high level, and the transistor 144 is turned on. Since the collector of the transistor 144 is connected to the base of the voltage-controlled switching element Tri through the resistor 145, when the transistor 144 is turned on, the base voltage V of the voltage-controlled switching element Tri is increased. resistor 1
The voltage can be reduced to the voltage divided by 29 and resistor +45, and the current flowing through the voltage-controlled switching element Tri can be limited.

Next, the alarm signal output circuit 15 will be explained.

The comparator 151 compares the reference voltage 154 and the voltage of the capacitor 155, and the voltage of the capacitor 155 is the reference voltage +5.
When it becomes larger than 4, the output of comparator +51 becomes low level, and the circuit outputs an alarm signal ALI. The capacitor 155 is a circuit that is charged through the resistor 152 with the output voltage of the comparator 142 in the drive voltage limiting circuit 14, and the resistor 152 and the capacitor 1
By setting the time constant determined by 55 and the reference voltage 154, it is possible to detect a load short-circuit state of the voltage-controlled switching element Tri, and to protect the voltage-controlled switching element Trl. The diode 153 is connected to the comparator 14
When the output of 2 becomes low level, the capacitor 155
This is to clear the voltage.

[Effects of the Invention] As explained above, the present invention detects the potential difference across a voltage-controlled switching element, and when this potential difference becomes higher than a predetermined level, the drive voltage of the voltage-controlled switching element is reduced. The motor is isolated by having a circuit that limits the current flowing through the voltage-controlled switching element and outputs an alarm signal when the drive limit circuit operates for longer than a predetermined time. This has the effect of protecting the voltage-controlled switching element even if the voltage-controlled switching element short-circuits the load due to deterioration or incorrect connection.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a motor drive device according to an actual example of the present invention, FIG. 2 is a detailed circuit diagram of the control circuit 1 in FIG. 1, and FIG.
The figure is a block diagram of a conventional example of a motor drive device.

Claims (1)

[Claims] 1. A motor drive device including a DC power source, a plurality of pairs of voltage-controlled switching elements connected in parallel to the DC power source for controlling power, and a drive circuit that turns on/off the voltage-controlled switching elements, a potential difference detection circuit that detects a potential difference across the voltage-controlled switching element; a drive voltage limiting circuit that reduces the drive voltage of the voltage-controlled switching element when the potential difference becomes higher than a predetermined level; 1. A motor drive device comprising: an alarm signal output circuit that detects the time during which the limiting circuit is operating and outputs an alarm signal when the operating time becomes longer than a predetermined time.