JPH0337393B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a drive stop circuit that drives and stops a DC motor.

[Prior Art] When it is necessary to quickly stop a motor at a predetermined stop position, such as with a DC motor used in an actuator that operates a mechanical operation part in response to an electrical signal, a A braking circuit is provided to brake the motor by cutting off the current supply to the motor and short-circuiting the voltage induced in the armature at the same time.

Figure 1 shows a drive stop circuit for a conventional DC motor. In the figure, 1 is a battery, 2 is an armature of the DC motor whose one end is connected to the positive terminal of the battery, and 3 is an armature. A motor driving transistor switch is connected in series with 2 to turn on and off the current to the armature, and 4 is a resistor constituting a braking circuit. transistor switch 3
is composed of an NPN transistor T1, and the collector of the transistor T1 is connected to the other end of the armature 2. The emitter of the transistor T1 is connected to the negative terminal of the battery via a diode 5, and a resistor 4 is connected in parallel to both ends of the armature 2. 6
A drive circuit supplies a control signal for controlling the on/off of the transistor switch 3, and the voltage of the battery 1 is applied to this drive circuit via the switch 7.

In the above example, the drive circuit 6 is, for example, as shown in FIG.
As shown in FIG. 2, when the switch 7 is closed at time t1, a voltage Vbe is applied between the base and emitter of the transistor T1 to make the transistor T1 conductive, thereby causing a current Ia to flow through the armature 2 and rotating the motor. When the rotation angle of the motor reaches a predetermined value at time t2, the voltage Vbe is made zero to cut off the transistor T1 and stop the motor.
When the switch 7 is opened at time t3, the voltage Vbe is again applied between the base and emitter of the transistor T1 to rotate the motor, and when the rotation angle of the motor reaches a predetermined value at time t4, the voltage Vbe
to zero and stop the motor.

In this case, changes in the voltage V1 between the collector and emitter of the transistor T1, the current Ib flowing through the resistor 4, and the armature current Ia are as shown in FIG. 2 B, C, and D, respectively. A current that is the sum of the armature current Ia and the current Ib flowing through the resistor 4 flows. When the transistor switch 3 is cut off, a current Ib flows through the resistor 4 due to the voltage induced in the armature 2, and the rotation of the motor is braked.

[Problem to be solved by the invention] In the above conventional circuit, the transistor switch 3
Current Ib flowing through armature current Ia and resistor 4
Since the sum of current flows, the current burden on the transistor 3 increases, resulting in a disadvantage that a large capacity transistor is required. Furthermore, since the armature is short-circuited through a resistor, a large braking current cannot be passed, and a large braking effect cannot be obtained.

Also, as shown in Utility Model Application No. 52-26912,
A circuit in which a braking transistor switch is connected in parallel to the armature of a DC motor, and when the motor is stopped, the braking transistor switch is made conductive to short-circuit the armature and apply braking to the motor. is proposed.

In this proposed circuit, when the switch connected in series with the armature is opened to stop the motor, the base current is applied to the braking transistor switch via the capacitor by the power supply voltage and the induced voltage of the armature. The braking transistor switch is made conductive until the charging of the capacitor is completed.

According to this proposed circuit, since the braking transistor switch is cut off when the motor is being driven, the current load on the switch connected in series with the armature can be reduced. Further, when the motor is stopped, the armature is short-circuited by a braking transistor switch, so a great braking effect can be obtained.

However, in this previously proposed circuit, the time during which the braking transistor switch is turned on varies depending on variations in the power supply voltage, so there was a problem in that the braking effect varied due to variations in the power supply voltage.

In addition, in this proposed circuit, if the switch connected in series with the armature is closed while the braking transistor switch is in the on state, the power supply is short-circuited through the braking transistor switch. There was a problem in that the braking transistor switch was destroyed due to current flow.

An object of the present invention is to eliminate the risk of overcurrent flowing from the power source through the braking transistor switch when the motor drive switch connected in series with the armature is closed, and to keep the braking transistor switch conductive for a long period of time. It is an object of the present invention to provide a DC motor drive stop circuit that keeps the braking effect constant and prevents variations in braking effect due to variations in power supply voltage.

[Means for Solving the Problems] The present invention provides a motor drive transistor switch connected in series to the armature of a DC motor, a drive circuit that supplies the transistor switch with a control signal for turning on and off the transistor switch, The invention relates to a DC motor drive stop circuit that includes a braking circuit that substantially shorts the armature and brakes the DC motor when a transistor switch is cut off.

In the present invention, the braking circuit includes a braking transistor switch connected in parallel to the armature, a Zener diode connected in parallel through a resistor across both ends of the motor driving transistor switch, and a motor driving transistor switch. When the motor drive transistor switch is cut off, the capacitor is charged to the Zener voltage of the Zener diode through the resistor by the voltage across the motor drive transistor switch, and the base current flows to the braking transistor switch by conducting the capacitor's charging current as a base current. a transistor switch for conduction control provided to allow the braking transistor switch to conduct, and a transistor switch for cutoff control provided to maintain the braking transistor switch in a cutoff state when the base current is applied and the transistor switch becomes conductive. ing. A control signal for turning on the motor drive transistor switch is inputted to the base current input terminal of the cutoff control transistor switch through a differentiating circuit.

[Function] With the above configuration, only the armature current flows through the motor drive transistor switch while the motor is rotating, and no braking circuit current flows, so the current burden on the motor drive transistor switch can be reduced. can. Further, when the motor is stopped, the braking transistor switch is turned on and a large braking current flows, so that a large braking effect can be obtained.

Furthermore, as mentioned above, a capacitor is provided which is charged to the Zener voltage of the Zener diode by the voltage across the motor drive transistor switch through the resistor, and the capacitor is charged to a fixed voltage (Zener voltage) with a fixed time constant. By making the braking transistor switch conductive for a certain period, the time during which the braking transistor switch is conductive can be kept constant, and it is possible to prevent variations in the braking effect due to fluctuations in the power supply voltage.

Furthermore, as mentioned above, a control signal for turning on the motor drive transistor switch is inputted through a differential circuit to the base current input terminal of the cutoff control transistor switch, and the braking control signal is turned on by the cutoff control transistor switch. By placing the transistor switch in the cut-off state, the cut-off control transistor switch can be made conductive faster than the motor drive transistor switch. Therefore, when the drive circuit outputs a control signal that turns on the motor drive transistor switch while the braking transistor switch is conductive, the braking transistor switch is turned on before the motor drive transistor switch turns on. This can prevent the motor driving transistor switch and the braking transistor switch from being electrically connected at the same time, thereby preventing the power supply from being short-circuited through both transistor switches.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

FIG. 3 shows an embodiment of the present invention, in which 1 is a battery, 2 is an armature of a DC motor whose one end is connected to the positive terminal of the battery, and 3 is a collector whose other end is the armature 2. 5 is a diode connected between the emitter of transistor T1 and the load terminal of battery 1; 6 is a drive circuit that provides a control signal to transistor T1; 7 is a motor drive transistor switch consisting of an NPN transistor T1 connected to This is a switch that applies battery voltage to the drive circuit 6, and these are the same as the conventional example shown in FIG.

This embodiment differs from the circuit shown in FIG. 1 in the configuration of the braking circuit 10. The braking circuit 10 of this embodiment includes a braking transistor switch 11 consisting of a PNP transistor T2, and the transistor T2 is connected in parallel to both ends of the armature 2 with its emitter-collector circuit facing the positive electrode side of the battery. There is. One end of a resistor 12 is connected to the collector of the transistor T2, and one end of a capacitor 13 is connected to the other end of the resistor 12. The other end of the capacitor 13 is connected to the base of the transistor T3, and the emitter of the transistor T3 is connected to the emitter of the transistor T1.
A resistor 1 is connected between the base and emitter of the transistor T3.
A diode 15 whose anode is directed toward the emitter of the transistor T3 is connected in parallel to both ends of the resistor 14. The cathode of a Zener diode 16 is connected to one end of the capacitor 13, and the anode of the Zener diode is connected to the emitter of the transistor T3. The collector of the transistor T3 is connected to the base of the transistor T2 via a resistor 17,
When the transistor T2 becomes conductive, a base current flows through the transistor T2 so that the transistor T2 becomes conductive. In this embodiment, the transistor T3
and a conduction control transistor switch 18 that conducts the charging current of the capacitor 13 as a base current through the resistors 14 and 17 and allows the base current to flow to the braking transistor switch 11.
is configured.

Further, the collector of a transistor T4 whose emitter is connected to the positive terminal of the battery is connected to the base of the PNP transistor T2.
A resistor 20 is connected between the base and emitter of 4. The base of the transistor T4 is connected to the collector of the transistor T5 via a resistor 21.
The emitter of the transistor T5 is the transistor T5.
Commonly connected to 3 emitters. A resistor 22 is connected between the base and emitter of the transistor T5, and a resistor 23 and a capacitor 24 are connected between the base of the transistor T5 and the base of the transistor T1.
A differential circuit consisting of a parallel circuit with is connected. When a voltage Vbe (a control signal for turning on the transistor T1) is applied from the drive circuit between the base and emitter of the transistor T1, a base current is applied to the transistor T5 through a differentiating circuit consisting of a resistor 23 and a capacitor 24, and the transistor T5 becomes conductive. do. Transistors T1 and T5 are made conductive by being given a base current by the same control signal given from the drive circuit, but since the base current is given to transistor T5 via a differentiating circuit, the transistor T5 becomes conductive quickly. In this case, transistor T5 becomes conductive before transistor T1.

When transistor T5 becomes conductive, transistor T
Since the base current flows through the transistor T4
becomes conductive, and the transistor T4 becomes conductive.
The base and emitter of the transistor T2 is short-circuited to maintain the transistor T2 in a cut-off state.

In this embodiment, transistors T4 and T5, and resistor 2
0 to 23 and the capacitor 24 constitute a cut-off control transistor switch 25 that is conductive when the motor drive transistor switch 3 is conductive to maintain the control transistor switch 11 in a cut-off state.

As described above, in this embodiment, when the drive circuit 6 generates a control signal to turn on the motor drive transistor switch 3, the cutoff control transistor switch 25 is turned on before the motor drive transistor switch becomes conductive. In order to turn on the braking transistor switch 11 and cut it off, when the drive circuit 6 generates a control signal that turns on the motor drive transistor switch while the braking transistor switch is conducting, the braking transistor switch 11 is turned on. It is possible to prevent a period in which the transistor switch and the motor drive transistor switch are conductive at the same time from occurring. Therefore, it is possible to prevent the power supply from being short-circuited through the braking transistor switch 11 and the motor drive transistor switch 3 and causing an excessive current to flow through the transistors constituting both transistor switches, thereby preventing the transistors from being destroyed. Can be done.

The above-mentioned braking transistor switch 11, capacitor 13, conduction control transistor switch 1
8 and the cutoff control transistor switch 25 constitute a braking circuit 10.

Next, the operation of the above embodiment will be explained with reference to FIGS. 4A to 4J. Figures 4A to 4J show voltage or current waveforms at various parts of the circuit in Figure 3, and Figure A shows the voltage between the base and emitter of transistor T1.
Vbe, and B, E, F, G, and H represent collector-emitter voltages V1, V3, V5, V4, and V2 of transistors T1, T3, T5, T4, and T2, respectively.

In addition, Fig. 4C shows the terminal voltage Vc of the capacitor 13.
, and D indicates the current Ic flowing into the base of the transistor T3 through the capacitor 13.
Furthermore, FIGS. 4I and 4J show the braking current Ib and the armature current Ia, respectively.

In the above embodiment, the switch 7 is closed at time t1 as shown in FIG.
When Vbe is applied, first transistors T5 and T4 conduct, preventing transistor T2 from conducting. When the transistor T4 is conductive, the transistor T4 is turned off.

After the conduction of the transistor T2 is blocked by the conduction of the transistors T4 and T5, the transistor T1 becomes conductive, and the voltage Vc between the collector and emitter of the transistor becomes approximately zero as shown in FIG. 4B.
At this time, a current Ia flows through the armature 2, causing the motor to rotate.

During rotation of the motor, the cut-off control transistor switch 25 conducts and prevents the braking transistor switch 11 from conducting, so no current flows through the braking transistor switch 11.
Only the armature current Ia flows through the motor drive transistor switch 3. Therefore, as the transistors constituting the transistor switch 3, transistors having a smaller current capacity than conventional ones can be used.

Next, at time t2, when the rotation angle of the motor reaches a predetermined value and the drive circuit 6 makes the voltage Vbe between the base and emitter of the transistor T1 zero, the transistor T1 is cut off and the armature current Ia is cut off. At this time, a current flows through the resistor 12, the capacitor 13, and the base-emitter of the transistor T3 due to the collector-emitter voltage V1 of the transistor T1, and the capacitor 13 is charged to the polarity shown. While the charging current is flowing through the capacitor 13, the transistor T3 is conductive. Therefore, when a voltage is induced in the armature 2 after the transistor T1 is cut off, a base current flows through the transistor T2, making the transistor T2 conductive, and the transistor T2 short-circuits the armature 2, causing a large braking current Ib to flow. When the charging voltage of the capacitor 13 reaches the Zener voltage Vz of the Zener diode 16, charging of the capacitor 13 is stopped, the transistor T3 is cut off, and the transistor T2 is cut off.

In this way, in the present invention, the capacitor 13
The braking transistor is conductive only during the period when the voltage is charged to a certain voltage with a certain time constant, so even if the power supply voltage fluctuates, the braking transistor switch can always be made conductive for a certain period of time.
A constant braking effect can always be obtained.

In addition, in the present invention, the braking transistor switch 11 directly shorts the armature 2 to flow a large braking current, so a larger braking force can be obtained compared to the conventional circuit shown in FIG. 1, and the motor can be operated for a short time. It can be stopped with . Therefore, the variation range of the stop position of the motor when a stop command is given to the motor can be reduced, and when a specific operating mechanism is operated by the motor, the operation can be performed accurately.

The charge on capacitor 13 is then transferred to transistor T1
When it becomes conductive, it discharges through the resistor 12, transistor T1 and diode 15.

In order to show an example of the drive circuit 6, FIG. 5 shows an embodiment in which the present invention is applied to an actuator that drives an operating arm using a DC motor.
In this figure, the braking circuit 10 is similar to the embodiment shown in FIG. 3 except that a protective varistor 26 is connected in parallel between the emitter and collector of the transistor T2.

The drive circuit 6 includes transistors T6 and T7 whose emitters are commonly connected to the emitter of the transistor T1, and the collector of the transistor T6 is connected via a resistor 30 to the base of the transistor T7. The base of transistor T6 is resistor 31
A resistor 32 is connected in parallel between the base and emitter of the transistor T6. transistor T6
The collector of is connected to the cathode of a diode 34 via a resistor 33, and the anode of the diode 34 is connected to the positive electrode of the battery via a switch 7. A capacitor 35 is connected between the cathode of the diode 34 and the emitter of the transistor T6, so that when the switch 7 is closed, the capacitor 35 is charged to the polarity shown. The collector of the transistor T6 is connected to one end of a resistor 36 via a position detection switch LB such as a limit switch, and the other end of the resistor 36 is connected to the cathode of a diode 34. The collector of transistor T7 is the position detection switch LA.
and a parallel circuit of resistor 23 and capacitor 24 to the base of transistor T5 of the damping circuit.

In the above embodiment, the position detection switch LA and
The LBs are adapted to close when the operating arms, each driven by a motor, are in a first position and a second position. In the initial state when switch 7 is open, the operating arm is in the first position, position detection switch LA is closed, and position detection switch LB is closed.
is open. When the switch 7 is closed in this state, the base current flows to the transistor T6 through the resistor 31, so the transistor T6 becomes conductive.
Transistor T7 is held in the cut-off state. At this time, a base current flows from the battery 1 to the transistor T1 through the diode 34 and the resistor 36, and the transistor T1 becomes conductive. Therefore the armature current
Ia flows, the motor rotates, and the position detection switch
LA opens. At this time, the capacitor 35 is charged from the battery 1 via the diode 34 to the polarity shown. When the motor rotates a certain angle and the operating arm (not shown) reaches the second position, the position detection switch LB closes, and the base current of the transistor T1 is bypassed through the position detection switch LB and the transistor T6 (between the base and emitter of the transistor T1). The voltage Vbe becomes zero), and the transistor T1 becomes cut off. Therefore, the armature current Ia
is cut off and the motor stops. At this time, the motor is braked by the above-described operation. Next, when the switch 7 is opened in this state, the base current of the transistor T6 is cut off, so that the transistor T6 becomes cut off. At this time, from capacitor 35 to resistor 3
Since the base current is supplied to the transistor T1 through 6, the transistor T1 becomes conductive, and the armature current Ia flows and the motor rotates. Position detection switch LB opens at the same time as the motor rotates. When the operating arm (not shown) returns to the first position due to rotation of the motor, the position detection switch LA closes and the transistor T7 becomes conductive. Therefore transistor T1
The base-emitter voltage Vbe of becomes zero, transistor T1 is cut off, and the motor stops.

The configuration of the drive circuit 6 is not limited to the above-mentioned example, but may be one in which the transistor T1 is turned on and off according to the on/off of the switch 7 at the end, for example.

[Effects of the Invention] As described above, according to the present invention, only the armature current flows through the motor drive transistor switch while the motor is rotating, and the braking circuit current does not flow. The load can be reduced, and inexpensive transistors with smaller current capacity than conventional transistors can be used as the transistors constituting the transistor switch.
Furthermore, when the motor is stopped, the braking transistor switch is turned on to directly short-circuit the armature, allowing a large braking current to flow, thereby providing a great braking effect.

Particularly, according to the present invention, a capacitor is provided which is charged to the Zener voltage of the Zener diode through a resistor by the voltage across the motor drive transistor switch, and the braking is performed during a period during which the capacitor is charged to a fixed voltage with a fixed time constant. Since the braking transistor switch is made conductive, the time during which the braking transistor switch is conductive can be kept constant, and it is possible to prevent variations in the braking effect due to fluctuations in the power supply voltage.

Further, according to the present invention, a control signal for turning on a motor drive transistor switch is inputted through a differential circuit to the base current input terminal of a cutoff control transistor switch, and braking is performed by conduction of the cutoff control transistor switch. Since the brake transistor switch is turned off, the conduction of the cutoff control transistor switch can be made faster than the conduction of the motor drive transistor switch, and the drive circuit can be turned on while the braking transistor switch is conductive. When a control signal for turning on the motor driving transistor switch is output, the braking transistor switch can be turned off before the motor driving transistor switch is turned on. Therefore, it is possible to prevent the power supply from being short-circuited through both transistor switches due to a period in which the motor driving transistor switch and the braking transistor switch are conductive at the same time, and the transistors constituting both transistor switches being destroyed due to overcurrent. can be prevented and reliability can be improved.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional circuit, Figure 2 is a voltage or current waveform diagram of each part of Figure 1, Figure 3 is a circuit diagram showing an embodiment of the present invention, and Figure 4 is Figure 3. FIG. 5 is a circuit diagram showing another embodiment of the present invention. 1... Battery, 2... Armature, 3... Motor drive transistor switch, 6... Drive circuit,
7... Switch, 10... Braking circuit, 11... Braking transistor switch, 13... Capacitor, 18... Continuity control transistor switch,
25...transistor switch for cutoff control.

Claims (1)

[Scope of Claims] 1. A motor drive transistor switch connected in series to an armature of a DC motor, a drive circuit that supplies the transistor switch with a control signal for turning on and off the transistor switch, and the transistor switch and a braking circuit that brakes the DC motor by substantially shorting the armature when cut off, the braking circuit being connected in parallel to the armature. a braking transistor switch and a Zener diode connected in parallel through a resistor to both ends of the motor driving transistor switch;
When the motor drive transistor switch is cut off, the capacitor is charged by the voltage across the motor drive transistor switch to the Zener voltage of the Zener diode through the resistor, and the charging current of the capacitor is conducted as a base current. A conduction control transistor switch is provided to allow a base current to flow through the braking transistor switch, and a conduction control transistor switch is provided to maintain the braking transistor switch in a cut-off state when the base current is applied and the transistor switch becomes conductive. A control signal for turning on the motor drive transistor switch is inputted to a base current input terminal of the cutoff control transistor switch through a differentiating circuit. Features a DC motor drive stop circuit.