JPH0349585A - Drive circuit for dc motor - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost of a circuit by controlling so as to switch a relay off based on the time intervals of motor pulses generated with the rotation of a DC motor as well as switch the relay on based on the magnitude of an induced electromotive force of the motor. CONSTITUTION:A constrained stopping of a DC motor M is detected based on the magnitude of its induced electromotive force EM as well as its rotation speed is detected based on the generation time intervals of motor pulses P. A relay 4 is ON-OFF controlled by use of there detected outputs. Therefore, the control in which a drive circuit 12 is switched off to the magnitude of the induced electromotive force when the rotation speed of the DC motor M is lowered and based on the detected result the drive circuit 12 is switched off or switched on again, becomes possible using the relay 4 whose response speed is low in comparison with semiconductor elements.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a DC moke drive circuit, and is particularly suitable for use in a drive circuit that detects and drives the rotation of a DC motor.

(Existing Requirements of the Invention) By controlling the relay to turn on based on the magnitude of the induced electromotive force and turn off the relay based on the interval of motor pulses generated as the DC motor rotates. , a relay is used instead of a large-capacity semiconductor element for driving a DC motor to perform drive control that shuts off the drive circuit when the DC motor is restrained, and turns the drive circuit on again if the rotation continues after the shutdown. This is a DC motor drive circuit that can be used to drive motors.

[Conventional technology]

? A DC motor drive circuit detects the rotational state of the DC motor and applies a drive voltage if the DC motor is rotating, and controls not to apply the drive voltage if the DC motor is stopped due to restraint. Are known. FIG. 4 is a circuit diagram of a conventional rotation detection type DC motor drive circuit.

The circuit shown in FIG. 4 remains off when the DC motor M is stopped, and no drive voltage is supplied from the power source E. In such a state, the motor terminal T. When the DC motor M is rotated by an external force so that a positive voltage is generated at T2 and a negative voltage is generated at T2, the induced electromotive force El. Rotation detection transistor Q. is turned on. As a result, a collector current flows through the resistor R1■, so that the collector potential of the rotation detection transistor Q1 becomes high level.

The output voltage of the rotation detection transistor Q1 is applied to one input terminal 30a of the AND circuit 30.

Therefore, this human power terminal 30a has a high potential when the DC motor M is rotating. In this way, one input terminal 30a becomes a high potential? The driving pulse P, which is applied from the oscillator 31 to the other input terminal 30b of the AND circuit 30, is applied to the gate electrode of the driving transistor Q+z. As a result, the driving transistor Ql2 is turned on, and the DC motor M is supplied with a driving voltage from the power source E and continues to rotate. While driving the DC motor M in this manner, the driving transistor l2 is momentarily turned off during the space period of the pulse P. Therefore, during the off-period, no drive voltage is supplied to the DC motor M, but if the DC motor M continues to rotate due to penetrability, the induced electromotive force E. continues to occur, so the circuit turns on again.

However, if the DC motor M is restricted, the rotation detection transistor Q. is turned off, so the oscillator 31
The drive pulse P3 output from the drive transistor Q
1■ will no longer be given. Therefore, the drive voltage will not be supplied again to the DC motor M after the cutoff, and the drive circuit will be in the cutoff state, thereby preventing the flow of the constraint current.

[Problem to be solved by the invention]

In this circuit, in order to periodically and instantaneously cut off the drive voltage supplied to the DC motor M, it is necessary to use a motor drive element with a fast switching speed.

Further, since a large inrush current flows when the DC motor M is started or locked, the motor drive element must have a large allowable current. Motor drive elements that satisfy all of these conditions include semiconductor elements such as large-capacity transistors, but large-capacity semiconductor elements are extremely expensive. Therefore, conventionally, if the drive voltage is instantaneously cut off and the drive circuit is turned on again if the rotation continues for m after the cutoff, the manufacturing cost of the circuit increases.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a similar function by using a relay instead of a large-capacity semiconductor element for driving a DC motor.

[Means to solve the problem]

The DC motor drive circuit of the present invention has a terminal T of a DC motor M.
．． The induced electromotive force generated in E. and a pulse interval detection circuit that detects the motor pulse P generated when switching the polarity of the commutator of the DC motor M and generates a voltage S of a magnitude corresponding to the generation interval. 11, and a terminal T. of the DC motor M to promote the generation of the motor pulse P. The relay 4 is turned on based on the output Sh of the inductor L connected to the inductor L, the relay 4 for supplying drive voltage to the DC motor M, and the rotation detection transistor Q, and the pulse interval is A drive circuit 12 is provided that turns off the relay 4 based on the output St of the detection circuit 11.

[Effect]

The rotational speed of the DC motor M is detected at the generation interval of the motor pulse P, and the induced electromotive force E is used to detect the restraint stop. The relay 4 is controlled to turn on and off based on the magnitude of the detection output. Therefore, when the rotational speed of the DC motor M decreases, the drive circuit is cut off, the magnitude of the induced electromotive force is detected, and based on the detection result, the drive circuit is cut off or turned on again. This can be accomplished using the relay 4, which has a slower response speed than semiconductor devices.

〔Example〕

FIG. 1 is a circuit diagram of a DC motor drive circuit showing an embodiment of the present invention, and FIG. 2 is an operation waveform diagram of each part.

The circuit shown in FIG. 1 maintains an off state when the DC motor M is stopped, so that no driving voltage is supplied from the power source E to the DC motor M. Here, when the DC motor M is rotated by an external force so that a positive voltage is generated at the motor terminal T1 and a negative voltage is generated at the motor terminal T2, the induced electromotive force E. 4
is applied to the base of the rotation detection transistor Q1 through the resistor R1, and this transistor Q is turned on.

As a result, a collector current flows through the resistor R2, and the collector voltage of the rotation detection transistor Q+ rises to a high level.

The collector voltage of the rotation detection transistor Q1 is applied as a rotation detection output S to the human power terminal 1b of the first NAND circuit 1. One input terminal 1a of the first NAND circuit 1 is connected to a resistor Rl connected to the output side of the inverting amplifier 5.
The voltage at the connection point 6 between L and capacitor C3 is applied, and in this case, one input terminal 1a is at a high level.

Therefore, when the collector voltage of the rotation detection transistor Q, which is applied to the other human power terminal 1b, becomes high level, the output S of the first NAND circuit 1 becomes high. is reversed to a low level.

This output S is given to the input terminal 2b of the second NAND circuit 2. The other input terminal 2 of the second NAND circuit 2
The output S of the inverting amplifier 5 is applied to the input terminal a, and in this case, the potential of the input terminal 2a is at a high level. Therefore, the first
When the output of the second NAND circuit 2 becomes low level, the output Se of the second NAND circuit 2 becomes high level. This high potential is applied to the base of switching transistor Q4 via resistor R, turning on transistor Q4. When the switching transistor Q4 is turned on, an exciting current flows through the coil 4a of the motor drive relay 4, and the contact 4b is closed. As a result, a drive voltage is applied from the power source E to the DC motor M, and the rotation continues.

On the other hand, when the DC motor M rotates, a motor pulse P generated at the time of polarity switching appears at the motor terminals T+ and Tt.

As shown in FIG. 2A, motor pulses P are instantaneously generated in both positive and negative directions. In the embodiment, an inductor L having a high resistance to the motor pulse P is connected in series with the motor terminal T to facilitate generation of the motor pulse P.

The motor pulse P is taken out from the connection point 7 between the motor terminal T1 and the inductor L, and is applied to a pulse interval detection circuit 11 consisting of a pulse detection circuit 8 and a control voltage generation circuit 9. The pulse detection circuit 8 includes a transistor Q2 provided for pulse detection and a bias resistor R. connected to the base of the transistor Q2. , R4, a resistor R connected to the collector, and a third Nando circuit 3
Consisting of The pulse P taken out from the connection point 7 is applied through the capacitor C1 to the connection point between the resistors R3 and R4, and is applied to the base of the transistor Q2 via the resistor R4. The transistor Q2 turns on instantaneously every time the motor pulse P is applied, and a positive pulse voltage corresponding to the generation interval of the motor pulse P is generated at its collector. It is applied to terminal 3a.

The output Sc of the second NAND circuit 2 is applied to the other human power terminal 3b of the third NAND circuit 3, and at this time, the input terminal 3b is at a high level.

Therefore, the output S of the third NAND circuit 3. becomes instantaneously low level every time the motor pulse PI%PZ, 1...1...-P,l occurs.

The output S. of the third NAND circuit 3. is the control voltage generation circuit 9
It is added to the resent transistor Q3, which constitutes the resent transistor Q3.

A PNP type transistor is used for the reset transistor Q, and the output S of the NAND circuit output 3 is used. It turns on momentarily every time P falls to a low level, that is, every time motor pulse P occurs.

When the reset transistor Q3 is turned on, the capacitor C2 of the time constant circuit 10 connected to its collector is charged, and the output S1 of the time constant circuit derived from the output terminal 10a rises to the voltage E0 of the power supply E.

This output S, is derived as a pulse interval detection output and is applied to the inverting amplifier 5 which monitors the drive circuit 12 at the next stage. As shown in FIG. 2B, after the output S of the time constant circuit and the centration transistor Q are turned off, the voltage value decreases with a time constant determined by the capacitor C2 and the resistor R.

If the next motor pulse P occurs before it becomes lower than the threshold value 5a of the inverting amplifier 5, the capacitor C2 is charged again and the output S becomes E. Stand up to bolt. Therefore, when the DC motor M is rotating at a predetermined speed or higher, the output sr of the time constant circuit 10 is held at a high level, so the output Sb of the inverting amplifier 5 is kept at a low level as shown in FIG. 2C. level. As a result, the output Sc of the second AND circuit 2 is kept at a high level, and the contact 4b of the motor drive relay 4 is kept on.

As the rotational speed of the DC motor M decreases, the interval between motor pulses P occurring increases accordingly. Therefore, when the rotational speed decreases to a point close to a restraint stop, the pulse P is applied as shown in FIG. 2B. After the occurrence of the next pulse Pfi.

1 occurs, the output Sf of the time constant circuit reaches the threshold value 5.
It will be lower than a. In this case, the output S, of the inverting amplifier 5 is inverted to a high level.

When the inverting amplifier output S, becomes high level, the connection point 6
delay circuit output S9 given to the first NAND circuit l from
rises to a high level with a time constant determined by resistor R8 and capacitor C3. In other words, there is a time delay in reaching a high level. Therefore, for example, the third
When the inverting amplifier output Sb becomes high level at time t1 as shown in the operating waveform diagram A when the rotation speed decreases, the delay circuit output S9 becomes Δ higher than the time t1 as shown in the diagram B.
The level becomes high at time t2, delayed by time t. Therefore, as shown in FIG. 3D, the first NAND circuit output S1 is kept at a high level until time t2, and the second NAND circuit output Sc is at a low level only during the period from time t1 to t2. (Figure 3E). When the second NAND circuit output Sc becomes a low level, the transistor Q4 is turned off and no excitation current flows through the coil 4b, so the contact 4b is turned off and the drive voltage of the DC motor M is cut off.

If the DC motor M continues to rotate after the drive circuit is cut off in this way, a high-level rotation detection output S1 is given from the rotation detection transistor Q1 to the first NAND circuit 1, so the drive circuit is turned on again. Therefore, as shown in FIG. 3C, if the rotation detection output Sh obtained from the collector of the rotation detection transistor Q■ maintains a high level, as shown in FIG.
After 2, the drive voltage is supplied to the DC motor M.

However, if the rotational speed has decreased to near the locked stop, the rotation detection output S will be at a low level, so the drive circuit will be in a cut-off state after time h.

In the embodiment, the values of the resistor Rs and the capacitor C3 are selected so that the rise delay time Δt of the delay circuit output S9 is longer than the response speed of the motor drive relay 4. Therefore, even if the response speed of the motor drive relay 4 is slow, it can be turned off reliably. Further, the rotation detection output Sh of the rotation detection transistor Q1 is not accepted unless the delay circuit output S rises to a high level, and in the case of the embodiment, the delay circuit Output S9 rises to high level. Therefore, when the rotational speed decreases, restraint detection can be performed reliably, and the same function as using a large-capacity semiconductor element can be obtained.

Note that the minimum rotational speed of the DC motor M at which the rotation detection transistor Q1 can be turned on is NE, and the output St of the time constant circuit 10 is
If NP is the minimum number of revolutions that can keep DC motor M at a low level, then if the values of capacitor C2 and resistor R7 are chosen so that N, ≦N, relay contact 4b turns on immediately before DC motor M stops.・It is possible to prevent inconveniences such as repeated turning off.

〔Effect of the invention〕

As described above, the present invention uses a relay in the drive unit that intermittents the drive voltage supplied to the DC motor, and turns on the relay based on the output of the transistor that is turned on by the induced electromotive force of the DC motor. Motor pulses generated as the DC motor rotates are detected, and the relay is turned off when the interval between occurrences of the motor pulses becomes longer than a predetermined interval. Therefore, when driving a DC motor, the drive voltage is cut off and induced electromotive force is detected, and if induced electromotive force is generated at that time, the drive circuit is turned on again and the induced electromotive force is generated. An induced electromotive force sensing type DC motor drive circuit that shuts off the drive circuit if it is not present can be constructed using an inexpensive relay instead of a large-capacity semiconductor element. This results in
The manufacturing cost of an induced electromotive force sensing type DC motor drive circuit can be reduced, and the same functionality as that obtained using a large-capacity semiconductor element can be obtained.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a DC motor drive circuit showing an embodiment of the present invention, Fig. 2 is an operation waveform diagram of each part, Fig. 3 is an operation waveform diagram showing an example of operation when speed decreases, and Fig. 4 is a circuit diagram of a conventional DC motor drive circuit. In addition, in the symbols used in the drawings, 4...1-1--1---Motor drive relay 11--Pulse interval detection circuit 12
−−−−−−1・1・・− Drive circuit M −1−
11...11111 DC motor T,,T. −・−Motor terminal E E・−−−−・・Induced electromotive force Q, −・−・
・・1 Rotation detection transistor Q2 ・1・1・−・−・Ha7L/S detection transistor S, time constant circuit output P−・・11111・−Motor pulse. Agent Masaru Tsuchiya

Claims (1)

[Scope of Claims] A rotation detection transistor that is turned on by an induced electromotive force generated at a terminal of a DC motor, and a motor pulse that detects a motor pulse generated when switching the polarity of a commutator of the DC motor and has a magnitude corresponding to the generation interval. a pulse interval detection circuit that generates a voltage, an inductor connected to a terminal of the DC motor to facilitate generation of the motor pulse, a relay for supplying a drive voltage to the DC motor, and the rotation A drive circuit that turns on the relay based on the output of the detection transistor to drive the DC motor, and turns off the relay based on the output of the pulse interval detection circuit to enable detection of the induced electromotive force. A DC motor drive circuit comprising: