JPS62123989A - Step motor drive circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 1 The present invention relates to a step motor drive circuit, and more specifically to a so-called chopper type drive circuit that drives the step motor by controlling the current flowing through the step motor to a predetermined current. This relates to 6) three circuits for driving a step motor.

[Prior Art] Conventionally, a so-called chopper type drive circuit has been used as one of the step motor drive circuits, which controls the application time of the power supply voltage to the step motor to control the current flowing through the step motor to a predetermined value. or known.

Taking a four-phase step motor in which the windings are bifilar-wound as an example, this type of drive circuit, as shown in FIG. ), excitation circuits 12a and 12b that excite each winding 1a and lb according to an excitation signal, a current detection resistor R1 for detecting the current flowing through the windings a and lb, and this resistor R1. The detection voltage Vi generated across the terminal is inputted via the buffer amplifier 14, and the reference voltage V
A control circuit 1G outputs a signal i, +1 i1 compared to When the detected voltage i becomes larger than the reference voltage Vr by a predetermined value or more, the switching circuit M18 is turned off, and the detected voltage Vi becomes larger than the reference voltage Vr by a predetermined value or more. When the current is lower than that, the switching circuit 18 is turned on and the current flowing through the step motor 10 is controlled to a predetermined current.

At this point, the transistor Tr1 in the switching circuit 18 is set to 0N-O according to the control signal from the control circuit 16.
The PNP type switching transistor and diode D1 that are turned off are flywheel diodes that supply current flowing to the windings of the step motor 10 when the switching circuit 18 is turned off. Also, the excitation circuit 12a
In order to excite the windings la and Lb of the step motor 10 according to the excitation signal, the transistors Tra and Trb in the transistors 12b and 12b connect the windings La and Lb and the current detection resistor R1.
The switching transistors and diodes Da1 and Dbl are connected to the transistors Tra and Tr.
A Zener diode is a reverse current blocking diode that prevents reverse current from flowing to each winding 1-a and Lb of the step motor 10 through the strange diodes Da2 and Db2 present in the transistor Tra.
Alternatively, it is a diode for absorbing the electromotive force generated in the winding La or B when Trb is set to 0FFL.

[Problems to be solved by the invention] However, in this type of circuit, the step motor 1
If an abnormality occurs in 0 and the winding 1a or Lb comes into contact with the motor housing and the current path is grounded midway, no current will flow through the current detection resistor R1 and the switching circuit 18
is controlled to be in the ON state, a large current flows in the switching circuit 18, and the switching transistor Tr inside the circuit is controlled to be in the ON state.
There was a problem that the first prize was destroyed.

In other words, for example, if this type of circuit is applied to the drive circuit of a step motor installed in a vehicle, such as a step motor that opens and closes the throttle valve of an internal combustion engine, the chassis of the vehicle is connected to the ground terminal of the battery. When the windings inside the step motor 10 come into contact with the housing, they are connected to the ground terminal of the battery through the chassis to which the housing is attached, and as mentioned above, ON-OFF control of the switching circuit 18 cannot be executed. A problem arises in that a large current flows within the switching circuit 18.

To solve this problem, the current flowing through the switching circuit 18 is detected, and when the current exceeds the upper limit, the switching circuit is forcibly switched even if the detection voltage 1 detected by the current detection resistor is low. It may be configured to control the switching circuit 1 to be in the OFF state for one day, but in this case, the switching circuit 1
Since it is necessary to provide a detection circuit for detecting the current flowing through the circuit 8, there is a problem that a conventional switching circuit cannot be used as is.

Therefore, the present invention provides a step motor drive circuit that detects an abnormality in the step motor 10 without detecting the current flowing in the switching circuit 18, and prevents a large current from flowing in the switching circuit 18 and damaging the circuit. It was created with the purpose of providing the following, and has the following structure.

[Means for Solving the Problems] That is, the configuration of the present invention as a means for solving the above problems includes a switching circuit that is turned on and off in response to a control signal and applies a power supply voltage to the step motor. and a current detection circuit that detects the current flowing through the step motor, and outputs a control signal to the switching circuit to control the on/off time of the switching circuit so that the detected current becomes a predetermined value. A step motor drive circuit comprising: a control circuit for driving the step motor; An abnormality detection circuit that detects an abnormality in the step motor and controls the switching circuit to be turned off when the determination circuit determines that the current flowing through the step motor is below a lower limit value. The gist of this paper is a step motor drive circuit.

[Function] In the step motor drive circuit of the present invention configured as described above, when the current detected by the current detection circuit falls below the lower limit value while the step motor is being driven, an abnormality occurs in the step motor. It is determined that the switching circuit is turned off.

[Example 1 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram showing a step motor drive circuit according to a first embodiment, in which a discrimination circuit for realizing the present invention is added to the four-phase step motor drive circuit described as an example in the prior art section. 20 and an abnormality detection circuit 22 is added.

That is, as shown in the figure, the drive circuit of this embodiment, like the conventional drive circuit shown in FIG. Excitation circuits 12a and 12b that excite each winding La and Lb, a current detection resistor R1 for detecting the current flowing to the step motor 10, and this resistor 1te1.
A control circuit 16 inputs the detection voltage ■i generated at both ends of the buffer 7 via the buffer 7 amplifier 14, compares it with the reference voltage Vr, and outputs a control signal. - OFF, step motor 10
a switching circuit 18 for applying a power supply voltage to a detection voltage i and a preset lower limit voltage Vmin;
a determination circuit 20 that determines whether the current flowing through the winding 1a or 1-b has become below the lower limit value by comparing the
While the step motor is being driven, the determination circuit 20 determines whether the winding is a or L.
When it is determined that the current flowing through b is below the lower limit,
An abnormality detection circuit 22 that detects an abnormality in the step motor 10 and controls the switching circuit 18 to be in an OFF state is provided.

Here, the configurations of the excitation circuits 12a and 12b and the switching circuit 18 are exactly the same as the circuit shown in FIG.
To excite l-b, 0N-OFF by excitation signal
switching transistors Tra and Trb;
Reverse current blocking diodes Dal and Dbl prevent reverse current from flowing through the wires a and Lb, and each transistor Tr.
Zener diodes [)Za and Qzb are provided to absorb the electromotive force generated when a or Trb is turned off, and the switching circuit 18 is provided with a flywheel diode D1 and a switching transistor Tr1.

Further, the control circuit 16 compares the detection voltage v1 outputted from the buffer amplifier 14 and the reference voltage Vr to generate a detection voltage V1.
When i is larger than the reference voltage ■r and the current flowing through the winding 1a or Lb exceeds a predetermined value, the switching circuit 18 is set to 0FFI, and conversely, the detection voltage Vi is smaller than the reference voltage Vr and the winding 1-a is set to 0FFI. Or, in order to turn on the switching circuit 18 when the current flowing through Lb becomes less than a predetermined value,
A Schmitt circuit configured using an operational amplifier OP1 and resistors R2 and R3 is turned on when the output voltage from the Schmitt circuit reaches Hiqh level, and the base of the transistor Tr1 in the switching circuit 18 is connected to the resistor R.
An NPN switching transistor Tr2 that is grounded via a transistor Tr2 is provided.

Next, the discrimination circuit 20 is configured using an operational amplifier OP2 to compare the detection voltage VI and the lower limit voltage Vmin as described above, and when the detection voltage i is lower than the lower limit voltage V, min, the f-1i Q h level is determined. Outputs the signal.

The abnormality detection circuit 22 detects an abnormality when the detection voltage Vi falls below the lower limit voltage Vmin while the step motor 10 is being driven, and therefore outputs a signal at H1gh level when an excitation signal is input to either of the excitation circuits 12a12b. and an AND circuit ANDI which outputs a High level signal to detect an abnormality in the step motor 10 when the signals from the OR circuit OR1 and the discrimination circuit 20 both reach the 1-1 r ah level. ing. The abnormality detection circuit 22 also detects an abnormality when it immediately determines that an abnormality has occurred in the step motor 10 when the output signals from the discrimination circuit 20 and the OR circuit OR1 both reach the l-1-1i level. To avoid false detection, a delay circuit consisting of a capacitor C1 and a resistor R5 is provided to detect an abnormality when both detection signals from each of the circuits are at a high level for a certain period of time. . Furthermore, this abnormality detection circuit 22 is configured to forcibly control the switching circuit 18 to turn off the switching circuit 18 when an abnormality of the step motor 10 is detected.
In order to prevent a large current from flowing to the step motor 1o side via the above-mentioned capacitor C1 and resistor R5, a negative circuit N0T1 is used to invert the -1high level abnormality detection signal outputted via the delay circuit consisting of the capacitor C1 and resistor R5. , negative circuit N
When the output signal from 0TI becomes LOW level, that is, when an abnormality in the step motor 10 is detected, it is turned on and the transistor Tr in the switching circuit 18 is turned on.
A switching transistor Tr3 is provided which applies a power supply voltage directly to the base of the switching transistor Tr3 to control the switching circuit 18 to an OFF state.

In the step motor drive circuit of this embodiment configured as described above, when the step motor 10 is normal, the Bach amp 1 detected by the current detection resistor R1
When the detection voltage Vi output from 4 becomes larger than the reference voltage vr by a predetermined value or more, the transistor T in the control circuit 16
When r2 is turned off, the transistor Tr1 in the switching circuit 18 is turned off, and conversely, when the detection voltage V1 is lower than the reference voltage vr by a predetermined value or more, the transistor Tr1 is turned off.
2 is turned on, and the transistor Tr1 in the switching circuit 18 is turned on. Therefore, the current flowing through the winding 1-a or 1-b is controlled to a predetermined value determined by the reference voltage Vr, and the step motor 10 is driven with a constant current vJ.
It becomes possible to In addition, O of the switching circuit 18
The reason why current flows through the winding [a or lb] even during FF is that, as is well known, a positive current flows in the closed circuit formed by the flywheel diode D1 via the ground.

On the other hand, an abnormality occurs in the step motor 1o, and the excitation circuit 12a
Or, if the current flowing through the current detection resistor R1 is below the lower limit value even though the excitation signal is input to 12b, the OR circuit OR1 in the discrimination circuit 20 and the abnormality detection circuit 22 An output signal of level 119h is outputted from the output signal, and is sent to the inverter N via the delay circuit (01 and R5).

A signal at H1gh level is output to T1. Then, the output terminal of the NOT circuit N0T1 becomes LOW level, and the transistor Tr3 is turned on.

At this time, in the control circuit 16, since the detection voltage Vi is smaller than the reference voltage ■r, the transistor Tr2 is in the ON state, but the transistor Tr2 in the abnormality detection circuit 22 is in the ON state.
3, the transistor Tri of the switching circuit 18
Since the power supply voltage vb is directly applied to the base of the transistor Tr1 in the switching circuit 18, the voltage is 0FFL.
, power supply to winding La or 1b is stopped. Therefore, if the winding a or Lb in the step motor 10 comes into contact with a housing or the like and the current path is grounded, the switching circuit 18 is always turned off, and a large current flows inside the switching circuit 18. can be prevented from flowing.

Here, in the above embodiment, when the current detected by the current detection resistor R1 falls below the lower limit (just below) while the step motor is being driven, an abnormality is detected and the switching circuit 18 is turned off. explained the drive circuit that prevents a large current from flowing through the switching circuit 18 and damaging the circuit. However, if the control circuit 16 fails, for example, the step motor 10 is normal and the current detection resistor is Therefore, even though the current flowing through the winding 1a or Lb can be detected well, the switching circuit 1
It is conceivable that a large current may flow through the circuit 8 and the circuit may be damaged.

Therefore, as a second embodiment of the present invention, in addition to the drive circuit of the first embodiment, the switching circuit 18 is also turned off when the current flowing through the @ line La or Lb exceeds the upper limit value.
A description will be given of a step motor drive circuit configured to control the motor to the F state and also prohibit control of the excitation circuits 12a and 12b.

As shown in FIG. 2, the drive circuit of this embodiment includes a current detection paper IAR1 and an excitation circuit 12a similar to those of the first embodiment.
, 12b, a buffer amplifier 14, a control circuit 16, a switching circuit 18, a 'rll separate circuit 20, and an abnormality detection circuit 22.The detection voltage vi output from the buffer amplifier 14 exceeds a predetermined upper limit voltage ymax. When the excitation prohibition circuit 24 prohibits the operation of the excitation circuits 12a and 12b, and when both the excitation circuits 12a and 12b are not operating, that is, when no excitation signal is input to both excitation circuits 12a and 12b, the abnormality detection circuit Turn ON the transistor Tr3 in 22 and turn OFF the switching circuit 18.
A buffer amplifier 26 for controlling to the F state is provided.

Note that the excitation 11 prohibition circuit 24 has a detection voltage Vi that is lower than the upper limit voltage V.
An operational amplifier OP3 that outputs a LOW level output signal when it exceeds max, a negative circuit N0T2 that inverts the output signal from the operational amplifier OP3, and a negative circuit N0.
The R-S flip-flop F1 is set when the output terminal of T2 reaches the H10h level, that is, when the detection voltage 1 becomes higher than the upper limit voltage Vmax, and is reset when the drive circuit is powered on. , R-S flip-flop F1 is in a reset state and is comprised of AND circuits ANDa and ANDb which output an excitation signal to each excitation circuit 12a, 12b when an excitation signal is input.

In the step motor drive circuit of this embodiment configured in this way, as in the previous embodiment, the current flowing through the winding 1-a or Lb detected by the current detection resistor when the step motor is driven is When the value is below the lower limit, an abnormality in the step motor 10 is detected and the switching circuit 18 is turned off.
In addition to operating to control the FF state, the step motor 10
When the current flowing through exceeds the upper limit value, the R-8 flip-flop in the excitation inhibit circuit 24 is set to 1, no excitation signal is input to the excitation circuits 12a and 12b, and the drive of the step motor 10 is stopped. The transistor Tr in the abnormality detection circuit 22 via the Bacher amplifier 26
3 is turned on, and the switching circuit 18 is also turned off. Therefore, in this embodiment, while the step motor 10 is being driven,
Even when the current flowing through the winding 1-a or Lb exceeds the upper limit value, it is possible to prevent a large current from flowing into the switching circuit 18, and to prevent damage to the circuit. .

Although each of the above embodiments has been explained by taking as an example a drive circuit for a step motor in which the windings are wound in a pipe filler, the present invention can be implemented with any drive circuit that drives a step motor at a constant current.

[Effects of the Invention] As detailed above, according to the step motor drive circuit of the present invention, a large current flows through the switching circuit without detecting the current flowing through the switching circuit that applies the power supply voltage to the step motor. It is possible to prevent this and to maintain the switching circuit.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing a step motor drive circuit according to a first embodiment of the present invention, FIG. 2 is an electric circuit diagram showing a step motor drive circuit according to a second embodiment of the present invention, and FIG. FIG. 1 is an electric circuit diagram showing a drive circuit of a conventional step motor. 10...Step motor 16...Control circuit 18...Switching circuit 20...Discrimination circuit 22...Abnormality detection circuit R1...Current detection resistor cost, embedded Patent attorney Tsutomu Sateri

Claims (1)

[Claims] 1. A switching circuit that is turned on and off in response to a control signal and applies a power supply voltage to the step motor; a current detection circuit that detects the current flowing through the step motor; and a switching circuit that detects the current flowing through the step motor; a control circuit that outputs a control signal to the switching circuit to control the on/off time of the switching circuit so that the current is a predetermined value; a determination circuit that determines whether the current is less than or equal to a preset lower limit value; and a determination circuit that determines whether the current flowing through the step motor is less than or equal to the lower limit value while the step motor is being driven; A step motor drive circuit comprising: an abnormality detection circuit that detects an abnormality in the motor and controls the switching circuit to an OFF state. 2. The step motor drive circuit according to claim 1, wherein the current detection circuit is a resistor having a predetermined electrical resistance provided between the step motor and ground.