JPH11206191A - Motor control circuit - Google Patents

Abstract

(57) [Problem] To accurately control a rotation operation of a motor by measuring an accurate value of a winding current flowing in a motor winding. A base current detection unit detects a base current of a switching transistor, and outputs a current having the same current value as the current to a current detection resistor. The differential voltage between the current detection resistors 25 and 31 is obtained by the operational amplifier 32, and the base current is subtracted from the difference voltage. Therefore, the PWM oscillator 28 is set without depending on the current amplification factor of the switching transistor 18. winding current I _L performs control flowing through the motor windings 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a motor control circuit called an H-bridge circuit used for current driving of a motor.

[0002]

2. Description of the Related Art Conventionally, motors used in electrophotographic copying machines and ink jet printers include high speed, high precision,
No adjustment is required. In particular, since high position accuracy is required at the time of printing and image reading, an absolute position is determined by the number of pulses, and a stepping motor which operates in an open loop and is easily controlled has been frequently used.

For example, a two-phase stepping motor has two motor windings, and a motor control circuit is provided for each of the windings. Here, in order to improve the torque characteristics of the motor, a so-called bipolar drive system, which is a current drive system that can use the motor winding without waste, is adopted. In this bipolar drive system, current flows in both forward and reverse directions to the motor winding,
Conventionally, a circuit called an H-bridge circuit in which four switching transistors are combined has been used.

FIG. 4 shows an example of a motor control circuit using a conventionally used H-bridge circuit. The conventional motor control circuit includes AND gates 11 to 14, switching transistors 15 to 18, a motor drive power supply terminal 19, flywheel diodes 21 to 24,
It comprises a current detection resistor 25, a comparison reference voltage source 26, a comparator 27, and a PWM oscillator 28 whose pulse width changes according to the input level. Then, this motor control circuit includes one motor winding 20 of the stepping motor.
The operation of flowing current in both forward and reverse directions is performed.

Therefore, a two-phase stepping motor prepares two circuits to control the operation of the motor. The AND gates 11 to 14 each have one input terminal to which a control signal for controlling the operation of the motor is input, and the other input terminal to which a pulse signal output from the PWM oscillator 28 is commonly input. I have.

Switching transistors 15-18
Are npn transistors, and gates 11 and 1
Output signals 3, 12, and 14 are input to the base. And the switching transistors 15, 1
7 has a collector connected to the motor driving power supply terminal 19 and an emitter connected to one terminal and the other terminal of the motor winding 20. And switching
The transistors 16 and 18 have a collector connected to the motor winding 20.
Are connected to one terminal and the other terminal, respectively, and the emitter is connected to one terminal of the current detection resistor 25.

The motor drive power supply terminal 19 is applied with a motor drive voltage having a voltage value Vm which is a DC voltage for driving the motor.

[0008] Flywheel diodes 21 to 24
Are provided for the switching transistors 15 to 18, respectively. The cathodes are connected to the collectors of the switching transistors 15 to 18, respectively, and the anodes are connected to the emitters. The flywheel diodes 21 to 24 are provided to absorb the back electromotive voltage generated by the motor winding 20 and protect the switching transistors 15 to 18.

One of the current detecting resistors 25 is commonly connected to the emitters of the switching transistors 16 and 18, and the other is connected to the ground. Then, the current Is output from the emitter of the switching transistor 16 or the switching transistor 18 flows through the current detection resistor 15, so that a voltage Vs is generated at the terminal of the current detection resistor 15 that is not connected to the ground.

The comparison reference voltage source 26 outputs a voltage having a predetermined voltage value Vref as a comparison reference voltage.

The comparator 27 has a comparison reference voltage Vref.
Is compared with the voltage Vs generated by the current detection resistor 25. When the voltage Vs is higher than the comparison reference voltage Vref, a high-level (hereinafter, referred to as H) signal is output, and the voltage Vs
Is lower than the comparison reference voltage Vref, a low-level (hereinafter, referred to as L) signal is output.

The PWM oscillator 28 includes AND gates 11 to
A pulse signal is output to the other terminal of the comparator 14. When the H signal is output from the comparator 27, control is performed so that the pulse width of the pulse signal is reduced, and the L signal is output from the comparator 27. If so, control is performed to increase the pulse width of the pulse signal.

Next, the operation of the conventional motor control circuit will be described.

First, when H is input to the input terminals of the AND gates 11 and 14, and L is input to the input terminals of the AND gates 12 and 13, when the switching transistors 16, 1 constituting the H bridge are input.
7 turns off, and the switching transistors 15 and 18 turn on / off according to the pulse signal output from the PWM oscillator 28. At this time, the path of the current from the motor driving power supply terminal 19 to which the motor driving voltage of the voltage value Vm is applied passes through the switching transistor 15, the motor winding 20, the switching transistor 18, and the current detection resistor 25. Flow, to the ground. In this case, the motor windings 20, the current I _L flows in the direction as shown in FIG flows current Is to the current sensing resistor 25.

In the comparator 27, the current Is
Is compared with the reference voltage Vref from the comparison reference voltage source 26, and the result is input to the PWM oscillator 28.

Here, the PWM oscillator 28 has a relation of Vs> Vref.
In this case, a current larger than the predetermined current is
And the control is performed so that the pulse width of the output pulse signal is reduced. When Vs <Vref, the PWM oscillator 28 determines that a current smaller than the predetermined current is flowing through the motor winding 20 and performs control such that the duty ratio of the output pulse signal is increased. I do. In this way, control is performed such that the current flowing through the motor winding 20 becomes a constant value.

The input terminals of the AND gates 11 and 14 are L,
When H is input to the input terminals of the AND gates 12 and 13, the switching transistors 15 and 18 are turned off, and the switching transistors 16 and 17 are turned on / off according to the pulse signal output from the PWM oscillator 28. I do. At this time, the state described above means that the motor winding 2
However, only the direction of the current flowing through 0 is reversed, and I
_{Although the} current flows in the opposite direction to _L. The operation for controlling the current to be a constant value is the same as described above.

However, in the above conventional motor control circuit,
Detection current flowing through the current detection resistor 25 Is is not equal to the winding current I _L flowing through the motor windings 20. When the switching transistor 18 is on, there is a difference of the base current Ib between the emitter current and the collector current of the switching transistor 18, so that the detection current Is and the winding current I _L Has a relationship of Is = I _L + Ib. Usually, the current flowing through the motor winding 20 is several hundred mA or more, and considering the characteristics of the switching transistor 18 at this time, the current amplification factor hfe
Is only several tens, so this base current is approximately several tens
mA. In other words, only a smaller amount of current than the current to be adjusted flows through the motor winding 20, and in some cases, this error may be several tens of the desired current value.

If the current amplification factor hfe of the switching transistor is constant, the error can be compensated by adding or reducing the offset voltage to the comparison reference voltage Vref. However, this current amplification factor h
fe varies depending on the temperature and device variation. further,
The base current cannot be completely and properly compensated by the method of adjusting with the offset voltage since the base current changes delicately depending on the operating current of the transistor. When the current flowing through the motor winding 20 is large, the amount of change in the current amplification factor hfe is further increased.

As described above, since the current amplification factor hfe greatly changes due to environmental changes and element variations, it is difficult to accurately estimate the current flowing through the motor winding 20.
As a result, the current actually flowing through the motor winding 20 is greatly deviated from the initially designed current value, so that the rotation operation of the motor may not be accurately controlled.

[0021]

As described above, the conventional motor control circuit cannot set an accurate value of the winding current flowing through the motor winding, so that the rotation operation of the motor can be accurately performed. There was a problem that control could not be performed.

An object of the present invention is to provide a motor control circuit capable of accurately controlling the rotation operation of a motor by setting an accurate value of a winding current flowing through a motor winding.

[0023]

According to a first aspect of the present invention, there is provided a motor control circuit comprising an H-bridge circuit including four switching transistors to which a pulse signal is input. A motor control circuit that controls a current flowing through a motor winding by the H-bridge circuit, wherein a first current detection resistor provided between the H-bridge circuit and ground; The switching transistor is provided between the base of each of the two switching transistors provided between the motor winding and the circuit that outputs the pulse signal, and has a current value substantially equal to the base current of each of the switching transistors. A base current detection unit that outputs a current, one end of which is connected to the ground, and has a resistance value substantially equal to that of the first current detection resistor; A second current detection resistor through which a current output from each of the base current detection units passes, a voltage generated by the first current detection resistor, and a voltage generated by the second current detection resistor. An operational amplifier that outputs a difference voltage, a comparator that compares the difference voltage output from the operational amplifier with a voltage value of a comparison reference voltage having a predetermined voltage value, and a pulse signal of each of the pulse signals based on an output signal from the comparator. And current control means for controlling the pulse width.

According to the present invention, the base currents of two switching transistors provided between the H-bridge circuit and the ground are detected by the respective base current detectors.
These currents are converted into voltages by a second current detection resistor, and are subtracted from the voltage generated by the first current detection resistor using an operational amplifier.

Therefore, since the base current is subtracted from the difference voltage compared with the comparison reference voltage by the comparator, the current control means can be set at the time of design without depending on the current amplification factor of the switching transistor. It is possible to control the flow of different winding currents to the motor windings.

According to a second aspect of the present invention, each of the base current detectors outputs a transistor for supplying a base current of the connected switching transistor and a current equivalent to a collector current of the transistor. A first current source, and a second current source that outputs a current equivalent to the emitter current of the transistor, wherein a difference between an output of the first current source and an output of the second current source is obtained. Output.

According to the present invention, in the base current detecting section, a current equivalent to a collector current of a transistor for supplying a current to the switching transistor connected by the first current source is output, and the current is connected by the second current source. A current equivalent to the emitter current of a transistor that supplies a current to the switching transistor is output, and the outputs of the first and second current sources are obtained as output currents.

Therefore, a current having the same current value as the base current of each of the connected switching transistors can be generated and output.

According to a third aspect of the present invention, each of the base current detectors outputs a transistor that supplies a base current of the connected switching transistor and a current equivalent to a collector current of the transistor. And an output of the current source.

According to the present invention, in the base current detecting section, a current equivalent to a collector current of a transistor for supplying a current to a switching transistor connected by a current source is obtained as an output current.

Therefore, since a current source using a negative power supply is not required, the circuit configuration can be simplified and the external power supply circuit can be simplified.

The invention according to claim 4 further comprises an H-bridge circuit composed of four switching transistors whose pulse signals are inputted to the base, and the H-bridge circuit controls the current flowing through the motor winding. In the motor control circuit to be performed, a current detection resistor provided between the H-bridge circuit and ground, and a base of each of the two switching transistors provided between the current detection resistor and the motor winding. And a circuit that outputs the pulse signal, and a base current detection unit that outputs a current having substantially the same current value as the base current of each switching transistor so as to pass through the current detection resistor. A comparator for comparing a voltage generated by the current detection resistor with a voltage value of a comparison reference voltage having a predetermined voltage value When, characterized in that it is composed of a current control means for the controlling the pulse width of each pulse signal based on the output signal from the comparator.

According to the present invention, each base current detecting section inputs a current having substantially the same current value as the base current of each of the connected switching transistors from the emitter of the switching transistor. And only the current having the same current value as the collector current flows through the current detection resistor.

Therefore, the operational amplifier and the second current detection resistor for generating the difference voltage can be omitted from the invention of the first aspect, and the circuit can be simplified.

According to a fifth aspect of the present invention, each of the base current detectors outputs a transistor for supplying a base current of the connected switching transistor and a current equivalent to a collector current of the transistor. It comprises a first current source, and a second current source that inputs a current equivalent to the current output from the first current source from the emitter of the switching transistor connected thereto.

The motor control circuit according to claim 6 is
In a motor control circuit including a switching transistor having a pulse signal input to a base and controlling a current flowing through a motor winding by the switching transistor, a first circuit provided between the switching transistor and a ground. A current detection resistor, a base current detection unit that is provided between the base of the switching transistor and a circuit that outputs the pulse signal, and outputs a current having substantially the same current value as the base current of the switching transistor; Is connected to ground, and the first
A second current detection resistor having substantially the same resistance value as the current detection resistor, and through which a current output from each of the base current detection units passes, and a voltage generated by the first current detection resistor. An operational amplifier that outputs a difference voltage from a voltage generated by the second current detection resistor, and a comparator that compares the difference voltage output from the operational amplifier with a voltage value of a comparison reference voltage having a predetermined voltage value. And current control means for controlling a pulse width of each of the pulse signals based on an output signal from the comparator.

The present invention is applied to a motor control circuit of a unipolar drive system, and controls the flow of a winding current as desired at the time of design to the motor windings in the same manner as in the invention described in claim 1. It can be carried out.

[0038]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

(First Embodiment) First, a motor control circuit according to a first embodiment of the present invention will be described.

FIG. 1 is a circuit diagram of a motor control circuit according to a first embodiment of the present invention. The same components as those of the conventional motor control circuit in FIG. 4 are denoted by the same reference numerals.

The motor control circuit of this embodiment is different from the conventional motor control circuit of FIG. 4 in that a base current detection unit 30 is provided between the output signal of the AND gate 14 and the base of the switching transistor 18, and A base current detection unit 33 is provided between the output signal of the gate 13 and the base of the switching transistor 16, and an operational amplifier 32,
A current detection resistor 31 having a resistance value Rx is provided.

The base current detector 30 is provided with a switching
It detects the base current of the transistor 18 and outputs a current having the same current value as the base current to the current detection resistor 31 via the terminal 34. In addition, the base current detector 3
Reference numeral 3 also denotes a circuit for detecting the base current of the switching transistor 16, and its configuration is the same as that of the base current detection unit 30, so that the details are omitted.

Since the switching transistor 16 and the switching transistor 18 do not turn on at the same time, the operational amplifier 32 and the resistor 31 are shared, but they may be prepared separately.

The base current detector 30 includes a resistor 30
1, 302; transistors 303 and 304; transistor 305; resistor 306;
309 and resistors 310 to 312.

The transistor 303 has a resistor 3
01 is a pnp transistor connected to the power supply voltage Vcc via a base 01 and having a base and a collector connected to each other.

The transistor 304 has a resistor 3
02 is a pnp transistor connected to the power supply voltage Vcc via 02 and having a base connected to the base of the transistor 303.

Here, the resistors 301 and 302 have the same resistance value, and the transistors 303 and 304
Are transistors having the same characteristics, and a current mirror circuit is formed by these elements.

Transistor 305 has an npn having a base connected to the output signal of AND gate 14, a collector connected to the collector of transistor 303, and an emitter connected to the base of switching transistor 18.
It is a transistor.

The transistor 309 has a collector connected to the resistor 3
06 is connected to the power supply voltage Vcc, the base and the collector are connected, and the emitter is an npn transistor connected to the negative power supply Vss through the resistor 312.

The transistor 308 has a base connected to the base of the transistor 309, a collector connected to the collector of the transistor 304, and an emitter connected to the resistor 311.
Is an npn transistor connected to the minus power supply Vss through the NPN transistor.

The transistor 307 has a collector connected to the emitter of the transistor 305, a base connected to the base of the transistor 309, and an emitter connected to the resistor 310.
Is an npn transistor connected to the minus power supply Vss through the NPN transistor.

Here, the transistors 307 to 309 are
Each of the transistors has uniform characteristics, and the resistor 310
To 212 are resistors having the same resistance value, and a current mirror circuit is formed by these elements.

The current detection resistor 31 is provided between the terminal 34 and the ground, and converts the current Ix output from the terminal 34 into a voltage Vx.

The operational amplifier 32 outputs a difference voltage between the voltage Vs and the voltage Vx as a voltage Vd.

Next, the operation of this embodiment will be described with reference to FIG.

First, the internal operation of the base current detector 30 will be described.

The current flowing through the resistor 312 is determined by the resistor 306, the transistor 309, and the resistor 312. Then, the resistor 312 and the transistor 309, the resistor 311 and the transistor 308, and the resistor 310 and the transistor 307
Constitute a current mirror circuit. Therefore, Ie (308) = Ie (307) (1). Further, the resistor 301 and the transistor 30
3. A current mirror circuit is formed by the resistor 302 and the transistor 304. Therefore, Ie (303) = Ie (304) (2).

Here, Ie (308) indicates the current value of the emitter current of the transistor 308. Similarly,
Ib indicates the current value of the base current, and Ic indicates the current value of the collector current. Since the operating current of each transistor is almost steady and minute, Ic = Ie.

Now, the output signal from the AND gate 14 becomes L
In this case, the transistor 305 is turned on because the emitter is connected to the minus ground via the transistor 307 and the resistor 310, but remains off because the base voltage of the switching transistor 18 is L and the switching transistor No base current flows through 18. Further, since the emitter current of the transistor 305 is a small current and the current amplification factor hfe does not decrease, the base current of the transistor 305 is almost negligible compared to the emitter current of the switching transistor 18. , Ie (303) = Ie (307) (3), and from the above equations (1) and (2), the relationship becomes Ie (304) = Ie (308) (4). The current input / output from terminal 34 is 0
Becomes

Next, when the output signal from the AND gate 14 is H, the switching transistor 18 is turned on and the switching transistor 18
Pull in (18). Therefore, Ie (307) + Ib (18) = Ie (303) + Ib
(305) Here, the base current of the transistor 305 is smaller than the emitter current of the switching transistor 18,
Since it is sufficiently small, it can be neglected, and from the above equations (1) and (2), Ie (308) + Ib (18) = Ie (304). Therefore, the current Ix flowing into and out of the terminal 34 is Ix = Ie (304) −Ie (308) = Ib (18) (5), and a current substantially equal to the base current of the switching transistor 18 is output. Here, the relationship when the switching transistor 18 is turned on has been described for convenience. Here, the output currents from the base current detectors 30 and 33 are directly connected and output to the terminal 34. However, since the switching transistors 18 and 16 do not turn on at the same time, the terminal 34 Switching
The base current or switching of transistor 18
A current substantially equal to the base current of the transistor 16 is output.

Next, a control loop using the output current Ix from the terminal 34 will be described.

The output current Ix from the terminal 34 is converted into a voltage Vx by flowing through the current detection resistor 31. The voltage Vx at this time is Vx = Rx × Ix. Then, the emitter current Is of the switching transistor 16 or 18 which is actually passing the current through the motor winding 20 is converted into a voltage by the current detecting resistor 25 connected to the terminal. The voltage Vs at this time is as follows: Vs = Rs × Is

Then, the voltage Vs,
A difference voltage of Vx is output, and the difference voltage Vd is as follows: Vd = Vs−Vx = Rs · Is−Rx · Ix Here, when the resistance values of the current detection resistors 25 and 31 are made equal to Rs = Rx, according to equation (5), Vd = Rs · (Is−Ix) = Rs · (Ie (18) −Ib (18)) = Rs · Ic (18) Here, for convenience, the switching transistor 1
8 is turned on. This difference voltage Vd is equal to the collector current of the switching transistor 18 (or the switching transistor 16), that is, the winding current _IL.
The voltage is proportional to the voltage itself and does not depend on the base current of the switching transistor 18.

The difference voltage Vd is compared with a reference voltage Vref to be controlled by a comparator 27, and the magnitude is transmitted to a PWM oscillator 28. Then, the PWM oscillator 28
Is determined according to the magnitude of the comparison reference voltage Vref and the difference voltage Vd.
By adjusting the pulse width of the WM, the motor winding 20
, A predetermined current flows.

(Second Embodiment) Next, a second embodiment of the present invention will be described.

FIG. 2 is a circuit diagram of a motor control circuit according to a second embodiment of the present invention. The same components as those in the first embodiment in FIG. 1 are denoted by the same reference numerals.

This embodiment is different from the first embodiment shown in FIG. 1 in that the base current detectors 30 and 33 are replaced with base current detectors 40 and 43.

The base current detector 40 is provided with a switching
It detects a base current of the transistor 18 and outputs a current having the same current value as the base current to the current detection resistor 31. The base current detection unit 43 is also a circuit for detecting the base current of the switching transistor 16, and the configuration is the same as that of the base current detection unit 40, so that the details are omitted.

The base current detector 40 includes a resistor 40
1 and 402, and transistors 403 to 405.

The transistor 403 has a resistor 4
01 is a pnp transistor connected to the power supply voltage Vcc via a base 01 and having a base and a collector connected to each other.

The transistor 404 has a resistor 4
02 is a pnp transistor connected to the power supply voltage Vcc via 02 and having a base connected to the base of the transistor 303.

Here, the resistors 401 and 402 have the same resistance value, and the transistors 403 and 404 are transistors having uniform characteristics, respectively. These elements form a current mirror circuit.

Transistor 405 has an npn having a base connected to the output signal of AND gate 14, a collector connected to the collector of transistor 403, and an emitter connected to the base of switching transistor 18.
The transistor is turned on when the output signal from the AND gate 14 becomes H, and the switching transistor 18 is turned on.

Next, the operation of this embodiment will be described with reference to FIG.

First, the internal operation of the base current detector 40 will be described.

First, when the output signal from the AND gate 14 is L, the transistor 405 is turned off and the switching transistor 18 is also turned off. Therefore, neither the base current of the switching transistor 18 nor the emitter current of the transistor 405 flows. Since the emitter current of the transistor 403 does not flow and the emitter current of the transistor 404 forming a current mirror circuit with the transistor 403 does not flow, the current output from the base current detection unit 40 to the current detection resistor 31 is 0. Become.

Next, when the output signal from the AND gate 14 is H, the transistor 405 is turned on and the switching transistor 18 is also turned on. Therefore, here, the relationship Ib (18) = Ie (405) (6) holds. In this case, the transistor 405
Since the base current is almost negligible compared to the emitter current, Ie (405) = Ic (405) (7)

On the other hand, since a current mirror circuit is formed by the transistors 403 and 404 and the resistors 401 and 402, Ic (405) = Ic (404). Therefore, as the current Ix flowing into and out of the terminal 34, Ix = Ic (404) = Ic (405) = Ie (405) = Ib (18), and a current substantially equal to the base current of the switching transistor 18 is output. Here, the relationship when the switching transistor 18 is turned on has been described for convenience. The output signals from the base current detector 40 and the base current detector 43 are directly connected and output to the terminal 34. However, since the switching transistors 18 and 16 do not turn on simultaneously, the current output to the terminal 34 Is
When the switching transistor 18 is on, a base current of the switching transistor 18 is output. When the switching transistor 16 is on, a base current of the switching transistor 16 is output. Also in the present embodiment, the resistor 31 and the operational amplifier 32 may be prepared in the base current detection units 40 and 43, respectively, as described in the first embodiment.

[0079] Then, to that operation of the control loop winding current I _L of the motor windings 20 by PWM generator 8 using the output current from the terminal 34 is controlled as described in the first embodiment of FIG. 1 The description is omitted because it is the same.

In this embodiment, the circuit configuration is simplified as compared with the first embodiment, and the current mirror circuit on the Vss side can be omitted, so that it is not necessary to prepare a negative power supply, and the external power supply circuit is also simplified. Is done.

(Third Embodiment) Next, a third embodiment of the present invention will be described.

FIG. 3 is a circuit diagram of a motor control circuit according to a third embodiment of the present invention. The same components as those of the conventional motor control circuit in FIG. 4 are denoted by the same reference numerals.

The motor control circuit of this embodiment is different from the conventional motor control circuit of FIG.
53 are provided.

The base current detector 50 is provided with the AND gate 1
4 and a base of the switching transistor 18, the circuit has a circuit configuration that detects the base current of the switching transistor 18 and draws a current having the same current value as the base current.

Similarly, the base current detecting section 53 is provided between the AND gate 13 and the base of the switching transistor 16, detects the base current of the switching transistor 16, and outputs a current having the same current value as the base current. It has a circuit configuration that pulls in.

The base current detector 50 includes resistors 501, 5
02, transistors 503 and 504, transistors 505, 506 and 507, and resistors 508 and 509.

The transistor 503 has an emitter connected to the resistor 5
01 is a pnp transistor connected to the power supply voltage Vcc via a base 01 and having a base and a collector connected to each other.

The transistor 504 has a resistor 5
02 is a pnp transistor connected to the power supply voltage Vcc via O2 and having a base connected to the base of the transistor 503.

Here, the resistors 501 and 502 have the same resistance value, and the transistors 503 and 504 are transistors having the same characteristics. A current mirror circuit is formed by these elements.

The transistor 505 has an npn base connected to the output signal of the AND gate 14, a collector connected to the collector of the transistor 503, and an emitter connected to the base of the switching transistor 18.
The transistor is turned on when the output signal from the AND gate 14 becomes H, and the switching transistor 18 is turned on.

The transistor 506 is an npn transistor whose collector is connected to the collector of the transistor 504, whose base and collector are connected, and whose emitter is connected to the minus power supply Vss via the resistor 508.

The transistor 507 is an npn transistor whose base is connected to the base of the transistor 506, whose collector is connected to the emitter of the switching transistor 18, and whose emitter is connected via the resistor 509 to the negative power supply Vss.

Here, the transistors 507 and 506 are
Each of the transistors has uniform characteristics and has a resistance of 50
Reference numerals 9 and 508 denote resistors having the same resistance value, and a current mirror circuit is formed by these elements.

The base current detecting section 53 includes a resistor 51
1, 512, transistors 513, 514, transistors 515, 516, 517, resistors 518, 519
Since the configuration is the same as that of the base current detection unit 50, the description of the configuration is omitted.

Next, the operation of this embodiment will be described with reference to FIG.

First, the operation of the base current detectors 50 and 53 will be described.

In the base current detecting section 50, since a current mirror circuit is formed by the transistors 501 and 502, Ic (505) = Ic (504). Further, since a current mirror circuit is also configured by the transistors 507 and 506, Ic (504) = Ic (507).

In the base current detecting section 53, since a current mirror circuit is formed by the transistors 513 and 514, Ic (515) = Ic (513), and the transistors 516 and 517 form a current mirror circuit. Therefore, Ic (513) = Ic (517).

As in the first and second embodiments, since the base currents of the transistors 505 and 515 are small and can be ignored, Ib (18) = Ie (505) = Ic (505) Ib (16) = Ie (515) = Ic (515) From these relationships, the relationship Ib (18) = Ic (507) Ib (16) = Ic (517) is derived.

Since the emitter of the switching transistor 18 is connected to the collector of the transistor 507 and the emitter of the switching transistor 16 is connected to the collector of the transistor 517, the current Is output to the terminal 38 is connected. Is Becomes The combination in which the transistors are actually turned on at the same time is the switching transistor 18 and the transistor 15 or the switching transistor 16 and the transistor 17.
Since 6,18 never turned on at the same time, the current Is becomes winding current I _L itself flowing through the motor windings 20.

Then, using the output current Is from the terminal 38, the PWM oscillator 8 uses the winding current I
The operation of the control loop in which _L is controlled is the same as that described in the conventional motor control circuit of FIG.

In this embodiment, since the base current can be subtracted from the emitter currents output from the switching transistors 16 and 18 by the base current detectors 50 and 53, an operational amplifier for generating a difference voltage is omitted. And the number of current detection resistors can be reduced from two to one.

In the first to third embodiments, the present invention is applied to the motor control circuit of the bipolar drive system. However, the present invention is not limited to this. The present invention can be applied to a so-called unipolar drive type motor control circuit in which current flows only in one direction. For example, the simplest example is a motor control circuit in which one terminal of a motor winding is directly connected to a power supply (ground) and a switching transistor is provided between the other terminal and the ground (power supply). Can also be applied. Further, in this case, if a pulse signal is input to the base of this switching transistor via the base current detector as described in the first to third embodiments, the same as in the above-described embodiment. The current control of the motor winding can be performed by subtracting the influence of the base current.

[0104]

As described above, according to the present invention, the current value of the base current flowing through the switching transistor is detected, and the effect of the current value is subtracted to make the current value of the winding current constant. Since such control is performed, it is possible to control the winding current without being affected by the fluctuation of the base current due to the temperature or the element variation, and to obtain an effect that a stable rotation operation of the motor can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor control circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a motor control circuit according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a motor control circuit according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional motor control circuit.

[Explanation of symbols]

 Reference numerals 11 to 14 AND gate 15 to 18 switching transistor 19 motor drive power supply terminal 20 motor winding 21 to 24 flywheel diode 25 current detection resistor 26 comparison reference voltage source 27 comparator 28 PWM oscillator 30 base current detection unit 31 current detection resistor REFERENCE SIGNS LIST 32 operational amplifier 33 base current detecting unit 34 terminal 38 terminal 40 base current detecting unit 43 base current detecting unit 50 base current detecting unit 53 base current detecting unit 301, 302 resistor 303, 304, 305 transistor 306 resistor 307 to 309 transistor 310 to 312 Resistance 401, 402 Resistance 403, 404, 405 Transistor 501, 502 Resistance 503 to 507 Transistor 508, 509 Resistance 511, 512 Resistance 513, 514, 515 Transistor 516, 517 npn transistor 518, 519 resistor

Claims (15)

[Claims] 1. A motor control circuit, comprising: an H-bridge circuit including four switching transistors each having a pulse signal input to a base, wherein the H-bridge circuit controls a current flowing through a motor winding. A first circuit provided between the bridge circuit and the ground
A current detection resistor provided between the base of each of the two switching transistors provided between the first current detection resistor and the motor winding and a circuit that outputs the pulse signal. A base current detection unit that outputs a current having substantially the same current value as the base current of each switching transistor; one end connected to ground, having a resistance value substantially equal to the first current detection resistor; A second current detection resistor through which a current output from each of the base current detection units passes; a voltage generated by the first current detection resistor; and a voltage generated by the second current detection resistor. An operational amplifier that outputs a differential voltage; a comparator that compares the differential voltage output from the operational amplifier with a voltage value of a comparison reference voltage having a predetermined voltage value; Motor control circuit, characterized in that is composed of a current control means for controlling the pulse width of each pulse signal based on the output signal from the. 2. A transistor for supplying a base current of the switching transistor connected to each of the base current detectors; a first current source for outputting a current equivalent to a collector current of the transistor; The second current source that outputs a current equivalent to the emitter current of the transistor, wherein the output is a difference between the output of the first current source and the output of the second current source. Motor control circuit. 3. Each of the base current detectors comprises: a transistor for supplying a base current of the connected switching transistor; and a current source for outputting a current equivalent to a collector current of the transistor. 2. The motor control circuit according to claim 1, wherein an output of the current source is output. 4. A motor control circuit, comprising: an H-bridge circuit including four switching transistors each having a pulse signal input to a base, wherein the H-bridge circuit controls a current flowing through a motor winding. A current detection resistor provided between a bridge circuit and ground, a circuit for outputting the pulse signal and a base of each of the two switching transistors provided between the current detection resistor and the motor winding; And a base current detection unit that outputs a current having substantially the same current value as the base current of each switching transistor so as to pass through the current detection resistor; and a voltage generated by the current detection resistor. And a comparator that compares a voltage value of a comparison reference voltage having a predetermined voltage value with the comparator. Motor control circuit, characterized in that is composed of a current control means for controlling the pulse width of each pulse signal based on the output signal of the. 5. A transistor, wherein each of the base current detectors supplies a base current of the connected switching transistor; a first current source that outputs a current equivalent to a collector current of the transistor; 5. The motor control circuit according to claim 4, further comprising a second current source that inputs a current equivalent to a current output from the first current source from an emitter of the switching transistor. 6. A motor control circuit comprising a switching transistor having a base to which a pulse signal is input, and controlling a current flowing through a motor winding by the switching transistor, wherein the motor control circuit is provided between the switching transistor and ground. And a base current that is provided between the base of the switching transistor and a circuit that outputs the pulse signal, and that outputs a current having substantially the same current value as the base current of the switching transistor. A second current detection resistor, one end of which is connected to ground, has a resistance value substantially the same as the first current detection resistor, and through which the current output from each of the base current detection units passes; A voltage generated by the first current detection resistor and a voltage generated by the second current detection resistor. An operational amplifier that outputs a voltage difference between the operational amplifier and a comparator that compares the differential voltage output from the operational amplifier with a voltage value of a comparison reference voltage having a predetermined voltage value. A motor control circuit, comprising: current control means for controlling a pulse width of a signal. 7. Each of the base current detectors includes: a transistor that supplies a base current of the switching transistor; a first current source that outputs a current equivalent to a collector current of the transistor; and an emitter current of the transistor. 7. The motor control circuit according to claim 6, further comprising: a second current source that outputs a current equivalent to the output of the first current source and an output of a difference between an output of the first current source and an output of the second current source. 8. Each of the base current detectors comprises: a transistor for supplying a base current of the switching transistor; and a current source for outputting a current equivalent to a collector current of the transistor. 7. The motor control circuit according to claim 6, wherein the output is obtained by: 9. A motor control circuit, comprising: a switching transistor having a base to which a pulse signal is input, wherein the switching transistor controls a current flowing through a motor winding, wherein the motor control circuit is provided between the switching transistor and a ground. A current detection resistor provided between the base of the switching transistor and the circuit that outputs the pulse signal, and passes a current having substantially the same current value as the base current of the switching transistor through the current detection resistor. And a comparator that compares a voltage generated by the current detection resistor with a voltage value of a comparison reference voltage having a predetermined voltage value, based on an output signal from the comparator. Current control means for controlling the pulse width of the pulse signal. Motor control circuit, characterized in that there. 10. Each of the base current detection units includes: a transistor that supplies a base current of the switching transistor; a first current source that outputs a current equivalent to a collector current of the transistor; 10. The motor control circuit according to claim 9, further comprising a second current source that inputs a current equivalent to the current output from the source from the emitter of the switching transistor connected thereto. 11. A motor control circuit including a switching transistor having a base to which a pulse signal is input, and controlling a current flowing through a motor winding by the switching transistor, wherein the motor control circuit is provided between the switching transistor and a power supply. And a base current that is provided between the base of the switching transistor and a circuit that outputs the pulse signal, and that outputs a current having substantially the same current value as the base current of the switching transistor. A second current detection resistor, one end of which is connected to a power supply, having a resistance value substantially the same as the first current detection resistor, and through which the current output from each of the base current detection units passes; A voltage generated by the first current detection resistor and a voltage generated by the second current detection resistor; An operational amplifier that outputs a voltage, a comparator that compares a difference voltage output from the operational amplifier with a voltage value of a comparison reference voltage having a predetermined voltage value, and a pulse of each of the pulse signals based on an output signal from the comparator. A motor control circuit, comprising: a current control means for controlling a width. 12. Each of the base current detectors includes: a transistor that supplies a base current of the switching transistor; a first current source that outputs a current equivalent to a collector current of the transistor; and an emitter current of the transistor. The motor control circuit according to claim 11, further comprising a second current source that outputs a current equivalent to the first current source, and using the difference between the output of the first current source and the output of the second current source as an output. 13. Each of the base current detectors comprises: a transistor for supplying a base current of the switching transistor; and a current source for outputting a current equivalent to a collector current of the transistor. The motor control circuit according to claim 11, wherein the output is obtained by: 14. A motor control circuit comprising a switching transistor having a base to which a pulse signal is input, and controlling a current flowing through a motor winding by the switching transistor, wherein the motor control circuit is provided between the switching transistor and a power supply. A current detection resistor provided between the base of the switching transistor and the circuit that outputs the pulse signal, and passes a current having substantially the same current value as the base current of the switching transistor through the current detection resistor. And a comparator that compares a voltage generated by the current detection resistor with a voltage value of a comparison reference voltage having a predetermined voltage value, based on an output signal from the comparator. Current control means for controlling the pulse width of the pulse signal. Motor control circuit according to claim Rukoto. 15. Each of the base current detectors includes: a transistor that supplies a base current of the switching transistor; a first current source that outputs a current equivalent to a collector current of the transistor; 15. The motor control circuit according to claim 14, further comprising: a second current source that inputs a current equivalent to a current output from the source from an emitter of the switching transistor connected thereto.