JPH0522989A - Motor driving circuit - Google Patents

Abstract

PURPOSE:To provide a motor driving circuit which can make smooth rotation with no timing of interrupting a motor coil current at the time of switching an output. CONSTITUTION:A base current is supplied to inlow side transistors 4, 2 by the first current mirror circuits 101, 102, and the second current mirror circuits 201, 202 are connected to bases of outflow side transistors 1, 3 to absorb leak currents of PNP transistors 5, 6 by the second current mirror circuits 201, 202.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit, and more particularly to a motor drive circuit having improved operating characteristics.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram of a conventional two-phase motor drive circuit. In the figure, A and B are output terminals to which an armature coil L of the motor is connected. And output terminal A,
Outflow side output transistors 1 and 3 and inflow side output transistors 2 and 4 are connected to B, and current mirror circuits 102 and 101 are connected to the inflow side output transistors 2 and 4, respectively. Further, i ₁ and i ₂ are input to the current mirror circuits 101 and 102, and output transistors 4 and
2 is a bias current for controlling 2. Reference numerals 5 and 6 are PNP transistors (pre-driver circuits) for supplying a base current to the output side output transistors 1 and 3.
The current mirror circuits 102 and 10 are provided on the respective bases.
The collectors of the transistors 9 and 8 constituting the circuit 1 are connected to each other, and the leak current cutting resistors 12 and 11 are connected between the respective bases and emitters. For example, when a small leak current flows through the transistor 8 of the current mirror circuit 101 while the transistors 1 and 2 are turned on, the transistor 6 tries to turn on, but the resistor 11 inserted between the base and the emitter thereof is used. Therefore, the transistor 3 is prevented, and at the same time, the transistor 3 is prevented from being turned on and is prevented from malfunctioning.

Next, the operation will be described. FIG. 4 is an operation timing chart of the circuit shown in FIG. 3. In the figure, it is assumed that the bias currents i ₁ and i ₂ are 180 degrees out of phase with each other, and there is no timing of simultaneous energization and simultaneous interruption. Figure 4
At timing t ₁ , when the bias current i ₁ flows, the output inflow side transistor 4 connected to the output terminal A is turned on. When the bias current i ₁ flows, the transistors 6 and 8 of the current mirror circuit 101 try to turn on the transistor 6, but the leak cut resistor 11 connected between the emitter and the base of the transistor 6 causes the transistor 6 and the output to be output. The timing t _{2 at} which the outflow side output transistor 3 connected between the terminals B is turned on is delayed from the timing t _{1 at} which the inflow side output transistor 4 is turned on. During this timing t ₁ to t ₂ , the power supply to the motor coil L is cut off.

Further, when the outflow side output transistor 3 is turned on at the timing t ₂ , the output terminal B becomes "H" potential,
A motor drive current flows from the terminal B to the terminal A in the motor coil L.

Next, the case where the bias current i ₁ decreases will be described. The transistor 4 turns off at the timing t _{4 when} i ₁ = 0, whereas the transistor 3 turns off because of the leak cut resistance 11.
It is turned off at the timing t ₃ before the operation. During the period from the timing t ₃ to t ₄ , the power supply to the motor coil L is cut off.

Similarly, in the outflow side transistor 1 and the inflow side transistor 2, even when the bias current i ₂ is switched, a current is supplied to the motor coil L by the leak cut resistor 12 connected between the emitter and the base of the transistor 5. There is a timing that does not flow.

[0007]

The conventional motor drive circuit is constructed as described above, and is connected between the emitter and base of the PNP transistors 5 and 6 which supply the base current to the output side output transistors 1 and 3. Due to the leak cut resistors 11 and 12, the timings at which the transistors 4 and 3 or the transistors 2 and 1 are turned on and off are deviated, and the motor coil L is de-energized during that time, which impairs smooth motor rotation. There was a problem.

The present invention has been made in order to solve the above-mentioned problems, and does not cause a malfunction due to leakage, and shifts the ON / OFF timing of the outflow side transistor and the inflow side transistor at the time of output switching. It is an object of the present invention to provide a motor drive circuit that is capable of obtaining smooth motor rotation.

[0009]

A motor drive circuit according to the present invention comprises a carrier discharge circuit for discharging carriers in the base region of a transistor that drives a power supply side transistor of a series circuit.

[0010]

According to the present invention, the leak cut resistor which causes the operation timing difference between the outflow side transistor and the inflow side transistor when the output is switched is eliminated, and the carrier in the base region of the transistor that drives the power supply side transistor of the series circuit is eliminated. Since the carrier discharging circuit for discharging the motor is provided, when the output is switched, there is no timing for shutting off the motor coil current, the motor rotates smoothly, and no malfunction occurs due to leakage.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the same reference numerals as those in FIG. 3 indicate the same or corresponding portions, and 201 and 202 are second current mirror circuits (carrier discharging circuits) which are current mirror circuits for cutting the leak currents of the transistors 5 and 6.

Next, the operation will be described. FIG. 2 is an operation timing chart thereof, and it is assumed that the bias currents i ₁ and i ₂ have a phase difference of 180 degrees as in the conventional case, and there is no timing of simultaneous energization and simultaneous interruption. Timing t ₁
When the bias current i ₁ flows in, the inflow side output transistor 4 connected to the output terminal A is turned on, and at the same time, the transistor 6 and the outflow side transistor 3 are turned on simultaneously through the transistors 7 and 8 of the current mirror circuit 101. In addition, the inflow side transistor 4 and the outflow side transistor 3 are simultaneously turned off at the timing t ₄ when the bias current i ₁ becomes zero from the bias state.

Even when the bias current i ₂ is biased, the outflow side transistor 2 and the inflow side transistor 1
The ON and OFF operation timings are also simultaneously performed.

Further, the bias current i ₁ is biased,
Even if a leak current flows between the emitter and collector of the PNP transistor 5 when the outflow side transistor 4 and the inflow side transistor 3 are turned on, the leak current is extracted by the bias current i ₃ of the second current mirror circuit 201, and the leak current is generated. Since it is cut, it is possible to prevent a shoot-through current due to the outflow side transistor 4 and the inflow side transistor 3 being turned on at the same time. Similarly, when the bias current i ₂ is biased, the leak current due to the outflow side transistor 2 and the inflow side transistor 1 being turned on at the same time is also cut by the bias current i ₄ of the second current mirror circuit 202.

As described above, according to this embodiment, the first current mirror circuits 101, 1 are provided to the inflow side transistors 4, 2.
The base current is supplied at 02, and the outflow side transistors 1 and 3
When the second current mirror circuits 201 and 202 are connected to the base of the transistor 6 and the transistors 1 and 2 (3 and 4) are turned on, the current flows between the emitter and collector of the transistor 6 (5) and the transistor 3 (1 The current toward the base of) is extracted by the second current mirror circuit 202 (201). Therefore, when the output is switched, the motor coil current is not interrupted, the motor rotates smoothly, and malfunctions due to leakage occur. Does not occur.

[0016]

As described above, according to the motor drive circuit of the present invention, the leak cut resistor which causes the shift of the operation timing of the outflow side transistor and the inflow side transistor at the time of switching the output is eliminated, and the series circuit is eliminated. Since a carrier discharge circuit that discharges carriers in the base region of the transistor that drives the power supply side transistor is provided, malfunction does not occur due to leakage, and the coil energization cutoff timing disappears when the output switches, and the motor rotates smoothly. The effect is that you can.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a motor drive circuit according to an embodiment of the present invention.

FIG. 2 is an operation timing chart of the motor drive circuit according to the embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a conventional motor drive circuit.

FIG. 4 is an operation timing chart of a conventional motor drive circuit.

[Explanation of symbols]

1, 3 Outflow-side output NPN transistor 2, 4 Inflow-side output NPN transistor 5, 6 PNP transistor (pre-driver circuit) 101 First current mirror circuit (driving current supply circuit) 102 First current mirror circuit (driving current supply) Circuit) 201 second current mirror circuit (carrier discharging circuit) 202 second current mirror circuit (carrier discharging circuit)

Claims (2)

[Claims] 1. A two-series circuit, which is inserted in parallel between a power supply and a ground and is formed by connecting two transistors in series, a pre-driver circuit including a transistor for driving a power-supply-side transistor of the series circuit, and the above-mentioned series circuit. Connection of the drive current supply circuit for supplying a drive current to the ground side transistor of the circuit and the pre-driver circuit, the carrier discharge circuit for discharging the carrier in the base region of the transistor forming the pre-driver circuit, and the transistor of the series circuit A motor drive circuit comprising a motor load connected between points. 2. The motor drive circuit according to claim 1, wherein the carrier discharge circuit is a current mirror circuit whose input terminal is connected to the base electrode of the power supply side transistor.