JPH05122988A - Motor driving circuit - Google Patents

Abstract

PURPOSE:To obtain a smooth rotation of a motor by cutting a leakage current of a P-N-P transistor at the time of a high temperature. CONSTITUTION:Leakage currents of P-N-P transistors 11, 12 opened at bases are amplified by transistors 13, 14, and leakage currents of transistors 5, 6 are cut. Since the transistors 13, 14 are turned OFF by transistors 19, 20 when the transistors 5, 6 are turned ON, the cutting of the leakage currents of the transistors 13, 14 does not affect influence to a normal operation.

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.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a conventional two-phase motor drive circuit. Output terminals A and B are connected to the armature coil 201 of the motor. 1, 2, 3, 4 are output transistors, 1, 3 are outflow side, 2, 4 are inflow side, i ₁ , i ₂
Is a control current for controlling the output transistor, 7, 8, 9,
10 is a transistor, 101, 103, 104, 106
Is a resistor, and transistors 7, 8 and resistors 101, 10
Reference numeral 3 forms a first current mirror circuit, and transistors 9 and 10 and resistors 104 and 106 form a second current mirror circuit. The transistor 5 is a pre-driver transistor that supplies a base current to the output transistor 1, and the transistor 6 is a resistor 10 that supplies a base current to the output transistor 3.
Reference numerals 7 and 108 denote resistors for cutting off the leak current of the transistors 5 and 6 at high temperature.

Next, the operation will be described. FIG. 5 shows an operation timing chart of the conventional circuit shown in FIG. In FIGS. 4 and 5, the bias currents i ₁ and i ₂ have a phase difference of 180 degrees, the current directions are only one direction from A to B and B to A, and there is no bidirectional interruption.

However, when the bias current i ₁ flows at t ₁ in the operation timing chart shown in FIG. 5, the transistor 6 is turned on by the first current mirror circuit composed of the transistors 7 and 8 and the resistors 101 and 103. However, the timing at which the transistor 6 and the output transistor 3 are turned on by the resistor 108 connected to cut off the leakage current of the transistor 6 at a high temperature is t ₂ , and the timing at which the transistor 4 is turned on t ₁
More late. Between t ₁ to t _2, the motor coil 2
The power supply to 01 is cut off. Further, when the transistor 3 is turned on at the timing of t ₂ , the output terminal B becomes the “Hi” potential, and the current flows through the coil 201 from the B terminal to the A terminal.

Next, the case where the bias current i ₁ is cut off will be described. The output transistor 4 is t when i ₁ is 0.
_While the output transistor 3 is turned off at the timing of ₄ , the output transistor 3 is turned off at the timing of t ₃ before the timing t _{4 at} which the output transistor 4 is turned off by the leak cut resistor 108. From t ₃ to t ₄ , the energization of the motorno coil 201 is cut off.

Similarly, when the bias current i ₂ is switched, the leak cut resistance 107 of the transistor 5 is also changed.
Therefore, there is a timing when no current flows in the coil 201 of the motor.

[0007]

In the conventional leak cut method at a high temperature, there is a difference in the timings at which the output transistors 4 and 3 or the transistors 2 and 1 are turned on and off, and during that time, the coil of the motor is energized. However, there is a problem in that the motor can be turned off at a certain timing and smooth motor rotation is impaired.

The present invention has been made in order to solve the above-mentioned problems, in which the ON / OFF timings of the output transistors 4 and 3, 2 and 1 at the time of output switching are made to coincide with each other to energize the coil. It is an object of the present invention to obtain a motor drive circuit that can obtain smooth motor rotation without being shut off.

[0009]

SUMMARY OF THE INVENTION A motor drive circuit according to the present invention includes a leak cut resistor 107, which causes a difference in ON / OFF timing of output transistors 4 and 3 or transistors 2 and 1 when switching outputs. 108 is deleted, and a circuit for cutting leak currents of the transistors 5 and 6 at high temperature is added.

[0010]

In the motor drive circuit according to the present invention, when the output is switched, the current flowing through the coil is not interrupted, so that the motor rotates smoothly.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a motor drive circuit according to the present invention. In the figure, 1 to 10 transistors, 101,
The resistors 103, 104 and 106 and the coil 201 are exactly the same as those in the conventional circuit.

Reference numerals 11 and 12 are base open PNP transistors, 13 and 14 are NPN transistors for amplifying leak currents of the base open PNP transistors 11 and 12, and 15 to 18 are diodes. 19, 20
Are transistors that perform switching operations in synchronization with the transistors 8 and 9, respectively, and 102 and 105 are resistors connected to the emitters of the transistors 19 and 20, respectively. The transistors 7 and 19 and the resistors 101 and 102 form a third current mirror. A circuit is formed, and the transistors 9 and 20 and the resistors 104 and 105 form a fourth current mirror circuit.

Next, the operation will be described. FIG. 1 shows a motor drive circuit according to the present invention, and FIG. 3 shows a timing chart in the motor drive circuit according to the present invention. As in the conventional circuit, the bias currents i ₁ and i ₂ are 180 degrees out of phase with each other, the direction of the current flowing through the coil 201 is only one direction from terminals A to B or terminals B to A, and there is no simultaneous energization. In principle, there is no simultaneous blocking in both directions.

When the bias current i ₁ flows at the timing of t ₁ shown in FIG. 3, the output transistor 4 is turned on. At the same time, the transistor 6 is turned on and the output transistor 3 is turned on via the first current mirror circuit composed of the transistors 7 and 8 and the resistors 101 and 103. Also,
Even at the timing of t ₄ when the bias current i ₁ is cut off, the output transistors 3 and 4 are turned off at the same time because the leak cut resistance is deleted.

_I which is 180 degrees out of phase with the bias current i ₁
The operation of i _{1 is} the same when ₂ flows and when it is cut off.

Here, regarding the leakage cut at the time of high temperature of the PNP transistors 5 and 6, the base open PN
Similar to the transistors 5 and 6, the P transistors 11 and 12 generate a leak current at high temperature. The leak current is NP
Amplified (hfe times) by N-transistors 13 and 14,
The leakage current of the transistors 5 and 6 is cut.

Since the transistor 19 operates in synchronization with the transistor 8, the transistor 13 is turned off when the transistor 5 is turned on, and similarly, the transistor 20 is turned on.
Operates in synchronization with the transistor 9, the transistor 14 is turned off when the transistor 6 is turned on, so that the base currents of the output transistors 1 and 3 are not cut off in the normal operation.

In this embodiment, the transistors 5 and 6 for supplying the base current are eliminated by eliminating the leakage / cutting resistor and using the amplifier circuit constituted by the NPN transistor.
Since the leakage current at high temperature is cut, the current flowing through the coil is not interrupted when the output is switched, and the motor rotates smoothly.

In the above embodiment, the leak currents of the base open PNP transistors 11 and 12 are amplified (hfe times) by the transistors 13 and 14.
As shown in the second embodiment of FIG. 2, transistors 21 and 1
Amplification may be performed by a current mirror circuit composed of 3 and transistors 22 and 14.

[0020]

As described above, according to the present invention, in the motor drive circuit, the leak cut which causes the timing difference of ON / OFF of the output transistors 4 and 3 or the transistors 2 and 1 at the time of switching the output. Resistor 107,
108 is deleted, and the transistor 5 is formed by an amplifier circuit composed of an NPN transistor or a current mirror circuit.
Since the leak current at the time of high temperature of 6 was cut,
Since there is no timing to cut off the coil energization when the output is switched, there is an effect that smooth motor rotation can be obtained.

[Brief description of drawings]

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

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

FIG. 3 is an operation timing chart of the first and second embodiments.

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

FIG. 5 is a conventional operation timing chart.

[Explanation of symbols]

 1-4 Output transistor 5-14 Transistor 19-22 Transistor 101-108 Resistance 15-18 Diode 201 Coil

Claims (3)

[Claims] 1. An output transistor configured as an H-bridge, four PNP transistors for supplying a base current to the outflow side of the output transistor, and an output transistor on the inflow side for controlling the PNP transistor. In a motor drive circuit including a first and a second current mirror circuit for driving, two base open PNP transistors, an amplifier circuit for amplifying a leak current of the base open PNP transistor, and the first A third current mirror circuit that operates in synchronization with the current mirror circuit of, and a fourth current mirror circuit that operates in synchronization with the second current mirror circuit.
With the current mirror circuit of, the output transistor is turned on and off when the output is switched.
A motor drive circuit characterized in that a leak current of the PNP transistor is cut by the amplifier circuit without causing a shift in timing of F. 2. The motor drive circuit according to claim 1, wherein the amplifier circuit is an NPN transistor. 3. The motor drive circuit according to claim 1, wherein the amplifier circuit is a current mirror circuit.