JPH044791A - Motor drive circuit - Google Patents

Abstract

PURPOSE:To reduce a cost by setting a base voltage for turning OFF a transistor to a value slightly lower than a threshold value voltage at an ambient temperature of the transistor. CONSTITUTION:When a voltage of a level H is applied to a normal rotation input terminal 13 and a voltage of a level L is applied to a reverse rotation input terminal 14, a transistor Q1 is turned ON, a transistor Q3 is turned OFF, a transistor Q2 is turned OFF, and a transistor Q4 is turned ON. When a voltage drop of a resistor R2 is VR2, a voltage between the collector and the emitter of the transistor Q1 is VCE1, a threshold voltage between the base and the emitter of the transistor Q2 is Vth2, the transistor Q2 is turned OFF by setting to satisfy Vth2>VR2+VCE1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a motor drive circuit constructed on a semiconductor integrated circuit, and more particularly to a motor drive circuit having protection functions against temperature and voltage.

[Prior Art] FIG. 3 shows a conventional general motor drive circuit with a protection function. In this circuit, a motor drive signal applied to an input terminal 1.2 is input to an output control circuit 3 and sent to an output circuit 4, and this output circuit 4 drives a motor 5. A signal indicating the load condition applied to the protection circuit 6 is taken in to the reference voltage circuit 7.
The voltage applied to the output circuit 4 is changed and the motor drive operation of the output circuit 4 is changed when the comparison result deviates from the predetermined range. It is designed to stop.

For example, if this entire circuit is configured on a single-chip semiconductor integrated circuit, if a motor lock occurs (a state in which the motor shaft is physically fixed), excessive current will flow and self-heating will occur, causing the temperature of the semiconductor integrated circuit to drop. A situation occurs in which the guaranteed temperature of the circuit is exceeded.

In such a case, the protection circuit 6 detects the increase in load due to the motor rotor and changes the input voltage of the output circuit 4.

[Problems to be Solved by the Invention] However, the circuit system shown in FIG. 3 requires the protection circuit 6 and the voltage reference circuit 7, but these do not perform any function other than the protection function, so the circuit becomes complicated. , there is a problem of high costs.

The present invention has been made in view of these points, and its purpose is to provide a protection function against temperature and voltage without requiring a special protection circuit, and which can be realized at low cost with a simple circuit. It is an object of the present invention to provide a motor drive circuit as described above.

[Means for Solving the Problems] In order to achieve the above object, the present invention consists of an output control circuit and an output circuit that drives a motor by a control signal from the output control circuit, and the entire structure excluding the motor is one unit. In a motor drive circuit configured on a semiconductor integrated circuit of a chip, a transistor is provided in the output control circuit, and a transistor is provided in the output control circuit, and a transistor is provided in the output control circuit, and the transistor is turned on to deactivate the motor and turned off to drive the motor. The threshold voltage was set slightly lower than the threshold voltage of the transistor at room temperature.

In the present invention, the base voltage can be generated by a resistor connected between a power supply and a collector-emitter voltage of another transistor.

[Examples] Examples of the present invention will be described below. FIG. 1 is a diagram showing a motor drive circuit of one embodiment. 11 is a power supply terminal, 12 is a ground terminal, 13 is a forward rotation input terminal, 14 is a reverse rotation input terminal, and 15 is a brake terminal. Further, resistors R1 to R3 and transistors Q1 and Q2 constitute a normal output control circuit A, and resistors R4 to R6 and transistors Q3 and Q
4 constitutes a reverse rotation output control circuit B. Further, transistors Q5 to Q10 constitute an H-bridge type output circuit C, and transistors Q11 and Q12 constitute a brake circuit.

Now, when a level H voltage is applied to the forward input terminal 13 and a level L voltage is applied to the reverse input terminal 14, the transistor Q1 is turned on and the transistor Q3 is turned off.
Transistor Q2 is turned off and transistor Q4 is turned on.

To turn off the transistor Q2, set the value of the resistor R2 appropriately, set the voltage drop across the resistor R2 as VR2, and set the voltage between the collector and emitter of the transistor Q1 as Vo, , , ,
If the threshold voltage between the base and emitter of transistor Q2 is Vth2, then "vth2>vR2+VcE□"
This is achieved by setting the following.

Here, if a level L voltage is applied to the brake terminal 15 in advance to turn off the transistors Q11 and Q12,
When the transistor Q2 is turned off, the transistor Q8 is turned on, and the transistors Q9 and Q10 are turned on. At this time, since transistor Q4 is on as described above, transistors Q5 to Q7 are off.

Therefore, current flows through the motor 5 in the direction indicated by arrow a.
The motor 5 rotates normally.

In the above operating conditions, the base of transistor Q2
The voltage V□,,2 applied between the emitters is the resistance R1, R
Letting the values of 2 be R1 and R2, respectively, it becomes .-(1). In general, the collector-emitter voltage VC of a transistor, ! has a positive temperature coefficient when the transistor is saturated, and the base-emitter threshold voltage vth has a negative temperature coefficient.

Therefore, as the temperature increases, the voltage V□2 in equation (1) increases, and the threshold value V th 2 of the transistor Q2 decreases. And the relationship is VBK2≧V! h
When the temperature becomes high enough to satisfy 2, the transistor Q2 is turned on and the transistor Q8 is turned off. As a result, the current to the motor 5 is cut off.

From the above, it can be seen that by utilizing this effect and adjusting the resistance value and the characteristics of the transistor, the normal output control circuit A can also function as a temperature protection circuit.

Furthermore, since equation (1) also includes the term of the power supply voltage VCC, the normal rotation output control circuit A also has a voltage protection function. In other words, the power supply voltage ■. When 0 becomes high, voltage VBE□
becomes high, so that VBE2≧V t h 2 is satisfied, transistor Q2 is turned on, and the protection function is activated.

The above is an explanation of the normal rotation output control circuit A, but
Exactly the same operation is performed for the reverse rotation output control circuit B, but a detailed explanation will be omitted.

Note that when the brake is applied, a voltage of level H is applied to the forward rotation input terminal 13, reverse rotation input terminal 14, and brake terminal 15, transistors Q5, Q8, Q6, and Q9 are turned on, transistors Q7 and QIO are turned off, and the motor 5 is turned off. is short-circuited by transistors Q6 and Q9, and dynamic braking is applied to rapidly stop the motor.

The above temperature/voltage protection functions all share output control elements in the forward output control circuit A and reverse output control circuit B, so the circuit configuration is very simple as shown in Figure 2. It will be easy.

[Effects of the Invention] As explained above, according to the present invention, a special circuit is not required as a protection circuit, so a motor drive circuit with a protection function can be realized at low cost without requiring a complicated circuit configuration. It has the advantage of being able to do this.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a motor drive circuit with a protection function according to an embodiment of the present invention, FIG. 2 is a block diagram thereof, and FIG. 3 is a block diagram of a conventional motor drive circuit with a protection function. 1.2...Input terminal, 3...Output control circuit, 4...
・Output, power circuit, 5...motor, 6...protection circuit, 7
...Reference voltage circuit, 11...Power terminal, 12...
Earth terminal, 13... Forward rotation input terminal, 14-... Reverse rotation input terminal, 15... Brake terminal, A... Forward rotation output control circuit, B... Reverse rotation output control circuit, C.-H Bridge type output circuit, D...Brake circuit. Agent Patent Attorney Tsuneaki Nagao Diagram 1 Circle B

Claims (2)

[Claims] (1). In a motor drive circuit that consists of an output control circuit and an output circuit that drives a motor using a control signal from the output control circuit, and is configured entirely on a single-chip semiconductor integrated circuit except for the motor, the above-mentioned The output control circuit is provided with a transistor that is driven by making the motor non-driven and turned off, and the base voltage for turning off the transistor is set slightly lower than the threshold voltage of the transistor at room temperature. Motor drive circuit. (2). 2. The motor drive circuit according to claim 1, wherein the base voltage is generated by a resistor connected between a power supply and a collector-emitter voltage of another transistor.