JP3064327B2 - Motor drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive circuit formed on a semiconductor integrated circuit, and more particularly to a motor drive circuit having a temperature and voltage protection function.

[Prior Art] FIG. 3 shows a conventional general motor drive circuit with a protection function. In this circuit, a motor drive signal applied to input terminals 1 and 2 is input to an output control circuit 3 and sent to an output circuit 4 so that the output circuit 4 drives a motor 5. Is applied to the protection circuit 6 and compared with a reference voltage input from the reference voltage circuit 7 corresponding to a preset proper load state. The comparison result deviates from a predetermined range. In such a case, the voltage applied to the output circuit 4 is changed to stop the motor driving operation of the output circuit 4.

For example, when the entire circuit is configured on a one-chip semiconductor integrated circuit, when a motor lock (a state in which the motor shaft is physically fixed) occurs, an excessive current flows and self-heating occurs, and the temperature is reduced. A situation occurs where the temperature exceeds the guaranteed temperature of the circuit.

In such a case, the protection circuit 6 detects an increase in load due to the motor lock 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 circuits do not perform any function other than the protection function. There is a problem that the cost is increased.

The present invention has been made in view of such a point,
An object of the present invention is to provide a motor drive circuit which has a protection function against temperature and voltage but does not require a special protection circuit, and can be realized with a simple circuit at low cost.

[Means for Solving the Problems] To achieve the above object, a first aspect of the present invention is an H-bridge type output circuit for supplying a forward rotation current or a reverse rotation current to a motor,
A forward rotation output control circuit for controlling so that the forward rotation current flows from the H-bridge type output circuit to the motor by setting the voltage of the forward rotation input terminal to a high level and the forward rotation current is cut off by setting the voltage to a low level. And a reverse output control circuit that controls so that the reverse current flows from the H-bridge type output circuit to the motor by setting the voltage of the reverse input terminal to high level and the reverse current is cut off by setting the voltage to low level. A motor drive circuit comprising the H-bridge type output circuit, the forward rotation output control circuit, and the reverse rotation output control circuit on a one-chip semiconductor integrated circuit, wherein the forward rotation output control circuit has one end. A first resistor connected to the power supply, a second resistor having one end connected to the other end of the first resistor, a third resistor having one end connected to the power supply, A first transistor having a base connected to the non-inverting input terminal, an emitter grounded, and a collector connected to the other end of the second resistor, and a base connected to a common connection point of the first and second resistors; A second transistor having a grounded emitter and a collector connected to the other end of the third resistor, and the collector voltage of the second transistor being at a high level, whereby the H-bridge type output circuit is provided. A forward rotation current flows through the motor, the reverse rotation output control circuit includes a fourth resistor having one end connected to a power supply, a fifth resistor having one end connected to the other end of the fourth resistor, A sixth resistor having one end connected to a power supply, a third transistor having a base connected to the inverted input terminal and an emitter grounded, a collector connected to the other end of the fifth resistor, and 4th A fourth transistor connected to a common connection point of the fifth and fifth resistors, having an emitter grounded, and a collector connected to the other end of the sixth resistor, and the collector voltage of the fourth transistor is at a high level. As a result, a reverse rotation current flows from the H-bridge type output circuit to the motor, and the threshold voltage of the second transistor is V _th2 ,
Assuming that the voltage generated at the second resistor is V _R2 and the voltage between the collector and the emitter when the first transistor is conductive is V _CE1 , {V _th2 > V _R2 + V _CE1 } at room temperature and steady power supply voltage.
When the first transistor is conducting, the second transistor is turned off, and when the temperature rises above a predetermined value or the power supply voltage rises above a predetermined value, {V _th2 <V _R2 + V _CE1 }
When the first transistor is on, the second transistor is on, the threshold voltage of the fourth transistor is V _th4 , the voltage generated at the fifth resistor is V _R5 , when the collector-emitter voltage during conduction of the third transistor and V _CE3, a fourth when the third transistor is in normal temperature and normal supply voltage _{{V th4> V R5 + V} CE3} is conducting When the transistor shuts off and the temperature rises above a predetermined value or the power supply voltage rises above a predetermined value, {V _th4 <V _R5 + V _CE3 } holds, and the fourth transistor becomes conductive when the third transistor is conductive. It was configured to be.

[Example] Hereinafter, an example of the present invention will be described. FIG. 1 is a diagram showing a motor drive circuit according to one embodiment. 11 is a power supply terminal, 12 is a ground terminal, 13 is a forward input terminal, 14 is a reverse input terminal, and 15 is a brake terminal. The resistors R1 to R3 and the transistors Q1 and Q2 constitute a non-inversion output control circuit A, and the resistors R4 to R6 and the transistors Q3 and Q4 constitute a reverse output control circuit B. Further, the transistors Q5 to Q10 constitute an H-bridge type output circuit C, and the transistors Q11 and Q12 constitute a brake circuit D.

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 turns on, the transistor Q3 turns off, the transistor Q2 turns off, and the transistor Q4 turns on. Turn on.

When the transistor Q2 is turned off, the value of the resistor R2 is appropriately set, and the voltage drop at the resistor R2 is set to V _R2 and the transistor Q
The collector-emitter voltage of 1 is V _CE1 , transistor Q2
_Assuming that the threshold voltage above the base / emitter is V _th2 , this is realized by setting “V _th2 > V _R2 + V _CE1 ”.

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

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

In the above operating state, the base of transistor Q2
The voltage V _BE2 applied between the emitters is given assuming that the values of the resistors R1 and R2 are R1 and R2, respectively. Becomes Generally, the collector-emitter voltage V _CE of a transistor has a positive temperature coefficient when the transistor is in a saturated state, and the base-emitter threshold voltage V _CE
th has a negative temperature coefficient.

Therefore, when the temperature rises, the voltage V _BE2 in equation (1) increases, and the threshold value V _{th2 of the} transistor Q2 decreases. When the temperature rises to the extent that the relationship satisfies V _BE2 ≧ V _th2 , the transistor Q2 turns on and the transistor Q2 turns on.
Q8 turns off. As a result, the current to the motor 5 is cut off.

From the above, it is understood that the normal output control circuit A can also function as a temperature protection circuit by adjusting the resistance value and the characteristics of the transistor by using this action.

Since the equation (1) also includes the term of the power supply voltage V _CC , the normal output control circuit A also has a voltage protection function. That is, when the power supply voltage V _CC increases, the voltage V _BE2 increases, so that V _BE2 ≧ V _th2 is satisfied, and the transistor Q2 is turned on to perform the protection function.

The above is the description of the normal rotation output control circuit A. The same operation is performed for the reverse rotation output control circuit B, but the detailed description is omitted.

When a brake is applied, a voltage of level H is applied to the forward input terminal 13, the reverse input terminal 14, and the brake terminal 15, and the transistors Q5, Q8, Q6, and Q9 are turned on, and the transistors Q7 and Q10 are turned off. Motor 5 has transistors Q6 and Q
Short circuit occurs due to 9 and the power generation moves and stops quickly.

All of the above temperature / voltage protection functions also serve as output control elements in the forward rotation output control circuit A and the reverse rotation output control circuit B. Therefore, as shown in FIG. It's easy.

[Effects of the Invention] As described above, according to the present invention, since a special circuit is not required as a protection circuit, a complicated circuit configuration is not required, and a motor drive circuit with a protection function can be realized at low cost. There is an advantage that can be.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a motor drive circuit with a protection function according to one 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 circuit, 5 ... motor, 6 ... protection circuit, 7 ... reference voltage circuit, 11 ... power supply terminal, 12 ... earth terminal , 13: forward input terminal, 14: reverse input terminal, 15: brake terminal,
A: forward output control circuit, B: reverse output control circuit, C
…… H-bridge type output circuit, D …… Brake circuit.

Claims (1)

(57) [Claims] An H-bridge type output circuit for supplying a forward rotation current or a reverse rotation current to a motor, and the forward rotation current is supplied from the H-bridge type output circuit to the motor by setting the voltage of a forward rotation input terminal to a high level. A forward rotation output control circuit for controlling the forward rotation current to be cut off by setting the flow low level, and a reverse rotation current to the motor from the H-bridge type output circuit by setting the voltage of the reverse rotation input terminal to a high level. A reverse output control circuit that controls the reverse current to be cut off by setting the flow to a low level,
A motor drive circuit in which the H-bridge type output circuit, the forward rotation output control circuit, and the reverse rotation output control circuit are formed on a one-chip semiconductor integrated circuit, wherein the forward rotation output control circuit has one end connected to a power supply The first
And a second resistor having one end connected to the other end of the first resistor.
A third resistor having one end connected to a power supply, a first transistor having a base connected to the non-inverting input terminal, an emitter grounded, and a collector connected to the other end of the second resistor. , A base connected to a common connection point of the first and second resistors, an emitter grounded, and a collector connected to the third resistor.
A second transistor connected to the other end of the resistor, and a forward rotation current flows from the H-bridge type output circuit to the motor when the collector voltage of the second transistor becomes a high level; A reverse output control circuit is connected to a fourth terminal having one end connected to a power supply.
And a fifth resistor having one end connected to the other end of the fourth resistor.
A sixth resistor having one end connected to a power supply, a third transistor having a base connected to the inverting input terminal, an emitter grounded, and a collector connected to the other end of the fifth resistor. A base is connected to a common connection point of the fourth and fifth resistors, an emitter is grounded, and a collector is connected to the sixth and fifth resistors.
A fourth transistor connected to the other end of the resistor, and a reverse current flows from the H-bridge type output circuit to the motor when the collector voltage of the fourth transistor becomes a high level; and When the threshold voltage of the second transistor is V _th2 , the voltage generated at the second resistor is V _R2 , and the collector-emitter voltage when the first transistor is conductive is V _CE1 , the temperature is normal and steady. When the power supply voltage becomes {V _th2 > V _R2 + V _CE1 } and the first transistor is on, the second transistor is turned off and the temperature rises above a predetermined value or the power supply voltage rises above a predetermined value. When {V _th2 <V _R2 + V _CE1 } and the first transistor is conducting, the second transistor is conducting. The threshold voltage of the fourth transistor is V _th4 , and the fifth resistor is connected to the fifth resistor. Occur The voltage V _R5, when the collector-emitter voltage during conduction of said third transistor and V _CE3, the third transistor is turned on is at normal temperature and normal supply voltage _{{V th4> V R5 + V} CE3} When the fourth transistor is turned off, when the temperature rises above a predetermined value or the power supply voltage rises above a predetermined value, {V _th4 <V _R5 + V _CE3 } is established and the third transistor is turned on. Wherein the fourth transistor is configured to conduct at the time.