JP3437588B2 - Load drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high load drive circuit for driving a high load having a large current capacity, such as a motor or a solenoid mounted on a vehicle. 2. Description of the Related Art As is well known, a drive circuit for driving a large load having a large current capacity such as a motor mounted on a vehicle includes:
Drives a large current of several amps. In such a drive circuit that drives a large current, a current of several mA to several tens mA constantly flows even when the motor is stopped or in standby (hereinafter, referred to as standby). Therefore, since there is a possibility that a voltage of a battery mounted on the vehicle may be reduced, a relay is added to a power supply line of the drive circuit so that a current does not flow to the drive circuit when the motor is in a standby state. Power supply to the drive circuit was interrupted. [0003] However, in such a case, a relay is required separately from the drive circuit, and
In order to control this relay, a circuit for detecting a standby state of the motor and generating a control signal is separately required, so that the circuit configuration becomes complicated. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to cut off a current flowing during standby with a simple circuit configuration without requiring a dedicated circuit or signal separately. It is intended to provide a high-load drive circuit capable of performing such operations. [0005] The load drive circuit of the present invention.
The path is provided with a logic signal to solve the above problem,
A drive circuit for driving a load according to the logic signal;
The logic signal is supplied, and control is performed in accordance with the logic signal.
A logic circuit for outputting a control signal; and a battery for the drive circuit.
And the level of the control signal is
If the load indicates that it is in standby mode,
A constant voltage circuit for stopping power supply to the drive circuit,
It is characterized by having. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a case where the present invention is applied to a drive circuit for driving a motor mounted on a vehicle. In FIG. 1, input signals IN1 and IN2 are supplied to signal input terminals 11 and 12, respectively. These signal input terminals 11 and 12 are connected to input terminals of a control logic circuit 15 via buffer circuits 13 and 14. As shown in FIG. 2, the control logic circuit 15 generates a signal for setting the operating state of the motor in accordance with the logic level of the input signal. The output signal of the control logic circuit 15 is an output drive circuit. 1
6. The output drive circuit 16 generates a control signal of a transistor for driving a motor in accordance with an output signal of the control logic circuit 15, and the output signal of the output drive circuit 16 is
7, 18, 19 and 20 respectively.
The collectors of the transistors 17 and 18 are connected to a power supply terminal (V
cc) 21, and the emitters of these transistors 17 and 18 are connected to one end and the other end of the motor 22, respectively. The collectors of the transistors 19 and 20 are connected to one end and the other end of the motor 22, respectively. The emitters of these transistors 19 and 20 are connected to the ground terminal 23 together with the ground terminals of the control logic circuit 15 and the output drive circuit 16. A battery BT is connected to the power terminal 21 and the ground terminal 23. The output terminals of the buffer circuits 13 and 14 are connected to the input terminal of an OR circuit 24. The output terminal of the OR circuit 24 is connected to one input terminal of the constant voltage circuit 25. The other input terminal of the constant voltage circuit 25 is connected to the power terminal 21, and the output terminal is connected to the power terminals of the control logic circuit 15 and the output drive circuit 16. The constant voltage circuit 26 applies a constant voltage to the control logic circuit 15 and the output drive circuit 16 except when the input signals IN1 and IN2 are both at a low level (L) (standby mode, that is, a stop mode in which the output is high impedance). A voltage is supplied, and the supply of the constant voltage to the control logic circuit 15 and the output drive circuit 16 is stopped in the standby mode in which the input signals IN1 and IN2 are both at the low level. Therefore, the output signals of the control logic circuit 15 and the output drive circuit 16 are all turned off,
Control logic circuit 15, output drive circuit 1
6, transistors 17, 18, 19, 20, motor 22
No current flows through. FIG. 3 shows the buffer circuit 13,
14 shows an example of an OR circuit 24 and a constant voltage circuit 25, and the same parts are denoted by the same reference numerals. The signal input terminal 11 is connected to one end of a resistor 13a constituting the buffer circuit 13. This resistance 13
The other end of a is connected to the base of the transistor 13b and to the emitter of the transistor 13b via the resistor 13c. Further, the signal input terminal 12 is connected to one end of a resistor 14a constituting the buffer circuit 14. The other end of the resistor 14a is connected to the base of the transistor 14b and to the emitter of the transistor 14b via the resistor 14c. The collectors of these transistors 13b and 14b are diodes 31, 3
2 through the control logic circuit 15
Of the transistors 35 and 36 via resistors 33 and 34, respectively. These transistors 3
The emitters 5 and 36 are connected to the power supply terminal 21, and the second collectors are connected to the anodes of the diodes 24a and 24b constituting the OR circuit 24, respectively.
The cathodes of these diodes 24a and 24b are connected to the base of a transistor 25a constituting the constant voltage circuit 25. The collector of the transistor 25a is connected to the power supply terminal 21, the emitter is connected to the power supply terminals of the control logic circuit 15 and the output drive circuit 16, and the transistor 25a is connected via a resistor 25b.
Connected to the base. The base of the transistor 25a is connected to the ground terminal 23 via a Zener diode 25c. In the above configuration, the input signals IN1, IN
When at least one of the transistors 2 is at a high level, at least one of the transistors 13b and 14b of the buffer circuits 13 and 14 conducts. The control logic circuit 15 operates as described above according to the conduction state of the transistors 13b and 14b. At this time, at least one of the transistors 35 and 36 is turned on, so that at least one of the diodes 24a and 24b forming the OR circuit 25 is turned on, and the Zener diode 25c forming the constant voltage circuit 25 is biased. Therefore, a constant current corresponding to the output voltage of the Zener diode 25c is output from the emitter of the transistor 25a constituting the constant voltage circuit 25.
And output drive circuit 16. On the other hand, when both of the input signals IN1 and IN2 are at the low level, the transistors 13b and 14b of the buffer circuits 13 and 14 are all turned off. Therefore, the input terminal of the control logic circuit 15 becomes high impedance, and the output logic becomes the standby mode. At this time, since the transistors 35 and 36 are both non-conductive, the diodes 24a and 24b constituting the OR circuit 25 are both non-conductive. Therefore, power is not supplied to control logic circuit 15 and output drive circuit 16 because Zener diode 25c and transistor 25a are turned off. According to the above embodiment, the logical level of the input signal is detected by the OR circuit 25, and when the output of the OR circuit 25 is at the low level, that is, in the standby mode, the operation of the constant voltage circuit 25 is stopped. Then, the power supply to the control logic circuit 15 and the output drive circuit 16 is stopped. Therefore, in the standby mode, no current flows through the control logic circuit 15 and the output drive circuit 16, so that the battery B
T voltage drop can be prevented. In the standby mode, the OR circuit 25
The operation of the transistor 25a forming the constant voltage circuit 25 is controlled by the output signal of the OR circuit 25, so that the battery BT has a simpler configuration than the conventional one. Voltage drop can be prevented. Although the above embodiment has been described with reference to the case where the present invention is applied to a motor, the present invention is not limited to this. For example, the present invention can be applied to a high load such as a solenoid. In the above embodiment, the logic of the input signal is detected by the OR circuit. However, the present invention is not limited to this, and a circuit corresponding to the logic set in the control logic circuit may be used. In addition, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the invention. As described in detail above, according to the present invention,
It is possible to provide a high-load drive circuit that does not require a dedicated circuit or a signal, can cut off the current flowing during standby with a simple circuit configuration, and can prevent a decrease in battery capacity.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing the logic of an input signal of the circuit shown in FIG. FIG. 3 is a circuit diagram specifically showing the circuit shown in FIG. 1; [Description of References] 15: control logic circuit, 16: output drive circuit, 22: motor, 24: OR circuit, 25: constant voltage circuit, IN1, IN2: input signal, BT: battery.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H02P 5/00-5/26 H02P 7/00-7/34 H02P 3/08

Claims (1)

(57) Patent Claims 1. A logic signal is supplied, a drive circuit for driving a load and response to the logic signal, the logic signal is supplied, out of and corresponding to the logic signal
A logic circuit for outputting a force signal ; and supplying power from a battery to the drive circuit; and
A constant voltage circuit for stopping power supply to the drive circuit when an output signal of a logic circuit is supplied and the logic signal indicates that the load is in a standby mode. And load drive circuit.