Motor Control Circuit

Abstract

To provide a technique for inexpensively suppressing overcurrent that flows in a motor control circuit because of short circuit of a power supply.SOLUTION: A motor control circuit according to one embodiment of the present disclosure outputs a state signal indicating a rotational state of a motor, and comprises a voltage dividing unit 20 and an amplifying unit 30. In the voltage dividing unit, a first resistor 22 and a second resistor 24 are connected in this order on an input side for the state signal to divide a voltage of the state signal. The amplifying unit has a transistor 40 and a third resistor 50 to amplify the state signal which is voltage-divided in the voltage dividing unit. A base 42 of the transistor is connected to between the first resistor and the second resistor. An emitter 44 of the transistor is connected to the third transistor. A collector 46 of the transistor outputs the amplified state signal. A resistance value of the third resistor is smaller than a resistance value of the second resistor. The resistance value of the second resistor is smaller than a resistance value of the first resistor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a technique for outputting a status signal indicating a rotation state of a motor. [Background technology]

[0002] There is known a technology for outputting a status signal that indicates the rotational state of a motor. For example, the following Patent Document 1 describes a technology in which a control IC PWM controls a drive circuit that generates a drive voltage for a motor, and the control IC outputs a PWM signal as a status signal to a vehicle ECU that monitors the rotational state of the motor. ECU is an abbreviation for Electronic Control Unit, and PWM is an abbreviation for Pulse Width Modulation. The PWM signal output from the control IC is amplified by an amplifier that uses a transistor.

[0003] In the technology described in Patent Document 1, in order to prevent an overcurrent from flowing through a transistor in the amplifier section due to a short circuit in the power supply, a transistor for limiting an overcurrent is used in addition to a transistor for amplification. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-126265 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, using a dedicated transistor to suppress an overcurrent caused by a short circuit in the power supply causes a problem of increased costs. One aspect of the present disclosure is to provide a technique for inexpensively suppressing an overcurrent that flows through a motor control circuit due to a short circuit in a power supply. [Means for solving the problem]

[0006] A motor control circuit (10) according to one aspect of the present disclosure is a motor control circuit that outputs a status signal indicative of the rotation status of a motor (6), and includes a voltage divider unit (20) and an amplifier unit (30).

[0007] The voltage divider section is connected to the input side of the status signal in the order of a first resistor (22) and a second resistor (24), and divides the status signal. The amplifier section has a transistor (40) and a third resistor (50), and amplifies the status signal divided by the voltage divider section.

[0008] The base (42) of the transistor is connected between the first and second resistors, the emitter (44) of the transistor is connected to the third resistor, and the collector (46) of the transistor outputs the amplified state signal.

[0009] The third resistor has a resistance value less than the resistance value of the second resistor, which in turn has a resistance value less than the resistance value of the first resistor. According to this configuration, the resistance value of the second resistor can be made smaller than the resistance value of the first resistor within a range in which the transistor is turned on. As a result, in a normal state in which the power supply is not shorted to the collector side of the transistor, it is possible to prevent the voltage of the status signal divided by the first resistor and the second resistor from being applied to the base of the transistor at an excessively large level.

[0010] In addition, since the resistance value of the third resistor connected to the emitter of the transistor is smaller than the resistance value of the second resistor, the current value of the status signal that is amplified and flows between the collector and emitter of the transistor can be maximized.

[0011] When the power supply is shorted to the collector side of the transistor, the third resistor is connected to the emitter of the transistor, thereby making it possible to minimize the overcurrent flowing through the transistor. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a block diagram showing a schematic configuration of a motor control circuit. [Diagram 2]FIG. 2 is a block diagram showing a detailed configuration of a motor control circuit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [1. Configuration] In the motor control circuit 10 shown in FIGS. 1 and 2, the control IC 2 amplifies a PWM signal used for PWM control of the drive circuit 4, and outputs the amplified PWM signal to the vehicle ECU .

[0014] The motor 6 is, for example, a brushless motor used in an in-vehicle air conditioner. The drive circuit 4 has an inverter circuit using, for example, FETs as switching elements. The inverter circuit of the drive circuit 4 is switched by PWM control using a control IC 2. This controls the magnitude of the drive voltage applied to the motor 6 from the drive power supplied from a drive power source (not shown).

[0015] 1 and 2, the motor control circuit 10 includes a voltage dividing section 20 and an amplifier section 30. The voltage dividing section 20 includes a resistor 22 and a resistor 24. The amplifier section 30 includes a transistor 40, a resistor 50, and a capacitor 52.

[0016] The resistor 22 and the resistor 24 are connected, in this order, to the input side of the PWM signal output from the control IC 2. The side of the resistor 24 opposite the resistor 22 is grounded. The base 42 of the transistor 40 is connected between the resistor 22 and the resistor 24. That is, the PWM signal output from the control IC 2 is voltage-divided by the resistor 22 and the resistor 24. The voltage-divided PWM signal is then applied to the base 42 of the transistor 40.

[0017] One end of resistor 50 is connected to emitter 44 of transistor 40, and the other end of resistor 50 is connected to ground. The relationship in resistance value between resistor 22, resistor 24, and resistor 50 is resistor 22>resistor 24>resistor 50. The PWM signal is voltage-divided by resistor 22 and resistor 24 and applied to base 42 of transistor 40. The resistance values ​​of resistor 22 and resistor 24 are set within a range in which transistor 40 turns on.

[0018] One end of the capacitor 52 is connected to the collector 46 of the transistor 40, and the other end of the capacitor 52 is grounded. The capacitor 52 reduces noise input to the motor control circuit 10 and noise output from the motor control circuit 10.

[0019] A power supply 60 is electrically connected to the collector 46 of the transistor 40 through a resistor 62. The current flowing from the power supply 60 through the resistor 62, the collector 46, the emitter 44 and the resistor 50 varies in response to the PWM signal amplified by the transistor 40.

[0020] The resistance value of resistor 62 is greater than the resistance value of resistor 50. The voltage of the PWM signal amplified by the motor control circuit 10 is divided by resistors 62 and 50. This allows the voltage value of the PWM signal input to the vehicle ECU 70 via resistor 64 to be set to an upper limit value that the vehicle ECU 70 can recognize or lower. Capacitor 66 reduces noise input to the vehicle ECU 70 and noise output from the vehicle ECU 70.

[0021] The vehicle ECU 70 receives a PWM signal from the motor control circuit 10 that the control IC 2 uses to PWM control the drive circuit 4, and monitors the rotation state of the motor 6. [2. Operation] (1) Normal time In a normal state where the power supply 60 is not shorted to the collector 46 side of the transistor 40 , the PWM signal divided by the resistors 22 and 24 is amplified by the transistor 40 and input to the vehicle ECU 70 .

[0022] Since the resistance value of resistor 50 is smaller than the resistance value of resistor 24, the amplified PWM signal is input to vehicle ECU 70 with a current value as large as possible. (2) When a short circuit occurs When power supply 60 is shorted to collector 46 of transistor 40, as indicated by dotted line 100 in FIG. 1, resistor 50 connected to emitter 44 of transistor 40 reduces the excess current flowing through transistor 40.

[0023] [1-3. Effects] According to the present embodiment described above, the following effects can be obtained. (1a) The resistance value of resistor 22, the resistance value of resistor 24, and the resistance value of resistor 50 are set to be resistor 22 > resistor 24 > resistor 50. This makes it possible to inexpensively suppress the overcurrent flowing through the motor control circuit 10 when the power supply 60 is short-circuited to the motor control circuit 10 without using any elements other than resistors.

[0024] In the embodiment described above, the resistor 22 corresponds to the first resistor, the resistor 24 corresponds to the second resistor, the resistor 50 corresponds to the third resistor, the resistor 62 corresponds to the fourth resistor, and the capacitor 52 corresponds to the capacitor that reduces noise.

[0025] 2. Other embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0026] (2a) Although a PWM signal has been exemplified as the status signal indicating the status of the motor 34, the status signal is not limited to this. For example, the status signal may be the number of rotations of the motor, the rotation position, a diagnostic signal of the motor, etc.

[0027] (2b) Multiple functions possessed by one component in the above-described embodiments may be realized by multiple components, or one function possessed by one component may be realized by multiple components. Also, multiple functions possessed by multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above-described embodiments may be omitted.

[0028] (2c) In addition to the motor control circuit 10 described above, the present disclosure can be realized in various forms, such as a system that includes the motor control circuit 10 as a component. [Explanation of symbols]

[0029] 6: motor, 10: motor control circuit, 20: voltage division section, 22: resistor (first resistor), 24: resistor (second resistor), 30: amplifier section, 40: transistor, 42: base, 44: emitter, 46: collector, 50: resistor (third resistor), 52: capacitor, 60: power supply, 62: resistor (fourth resistor)

Claims

1. A motor control circuit (10) that outputs a status signal representing a rotation status of a motor (6), a voltage dividing section (20) that divides a voltage of the status signal, the voltage dividing section (20) being connected in this order to a first resistor (22) and a second resistor (24) on an input side of the status signal; an amplifier section (30) having a transistor (40) and a third resistor (50) and amplifying the state signal voltage-divided by the voltage divider section; Equipped with a base (42) of the transistor connected between the first resistor and the second resistor, an emitter (44) of the transistor connected to the third resistor, and a collector (46) of the transistor outputting the amplified state signal; a resistance value of the third resistor is smaller than a resistance value of the second resistor, and a resistance value of the second resistor is smaller than a resistance value of the first resistor; Motor control circuit.

2. 2. The motor control circuit according to claim 1, the collector is connected to a power supply (60) through a fourth resistor (62), the resistance value of the third resistor being smaller than the resistance value of the fourth resistor; Motor control circuit.

3. 3. The motor control circuit according to claim 1, The amplifier unit further includes a capacitor (52) having one end connected to the collector of the transistor and the other end grounded to reduce noise on the collector side. Motor control circuit.

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