JP5501739B2 - Motor drive device - Google Patents

Description

  The present invention relates to a motor drive device.

  2. Description of the Related Art Conventionally, there has been known a control circuit that prevents the occurrence of an overvoltage when a motor is rotated by an external force when a power is shut off using a protection circuit (see, for example, Patent Document 1). Also, an electric motor control device that uses a circuit unit to prevent an overvoltage of a power transistor when a battery terminal is disconnected is known (see, for example, Patent Document 2).

JP-A-10-70897 JP-A-5-207786

  However, the techniques described in Patent Document 1 and Patent Document 2 have a problem that the circuit scale of the protection circuit and the circuit unit is increased, and a problem that the cost of the protection circuit and the circuit unit is high.

  The present invention has been made to solve the above-described problems, and has an object to provide a motor drive device that can be reduced in circuit scale and cost as compared with the prior art and can prevent the occurrence of overvoltage. And

In order to achieve the above object, a motor drive device according to a first aspect of the present invention includes a drain terminal, a gate terminal, and a source terminal, and a voltage higher than a predetermined voltage is applied to the gate terminal from a voltage application unit. A transistor having a withstand voltage of a predetermined magnitude between the drain terminal and the source terminal at the time of non-conduction while supplying driving power from the power supply to the motor from the connection end to the power supply. If the first is the other end connected to the cathode to the resistor, is pre SL connected anode to the gate terminal, and the Zener voltage is greater and the resistance from the power supply voltage of said power supply in which one end is connected to the connection end a voltage less than the drain voltage protection Zener diode, one end is connected before Symbol voltage applying unit and the other end anode of the drain voltage protection Zener diode Is connected to, when the reverse voltage of the drain voltage protection Zener diode reverse current flows in the zener voltage larger than it by the drain voltage protection Zener diode, the gate by the voltage generated by the inflow of the reverse current wherein a second resistor having a resistance value of the size for applying a predetermined voltage or higher, and is configured to include a terminal.

According to the invention described in claim 1, when the reverse voltage of the drain voltage protection Zener diode reverse current flows through the drain overvoltage protection Zener diode is greater than the Zener voltage, generated by flow of the reverse current A voltage higher than the predetermined voltage is applied to the gate terminal by the voltage , and the transistor is turned on. Thus, for example, when the motor is rotated by an external force, even if the motor in a case where power is disconnected accidentally generate a high voltage becomes a generator, the voltage equal to or higher than a predetermined voltage is applied to the gate terminal Since the transistor becomes conductive, the voltage between the drain terminal and the source terminal becomes equal to or lower than the withstand voltage, and generation of an overvoltage to the transistor can be prevented. In addition, since the occurrence of overvoltage can be prevented only by the drain overvoltage protection Zener diode, the first resistor, and the second resistor, the circuit scale and cost can be reduced as compared with the conventional technique.

  Therefore, according to the first aspect of the present invention, the circuit scale and cost can be reduced as compared with the prior art, and the occurrence of overvoltage can be prevented.

According to a second aspect of the present invention, there is provided the motor driving device according to the first aspect, wherein the cathode is connected to the cathode of the drain overvoltage protection Zener diode and the anode is the drain terminal. The gate overvoltage protection Zener diode further includes a Zener voltage corresponding to the withstand voltage of the gate terminal of the drain overvoltage protection Zener diode . By including such a gate overvoltage protection Zener diode, it is possible to prevent the voltage applied to the gate terminal from exceeding the gate breakdown voltage (withstand voltage of the gate terminal) , and the transistor of the transistor due to a surge when the motor is off. Oscillation can be suppressed.

Further, the motor driving apparatus according to claim 3, in the motor driving apparatus according to claim 1 or claim 2, R ₁ a resistance value of said first _resistor, a voltage of the plant constant V _1, the Zener voltage V _Z of the drain voltage protection Zener _diode, so as to satisfy the following equation (1) the resistance value of the second resistor when the R _2, the resistance value R _1, The voltage V ₁ , the Zener voltage V _Z , and the resistance value R ₂ are determined.

It is a block diagram of the motor drive device which concerns on embodiment of this invention. It is a figure for demonstrating the drain overvoltage protection method which concerns on embodiment of this invention. It is a figure for demonstrating the gate overvoltage protection method which concerns on embodiment of this invention. It is a figure for demonstrating operation | movement of the motor drive device which concerns on embodiment of this invention.

  Embodiments of a motor drive device according to the present invention will be described below in detail with reference to the drawings.

  As shown in FIG. 1, the motor drive device 10 of this embodiment includes resistors R1, R2, R3, R4, R5, R6, Zener diodes D1, D2, D3, D4, D5, D6, transistors T1, T2, And a control signal generator 12. The motor driving device 10 is for rotating the motor 14.

  The control signal generator 12 is connected to the gate terminals of the transistors T1 and T2. The control signal generator 12 controls the current flowing through the coils 14 a and 14 b of the motor 14 in order to drive the motor 14 to rotate. More specifically, the control signal creation unit 12 creates and outputs a signal for controlling conduction and non-conduction (ON / OFF) of the transistors T1 and T2. For example, the control signal generator 12 applies a voltage of a predetermined value α or more to the gate terminals of the transistors T1 and T2 when the transistors T1 and T2 are turned on, and the gates of the transistors T1 and T2 when turned off. A control signal is generated so that a voltage less than a predetermined value α is applied to the terminal, and is output to the gate terminals of the transistors T1 and T2. The control signal creation unit 12 corresponds to a voltage application unit.

  The motor 14 includes coils 14a and 14b and a rotor 14c. The coils 14a and 14b generate a magnetic field when a current flows. The rotor 14c includes a magnet having S and N poles, and is rotated by a magnetic force based on the magnetic field generated by the coils 14a and 14b. As a result, the motor 14 is driven to rotate. The rotor 14c of the present embodiment can also be rotated by an external force that is a force different from the magnetic force. One end of each of the coils 14a and 14b is connected to a power source (B +) via a connection end 14d. As a result, the driving power is supplied from the power source (B +) to the motor 14 via the connection end 14d to the power source (B +).

  The other end of the coil 14a is connected to the drain terminal of the transistor T1. The other end of the coil 14b is connected to the drain terminal of the transistor T2.

  The transistors T1 and T2 include a drain terminal, a gate terminal, and a source terminal. The transistors T1 and T2 are electrically connected between the drain terminal and the source terminal when a voltage of a predetermined value α or more is applied to the gate terminal, and are drained when a voltage of less than the predetermined value α is applied to the gate terminal. The terminal-source terminal becomes non-conductive. The transistors T1 and T2 have a predetermined withstand voltage between the drain terminal and the source terminal when not conducting. The source terminals of the transistors T1 and T2 are connected to a portion having a predetermined potential. For example, the source terminals of the transistors T1 and T2 are grounded.

The Zener diode D1 has a cathode connected to the other end of the resistor R1 whose one end is connected to the connection end 14d, and an anode connected to the gate terminal of the transistor T1 via the resistor R3. Further, in this embodiment, the Zener diode D1 is greater than the supply voltage of the Zener voltage V _Z is the power (B +), and used smaller than the withstand voltage of the transistor T1 as described above. The Zener diode D1 corresponds to a drain overvoltage protection Zener diode.

  The Zener diode D2 has an anode connected to the other end of the resistor R1, and a cathode connected to the cathode of the Zener diode D3. The Zener diode D2 is used, for example, to suppress a surge voltage when the transistor T1 changes from a conductive (on) state to a non-conductive (off) state. The anode of the Zener diode D3 is connected to the drain terminal of the transistor T1. That is, the anode of the Zener diode D3 is connected to the cathode of the Zener diode D1 through the Zener diode D2. The Zener diode D3 corresponds to a gate overvoltage protection Zener diode.

  Note that the Zener diode D2 may not be provided.

The resistor R2 has one end connected to the control signal generator (voltage application unit) 12 and the other end connected to the anode of the Zener diode D1. In this embodiment, as the withstand voltage more than the voltage between the drain and source terminals of the transistor T1 is not applied, the Zener diode reverse voltage of the Zener diode D1 becomes larger than the Zener voltage V _Z of the Zener diode D1 When a reverse current flows through D1, a voltage higher than a predetermined value α is applied to the gate terminal of the transistor T1 by the voltage generated by the reverse current, the transistor T1 is turned on, and the potential of the drain terminal becomes the potential of the source terminal. The resistance values of the resistors R1, R2, and R3 and the Zener voltages of the Zener diodes D1, D2, and D3 are determined so as to be (eg, 0 V when grounded to GND).

  That is, the overvoltage detection unit 16 shown in FIG. 1 including the resistor R1, the Zener diode D1, and the resistor R2 detects the occurrence of the overvoltage and controls the transistor T1 so that the transistor T1 is turned on when the overvoltage occurs. .

As an example of how to determine each resistance value and each zener voltage, when the zener diode D2 and the resistor R3 are not provided, the resistance value of the resistor R1 is R ₁ , the voltage of the predetermined value α is V ₁ , and the zener diode D1. The values of R ₁ , V ₁ , V _Z , and R ₂ can be determined so that the following expression (2) is satisfied when the zener voltage of V _z is V _Z and the resistance value of the resistor R ₂ is R ₂ .

Further, the resistance value R ₃ of the resistor R3 is also determined by the size of the gate breakdown voltage of the transistor T1.

  Since the resistors R4, R5, R6, the Zener diodes D4, D5, D6, and the transistor T2 are the same as the resistors R1, R2, R3, the Zener diodes D1, D2, D3, and the transistor T1 described above, details thereof This description will be omitted, and the same shall apply hereinafter. The resistor R4 is the resistor R1, the resistor R5 is the resistor R2, the resistor R6 is the resistor R3, the Zener diode D4 is the Zener diode D1, the Zener diode D5 is the Zener diode D2, the Zener diode D6 is the Zener diode D3, The transistor T2 corresponds to the transistor T1.

  Here, with reference to FIG. 2, a method of protecting the drain terminal from an overvoltage by the motor drive circuit 10 of the present embodiment will be described.

As shown in the figure, if the potential difference between the source terminal of the transistor T1 and the one end of the resistor R2 is V _SIG and the potential difference between the source terminal of the transistor T1 and the one end of the resistor R1 is V _S , If _S -V _SIG) is less than or equal to the Zener voltage _{V Z} is a reverse current (zener current to the zener diode D1) Iz does not flow.

On the other _hand, it is greater than (V _{S -V SIG)} is a Zener voltage _{V Z} is the reverse current Iz flows in the Zener diode D1. That is, a voltage is applied to the resistors R1 and R2. Therefore, even when the transistor T1 is turned off (non-conducting) for control, that is, when the voltage less than the predetermined value α is applied to the gate terminal of the transistor T1, the transistor T1 A voltage of (R ₂ × Iz) having a magnitude greater than or equal to a predetermined value α is applied to the gate terminal, and the transistor T1 is turned on. Thus, the potential of the drain terminal of the transistor T1 is the same (or almost the same) as the potential of the source terminal, and the voltage between the drain terminal and the source terminal can be prevented from being higher than the withstand voltage. That is, the occurrence of overvoltage can be prevented. In addition, since only the Zener diode D1 ( drain Zener diode for drain overvoltage protection), the resistor R1 (first resistor), and the resistor R2 (second resistor) can prevent the occurrence of overvoltage, compared with the prior art. The circuit scale and cost can be reduced.

  Next, a method for protecting the gate terminal from an overvoltage by the motor drive circuit 10 of the present embodiment will be described with reference to FIG.

For example, the voltage Vs (gate voltage) applied to the gate terminal of the transistor T1 increases as the magnitude of V _S described above increases. Therefore, protection is required so as not to exceed the withstand voltage of the gate terminal (gate withstand voltage). In the conventional general protection method, as shown in FIG. 3A, protection is performed by inserting a Zener diode D9 between the gate terminal and the ground (GND).

However, since the number of elements increases in such a conventional method, since the source terminal is grounded in this embodiment, the drain voltage (the voltage applied to the drain terminal) when the transistor T1 is conductive. As shown in FIG. 3B, focusing on the fact that the voltage becomes almost 0 V and the potential becomes the GND level, and that a rectifier diode D8 is conventionally provided between the drain terminal and the gate terminal to prevent oscillation of the transistor T1. to have integrated the gate overvoltage protective function of the transistor T1 and the oscillation prevention function into a single Zener diode D3. Thereby, compared with the prior art, it is possible to realize cost reduction by reducing the number of mounted elements, and it is possible to realize miniaturization by reducing the substrate area.

In the example shown in FIG. 3B, the maximum voltage applied to the gate terminal is (Zener voltage of Zener diode D3) − ((Zener voltage V _Z of Zener diode D1) − (Zener diode). D2 forward voltage)).

When the Zener diode D2 is not provided, the maximum voltage applied to the gate terminal is (Zener voltage of the Zener diode D3) − (Zener voltage V _Z of the Zener diode D1).

In FIG. 4, in the motor drive circuit 10 of the present embodiment, the above V _S when V _SIG = 0, the reverse current I of the Zener diode D1, the gate voltage V _{g of} the transistor T1, and the drain voltage V of the transistor T1. The relationship of _d is shown. Note that the vertical axis indicates the potential difference for V _S , the current for I, the voltage for V _g and V _d , and the time (time) for the horizontal axis.

As shown in the figure, at time t1, VS exceeds the Zener voltage V _Z of the Zener diode D1, starts the reverse current I flows. At time t2, the magnitude of the gate voltage Vg exceeds the predetermined value α, and the transistor T1 is turned on (turned on). Then, at time t3, the gate voltage Vg is limited by the Zener diode D3 so that the magnitude of the gate voltage does not exceed the gate withstand voltage.

  As described above, according to the motor drive circuit 10 of the present embodiment, the circuit scale and cost can be reduced as compared with the prior art, and the occurrence of overvoltage can be prevented. In addition, the voltage applied to the gate terminal can be prevented from exceeding the gate breakdown voltage, and transistor oscillation due to a surge when the motor is off can be suppressed.

  It should be noted that the present invention is not limited to such embodiments, and it will be apparent to those skilled in the art that other various embodiments are possible within the scope of the present invention.

  For example, although an example in which an FET is used as an example of a transistor as a switching element has been described above, an element other than an FET can be used.

DESCRIPTION OF SYMBOLS 10 ... Motor drive device, 12 ... Control signal preparation part, 14 ... Motor, 16 ... Overvoltage detection part, D1, D2, D3, D4, D5, D6 ... Zener diode, R1, R2, R3, R4, R5, R6 ... Resistance, T1, T2 ... Transistor

Claims (3)

A drain terminal, a gate terminal, and a source terminal are provided, and when a voltage higher than a predetermined voltage is applied to the gate terminal from the voltage application unit and is conducted, power for driving is supplied from the power source to the motor from the connection end to the power source. A transistor having a withstand voltage of a predetermined magnitude between the drain terminal and the source terminal during non-conduction,
One end cathode connected to the first end of the resistor connected to the connection end, before Symbol anode connected to the gate terminal, and the Zener voltage, large and the withstand voltage less than the power supply voltage of the power supply Zener diode for drain overvoltage protection,
One end is connected before Symbol voltage application unit, the other end is connected to the anode of the drain overvoltage protection zener diode, the drain overvoltage reverse voltage of the drain voltage protection Zener diode is greater than the Zener voltage when the reverse current flows through the protection Zener diode, a second resistor having a magnitude of resistance which applies a predetermined voltage or higher voltage to the gate terminal by the voltage generated by the inflow of the reverse current,
A motor driving device. A gate is connected to a cathode of the drain overvoltage protection Zener diode, an anode is connected to the drain terminal, and a Zener voltage is a Zener for gate overvoltage protection according to a withstand voltage of the gate terminal of the drain overvoltage protection Zener diode. The motor driving apparatus according to claim 1, further comprising a diode. The resistance value R ₁ of the first _resistor, the plant V ₁ the voltage of the constant, if the Zener voltage V _Z of the drain voltage protection Zener _diode, a resistance value of the second resistor and the R ₂ 3. The motor according to claim 1, wherein the resistance value R ₁ , the voltage V ₁ , the Zener voltage V _Z , and the resistance value R ₂ are determined so as to satisfy the following expression (1): Drive device.

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