JP5087376B2 - Motor drive circuit, fan motor, electronic device, and notebook personal computer - Google Patents

Description

  The present invention relates to a motor drive circuit, a fan motor, an electronic device, and a notebook personal computer.

  In an electronic device such as a notebook personal computer, a fan motor is used to cool a heat-generating component such as a processor, for example. In the fan motor, control is performed so that the motor rotates in a desired manner by controlling the drive voltage applied to the motor coil in accordance with a signal indicating the rotational position of the motor (see, for example, Patent Document 1).

  FIG. 3 is a diagram illustrating an example of a configuration of a motor drive circuit that drives a single-phase fan motor. The motor drive circuit 100 includes P-channel MOSFETs 110 and 111, N-channel MOSFETs 112 and 113, and a drive control circuit 120. The P-channel MOSFETs 110 and 111 and the N-channel MOSFETs 112 and 113 constitute an H-bridge circuit, and the motor rotates as desired by being appropriately turned on and off by the drive control circuit 120. For example, at a certain timing, the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned on, and the P-channel MOSFET 111 and the N-channel MOSFET 112 are turned off, so that a current flows through the motor coil L from the terminal OUT1 to the terminal OUT2. . At another timing, when the P-channel MOSFET 111 and the N-channel MOSFET 112 are turned on and the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned off, a current flows from the terminal OUT2 to the terminal OUT1 to the motor coil L. Become.

When the direction of the current of the motor coil L is switched, the P-channel MOSFETs 110 and 111 and the N-channel MOSFETs 112 and 113 are all turned off. For example, the P-channel MOSFET 111 and the N-channel MOSFET 112 are turned on after the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned off from the state where the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned on and the P-channel MOSFET 111 and the N-channel MOSFET 112 are turned off. .
JP 2006-174648 A

  In the motor drive circuit 100, for example, when the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned off from the state where the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned on and the P-channel MOSFET 111 and the N-channel MOSFET 112 are turned off, the P-channel MOSFET 110 and the N-channel MOSFET 113 are turned off. Does not flow current, but the motor coil L tries to continue to flow current due to the accumulated energy. Therefore, a current flows from the ground side to the power supply side through the parasitic diode of the N-channel MOSFET 112, the motor coil L, and the parasitic diode of the P-channel MOSFET 111.

  Thus, when a current flows from the ground side through the N-channel MOSFET 112, the voltage of the drain electrode of the N-channel MOSFET 112 becomes lower than the ground voltage. As illustrated in FIG. 4, the P-channel MOSFETs 110 and 111 and the N-channel MOSFETs 112 and 113 are formed on a grounded P-type substrate 130, and the voltage of the drain electrode 131 of the N-channel MOSFET 112 is equal to or lower than the ground voltage. Thus, a parasitic transistor is formed together with an arbitrary N-type region 132 on the P-type substrate 130. If the parasitic transistor is formed in this manner, the charge is extracted from the N-type region 132, so that a malfunction may occur in the integrated circuit. In addition, when a current flows from the ground side to the power source side, the voltage on the power source side may increase, and excessive stress may be applied to the components of the motor drive circuit 100.

  The present invention has been made in view of the above problems, and an object thereof is to suppress the occurrence of abnormal operation.

  In order to achieve the above object, the motor drive circuit of the present invention includes a first transistor in which an input electrode is connected to the power supply side, an output electrode is connected to one end of the motor coil, and an input electrode is connected to the one end of the motor coil. A second transistor connected to the ground side, an output electrode connected to the power source, a third transistor connected to the other end of the motor coil, and an input electrode connected to the motor coil The fourth transistor is connected to the other end of the transistor and the output electrode is connected to the ground side, and the first and fourth transistors are on and the first to fourth transistors are all off. In order to drive the motor coil, a drive control circuit for controlling the first to fourth transistors, an input electrode is connected to the power supply side, and an output electrode is the one of the motor coil. , The control electrode is connected to the ground side, the first and fourth transistors are switched from the ON state to the OFF state, and the voltage at the one end of the motor coil is grounded. And a protection circuit that turns on the fourth transistor when the fifth transistor is turned on.

  The occurrence of abnormal operation can be suppressed.

  FIG. 1 is a diagram illustrating a configuration example of a motor drive circuit according to an embodiment of the present invention. The motor drive circuit 10 is incorporated in a fan motor for cooling a heat-generating component (cooled device) such as a processor in an electronic device such as a notebook personal computer, and rotates the cooling fan. Used to drive a motor.

  The motor drive circuit 10 of this embodiment is a circuit that drives a single-phase fan motor, and includes P-channel MOSFETs 15 to 18, N-channel MOSFETs 20 and 21, NPN transistors 25 and 26, resistors 28 and 29, and a drive control circuit 35. It is configured to include. In this embodiment, the motor drive circuit 10 is integrated on a P-type substrate, and a motor coil L is connected between the terminals OUT1 and OUT2.

  The P-channel MOSFET 15 (first transistor) and the N-channel MOSFET 20 (second transistor) are connected in series. The power supply voltage Vdd is applied to the source of the P-channel MOSFET 15 and the ground voltage is applied to the source of the N-channel MOSFET 20. Yes. A connection point between the P-channel MOSFET 15 and the N-channel MOSFET 20 is connected to the terminal OUT1. Similarly, the P-channel MOSFET 16 (third transistor) and the N-channel MOSFET 21 (fourth transistor) are connected in series, the power supply voltage Vdd is applied to the source of the P-channel MOSFET 16, and the ground voltage is applied to the source of the N-channel MOSFET 21. Applied. A connection point between the P-channel MOSFET 16 and the N-channel MOSFET 21 is connected to the terminal OUT2. That is, the P-channel MOSFETs 15 and 16 and the N-channel MOSFETs 20 and 21 constitute an H bridge circuit for driving the motor coil L.

  The drive control circuit 35 is a circuit that appropriately controls on / off of the P-channel MOSFETs 15 and 16 and the N-channel MOSFETs 20 and 21 in accordance with the rotational position of the motor. For example, when a current is passed through the motor coil L from the terminal OUT1 to the terminal OUT2, the drive control circuit 35 turns on the P-channel MOSFET 15 and the N-channel MOSFET 21, and turns off the P-channel MOSFET 16 and the N-channel MOSFET 20. Further, when a current is passed through the motor coil L from the terminal OUT2 to the terminal OUT1, the drive control circuit 35 turns on the P-channel MOSFET 16 and the N-channel MOSFET 20, and turns off the P-channel MOSFET 15 and the N-channel MOSFET 21.

  In the drive control circuit 35, the P channel MOSFET 16 and the N channel MOSFET 20 are turned on, and the P channel MOSFET 15 and the N channel MOSFET 21 are turned off from the state where the P channel MOSFET 15 and the N channel MOSFET 21 are turned on and the P channel MOSFET 16 and the N channel MOSFET 20 are turned off. When switching to this state, the P-channel MOSFETs 15 and 16 and the N-channel MOSFETs 20 and 21 are all turned off. The same applies when the P-channel MOSFET 16 and the N-channel MOSFET 20 are turned on, the P-channel MOSFET 15 and the N-channel MOSFET 21 are turned off, and the P-channel MOSFET 15 and the N-channel MOSFET 21 are turned on and the P-channel MOSFET 16 and the N-channel MOSFET 20 are turned off. is there.

  In the NPN transistor 25 (fifth transistor), the ground voltage is applied to the base, the emitter is connected to the terminal OUT1, and the power supply voltage Vdd is applied to the collector via the resistor 28. In the P-channel MOSFET 17, the power supply voltage Vdd is applied to the source, the gate is connected to the collector of the NPN transistor 25, and the drain is connected to the drive control circuit 35. In the NPN transistor 26, the ground voltage is applied to the base, the emitter is connected to the terminal OUT2, and the power supply voltage Vdd is applied to the collector via the resistor 29. In the P-channel MOSFET 18, the power supply voltage Vdd is applied to the source, the gate is connected to the collector of the NPN transistor 26, and the drain is connected to the drive control circuit 35. A circuit constituted by the P-channel MOSFET 17 and the resistor 28 corresponds to the protection circuit of the present invention.

  The P-channel MOSFET 16 is composed of a first transistor, the N-channel MOSFET 21 is composed of a second transistor, the P-channel MOSFET 15 is composed of a third transistor, the N-channel MOSFET 20 is composed of a fourth transistor, the NPN transistor 26 is composed of a fifth transistor, the N-channel MOSFET 18 and a resistor 29. The circuit to be used can be a protection circuit.

  Here, the ground voltage is applied to the base of the NPN transistor 25, and the emitter is connected to the terminal OUT1. Since the voltage at the terminal OUT1 rises to near the power supply voltage Vdd when the P-channel MOSFET 15 is on, the reverse bias withstand voltage between the emitter and base of the NPN transistor 25 needs to be increased according to the power supply voltage Vdd. Therefore, in this embodiment, the NPN transistors 25 and 26 are configured using N-channel MOSFETs having a triple well structure.

  FIG. 2 is a diagram illustrating a configuration example of an NPN transistor 25 using an N-channel MOSFET having a triple well structure. In the N-channel MOSFET having a triple well structure, an N-type well 41 is formed on a P-type substrate 40, a P-type well 42 is formed on the N-type well 41, and a drain electrode 43 in the N-type region is formed on the P-type well 42. The source electrode 44 is formed, and the gate electrode 45 is further formed. The P-type well 42 is used as the base of the NPN transistor 25, the drain electrode 43 and the source electrode 44 are used as the emitter of the NPN transistor 25, and the N-type well 41 is used as the collector of the NPN transistor 25. Note that only one of the drain electrode 43 and the source electrode 44 may be used as the emitter of the NPN transistor 25.

  The reverse bias withstand voltage between the drain electrode 43 and the source electrode 44 of the triple-well N-channel MOSFET and the P-type well 42 (back gate) is the reverse bias withstand voltage between the emitter and the base in a general NPN transistor. It is known to be higher. Therefore, by forming the NPN transistor 25 using an N-channel MOSFET having a triple well structure as shown in FIG. 2, the withstand voltage of the reverse bias between the emitter and the base can be increased as compared with the case of using a general NPN transistor. It becomes possible. The same applies to the NPN transistor 26.

  An example of the operation of the motor drive circuit 10 will be described. First, it is assumed that the drive control circuit 35 turns on the P-channel MOSFET 15 and the N-channel MOSFET 21 and turns off the P-channel MOSFET 16 and the N-channel MOSFET 20. At this time, a current flows through the motor coil L from the terminal OUT1 to the terminal OUT2. Further, since the voltage at the terminal OUT1 has risen to near the power supply voltage Vdd, the NPN transistor 25 is off. Therefore, the gate voltage of the P-channel MOSFET 17 becomes the power supply voltage Vdd, and the P-channel MOSFET 17 is also turned off.

  Next, the drive control circuit 35 turns off the P-channel MOSFET 15 and the N-channel MOSFET 21 in order to switch the direction of the current of the motor coil L. At this time, since the motor coil L continues to flow current, current flows from the ground side through the parasitic diode of the N-channel MOSFET 20, the motor coil L, and the parasitic diode of the P-channel MOSFET 16 to the power supply side.

  Then, when a current flows through the parasitic diode of the N-channel MOSFET 20, the voltage at the terminal OUT1 becomes lower than the ground voltage. That is, the emitter voltage of the NPN transistor 25 is lower than the ground voltage. Assuming that the threshold voltage of the NPN transistor 25 is Vth, the ground voltage is applied to the base of the NPN transistor 25. Therefore, when the voltage at the terminal OUT1 becomes lower than -Vth, the NPN transistor 25 is turned on. When the NPN transistor 25 is turned on, the voltage at the gate of the P-channel MOSFET 17 becomes a voltage dropped from the power supply voltage Vdd by the resistance 28, and the P-channel MOSFET 17 is turned on. When the P-channel MOSFET 17 is turned on, the power supply voltage Vdd is input to the drive control circuit 35. At this time, the drive control circuit 35 raises the voltage of the gate of the N-channel MOSFET 21 to near the power supply voltage Vdd, and turns on the N-channel MOSFET 21.

  When the N-channel MOSFET 21 is turned on, the current flowing from the motor coil L through the parasitic diode of the P-channel MOSFET 16 to the power supply side passes through the N-channel MOSFET 21 having a lower on-resistance than the parasitic diode of the P-channel MOSFET 16 to the ground side. As a result, the energy stored in the motor coil L is rapidly consumed. When the energy stored in the motor coil L is consumed, the current stops flowing, and the state where the voltage at the terminal OUT1 is lower than the ground voltage is eliminated. Then, the NPN transistor 25 and the P-channel MOSFET 17 are turned off, and the N-channel MOSFET 21 is turned off.

  In the motor drive circuit 10, a parasitic transistor is configured with the drain of the N-channel MOSFET 20 as an emitter and a P-type substrate as a base. Generally, the threshold voltage of the parasitic transistor (for example, about 0.9 V) is Since it is higher than the threshold voltage of the NPN transistor 25 (for example, about 0.7 V), the parasitic transistor is difficult to turn on.

  Then, the drive control circuit 35 turns on the P-channel MOSFET 16 and the N-channel MOSFET 20 and turns off the P-channel MOSFET 15 and the N-channel MOSFET 21. Thereafter, at the timing when the drive control circuit 35 turns off the P-channel MOSFET 16 and the N-channel MOSFET 20, a state in which the voltage at the terminal OUT2 is lower than the ground voltage occurs, but as with the terminal OUT1, the NPN transistor 26, P Control by the channel MOSFET 18 and the resistor 29 is performed.

  The motor drive circuit 10 of the present embodiment has been described above. According to the motor drive circuit 10, when the P-channel MOSFET 15 and the N-channel MOSFET 21 are turned off from the state where the P-channel MOSFET 15 and the N-channel MOSFET 21 are on and the P-channel MOSFET 16 and the N-channel MOSFET 20 are off, the voltage at the terminal OUT1 is changed. When the voltage is lower than the ground voltage, the NPN transistor 25 is turned on, the N-channel MOSFET 21 is turned on, and the current that the motor coil L keeps flowing flows through the N-channel MOSFET 21 to the ground side. For this reason, it is possible to suppress the current from flowing through the parasitic diode of the P-channel MOSFET 16 to the power supply side, and to suppress the generation of an abnormal voltage. In addition, since the NPN transistor 25 is more easily turned on than the parasitic diode having the drain of the N-channel MOSFET 20 as an emitter, it is possible to suppress malfunction due to the parasitic diode. The same applies when the P-channel MOSFET 16 and the N-channel MOSFET 20 are turned off from the state where the P-channel MOSFET 16 and the N-channel MOSFET 20 are turned on and the P-channel MOSFET 15 and the N-channel MOSFET 21 are turned off.

  In addition, by configuring the NPN transistors 25 and 26 using triple-channel N-channel MOSFETs, it becomes possible to improve the withstand voltage of reverse bias between the emitter and base of the NPN transistors 25 and 26, and the power supply voltage Vdd is reduced. The NPN transistors 25 and 26 can be made difficult to break even when the height is high.

  And, by using such a motor drive circuit 10 to constitute a fan motor incorporated in an electronic device such as a notebook personal computer, it is possible to suppress the operation of the fan motor from being abnormal, It becomes possible to appropriately cool the component to be cooled.

  In addition, the said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof. For example, in this embodiment, the motor drive circuit 10 is used for driving a single-phase fan motor, but the motor to be driven is not limited to a fan motor, and the number of phases is not limited to a single phase.

It is a figure which shows the structure of the motor drive circuit which is one Embodiment of this invention. It is a figure which shows the structural example of the NPN transistor using N channel MOSFET of a triple well structure. It is a figure which shows an example of a structure of the motor drive circuit which drives a single phase fan motor. It is a figure which shows an example of the parasitic transistor formed in a motor drive circuit.

Explanation of symbols

10 Motor drive circuit 15-18 P-channel MOSFET
20, 21 N-channel MOSFET
25, 26 NPN transistor 28, 29 Resistance 35 Drive control circuit 40 P-type substrate 41 N-type well 42 P-type well 43 Drain electrode 44 Source electrode 45 Gate electrode

Claims (5)

A first transistor having an input electrode connected to the power supply side and an output electrode connected to one end of the motor coil;
A second transistor having an input electrode connected to the one end of the motor coil and an output electrode connected to the ground side;
A third transistor having an input electrode connected to the power source and an output electrode connected to the other end of the motor coil;
A fourth transistor having an input electrode connected to the other end of the motor coil and an output electrode connected to the ground;
Drive control for controlling the first to fourth transistors so as to drive the motor coil by appropriately selecting a state in which the first and fourth transistors are on and a state in which all the first to fourth transistors are off. Circuit,
An input electrode is connected to the power supply side, an output electrode is connected to the one end of the motor coil, a control electrode is connected to the ground side, and the first and fourth transistors are turned on from the first and fourth transistors. A fifth transistor that turns on when all switches to the off state and the voltage at the one end of the motor coil is lower than the ground side;
A protection circuit that turns on the fourth transistor when the fifth transistor is turned on;
A motor drive circuit comprising: The motor drive circuit according to claim 1,
An N-type triple well MOSFET having an N-type well formed on a P-type substrate, a P-type well formed on the N-type well, and a source electrode and a drain electrode formed on the P-type well. The input electrode of the fifth transistor is configured using a mold well,
The output electrode of the fifth transistor is configured using at least one of the source electrode and the drain electrode of the MOSFET,
The control electrode of the fifth transistor is configured using the P-type well of the MOSFET;
A motor drive circuit characterized by the above. With fans,
A motor for driving the fan;
A motor drive circuit for driving the motor;
With
The motor drive circuit is
A first transistor having an input electrode connected to the power supply side and an output electrode connected to one end of the motor coil;
A second transistor having an input electrode connected to the one end of the motor coil and an output electrode connected to the ground side;
A third transistor having an input electrode connected to the power source and an output electrode connected to the other end of the motor coil;
A fourth transistor having an input electrode connected to the other end of the motor coil and an output electrode connected to the ground;
Drive control for controlling the first to fourth transistors so as to drive the motor coil by appropriately selecting a state in which the first and fourth transistors are on and a state in which all the first to fourth transistors are off. Circuit,
An input electrode is connected to the power supply side, an output electrode is connected to the one end of the motor coil, a control electrode is connected to the ground side, and the first and fourth transistors are turned on from the first and fourth transistors. A fifth transistor that turns on when all switches to the off state and the voltage at the one end of the motor coil is lower than the ground side;
A protection circuit that turns on the fourth transistor when the fifth transistor is turned on;
A fan motor comprising: With fans,
A motor for driving the fan;
A motor drive circuit for driving the motor;
A cooled device cooled by the fan;
With
The motor drive circuit is
A first transistor having an input electrode connected to the power supply side and an output electrode connected to one end of the motor coil;
A second transistor having an input electrode connected to the one end of the motor coil and an output electrode connected to the ground side;
A third transistor having an input electrode connected to the power source and an output electrode connected to the other end of the motor coil;
A fourth transistor having an input electrode connected to the other end of the motor coil and an output electrode connected to the ground;
Drive control for controlling the first to fourth transistors so as to drive the motor coil by appropriately selecting a state in which the first and fourth transistors are on and a state in which all the first to fourth transistors are off. Circuit,
An input electrode is connected to the power supply side, an output electrode is connected to the one end of the motor coil, a control electrode is connected to the ground side, and the first and fourth transistors are turned on from the first and fourth transistors. A fifth transistor that turns on when all switches to the off state and the voltage at the one end of the motor coil is lower than the ground side;
A protection circuit that turns on the fourth transistor when the fifth transistor is turned on;
An electronic device characterized by comprising. With fans,
A motor for driving the fan;
A motor drive circuit for driving the motor;
A processor cooled by the fan;
With
The motor drive circuit is
A first transistor having an input electrode connected to the power supply side and an output electrode connected to one end of the motor coil;
A second transistor having an input electrode connected to the one end of the motor coil and an output electrode connected to the ground side;
A third transistor having an input electrode connected to the power source and an output electrode connected to the other end of the motor coil;
A fourth transistor having an input electrode connected to the other end of the motor coil and an output electrode connected to the ground;
Drive control for controlling the first to fourth transistors so as to drive the motor coil by appropriately selecting a state in which the first and fourth transistors are on and a state in which all the first to fourth transistors are off. Circuit,
An input electrode is connected to the power supply side, an output electrode is connected to the one end of the motor coil, a control electrode is connected to the ground side, and the first and fourth transistors are turned on from the first and fourth transistors. A fifth transistor that turns on when all switches to the off state and the voltage at the one end of the motor coil is lower than the ground side;
A protection circuit that turns on the fourth transistor when the fifth transistor is turned on;
A notebook personal computer comprising:

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