JP2006262628A - Motor drive circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a motor and a motor drive circuit from being damaged by the rise of a supply voltage caused by back electromotive force induced by the motor when the supply voltage drops in the motor drive circuit for forming a bridge. <P>SOLUTION: When the supply voltage drop detection circuits 70, 60, or a back electromotive force detection circuit detect that the supply voltage becomes smaller than that in normal operation, brakes are applied to the rotation of the motor by turning on ground-side output transistors Q2, Q4 for preventing the rise of the supply voltage. When the supply voltage becomes lower than that of a logic circuit 26, a capacitor C3 or the back electromotive force is utilized for pulling up the gate input of the ground-side output transistors Q2, Q4, and the brakes are applied to the rotation of the motor by turning on the ground-side output transistors Q2, Q4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor drive circuit having a plurality of power transistors having an H-bridge configuration and driving a motor. In particular, the present invention detects a drop in the power supply voltage, turns on the ground-side output transistor, and brakes the rotation of the motor, thereby improving the protection performance of the motor.

  As a prior art of a motor drive circuit that has a plurality of power transistors and drives a motor having an H-bridge configuration, for example, there is a technique disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-37276). The technique described in Patent Document 1 will be described with reference to FIG.

  A power supply circuit 12 built in the motor driving circuit 10 of the conventional example shown in FIG. 9 generates a DC constant voltage by performing both-wave rectification of AC 100V. The output of the power supply circuit 12 is connected to an H bridge circuit 14 for supplying electric power for driving the motor M at the branch point P.

  The H bridge circuit 14 includes power supply side output transistors Q1, Q3, ground side output transistors Q2, Q4, diodes D1, D2, D3, D4, and resistors R1, R2, R3, R4. A total of four output transistors are the transistors Q1 and Q2 and the transistors Q3 and Q4, respectively, and the connection terminals of each transistor set are M + and M−. A motor M is connected to connection terminals M + and M− of the output transistor group (output circuit). The motor M is driven by causing a driving current to flow from the two sets of output transistors to the motor M.

  The motor drive circuit 10 includes a motor voltage detection circuit 16 that detects an average voltage of the connection terminals M + and M− in the motor M and outputs a feedback voltage F to the error amplification circuit 22. The motor voltage detection circuit 16 is configured as follows. A connection terminal M + to the motor M is connected to the resistor R6. The other end of the resistor R6 is connected to the resistor R8, the capacitor C1, and the resistor R10. The resistor R8 and the other end of the capacitor C1 are grounded. The other end of the resistor R10 is connected to a resistor R12 having one end grounded and a positive phase input terminal of the operational amplifier IC1.

  On the other hand, the connection terminal M- is connected to the resistor R7. The other end of the resistor R7 is connected to the resistor R9, the capacitor C2, and the resistor R11. The resistor R9 and the other end of the capacitor C2 are grounded. The other end of the resistor R11 is connected to the resistor R13, the other end of which is connected to the output of the operational amplifier IC1, and the negative phase input terminal of the operational amplifier IC1. The output F of the operational amplifier IC1 is input to the error amplifier circuit 22.

  In this way, a current corresponding to the average voltage of the connection terminal M + is accumulated in the capacitor C1, while a current corresponding to the average voltage of the connection terminal M− is accumulated in the capacitor C2.

  The power supply voltage detection circuit 20 built in the motor drive circuit 10 has Zener diodes D5, D6, D7 and a resistor R5, the cathode of the Zener diode D5 is connected to the branch point P, and the resistor R5 is the other end of the resistor R7. Connected to.

  A target voltage setting circuit 18 incorporated in the motor drive circuit 10 sets a target value T of the motor voltage of the motor M in accordance with signals connected to the UP terminal and DW terminal which are externally rising and falling commands. In the present embodiment, it is assumed that the H level signal is not simultaneously applied to both the UP terminal and the DW terminal.

  The motor drive circuit 10 includes an error amplification circuit 22 that outputs an error voltage Y obtained by amplifying an error between the target value T output from the target voltage setting circuit 18 and the feedback voltage F to the PWM circuit 24. The PWM circuit 24 compares the error voltage Y output from the error amplifying circuit 22 with the triangular wave voltage generated in the PWM circuit 24, and a pulse that makes the voltage proportional to the error voltage Y an average value of the motor voltage. Output PWM signal of width.

  The PWM signal set in this way is input to the logic circuit 26, and the AH terminal, the BH terminal, the AL terminal, and the BL terminal are set to the H level in order to turn on / off the switching elements Q1 to Q4 of the H bridge circuit 14. Set to L level. Here, during normal rotation, the AH terminal and the BL terminal are paired, the BH terminal and the AL terminal are paired, and the pair of the transistors Q1 and Q4 and the transistors Q2 and Q3 are simultaneously turned on / off. Thus, by turning on the transistors Q1 and Q4, the motor M can be rotated (increased) in the forward direction, and by turning on the transistors Q2 and Q3, the motor M can be rotated (lowered) in the reverse direction. it can.

When the motor M rotates in the reverse direction from the stopped state, the power supply voltage rises due to an induced voltage noise component caused by the induced back electromotive force. At this time, when a predetermined voltage preset by the power supply voltage detection circuit 20 is exceeded, the Zener diodes D5, D6, and D7 in the power supply voltage detection circuit 20 are turned on, and the capacitor C2 is charged through the resistor R5. To do. As a result, the reverse phase input terminal input voltage of the operational amplifier IC1 rises, passes through the error amplifier circuit 22, and increases the forward rotation duty of the PWM circuit 24. Then, the logic circuit 26 controls each output transistor of the H bridge circuit 14 and brakes the reverse rotation operation. As a result, the influence of the counter electromotive force induced by the motor M is suppressed, and the motor drive circuit and the motor M are protected.
JP 2001-37276 A

  However, the above-described prior art has the effect of the counter electromotive force generated when the motor M rotates in the reverse direction in a state where the power supply circuit 12 outputs an appropriate power supply voltage for the circuit to operate. This is a technique that can be canceled by increasing the duty to be rotated. However, in a portable device such as a digital camera or a digital video camera, a dry battery or a rechargeable battery is generally used as the power source. When the output of the battery is reduced or grounded, the PWM circuit 24 or The logic circuit 26 does not operate. Therefore, the present technology has a problem that the motor drive circuit and the motor M cannot be protected from the counter electromotive force generated.

  SUMMARY OF THE INVENTION The present invention solves the above-described problem. In a motor driving circuit for driving a motor having a plurality of power transistors having an H-bridge configuration, even when the output voltage of the power supply VCC is reduced or grounded (ground), the motor Protects the motor drive circuit and motor from overvoltage without the power supply voltage VCC exceeding the voltage during normal operation due to the back electromotive force of the motor, and destroys the motor and motor drive circuit due to the back electromotive force induced in the motor when the power supply voltage drops An object of the present invention is to provide a motor drive circuit capable of preventing the occurrence of the failure.

  In order to solve the above problems, the motor drive circuit of the present invention has the power supply voltage lowered or grounded in parallel with the control voltage generating means that operates when an appropriate power supply voltage is applied. In some cases, a protective means that performs a protective function is provided. When the power supply voltage drop or grounding (ground) is detected, the protection means detects the power supply voltage drop detection means, or the counter electromotive force rise detection means is induced in the motor by the power supply voltage drop. When the back electromotive force is detected, the ground side output transistor is turned on. As a result, the induced voltage noise component generated at the motor end is regenerated to the ground to brake the rotation of the motor. By regenerating the induced voltage noise component generated at the motor end to the ground, it is possible to prevent the power supply VCC from rising due to the induced voltage noise component, and it is possible to prevent destruction of the motor drive circuit and the motor due to overvoltage.

  In the present invention, the output of the power supply voltage drop detection means or the back electromotive force rise detection means and the output of the control voltage generation means that operates when an appropriate power supply voltage is applied are logically synthesized by the logic synthesis means. And a pull-up means at the output of the logic synthesis means. For this reason, when the power supply voltage drops or becomes ground (ground), the ground-side output transistor constituting the H-bridge is turned on by either the logic synthesis means or the pull-up means according to the degree of the power supply voltage drop. By turning off the power supply side output transistor, the overvoltage generated at the motor end can be regenerated to the ground.

  This will be specifically described below.

  The motor drive circuit of the present invention comprises a power supply side output transistor and a ground side output transistor connected in series, and an intermediate connection point between them is used as an output terminal, and two sets of output circuits in which the motor is connected between the two output terminals. And control voltage generating means for applying a control voltage to each of the power supply side output transistor and the ground side output transistor of the two sets of output circuits, and two sets of outputs in response to a decrease in the power supply voltage applied to the two sets of output circuits Protection means for suppressing an overvoltage caused by a counter electromotive force generated from the motor by forcibly turning on each ground side transistor of the circuit.

  The protection means preferably includes power supply voltage drop detection means for detecting a drop in power supply voltage. Moreover, you may have a back electromotive force raise detection means which detects the raise of the back electromotive force which generate | occur | produces in the both ends of a motor as a fall of a power supply voltage.

  The motor drive circuit having the above-described configuration includes a charged capacitor connected between the power supply terminal and the ground terminal, and the protection means turns on the ground-side transistor of each of the two sets of output circuits by connecting the voltage between the terminals of the capacitor. It is preferable to use it as a power source.

  In the motor drive circuit having the above configuration, the protection means may use the back electromotive force generated at both ends of the motor as a power source for turning on the ground side output transistor.

  Further, the motor drive circuit having the above configuration includes a capacitor connected to a power source and a ground, and the protection means provides either a voltage between the terminals of the capacitor or a counter electromotive force generated at both ends of the motor. It may be used as a power source for turning on the side output transistor.

  In the above configuration, when the power supply voltage drop detecting means for detecting the power supply voltage drop is provided, the protection means disables the control voltage of the control voltage generating means in response to the power supply voltage drop detection by the power supply voltage drop detection means. It is preferable to have logic synthesis means for applying an off drive voltage and an on drive voltage to the power supply side output transistor and the ground side output transistor of each of the output circuits in the set.

  In addition, when having a back electromotive force rise detection means for detecting a rise in the back electromotive force generated at both ends of the motor as a drop in the power supply voltage, the protection means responds to the back electromotive force rise detection by the back electromotive force rise detection means. It is preferable to have logic synthesis means for disabling the control voltage of the control voltage generation means and supplying an off drive voltage and an on drive voltage to the power supply side output transistor and the ground side output transistor of each of the two sets of output circuits.

  As described above, when the logic synthesis unit is included, the motor drive circuit having the above configuration includes a charged capacitor connected between the power supply terminal and the ground terminal, and the protection unit outputs the voltage between the terminals of the capacitor on the ground side. It is preferable to have pull-up means used as a power source for turning on the transistor at the output terminal of the logic synthesis means.

  In addition, in the case of having logic synthesis means, the protection means has pull-up means at the output terminal of the logic synthesis means using the back electromotive force generated at both ends of the motor as a power source for turning on the ground side output transistor. Is preferred.

  In addition, when the logic synthesis unit is provided, the motor drive circuit having the above configuration includes a capacitor connected to a power source and a ground and charged, and the protection unit includes a voltage between terminals of the capacitor or a back electromotive force generated at both ends of the motor. It is preferable to have pull-up means using any of the power as a power source for turning on the ground-side output transistor at the output terminal of the logic synthesis means.

  As described above, according to the present invention, it is possible to protect the motor drive circuit and the motor against the counter electromotive force generated in the motor even when the power supply voltage is lowered or grounded. The effect can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a first embodiment of the present invention. A DC power supply VCC that outputs a voltage VCC is connected to the motor drive circuit 10. The H bridge 14 included in the motor drive circuit 10 constitutes two sets of output circuits. The power supply side output transistors Q1 and Q3, the ground side output transistors Q2 and Q4, and diodes D1 and D2 connected in parallel to the transistors, One end is connected to D3, D4 and the gate of each transistor, and the other end is configured by resistors R1, R2, R3, R4 connected to the AAH terminal, AAL terminal, BBH terminal, and BBL terminal of the protection means 50 described later. The In the example shown in FIG. 1, the power supply side output transistors Q1 and Q3 are configured by P-channel MOSFETs, and the ground side output transistors Q2 and Q4 are configured by N-channel MOSFETs.

  The source of the power supply side output transistor Q1 is connected to the DC power supply VCC at the branch point P and simultaneously connected to the cathode of the diode D1. The drain of the power supply side output transistor Q1 is connected to the anode of the diode D1. The gate of the power supply side output transistor Q1 is connected to the output terminal AAH of the switch circuit 90 via the resistor R1.

  The drain of the ground side output transistor Q2 is connected to the cathode of the diode D2 and the drain of the power source side output transistor Q1 through the connection terminal M +. The source of the ground side output transistor Q2 is connected to the anode of the diode D2, and the connection end thereof is grounded. The gate of the ground side output transistor Q2 is connected to the output terminal AAL of the switch circuit 90 via the resistor R2.

  Similarly, in the other set, the source of the power supply side output transistor Q3 is connected to the DC power supply VCC at the branch point P and simultaneously connected to the cathode of the diode D3. The drain of the power supply side output transistor Q3 is connected to the anode of the diode D3. The gate of the power supply side output transistor Q3 is connected to the output terminal BBH of the switch circuit 90 through the resistor R3.

  The drain of the ground side output transistor Q4 is connected to the cathode of the diode D4 and the drain of the power source side output transistor Q3 through the connection terminal M−. The source of the ground side output transistor Q4 is connected to the anode of the diode D4, and the connection end thereof is grounded. The gate of the ground side output transistor Q4 is connected to the output terminal BBL of the switch circuit 90 via the resistor R4.

  The control voltage generation means 28 includes a target voltage setting circuit 18, a motor voltage detection circuit 16, an error amplification circuit 22, a PWM circuit 24, and a logic circuit 26 which will be described later. The target voltage setting circuit 18 outputs a target value T of the motor voltage of the motor M in accordance with forward and reverse rotation command signals input from the outside to the FW terminal and the RV terminal. It is assumed that the signals are not simultaneously input to the FW terminal and the RV terminal. On the other hand, the motor voltage detection circuit 16 receives the connection terminals M + and M− at both ends of the motor M as inputs.

  The output F of the motor voltage detection circuit 16 and the output T of the target voltage setting circuit 18 are input to the error amplification circuit 22. The output Y of the error amplification circuit 22 is input to the PWM circuit 24.

  Here, when the output F of the motor voltage detection circuit 16 that extracts the average voltage between the terminals of the motor M is lower than the output T of the target voltage setting circuit 18 according to the FW signal input from the outside, The output Y of the error amplifier circuit 22 is changed so as to increase the forward duty of the PWM circuit 24.

  On the other hand, when the output F of the motor voltage detection circuit 16 that extracts the average voltage between the terminals of the motor M is higher than the output T of the target voltage setting circuit 18, the PWM circuit 24 is used as the output Y of the error amplification circuit 22. The forward duty is changed so as to decrease.

  Here, as a detection method, the motor M is controlled by detecting the terminal voltage of the motor M, but it is also possible to detect the current flowing through the motor M and thereby control the motor M.

  The output of the PWM circuit 24 set in this way is input to the logic circuit 26, and AH, BH, AL, and BL are output as the output of the control voltage generating means 28.

  In the present embodiment, the switch circuit 90 includes logic synthesis means (logical sum) 101, 102, 103, 104 and logic synthesis means (negative) 105. The switch circuit 90 is supplied with the output of the comparator 70 and the outputs AH, AL, BH, and BL of the control voltage generator 28. The output of the comparator 70 is input to the logic synthesis unit 105, and the output of the logic synthesis unit 105 is input to the logic synthesis units 101, 102, 103, and 104. The outputs AH, AL, BH, and BL of the control voltage generating unit 28 are input to the logic synthesis units 101, 102, 103, and 104, respectively.

  One of the output AH of the control voltage generation means 28 and the output of the comparator 70 of the protection means 50 described later is selected in the switch circuit 90 as the output of the switch circuit 90, and the output AAH is pulled up via the pull-up means 81. Is done. The output AAH is connected to the gate of the power supply side output transistor Q1 through the resistor R1.

  One of the output AL of the control voltage generation means 28 and the output of the comparator 70 of the protection means 50 described later is selected in the switch circuit 90 as the output of the switch circuit 90, and the output AAL is pulled up via the pull-up means 82. Is done. The output AAL is connected to the gate of the ground side output transistor Q2 via the resistor R2.

  One of the output BH of the control voltage generation means 28 and the output of the comparator 70 of the protection means 50 described later is selected in the switch circuit 90 as the output of the switch circuit 90, and the output BBH is pulled up via the pull-up means 83. Is done. The output BBH is connected to the gate of the power supply side output transistor Q3 via the resistor R3.

  One of the output BL of the control voltage generation means 28 and the output of the comparator 70 of the protection means 50 described later is selected in the switch circuit 90 as the output of the switch circuit 90, and the output BBL is pulled up via the pull-up means 84. Is done. The output BBL is connected to the gate of the ground side output transistor Q4 via the resistor R4.

  In this embodiment, the switch circuit 90 is realized by the OR gates 101, 102, 103, and 104 and the logic NOT gate 105, but the output of the switch circuit 90 may be selected by other means.

  The protection means 50 includes a reference voltage generation circuit 60, a comparator 70, a switch circuit 90, for example, pull-up means 81, 82, 83, 84 constituted by resistors or constant current sources, and a capacitor C3. Here, the reference voltage generation circuit 60 and the comparator 70 constitute power supply voltage drop detection means.

  The comparator 70 receives the power supply voltage VCC and the output VREF of the reference voltage generating circuit 60 as inputs. The output of the comparator 70 is input to the switch circuit 90 and is logically synthesized with AH, AL, BH, and BL by the logic synthesis circuit in the switch circuit 90, and outputs AAH, AAL, BBH, and BBL, respectively. The capacitor C3 is connected between the DC power supply VCC and the ground, and is charged by the DC power supply VCC. In the present embodiment, the capacitor C3 is included in the motor drive circuit 10, but may be provided outside the motor drive circuit 10.

  As shown in FIG. 2, the comparator 70 has hysteresis. When the power supply voltage VCC drops from a high voltage, the comparator 70 outputs H when the power supply voltage VCC is equal to or higher than the output VREF of the reference voltage generating circuit 60. When the voltage VCC is equal to or lower than the output VREF of the reference voltage generating circuit 60, L is output. Conversely, when the power supply voltage VCC rises from a low voltage, the output of the comparator 70 starts from L, and the power supply voltage VCC is a voltage obtained by adding a preset hysteresis width to the output VREF of the reference voltage generating circuit 60. When it rises up, the output is set to H.

  Here, the threshold when switching the output of the comparator 70 from H to L, that is, the voltage VREF is set to be equal to or higher than the operation lower limit voltage of the logic synthesis means in the control voltage generation means 28 and the switch circuit 90. Also, by setting the hysteresis width of the comparator 70 to be larger than the induced voltage noise component superimposed on the power supply voltage in the transition period when the power supply voltage is lowered, the brake operation is stopped due to a transient rise in the power supply VCC. It is possible to avoid problems that occur. The relationship between the output of the comparator 70 and the power supply voltage VCC is shown in FIG.

  The output state of the power supply voltage VCC shown in FIG. 2 is (A) steady state (VCC> output VREF of the reference voltage creating circuit 60), the power supply voltage VCC is lowered, and (B) the power supply voltage lowered state (of the reference voltage creating circuit 60). The output VREF> VCC> the control voltage generating means 28 or the maximum value Vx of the operation lower limit voltages of the switch circuit 90), and the power supply voltage VCC is further lowered. (C) Power supply voltage output ground (ground) state (control voltage generating means 28) Alternatively, the operation of the present invention will be described by dividing it into the maximum value Vx> VCC> 0 V) among the operation lower limit voltages of the switch circuit 90.

  In the embodiment shown in FIG. 1, since the PWM circuit 24 is provided, the ON / OFF operation is repeated as appropriate. However, the control voltage generator 28 AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (VCC> output VREF of reference voltage generation circuit 60)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the output of the comparator 70 is H as shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, and 104 transmits the outputs AH, AL, BH, and BL of the control voltage generation means 28 as they are, and passes through the resistors R1, R2, R3, and R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (output VREF>VCC> reference voltage generation circuit 60> control voltage generation means 28 or maximum value Vx of operation lower limit voltage of switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of grounding (ground) → diode D2 → connection terminal M + → motor M tends to flow. At this time, the output of the comparator 70 becomes L as shown in FIG.

  At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104, In 105, the output is combined with the output of the comparator 70, and AAH = AAL = BBH = BBL = H, and the power supply side output transistor configured by P-channel MOSFETs via the resistors R1, R2, R3, and R4, respectively. By turning off Q1 and Q3 and turning on ground side output transistors Q2 and Q4 composed of N-channel MOSFETs, the motor rotation can be braked, and the induced voltage noise component due to the back electromotive force generated is grounded. Regenerate to (Grand).

  In digital cameras and the like, the power supply voltage may drop instantaneously and then return to the appropriate voltage when charging the capacity of the built-in flash function or when transferring data to a microcomputer. Even if the power supply voltage drop at this time falls only to the extent that it does not fall below the lower limit of the operation of the logic circuit 26 included in the control voltage generation means 28, the motor drive circuit and the motor can be protected by this method.

(C) Power supply voltage output ground (ground) state (maximum value Vx>VCC> 0 V among the operation lower limit voltages of the control voltage generating means 28 or the switch circuit 90)
VCC = 0V when the power supply voltage is further reduced, the control voltage generating means 28 or the switch circuit 90 is lower than the operation lower limit voltage, or the power supply means (for example, dry cell) applied to the power supply VCC from the outside is suddenly removed. When this occurs, an induced voltage noise component due to the counter electromotive force is induced at the motor end as in (B). At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite.

  Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 by the pull-up means 81, 82, 83, and 84 and the capacitor C3 charged to the power supply voltage VCC, and the P-channel MOSFET is configured. The power supply side output transistors Q1 and Q3 can be turned off, and the ground side output transistors Q2 and Q4 formed of N-channel MOSFETs can be turned on. The induced voltage noise component due to the generated back electromotive force is grounded (ground). Can be regenerated.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

(Embodiment 2)
FIG. 3 shows a second embodiment of the present invention. The parts corresponding to the first embodiment of the present invention shown in FIG. The description of the same parts as those of the first embodiment of the present invention shown in FIG. In this embodiment, the protection means 51 includes a reference voltage generation circuit 61, a comparator 71, a back electromotive force detection circuit 75, a switch circuit 90, for example, pull-up means 81, 82, 83 constituted by resistors or constant current sources, 84, having a capacity C3. Here, the reference voltage generating circuit 61, the comparator 71, and the counter electromotive force detection circuit 75 constitute a counter electromotive force increase detection means.

  The comparator 71 receives the output BEMF of the back electromotive force detection circuit 75 and the output VREF1 of the reference voltage generation circuit 61 as inputs. As shown in FIG. 4, the comparator 71 has hysteresis. When the output BEMF of the back electromotive force detection circuit 75 rises from a low voltage, the comparator 71 outputs H when the output is lower than the output VREF1 of the reference voltage generation circuit 61. When the output BEMF of the back electromotive force detection circuit 75 is equal to or higher than the output VREF1 of the reference voltage generation circuit 60, L is output. The threshold value for switching the output of the comparator 71 from H to L, that is, the voltage VREF1, is set to be equal to or higher than the counter electromotive force generated between the terminals of the motor M when the power supply voltage VCC is applied with an appropriate voltage. On the contrary, when the output BEMF of the back electromotive force detection circuit 75 falls from the high voltage, the output of the comparator 71 is changed from L, (the back electromotive force detection circuit 75 outputs VREF1 of the reference voltage generation circuit 61) − ( The output is set to H when it falls to a preset hysteresis width).

  The back electromotive force detection circuit 75 receives the voltage at the connection terminal M + and the connection terminal M−, the signals at the FW terminal and the RV terminal, and the output PWMOFF of the PWM circuit 24 as inputs. The back electromotive force detection circuit 75 determines which voltage of the connection terminal M + or the connection terminal M− is higher in accordance with a forward or reverse rotation command signal input from the FW terminal or the RV terminal, and the PWM circuit. The absolute value of the potential difference between the connection terminal M + and the connection terminal M− is output as the output BEMF only during a period in which the H bridge is regenerated by 24 output PWMOFF. When the H bridge is energized, the back electromotive force detection circuit 75 outputs 0V. Of course, the counter electromotive force induced in the motor M may be detected without using the counter electromotive force detection circuit 75.

  The output state of the back electromotive force detection circuit 75 is shown in FIG. 4 (A) steady state (BEMF <output VREF1 of the reference voltage generation circuit 60), the power supply voltage VCC decreases (B) the power supply voltage decrease state (BEMF> reference voltage) The output VREF1 of the generating circuit 60 and the power supply voltage VCC> the control voltage generating means 28 or the maximum value of the operation lower limit voltages of the switch circuit 90), and the power supply voltage has further decreased (C) Power supply voltage ground (ground) state (control) The operation of the present invention will be described by dividing it into the maximum value> VCC> 0V of the operation lower limit voltage of the voltage generating means 28 or the switch circuit 90).

  In the embodiment shown in FIG. 3, since the PWM circuit 24 is provided, the ON / OFF operation is repeated as appropriate. However, the control voltage generator 28 AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (BEMF <output VREF1 of reference voltage generation circuit 61)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the counter electromotive force generated between the terminals of the motor M is less than or equal to the output VREF1 of the reference voltage generating circuit 61, and therefore the output of the comparator 71 is As shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, and 104 transmits the outputs AH, AL, BH, and BL of the control voltage generation means 28 as they are, and passes through the resistors R1, R2, R3, and R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (BEMF> output VREF1 of reference voltage generation circuit 61 and power supply voltage VCC> maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of grounding (ground) → diode D2 → connection terminal M + → motor M tends to flow. At this time, since the counter electromotive force induced in the motor M becomes larger than the output VREF1 of the reference voltage generating circuit 61, the output of the comparator 71 becomes L as shown in FIG.

  At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104 Are combined with the output of the comparator 71, AAH = AAL = BBH = BBL = H, and the power supply side output transistor Q1, which is composed of a P-channel type MOSFET, through resistors R1, R2, R3, R4, respectively. By turning off Q3 and turning on the ground side output transistors Q2 and Q4 formed of N-channel MOSFETs, the rotation of the motor can be braked, and the induced voltage noise component due to the generated back electromotive force is grounded (ground) ).

(C) Power supply voltage ground (ground) state (maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90>VCC> 0 V): power supply voltage VCC is an operation of control voltage generation means 28 or switch circuit 90 The area below the maximum value of the lower limit voltage The power supply voltage is further lowered, is equal to or lower than the operation lower limit voltage of the control voltage generating means 28 or the switch circuit 90, and further, the power supply means applied to the power supply VCC from the outside (for example, dry cell) When VCC is suddenly removed, VCC induced voltage noise component due to counter electromotive force is induced at the motor end as in (B).

  At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite. Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 by the pull-up means 81, 82, 83, and 84 and the capacitor C3 charged to the voltage VCC, and the P-channel MOSFET is configured. The power supply side output transistors Q1 and Q3 can be turned off, and the ground side output transistors Q2 and Q4 composed of N-channel MOSFETs can be turned on, and the induced voltage noise component due to the generated back electromotive force can be regenerated to the ground (ground). can do.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

(Embodiment 3)
FIG. 5 shows a third embodiment of the present invention. The portions corresponding to the first embodiment of the present invention shown in FIG. 1 and the second embodiment of the present invention shown in FIG. 4 use the same reference numerals. The description of the same parts as those of the first embodiment of the present invention shown in FIG. 1 and the second embodiment of the present invention shown in FIG. 4 is omitted. In the present embodiment, the protection means 52 includes a reference voltage generating circuit 60, a comparator 70, a back electromotive force detection circuit 75, a switch circuit 90, for example, pull-up means 81, 82, 83 constituted by resistors or constant current sources, 84, a pull-up voltage selection circuit 76 is provided.

  In this embodiment, the pull-up voltage selection circuit 76 is realized by the method described below, but may naturally be realized by other means. The pull-up voltage selection circuit 76 includes diodes D761 and D762 and a resistor R763. The anode of the diode D761 is connected to the power supply VCC, and the cathode is connected to one end of the resistor R763. The other end of the resistor R763 is connected to the ground. The anode of the diode D762 is connected to the output BEMF of the back electromotive force detection circuit 75, and the cathode is connected to the cathode of the diode D761. The output of the pull-up voltage selection circuit 76 is the larger of the input power supply VCC and the output BEMF of the back electromotive force detection circuit 75. The output of the pull-up voltage selection circuit 76 is connected to pull-up means 81, 82, 83, 84. The input of the comparator 70 receives the output VREF of the reference voltage generation circuit 60 and the power supply voltage VCC.

  The output state of the power supply voltage VCC shown in FIG. 2 is (A) steady state (VCC> output VREF of the reference voltage creating circuit 60), the power supply voltage VCC is lowered, and (B) the power supply voltage lowered state (of the reference voltage creating circuit 60). The output VREF> VCC> the control voltage generating means 28 or the maximum value Vx of the operation lower limit voltages of the switch circuit 90), and the power supply voltage VCC is further lowered. (C) Power supply voltage output ground (ground) state (control voltage generating means 28) Alternatively, the operation of the present invention will be described by dividing it into the maximum value Vx> VCC> 0 V) among the operation lower limit voltages of the switch circuit 90.

  In the embodiment shown in FIG. 5, since the PWM circuit 24 is included, the ON / OFF operation is repeated as appropriate. However, the control voltage generating means 28 uses AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (VCC> output VREF of reference voltage generation circuit 60)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the output of the comparator 70 is H as shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, 104, 105 transmits the outputs AH, AL, BH, BL of the control voltage generation means 28 as they are, and the resistors R1, R2, R3, R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (output VREF>VCC> reference voltage generation circuit 60> control voltage generation means 28 or maximum value Vx of operation lower limit voltage of switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of grounding (ground) → diode D2 → connection terminal M + → motor M tends to flow.

  At this time, the output of the comparator 70 becomes L as shown in FIG. At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104, In 105, the output is combined with the output of the comparator 70, and AAH = AAL = BBH = BBL = H, and the power supply side output transistor configured by P-channel MOSFETs via the resistors R1, R2, R3, and R4, respectively. By turning off Q1 and Q3 and turning on ground side output transistors Q2 and Q4 composed of N-channel MOSFETs, the motor rotation can be braked, and the induced voltage noise component due to the back electromotive force generated is grounded. Regenerate to (Grand).

(C) Power supply voltage output ground (ground) state (maximum value Vx>VCC> 0 V among the operation lower limit voltages of the control voltage generating means 28 or the switch circuit 90)
VCC = 0V when the power supply voltage is further reduced, the control voltage generating means 28 or the switch circuit 90 is lower than the operation lower limit voltage, or the power supply means (for example, dry cell) applied to the power supply VCC from the outside is suddenly removed. When this occurs, an induced voltage noise component due to the counter electromotive force is induced at the motor end as in (B). At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite.

  Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 in the pull-up means 81, 82, 83, and 84 and the pull-up voltage selection circuit 76, and the power supply side that is constituted by a P-channel MOSFET is used. The output transistors Q1 and Q3 can be turned off, and the ground-side output transistors Q2 and Q4 composed of N-channel MOSFETs can be turned on, and the induced voltage noise component due to the generated back electromotive force can be regenerated to the ground (ground). Can do.

  Even when the power supply voltage VCC becomes 0 V, for example, the power supply output transistors Q1 and Q3 are turned off and the voltage required to turn on the ground output transistors Q2 and Q4 falls below the voltage required for the motor M. The back electromotive force is output from the pull-up voltage selection circuit 76, and H can be applied to the transistors Q1, Q2, Q3, and Q4.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

(Embodiment 4)
FIG. 6 shows a fourth embodiment of the present invention. The parts corresponding to the first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, and the third embodiment of the present invention shown in FIG. Used. Also, the description of the same part as the first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, and the third embodiment of the present invention shown in FIG. Omitted.

  The protection means 53 in this embodiment is a reference voltage generating circuit 61, a comparator 71, a back electromotive force detection circuit 75, a switch circuit 90, for example, pull-down means 81, 82, 83, 84 constituted by resistors or constant current sources. And a pull-up voltage selection circuit 76. The output of the back electromotive force detection circuit 75 is input to the comparator 71 and also input to the pull-up voltage selection circuit 76. The output of the pull-up voltage selection circuit 76 is connected to pull-up means 81, 82, 83, 84.

  The output state of the back electromotive force detection circuit 75 is shown in FIG. 4 (A) steady state (BEMF <output VREF1 of the reference voltage generation circuit 61), the power supply voltage VCC decreases (B) the power supply voltage decrease state (BEMF> reference voltage) The output VREF1 of the generation circuit 61 and the power supply voltage VCC> the control voltage generation means 28 or the maximum value of the operation lower limit voltages of the switch circuit 90), and the power supply voltage further decreases (C) the power supply voltage ground (ground) state (control) The operation of the present invention will be described by dividing it into the maximum value> VCC> 0V of the operation lower limit voltage of the voltage generating means 28 or the switch circuit 90).

  In the embodiment shown in FIG. 6, since the PWM circuit 24 is included, the ON / OFF operation is repeated as appropriate. However, the control voltage generator 28 AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (BEMF <output VREF1 of reference voltage generation circuit 61)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the counter electromotive force generated between the terminals of the motor M is less than or equal to the output VREF1 of the reference voltage generating circuit 61, and therefore the output of the comparator 71 is As shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, and 104 transmits the outputs AH, AL, BH, and BL of the control voltage generation means 28 as they are, and passes through the resistors R1, R2, R3, and R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (BEMF> output VREF1 of reference voltage generation circuit 61 and power supply voltage VCC> maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of ground (ground) → diode D2 → connection terminal M + motor M tends to flow.

  At this time, since the counter electromotive force induced in the motor M becomes larger than the output VREF1 of the reference voltage generating circuit 61, the output of the comparator 71 becomes L as shown in FIG. At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104, In 105, the output is combined with the output of the comparator 71, and AAH = AAL = BBH = BBL = H is obtained, and the power supply side output transistor configured by a P-channel MOSFET is passed through resistors R1, R2, R3, and R4, respectively. By turning off Q1 and Q3 and turning on ground side output transistors Q2 and Q4 composed of N-channel MOSFETs, the motor rotation can be braked, and the induced voltage noise component due to the back electromotive force generated is grounded. Regenerate to (Grand).

(C) Power supply voltage ground (ground) state (maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90>VCC> 0 V): power supply voltage VCC is an operation of control voltage generation means 28 or switch circuit 90 The area below the maximum value of the lower limit voltage The power supply voltage is further lowered, is equal to or lower than the operation lower limit voltage of the control voltage generating means 28 or the switch circuit 90, and further, the power supply means applied to the power supply VCC from the outside (for example, dry cell) When VCC is suddenly removed, VCC induced voltage noise component due to counter electromotive force is induced at the motor end as in (B). At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite.

  Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 in the pull-up means 81, 82, 83, and 84 and the pull-up voltage selection circuit 76, and the power supply side that is constituted by a P-channel MOSFET is used. The output transistors Q1 and Q3 can be turned off, and the ground-side output transistors Q2 and Q4 composed of N-channel MOSFETs can be turned on, and the induced voltage noise component due to the generated back electromotive force can be regenerated to the ground (ground). Can do.

  Even when the power supply voltage VCC becomes 0 V, for example, the power supply output transistors Q1 and Q3 are turned off and the voltage required to turn on the ground output transistors Q2 and Q4 falls below the voltage required for the motor M. The back electromotive force is output from the pull-up voltage selection circuit 76, and H can be applied to the transistors Q1, Q2, Q3, and Q4.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

(Embodiment 5)
FIG. 7 shows a fifth embodiment of the present invention. The parts corresponding to the first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, and the third embodiment of the present invention shown in FIG. Used. Also, the description of the same part as the first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, and the third embodiment of the present invention shown in FIG. Omitted.

  In the present embodiment, the protection means 54 includes a reference voltage generating circuit 60, a comparator 70, a counter electromotive force detection circuit 75, a switch circuit 90, for example, pull-up means 81, 82, 83 constituted by resistors or constant current sources, 84, a pull-up voltage selection circuit 76, and a capacitor C3.

  The output state of the power supply voltage VCC shown in FIG. 2 is (A) steady state (VCC> output VREF of the reference voltage creating circuit 60), the power supply voltage VCC is lowered, and (B) the power supply voltage lowered state (of the reference voltage creating circuit 60). The output VREF> VCC> the control voltage generating means 28 or the maximum value Vx of the operation lower limit voltages of the switch circuit 90), and the power supply voltage VCC is further lowered. (C) Power supply voltage output ground (ground) state (control voltage generating means 28) Alternatively, the operation of the present invention will be described by dividing it into the maximum value Vx> VCC> 0 V) among the operation lower limit voltages of the switch circuit 90.

  In the embodiment shown in FIG. 7, since the PWM circuit 24 is included, the ON / OFF operation is repeated as appropriate. However, the control voltage generator 28 AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (VCC> output VREF of reference voltage generation circuit 60)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the output of the comparator 70 is H as shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, 104, 105 transmits the outputs AH, AL, BH, BL of the control voltage generation means 28 as they are, and the resistors R1, R2, R3, R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (output VREF>VCC> reference voltage generation circuit 60> control voltage generation means 28 or maximum value Vx of operation lower limit voltage of switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of grounding (ground) → diode D2 → connection terminal M + → motor M tends to flow. At this time, the output of the comparator 70 becomes L as shown in FIG.

  At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104, In 105, the output is combined with the output of the comparator 70, and AAH = AAL = BBH = BBL = H, and the power supply side output transistor configured by P-channel MOSFETs via the resistors R1, R2, R3, and R4, respectively. By turning off Q1 and Q3 and turning on ground side output transistors Q2 and Q4 composed of N-channel MOSFETs, the motor rotation can be braked, and the induced voltage noise component due to the back electromotive force generated is grounded. Regenerate to (Grand).

(C) Power supply voltage output ground (ground) state (maximum value Vx>VCC> 0 V among the operation lower limit voltages of the control voltage generating means 28 or the switch circuit 90)
VCC = 0V when the power supply voltage is further reduced, the control voltage generating means 28 or the switch circuit 90 is lower than the operation lower limit voltage, or the power supply means (for example, dry cell) applied to the power supply VCC from the outside is suddenly removed. When this occurs, an induced voltage noise component due to the counter electromotive force is induced at the motor end as in (B). At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite.

  Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 in the pull-up means 81, 82, 83, and 84 and the pull-up voltage selection circuit 76, and the power supply side that is constituted by a P-channel MOSFET is used. The output transistors Q1 and Q3 can be turned off, and the ground-side output transistors Q2 and Q4 composed of N-channel MOSFETs can be turned on, and the induced voltage noise component due to the generated back electromotive force can be regenerated to the ground (ground). Can do.

  Even when the power supply voltage VCC becomes 0V or the like, the power supply side output transistors Q1 and Q3 are turned off, and even if the voltage is lower than the voltage necessary for turning on the ground side output transistors Q2 and Q4, the output from the pull-up voltage selection circuit 76 H can be applied to the transistors Q1, Q2, Q3, and Q4 by the back electromotive force induced at the terminal of the motor M or the capacitor C3 charged to the voltage VCC.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

(Embodiment 6)
FIG. 8 shows a sixth embodiment of the present invention. The first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, the third embodiment of the present invention shown in FIG. 5, and the first embodiment of the present invention shown in FIG. The same reference numerals are used for the portions corresponding to the fourth embodiment. Further, the first embodiment of the present invention shown in FIG. 1, the second embodiment of the present invention shown in FIG. 4, the third embodiment of the present invention shown in FIG. 5, and the present invention shown in FIG. Description of the same parts as those in the fourth embodiment will be omitted.

  The protection means 55 in this embodiment is a reference voltage generating circuit 61, a comparator 71, a back electromotive force detection circuit 75, a switch circuit 90, for example, pull-down means 81, 82, 83, 84 composed of resistors or constant current sources. , A pull-up voltage selection circuit 76, and a capacitor C3. The output of the back electromotive force detection circuit 75 is input to the comparator 71 and also input to the pull-up voltage selection circuit 76. The output of the pull-up voltage selection circuit 76 is connected to pull-up means 81, 82, 83, 84.

  The output state of the back electromotive force detection circuit 75 is shown in FIG. 4 (A) steady state (BEMF <output VREF1 of the reference voltage generation circuit 61), the power supply voltage VCC decreases (B) the power supply voltage decrease state (BEMF> reference voltage) The output VREF1 of the generation circuit 61 and the power supply voltage VCC> the control voltage generation means 28 or the maximum value of the operation lower limit voltages of the switch circuit 90), and the power supply voltage further decreases (C) the power supply voltage ground (ground) state (control) The operation of the present invention will be described by dividing it into the maximum value> VCC> 0V of the operation lower limit voltage of the voltage generating means 28 or the switch circuit 90).

  In the embodiment shown in FIG. 6, since the PWM circuit 24 is included, the ON / OFF operation is repeated as appropriate. However, the control voltage generator 28 AH = AAH = L, BH = BBH = H, AL = AAL = L, BL = BBL = H, power supply side output transistor Q1 and ground side output transistor Q4 are turned on, branch point P where current is applied with power supply voltage VCC → transistor Q1 → connection terminal M + → motor M → connection Consider a period in which the terminal M-> transistor Q4-> ground (ground) is energized and rotating in the forward direction.

(A) Steady state (BEMF <output VREF1 of reference voltage generation circuit 61)
When the power supply voltage VCC is in a steady state where an appropriate voltage is applied, the counter electromotive force generated between the terminals of the motor M is less than or equal to the output VREF1 of the reference voltage generating circuit 61, and therefore the output of the comparator 71 is As shown in FIG. At this time, the logic synthesis unit 101 outputs the output AH of the control voltage generation unit 28 as AAH. The logic synthesis unit 102 outputs the output AL of the control voltage generation unit 28 as AAL. The logic synthesis unit 103 outputs the output BH of the control voltage generation unit 28 as BBH. The logic synthesis unit 104 outputs the output BL of the control voltage generation unit 28 as BBL.

  That is, the switch circuit 90 constituted by the logic synthesis means 101, 102, 103, and 104 transmits the outputs AH, AL, BH, and BL of the control voltage generation means 28 as they are, and passes through the resistors R1, R2, R3, and R4, respectively. The ground side output transistors Q2 and Q4 are turned off and on, respectively, and the power source side output transistors Q1 and Q3 are turned on and off, respectively. Thus, during normal operation, the circuit according to the present invention does not affect the normal control system of the control voltage generating means 28.

(B) Power supply voltage drop state (BEMF> output VREF1 of reference voltage generation circuit 61 and power supply voltage VCC> maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90)
When the power supply voltage VCC decreases, the drive current that has flown to drive in the forward direction decreases, but the connection terminal M− → diode D3 → branch point P → power supply VCC → A regenerative current of ground (ground) → diode D2 → connection terminal M + motor M tends to flow. At this time, since the counter electromotive force induced in the motor M becomes larger than the output VREF1 of the reference voltage generating circuit 61, the output of the comparator 70 becomes L as shown in FIG.

  At this time, the control voltage generation means 28 outputs AH = L, AL = L, BH = H, BL = H based on the forward rotation command FW, but the logic synthesis means 101, 102, 103, 104, In 105, the output is combined with the output of the comparator 71, and AAH = AAL = BBH = BBL = H is obtained, and the power supply side output transistor configured by a P-channel MOSFET is passed through resistors R1, R2, R3, and R4, respectively. By turning off Q1 and Q3 and turning on ground side output transistors Q2 and Q4 composed of N-channel MOSFETs, the motor rotation can be braked, and the induced voltage noise component due to the back electromotive force generated is grounded. Regenerate to (Grand).

(C) Power supply voltage ground (ground) state (maximum value of operation lower limit voltage of control voltage generation means 28 or switch circuit 90>VCC> 0 V): power supply voltage VCC is an operation of control voltage generation means 28 or switch circuit 90 The area below the maximum value of the lower limit voltage The power supply voltage is further lowered, is equal to or lower than the operation lower limit voltage of the control voltage generating means 28 or the switch circuit 90, and further, the power supply means applied to the power supply VCC from the outside (for example, dry cell) When VCC is suddenly removed, VCC induced voltage noise component due to counter electromotive force is induced at the motor end as in (B). At this time, the outputs AAH, BBH, AAL, BBL of the switch circuit 90 are indefinite.

  Also in this case, H is applied to the gates of the transistors Q1, Q2, Q3, and Q4 in the pull-up means 81, 82, 83, and 84 and the pull-up voltage selection circuit 76, and the power supply side that is constituted by a P-channel MOSFET is used. The output transistors Q1 and Q3 can be turned off, and the ground-side output transistors Q2 and Q4 composed of N-channel MOSFETs can be turned on, and the induced voltage noise component due to the generated back electromotive force can be regenerated to the ground (ground). Can do.

  Even when the power supply voltage VCC becomes 0V or the like, the power supply side output transistors Q1 and Q3 are turned off, and even if the voltage is lower than the voltage necessary for turning on the ground side output transistors Q2 and Q4, the output from the pull-up voltage selection circuit 76 H can be applied to the transistors Q1, Q2, Q3, and Q4 by the back electromotive force induced at the terminal of the motor M to be driven or the capacitor C3 charged to the voltage VCC.

  In this way, even when the power supply voltage is lowered, and even when the power supply voltage VCC = 0V, the induced voltage noise component due to the back electromotive force induced at the motor end is turned to ground (ground) by turning on the ground side output transistor. The motor can be regenerated and the motor drive circuit and the motor can be protected. In addition, this protection configuration can be realized without affecting the operation during the normal operation controlled by the control voltage generator 28 as described above.

  In the control voltage generating means 28 of the present embodiment, the circuit configuration having the PWM circuit 24 has been described in detail as an example, but it goes without saying that the same applies to a circuit configuration having no PWM circuit 24. In this embodiment, the case where the motor is rotated in the forward direction has been described in detail as an example, but it is needless to say that the same countermeasure can be taken when the motor is rotated in the reverse direction.

  As described above, the present invention relates to a motor drive circuit by a back electromotive force induced when the power supply voltage is lowered and further grounded (ground) in the motor drive circuit, and a method for protecting against destruction of the motor. It is valid.

It is a circuit diagram showing a motor drive circuit of a 1st embodiment of the present invention. FIG. 5 is a relationship diagram between a VCC power supply voltage and an output voltage of a comparator in the first, third, and fifth embodiments of the present invention. It is a circuit diagram which shows the motor drive circuit of the 2nd Embodiment of this invention. FIG. 10 is a relationship diagram between a counter electromotive force and an output voltage of a comparator 71 in the second, fourth, and sixth embodiments of the present invention. It is a circuit diagram which shows the motor drive circuit of the 3rd Embodiment of this invention. It is a circuit diagram which shows the motor drive circuit of the 4th Embodiment of this invention. It is a circuit diagram which shows the motor drive circuit of the 5th Embodiment of this invention. It is a circuit diagram which shows the motor drive circuit of the 6th Embodiment of this invention. It is a circuit diagram which shows the motor drive circuit of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor drive circuit 12 Power supply circuit 14 H bridge circuit 16 Motor voltage detection circuit 18 Target voltage setting circuit 20 Power supply voltage detection circuit 22 Error amplification circuit 24 PWM circuit 26 Logic circuit 28 Control voltage generation means 50 Protection means 51 Protection means 52 Protection means 53 Protection means 54 Protection means 55 Protection means 60 Reference voltage generation circuit 61 Reference voltage generation circuit 70 Comparator 71 Comparator 75 Back electromotive force detection circuit 76 Pull-up voltage selection circuit 81 Pull-up means 82 Pull-up means 83 Pull-up means 84 Pull-up means 90 Switch circuit 101 Logic synthesizing means 102 Logic synthesizing means 103 Logic synthesizing means 104 Logic synthesizing means 105 Logic synthesizing means C1 Capacitance C2 Capacitance C3 Capacitance D1 Diode D2 Diode D3 Diode D4 Diode D5 Zener diode D6 Zener diode D7 Zener diode D761 Diode D762 Diode IC1 Operational amplifier M Motor Q1 Power supply output transistor Q2 Ground output transistor Q3 Power supply output transistor Q4 Ground output transistor R1 Resistor R2 Resistor R3 Resistor R4 Resistor R5 Resistor R6 Resistor R7 Resistor R8 Resistor R9 Resistor R10 Resistor R11 Resistor R12 Resistor R13 Resistor R763 Resistor VCC DC power supply

Claims (19)

Two sets of output circuits comprising a power supply side output transistor and a ground side output transistor connected in series, the intermediate connection point of which is an output terminal, and a motor connected between the two output terminals;
Control voltage generating means for applying a control voltage to each of the power supply side output transistor and the ground side output transistor of the two sets of output circuits;
An overvoltage generated by a counter electromotive force generated from the motor by forcibly turning on the ground side transistors of each of the two sets of output circuits in response to a decrease in power supply voltage applied to the two sets of output circuits. A motor drive circuit comprising a protection means for suppressing.   The motor drive circuit according to claim 1, wherein the protection means includes power supply voltage drop detection means for detecting a drop in power supply voltage.   2. The motor drive circuit according to claim 1, wherein the protection unit includes a back electromotive force increase detection unit that detects an increase in back electromotive force generated at both ends of the motor as a decrease in power supply voltage.   A capacitor connected between a power supply terminal and a ground terminal is charged, and the protection unit uses the voltage between the terminals of the capacitor as a power source for turning on the ground side transistors of the two sets of output circuits. The motor drive circuit according to claim 1.   2. The motor drive circuit according to claim 1, wherein the protection means uses a back electromotive force generated at both ends of the motor as a power source for turning on the ground-side output transistor.   3. The capacitor according to claim 2, further comprising a charged capacitor connected between a power supply terminal and a ground terminal, wherein the protection unit uses a voltage between the terminals of the capacitor as a power supply for turning on the ground-side output transistor. Motor drive circuit.   4. The capacitor according to claim 3, further comprising a charged capacitor connected between a power supply terminal and a ground terminal, wherein the protection unit uses a voltage between the terminals of the capacitor as a power supply for turning on the ground-side output transistor. Motor drive circuit.   The motor drive circuit according to claim 2, wherein the protection means uses a back electromotive force generated at both ends of the motor as a power source for turning on the ground-side output transistor.   The motor drive circuit according to claim 3, wherein the protection means uses a back electromotive force generated at both ends of the motor as a power source for turning on the ground-side output transistor.   A capacitor connected to a power source and a ground is charged, and the protection unit turns on the ground-side output transistor by either a voltage across the capacitor or a counter electromotive force generated at both ends of the motor. The motor drive circuit of Claim 2 used as a power supply for a.   A capacitor connected to a power source and a ground is charged, and the protection unit turns on the ground-side output transistor by either a voltage across the capacitor or a counter electromotive force generated at both ends of the motor. The motor drive circuit according to claim 3, wherein the motor drive circuit is used as a power source.   The protection means disables the control voltage of the control voltage generation means in response to the detection of the power supply voltage drop by the power supply voltage drop detection means, and the power supply side output transistor and the ground side output transistor of each of the two sets of output circuits The motor drive circuit according to claim 2, further comprising logic synthesis means for providing an off drive voltage and an on drive voltage respectively.   The protection means disables the control voltage of the control voltage generating means in response to detection of the back electromotive force rise detected by the back electromotive force rise detection means, and the power supply side output transistor and ground side of each of the two sets of output circuits 4. The motor drive circuit according to claim 3, further comprising logic synthesis means for applying an off drive voltage and an on drive voltage to the output transistor.   A capacitor connected between a power supply terminal and a ground terminal and charged; and the protection means includes a pull-up means using the voltage between the terminals of the capacitor as a power supply for turning on the ground-side output transistor. The motor drive circuit according to claim 12, wherein the motor drive circuit is provided at an output end of the synthesizing means.   A capacitor connected between a power supply terminal and a ground terminal and charged; and the protection means includes a pull-up means using the voltage between the terminals of the capacitor as a power supply for turning on the ground-side output transistor. The motor drive circuit according to claim 13, wherein the motor drive circuit is provided at an output end of the combining means.   The said protection means has the pull-up means which used the back electromotive force which generate | occur | produces in the both ends of the said motor as a power supply for turning on the said ground side output transistor in the output terminal of the said logic synthesis means. Motor drive circuit.   The said protection means has the pull-up means which used the back electromotive force which generate | occur | produces at the both ends of the said motor as a power supply for turning on the said ground side output transistor in the output terminal of the said logic synthetic | combination means. Motor drive circuit.   A capacitor connected to a power source and a ground is charged, and the protection unit turns on the ground-side output transistor by either a voltage across the capacitor or a counter electromotive force generated at both ends of the motor. The motor drive circuit according to claim 12, further comprising pull-up means used as a power source for output at an output terminal of the logic synthesis means. A capacitor connected to a power source and a ground is charged, and the protection unit turns on the ground-side output transistor by either a voltage across the capacitor or a counter electromotive force generated at both ends of the motor. The motor drive circuit according to claim 13, further comprising pull-up means used as a power source for output at an output terminal of the logic synthesis means.

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