JP2010110092A - Drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive device that accurately ensures and maintains reliability of an overcurrent protection function even when a threshold voltage for determining the presence or the absence of an overcurrent of a power element is set on the basis of a load driving voltage. <P>SOLUTION: The drive device includes a comparator 61 that compares a voltage Vs on the side of a source terminal of a power element 13 with a threshold voltage so as to output a signal based on the comparison result. The drive device has an overcurrent protection function for detecting the presence or the absence of an overcurrent of the power element 13 on the basis of the output signal of the comparator 61. Here, a voltage inputted to a reference voltage terminal 61a of the comparator 61 is shift-adjusted to a voltage smaller than the threshold voltage. The voltage Vs on the side of the source terminal of the power element 13 is shift-adjusted at the ratio equal to the shift adjustment ratio so as to input it to a detection voltage terminal 61b of the comparator 61. The presence or the absence of an overcurrent of the power element 13 is detected through the comparison of each input voltage of the reference-voltage terminal 61a and the detection voltage terminal 61b by the comparator 61. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving device for controlling driving of a load such as a motor.

  2. Description of the Related Art Conventionally, electronic control devices that drive and control electromagnetic actuators such as in-vehicle motors, for example, have been provided with power elements such as power MOSFETs (MOS field effect transistors) on the power supply line to those drive control targets. Thus, the drive of the same drive control object is controlled through the on / off control of the power element. Usually, such a power element is often mounted as a driving device such as a driver IC integrated on a substrate together with various electronic components. Conventionally, as such a driving device, there is a driving device described in Patent Document 1, for example. FIG. 3 shows an outline of a drive circuit for a drive device that has been generally employed, including the drive device described in Patent Document 1.

  As shown in FIG. 3, in this drive device, when a drive command Sd is transmitted from the microcomputer 20 that generally controls various controls related to driving of the electric actuator, the drive command Sd is transmitted to the control circuit 12. In addition to the input, the control circuit 12 switches the power element 13 on and off based on the input drive command Sd. In this drive device, when the power element 13 is turned on, the voltage applied to the load drive power supply terminal 14a, which is one of the power supply terminals, that is, the power supply voltage VB of the in-vehicle battery BT is used as the load drive voltage Vp. 30 is applied as it is to supply power. Incidentally, this drive device is also provided with a control power supply terminal 14b to which a voltage (control voltage Vb) obtained by smoothing the power supply voltage VB of the in-vehicle battery BT through the smoothing circuit 40 is applied. A driving power source for the control circuit 12 is secured through a constant voltage circuit 11 connected to 14b. The smoothing circuit 40 includes a diode 41, a resistor 42, and a capacitor 43. Reference numeral 50 denotes a vehicle accessory switch.

According to such a configuration as the driving device, switching of a large current by the power element 13 is possible, so that the degree of freedom in design as the driving device is improved. Further, since the power element 13 is a voltage-driven element, for example, the design of a gate drive circuit provided in the control circuit 12 becomes relatively easy. Further, even when an unstable power source such as the in-vehicle battery BT is used as a driving power source for the control circuit 12, a stable voltage that is smoothed and constant voltage is obtained through the smoothing circuit 40 and the constant voltage circuit 11. Can be applied to the control circuit 12. For this reason, the stable operation of the control circuit 12 can be ensured, and as a result, the drive control of the motor 30 can be performed more accurately.
JP 2003-316455 A

  As described above, by adopting the power element 13 as the switching element of the driving device, it is possible to perform switching of a large current or to obtain an advantage that the design of the gate driving circuit becomes relatively easy. Will be able to. However, since the power element 13 is generally vulnerable to overcurrent, for example, a short circuit occurs between the power supply path of the motor 30 and the ground path as shown by the two-dot chain line in FIG. If an abnormal situation such as a current exceeding a specified value flows, the element 13 may be damaged. For this reason, in order to prevent such breakage of the power element 13, an apparatus having a protection function for preventing an overcurrent from flowing through the power element 13 has been proposed. FIG. 4 shows an outline of an example of a drive device having such an overcurrent protection function.

  As shown in FIG. 4, the driving device takes in a voltage Vs on the terminal (source terminal) side connected to the motor 30 of the power element 13 and monitors the applied voltage of the power element 13. 60. Here, in the voltage detection circuit 60, the voltage Vs on the source terminal side of the power element 13 is input to the non-inverting input terminal (detection voltage terminal) 61 b of the comparator (comparator) 61, and the inversion of the comparator 61 is performed. The signal is binarized through comparison with the threshold voltage Vr input to the input terminal (reference voltage terminal) 61 a, and the binarized signal is output to the control circuit 12. Incidentally, the threshold voltage Vr is set to, for example, a divided value (for example, Vb / 2) of the voltage dividing resistors R1 and R2 of the control voltage Vb. When the control circuit 12 detects that the output signal of the comparator 61 has been switched from the logic high level to the logic low level, the control circuit 12 turns off the power element 13 to forcibly cut off the power supply to the motor 30. According to such a configuration as the driving device, for example, if a short circuit occurs between the power supply path and the ground path of the motor 30, the voltage Vs on the source terminal side of the power element 13 is significantly reduced, and thus the voltage Vs is reduced. When the voltage becomes lower than the threshold voltage Vr, the output signal of the comparator 61 is switched from the logic high level to the logic low level. When the output signal of the comparator 61 is switched from the logic high level to the logic low level in this way, the power element 13 can be turned off and an overcurrent can be prevented from flowing through the element 13. It becomes possible to prevent damage to the battery.

  On the other hand, in such a drive device, the load voltage Vp and the control voltage Vb are normally in a steady state where the power voltage VB of the in-vehicle battery BT is reached. The magnitude of the threshold voltage Vr is set. For this reason, when the driving device is in a transient state where the fluctuation of the power supply voltage VB of the in-vehicle battery BT is large, for example, when the engine of the vehicle is started, that is, when the fluctuations of the load driving voltage Vp and the control voltage Vb are large. In that case, the following problems cannot be ignored.

  First, for example, as shown in FIG. 5, if the user of the vehicle turns on the accessory switch 50 at time t1, the load driving voltage Vp immediately rises to the power supply voltage VB of the in-vehicle battery BT. On the other hand, the control voltage Vb gradually rises from time t1 due to the operation of the smoothing circuit 40, and becomes the power supply voltage VB of the in-vehicle battery BT at the time t2, and the load driving voltage Vp and the control voltage Vb. Both of them reach the power supply voltage VB. Thereafter, if the user turns on the engine start switch of the vehicle at time t3, a large amount of power is consumed to drive an in-vehicle device such as a starter motor of the vehicle, and the power supply voltage VB of the in-vehicle battery BT Is greatly reduced temporarily, and accordingly, the load driving voltage Vp is also temporarily reduced. That is, following the decrease in the load driving voltage Vp, the voltage input to the detection voltage terminal 61b of the comparator 61 is also greatly decreased. On the other hand, the control voltage Vb gradually decreases from the time t3 due to the operation of the smoothing circuit 40, and is input to the reference voltage terminal 61a of the comparator 61 following the change of the control voltage Vb. The voltage gradually decreases. Therefore, in this drive device, the voltage input to the detection voltage terminal 61b of the comparator 61 is higher than the voltage input to the reference voltage terminal 61a during a period from the time t3 until a predetermined time elapses. Since such a situation may occur, if such a situation occurs, the output signal of the comparator 61 becomes a logic low level. That is, in this case, there is a possibility that the overcurrent protection function works and the power supply to the motor 30 is interrupted even though the power element 13 is not in an overcurrent state.

  Therefore, in order to solve such a problem, for example, as shown in FIG. 6, the reference voltage terminal 61 a of the comparator 61 is replaced with the load drive voltage Vp instead of the divided value “Vb / 2” of the control voltage Vb. The present applicant has proposed a configuration in which the partial pressure value “Vp / 2” is input. That is, by adopting such a configuration as the driving device, when the power supply voltage VB of the in-vehicle battery BT is temporarily greatly reduced, it is input to the reference voltage terminal 61a of the comparator 61 following this change. The voltage is also greatly reduced. For this reason, a situation in which the voltage input to the detection voltage terminal 61b of the comparator 61 is smaller than the voltage input to the reference voltage terminal 61a is less likely to occur, and thus the malfunction of the overcurrent protection function is suppressed. Will be able to.

However, when the configuration in which the threshold voltage Vr is set based on the load driving voltage Vp as described above is adopted, the following problem cannot be ignored.
First, as shown in FIG. 6, in the conventional general driving device including such a driving device, the control voltage Vb is used as the power supply voltage of the comparator 61. By the way, normally, when the control voltage Vb is applied as the power supply voltage of the comparator, the voltage is equal to or higher than an upper limit voltage Vmax (for example, “Vb−1 [V]”) determined based on the control voltage Vb. Is input to the reference voltage terminal 61a or the detection voltage terminal 61b, the output signal of the comparator is abnormal, for example, saturated to a logic high level. For this reason, if the voltage input to the reference voltage terminal 61a becomes equal to or higher than the upper limit voltage Vmax, the output of the comparator 61 is output even when the voltage input to the detection voltage terminal 61b is smaller than the upper limit voltage Vmax. The signal shows a logic high level. In other words, an abnormality such as a logic high level output signal occurs despite the fact that the comparator 61 should originally output a logic low level output signal, and the overcurrent of the power element 13 can be detected. It may not be possible. In the comparator 61, the voltage input to the reference voltage terminal 61a is smaller than the upper limit voltage Vmax and the voltage input to the detection voltage terminal 61b is equal to or higher than the upper limit voltage Vmax. The output signal indicates a logic high level. However, in this case, the comparator 61 shows a logic high level signal in a situation where it should originally show a logic high level output signal. As described above, in this drive device, in particular, the use of the voltage input to the reference voltage terminal 61a of the comparator 61 within a range where the voltage is smaller than the upper limit voltage Vmax ensures the normal operation of the overcurrent protection function. This is desirable.

  On the other hand, in the driving device shown in FIG. 6, as described above, the voltage input to the reference voltage terminal 61a of the comparator 61 is set to the divided value of the voltage dividing resistors R1 and R2 of the load driving voltage Vp. Therefore, in order to ensure the normal operation of the comparator 61, it is necessary to set the value of the load driving voltage Vp within a predetermined range determined based on the upper limit voltage Vmax. In FIG. 7, it is assumed that the upper limit voltage Vmax of the comparator 61 is set to “Vb−1 [V]” and the voltage input to the reference voltage terminal 61 a is set to “Vp / 2 [V]”. An example of a range in which the comparator 61 operates normally is shown. In FIG. 7, the horizontal axis indicates the load driving voltage Vp, and the vertical axis indicates the control voltage Vb. That is, as shown in FIG. 7, in this comparator 61, the normal operation of the comparator 61 can be ensured within the range satisfying the condition of “Vb ≧ (Vp / 2 + 1)”. In the range (the range indicated by line hatching in the figure), an abnormality occurs in the output signal of the comparator 61, which may cause malfunction of the overcurrent protection function.

  By the way, in such a drive device, in order to guarantee the operation, the standard ranges of the load drive voltage Vp and the control voltage Vb are usually ranges surrounded by a two-dot chain line in FIG. It is set in the range of “6 [V] ≦ Vp ≦ 16 [V], 6 [V] ≦ Vb ≦ 16 [V]”. However, as shown in the figure, in this driving apparatus, when the load driving voltage Vp and the control voltage Vb fluctuate within the range indicated by the point hatching, that is, the load driving voltage Vp is much larger than the control voltage Vb. When the value becomes larger, an abnormality occurs in the output signal of the comparator 61, which may cause malfunction of the overcurrent protection function. As a situation in which the load driving voltage Vp becomes significantly larger than the control voltage Vb, for example, as shown in FIG. 5 above, from the time t1 immediately after the user of the vehicle turns on the accessory switch 50. A period until a predetermined time elapses is assumed.

  As described above, in the drive device configured to set the threshold voltage Vr for determining whether or not the overcurrent of the power element 13 exists based on the load drive voltage Vp, the load drive voltage Vp is the control voltage. There is still room for improvement in that a new problem arises that the overcurrent protection function may malfunction when it becomes significantly larger than Vb.

  The present invention has been made in view of such circumstances, and its purpose is to set a threshold voltage for determining the presence or absence of an overcurrent of a power element based on a load driving voltage. An object of the present invention is to provide a drive device that can accurately ensure and maintain the reliability of the overcurrent protection function.

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided in a power supply path of a load to be driven, and a power element for supplying power to the load from the load driving power source and cutting off the load, The threshold voltage is set based on the voltage of the load driving power supply while the terminal is connected to the load of the power element while being driven by power supply from a control power supply provided separately from the load driving power supply. And a comparator for outputting a signal based on the comparison result, and an overcurrent protection function for monitoring the current flowing through the power element through the output signal of the comparator and detecting the presence or absence of the overcurrent A reference voltage adjusting means for shifting and adjusting a voltage input to an input terminal on a reference voltage side of the comparator to a voltage smaller than the threshold voltage; and the reference voltage adjusting device. Detection voltage adjustment means for shifting and adjusting the voltage on the terminal side connected to the load of the power element and inputting it to the input terminal on the detection voltage side of the comparator at a ratio equivalent to the ratio of shift adjustment by the means A comparison between the voltage on the terminal side connected to the load of the power element and the threshold voltage, the input to the input terminal on the detection voltage side by the comparator and the input on the reference voltage side The main point is that the comparison is made with the voltage input to the terminal.

  According to this configuration, the voltage input to the input terminal on the reference voltage side of the comparator through the reference voltage adjusting means can be suppressed to a small value. For this reason, for example, immediately after the vehicle user turns on the accessory switch, Even in a situation where the voltage of the power supply is significantly higher than the voltage of the control power supply, it is possible to suppress the abnormality of the output signal of the comparator. Further, the voltage at the terminal side connected to the load of the power element is shift-adjusted to the input terminal on the detection terminal side of the comparator through the detection voltage adjustment means at a ratio equivalent to the shift adjustment by the reference voltage adjustment means. Since the voltage is input, if the voltage on the terminal side connected to the load of the power element is smaller than the threshold voltage, the voltage on the input terminal on the detection voltage side of the comparator is higher than the voltage on the input terminal on the reference voltage side. Becomes smaller and a change occurs in the output signal of the comparator. Therefore, since the overcurrent of the power element can be detected when the voltage on the terminal side connected to the load of the power element becomes smaller than the reference voltage, it is possible to maintain the same overcurrent detection capability as before. it can. Therefore, even when the threshold voltage for determining whether or not there is an overcurrent of the power element is set based on the voltage of the power supply for driving the load, the reliability of the overcurrent protection function of the drive device is accurately ensured. Will be able to maintain.

  According to a second aspect of the present invention, in the driving device according to the first aspect, each voltage of the control power source and the load driving power source is provided with a standard range determined for each driving device, The reference voltage adjusting means is configured so that when the voltage of the control power supply is set to the minimum value of the standard range and the voltage of the load driving power supply is set to the maximum value of the standard range, The gist is that the voltage input to the input terminal on the reference voltage side of the comparator is shift-adjusted in such a manner that the operation can be ensured.

  As described above, in the driving device in which the threshold voltage for determining the presence or absence of the overcurrent of the power element is set based on the voltage of the load driving power supply, in particular, the voltage of the load driving power supply is There is a possibility that an abnormality may occur in the output signal of the comparator under a situation where the voltage is significantly larger than the voltage of the control power supply. Therefore, in a drive device in which a standard range is provided for each voltage of the control power supply and the load drive power supply, as the voltage of the control power supply approaches the minimum value of the standard range, As the voltage of the power supply approaches the maximum value in the standard range, an abnormality is likely to occur in the output signal of the comparator. In this regard, as described above, the voltage of the control power supply is reduced to the minimum value in the standard range through the shift adjustment of the voltage input to the input terminal on the reference voltage side of the comparator by the reference voltage adjusting means, and the load If the normal operation of the comparator is ensured when the voltage of the drive power supply is set to the maximum value within the standard range, the voltage of the control power supply and the load drive power supply will fluctuate within the standard range. Under such circumstances, normal operation of the comparator can be ensured. For this reason, it becomes possible to secure and maintain the reliability of the overcurrent protection function in a form more suitable for the operating environment of the drive device.

  According to a third aspect of the present invention, in the driving device according to the first or second aspect, the threshold voltage is set as a divided value of a voltage dividing resistor connected in parallel to the power element, and the reference voltage is set. The gist is that the adjusting means is configured to have a resistor connected in series to the voltage dividing resistor.

  In the driving device in which the threshold voltage is set as the divided value of the voltage dividing resistor connected in parallel to the power element as in the same configuration, the reference voltage can be obtained simply by connecting the resistor in series with the voltage dividing resistor. Since the adjusting means can be realized, the invention according to claim 1 or 2 can be easily realized.

  According to a fourth aspect of the present invention, in the driving device according to any one of the first to third aspects, the detection voltage adjusting unit divides a voltage on a terminal side connected to the load of the power element. Therefore, the gist of the present invention is to have a voltage dividing resistor for the purpose.

  According to this configuration, the detection voltage adjusting means can be provided simply by connecting a voltage dividing resistor in series to the power element, so that the inventions of claims 1 to 3 can be easily realized.

  According to the driving device of the present invention, the reliability of the overcurrent protection function can be accurately determined even when the threshold voltage for detecting the presence or absence of the overcurrent of the power element is set based on the load driving voltage. Can be secured and maintained.

Hereinafter, an embodiment in which the drive device according to the present invention is embodied as a drive device for controlling the drive of a vehicle-mounted motor will be described with reference to FIGS.
FIG. 1 shows an outline of a drive circuit of the drive device according to the present embodiment. First, the circuit configuration of the drive device will be specifically described with reference to FIG. The drive apparatus shown in FIG. 1 is basically the same as the drive apparatus illustrated in FIG. 6 in the configuration for realizing the drive control of the motor. That is, the driving apparatus shown in FIG. 1 also turns on and off the power element 13 through the control circuit 12 to supply power to the motor 30 and cut off the power supply. This driving device also monitors the voltage Vs on the source terminal side of the power element 13 through the voltage detection circuit 60, and when the voltage Vs on the source terminal side becomes smaller than the threshold voltage Vr, It detects that the flowing current is an overcurrent. Incidentally, the threshold voltage Vr is also set to a divided value (for example, “Vp / 2”) of the voltage dividing resistors R1 and R2 of the load driving voltage Vp. Then, when it is detected that the current flowing through the power element 13 is an overcurrent, an overcurrent flows through the power element 13 by turning off the power element 13 to forcibly cut off the power supply to the motor. To prevent. In FIG. 1, elements having the same functions as those shown in FIG. 6 are denoted by the same reference numerals, and redundant description of these elements is omitted.

  As shown in FIG. 1, this driving device is provided with a resistor R10 connected in series to the voltage dividing resistors R1 and R2, and this resistor R10 causes the inverting input terminal ( A voltage (for example, “Vp / 4”) smaller than the divided value “Vp / 2” by the voltage dividing resistors R1 and R2 of the load driving voltage Vp is input to the reference voltage terminal 61a. That is, in this driving apparatus, the voltage input to the reference voltage terminal 61a of the comparator 61 is shifted and adjusted to a voltage smaller than the threshold voltage Vr. On the other hand, this driving device is also provided with voltage dividing resistors R21 and R22 for dividing the voltage Vs on the source terminal side of the power element and inputting it to the non-inverting input terminal (detection voltage terminal) 61b of the comparator 61. It is installed. Incidentally, the voltage Vs on the source terminal side of the power element is shifted to the detection voltage terminal 61b of the comparator 61 at a ratio equivalent to the ratio of the shift adjustment of the voltage input to the reference voltage terminal 61a of the comparator 61. An adjusted voltage, that is, a voltage of “Vs / 2” is input.

  In the drive device according to the present embodiment, for example, a short circuit occurs between the power supply path and the ground path of the motor 30 and the voltage Vs on the source terminal side of the power element is smaller than the threshold voltage Vr, that is, “Vp / If it becomes smaller than “2”, the voltage input to the detection voltage terminal 61b of the comparator 61 becomes smaller than “Vp / 4”. In this driving device, when the voltage input to the detection voltage terminal 61b of the comparator 61 becomes smaller than “Vp / 4”, the output signal of the comparator 61 is switched from the logic high level to the logic low level. . That is, even in this driving apparatus, since the overcurrent of the power element 13 can be detected when the voltage Vs on the source terminal side of the power element 13 becomes smaller than the threshold voltage Vr, it is exemplified in FIG. The overcurrent detection capability equivalent to that of the driving device can be maintained.

  Further, in this drive device, the voltage input to the reference voltage terminal 61a of the comparator 61 is changed from “Vp / 2” to “Vp / 4”, whereby each of the load drive voltage Vp and the control voltage Vb is obtained. The voltage range that can ensure the normal operation of the comparator 61 determined based on the magnitude of is changed.

  FIG. 2 is a diagram corresponding to FIG. 7, and the upper limit voltage Vmax of the voltage input to the reference voltage terminal 61a and the detection voltage terminal 61b of the comparator 61 is “Vb−1 [V]”. The range in which the comparator 61 operates normally when the voltage input to the reference voltage terminal 61a of the device 61 is set to “Vp / 4” is shown. In FIG. 2, the horizontal axis represents the load driving voltage Vp, and the vertical axis represents the control voltage Vb. A range indicated by line hatching indicates a range where an abnormality occurs in the output of the comparator 61, and a range surrounded by a two-dot chain line indicates respective standard ranges of the load driving voltage Vp and the control voltage Vb. Yes.

  As shown in FIG. 2, in the driving apparatus according to the present embodiment, the normal operation of the comparator 61 can be ensured within a range satisfying the condition of “Vb ≧ (Vp / 4 + 1)”. The range in which the comparator 61 operates normally includes the respective standard ranges of the load driving voltage Vp and the control voltage Vb. Therefore, even if the load driving voltage Vp is significantly larger than the control voltage Vb, for example, immediately after the user of the vehicle turns on the accessory switch, each of them may vary within the standard range. Thus, normal operation of the comparator 61 can be ensured. For this reason, it becomes possible to secure and maintain the reliability of the overcurrent protection function in a form suitable for the usage environment of the drive device.

As described above, according to the drive device according to the present embodiment, the following effects can be obtained.
(1) A voltage half the threshold voltage Vr (= Vp / 2), that is, a voltage of “Vp / 4” is input to the reference voltage terminal 61a of the comparator 61. Further, the voltage Vs on the source terminal side of the power element is shifted and adjusted to the detection voltage terminal 61b of the comparator 61 at a ratio equivalent to the shift adjustment ratio of the voltage input to the reference voltage terminal 61a of the comparator 61. A voltage, that is, a voltage of “Vs / 2” was input. Then, the comparison between the voltage Vs on the source terminal side of the power element 13 and the threshold voltage Vr is performed by comparing the voltage input to the detection voltage terminal 61b and the voltage input to the reference voltage terminal 61a by the comparator 61. I made it. As a result, even if the load driving voltage Vp is significantly larger than the control voltage Vb, the abnormality of the output of the comparator 61 is suppressed and the normality of the load driving voltage Vp is suppressed under the situation where each of them varies within the standard range. Therefore, it is possible to ensure and maintain the reliability of the overcurrent protection function in a form more suitable for the operating environment of the drive device.

  (2) A reference voltage adjusting means for shifting and adjusting the voltage input to the reference voltage terminal 61a of the comparator 61 to a voltage smaller than the threshold voltage Vr is provided by a resistor R10 connected in series to the voltage dividing resistors R1 and R2. I made it up. Thereby, since it becomes possible to easily provide the reference voltage adjusting means in the driving device, the driving device according to the present invention can be easily realized.

  (3) The voltage on the source terminal side of the power element 13 is shifted and adjusted and input to the detection voltage terminal 61b of the comparator at a ratio equivalent to the ratio of voltage shift adjustment input to the reference voltage terminal 61a of the comparator 61. The detection voltage adjusting means for this purpose is constituted by voltage dividing resistors R21 and R22 that divide the voltage Vs on the source terminal side of the power element 13. Thereby, since it becomes possible to easily provide the detection voltage adjusting means in the driving device, the driving device according to the present invention can be easily realized.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the reference voltage terminal 61a of the comparator 61 is input with a voltage obtained by shifting the threshold voltage Vr by half, that is, a voltage of “Vp / 4”. For example, a voltage of “Vp / 3” or a voltage of “Vp / 5” may be input by appropriately changing the resistance value of R10. When the reference voltage terminal 61a of the comparator 61 is input with, for example, a voltage of “Vp / 3” or a voltage of “Vp / 5” as described above, the detection voltage terminal 61b of the comparator 61 is used. Also, it is desirable that the voltage input to be shifted and adjusted at a ratio equivalent to the ratio of the shift adjustment of the voltage input to the reference voltage terminal 61a of the comparator 61. That is, by appropriately changing the resistance values of the voltage dividing resistors R21 and R22, a voltage of “(2/3) Vs” or a voltage of “(2/5) Vs” is applied to the detection voltage terminal 61b of the comparator 61. It is desirable to adopt a configuration such as inputting. In short, a voltage smaller than the threshold voltage Vr is inputted to the reference voltage terminal 61a of the comparator 61, and a shift of the voltage inputted to the reference voltage terminal 61a of the comparator 61 is inputted to the detection voltage terminal 61b of the comparator 61. What is necessary is just to input a voltage obtained by shifting the voltage Vs on the source terminal side of the power element 13 at a ratio equivalent to the adjustment ratio.

  In the above embodiment, the driving device according to the present invention is applied to a driving device in which the threshold voltage Vr is set to a voltage of “Vp / 2”, but instead of this, for example, the threshold voltage Vr May be applied to a driving device set to a voltage of “Vp / 3” or a voltage of “Vp / 4”. In short, as long as the threshold voltage Vr is a driving device determined based on the load driving voltage Vp, the driving device according to the present invention can be applied.

  As described above, in the drive device in which the threshold voltage for determining the presence or absence of the overcurrent of the power element 13 is set based on the load drive voltage Vp, the load drive voltage Vp is particularly There is a possibility that an abnormality occurs in the output signal of the comparator 61 under a situation where the voltage is significantly higher than the control voltage Vb. Therefore, in the above drive device, as the control voltage Vb approaches the minimum value “6 [V]” of the standard range, the load drive voltage Vp becomes the maximum value “16 [V] of the standard range. As the value approaches "," the output signal of the comparator 61 tends to become abnormal. Therefore, at least when the control voltage Vb is set to the minimum value “6 [V]” of the standard range, and the load drive voltage Vp is set to the maximum value “16 [V]” of the standard range. The voltage input to the reference voltage terminal 61a of the comparator 61 may be shifted and adjusted so that the normal operation of the comparator 61 can be ensured. Specifically, as shown in FIG. 2 above, a straight line indicating a boundary between a range in which the normal operation of the comparator 61 can be secured and a range in which the comparator 61 cannot be secured is a control voltage Vb “ The voltage input to the reference voltage terminal 61a of the comparator 61 is shifted and adjusted so that the load driving voltage Vp becomes a straight line m passing through the point where the voltage is 6 [V]. May be. As a result, the normal operation of the comparator 61 can be ensured at least under the circumstances where the control voltage Vb and the load driving voltage Vp fluctuate within the standard range.

  In the above embodiment, the standard ranges of the load driving voltage Vp and the control voltage Vb are in the range of “6 [V] ≦ Vp ≦ 16 [V], 6 [V] ≦ Vb ≦ 16 [V]”. However, these standard ranges may be appropriately changed according to the use environment of the drive device.

In the above embodiment, the drive device according to the present invention is applied to a drive device for driving and controlling a vehicle-mounted motor. Instead, for example, on / off control of a vehicle light is performed. You may make it apply to the drive device for this. In addition, the power element is a bridge, such as a drive device that drives a motor for opening and closing a side mirror of a vehicle, or a drive device that drives a motor for opening and closing a window of a vehicle door. The drive device according to the present invention can also be applied to the connected drive device. In short, any drive device may be used as long as it is provided in the power supply path of the load to be driven and includes a power element for supplying power to the load from the load driving power source and blocking the load.
(Appendix)
Next, a technical idea that can be grasped from the above embodiment and its modifications will be additionally described.

  (A) The drive apparatus according to any one of claims 1 to 4, wherein the load is a motor for driving the side mirror of the vehicle to open and close. Specifically, as in the invention described in Appendix A, it is possible to employ a configuration in which the load is composed of a motor for driving the side mirror of the vehicle to open and close.

  (B) The drive device according to any one of claims 1 to 4, wherein the load is a vehicle light. Specifically, as in the invention described in Appendix B, it is possible to employ a configuration in which the load is a vehicle light.

The circuit diagram which shows the structure of the drive circuit about one Embodiment of the drive device concerning this invention. The graph which shows the range which an abnormality produces in the output of the comparator about the drive device of the embodiment, and the standard range of the voltage for control and the voltage for load drive, respectively. The circuit diagram which shows the structure of the drive circuit about an example of the conventional drive device. The circuit diagram which shows the structure of the drive circuit about an example of the drive device provided with the conventional overcurrent protection function. (A)-(c) is a time chart which respectively shows transition of the voltage of the vehicle-mounted battery, the voltage for load drive, and the voltage for control from the time of ON operation of the accessory switch of a vehicle, and ON operation of an ignition switch being performed. . The circuit diagram which shows the structure of the drive circuit about the other example of the drive device provided with the conventional overcurrent protection function. The graph which shows the range which the abnormality produces in the output of the comparator about the other example of the drive device provided with the same overcurrent protection function, and the standard range of the voltage for control and the load drive voltage, respectively.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Constant voltage circuit, 12 ... Control circuit, 13 ... Power element, 14a ... Load drive power supply terminal, 14b ... Control power supply terminal, 20 ... Microcomputer, 30 ... Motor, 40 ... Smoothing circuit, 41 ... Diode, 42 DESCRIPTION OF SYMBOLS ... Resistance 43 ... Capacitor 50 ... Accessory switch 60 ... Voltage detection circuit 61 ... Comparator 61a ... Reference voltage terminal (inverting input terminal) 61b ... Detection voltage terminal (non-inverting input terminal)

Claims (4)

A power element provided in a power supply path of a load to be driven to supply power to the load from the load driving power source and to cut off the load, and power supply from a control power source provided separately from the load driving power source And a comparator for driving the power device and comparing the voltage on the terminal side connected to the load of the power element with a threshold voltage set based on the voltage of the load driving power source and outputting a signal based on the comparison result In a drive device having an overcurrent protection function for monitoring the current flowing through the power element through the output signal of the comparator and detecting the presence or absence of the overcurrent,
Reference voltage adjustment means for shifting the voltage input to the input terminal on the reference voltage side of the comparator to a voltage smaller than the threshold voltage, and a ratio equivalent to the ratio of shift adjustment by the reference voltage adjustment means Detecting voltage adjusting means for shifting and adjusting the voltage on the terminal side connected to the load of the power element and inputting the voltage to the input terminal on the detection voltage side of the comparator, and the load of the power element The voltage on the terminal side to be connected is compared with the threshold voltage by comparing the voltage inputted to the input terminal on the detection voltage side and the voltage inputted to the input terminal on the reference voltage side by the comparator. A drive device characterized by that. Each voltage of the control power supply and the load drive power supply is provided with a standard range determined for each drive device, and the reference voltage adjusting means is configured such that the voltage of the control power supply is the minimum value of the standard range. In addition, when the voltage of the load driving power supply is set to the maximum value of the standard range, the comparator can be operated in a manner that can ensure the normal operation of the comparator on the reference voltage side. The drive device according to claim 1, wherein the voltage input to the terminal is shift-adjusted. The threshold voltage is set as a divided value of a voltage dividing resistor connected in parallel to the power element, and the reference voltage adjusting means is configured to have a resistor connected in series to the voltage dividing resistor. The drive device according to claim 1 or 2. The said detection voltage adjustment means is comprised including a voltage dividing resistor for dividing the voltage of the terminal side connected to the said load of the said power element. Drive device.

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