JP5609805B2 - Load drive device - Google Patents

Description

  The present invention relates to a load driving device.

  2. Description of the Related Art Conventionally, a load driving device that drives a load (such as a motor) mounted on a vehicle by PWM control is provided. In this type of drive system, for example, the current supplied to the load is controlled by a switching operation of the drive MOS, and further, an overcurrent protection function is provided, and this overcurrent flows when an overcurrent flows due to a short circuit or the like. It is configured to detect a current state and perform a protection operation. In addition, as a technique relevant to such a load drive device, things like patent documents 1-3 are provided, for example.

JP 2006-238673 A JP-A-8-183212 JP 2000-245142 A

  By the way, in the load driving device as described above, there is a case where a high driving frequency is required. For example, in an in-vehicle load drive device, noises such as AM band, smart key band, FM band, and TV band may be applied. Therefore, capacitors and coils are mounted to reduce such noise. Yes. In such a configuration, when the drive frequency is increased, charge / discharge ripples can be suppressed, and the scale of the capacitors and coils can be suppressed. Therefore, the entire circuit can be reduced in size.

  However, in the configuration in which the load current is controlled by the switching operation of the driving transistor as described above, a certain amount of time is required from the start of the on-operation of the driving transistor until the on-resistance is stabilized. Thus, when the on-time is shortened, the on-resistance of the drive transistor becomes difficult to stabilize during the on-time. That is, it becomes difficult to stabilize the current flowing through the drive transistor during the on-time, and if overcurrent is detected in such an unstable state, there is a concern that overcurrent may be erroneously detected, resulting in a decrease in detection accuracy. Will be invited.

  Here, considering the prior literature, in the technique of Patent Document 1, an overcurrent protection circuit (6) is interposed in the inverter circuit, and the frequency of the input power supply is changed and output. The overcurrent protection circuit (6) is provided with overcurrent detection means (4) and frequency control means (5) for reducing the output frequency of the inverter to a predetermined constant frequency when overcurrent is detected. The overcurrent detection means (4) detects the current state every predetermined time, and stops the output of the inverter when the overcurrent state is detected a predetermined number of times within the predetermined time. The frequency control means (5) performs control so as to return to normal control after a predetermined time has elapsed. In this technology, when an overcurrent is detected during steady operation, control is performed so that the output frequency of the inverter is lowered to a fixed frequency. However, the frequency at which the overcurrent is detected (in the steady state) Regarding frequency), no characteristic configuration is mentioned, and the above-described problem when switching operation is performed at a high frequency cannot be solved.

  In the technique of Patent Document 2, a control IC (11) is provided, and this control IC (11) turns on and off the main switch (Q1) at a predetermined switching frequency (fo) in a steady state. The output voltage (Vo) is stabilized by the duty ratio. On the other hand, the overcurrent protection circuit (1) forcibly turns off the main switch (Q1) when an overcurrent is detected by the voltage (V1) from the current transformer (CT) during the ON period of the main switch (Q1). The control is performed. However, if the voltage (V1) still increases, the switching frequency (fo) is switched to a lower frequency. This technique also does not mention any characteristic configuration regarding the steady-state frequency at which the overcurrent is to be monitored, and cannot solve the above-described problem when switching operation is performed at a high frequency.

  Patent Document 3 also discloses a technique for limiting the current by slowing the oscillation frequency (driving frequency) during overcurrent. In this technique, the comparator (15) slices the triangular wave from the oscillator (16) corresponding to the difference between the divided value (Vadj) of the output voltage (Vo) and the reference voltage (Vref1), and the drive circuit (19). Is configured to control the transistor (Tr1), and when the overcurrent is detected by the overcurrent detection circuit (11), the first oscillation frequency changing circuit (17) reduces the oscillation frequency of the oscillator (16). In addition, the RS flip-flop circuit (12) performs the overcurrent protection operation. Further, when the output voltage (Vo) decreases due to an output short circuit or the like, the second oscillation frequency changing circuit (18) decreases the oscillation frequency of the oscillator (16). This technique also does not mention any characteristic configuration regarding the steady-state frequency at which the overcurrent is to be monitored, and cannot solve the above-described problem when switching operation is performed at a high frequency.

  The present invention has been made to solve the above-described problem, and can switch a drive element for controlling a drive current at a higher frequency and more accurately and stably detect an abnormality in the drive current. It is an object of the present invention to provide a load driving device that can handle the above.

In order to achieve the above object, a load driving device according to the present invention comprises:
The control input terminal is connected to an energization path through which a drive current to the load flows, and a control signal is input. When an on signal is given to the control input terminal, the energization state is established and an off signal is given. A switch element that is sometimes in a non-energized state;
Control is performed so that the ON signal is periodically output to the control input terminal of the switch element, and the length of the output period of the ON signal in each cycle is changed within a predetermined fluctuation range. A signal control circuit to perform,
A detection circuit for detecting a state of the drive current in the energization path;
An abnormality determination circuit that performs abnormality determination based on the state of the drive current detected by the detection circuit;
A protection circuit that performs a protection operation to suppress the drive current on condition that the abnormality is determined to be abnormal by the abnormality determination circuit;
With
The signal control circuit is configured to change the cycle of the on signal by varying at least the output frequency of the on signal.
The abnormality determination circuit
In the period in which the cycle of the ON signal is set to be larger than the minimum cycle that can be changed by the signal control circuit, the length of the output period of the ON signal is made shorter than the minimum length in the variation range by the signal control circuit. when also set to a long predetermined length, it has rows abnormality determination based on the detection result of said detection circuit,
The abnormality determination is not performed at least in a period of a minimum cycle in which the cycle of the ON signal can be changed by the signal control circuit .

According to the first aspect of the present invention, the ON signal is periodically output from the signal control circuit to the control input terminal of the switch element, and the signal control circuit further includes the length of the ON signal output period in each cycle Is controlled to be changed within a predetermined fluctuation range. The abnormality determination circuit performs abnormality determination based on the detection result of the detection circuit when the output period of the ON signal is set to a predetermined length longer than the minimum length in the fluctuation range by the signal control circuit. Is going.
In this configuration, in the variation range of the output period (on period) that is variably controlled by the signal control circuit, the state of the drive current can be detected and the abnormality can be determined aiming at the time when the on period is set to be somewhat long. Therefore, when an abnormality is determined, the operation of the switch element can be stabilized during the ON period, and the abnormality can be determined more accurately based on the stable drive current during the ON period after the ON operation starts. .

In the configuration of claim 2, the signal control circuit changes the length of the ON signal output period to a predetermined monitoring length longer than the minimum length in the fluctuation range when the abnormality determination circuit determines that an abnormality has occurred. The abnormality determination circuit determines abnormality again based on the detection result in the detection circuit during the monitoring period in which the output period of the ON signal is set to the monitoring length by the signal control circuit. The protection circuit performs a protection operation for suppressing the drive current on condition that the abnormality determination circuit determines that the abnormality is detected again during the monitoring period.
In this configuration, it is possible to perform abnormality determination more accurately and stably aiming at a long on-time during normal operation, and if an abnormality is estimated during normal operation, the long on-time is forcibly set again. Abnormality can be confirmed. Therefore, it can be determined more accurately whether or not an abnormality has occurred in the drive current.

  According to a third aspect of the present invention, the signal control circuit changes the length of the ON signal output period within the variation range by varying at least the output frequency of the ON signal within a predetermined frequency range. In this way, since the drive frequency can be expanded to a certain high frequency, while realizing a configuration that can enjoy the benefits (high ripple reduction, downsizing of the device configuration, etc.) due to high frequency, Since the detection can be performed with a relatively low frequency, it is possible to suppress erroneous detection due to speeding up, and more accurate abnormality determination is possible. Further, when the drive frequency is simply increased, there is a concern about noise (FM noise or the like) due to high frequency. However, if the drive frequency is varied within a certain fluctuation range, such noise can be easily suppressed. .

In the configuration of claim 4, the signal control circuit performs control so that the output frequency can be changed in a plurality of stages, and the output frequency is gradually decreased in steps from the maximum frequency to the minimum frequency in the frequency range. Yes.
According to this configuration, voltage ripple and current ripple can be suppressed as compared with a control method in which the output period of the ON signal is abruptly increased, which is advantageous in terms of protection of the switch element.

In the configuration of claim 5, the abnormality determination circuit sets a non-determination period in which abnormality determination is not performed for a predetermined time from the start of output of the on signal in each cycle in which the on signal is output. It is configured to set a determination period for performing an abnormality determination later, and the abnormality determination is performed under a condition in which the ON signal output frequency and the duty ratio are set so that the ON signal output period and the determination period overlap. Is going.
According to this configuration, when performing the abnormality determination, it is possible to prevent the abnormality determination from being performed in the non-determination period immediately after the start of output of the ON signal, so that the ON resistance is difficult to stabilize and the current is unstable. It is possible to prevent erroneous detection caused by performing abnormality determination, and to perform abnormality determination more accurately based on the detection result obtained at the time of relative stabilization (time after the non-determination period) Can do.

In the configuration of claim 6, the abnormality determination circuit includes a reference current generation unit that generates a reference current based on the band gap reference voltage circuit and the metal thin film resistor, and a reference generated by the reference current generation unit is provided. An abnormality determination of the drive current is performed based on the current and the current flowing through the energization path.
If a reference current is generated based on a bandgap reference voltage circuit and a metal thin film resistor having a small temperature dependency as described above, and an abnormality in the drive current is determined based on the reference current, a thermally stable reference current is generated. An abnormality in the drive current can be accurately determined.

According to the seventh aspect of the present invention, in the abnormality determination circuit, a current mirror circuit is provided that causes a sense current corresponding to the current flowing through the switch element to flow in a current mirror system, and based on the sense current generated by the current mirror circuit. The drive current abnormality is judged.
With this configuration, even if the on-resistance of the switch element is low, it becomes easy to stably detect an abnormality in the drive current based on the sense current.

In the invention of claim 8, the switch element and the detection circuit are arranged in a single semiconductor chip.
In this way, if the switch element and the detection circuit are arranged in a single semiconductor chip, wiring drops and temperature gradients can be suppressed, and abnormality in the drive current can be detected with higher accuracy.

In the invention of claim 9, the abnormality determination circuit includes a first abnormality determination unit that performs abnormality determination based on a current value flowing through the energization path, and a second abnormality determination unit that performs abnormality determination based on the temperature state of the switch element. The protection circuit performs a protection operation to suppress the drive current when an abnormality determination is made by at least one of the first abnormality determination unit and the second abnormality determination unit.
Thus, when the temperature of the switch element is high, there is a high possibility that an overcurrent has occurred, so check not only the current value flowing through the energization path but also the temperature state of the switch element, If the protection operation is activated by a combination of both confirming abnormality and the like, the product can be more reliably protected based on multifaceted abnormality confirmation.

In the invention of claim 10, the abnormality determination circuit is used for a comparison unit that compares a voltage value corresponding to a current flowing through the switch element with a reference voltage, a temperature detection unit that detects a temperature state of the switch element, and a comparison unit. And a changing unit that changes the reference voltage to a value corresponding to the temperature state of the switch element detected by the temperature detecting unit.
In this configuration, after setting the reference voltage to a value corresponding to the temperature state of the switch element, it is possible to determine abnormality by comparing the reference voltage with a voltage value corresponding to the current flowing through the switch element. That is, the abnormality determination can be performed more appropriately in consideration of the temperature characteristics of the switch element. Note that the invention of claim 10 is not limited to the configuration using the comparator, and for example, it is possible to determine the abnormality based on the digital data after the AD conversion of the detection voltage by the AD converter. is there.

FIG. 1 is a schematic diagram for schematically explaining the electrical configuration of the load driving device according to the first embodiment of the present invention. FIG. 2 is a circuit diagram schematically showing a circuit configuration of the load driving device of FIG. FIG. 3 is a circuit diagram specifically illustrating a partial circuit configuration of the load driving device of FIG. 1. 4A is an explanatory diagram for schematically explaining the arrangement of the load driving device of FIG. 1 on the substrate, and FIG. 4B is an explanatory diagram showing a first modification thereof, and FIG. C) is an explanatory view showing the second modification. FIG. 5 is a timing chart illustrating an example of normal control in the load driving apparatus according to the first embodiment. FIG. 6 is a timing chart showing an example of control at the time of abnormality in the load driving device according to the first embodiment. FIG. 7 is a timing chart illustrating the concept of changing the duty ratio in the load driving device according to the second embodiment and the timing of abnormality determination. FIG. 8 is a timing chart for explaining the concept of changing the duty ratio and the timing of abnormality determination in the load driving device according to the modified example of the second embodiment. FIG. 9 is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device of the third embodiment. FIG. 10 is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device of the fourth embodiment. FIG. 11 is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device according to the first modification of the fourth embodiment. FIG. 12 is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device according to the second modification of the fourth embodiment. FIG. 13 is a circuit diagram illustrating an overcurrent detection circuit used in a load driving device according to Modification 3 of the fourth embodiment. FIG. 14 is a timing chart for explaining return control from the protection operation in the load driving device of the fifth embodiment. FIG. 15 is a schematic diagram schematically illustrating a load driving device according to Example 1 of another embodiment. FIG. 16 is a schematic diagram schematically illustrating a load driving device according to Example 2 of another embodiment. FIG. 17 is a schematic diagram schematically illustrating a load driving device according to Example 3 of another embodiment. FIG. 18 is a timing chart illustrating an example of control at the time of abnormality in the load driving device according to Example 4 of another embodiment.

[First embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment in which a load driving device of the invention is embodied will be described with reference to the drawings.
A load driving device 1 shown in FIG. 1 is configured as a device that drives an electrical load M (hereinafter also simply referred to as a load M) such as a vehicle-mounted motor or a vehicle-mounted lamp. The load driving device 1 is configured as a driving device that supplies a voltage to the load M by PWM control, and is configured to be able to control the load current flowing through the current path 7 from the power source VB to the load M. ing. Specifically, the level of the voltage supplied to the load M is adjusted by switching the output of the power supply VB by a pulse width modulation (PWM) control method. In the load driving device 1, an instruction signal for supplying the level of the supply voltage or supply current is input from the outside (for example, an ECU (not shown)) to the input terminal, and based on this input and the voltage to be controlled. Control is performed so as to set the duty ratio of the PWM signal.

  The load driving device 1 has a configuration as shown in FIGS. 1 and 2, and includes a switch element T1 configured as a driving MOS transistor (hereinafter also referred to as a driving MOS) and a regeneration MOS transistor (hereinafter referred to as a driving MOS transistor). Switch element T2, which is configured as a regenerative MOS), a coil L1, a capacitor C1, and a control unit 3, and receives power supply from the vehicle power supply VB and controls driving of the load M. Is configured to do.

  The switch element T1 is configured as an n-channel power MOSFET, for example, and has a drain side connected to the battery and a source side connected to one end side of the load M with a coil L1 interposed. The gate is connected to the driver circuit 11 so that a control signal (PWM signal) output from the driver circuit 11 is input. The gate of the switch element T1 corresponds to an example of a “control input terminal” to which a control signal (PWM signal) is input. In the present embodiment, a path from the power source VB to the load M via the switch element T1 and the coil L1 is configured as the energization path 7, and a drive current flows through the energization path 7.

  The switch element T1 is connected to the energization path 7 through which the drive current to the load M flows as described above, and is energized when an ON signal (H level signal) is given from the driver circuit 11 to the gate (control input terminal). The power supply VB and the load M are brought into conduction, and when an off signal (L level signal) is applied to the gate, the power supply VB and the load M are electrically disconnected when the off signal (L level signal) is applied. It is configured as follows. Further, a parasitic diode D2 is connected in parallel to the switch element T1 (FIG. 3).

  Further, as shown in FIG. 2, a snubber circuit is connected in parallel with the switch element T1, and in this snubber circuit, a capacitor C3 and a resistor R1 connected in series absorb a transient high voltage generated when the switch is shut off. Is configured to do. 1 and 2, the parasitic diode D2 is omitted, and the snubber circuit is omitted in the configurations of FIGS.

  The switch element T2 is configured, for example, as an n-channel power MOSFET, the drain side is connected to the source of the switch element T1, and the source side is connected to the other end side of the load M. Further, the gate is connected to the driver circuit 12, and a control signal (PWM signal) output from the driver circuit 11 is input. The switch element T2 functions as a switch element for regeneration so that a regenerative current flows when the switch element T1 is switched from the on state to the off state and the switch element T2 is switched from the off state to the on state. It is configured. A parasitic diode D3 is also connected in parallel to the switch element T2 (FIG. 3).

  Further, as shown in FIG. 2, a snubber circuit is connected in parallel with the switch element T2. In this snubber circuit, a transient high voltage generated when the switch is shut off is generated by a capacitor C4 and a resistor R2 connected in series. It is configured to absorb. 1 and FIG. 2, the parasitic diode D3 is omitted, and the snubber circuit is omitted in the configurations of FIG. 1 and FIG.

  The coil L1 is interposed in the energizing path 7, and one end side is connected to the source of the switch element T1 and the drain of the switch element T2, and the other end side is connected to one end side of the load M. The capacitor C1 has one end connected between the coil L1 and the load M, and the other end connected to the ground line. The coil L1 and the capacitor C1 constitute a known noise filter.

  As shown in FIGS. 1 and 3, the control unit 3 includes a control circuit 10, a high-side driver circuit (also referred to as a gate driver in FIG. 3) 11, a low-side driver circuit 12, and an overcurrent detection. A circuit 13 and an overheat detection circuit 15 are provided.

The control circuit 10 includes parts that function as a signal processing unit, a frequency setting unit, and an output voltage monitoring unit.
The frequency setting unit is configured to vary the frequency range of the PWM periodic signal stepwise within a predetermined frequency range. In the representative example shown in FIG. 5 and the like, the frequency is set in the frequency range of 200 kHz to 500 kHz. There are three stages. In the example of FIG. 5 and the like, the period is set to X1 when the frequency is the smallest (first stage), and the period is set to X2 when the frequency is medium (second stage). When the frequency is the highest (in the third stage), the cycle is set to X3. In the configuration of the present embodiment, the frequency of the PWM periodic signal is adjusted without changing the period of the source oscillation in the oscillator.

The output voltage monitor unit is configured to detect, for example, the voltage across the load M (voltage applied to the motor in FIG. 2 and the like) and to provide the voltage detection signal to the signal processing unit.
The signal processing unit is a pulse-shaped pulse width modulation signal (hereinafter, referred to as a pulse voltage modulation signal based on a comparison result between a DC voltage signal given from an external device and a motor voltage fed back through the output voltage monitoring unit, and a reference clock signal from the oscillation unit. (PWM signal) is a well-known configuration that performs an operation of generating a PWM signal), and the PWM signal is provided to the driver circuit 11.

  The driver circuit 11 performs PWM driving of the load M by applying a voltage signal obtained by amplifying the PWM signal between the gate and source of the switch element T1 and switching the voltage signal. As a result of such PWM driving of the load M, the voltage applied to the load M can be controlled as an average voltage.

  In the present embodiment, the control circuit 10 and the driver circuit 11 correspond to an example of a “signal control circuit”, and are configured to periodically output an ON signal to the gate (control input terminal) of the switch element T1, and Control is performed so as to change the length of the ON signal output period in each cycle within a predetermined fluctuation range. Specifically, in the signal control circuit, the output frequency of the ON signal is changed stepwise in a predetermined frequency range (for example, 200 kHz to 500 kHz) as described above, and the duty ratio of the PWM signal is set to a predetermined duty range. By varying within (for example, 0 to 100%), the length of the output period of the ON signal is changed within a predetermined variation range.

  The overcurrent detection circuit 13 is configured to detect when an overcurrent flows through the load M due to a motor lock or a load wiring short circuit. As shown in FIG. 3, the drain-source voltage of the switch element T1 is input to the overcurrent detection circuit 13, and the period when the switch element T1 is on (PWM signal on-signal output period) It is configured to determine whether or not the load current flowing through the load M is in an overcurrent state based on the drain-source voltage.

  The overcurrent detection circuit 13 includes a voltage / current conversion unit 19 including a reference resistor R1 for determining a reference and a constant current circuit 21, and a comparison unit 17 configured as a comparator. In the present embodiment, a diode D1 for detecting a temperature in the vicinity of the switch element T1 is provided in the vicinity of the switch element T1, and a constant current flows from the constant current circuit 25 to the diode D1. ing. The resistance value of the diode D1 changes according to the temperature, and the voltage value on the anode side of the diode D1 becomes a value corresponding to the temperature. Therefore, the voltage-current conversion unit 19 has a value corresponding to the temperature of the switch element T1 ( The voltage value on the anode side of the diode D1) is input via the detection line 18. The diode D1 corresponds to an example of a “temperature detector” and functions to detect the temperature state of the switch element T1.

  In the voltage-current converter 19, one end side of the reference resistor R1 is connected to the drain side of the switch element T1, and the other end side of the reference resistor R1 is connected to the constant current circuit 21. A constant current set by the constant current circuit 21 flows through the reference resistor R1. The constant current value of the constant current circuit 21 is such that the reference voltage input to the positive side of the comparison unit 17 increases as the voltage value input from the detection line 18 decreases. Specifically, for example, the reference voltage input to the positive side of the comparison unit 17 in proportion to the voltage value on the anode side of the diode D1 (that is, in proportion to the temperature of the switch element T1). The current value of the constant current circuit 21 is controlled so as to change.

  The comparison unit 17 functions to compare a voltage value (drain-source voltage) corresponding to the current flowing through the switch element T1 with a reference voltage, and the source voltage of the switch element T1 is on the positive side of the comparison unit 17. When the reference voltage is higher than the input reference voltage, an L level signal indicating that the current is normal is output to the control circuit 10. On the other hand, when a short circuit occurs in the load M and the source voltage of the switch element T1 becomes lower than the reference voltage of the comparison unit 17, it indicates to the control circuit 10 that it is an overcurrent (abnormal current). An H level signal is output.

  The voltage-current conversion unit 19 corresponds to an example of a “change unit”, and the reference voltage used for the comparison unit 17 corresponds to the temperature state of the switch element T1 detected by the diode D1 (temperature detection unit). It functions to change to a value (specifically, to change the reference voltage in proportion to the temperature of the switch element T1).

  The overheat detection circuit 15 detects the overheat state of the switch element T1 based on the voltage value monitored on the detection line 18 (the voltage value on the anode side of the diode D1). For example, the detection detected from the detection line 18 A voltage (a voltage value on the anode side of the diode D1) is compared with a predetermined threshold voltage, and a detection signal (for example, an H level signal) indicating an overheat state to the control circuit 10 when the detection voltage falls below the threshold voltage When the detected voltage is equal to or lower than the threshold voltage, a signal indicating that the temperature is normal (for example, an L level signal) is output to the control circuit.

  In the present embodiment, the diode D1, the overcurrent detection circuit 13, and the overheat detection circuit correspond to an example of a “detection circuit”, and function to detect the state of the drive current in the energization path 7.

  Further, for example, as shown in FIG. 4A, the control unit 3 is mounted on the substrate B as a control IC configured as a bare chip, and the switch element T1 and the switch element T2 are also mounted on the substrate B, respectively. . The gate terminals of the switch elements T1 and T2 are connected to the control unit 3 (control IC) by wire bonding or the like.

Next, drive control by the load drive device 1 will be described.
In the present embodiment, as described above, the control unit 3 performs control to switch the frequency of the PWM signal to a plurality of stages (three stages in the example of FIG. 5 and the like). In the example of FIG. Are changed stepwise in the order of f1, f2, and f3, f1 being the smallest frequency in the variable frequency range, and f3 being the largest frequency in the variable frequency. Further, f2 is an intermediate frequency, and f1 <f2 <f3. The duty ratio can be controlled at any frequency, and the length of the ON signal output period is determined by determining the frequency and duty ratio of the PWM signal.

  In the present embodiment, the frequency of the PWM signal generated and output by the control circuit 10 and the driver circuit 11 is changed stepwise to control the duty ratio, and the on period determined by these frequency and duty ratio The length of the (ON signal output period) varies. The control circuit 10 is driven by the overcurrent detection circuit 13 and the overheat detection circuit 15 (detection circuit) when the length of the output period of the ON signal is set to a predetermined length longer than the minimum length in the fluctuation range. The current state is detected, and abnormality determination is performed based on the detection result. Specifically, for each frequency f1, f2, and f3 set in a plurality of stages within a predetermined frequency range, for example, abnormality determination is performed in the period of the smallest frequency f1. In the period of the frequencies f2 and f3, abnormality determination is not performed, and even if an overcurrent state or an overheat state is detected, it is ignored.

  Specifically, in each cycle in which the ON signal is output, a non-determination period (mask period) in which abnormality determination is not performed for a predetermined time from the start of output of the ON signal is set. In the example shown in FIGS. 5 and 6, the abnormality determination is not performed until the period Ya has elapsed since the start of the output of the ON signal. During this period Ya, the overcurrent detection circuit 13 and the overheat detection circuit 15 are not detected. Even if an overcurrent state or an overheat state is detected by this, it is not determined as an abnormality but ignored. The length of the non-determination period (mask period) is set in consideration of the time until the drive current is stabilized after the ON operation. For example, in a configuration that requires about 1 μs to 2 μs until the on-resistance of the switch element T1 is stabilized, the non-determination period is set slightly larger than 2 μs.

  In each cycle, a determination period for performing an abnormality determination is set after the non-determination period, and the ON signal output frequency and the duty ratio are set so that the ON signal output period and the determination period overlap. An abnormality is being judged. For example, in the example of FIG. 5, a determination period is secured after the non-determination period (mask period) in the period Y1 in which the frequency is set to f1, and in this period Y1, the output period of the ON signal is non-determination. The output frequency and duty ratio of the PWM signal are set so as to be longer than the period (mask period), and a determination period in which a part of the ON signal output period is secured after the non-determination period (mask period) It is supposed to overlap. In the example of FIG. 5, the overcurrent detection signal is not output from the overcurrent detection circuit 13 within the determination period secured after the non-determination period (mask period) in the period Y1 in which the frequency is set to f1, An example is shown in which an overheat detection signal is not output from the overheat detection circuit 15 (the overheat detection signal is not shown), and it is not determined to be abnormal in the period Y1.

  On the other hand, in FIG. 6, the frequency and duty ratio of the PWM signal are set as in FIG. 5, and within the determination period secured after the non-determination period (mask period) in the period Y <b> 1 where the frequency is set to f <b> 1. The drive current is in an overcurrent state, and an overcurrent detection signal is output from the overcurrent detection circuit 13. Therefore, it is determined to be abnormal in the period Y1 (see the alternate long and short dash line Z1). Note that, even if an overheat detection signal is output from the overheat detection circuit 15 in the determination period set in the period Y1, it is determined to be abnormal. However, in the example of FIG. 6, the abnormality determination is not continued unless the abnormality determination is continued a plurality of times (for example, twice), and the abnormality determination is continuously performed in a cycle after the abnormality determination of the symbol Z1. Therefore, the protection operation based on the abnormality determination of the code Z1 is not performed.

  In the example of FIG. 6, the frequency is set to f1 even in the period Y4. In this period Y4, an overcurrent state is detected in the determination period in two consecutive cycles, and an abnormality determination is made in two consecutive cycles. Yes. As described above, when the abnormality determination is continued twice, the length of the ON signal output period is changed to a predetermined monitoring length longer than the minimum length in the fluctuation range at the steady state, and the ON signal is output in this way. During the monitoring period in which the period is set to the monitoring length, the abnormality is determined again based on the detection result of the detection circuit. In the example of FIG. 6, when abnormality determination is made in two consecutive cycles as indicated by reference numerals Z2 and Z3, the frequency of the PWM signal is set to a frequency f0 lower than the frequency in the period Y4, and thus In the period Yn set to the frequency f0, the abnormal state of the drive current is monitored in each determination period (period after the non-determination period Ya immediately after the start of the ON signal output) set in each cycle. The control circuit 10 determines whether or not the abnormality determination has been repeated a predetermined number of times in the monitoring period Yn set as described above, and when it has been repeated the predetermined number of times, the control circuit 10 stops the PWM signal applied to the switch element T1. Perform the action. In addition, a return operation is started to start the output of the PWM signal when the stop of the PWM signal elapses for a certain period after the protection operation for stopping the PWM signal.

  In the present embodiment, the control circuit 10, the overcurrent detection circuit 13, and the overheat detection circuit 15 correspond to an example of an “abnormality determination circuit”. Specifically, the control circuit 10 and the overcurrent detection circuit 13 correspond to an example of a “first abnormality determination unit” and function to perform abnormality determination based on a current value flowing through the energization path 7. The control circuit 10 and the overheat detection circuit 15 correspond to an example of a “second abnormality determination unit”, and function to perform abnormality determination based on the temperature state of the switch element T1. The control circuit 10 corresponds to an example of a “protection circuit”, and performs a protection operation that suppresses the drive current on the condition that the abnormality determination circuit determines that there is an abnormality. Protective operation to suppress drive current on condition that abnormality is determined again by abnormality determination circuit during monitoring period when abnormality determination is made by at least one of first abnormality determination unit and second abnormality determination unit It is carried out.

(Main effects of the first embodiment)
In the load driving device 1 according to the present embodiment, an ON signal is periodically output from the signal control circuit to the control input terminal of the switch element T1, and the signal control circuit further outputs an ON signal in each cycle. Control is performed so as to change the length of the output period within a predetermined fluctuation range. The abnormality determination circuit performs abnormality determination based on the detection result of the detection circuit when the output period of the ON signal is set to a predetermined length longer than the minimum length in the fluctuation range by the signal control circuit. Is going.
In this configuration, in the variation range of the output period (on period) that is variably controlled by the signal control circuit, the state of the drive current can be detected and the abnormality can be determined aiming at the time when the on period is set to be somewhat long. Therefore, when determining the abnormality, the operation of the switch element can be stabilized during the ON period, and the abnormality can be determined more accurately based on the stable drive current after the ON operation.

In the above configuration, the signal control circuit changes the length of the output period of the ON signal to a predetermined monitoring length longer than the minimum length in the fluctuation range when the abnormality determination circuit determines that the abnormality is present, The abnormality determination circuit determines abnormality again based on the detection result in the detection circuit during the monitoring period in which the output period of the ON signal is set to the monitoring length by the signal control circuit. The protection circuit performs a protection operation for suppressing the drive current on condition that the abnormality determination circuit determines that the abnormality is detected again during the monitoring period.
In this configuration, it is possible to perform abnormality determination more accurately and stably aiming at a long on-time during normal operation, and if an abnormality is estimated during normal operation, the long on-time is forcibly set again. Abnormality can be confirmed. Therefore, it can be determined more accurately whether or not an abnormality has occurred in the drive current.

  Further, in the above configuration, the signal control circuit changes the length of the ON signal output period within the fluctuation range by changing at least the output frequency of the ON signal within a predetermined frequency range. In this way, since the drive frequency can be expanded to a certain high frequency, while realizing a configuration that can enjoy the benefits (high ripple reduction, downsizing of the device configuration, etc.) due to high frequency, Since the detection can be performed with a relatively low frequency, it is possible to suppress erroneous detection due to speeding up, and more accurate abnormality determination is possible. Further, when the drive frequency is simply increased, there is a concern about noise (FM noise or the like) due to high frequency. However, if the drive frequency is varied within a certain fluctuation range, such noise can be easily suppressed. .

Further, in the above configuration, the signal control circuit can control the output frequency so that the output frequency can be changed in a plurality of stages, and the output frequency is gradually decreased from the maximum frequency to the minimum frequency in the frequency range. .
According to this configuration, voltage ripple and current ripple can be suppressed as compared with a control method in which the output period of the ON signal is abruptly increased, which is advantageous in terms of protection of the switch element.

Further, in the above configuration, the abnormality determination circuit sets a non-determination period in which abnormality determination is not performed for a predetermined time from the start of output of the ON signal in each cycle in which the ON signal is output, and after each non-determination period in each cycle. It is configured to set a determination period for performing abnormality determination, and performs abnormality determination under conditions in which the ON signal output frequency and the duty ratio are set so that the ON signal output period and the determination period overlap. ing.
According to this configuration, when performing the abnormality determination, it is possible to prevent the abnormality determination from being performed in the non-determination period immediately after the start of output of the ON signal, so that the ON resistance is difficult to stabilize and the current is unstable. It is possible to prevent erroneous detection caused by performing abnormality determination, and to perform abnormality determination more accurately based on the detection result obtained at the time of relative stabilization (time after the non-determination period) Can do.

In the above configuration, the abnormality determination circuit includes a first abnormality determination unit that performs abnormality determination based on a current value flowing through the energization path, a second abnormality determination unit that performs abnormality determination based on the temperature state of the switch element, The protection circuit performs a protection operation to suppress the drive current when an abnormality determination is made by at least one of the first abnormality determination unit and the second abnormality determination unit.
In this way, when the temperature of the switch element is high, there is a high possibility that an overcurrent has occurred. Therefore, not only the current value flowing through the current path but also the temperature state of the switch element is confirmed, and any abnormality is confirmed. If the protection operation is performed in such a case, the product can be more reliably protected based on multifaceted abnormality confirmation.

In the above configuration, the abnormality determination circuit includes a comparison unit that compares a voltage value corresponding to a current flowing through the switch element with a reference voltage, a temperature detection unit that detects a temperature state of the switch element, and a reference used for the comparison unit. And a change unit that changes the voltage to a value corresponding to the temperature state of the switch element detected by the temperature detection unit.
In this configuration, after setting the reference voltage to a value corresponding to the temperature state of the switch element, it is possible to determine abnormality by comparing the reference voltage with a voltage value corresponding to the current flowing through the switch element. That is, the abnormality determination can be performed more appropriately in consideration of the temperature characteristics of the switch element.

[Second Embodiment]
Next, a second embodiment will be described. FIG. 7 is a timing chart illustrating the concept of changing the duty ratio in the load driving device according to the second embodiment and the timing of abnormality determination.
The second embodiment is different from the first embodiment in the method for setting the frequency and duty ratio of the PWM signal and the timing for performing abnormality determination, and is otherwise the same as in the first embodiment. Therefore, about the structure similar to 1st Embodiment, the code | symbol same as 1st Embodiment is attached | subjected and detailed description is abbreviate | omitted. In addition, FIGS. 1 to 4 will be referred to as appropriate.

  In the first embodiment, the frequency of the PWM signal is configured to be switched stepwise, and an example in which abnormality determination is performed in the determination period when the frequency is low is shown. However, in the second embodiment, the duty ratio is periodically changed. Each period of a period in which the control is forcibly set to a predetermined value or more (relatively large value in the range of variable duty ratio, for example, 90% or more), and thus the duty ratio is forcibly increased. The abnormality determination is performed during the determination period during the ON signal output period (a certain period after the non-determination period immediately after output has elapsed).

  In this case, if a predetermined number of abnormalities are determined during the period in which the duty ratio is forcibly increased, the PWM signal may be forcibly turned off, and the duty ratio may be further increased for each output. An abnormality determination may be further performed during the period, and the PWM signal may be forcibly turned off when a predetermined number of abnormalities are confirmed.

[Modification Example of Second Embodiment]
FIG. 8 is a timing chart for explaining the concept of changing the duty ratio and the timing of abnormality determination in the load driving device according to the modified example of the second embodiment.
In the example of FIG. 7, the control is performed such that the duty ratio is forcibly set to a predetermined value or more on a regular basis. However, as shown in FIG. 8, the determination during the output period of the ON signal in each cycle in the steady state is performed. When an abnormality is determined during a period (a certain period after the non-determination period immediately after output), and the abnormality is confirmed a predetermined number of times, the duty ratio is forcibly exceeded by a predetermined value (the range of variable duty ratios) The control may be performed so as to set a relatively large value (for example, 90% or more). Then, in each cycle of the period for forcibly increasing the duty ratio in this way, abnormality determination is performed during a determination period during the ON signal output period (a fixed period after the non-determination period immediately after output has passed) The control can be performed so that the PWM signal is forcibly turned off when the abnormality of the rotation is confirmed.

[Third Embodiment]
Next, a third embodiment will be described. FIG. 9 is a circuit diagram illustrating an overcurrent detection circuit and the like used in the load driving device of the third embodiment.
The third embodiment is different from the first embodiment in the configuration of the overcurrent detection circuit 13, and is otherwise the same as the first embodiment. Therefore, in the following, the overcurrent detection circuit 13 different from the first embodiment will be described in detail, and the same parts as those of the first embodiment will be denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. . In addition, FIGS. 1 to 4 will be referred to as appropriate.

The configuration of FIG. 9 is an example of a more specific example of the configuration of FIG. 3. In the overcurrent detection circuit 13, the reference is based on the band gap reference voltage circuit 54 and the metal thin film resistors R 11, R 12, R 13, R 14, R 15. A reference current generation unit 301 that generates current is provided. The reference current generator 301 corresponds to the constant current circuit 31 shown in FIG. 3, the temperature sensing element 52 corresponds to the diode D1 shown in FIG. 3, and the constant current circuit 51 corresponds to the constant current circuit 25 shown in FIG. The comparison unit 55 corresponds to the comparison unit 17 shown in FIG. 3, and the reference current generated by the reference current generation unit 301 and the current flowing through the energization path 7 (current flowing through the switch element T1) Based on the above, the abnormality determination of the current flowing through the switch element T1 is performed in the same manner as in the first embodiment, and a detection signal (for example, an H level signal) is output from the comparison unit 55 when in an overcurrent state. ing.
If a reference current is generated based on a bandgap reference voltage circuit and a metal thin film resistor having a small temperature dependency as described above, and an abnormality in the drive current is determined based on the reference current, a thermally stable reference current is generated. An abnormality in the drive current can be accurately determined.

[Fourth Embodiment]
Next, a fourth embodiment will be described. FIG. 10 is a circuit diagram illustrating an overcurrent detection circuit and the like used in the load driving device of the fourth embodiment.
The fourth embodiment differs from the first embodiment in the configuration of the overcurrent detection circuit 13, and is otherwise the same as the first embodiment. Therefore, in the following, the overcurrent detection circuit 13 different from that of the first embodiment will be described in detail, and the same parts as those of the first embodiment will be denoted by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted. To do. In addition, FIGS. 1 to 4 will be referred to as appropriate.

  The overcurrent detection circuit 13 used in the load driving device of FIG. 10 is provided with a current mirror circuit 401 for flowing a sense current corresponding to the current flowing through the switch element T1 by a current mirror method. Based on the generated sense current, the determination circuit 61 makes an abnormality determination. With this configuration, even if the on-resistance of the switch element is low, it becomes easy to stably detect an abnormality in the drive current based on the sense current.

  Further, instead of the configuration of FIG. 10, FIG. 11, which may be configured as FIG. 11, is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device according to the first modification of the fourth embodiment. The overcurrent detection circuit 13 used in the load driving device of FIG. 11 is also provided with a current mirror circuit 411 for flowing a sense current corresponding to the current flowing through the switch element T1 by a current mirror method. Based on the sensed current, the determination circuit 71 makes an abnormality determination.

  Moreover, it may replace with the structure of FIG. 10, FIG. FIG. 12 is a circuit diagram illustrating an overcurrent detection circuit used in the load driving device according to the second modification of the fourth embodiment. The overcurrent detection circuit 13 used in the load driving device of FIG. 12 is also provided with a current mirror circuit 412 for flowing a sense current corresponding to the current flowing through the switch element T1 by a current mirror method, and is generated by the current mirror circuit 412. The determination circuit 81 makes an abnormality determination based on the sensed current.

  Moreover, it may replace with the structure of FIGS. 10-12, and you may make it like FIG. FIG. 13 is a circuit diagram illustrating an overcurrent detection circuit used in a load driving device according to Modification 3 of the fourth embodiment. In the configuration of FIG. 13, the potential difference between both ends of the switch element T1 is input and amplified at a predetermined amplification factor, and the determination circuit 91 performs abnormality determination based on the amplified output Vout. For example, the determination circuit 91 compares the output Vout with a predetermined threshold, and outputs an overcurrent detection signal when Vout exceeds the threshold.

[Fifth Embodiment]
Next, a fifth embodiment will be described. FIG. 14 is a circuit diagram illustrating an overcurrent detection circuit and the like used in the load driving device of the fourth embodiment.
In the first embodiment, a protection operation (PWM signal OFF operation) is performed after an abnormality in the drive current is detected, and a return operation is started that starts outputting the PWM signal after a fixed period of time has elapsed. However, after the protection operation for stopping the PWM signal is performed, when returning from the protection operation, the duty ratio of the PWM signal is gradually increased from a predetermined low level to a predetermined high level as shown in FIG. The abnormality determination may be performed in the determination period (period after the non-determination period has elapsed) at the predetermined high level, and the normal control may be restored when no abnormality is confirmed.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  In the above embodiment, MOS transistors are exemplified as the switch elements T1 and T2, but other semiconductor switch elements such as IGBTs may be used.

  In the example of FIG. 4A, an example in which the control unit 3 is configured as a bare chip is shown. However, as illustrated in FIG. 4B, the control unit 3 is configured as a mold IC that is covered with a mold resin, You may make it mount in the board | substrate B. FIG. In this case, the mold IC and each switch element T1, T2 can be connected by pattern wiring, wire bonding, or the like.

  In the example of FIG. 4A, the control unit 3 is configured as a bare chip and is arranged separately from the switch elements T1 and T2. However, as shown in FIG. 4C, the switch element T1 and the control unit are arranged. 3 may be arranged in a single semiconductor chip. In this way, if the switch element T1 and the control unit 3 are arranged in a single semiconductor chip, wiring drops and temperature gradients can be suppressed, and an abnormality in the drive current can be detected more accurately. it can.

  In the above embodiment, the frequency is changed to a plurality of stages in the steady state, and the abnormality determination is performed in the period in which the frequency is the smallest (period in which the period is the longest). It is not limited to this, and two or more frequencies may be candidates.

  In the first embodiment, the configuration as shown in FIG. 1 is used, but this may be changed to the configuration as shown in FIG. That is, in the configuration of FIG. 1, the overcurrent is detected based on the potential difference between both ends of the switch element T1, but as shown in FIG. 16, the overcurrent is detected based on the potential difference between both ends of the coil L1. Also good.

  Further, the configuration of FIG. 16 may be changed as shown in FIG. In the configuration of FIG. 17, a regenerative diode Da is used in place of the regenerative MOS (switch element T2). In the configuration of FIG. 1, a regenerative diode Da may be used instead of the regenerative MOS (switch element T2).

  In the above-described embodiment, an example of the frequency switching method has been described. However, the control is performed so that the frequency (output frequency) of the PWM signal is gradually decreased from the maximum frequency to the minimum frequency in the frequency range. For example, if the frequency candidates that can be switched in the normal state are f1, f2, and f3, and f1 <f2 <f3, the frequency is forcibly switched in the order of f3 → f2 → f1, and the frequency is f1. The abnormality may be determined during the ON period. According to this configuration, voltage ripple and current ripple can be suppressed as compared with a control method in which the output period of the ON signal is abruptly increased, which is advantageous in terms of protection of the switch element.

  In the first embodiment, an example in which a load such as a direct current motor is driven has been described. However, the apparatus may be configured as a device for driving a three-phase motor as shown in FIG. In the example of FIG. 18, the three-phase motor M2 is controlled by a known voltage vector control method using six switching elements (transistors T11 to T16), drive drivers 103 and 105, and the control circuit 10, and each transistor T11 to T16 is controlled. The three-phase motor M2 is controlled by outputting PWM signals respectively. Even in this configuration, the period of the PWM signal applied to each of the transistors T11 to T16 is configured to vary stepwise by, for example, f1 to f3, and the energization current flowing through the transistor based on the voltage across at least one of the transistors is reduced. It is configured to detect, and in each period when the period of the PWM signal is set to f1, an abnormality of the energization current is determined in a determination period after a certain period (after the non-determination period) immediately after the transistor is turned on. Can be.

  In the first embodiment, the monitoring period Yn is set when an abnormality is determined in a plurality of consecutive periods in the steady state, and the protection operation is performed when an abnormality is confirmed again in the monitoring period Yn. However, when the abnormality determination is made even once in the above-described determination period in the steady state, the monitoring period Yn may be set, and the abnormality may be confirmed again in the monitoring period Yn. For example, as shown in FIG. 18, at a plurality of frequencies f1, f2, and f3 that change stepwise in the steady state, after each of the determination periods (non-determination period Ya (mask period)) in each cycle of the period Y1 of the low frequency f1. If an abnormality is detected even once in each determination period, the period is switched to the monitoring period Yn, and after the non-determination period Ya (mask period) in each cycle at a low frequency f0. You may make it confirm abnormality again in the determination period.

DESCRIPTION OF SYMBOLS 1 ... Load drive device 7 ... Current supply path 10 ... Control circuit (Signal control circuit, abnormality determination circuit, 1st abnormality determination part, 2nd abnormality determination part, protection circuit)
11 ... Driver circuit (signal control circuit)
13: Overcurrent detection circuit (detection circuit, abnormality determination circuit, first abnormality determination unit)
15 ... Overheat detection circuit (detection circuit, abnormality determination circuit, second abnormality determination unit)
17 ... Comparison unit 19 ... Voltage-current conversion unit (change unit)
54 ... Band gap reference circuit 301 ... Reference current generation unit 401, 411, 421 ... Current mirror circuit D1 ... Diode (detection circuit, temperature detection unit)
T1 ... Switch element M ... Load R11-R15 ... Resistance (metal thin film resistor)

Claims (10)

The control input terminal is connected to an energization path through which a drive current to the load flows, and a control signal is input. When an on signal is given to the control input terminal, the energization state is established and an off signal is given. A switch element that is sometimes in a non-energized state;
Control is performed so that the ON signal is periodically output to the control input terminal of the switch element, and the length of the output period of the ON signal in each cycle is changed within a predetermined fluctuation range. A signal control circuit to perform,
A detection circuit for detecting a state of the drive current in the energization path;
An abnormality determination circuit that performs abnormality determination based on the state of the drive current detected by the detection circuit;
A protection circuit that performs a protection operation to suppress the drive current on condition that the abnormality is determined to be abnormal by the abnormality determination circuit;
With
The signal control circuit is configured to change the cycle of the on signal by varying at least the output frequency of the on signal.
The abnormality determination circuit
In the period in which the cycle of the ON signal is set to be larger than the minimum cycle that can be changed by the signal control circuit, the length of the output period of the ON signal is made shorter than the minimum length in the variation range by the signal control circuit. when also set to a long predetermined length, it has rows abnormality determination based on the detection result of said detection circuit,
The load driving device is characterized in that the abnormality determination is not performed at least in a period of a minimum cycle in which the cycle of the ON signal can be changed by the signal control circuit . The signal control circuit, when it is determined as abnormal by the abnormality determination circuit, the length of the output period of the ON signal is changed to a predetermined monitoring length longer than the minimum length in the fluctuation range,
The abnormality determination circuit determines an abnormality again based on the detection result in the detection circuit during the monitoring period in which the output period of the ON signal is set to the monitoring length by the signal control circuit,
2. The load driving device according to claim 1, wherein the protection circuit performs a protection operation for suppressing the drive current on the condition that the abnormality determination circuit determines that the abnormality again occurs during the monitoring period.   The signal control circuit changes the length of the output period of the ON signal within the fluctuation range by changing at least the output frequency of the ON signal within a predetermined frequency range. Item 3. The load driving device according to Item 2.   The signal control circuit is capable of changing the output frequency in a plurality of stages and performing control so that the output frequency is gradually decreased in a stepwise manner from the maximum frequency to the minimum frequency in the frequency range. The load driving device according to claim 3.   The abnormality determination circuit sets a non-determination period in which abnormality determination is not performed for a predetermined time from the start of output of the ON signal in each cycle in which the ON signal is output, and abnormality determination is performed after the non-determination period in each cycle. And determining the abnormality under the condition that the output frequency of the on signal and the duty ratio are set so that the output period of the on signal and the determination period overlap each other. The load driving device according to claim 1, wherein the load driving device is performed.   The abnormality determination circuit includes a reference current generation unit that generates a reference current based on a band gap reference voltage circuit and a metal thin film resistor, and the reference current generated by the reference current generation unit and a current flowing through the energization path The load drive device according to any one of claims 1 to 5, wherein abnormality determination of the drive current is performed based on the following.   The abnormality determination circuit includes a current mirror circuit that causes a sense current corresponding to a current flowing through the switch element to flow in a current mirror system, and performs an abnormality determination of the drive current based on the sense current generated by the current mirror circuit. The load driving device according to claim 1, wherein the load driving device is performed.   The load driving device according to any one of claims 1 to 7, wherein the switch element and the detection circuit are arranged in a single semiconductor chip. The abnormality determination circuit includes a first abnormality determination unit that performs abnormality determination based on a current value flowing through the energization path, and a second abnormality determination unit that performs abnormality determination based on a temperature state of the switch element,
The said protection circuit performs the protection operation which suppresses the said drive current, when abnormality determination is made by at least any one of a said 1st abnormality determination part and a said 2nd abnormality determination part. Item 9. The load driving device according to any one of Items 8 to 8. The abnormality determination circuit
A comparison unit that compares a voltage value corresponding to a current flowing through the switch element with a reference voltage;
A temperature detector for detecting a temperature state of the switch element;
A change unit that changes the reference voltage used in the comparison unit to a value corresponding to a temperature state of the switch element detected by the temperature detection unit;
The load driving device according to any one of claims 1 to 8, wherein the load driving device is provided.

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