Over-current protection circuit and power distribution device

Abstract

To provide an over-current protection circuit capable of appropriately generating an over-current protection level signal for detecting over current in the over-current protection circuit.SOLUTION: An over-current protection circuit includes a first MOS 31, a second MOS 32, a current detection circuit 40, a drive circuit 20, and a control circuit 10. The over-current protection circuit 1 further includes an over-current determination circuit 100 for generating an over-current protection level signal and determining that over current has been detected if a value of load current is a value of the over-current protection level signal or more. The over-current determination circuit 100 generates the over-current protection level signal so that the value of the load current becomes constant at a value of a first rating current if a voltage of a supply voltage from a battery is equal to or more than a value of a first voltage, which is a voltage value in normal operation. The over-current determination circuit 100 also generates the over-current protection level signal so that the value of the load current becomes lower than the first rating current if the voltage of the supply voltage is less than the value of the first voltage.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an overcurrent protection circuit and a power distribution device. [Background technology]

[0002] Conventionally, in an overcurrent protection circuit for protecting circuit elements provided in a semiconductor integrated circuit, a technique has been proposed for detecting an overcurrent even in a reduced voltage state to protect the circuit elements. Patent Document 1 discloses a semiconductor integrated circuit that makes it possible to detect an overcurrent even in a reduced voltage state. The semiconductor integrated circuit disclosed in Patent Document 1 generates an overcurrent threshold signal based on a reference current that has power supply voltage dependency, making it possible to detect an overcurrent even in a reduced voltage state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-208092 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, in a power distribution device that supplies a power supply voltage to a load, a harness connects the power supply and the power distribution device, and the power distribution device and the load. This harness is required to be resistant to overcurrent, but its limiting current is constant regardless of the power supply voltage. Meanwhile, the semiconductor integrated circuit disclosed in Patent Document 1 generates an overcurrent threshold signal that depends on the power supply voltage over the entire power supply voltage range to detect overcurrent. Therefore, if an overcurrent threshold signal that depends on the power supply voltage is set, as in the semiconductor integrated circuit disclosed in Patent Document 1, when the power supply voltage exceeds a certain value, the limiting current of the harness may be exceeded, and the harness may no longer be protected.

[0005] The present disclosure has been made in consideration of the problems inherent in the conventional technology, and an object of the present disclosure is to provide an overcurrent protection circuit that is capable of appropriately generating an overcurrent protection level signal for detecting an overcurrent. [Means for solving the problem]

[0006] An overcurrent protection circuit according to an embodiment of the present disclosure includes a first MOS connected to a battery and controlling the on / off of a load current flowing to a load, a current detection circuit that detects the load current, a second MOS connected to the battery, connected in parallel with the first MOS, and connected to the current detection circuit, a drive circuit that drives the first MOS and the second MOS, a control circuit that controls the drive circuit to turn off the first MOS and the second MOS when an overcurrent is detected, and an overcurrent determination circuit that generates an overcurrent protection level signal and determines that an overcurrent has been detected when the value of the load current is equal to or greater than the value of the overcurrent protection level signal, wherein the overcurrent determination circuit generates the overcurrent protection level signal so that its value is constant at the value of a first rated current when the voltage of the supply voltage from the battery is equal to or greater than a first voltage that is a voltage value during normal operation, and the overcurrent determination circuit generates the overcurrent protection level signal so that its value is lower than the first rated current when the voltage of the supply voltage is less than the first voltage.

[0007] A power distribution device according to another aspect of the present disclosure includes a battery, the above-described overcurrent protection circuit, and a load to which a load current is supplied from the overcurrent protection circuit. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide an overcurrent protection circuit that is capable of appropriately generating an overcurrent protection level signal for detecting an overcurrent. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 1A is a diagram illustrating an example of a connection diagram of a power distribution device. [Figure 1B]FIG. 1B is a diagram illustrating an example of a load short-circuit model of a power distribution device. [Figure 2] FIG. 2 is a diagram for explaining the smoke generation characteristics of the harness. [Figure 3] FIG. 3 is a diagram for explaining the relationship between the supply voltage and the current when the load is short-circuited. [Figure 4A] FIG. 4A is a diagram showing a configuration of an overcurrent detection circuit. [Figure 4B] FIG. 4B is a diagram for explaining the operation of the overcurrent detection circuit. [Figure 5] FIG. 5 is a diagram showing the configuration of the overcurrent protection circuit according to the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining the operation of the overcurrent protection circuit according to the first embodiment. [Figure 7] FIG. 7 is a diagram for explaining the overcurrent protection level in the overcurrent protection circuit according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing the configuration of an overcurrent protection circuit according to the second embodiment. [Figure 9] FIG. 9 is a diagram for explaining the operation of the overcurrent protection circuit according to the second embodiment. [Figure 10] FIG. 10 is a diagram for explaining the overcurrent protection level in the overcurrent protection circuit according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Overcurrent protection circuits 1 and 2 and a power distribution device 1000 according to several embodiments of the present disclosure will be described in detail below with reference to the drawings. Identical or equivalent parts in the drawings of the overcurrent protection circuits 1 and 2 and the power distribution device 1000 according to each embodiment will be designated by the same reference numerals, and their description will be omitted.

[0011] (Overcurrent protection circuit) FIG. 1A shows an example of a connection diagram for a power distribution device. FIG. 1B shows an example of a load short-circuit model for a power distribution device. When a harness is used between a power source and a power distribution device, or between a power distribution device and a load, the weight of the power distribution device can be reduced by selecting a wire diameter that takes into account the smoke-emission characteristics of the harness. The switch IC (IPD: Intelligent Power Device) that drives this load turns off the current supply to the load when the current flowing during a load short-circuit exceeds a protection level.

[0012] In the example shown in FIG. 1B, the rated current is 30 A and R on This shows a load short-circuit model in which the overcurrent protection operates in an IPD with a load resistance of 1 mΩ. In this case, the current that flows when the load is short-circuited is expressed by the following equation (1). [Number 1] I short =V supply ÷(R supply +R on +R short )···(1)

[0013] In other words, the wiring resistance becomes non-negligible compared to the ON resistance of the IPD.

[0014] Furthermore, in the case of a load with a large temperature characteristic of the load resistance, such as an O2 heater or a bulb, the current value at startup (when cold) is larger than the current value at steady state. Figure 2 is a diagram for explaining the smoke generation characteristics of the harness.

[0015] For example, in the dotted line in Figure 2, when the temperature is not rising (when cold) at startup, the current value is I4, and over time it decreases to I3 at steady state. Therefore, when it comes to harnesses used for loads, weight can be reduced by selecting a wire diameter that takes into account the smoke generation characteristics shown in Figure 2.

[0016] The overcurrent protection circuit according to this embodiment provides a function suitable for a switch IC (IPD) that drives such a load (harness).

[0017] In general switch ICs, the overcurrent protection threshold (overcurrent protection operating current) is set based on the rated current (corresponding to I1 in Figure 2). However, as mentioned above, the current value rises during startup (when cold), so if overcurrent protection is determined based on the steady-state rated current, a load short circuit will be detected. For this reason, harness protection functions based on the rated current must take into account the smoke generation characteristics of the harness.

[0018] Figure 3 is a diagram illustrating the relationship between the supply voltage and the current when the load is short-circuited. In Figure 3, (1) shows the current value (which depends on VDD) that should be supplied during normal operation, and (2-1) shows the OCP (Over Current Protection) level at that time. By setting the OCP level in (2-1) to a value that allows for some margin relative to the current value at VMAX for the current value in (1), operation can continue during normal operation within the operating power supply range of VDD, and protection can be provided when an overcurrent flows.

[0019] It is also possible to set the OCP threshold to a value dependent on the power supply voltage, as in the semiconductor integrated circuit described in the prior art (2-2). On the other hand, as shown in the figure, the current to be supplied increases when the device is cold. The current to be supplied in this case is shown in Figure 3 (3).

[0020] In addition, in the short-circuit test model shown in Figure 1B, the short-circuit current, defined by the short-circuit resistance and wiring resistance, is shown as (4) in Figure 3. For overcurrent protection to function effectively, the OCP must be appropriately set between (3) and (4) (RG1). For example, as shown in prior art documents, the OCP level that changes with VDD is shown as (5) in the figure. As shown in Figure 3, the values ​​of (3) and (4) in the figure are very large, so the value shown as (5) in the figure is also very large.

[0021] The "Wire Harness Limit Current" in Figure 3 shows the limit current of the harness. This limit current of the harness is determined by the wire diameter and material, and is not dependent on VDD. Therefore, if the current is increased depending on VDD, as disclosed in prior art documents, the OCP level will rise too much. As a result, the OCP will exceed the system's current limit, such as the harness limit current.

[0022] Therefore, the OCP used in such a system must have a range (characteristic) that varies with VDD and a clamping range (characteristic), as shown in "Variation with VDD + OCP level that clamps before the wire harness reaches its limit" in Figure 3. In other words, an overcurrent protection circuit is needed that can properly detect short-circuit current while making the most of the harness's performance.

[0023] Fig. 4A is a diagram showing the configuration of a general overcurrent detection circuit. Fig. 4B is a diagram for explaining the operation of a general overcurrent detection circuit. As shown in Fig. 4A, a voltage (Vsense) corresponding to the load current Io detected by the current detection circuit is compared with a reference voltage Vref by a comparator. When Vsense exceeds the value of the reference voltage Vref, an overcurrent detection signal is turned on, and an overcurrent due to a short circuit is detected.

[0024] 4A and 4B, the reference voltage Vref is always constant regardless of the value of the load current Io, which causes a problem that an overcurrent cannot be detected when the value of Vsense is lower than the value of the reference voltage Vref.

[0025] The overcurrent protection circuit of this embodiment makes it possible to appropriately generate an overcurrent protection level signal for detecting overcurrent when the supply voltage is other than the steady-state voltage, both when the supply voltage is lower than the steady-state voltage and when the supply voltage is higher than the steady-state voltage.

[0026] (First embodiment) 5 is a diagram showing the configuration of a power distribution device 1000 to which the overcurrent protection circuit 1 according to the first embodiment is applied. As shown in FIG. 5, the power distribution device 1000 includes a battery (Vbatt), the overcurrent protection circuit 1, and a load.

[0027] The overcurrent protection circuit 1 includes a first MOS 31 connected to a battery and controlling the on / off of a load current Io flowing to a load, and a current detection circuit 40 that detects the load current Io. The overcurrent protection circuit 1 also includes a second MOS 32 connected to the battery, connected in parallel with the first MOS 31, and connected to the current detection circuit 40, and a drive circuit 20 that drives the first MOS 31 and the second MOS 32.

[0028] The overcurrent protection circuit 1 also includes a control circuit 10 that controls the drive circuit 20 to turn off the first MOS 31 and the second MOS 32 when an overcurrent is detected. The overcurrent protection circuit 1 further includes an overcurrent determination circuit 100 that generates an overcurrent protection level signal and determines that an overcurrent has been detected when the value of the load current Io is equal to or greater than the value of the overcurrent protection level signal.

[0029] When the voltage supplied from the battery is equal to or higher than a first voltage value, which is the voltage value during normal operation, the overcurrent determination circuit 100 generates an overcurrent protection level signal so that the value is constant at the value of the first rated current.

[0030] Moreover, when the voltage of the supply voltage is less than the value of the first voltage, the overcurrent determination circuit 100 generates the overcurrent protection level signal so that the value is lower than the first rated current.

[0031] 6 is a diagram for explaining the operation of the overcurrent protection circuit 1 according to the first embodiment. As shown in FIG. 6, the value of the overcurrent protection level signal is lower than the first rated current when the voltage of the supply voltage is lower than the value of the first voltage.

[0032] 7 is a diagram for explaining the overcurrent protection level signal in the overcurrent protection circuit 1 according to the first embodiment. As shown in Fig. 7, when the value of Vsupply, which is the supply voltage, is less than the first voltage, the value of the overcurrent protection level signal in the overcurrent protection circuit 1 is lower than the first rated current, making it possible to detect a short-circuit current even when the supply voltage is less than the first voltage.

[0033] (Overcurrent judgment circuit 100) Next, the overcurrent determination circuit 100 according to the first embodiment will be described in detail. The overcurrent determination circuit 100 according to the first embodiment includes a Zener diode 120 that keeps the voltage constant when the supply voltage exceeds a first voltage value. The anode side of the Zener diode 120 is connected to GND.

[0034] Specifically, the overcurrent determination circuit 100 includes a comparator cmp0 that compares the value of the load current detected by the current detection circuit 40 with the value of the overcurrent protection level signal. The overcurrent determination circuit 100 also includes a first resistor R11 that has one end connected to the battery power supply terminal VB and the other end connected to the cathode side of the Zener diode 120.

[0035] The overcurrent determination circuit 100 also includes a second resistor R12 having one end connected to the other end of the first resistor R11 and the cathode side of the Zener diode 120, and the other end connected to the comparator cmp0. The overcurrent determination circuit 100 also includes a third resistor R13 having one end connected to the other end of the second resistor R12 and the comparator cmp0.

[0036] As a result, when the value of the supply voltage is less than the first voltage, the overcurrent determination circuit 100 generates the overcurrent protection level signal such that the value of the overcurrent protection level signal increases in proportion to an increase in the value of the supply voltage.

[0037] Furthermore, when the value of the supply voltage is equal to or greater than the first voltage, the overcurrent determination circuit 100 generates an overcurrent protection level signal using the Zener diode 120 so that the value of the overcurrent protection level signal is constant at the value of the first rated current.

[0038] This allows the overcurrent protection circuit 1 according to the first embodiment to appropriately generate an overcurrent protection level signal for detecting an overcurrent. For example, in conventional overcurrent protection circuits, the overcurrent threshold value increases in proportion to (depends on) the power supply voltage even in a range above the voltage during normal operation, which has been a problem in that the harness cannot be appropriately protected from overcurrent.

[0039] The overcurrent protection circuit 1 according to the first embodiment is capable of generating an overcurrent protection level signal that is a constant value independent of the power supply voltage in the high-voltage region in a range equal to or greater than the voltage during normal operation, thereby enabling appropriate protection of the harness connected to the load. Moreover, by generating an overcurrent protection level signal independent of the power supply voltage in the high-voltage region in a range equal to or greater than the voltage during normal operation, the overcurrent protection circuit 1 according to the first embodiment can also reduce power consumption during overcurrent detection compared to conventional configurations.

[0040] (Second embodiment) As described above, one specific embodiment has been described, but the above-described embodiment is merely an example and is not intended to limit the scope of the present invention. For example, in the above-described embodiment, an example has been shown in which the overcurrent determination circuit 100 is configured using a Zener diode 120. Here, a description will be given of an overcurrent protection circuit 2 according to a second embodiment in which the overcurrent determination circuit 200 is configured using a plurality of voltage dividing resistors, with a configuration different from that of the first embodiment.

[0041] Fig. 8 is a diagram showing the configuration of an overcurrent protection circuit 2 according to the second embodiment. As shown in Fig. 8, the overcurrent protection circuit 2 according to the second embodiment differs from the overcurrent determination circuit 200 according to the first embodiment in that the overcurrent protection level signal is generated by a plurality of voltage dividing resistors in the overcurrent determination circuit 200.

[0042] The overcurrent determination circuit 200 according to the second embodiment includes a comparator cmp0 that compares the value of the load current detected by the current detection circuit 40 with the value of the overcurrent protection level signal. The overcurrent determination circuit 200 also includes a power supply V that supplies a second voltage for generating the overcurrent protection level signal. DD Equipped with.

[0043] The overcurrent determination circuit 200 also includes a plurality of voltage dividing resistors that divide the second voltage supplied by the power supply VDD. In the example shown in Fig. 8, the plurality of voltage dividing resistors are composed of a first voltage dividing resistor R21, a second voltage dividing resistor R22, a third voltage dividing resistor R23, a fourth voltage dividing resistor R24, a fifth voltage dividing resistor R25, and a sixth voltage dividing resistor R26.

[0044] One end of the first voltage dividing resistor R21 is connected to the power supply VDD, and the other end is connected to the comparator cmp0. Furthermore, one end of the second voltage dividing resistor R22 is connected to the other end of the first voltage dividing resistor R21 and the comparator cmp0. Subsequently, the third to sixth voltage dividing resistors R23 to R26 are connected in series.

[0045] Moreover, overcurrent determination circuit 200 includes a plurality of voltage sources that enable a plurality of voltage dividing resistors in stages according to the value of the supply voltage, a plurality of comparators, and a plurality of switches. In the example shown in Fig. 8, the plurality of voltage sources are composed of first voltage source 221, second voltage source 222, third voltage source 223, and fourth voltage source 224.

[0046] In the example shown in FIG. 8, the plurality of comparators are made up of four comparators: a first comparator cmp1, a second comparator cmp2, ​​a third comparator cmp3, and a fourth comparator cmp4.

[0047] In the example shown in FIG. 8, the plurality of switches are configured by four switches: a first switch 231, a second switch 232, a third switch 233, and a fourth switch 234.

[0048] 8, the first comparator cmp1 has one input terminal connected to the first voltage source 221 and the other input terminal connected to the battery power supply terminal VB, and compares the voltage of the first voltage source 221 with the supply voltage supplied from the battery power supply terminal VB. If the supply voltage exceeds the voltage of the first voltage source 221, the first switch 231 connected to the first comparator cmp1 is turned off.

[0049] Similarly to the first comparator cmp1, the second to fourth comparators cmp2 to cmp4 have one input terminal connected to the second to fourth voltage sources 222 to 224, respectively, and the other input terminal connected to the battery power supply terminal VB.

[0050] It should be noted that the voltage values ​​increase in the order from first voltage source 221 to fourth voltage source 224. That is, as the supply voltage increases, the switches are turned off in order starting from fourth switch 234, and finally first switch 231 is turned off.

[0051] As a result, when all the switches from the first switch 231 to the fourth switch 234 are on, an overcurrent protection level signal is generated that is voltage-divided by two resistors, the first voltage-dividing resistor R21 and the second voltage-dividing resistor R22. Thereafter, as the switches are turned off in order starting from the fourth switch 234, the third voltage-dividing resistor R23, the fourth voltage-dividing resistor R24, the fifth voltage-dividing resistor R25, and the sixth voltage-dividing resistor R26 become effective, and the value of the overcurrent protection level signal increases stepwise.

[0052] 9 is a diagram for explaining the operation of the overcurrent protection circuit 2 according to the second embodiment. As shown in Fig. 9, as the supply voltage of the battery power terminal VB increases, the value of the overcurrent protection level signal increases stepwise.

[0053] That is, the overcurrent determination circuit 200 of the overcurrent protection circuit 2 according to the second embodiment enables multiple voltage dividing resistors in stages according to the value of the supply voltage. Moreover, the overcurrent determination circuit 200 generates an overcurrent protection level signal such that the value becomes the value of the first rated current when all of the multiple voltage dividing resistors are enabled.

[0054] 10 is a diagram illustrating the overcurrent protection level in the overcurrent protection circuit 2 according to the second embodiment. As shown in FIG. 10, the value of the overcurrent protection level signal becomes the value of the first rated current when all of the multiple voltage dividing resistors are enabled. That is, when the supply voltage is equal to or higher than the first voltage, the overcurrent protection circuit 2 according to the second embodiment keeps the value of the overcurrent protection level signal constant at the value of the first rated current.

[0055] This allows the overcurrent protection circuit 2 according to the second embodiment to appropriately generate an overcurrent protection level signal for detecting an overcurrent. That is, the overcurrent protection circuit 2 according to the second embodiment can generate an overcurrent protection level signal that is a constant value independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation, thereby enabling appropriate protection of the harness connected to the load. Furthermore, the overcurrent protection circuit 1 according to the first embodiment can reduce power consumption during overcurrent detection compared to conventional configurations by generating an overcurrent protection level signal independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation.

[0056] (Other embodiments) Although the embodiments have been described in detail with reference to the drawings, the present embodiments are not limited to the contents described in the above embodiments. Furthermore, the components described above include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described above can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the embodiments.

[0057] The features of the overcurrent protection circuits 1 and 2 and the power distribution device 1000 will be described below.

[0058] The overcurrent protection circuits 1 and 2 according to the first aspect include a first MOS 31 connected to a battery and controlling the on / off of a load current flowing to a load, and a current detection circuit 40 that detects the load current. The overcurrent protection circuits 1 and 2 also include a second MOS 32 connected to the battery, connected in parallel with the first MOS 31, and connected to the current detection circuit 40, and a drive circuit 20 that drives the first MOS 31 and the second MOS 32. The overcurrent protection circuits 1 and 2 also include a control circuit 10 that controls the drive circuit 20 to turn off the first MOS 31 and the second MOS 32 when an overcurrent is detected. The overcurrent protection circuits 1 and 2 also include an overcurrent determination circuit 100 or 200 that generates an overcurrent protection level signal and determines that an overcurrent has been detected when the value of the load current is equal to or greater than the value of the overcurrent protection level signal. The overcurrent determination circuits 100 and 200 generate an overcurrent protection level signal so that its value remains constant at the first rated current when the voltage supplied from the battery is equal to or greater than a first voltage, which is the voltage value during normal operation. Also, the overcurrent determination circuits 100 and 200 generate an overcurrent protection level signal so that its value becomes lower than the first rated current when the voltage supplied from the battery is less than the first voltage.

[0059] This configuration enables overcurrent protection circuits 1 and 2 to appropriately generate an overcurrent protection level signal for detecting an overcurrent in both cases where the supply voltage is other than the steady-state voltage and is lower than the steady-state voltage, and higher than the steady-state voltage. In other words, overcurrent protection circuits 1 and 2 can appropriately generate an overcurrent protection level signal for detecting an overcurrent while taking into account the smoke generation characteristics of the load, and appropriately protect against overcurrent.

[0060] The overcurrent determination circuit 100 of the overcurrent protection circuit 1 according to the second aspect may include a Zener diode 120 that keeps the voltage constant when the supply voltage exceeds a first voltage value. When the supply voltage value is less than the first voltage, the overcurrent determination circuit 100 may generate the overcurrent protection level signal such that the value of the overcurrent protection level signal increases in proportion to an increase in the supply voltage value. When the supply voltage value is equal to or greater than the first voltage, the overcurrent determination circuit 100 may use the Zener diode 120 to generate the overcurrent protection level signal such that the value of the overcurrent protection level signal remains constant at the value of the first rated current.

[0061] This configuration enables the overcurrent protection circuit 1 to appropriately generate an overcurrent protection level signal for detecting an overcurrent. That is, the overcurrent protection circuit 1 can generate an overcurrent protection level signal that has a constant value independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation, thereby appropriately protecting the harness connected to the load. Furthermore, the overcurrent protection circuit 1 according to the first embodiment generates an overcurrent protection level signal independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation, thereby reducing power consumption during overcurrent detection compared to conventional configurations.

[0062] The overcurrent determination circuit 200 of the overcurrent protection circuit 2 according to the third aspect is connected to a power supply V DD The overcurrent determination circuit 200 may also include a plurality of voltage dividing resistors that divide the second voltage, and a plurality of voltage sources, a plurality of comparators, and a plurality of switches that enable the plurality of voltage dividing resistors in stages according to the value of the supply voltage. The overcurrent determination circuit 200 may also enable the plurality of voltage dividing resistors in stages according to the value of the supply voltage. The overcurrent determination circuit 200 may also generate an overcurrent protection level signal such that the value becomes the value of the first rated current when all of the plurality of voltage dividing resistors are enabled.

[0063] This configuration enables the overcurrent protection circuit 2 to appropriately generate an overcurrent protection level signal for detecting an overcurrent. That is, the overcurrent protection circuit 2 can generate an overcurrent protection level signal that has a constant value independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation, thereby appropriately protecting the harness connected to the load. Furthermore, the overcurrent protection circuit 1 according to the first embodiment generates an overcurrent protection level signal independent of the power supply voltage in the high-voltage region in a range equal to or higher than the voltage during normal operation, thereby reducing power consumption during overcurrent detection compared to conventional configurations.

[0064] A power distribution device 1000 according to the fourth aspect includes a battery, the above-described overcurrent protection circuit, and a load to which a load current is supplied from the overcurrent protection circuit.

[0065] This configuration enables power distribution device 1000 to appropriately generate an overcurrent protection level signal for detecting an overcurrent when the supply voltage is other than the steady-state voltage, both when the supply voltage is lower than the steady-state voltage and when the supply voltage is higher than the steady-state voltage. In other words, power distribution device 1000 can appropriately generate an overcurrent protection level signal for detecting an overcurrent while taking into account the smoke generation characteristics of the load, and appropriately protect against an overcurrent. [Explanation of symbols]

[0066] cmp0 comparator cmp1 1st comparator cmp2 2nd comparator cmp3 3rd comparator cmp4 4th comparator R11 1st resistor R12 Second resistor R13 Third resistor R21 1st voltage dividing resistor R22 Second voltage dividing resistor R23 Third voltage dividing resistor R24 4th voltage dividing resistor R25 5th voltage divider resistor R26 6th voltage dividing resistor Vlim Overcurrent protection level signal 1, 2 Overcurrent protection circuit 10 Control circuit 20 Drive circuit 31 First MOS 32 Second MOS 40 Current detection circuit 100, 200 Overcurrent judgment circuit 120 Zener diode 221 First Voltage Source 222 Second Voltage Source 223 Third Voltage Source 224 Fourth Voltage Source 231 First Switch 232 Second Switch 233 Third Switch 234 4th Switch 1000 Power distribution equipment

Claims

1. a first MOS connected to the battery and controlling on / off of a load current flowing to a load; a current detection circuit for detecting the load current; a second MOS connected to the battery, connected in parallel with the first MOS, and connected to the current detection circuit; a drive circuit for driving the first MOS and the second MOS; a control circuit that controls the drive circuit to turn off the first MOS and the second MOS when an overcurrent is detected; an overcurrent determination circuit that generates an overcurrent protection level signal and determines that an overcurrent has been detected when the value of the load current is equal to or greater than the value of the overcurrent protection level signal; the overcurrent determination circuit generates the overcurrent protection level signal so that its value is constant at a first rated current value when the voltage supplied from the battery is equal to or higher than a first voltage value that is a voltage value during normal operation; The overcurrent protection circuit generates the overcurrent protection level signal so that its value is lower than the first rated current when the voltage of the supply voltage is less than the value of the first voltage.

2. the overcurrent determination circuit includes a Zener diode that keeps the supply voltage constant when the supply voltage exceeds the first voltage value; the overcurrent determination circuit generates the overcurrent protection level signal such that the value of the overcurrent protection level signal increases in proportion to an increase in the value of the supply voltage when the value of the supply voltage is less than the first voltage; 2. The overcurrent protection circuit according to claim 1, wherein when the value of the supply voltage is equal to or greater than the first voltage, the overcurrent determination circuit generates the overcurrent protection level signal by the Zener diode so that the value of the overcurrent protection level signal is constant at the value of the first rated current.

3. The overcurrent determination circuit a power supply that provides a second voltage for generating the overcurrent protection level signal; a plurality of voltage dividing resistors that divide the second voltage; a plurality of voltage sources, a plurality of comparators, and a plurality of switches that enable the plurality of voltage dividing resistors in a stepwise manner according to the value of the supply voltage; the overcurrent determination circuit enables the plurality of voltage dividing resistors in stages according to the value of the supply voltage; 2. The overcurrent protection circuit according to claim 1, wherein the overcurrent determination circuit generates the overcurrent protection level signal so that a value of the overcurrent protection level signal becomes the value of the first rated current when all of the plurality of voltage dividing resistors become effective.

4. the battery; an overcurrent protection circuit according to any one of claims 1 to 3; a load to which the load current is supplied from the overcurrent protection circuit.

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