Overcurrent detection circuit and overcurrent detection method

Abstract

An overcurrent detection circuit (1) appropriately combines the ON / OFF timing of a current sensor power supply circuit (101) and a threshold value and a setting timing of an overcurrent detection circuit (110) to generate a state similar to the overcurrent. The overcurrent detection circuit (1) changes the ON / OFF timing of each phase of the current sensor power supply circuit (101), thereby switching the signal of a current sensor (100) between an overcurrent state signal and a normal state signal at different timings. The overcurrent detection circuit (1) diagnoses the presence or absence of a failure in the overcurrent detection function of the overcurrent detection circuit (1) without actually creating an overcurrent state, and without applying a load to the components of an electronic circuit.

Description

Overcurrent detection circuit and overcurrent detection method

[0001] The present invention relates to an overcurrent detection circuit and an overcurrent detection method.

[0002] For example, Patent Document 1 discloses a technique for diagnosing a current sensor fault by switching the pattern of a PWM signal from a microcomputer in an electronic circuit. This technique actually generates an overcurrent state using the PWM signal pattern to diagnose whether or not there is a fault in the overcurrent detection function.

[0003] Japanese Patent Application Laid-Open No. 2022-070477

[0004] However, in the above-mentioned conventional technology, an overcurrent state is generated in an electronic circuit by forming a current path that passes through components such as the switching elements and loads of the electronic circuit, which has the problem of placing a load on these components outside of normal use.

[0005] The present invention has been made in consideration of the above circumstances, and has as its object to diagnose whether or not there is a failure in the overcurrent detection function without placing a load on the components of the electronic circuit.

[0006] As one aspect for solving the above problem, an overcurrent detection circuit for detecting an overcurrent flowing through a conductor includes a plurality of current sensors for measuring the current flowing through the conductor, a current sensor power supply circuit for supplying power to the plurality of current sensors, a plurality of comparison circuits for comparing each of the output values ​​of the plurality of current sensors with a threshold value to detect whether the output value is within a normal range, a voltage output circuit for outputting respective voltage values ​​according to the comparison results between the output values ​​of the plurality of comparison circuits and the threshold value, an abnormality determination circuit for determining whether an abnormality has occurred in the plurality of comparison circuits based on the output of the voltage output circuit, and a timing change circuit for starting the supply or cut-off of power to the plurality of current sensors at different timings, wherein the threshold value is set so that the comparison result by each of the comparison circuits is inverted before and after the timing at which the supply or cut-off of power to the plurality of current sensors is started.

[0007] According to the present invention, it is possible to diagnose whether or not there is a malfunction in the overcurrent detection function without placing a load on the components of the electronic circuit.

[0008] 1 is a timing chart showing the configuration of an electronic circuit according to an embodiment of the present invention;

[0009] Hereinafter, embodiments of the present application will be described with reference to the drawings. Note that the following embodiments do not limit the present invention, and not all of the components and combinations thereof described in the embodiments are necessarily essential to the solution of the invention. The number of each component in the following embodiments may be singular or plural, unless otherwise specified.

[0010] In the following embodiments, the same reference numerals are used to designate the same features as those in the previous embodiments, and the description of the latter embodiments will be omitted, with the focus being on the differences. Furthermore, in the following embodiments, a combination of part or all of one embodiment with part or all of another embodiment is also included in the present application as long as there is no contradiction and there is consistency.

[0011] In the following description, identical or similar components will be denoted by the same reference numeral. When there are multiple identical or similar components, they may be denoted by the same reference numeral with different subscripts. When there is no need to distinguish between multiple components, the subscripts may be omitted.

[0012] (Configuration of overcurrent detection circuit 1 according to embodiment) Fig. 1 is a diagram showing the configuration of an overcurrent detection circuit 1 according to an embodiment. The overcurrent detection circuit 1 is assumed to be an electronic circuit or a part thereof mounted on a vehicle such as an automobile, but is not limited to this. The overcurrent detection circuit 1 is also assumed to be a circuit that detects overcurrent in three-phase power, but is not limited to three phases.

[0013] The overcurrent detection circuit 1 includes a current sensor 100 , a current sensor power supply circuit 101 , a delay circuit 102 , a microcomputer (hereinafter referred to as a microcomputer) 103 , a safety circuit 104 , and an overcurrent detection circuit 110 .

[0014] The current sensor 100 includes a U-phase current sensor 100u, a V-phase current sensor 100v, and a W-phase current sensor 100w, which measure the currents flowing through conductors that supply power to each phase of the three-phase inverter. Current measurement is possible with only the current sensors for any two phases. There are various methods for current detection, such as Hall IC type and current shunt type, and there is no particular limitation.

[0015] The current sensor power supply circuit 101 is a power supply circuit dedicated to the current sensor 100, which supplies power to the U-phase current sensor 100u, the V-phase current sensor 100v, and the W-phase current sensor 100w of the current sensor 100. However, the current sensor power supply circuit 101 is not necessarily limited to a power supply circuit dedicated to the current sensor 100.

[0016] The current sensor power supply circuit 101 includes a sensor power supply control unit 101a, which turns on the operation of the current sensor power supply circuit 101 in response to an enable signal output from the microcomputer 103, and turns off the operation of the current sensor power supply circuit 101 in response to a disable signal.

[0017] The delay circuit 102 includes a U-phase delay circuit RU1, a V-phase delay circuit RV1, and a W-phase delay circuit RW1 provided for each of the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w.

[0018] The U-phase delay circuit RU1, V-phase delay circuit RV1, and W-phase delay circuit RW1 are set with timings that differ from each other in the delay time of the phase of the power supplied from the current sensor power supply circuit 101 to each phase of the current sensor 100. The U-phase delay circuit RU1, V-phase delay circuit RV1, and W-phase delay circuit RW1 are examples of timing change circuits that start supplying or cutting off power to the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w at different times.

[0019] The delay circuit 102 may be configured in various ways, such as an RC delay circuit using a resistor and a capacitor, or a timer circuit, but is not particularly limited to this.

[0020] The overcurrent detection circuit 110 includes a detection threshold circuit 111 and a detection circuit 112 .

[0021] The detection circuits 112 include a U-phase detection circuit 112u, a V-phase detection circuit 112v, and a W-phase detection circuit 112w corresponding to the U-phase current sensor 100u, the V-phase current sensor 100v, and the W-phase current sensor 100w, respectively.

[0022] The U-phase detection circuit 112u, V-phase detection circuit 112v, and W-phase detection circuit 112w each further include a positive-side detection circuit and a negative-side detection circuit for the positive current direction. Therefore, the detection circuit 112 employs a window comparator system, but is not limited to this. For individual diagnosis, resistors with different resistance values ​​are set in the positive and negative output stages of the U-phase detection circuit 112u, V-phase detection circuit 112v, and W-phase detection circuit 112w, respectively, to change the output voltages.

[0023] Specifically, the U-phase detection circuit 112u has a comparison circuit OUH as a positive-side detection circuit and a comparison circuit OUL as a negative-side detection circuit. The U-phase detection circuit 112u has a voltage output circuit RU2 on the output side of the comparison circuit OUH and a voltage output circuit RU3 on the output side of the comparison circuit OUL. The V-phase detection circuit 112v has a comparison circuit OVH as a positive-side detection circuit and a comparison circuit OVL as a negative-side detection circuit. The V-phase detection circuit 112v has a voltage output circuit RV2 on the output side of the comparison circuit OVH and a voltage output circuit RV3 on the output side of the comparison circuit OVL. The W-phase detection circuit 112w has a comparison circuit OWH as a positive-side detection circuit and a comparison circuit OWL as a negative-side detection circuit. The W-phase detection circuit 112w has a voltage output circuit RW2 on the output side of the comparison circuit OWH and a voltage output circuit RW3 on the output side of the comparison circuit OWL.

[0024] In this way, the comparison circuits OUH, OUL, OVH, OVL, OWH, and OWL compare each output value of the current sensor 100 with a threshold value to detect whether the output value is within a normal range.

[0025] The voltage output circuits RU2, RU3, RV2, RV3, RW2, and RW3 output divided voltage values ​​obtained by dividing the voltage at different voltage division ratios depending on the comparison results between the output value of the current sensor 100 and a threshold value by the comparison circuits OUH, OUL, OVH, OVL, OWH, and OWL. The divided voltage values ​​are determined by the combination of the VCC pull-up resistors and the resistance values ​​of the voltage output circuits RU2, RU3, RV2, RV3, RW2, and RW3 set in the outputs of the comparison circuits OUH, OUL, OVH, OVL, OWH, and OWL. In other words, when an overcurrent is detected, the resistance of the output of the voltage output circuit becomes effective in the voltage divider circuit and acts as a combined resistance, resulting in different divided voltage values, which allows individual diagnosis.

[0026] The output of the detection circuit 112 is connected to the microcomputer 103 and the safety circuit 104. The microcomputer 103 is an example of an abnormality determination circuit, and checks the voltage value based on the output from the detection circuit 112 to determine the location of the fault. The safety circuit 104 recognizes an overcurrent state based on the output from the detection circuit 112.

[0027] The detection threshold circuit 111 inputs a positive threshold ThH, which determines the upper limit of the normal range of current values, to the comparators of the positive detection circuits of the U-phase detection circuit 112u, the V-phase detection circuit 112v, and the W-phase detection circuit 112w (see the triangle "a" in FIG. 1). The detection threshold circuit 111 also inputs a negative threshold ThL, which determines the lower limit of the normal range of current values, to the comparators of the negative detection circuits of the U-phase detection circuit 112u, the V-phase detection circuit 112v, and the W-phase detection circuit 112w (see the square "b" in FIG. 1). The positive threshold ThH and the negative threshold ThL are also input to the microcomputer 103 for monitoring.

[0028] The delay circuit 102 requires resistors for all phases, whereas the overcurrent detection circuit 110 only requires the difference in current value between the phases to be detected, so the resistor can be omitted for only one phase.

[0029] (Timing Chart of Processing in Overcurrent Detection Circuit 1 According to the Embodiment) Fig. 2 is a timing chart of processing in the overcurrent detection circuit 1 according to the embodiment. In Fig. 2, times t1 to t4 correspond to vehicle startup, and times t5 to t8 correspond to vehicle shutdown.

[0030] First, at time t1, the current sensor power supply circuit 101 is turned on (enabled), and the outputs of the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w rise from a voltage of 0 A to a predetermined voltage (e.g., 2.5 V) at different times due to the delay circuit 102.

[0031] The positive threshold value ThH and negative threshold value ThL of the detection threshold circuit 111 start rising at the same timing as the outputs of the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w, and rise to a predetermined threshold value earlier than each output. Here, for example, the positive threshold value ThH is set to 4.5 V, and the negative threshold value ThL is set to 0.5 V.

[0032] Through the above-described operation, the negative-side detection circuits of each phase of the detection circuit 112 can transition from normal to abnormal by crossing the negative-side threshold ThL. The timing of the transitions can be used to determine which phase has transitioned from normal to abnormal. At this time, the positive-side detection circuits of each phase of the detection circuit 112 maintain their normal state. This results in, for example, a detection of an abnormal state on the negative side of the U phase at time t1, followed by a detection of an abnormal state on the negative side of the U and V phases at time t2, followed by a detection of an abnormal state on the negative side of the U, V, and W phases at time t3. As a result, the overcurrent detection voltage changes as follows: V1 between times t1 and t2, V2 (> V1) between times t2 and t3, V3 (> V2) between times t3 and t4, and V4 (> V3) after time t4. Between times t1 and t4, the overcurrent detection state is recognized as Lo (overcurrent).

[0033] In other words, the threshold values ​​that the comparison circuits OUH, OUL, OVH, OVL, OWH, and OWL compare with the output value of current sensor 100 are set so that the comparison results by each comparison circuit are inverted before and after the timing when power supply to or cut-off from current sensor 100 begins.

[0034] Furthermore, before the supply of power to the current sensors 100 of each phase is cut off, the positive-side threshold ThH is set to 4.5 V, which is lower than the output value of 5.0 V of the current sensors 100 of each phase when no current flows through the conductor. Furthermore, before the supply of power to the U-phase current sensor 100u, the V-phase current sensor 100v, and the W-phase current sensor 100w starts, the negative-side threshold ThL is set to 0.5 V, which is higher than the output value of the current sensors when no power is being supplied.

[0035] By identifying and detecting which of the negative phases (U, V, or W) has become abnormal, the overcurrent detection function for the negative side of the faulty phase is disabled. The overcurrent detection functions for the positive and negative sides of the other phases that are not faulty, as well as the overcurrent detection function for the positive side of the faulty phase, continue to operate. This allows the operating range of the overcurrent detection function of the overcurrent detection circuit 1 to be expanded.

[0036] Meanwhile, at time t5, the current sensor power supply circuit 101 is turned OFF (disabled). As a result, the outputs of the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w fall from a voltage of 5.0 V to a voltage equal to or greater than the negative maximum current (for example, 0 V) ​​at different times due to the delay circuit 102.

[0037] At this time, it is necessary to change the positive side threshold value ThH in order to diagnose the positive side detection circuit of each phase of the detection circuit 112. For this reason, the same power supply V_AD as that of the current sensor power supply circuit 101 is used as the power supply for the detection threshold circuit 111, and is turned off at time t5 to set it to 0 V.

[0038] Then, at time t5, the positive threshold value ThH and the negative threshold value ThL of the detection threshold circuit 111 both become 0 V. At this time, the output voltages of the U-phase current sensor 100u, the V-phase current sensor 100v, and the W-phase current sensor 100w fall from 0 A (2.5 V) to a value equal to or greater than the maximum negative current value (e.g., 0 V).

[0039] The positive-side detection circuits of each phase of the detection circuit 112 transition from normal to abnormal by crossing the positive-side threshold ThH, and the timing of the transition can be used to determine which phase has transitioned from normal to abnormal. Meanwhile, the negative-side detection circuits of each phase of the detection circuit 112 maintain an abnormal state. This results in, for example, a detection of an abnormal state on the positive and negative sides of the U phase at time t5, followed by a detection of an abnormal state on the positive and negative sides of the U and V phases at time t6, followed by a detection of an abnormal state on the positive and negative sides of the U, V, and W phases at time t7. This results in the overcurrent detection voltage changing from V5 between times t5 and t6, to V6 (>V5) between times t6 and t7, to V7 (>V6) between times t7 and t8, and to V8 (>V7) after time t8. Between times t5 and t8, the overcurrent detection state is recognized as Lo (overcurrent).

[0040] By identifying and detecting which of the U, V, and W phases has become abnormal in this way, the overcurrent detection function of only the faulty phase is disabled, while the overcurrent detection functions of the other phases that are not faulty continue to operate. In this way, the operating range of the overcurrent detection function of the overcurrent detection circuit 1 can be expanded.

[0041] In this way, the voltage state of each output of the U-phase current sensor 100u, V-phase current sensor 100v, and W-phase current sensor 100w, as well as the positive threshold value ThH and the negative threshold value ThL, are changed by turning on / off the current sensor power supply circuit 101. In this way, the normality or abnormality of the overcurrent detection function is diagnosed.

[0042] (Effects of the embodiment) In the above-described embodiment, a state similar to an overcurrent is generated by appropriately combining the ON / OFF timing of the current sensor power supply circuit 101 and the threshold and setting timing of the overcurrent detection circuit 110. Furthermore, by varying the ON / OFF timing of each phase of the current sensor power supply circuit 101, the signal of the current sensor 100 is switched between an overcurrent state signal and a normal state signal at different timings. Therefore, it is possible to reliably diagnose whether or not there is a failure in the overcurrent detection function of the overcurrent detection circuit 1 without actually creating an overcurrent state or placing a load on the components of the electronic circuit.

[0043] Furthermore, in the above-described embodiment, by setting the negative threshold value ThL to a value greater than 0 V by a predetermined value, such as 0.5 V, rather than 0 V, an overcurrent state is detected by the negative threshold value ThL when the sensor signal is set to 5.0 V. By setting the negative threshold value ThL before turning on the current sensor power supply circuit 101 to set the sensor signal to 5.0 V, an overcurrent state can be created, and the presence or absence of a malfunction in the overcurrent detection function of the overcurrent detection circuit 1 can be accurately confirmed.

[0044] Furthermore, in the above-described embodiment, by setting the positive threshold value ThH to a value that is a predetermined value smaller than 0 V, such as 4.5 V instead of 5.0 V, an overcurrent state is detected by the positive threshold value ThH when the sensor signal is set to 0 V. By setting the positive threshold value ThH before turning off the current sensor power supply circuit 101 in order to set the sensor signal to 0 V, an overcurrent state can be created, and the presence or absence of a malfunction in the overcurrent detection function of the overcurrent detection circuit 1 can be accurately confirmed.

[0045] In the above-described embodiment, the voltage division and the time delay provided by the delay circuit are combined, which allows overcurrents in the U-phase current sensor 100u, the V-phase current sensor 100v, and the W-phase current sensor 100w to be detected individually, as well as overcurrents in the positive and negative currents.

[0046] Although the embodiments of the present application have been described in detail above, the present disclosure is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, some of the configurations of the above-described embodiments can be added to, deleted from, or replaced with other configurations.

[0047] 1: overcurrent detection circuit, 100: current sensor, 100u: U-phase current sensor, 100v: V-phase current sensor, 100w: W-phase current sensor, 101: current sensor power supply circuit, 102: delay circuit, RU1: U-phase delay circuit, RV1: V-phase delay circuit, RW1: W-phase delay circuit, OUH, OUL, OVH, OVL, OWH, OWL: comparison circuit, RU2, RU3, RV2, RV3, RW2, RW3: voltage output circuit, 103: microcontroller, 104: safety circuit, 110: overcurrent detection circuit, 111: detection threshold circuit, 112: detection circuit, 112u: U-phase detection circuit, 112v: V-phase detection circuit, 112w: W-phase detection circuit, ThH: positive side threshold, ThL: negative side threshold.

Claims

1. An overcurrent detection circuit that detects overcurrent flowing in a conductor, comprising: a plurality of current sensors that measure the current flowing in the conductor; a current sensor power supply circuit that supplies power to the plurality of current sensors; a plurality of comparison circuits that compare each output value of the plurality of current sensors with a threshold value to detect whether the output value is within a normal range; a voltage output circuit that outputs each voltage value according to the comparison result between the output value of the plurality of comparison circuits and the threshold value; an abnormality determination circuit that determines whether an abnormality has occurred in the plurality of comparison circuits based on the output of the voltage output circuit; and a timing change circuit that starts supplying or cutting off the power to the plurality of current sensors at different timings, respectively, wherein the threshold value is set so that the comparison result by each comparison circuit is inverted before and after the timing at which the supplying or cutting off of the power to the plurality of current sensors is started.

2. An overcurrent detection circuit as claimed in claim 1, wherein the lower limit threshold indicating the lower limit of the normal range among the threshold values is set to a value higher than the output values of the plurality of current sensors when no power is being supplied, before the supply of power to the plurality of current sensors begins.

3. An overcurrent detection circuit as claimed in claim 1, wherein an upper threshold indicating the upper limit of the normal range among the threshold values is set to a value lower than the output values of the plurality of current sensors when no current is flowing through the conductor, before the supply of power to the plurality of current sensors is cut off.

4. An overcurrent detection circuit according to claim 1, wherein the voltage output circuit outputs a voltage value divided at a voltage division ratio according to the comparison results of the plurality of comparison circuits.

5. An overcurrent detection method executed by an overcurrent detection circuit that detects overcurrent flowing in a conductor, comprising: a plurality of current sensors that measure the current flowing in the conductor; a current sensor power supply circuit that supplies power to the plurality of current sensors; a plurality of comparison circuits that compare each output value of the plurality of current sensors with a threshold value to detect whether the output value is within a normal range; a voltage output circuit that outputs each voltage value according to the comparison result between the output value of the plurality of comparison circuits and the threshold value; an abnormality determination circuit that determines whether an abnormality has occurred in the plurality of comparison circuits based on the output of the voltage output circuit; a timing change circuit that starts supplying or cutting off the power to the plurality of current sensors at different timings, respectively; and the threshold value is set so that the comparison result by each comparison circuit is inverted before and after the timing at which the supplying or cutting off of the power to the plurality of current sensors is started.

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