JP7735706B2 - Electronic control unit - Google Patents

Description

The present invention relates to an electronic control device that protects a wire harness.

Electronic control devices that protect wire harnesses have been proposed (see, for example, Patent Document 1). Specifically, in these electronic control devices, a load is connected to the wire harness, and the current flowing through the load (i.e., the wire harness) is controlled by turning a switching element on and off.

The electronic control unit then detects the current flowing through the switching element and converts the detected current into a squared current value using a conversion unit that uses the translinear principle. The electronic control unit outputs the squared current value to a thermal equivalent circuit consisting of a CR circuit to derive the heat generated in the wire harness, and compares the heat generation with the smoke-emission characteristics of the wire harness to control the on/off state of the switching element.

JP 2009-142146 A

However, when constructing an electronic control device using the translinear principle as described above, the quality of the transistors used to realize the translinear principle depends on the protection accuracy. As a result, in electronic control devices such as those described above, the protection accuracy of the wire harness tends to vary greatly from product to product, depending on the quality of the transistors.

In view of the above, the present invention aims to provide an electronic control device that can reduce variations in the protection accuracy of wire harnesses.

In order to achieve the above object, claim 1 provides an electronic control device for controlling a current flowing through a wire harness (40), comprising: a main element (110) for controlling the current flowing through the wire harness; a sense element (111) through which a current corresponding to the current flowing through the main element flows; a detection resistor (130) connected to the sense element and generating a sense voltage corresponding to the current flowing through the sense element; a comparison voltage generation circuit (220) for generating a comparison voltage whose voltage changes at a predetermined cycle; a first comparator (210) for outputting a first output signal (Vout1) based on the sense voltage and the comparison voltage corresponding to the resistance value of the detection resistor and the current flowing through the sense element; a charge/discharge capacitor (261) that is charged and discharged based on the sense voltage; a second comparator (250) that outputs a second output signal (Vout2) corresponding to the first output signal and a reference voltage (Vref); a judgment circuit (310) that generates a judgment signal (Vj) as a multiplication signal based on the first output signal and the second output signal; an integration circuit (330) that counts and integrates the judgment signal to generate an integration signal; a control circuit (350) that compares the integration signal with an integration threshold that can be set according to the heat generation characteristics of the wire harness and cuts off the current flowing through the wire harness when the integration signal is greater than the integration threshold; and a subtraction circuit (340) that generates a corrected integration signal by subtracting the integration signal based on a subtraction rate that can be set according to the heat dissipation characteristics of the wire harness, and the control circuit compares the corrected integration signal generated by the subtraction circuit with the integration threshold .

This technology protects the wire harness by comparing an integrated signal, obtained by integrating a multiplication signal obtained according to the voltage at the time of discharge in the charge-discharge capacitor, with an integration threshold. If the integrated signal is greater than the integration threshold, the current flowing through the wire harness is cut off. In this case, there is a possibility that the quality of the charge-discharge capacitor may vary, but the integrated signal is generated according to the voltage at the time of discharge of the charge-discharge capacitor. Furthermore, the voltage at the time of discharge of the charge-discharge capacitor depends on the voltage at the time of charging. Therefore, this potential control device makes it easier to cancel out the variation in the quality of the charge-discharge capacitor due to charging and discharging. This reduces variation in the protection accuracy of the wire harness.

Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described below.

FIG. 2 is a diagram showing a circuit configuration of an electronic control device according to the first embodiment. FIG. 10 is a diagram showing smoke generation characteristics of a wire harness. FIG. 1 is a diagram showing normalized smoke emission characteristics of a wire harness. FIG. 10 is a diagram showing the relationship between the charge and the charging current to a charge/discharge capacitor. 4 is a timing chart of the electronic control device in the first embodiment. 4 is a timing chart of the electronic control device in the first embodiment. FIG. 10 is a diagram showing a circuit configuration of an electronic control device according to a second embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

(First embodiment)
An electronic control device according to a first embodiment will be described with reference to the drawings. The electronic control device according to the present embodiment is preferably mounted on a vehicle such as an automobile and used as a device for driving various electronic devices for the vehicle.

As shown in FIG. 1, the electronic control unit 10 of this embodiment is disposed between the power source 20 and the load 30 via a wire harness 40 and connected to an external control unit 50. The electronic control unit 10 is configured to include a main element 110, a sense element 111, a detection resistor 130, a multiplication circuit 200, an arithmetic circuit 300, a communication circuit 410, a diagnostic circuit 420, and the like. The electronic control unit 10 of this embodiment integrates the main element 110, the sense element 111, the detection resistor 130, the multiplication circuit 200, the arithmetic circuit 300, the communication circuit 410, the diagnostic circuit 420, and the like into a package to form an intelligent power device (IPD).

In this embodiment, the main element 110 and the sense element 111 are configured as identical n-channel MOSFETs (short for Metal Oxide Semiconductor). Specifically, the main element 110 has a three-terminal configuration having a gate electrode MG as a control terminal, and drain and source electrodes MD and MS through which a current IM flows. Similarly, the sense element 111 has a three-terminal configuration having a gate electrode SG as a control terminal, and drain and source electrodes SD and SS through which a current IS flows. However, the main element 110 and the sense element 111 may be configured as IGBTs (short for Insulated Gate Bipolar Transistors) or the like instead of MOSFETs.

The gate electrode MG of the main element 110 and the gate electrode SG of the sense element 111 are connected to a drive circuit 120 that applies a predetermined gate voltage. The main element 110 and the sense element 111 are switched between an ON state, in which currents IM and IS flow, and an OFF state, in which currents IM and IS are blocked, depending on the gate voltage applied. The drive circuit 120 is connected to a control circuit 350, described below, and controls the ON and OFF states of the main element 110 and the sense element 111 based on drive instructions from the control circuit 350.

The main element 110 and the sense element 111 are formed to have a predetermined area ratio. Therefore, the current IM flowing through the main element 110 and the current IS flowing through the sense element 111 have values that correspond to the area ratio. In this embodiment, the main element 110 and the sense element 111 are formed on a common semiconductor substrate, although details are not specifically shown. In this embodiment, the detection resistor 130, multiplication circuit 200, arithmetic circuit 300, communication circuit 410, diagnostic circuit 420, etc. are formed on a semiconductor substrate separate from the semiconductor substrate on which the main element 110 and the sense element 111 are formed. The electronic control device is packaged by integrating the semiconductor substrate on which the main element 110 and the sense element 111 are formed with the semiconductor substrate on which the detection resistor 130, etc. are formed, using a sealing member.

The main element 110 and sense element 111 are arranged so that their drain electrodes MD and SD are connected to the power supply 20 via the first terminal 11 provided on the electronic control device 10. The main element 110 is also arranged so that its source electrode MS is connected to the load 30 via the second terminal 12 provided on the electronic control device 10 and the wire harness 40, and is also connected to the negative terminal 140b of the current detection amplifier 140, which will be described later. The sense element 111 is arranged so that its source electrode SS is connected to the positive terminal 140a of the current detection amplifier 140, which will be described later.

The detection resistor 130 is connected to the sense element 111 via a current detection amplifier 140 and an npn transistor (hereinafter simply referred to as a transistor) 141 so that the current IS flows through the sense element 111. In this embodiment, the source electrode MS of the main element 110 is connected to the negative terminal 140b of the current detection amplifier 140, and the source electrode SS of the sense element 111 is connected to the positive terminal 140a. The collector terminal of the transistor 141 is connected between the source electrode SS of the sense element 111 and the positive terminal 140a of the current detection amplifier 140, and the emitter terminal is connected to the detection resistor 130. The base terminal of the transistor 141 is connected to the output terminal 140c of the current detection amplifier 140.

In this embodiment, the detection resistor 130 includes a first resistor 131, a second resistor 132, a first switch 133, and a second switch 134. Specifically, the first resistor 131 and the second resistor 132 are connected in series between ground and the transistor 141, with the first resistor 131 and the second resistor 132 connected in series from the transistor 141 side. The first switch 133 is connected between the second resistor 132 and ground. The second switch 134 is connected between the first resistor 131 and the second resistor 132 and ground. Therefore, when the first switch 133 is on, the resistance of the detection resistor 130 is the sum of the resistances of the first resistor 131 and the second resistor 132. When the second switch 134 is on, the resistance is the resistance of the first resistor 131. In other words, the resistance of the detection resistor 130 can be changed by the first switch 133 and the second switch 134. The resistance value of the detection resistor 130 can be changed by controlling the on/off states of the first switch 133 and the second switch 134 using a communication circuit 410 (described below). In other words, the detection resistor 130 of this embodiment can be switched between multiple resistance values.

Note that the example described here is one in which the detection resistor 130 is configured to include a first resistor 131, a second resistor 132, a first switch 133, and a second switch 134. However, an actual detection resistor 130 will include multiple resistors and multiple switches, allowing the resistance value to be set more precisely.

Here, the wire harness 40 has the smoke generation characteristics shown in Figure 2. Note that the smoke generation time in Figure 2 is calculated using the following formula, where t is the smoke generation time, Ia is the basic smoke generation current, Ib is the wire current, and Ic is the steady-state maximum current.

(Math. 1) t=Ia ² ÷ (Ib ² - Ic ² )
The basic smoke-generating current is the current value at which smoke is generated in 1 second, and the steady-state maximum current is the maximum current value at which smoke generation does not begin.

As shown in FIG. 2, the smoke-generating characteristics of the wire harness 40 vary in detail depending on the type, but are all represented by a square product similarity curve. As will be described in detail later, the electronic control unit 10 of this embodiment derives the temperature rise of the wire harness 40 based on the sense voltage Vs generated when the current IS flows through the detection resistor 130. The temperature rise here refers to the difference from the ambient temperature (i.e., the surrounding environmental temperature). As described above, the main element 110 and the sense element 111 each pass currents I M and I S according to their area ratio. Therefore, by changing the resistance value of the detection resistor 130, the smoke-generating characteristics of the wire harness 40 can be standardized, as shown in FIG. 3. In other words, by adjusting the resistance value of the detection resistor 130, the apparent current I M flowing through the wire harness 40 can be adjusted to the standardized current so as to satisfy the smoke-generating time and standardized current of the wire harness 40 shown in FIG. 3.

For example, by lowering the resistance value of the detection resistor 130 relative to a predetermined reference value, the apparent current IM can be made lower than the actual current IM compared to when the resistance value is the reference value. Conversely, by increasing the resistance value of the detection resistor 130 relative to the reference value, the apparent current IM can be made higher than the actual current IM compared to when the resistance value is the reference value. For this reason, the resistance value of the detection resistor 130 is adjusted to match the characteristics of the wire harness 40 so that the smoke generation characteristics of the wire harness 40 become the standardized smoke generation time and standardized current shown in Figure 3.

The multiplication circuit 200 is configured to include a first comparator 210, a comparison voltage generation circuit 220, a charge/discharge circuit 230, a power supply 240, a first constant current circuit 241, a second constant current circuit 242, a second comparator 250, a reference power supply 260, a charge/discharge capacitor 261, etc.

The positive terminal 210a of the first comparator 210 is connected to the emitter terminal of the transistor 141 (i.e., the detection resistor 130), and the negative terminal 210b is connected to the comparison voltage generation circuit 220. In this embodiment, the comparison voltage generation circuit 220 inputs a comparison voltage Vsaw, which is a so-called sawtooth wave, to the first comparator 210.

The sawtooth wave used as the comparison voltage Vsaw is a signal in which the voltage gradually rises from an L signal over a predetermined period, reaches an H signal, and then returns to the L signal, with the period from the L signal to the H signal being longer than the period from the H signal to the L signal. In this embodiment, the sawtooth wave used as the comparison voltage Vsaw is a signal in which a rise period in which the signal rises from an L signal to an H signal and a sustain period in which the signal remains at L are repeated alternately, making it a so-called intermittent signal. This allows for a reduction in the number of bits in the counter that makes up the integrator circuit 330 (described below), compared to when the comparison voltage Vsaw is a continuous signal that does not include a sustain period, thereby enabling miniaturization.

The rise period and sustain period are set appropriately depending on the required detection accuracy, etc., and for example, the sum of one rise period and sustain period is set to 10 ms. Furthermore, the magnitude of the H signal in the comparison voltage Vsaw is set to a voltage higher than the highest sense voltage Vs expected when the detection resistor 130 is changed. In other words, the comparison voltage Vsaw is configured to have a period during which it is greater than the sense voltage Vs.

The first comparator 210 then compares the sense voltage Vs, which corresponds to the resistance value of the detection resistor 130 and the current IS flowing through the sense element 111, with the comparison voltage Vsaw. If the sense voltage Vs is higher than the comparison voltage Vsaw, the first comparator 210 outputs an H signal as the first output signal Vout1, and if the sense voltage Vs is lower than the comparison voltage Vsaw, the first comparator 210 outputs an L signal as the first output signal Vout1.

The charge/discharge circuit 230 is connected to the first comparator 210 and the detection resistor 130, and is also connected to the comparison voltage generation circuit 220. The charge/discharge circuit 230 is also connected to a first constant current circuit 241 and a second constant current circuit 242, which are connected in series between the power supply 240 and ground.

The positive terminal 250a of the second comparator 250 is connected to the reference power supply 260, and the negative terminal 250b is connected between the first constant current circuit 241 and the second constant current circuit 242. A charge/discharge capacitor 261 is also disposed between the negative terminal 250b of the second comparator 250 and the first constant current circuit 241 and second constant current circuit 242.

The charge/discharge circuit 230 charges or discharges the charge/discharge capacitor 261 depending on the first output signal Vout1 from the first comparator 210 and the state of the comparison voltage Vsaw. In other words, the charge/discharge capacitor 261 is charged or discharged depending on the relationship in magnitude between the sense voltage Vs and the comparison voltage Vsaw, and the state of the comparison voltage Vsaw.

Specifically, when the first comparator 210 inputs an H signal and the comparison voltage Vsaw is different from the L signal, the charge/discharge circuit 230 controls the first constant current circuit 241 and the second constant current circuit 242 so that the charge/discharge capacitor 261 is charged with the charging current Ichg. The charge/discharge circuit 230 adjusts the first constant current circuit 241 so that the charging current Ichg is proportional to the sense voltage Vs. As a result, the charge Qchg stored in the charge/discharge capacitor 261 is Ichg × tchg, where tchg is the charging period. Note that "proportional" here also includes a multiplication (i.e., square) characteristic. In this embodiment, as the sense voltage Vs increases, the period during which the sense voltage Vs exceeds the comparison voltage Vsaw becomes longer, and therefore the charging period tchg also becomes longer in proportion to the sense voltage Vs. Since the charging current Ichg is proportional to the sense voltage Vs, the charging current Ichg is also proportional to the current Is. Therefore, in terms of the relationship between the current Is and the charging period tchg, the charge Qchg increases in proportion to the current Is, as shown in Figure 4. In other words, the charge Qchg stored in the charging/discharging capacitor 261 increases in proportion to the heat generated by the wire harness 40. That is, the voltage Vcx of the charging/discharging capacitor 261 increases in proportion to the sense voltage Vs (i.e., the current Is).

Furthermore, when an L signal is input from the first comparator 210, the charge/discharge circuit 230 controls the first constant current circuit 241 and the second constant current circuit 242 so that the charge/discharge capacitor 261 discharges at the discharge current Idis. In this case, the charge/discharge circuit 230 controls the second constant current circuit 242 so that the discharge current Idis is a constant current. Therefore, the more charge accumulated in the charge/discharge capacitor 261, the longer the discharge current Idis flows.

The second comparator 250 compares the reference voltage Vref input from the reference power supply 260 with the voltage Vcx of the charge/discharge capacitor 261, and outputs the comparison result as the second output signal Vout2. Specifically, the second comparator 250 outputs an H signal when the voltage Vcx is equal to or greater than the reference voltage Vref, and outputs an L signal when the voltage Vcx is less than the reference voltage Vref. The reference voltage Vref is set to a minimum value taking noise, etc. into consideration, for example.

The arithmetic circuit 300 includes a judgment circuit 310, an acquisition circuit 320, an integration circuit 330, a subtraction circuit 340, and a control circuit 350.

The judgment circuit 310 generates a multiplication signal corresponding to the voltage of the charge/discharge capacitor 261. In this embodiment, the judgment circuit 310 is configured with an AND circuit or the like, and receives the first output signal Vout1 and the second output signal Vout2 as input to generate and output the judgment signal Vj as a multiplication signal. Specifically, the judgment circuit 310 outputs an H signal as the judgment signal Vj when the second output signal Vout2 is an H signal and the first output signal Vout1 is an L signal. In other words, the judgment circuit 310 outputs an H signal when the charge/discharge capacitor 261 is discharging. Furthermore, the judgment circuit 310 outputs an L signal as the judgment signal Vj when the second output signal Vout2 is an H signal and the first output signal Vout1 is not an L signal.

The acquisition circuit 320 is connected to the determination circuit 310 and acquires the waveform of the determination signal Vj. The integration circuit 330 counts the period during which the determination signal Vj acquired by the acquisition circuit 320 is an H signal to generate an integration signal. That is, the integration circuit 330 counts the pulse width of the determination signal Vj and generates an integration signal by integrating the multiplication signal. In other words, the integration circuit 330 generates an integration signal by integrating the multiplication signal obtained according to the voltage during discharge of the charge-discharge capacitor 261. In this case, because the period of the determination signal Vj corresponds to the charge accumulated in the charge-discharge capacitor 261, the integration signal becomes larger as the accumulated charge increases. In other words, the integration signal becomes larger as the sense voltage Vs increases. Then, by counting and integrating the determination signal Vj, the heat generation amount of the wire harness 40 is integrated, and an integration signal corresponding to the heat generation of the wire harness 40 is generated. The integration circuit 330 counts the integration signal using, for example, a 20-bit counter.

The integration circuit 330 is also connected to the subtraction circuit 340, control circuit 350, and diagnostic circuit 420. When a correction integration signal (described below) is input from the subtraction circuit 340, the integration circuit 330 outputs the correction integration signal to the control circuit 350 and diagnostic circuit 420.

The subtraction circuit 340 is connected to the integration circuit 330 and performs subtraction processing on the integration signal from the integration circuit 330 using a predetermined bit shift. Specifically, the wire harness 40 generates heat when current IM flows through it, but it also dissipates heat at the same time. For example, if the heat dissipation characteristic of the wire harness 40 is -5%/s and sampling is performed every 1 ms, the subtraction rate is -0.005%. Therefore, the subtraction circuit 340 generates a corrected integration signal by performing a 15-bit bit shift on the integration signal and outputs the corrected integration signal that takes heat dissipation into account to the integration circuit 330. Note that the heat dissipation characteristics of the wire harness 40 vary depending on the type. For this reason, the subtraction circuit 340 is also connected to the communication circuit 410, which will be described later. If the wire harness 40 is changed, the subtraction rate is updated using a subtraction rate adjustment signal from the communication circuit 410.

The control circuit 350 is connected to the drive circuit 120 and inputs drive instructions to the drive circuit 120 to control the on/off states of the main element 110 and the sense element 111. The control circuit 350 then compares the corrected integration signal with an integration threshold, and switches the main element 110 and the sense element 111 to an off state when the corrected integration signal reaches the integration threshold. In other words, the control circuit 350 cuts off the current IM flowing through the wire harness 40 when the corrected integration signal reaches the integration threshold. The control circuit 350 is also connected to the diagnostic circuit 420 and inputs the determination result to the diagnostic circuit 420. The integration threshold is set according to the standardized smoke-emission characteristics of the wire harness 40 shown in Figure 3 and is set so that the wire harness 40 does not emit smoke.

The communication circuit 410 is connected to the external control unit 50 via the third terminal 13 provided on the electronic control unit 10, and is configured to be able to communicate with the external control unit 50. When a resistance adjustment signal for adjusting the detection resistor 130 to a predetermined resistance value is input from the external control unit 50, the communication circuit 410 controls the first switch 133 and the second switch 134 to adjust the resistance value of the detection resistor 130. When a subtraction rate adjustment signal for adjusting the subtraction rate of the wire harness 40 is input from the external control unit 50, the communication circuit 410 updates the subtraction rate in the subtraction circuit 340.

The communication circuit 410 is also connected to the diagnostic circuit 420, and inputs to the diagnostic circuit 420 signals indicating the adjusted resistance value of the detection resistor 130 and the adjusted subtraction rate of the wire harness 40.

The resistance adjustment signal input from the external control unit 50 is a signal that corresponds to the type of wire harness 40, and is a signal that achieves the smoke-producing characteristics shown in Figure 3 by adjusting the resistance value of the detection resistor 130. Communication between the external control unit 50 and the communication circuit 410 may be SPI (abbreviation for Serial Peripheral Interface) communication, I2C (abbreviation for Inter-Integrated Circuit) communication, or other communication methods.

The diagnostic circuit 420 is connected to the integration circuit 330, control circuit 350, and communication circuit 410, and is also connected to the external control unit 50 via the fourth terminal unit 14 provided on the electronic control unit 10. The diagnostic circuit 420 outputs the corrected integration signal input from the integration circuit 330 to the external control unit 50, and also outputs the determination result input from the control circuit 350 to the external control unit 50. The diagnostic circuit 420 also outputs a signal indicating the adjusted resistance value of the detection resistor 130 and a signal indicating the adjusted subtraction rate to the external control unit 50.

The above is the configuration of the electronic control unit 10 in this embodiment. The external control unit 50 connected to the electronic control unit 10 is composed of a microcomputer or the like equipped with a CPU and storage units such as ROM, RAM, and non-volatile RAM. The external control unit 50 performs various control operations by having the CPU read and execute programs from the ROM or non-volatile RAM. The ROM or non-volatile RAM pre-stores various data used when executing the programs (e.g., initial values, lookup tables, maps, etc.). Storage media such as ROM are non-transient tangible storage media. CPU stands for Central Processing Unit, ROM stands for Read Only Memory, and RAM stands for Random Access Memory.

In this embodiment, the external control unit 50 performs predetermined processing based on the correction integration signal and the judgment results. The external control unit 50 also inputs a resistance adjustment signal to the communication circuit 410 so that the detection resistor 130 has a predetermined resistance value appropriate for the wire harness 40. The external control unit 50 also inputs a subtraction rate adjustment signal to the communication circuit 410 so that the subtraction rate used in the subtraction circuit 340 matches the heat dissipation characteristics of the wire harness 40.

Next, the operation of the electronic control unit 10 will be described with reference to Figures 5 and 6. Note that Figures 5 and 6 show timing charts in which the current IM is larger in Figure 6 than in Figure 5, and illustrate a case in which the current IM changes when the load 30 is composed of a motor or the like.

As shown in Figures 5 and 6, when current IM flows at time T1, current IS corresponding to current IM flows through detection resistor 130, and sense voltage Vs becomes a value corresponding to current IS and the resistance value of detection resistor 130. Then, after time T1, sense voltage Vs becomes larger than comparison voltage Vsaw, and first output signal Vout1 becomes an H signal.

Then, at time T2, the comparison voltage Vsaw begins to rise, and at time T3, the comparison voltage Vsaw becomes higher than the sense voltage Vs. As a result, the first output signal Vout1 outputs an H signal during the period from time T1 to time T3.

Furthermore, during the period from time T2 to time T3, an H signal is output as the first output signal Vout1, and because the comparison voltage Vsaw is a signal different from the L signal, the charge/discharge capacitor 261 is charged by the charge/discharge circuit 230. Then, when the voltage Vcx of the charge/discharge capacitor 261 becomes greater than the reference voltage Vref as a result of charging the charge/discharge capacitor 261, the second output signal Vout2 becomes an H signal.

As described above, the charging current Ichg that charges the charge/discharge circuit 230 is adjusted to a value proportional to the sense voltage Vs. As the current IM increases, the period during which the sense voltage Vs is greater than the comparison voltage Vsaw becomes longer, and the period during which the charge/discharge capacitor 261 is charged also becomes longer.

At time T3, the comparison voltage Vsaw becomes higher than the sense voltage Vs, causing the first output signal Vout1 to become an L signal, and the charge/discharge circuit 230 discharges the charge/discharge capacitor 261. Then, at time T4, when the voltage Vcx of the charge/discharge capacitor 261 becomes lower than the reference voltage Vref, the second output signal Vout2 becomes an L signal. Therefore, from time T3 to time T4, the first output signal Vout1 is an L signal and the second output signal Vout2 is an H signal, and the determination signal Vj becomes an H signal.

Then, when the comparison voltage Vsaw becomes an L signal at time T5, the sense voltage Vs becomes greater than the comparison voltage Vsaw, and an H signal is output as the first output signal Vout1. Thereafter, the same processing as at times T2 to T5 is carried out in sequence at times T6 to T9 and times T10 to T13.

Then, as described above, the integration circuit 330 integrates the determination signal Vj as a multiplication signal to generate an integration signal, and the subtraction circuit 340 generates a corrected integration signal that takes into account the subtraction rate. The control circuit 350 compares the corrected integration signal with an integration threshold, and if it determines that the corrected integration signal is equal to or greater than the integration threshold, it controls the drive circuit 120 to turn off the main element 110 and the sense element 111. In this embodiment, the wire harness 40 is protected in this manner.

According to the present embodiment described above, a charge/discharge capacitor 261 is provided, and the charge/discharge capacitor 261 is charged or discharged based on the sense voltage Vs. In other words, according to this embodiment, the charge/discharge capacitor 261 is charged or discharged based on the current IM flowing through the wire harness 40. The electronic control device then compares an integrated signal obtained by integrating a multiplication signal obtained according to the voltage at the time of discharge in the charge/discharge capacitor 261 with an integration threshold, and protects the wire harness 40 by cutting off the current IM flowing through the wire harness 40 if the integrated signal is greater than the integration threshold.

In this case, even in the electronic control unit 10 of this embodiment, there is a possibility that the quality of the charge/discharge capacitor 261 may vary. However, the integration signal is generated according to the voltage at the time of discharge in the charge/discharge capacitor 261. Furthermore, the voltage at the time of discharge in the charge/discharge capacitor 261 depends on the voltage at the time of charge in the charge/discharge capacitor 261. Therefore, charging and discharging tend to cancel out the variation in the quality of the charge/discharge capacitor 261. This makes it possible to suppress variation in the protection accuracy of the wire harness 40.

(1) In this embodiment, a comparison voltage generation circuit 220 is provided, and the charging and discharging of the charge-discharge capacitor 261 is controlled according to the magnitude relationship between the comparison voltage Vsaw and the sense voltage Vs, and the state of the comparison voltage Vsaw. This makes it easy to implement a configuration that charges and discharges the charge-discharge capacitor 261.

(2) In this embodiment, a corrected integrated signal is generated that takes into account a subtraction rate based on the heat dissipation characteristics of the wire harness 40, and the corrected integrated signal is compared with an integrated threshold value. This improves the accuracy of the determination.

(3) In this embodiment, the detection resistor 130 is switchable between multiple resistance values and is set to a predetermined resistance value depending on the type of wire harness 40. This makes it possible to achieve the standardized smoke-emission characteristics shown in FIG. 3, and the wire harness 40 can be protected by similar processing even when it is replaced. In addition, the resistance value of the detection resistor 130 is output to the external control unit 50 via the diagnostic circuit 420. This allows the external control unit 50 to easily determine whether the resistance value of the detection resistor 130 has been adjusted to match the smoke-emission characteristics of the wire harness 40.

(4) In this embodiment, the electronic control unit 10 integrates the main element 110, sense element 111, detection resistor 130, charge/discharge capacitor 261, control circuit 350, etc. into a package. This improves mountability on a vehicle or other mounting member. Furthermore, when adjusting the resistance value of the detection resistor 130, this can be done using the internal circuitry, making the adjustment process easier than when replacing a new part, etc.

(5) As described above, an electronic control device that protects the wire harness 40 has been proposed that uses a thermal equivalent circuit including a CR circuit that is tailored to the smoke-emission characteristics of the wire harness. However, in practice, the thermal equivalent circuit of this electronic control device tends to become very large. Therefore, if an attempt is made to incorporate the thermal equivalent circuit into a single package, the physical size tends to increase. In contrast, the electronic control device 10 of this embodiment protects the wire harness 40 by comparing an integrated signal obtained by integrating a multiplication signal based on the voltage of the charge/discharge capacitor 261 with an integrated threshold value. Therefore, compared to configuring a thermal equivalent circuit that includes a CR circuit, the size can be reduced.

Furthermore, when configuring an electronic control unit using a thermal equivalent circuit that matches the heat generation characteristics of the wire harness 40, it is also possible to configure the thermal equivalent circuit as a separate external component. However, this configuration increases the number of components, which places greater constraints on the mounted component, such as a vehicle, and increases the likelihood of malfunctions such as component detachment. In contrast, the electronic control unit 10 of this embodiment integrates the main element 110, sense element 111, detection resistor 130, charge/discharge capacitor 261, control circuit 350, etc. This prevents an increase in the number of components compared to when the thermal equivalent circuit is arranged as a separate component. Therefore, the electronic control unit of this embodiment prevents greater constraints on the mounted component and reduces the likelihood of component detachment.

(6) As an electronic control device that protects the wire harness 40, it is also possible to protect the wire harness 40 by storing the smoke-emission characteristics of the wire harness 40 in a ROM or the like. However, this configuration places greater constraints on the installation of the ROM than when a detection resistor 130 or the like is provided, thereby increasing costs. Furthermore, with such an electronic control device, if the connected wire harness 40 is changed, the ROM must be rewritten, etc., which complicates adjustment and is likely to further increase costs. In contrast, in this embodiment, the resistance value of the detection resistor 130 is set according to the characteristics of the wire harness 40. As a result, this embodiment can reduce installation constraints and prevent costs from increasing.

Second Embodiment
A second embodiment will be described. This embodiment is different from the first embodiment in that a sense element 111 is added. As the rest of the configuration is the same as the first embodiment, a description thereof will be omitted here.

In the electronic control device 10 of this embodiment, as shown in FIG. 7, the sense element 111 is configured as a first sense element 111a and a second sense element 111b arranged in parallel. Similar to the first embodiment, the first sense element 111a is connected to the current detection amplifier 140, etc. The second sense element 111b is connected to the control circuit 350 via the current detection circuit 430. The first sense element 111a and the second sense element 111b have the same configuration.

The control circuit 350 compares the current IS flowing through the second sense element 111b with a current threshold, and if the current IS is equal to or greater than the current threshold, it cuts off the current IM and current IS. The current threshold is set according to the value at which the current IS becomes an overcurrent. In other words, in this embodiment, the current IM and current IS are cut off even if the current flowing through the load 30 is an overcurrent.

According to the present embodiment described above, the wire harness 40 is protected by comparing an integrated signal obtained by integrating a multiplication signal obtained in response to the voltage at the time of discharge in the charge/discharge capacitor 261 with an integrated threshold value. Therefore, the same effects as those of the first embodiment can be obtained.

(1) In this embodiment, the sense element 111 includes a first sense element 111a and a second sense element 111b. The control circuit 350 compares the current IS flowing through the second sense element 111b with a current threshold, and cuts off the current IM and current IS if the current is greater than the current threshold. This prevents the electronic control device 10 and the load 30 from being damaged by an overcurrent.

(Other embodiments)
Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

For example, in each of the above embodiments, the control circuit 350 may compare the integration signal with an integration threshold. In other words, the electronic control unit 10 may be configured without the subtraction circuit 340. Even with this configuration, the wire harness 40 is protected by comparing the integration signal, which is obtained by integrating the multiplication signal based on the voltage Vcx of the charge/discharge capacitor 261, with the integration threshold, thereby achieving the same effects as in each of the above embodiments.

Furthermore, in each of the above embodiments, the main element 110, sense element 111, detection resistor 130, multiplication circuit 200, arithmetic circuit 300, communication circuit 410, diagnostic circuit 420, etc. do not have to be integrated. In this case, for example, the detection resistor 130 may be an external component.

In each of the above embodiments, the resistance value of the detection resistor 130 may be adjusted taking into account variations in the resistance value of the sense element 111. In other words, the detection resistor 130 may be adjusted to meet the smoke generation characteristics shown in Figure 3 taking into account the type of wire harness 40 and variations in the resistance value of the sense element 111. This can further improve the accuracy of the determination.

Furthermore, in each of the above embodiments, as long as the charging and discharging capacitor 261 is charged and discharged at the timing described above and the integrated signal is appropriately acquired, the relationship between the H and L signals of each signal and voltage, the configuration of each part, etc. can be changed as appropriate.

In addition, in each of the above embodiments, the comparison voltage Vsaw may be a continuous sawtooth wave without a sustain period. Furthermore, instead of a sawtooth wave, the comparison voltage Vsaw may be a triangular wave in which the period during which it rises from an L signal to an H signal is equal to the period during which it falls from an H signal to an L signal. This allows the period during which it falls from an H signal to an L signal to be compared with the sense voltage Vs. Note that when the comparison voltage Vsaw is a triangular wave, it may be an intermittent signal with a sustain period maintained by an L signal, similar to the sawtooth wave described above, or it may be a continuous signal without a sustain period.

In the second embodiment, the current detection circuit 430 may be connected to the external control unit 50 via the diagnostic circuit 420. The external control unit 50 may then compare the current Is with an electrode threshold value and cut off the currents IM and IS if the current IS is an overcurrent.

The control circuitry and methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control circuitry and methods described herein may be implemented by a special-purpose computer configured with a processor comprising one or more dedicated hardware logic circuits. Alternatively, the control circuitry and methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to perform one or more functions in combination with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

30 Load 40 Wire harness 110 Main element 111 Sense element 130 Detection resistor 261 Charging/discharging capacitor 350 Control circuit

Claims (5)

An electronic control device that controls a current flowing through a wire harness (40),
a main element (110) for controlling the current flowing through the wire harness;
a sense element (111) through which a current corresponding to the current flowing through the main element flows;
a detection resistor (130) connected to the sense element and generating a sense voltage according to a current flowing through the sense element;
a comparison voltage generating circuit (220) for generating a comparison voltage whose voltage changes at a predetermined cycle;
a first comparator (210) that outputs a first output signal (Vout1) based on a sense voltage corresponding to the resistance value of the detection resistor and the current flowing through the sense element and the comparison voltage;
a charge/discharge capacitor (261) that is charged and discharged based on the sense voltage;
a second comparator (250) for outputting a second output signal (Vout2) according to the voltage of the charging/discharging capacitor and a reference voltage (Vref);
a decision circuit (310) that generates a decision signal (Vj) as a multiplication signal based on the first output signal and the second output signal ;
an integrating circuit (330) that counts and integrates the determination signals to generate an integrated signal;
a control circuit (350) that compares the integration signal with an integration threshold that can be set according to the heat generation characteristics of the wire harness, and cuts off the current flowing through the wire harness when the integration signal is greater than the integration threshold;
a subtraction circuit (340) that subtracts the integrated signal based on a subtraction rate that can be set according to the heat dissipation characteristics of the wire harness to generate a corrected integrated signal;
The control circuit is an electronic control device that compares the corrected integration signal generated by the subtraction circuit with the integration threshold value . 2. The electronic control device according to claim 1, wherein the charge/discharge capacitor is charged or discharged according to the relationship between the magnitudes of the sense voltage and the comparison voltage and the state of the comparison voltage. 3. The electronic control device according to claim 1, wherein the main element, the sense element, the detection resistor, the charge/discharge capacitor, and the control circuit are packaged and integrated. The detection resistor is switchable between a plurality of resistance values and is set to a predetermined resistance value according to the type of the wire harness,
4. The electronic control device according to claim 1, further comprising a diagnostic circuit (420) for outputting the set resistance value to an external control unit (50). The sense element includes a first sense element (111a) and a second sense element (111b),
the detection resistor is connected to the first sense element;
The second sense element is connected to a current detection circuit (430);
5. The electronic control device according to claim 1, wherein the current flowing through the wire harness is interrupted when the current flowing through the current detection circuit is greater than a current threshold value.