Switch control device and switch system

Abstract

The wiring carrying the output current is properly protected from excessive temperatures. [Solution] The control circuit (11) controls the output transistor (M1) connected in series to the target wiring in response to an output command signal from an external device (20). The current detection circuit (14) detects the output current (I) flowing through the output transistor. OUT It generates a current detection signal corresponding to the current detection signal, and the output current is set to one of several current ranges (I RNG [1]~I RNG The control circuit detects which of [n+1] it belongs to. After switching the output transistor from off to on, the control circuit can perform a protection operation that switches the output transistor from on to off according to the protection characteristics based on the detection result of the current detection circuit, and sets the protection characteristics variably based on the protection characteristic command signal output from an external device to the switch control device in response to the current detection signal.

Description

Technical Field

[0001] The present disclosure relates to a switch control device and a switch system.

Background Art

[0002] There is a device that controls the presence or absence of current flowing through a target wiring by turning on and off an output transistor connected to the target wiring.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] [Summary] In order to ensure the safety of the target wiring, appropriate measures against overcurrent are required.

[0005] A switch control device according to an aspect of the present disclosure includes a control circuit configured to control on or off of an output transistor connected in series to a target wiring in response to an output command signal supplied from an external device to the switch control device, and a current detection circuit configured to generate a current detection signal corresponding to an output current flowing through the output transistor and detect to which of a plurality of current ranges the output current belongs based on the current detection signal. The control circuit is configured to be able to execute a protection operation of switching the output transistor from on to off according to a protection characteristic based on a detection result of the current detection circuit after switching the output transistor from off to on, and the control circuit variably sets the protection characteristic based on a protection characteristic command signal output from the external device to the switch control device in response to the current detection signal output from the switch control device to the external device.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is an overall configuration diagram of a switch system according to an embodiment of the present disclosure. [Figure 2] Figure 2 is an external perspective view of a switch device according to an embodiment of this disclosure. [Figure 3] Figure 3 is a schematic diagram of a vehicle according to the embodiment of this disclosure. [Figure 4] Figure 4 is an internal configuration diagram of the current range determination circuit according to the present disclosure. [Figure 5] Figure 5 is an explanatory diagram of multiple voltage ranges and multiple current ranges. [Figure 6] Figure 6 is an explanatory diagram of three areas related to wiring safety in an embodiment of the present disclosure. [Figure 7] Figure 7 is a diagram illustrating the relationship between three areas related to wiring safety and protective characteristics according to an embodiment of the present disclosure. [Figure 8] Figure 8 shows a list of candidate protection characteristics used in a switch control device according to an embodiment of the present disclosure. [Figure 9] Figure 9 is a flowchart relating to the setting of protection characteristics in an embodiment of the present disclosure. [Figure 10] Figure 10 is a timing chart of a switch system relating to a first embodiment belonging to the embodiments of this disclosure. [Figure 11] Figure 11 relates to a second embodiment belonging to the embodiments of this disclosure and is a diagram illustrating the dependence of the rate of increase of the count value in the count-up operation on the protection characteristics. [Figure 12] Figure 12 is a timing chart of a switch system relating to a third embodiment belonging to the embodiments of this disclosure. [Figure 13] Figure 13 is a timing chart of a switch system relating to a third embodiment belonging to the embodiments of this disclosure. [Figure 14] Figure 14 is a timing chart of a switch system relating to a fourth embodiment belonging to the embodiments of this disclosure. [Figure 15] Figure 15 is a modified overall configuration diagram of a switch system relating to a seventh embodiment belonging to the embodiments of this disclosure. [Figure 16]Figure 16 is a modified overall configuration diagram of a switch system relating to a seventh embodiment belonging to the embodiments of this disclosure.

[0007] [Detailed explanation] Hereinafter, examples of embodiments of the present disclosure will be specifically described with reference to the drawings. In each of the referenced drawings, the same parts are denoted by the same reference numerals, and redundant descriptions relating to the same parts are omitted as a general rule. In addition, for the sake of simplification of the description, in this specification, symbols or reference numerals that refer to information, signals, physical quantities, functional parts, circuits, elements, or components may be indicated, and the names of the information, signals, physical quantities, functional parts, circuits, elements, or components corresponding to such symbols or reference numerals may be omitted or abbreviated.

[0008] First, some terms used in the description of embodiments of this disclosure will be explained. Ground refers to a reference conductor having a reference potential of 0V (zero volts), or the potential of 0V itself. The reference conductor may be formed using a conductor such as metal. The potential of 0V is sometimes referred to as the ground potential. In embodiments of this disclosure, voltages shown without specifying a reference represent the potential as seen from ground. Level refers to the level (height) of the potential, and for any signal or voltage of interest, a high level has a higher potential than a low level.

[0009] For any transistor configured as a FET (field-effect transistor), as exemplified by a MOSFET, the "on" state refers to the state where the drain and source of the transistor are conducting, and the "off" state refers to the state where the drain and source of the transistor are not conducting (blocked state). The same applies to transistors not classified as FETs. Unless otherwise specified, a MOSFET is understood to be an enhancement-type MOSFET. MOSFET is an abbreviation for "metal-oxide-semiconductor field-effect transistor". Also, unless otherwise specified, it can be assumed that the back gate is short-circuited to the source in any MOSFET.

[0010] Hereinafter, for any transistor, the on state and off state may also be simply expressed as on and off. For any transistor, the period during which the transistor is in the on state is referred to as the on period, and the period during which the transistor is in the off state is referred to as the off period.

[0011] For any signal having a high-level or low-level signal level, the period during which the level of the signal is high is referred to as the high-level period, and the period during which the level of the signal is low is referred to as the low-level period. The same applies to any voltage having a high-level or low-level voltage level.

[0012] The connection between a plurality of parts forming a circuit, such as any circuit element, wiring, node, etc., may be understood to refer to an electrical connection unless otherwise specified.

[0013] When any two voltages to be compared are voltage v1 and v2, "v1>v2" represents that voltage v1 is higher than voltage v2, "v1<v2" represents that voltage v1 is lower than voltage v2, and "v1=v2" represents that the value of voltage v1 is the same as the value of voltage v2. The same applies to other expressions including physical quantities other than voltage.

[0014] FIG. 1 shows an overall configuration diagram of a switch system SYS according to an embodiment of the present disclosure. The switch system SYS includes, as main components, a switch control device 10, a MCU (Micro Controller Unit) 20, and a temperature detection circuit 30, and also includes an output transistor M1, a sense resistor R SNS , a gain resistor R GAIN and a voltage conversion resistor R CSOIt includes. The MCU 20 is an example of an external device (external control device) that controls the operation of the switch control device 10. Note that the installation of the temperature detection circuit 30 in the switch system SYS is not essential. A voltage source VS and a load LD are connected to the switch system SYS. Although not particularly shown, an output capacitor may be connected in parallel to the load LD. Since the load LD is driven by the switch system SYS, the switch system SYS can also be referred to as a load driving system. The output transistor M1 is an N-channel MOSFET.

[0015] The switch control device 10 includes a power supply terminal IN, a ground terminal GND, a gate connection terminal NG, a source connection terminal NS, current detection terminals CSIP and CSIN, and a signal output terminal CSO, and also includes a communication terminal group CTG. The wirings WR1 to WR3 are wirings provided outside the switch terminal 10. The communication wiring group CWG consists of two or more other wirings provided outside the switch terminal 10.

[0016] FIG. 2 is an external perspective view of the switch control device 10. The switch control device 10 is an electronic component including a semiconductor chip having a semiconductor integrated circuit formed on a semiconductor substrate, a housing CS (package) that houses the semiconductor chip, and a plurality of external terminals that are exposed from the housing CS to the outside of the switch control device 10. The switch control device 10 is formed by encapsulating the semiconductor chip in a housing CS made of resin. Note that the number of external terminals of the switch control device 10 shown in FIG. 2 and the type of the housing CS of the switch control device 10 are merely examples, and they can be designed arbitrarily. The power supply terminal IN, the ground terminal GND, the gate connection terminal NG, the source connection terminal NS, the current detection terminals CSIP and CSIN, and the signal output terminal CSO are part of the plurality of external terminals provided on the switch control device 10. The communication terminal group CTG is composed of two or more of the plurality of external terminals. Other external terminals can also be provided on the switch control device 10.

[0017] The voltage source VS is connected to the ground and the wiring WR1, and outputs a power supply voltage VB which is a positive DC voltage with respect to the ground. The power supply voltage VB is applied to the wiring WR1. The wiring WR1 is provided between the voltage source VS and the output transistor M1, and the wiring WR2 is provided between the output transistor M1 and the ground.

[0018] Specifically, the voltage source VS includes a negative output terminal connected to the ground and a positive output terminal connected to the wiring WR1, and outputs the power supply voltage VB with respect to the positive output terminal. The positive output terminal of the voltage source VS is connected to the drain of the output transistor M1 via the wiring WR1. Incidentally, an active clamp (not shown) for protecting the output transistor M1 from the back electromotive force generated by the inductive load may be provided between the drain and the gate of the output transistor M1, or between the ground and the gate of the output transistor M1. The source of the output transistor M1 is connected to the wiring WR2. Specifically, the source of the output transistor M1 is connected to the first end of the sense resistor R SNS at the node ND1 through a part of the wiring WR2, and the second end of the sense resistor R SNS is connected to the node ND2. The node ND2 is connected to the first end of the load LD through another part of the wiring WR2. The second end of the load LD is connected to the ground. Thus, the sense resistor R SNS and the load LD are inserted in series on the wiring WR2. Incidentally, the sense resistor R SNS may be inserted in series on the wiring WR1 (that is, the sense resistor R SNS )]]may be provided between the positive output terminal of the voltage source VS and the drain of the output transistor M1).

[0019] The drain current of the output transistor M1 is referred to as the output current I OUT In the on period of the output transistor M1, the output current I OUT flows from the voltage source VS through the wiring WR1, the output transistor M1 and the wiring WR2 towards the ground. At this time, it passes through the sense resistor R SNS and the load LD. The load LD is any load that is driven using the voltage at the node ND2 as its own power supply voltage. The output current IOUT This corresponds to the current consumption of the load LD. During the ON period of the output transistor M1, the drain-source voltage of the output transistor M1 and the sense resistor R are compared to the magnitude of the power supply voltage VB. SNS The voltage drop is minimal, and a voltage similar to the power supply voltage VB is applied to node ND2.

[0020] The power terminal IN is connected to wiring WR1, and the switch terminal 10 receives the power supply voltage VB at the power terminal IN. The gate connection terminal NG is connected to the gate of output transistor M1, and the source connection terminal NS is connected to the source of output transistor M1. The current sensing terminal CSIP is connected to the gain resistor R GAIN Connected to the first end, gain resistor R GAIN The second terminal is connected to node ND1. The current sensing terminal CSIN is connected to node ND2. The ground terminal GND is connected to ground. The signal output terminal CSO is connected to MCU20 via wiring WR3. Voltage conversion resistor R CSO The first end is connected to wiring WR3, and the voltage conversion resistor R CSO The second end is connected to ground.

[0021] The MCU20 is supplied with a power supply voltage VCC having a predetermined positive DC voltage value and is connected to ground, and is driven based on the power supply voltage VCC. As described above, the communication wiring group CWG consists of two or more wires, and the communication terminal group CTG is connected to the MCU20 through the communication wiring group CWG. The switch control device 10 and the MCU20 communicate bidirectionally with each other through the communication wiring group CWG. The MCU20 can send various command signals to the switch control device 10 through the communication wiring group CWG. Note that sending a command signal and outputting a command signal are synonymous. Communication between the switch control device 10 and the MCU20 is serial communication, and SPI (Serial Peripheral Interface) can be used as the serial communication interface. Note that the serial communication interface between the switch control device 10 and the MCU20 is not limited to SPI, for example I 2The interface may be via C (Inter-Integrated Circuit) or Microwire.

[0022] The MCU20 is also provided with an AD conversion circuit 21. The AD conversion circuit 21 is connected to wiring WR3 and the detection voltage V described later is CSO The AD conversion circuit 21 receives the signal. The detection voltage V is an analog signal. CSO to digital signal D CSO The system performs an A / D conversion process to convert the digital signal to D. CSO The detected voltage is V CSO It has a value proportional to [the given value].

[0023] The temperature detection circuit 30 detects the ambient temperature Tmp of the switch system SYS and generates a temperature detection signal Tsns indicating the detection result of the ambient temperature Tmp. The temperature detection signal Tsns is output from the temperature detection circuit 30 to the MCU 20. The ambient temperature Tmp is the temperature in the target space outside the switch control device 10 and around the switch control device 10. The target space is the space where wiring WR1 and wiring WR2 are located. The target space may also be the space where either wiring WR1 or wiring WR2 is located. The temperature detection circuit 30 has a temperature measuring element (such as a resistance thermometer, linear resistor, or thermistor) placed in the target space and can detect the ambient temperature Tmp using this temperature measuring element. Alternatively, the temperature detection circuit 30 may be a semiconductor temperature sensor. The semiconductor temperature sensor has a silicon diode placed in the target space and detects the ambient temperature Tmp using the temperature characteristics of the forward voltage of the diode. Instead of the forward voltage of the diode, the base-emitter voltage of a bipolar transistor may be used to detect the ambient temperature Tmp.

[0024] The temperature detection signal Tsns is a voltage signal representing the ambient temperature Tmp (a voltage signal indicating the detected value of the ambient temperature Tmp). The temperature detection signal Tsns may be an analog voltage signal or a digital voltage signal. In either case, the value of the ambient temperature Tmp can be determined from the signal value of the temperature detection signal Tsns.

[0025] Referring to Figure 3, in this embodiment, it is assumed that the switch system SYS is mounted on a vehicle VHCL such as an automobile. In this case, the voltage source VS may be a battery installed in the vehicle VHCL. The vehicle VHCL is equipped with an electrical block BLK consisting of various electrical components, and the components of the electrical block BLK include the switch system SYS and the load LD, as well as various wiring including wiring WR1 to WR3. Therefore, the target space described above is the space inside the vehicle VHCL. The load LD includes an ECU (Electronic Control Unit), as well as actuators such as motors driven and controlled by the ECU, lighting devices, and air conditioners.

[0026] The switch control device 10 comprises a group of circuits made of semiconductors, which are housed within the enclosure CS. The group of circuits made of semiconductors in the switch control device 10 includes a control circuit 11, a driver 12, a charge pump circuit 13, a current detection circuit 14, an error output circuit 15, and an internal power supply circuit 16.

[0027] Command signals transmitted from the MCU 20 are received by the switch control device 10, and more specifically, by the control circuit 11. The command signal is a signal that gives some kind of instruction to the control circuit 11, and the control circuit 11 performs an action according to the content of the command signal. The control circuit 11 may also send a response signal to the MCU 20 in response to the command signal.

[0028] The MCU20 can send output command signals to the switch control device 10 as a type of command signal. The output command signals include an output ON command signal that commands the output transistor M1 to be turned ON, and an output OFF command signal that commands the output transistor M1 to be turned OFF.

[0029] When the control circuit 11 receives an output command signal, it generates a drive control signal Sdrv corresponding to the output command signal and outputs it to the driver 12. The drive control signal Sdrv is a binary signal with a value of "1" or "0". A drive control signal Sdrv of "1" is a signal to turn on the output transistor M1, and a drive control signal Sdrv of "0" is a signal to turn off the output transistor M1. Therefore, when the control circuit 11 receives an output ON command signal, it outputs a drive control signal Sdrv with a value of "1" to the driver 12, and thereafter maintains the value of the drive control signal Sdrv at "1" until it receives an output OFF command signal or until the overcurrent protection operation described later is performed. When the control circuit 11 receives an output OFF command signal, it outputs a drive control signal Sdrv with a value of "0" to the driver 12, and thereafter maintains the value of the drive control signal Sdrv at "0" until it receives an output ON command signal. The counter 111 and setting information storage unit 112 provided in the control circuit 11 will be described later.

[0030] The driver 12 is connected to the gate connection terminal NG and the source connection terminal NS. Therefore, the driver 12 is connected to the gate and source of the output transistor M1 through the gate connection terminal NG and the source connection terminal NS. When the drive control signal Sdrv is set to "1", the driver 12 sets the output transistor M1 to the ON state by supplying the drive voltage Vcp supplied from the charge pump circuit 13 to the gate of the output transistor M1. When the drive control signal Sdrv is set to "0", the driver 12 sets the output transistor M1 to the OFF state by supplying the voltage at the source of the output transistor M1 to the gate of the output transistor M1.

[0031] The charge pump circuit 13 is connected to the power supply terminal IN and, under the control of the control circuit 11, generates a drive voltage Vcp that is higher than the power supply voltage VB by boosting the power supply voltage VB. The drive voltage Vcp is supplied to the driver 12. The difference between the drive voltage Vcp and the power supply voltage VB is greater than the gate threshold voltage of the output transistor M1.

[0032] The current detection circuit 14 detects the drain current of the output transistor M1 during the ON period of the output transistor M1, that is, the output current I flowing through the output transistor M1. OUT The current detection circuit 14 detects the output current I OUT The detection voltage V is used as the current detection signal indicating the detection result. CSO It generates and outputs the following. During the ON period of the output transistor M1, the detected voltage V CSO Output current I OUT The value (detected value) is shown. In addition, the current detection circuit 14 detects the voltage V during the ON period of the output transistor M1. CSO Based on the output current I OUT It can also detect which of the multiple current ranges it belongs to.

[0033] Specifically, the current detection circuit 14 comprises an operational amplifier 141, a transistor 142, and a current range determination circuit 143. Transistor 142 is a P-channel type MOSFET. The inverting input terminal of operational amplifier 141 is commonly connected to the current detection terminal CSIP and the source of transistor 142. The non-inverting input terminal of operational amplifier 141 is connected to the current detection terminal CSIN. The output terminal of operational amplifier 141 is connected to the gate of transistor 142. The drain of transistor 142 is connected to the signal output terminal CSO. The voltage at the drain of transistor 142 is the detected voltage V. SCO The current range determination circuit 143 is connected to the drain of transistor 142. The current range determination circuit 143 detects voltage V SCO Based on the (current detection signal), output current I OUT The system detects which of the multiple current ranges the output current I belongs to, and then determines the output current I OUT A determination signal Sdet, indicating which of the multiple current ranges the current belongs to, is output to the control circuit 11.

[0034] Figure 4 shows the internal configuration of the current range determination circuit 143. Figure 5 shows the detected voltage V CSO Voltage range V to which it may belong RNG [1]~V RNG [n+1] and voltage range V RNG [1]~V RNG Current range I corresponding to [n]RNG [1]~I RNG [n+1] is shown. The above multiple current ranges are current range I RNG [1]~I RNG It is [n+1], where n is any integer greater than or equal to 2.

[0035] The current range determination circuit 143 has n comparators 143[1] to 143[n]. A detection voltage V is applied to each non-inverting input terminal of comparators 143[1] to 143[n]. CSO A reference voltage V is supplied. The inverting input terminals of comparators 143[1] to 143[n] are each supplied with a reference voltage V. REF [1]~V REF [n] is input. That is, the reference voltage V is input to the inverting input terminal of comparator 143[i]. REF [i] is input. i represents any integer between 1 and n (inclusive). For any integer i satisfying "1≦i≦(n-1)", the reference voltage V REF [i] Reference voltage V REF [i+1] is higher. The current range determination circuit 143 uses comparators 143[1]~143[n] to detect the voltage V CSO The reference voltage V REF [1]~V REF Each of [n] is compared with the result, and a decision signal Sdet is generated and output as a signal indicating the comparison result.

[0036] Comparator 143[i] is “V CSO >V REF When [i]” is met, a high-level signal is output, and “V CSO <V REF [i] When this condition is met, a low-level signal is output. CSO =V REF When [i]” is true, the output signal of comparator 143[i] will be either high or low, but here we assume it will be high. The decision signal Sdet is a bundle of the output signals of comparators 143[1] to 143[n]. Based on the decision signal Sdet, the detected voltage V CSO and reference voltage V REF [1]~V REFThe relative heights of each of [n] are shown. In practice, hysteresis characteristics may be applied to comparators 143[1] to 143[n].

[0037] Voltage range V RNG [1] is the reference voltage V REF [1] is a voltage range less than the reference voltage V. REF [1] Voltages less than the voltage range V RNG It belongs to [1]. For any integer i satisfying "2≦i≦n", the voltage range V RNG [i] is the reference voltage V REF [i-1] or higher and reference voltage V REF The voltage range is less than [i]. Therefore, for any integer i that satisfies "2≦i≦n", the reference voltage V REF [i-1] or higher and reference voltage V REF [i] Voltages less than the voltage range V RNG Belongs to [i]. Voltage range V RNG [n+1] is the reference voltage V REF The voltage range is greater than or equal to [n]. Therefore, the reference voltage V REF [n] or higher voltages are within the voltage range V RNG It belongs to [n+1]. The detection voltage V is determined by the decision signal Sdet. SCO Voltage range V RNG [1]~V RNG It will be shown which of [n+1] it belongs to.

[0038] The operational amplifier 141 controls the gate potential of transistor 142 so that the potential difference between its inverting input terminal and non-inverting input terminal is substantially zero. Therefore, during the ON period of output transistor M1, the output current I OUT A current proportional to R is generated as the drain current of transistor 142, and the drain current of transistor 142 is connected to the voltage conversion resistor R CSO The detected voltage V CSO It is converted to the following. Furthermore, the input impedance of MCU20 as seen from wiring WR3 is assumed to be sufficiently high, and unless otherwise specified, transistor 151 described later is kept off, and therefore the drain current of transistor 142 is all converted to the voltage conversion resistor R CSOshall flow to the ground through. Then, the detection voltage V CSO is expressed by the formula "V CSO =R CSO ×I OUT ×R SNS / R GAIN ". Here, R CSO , R SNS , R GAIN represent the resistance values of the voltage conversion resistor R CSO , the sense resistor R SNS , and the gain resistor R GAIN respectively.

[0039] The current range I RNG [1] is a current range less than the threshold I TH [1]. Therefore, the output current I TH [1] with a current value less than the threshold I OUT belongs to the current range I RNG [1]. For any integer i satisfying "2≦i≦n", the current range I RNG [i] is a current range greater than or equal to the threshold I TH [i - 1] and less than the threshold I TH [i]. Therefore, for any integer i satisfying "2≦i≦n", the output current I TH [i - 1] with a current value greater than or equal to the threshold I TH [i] and less than the threshold I OUT belongs to the current range I RNG [i]. The current range I RNG [n + 1] is a current range greater than or equal to the threshold I TH [n]. Therefore, the output current I TH [n] with a current value greater than or equal to the threshold I OUT belongs to the current range I RNG [n + 1]. For any integer i satisfying "1≦i≦(n - 1)", the threshold I TH [i] is smaller than the threshold I TH [i + 1].

[0040] For any integer i satisfying "1≦i≦n", during the on - period of the output transistor M1, when "V CSO =V REF [i]" holds, the output current I OUTThe value of threshold I TH This matches [i]. Therefore, during the ON period of the output transistor M1, the output current I is determined by the decision signal Sdet. OUT Current range I RNG [1]~I RNG It will be indicated which of [n] it belongs to. Detected voltage V SCO Voltage range V RNG The determination signal Sdet, which indicates that it belongs to [i], is the output current I OUT Current range I RNG This indicates that it belongs to [i]. During the ON period of output transistor M1, “V CSO <V REF [1]” is a state that satisfies “I OUT TH [1]” is equivalent to the state that satisfies V REF [i]≦V CSO <V REF The state that satisfies [i+1] is "I TH [i]≦I OUT TH This is equivalent to the state that satisfies [i+1] (where i is an integer between 1 and (n-1) inclusive), and "V REF [n]≦V CSO The state that satisfies "I TH [n]≦I OUT This is equivalent to the state that satisfies ". Threshold I TH [1] The current range above is the overcurrent detection range, and within the overcurrent detection range, threshold I TH [1] acts as the minimum overcurrent threshold, threshold I TH [n] functions as an immediate cutoff threshold.

[0041] For example, if "n=4", then "V REF [1] <V REF [2] <V REF [3] <V REF [4]" and "I TH [1] TH [2] TH [3] TH [4]” The reference voltage V REF [1]~V REF [n] may be n types of DC voltages that are set in advance and fixed. However, the reference voltage V REF ​​​​​[1]~V REF Each value of [n] may be specified and controlled by the control circuit 11. Reference voltage V REF [i] and threshold I TH The relationship with [i] is the resistance R CSO , R SNS and R GAIN It depends on the resistance values ​​of each element.

[0042] An abnormality detection circuit (not shown) that detects multiple types of abnormalities that may occur in the switch control device 10 is built into the control circuit 11, or is built into the switch control device 10 separately from the control circuit 11. The multiple types of abnormalities include an overcurrent abnormality in which the current flowing through the output transistor M1 is excessive, a temperature abnormality in which the temperature of a specific part in the switch control device 10 exceeds a predetermined protection temperature, and an undervoltage abnormality in which the voltage supplied to the power supply terminal IN falls below an undervoltage threshold. An overcurrent abnormality is detected by the control circuit 11 based on the determination signal Sdet.

[0043] The error output circuit 15 is a circuit that transmits a signal to the MCU 20 indicating that an abnormality has been detected when the switch control device 10 detects any abnormality. Specifically, the error output circuit 15 has a transistor 151. Transistor 151 is a P-channel type MOSFET. A DC voltage that matches or is approximately the same as the power supply voltage VCC is applied to the source of transistor 151. Although not specifically shown in the diagram, the power supply voltage VCC may be supplied to the switch terminal 10. Here, we assume that the power supply voltage VCC is supplied to the source of transistor 151. The drain of transistor 151 is connected to the signal output terminal CSO. The gate of transistor 151 is connected to the control circuit 11. In principle, the control circuit 11 turns off transistor 151 by supplying a voltage to the gate of transistor 151 that makes the potential difference between the gate and source of transistor 151 zero. When the switch control device 10 detects any abnormality, the control circuit 11 turns on transistor 151 by supplying a sufficiently low voltage to the gate of transistor 151. During the ON period of transistor 151, the voltage at the signal output terminal CSO is equal to the above-mentioned reference voltage VREF [n] is sufficiently higher, and the MCU20 can recognize that some abnormality has been detected in the switch control device 10 based on the voltage of wiring WR3.

[0044] During the ON period of transistor 151, the output current I OUT Regardless of the reference voltage, the voltage at the signal output terminal CSO is the reference voltage V REF It is fixed at a voltage sufficiently higher than [n], and therefore the voltage of the signal output terminal CSO (detection voltage V) CSO ) is the output current I OUT It does not represent the detected value. The determination signal Sdet is only when transistor 151 is off and output transistor M1 is on, output current I OUT Current range I RNG [1]~I RNG This indicates which of [n+1] it belongs to. In the following, unless otherwise specified, it is assumed that transistor 151 remains in the OFF state.

[0045] The internal power supply circuit 16 is connected to the power supply terminal IN and generates an internal power supply voltage of 1 or more by stepping down the power supply voltage VB with respect to the ground voltage. Each internal power supply voltage has a predetermined positive DC voltage value. Each circuit in the switch control device 10 can be driven based on any of the internal power supply voltages with respect to the ground potential.

[0046] It is connected in series with the output transistor M1, and the output current I OUT The wiring through which the current flows is called the target wiring. The target wiring forms a current loop that runs from the negative output terminal of the voltage source VS, through wiring WR1, output transistor M1, and wiring WR2 to the load LD, and returns to the negative output terminal of the voltage source VS through a metal body with ground potential. Wires WR1 and WR2 are part of the target wiring. The target wiring consists of electrical wiring components made of copper wire with insulating coating and wiring patterns on a printed circuit board. For example, wiring WR1 and WR2 of the target wiring can be made up of wiring patterns on a printed circuit board, and the remaining part can be made up of electrical wiring components. The switch control device 10 has a function to protect the target wiring from excessive heat generation due to excessive current. This function corresponds to the function of a so-called electronic fuse.

[0047] Referring to Figure 6, the characteristics of the target wiring will be explained. The length of time that the output transistor M1 remains in the ON state, i.e., the output current I through the target wiring. OUT The length of time during which it continues to flow is called the continuous on time t ON This is referred to as [the operating region]. The operating region of the target wiring (in other words, the operating region of output transistor M1) is divided into three regions 610, 620, and 630. In Figure 6, regions 610 and 630 are represented as the first and second shaded regions (the same applies to Figure 7 and others described later). In Figure 6, region 620 is represented as the dotted region.

[0048] Area 610 is the normal operating area. Area 620 is the recommended protection area. Area 630 is the prohibited area. The horizontal axis represents the continuous on time t. ON The vertical axis represents the output current I. OUT On the graph, the recommended protection region 620 is located between the normal operating region 610 and the prohibited use region 630. The normal operating region 610 is the region where the target wiring can be used safely. Unless a malfunction occurs, the SYS switch system drives the output transistor M1 within the normal operating region 610. The prohibited use region 630 is the region where the target wiring cannot be used safely, and using the target wiring in the prohibited use region 630 (in other words, using the output transistor M1 in the prohibited use region 630) is prohibited for safety reasons. Therefore, if the output transistor M1 operates within the recommended protection region 620 for any reason, it is necessary to perform overcurrent protection before reaching the prohibited use region 630. In the overcurrent protection operation, the control circuit 11 switches the output transistor M1 from the on state to the off state. After switching the output transistor M1 from the on state to the off state in the overcurrent protection operation, the control circuit 11 maintains the output transistor M1 in the off state until predetermined recovery conditions are met. The information that identifies the prohibited use region 630 is the It characteristic or I of the target wiring. 2 It is expressed using the t-characteristic.

[0049] Here, a reference switch system having a reference switch control device different from the switch control device 10 will be described (the reference switch control device and the reference switch system are not shown). In the reference switch control device, the current flowing through the target wiring is detected using an AD conversion circuit, and based on the digital value detected by the AD conversion circuit, the reference switch control device performs overcurrent protection operation as needed. To give a numerical example to make the explanation more concrete, in the reference switch system, when a current of 1000A flows through the target wiring for only 1 microsecond, it is necessary to turn off the output transistor to protect the target wiring, while when a current of 10A flows through the target wiring for only 1000 seconds, it is also necessary to turn off the output transistor to protect the target wiring. In that case, the reference switch control device requires an AD conversion circuit with a full scale of current range from 10A to 1000A, and a counter (a 9-digit counter in decimal notation) to measure time from 1 microsecond to 1000 seconds. If such an AD conversion circuit and counter are installed in the reference switch control device, the circuit size of the reference switch control device will increase.

[0050] Another approach is to not perform current detection in the reference switch control device, but instead have the MCU connected to the reference switch control device perform current detection and time measurement from 1 microsecond to 1000 seconds. However, MCUs are often designed to execute various processes in parallel, and having the MCU handle overcurrent detection on the order of microseconds would place an excessive processing load on the MCU, or it would simply not be practical to have the MCU handle overcurrent detection on the order of microseconds.

[0051] Therefore, from the perspective of both cost and response speed, the SYS switch system handles short-term overcurrents on the switch control device 10 side and long-term overcurrents on the MCU 20 side. Specifically, for example, the switch control device 10 is equipped with a counter (a 7-digit decimal counter) called counter 111 that measures time from 1 microsecond to 10 seconds, and the current detection circuit 14 outputs current I in the current range from 10A to 100A. OUT Detect (i.e., threshold I TH[1] and I TH Set [n] to 10A and 100A respectively. Then, for example, set the output current I to 100A. OUT When the control circuit 11 detects that the current has flowed continuously for only 1 microsecond, it turns off the output transistor M1 by overcurrent protection operation, regardless of the signal from the MCU 20, in order to protect the target wiring. Also, for example, if the output current I is 10A OUT When the control circuit 11 detects that current has flowed continuously for 10 seconds, it turns off the output transistor M1 by overcurrent protection operation, regardless of the signal from the MCU 20, in order to protect the target wiring. This allows the number of digits for current detection on the switch control device 10 side to be limited to one digit (effectively one digit of current detection from 10A to 100A) and the number of digits for time measurement on the switch control device 10 side to be limited to seven digits (effectively seven digits of time measurement from 1 microsecond to 10 seconds), thereby reducing the circuit size of the switch control device 10 compared to the reference switch control device.

[0052] On the other hand, for example, an output current of 5A I OUT If the output transistor needs to be shut down when the current flows continuously for 500 seconds, the MCU20 is responsible for this control. Specifically, the MCU20 turns on the output transistor M1 by outputting an output ON command signal to the switch control device 10, and then uses the AD conversion circuit 21 to detect the voltage V at wiring WR3. CSO It periodically monitors the output current I of 5A. OUT When it is detected that the current has been flowing continuously for 500 seconds, the MCU 20 outputs an output-off command signal to the switch control device 10 to protect the target wiring, thereby turning off the output transistor M1. Of course, the values ​​given here are just examples and can be changed in various ways.

[0053] The control circuit 11 performs overcurrent protection operation according to the set protection characteristics. The control circuit 11 uses the protection characteristic value P stored in the setting information storage unit 112 (see Figure 1). SET The control circuit 11 protects the target wiring by determining whether or not to perform overcurrent protection operation according to the protection characteristics set in (protection characteristics setting information). SETDepending on the situation, one of the 1st to mth characteristics is set as the protection characteristic. m represents any integer greater than or equal to 2. The 1st to mth characteristics are referred to as characteristics PP[1] to PP[m], respectively. SET When =j'', the control circuit 11 sets the characteristic PP[j] to the protection characteristic. Here, j represents an integer between 1 and m, and therefore the protection characteristic value P SET has an integer between 1 and m. Since each of characteristics PP[1] to PP[m] is a candidate for a protection characteristic, characteristics PP[1] to PP[m] can also be referred to as the 1st to mth candidate characteristics. The setting information storage unit 112 is composed of volatile memory, non-volatile memory, or a combination thereof.

[0054] Figure 7 shows two characteristic PP[1] and PP[m]. In Figure 7, characteristic PP[1] is represented by a solid line within the protection recommendation region 620, and characteristic PP[m] is represented by a dashed line within the protection recommendation region 620. Unlike Figure 6, in Figure 7, the dots for the protection recommendation region 620 are omitted to avoid cluttering the illustration. Characteristic PP[1] is calculated based on the threshold I after switching the output transistor M1 from off to on under certain assumed environmental conditions. TH Output current I with [n-1] OUT But time t A [1] indicates that when only this current flows continuously, overcurrent protection should be performed. Furthermore, characteristic PP[1] indicates that, under certain assumed environmental conditions, after switching the output transistor M1 from off to on, threshold I TH [1] Output current I OUT But time t B [1] indicates that overcurrent protection should be performed when only this much current flows continuously. Therefore, in cases where characteristic PP[1] is set as a protection characteristic (i.e., “P SET In the case where = 1”, after switching the output transistor M1 from off to on, the threshold I TH Output current I with [n-1] OUT But time t A When [1] flows continuously, the control circuit 11 performs overcurrent protection. Also, in the case where characteristic PP[1] is set to protection characteristic, after switching the output transistor M1 from off to on, threshold ITH [1] Output current I OUT But time t B [1] If only this much current flows continuously, the control circuit 11 performs an overcurrent protection operation.

[0055] The characteristic PP[m] is the threshold I after switching the output transistor M1 from off to on under certain assumed environmental conditions. TH Output current I with [n-1] OUT But time t A This indicates that overcurrent protection should be activated when a current of [m] flows continuously. Furthermore, characteristic PP[m] represents the threshold I of the output transistor M1 after switching it from off to on under certain assumed environmental conditions. TH [1] Output current I OUT But time t B This indicates that overcurrent protection should be activated when the current flows continuously for [m]. Therefore, in cases where characteristic PP[m] is set as the protection characteristic (i.e., “P SET In the case where =m'', after switching the output transistor M1 from off to on, the threshold I TH Output current I with [n-1] OUT But time t A When a current of [m] flows continuously, the control circuit 11 performs overcurrent protection. Also, in the case where characteristic PP[m] is set to the protection characteristic, after switching the output transistor M1 from off to on, threshold I TH [1] Output current I OUT But time t B When the current flows continuously for [m], the control circuit 11 performs an overcurrent protection operation.

[0056] Here “t A [1] <t B [1]" and “t A [m] <t B [m]” is true. In addition, “t A [m] <t A [1]" and “t B [m] <t B [1]” holds true. Also, in the example in Figure 7, time t A [1] and t B Regarding [m], “tA [1] <t B [m]" is valid, but “t A [1]≧t B It could be [m]”

[0057] Figure 8 schematically shows the characteristics PP[1] to PP[8] when "m=8" is assumed. After switching the output transistor M1 from off to on, the threshold I TH Output current I with [n-1] OUT Assuming that the current flows continuously, the duration of the on-time t is shorter when the protection characteristic is characteristic PP[j] than when the protection characteristic is characteristic PP[j-1]. ON Overcurrent protection is performed (where j is an integer between 2 and m). Also, after switching the output transistor M1 from off to on, threshold I TH [1] greater than or equal to threshold I TH Output current I with a constant current value less than [n-1] OUT for a certain period of time t CNST The control circuit 11 performs overcurrent protection when the current continues to flow. In this case, the constant current value is smaller when the protection characteristic is characteristic PP[j] than when the protection characteristic is characteristic PP[j-1] (where j is an integer between 2 and m). Note that the symbol “t” shown in Figure 8 J "The above-mentioned certain time t CNST This represents an immediate blockage decision time that is significantly shorter than t. J This will be discussed later.

[0058] Which of the characteristics PP[1] to PP[m] should be set as the protection characteristic depends on the structure of the target wiring (wire diameter, etc.) and the state of the target wiring at any given time. In this embodiment, the state of the target wiring can be considered to refer to the temperature state of the target wiring. The MCU20 responds to the temperature detection signal Tsns and the past output current I OUT Based on the time-series information, the current state of the target wiring can be predicted, and based on the prediction result, the switch control device 10 (control circuit 11) can be instructed via the output of a command signal to decide which of the characteristics PP[1] to PP[m] to set as the protection characteristic.

[0059] The command signal used to instruct the setting of protection characteristics is specifically called the protection characteristic command signal. The protection characteristic command signal specifies which of characteristics PP[1] to PP[m] should be set as the protection characteristic. Specifically, the protection characteristic command signal sets the protection characteristic value P SET The value to be set is specified. Figure 9 shows a flowchart of the switch system SYS involved in the transmission and reception of the protection characteristic command signal. First, in step S11, the MCU 20 outputs (transmits) a protection characteristic command signal to the switch control device 10. In the following step S12, the control circuit 11 receives the protection characteristic command signal, and the control circuit 11 sets the value specified in the protection characteristic command signal to the protection characteristic value P in the information storage unit 112. SET Write to (in other words, the protection characteristic value P is specified by the protection characteristic command signal) SET (Updates the latest protection characteristic value P). Subsequently, in step S13, the control circuit 11 updates the latest protection characteristic value P. SET The protection characteristics are set accordingly. As mentioned above, “P SET When =j'', the control circuit 11 sets the characteristic PP[j] to the protection characteristic. Note that in a situation where no protection characteristic command signal is received, the protection characteristic value P SET It has a predetermined default value that is 1 or greater and less than or equal to m.

[0060] The control circuit 11 can perform overcurrent protection operations α and β. In both overcurrent protection operations α and β, the control circuit 11 switches the output transistor M1 from the ON state to the OFF state, and then maintains the output transistor M1 in the OFF state until a predetermined recovery condition is met. Overcurrent protection operation α is performed during the immediate cutoff determination time t shown in Figure 8. J Related to this, the control circuit 11 detects the voltage V SCO Voltage range V RNG The state belonging to [n+1] is determined by a predetermined immediate shutdown determination time t J When this continues, the overcurrent protection operation α is performed regardless of the protection characteristic setting (i.e., regardless of whether the protection characteristic is set to characteristic PP[1]~PP[m]). That is, after the output transistor M1 is switched from the off state to the on state, the output current I OUTThe value of threshold I TH [n] or more is determined by the immediate shutdown determination time t J If this continues, the control circuit 11 will perform the overcurrent protection operation α regardless of the setting state of the protection characteristics (i.e., regardless of whether the protection characteristics are set to characteristics PP[1] to PP[m]). Immediate interruption decision time t J This is, for example, 1 microsecond. The overcurrent protection action α can suppress adverse effects that may occur when a considerably large current flows through the target wiring, even for a short period of time.

[0061] In contrast, threshold I TH Output current I less than [n] OUT The immediate blocking determination time t J To suppress the adverse effects that may occur due to the current flowing for a longer period of time, an overcurrent protection operation β is performed. A counter 111 (see Figure 1) is used to determine whether or not to perform the overcurrent protection operation β. The counter 111 counts to a value VAL according to the determination signal Sdet. C The counter 111 counts the count value VAL. C is a predetermined lower limit LIM L From a predetermined upper limit LIM H The count value VAL has integer values ​​up to a certain point. C Count the lower limit (LIM). L and upper limit LIM H is “LIM L <LIM H These are two integer values ​​that satisfy the condition ". Typically, "LIM L =0” but “LIM L It's also acceptable if it's >0".

[0062] Counter 111 is count value VAL C In the counting process, count-up and count-down operations are performed. The count-up operation is performed when the lower limit LIM is set. L From upper limit LIM H The count value VAL is in the direction toward C Actions that change the count value VAL C This is an action that increases the value. In the count-up operation, the counter 111 is the count value VAL CIt increases by 1 at a predetermined period. However, counter 111 is “VAL C >LIM H The count-up operation that would make "VAL" true is not performed, therefore "VAL C =LIM H When the condition is met, the count-up operation is prohibited. The count-down operation is limited by the upper limit LIM. H From the lower limit LIM L The count value VAL is in the direction toward C Actions that change the count value VAL C This is a decreasing operation. In the countdown operation, the counter 111 is the count value VAL C It decreases by 1 at a predetermined interval. However, counter 111 is “VAL C <LIM L The countdown operation that would make "VAL" true is not performed, therefore "VAL C =LIM L The countdown operation is prohibited when the condition is met.

[0063] The following describes several specific operational examples, application techniques, and modification techniques related to the SYS switch system within a series of practical examples. Unless otherwise specified and without contradiction, the matters described above apply to each of the following examples. In the event of any inconsistency between the above and the above in any example, the description in that example may take precedence. Furthermore, unless there is a contradiction, the matters described in any of the following examples can be applied to any other example (i.e., any two or more examples from the multiple examples can be combined).

[0064] <<First Example>> A first embodiment will be described. Figure 10 shows the timing chart related to the overcurrent protection of the switch system SYS. In Figure 10, the output current I is shown from top to bottom. OUT waveform, count value VAL C Waveform, state of output transistor M1, detected voltage V CSO The waveform is shown. As time progresses, time TA1 , T A2 , T A3 , T A4 , T A5 , T A6 , T A7 However, these will occur in this order. Furthermore, in the first embodiment, the protective characteristic value P SET It is assumed that is fixed to a constant value. In the first embodiment, it is assumed that "n=4". Therefore, the detection voltage V is determined by the determination signal Sdet. CSO Voltage range V RNG [1]~V RNG [5] It is indicated which of the following categories it belongs to, and the output current I OUT Current range I RNG [1]~I RNG [5] It is indicated which category it belongs to (see Figure 5).

[0065] The counter 111 according to the first embodiment is “V REF [1]≦V CSO During the period in which “I” was established, that is, “I TH [1] ≤ I OUT The counter 111 according to the first embodiment performs a count-up operation during the period in which "V REF [1]>V CSO During the period in which “I” was established, that is, “I TH [1]>I OUT The countdown operation is performed during the period in which the condition is met. However, the count value VAL C This is the lower limit (LIM). L Because it never falls below "VAL C =LIM L When " is established, "V REF [1]>V CSO Even if (that is, "I TH [1]>I OUT Even if the countdown operation is performed, the "VAL C =LIM L It is maintained at time T. A1 Prior to time T, the output transistor M1 is kept off for a sufficiently long time. A1 The count value VAL C This is the lower limit (LIM). L Assume that it is consistent with the above.

[0066] Time T A1 At this point, the MCU20 outputs an output-on command signal to the switch control device 10, and the control circuit 11 responds to the reception of the output-on command signal by switching the value of the drive control signal Sdrv from "0" to "1". As a result, at time T A1 At time T, the driver 12 switches the output transistor M1 from the off state to the on state. A1 From then on, at least time T A7 Until then, the MCU20 shall not output an output-off command signal to the switch control device 10.

[0067] Time T A1 From here on, the output current I OUT As a result of the flow of current, the output current I OUT The corresponding positive detection voltage V CSO This occurs at time T. A1 From time T A2 Up until just before that, “I OUT TH [1]” Therefore, time T A1 From time T A2 Up until just before that, “VAL C =LIM L It is maintained at ".

[0068] Time T A2 In this case, the output current I OUT Due to the increase of “I OUT TH [1] From a state that satisfies “I TH [2] ≤ I OUT TH The system abruptly switches to a state that satisfies [3]. Then, at time T A3 Up until just before "I TH [2] ≤ I OUT TH [3]” is satisfied. Time T A2 and T A3 At the time interval, the output current I OUT The output current I begins to decrease. OUT The decrease occurs at time T A4 and T A5 ​​​​It continues until the time in between. Time T A3 In “I TH [2] ≤ I OUT TH [3] From a state that satisfies “I TH [1] ≤ I OUT TH The state switches to one that satisfies [2]” at time T A4 In “I TH [1] ≤ I OUT TH [2] From a state that satisfies “I OUT TH [1]” switches to a state that satisfies condition [1].

[0069] Subsequently, the output current I OUT It increased again, at time T A5 In “I OUT TH [1] From a state that satisfies “I TH [1] ≤ I OUT TH The state switches to one that satisfies [2]. Time T A4 From time T A5 Up until just before "I OUT TH [1]” is true, and time T A5 From time T A6 Up until just before "I TH [1] ≤ I OUT TH [2]” is true.

[0070] As mentioned above, counter 111 is “I TH [1] ≤ I OUT The count-up operation is performed during the period in which "I" is established. However, TH [i]≦I OUT TH VAL is the count value during the period in which [i+1] is true. C Compared to the rate of increase, “I TH [i+1]≦I OUT TH [i+2]” count value during the period in which the condition is met VAL C ​​​​​​​​​​The growth rate is larger (where i here represents an integer satisfying "1 ≦ i" and "(i + 2) ≦ n = 4"). That is, the increase amount of the count value VAL per unit time C of "I TH [i] ≦ I OUT <I TH [i + 1]" is smaller than the period during which "I TH [i + 1] ≦ I OUT <I TH [i + 2]" holds.

[0071] "I TH [i] ≦ I OUT <I TH [i + 1]" during the period when it holds, the increase rate of the count value VAL C is specifically referred to as the increase rate R[i]. Then, under the condition that the protection characteristic value P SET is fixed at a constant value, "R[i] < R[i + 1]" holds. In the timing chart of FIG. 10, compared with the increase rate R[2] of the count value VAL A2 between times T A3 and T C , the increase rate R[1] of the count value VAL A3 between times T A4 and T C is small. The increase rate between times T A5 and T A6 of the count value VAL C is the same as the increase rate between times T A3 and T A4 of the count value VAL C , which is the increase rate R[1].

[0072] In addition, although not specifically shown, the counter 111 may also increase the count value VAL TH during the period when "I TH [n] = I OUT " holds. At this time, the increase rate of the count value VAL C during the period when "I TH [n] = I TH [4] ≦ I OUT " holds is "I C TH [n - 1] ≦ I​OUT TH [n]” count value during the period in which the condition is met VAL C It is higher than the rate of increase. TH [n]=I TH [4] ≤ I OUT "Immediate blocking determination time t J As soon as that condition is met, the control circuit 11 forcibly sets the count value VAL C against upper limit LIM H You can also set it to that.

[0073] Also, counter 111 is “I OUT TH [1] During the period in which “VAL C =LIM L The countdown operation is performed on the condition that the following condition is not met. In the countdown operation, the counter 111 is the count value VAL C The value is reduced at a predetermined rate. After the countdown operation, the count value VAL C The lower limit is LIM L Once it drops to this level, counter 111 will then be "I OUT TH [1] Even if “VAL C =LIM L "Maintain."

[0074] In the timing chart of Figure 10, time T A2 and T A3 Count value VAL C The lower limit is LIM L It gradually increases at a rate of increase R[2], and then at time T A3 and T A4 Count value VAL C It gradually increases at a rate of increase R[1] which is smaller than the rate of increase R[2]. Then, at time T A4 and T A5 Count value VAL C It gradually decreases at a predetermined rate of decrease. Count value VAL C The rate of decrease is the count value VAL per unit time. C This represents the decrease in time T. A5 ​​​The count value VAL C The direction of change shifts from decreasing to increasing, at time T A5 From time T A6 The count value VAL C It gradually increases at a rate of increase R[1]. In the timing chart of Figure 10, at time T A6 Count value VAL C The upper limit is LIM H It did not reach time T A6 The count value VAL C The upper limit is LIM H It reaches.

[0075] The control circuit 11 switches the output transistor M1 from the off state to the on state, and then sets the count value VAL C Monitor the count value VAL C The upper limit is LIM H When it reaches this point, the overcurrent protection operation β is performed. Therefore, at time T A6 In this configuration, even if the control circuit 11 does not receive an output off command signal from the MCU 20, it switches the output transistor M1 from the on state to the off state by the overcurrent protection operation β, and then maintains the output transistor M1 in the off state until predetermined recovery conditions are met.

[0076] Time T A6 When output transistor M1 is turned off, “0=I OUT TH [1]” so time T A6 From this point onward, the counter 111 performs a countdown operation. Therefore, time T A6 From now on, the count value VAL C It gradually decreases at a predetermined rate of decrease. Count value VAL C The decrease occurs at time T A7 Continue until time T A7 The count value VAL C The lower limit is LIM L It drops to this level. After that, output transistor M1 is set to ON again and “I TH [1] ≤ I OUT Unless the condition is met, the count value VAL C This is the lower limit (LIM).​L It is maintained at [location / location].

[0077] Furthermore, the control circuit 11 operates at time T A6 In conjunction with the overcurrent protection operation β which switches output transistor M1 to the off position, the transistor 151 of the error output circuit 15 is switched from off to on (see Figure 1). Based on the voltage of the signal output terminal CSO due to transistor 151 being turned on, the MCU 20 can recognize that some abnormality has been detected in the switch control device 10. The voltage of the signal output terminal CSO (detection voltage V) is only detected during the off period of transistor 151. CSO ) is the output current I OUT This represents the information, and during the ON period of transistor 151, the voltage at the signal output terminal CSO is equal to the output current I OUT This does not represent the information. Furthermore, the installation and control of transistor 151 are not essential for realizing the technology of this disclosure. A diagnostic terminal (not shown) separate from the signal output terminal CSO may be provided on the switch control device 10, and when any abnormality is detected by the switch control device 10, the occurrence of the abnormality may be transmitted to the MCU 20 via the diagnostic terminal.

[0078] Time T A6 The following describes the subsequent operation. The control circuit 11 switches off the output transistor M1 by the overcurrent protection operation β, and then the count value VAL C The lower limit is LIM L The output transistor M1 is prohibited from being turned on again until the count value VAL decreases. C The lower limit is LIM L It would be good to allow the output transistor M1 to be turned on again after it has dropped to that level.

[0079] For example, an automatic recovery method may be employed in the control circuit 11. The control circuit 11 related to the automatic recovery method switches the output transistor M1 off by the overcurrent protection operation β, and then the count value VAL C The lower limit is LIM L When the value drops to this level, it is determined that the recovery condition has been met. When the control circuit 11 related to the automatic recovery method determines that the recovery condition has been met, at time TA1 In addition to receiving the output ON command signal, a recovery operation is performed to switch the output transistor M1 from the OFF state to the ON state, even if the MCU20 does not receive another output ON command signal from the MCU20.

[0080] Alternatively, for example, an off-latch method may be employed in the control circuit 11. The control circuit 11 related to the off-latch method switches the output transistor M1 off by the overcurrent protection operation β, and then the count value VAL C The lower limit is LIM L After it drops to that point, it waits for the reception of another output ON command signal from MCU20. Then the count value VAL C The lower limit is LIM L After it has decreased to this point (and therefore time T A7 (After that), only when the MCU20 receives another output ON command signal, the control circuit 11 related to the off-latch method determines that the recovery condition has been met and performs a recovery operation to switch the output transistor M1 from the OFF state to the ON state.

[0081] During the countdown operation, the target wiring dissipates heat. However, the heat dissipation status of the target wiring varies depending on the surrounding environment. Taking this into consideration, the SYS switch system sets the count value VAL during the countdown operation. C The reduction rate can be variably set. Referring again to Figure 1, the setting information storage unit 112 is set to the protection characteristic value P SET Separately, Information Q SET Remember this. Information Q SET It has one of several values. MCU20 uses information Q as a type of command signal. SET A setting signal specifying the value can be output to the switch control device 10 (control circuit 11), and upon receiving the setting signal, the control circuit 11 stores the value specified by the setting signal in the information Q in the setting information storage unit 112. SET Write to it. Control circuit 111 is information Q SET (i.e., information Q) SET (Depending on the value it holds) Count value in countdown operation VAL CSet the rate of decrease. For example, the count value VAL in the countdown operation. C The rate of decrease is information Q SET When the value is "1" and information Q SET The result differs depending on whether the value is "2".

[0082] The MCU20 uses the temperature detection signal Tsns (i.e., according to the ambient temperature Tmp) to process information Q. SET A setting signal that specifies the value (i.e., the count value VAL in the countdown operation) C A signal specifying the rate of decrease can be output to the switch control device 10 (control circuit 11) as a type of command signal.

[0083] For example, when the ambient temperature Tmp falls within the first temperature range, the count value VAL in the countdown operation C MCU20 sets information Q so that the rate of decrease is set to the first rate of decrease. SET A setting signal specifying the value to "1" is output to the switch control device 10. Information Q SET Upon receiving a setting signal specifying the value as "1", the switch control device 10 (control circuit 11) processes the information Q in the setting information storage unit 112 according to the setting signal. SET Write "1" in it. Information Q SET When the value is "1", the control circuit 11 sets the count value VAL in the countdown operation. C The rate of decrease of is defined as the first rate of decrease. When the ambient temperature Tmp falls within the second temperature range, the count value VAL in the countdown operation is defined as follows. C MCU20 sets information Q so that the rate of decrease is set to the second rate of decrease. SET A setting signal specifying the value to "2" is output to the switch control device 10. Information Q SET Upon receiving a setting signal specifying the value as "2", the switch control device 10 (control circuit 11) adjusts the information Q in the setting information storage unit 112 according to the setting signal. SET Write "2" in it. Information Q SET When the value is "2", the control circuit 11 sets the count value VAL in the countdown operation. CLet the rate of decrease be the second rate of decrease. Here, the second temperature range is higher than the first temperature range. The higher the ambient temperature Tmp, the less efficiently the target wiring dissipates heat, so the second rate of decrease is smaller than the first rate of decrease.

[0084] However, the rate of decrease specified above in the countdown operation may be a predetermined and fixed rate of decrease.

[0085] The control circuit 11 switches off the output transistor M1 by the overcurrent protection operation β, and then the count value VAL C During the decline process, “VAL C >LIM L Even in this case, it is permissible to turn on the output transistor M1 again. That is, for example, the control circuit 11 switches off the output transistor M1 by the overcurrent protection operation β, and then the count value VAL C During the deceleration process, when the output ON command signal is received again from MCU20, “VAL C >LIM L "Even if (i.e., the count value VAL at the time of receiving the output ON command signal) C (Regardless of the above) it is also possible to perform a recovery operation that switches the output transistor M1 from the off state to the on state when it is determined that the recovery condition has been met.

[0086] <<Second Example>> A second embodiment will now be described. The second embodiment and the embodiments described later are based on the first embodiment, and unless otherwise specified in the second embodiment, the description in the first embodiment also applies to the second embodiment and the embodiments described later.

[0087] Protection characteristic value P in the first embodiment SET In the first embodiment, we assumed a situation where the protection characteristic value P is fixed at a constant value. SET It is assumed that this can vary in various ways (i.e., that the protective properties can vary between properties PP[1] and PP[m]).

[0088] The protective properties are characteristic PP[j A Even if it is set to ], the protection characteristic is characteristic PP[jB Even if set to ], the same operation as shown in the timing chart in Figure 10 is performed by the switch system SYS. Here, j A and j B This represents two distinct integers between 1 and m (inclusive).

[0089] However, the protective properties of characteristic PP[j A ] is set and the protective properties have characteristic PP[j B The rate of increase R[i] in the count-up operation differs depending on whether ] is set or not. To obtain the characteristics shown in Figures 7 and 8, set “j A <j B If this is the case, the protective properties are characteristic PP[j A Compared to the growth rate R[1] when ], the protective properties have characteristic PP[j B The rate of increase R[1] is higher when ] is true. Similarly, “j A <j B If this is the case, the protective properties are characteristic PP[j A Compared to the increase rate R[2] when ], the protective properties have characteristic PP[j B The growth rate R[2] is higher when ]. The same applies to growth rates R[3], etc.

[0090] For example, comparing the characteristics PP[1] and PP[8] shown in Figure 8, as shown in Figure 11, the increase rate R[i] when the protection characteristic is characteristic PP[8] is higher than the increase rate R[i] when the protection characteristic is characteristic PP[1]. Therefore, after switching the output transistor M1 from off to on, the threshold I TH [1] or greater and threshold I TH Output current I with a constant current value less than [n] OUT Assuming that the signal continues to flow, the count value VAL will be lost in a shorter time when the protection characteristic is characteristic PP[8] than when the protection characteristic is characteristic PP[1]. C The upper limit is LIM H When this value is reached, the overcurrent protection operation β is performed.

[0091] Thus (see also Figure 5), the output current I OUT Current range I RNG[2]~I RNG Current range I is one of [n] RNG During the period belonging to [i], the control circuit 11 controls the count value VAL in the count-up operation. C The rate of increase of (i.e., the count value per unit time in the count-up operation) VAL C The amount of increase (of the output current I) is varied according to the setting state of the protection characteristics. OUT Current range I RNG [2]~I RNG Current range I is one of [n] RNG During the period belonging to [i], the control circuit 11 controls the count value VAL in the count-up operation. C The rate of increase is determined by the protective properties of the characteristic PP[j A ] is set and the protective properties have characteristic PP[j B This makes the settings different depending on whether ] is set or not. This allows the protection characteristics to be switched between characteristics PP[1] and PP[m] so that the target wiring is properly protected.

[0092] Furthermore, regardless of which of the characteristics PP[1] to PP[m] is set for the protection characteristics, the count value VAL will be generated by the count-up operation. C The lower limit is LIM L From upper limit LIM H The time required to increase to the above is the immediate blocking determination time t mentioned above. J It is longer than (for example, 1 microsecond). Further explanation is provided. Under conditions where characteristic PP[m] is set for the protection characteristics, “I TH [n-1]≦I OUT TH Output current I that satisfies [n]” OUT During a period when it flows for a specific amount of time, the count value VAL is increased by the count-up operation. C The lower limit is LIM L From upper limit LIM H It is assumed that it will increase to this point. At a specific time here, the count value VAL is determined by the count-up operation. C The lower limit is LIM L From upper limit LIM H ​This is the minimum time required to increase to that point, but the immediate blocking decision time t J It is longer than that.

[0093] <<Third Example>> A third embodiment will now be described. In this third embodiment, the differences between overcurrent protection by the switch control device 10 and overcurrent protection by the MCU 20 will be explained with specific examples. In addition to the first embodiment, the matters described in the second embodiment also apply to the third embodiment.

[0094] Figure 12 shows the timing chart of the switch system SYS according to the third embodiment. In Figure 12, from top to bottom, the output ON command signal transmission state, the output OFF command signal transmission state, the state of output transistor M1, and the output current I are shown. OUT waveform, count value VAL C The waveform is shown (the same is true in Figure 13 described later). Note that in the third embodiment, the protective characteristic value P SET Assume that is fixed at a constant value. As time progresses, time T B1 , T B2 , T B3 However, they will occur in this order. Time T B1 Prior to time T, the output transistor M1 is kept off for a sufficiently long time. B1 The count value VAL C This is the lower limit (LIM). L Assume that it is consistent with the above.

[0095] Time T B1 At this point, the MCU20 outputs an output-on command signal to the switch control device 10, and the control circuit 11 responds to the reception of the output-on command signal by switching the value of the drive control signal Sdrv from "0" to "1". As a result, at time T B1 At time T, the driver 12 switches the output transistor M1 from the off state to the on state. B1 From then on, at least time T B3 The MCU20 shall not output an output-off command signal to the switch control device 10 until the threshold is exceeded.

[0096] Time T B1 From here on, the output current I OUT This occurs, but at time T B1 From time T B2 Output current I immediately before this point OUT It is sufficiently small, and here we consider it to be practically zero (it may actually be zero). Therefore, time T B1 From time T B2 Up until just before that, “VAL C =LIM L It is maintained at time T. B2 In this case, the output current I OUT Due to the increase of “I OUT TH [1] From a state that satisfies “I OUT The system abruptly switches to a state that satisfies =Ix'', and then at time T B3 Up until just before "I OUT The value of the current Ix is "I TH [1] ≤ Ix TH Assume that the current is constant and satisfies [2]”

[0097] Therefore, counter 111 is time T B2 The count-up operation starts from time T B3 It continues until just before time T. B2 and T B3 VAL is the count value during the count-up operation. C The rate of increase is given by the rate of increase R[1] at time T. B3 The count-up operation performed immediately before this caused "VAL C <LIM H From the state of "VAL C =LIM H It switches to the state of "VAL C =LIM H In response to the switch to the state of ", at time T B3 At time T B3 ​​In this configuration, even if the control circuit 11 does not receive an output off command signal from the MCU 20, it switches the output transistor M1 from the ON state to the OFF state by the overcurrent protection operation β, and then maintains the output transistor M1 in the OFF state until a predetermined recovery condition is met. When the output transistor M1 is turned off, “0=I OUT TH As shown in the first embodiment, a countdown operation is performed when [1]” occurs.

[0098] In the timing chart of Figure 12, time tx is time T B2 and T B3 This shows the time difference between the two. The control circuit 11 switches the output transistor M1 from on to off, and then outputs current I OUT The value of threshold I TH [1] When the condition remains above the minimum overcurrent threshold for a duration of time tx, the overcurrent protection operation β will be executed.

[0099] As can be understood from the matters shown in the second embodiment, when characteristic PP[i+1] is set to a protection characteristic, time T B2 and T B3 The rate of increase R[1] between these times is given by the time T when characteristic PP[i] is set to the protection characteristic. B2 and T B3 The rate of increase between these points is greater than R[1]. Therefore, time tx is maximized when characteristic PP[1] is set as the protective characteristic, and minimized when characteristic PP[m] is set as the protective characteristic. Here, “I TH [1] ≤ Ix TH [2]” is assumed to be true, but “I TH [2] ≤ Ix TH [3]" or "I TH [3] ≤ Ix TH The same applies when [4]" etc. is true. In other words, the control circuit 11 switches the output transistor M1 from off to on, and then "I TH [1] ≤ I OUT TH ​​​​​If the condition "[n]" continues for a time tx corresponding to the protection characteristic setting, the protection action will be executed. However, if "I TH [1] ≤ I OUT TH During the period when [n]” is satisfied, the output current I OUT Current range I RNG [2]~I RNG The time x changes depending on which of [n] it belongs to. Also, under any conditions, the time tx is the immediate blocking decision time t J It is longer than that.

[0100] Figure 13 shows another timing chart for the switch system SYS according to the third embodiment. Time T C1 , T C2 , T C3 However, they will occur in this order. Time T C1 Prior to time T, the output transistor M1 is kept off for a sufficiently long time. C1 The count value VAL C This is the lower limit (LIM). L Assume that it is consistent with the above.

[0101] Time T C1 At this point, the MCU20 outputs an output-on command signal to the switch control device 10, and the control circuit 11 responds to the reception of the output-on command signal by switching the value of the drive control signal Sdrv from "0" to "1". As a result, at time T C1 At time T, the driver 12 switches the output transistor M1 from the off state to the on state. C1 From now on, time T C3 Up until immediately before this point, the MCU20 shall not output an output-off command signal to the switch control device 10.

[0102] Time T C1 From here on, the output current I OUT This occurs, but at time T C1 From time T C2 Up until immediately before, the output current I OUT This is sufficiently small to be considered virtually zero (and may actually be zero) compared to the current Iy, which will be discussed later. Time T​C2 In this case, the output current I OUT Due to the steep rise of “I OUT The state switches to one that satisfies =Iy''. Then, at time T C3 Up until just before "I OUT The value of "=Iy" is satisfied. The current Iy is "0 <Iy<I TH Assume that the current is constant and satisfies [1]”

[0103] Therefore, in the timing chart of Figure 13, the counter 111 does not perform a count-up operation, and at time T C1 Previously, the time T C3 Up to “VAL C =LIM L " is maintained, in addition to time T C3 Even later, “VAL C =LIM L This condition is maintained. In other words, in the timing chart of Figure 13, the overcurrent protection operation β based on the determination signal Sdet by the switch control device 10 is not performed, and the overcurrent protection operation α is also not performed.

[0104] On the other hand, after the MCU 20 outputs an output ON command signal to the switch control device 10, it continues to perform protective monitoring processing. In protective monitoring processing, the MCU 20 periodically controls the output current I using the AD conversion circuit 21. OUT By obtaining information on the output current I OUT It monitors the following. More specifically, in the protective monitoring process, the MCU20 detects the detection voltage V, which is an analog signal in wiring WR3. CSO The signal is sampled at a constant period by the AD conversion circuit 21 to obtain a digital signal D CSO Converts to a digital signal D. CSO The output current I OUT Information (Output current I OUT This is information indicating the value of the output current I, which is acquired sequentially. OUT Based on the information, the output current I OUT Time-series information (output current I at multiple time points) OUT A collection of information is formed.

[0105] In the protective monitoring process, the MCU20 sequentially acquires the output current I OUT Based on the information and the ambient temperature Tmp represented by the temperature detection signal Tsns, the state of the target wiring is predicted, and based on the prediction result, a protective stop operation γ is performed as necessary to prevent the target wiring from being used in the restricted area 630 (see Figure 6). The protective stop operation γ may also be referred to as an overcurrent protection operation separate from the overcurrent protection operations α and β. In protective stop operation γ, the MCU 20 outputs an output off command signal to the switch control device 10 in order to protect the target wiring because its temperature has become excessive. In response to receiving the output off command signal, the control circuit 11 switches the value of the drive control signal Sdrv from "1" to "0". As a result, the driver 12 switches the output transistor M1 from the on state to the off state.

[0106] In the timing chart of Figure 13, time T C1 After the output ON command signal is output to the switch control device 10, the MCU 20 continues to execute the protective monitoring process. Time T C1 From time T C3 Output current I immediately before OUT Based on the time-series information, and referring to the temperature detection signal Tsns, the MCU20 determines the time T C3 It is determined that the operating point of the target wiring immediately before time T has reached a specific point within the recommended protection area 620, C3 The protective shutdown operation γ is performed.

[0107] In the timing chart in Figure 13, time ty is time T. C2 and T C3 This shows the time difference between them. After the MCU20 switches the output transistor M1 from on to off, the output current I OUT Threshold I TH [1] When a specific current value (i.e., the value of current Iy) smaller than the minimum overcurrent threshold persists for a time ty, the protective shutdown operation γ will be executed.

[0108] Here, time ty is longer than time tx. Time ty varies depending on the value of the current Iy corresponding to a specific current value. As the specific current value increases, time ty becomes shorter, but it is at least longer than time tx. For example, if time tx is 10 seconds, time ty is several tens of seconds to several thousand seconds. Time x depends on the setting state of the protection characteristics and the current Ix mentioned above, which is within the current range I RNG [2]~I RNG It varies depending on which of [n] it belongs to, but time ty is longer than the maximum time x can take. Note that time T shown in Figure 12 B1 and T B3 Although protective monitoring processing can be performed by the MCU20 during this time, the overcurrent protection operation β is performed by the switch control device 10 before the protective monitoring processing determines whether to perform protective shutdown operation γ. Therefore, in the example shown in Figure 12, protective shutdown operation γ is not performed.

[0109] In this way, the SYS switch system assigns the switch control device 10 to handle overcurrents over relatively short periods, while the MCU 20 handles overcurrents over relatively long periods. This allows for the construction of a system that is well-balanced in terms of both cost and response speed.

[0110] In Figures 12 and 13, for the sake of simplicity, the output current I over a certain period of time is shown. OUT It was assumed that the currents (Ix, Iy) would be fixed at a constant value, but in reality, the output current I during the ON period of the output transistor M1 OUT It varies in various ways. Output current I OUT Even if the output current I fluctuates in various ways, OUT The value of threshold I TH [1] In the region where the value exceeds this, the switch control device 10 performs overcurrent countermeasures, and the output current I OUT The value of threshold I TH In the region where the value is less than [1], the MCU20 handles overcurrent protection.

[0111] <<Fourth Example>> A fourth embodiment will be described. In the fourth embodiment, the overcurrent response operation by the interoperation of the switch control device 10 and the MCU 20 will be described. In the fourth embodiment, the technologies shown in the first to third embodiments are combined and implemented.

[0112] Figure 14 is a timing chart of the switch system SYS according to the fourth embodiment. In Figure 14, from top to bottom, the output ON command signal transmission state, the output OFF command signal transmission state, the protection characteristic command signal transmission state, the state of output transistor M1, and the output current I are shown. OUT The waveform and the state of the protection characteristics in the switch control device 10 are shown. As time progresses, time T D1 , T D2 , T D3 , T D4 , T D5 , T D6 However, we will assume that they occur in this order. In the example in Figure 14, time T D1 and T D6 In between, the count value VAL C The upper limit is LIM H It is assumed that the current will not reach this level, and therefore the overcurrent protection operations α and β by the control circuit 11 will not be performed. Also, at time T D1 The protection characteristic value P was obtained through the transmission and reception of the protection characteristic command signal that occurred earlier. SET "1" is set for this (see Figure 9), and as a result, time T D1 Let's assume that characteristic PP[1] is set to the protection characteristic. Alternatively, the protection characteristic value P is set without the transmission or reception of a protection characteristic command signal. SET A default value of "1" is set for this, and as a result, time T D1 Therefore, we can assume that the characteristic PP[1] is set as a protective characteristic.

[0113] Time T D1 At this point, the MCU20 outputs an output-on command signal to the switch control device 10, and the control circuit 11 responds to the reception of the output-on command signal by switching the value of the drive control signal Sdrv from "0" to "1". As a result, at time T D1 At time T, the driver 12 switches the output transistor M1 from the off state to the on state.D1 From now on, time T D6 Up until immediately before this, the MCU20 shall not output an output-off command signal to the switch control device 10.

[0114] In the example in Figure 14, time T D1 Immediately after, “I TH [1] ≤ I OUT TH A relatively large output current I that satisfies [n]” OUT This occurs for only a short time. This relatively large output current I OUT This corresponds to the inrush current to the load LD or the output capacitor connected in parallel to the load LD. Time T D1 After that, the output current I OUT is time T D2 It decreases during the process leading up to time T. D1 and T D2 “I TH [1] ≤ I OUT TH During the period when [n]" is true, the counter 111 performs a count-up operation, but the count value VAL C The upper limit is LIM H It does not reach (in Figure 14, the count value VAL C The upper limit is LIM H (Illustrations showing the state not reaching this point are omitted.) Although it differs from the example in Figure 14, let's assume that time T D1 and T D2 During the count-up operation, the count value VAL C The upper limit is LIM H If it reaches “VAL C =LIM H When the condition is met, the control circuit 11 executes the overcurrent protection operation β and switches the output transistor M1 off. Also, although it differs from the example in Figure 14, let's assume that time T D1 and T D2 In between, “I TH [n]≦I OUT Output current I that satisfies " OUT The immediate blocking determination time t J If the above occurs, the control circuit 11 will perform the overcurrent protection operation α and the output transistor M1 will be switched off. ​​

[0115] In the example in Figure 14, time T D1 and T D2 During this time, overcurrent protection operations α and β were not performed, and thereafter, at time T D2 and T D3 At this point, current Ia is output current I OUT It flows as follows. Current Ia corresponds to the steady-state current, and the value of current Ia is the threshold I TH [1] is smaller than the current Ia with a duration of on time t. ON Regardless of this, it is a current that belongs to the normal operating region 610 (Figure 6), and "I OUT As long as =Ia'', neither the overcurrent protection operations α and β by the switch control device 10 nor the protective shutdown operation γ by the MCU 20 will be performed. Time T D3 and T D4 In between, for some reason the output current I OUT The current increases from Ia to Ib, and at time T D4 From time T D6 Up until just before "I OUT It is kept as "=Ib". Here "Ia <Ib<I TH [1]” is true. Therefore, time T D2 and T D4 Time T D4 and T D6 During this time, the counter 111 does not perform a count-up operation, and therefore the overcurrent protection operation β by the control circuit 11 is not performed.

[0116] However, the value of current Ib is the threshold I TH [1] is close to “I OUT Output current I that satisfies =Ib OUT If the current continues to flow for an extended period, the temperature of the target wiring will become excessive. To prevent the temperature of the target wiring from becoming excessive, the MCU20 sets a time T D1 After outputting an output ON command signal to the switch control device 10, the protective monitoring process is continued. The contents of the protective monitoring process are as shown in the third embodiment. In the example in Figure 14, time T D1 From time T D6 Output current I immediately before OUT Time-series information (especially time T) D4 From time T D6Output current I immediately before OUT Based on the time-series information, and referring to the temperature detection signal Tsns, the MCU20 will determine the time T C6 It is determined that the operating point of the target wiring immediately before time T has reached a specific point within the recommended protection area 620, D6 The protective shutdown operation γ is performed at time T. D6 During the protective stop operation γ, the MCU20 outputs an output off command signal to the switch control device 10. In response to receiving the output off command signal, the control circuit 11 switches the value of the drive control signal Sdrv from "1" to "0". As a result, the driver 12 switches the output transistor M1 from the ON state to the OFF state.

[0117] The MCU20 can command the switch control device 10 to change the protection characteristics to desired characteristics based on the prediction result of the state of the target wiring obtained by the protection monitoring process. In the example in Figure 14, time T D4 The following relatively large output current I OUT The MCU20 predicts a temperature rise in the target wiring based on this. As a result of this temperature rise, the MCU20 determines that the protection characteristics of the switch control device 10 are inappropriate with characteristic PP[1] and that it is appropriate to change the protection characteristics of the switch control device 10 to characteristic PP[5]. Based on this determination, at time T D5 In MCU20, the protection characteristic value P SET A protection characteristic command signal is output to the switch control device 10, specifying that the protection characteristic value P should be set to "5". In response to receiving this protection characteristic command signal, the control circuit 11 sets the protection characteristic value P in the setting information storage unit 112. SET Substitute "5" into this. This effectively gives us time T D5 The protection characteristics used in the switch control device 10 are switched from characteristic PP[1] to characteristic PP[5].

[0118] Thus, the detection voltage V corresponds to the current detection signal. CSOBased on this, the MCU20 predicts the state of the target wiring. Based on this prediction, the MCU20 decides whether to output a protection characteristic command signal to the switch control device 10 to change the protection characteristic from one characteristic (here, characteristic PP[1]) to another characteristic (here, characteristic PP[5]). If it is decided to output the protection characteristic command signal, the protection characteristic command signal is actually output from the MCU20 to the switch control device 10, and the switch control device 10 (control circuit 11) changes the protection characteristic to the other characteristic (here, characteristic PP[5]) according to the received protection characteristic command signal. In this way, the protection characteristic of the switch control device 10 can be dynamically changed to an appropriate one in response to the constantly changing state of the target wiring.

[0119] Although it differs from the example shown in Figure 14, let's assume that time T D5 Immediately after, the output current I OUT The state is “I TH [1] ≤ I OUT TH The state changes to one that satisfies [n], and time T D5 The time (T) is a time that is ΔT later. D5 Count value VAL (+ΔT) C The upper limit is LIM H If it reaches “VAL C =LIM H At this point, the control circuit 11 executes the overcurrent protection operation β. In this case, the protection stop operation γ is not executed afterward. Time T D5 Compared to the case where the protective characteristics are maintained with characteristic PP[1] thereafter, time T D5 When the protection characteristics are changed to characteristic PP[5], the time ΔT is shorter. This is because time T D5 This means that, in light of the condition of the target wiring, the target wiring can be protected more safely.

[0120] Furthermore, MCU20 will, at any time, display the current count value VAL C A command signal to read the current count value VAL can be sent to the switch control device 10 as an inquiry signal. When the switch control device 10 receives the inquiry signal, the control circuit 11 will read the current count value VAL​C The value is transmitted to the MCU20 via the communication wiring group CWG. The MCU20 receives the acquired count value VAL C This can be used, for example, as one of the indicators for predicting the state of the target wiring.

[0121] <<Example 5>> A fifth embodiment will be described. Count value VAL C You can also perform a transformation MOD5 that reverses the direction of change described above. That is, the count value VAL C Initial value is upper limit LIM H After setting it to “I TH [1] ≤ I OUT During the period in which the condition is met, the countdown operation is performed and the count value VAL C The lower limit is LIM L The overcurrent protection operation β is performed when the voltage drops to this level, and "I OUT TH [1]” may be set to perform a count-up operation during the period in which the condition is met. In this case, in the first to fourth embodiments, the count value VAL C The increase and rate of increase are shown by the count value VAL C This can be interpreted as a decrease and a rate of decrease, and the count value VAL C The decrease and the rate of decrease are shown in the count value VAL. C This can be interpreted as an increase and a rate of increase (the same applies to other similar expressions).

[0122] The count-up operation is performed using the count value VAL C This is an example of the first count operation, which changes the count value VAL in the first direction, from the first value to the second value, and the countdown operation is performed by changing the count value VAL C This is an example of a second count operation that changes the direction to a second direction opposite to the first direction. In the first to fourth embodiments, the first value and the second value are the lower limit LIM, respectively. L , upper limit LIM H Furthermore, the first direction and the second direction are the direction of increase and decrease, respectively. When deformation MOD5 is applied, the first value and the second value are the upper limit LIM, respectively. H Lower limit LIM L ​Furthermore, the first direction and the second direction are the direction of decrease and the direction of increase, respectively.

[0123] <<Sixth Example>> A sixth embodiment will be described. A modified MOD6 can be adopted in which the output transistor M1 is configured as a P-channel type MOSFET, and when the modified MOD6 is adopted, the charge pump circuit 13 is not required.

[0124] <<Example 7>> A seventh embodiment will now be described. As shown in Figure 15, in the switch system SYS, a modification MOD7 may be applied in which an output transistor M2 configured as a P-channel MOSFET is provided in addition to the output transistor M1 configured as an N-channel MOSFET. In this case, a driver 12P is added to the switch control device 10, and the source of the output transistor M2 is connected to wiring WR1, while the drain of the output transistor M2 is connected to wiring WR2. The driver 12P is connected to the gate of the output transistor M2 and drives the gate of the output transistor M2 under the control of the control circuit 11. That is, the control circuit 11 sets the output transistor M1 on or off through the control of the driver 12, and sets the output transistor M2 on or off through the control of the driver 12P.

[0125] In the SYS switch system shown in Figure 15, to which the modified MOD7 is applied, the control circuit 11 operates in either the first or second mode, and the MCU 20 can set the operating mode of the control circuit 11 to the first or second mode by outputting a command signal to the switch control device 10.

[0126] When the operating mode of the control circuit 11 is set to the first mode, as described above, the control circuit 11 turns on the output transistor M1 in response to the reception of an output ON command signal and turns off the output transistor M1 in response to the reception of an output OFF command signal. When the operating mode of the control circuit 11 is set to the first mode, as described above, the control circuit 11 switches the output transistor M1 from ON to OFF by the overcurrent protection operation α or β. When the operating mode of the control circuit 11 is set to the first mode, the control circuit 11 keeps the output transistor M2 OFF through the control of the driver 12P.

[0127] When the operating mode of the control circuit 11 is set to the second mode, the control circuit 11 turns on the output transistor M2 in response to the reception of an output ON command signal and turns off the output transistor M2 in response to the reception of an output OFF command signal. When the operating mode of the control circuit 11 is set to the second mode, the control circuit 11 switches the output transistor M2 from ON to OFF by overcurrent protection operation α or β. When the operating mode of the control circuit 11 is set to the second mode, the control circuit 11 keeps the output transistor M1 OFF through the control of the driver 12.

[0128] When the operating mode of the control circuit 11 is set to the first mode, the charge pump circuit 13 must be operated for at least the period during which the output transistor M1 should be turned on. In contrast, when the operating mode of the control circuit 11 is set to the second mode, the control circuit 11 stops the operation of the charge pump circuit 13. For this reason, the second mode contributes to power saving of the switch control device 10. However, the output current I OUT When the output current I is relatively large, the first mode can keep the losses at the output transistor lower than the second mode. The MCU20 has an output current I OUT The operating mode of the control circuit 11 can be set to the first or second mode depending on its size.

[0129] Furthermore, in the switch system SYS to which the modified MOD7 is applied, the signal PGEN may be input to the driver 12P as shown in Figure 16. In this case, an external terminal for receiving the signal PGEN is added to the switch control device 10. The signal PGEN is a voltage signal that has a high level or a low level. As shown in Figure 16, the MCU 20 may supply the signal PGEN to the switch control device 10, or the signal PGEN may be fixed at a high level or a low level on the board on which the switch control device 10 is mounted. In the switch system SYS of Figure 16, when the signal PGEN has a high level, the output transistor M2 is turned on by the driver 12P regardless of the control of the control circuit 11 (and therefore even if the switch control device 10 has not received an output ON command signal). The operation of the switch control device 10 during the low-level period of the signal PGEN is the same between the switch system SYS of Figure 15 and the switch system SYS of Figure 16.

[0130] <<Example 8>> An eighth embodiment will be described. Although not specifically shown, in the switch system SYS of Figure 1, a modification may be made in which the output transistor M1 is built into the switch control device 10, and in addition to or instead of this modification, a sense resistor R SNS and gain resistor R GAIN A modification may be made to incorporate it into the switch control device 10.

[0131] Similarly, although not specifically shown in the figures, in the switch system SYS of Figure 15 or Figure 16, a modification may be made in which the output transistors M1 and M2 are built into the switch control device 10, and in addition to or instead of this modification, a sense resistor R SNS and gain resistor R GAIN A modification may be made to incorporate it into the switch control device 10.

[0132] Furthermore, in the switch system SYS shown in Figure 1, Figure 15, or Figure 16, the voltage conversion resistor R CSO It is also possible to modify the system to integrate it into the switch control device 10. However, the output current I from the MCU 20 OUTTo improve the accuracy of monitoring, a voltage conversion resistor R CSO It is preferable to provide this as a discrete component outside the switch control device 10.

[0133] <<Ninth Example>> A ninth embodiment will be described.

[0134] In the configuration illustrated in Figure 1, the switch control device 10 is used as a control device for a so-called high-side switch, but the switch control device 10 may also be used as a control device for a so-called low-side switch. That is, the load LD may be inserted in series with the wiring WR1, rather than between node ND1 and ground. In this case, the charge pump circuit 13 is unnecessary, and the power supply voltage VCC can be supplied to the switch terminal 10 as the power supply voltage for driving the switch control device 10.

[0135] In this embodiment, an example of applying the switch control device 10 to a vehicle VHCL is given, but the application of the switch control device 10 is not limited to vehicle VHCLs and is arbitrary. For example, the switch control device 10 may be installed in any industrial machine or any home appliance.

[0136] With respect to any signal or voltage, the relationship between their high and low levels can be the reverse of that described above, without undermining the main point stated above.

[0137] The channel types of the FETs (field-effect transistors) shown in the embodiments described above are illustrative. Without compromising the intent described above, the channel type of any FET can be changed between P-channel and N-channel types.

[0138] As long as no inconvenience arises, any transistor described above may be any type of transistor. For example, any transistor described above as a MOSFET (especially output transistor M1 or M2) can be replaced with a junction FET, IGBT (Insulated Gate Bipolar Transistor), or bipolar transistor, as long as no inconvenience arises. Any transistor has a first electrode, a second electrode, and a control electrode. In an FET, one of the first and second electrodes is the drain and the other is the source, and the control electrode is the gate. In an IGBT, one of the first and second electrodes is the collector and the other is the emitter, and the control electrode is the gate. In a bipolar transistor that does not belong to the IGBT category, one of the first and second electrodes is the collector and the other is the emitter, and the control electrode is the base.

[0139] The embodiments of this disclosure can be modified in various ways as appropriate within the scope of the technical idea set forth in the claims. The embodiments described above are merely examples of embodiments of this disclosure, and the meaning of the terms in this disclosure or each constituent element is not limited to those described above. The specific numerical values ​​given in the above description are merely examples and can, of course, be changed to various numerical values.

[0140] <<Note>> A note is provided regarding this disclosure in which specific configuration examples are shown in the embodiments described above.

[0141] A switch control device (10) relating to one aspect of this disclosure includes a control circuit (11) configured to control the on or off of output transistors (M1, M2) connected in series with the target wiring in response to an output command signal supplied to the switch control device from an external device (20), and an output current (I) flowing through the output transistors. OUT Current detection signal (V) corresponding to ) CSO ) generates, and based on the current detection signal, the output current is set to one of several current ranges (I RNG [1]~I RNGThe control circuit includes a current detection circuit (14) configured to detect which of [n+1] the current falls into, and the control circuit is configured to perform a protection operation (overcurrent protection operation α, β) which switches the output transistor from off to on and then switches the output transistor from on to off according to the protection characteristics based on the detection result of the current detection circuit, and the control circuit is configured to variably set the protection characteristics based on a protection characteristic command signal output from the external device to the switch control device in response to the current detection signal output from the switch control device to the external device (first configuration).

[0142] Depending on the magnitude of the output current and the duration of the output current flow, the state of the target wiring placed in the output current path changes moment by moment. According to the first configuration, the protection characteristics of the switch control device can be dynamically changed to an appropriate level according to the state of the target wiring, thereby ensuring proper protection of the target wiring.

[0143] In the switch control device according to the first configuration described above, the control circuit switches the output transistor from off to on, and then the value of the output current is set to the minimum overcurrent threshold (I TH [1]) The protection operation is executed when the condition is greater than or equal to the protection characteristics for a first time (tx) corresponding to the protection characteristics, and the output command signal is an output on command signal that commands to turn on the output transistor, or an output off command signal that commands to turn off the output transistor, and the control circuit may be configured to switch the output transistor from on to off when, after switching the output transistor from off to on, the output current has a specific current value smaller than the minimum overcurrent threshold for a second time (ty) longer than the first time, and the control circuit receives the output off command signal output from the external device in response to the current detection signal. (Second configuration)

[0144] In the second configuration, overcurrent handling for relatively short periods is performed by the switch control device, while overcurrent handling for relatively longer periods is performed by the external device. This makes it possible to construct a system that is balanced in terms of both cost and response speed.

[0145] In the switch control device according to the second configuration described above, the control circuit sets the protection characteristic to one of a plurality of characteristics (PP[1] to PP[n]) based on the protection characteristic command signal, and after the control circuit switches the output transistor from off to on, an immediate cutoff threshold (I) is set when the value of the output current is greater than the minimum overcurrent threshold. TH [n]) The state is greater than or equal to the immediate blockage determination time (t J ) If this continues for only a certain period, the protection operation will be performed regardless of the setting state of the protection characteristics, and the control circuit may be configured (third configuration) to perform the protection operation if, after switching the output transistor from off to on, the output current value is less than the immediate cutoff threshold and greater than or equal to the minimum overcurrent threshold, and this state continues for a certain first time according to the setting state of the protection characteristics.

[0146] In the switch control device relating to the third configuration described above, the plurality of current ranges consist of the first to the (n+1) current ranges, the current value belonging to the (i+1) current range is greater than the current value belonging to the i current range, n represents an integer of 2 or more, i represents an integer of 1 or more and less than or equal to n, the second current range is a current range greater than or equal to the minimum overcurrent threshold, the (n+1) current range is a current range greater than or equal to the immediate cutoff threshold, and the control circuit controls the count value (VAL C The control circuit has a counter (111) configured to count the following: after switching the output transistor from off to on, the output current is within the second current range to the nth current range (I RNG [2]~I RNG [n]) When the count value belongs to any of the first values ​​(e.g., LIM L ) to the second value (e.g., LIM HThe count value is changed toward the second value, and when the count value reaches the second value, the protection operation is executed, and the amount of change in the count value per unit time during the period when the output current belongs to a specific current range within the second current range to the nth current range may be configured differently (fourth configuration) depending on the setting state of the protection characteristics.

[0147] In the switch control device according to the fourth configuration described above, the amount of change in the count value per unit time is larger during the period when the output current belongs to the (i+1) current range compared to the period when the output current belongs to the i current range which is any of the second current range to the n current range (fifth configuration).

[0148] In the switch control device according to the fourth or fifth configuration described above, the counter is capable of performing a first count operation (e.g., a count-up operation) that changes the count value in a first direction from the first value toward the second value, and a second count operation (e.g., a count-down operation) that changes the count value in a second direction opposite to the first direction, and the control circuit may be configured to change the count value in the second direction at a specified rate of change (sixth configuration) on the condition that the value of the output current is less than the minimum overcurrent threshold and the count value is different from the first value.

[0149] In the switch control device according to the sixth configuration described above, the control circuit may be configured such that, in response to the count value reaching the second value, the output transistor is switched from on to off by the protection operation, and the count value is changed in the second direction at the specified rate of change until the count value reaches the first value (seventh configuration).

[0150] A switch system (SYS) relating to one aspect of this disclosure may have a configuration (the eighth configuration) comprising a switch control device (10) relating to any of the first to seventh configurations described above, and an external device (20) that is communicatively connected to the switch control device.

[0151] A switch system (SYS) relating to one aspect of the present disclosure comprises a switch control device (10) relating to any of the second to seventh configurations described above, and an external device (20) that is communicatively connected to the switch control device, wherein the external device may be configured to cause the switch control device to switch the output transistor from off to on through the output of the output ON command signal, monitor the value of the output current based on the current detection signal, and if the output current has the specified current value for the second time, cause the switch control device to switch the output transistor from on to off through the output of the output OFF command signal (the ninth configuration).

[0152] According to the ninth configuration, overcurrent handling for relatively short periods is performed by the switch control device, while overcurrent handling for relatively longer periods is performed by the external device. This makes it possible to construct a switch system that is balanced in terms of both cost and response speed.

[0153] In the switch system according to the ninth configuration described above, the external device may be configured to cause the switch control device to switch the output transistor from off to on via the output of the output ON command signal, and then decide whether to output the protection characteristic command signal to the switch control device for changing the protection characteristic based on the monitoring result of the value of the output current (the tenth configuration).

[0154] Depending on the magnitude of the output current and the duration of the output current flow, the state of the target wiring placed in the output current path changes moment by moment. According to the ninth configuration, the protection characteristics of the switch control device can be dynamically changed to an appropriate level according to the state of the target wiring, thereby ensuring proper protection of the target wiring.

[0155] A switch system (SYS) relating to one aspect of the present disclosure comprises a switch control device (10) relating to the sixth or seventh configuration described above, and an external device (20) that is communicatively connected to the switch control device, wherein the external device may be configured to output a signal to the switch control device specifying the predetermined rate of change according to the temperature of the space in which the target wiring through which the output current flows is located (the eleventh configuration).

[0156] The heat dissipation of the target wiring changes depending on the temperature of the space in which the wiring is placed. According to the 11th configuration, the above-specified rate of change can be optimized by taking into account the heat dissipation of the target wiring which depends on the above temperature, thereby allowing adjustment of the time until the output transistor is permitted to be turned on again, for example. [Explanation of Symbols]

[0157] SYS Switch System 10 Switch control device 11 Control circuits 111 counter 112 Configuration Information Storage Unit 12, 12P driver 13. Charge pump circuit 14 Current detection circuit 141 Op-amps 142 transistors 143 Current Range Determination Circuit 143[1]~143[n] Comparator 15 Error output circuit 151 transistors 16 Internal power circuit 20 MCU 21 AD Conversion Circuit 30 Temperature detection circuit IN power supply terminal NG gate connection terminal NS source connection terminal CSIP, CSIN current detection terminals GND ground terminal CSO signal output terminal CTG communication terminal group CWG communication wiring group M1, M2 Output Transistors LD load VS Voltage Source R SNS Sense resistance R GAIN Gain resistor R CSO Voltage conversion resistor WR1~WR3 Wiring VB, VCC power supply voltage V CSO Detected voltage I OUT Output current Tsns temperature detection signal Sdet determination signal Sdrv drive control signal CS cabinet BLK Electrical Block VHCL vehicles V REF [1]~V REF [n] Reference voltage V RNG [1]~V RNG [n+1] Voltage range I RNG [1]~I RNG [n+1] Current range I TH [1]~I TH [n] threshold 610 Normal operating area 620 Recommended Protection Areas 630 Prohibited area VAL C Count value

Claims

1. In a switch control device, A control circuit configured to control the on / off state of an output transistor connected in series with the target wiring in response to an output command signal supplied to the switch control device from an external device, The system includes a current detection circuit configured to generate a current detection signal corresponding to the output current flowing through the output transistor, and to detect which of a plurality of current ranges the output current belongs to based on the current detection signal, The control circuit is configured to perform a protection operation in which, after switching the output transistor from off to on, it switches the output transistor from on to off according to the protection characteristics based on the detection result of the current detection circuit. The control circuit variably sets the protection characteristics based on the protection characteristic command signal output from the external device to the switch control device in response to the current detection signal output from the switch control device to the external device. Switch control device.

2. The control circuit switches the output transistor from off to on, and then, when the output current value remains above the minimum overcurrent threshold for a first time according to the protection characteristics, it executes the protection operation. The output command signal is an output on command signal that commands the output transistor to be turned on, or an output off command signal that commands the output transistor to be turned off. If, after the control circuit switches the output transistor from off to on, the output current remains at a specific current value smaller than the minimum overcurrent threshold for a second time longer than the first time, and the control circuit receives the output off command signal output from the external device in response to the current detection signal, the control circuit switches the output transistor from on to off. The switch control device according to claim 1.

3. The control circuit sets the protection characteristic to one of a plurality of characteristics based on the protection characteristic command signal. After switching the output transistor from off to on, the control circuit executes the protection operation regardless of the protection characteristic setting state if the output current value remains above an immediate cutoff threshold (which is greater than the minimum overcurrent threshold) for the duration of the immediate cutoff determination time. The control circuit switches the output transistor from off to on, and then, if the output current value remains below the immediate cutoff threshold and above the minimum overcurrent threshold for a period of time corresponding to the protection characteristic setting, it executes the protection operation. The switch control device according to claim 2.

4. The aforementioned multiple current ranges consist of a first to (n+1) current range, where the current value belonging to the (i+1) current range is greater than the current value belonging to the i current range, where n is an integer of 2 or more, and i is an integer of 1 or more and less than or equal to n, the second current range is a current range above the minimum overcurrent threshold, and the (n+1) current range is a current range above the immediate cutoff threshold. The control circuit has a counter configured to count a count value, The control circuit, after switching the output transistor from off to on, changes the count value from a first value to a second value when the output current falls within any of the second current range to the nth current range, and when the count value reaches the second value, it executes the protection operation. During the period in which the output current belongs to a specific current range within the second current range to the nth current range, the amount of change in the count value per unit time differs depending on the setting state of the protection characteristics. The switch control device according to claim 3.

5. Compared to the period when the output current belongs to the i-th current range, which is one of the second to n-th current ranges, the change in the count value per unit time is larger during the period when the output current belongs to the (i+1)th current range. The switch control device according to claim 4.

6. The counter is capable of performing a first counting operation that changes the count value in a first direction from the first value toward the second value, and a second counting operation that changes the count value in a second direction opposite to the first direction. The control circuit changes the count value in the second direction at a specified rate of change, provided that the value of the output current is less than the minimum overcurrent threshold and the count value differs from the first value. or the switch control device according to claim 4 or 5.

7. When the control circuit switches the output transistor from on to off due to the protection operation in response to the count value reaching the second value, it changes the count value in the second direction at the specified rate of change until the count value reaches the first value. The switch control device according to claim 6.

8. A switch control device according to any one of claims 1 to 5, The external device is connected to the switch control device in a communicative manner. Switch system.

9. A switch control device according to any one of claims 2 to 5, In a switch system comprising the switch control device and the external device which is communicatively connected, The external device, after causing the switch control device to switch the output transistor from off to on via the output of the output ON command signal, monitors the value of the output current based on the current detection signal, and if the output current remains at the specified current value for the second time, it causes the switch control device to switch the output transistor from on to off via the output of the output OFF command signal. Switch system.

10. The external device, after causing the switch control device to switch the output transistor from off to on via the output of the output ON command signal, decides whether to output the protection characteristic command signal to the switch control device to change the protection characteristic based on the monitoring result of the output current value. The switch system according to claim 9.

11. The switch control device according to claim 6, In a switch system comprising the switch control device and the external device which is communicatively connected, The external device is configured to output a signal to the switch control device specifying the predetermined rate of change, depending on the temperature of the space where the target wiring is located. Switch system.

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