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JP-7854832-B2 - protection device

JP7854832B2JP 7854832 B2JP7854832 B2JP 7854832B2JP-7854832-B2

Inventors

  • 安井 崇博
  • 遠山 陽平

Assignees

  • 古河電気工業株式会社
  • 古河ＡＳ株式会社

Dates

Publication Date
20260507
Application Date
20220330

Claims (7)

  1. A switch control unit controls a switch that turns on or off in response to an input pulse signal, supplying power from a power source to a load when on, and cutting off the power supply from the power source to the load when off. A voltage measuring unit obtains the voltage value of a first voltage between the power supply and the switch, and the voltage value of a second voltage between the switch and the load, measured within a predetermined time after the pulse signal is input to the switch, from a voltage measuring unit that measures the voltage values, and calculates the resistance value of the stage downstream of the switch based on the resistance value of the switch and the obtained voltage values of the first and second voltages . It has, The aforementioned power supply has its negative terminal connected to ground. The switch is connected in series between the positive terminal of the power supply and the load, The load is connected in series with respect to the switch and the ground between the switch and the ground. The time during which the switch turns on in response to the pulse signal is the time during which the load is not operating. The switch control unit is a protective device that turns off the switch if the resistance value calculated by the calculation unit is less than a threshold value.
  2. The pulse signal is a PWM signal with a duty cycle in which the load does not operate. The calculation unit obtains the output voltage of the low-pass filter that smooths the voltage change between the switch and the load as the voltage value of the second voltage between the switch and the load . The low-pass filter is connected between the switch and the load and to the voltage measuring unit. The protective device according to claim 1.
  3. The protection device according to claim 2, wherein the calculation unit calculates the ground potential of the load based on the acquired voltage value of the first voltage, the voltage value of the second voltage , and the duty cycle, and calculates the resistance value of the stage downstream of the switch based on the calculated potential, the voltage value acquired by the calculation unit, and the resistance value of the switch.
  4. The protective device according to claim 3, wherein the calculation unit calculates the potential based on the voltage value obtained when the PWM signal has a first duty cycle, the voltage value obtained when the PWM signal has a second duty cycle, the first duty cycle, and the second duty cycle.
  5. The switch control unit controls a first sub-switch provided in parallel with the switch and a second sub-switch provided in parallel with the load. The protective device according to claim 1, wherein the calculation unit calculates the potential difference between the ground potential of the load and the ground potential of the voltage measuring unit based on the voltage value of the voltage applied to the load acquired when the first sub-switch is ON and the switch and the second sub-switch are OFF, the voltage value of the voltage applied to the load acquired when the first sub-switch and the second sub-switch are ON and the switch is OFF, and the current value of the current flowing through the second sub-switch, and calculates the resistance value of the stage downstream of the switch based on the calculated potential difference, the voltage value acquired by the calculation unit, and the resistance value of the switch.
  6. The protection device according to claim 1, wherein the voltage value acquired by the calculation unit is the voltage value measured by the voltage measuring unit during the falling edge of the pulse signal.
  7. The aforementioned switch is an FET, The voltage value applied to the gate of the FET when the switch is turned on by the pulse signal is the voltage value obtained by adding a predetermined voltage value to the gate threshold value of the FET. The protective device according to claim 1, wherein the switch control unit turns off the switch when the switch is turned on by the pulse signal if the voltage value of the second voltage between the switch and the load is less than the predetermined voltage value.

Description

This invention relates to a protective device. As an invention to prevent overcurrent from flowing from a power source to a load, there is a switch device disclosed in, for example, Patent Document 1. This switch device has a switch circuit and a connector connected to the load. The switch circuit has a main switch provided in the first current path from the DC power source to the connector, and a sub-switch provided in the second current path from the DC power source to the connector. The switch circuit also has resistors in parallel with the main switch and the sub-switch. In the switch circuit, the resistance value when the sub-switch is on is greater than the resistance value when the main switch is on. The switch device acquires the voltage at the connection nodes downstream of the main switch and the sub-switch when the main switch is off and the sub-switch is on. The switch circuit then determines, based on the acquired voltage, whether the current flowing through the main switch when the main switch is switched on is below a threshold. This threshold is a voltage that is less than the DC power supply voltage and exceeds the voltage obtained by the resistor and load dividing the DC power supply voltage. If the acquired voltage is above this threshold, the switch device maintains the main switch off. International Publication No. 2021/117492 Figure 1 is a block diagram showing the configuration according to the first embodiment.Figure 2 shows an example of a signal waveform related to the control of the first embodiment.Figure 3 is a block diagram showing the configuration according to the second embodiment.Figure 4 is a graph showing the relationship between the voltage applied to the load and the duty cycle of the PWM signal input to the semiconductor switch.Figure 5 is a block diagram showing the configuration according to the third embodiment.Figure 6 shows an example of a signal waveform related to control in the third embodiment.Figure 7 shows an example of a signal waveform related to control in the third embodiment.Figure 8 is a block diagram showing the configuration according to the fourth embodiment. The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below. Furthermore, in the drawings, the same or corresponding elements are denoted by the same reference numerals as appropriate. [First Embodiment] Figure 1 is a block diagram showing the configuration of a protective device 1A according to a first embodiment of the present invention. The power supply 2 is, for example, a storage battery mounted in a vehicle. The power supplied by the power supply 2 is supplied from the positive terminal of the power supply 2 to the load 3 via a semiconductor switch 4. The semiconductor switch 4 is a switch including, for example, an FET (Field Effect Transistor), and is connected to the positive terminal of the power supply 2. The semiconductor switch 4 is turned on or off by a signal output from the protective device 1A, and controls the output and interruption of the power supplied from the power supply 2. The load 3 is an electrical component in the vehicle that is driven by the power supplied from the semiconductor switch 4. The load 3 is connected to the negative terminal of the power supply 2 by a ground line G. The protective device 1A is a device that prevents short circuits and is mounted in a vehicle. The protective device 1A comprises a control unit 10, a first voltage measuring unit 11A, and a second voltage measuring unit 11B. The first voltage measuring unit 11A has a voltage measuring circuit and is connected between the semiconductor switch 4 and the power supply 2, and to the ground line G. The first voltage measuring unit 11A measures the voltage value between the semiconductor switch 4 and the power supply 2. The voltage value measured by the first voltage measuring unit 11A is output to the control unit 10. The second voltage measuring unit 11B has a voltage measuring circuit and is connected between the semiconductor switch 4 and the load 3, and to the ground line G. The second voltage measuring unit 11B measures the voltage value between the semiconductor switch 4 and the load 3. The voltage value measured by the second voltage measuring unit 11B is output to the control unit 10. The control unit 10 includes a calculation unit 101 and a switch control unit 102 to implement a function to prevent short circuits. The calculation unit 101 acquires the voltage values measured by the first voltage measurement unit 11A and the voltage values measured by the second voltage measurement unit 11B. Based on the acquired voltage values and the resistance value of the semiconductor switch 4 when it is turned on, the calculation unit 101 calculates the resistance value of the load 3. The calculation unit 101 also acquires an operation signal from an ECU (Electronic Control