Abstract: A power supply switching apparatus includes a first switching unit supplying power from a first conductive path to a first output path when the voltage of the first conductive path is greater than the voltage of a second conductive path, and supplies power from the second conductive path to the first output path. A second switching unit 80 supplies power from a fourth conductive path to a second output path when the voltage of a fourth conductive path is greater than the voltage of a third conductive path, and supplies power from the third conductive path to the second output path. An element unit allows a current to flow from the second conductive path to the third conductive path when the voltage of the third conductive path is smaller than the voltage of the second conductive path, and otherwise blocks a current.

Abstract: A power supply switching apparatus includes a first switching unit supplying power from a first conductive path to a first output path when the voltage of the first conductive path is greater than the voltage of a second conductive path, and supplies power from the second conductive path to the first output path. A second switching unit 80 supplies power from a fourth conductive path to a second output path when the voltage of a fourth conductive path is greater than the voltage of a third conductive path, and supplies power from the third conductive path to the second output path. An element unit allows a current to flow from the second conductive path to the third conductive path when the voltage of the third conductive path is smaller than the voltage of the second conductive path, and otherwise blocks a current.

Abstract: A power-supply control device that includes a transistor that is interposed between a power source and a load; a control circuit to which a voltage from the power source is applied, the voltage being applied across a high-voltage side input terminal and a low-voltage side input terminal of the control circuit, and that is configured to turn the transistor on or off based on an operating signal for the load that is applied from an external device, and controlling supply of power to the load; a voltage detector that is configured to detect a value of the voltage applied to the control circuit by the power source, and is configured to determine whether or not the applied voltage value detected is lower than a predetermined voltage value; and a negative voltage output circuit.

Abstract: A power-supply control device that includes a transistor that is interposed between a power source and a load; a control circuit to which a voltage from the power source is applied, the voltage being applied across a high-voltage side input terminal and a low-voltage side input terminal of the control circuit, and that is configured to turn the transistor on or off based on an operating signal for the load that is applied from an external device, and controlling supply of power to the load; a voltage detector that is configured to detect a value of the voltage applied to the control circuit by the power source, and is configured to determine whether or not the applied voltage value detected is lower than a predetermined voltage value; and a negative voltage output circuit.

Abstract: An electric power supply control circuit includes a bypass circuit connected in parallel with a semiconductor switch. Upon a control circuit being in an inactive state while a load being in a non-electrifying state or in a standby state, the bypass circuit connects a power source to the load. The bypass circuit includes a electrifying decision circuit that generates an activation signal for activating the control circuit in accordance with the load being put in an operation state. The electrifying decision circuit supplies the activation signal to the control circuit so as to turn on the semiconductor switch and allow electric power supply to the load through an electrifying line.

Abstract: A first current corresponding to the drain-to-source voltage of a power MOSFET can pass through an FET; and a second current corresponding to a constant voltage can pass through an FET; a third current corresponding to the difference determined by subtracting the first current from the second current can pass into threshold setting resistors from the connecting point between FETs. Consequently, divided voltages at the connecting points between the threshold setting resistors varies directly with a voltage corresponding to the difference determined by subtracting the drain-to-source voltage of the power MOSFET from the constant voltage.

Abstract: An inrush current higher than a second anomaly threshold current ILfc passes through a power MOSFET 14, when a control signal S1 of low level is applied to a gate driver 28 so that the power MOSFET 14 and the like turn to a conductive state. A first forcing shutoff operation for the power MOSFET 14 is then prevented, because a first anomaly threshold current ILoc is set to an initial level higher than the inrush current. A fuse time counter 73 starts a count-up operation in response to the occurrence of the inrush current, and continues to increment its count value until a load current IL falls below the second anomaly threshold current ILfc. According to the count value, the first anomaly threshold current ILoc is decreased stepwise with time.

Abstract: A gate driver 28 performs a normal charging operation for a power MOSFET 14 by driving a charge pump 90 solely, when a low-level control signal S1 (ON signal) is received during a normal state. On the other hand, if a low-level control signal S1 (ON signal) is received during a load anomaly state, an urgent charge FET 92, as well as the charge pump 90, is turned on when a load current IL exceeds a second anomaly threshold current ILfc, so that a rapid charging operation is performed.

Abstract: An electric power supply control circuit includes a bypass circuit connected in parallel with a semiconductor switch. Upon a control circuit being in an inactive state while a load being in a non-electrifying state or in a standby state, the bypass circuit connects a power source to the load. The bypass circuit includes a electrifying decision circuit that generates an activation signal for activating the control circuit in accordance with the load being put in an operation state. The electrifying decision circuit supplies the activation signal to the control circuit so as to turn on the semiconductor switch and allow electric power supply to the load through an electrifying line.

Abstract: A voltage-dividing circuit 60, which is formed of serially connected voltage-dividing resistors R1, R2, R3, is disposed between the source terminal S of a power MOSFET 15 and the ground. The divided voltage Va at a connecting point A is applied to one of the input terminals of a comparator 62, while the divided voltage Vb at a connecting point B is applied to one of the input terminals of a comparator 64. The other input terminals of the comparators 62, 64 are connected to the connecting line between an external terminal P4, to which an external resistor 12 is connected, and an FET 30.

Abstract: A second forcing shutoff operation is performed for a power MOSFET 15 and the like, if a time when a load current (or a sense current Is) passing on a power supply line L exceeds a first threshold current Ia reaches a first reference time. On the other hand, the count value of a fuse time counter 71 is cleared to be “zero” so that the shutoff operation for the power MOSFET 15 and the like is not performed, if a normal state, in which neither an overcurrent nor a fuse current has occurred, continues for a second reference time without the first reference time being reached.

Abstract: A second forcing shutoff operation is performed for a power MOSFET 15 and the like, if a time when a load current (or a sense current Is) passing on a power supply line L exceeds a first threshold current Ia reaches a first reference time. On the other hand, the count value of a fuse time counter 71 is cleared to be “zero” so that the shutoff operation for the power MOSFET 15 and the like is not performed, if a normal state, in which neither an overcurrent nor a fuse current has occurred, continues for a second reference time without the first reference time being reached.

Abstract: In a power supply controller 10 having a self-protective mechanism for performing, intermittently or periodically, a forced ON-OFF operation which causes a power MOSFET 15 to perform an automatically restorable primary disconnecting operation and a restoring operation when an overcurrent anomaly or an short-circuiting anomaly is detected, an automatically unrestorable secondary disconnecting operation is performed when the accumulated amount of the duration of the forced ON-OFF operation reaches an accumulation threshold.

Abstract: After an output signal S4 is level-inverted, first and second shorting FETs 55, 56 as a level-inversion inhibiting circuit inhibit level-inversion so that the signal is maintained to the inverted state. Thereafter the inhibition of level-inversion is released, when the signal is subsequently level-inverted at a proper time according to a desired duty ratio of a PWM signal S1. Thus chattering can be prevented and thereby a PWM signal S1 of a stable duty ratio can be generated, even if the level of a reference signal S3 fluctuates due to a noise or the like during vehicle acceleration, for example.

Abstract: A first current corresponding to the drain-to-source voltage of a power MOSFET can pass through an FET; and a second current corresponding to a constant voltage can pass through an FET; a third current corresponding to the difference determined by subtracting the first current from the second current can pass into threshold setting resistors from the connecting point between FETs. Consequently, divided voltages at the connecting points between the threshold setting resistors varies directly with a voltage corresponding to the difference determined by subtracting the drain-to-source voltage of the power MOSFET from the constant voltage.

Abstract: A parallel circuit 27 of a frequency control circuit 11 is provided as an external circuit. Thereby, the charging time t1 depends on the characteristics of the circuit elements, which are provided in the package of a semiconductor device 70 and therefore subject to manufacturing variations of the semiconductor device 70. The discharging time t2 depends on the parallel circuit 27, which is provided external to the semiconductor device 70 and therefore can be selected to have appropriate characteristics after the semiconductor device 70 has been manufactured. The circuit constants of circuits are set so that the discharging time t2 that depends on the device characteristics of the external parallel circuit 27 is longer than the charging time t1 that depends on the device characteristics of the internal circuits of the semiconductor device 70.

Abstract: A voltage-dividing circuit 60, which is formed of serially connected voltage-dividing resistors R1, R2, R3, is disposed between the source terminal S of a power MOSFET 15 and the ground. The divided voltage Va at a connecting point A is applied to one of the input terminals of a comparator 62, while the divided voltage Vb at a connecting point B is applied to one of the input terminals of a comparator 64. The other input terminals of the comparators 62, 64 are connected to the connecting line between an external terminal P4, to which an external resistor 12 is connected, and an FET 30.

Abstract: An inrush current higher than a second anomaly threshold current ILfc passes through a power MOSFET 14, when a control signal S1 of low level is applied to a gate driver 28 so that the power MOSFET 14 and the like turn to a conductive state. A first forcing shutoff operation for the power MOSFET 14 is then prevented, because a first anomaly threshold current ILoc is set to an initial level higher than the inrush current. A fuse time counter 73 starts a count-up operation in response to the occurrence of the inrush current, and continues to increment its count value until a load current IL falls below the second anomaly threshold current ILfc. According to the count value, the first anomaly threshold current ILoc is decreased stepwise with time.

Abstract: After an output signal S4 is level-inverted, first and second shorting FETs 55, 56 as a level-inversion inhibiting circuit inhibit level-inversion so that the signal is maintained to the inverted state. Thereafter the inhibition of level-inversion is released, when the signal is subsequently level-inverted at a proper time according to a desired duty ratio of a PWM signal S1. Thus chattering can be prevented and thereby a PWM signal S1 of a stable duty ratio can be generated, even if the level of a reference signal S3 fluctuates due to a noise or the like during vehicle acceleration, for example.

Abstract: A power supply controller including a MOSFET between a power source and a load, a ground terminal, a gate driving circuit structured to control a gate potential of the MOSFET to turn on power and control the gate potential of the MOSFET to turn off power based on a ground terminal potential, and a turn-off circuit structured to switch the MOSFET into a turn-off state regardless of control by the gate driving circuit when the ground terminal potential is at a higher value than a source potential of the MOSFET.