Yazaki Corporation

Shunzou Ohshima

Hiroko Aono

Teruki Yamauchi

A load control apparatus is provided in which a circuit of detecting an overcurrent can be correctly operated even if a first capacitor (C) for noise measures is disposed. Since a second capacitor (C) is provided between a gate and a drain of an FET (T), when the voltage (V) of a point (P) decreases, a part of the gate current of the FET (T) bypasses the FET (T) and flows to the capacitor (C), and the amount of charge supplied to the gate of the FET (T) decreases. Therefore, the increase of the drain current of the FET (T) can be suppressed and a sudden change of the voltage (V) can be prevented. As a result, the voltage (V) can be prevented from decreasing to such a degree that the comparator (CMP) cannot operate, and the comparator (CMP) can be prevented from malfunctioning.

Load control apparatus

A resistor is provided between an exciting coil and the ground, and a diode is provided between a point pand a point p. An exciting current flows on the ground side via the diode until a relay contact is closed immediately after a switch is turned on. Thus, a voltage applied to the exciting coil becomes almost same as a power supply voltage, the relay contact can be surely closed. Further, when the relay contact is closed, since the exciting current flows on the ground side via the resistor the voltage applied to the exiting coil reduces and hence the heat generation amount can be reduced.

Heat generation inhibiting circuit for exciting coil in relay

An overcurrent protection apparatus for a load circuit can detect an overcurrent with a high accuracy without being influenced by a deviation &#xb1;&#x394;Ron of the on-resistance of a semiconductor element (T). Supposing that a ratio (R/R) between a resistor Rand a resistor Ris an amplification factor m, a determination voltage generated by resistors R, Ris Vand the average value of the on-resistance of a MOSFET (T) is Ron, the overcurrent protection apparatus for a load circuit controls either a current Iflowing through the resistor Ror a current IRflowing through the resister Rso that the output signal of a compactor CMPis inverted when a current having a value of (V/m/Ron) flows into the MOSFET (T).

Overcurrent protection apparatus for load circuit

To provide a power supply device which can reduce energy loss caused due to the forward-direction voltage of a flywheel diode. In a load circuit for subjecting an electronic switch Tprovided between a DC power supply VB and a motor Mto the PWM control to thereby drive the motor M, a MOSFET (T) is provided in parallel to the motor M. A parasitic diode Dp of the MOSFET (T) is provided in a manner that its forward direction is in opposite to the flowing direction of a load current ID. The MOSFET (T) is turned on during a part of a period during which the electronic switch Tis placed in an off state to thereby flow a circulation current flowing through the motor Minto the MOSFET (T). Thus, the energy loss can be remarkably reduced as compared with the case of using the flywheel diode.

Power supply device

A motor load control apparatus capable of suppressing heat generation of an electronic switch and suppressing occurrence of noise associated with rotation of a fan and vibration of the fan is provided. A switch section () in which a first electronic switch (T) and a second electronic switch (T) are connected in parallel is provided, and the first electronic switch (T) is driven by a PWM signal with a predetermined duty ratio and a predetermined frequency and the second electronic switch (T) is driven in a state of delaying the PWM signal by which the first electronic switch (T) is driven by a predetermined time. Consequently, as compared with the case of one electronic switch, a heating value of each of the electronic switches can be reduced and radiation measures of the whole apparatus can be reduced. Further, noise or vibration occurring by PWM control can be reduced by changing delay time at random.

Motor load control apparatus

A voltage (V&#x2212;V) between a predetermined point Pon a copper foil patternconnected to a source of a switching FET (T) and a drain Pof the FET (T) is input into an input terminal of a comparator CMPas an overcurrent determination voltage for comparison with a reference voltage V. As this occurs, since there exists a voltage that is to be dropped by a resistor Rp possessed by the copper foil, the voltage (V&#x2212;V) becomes larger than an inter-terminal voltage VDS of the FET (T), and as a result, the effect imposed by an offset voltage Vpossessed by the comparator CMPcan be reduced.

Overcurrent detecting apparatus

A protective device for a load circuit that instantly cuts off the load circuit when a dead short-circuit has occurred in the load circuit. The protective device includes a first detection circuit which detects a counter-electromotive force Einduced in a common wiring line for connecting a plurality of load circuits and a power source, and a second detection circuit which detects a counter-electromotive force Einduced at part of a load connection wiring line for connecting the individual load circuits. The load circuit is cut off when the first detection circuit detects that the counter-electromotive force Einduced in the common wiring line has exceeded a predetermined value, and the second detection circuit detects that the counter-electromotive force Ethat has the same direction as that of Ehas been generated in the load connection wiring line.

Protective device for load circuit

An overcurrent protection apparatus which, when a layer short or a dead short occurs in a load circuit, interrupts the circuit in accordance with respective situations, whereby the load circuit is protected is provided. The apparatus includes a first overcurrent detecting section for detecting a counter electromotive force generated in a power supply wiring, and a second overcurrent detecting section, disposed in each of the plural load circuits, for detecting that a load current ID becomes an overcurrent. The apparatus includes a delaying section for outputting a delay signal at a first delay time when an overcurrent is detected by the second overcurrent detecting section, and for outputting the delay signal at a second delay time which is shorter than the first delay time when an overcurrent is detected by both of the first overcurrent detecting section and the second overcurrent detecting section. According to the configuration, in the case of the occurrence of a layer short, the load circuit can be interrupted at the first delay time, and, in the case of the occurrence of a dead short, the load circuit can be interrupted at the second delay time.

Overcurrent protection apparatus

To provide an overcurrent protection apparatus for a load circuit which can detect an overcurrent accurately without being influenced by the offset voltage Voff of an amplifier (AMP). When the amplifier (AMP) has the offset voltage Voff which is a positive value (Voff&#x3e;0), a current obtained by subtracting a current Ia from a current Iflowing through a resistor Rby conducting a current source IA is flown into a resistor R. In contrast, when the amplifier (AMP) has the offset voltage Voff which is a negative value (Voff&#x3c;0), a voltage drop is generated at a resistor Rby conducting a current source IB to thereby control so that a voltage Vds becomes same as the voltage generated at the resistor R. Thus, since a voltage Vgenerated at the resistor Rbecomes a voltage from which the influence of the offset voltage Voff is eliminated, it is possible to determine an overcurrent accurately by eliminating the influence of the offset voltage Voff.

A booster device for increasing a voltage at a voltage supply point of a power supply circuit for supplying a driving voltage to an electronic control circuit is provided. The power supply circuit includes a series-connected circuit having a diode, a resistor, and a capacitor which is connected to a DC power supply. One end of the capacitor is connected to a ground and a connection point of the resistor and the capacitor serves as the voltage supply point. The booster device includes a clamp circuit, an oscillation circuit, and a booster circuit that increase a voltage output from the DC power supply. When the voltage at the voltage supply point falls below a predetermined threshold voltage, the booster device supplies the increased voltage at the voltage supply point.

Booster device

In an electric supply device of the present invention, since a semiconductor element Tis interrupted before a drain voltage Vof the semiconductor element Tis lower than an in-phase input minimum voltage, a load circuit can be assuredly protected. Further, assuming that a first decided voltage is L-Vand a second decided voltage V, when the voltage Vbecomes 'V&#x3c;L-V', a retry operation is carried out. When the number of times of 'V&#x3c;L-V' reaches Ntimes, or when the number of times of &#x201c;L-V&#x3c;V&#x3c;V&#x201d; reaches Ntimes, an interrupted state of the semiconductor element Tis held to protect the load circuit. Further, when the voltage Vsuddenly drops due to an imperfect contact of a connector, a minimum value of the voltage Vis not a stable value and the interrupted state of the semiconductor Tis not held.

Electric power supply device

To provide an overcurrent protection apparatus which can surely protect a load circuit from an overcurrent with a simple configuration. Supposing that the temperature increasing amount of a semiconductor element caused when the semiconductor element is turned on is &#x394;Tch, the on-resistance value of the semiconductor element (T) is Ron, the thermal resistance value of the semiconductor element (T) is Rth_f, the temperature increasing amount of a connecting wiring is &#x394;Tw when a current flows into the connecting wiring (WL), the resistance value per unit length of the connecting wiring is Rw, and the thermal resistance value per unit length of the connecting wiring is Rth_w, &#x394;Tch is obtained based on an expression of &#x394;TW/&#x394;Tch=Rth_w/Rth_f*Rw/Ron with respect to the temperature increasing amount &#x394;Tw not exceeding a difference between the upper limit of the permissible temperature of the connecting wiring (WL) and the upper limit of an operational peripheral temperature, then a voltage Vds is obtained based on an expression of &#x394;Tch=Rth_f*Vds/Ron with respect to the &#x394;Tch thus obtained, and the voltage Vds thus obtained is set as a determination voltage.

Disclosed is an overcurrent detection device for detecting an overcurrent in a load circuit which is arranged to control the driving and the stopping of a loadby a semiconductor switch (FET) provided between a battery VB and the load. An added voltage (V&#x2212;V) is generated which is obtained by adding a voltage (V&#x2212;V) generated across the both ends of the semiconductor switch (FET) to a voltage (V&#x2212;V) which is generated at the time of current change due to the inductance Lp of a copper foil wiring patternfor coupling the semiconductor switch (FET) and the load. A comparator CMPfor comparing the added voltage with an overcurrent determination voltage (V&#x2212;V) set in advance is provided. When the comparator CMPdetects that the added voltage exceeds the overcurrent determination voltage, it is determined that an overcurrent is generated.

Overcurrent detection device

A control apparatus includes a semiconductor switch that is arranged between a DC power supply and a load to control a turning ON/OFF operation of the load, a counter electromotive force judging unit that determines whether a counter electromotive force produced on a first wiring line is greater than a threshold voltage, the first wiring line connecting the semiconductor switch to the DC power supply, and a control unit that controls the semiconductor switch so as to be turned OFF when the counter electromotive force judging unit determines that the counter electromotive force is greater than the threshold voltage.

Control apparatus of semiconductor switch

An ON failure detecting apparatus detects an ON failure of an FET Tof a power supply circuit which includes the FET Tdisposed between a battery E and a load RL, and controls driving and stopping of the load RL. The ON failure detecting apparatus includes a driver circuitthat supplies a driving voltage VD for switching ON and OFF of the FET Tto a gate of the FET T, a gate resistor Rg that is provided between the driver circuitand a gate of the FET T, and an ON failure determining circuitthat detects whether a voltage drop in the gate resistor Rg exceeds a predetermined value, and determines that an ON failure occurs in the FET T, when the voltage drop in the gate resistor Rg exceeds the predetermined value.

Growing community of inventors

Kosai, Japan

Shunzou Ohshima