Denso Corporation

Kingo Ota

Shoichi Okuda

Hirofumi Abe

Hiroyuki Ban

Hirokazu Itakura

A switching circuit of the present invention can be advantageously used in an electronic control unit mounted on an automotive vehicle. The switching circuit is constituted by a pair of P-channel MOS-FETs connected in series between an input terminal and an output terminal. Sources of both MOS-FETs are connected to a common source junction and gates thereof are connected to a common gate junction. A Zener diode connected between the common source junction and the common gate junction is used for protecting the MOS-FETs. A resistor is connected in parallel to the Zener diode to bring the switching circuit to a non-conductive state when the gate voltage at the common gate junction becomes indefinite and a high voltage is supplied to the output terminal. In place of the resistor, an additional P-channel MOS-FET may be used in the switching circuit to bring the switching circuit to the non-conductive state when the voltage at the common gate junction becomes indefinite.

Switching circuit having two MOS-FETS

A semiconductor device for driving a load includes a first semiconductor switching element interposed between a power supply terminal and a load, a second semiconductor switching element interposed between the load and a ground terminal, a high-side driver, a low-side driver, and a voltage regulator. The voltage regulator reduces a voltage applied to a control terminal of the second switching element, when a voltage of a load terminal of the second switching element is lower than a predetermined voltage. Then, a voltage applied between the load terminal and the ground terminal of the second switching element increases, and accordingly a voltage applied between the power supply terminal and the load terminal of the first switching element decreases.

Semiconductor device for driving a load

In a voltage booster, a voltage detection circuit detects a battery voltage as an input voltage. If the input voltage is lower than a threshold level, an oscillation circuit outputs a gate signal having a relatively high frequency to increase the driving performance of a driving circuit. If the input voltage is higher than the threshold level, the frequency of the gate signal is lowered so as to prevent the driving performance of the driving circuit from rising to an excessively high value. As a result, a predetermined boosted voltage can be obtained regardless of variations in input voltage without using a filter for eliminating noise.

Voltage booster having noise reducing structure

In a current mirror circuit, a compensation resistor having a positive temperature coefficient is connected between the source of a MOS transistor and a power supply line. When the temperature rises, a current output by the constant current circuit and a current flowing through the drain of the MOS transistor decrease. Since the resistance of the compensation resistor increases, however, a voltage between the gate and source of another MOS transistor can be prevented from declining due to the decrease in the drain current so that an electric potential at the gate of a further MOS transistor, hence, a main current, can be prevented from fluctuating. In addition, a constant current output circuit is configured to shunt a feedback control current thereby to adjust an output current of each channel.

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Nukata-gun, Japan

Kingo Ota