Denso Corporation

Hirokazu Itakura

Hiroyuki Ban

Junichi Nagata

Hiroshi Imai

Kiyoshi Yamamoto

Hirofumi Abe

Shoichi Okuda

Masahiro Kitagawa

Kingo Ota

Shinichi Maeda

Hiroyuki Kawabata

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

A semiconductor device includes an output power device, which generates an electrical noise, and an on-chip circuit, to which the noise is transmitted. The output power device is surrounded by two isolating regions. The area between the two isolating regions is electrically connected to a field ground area by a first wiring line. The field ground area is electrically connected to a point of contact, which has ground potential. The area between the outer isolating region of the two isolating regions and another isolating region around the on-chip circuit is also electrically connected to the field ground area by a second wiring line. The first and second wiring lines are separated from each other. The electrical noise is transmitted to the field ground area and released to the point of contact. Therefore, the noise is attenuated and the transmission of the noise to the on-chip circuit is suppressed.

Semiconductor device having isolating region for suppressing electrical noise

A semiconductor device has plural output circuits. Each of the plural output circuits has a semiconductor switching element and a heat protection circuit including a diode. When the heat protection circuit in a predetermined output circuit detects that heat emitted from the semiconductor switching element in the predetermined output circuit, the heat protection circuit turns off the semiconductor switching element in the predetermined output circuit. The plural output circuits are thermally isolated from each other by a trench and an insulation film. The trench and the insulation film prevent the heat from being transmitted from the predetermined output circuit to an adjacent output circuit. Therefore, even if the heat, by which the semiconductor switching element in the predetermined output circuit is turned off, is generated at the predetermined output circuit, the semiconductor switching element in the adjacent output circuit is not turned off by the heat.

Semiconductor device having heat protection circuits

A constant voltage circuit robust to the input voltage lowering is disclosed. The invention is applied to a constant voltage circuit fed with an input voltage through first and second power conductors for transferring the input voltage to a load as an output voltage through an output transistor. An inventive constant voltage circuit is provided with a substitute circuit, responsive to a detection of the lowing of the input voltage to a predetermined voltage, for providing a substitute output path that is connected in parallel with the output transistor. Doing this minimize the degree of lowering of the second voltage due to the lowering of said first voltage. The output transistor may be nay of NPN and PNP transistors and P-type and N-type MOS FETs.

Constant voltage circuit with a substitute circuit in case of input voltage lowering

A load actuation circuit is provided which is capable of placing a limit on load current to a load below a predetermined value with high accuracy. In the load actuation circuit, a series circuit comprising a detection transistor and an NPN transistor is connected in parallel with an output transistor for supplying a load current to the load, and a diode is placed between the gates of the output transistor and the detection transistor for producing a voltage drop equal to a voltage drop in the NPN transistor. In addition, a constant-current circuit for supplying a constant current is connected to the gate of the detection transistor, and another transistor for constituting a current mirror circuit together with the NPN transistor is connected to the gate of the output transistor. This circuit arrangement prevents a limit value of the load current from fluctuating due to the non-uniformity of circuit elements or the like, thus achieving high-accuracy load-current limitation.

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Hazu-gun, Japan

Hirokazu Itakura