Denso Corporation

Nippondenso Co., Ltd.

Anden Co., Ltd.

Junji Hayakawa

Hiroyuki Ban

Junichi Nagata

Tomohisa Yamamoto

Takaaki Kawai

Takeshi Miki

Akinobu Umemura

Norio Kitao

Fukuo Ishikawa

Takeshi Ishikawa

Tetsuya Katayama

Shigekazu Sugimoto

Masami Kataoka

Yoshichika Abe

Hirokazu Ito

Jyunichi Nagata

Tukasa Miyake

Masashi Masuda

A capacitive physical quantity detection device comprising a plurality of capacitive physical quantity sensors, wherein each sensor includes: a detection unit having a movable electrode and a fixed electrode; a C-V conversion circuit having a differential amplifier circuit, wherein a first input terminal of the differential amplifier circuit is coupled with the movable electrode, a second input terminal of the differential amplifier circuit inputs a reference voltage and a self-diagnosis voltage therein during a normal operation and a self-diagnosis operation, respectively, and the C-V conversion circuit outputs an output voltage; and a signal processing circuit that performs a signal processing of the output voltage, wherein the reference voltage in each sensor is substantially the same, the plurality of sensors performs the self-diagnosis operation simultaneously, and the self-diagnosis voltage in one of the sensors is a first self-diagnosis voltage that is different in magnitude from the self-diagnosis voltage in another one of the sensors.

Capacitive physical quantity detection device

A capacitive physical quantity sensor includes a sensor element and a detecting element. The sensor element includes first and second fixed electrodes facing a movable electrode. A first voltage is applied to the first fixed electrode and a second voltage is applied to the second fixed electrode. The detecting circuit includes a capacitance-voltage conversion circuit, in which an operational amplifier, a capacitor and a switch including a P-channel MOS transistor and a N-channel MOS transistor are disposed. The transistors have a back gate potential, which is approximately equal to an average voltage of the first voltage and the second voltage.

Capacitive physical quantity sensor

A sensor apparatus includes a sensor circuit and a nonlinear signal processing circuit. The sensor circuit detects a physical quantity and outputs a detection signal indicative of the detected physical quantity. The signal processing circuit includes a logarithmic converter, an analog-to-digital converter, and an antilogarithmic converter. The logarithmic converter produces a logarithm signal corresponding to a logarithm of the detection signal. The analog-to-digital converter digitalizes the logarithm signal. The antilogarithmic converter produces an antilogarithmic signal corresponding to an antilogarithm of the digitalized logarithm signal.

Sensor apparatus

A filter circuit includes a voltage amplifier, a resistor, a capacitor, and an analog switch connected between the voltage amplifier and the capacitor. When the voltage amplifier is turned on, the analog switch is opened so that the capacitor is disconnected from the voltage amplifier. Thus, an output voltage of the voltage amplifier sharply increases to its steady state value, as soon as the voltage amplifier is turned on. When the output voltage of the voltage amplifier is fully stabilized, the analog switch is closed so that the capacitor is connected to the voltage amplifier. During the period of time when the analog switch is closed, the filter circuit is configured as an imperfect integrator circuit with filter characteristics that depend on a capacitance of the capacitor and a resistance of the resistor.

Filter circuit

A substrate forming a sensor element is connected to a non-inverting input terminal of an operational amplifier, and a common voltage is applied thereto from a reference voltage supply circuit to fix them to the same potential. Thus, the impedances of the non-inverting input terminal and of the inverting input terminal of the operational amplifier are matched with respect to the power source. Therefore, noise superposed on a power source line can be greatly decreased by noise-removing characteristics determined by CMRR characteristics of the operational amplifier. As a result, a capacitive-type acceleration sensor exhibits sensor characteristics of frequency noise suppressing effect.

Capacitive-type physical quantity sensor

An output signal cutting-off circuit includes a first switching element, a driving circuit and a voltage-drop-signal generating circuit. When a voltage to be monitored becomes lower than a threshold voltage, a voltage-drop-signal is generated and supplied to the driving circuit. The driving circuit turns on the first switching element based on the voltage-drop-signal to thereby cut off an output signal voltage by bringing it to a ground potential. When the voltage-drop-signal disappears, the first switching element is turned off to bring the output signal to a normal state. Preferably, a second switching element for charging a capacitor and a third switching element for discharging the capacitor are used in the driving circuit. In this case, the first switching element is turned on or off based on a voltage of the capacitor.

Circuit for cutting-off output signal

In a capacitive physical quantity sensor, a C-V converter converts a variation in a capacitance between a movable electrode and a fixed electrode into a voltage to output the converted voltage in a first operating mode. The C-V converter also outputs a constant voltage in a second operating mode. An amplifier amplifies the converted voltage to output a first voltage, and amplifies the constant voltage to output a second voltage. A first sample and hold circuit operates in the first operating mode to sample and hold the first voltage. A second sample and hold circuit operates in the second operating mode to sample and hold the second voltage. A first differential amplifier obtains a difference voltage between the first voltage held by the first sample and hold circuit and the second voltage held by the second sample and hold circuit.

In a power supply apparatus, a switching circuit selectively applies one of an input voltage of a power converting circuit and an output voltage of the power converting circuit to a voltage reducing power supply circuit. When the input voltage is applied to the power converting circuit, the switching circuit selects this input voltage, so that the output voltage of the voltage reducing power supply circuit can quickly rise. Thereafter, when the output voltage of the power converting circuit exceeds this output voltage, the switching circuit selects the output voltage of the power converting circuit. As a result, a difference between the input voltage and the output voltage of the voltage reducing power supply circuit is decreased. Thus, a power loss is lowered and noise produced in the power converting circuit is suppressed.

Electric power supply apparatus having input switching circuit

An operational amplifier comprises a differential amplifying circuit and an output circuit. The differential amplifying circuit comprises a pair of input transistors having control terminals connected to an inverting input terminal and a non-inverting input terminal, respectively. The output circuit is connected to the differential amplifying circuit for amplifying an output signal of the differential amplifying circuit and generating an amplified output from its output terminal. In this operational amplifier, the input transistors are bipolar transistors and other transistors are MOS transistors.

Operational amplifier

A charge pump circuit comprises a plurality of capacitors arranged to charge and discharge for generating a charged-up voltage. An oscillation circuit generates a clock signal to be applied to the plurality of capacitors to alternately charge and discharge these charge-up capacitors. A monitoring circuit detects electrical potentials on at least two of the charge-up capacitors and controls the clock signal. An oscillating condition of the oscillation circuit based on the electrical potentials on the at least two of the charge-up capacitors.

Charge pump circuit

A current-measuring circuit is provided which is designed to measure the current flowing through an electric load and a switching transistor. The current-measuring circuit includes a current-measuring device. The current-measuring device includes a current-measuring transistor and a voltage control circuit. The current-measuring transistor is disposed in parallel to the switching transistor and allows the current to flow therethrough that is proportional to the current flowing through the electric load and the switching transistor and that is used to measure the current flowing through the switching transistor and the electric load. The voltage control circuit controls a potential difference across the current-measuring transistor so as to match a potential difference across the switching transistor, thereby achieving the proportion of the current flowing through the current-measuring transistor to the current flowing through the switching transistor and the electric load.

Structure of current measuring circuit

An output MOS transistor and a current-detecting MOS transistor are connected commonly at their drains and gates. A gate voltage is fed to the gates of these transistors via signal lines. When the voltage of an output terminal is increased in response to excessive load current, a current-mirror circuit consisting of first and second transistors pulls in current from the signal line to reduce the gate voltage. Thus, the output current of output MOS transistor is limited within a predetermined level. Furthermore, a diode, provided in the signal line, produces a voltage drop equivalent to the base-emitter voltage of first transistor. By the function of this diode, the gate-source voltage of output MOS transistor is equalized with the gate-source voltage of current-detecting MOS transistor. As a result, the same operating point can be set for the output transistor and the current-detecting transistor.

Load actuation circuit

An analog switching circuit comprises an insulated-gate field-effect transistor (Q20) having two n-type input-side and outpu-side semiconductor regions (201, 202) and a p-type semiconductor substrate region 203, for controlling conductiveness between an input terminal (IN) and an output terminal (OUT) based on a gate potential. A surge pulse detecting circuit (1020), responsive to an electric potential (Vi) of the input terminal (IN), produces a detection signal of a surge pulse equivalent to a forward bias of a PN junction formed between the semiconductor substrate region (203) and the input-side semiconductor region (201). A substrate potential setting circuit (1010) varies an electric potential of the semiconductor substrate region (203) in response to the electric potential (Vi) of the input terminal (IN) when aby detection signal is produced. Furthermore, a gate potential control circuit (1030) varies the gate potential of the insulated-gate field-effect transistor (Q20) in the same direction as the electric potential of the semiconductor substrate region (203) when the detection signal is produced.

Analog switching circuit

A constant-voltage power supply circuit includes a first output device provided in a first power feed line from a dc power supply to a first load. The first output device includes a first voltage control element for controlling an output voltage to the first load. A first control device operates for detecting the output voltage from the first output device to the first load, and controlling the first voltage control element to equalize the output voltage from the first output device with a first predetermined constant voltage. A second power feed line is connected to the first power feed line for feeding electric power to a second load. A second output device provided in the second power feed line includes a second voltage control element for controlling an output voltage to the second load. A second control device operates for detecting the output voltage from the second output device to the second load, and controlling the second voltage control element to equalize the output voltage from the second output device with a second predetermined constant voltage.

Constant-voltage power supply circuit

A first switching element opens or closes a power supply route of an inductive load in accordance with a first driving signal. A clamping element prevents a voltage ot the power supply route from exceeding a first clamp voltage when the power supply route is opened. A second switching element opens or closes the current flow route, provided in parallel with the power supply route, in response to a second driving signal. A rectifying means is responsive to the second switching element to change the clamp voltage to a second clamp voltage when the first switching element is turned off. The second switching element is constituted by a MOSFET. A charging element charges a capacitor of MOSFET.

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Okazaki, Japan

Junji Hayakawa