Abstract: A water meter that requires neither a smoothing capacitor of large capacitance nor a high frequency reference clock is offered. A rotation detection unit is formed to include a first coil, a first capacitor, a charging transistor, a power supply line, an activation transistor, an output buffer circuit, a DA converter, a comparator and a counter. A first LC resonant circuit is provided with the activation transistor connected in series with the first coil, the first capacitor connected in parallel with the first coil and the charging transistor for charging the first capacitor. The first LC resonant circuit is activated by turning on the activation transistor after the first capacitor is charged by turning on the charging transistor.

Abstract: There is offered a water meter that requires no coil so that its cost is reduced. The water meter is formed to include an impeller, a rotation reduction unit, a first circular plate, a second circular plate, a rotation detection unit and an arithmetic unit. The rotation detection unit forms first, second and third combination capacitors with a switching circuit. The rotation detection unit detects changes in capacitances of the first, second and third combination capacitors associated with a rotation of the first circular plate. The arithmetic unit is configured so as to electrically detect the rotation angle ? of the first circular plate based on the changes in the capacitances.

Abstract: There is offered a water meter that requires no coil so that its cost is reduced. The water meter is formed to include an impeller, a rotation reduction unit, a first circular plate, a second circular plate, a rotation detection unit and an arithmetic unit. The rotation detection unit forms first, second and third combination capacitors with a switching circuit. The rotation detection unit detects changes in capacitances of the first, second and third combination capacitors associated with a rotation of the first circular plate. The arithmetic unit is configured so as to electrically detect the rotation angle ? of the first circular plate based on the changes in the capacitances.

Abstract: A water meter that requires neither a smoothing capacitor of large capacitance nor a high frequency reference clock is offered. A rotation detection unit is formed to include a first coil, a first capacitor, a charging transistor, a power supply line, an activation transistor, an output buffer circuit, a DA converter, a comparator and a counter. A first LC resonant circuit is provided with the activation transistor connected in series with the first coil, the first capacitor connected in parallel with the first coil and the charging transistor for charging the first capacitor. The first LC resonant circuit is activated by turning on the activation transistor after the first capacitor is charged by turning on the charging transistor.

Abstract: An LED driving circuit includes: a current generating circuit configured to generate a drive current corresponding to a voltage level of a drive voltage applied to anodes of the first to fourth LEDs so as to alternately drive the first and second LEDs and the third and fourth LEDs; a first drive control circuit connected to cathodes of the first and third LEDs, and configured to drive the first or third LED with the drive current in response to a first control signal for controlling driving of the first or third LED; and a second drive control circuit connected to cathodes of the second and fourth LEDs, and configured to drive the second or fourth LED with the drive current in response to a second control signal for controlling driving of the second or fourth LED.

Abstract: A battery-voltage detection circuit comprising: a first-capacitor; an operational-amplifier; a second-capacitor; a voltage-application-circuit to sequentially apply one and the other-battery-terminal-voltages to the other-first-capacitor-end; a discharge circuit to allow the second-capacitor to discharge before the other-battery-terminal-voltage is applied to the other-first-capacitor-end; a constant current circuit to output a constant-current causing predetermined-speed-discharge of electric charge accumulated in the second-capacitor in response to a discharge-start-signal input after voltage is applied to the other-first-capacitor-end; a comparator; and a measurement-circuit to measure a time-period from a time when the discharge-start-signal is input until a time when an comparator-output-signal changes to one logic level as a time-period corresponding to a battery-voltage, at least one of the operational-amplifier and the comparator being provided with an offset so that the comparator-output-signal chang

Abstract: A voltage detecting circuit comprises: an operational amplifier whose one input terminal is applied with a first reference voltage; a first capacitor whose one end is connected to the other input terminal of the operational amplifier; a second capacitor whose one end is connected to an output terminal of the operational amplifier, and whose other end is connected to the other input terminal of the operational amplifier; a switch circuit for applying a first voltage and a second voltage sequentially to the other end of the first capacitor; and a discharging circuit for discharging the second capacitor before the second voltage is applied to the other end of the first capacitor, a difference between the first voltage and the second voltage being detected based on a voltage at the output terminal of the operational amplifier after the second voltage is applied to the other end of the first capacitor.

Abstract: A battery voltage detecting circuit includes: a first capacitor having one end connected to one input terminal of an operational amplifier; a second capacitor having one end connected to an output terminal of the operational amplifier and the other end connected to the one input terminal of the operational amplifier; a third capacitor having one end connected to the other input terminal of the operational amplifier; a fourth capacitor having one end applied with a reference voltage and the other end connected to the other input terminal of the operational amplifier; and a switching circuit configured to electrically connect the one input terminal of the operational amplifier to the one end of the first capacitor after the transient current has stopped flowing.

Abstract: A battery-voltage detection circuit comprising: a first-capacitor; an operational-amplifier; a second-capacitor; a voltage-application-circuit to sequentially apply one and the other-battery-terminal-voltages to the other-first-capacitor-end; a discharge circuit to allow the second-capacitor to discharge before the other-battery-terminal-voltage is applied to the other-first-capacitor-end; a constant current circuit to output a constant-current causing predetermined-speed-discharge of electric charge accumulated in the second-capacitor in response to a discharge-start-signal input after voltage is applied to the other-first-capacitor-end; a comparator; and a measurement-circuit to measure a time-period from a time when the discharge-start-signal is input until a time when an comparator-output-signal changes to one logic level as a time-period corresponding to a battery-voltage, at least one of the operational-amplifier and the comparator being provided with an offset so that the comparator-output-signal chang

Abstract: A light emitting device drive controller is disclosed that comprises a first port that is connected to one end of a first light emitting device group where two light emitting devices are connected in parallel in the opposite directions; a second port that is connected to the other end of the first light emitting device group as well as connected to one end of a second light emitting device group where two light emitting devices are connected in parallel in the opposite directions; a third port that is connected to the other end of the second light emitting device group; and a port state setting unit that selectively sets each of the first, second, and third ports to any one of a state of a first voltage, a state of a second voltage which is less than the first voltage, and a high impedance state for each consecutive predetermined period, wherein the light emitting device drive controller drives selectively the light emitting devices constituting the first light emitting device group and the second light emitt

Abstract: A battery voltage detecting circuit includes: a first capacitor having one end connected to one input terminal of an operational amplifier; a second capacitor having one end connected to an output terminal of the operational amplifier and the other end connected to the one input terminal of the operational amplifier; a third capacitor having one end connected to the other input terminal of the operational amplifier; a fourth capacitor having one end applied with a reference voltage and the other end connected to the other input terminal of the operational amplifier; and a switching circuit configured to electrically connect the one input terminal of the operational amplifier to the one end of the first capacitor after the transient current has stopped flowing.

Abstract: An LED driving circuit includes: a current generating circuit configured to generate a drive current corresponding to a voltage level of a drive voltage applied to anodes of the first to fourth LEDs so as to alternately drive the first and second LEDs and the third and fourth LEDs; a first drive control circuit connected to cathodes of the first and third LEDs, and configured to drive the first or third LED with the drive current in response to a first control signal for controlling driving of the first or third LED; and a second drive control circuit connected to cathodes of the second and fourth LEDs, and configured to drive the second or fourth LED with the drive current in response to a second control signal for controlling driving of the second or fourth LED.

Abstract: A voltage detecting circuit comprises: an operational amplifier whose one input terminal is applied with a first reference voltage; a first capacitor whose one end is connected to the other input terminal of the operational amplifier; a second capacitor whose one end is connected to an output terminal of the operational amplifier, and whose other end is connected to the other input terminal of the operational amplifier; a switch circuit for applying a first voltage and a second voltage sequentially to the other end of the first capacitor; and a discharging circuit for discharging the second capacitor before the second voltage is applied to the other end of the first capacitor, a difference between the first voltage and the second voltage being detected based on a voltage at the output terminal of the operational amplifier after the second voltage is applied to the other end of the first capacitor.

Abstract: A voltage-frequency conversion apparatus which comprises a variable current source for charging a capacitor; a current amount adjustment circuit which has a first resistor for applying a first voltage and a second resistor for applying a second voltage and adjusts the amount of a current from the variable current source to be corresponding to a differential voltage between the first voltage and the second voltage; a comparator that compares a charging voltage across the capacitor and a reference voltage; and a discharge circuit that discharges the capacitor when the charging voltage exceeds the reference voltage. The comparator generates a frequency signal according to the differential voltage.

Abstract: A voltage-frequency conversion apparatus which has a variable current source for charging a capacitor; a current amount adjustment unit that adjusts a current amount of the variable current source for charging the capacitor to be corresponding to a differential voltage between a first voltage and a second voltage; a comparator that compares in level a charging voltage produced at one end of the capacitor and a reference voltage; a discharge unit that discharges the charging voltage of the capacitor according to the comparison result of the comparator when the charging voltage exceeds the reference voltage; and a reference voltage fluctuation unit that makes the reference voltage fluctuate. A frequency signal is generated from the comparator corresponding to the differential voltage between the first voltage and the second voltage.

Abstract: A light emitting device drive controller is disclosed that comprises a first port that is connected to one end of a first light emitting device group where two light emitting devices are connected in parallel in the opposite directions; a second port that is connected to the other end of the first light emitting device group as well as connected to one end of a second light emitting device group where two light emitting devices are connected in parallel in the opposite directions; a third port that is connected to the other end of the second light emitting device group; and a port state setting unit that selectively sets each of the first, second, and third ports to any one of a state of a first voltage, a state of a second voltage which is less than the first voltage, and a high impedance state for each consecutive predetermined period, wherein the light emitting device drive controller drives selectively the light emitting devices constituting the first light emitting device group and the second light emitt

Abstract: A voltage-frequency conversion apparatus which comprises a variable current source for charging a capacitor; a current amount adjustment circuit which has a first resistor for applying a first voltage and a second resistor for applying a second voltage and adjusts the amount of a current from the variable current source to be corresponding to a differential voltage between the first voltage and the second voltage; a comparator that compares a charging voltage across the capacitor and a reference voltage; and a discharge circuit that discharges the capacitor when the charging voltage exceeds the reference voltage. The comparator generates a frequency signal according to the differential voltage.

Abstract: A voltage-frequency conversion apparatus which has a variable current source for charging a capacitor; a current amount adjustment unit that adjusts a current amount of the variable current source for charging the capacitor to be corresponding to a differential voltage between a first voltage and a second voltage; a comparator that compares in level a charging voltage produced at one end of the capacitor and a reference voltage; a discharge unit that discharges the charging voltage of the capacitor according to the comparison result of the comparator when the charging voltage exceeds the reference voltage; and a reference voltage fluctuation unit that makes the reference voltage fluctuate. A frequency signal is generated from the comparator corresponding to the differential voltage between the first voltage and the second voltage.