Current waste suppressing power supply apparatus

• US 20050024034A1
• Filed: 08/02/2004
• Published: 02/03/2005
• Est. Priority Date: 07/31/2003
• Status: Active Grant

• Current Assignee: RICOH Electronic Devices Co., Ltd. (Nisshinbo Holdings Incorporated)
• Original Assignee: Ricoh Company Limited
• Inventors: Ibaraki, Tooru
• Granted Patent: US 7,279,879 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence

Abstract

A power supply apparatus supplies power to one of an interior circuit and external instruments. The power supply apparatus includes a voltage regulator that regulates and outputs a constant voltage through an output driver by comparing the power with a regulator reference voltage, and a power supply voltage detecting device that detects a power supply voltage and determines if the power supply voltage is less than a power supply reference voltage based upon the output of the voltage regulator.

Claims

1. A power supply apparatus comprising:

a voltage regulator having an output driver and configured to regulate and output a constant voltage through the output driver by comparing the power with a regulator reference voltage; and

a power supply voltage detecting device configured to detect a power supply voltage and determine if the power supply voltage is less than a power supply reference voltage based upon the output of the voltage regulator.

2. The power supply apparatus according to claim 1, wherein the power supply voltage detecting device includes;

a buffer having a hysteresis performance configured to

output two stable voltage levels to the output driver in accordance with an input voltage;

a comparison use amplifier configured to compare the regulator reference voltage with a feedback voltage obtained by dividing a voltage output from the output driver;

wherein said buffer is provided at an output side of the comparison use amplifier to perform said determination in accordance with an input voltage, said input voltage being output from the comparison use amplifier in order to control the output driver, and wherein said buffer transmits a control signal to one of an interior circuit and external instruments so as to prevent erroneous operations when the determined is positive.

3. The power supply apparatus according to claim 2, wherein a bias voltage of a MOS transistor included in the comparison use amplifier is controlled to decreases an amount of current flowing through the comparison use amplifier when the determination is positive.

4. The power supply apparatus according to claim 2, wherein the voltage to be supplied to one of the interior circuit and external instruments is divided by a feedback resistance and fed back to the comparison use amplifier as the feedback voltage, wherein a ratio of the feedback resistance is changeable.

5. The power supply apparatus according to claim 2, wherein a bias voltage of the output driver is controlled to enable the output driver to supply the power supply voltage to one of the interior circuit and external instruments as it is when the determination is positive.

6. The power supply apparatus according to claim 2, wherein a bias voltage of the output driver is controlled to enable the output driver to output substantially the zero volts to one of the interior and external instruments when the determination is positive.

7. The power supply apparatus according to claim 2, wherein the power supply voltage itself is divided at the feedback resistance ratio and fed back to the comparison use amplifier as the feedback voltage, when the determination is positive.