POWER SUPPLY SWITCHING CIRCUIT, REAL TIME CLOCK DEVICE, ELECTRONIC APPARATUS, MOBILE UNIT, AND METHOD OF CONTROLLING POWER SUPPLY SWITCHING CIRCUIT

• US 20140008984A1
• Filed: 06/26/2013
• Published: 01/09/2014
• Est. Priority Date: 07/09/2012
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kiya, Hiroshi, Kamiyama, Masayuki
• Granted Patent: US 9,438,073 B2
• Time in Patent Office: Days
• US Class Current: 307/64
• CPC Class Codes: G06F 1/263 Arrangements for using multiple switchable power supplies, e.g. battery and AC G06F1/30 takes precedence
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: H02J 9/06 with automatic change-over , e.g. UPS systems
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

A power supply switching circuit includes a switching circuit that electrically connects a VCC terminal and a VBK terminal in a connected state, a switch control circuit, and a power supply monitoring circuit that monitors a voltage of the VCC terminal, and outputs a voltage of the VBK terminal. The switch control circuit switches a mode from a normal mode in which the switching circuit is intermittently connected to a standby mode in which the switching circuit is opened according to an output signal of the power supply monitoring circuit.

Claims

1. A power supply switching circuit comprising:

a power supply monitoring circuit that monitors a voltage of a first power supply node;

a switching circuit that switches electrical connection and opening between the first power supply node and a second power supply node; and

a switch control circuit that switches a mode from a first mode in which the switching circuit is intermittently connected to a second mode in which the switching circuit is opened according to an output signal of the power supply monitoring circuit,

wherein a voltage of the second power supply node is output.

2. The power supply switching circuit according to claim 1, wherein the power supply monitoring circuit monitors the voltage of the first power supply node when the switching circuit is opened in the first mode.

3. The power supply switching circuit according to claim 2, wherein the voltage of the first power supply node is monitored when the switching circuit is opened, and, as a result, if the voltage of the first power supply node is equal to or smaller than a voltage having a desired value, the mode is switched to the second mode and the voltage of the second power supply node is output.

4. The power supply switching circuit according to claim 1, wherein the switching circuit includes a first switch element having a parasitic diode,

the first switch element is provided with an anode side of the parasitic diode at the first power supply node side and a cathode side of the parasitic diode at the second power supply node side, and

the switch control circuit connects the first switch element for connecting the switching circuit and opens the first switch element for opening the switching circuit.

5. The power supply switching circuit according to claim 1, further comprising a pull-down resistor electrically connected to the first power supply node.

6. The power supply switching circuit according to claim 1,

wherein the switching circuit serves as a first switching circuit,

the power supply switching circuit further comprises a second switching circuit that electrically connects the second power supply node and a third power supply node in a connected state, and

the switch control circuit intermittently connects both the first switching circuit and the second switching circuit in the first mode, and opens the first switching circuit and connects the second switching circuit in the second mode.

7. The power supply switching circuit according to claim 6, suppose that the power supply monitoring circuit is a first power supply monitoring circuit, further comprising a second power supply monitoring circuit that monitors a voltage of the third power supply node,

wherein the control circuit switches the mode from the first mode to a third mode in which the first switching circuit is connected and the second switching circuit is opened according to an output signal of the second power supply monitoring circuit.

8. The power supply switching circuit according to claim 6, further comprising a third power supply monitoring circuit that monitors a magnitude relationship between the voltage of the first power supply node and the voltage of the third power supply node,

wherein the control circuit switches the mode from the first mode to the third mode according to an output signal of the third power supply monitoring circuit.

9. The power supply switching circuit according to claim 6, wherein, suppose that the second switching circuit includes a second switch element and a third switch element having parasitic diodes,

the second switch element is provided with an anode side of the parasitic diode at the second power supply node side and a cathode side at the third power supply node side,

the third switch element is provided in series with the second switch element with an anode side of the parasitic diode at the third power supply node side and a cathode side at the second power supply node side, and

the switch control circuit connects both the second switch element and the third switch element for connecting the second switching circuit and opens the second switch element and connects the third switch element for opening the second switching circuit in the first mode.

10. A real time clock device comprising:

the power supply switching circuit according to claim 1; and

a real time clock circuit to which an output voltage of the power supply switching circuit is supplied as a power supply voltage.

11. A real time clock device comprising:

the power supply switching circuit according to claim 2; and

a real time clock circuit to which an output voltage of the power supply switching circuit is supplied as a power supply voltage.

12. An electronic apparatus comprising:

the power supply switching circuit according to claim 1;

a first power supply that supplies a power supply voltage to the first power supply node; and

a second power supply electrically connected to the second power supply node or the third power supply node.

13. An electronic apparatus comprising:

the power supply switching circuit according to claim 2;

a first power supply that supplies a power supply voltage to the first power supply node; and

a second power supply electrically connected to the second power supply node or the third power supply node.

14. A mobile unit comprising:

the power supply switching circuit according to claim 1;

a first power supply that supplies a power supply voltage to the first power supply node; and

a second power supply electrically connected to the second power supply node or the third power supply node.

15. A mobile unit comprising:

the power supply switching circuit according to claim 2;

a first power supply that supplies a power supply voltage to the first power supply node; and

a second power supply electrically connected to the second power supply node or the third power supply node.

16. A method of controlling a power supply switching circuit including a power supply monitoring circuit that monitors a voltage of a first power supply node and a switching circuit that electrically connects the first power supply node and a second power supply node in a connected state, and outputting a voltage of the second power supply node, comprising switching a mode from a first mode in which the switching circuit is intermittently connected to a second mode in which the switching circuit is opened according to an output signal of the power supply monitoring circuit.