Power supply for an electronic device and power delivery method therefor

• US 5,739,596 A
• Filed: 04/05/1996
• Issued: 04/14/1998
• Est. Priority Date: 04/06/1995
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Ikeda, Shigeo, Nagao, Katsunori, Takizawa, Yasutoshi
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US08/630,956
• Time in Patent Office: 739 Days
• Field of Search: 307/66, 307/65, 307/64, 307/85, 307/139, 307/44, 307/48, 320/2, 320/7, 320/30, 320/43, 364/492, 364/273-273.5
• US Class Current: 307/66
• 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

Abstract

An electronic apparatus comprises a main circuit having a main CPU and a power supply system which includes plural main batteries for supplying operating power to said main circuit, a back-up battery, a switching circuit connected between each main battery and the main circuit, power means for enabling the operation of the main circuit, a charge detector for detecting the charging level of each main battery, and power controller responsive to the power means and the charge detector and having a sub-CPU for individually controlling the switching circuit according to either a single connection mode or a multiple connection mode. In the single connection mode only one of the main batteries is connected to said main circuit. In the multiple connection mode, at least two main batteries, each in series with a respective diode means, are connected in parallel to the main circuit. The back-up battery is connected to supply power to the power controller only when either no main battery is installed or the charging level of each of the installed main batteries is below a predetermined value required for back-up operation.

Claims

1. A power supply for an electronic device, comprising:

first and second main power sources;

a charge detector in communication with said first and second main power sources to individually detect the charge levels of each said first and second main power sources;

a switching circuit in communication with said first and second main power sources for selectively routing respective power signals generated by said first and second main power sources to the electronic device; and

a power controller in communication with said charge detector and said switching circuit for controlling the switching circuit between a single connection mode and a default multiple connection mode according to the charge levels detected by said charge detector, said power controller setting said switching circuit in the multiple connection mode upon electronic device startup;

wherein said power controller sets said switching circuit into the multiple connection mode when the respective charge levels of both said main power sources fail to exceed a predetermined threshold as detected by said charge detector;

wherein, in the single connection mode, said switching circuit electrically connects a selected one of said first and second main power sources to a power input of the electronic device while disconnecting the remaining main power source; and

wherein, in the multiple connection mode, said switching circuit electrically connects both said first and second main power sources in series with respective first and second diode means and in parallel with a power input of the electronic device.

2. The power supply of claim 1, further comprising a back-up battery in communication with said power controller for delivering power thereto when the respective charge levels of both said main power sources fail to exceed a predetermined threshold as detected by said charge detector.

3. The power supply of claim 1, wherein said switching circuit comprises:

first and second switching elements connected in series and electrically interposing said first main power source and the power input of the electronic device; and

third and fourth switching elements electrically connected in series interposing said second main power source and the power input of the electronic device, wherein each said switching element includes a diode and an electronic switch connected in parallel, said electronic switch of each said switching element including a control terminal in communication with said power controller.

4. The power supply of claim 3, wherein each said switching element diode comprises a Schottky barrier diode.

5. The power supply of claim 3, wherein

each said electronic switch comprises a field effect transistor including a parasitic diode connected in parallel to a source-drain path of said field effect transistor;

and

wherein said respective field effect transistors of said first and second electronic switches are coupled in series such that anodes of their respective parasitic diodes are electrically connected.

6. The power supply of claim 5, wherein said respective field effect transistors of said third and fourth electronic switches are coupled in series such that anodes of their respective parasitic diodes are electrically connected.

7. The power supply of claim 5, wherein said respective field effect transistors of said third and fourth electronic switches are coupled in series such that cathodes of their respective parasitic diodes are electrically connected.

8. The power supply of claim 3, wherein

each said electronic switch comprises a field effect transistor including a parasitic diode connected in parallel to a source-drain path of said field effect transistor;

and

wherein said respective field effect transistors of said first and second electronic switches are coupled in series such that cathodes of their respective parasitic diodes are electrically connected.

9. The power supply of claim 8, wherein said respective field effect transistors of said third and fourth electronic switches are coupled in series such that anodes of their respective parasitic diodes are electrically connected.

10. The power supply of claim 8, wherein said respective field effect transistors of said third and fourth electronic switches are coupled in series such that cathodes of their respective parasitic diodes are electrically connected.

11. The power supply of claim 3, wherein

said first and second main power sources each comprise a battery having power output terminals, each said battery exhibiting a charge level directly proportional to a terminal voltage measured across said respective power output terminals;

and

wherein said charge detector comprises a voltage detection means coupled to said power output terminals of said first and second batteries for measuring the terminal voltage of said first and second batteries.

12. An electronic device, comprising:

a main circuit;

a power input port in communication with said main circuit; and

a power supply for supplying power to said main circuit, comprising;

first and second main power sources;

a charge detector in communication with said first and second main power sources to individually detect the charge levels of each said first and second main power sources;

a switching circuit in communication with said first and second main power sources for selectively routing respective power signals generated by said first and second main power sources to said power input port; and

a power controller in communication with said charge detector and said switching circuit for controlling the switching circuit between a single connection mode and a multiple connection mode according to the charge levels detected by said charge detector, said power controller setting said switching circuit in the multiple connection mode upon device startup.

13. The electronic device of claim 12, wherein said power controller sets said switching circuit into the multiple connection mode when the respective charge levels of both said main power sources fail to exceed a predetermined threshold as detected by said charge detector.

14. The electronic device of claim 12, wherein,

in the multiple connection mode, said switching circuit electrically connects both said first and second main power sources in series with respective first and second diode means and in parallel with said power input port;

and

wherein, in the single connection mode, said switching circuit electrically connects a selected one of said first and second main power sources to said power input port while disconnecting the remaining main power source.

15. A method of controlling a power supply for an electronic device including an external housing, plural power sources detachably mounted within the external housing and accessible via a corresponding plurality of removable covers defined on said housing, the method comprising the steps of:

(a) detecting whether at least one of the covers is open;

(b) switching the power sources into a multiple connection mode if at least one of the covers is open as detected in said detecting step (a);

(c) determining whether any of the power sources other than power sources corresponding to the at least one opened cover has a charge level exceeding a first predetermined reference value;

(d) selecting one of the power sources, if any, whose charge level exceeds the first predetermined reference value as determined in said determining step (c); and

(e) switching the power sources in a single connection mode utilizing the selected power source selected in said selecting step (d) to power the electronic device.

16. A method of controlling a power supply for an electronic device having plural power sources, comprising the steps of:

(a) switching the power sources into a multiple connection mode;

(b) detecting if the charge level of at least one of said power sources exceeds a first predetermined reference value;

(c) selecting one of said power sources, if any, whose charge level exceeds the first predetermined reference value as detected in said detecting step (b);

(d) switching the power sources into a single connection mode utilizing the selected power source selected in said selecting step (c) to power the electronic device;

(e) detecting if the selected power source charge level falls below a second predetermined reference value;

(f) performing the following when the selected power source charge level falls below a second predetermined reference value as detected in said detecting step (e);

(1) detecting if the charge level of at least one of said power sources exceeds a third predetermined reference value;

(2) selecting one of said power sources, if any, whose charge level exceeds the third predetermined reference value as detected in said detecting step (f)(1); and

(3) switching the power sources into a single connection mode utilizing the selected power source selected in said selecting step (f)(2) to power the electronic device; and

(g) re-switching the power sources back into a multiple connection mode when the power source selected in one of said selecting steps (c) and (f)(2) falls below the second predetermined reference value.

17. The method of claim 16, further comprising the steps of:

(h) detecting whether the selected power source is about to be removed; and

(i) performing the following if the power source is about to be removed as detected in said detecting step (h);

(1) measuring the charge level of at least one of the non-selected main power sources;

(2) switching the power sources into a single connection mode utilizing a non-selected power source, if any, whose charge level measured in said measuring step (i)(1) exceeds the first predetermined reference value; and

(3) if there is no non-selected power source whose charging level is higher than the first predetermined reference value as measured in said measuring step (i)(1), switching the power sources according to the multiple connection mode.