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Charging circuit for secondary battery

A backup battery and charging circuit technology, applied in the direction of secondary battery charging/discharging, battery circuit devices, circuit devices, etc., can solve the problem that the input bias voltage cannot be ignored, the detection charging current accuracy becomes low, and it is impossible to charge the backup battery and other issues to achieve the effect of shortening charging time, reducing detection errors, and increasing flexibility

Inactive Publication Date: 2008-02-13
RICOH KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, by performing constant voltage charging, the detected current at the end of charging is small, and since the voltage drop across resistor R1 is low, the input bias voltage of the operational amplifier A1 used to detect the resulting voltage cannot be ignored
In other words, there is a problem that the accuracy of detecting the charging current becomes lower
Also, there is a problem that since operational amplifiers with small configuration voltages are expensive, manufacturing costs increase when they are used
[0014] Also, a problem arises when a large current is supplied to the backup battery at the start of charging in case the backup battery is in an over-discharged state
Therefore, with this charging circuit, it is impossible to charge a backup battery that is in an over-discharged state

Method used

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Examples

Experimental program
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Effect test

no. 1 example

[0053] FIG. 1 shows a structural diagram of a charging circuit for a backup battery according to a first embodiment of the present invention. It should be noted that Fig. 1 shows an example of a charging circuit for a lithium-ion battery of a mobile phone.

[0054] In Fig. 1, the charging circuit 1 of the backup battery comprises: an adapter detection circuit 2 for outputting a predetermined signal when the power supply voltage from an AC adapter 10 as a DC power supply is equal to or greater than a predetermined value; a battery voltage detection circuit 3 for for detecting and outputting a positive voltage Vb (hereinafter referred to as "battery voltage") Vb of a lithium ion battery 11 used as a backup battery; and a constant voltage circuit 4 for charging the lithium ion battery 11 at a constant voltage.

[0055] In addition, the charging circuit 1 includes: a constant current circuit 5 for pre-charging the lithium-ion battery 11 with a predetermined constant current; a cha...

no. 2 example

[0083] Fig. 5 shows a charging circuit according to a second embodiment of the present invention. In Fig. 5, the charging circuit includes: AC adapter B10 for providing charging current; adapter detection circuit 12 for detecting the connection of AC adapter B10; battery voltage detection circuit 16 for detecting the voltage of backup battery 14; constant voltage The circuit 18 is used to perform constant voltage charging on the backup battery 14; the constant current circuit 20 is used to provide a constant current to the backup battery 14; the gate voltage detection circuit B22 is used to detect the voltage of the control terminal of the control transistor M1; the diode D1 , for preventing current from flowing into the AC adapter B10 from the backup battery B24; and a charge control circuit B24 for performing drive control of the constant voltage circuit 18 and the constant current circuit 20. An AC adapter B10 is connected to terminal 30 . The constant voltage circuit 18 i...

no. 3 example

[0095] FIG. 8 shows a charging circuit diagram of the backup battery 14 according to the third embodiment of the present invention. In FIG. 8, the same components as those corresponding to those in FIG. 5 are denoted by the same reference numerals, and descriptions thereof are omitted. The charging circuit according to the third embodiment includes, in addition to the charging circuit shown in FIG. 5 : a current control circuit 50 for controlling the charging current output from the pMOS transistor M1 ; and a load resistor R2 . In addition, a diode D3 is connected between the operational amplifier A1 of the constant voltage circuit 18 and the pMOS transistor M1. The current control circuit 50 includes a constant voltage generating circuit 46 , an operational amplifier A4 and a diode D2 . One end of the load resistor R2 is grounded, and the other end is connected to the gate terminal of the pMOS transistor M1.

[0096] 9A, 9B and 9B respectively show a change in the battery v...

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PUM

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Abstract

A charging circuit for a secondary battery includes a constant-voltage circuit part outputting one of a plurality of predetermined constant voltages and charges the secondary battery by applying the constant voltage thereto, a detection circuit part detecting a battery voltage of the secondary battery, and a control circuit part controlling the selection of the constant-voltage in response to the detected battery voltage. Another charging circuit includes a constant-current circuit part outputting, to the secondary battery, one of two predetermined constant currents, a constant-voltage circuit part charging the secondary battery by applying a predetermined constant voltage thereto, a battery voltage detection circuit part detecting a battery voltage of the secondary battery, a charge current detection circuit part outputting a predetermined charge completion signal, and a charge control circuit part stopping operations of the constant-current circuit part and constant-voltage circuit part when receiving the charge completion signal.

Description

[0001] This application is a divisional application of an invention patent application with an application date of September 12, 2002, an application number of 02809443.3, and an invention title of "charging circuit for a backup battery". technical field [0002] The present invention relates generally to a charging circuit for a rechargeable backup battery, and more particularly to a charging circuit for a backup battery capable of rapid charging and avoiding the generation of noise in a frequency band that would be detrimental to devices using the charging circuit, such as mobile phones have negative impacts. Background technique [0003] As a charging method of a lithium ion battery, when generally divided, a constant current / constant voltage charging method and a pulse charging method are used. In the constant current / constant voltage charging method, the charging time can be shortened by increasing the charging current to the Li-ion battery and making the charging const...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J7/10H01M10/44H02J7/04
CPCY02E60/12Y02E60/10
Inventor 西田淳二真锅晋也
Owner RICOH KK
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