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# Battery Charger Circuit which improved charge time

IP.com Disclosure Number: IPCOM000011902D
Original Publication Date: 2003-Mar-25
Included in the Prior Art Database: 2003-Mar-25
Document File: 3 page(s) / 26K

IBM

## Abstract

The traditional lithium-ion battery charger circuit needs very long time to charge batteries. This invention can reduce battery charging time by changing the constant voltage charge process.

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Battery Charger Circuit which improved charge time

Disclosed is a circuit for cutting short time of battery charging. The process of traditional circuit consists of two ways, "constant current charge" and "constant voltage charge". The "constant voltage charge" process takes a long time (fig. 1). This invention can work out by controling the configuration that is MAX voltage to charge a battery (fig. 2).

4.2V

Fig. 1

4.2V + ⊿V

⊿V

Fig. 2

The following example is a case of using 4.2V lithium-ion battery. (fig.3 - fig 5)

4.2V

SW off

1

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ON

X

Y

X

Y

I

VBAT = 4.2[V]

VB

fig. 3

OFFI = 0

V'BAT = 4.2[V] - ⊿V

VB= 4.2[V] - ⊿V

fig. 4

ON

X

Y

fig. 5

Step 1.

Charge the battery by traditional charging (fig. 3)

Step 2.

Switch "Q" becomes OFF and the current "I" becomes zero. Then the IC detects " V = 4.2[V] - V'BAT "（fig.4）

Step 3.

The IC sets the configuration of charging voltage "VBAT = 4.2[V] + V", which means the switch "Q" will become OFF by 4.2[V] + V

Step 4.

Switch "Q" becomes ON and this circuit starts to charge the battery again

Step 5.

The IC detects "VBAT = 4.2[V] + V", and the swithc "Q" becomes OFF

I

VBAT = 4.2[V] + ⊿V

VB= 4.2[V]

2

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VBAT = V + VB <=> 4.2[V] + V = V + VB

<=> VB = 4.2[V] （fig.5）

Step 6.

Use or discarge the battery

Step 7.

Return to Step.1 when the IC detects the VBAT as the minimam voltage

To prevents...