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AN026 の電気的特性と機能

AN026のメーカーはAICです、この部品の機能は「The Charger Design with SEPIC Converter」です。


製品の詳細 ( Datasheet PDF )

部品番号 AN026
部品説明 The Charger Design with SEPIC Converter
メーカ AIC
ロゴ AIC ロゴ 




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AN026 Datasheet, AN026 PDF,ピン配置, 機能
AN026
The Charger Design with SEPIC Converter
Introduction
Recently, the hand-held devices become more and
more popular, such as Personal Digital Assistant
(PDA), CD workman, digital camera etc… need a
great quantity battery for normal operation.
Considering the economic effect, the battery chargers
for recycle rechargeable battery, like NiMH or NiCd,
are extremely important. In this article will introduce
the design idea of charger circuit at first. Then directed
against the characteristics of rechargeable battery and
use AIC1781 to design a charge protector only for
NiMH/NiCd battery.
Design Idea of Battery Charger
I’ll give an example to illustrate the relationship
between rechargeable battery and battery charger.
Assume that the battery is a cup, and regards the
constant current, which from charger, as the water
pour into the cup. The more water pour into the cup,
the more volumes will be in the cup. Contrast with the
battery and charger, the more current flow into the
battery the more battery voltage will be appeared.
Therefore we can use this concept to design an ideal
charger.
The ideal charger must provide following
characteristics:
When the battery voltage achieves it’s maximum
voltage, the charger must be turn off to prevent
damaging the device, which connect to battery.
It can supply a constant current to the battery. And
terminate the charge current when the battery voltage
October, 2003
doesn’t increase any more or decreases cause the
saturation voltage.
It must terminate the charge current when the charge
time is too long to prevent damaging the device.
It must provide a function of discharge- before-charge
to precondition the battery, which suffer from “memory
effect”.
When the battery terminate charge, the charger must
supply a trickle charge current to prevent the loss of
battery due to it’s self-discharging.
When the battery voltage is lower than the initial
voltage, the charger doesn’t proceed charging due to
estimates the battery hasn’t put in or broken. When
the battery voltage is higher than the initial voltage, the
charger supplies a constant current to battery for fast
charging. When the battery voltage achieves the
saturation voltage, the charger terminates fast
charging. After fast charging, the charger supplies a
trickle current to prevent the loss of battery due to it’s
self-discharging. Fig. 1 illustrates the characteristics of
charger.
Charge Voltage
Maximum
Saturation
Battery Voltage
Trickle Current
Charge
Current
Initial Voltage
Terminate Charge
Time
Fig.1 The charge curve of charger
1

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AN026 pdf, ピン配列
AN026
Q1-ON
VGS
0
IL1 or IL2
Q1-OFF
0
IC1 0
0
VD1
IM1
0
IL1-IC1
Fig. 6. The voltage waveforms of SEPIC
Q1-ON
VGS
Q1-OFF
0
VL1
0
VL2
0
VC1
Vin
VIN
VIN
-VO
-VO
0
VD1 0
- (VIN -VO)
Fig. 7 The current waveforms of SEPIC
A.2 Components Selection
At steady state, the characteristic of inductor is the
voltage-second balance. If the powers lose can be
ignored then the input power equal to the output one.
The relationship of power when the switch turns ON
and OFF can be shown as
VIN × D × TS = VOUT × (1 - D) × TS …………(1)
Then we can get the relationship between input and
output voltage
VOUT
VIN
=
D
1D
…………(2)
Similarly, the relationship between input and output
current can be shown as
IIN
IOUT
D
= 1D …………(3)
When the duty cycle is determined the value of
inductor can be decided also
L1
VOUT × TS × (1D)2
2 × IOUT BOUNDARY
…………(4)
And the capacitor can be calculated as
C1
=
D ×TS × IIN
VC1
…………(5)
B. Charger Protector Design
We use AIC1781 to accomplish the charger protector.
Fig. 8 shows the pin configuration of AIC1781. This
IC has following characteristics
Fast charge control of NiMH/NiCd batteries,
even with a fluctuating charging current.
Fast charge termination by: T/t, -V, 0V,
safety timer, maximum temperature, maximum
voltage.
Selectable LED display mode for battery status.
Five pulsed trickle charge mode.
Discharge-before-charge function available for
eliminating memory effect.
Due to the datasheet of AIC1781 describes the design
guide in detail. Next, we will enter the charger design
directly.
3


3Pages


AN026 電子部品, 半導体
(Top Over layer)
Fig. 10 The recommend layout
Q1 ON
VGS, 5V/DIV
Q1 OFF
IL1 500mA/DIV
IC1, 1A/DIV
Q1 ON
Q1 OFF
VL1 10V/DIV
AN026
VGS, 5V/DIV
VC1, 4V/DIV
VQ1, 10V/DIV
Fig. 12. The Voltage Waveforms of SEPIC
IQ1, 1A/DIV
Fig. 11 The Current Waveforms of SEPIC
6

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