參數(shù)資料
型號(hào): FA13842
廠商: FUJI ELECTRIC HOLDINGS CO., LTD.
元件分類: 基準(zhǔn)電壓源/電流源
英文描述: CMOS IC(For Switching Power Supply Control)
中文描述: CMOS集成電路開關(guān)電源控制(對(duì))
文件頁數(shù): 14/15頁
文件大小: 151K
代理商: FA13842
FA13842, 13843, 13844, 13845
14
Fig. 22
Fig. 23
Fig. 24
to
t1
iL′
iL
Converge
iL′s
iL′
iL
-Kc
Lu
Ton
T
to
t1
Compensated
-Ld
Is
Vcc
ENB
2.5V
5VREF
ENB
UVLO
OSC
30V
RT/CT
FB
C13
COMP
ISNS
VREF
8
OUT
GND
ER AMP
2R
C10
Rs
R18
M
1R
1V
S
FFQ
QB
R
Vcc
Vin
VCC
UVLO
Output
R25
R24
R27
R26
Tr7
7
4
2
1
6
5
3
R
T
C
T
Fig. 25
Vcc
ENB
2.5V
5VREF
ENB
UVLO
OSC
30V
RT/CT
FB
C13
COMP
ISNS
VREF
8
OUT
GND
ER AMP
2R
C10
Rs
R18
M
1R
1V
S
FFQ
QB
R
Vcc
Vin
VCC
UVLO
Output
R25
R24
R27
R26
Tr7
7
6
5
4
2
1
3
R
T
C
T
Fig. 22 illustrates a case when the inductor current variation
i
L
’ at t1 is smaller than
i
L
at t0. In this case, inductor current
variations gradually converges and the inductor current
becomes stable.
It is necessary to apply slope compensation to the control
signals in order to prevent such subharmonic oscillations when
the inductor current is continuous and the duty cycle is greater
than 50%.
The waveform of the inductor current when slope
compensation is applied is shown in Fig. 23.
Slope compensation adds the negative slope of inclination
–Kc to the control signal of the inductor peak current.
i
L
’ shows the variation of the inductor current at t1 when
slope compensation is not applied, and
i
L
’ s shows the
variation of the inductor current at t1 when slope compensation
is applied.
Thus,
i
L
’ can be changed by –Kc, and
I
L
’ s becomes smaller
when –Kc is large. It is necessary to apply slope
compensation to satisfy the equation
i
L
i
L
’s, that is,
I –Kc I
I –1/2 Ld I as the condition which achieves stable
operation.
Typical circuits are shown in Fig. 24 and 25.
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