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參數(shù)資料
| 型號： | HA17384HRP |
| 廠商： | Hitachi,Ltd. |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | High Speed Current Mode PWM Control IC for Switching Power Supply |
| 中文描述： | 高速開關電源電流模式PWM控制IC |
| 文件頁數(shù)： | 26/31頁 |
| 文件大?。?/td> | 145K |
| 代理商： | HA17384HRP |
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HA17384SPS/SRP, HA17384HPS/HRP, HA17385HPS/HRP
26
Application Examples for Fuller Exploitation of Power Supply Functions
A number of application examples are briefly described below.
1. Soft start
A soft start is a start method in which the PWM pulse width is gradually increased when the power
supply is activated. This prevents the stress on the transformer and switch element caused by a rapid
increase in the PWM pulse width, and also prevents overshoot when the secondary-side output voltage
rises. The circuit diagram is shown in figure 14.
+EA
I
800
μ
A typ
Vref
5V
(3V)
(4.4V)
(3.7V)
(5V)
7
V
IN
D
IN
V
REF
R
CU
C
ST
D2
D1
2
2.5V
IC internal circuit
(around error amp.)
External circuit
(only partially shown)
FB
R
1V
To power supply
detection
comparator
(1V)
COMP
8
1
2R
Figure 14 Circuit Diagram for Soft Start
Operation: In this circuit, error amp output source current I
O
(800
μ
A typ.) gradually raises the switch
element current detection level, using a voltage slope that charges soft start capacitance C
ST
. When the
voltage at each node is at the value shown in parentheses in the figure, the soft start ends. The soft start
time is thus given by the following formula:
T
ST
= (3.7 V/800
μ
A)
×
C
ST
≈
4.62 C
ST
(ms)
(C
ST
unit:
μ
F)
External parts other than C
ST
operate as follows:
Diode D1
Diode D2
Resistance R
CU
: For C
ST
charge-up at end of soft start. (Use a high resistance of the order of several
hundred k
.)
Note:
During a soft start, since PWM pulses are not output for a while after the IC starts operating, there
is a lack of energy during this time, and intermittent mode may be entered. In this case, the
capacitance between Vref and GND should be increased to around 4.7
μ
F to 10
μ
F.
: Current detection level shift and current reverse-flow prevention.
: Together with diode D
IN
in the IC, C
ST
charge drawing when power supply falls.
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| HA17385HPS | High Speed Current Mode PWM Control IC for Switching Power Supply |
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| HA17384PS | 制造商:HITACHI 制造商全稱:Hitachi Semiconductor 功能描述:CURRENT MODE PWM CONTROL SWITTCHING REGULATOR ICS |
| HA17384SPS | 制造商:HITACHI 制造商全稱:Hitachi Semiconductor 功能描述:High Speed Current Mode PWM Control IC for Switching Power Supply |
| HA17384SPS-E | 制造商:Renesas Electronics 功能描述:Current Mode PWM Controller 1A 8-Pin PDIP Bulk |
| HA17384SRP | 制造商:RENESAS 制造商全稱:Renesas Technology Corp 功能描述:High Speed Current Mode PWM Control IC for Switching Power Supply |
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