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參數(shù)資料
| 型號： | SE5560 |
| 廠商： | NXP Semiconductors N.V. |
| 英文描述： | Switched-mode power supply control circuit |
| 中文描述： | 開關(guān)電源控制電路 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大小： | 240K |
| 代理商： | SE5560 |
Philips Semiconductors
Product specification
NE/SE5560
Switched-mode power supply control circuit
1994 Aug 31
12
V
11
(CURRENT LIMITING)
NORMAL OPERATING
LEVEL 1 LEVEL 2
.48
.60 (V)
R
O
OC
1
OC
2
SL00374
Figure 15. Output Characteristics
Dynamic Current Limit and Current Protection
(Pin 11)
In many applications, it is not necessary to have a real
constant-current output of the SMPS.
Protection of the power transistor will be the prime goal. This can be
realized with the NE5560 in an economical way. A resistor (or a
current transformer) in the emitter of the power transistor gives a
replica of the collector current. This signal must be connected to Pin
11. As can be seen in Figure 14, this input has two comparators with
different reference levels. The output of the comparator with the
lower 0.48V reference is connected to the same gate as the output
of the PWM.
When activated, it will immediately reset the output flip-flop, so
reducing the duty cycle. The effectiveness of this cycle-by-cycle
current limit diminishes at low duty cycle values. When
δ
becomes
very small, the storage time of the power transistor becomes
dominant. The current will now increase again, until it surpasses the
reference of the second comparator. The output of this comparator
activates the start-stop circuit and causes an immediate inhibit of the
output pulses. After a certain deadtime, the circuit starts again with
very narrow output pulses. The effect of this two-level current
protection circuit is visualized in Figure 15.
The Start-Stop Circuit
The function of this protection circuit is to stop the output pulses as
soon as a fault occurs and to keep the output stopped for several
periods. After this dead-time, the output starts with a very small,
gradually increasing duty cycle. When the fault is persistent, this will
cause a cyclic switch-off/switch-on condition. This “hiccup” mode
effectively limits the energy during fault conditions. The realization
and the working of the circuit are indicated in Figures 12 and 13.
The dead time and the soft-start are determined by an external
capacitor that is connected to Pin 6 (
δ
MAX
setting).
An RS flip-flop can be set by three different functions:
1. Remote on/off on Pin 10.
2. Overcurrent protection on Pin 11.
3. Low supply voltage protection (internal).
As soon as one of these functions cause a setting of the flip-flop, the
output pulses are blocked via the output gate. In the same time
transistor Q1 is forward-biased, resulting in a discharge of the
capacitor on Pin 6.
The discharging current is limited by an internal 150
resistor in the
emitter of Q1. The voltage at Pin 6 decreases to below the lower
level of the sawtooth. When V6 has dropped to 0.6V, this will
activate a comparator and the flip-flop is reset. The output stage is
no longer blocked and Q1 is cut off. Now V
Z
will charge the
capacitor via R1 to the normal
δ
MAX
voltage. The output starts
delivering very narrow pulses as soon as V6 exceeds the lower
sawtooth level. The duty cycle of the output pulse now gradually
increases to a value determined by the feedback on Pin 3, or by the
static
δ
MAX
setting on Pin 6.
15
14
2
6
12
11
10
LATCH
STOP
SET
RESET
0.6V
0.48V
0.6V
LVOLTAGE
PROTECTION
100
R
1
R
2
C
SS
Q
1
Q
2
PWM
V
Z
SL00375
Figure 16. Start-Stop Circuit
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SE5560F | Switched-mode power supply control circuit |
| SE5560N | Switched-mode power supply control circuit |
| SE5561FE | CONNECTOR ACCESSORY |
| SE5561 | Switched-mode power supply control circuit |
| SE5561N | Switched-mode power supply control circuit |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SE5560F | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Switched-mode power supply control circuit |
| SE5560N | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Switched-mode power supply control circuit |
| SE5561 | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Switched-mode power supply control circuit |
| SE5561FE | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Switched-mode power supply control circuit |
| SE5561N | 制造商:PHILIPS 制造商全稱:NXP Semiconductors 功能描述:Switched-mode power supply control circuit |
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