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參數資料
| 型號： | NCP1207P |
| 廠商： | ON SEMICONDUCTOR |
| 元件分類： | 穩壓器 |
| 英文描述： | PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| 中文描述： | 0.5 A SWITCHING CONTROLLER, PDIP8 |
| 封裝： | PLASTIC, DIP-8 |
| 文件頁數： | 10/18頁 |
| 文件大小： | 202K |
| 代理商： | NCP1207P |
NCP1207
http://onsemi.com
10
Figure 19. A patented method allows for skip level
selection via a series resistor inserted in series
with the current
+
RESET
DRIVER
R
sense
R
skip
+
DRIVER = HIGH I = 0
DRIVER = LOW I = 200 A
2
3
The skip level selection is done through a simple resistor
inserted between the current sense input and the sense element.
Every time the NCP1207 output driver goes low, a 200 A
source forces a current to flow through the sense pin
(Figure 19): when the driver is high, the current source is off
and the current sense information is normally processed. As
soon as the driver goes low, the current source delivers 200 A
and develops a ground referenced voltage across R
skip
. If this
voltage is below the feedback voltage, the current sense
comparator stays in the high state and the internal latch can be
triggered by the next clock cycle. Now, if because of a low load
mode the feedback voltage is below R
skip
level, then the
current sense comparator permanently resets the latch and the
next clock cycle (given by the demagnetization detection) is
ignored: we are skipping cycles as shown by Figure 20. As
soon as the feedback voltage goes up again, there can be two
situations: the recurrent period is small and a new
demagnetization detection (next wave) signal triggers the
NCP1207. To the opposite, in low output power conditions, no
more ringing waves are present on the drain and the toggling
of the current sense comparator together with the internal 5 s
timeout initiates a new cycle start. In normal operating
conditions, e.g. when the drain oscillations are generous, the
demagnetization comparator can detect the 50 mV crossing
and gives the “green light”, alone, to reactive the power
switch. However, when skip cycle takes place (e.g. at low
output power demands), the restart event slides along the
drain ringing waveforms (actually the valley locations) which
decays more or less quickly, depending on the
L
primary
C
parasitic
network damping factor. The situation can
thus quickly occur where the ringing becomes too weak to be
detected by the demagnetization comparator: it then
permanently stays locked in a given position and can no longer
deliver the “green light” to the controller. To help in this
situation, the NCP1207 implements a 5 s timeout generator:
each time the 50 mV crossing occurs, the timeout is reset. So,
as long as the ringing becomes too low, the timeout generator
starts to count and after 5 s, it delivers its “green light”. If the
skip signal is already present then the controller restarts;
otherwise the logic waits for it to set the drive output high.
Figure 20 depicts these two different situations:
Demag Restart
Current Sense and Timeout Restart
5 s
5 s
Drain
Signal
Timeout
Signal
Drain
Signal
Timeout
Signal
Figure 20. When the primary natural ringing becomes too low, the internal timeout together with the sense
comparator initiates a new cycle when FB passes the skip level.
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| NCP1207PG | 功能描述:IC CTRLR PWM CM OVP OCP HV 8DIP RoHS:是 類別:集成電路 (IC) >> PMIC - AC-DC 轉換器，離線開關 系列:- 標準包裝:1 系列:FPS™ 輸出隔離:隔離 頻率范圍:61kHz ~ 73kHz 輸入電壓:8 V ~ 26 V 輸出電壓:650V 功率（瓦特）:12W 工作溫度:-40°C ~ 115°C 封裝/外殼:8-DIP（0.300"，7.62mm） 供應商設備封裝:8-MDIP 包裝:Digi-Reel® 其它名稱:FSL206MRBNFSDKR |
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