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參數(shù)資料
| 型號： | NCP1207ADR2 |
| 廠商： | ON SEMICONDUCTOR |
| 元件分類： | 穩(wěn)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, PDSO8 |
| 封裝： | SOIC-8 |
| 文件頁數(shù)： | 11/16頁 |
| 文件大?。?/td> | 197K |
| 代理商： | NCP1207ADR2 |
NCP1207A
http://onsemi.com
11
Latching Off the NCP1207A
In certain cases, it can be very convenient to externally
shut down permanently the NCP1207A via a dedicated
signal, e.g. coming from a temperature sensor. The reset
occurs when the user unplugs the power supply from the
mains outlet. To trigger the latchoff, a CTN (Figure 21) or
a simple NPN transistor (Figure 22) can do the work.
Figure 21. A simple CTN triggers the latchoff as
soon as the temperature exceeds a given setpoint
1
2
3
4
8
7
6
5
CTN
Aux
NCP1207A
ON/OFF
Figure 22. A simple transistor arrangement allows
to trigger the latchoff by an external signal
1
2
3
4
8
7
6
5
NCP1207A
Aux
Shutting Off the NCP1207A
Shutdown can easily be implemented through a simple
NPN bipolar transistor as depicted by Figure 23. When OFF,
Q1 is transparent to the operation. When forward biased, the
transistor pulls the FB pin to ground (V
CE(sat)
≈
200 mV) and
permanently disables the IC. A small time constant on the
transistor base will avoid false triggering (Figure 23).
Figure 23. A simple bipolar transistor totally
disables the IC
1
2
3
4
8
7
6
5
NCP1207A
10 nF
Q1
10 k
ON/OFF
1
2
3
Power Dissipation
The NCP1207A is directly supplied from the DC rail
through the internal DSS circuitry. The DSS being an
autoadaptive circuit (e.g. the ON/OFF dutycycle adjusts
itself depending on the current demand), the current flowing
through the DSS is therefore the direct image of the
NCP1207A current consumption. The total power
dissipation
can
be
(VHVDC
11 V)
ICC2
. If we operate the device on a 250
Vac rail, the maximum rectified voltage can go up to 350
Vdc. As a result, the worse case dissipation occurs at the
maximum switching frequency and the highest line. The
dissipation is actually given by the internal consumption of
the NCP1207A when driving the selected MOSFET. The
best method to evaluate this total consumption is probably
to run the final circuit from a 50 Vdc source applied to pin 8
and measure the average current flowing into this pin.
Suppose that we find 2.0 mA, meaning that the DSS
dutycycle
will
be
From the 350 Vdc rail, the part will dissipate:
350 V
2.0 mA
700 mW
(however this 2.0 mA number
will drop at higher operating junction temperatures).
A DIP8 package offers a junctiontoambient thermal
resistance R
JA
of 100
°
C/W. The maximum power
dissipation can thus be computed knowing the maximum
operating ambient temperature (e.g. 70
°
C) together with
the maximum allowable junction temperature (125
°
C):
Tjmax
TAmax
RJA
do not reach the worse consumption budget imposed by the
operating conditions. Several solutions exist to cure this
trouble:
The first one consists in adding some copper area around
the NCP1207A DIP8 footprint. By adding a min pad area
of 80 mm
2
of 35 m copper (1 oz.), R
JA
drops to about
75
°
C/W. Maximum power then grows up to 730 mW.
A resistor R
drop
needs to be inserted with pin 8 to
a) avoid
negative spikes at turnoff (see below)
b) split the power budget between this resistor and the
package. The resistor is calculated by leaving at least 50 V
on pin 8 at minimum input voltage (suppose 100 Vdc in
Vbulkmin
evaluated
using:
2.0/7.0
=
28.6%.
Pmax
550 mW
. As we can see, we
our case):
Rdrop
power dissipated by the resistor is thus:
50 V
7.0 mA
7.1 k
. The
Pdrop
VdropRMS
2
Rdrop
IDSS
Rdrop
DSSduty
cycle
2
Rdrop
7.0 mA
7.1 k
7.1 k
0.286
2
99.5 mW
Please refer to the application note AND8069 available
from www.onsemi.com/pub/ncp1200.
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PDF描述 |
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| NCP1207ADR2G | PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| NCP1207A | PWM Current Mode Controller for Free Running Quasi Resonant Operation(電流模式控制的PWM控制器，用于自由振蕩的“準諧振”操作) |
| NCP1207B | PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| NCP1207BDR2G | PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| NCP1207 | PWM Current-Mode Controller for Free Running Quasi-Resonant Operation(電流模式控制的PWM控制器，用于自由振蕩的“準諧振”操作) |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| NCP1207ADR2G | 功能描述:電流型 PWM 控制器 Quasi Resonant Current Mode PWM RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1207AP | 功能描述:電流型 PWM 控制器 Quasi Resonant RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1207APG | 功能描述:電流型 PWM 控制器 Quasi Resonant Current Mode PWM RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
| NCP1207B | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:PWM Current-Mode Controller for Free Running Quasi-Resonant Operation |
| NCP1207BDR2G | 功能描述:電流型 PWM 控制器 ANA QUASI RESNT SMPS RoHS:否 制造商:Texas Instruments 開關頻率:27 KHz 上升時間: 下降時間: 工作電源電壓:6 V to 15 V 工作電源電流:1.5 mA 輸出端數(shù)量:1 最大工作溫度:+ 105 C 安裝風格:SMD/SMT 封裝 / 箱體:TSSOP-14 |
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