参数资料
型号: NCP1351DPG
厂商: ON Semiconductor
文件页数: 12/27页
文件大小: 0K
描述: IC CTRLR PWM PROG CM OTP 8DIP
标准包装: 50
输出隔离: 隔离
频率范围: 调节
输入电压: 9.5 V ~ 28 V
工作温度: -25°C ~ 125°C
封装/外壳: 8-DIP(0.300",7.62mm)
供应商设备封装: 8-PDIP
包装: 管件
NCP1351
V Ct
Controlled by the
FB Current
Minimum Frequency
P out
I Ct = 10 m A
Decreases
P out
Increases
Maximum Frequency
Figure 10. The Current Injected into the Feedback Loop Adjusts the Switching Frequency
C t Voltage
C t Voltage
Figure 11. In Light Load Conditions, the
Oscillator Further Delays the Restart Time
In light load conditions, the frequency can go down to a
few hundred Hz without any problem. The internal circuitry
naturally blocks the oscillator and softly shifts the restart
time as shown on Figure 11 scope shot.
Delays The Restart Time
In lack of feedback current, for instance during a startup
sequence or a short circuit, the oscillator frequency is pushed
to the limit set by the timing capacitor. In this case, the lower
threshold imposed to the timing capacitor is blocked to
500 mV (parameter V fault ). This is the maximum power the
Figure 12. C t Voltage Swing at a Moderate
Loading
power supply can deliver at low line. This discrepancy
relates to the propagation delay from the point where the
peak is detected to the MOSFET gate effective pulldown. It
naturally includes the controller reaction time, but also the
driver capability to pull the gate down. If the MOSFET Q g
is too large, then this parameter will greatly affect your
overpower parameter. Sometimes, the small PNP can help
and we recommend it if you use a large Q g MOSFET:
D1
1N4148
converter can deliver. To the opposite, as you inject current
via the optocoupler in the feedback pin, the off time expands
and the power delivery reduces. The maximum threshold
DRV
Q1
2N2907
level in standby conditions is set to 6 V.
GND
Over Power Protection
As any universal-mains operated converters, the output
power slightly increases at high line compared to what the
Figure 13. A Low-Cost PNP Improves the Drive
Capability at Turn-off
http://onsemi.com
12
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