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| 型号： | FSQ321 |
| 厂商： | Fairchild Semiconductor |
| 文件页数： | 12/21页 |
| 文件大小： | 0K |
| 描述： | IC SWIT PWM GREEN OVP UVLO 8DIP |
| 标准包装： | 50 |
| 输出隔离： | 隔离 |
| 频率范围： | 55kHz ~ 67kHz |
| 输入电压： | 9 V ~ 20 V |
| 输出电压： | 650V |
| 功率（瓦特）： | 12W |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 8-DIP（0.300"，7.62mm） |
| 供应商设备封装： | 8-DIP |
| 包装： | 管件 |
| 产品目录页面： | 1219 (CN2011-ZH PDF) |
Functional Description
1. Startup : At startup, an internal high-voltage current
source supplies the internal bias and charges the
external capacitor (C a ) connected to the V CC pin, as
illustrated in Figure 20. When V CC reaches 12V, the
FPS? begins switching and the internal high-voltage
current source is disabled. The FPS continues its
V O
FOD817A
V FB
C B
3
V CC
I delay
D1
V ref
I FB
D2
3R
OSC
SenseFET
normal switching operation and the power is supplied
from the auxiliary transformer winding unless V CC goes
below the stop voltage of 8V.
V DC
KA431
V SD
+
V FB *
-
R
OLP
Gate
driver
R sense
FSQ0365RN Rev. 00
C a
Figure 21. Pulse-Width-Modulation (PWM) Circuit
2
V CC
5
V str
3. Synchronization : The FSQ-series employs a valley
switching technique to minimize the switching noise and
loss. The basic waveforms of the valley switching
I CH
converter are shown in Figure 22. To minimize the
MOSFET's switching loss, the MOSFET should be
8V/12V
FSQ0365RN Rev.00
V CC good
V ref
Internal
Bias
turned on when the drain voltage reaches its minimum
value, as shown in Figure 22. The minimum drain
voltage is indirectly detected by monitoring the V CC
winding voltage, as shown in Figure 22.
V ds
Figure 20. Startup Circuit
2. Feedback Control : FPS employs Current Mode
V RO
control, as shown in Figure 21. An opto-coupler (such as
FOD817A) and shunt regulator (such as KA431) are
often used to implement
the feedback network.
V DC
V RO
Comparing the feedback voltage with the voltage across
the R SENSE resistor makes it possible to control the
switching duty cycle. When the reference pin voltage of
V sync
t F
V ovp (6V)
the shunt regulator exceeds the internal reference
voltage of 2.5V, the opto-coupler LED current increases,
pulling down the feedback voltage and reducing the duty
cycle. This event typically occurs when input voltage is
increased or output load is decreased.
2.1 Pulse-by-Pulse Current Limit : Because Current
Mode control is employed, the peak current through the
SenseFET is limited by the inverting input of PWM
MOSFET Gate
0.7V
0.2V
300ns Delay
comparator (V FB *), as shown in Figure 21. Assuming
that the 0.9mA current source flows only through the
ON
ON
internal resistor (3R + R = 2.8k ? ), the cathode voltage
of diode D2 is about 2.5V. Since D1 is blocked when the
feedback voltage (V FB ) exceeds 2.5V, the maximum
voltage of the cathode of D2 is clamped at this voltage,
clamping V FB *. Therefore, the peak value of the current
through the SenseFET is limited.
2.2 Leading-Edge Blanking (LEB) : At the instant the
internal SenseFET is turned on, a high-current spike
usually occurs through the SenseFET, caused by
primary-side capacitance and secondary-side rectifier
reverse recovery. Excessive voltage across the R sense
resistor would lead to incorrect feedback operation in the
Current Mode PWM control. To counter this effect, the
FPS employs a leading-edge blanking (LEB) circuit. This
circuit inhibits the PWM comparator for a short time
(t LEB ) after the SenseFET is turned on.
? 2007 Fairchild Semiconductor Corporation
FSQ0365, FSQ0265, FSQ0165, FSQ321 ? Rev. 1.0.6
FSQ0365RN Rev.00
Figure 22. Valley Resonant Switching Waveforms
4. Protection Circuits : The FSQ-series has several
self-protective functions, such as Overload Protection
(OLP), Abnormal Over-Current protection (AOCP),
Over-Voltage Protection (OVP), and Thermal Shutdown
(TSD). All the protections are implemented as Auto-
Restart Mode. Once the fault condition is detected,
switching is terminated and the SenseFET remains off.
This causes V CC to fall. When V CC falls down to the
Under-Voltage Lockout (UVLO) stop voltage of 8V, the
protection is reset and the startup circuit charges the
V CC capacitor. When the V CC reaches the start voltage
of 12V, the FSQ-series resumes normal operation. If the
fault condition is not removed, the SenseFET remains
off and V CC drops to stop voltage again. In this manner,
www.fairchildsemi.com
12
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相关代理商/技术参数 |
参数描述 |
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| FSQ321L | 功能描述:开关变换器、稳压器与控制器 SMPS Power Switch RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FSQ321LX | 功能描述:开关变换器、稳压器与控制器 0.5A, 650V SMPS Power Switch RoHS:否 制造商:Texas Instruments 输出电压:1.2 V to 10 V 输出电流:300 mA 输出功率: 输入电压:3 V to 17 V 开关频率:1 MHz 工作温度范围: 安装风格:SMD/SMT 封装 / 箱体:WSON-8 封装:Reel |
| FSQ3W | 制造商:RFE 制造商全称:RFE international 功能描述:FUSIBLE RESISTORS FM, FKN, & FSQ Series: Fusible |
| FSQ500HL | 功能描述:电源开关 IC - 配电 Green Mode Power Switch RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
| FSQ500L | 功能描述:电源开关 IC - 配电 Power Switch 0.245A RoHS:否 制造商:Exar 输出端数量:1 开启电阻（最大值）:85 mOhms 开启时间（最大值）:400 us 关闭时间（最大值）:20 us 工作电源电压:3.2 V to 6.5 V 电源电流（最大值）: 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:SOT-23-5 |
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