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| 型号： | 88EM8081XX-SAG2C000-T |
| 厂商： | MARVELL SEMICONDUCTOR INC |
| 元件分类： | 稳压器 |
| 英文描述： | 2 A POWER FACTOR CONTROLLER, 120 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | GREEN, SOIC-8 |
| 文件页数： | 14/64页 |
| 文件大小： | 667K |
| 代理商： | 88EM8081XX-SAG2C000-T |
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Functional Description
VIN – Input Voltage Sensing
Copyright 2010 Marvell
Doc. No. MV-S106340-01 Rev. B
August 6, 2010, Preliminary Information
Document Classification: Proprietary
Page 21
3.5
VIN – Input Voltage Sensing
The PFC function is implemented by sensing the input current waveform and forcing the average of
the input current to follow the input voltage sinusoidal waveform. A resistor divider is used between
AC input and a primary reference ground to sense the input voltage. The primary reference ground
is connected to the 88EM8080/88EM8081 IC reference ground and to the source pin of the external
switching MOSFET Q1 as in Figure 1, Universal Isolated LED Driver with PFC, on page 3. The
output of the resistor divider which is a half sinusoidal waveform is the input to the VIN pin. By
sensing the input voltage waveform at the VIN pin, the controller can generate its own internal
sinusoidal reference at the same frequency as the input. This is done by having an internal DC
threshold (0.72 Volts), a comparator and a zero-cross detection circuit. The details of the
calculations are described in Section 5.2.
It is recommended to use a high impedance divider network between the AC line to reference AC
ground to sense the input voltage at the VIN pin. This will help to reduce the no load input power and
will improve the efficiency in general. Due to the VIN pin being a high impedance input pin, a 10nF
(typical) decoupling noise capacitor between it and ground is required.
3.5.1
Brown-out Protection
VIN pin is also used for the brown-out protection function. A resistor divider of 100:1 ratio from the
high voltage side corresponds to a brown-out protection input voltage of around 50V RMS for the
defined internal threshold of 0.72 Volts. Increasing the high voltage divider turns ratio will increase
brown-out protection voltage.
3.6
FB – Output Voltage / Current Feedback
The 88EM8080/88EM8081 has an internal current loop and output voltage/current loop to
implement the PFC and the output voltage/current regulating function. FB pin is the inverting input of
a voltage error amplifier with 2.5 volts as the internal reference voltage. For steady state operation
100% of required output voltage/current is scaled to 2.5V at the feedback pin by external circuitry.
For output current regulation, the much smaller voltage across the load current sensing resistor
could be amplified to be 2.5V and then applied to the FB pin.
During startup, when FB pin is below 87.5% of the reference voltage, the PFC controller operates in
soft-start mode. The internal voltage error amplifier switches over to normal regulation phase once
the FB pin voltage reaches 87.5% of the reference value.
3.6.1
FB – Over Voltage Protection (OVP)
Over voltage protection is implemented through the FB pin. When the FB pin voltage exceeds
VFB_OVP threshold voltage (refer to Table 4, Electrical Characteristics, on page 16), the IC is
switched off and no PWM output is available at SW pin of the IC.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 88EM8082A1-SAG2C000 | 制造商:Marvell 功能描述:?ACTIVE PFC CONTROLLER FOR AC-DC FLYBACK LED APPLICATIONS - Bulk 制造商:Marvell 功能描述:88EM8082 Series - Single-Stage 120 kHz Fly-back AC/DC LED Driver - SOIC-8 |
| 88EM8182B0-SAE2C000-AL00 | 制造商:Marvell 功能描述:?NON-DIMMABLE, TRIAC AC/DC LED DRIVER, 110V/220V, LOW VOLTAG - Trays |
| 88EM8182B0-SAE2C000TAL00 | 制造商:Marvell 功能描述:?NON-DIMMABLE; TRIAC AC/DC LED DRIVER; 110V/220V; LOW VOLTAG - Tape and Reel 制造商:Marvell 功能描述:88EM8182 Series - Fly-back Non-Dimmable LED Driver 110V/220V - 8-Pin SOIC |
| 88EM8183B0-SAE2C000-AL00 | 制造商:MARVELL 功能描述:0 |
| 88EM8183B0-SAE2C000TAL00 | 制造商:Marvell 功能描述:?DIMMABLE; TRIAC AC/DC LED DRIVER; 110V/220V; LOW VOLTAGE + - Tape and Reel 制造商:Marvell 功能描述:Marvell 88EM8183 Series 19V Universal Triac Dimmable LED Driver - SOIC-8 |
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