参数资料
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: 17/64页
文件大小: 667K
代理商: 88EM8081XX-SAG2C000-T
88EM8080/88EM8081
Datasheet
Doc. No. MV-S106340-01 Rev. B
Copyright 2010 Marvell
Page 24
Document Classification: Proprietary
August 6, 2010, Preliminary Information
3.8
Mixed Modes of Operation
The 88EM8080/88EM8081 controller operates in Continuous Conduction Mode (CCM) or
Discontinuous Mode (DCM) modes of operation. The transformer primary inductance and the load
determine the modes of operation. The CCM mode will have lower peak current than the
discontinuous mode of operation. At high power levels CCM is recommended because of reduction
of copper losses in the transformer and also the conduction losses in the primary MOSFET. In
addition CCM could reduce the input filter size. DCM mode may be recommended at lower power
levels to reduce the turn-on switching losses and the Primary FET losses due to reverse recovery
time and charge of the output diode.
3.9
Compensation and Adaptive Control Loop
The LED current control is a feedback control system. The bandwidth of the voltage loop for the
single stage LED feedback control system has to be much less than twice the line frequency to
provide a high power factor and low THD. The entire feedback system needs to be designed for high
power factor and low THD at low line (90-132VAC) and high line (180-264VAC). Marvell has an
internal proportional and integral gain control feature for the voltage loop due to Marvell's DSP
Control Technology. This means by sensing the input voltage, the IC sets PI control automatically to
change the bandwidth for different AC input line ranges. This innovative adaptive feature will help
achieve low THD and high power factor at all lines and loads. Because of this proportional and
integral control within the IC, no external compensation is required for non-isolated outputs. Minimal
external compensation is required for isolated outputs mainly for the compensation on the error
amplifier (TL431) at the secondary side. This compensation network provides enough attenuation at
120Hz so that the second harmonic ripple voltage from the sensed current signal is attenuated and
not amplified.
3.10
Over Temperature Protection
The 88EM8080/88EM8081 IC has an internal over temperature sensing circuit. On over
temperature, the fault detection signal shuts off the PWM switching output at the SW pin.
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