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网上兼职赚钱项目挣钱的兼职APR34309CMPTR-G1 YUANZHUANGZHENGPINGONGSIXIANHUO

日期:2020-01-08 15:42    发布企业: 深圳市赛美科科技有限公司

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The operation of the SR is described with timing diagram shown in Figure 2. APR343 monitors the MOSFET drain-source voltage. When the drain voltage is lower than the turn-on threshold voltage VTHON, the IC outputs a positive drive voltage after a turn-on delay time (tDON). The MOSFET will turn on and the current will transfer from the body diode into the MOSFET’s channel. 
 
In the process of drain current decreasing linearly toward zero, the drain-source voltage rises synchronically. When it rises over the turn off threshold voltage VTHOFF, APR343 pulls the drive signal down after a turn off delay (tDOFF). 
 
Minimum On Time When the controlled MOSFET gate is turned on, some ringing noise is generated. The minimum on-time timer blanks the VTHOFF comparator, keeping the controlled MOSFET on for at least the minimum on time. If VTHOFF falls below the threshold before minimum on time expires, the MOSFET will keep on until the end of the minimum on time. 
 
The minimum on time is in direct proportion to the (VDET-VCC)*tONP. When (VDET-VCC)*tONP=5V*5µs, the minimum on time is about 1.8µs. 
 
The Value and Meaning of AREF Resistor As to DCM operation Flyback converter, after secondary rectifier stops conduction the primary MOSFET Drain-to-source ringing waveform is resulted from the resonant of primary inductance and equivalent switch device output capacitance. This ringing waveform probably leads to Synchronous Rectifier error conduction. To avoid this fault happening, APR343 has a special function design by means of volt-second product detecting. From the sensed voltage of VDET pin to see, the volt-second product of voltage above VCC at primary switch on time is much higher than the volt-second product of each cycle ringing voltage above VCC. Therefore, before every time Synchronous Rectifier turning on, APR343 judges if the detected volt-second product of VDET voltage above VCC is higher than a threshold and then turn on synchronous Rectifier. The purpose of AREF resistor is to determine the volt-second product threshold. APR343 has a parameter, Kqs, which converts RAREF value to voltsecond product. 
 
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