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STR5A162D bảng dữ liệu(PDF) 11 Page - Sanken electric |
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STR5A162D bảng dữ liệu(HTML) 11 Page - Sanken electric |
11 / 21 page STR5A100D Series STR5A100D-DS Rev.1.2 SANKEN ELECTRIC CO.,LTD. 11 Dec. 25, 2013 decreases to about 1.6 V or less, the IC is stops oscillation and restarts. The IC repeats the intermittent oscillation operation until the FB pin voltage keeps about 1.6 V or more after the output voltage increases. VOUT Output Current IOUT CV Mode CC Mode OUT OSC 2 DLIM P ) K P ( OUT V 2 f I L I Output Voltage Figure 10-9 CV/CC characteristics 10.8 Leading Edge Blanking Function The IC uses the peak-current-mode control method for the constant voltage control of output. In peak-current-mode control method, there is a case that the power MOSFET turns off due to unexpected response of FB comparator or overcurrent protection circuit (OCP) to the steep surge current in turning on a power MOSFET. In order to prevent this operation, Leading Edge Blanking Time, tBW = 250 ns is built-in. In the period of tBW, the IC does not respond to the surge voltage in turning on the power MOSFET. 10.9 Random Switching Function The IC modulates its switching frequency randomly by superposing the modulating frequency on fOSC(AVG) in normal operation. This function reduces the conduction noise compared to others without this function, and simplifies noise filtering of the input lines of power supply. 10.10 Auto Standby Function Auto Standby Function automatically changes the oscillation mode to green mode or burst oscillation mode, when the output load becomes lower, the drain current ID decreases and the oscillation frequency becomes lower gradually (Green Mode) as shown in Figure 10-10. In order to reduce the switching loss, the number of switching is reduced in green mode and the switching operation is stopped during a constant period in burst oscillation mode. The burst oscillation mode operates by the Standby Operation Cycle, TSTBOP = 1.3 ms and the switching frequency about 23 kHz. In light load, the number of minimum switching times is two times in TSTBOP (refer to Figure 10-11) Since the oscillator of burst oscillation cycle setting and the oscillator of switching oscillation frequency setting are not synchronized each other, the switching frequency may be high at near the Standby Operation Threshold Voltage, VSTBOP. Switching frequency fOSC Output power, PO 65kHz About 23kHz Burst oscillation Normal operation Standby power Green mode Burst cycle is 1.3ms Figure 10-10 Relationship between PO and fOSC Time ID TSTBOP = 1.3 ms About 23 kHz Figure 10-11 Switching waveform at burst oscillation 10.11 Overcurrent Protection Function (OCP) Overcurrent Protection Function (OCP) detects each drain peak current level of a power MOSFET on pulse-by-pulse basis, and limits the output power when the current level reaches to Drain Current Limit. When this OCP operation continues for more than the Constant Current Control Delay Time, tCCD = 90 ms, Constant Current (CC) control is activated (refer to 10.7 Constant Current (CC) Control). Input Compensation Function ICs with PWM control usually have some propagation delay time. The steeper the slope of the actual drain current at a high AC input voltage is, the larger the actual drain peak current is, compared to the Drain Current Limit. Thus, the peak current has some variation depending on the AC input voltage in the drain current limitation state. In order to reduce the variation of peak current in the drain current limitation state, the IC incorporates a built-in Input Compensation function. The Input Compensation function superposes a signal with a constant slope (Figure 10-12) into the internal current detection signal and varies the internal threshold voltage. |
Số phần tương tự - STR5A162D |
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Mô tả tương tự - STR5A162D |
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