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Off-Line Quasi-Resonant Switching Regulators
STRW6750 - Off-Line Quasi-Resonant Switching Regulators g n i h tors c t i a Sw egul R
Application Note 28103.30
Series STR-W6750 Off-Line Quasi-Resonant Switching Regulators
INTRODUCTION TERMINAL FUNCTIONS
VCC (Pin 4) Start-up circuit The start-up circuit detects the VCC pin voltage (pin 4), and makes the control IC start and stop operation. The power supply of the control IC (VCC pin input) employs a circuit as shown in Figure 1. At start-up, C3 is charged through a startup resistor R2. The R2 value needs to be set for more than the hold current of the latch circuit (140 µA max.) and to operate at the minimum ac input.
The Series STR-W6750 devices are hybrid integrated circuits (HICs) with a built-in power MOSFET and a control IC designed for quasi-resonant type switch-mode power supplies (SMPS). In normal operation, the HIC provides high efficiency and low EMI noise with bottom-skip quasi-resonant operation during light output loads. Low power consumption is also achieved by blocking (intermi