design feature 1 can be installed in the enlarged GU-10 lamp holder 2 Accurate primary side constant voltage / constant current controller eliminates secondary side control and optocoupler 2.1 Improve efficiency without current sense resistor 2.2 Low component quantity solution that reduces costs 3 Overheat protection – Strict tolerance range (±5%) plus hysteresis recovery ensures PCB temperature is safe under all conditions 4 automatic restart output short circuit and open loop protection 5 extremely energy efficient 5.1 Full load efficiency over the entire operating voltage range exceeds 74% 5.2 No-load power consumption <200 mW at 265 VAC input 6 Ultra-low leakage current: <5 μA at 265 VAC input (no Y capacitor required) 7 Green package: halogen-free and RoHS compliant working principle Figure 1 is a circuit diagram of a universal input 10.5 V, 350 mA constant voltage / constant current flyback power supply designed using the LinkSwitch-II LNK605DG (U1) for LED driver applications. This design is designed to drive three LED strings that provide the rated output current for the LED over the entire VF range. The integrated circuit U1 contains a power switching device, an oscillator, a CC/CV control engine, startup and protection functions. The U1 primary side constant voltage/constant current control function eliminates the need for a sense resistor and optocoupler, thus greatly saving space in the design, which allows the driver to be easily loaded into the GU-10 LED lamp housing. The bridge rectifier BR1 rectifies the AC input voltage. The rectified DC is filtered by bulk capacitors C1 and C3. Inductor L1 and capacitors C1 and C3 together form a π-type filter that attenuates differential mode conducted EMI noise. This configuration and One side of the T1 primary winding receives the rectified and filtered DC voltage. The MOSFET drives the other side of the primary winding. D2, R4, R5, and C4 form an RCD-R clamp circuit that limits the drain voltage spike caused by leakage inductance. Device U1 is fully self-powered via the bypass (BP) pin and decouples capacitor C2. U1 uses on/off control to regulate constant voltage (CV) output and constant current (CC) regulation through frequency control. The feedback resistors R1 and R2 should have a tolerance of 1% to help tightly control the current at the rated output voltage and constant current operating mode to the center. The constant voltage feature also provides overvoltage protection (OVP) in the event of an open-circuit fault in any LED. In multiple modes from no load to full load, the controller in U1 first operates in the constant voltage phase. Once the maximum power point is detected, the controller will enter constant current mode. During the constant voltage phase, U1 maintains the output voltage level by skipping the switching period and maintains regulation by adjusting the ratio of the enable period to the disable period. The current limit is also reduced to reduce the noise at low loads to an almost imperceptible level. As the load current increases, the current limit will also rise and the skipped period will be less and less to provide more output power. When U1 enters the skipped state without any switching cycle (the maximum output power point is reached), the controller in U1 will switch to constant current mode. When the load current needs to be further increased, the output voltage will drop. The drop in output voltage is reflected on the FB pin voltage. In response to a voltage drop on the FB pin, the switching frequency will drop to achieve a constant current output. The secondary winding of the transformer is rectified by D3 and a Schottky barrier diode (increased efficiency) and filtered by C5. In this application design, capacitor C5 has a low ESR to meet the required output voltage ripple requirements without the need for a post-stage LC filter. Design Points 1. The IC package provides a very large creepage distance (on the package and PCB) between the high voltage and low voltage pins, which is necessary for high humidity and high pollution environments, avoiding arcing and further improving reliability. Sex. 2. Place C2 as close as possible to the bypass pin. (Edit: Bright) Steel Miniature Weighing Sensor Steel Miniature Weighing Sensor,Load Cells For Weighing,Weight Indicator Load Cell,Weight Cell Sensor Xiaogan Yueneng Electronic Technology Co., Ltd. , https://www.xgsensor.com
The combination of Power Integrations transformer's E-shieldTM technology allows the design to meet EMI standard EN55015 Class B requirements with a 6 dB margin without the need for a Y capacitor. The fire-resistant fusible resistor RF1 limits the inrush current during AC power-up and during differential mode surges.