3 W non-isolated constant current LED driver

This engineering report describes an LED driver power supply that uses a member of the LinkSwitch-TN family of devices, the LNK306DN. The circuit regulates its load current to 300 mA while developing about 10 V across three series HB-LEDs. The design provides no safety isolation between the AC input and DC output. Therefore the enclosure must be designed to provide isolation. The report contains the power supply specification, a circuit diagram, a complete bill of materials, the PI Xls spreadsheet results for the design, the printed circuit board layouts, and performance data. 

Summary and Features

• Extremely small form factor, fits within GU10 lamp base
• Operates over the universal input voltage range (85 – 265 VAC)
• Meets EN55022 B conducted EMI requirements
• Drives LEDs in constant current (CC) mode
• Built-in, output overvoltage protection when unloaded
• Allows supply to be tested without the load connected
• Low parts count, low-cost solution: only 25 components
• Non-isolated buck converter configuration allows use of off-the-shelf inductors
(does not require a custom transformer)