Analog Devices LT3511EMS | Demoboard DC1517A

Description

Demonstration circuit 1517A is a monolithic high voltage isolated fl yback converter featuring the LT3511. This demo circuit is designed for a 5V isolated output from an input voltage range of 36V to 75V. The maximum output current is up to 300mA. The circuit doesn’t require an opto-isolator,due to the output voltage being sensed directly from the primary side transformer winding. A third winding off the transistor is used to bias the LT3511 for highest efficiency.

The fl yback converter requires a minimum load to maintain good regulation. A Zener diode is placed between VOUT + and VOUT – to clamp output voltage to ~7.5V if the minimum load requirement is not met. Depending on the input voltage and the output regulation requirement, a15mA to 20mA minimum load is usually sufficient.

This demo circuit uses a diode-Zener clamp to limit the peak spike voltage due to transformer leakage inductance. A diode-Zener clamp is more effi cient than a RCD clamp.

The LT3511 operates in boundary mode and also provides output voltage temperature compensation.

The LT3511 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this quick start guide.

More information

• Datasheet
• IC product information