Linear公司的LT3511是絕緣反激型電源轉換器,不需要第三個繞組或光隔離器.器件集成了240mA/150V功率開關,高壓電路和控制電路.器件工作電壓從4.5V到100V,絕緣輸出功率高達2.5W,主要用在絕緣的通信電源,家用電器電源和工業(yè),汽車與醫(yī)療設備電源.本文介紹了LT3511主要特性, 方框圖,多種絕緣反激轉換器應用電路和相應的元器件, 評估板電路圖和料清單（BOM）.

The LTspecifically designed for the isolated flyback topology. No third winding or opto-isolator is required for regulation as the part senses output voltage directly from the primary-side flyback waveform. The device integrates a 240mA, 150V power switch, high voltage circuitry, and control into a high voltage 16-lead MSOP package with four leads removed.

The LT3511 operates from an input voltage range of 4.5V to 100V and delivers up to 2.5W of isolated output power.

Two external resistors and the transformer turns ratio easily set the output voltage. Off-the-shelf transformers are available for several applications. The high level of integration and the use of boundary mode operation results in a simple, clean, tightly regulated application solution to the traditionally tough problem of isolated power delivery.

LT3511主要特性:

4.5V to 100V Input Voltage Range

Internal 240mA, 150V Power Switch

Boundary Mode Operation

No Transformer Third Winding or Opto-Isolator Required for Regulation

Improved Primary-Side Winding Feedback oad Regulation

VOUT Set with Two External Resistors

BIAS Pin for Internal Bias Supply and Power Switch Driver

No External Start-Up Resistor

16-Lead MSOP Package

LT3511應用:

Isolated ecom Power Supplies

Isolated Auxiliary/Housekeeping Power Supplies

Isolated Industrial, Automotive and Medical Power Supplies

圖1.LT3511方框圖

圖2.LT3511應用電路圖:48V到15V非絕緣反激轉換器


圖3.LT3511應用電路圖:48V到15V絕緣反激轉換器

圖4.LT3511應用電路圖:48V到24絕緣反激轉換器

圖5.LT3511應用電路圖:24到5V絕緣反激轉換器

圖6.LT3511應用電路圖:24V到15V絕緣反激轉換器

圖7.LT3511應用電路圖:12V到15V絕緣反激轉換器

圖8.LT3511應用電路圖:12V到+/-70V絕緣反激轉換器

圖9.LT3511應用電路圖:12V到3.3V絕緣反激轉換器

圖10.LT3511應用電路圖:48V到12V絕緣反激轉換器

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 effi ciency.

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, a 15mA to 20mA minimum load is usually suffi cient.

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.


圖11.LT3511評估板電路圖
LT3511評估板材料清單（BOM）: