Linear公司的LT3511是绝缘反激型电源转换器,不需要第三个绕组或光隔离器.器件集成了240mA/150V功率开关,高压电路和控制电路.器件工作电压从4.5V到100V,绝缘输出功率高达2.5W,主要用在绝缘的通信电源,家用电器电源和工业,汽车与医疗设备电源.本文介绍了LT3511主要特性, 方框图,多种绝缘反激转换器应用电路和相应的元器件, 评估板电路图和料清单(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应用:

Isolated Telecom Power Supplies

Isolated Auxiliary/Housekeeping Power Supplies

Isolated Industrial, Automotive and Medical Power Supplies

图1.LT3511方框图

图2.LT3511应用电路图:48V到15V非绝缘反激转换器


图3.LT3511应用电路图:48V到15V绝缘反激转换器

图4.LT3511应用电路图:48V到24绝缘反激转换器

图5.LT3511应用电路图:24到5V绝缘反激转换器

图6.LT3511应用电路图:24V到15V绝缘反激转换器

图7.LT3511应用电路图:12V到15V绝缘反激转换器

图8.LT3511应用电路图:12V到+/-70V绝缘反激转换器

图9.LT3511应用电路图:12V到3.3V绝缘反激转换器

图10.LT3511应用电路图:48V到12V绝缘反激转换器

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.


图11.LT3511评估板电路图
LT3511评估板材料清单(BOM):


详情请见:
http://cds.linear.com/docs/Datasheet/3511fa.pdf
和
http://cds.linear.com/docs/Demo%20Board%20Manual/dc1517afa.pdf