原标题：Maxim MAX17499电流模式PWM电源控制方案

　　Maxim公司的MAX17499是电流模式PWM控制器,包含了宽输入电压绝缘和非绝缘电源所需的所有电路.输入电压9.5V DC 到24V DC,通用输入电压(85VAC-265VAC)整流或-36V到-72VDC的通信电压.可编程开关频率高达625kHz,主要用在1/2,1/4和1 /8砖电源模块,高效绝缘通信电源,网络/服务器,12V升压和SEPIC稳压器, 绝缘和非绝缘HB LED,工业电源等.本文介绍了MAX17499主要特性,方框图, 次级调整和初级调整的电源等多种电源电路图.

　　The MAX17499/MAX17500 current-mode PWM controllers contain all the control circuitry required for the design of wide-input-voltage isolated and nonisolated power supplies. The MAX17499 is well suited for low input voltage (9.5V DC to 24V DC) power supplies. The MAX17500 is well suited for universal input (rectified 85V AC to 265V AC) or telecom (-36V DC to -72V DC) power supplies.

　　The ICs contain an internal error amplifier that regulates the tertiary winding output voltage that is used in primary-side-regulated isolated power supplies. Primary-side regulation eliminates the need for an optocoupler. An input undervoltage lockout (UVLO) is provided for programming the input-supply start voltage and to ensure proper operation during brownout conditions. An opendrain UVLO flag output, with 210μs internal delay,allows the sequencing of a secondary-side controller.

　　The input-supply start voltage is externally programmable with a voltage-divider.A UVLO/EN input is used to shut down the devices. Internal digital soft-start eliminates

　　output voltage overshoot.

　　The MAX17500 has an internal bootstrap UVLO with large hysteresis that requires a minimum 23.6V for startup. The MAX17499 does not have the internal bootstrap UVLO and can be biased directly from a minimum voltage of 9.5V.

　　The switching frequency for the ICs is programmable with an external resistor. The MAX17499A/MAX17500A provide a 50% maximum duty-cycle limit, while the MAX17499B/MAX17500B provide a 75% maximum duty-cycle limit. These devices are available in 10-pin μMAX packages and are rated for operation over the -40℃ to +85℃ temperature range.

　　MAX17499主要特性:

　　_ Current-Mode Control

　　_ Programmable Switching Frequency Up to 625kHz

　　_ Accurate UVLO Threshold (1%)

　　_ Open-Drain UVLO Flag Output with Internal Delay

　　_ 36V to 72V Telecom Voltage Range

　　_ Universal Offline Input Voltage Range Rectified 85V AC to 265V AC (MAX17500)

　　_ 9.5V to 24V Input (MAX17499)

　　_ Digital Soft-Start

　　_ Internal Bootstrap UVLO with Large Hysteresis (MAX17500)

　　_ Internal Error Amplifier with 1.5% Accurate Reference

　　_ 50μA (typ) Startup Supply Current

　　_ 50% Maximum Duty-Cycle Limit (MAX17499A/MAX17500A)

　　_ 75% Maximum Duty-Cycle Limit (MAX17499B/MAX17500B)

　　_ 60ns Cycle-by-Cycle Current-Limit Propagation Delay

　　_ Available in Tiny 10-Pin μMAX Packages

　　MAX17499应用:

　　1/2, 1/4, and 1/8 Brick Power Modules

　　High-Efficiency, Isolated Telecom Power

　　Supplies

　　Networking/Servers

　　Isolated Keep-Alive Power Supplies

　　12V Boost and SEPIC Regulators

　　Isolated and Nonisolated High-Brightness LED

　　Power Supplies

　　Industrial Power Conversion

　　图1. MAX17499功能方框图

　　图2. MAX17499可编输入起动电压非隔离电源电路图

　　图3. MAX17499次级调整的绝缘电源电路图

　　图4. MAX17499初级调整双输出绝缘的通信电源电路图

　　图5. MAX17499 12-15V输出升压稳压电源电路图

　　图6. MAX17499典型应用电路图