Maxim MAX17499電流模式PWM電源控制方案

作者：時(shí)間：2011-04-15 來(lái)源：網(wǎng)絡(luò )

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Maxim公司的MAX17499是電流模式PWM控制器,包含了寬輸入電壓絕緣和非絕緣電源所需的所有電路.輸入電壓9.5V DC 到24V DC,通用輸入電壓(85VAC-265VAC)整流或-36V到-72VDC的通信電壓.可編程開(kāi)關(guān)頻率高達625kHz,主要用在1/2,1/4和1/8磚電源模塊,高效絕緣通信電源,網(wǎng)絡(luò )/服務(wù)器,12V升壓和SEPIC穩壓器, 絕緣和非絕緣HB led,工業(yè)電源等.本文介紹了MAX17499主要特性,方框圖, 次級調整和初級調整的電源等多種電源電路圖.

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應用:

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