TI 公司的UC1825是PWM控制器件,非常適合高頻開關(guān)電源應(yīng)用. UC1825的特別之處是通過(guò)比較器和邏輯電路最小化傳輸時(shí)延,同時(shí)最大化誤差放大器的帶寬和轉(zhuǎn)換速率. UC1825的開關(guān)頻率高達(dá)1MHz,50ns傳輸時(shí)延至輸出,符合QML-V認(rèn)證和 SMD 5962-87681以及Rad容差為 30 kRad (Si) TID. UC1825具有大電流雙圖騰柱輸出,峰值電流1.5A,起動(dòng)電流僅為1.1mA,逐個(gè)脈沖進(jìn)行限流,軟起動(dòng)/最大占空比控制和帶滯后的欠壓鎖住.本文介紹了UC1825的主要特性, 方框圖以及采用UC1835的50W設(shè)計(jì)案例。The UC1825 PWM control device is optimized for

high-frequency switched mode power supply applications. Particular care was given to minimizing propagation delays through the comparators and logic circuitry while

maximizing bandwidth and slew rate of the error amplifier. This controller is designed for use in either current-mode or voltage mode systems with the capability for input voltage feed-forward.Protection circuitry includes a current limit comparator with a 1-V threshold, a TTL compatible shutdown port, and a soft start pin which will double as a maximum duty-cycle clamp. The logic is fully latched to

provide jitter-free operation and prohibit multiple pulses at an output. An undervoltage lockout section with 800 mV of hysteresis assures low start up current. During

undervoltage lockout, the outputs are high impedance.This device features totem pole outputs designed to source and sink high peak currents from capacitive loads, such as the gate of a power MOSFET. The on state is designed as a high level.UC1825主要特性:QML-V Qualified, SMD 5962-87681 Rad-Tolerant: 30 kRad (Si) TID(1) Compatible With Voltage- or Current-Mode Topologies Practical Operation Switching Frequencies to 1 MHz 50-ns Propagation Delay-to-Output High-Current Dual Totem Pole Outputs (1.5 A Peak) Wide Bandwidth Error Amplifier Fully Latched Logic With Double-Pulse Suppression Pulse-by-Pulse Current Limiting Soft Start/Maximum Duty-Cycle Control Undervoltage Lockout With Hysteresis Low Start-Up Current (1.1 mA)圖1.UC1825方框圖圖2.UC1825開環(huán)實(shí)驗(yàn)室測(cè)試電路圖3.采用UC1835的設(shè)計(jì)案例: 50 W, 48V到5V DC/DC 轉(zhuǎn)換器——1.5MHz時(shí)鐘頻率