Maxim MAX17498A峰值電流模式電源轉換方案
發布時間：2011-11-9 11:27
發布者：1640190015
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Maxim 公司的MAX17498A/B/C是用于反激/升壓電源的峰值電流模式AC/DC和DC/DC電源轉換器，包括了設計寬輸入電壓隔離和非隔離電源的所有控制電路，MAX17498A/MAX17498C反激轉換器的工作頻率250kHz，MAX17498B反激/升壓轉換器的工作頻率500kHz，具有極好的瞬態響應特性，主要用在工業應用的前端AC/DC電源，通信電源等。本文介紹了MAX17498A/MAX17498B/MAX17498C主要特性和優勢，方框圖和多種起動電路，以及智能電表和PLC電源的應用案例。 The MAX17498A/MAX17498B/MAX17498C devices are current-mode fixed-frequency flyback/boost converters with a minimum number of external components. They contain all the control circuitry required to design wide-input-voltage isolated and nonisolated power supplies. The MAX17498A has its rising/falling undervoltage lock out (UVLO) thresholds optimized for universal offline (85V AC to 265V AC) applications, while the MAX17498B/ MAX17498C support UVLO thresholds suitable to low-voltage DC-DC applications. The switching frequency of the MAX17498A/MAX17498C flyback converters is 250kHz, while that of the MAX17498B flyback/boost converter is 500kHz. These frequencies allow the use of tiny magnetic and filter components, resulting in compact, cost-effective power supplies. An EN/UVLO input allows the user to start the power supply precisely at the desired input voltage, while also function ing as an on/off pin. The OVI pin enables implementation of an input overvoltage-protection scheme that ensures that the converter shuts down when the DC input voltage exceeds the desired maximum value. The devices incorporate a flexible error amplifier and an accurate reference voltage (REF) to enable the end user to regulate both positive and negative outputs. Programmable current limit allows proper sizing and protection of the primary switching FET. The MAX17498B supports a maxi mum duty cycle of 92% and provides programmable slope compensation to allow optimization of control-loop performance. The MAX17498A/MAX17498C support a maximum duty cycle of 49%, and have fixed internal slope compensation for optimum control-loop performance. The devices provide an open-drain PGOOD pin that serves as a power-good indicator and enters the high-impedance state to indicate that the flyback/boost converter is in regula tion. An SS pin allows programmable soft-start time for the flyback/boost converter. Hiccup-mode overcurrent pro tection and thermal shutdown are provided to minimize dissipation under overcurrent and overtemperature fault conditions. The devices are available in a space-saving, 16-pin (3mm x 3mm) TQFN package with 0.5mm lead spacing. MAX17498A/MAX17498B/MAX17498C主要特性和優勢： Peak Current-Mode Flyback/Boost Converter Current-Mode Control Provides Excellent Transient Response Fixed Switching Frequency 250kHz (MAX17498A/MAX17498C) 500kHz (MAX17498B) Flexible Error Amplifier to Regulate Both Positive and Negative Outputs Programmable Soft-Start to Reduce Input Inrush Current Programmable Voltage or Current Soft-Start Power-Good Signal (PGOOD) Reduced Power Dissipation Under Fault Hiccup-Mode Overcurrent Protection Thermal Shutdown with Hysteresis Robust Protection Features Flyback/Boost Programmable Current Limit Input Overvoltage Protection Optimized Loop Performance Programmable Slope Compensation for Flyback /Boost Maximizes Obtainable Phase Margin High Efficiency 175mI, 65V Rated n-Channel MOSFET Offers Typical Efficiency Greater Than 80% No Current-Sense Resistor Optional Spread Spectrum Space-Saving, 16-Pin (3mm x 3mm) TQFN Package MAX17498A/MAX17498B/MAX17498C應用： Front-End AC-DC Power Supplies for Industrial Applications (Isolated and Nonisolated) Telecom Power Supplies Wide-Range DC Input Flyback/Boost Industrial Power Supplies 
圖1。MAX17498A/MAX17498B/MAX17498C方框圖
圖2。MAX17498A 基于RC的起動電路
圖3。MAX17498A 基于電流源的起動電路
圖4。MAX17498B/C采用偏壓繞組關斷Q1和降功耗的起動電路
圖5。MAX17498B/C采用輸入IN直接連接帶DC輸入的起動電路
圖6。MAX17498A典型應用電路（智能電表電源）
圖7。MAX17498B典型應用電路（PLC電源）
圖8。MAX17498C典型應用電路 詳情請見： 
MAX17498A-MAX17498C.pdf
(2.46 MB)
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