原标题：Maxim MAXREFDES112 10W反激电源解决方案

　　Maxim公司的MAXREFDES112#是采用MAX17597的隔离的24V输入12V输出的10W反激电源,12V 800mA,20%过载电流,输出精度±5%,具有最少的外接元件和紧凑的尺寸,可工作各种苛刻的工业环境如工业控制和自动化,过程控制,PLC和通信设备电源.本文介绍了MAX17595–MAX17597主要特性,框图和各种应用电路,评估板主要特性,电路图和材料清单,以及10W反激电源参考设计MAXREFDES112#主要特性,电路图,材料清单和PCB设计详图.

　　The MAX17595–MAX17597 is a family of peak-current-mode controllers for design of wide input-voltage flyback and boost regulators. The MAX17595 offers optimized input thresholds for universal input AC-DC converters and telecom DC-DC (36V to 72V input range) power supplies. The MAX17596/MAX17597 offer input thresholds suitable for low-voltage DC-DC applications (4.5V to 36V). The MAX17597 implements a boost converter. All three controllers contain a built-in gate driver for external n-channel MOSFETs.

　　The MAX17595–MAX17597 house an internal error amplifier with 1% accurate reference, eliminating the need for an external reference. The switching frequency is programma­ble from 100kHz to 1MHz with an accuracy of 8%, allow­ing optimization of magnetic and filter components, resulting in compact and cost-effective power conversion. For EMI-sensitive applications, the MAX17595–MAX17597 family incorporates a programmable frequency dithering scheme, enabling low-EMI spread-spectrum operation.

　　Users can start the power supply precisely at the desired input voltage, implement input overvoltage protection, and program soft-start time. A programmable slope compensation scheme is provided to ensuree stability of the peak-current-mode control scheme.

　　Hiccup-mode overcurrent protection and thermal shutdown are provided to minimize dissipation in overcurrent and overtemperature fault conditions.

　　MAX17595–MAX17597主要特性和优势:

　　Programmable Switching Frequency Allows Optimization of the Magnetic and Filter Components, Resulting in Compact, Cost-Effective, Efficient Isolated/Non-Isolated Power Supplies 100kHz to 1MHz Programmable Switching Frequency with Optional Synchronization

　　Peak Current Mode Control Provides Excellent Transient Response Offline (Universal Input AC) and Telecom (36V to 72V) Flyback Controller—MAX17595

　　DC-DC (4.5V to 36V) Flyback Controller— MAX17596

　　Nonsynchronous (4.5V to 36V) Boost PWM Controller—MAX17597

　　3mm x 3mm TQFN Package

　　Programmable Frequency Dithering Enables Low- EMI Spread-Spectrum Operation

　　Integrated Protection Features Enhance System Reliability Adjustable Current Limit with External Current- Sense Resistor

　　Fast Cycle-By-Cycle Peak Current Limiting

　　Hiccup-Mode Short-Circuit Protection

　　Overtemperature Protection

　　Programmable Soft-Start and Slope Compensation

　　Input Overvoltage Protection

　　MAX17595–MAX17597应用:

　　Universal Input Offline AC-DC Power Supplies

　　Wide-Range DC-Input Flyback/Boost Battery Chargers

　　Battery-Powered Applications

　　Industrial and Telecom Applications

　　图1.MAX17595/MAX17596/MAX17597框图

　　图2.MAX17595典型应用电路(通用离线隔离电源)

　　图3.MAX17596典型应用电路(DC/DC转换器)

　　图4.MAX17595典型应用电路(异步升压转换器)

　　MAX17596评估板

　　The MAX17596 evaluation kit (EV kit) is a fully assembledand tested circuit board that demonstrates an isolated20W fly-back DC-DC converter. The circuit uses thedevice’s peak current-mode controller in a 16-pin TQFNpackage with an exposed pad. The EV kit demonstratesthe IC’s cycle-by-cycle current limit, soft-start, and EN/UVLO features.

　　The EV kit circuit output is configured for an isolated +24Vand provides up to 833mA of output current. The EV kitis configured to operate at a 200kHz switching frequency.

　　An optocoupler, along with the transformer, providesgalvanic isolation between the input and output, up to1500VRMS.

　　MAX17596评估板特性:

　　●● 18V to 36V Input Range

　　●● Isolated Output: 24V DC at 20W

　　●● Cycle-by-Cycle Current Limit

　　●● Resistor Programmable UVLO/OVI Threshold

　　●● Low-Cost Flyback Design

　　●● Galvanic Isolation Up to 1500VRMS

　　●● Proven PCB Layout

　　●● Fully Assembled and Tested

　　The MAX17596 EV kit provides a proven design to evaluatethe high-efficiency, DC-DC, flyback converter in a spacesaving,16-pin TQFN package. The EV kit is configured for a 24V output voltage that can supply up to 840mAof current. The EV kit features a 200kHz fixed switchingfrequency for optimum efficiency and component size.

　　This EV kit uses the peak-current-mode, pulse-widthmodulating(PWM) controller IC in a 16-pin TQFNpackage with an exposed pad. This PWM controllervaries the duty cycle to compensate for the variationin input voltage (VIN) and the output load to maintain aconstant output voltage. The duty cycle determines theon/off duration of the MOSFET (Q1).

　　The detailed description of flyback design methodologyand the calculations for component value selection aredescribed in Application Note 5504: Designing Flyback

　　Converters Using Peak-Current-Mode Controllers. Thedetails of soft-start time programming, programming outputvoltage, peak-current-limit setting, switching frequency setting, and the EN/UVLO,OVI settings are described inthe MAX17595/MAX17596/MAX17597 IC data sheet.

　　图5.MAX17596评估板电路图

　　MAX17596评估板材料清单:

　　10W反激电源参考设计MAXREFDES112#

　　Maxim’s power supply experts have designed and built a series of isolated, industrial power-supply reference designs. Each of these power supplies efficiently converts 24V into useful voltage rails at a variety of power levels. Every power rail is isolated with a readily available transformer from multiple, global vendors, providing for quick, convenient transformer selection. Each design has been tested for load and line regulation, as well as efficiency and transient performance. As with all Maxim reference designs, the BOM, schematics, layout files, and Gerber files are all available. In addition, boards are available for purchase; most boards feature through-hole pins for immediate board placement and accelerated prototyping.

　　MAXREFDES112# is an efficient flyback topology with 24V input, and a 12V output at 10W of power (0.8A). The design features the MAX17596, a peak-current-mode converter with flexible switching frequency. This entire circuit fits on a 20.3mm (0.8in) x 59.7mm (2.35in) board.

　　图9.10W反激电源参考设计MAXREFDES112#外形图

　　10W反激电源参考设计MAXREFDES112#主要特性:

　　Functional insulation

　　Compact and flexible

　　Minimal external components

　　Robust operation in adverse industrial environments

　　12V 800mA with 20% over range current

　　±5% output accuracy

　　10W反激电源参考设计MAXREFDES112#应用:

　　Industrial control and automation

　　Process control

　　PLC

　　Telecom and Datacom power supplies

　　图10.10W反激电源参考设计MAXREFDES112#电路图

　　10W反激电源参考设计MAXREFDES112#材料清单: