TI公司的TPS7A78是120mA智能AC/DC線性電壓穩壓器，在容易使用非磁性AC/DC轉換方案中提高了整個效率和待機功耗.TPS7A78采用外接電容來創立電流源和箝位整流電壓。器件的獨特架構允許其待機功耗能從幾百毫瓦降低到十幾毫瓦.TPS7A78非隔離功率解決方案的輸入電壓70 VAC到 270VAC45 Hz 到65 Hz，高達75%的效率，支持輸出電壓從1.25V到5V，待機功耗15mW，線路壓降電容器為線性解決方案尺寸的1/4，對火線電壓，負載和溫度的精密電壓調整達到3%精度，具有電源故障檢測和電源良好指示。主要用在工廠自動化，建筑物自動化，白色家電，電能表表，煙霧檢測器和恒溫器控制。本文介紹了TPS7A78主要特性，功能框圖，單相AC電源和三相AC電源圖，單相E表電源圖以及評估模塊TPS7A78EVM-011主要特性和電指標性能，電路圖，材料清單和PCB設計圖。

The TPS7A78 improves the overall efficiency andstandby power in power supplies for an easy-to-usenon-magnetic approach to AC/DC conversion. TheTPS7A78 uses an external capacitor to create acurrent source and actively clamps the rectifiedvoltage. The device then regulates the voltage downto the application-specific operating voltage. Theunique architecture of the device allows the standbypower to be reduced from several 100s of milliwattsto just a few 10s of milliwatts. The TPS7A78 takesadvantage of an innovative switched capacitor stageto reduce the clamped voltage down byapproximately 1/4th of the value， which in turnmultiplies the current by 4. Thus， the current sourcecapacitor can be much smaller in size， whichminimizes standby power， reduces solution size， andcan lead to a lower system cost.

The TPS7A78 is optimized for e-meteringapplications where the power supply must be reliableand magnetic tamper-proof. The TPS7A78 requiresno external magnetics， which makes complying withIEC 61000-4-8 easier while minimizing costlymagnetic shielding in e-metering applications.

Additionally， the TPS7A78 also comes with a userprogrammablepower-fail detection threshold that canprovide an early alert to power failures so the systemcan save data before completely losing power. Apower-good indication can also be used forsequencing or to provide a reset to a micro-controller.

The TPS7A78 is available in a 14-pin TSSOP （PWP）package.

TPS7A78主要特性：

1? Non-isolated power solution for 70 VAC to 270VAC， 45 Hz to 65 Hz （bench tested）：

– Up to approximately 75% efficiency

? Supports output voltages from 1.25 V to 5 V

? Standby power consumption： 15 mW （cap-drop =150 nF）

? Line voltage drop capacitor can be 1/4th the sizeof linear solutions

? Power-fail detection

? Power-good indication

? 3% precision voltage regulation over line， load，temperature

? Package：

– 5-mm × 6.5-mm TSSOP-14 （PWP）

TPS7A78應用：

? Factory automation

? Building automation

? White goods

? Electricity Meters （E-Meters）

? Smoke detectors

? Thermostat controls

圖1. TPS7A78功能框圖

圖2. TPS7A78單相AC電源圖

圖3. TPS7A78三相AC電源圖

圖4. TPS7A78單相E表電源圖

評估模塊TPS7A78EVM-011

This user’s guide describes the operational use of the TPS7A78EVM-011 evaluation module （EVM） as areference design for engineering demonstration and evaluation of the TPS7A78， non-isolated smart linearvoltage regulator （LDO）。 Included in this user’s guide are setup and operating instructions， thermal andlayout guidelines， a printed circuit board （PCB） layout， a schematic diagram， and a bill of materials （BOM）。

Throughout this document， the terms demonstration kit， evaluation board， and evaluation module aresynonymous with the TPS7A78EVM-011.

Texas Instruments’TPS7A78EVM-011 helps design engineers evaluate the operation and performance ofthe TPS7A78 smart linear voltage regulator for possible use in their own circuit application. This particularEVM is intended for evaluation purposes and is not intended to be an end product. The EVM configurationcontains a single 3.3-V output regulator optimized for e-metering applications. The TPS7A78EVM-011regulates VAC supply to 3.3-V DC supply and can source up to 27 mA （max） current.

The EVM also features a power-fail detection signal and a power-good indication signal to warrant a VACsupply failure and to indicate to a microcontroller （MCU） that the regulated DC voltage is greater than 90%of the targeted regulation DC voltage.