原标题：Powerint PKS607YN 50W音频放大器电源设计方案

　　powerint公司的PKS607YN是PeakSwitch系列器件,能满足高峰值/连续功率比的应用需求.PeakSwitch系列集成了700V功率MOSFET,振荡器,用于起动的高压开关电流源,限流和热关断.此外,还包括自动重起,火线欠压检测和频率抖动等功能. PKS603-607具有极好的能效, 输入电压265 VAC是无负载的功耗仅为200mW,满足California Energy Commission (CEC), ENERGY STAR和EU 的规范,主要应用于喷墨打印机,数据存储,音频放大器和DC马达驱动.本文介绍了PeakSwitch系列PKS603-607的主要特性,功能方框图, 采用PKS606Y的连续功率32W(峰值功率81W)的通用电压输入电源电路图以及采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源设计的要点和详细电路图.

　　PeakSwitch is designed to address applications with high peak-to-continuous power ratio demands. The very high switching frequency during peak power loads and excellent load transient response reduce system cost as well as component count and size. PeakSwitch incorporates a 700 V power MOSFET, oscillator, high voltage switched current source for startup, current limit, and thermal shutdown onto a monolithic device. In addition, these devices incorporate auto-restart, line under-voltage sense and frequency jittering. An innovative design minimizes audio frequency components in the simple ON/OFF control scheme to practically eliminate audible noise with standard varnished transformer construction.

　　PKS603-607主要特性:

　　EcoSmart– Extremely Energy-Efficient

　　Standby output power ≥0.6 W for 1 W input (high line)

　　Sleep mode power ≥2.4 W at 3 W input (high line)

　　No-load consumption<200 mW at 265 VAC input

　　Surpasses California Energy Commission (CEC), ENERGY STAR, and EU requirements

　　PeakSwitch Features Reduce System Cost

　　Delivers peak power of up to three times maximum continuous output power

　　277 kHz operation during peak power significantly reduces transformer size

　　Programmable smart AC line sensing provides latching shutdown during short circuit, overload and open loop faults, and prevents glitches during power down or brownout

　　Two external components reset latch on AC removal

　　Adaptive switching cycle on-time extension increases low line peak output power, minimizing bulk capacitor size

　　Adaptive current limit reduces output overload power

　　Frequency jittering reduces EMI filter cost

　　Tight I2f tolerances and negligible temperature variation of key parameters ease design and lower cost

　　Accurate hysteretic thermal shutdown with automatic recovery provides complete system level overload protection and eliminates need for manual reset

　　Better System Cost/Performance over RCC & Discrete

　　Simple ON/OFF control – no loop compensation needed

　　Very low component count – higher reliability and single side printed circuit board

　　High bandwidth provides fast turn on with no overshoot and excellent transient load response

　　Peak current limit operation rejects line frequency ripple

　　Built-in current limit and hysteretic thermal protection

　　PKS603-607应用:

　　Inkjet printer

　　Data storage, audio amplifier, DC motor drives

图1.PKS603-607功能方框图

　　图2.采用PKS606Y的连续功率32W(峰值功率81W)的通用电压输入电源电路图

　　采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源设计要点

　　The universal input power supply has two main output voltages, +28 V and -28 V, and consists of two parallel converters. Each output can deliver 25 W continuous, 100 W peak.

　　Each converter uses a PeakSwitch (PKS607YN) which share a common input stage. The 12 V output is rated to provide an output current of 333 mA. Duration of peak power output is thermally limited, being determined by environment and heat-sinking.

　　Common mode chokes, L1 and L2 along with Y-capacitors C3, C4, C23 and C24 form the common mode EMI filter. Inductors L3, L4 and L5 and capacitors C5, C10 and C2 provide differential mode EMI filtering.

　　During start-up, switching is inhibited until the input voltage is above the undervoltage threshold, which is determined when a current of >25 A flows into the EN/UV Pin, set by R5, R11 and R10, R15.

　　The controller in U3 (U2) skips switching cycles to regulate the output voltage based on feedback to the EN/UV pin. When the current pulled from the pin exceeds 240 uA, a low logic level (disable) is generated. At the beginning of each cycle, the EN/UV pin state is sampled, and if high, the power MOSFET inside U3 (U2) is turned on for that cycle (enabled). Audio applications demand that the power supply output voltage droops during an overload condition, rather than shutting down completely. The shutdown inhibit circuit, driven by 555 timer U1, pulls current from the EN/UV pin every 30 ms to ensure the controller never enters output auto-restart mode, instead relying on the internal thermal shutdown to provide overload protection.

　　Two independent feedback loops are used to control the voltages on the ±28 V outputs. This ensures that both outputs are tightly regulated and also ensures excellent cross-regulation between outputs.

　　设计要点:

　　High crest factor of the audio loads allowed smaller heatsinks.

　　Drain to source snubbers (C14, R13 and C19, R18) were used to reduce EMI.

　　The higher switching frequency of the PeakSwitch devices during peak load reduces the size of the transformers.

　　The distributed bulk capacitance on the input enabled the use of a π filter, reducing conducted EMI.

　　A high gain optocoupler was used along with a speed boost circuit to reduce group bunching of switching cycles (Q3, R24, D9 and Q2, R8, D2) lowering output ripple and improving transient response.

　　设计亮点:

　　Replaces line-transformer based power supplies in home audio applications

　　Compact and lightweight

　　Fast transient response and high loop bandwidth allows for excellent results with Class-D amplifiers

　　High peak power matches crest factor requiements of audio signals

　　Saves cost by eliminating overdesign

　　Shutdown inhibit circuit allows output to droop during extreme overloads, preventing audible drop outs

　　Dual convertor design maintains excellent cross regulation between high voltage rails

　　Auxiliary output eliminates separate house-keeping power supply

　　High Efficiency

　　Efficiency greater than 75% at full load

　　图3.采用PKS607YN连续输出功率50W(峰值功率200W)的音频放大器电源电路图