IR IRS27951 220W开关电源解决方案

发布时间：2011-11-21 12:21 发布者：1046235000

IR公司的IRS27951/2是自振荡半桥驱动IC,每路的最大工作频率500kHz,占空比50%,工作电压高达+600VDC,可编程最小和最大开关频率,可编程软起动频率和软起动时间和死区时间,提供过流保护,欠压锁住,主要用在LCD和PDP TV,通信开关电源,PC开关电源和家庭音频系统.本文介绍了IRS27951/2主要特性, 功能方框图,典型应用电路以及220W评估板IRAC27951主要指标,电路图,材料清单和PCB布局图.

The IRS2795(1,2) is a self oscillating half-bridge driver IC for DC-DC resonant converter applications, especially the LLC resonant half-bridge converter. The frequency and dead time can be programmed externally using two external components. The IC offers over current protection using the on state resistance of the low-side MOSFET. The IC can be disabled by externally pulling the voltage at the CT/SD pin below its enable voltage threshold.

IRS27951/2主要特性:

· Simple primary-side control solution for fixed and variable frequency DC-DC resonant converters.

· Max 500kHz per channel output with 50% duty cycle

· Floating channel bootstrap operation up to +600Vdc

· Programmable minimum and maximum switching frequency

· Programmable soft start frequency and soft start time

· Programmable dead time

· Micropower start-up & ultra low quiescent current

· Over-current protection using low side MOSFET Rds(on)

· User initiated micropower “Sleep mode”

· Under-voltage Lockout

· Simple design with minimal component count.

· Lead-free

IRS27951/2典型应用:

· LCD & PDP TV

· Telecom SMPS, PC SMPS

· Home Audio Systems

图1. IRS27951/2功能方框图

图2. IRS27951/2典型应用电路图

IRAC27951-220W IRS27951评估板

The evaluation board consists of a front-end AC-DC rectifier stage cascaded with a half-bridge resonant DCDC converter with multiple output voltage rails (24V and 12V). The front end is a conventional rectifier stage with a rectifier bridge and an EMI filter.

The downstream converter is a multi-resonant half bridge LLC converter whose control is implemented with the IRS27951 (U1) controller HVIC. The controller drives the two half-bridge MOSFETs with a 50 percent fixed duty cycle with dead-time, changing the frequency according to the feedback signal in order to regulate the output voltages against load and input voltage variations. As described earlier, in addition to current protection, all the critical functions needed to control resonant converter designs can be externally programmed using this 8 pin controller IC.

The transformer uses the magnetic integration approach, incorporating the resonant series and shunt inductances in the power transformer. The transformer configuration chosen for the secondary winding is center-tap, and the output rectifiers are Schottky diodes. The feedback loop is implemented by means of a classical configuration using a TL431 (U3) to adjust the current in the optocoupler TLP621 (U2). Weighted resistive dividers from both voltages are summed at the reference node of the TL431 in order to achieve a better overall output voltage regulation. The optocoupler transistor modulates the current from the RT pin of the controller IC to modulate the switching frequency, thus achieving output voltage regulation.