</a>led" title="led">led" title="led">led 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典型應(yīng)用:

· LCD & PDP TV

· Telecom SMPS, PC SMPS

· Home Audio Systems

圖1. IRS27951/2功能方框圖

圖2. IRS27951/2典型應(yīng)用電路圖

IRAC27951-220W IRS27951評(píng)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.


圖3. IRAC27951 220W 評(píng)估板外形圖

IRAC27951 220W 評(píng)估板主要指標(biāo):


圖4.IRAC27951 220W 評(píng)估板電路圖
IRAC27951 220W 評(píng)估板材料清單:



圖5.IRAC27951 220W評(píng)估板PCB布局圖(頂層)

圖6.IRAC27951 220W評(píng)估板PCB布局圖(底層)
詳情請(qǐng)見:
http://www.irf.com/product-info/datasheets/data/irs27951s.pdf
和
http://www.irf.com/technical-info/refdesigns/irac27951-220w.pdf