EVLSRK2000-L-40 STMicroelectronics

AN3303 Application note Secondary-side rectification for LLC resonant converter featuring SRK2000 Silvio De Simone Introduction The EVLSRK2000 is a family of demonstration boards designed for the evaluation of the SRK2000 in LLC resonant converters with synchronous rectification (SR). The first part of this application note is a brief description of the IC features while the second is dedicated to the board description. Finally, some considerations regarding circuit optimization and performance are given. This board was realized in four different configurations depending on the mounted SR MOSFETs. Different board codes are shown in Table 1: Table 1. Demonstration board ordering codes MOSFET Ordering code SR MOSFET P/N MOSFET R MOSFET BV DS(on) DSS package EVLSRK2000-L-40 STL140N4LLF5 PowerFLAT 2.75 m 40 V EVLSRK2000-L-60 STL85N6F3 PowerFLAT 5.70 m 60 V EVLSRK2000-D-40 STD95N4F3 DPAK 5.80 m 40 V EVLSRK2000-S-40 STS15N4LLF3 SO-8 5.00 m 40 V Figure 1. EVLSRK2000: smart driving control for LLC resonant converter May 2017 DocID18164 Rev 4 1/27 www.st.com 27Contents AN3303 Contents 1 SRK2000 main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1 Drain MOSFET sensing and driving logic . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.2 Drain sensing optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.3 Blanking time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.4 Light load operation and sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.5 Enable pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2 Electrical diagram description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 Sensing optimization by waveform check . . . . . . . . . . . . . . . . . . . . . . 14 3.1 Power MOSFET turn-off compensation . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2 MOSFET turn-on delay compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 3.3 Sub-harmonic oscillation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4 How to implement the board in the converter . . . . . . . . . . . . . . . . . . . 17 5 Power losses and thermal design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.1 Power losses calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.2 Thermal design consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 7 Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 2/27 DocID18164 Rev 4