Asymmetrical_Half_Bridge_Converter_based_on_L65912010年电源技术研讨会讲稿.pptVIP

asymmetrical half bridge converter based on l6591,scott han - application engineer i&pc division stmicroelectronics sept2010,review of switching characteristics,the requirements of power converter include small size , light weight, high efficiency and high power density. hard-switching pwm converters suffer from high switching losses, high switching stresses and high emi noise. soft-switching pwm converters can alleviate these problems in which a high switching frequency operation can be achieved.,2,3,soft-switching converter configurations,ahb,mosfet switching losses,4,turn-off transition waveforms of a mosfet.,turn-on transition waveforms of a mosfet.,principle of zero-voltage switching,5,the block of asymmetrical half-bridge,6,lout current,d1 current,asimmetric,hysteresis loop,q1 current,hb midpoint voltage,tank circuit current,q1,q2,d2,d1,np,ns1,ns2,iload,iload,iload,ca,ip,it,lm,im,vp,lo,l6591,7,switching process,waveforms for switching process,8,ahb steady-state analysis (1),9,the following assumptions are made: the output filter inductance is high enough and the filter inductor operates in continuous conduction mode. the transformer leakage inductance is negligible and magnetizing inductance is referred to the primary. the parasitic capacitances of the switches do not depend on voltage and are considered to be constant. all elements of circuit are lossless. the capacitor ca is large enough. the dead time between the conduction interval is negligible. in steady state, zero volt-second integral across the transformer primary winding, so vca=vin*d then the voltage transfer ratio of converter could be derived from volt balance of output choke lo: vo=vin*d*(1-d)*(n1+n2) where n1=ns1/np, n2=ns2/np,ahb steady-state analysis (2),10,ahb,llc(“ contiguous sine shaped“ hypothesis),ahb steady-state analysis (3),based on above analysis , comparing to llc, we can take its advantage that smaller current stress at input &output side, especially to output capacitor, and simple circuit to implement synchronous rectification, take into account the more uneven voltage stress of output rectifier ahb is a good choice for low output voltage and high output current application.,11,12,l6591: hb zvs pwm primary controller,t,typical applications high power adapters/chargers 90w atx desktop pcs (80+, 85+ initiative) telecom smps audio applications printers,l6591: new high performance pwm controller,l6591: new high performance pwm controller,13,l6591: mosfet drivers,14,l6591: new high performance pwm controller,l6591:high voltage start-up & vcc,15,icharge = 0.85 ma typ. minimum start voltage: 80v typ. hv generator restart voltage: 5v/13v (dis tripping) vcc_on/off: 14v/10.5v typ adaptive uvlo: 2v shift vcc clamp: 25v,l6591: new high performance pwm controller,16,minimum dead-time:200ns cf typical value : 100 1000 pf pay attention to pcb layout of oscillator components up to 500khz oper. freq,l6591:oscillator,l6591: new high performance pwm controller,17,soft start,soft start is invoked at start-up or vcomp=high temporary overload delay programmable by user connecting a small signal diode to pin #6 (vref) a latch or autorestart mode in case of overload can be obtained,l6591: new high performance pwm controller,18,open-drain pin dedicated to on/off control of pfc controller used during burst mode operation for minimizing pfc losses or for protection purpose activated (low) if dis4.5 v, isen1.5 v, ss5 v and comp1.75v if function is not used leave pin open,i/f with a generic pfc controller,easy i/f with dap005 pfc controller,l6591: pfc_stop function,l6591: new high performance pwm controller,19,20,ahb architecture with synchronous rectification,ahb topology key features,21,control pwm fixed frequency (dmax = 50%) dead time between hg and lg to allow zvs half bridge zvs operation: soft switching - no switching losses turn-on secondary side balanced or unbalanced (ns1ns2) transformer output inductor needed can be coupled for multiple outputs transformer unbalanced transformer: no need of high llk to obtain zvs,22,90w-12v/7.5a adapter with pfc using l6591+l6563 (1),23,115vac,230vac,90w-12v/7.5a adapter with pfc using l6591+l6563 (2),24,90w-12v/7.5a adapter with pfc using l6591+l6563 (3),detailed zvs switching at full load,detailed zvs switching at half load,secondary side key waveforms at full load,zvs behavior the most critical transition is the one between lvg turn-off and hvg turn-on. in fact it is visible that the current available to move the half-bridge point is less with respect to the other transition the zvs condition is harder to meet as the load increases, so full load is the worst condition to have for a correct zvs operation,25,samples: available now (production phase) datasheets: available upon request demo boards: evl6591-90wadp 12v/90w ac-dc adapter with pfc using l6563 + l6591 evl6591-400watx (in progress) 12v and 5v outputs 400w atx, 85+ compliant, based on l6591 zvs ahb and l6563 pfc,l6591: promotional tools,power mosfets basics,rds(on): the weight of each single contribution change with the bvdss,confidential,hv power mosfets roadmap,mdmesh v series shows more than 35% rds(on) improvement vs. mdmesh ii series and extremely low fom rds(on)*qg allowing excellent conduction and switching performances,mdmesh v: best on-state resistance,- older competitor technology: vdss 600 v,- best competition: vdss 600 v,tj = 25 c,mdmesh v: product family availability,mdmesh v: ww best rds(on) * area,coming up next: 550v devices in the most popular packages.,31,mdmesh ii products range enlargement,32,mdmesh ii products range enlargement,stw55nm60nd source drain diode para