Simplified Analysis and Design of Series-
resonant LLC Half-bridge Converters
MLD GROUP
INDUSTRIAL & POWER CONVERSION DIVISION
Off-line SMPS BU Application Lab
I&PC Div. - Off-line SMPS Appl. Lab
Presentation Outline
• LLC series-resonant Half-bridge: operation
and significant waveforms
• Simplified model (FHA approach)
• 300W design example
I&PC Div. - Off-line SMPS Appl. Lab
Series-resonant LLC Half-Bridge
Topology and features
Q1
Half-bridge
Driver
Center-tapped output with full-
wave rectification
(low voltage and high current)
Cr
Ls
Vin
Q2
Lp
Vout
LLC tank circuit
Preferably integrated into a single
magnetic structure
Vout
3 reactive elements, 2 resonant frequencies
fr1
1
2
⋅ π⋅
Ls
⋅
Cr
1
2
⋅ π⋅
( Ls
+
Lp)
⋅
Cr
Single-ended output with
bridge rectifiication
(high voltage and low current)
f r1
>
f r2
Multi-resonant LLC tank circuit
Variable frequency control
Fixed 50% duty cycle for Q1 & Q2
Dead-time between LG and HG to
allow MOSFET’s ZVS @ turn-on
fsw
≈
fr, sinusoidal waveforms: low
turn-off losses, low EMI
Equal voltage & current stress for
secondary rectifiers; ZCS, then no
recovery losses
No output choke; cost saving
Integrated magnetics: both L’s can
be realized with the transformer.
High efficiency: >96% achievable
fr2
I&PC Div. - Off-line SMPS Appl. Lab
LLC Resonant Half-bridge
Waveforms at resonance (f
sw
= f
r1
)
Dead-time
Gate-drive
signals
HB mid-point
Voltage
Resonant cap
voltage
Tank circuit current is sinusoidal
Magnetizing current is triangular
Transformer
currents
Diode
voltages
CCM operation
Output current
Diode
currents
I&PC Div. - Off-line SMPS Appl. Lab
LLC Resonant Half-bridge
Switching details at resonance (f
sw
= f
r1
)
Dead-time
Gate-drive
signals
ZVS !
HB mid-point
Voltage
Resonant cap
voltage
Tank circuit current >0
Transformer
currents
Magnetizing current
V(D1)<0
Diode
voltages
I(D1)=0
ZCS !
Diode
currents
I&PC Div. - Off-line SMPS Appl. Lab
京公网安备 11010802033920号
Copyright © 2005-2024 EEWORLD.com.cn, Inc. All rights reserved
评论