[13] IXYS Corporation, IXFL32N120P Polar Power MOSFET HiperFET, IXYS Corporation Data Sheet, 2008, (www.ixys.com)
[14] IXYS Corporation, IXFN60N80P PolarHV Power HiperFET MOSFET, IXYS Corporation Data Sheet, 2006, (www.ixyys.com)
[15] STMicroelectronics, L6599 High-Voltage resonant controller,STMicroelectronics Data Sheet, 2006, (www.st.com)
[16] Infineon Technologies AG, SKW25N120 fast IGBT in NPT technology, Infineon Data Sheet, 2006
2
Introduction
PWM and resonant power converting ideas
Introduction
Block diagram of a typical PWM/resonant switching power supply
Low frequencyrectifier, filter
with PFCcorrection
MAINS AC230V/400V
50 Hz PWM/Resonantinverter
DC320V/560V
Vin High frequencyrectifierand filter
ACLoad
DCVout
ConverterController
PFCController
DC-DC converter
Introduction
The function of DC-DC converter are as follows:
- to convert a DC input voltage (Vin) into a DC output voltage (Vout)
- to control the DC output voltage (Vout) against load and mains variations
- to reduce the AC ripple on the DC output voltage (Vout) below the required level
- to provide isolation between the input source and the load
- to protect the supplied system from electromagnetic interference (EMI)
- to satisfy various international and national safety standards
3
Introduction
Voltage-switching half-bridge inverters with various resonant circuits
Introduction
Main features of the resonant circuits:
- circuits a), f) and g) supply a sinusoidal output current and are compatible with current-driven high frequency rectifiers
- inverters (b)-(e) produce a sinusoidal output voltage and are compatible with voltage-driven rectifier
- for the circuits (b)-(g) resonant frequency depends on the load
LLC inverter basics
4
LLC inverter basics
- the ratio of the inductance:2
1
L
LA =
- the equivalent inductance: ( )
+=+=+=A
LALLLL1
11 2221
- the undamped natural frequency: ( )CLLLC 21
0
11
+==ω
- the characteristic impedance:C
L
CLZ ===
000
1
ωω
LLC inverter basics
- the loaded quality factor at f0:00
0 Z
R
L
RCRQ LL
LL ===ω
ω
- the equivalent inductance of the damped circuits:
seq LLL += 1
2
22
22
1L
s
R
L
LL
ω+=where
- the resonant frequency: ( )CLLCL seq
r +==
1
11ω
( )s
sr
srr R
LL
CRQ
+== 11 ωω
- the quality factor at the resonant frequency:
where ( )22
22 /1 LR
RR
rL
Ls ω+
=
LLC inverter basics
f0
Gain
f
Mmax
capacitive regionZCS
inductive regionZVS
peak gain
5
LLC inverter basics
Capacitive region – current leads the voltage, bridge MOSFETs operate in zero current switching (ZCS). It means that power MOSFETs are turned-off (Vds decreases from Vin to 0) at zero current. Switching-off losses can be neglected.
Inductive region – current lags the voltage. Power switches are turned-on (Is is increasing from 0 to Ismax) at zero volts (ZVS). Switching-on losses can be neglected.
For frequency fsw = f0 the MOSFETs turn on and turn off at zero currents, resulting in zero switching losses and high efficiency.
LLC inverter basics
*Taken from „Resonant power converters”,
KazimierczukM.,Czarkowski D.[1]
LLC inverter basics
Operating below resonant frequency (ZCS):
a) conductive sequence is Q1, D1, Q2, D2
b) there are a few detrimental effects of switching-on MOSFET:
- reverse recovery of the antiparallel diode of the opposite switch
- second breakdown of the MOSFET parasitic bipolar transistor
- discharging of transistor output capacitance (additional losses)
LLC design procedureStep 3 - calculate the maximum normalized operating frequency (according to the definition):
rn f
ff max
max, =
Step 4 - calculate the effective load resistance reflected at transformer primaryside:
out
outLac P
VnRnR
22
22
2
88
ππ==
Step 5 - impose that the converter operates at maximum frequency at zero load and maximum input voltage, calculating the inductance ratio
1
12
max,
2max,
min
min
−−=
n
n
f
f
M
Mλ
16
LLC design procedureStep 6 - calculate the max Q value to work in the ZVS operating region atminimum input voltage and full load condition
1
195.0%95
2max
2max
maxmax1 −
+=⋅=M
M
MQQZVS λ
λ
Step 7 - calculate the max Q value to work in the ZVS operating region at no-load condition and maximum input voltage
( ) ZVSac
D
n
nZVS CR
T
f
fQ
λλλ
π −+= 2
max,
max,2
1
2
Step 8 - choose the max quality factor for ZVS in the whole operating range, such that:
{ }21,min ZVSZVSZVS QQQ ≤
strayOSSZVS CCC += 2
LLC design procedureStep 9 - calculate the minimum operating frequency at full load and minimum input voltage, according to the following approximate formula:
−+
=
+
4
max
1max
min
11
11
1
Q
Q
r
ZVS
M
ff
λ
Step 10 - calculate the characteristic impedance of the resonant tank and allcomponent values
