Application note design of a 600 W HB LLC converter using CoolMOS™ P6 01_00 | Aug 13, 2015 | PDF | 1.36 mb

Desi gn o f a 6 00 W H B LL C C on ver t er u si n g
600 V Co ol MOS™ P 6
Authors:
Francesco Di Domenico
Alois Steiner
Johnald Catly
Application Note
About this document
Scope and purpose
This note will describe the design and performance of a 600 W LLC SMPS Demo Board. This is a high
performance example with a complete Infineon solution, including HV & LV power MOSFETs, controllers,
and drivers, demonstrating a very effective way to design the HV DC/DC isolation stage of a Server PSU
fulfilling the 80Plus® Titanium Standard.
Besides design information and documentation of the LLC converter, the reader will receive additional
information how the 600 V CoolMOS™ P6 behaves in this LLC board and what benefits will be achieved. Plus
insights in how to develop LLC converters in similar power ranges adapted to your own requirements.
Intended audience
This document is intended for design engineers who wish to evaluate high performance alternative
topologies for medium to high power SMPS converters, and develop understanding of the design process.
Also, how to apply the somewhat complex LLC design methods to their own system applications.
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Table of Contents
1
Introduction ................................................................................................................................... 3
2
2.1
2.2
2.3
2.4
2.5
HB LLC converter principles of operation ...................................................................................... 5
Tank Configuration and Operational Modes ...................................................................................... 5
Analysis of the Basic Tank Characteristics using FHA ........................................................................ 9
Tank Q Values and m Inductance Ratio: System Implications ........................................................ 10
Benefits of Split Capacitor Cr ............................................................................................................ 11
Synchronous Rectification Concepts for LLC ................................................................................... 12
3
3.1
3.2
3.3
3.4
3.5
3.6
3.6.1
3.6.2
3.7
3.8
3.9
LLC design methodologies for specific application requirements ............................................... 13
Input Design Data .............................................................................................................................. 13
Gain Curve ......................................................................................................................................... 14
Suggested FHA Optimization Process .............................................................................................. 15
Notes on the Selection of the Inductance Factor m ........................................................................ 15
Resonant Components Calculation .................................................................................................. 17
The ZVS Behavior: Energy and Time Considerations ....................................................................... 17
Energy Related Equations........................................................................................................... 18
Time Related Equations .............................................................................................................. 18
The Main Transformer Design ........................................................................................................... 18
The Resonant Choke Design ............................................................................................................. 22
The Synchronous Rectification Stage .............................................................................................. 23
4
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.3
4.3.1
4.3.2
4.3.3
4.4
4.5
4.6
4.7
4.7.1
4.7.2
Board description ........................................................................................................................ 24
General Overview .............................................................................................................................. 24
Infineon BOM ..................................................................................................................................... 25
Primary HV MOSFETs CoolMOSTM IPP60R190P6......................................................................... 25
LLC analog controller ICE2HS01G .............................................................................................. 25
HB Gate Drive 2EDL05N06PFG .................................................................................................... 26
Bias QR Flyback Controller ICE2QR2280Z .................................................................................. 26
SR MOSFETs OptiMOSTM BSC010N04LS ...................................................................................... 27
Board Schematics ............................................................................................................................. 27
Mainboard Schematic ................................................................................................................. 27
Controller Board Schematic ....................................................................................................... 28
Bias Board Schematic ................................................................................................................. 29
Critical LLC Operation - Hard Commutation .................................................................................... 30
ZVS behavior analysis ....................................................................................................................... 32
Burst mode Operation ...................................................................................................................... 32
Efficiency ........................................................................................................................................... 33
80+ Titanium Efficiency Target ................................................................................................... 33
Losses Breakdown ...................................................................................................................... 34
5
Test/Power-up Procedure ............................................................................................................ 36
6
Useful material and links.............................................................................................................. 38
7
References ................................................................................................................................... 39
8
List of abbreviations..................................................................................................................... 40
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1
Introduction
The reduction of size in power converters by increasing switching frequency and reducing magnetics
component size is a goal pursued for decades. The development of resonant converters with Zero Voltage
Switching (ZVS) has been a cornerstone of this effort, but for a long time they have been considered as a way
to “make good power from mediocre semiconductors”, in fact limiting their usage. Moreover, with the
advent of CoolMOS™ high performance silicon switches based on the superjunction concept, the
improvements in Figure of Merit even lessened the need for using resonant topologies for many years. Now,
the industry requirements for high efficiency in converter performance, which drove a trend towards
resonant switching square wave converters, such as the Phase Shift Full Bridge converter, are creating a
need for a closer look at the somewhat more difficult to design multiresonant LLC converter.
Classically, fully resonant converters have had a nominal disadvantage in conduction losses compared with
soft switching square wave converters like the Phase Shift Full Bridge, due to the difference in peak versus
RMS current for sinusoidal current waveshapes versus trapezoidal. However, with the advent of the multiresonant converter, and its boost up mode of operation, it is possible with modern MOSFETs and their
excellent Figure of Merit to achieve better-optimized results with the LLC converter. This is in large due to
the fact that the square wave converter is optimized at maximum duty cycle, which is only achieved at low
line condition. Hence, to provide operational capability with typical PFC front ends, and some converter
hold up time capability, they will typically need to be optimized for DC input as low as 325 V or 300 V,
wherein they will normally operate at 380 V with a less favorable crest factor and higher net RMS current.
In contrast, an LLC converter can be optimized for the nominal DC input voltage, and use the boost up mode
below the main resonance to achieve low line regulation with proper design. Combine this with a favorable
silicon Bill of Material (BOM) situation, compared with a Phase Shift Full Bridge topology, the proper design
approach, and a high performance converter is readily in reach.
In Figure 1, you can find a very synthetic comparison of several Figure of Merit metrics based on cost and
performance between the Phase Shift Full Bridge converter and the LLC HB.
You see that the first (blue arrows) still keeps some important features especially in controllability and
flexibility in wide output regulation range, but the HB LLC (red arrows) provides some very important
benefits in a modern SMPS design, like reduced BOM, easier ZVS and more performant Synchronous
Rectification.
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Figure 1
Comparison of several Figure of Merit metrics based on cost and performance between the PS
FB (blue) converter and the LLC HB (red).
The principles of operation for the LLC converter will be examined in the next section, and the main tank
design concepts reviewed. This will be followed by detailed design methodologies using both First
Harmonic Approximation (FHA) and supplemented by exact design concepts.
The scope of this document is to describe the details of an analog controlled 600 W Half Bridge (HB) LLC
demo board fully designed using Infineon products. (Order information in ISAR: EVAL_600W_12V_LLC_P6_A)
The target efficiency of this design is fixed according to the need to fulfill at complete PSU stage the 80+
Titanium Standard; that means certain minimum efficiency requirements for the HV DC/DC stage are fixed at
10%, 20%, 50% and 100% load conditions.
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2
HB LLC converter principles of operation
The typical modes of operation of the LLC converter will be discussed in this chapter using an initial
description of the concept behind First Harmonic Approximation (FHA. The reasoning behind the basic
configuration of the resonant tank will be shortly introduced. Finally, the concepts and challenges for
successful implementation of synchronous rectification will be outlined.
The most important concepts are referred to here, in order to better understand the design considerations.
2.1
Tank Configuration and Operational Modes
The principle schematic of a Half Bridge LLC converter is shown in Figure 2.
Cr, Lr and Lm represent the so called “resonant tank”: together with the main transformer, they are the key
components in the LLC design.
The primary half bridge and the output rectification are the other two stages to be defined.
Figure 2
Principle schematic of a half Bridge LLC converter
The LLC is a resonant converter that operates with frequency modulation instead of the Pulse Width
Modulation (PWM), traditional approach to power conversion.
The following Figures 3, 4, 5 and 6 will graphically explain the fundamental operating mode of a HB LLC
converter.
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Figure 3
Fully resonant operating mode, at resonant point for Cr and Lr, with near ZCS turn-off of primay
side MOSFETs.
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Figure 4
Over resonant operation, above Cr-Lr resonance, for both half cycles, showing tank current
waveforms and non-ZCS turnoff of the primary side MOSFETs
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Figure 5
Under resonant DCM operation, (between resonant point of Cr and Lr, versus resonant point of
Cr and Lr+Lm) half cycle 1
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Figure 6
Under resonant DCM mode operation, (between resonant point of Cr and Lr, versus resonant
point of Cr and Lr+Lm) 2nd half cycle
2.2
Analysis of the Basic Tank Characteristics using FHA
Starting point in a resonant converter design is the definition of an energy transfer function, which can be
seen as a voltage gain function, so a mathematical relationship between input and output voltages of the
converter. Trying to get this function in an “exact” way involves several nonlinear circuital behaviors
governed by complex equations. However, under the assumption that the LLC operates in the vicinity of the
series resonant frequency, important simplifications can be introduced.
In fact, under this assumption, the current circulating in the resonant tank can be considered purely
sinusoidal, ignoring all higher order harmonics: this is the so-called First Harmonic Approximation Method
(FHA), which is the most common approach to the design of a LLC converter.
In the FHA, the voltage gain is calculated with reference to the equivalent resonant circuit shown in Figure 7.
Figure 7
First Harmonic Approximation equivalent resonant circuit
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The mathematical expression of the gain K is given in terms of a normalized resonant frequency Fx:
K (Q, m, Fx ) 
Vo _ ac( s)

Vin _ ac( s)
Fx ²(m  1)
(m  Fx ²  1)²  Fx ²  ( Fx ²  1)²  (m  1)²  Q²
(1)
Where:
m
Lr  Lm
;
Lr
fr 
1
Lr  Cr
;
Fx 
fs
;
fr
Rac 
8 Np ²

 Ro ;
 ² Ns ²
Lr
Q
Figure 8
Family of Q curves for a fixed m inductance ratio of 6
2.3
Tank Q Values and m Inductance Ratio: System Implications
Cr ;
Rac
(2)
The resonant tank gain K can be plotted as a function of the normalized driving frequency fx for different
values of the quality factor Q and any single value of the inductance ratio factor m.
Figure 9
Family of Q curves for m inductance ratios of 3, 6, and 12
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2.4
Benefits of Split Capacitor Cr
The design described in the present document uses the configuration shown in Figure 10, typically known as
“split resonant capacitor technique”. This solution provides a couple of important benefits.
The first one is the reduction of the AC current stress on the resonant and input “bulk” capacitors, with
consequent relaxed AC current requirements on those components, thus cost reduction and extended
lifetime.
The second one involves the typically critical LLC start-up sequence.
In fact, the split capacitor technique provides the possibility to charge the resonant capacitance
simultaneously to the input bulk cap, thus reducing the needed charging time. In fact, until the resonant
capacitor is completely charged, the transformer is not driven symmetrically, so there is a significant
difference in the up and down slopes of the resonant current and the current may not reverse in a switching
half-cycle. This condition might create a very dangerous operation where a MOSFET is turned on while the
body diode of the other HB MOSFET is conducting: this is the condition typically known as “hard
commutation on conducting body diode”, which submits the turning-off device to heavy stress and this may
happen for several cycles at the converter start-up.
Using the split resonant capacitor technique, the risk of having hard commutation is significantly reduced in
case the HV DC/DC converter is powered up in relatively short time after the input bulk capacitor has been
charged to the DC-link voltage.
Of course, we would like to make clear that this technique only may reduce the possible occurrence of hard
commutation, but does not guarantee 100% prevention.
A safe and reliable operation at start-up is only possible through a proper control algorithm and HV MOSFET
driving technique, along with a power device with rugged body diode.
For further details about this topic, please refer to the paragraph 4.4 of the present document and [4}.
Figure 10
Re-arranging the resonant capacitor into a split capacitor Half Bridge configuration
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2.5
Synchronous Rectification Concepts for LLC
Figure 11 shortly summarizes the technique to manage Synchronous Rectification in HB LLC Converter
Figure 11
SR in HB LLC Converter
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3
LLC design methodologies for specific application
requirements
An optimization procedure for the selection of the main LLC parameters, for both FHA method and using
exact calculation or simulation will be shown in the next section. The goal will be to achieve the best
performance while fulfilling input and output regulation requirements.
At the same time, Zero Voltage Switching operation of the primary HB MOSFETs must be ensured in order to
get full benefits out of the soft switching behavior, especially at light load.
3.1
Input Design Data
In Table 1, an overview of the major design parameter is displayed.
Table 1
Design parameters
Description
Input Voltage
Output Voltage
Output Power
Efficiency at 50% Pmax
Switching Frequency
Dynamic Output Voltage regulation
(0-90% Load step)
Vout_ripple
Minimum
350 VDC
11.9 VDC
Nominal
380 VDC
12 VDC
Maximum
410 VDC
12.1 VDC
600 W
97.4%
90 kHz
150 kHz
250 kHz
Max. overshoot =0.1 V
Max. undershoot=0.3 V
150 mVpk-pk
From the table above, the first important design parameters can be derived:
Main transformer turn ratio
Minimum needed Gain
Maximum needed Gain
Application Note
n
Np
Vin _ nom

 16
Ns 2  Vout _ nom
(3)
K min(Q, m, Fx) 
n  Vo _ min
 0.95
Vin _ max
2
(4)
K max (Q, m, Fx) 
n  Vo _ max
 1.08
Vin _ min
2
(5)
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3.2
Gain Curve
The resulting gain curves, Figure 3, for loads between 10% and 100% Pmax are in the following plot:
Figure 12
Gain Curve
Both the Mmin and Mmax limits cross all the gain curves of our LLC converter: that means the in-out regulation
is fully achieved in the specified ranges.
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3.3
Suggested FHA Optimization Process
Figure 13 shows a flow-chart including all the steps in the design of a HB LLC converter.
Figure 13
Suggested FHA Optimization Process
For all the details of this method you can refer to [2]
3.4
Notes on the Selection of the Inductance Factor m
The inductance factor (Equation 2) has an important impact on the converter operation. Lower values of m
achieve higher boost gain and narrower range of the frequency modulation, that means more flexible
control and regulation, which is valuable in applications with very wide input voltage range.
On the other hand, this also means smaller values of Lm, which leads to significantly high magnetizing
current circulating in the primary side: this current does not contribute to the power transferred, but mainly
generates conduction losses on the primary side.
In other words, there is a trade-off between flexible regulation and overall efficiency requirements,
especially at light load.
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In the case of the demo board described in the present document, the main goal is to achieve high
efficiency, so relatively high m is selected. This minimizes the circulating current from the magnetizing
inductance. This is allowable because the stated input range is relatively narrow, and a higher value of Lm
will be acceptable as long as sufficient current is available to achieve resonant transitions under light load
conditions.
We rely in the bulk capacitor in case of specific hold up time requirement at the complete AC/DC SMPS level.
However, high-density designs may not permit this, as the bulk capacitor does not shrink with increasing
switching frequency. In some cases, adjustment of the input voltage range may be needed.
In this case, the chosen value is m≈12.
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3.5
Resonant Components Calculation
Combining equations (1) and (2), we get a system where the unknown variables are Lr, Cr and Lm
Solving it, the following values are set for the LLC converter:
n
Np
Vin _ nom

 16  Np  16; Ns  1
Ns 2  Vout _ nom
(6)
Lr  Lm
 12  Lm  195H ; Lr  17 H
Lr
(7)
m
Cr  66nF
fr 
3.6
1
2  Lr  Cr
(8)
 150 KHz
(9)
The ZVS Behavior: Energy and Time Considerations
The ZVS calculations involve two kinds of analysis, the one in the energy domain and the other in the time
domain. The goal is to have enough energy in the resonant tank able to discharge the output capacitance of
the primary MOSFET, but also an appropriate dead time between the two devices.
Figure 14
Equivalent circuit in resonant drain to source transitions
The two key parameters in our analysis are the following:
Co(er) is the Coss energy related component of the used HV MOSFET, in our case IPP60R190P6.
Qoss is the charge stored in Coss at Vin(nom) = 380 VDC. Qoss is linked to the so called Co(tr) by the formula
Qoss = Co(tr)* Vin(nom)
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Co(er) and Co(tr) are the effective output capacitances of the MOSFET, respectively energy and time related.
3.6.1
Energy Related Equations
Im ag _ min 
2 2


n Vo
 0.672 A
2  fsw _ max  Lm
(10)
1
 ( Lm  Lr )  I ² mag _ min  95.1J
2
Enres _ min 
(11)
1
 (2Co ( er )) V ² DS _ max  9J
2
 Enres _ min  Encap _ max
Encap _ max 
3.6.2
(12)
(13)
Time Related Equations
It can be demonstrated that:
tdead 
tecs 2  Qoss, @ 400V

2
Im, pk
(14)
where tdead is the dead time set between the conduction time of the two HB devices and tecs is the time when
the channel of each MOSFET is still in conduction after turning it off (linear mode operation), which is
function of some device parameters like Vgs(th), Rg(tot) and Cgs/Cgd.
Using that formula, together with the min. and max. values of the magnetizing current and considering
tecs=10 ns:
Im ag _ min 
2 2
Im ag _ max 
3.7


2 2

n  Vo
 0.672 A
2  fsw _ max  Lm
(10)
n Vo
 1.66 A
2  fsw _ min  Lm
(11)

tdead, min 
tecs 2  Qoss, @ 400V

 130n sec
2
Im, ag, max
tdead, max 
tecs 2  Qoss, @ 400V

 311n sec
2
Im ag, min
(14)
(15)
The Main Transformer Design
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The most critical condition for the main transformer is the full load, mainly due to thermal reasons. The
selection of the core size and material is done according to this condition along with the power density
target (thus switching frequency) and the available airflow.
Keeping a due margin room in the design, the minimum efficiency requirement at full load is fixed for the HB
LLC converter to 97%, which means our goal is to keep the total dissipated power in that condition below
18 W.
In order to guarantee a balanced spread of power and heating, a good rule in the design of the LLC
Converter is to keep the total power dissipated on the main transformer below 1/6 of the total dissipated
power, which means the max allowed power should be 3 W. This is our first important design input.
Ptrafo _ MAX  3W
(16)
The max. operating temperature is 55°C, as in typical server applications. Due to the transformer safety
isolation approvals, the max. operating temperature of the transformer must be lower than 110°C, so:
Ttrafo _ MAX  (110  55)C  55C
(17)
From (16) and (17) the max. thermal resistance of the core shape can be easily derived:
Rth _ trafo _ MAX 
Ttrafo _ MAX 55 C

 18.3C
W
W
Ptrafo _ MAX
3
(18)
Our selected core shape must have thermal resistance lower than 18.3°C / W.
This requirement can be fulfilled through different methods: the preferred one will allow maximizing the
ratio between available winding area and effective volume, of course compatibly with the eq. (18).
Also considering the power density target (in the range of 20 W / inch³), the most suitable selection is
PQ 35/35, shown in Figure 15.
The related coil former shows a minimum winding area of 1.58 cm² and a thermal resistance of 16.5°C / W, so
lower than (18), thus able to dissipate up to 3.33 W by keeping the ΔTMAX < 55°C.
Once verified that the thermal equations are fulfilled, we can proceed with the design of the primary and
secondary windings and the core material selection with some important goals:

Fitting the geometry/overall dimensions of the core

Fulfilling the condition (16)

Try to split the losses between core and windings as equally as possible: ideally, “fifty-fifty” should
be achieved at full load, but any percentage close to it would be acceptable.
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Figure 15
TDK-Epcos PQ35/35 core
The selected core material is the ferrite TDK PC95, showing a very interesting plot of Core Losses (PCV) vs.
Flux Density vs. frequency (see Figure 16).
The final structure of the main transformer is shown in Figure 17 below. This has been developed in
cooperation with the partner company Kaschke Components Gmbh, Göttingen - Germany
So the primary is realized in a “sandwich” technique using 16 turns of 4 layers of Litz wire 45 strands 0.1 mm
diam. This allows to minimize the AC losses due to skin and proximity effect. The secondary is done with
copper band 20x0.5 mm.
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Figure 16
Ferrite core material TDK PC95
With this choice, at full load condition, the total copper losses (primary + secondary, DC+AC components)
are 1.1 W, the core losses are 1.8 W, so overall:
Ptrafo  Pcopper  Pcore  2.9W  Ptrafo _ MAX  3W
(19)
In other words, the (19) fulfils the thermal equation (18)
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Figure 17
Winding structure of the PQ 35/35 LLC transformer (Kaschke Components Gmbh)
An important transformer parameter involved in the LLC design is the primary or magnetizing inductance
Lm, which, according to eq. (7), must be 195 µH. This value is obtained with distributed air-gap on the side
legs of the PQ core: this construction is preferred since it minimizes the effect of the so called “fringing flux”
which generates additional losses in the windings close to the inner limb.
3.8
The Resonant Choke Design
In LLC designs with stringent power density requirements, the resonant choke is typically embedded in the
transformer, in the sense that the leakage inductance is utilized on this purpose. This technique has the big
advantage to save space and the cost of an additional magnetic component, but also some drawbacks, like
the not easy controllability of the Lr value in mass production.
In the case of the present design, it has been decided to use an external Lr. This is because the demo board is
intended to be primarily used for testing and benchmarking, and high power density is not in the main
focus: having the resonant inductance externally allows changing in a more flexible way the resonant tank.
According to eq. (7), the overall value of Lr shall be 17 µH, including the contribution of the transformer
primary leakage inductance.
The external resonant choke is realized using a RM-12 core and a winding construction illustrated in Figure
18 below and implemented by the partner company Kaschke Components Gmbh, Göttingen - Germany.
Figure 18
Winding structure of the RM12 resonant choke (Kaschke Components Gmbh)
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3.9
The Synchronous Rectification Stage
In applications that target high efficiency both at low and high loads (such as 80PLUS Titanium), while often
requiring high power densities, it is critical to select for the Synchronous Rectification Stage MOSFETs that
combine multiple key characteristics.
First of all, these Sync Rec MOSFETs should exhibit very low RDS(on). Indeed, due to the low voltages observed
on the secondary side of server power supplies, large currents flow through the Sync Rec MOSFETs.
Moreover, compared with other topologies such as ZVS PS FB (Zero Voltage Switching Phase-Shifted Full
Bridge), using LLC topology leads to not only increased peak currents for the Sync Rec MOSFETs, but also
higher root-mean-square currents IRMS.
The conduction losses Pcond of each Sync Rec MOSFET are given by:
Pcond _ SR  RDS , on  ( IRMS )²
(20)
These losses can only be mitigated through the use of a part with very low RDS(on)
Secondly, it is critical for these Sync Rec MOSFETs to exhibit low gate charges Qg.
At light load, the switching losses of the Sync Rec MOSFETs predominate over the conduction losses. In the
case of LLC topology, the main contributor of these switching losses is in fact Qg.
Most of the time, a driving voltage of 12 V is applied to Sync Rec MOSFETs. Although 12 V is not necessarily
the optimized driving voltage for Sync Rec MOSFETs, this driving voltage is very popular in server PSUs
because it is readily available: there is no need to derive it from another voltage rail. Therefore, we decided
to follow this trend for this demo board by driving the Sync Rec MOSFETs with 12 V.
This requirement for low Qg puts extra-strain on MOSFET manufacturers, especially considering that Sync
Rec MOSFETs need to exhibit at the same time a very low RDS(on). Such a feature was however possible for
Infineon because of the new Infineon OptiMOSTM 40 V generation, whose gate charges have been
significantly reduced in comparison with the previous generation.
Thirdly, the paralleled Sync Rec MOSFETs should turn on almost simultaneously.
This can be achieved because of a tightening of the voltage threshold VGS(th) range. For the newOptiMOSTM 40
V generation, the datasheet guarantees a very narrow VGS(th) range, with min. and max. values equal to 1.2 V
and 2.0 V respectively.
Finally, the MOSFET package is critical for a variety of reasons.
The package should exhibit low parasitic inductances in order to confine its contribution to the V DS
overshoot to a strict minimum. This is even more critical in server applications using LLC topology, due to
the limited headroom for the VDS overshoot between the transformer secondary voltage (25 V) and the 90%
derating (36 V max) or even 80% derating (32 V max) applied to the VDS of the Sync Rec MOSFETs;
Moreover, due to the conflicting requirements for high power density and high current capability, the
package should combine a minimum footprint with good power dissipation.
Because of the high current densities arising at the source pins, which can lead to electro-migration and
thereafter destruction of the Sync Rec MOSFETs, the package should provide an enlarged source
connection. While the first two sub-items are tackled by standard SuperSO8 packages, it is the addition of
source-fused leads implemented in the new Infineon OptiMOSTM 40 V generation that reduces the high
current densities above mentioned.
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4
Board description
4.1
General Overview
Figure 2 is the top view, bottom view and the assembly of 600 W HB LLC demo board. Key components are:
(1) heatsink assembly of primary side switches IPP60R190P6 (2) Resonant capacitor
(3) LLC analog controller ICE2HS01G (4) Resonant inductor (5) Main transformer (6) PCB assembly of the
auxiliary circuit with bias QR Flyback controller ICE2QR2280Z (7) Heatsink assembly for cooling the
synchronous rectifiers (8) Output capacitors (9) Output inductor (10) Half-Bridge MOSFET gate driver
2EDL05N06PFG and (11) Synchronous Rectifier OptiMOS™ BSC010N04LS.
10
11
600 W LLC Top View
1
Figure 19
2
3
600 W LLC Bottom View
4
5
6
7
8
9
IFX 600 W LLC Demonstration Board
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4.2
Infineon BOM
This HB LLC 600 W demo board is a full Infineon solution meeting the highest efficiency standard 80PPLUS®
Titanium using the following parts:
4.2.1
Primary HV MOSFETs CoolMOSTM IPP60R190P6
The 600 V CoolMOS™ P6 is a new addition to Infineon’s market leading high voltage CoolMOS™ portfolio. It is
the seventh technology platform of high voltage power MOSFETs designed according to the revolutionary
superjunction principle. This new and highly innovative product family is designed to enable higher system
efficiency whilst being easy to design in.
In LLC application, converter is in resonant operation with guaranteed ZVS even at a very light load
condition. Switching loss caused by Eoss during turn-on can be considered negligible in this topology. With
this consideration, CoolMOS™ P6 offers superior price/performance ratio with low FOMs (Ron*Qg and
Ron*QOSS), which means that MOSFET switching transitions can happen in a shorter dead time period. This
will result in lower turn-off losses, pushing further the efficiency. The following are the additional features
and benefits of CoolMOS™ P6 making it suitable and advantageous for resonant switching topologies like
LLC:
1. Reduced gate charge (Qg) improves the efficiency especially in light load condition due to a lower
driving capability requirement
2. Lower Qoss reduces the turn-on and turn-off time for a better usage of ZVS window
3. Optimized gate threshold voltage (Vth) lowers the turn-off losses in soft switching applications
4. Optimized integrated Rg ensures an optimum balance between efficiency and good
controllability of the switching behavior
5. Improved dv/dt compared to previous technologies assures high robustness.
6. Good body diode ruggedness
7. Outstanding reliability with proven CoolMOS™ quality
4.2.2
LLC Analog Controller ICE2HS01G
ICE2HS01G is Infineon’s 2nd generation half-bridge LLC controller designed especially for high efficiency halfbridge or full-bridge LLC resonant converter with synchronous rectification (SR) control for the secondary
side. With its new driving techniques, the synchronous rectification can be realized for LLC converter
operated with secondary switching current in both CCM and DCM conditions. No special synchronous
rectification controller IC is needed at the secondary side. The maximum switching frequency is supported
up to 1 MHz. Apart from the patented SR driving techniques, this IC provides very flexible design and
integrates full protection functions as well. It is adjustable for maximum/minimum switching frequency,
soft-start time and frequency, dead time between primary switches, turn-on and turn-off delay for
secondary SR MOSFETs. The integrated protections include input voltage brownout, primary three-levels
over current, secondary over load protection and no-load regulation. It also includes a burst mode function
which offers an operation with low quiescent current maintaining high efficiency at low output load while
keeping output ripple voltage low.
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4.2.3
HB Gate Drive 2EDL05N06PFG
Developers of consumer electronics and home appliances strive continuously for higher efficiency of
applications and smaller form factors. One area of interest in power supply design is the switching behavior
and power losses of new power MOSFETs, such as the latest generations of CoolMOS™ with dramatically
reduced gate charges, as dedicated driver ICs can optimize it.
The 2EDL05N06PFG IC is one of the drivers from Infineon’s 2EDL EiceDRIVER™ Compact 600 V half bridge
gate driver IC family with monolithic integrated low-ohmic and ultrafast bootstrap diode. Its level-shift SOI
technology supports higher efficiency and smaller form factors of applications. Based on the used SOItechnology there is an excellent ruggedness on transient voltages. No parasitic thyristor structures are
present in the device. Hence, no parasitic latch-up may occur at all temperature and voltage conditions. The
outputs of the two independent drivers are controlled at the low-side using two different CMOS resp. LSTTL
compatible signals, down up to 3.3 V logic. The device includes an under-voltage detection unit with
hysteresis characteristic, which is optimized for either IGBT or MOSFET. 2EDL05N06PF (DSO-8) and
2EDL05N06PJ (DSO-14) are driver ICs with undervoltage-lockout for MOSFETs. These two parts are
recommended for Server/Telecom SMPS, Low-Voltage Drives, e-Bike, Battery Charger and Half Bridge Based
Switch Mode Power Supply Topologies.
4.2.4
Bias QR Flyback Controller ICE2QR2280Z
ICE2QRxxxx is a second generation quasi-resonant PWM CoolSET with power MOSFET and startup cell in a
single package optimized for off-line power supply applications such as LCD TV, Notebook Adapter and
Auxiliary/Housekeeping Converter in SMPS. The digital frequency reduction with decreasing load enables a
quasi-resonant operation until very low load. As a result, the system average efficiency is significantly
improved compared to conventional solutions. The active burst mode operation enables ultra-low power
consumption at standby mode operation and low output voltage ripple. The numerous protection functions
give a full protection of the power supply system in failure situation. Main features of ICE2QR2280Z which
make it suitable as an auxiliary converter of this LLC demonstration board are:

High voltage (650 V/800 V) avalanche rugged CoolMOS™ with startup cell

Quasi-resonant operation

Load dependent digital frequency reduction

Active burst mode for light load operation

Built-in high voltage startup cell

Built-in digital soft-start

Cycle-by-cycle peak current limitation with built-in leading edge blanking time

Foldback Point Correction with digitalized sensing and control circuits

VCC undervoltage and overvoltage protection with Autorestart mode

Over Load /open loop Protection with Autorestart mode

Built-in Over temperature protection with Autorestart mode

Adjustable output overvoltage protection with Latch mode

Short-winding protection with Latch mode

Maximum on time limitation

Maximum switching period limitation
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4.2.5
SR MOSFETs OptiMOSTM BSC010N04LS
For the synchronous rectification stage, the selected device is BSC010N04LS, from the latest OptiMOS™ 40 V
family. SR is in fact naturally the best choice in high efficiency designs of low output voltage and high output
current LLC, as in our case. In applications that target high efficiency both at light and heavy loads – such as
80PLUS® Titanium- while often requiring high power densities, it is critical to select SR MOSFETs that
combine following key characteristics:

Very low RDS(on): BSC010N04LS provides the industry’s first 1 mΩ 40 V product in SuperSO8 package

Low gate charge Qg, which is important in order to minimize driving losses, with benefits on light load
efficiency

Very tight VGS(th) range: in fact, in case of paralleling this allows the MOSFETs to turn-on almost
simultaneously. Selected OptiMOSTM offer very close min. and max. of VGS(th), respectively 1.2 and 2 V

Monolithically integrated Schottky like diode, in order to minimize the conduction losses on it

Package; BSC010N04LS in SuperSO8 with source fused leads is able to address all the typical crucial
requirements for a suitable SR MOSFET package:
− Minimizing parasitic inductances
− Combining compact footprint with good power dissipation
− Enlarged source connection in order to minimize electro-migration occurrence.
4.3
Board Schematics
4.3.1
Mainboard Schematic
Figure 20
MainBoard Schematic
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4.3.2
Controller Board Schematic
Figure 21
Controller Board Schematic
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4.3.3
Bias Board Schematic
Figure 22
Bias Board Schematic
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Figure 23
Mainboard PCB with Controller – and Bias Board
4.4
Critical LLC Operation - Hard Commutation
In the LLC converter, hard commutation of the body diode might occur during the start-up, burst mode,
overload and short circuit condition. The occurrence of this condition can be prevented in the design by
using a proper control technique, a correct selection of resonant components and a proper setting of the
minimum and maximum operating frequency. Hard commutation happens in LLC during the commutation
period of the body diode. During this time, resonant inductor current is flowing through body diode of the
MOSFET creating ZVS condition upon this MOSFET’s turn-on. When the current is not able to change its
direction prior to the turn-on of the other MOSFET, more charges will be stored in the P-N junction of that
MOSFET. When the other MOSFET turns on, a large shoot-through current will flow due to reverse-recovery
current of the body diode. This results in high reverse recovery peak current IRRM and high reverse recovery
dV/dT, which sometimes could lead into MOSFET breakdown.
In this 600 W LLC analog controlled demonstation board, only the burst mode condition has the tendency of
undergoing hard commutation. In Figure 24, hard commutation at burst mode is minimal, so that
IPP60R190P6 is able to withstand without any problem.
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528V
Ch1: VDS_LS
Ch2: VGS_LS
Ch4: IDS_LS
26V
11A
Figure 24
Hard Commutation During Burst Mode Operation, VDS_pk , VGS_max/min and IRMM
The voltage spike on the gate VGS and drain VDS can be influenced by varying both turn-on and turn-off gate
resistors in the range of 10 ohm. This increased Rg will not affect the efficiency, thanks to the P6 technology
switching behavior.
It is important to highlight that in the present 600 W Analog LLC Demonstration board there is no other
observed hard commutation event, neither during start-up, nor at output short-circuit conditions.
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4.5
ZVS Behavior Analysis
Nearly full ZVS is achieved on the entire output load range as shown in Figure 25.
Ch1: VDS_LS
Ch2: VGS_LS
Ch4: IDS_LS
Nearly full ZVS
achieved
starting at 5 A load
Figure 25
Nearly Full Zero Voltage Switching (ZVS) starting at 5 A load
4.6
Burst Mode Operation
At no load or a very light load condition, LLC controller provides frequency approaching to its maximum
setting. In this condition, in order to still achieve full ZVS, magnetizing current should be high enough to
discharge the output capacitances. Due to magnetizing current limitation, switching loss especially turn-off
loss is relatively high if the devices, will continue to switch at the highest frequency. In order to overcome
this phenomenon, burst mode function is enabled and implemented. This results ineffective lower switching
losses and driving losses, because of the low burst frequency.
Additionally, this helps to achieve regulation even at no load condition, preventing the problems often seen
in LLC in that condition. These regulation problems are typically due to parasitic components like the
primary-secondary main transformer coupling capacitance and the SR MOSFETs output capacitance. The
combination of these factors generates the so-called third resonant frequency in the LLC gain curve, making
the converter virtually not controllable at no load. The burst mode allows overcoming this problem, by
limiting the unwanted primary to secondary power transfer, due to the above-mentioned parasitic effects.
For further details about this tricky operation of the LLC converter, please refer to the specific literature [7].
The waveforms in Figure 26 illustrate the Burst Mode technique applied in our 600 W LLC demo board.
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Ch1: VDS_LS
Ch3: VOUT
Ch4: IDS_LS
Burst Mode Operation at a Very Light Load
Condition
Ch2: VGS_LS
Figure 26
Burst Mode Operation at No-Load and Very Light Load Condition
4.7
Efficiency
4.7.1
80+ Titanium Efficiency Target
Figure 27 shows the efficiency measurement done on the 600 W LLC demo board with reference to the 80+
Titanium Standard Efficiency. As well known, the Titanium Standard fixes the minimum efficiency
requirement at the three most important load conditions in a Computing/Server Application, 10%, 50% and
100%.
The combination of proper converter design (resonant tank, transformer) and HV device selection allows to
fulfil with reasonable margin the efficiency targets especially in the range 10-40% load.
Proper selection of SR LV device and secondary side design more influences the performance in the range
40-100% load.
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600W LLC Board Efficiency
without Bias
0,98
0,975
0,97
Efficiency [%]
0,965
600 W LLC
Board
IPP60R190P6
0,96
0,955
0,95
0,945
80+ Titanium
Efficiency
standard (HV
DC-DC stage)
0,94
0,935
0
5
10
15
20
25
30
35
40
45
50
55
Load Current [A]
Figure 27
IFX 600 W LLC Demonstration Board Efficiency vs Titanium STD Efficiency
The measurement has been done in a fully automated setup, shown in Fig. 29. The total accuracy of the
measurement is in the ±0.1% range.
Figure 28
IFX 600 W LLC Automated Efficiency Measurement Setup
4.7.2
Losses Breakdown
In the graphs below, you can find the losses breakdown among the different components of the demo
board.
You can see how the contribution of Primary MOSFETs is progressively increasing from light to heavy load.
On the other side, the contribution of the main transformer is important at 10% load, but it tends to
decrease at higher load: this is mainly due to the core losses (higher at light load due to higher switching
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frequency) and the magnetizing inductance, which is almost constant and independent on the load. In fact,
this feature allows the HB LLC topology to easily achieve ZVS down to very light load and definitely
differentiates the HB LLC topology from other soft switching approaches, like the ZVS Phase Shift Full
Bridge.
4,96 1,59 0,12
4,000
2,65
3,500
19,12
30,27
[W]
3,000
41,30
2,500
2,000
1,500
Primary MOSFETs
Power trafo
1,000
SR osses
Resonant choke
0,500
Output choke
Output capacitance
0,000
Tracks, Cin, sensing
Figure 29
10% Load Losses Breakdown and Spread (@10% Pmax and 100 kHz)
7,000
6,000
5,02
4,56
1,71
4,56
32,94
24,29
5,000
26,92
[W]
4,000
3,000
2,000
1,000
0,000
Primary MOSFETs
Power trafo
SR losses
Resonant choke
Output choke
Output capacitance
Tracks, Cin, sensing
Figure 30
50% Load Losses Breakdown and Spread (@50% Pmax and 100 kHz)
18,000
4,25
16,000
2,73
3,79
14,000
38,56
24,15
12,000
[W]
9,10
17,43
10,000
8,000
6,000
4,000
Primary MOSFETs
SR losses
Output choke
Tracks, Cin, sensing
2,000
0,000
Figure 31
Power trafo
Resonant choke
Output capacitance
100% Load Losses Breakdown and Spread (@100% Pmax and 100 kHz)
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5
Test/Power-up Procedure
Test
Test procedure
Condition
1. Auxiliary Circuit Turn-On
Apply 30 Vdc on the input.
Vin: ~30 Vdc
Orange LED will light up
2. LLC Converter Turn-On
3. Operational switching
frequency
Apply 350 Vdc Converter will give Vout
=12 Vdc
Vin: 350 Vdc
Using voltage probe, monitor
switching frequency at following test
conditions:
Vin:380 Vdc
@5 A Output Load 10% Load - ~ 155
kHz*
Iout: 5 A
@25 A Output Load 50%Load - ~ 142
kHz*
Iout: 25 A
@50 A Output Load 100% Load - ~ 132
kHz*
Iout: 50 A
Vout:12 V
Vout:12 V
(*measure freq. at “Pri_LS_VGS“connector)
[* +-10 kHz]
4. Fan enable
Switch the load from 50 A to 5 A.
Increase the output load current from
11-14 A, fan should turn on.
Vin =380 Vdc
Iout= 5 A
ÞFan is off
Vin =380 Vdc
Iout= 11-14 A
ÞFan is on
5. Switch off Input Start-up at
No load
Switch off the Input
Vin= 0 Vdc
Iout= 0 A
Switch at 380 Vdc on no load output.
Operation should be in burst mode.
Vin =380 Vdc
Iout = 0 A
Vout = 11,5 – 12,5 Vdc
6. Switch off Input; Start-up
at Full load
7. Running No Load ->
Output Short Circuit
Application Note
Switch off the Input
Vin= 0 Vdc
Iout= 0 A
Apply 380 Vdc with full load @50 A
output. Vout is in between 11.8 – 12.2
Vdc*
(*measure
on the board-connector)
Vin =380 Vdc
Switch off load from 380 Vdc 50 A to 380
Vdc 0 A.
Vin =380 Vdc
Short circuit the load using the short
circuit function of the e-load.
Converter should latch.
(after short circuit) Vout = 0 Vdc
36
Vout: 11,8 – 12,3 Vdc
Iout = 50 A
Iout = 0 A
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8. Switch off Input & remove
short circuit
Switch off the Input.
Vin= 0 Vdc
9. Running Full Load -> Over
Current Protection
Remove short circuit function on the
load.
Iout= 0 A
Apply 380 Vdc 50 A with full load
output. Increase the current on the
output 1A each step until the
converter goes into protection starting
from 50 A. OCP occurs between 55 A
and 62 A.
Vin =380 Vdc
Apply 380 Vdc 50 A with full load
output. Short circuit the load using the
short circuit functions of the load.
Converter should latch.
Iout= 0 A
Switch off the Input.
Vin= 0 Vdc
10. Running Full Load ->
Output Short Circuit
11. Switch off Input; Start- Up
-> Output Short Circuit
Iout = 50 A
OCP = between 55 A – 62 A
Vin =380 Vdc
Iout = 50 A
(after short circuit) Vout=0 Vdc
Iout= 0 A
Apply 380 Vdc with output load short
circuit. Converter should be in
hiccup/latch mode.
Vin =380 Vdc
12. Switch off Input & remove
short circuit
Switch off the Input.
Vin= 0 Vdc
Remove short circuit function on the
load.
Iout= 0 A
13. Dynamic Loading
Apply 380 Vdc. Set the electronic load
to dynamic loading mode with the
following settings:
Vin =380 Vdc
CCDH1: Iout 5 A
Iout = 5 A…50 A
CCDH2: Iout 50 A
Vout = 11,5 – 12,5 Vdc
Iout = short circuit
Vout = 0 V short circuit
(hiccup/latch)
Dwell time: 10 ms
Load slew rate: 1 A/µS
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6
Useful material and links
In the following Links you can find more detailed information about the used devices from Infineon and the
magnetic components.

Primary HV MOSFETs CoolMOSTM IPP60R190P6:
https://www.infineon.com/dgdl/Infineon-IPX60R190P6-DS-v02_01en.pdf?fileId=db3a30433f2e70c5013f37c80e24240f

LLC analog controller ICE2HS01G
http://www.infineon.com/dgdl/ICE2HS01G_PDS_v2.1_20110524_Public.pdf?folderId=db3a304412b4079
50112b408e8c90004&fileId=db3a30432a40a650012a458289712b4c
HB Gate Drive 2EDL05N06PFG
http://www.infineon.com/dgdl/Infineon-2EDL05x06xx-DS-v02_05EN.pdf?fileId=db3a30433e30e4bf013e3c649ffd6c8b

Bias QR Flyback controller ICE2QR2280Z
http://www.infineon.com/dgdl/Datasheet_ICE2QR2280Z_v21_20110830.pdf?folderId=db3a304412b4079
50112b408e8c90004&fileId=db3a30432a7fedfc012a8d8038e00473

SR MOSFETs OptiMOSTM BSC010N04LS
http://www.infineon.com/dgdl/BSC010N04LS_rev2.0.pdf?folderId=db3a304313b8b5a60113cee8763b02
d7&fileId=db3a3043353fdc16013552c1c63647c4

Main Transformer and Resonant Choke ferrite cores
http://en.tdk.eu/blob/519704/download/2/ferrites-and-accessories-data-book-130501.pdf
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7
References
[1] T. Fujihira: “Theory of Semiconductor Superjunction Devices”, Jpn. J. Appl. Phys., Vol.36, pp. 62546262, 1997
[2] Sam Abdel Rahman: “Resonant LLC Converter: Operation and Design: 250 W 33Vin 400 Vout Design
Example”, Infineon Technology AN 2012
[3] Alois Steiner, Francesco Di Domenico and others: “600 W Half Bridge LLC Evaluation Board with 600 V
CoolMOS™ C7”, Infineon Technologies AN 2015
[4] Lawrence Lin, Gary Chang: “Consideration of Primary side MOSFET Selection for LLC topology”,
Infineon Technologies AN 2014
[5] Liu Jianwei, Li Dong: “Design Guide for LLC Converter with ICE2HS01G”, Infineon Technologies AN V1.0,
July 2011
[6] Alois Steiner, Johnald Catly: “600 V CoolMOS P6: 600 V Superjunction MOSFET for Server, Telecom , PC
Power and Consumer
[7] Jae-Hyun Kim, Chong-Eun Kim and others: “Analysis for LLC Resonant Converter Considering Parasitic
Components at Very Light Load Condition”, 8th International Conference on Power Electronics, 2011 –
Korea
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8
List of abbreviations
BOM.................................................................................................................................................Bill Of Materials
CGD ...........................................................................................................Internal Gate Drain Capacitance CGD=Crss
Ciss.............................................................................................................................input capacitance Ciss=CGS+CGD
Co(er) ............................................................................................................................effective output capacitance
Cr ............................................................................................................................................resonant capacitance
di/dt ..............................................................................................steepness of current slope at turn off / turn on
DUT ...............................................................................................................................................device under test
dv/dt .............................................................................................steepness of voltage slope at turn off / turn on
Eoff...................................................................................................................................energy losses at switch off
Eon............................................................................................................................energy losses loss at switch on
Eoss.............................................................................stored energy in output capacitance (Coss) at typ. VDS=400 V
FHA.............................................................................................................First Harmonic Approximation Method
FOM...................................................................................................................................................Figures of Merit
fr .................................................................................................................................................resonant frequency
ID............................................................................................................................................................drain current
IRMS.....................................................................................................................effective root mean square current
Imag ............................................................................................................................................magnatizing current
Im,pk...................................................................................................................................peak magnetizing current
K............................................................................................................................................................... gain factor
Lr ............................................................................................................................................. resonant inductance
Lm....................................................................................................................................... magnetizing inductance
m ................................................................................................................................................. inductance factor
Np ................................................................................................................................................... primary winding
NS................................................................................................................................................secondary winding
n ........................................................................................................................................... transformer turn ratio
MOSFET....................................................................................metal oxide semiconductor field effect transistor
Pcond_SR ..............................................................................................synchronous rectification conduction losses
PFC......................................................................................................................................power factor correction
PNP................................................................................................................ bipolar transistor type (pnp vs. npn)
QOSS ....................................................................................................................................Charge stored in the COSS
Q ..........................................................................................................................................................quality factor
Rac.......................................................................................................................................total equivalent resistor
RDS(on)............................................................................................................ ……drain-source on-state resistance
Rg,tot ..............................................................................................................................................total gate resistor
Ro ......................................................................................................................................................output resistor
Rth ...............................................................................................................................................thermal resistance
tdead ...........................................................................................................................................................dead time
tecs ............................................................................................................................early channel shut down time
VDS ..............................................................................................drain to source voltage, drain to source voltage
Vgs,th....................................................................................................................drain to source threshold voltage
VO_AC ............................................................................................................... output voltage, alternating current
Application Note
40
Revision1.0, 2015-07-31
Design Note DN 2013 -01
V1.0 January 2013
Design of a 600 W HB LLC Converter using 600 V CoolMOS™ P6
VIn_AC ................................................................................................................input voltage, alternating current
VIn_nom .................................................................................................................................nominal input voltage
Vout_nom..............................................................................................................................nominal output voltage
ZCS.....................................................................................................................................zero current switching
ZVS.....................................................................................................................................zero voltage switching
Revision History
Major changes since the last revision
Page or Reference
--
Application Note
Description of change
First Release
41
Revision1.0, 2015-07-31
Trademarks of Infineon Technologies AG
AURIX™, C166™, CanPAK™, CIPOS™, CIPURSE™, CoolGaN™, CoolMOS™, CoolSET™, CoolSiC™, CORECONTROL™, CROSSAVE™, DAVE™, DI-POL™, DrBLADE™,
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Integrated Products, Inc. MICROTEC™, NUCLEUS™ of Mentor Graphics Corporation. MIPI™ of MIPI Alliance, Inc. MIPS™ of MIPS Technologies, Inc., USA.
muRata™ of MURATA MANUFACTURING CO., MICROWAVE OFFICE™ (MWO) of Applied Wave Research Inc., OmniVision™ of OmniVision Technologies, Inc.
Openwave™ of Openwave Systems Inc. RED HAT™ of Red Hat, Inc. RFMD™ of RF Micro Devices, Inc. SIRIUS™ of Sirius Satellite Radio Inc. SOLARIS™ of Sun
Microsystems, Inc. SPANSION™ of Spansion LLC Ltd. Symbian™ of Symbian Software Limited. TAIYO YUDEN™ of Taiyo Yuden Co. TEAKLITE™ of CEVA, Inc.
TEKTRONIX™ of Tektronix Inc. TOKO™ of TOKO KABUSHIKI KAISHA TA. UNIX™ of X/Open Company Limited. VERILOG™, PALLADIUM™ of Cadence Design
Systems, Inc. VLYNQ™ of Texas Instruments Incorporated. VXWORKS™, WIND RIVER™ of WIND RIVER SYSTEMS, INC. ZETEX™ of Diodes Zetex Limited.
Last Trademarks Update 2014-07-17
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Edition 2015-05-01
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