Teorie SMPS rezonante

[Vizitator]

Ca sa nu mai incarcam topicul lui Maxente sa scriem aici de toate(rezonante) pt toti.

Pun intai ce am descarcat eu in anii de cand am intrat pe forum si cu google puteti da cautare dupa un titlu ce pare interesant.

 

Si o parte din ce am postat dincolo:

2) 1. Introduction

Resonant converters are DC-DC switching converters that include resonant tank circuit actively

 

participating in determining input to output power flow. Resonant DC-DC converters are

 

preferred over other conventional topologies due to its features like soft switching namely

 

ZVS and ZCS[1], high frequency operation, high efficiency, smaller size, light weight, low

 

component stress and reduced EM interference. Several topologies of resonant converters have

 

been designed and tested which can all be grouped in the form of one building block as

 

resonant inverter. The block diagram of resonant converter is shown in Figure 1.The resonant

 

DC-DC converter basically comprises of three main building blocks namely Resonant Inverter,

 

rectifier and a Low pass filter

 

The switch network can be half bridge or full bridge [2],[3] designed with various power

 

electronics switches. The second sub block of resonant inverter is resonant tank circuit. It

 

comprises of inductance and capacitor arranged in different configurations. Among all the

 

possible configurations, three main topologies namely Series Resonant Converter (SRC),

 

Parallel Resonant Converter (PRC) and Series Parallel Resonant Converter (SPRC) are widely

 

used for different applications.

In SRC shown in Figure 2. the resonant inductor and capacitor are in series and the load is

 

arranged in series with the resonant tank circuit. This operates quite efficiently in the ZVS

 

region, for switching frequency greater than resonant frequency but fails to operate in ZCS

 

region where switching frequency becomes less than resonant frequency, thus giving rise to

 

problems such as light load regulation, high circulating energy and high turn off current at

 

high input voltage conditions. Light load regulation can be overcome with additional control

 

techniques.

 

In PRC shown in Figure 3,load is connected in parallel to the resonant capacitor which is

 

actually connected in series with the resonant inductor. Light load regulation problem of SRC

 

is overcome in PRC but the circulating energy increases more than that of SRC. Also, the turn

 

off current is high at high input voltage thus increasing losses.

In SPRC which is a combination of SRC and PRC, an inductive or capacitive element is connected

 

in series with a series combination of resonant inductor and capacitor. The load is connected

 

in parallel to this third element. Based on the third element, two configurations are possible

 

as LCC & LLC. SPRC is formed to get the better qualities of both SRC and PRC. In LCC

 

configuration of SPRC shown in Figure 4, high conduction and switching losses occur. Moreover

 

it operates in ZCS region further increasing the loss and decreasing efficiency. On the other

 

hand, LLC [4]-[6]as shown in Figure 5, is considered to be the best among the above mentioned

 

converters due to its advantages like ZVS capability even at no load condition and the narrow

 

switching frequency range with light load.

 

CITAT @iop: Topologia rezonanta foloseste rezonanta unui circuit RLC in chiar modul de functionare si apare in functia de transfer.

 

Este ceea ce se afirma in cele 2 PDF-uri citate:

1---The AC voltage then is driven into a resonant tank which control energy flow to the output

 

2---Resonant converters are DC-DC switching converters that include resonant tank circuit actively

 

participating in determining input to output power flow.

Editat Iunie 28, 2018 de Vizitator

[iop95]

O prezentare f buna si destul de clara.

https://www.ti.com/seclit/ml/slup263/slup263.pdf?DCMP=FC&HQS=pwr-null-null-powertips-pwrhouse-20150710-mc-slup263-en

[Vizitator]

Designing an LLC Resonant

Half-Bridge Power Converter

Topic Category:

Design Reviews – Functional Circuit Blocks

Reproduced from

2010 Texas Instruments Power Supply Design Seminar

SEM1900, Topic 3

TI Literature Number: SLUP263

© 2010, 2011 Texas Instruments Incorporated

Daca tot vorbim de surse rezonante trebuiesc prezentate cat mai multe variante, SLUP263 se refera doar la LLC.

[Vizitator]

Extras de aici:

 

3 Resonant Converter Types

Resonant converters are an attractive alternative to traditional hard-switched ones because of reduced switching losses and the EMI due to the sinusoidal behaviour of the resonant circuit. Such converters (Fig. 2) could operate at high frequencies to reduce the size of their reactive components. These converters generally feature the second or the third order resonant tank circuit, i.e. the storage tank consists of two or three energy storage elements [8]. Resonant tanks can be divided into three groups asseries (Fig. 2a), parallel (Fig. 2b) and series-parallel. In turn, converters with seriesparallel

resonant tanks could be classified as LCC, and LLC (Figs. 2c and 2d,

respectively). In resonant converters regulation of output parameters is performed by

varying the IGBT switching frequency around the resonance frequency of the

converter [3].

A major advantage of a series-resonant converter is that the current in the power

devices decreases with a decrease in the load, leading to higher efficiency. However,

there are difficulties in regulating the output voltage at light load operation [9, 10].

Since the studied converter must operate with wide load variations, this topology is

not considered suitable. In contrast to the series-resonant converter, the parallelresonant

converter can regulate the output voltage at no load by running at a

frequency above resonance. On the other hand, such converters have higher device

current that is relatively independent of the load. This leads to high conduction losses

in semiconductor and reactive components, decreasing the efficiency, especially at

light loads.

 

 

4 LLC Resonant Converter

LLC resonant converters introduce several advantages over other resonant

converters. These converters require a relatively narrow variation of switching

frequency to control the output voltage; can operate with a wide load range and ZVS

could be achieved over the entire operating range. Moreover, the transformer leakage

and magnetizing inductances can be utilised as the resonant elements of the power

stage and, thus, reduce the overall part count. In addition, the series resonant capacitor

also provides DC blocking, favourable for an isolation transformer in the half-bridge

configuration. The LLC converter has two resonant frequencies: Lr and Cr determine

the higher resonant frequency, while lower resonant frequency is determined by Cr

and the series inductance of Lp and Lr. The characteristics of the converter are

dependent on the Lr/Lp inductor ratio. As Lr is reduced, the lower frequency needed at

low voltage input decreases. In this case variations in the switching frequency within

the operating range are increased, resulting in a complicated passive component

design. On the other hand, larger Lr will make the IGBT turn-off current higher,

which increases switching losses. Two resonant frequencies, fr1(LLC) and fr2(LLC) are

defined as follows [5]:

Since the load independent point (higher resonant frequency) is in the ZVS region

(Fig. 3a), the converter could be designed to operate around this point [10, 11]. High

efficiency is achievable by applying lossless capacitive snubbers across the inverter

transistors.

The LLC converter does not require an LC output filter used in traditional hardswitching

HB converter. Only the capacitor filter can be used, leading to a simpler

and lighter secondary part. The required capacitance value is estimated by

out sw(min) Load(min)

 

where ΔUout is the output voltage ripple, fsw(min) is the minimum switching

frequency, and RLoad(min) is the minimum equivalent load resistance.

 

 

5 LCC Resonant Converter

The series-parallel converter, also referred to as an LCC converter, aims at

combining the advantages of the series and the parallel converters, at the same time

reducing or eliminating their disadvantages. Similarly to the LLC, the LCC converter

does not require an LC output filter used in a traditional hard-switching HB converter.

The transformer leakage inductance can be utilised as the resonant element Lr.

The low resonant frequency is determined by a series resonant tank Lr and Cr while

the high resonant frequency is determined by Lr and an equivalent capacitance of Cr

and Cp in series. Two resonant frequencies, fr1(LCC) and fr2(LCC) are defined as follows

The behaviour is dependent on the Cr/Cp ratio. As Cp is reduced, the converter

resembles a series converter and the upper frequency needed at light loads increases.

On the other hand, with an increased Cp the converter resembles a parallel converter

and the circulating current no longer decreases with the load [8].

Unlike in the case of the LLC converter, the load independent point (lower

resonant frequency) is in the ZCS region, while in the ZVS region (the higher

resonant frequency) the converter is more sensitive to changes in the load (Fig. 3b).

Only the operation above the upper resonance will be considered in the following as it

is more desirable from the practical point of view since the ZVS is provided for the

IGBTs, allowing the use of capacitive snubbers to reduce turn-off losses.

 

 

6 Simulation Results and Loss Comparison

Design of resonant components is always a compromise between load power

range, operating frequency, input voltage range, circulating energy in the resonant

circuit etc.

From the efficiency point of view the LLC converter is best to be operated at the

resonant frequency fr1(LLC). In this case the both circulating energy in the resonant

network as well as the switching losses are low. Since this operating point is only

achievable for one given Uin and load power, the LLC resonant converter is usually

designed around fr1(LLC) for a full load and maximum Uin. With an increase in the load

or a decrease in the input voltage, the switching frequency is decreased to keep the

output voltage regulated.

Similarly, the LCC converter is usually designed around fr2(LCC) for a full load and

minimum Uin. The step-by-step analysis and design methods of LLC and LLC

converters were presented in a range of publications [8-13] and are beyond the scope

of this paper.

The values of the resonant tank components of both converters are selected so that

their switching frequency range is similar and relatively narrow (3…4 kHz) and the

isolation transformer turns ratio is the same. The main parameters of the analysed

converters are listed in Table 1. The input voltage and load power range as well as the

output voltage values are the same as for the hard-switched converter. Both converters

are able to operate with ZVS within desired conditions. The simulated waveformsof LLC and LCC converters operating at nominal conditions are shown in Figs. 4a

and 4b, respectively. Simulations show that the turn-off current of IGBT as well as

peak current of the rectifier diodes is essentially higher in the LCC converter (Fig. 5).

The estimated inverter IGBT power loss in the studied solutions is presented in Fig. 6.

The simulations of LLC and LCC converters include the IGBT loss reduction during

the turn-off with the snubber capacitors. Since reductions in the IGBT turn-off power

loss by help of capacitive snubbers have been reported to be lower than expected due

to increased current tail duration and could vary between different IGBTs, the

approximate average reduction of 50% [14-17] is considered in this paper. It should

be mentioned that in real converters, the power losses could be distinctly higher than

the simulated values due to additional power dissipation of passive components and

the output rectifier.

Despite operating with higher switching frequency than the hard-switched

converter, the resonant LLC converter is able to provide essential (up to 57%)

reduction of inverter losses. On the contrary, the power losses of the LCC converter

are higher, especially at higher input voltages. This situation could be improved by

adjusting Cr/Cp ratio. As a downside, the operation frequency range will increase.

 

 

7 Conclusions

Implementation of resonant converters instead of the hard switching half-bridge

topologies seems to be an attractive way of improving the efficiency of the power

converter. Both LLC and LCC converters can deliver low noise and ZVS of the

inverter switches over the whole range of operation conditions. From the two, the

LCC converter design requires additional adjustments in order to reduce switching

losses. This will result in a wider regulation frequency range, making design more

challenging. On the contrary, the LLC converter performance seems advantageous

due to lower power losses with a similar regulation frequency range. On the other

hand, the additional complexity of the topology, its control and protection as well as

possible reduction in robustness reliability may not overcome the advantages it

brings. The further research will focus on investigations of HB topology with phaseshifted

synchronous rectifier, which seems an advantageous alternative since it does

not require any modifications in the inverter part.

Acknowledgement. This research work has been supported by Estonian Ministry of

Education and Research (Project SF0140016s11), Estonian Science Foundation

(Grant ETF8020) and Estonian Archimedes Foundation (project - „Doctoral School of

Energy and Geotechnology II“).

Editat Iunie 28, 2018 de Vizitator

[Vizitator]

O prezentare mai cuprinzatoare:

Editat Iunie 28, 2018 de Vizitator

[sesebe]

Scuze daca se considera OFF-TOPIC dar cum acest topic cred ca a derivat si din cauza la unele "sa zicem nedumeriri" ale mele legate de convertoarele rezonante, as dori sa se prezinte si un caz de convertor ZVS sau ZCS care nu este REZONANT.

In topicul la care fac eu referire s-a sustinut contrar, parerii mele, ca nu toate convertoarele care lucreaza in ZVS sau ZCS sint convertoare rezonante.

Eu imi sustin in continuare punctul de vedere si de aceea cel mai bine este ca cei care nu sint de acond cu el sa prezinte o astfel de sursa ZVS sau ZCS care obtine aces mod de lucru fara a se baza pe o rezonanta, a tancului rezonant in cazul surselor rezonante clasice sau a elementelor parazite de circuit in cazul celor considerate de voi ca nefiind rezonante.

 

Va rog sa nu considerati ca vreau sa stirnesc o polemica, vreau doar sa mai invat ceva ce poate nu stapinesc prea bine (nu prea am proiectat si realizat surse rezonante -am citeva proiecte dar nu de putere mare).

 

Mai pe scurt, cum se obtine modul de lucru ZVS sau ZCS fara a avea o rezonanta?

[iop95]

Detalii despre ZVS.

http://www.powerguru.org/the-half-bridge-circuit-revealed/

https://www.youtube.com/watch?v=g4lyEoOMZkk

 

Pentru ZVS circuitul LC nu trebuie sa fie la rezonanta.

Topologia rezonanta se refera la cele care folosesc acest fenomen si se regaseste in functia de transfer.

ZVS nu tine de o anume topologie.

[Vizitator]

ZVS si ZCS mutat aici: https://www.elforum.info/topic/129816-zvs-si-zcs-in-convertoarele-dc-dc/

[iop95]

Un material bun despre ZVS in LLC la frecvente mari.

http://www.jeet.or.kr/LTKPSWeb/pub/pubfpfile.aspx?ppseq=1461

[dark_angel]

Un convertor ce are implementat un circuit care 'citeste' tensiunea sau curentul prin el pentru a închide/deschide elementul de comutație la un anume prag se cheamă ca e cvasi-rezonant. Am văzut buck sau flyback cu Zcs, nu trebuie neapărat sa aibă un tanc rezonant dedicat ca la un LLC.

Poate nenea asta explica mai bine: https://www.eetimes.com/document.asp?doc_id=1273266 ... așadar pt puteri mai mici flyback cvasi rezonant, pt puteri mai mari LLC sau similare.

[sesebe]

Tot pe baza unei rezonante lucreaza, nu-i o rezonanta prin load ci o rezonanta prin elementele "parazite" de circuit dar tot rezonanta este.

In cazul amintit de tine este vorba de o comutare sincronizata cu frecventa de rezonanta a oscilatiei libere cind s-a descarcat bobina.

[Vizitator]

Mi-a disparut topicul cu oscilograme surse rezonante.

Am o sursa LLC la depanat si pun 3 oscilograme.

1--sus, curentul prin mos-ul de jos-------jos, tens pe cond. rezonant

2--sus, acelasi curent------------------------jos, tens in drena mos jos.

3--sus, curentul primar traf------------------jos, tens drena mos jos

CURENT---0,5A/div TENSIUNE---100V/div

4--sursa

Editat Iunie 28, 2018 de Vizitator

[Vizitator]

Marfa proaspata, 2018:

 

Editat Iunie 28, 2018 de Vizitator

[iop95]

Pentru cine are chef de teorie... analiza completa a convertorului rezonant serie. Si facuta de unii dintre cei mai tari in domeniu.

https://authors.library.caltech.edu/79650/1/07072398.pdf

Editat Ianuarie 21, 2018 de iop95

[Vizitator]

REZONANTA serie

The converter can operate in the following three modes:
1. f < 1: In this mode fs/fr < 1, and it is called “below resonance mode”.
 In this mode, the impedance seen by the inverter is capacitive. This causes a
“leading” current with respect to the inverter output voltage vs. With the leading
current, the inverter operates with the zero current switching (ZCS).
2. f = 1: In this mode fs/fr = 1, and it is called “At resonance mode”.
 In this mode, the impedance seen by the inverter is resistive. Both the inductive and
capacitive impedances cancel each other. The output current ‘or’ voltage of the
converter is maximum. The inverter output current is in phase with the voltage.
With this the inverter operates with ZCS.
3. f > 1: In this mode fs/fr > 1, and it is called “above resonance mode”.
 In this mode, the impedance seen by the inverter is inductive. This causes a
“lagging” current with respect to the inverter output voltage vs. With the lagging
current, the inverter operates with the zero voltage switching (ZVS).
From Figure 4(a), it is clear that the maximum output voltage, therefore, the maximum power is
obtained at the resonance point. The output voltage can be controlled either by reducing the
operating frequency or by increasing the operating frequency. The operation of the converter is,
however, preferred by increasing the frequency because the converter operates with ZVS. ZVS is a
better technique than ZCS because with ZVS, both the turn-on and turn-off losses can be effectively
reduced. In ZCS, only the turn-off loss can be reduced. However, the ZCS technique is preferred
with the switches that rely on the external circuits to commutate. One example of such a switch is
the “thyristor or SCR”.
Advantages of the Series Resonant Circuit:
The main advantage of the series resonant converter is its simplicity and its high efficiency from
full-load to reduced-load.
Disadvantages of the Series Resonant Circuit:
The main drawback of the series resonant circuit is that it loses the output voltage control at very
reduced loads and no loads.

 

Series-parallel Resonant High Frequency Inverter for Standalone
Hybrid PV/Wind Power System
Peng Kong*, Jincheng Zhao, Yalang Xing

One solution for such hardship is the use of resonant converters in which the stresses and
losses upon the electronic devices can be minimized by controlling the switching times that occur at the
instants when the current through and/or voltage across the converter switches become zero. This
technology is known as soft-switching. In addition to the zero voltage/current switching conditions
(ZVS/ZCS), this approach has other advantages, such as: elimination of snubber losses, improvement of
device reliability, less dv/dt stress on magnetic device insulation, reduced EMI problems, reduction of
machine aging due to stresses and voltage boost effect at machine terminals with long cables

 

International Journal of Advanced Research in Electrical,
Electronics and Instrumentation Engineering
(An ISO 3297: 2007 Certified Organization)
Vol. 3, Issue 11, November 2014
10.15662/ijareeie.2014.0311106
Copyright to IJAREEIE www.ijareeie.com 12742
1.1.1 Advantages of resonant converters
1. The switches can be configured to operate at either zero current or voltage points in the waveform, greatly
reducing their stress levels.
2. The resonant sine wave minimizes higher frequency harmonics reducing noise levels which will make power
systems operating in the range of 500 kHz to 2.0 MHz
3. Lower switching losses and higher switching frequencies.
4. Zero-voltage switching reduces converter generated EMI.
5. Zero-current switching can be used to commutate SCR.
6. Size of magnetic components is reduced.
1.2 SWITCHING TECHNIQUES
1.2.1 Hard Switching
Hard switching refers to the stressful switching behavior of power electronic devices. The switching trajectory
of a hard switched power device is shown figure 1.3. During the turn on and turn off processes, the power device has to
withstand high voltage and current simultaneously, resulting in high switching losses and stress. Dissipative passive
snubbers are usually added to the power circuits so that dv/dt and di/dt of the power devices could be reduced, and the
switching loss and stress are diverted to the passive snubber circuits. However, the switching loss is proportional to the
switching frequency, thus limiting the maximum switching frequency power converters. The stray inductive and
capacitive components in the power circuits and power devices still cause considerable transient effects, which in turn
give rise to electromagnetic interference (EMI) problems.
1.2.2 Soft Switching
Soft switched converters have been developed by combining the advantages of conventional PWM converters
and resonant converters. Because the switching loss and stress have been reduced, soft switched converters can be
operated at very high frequency. It is used to suppress EMI. Various forms of soft switching techniques are ZVS, ZCS,
voltage clamping, zero voltage transition methods, etc. Generally MOSFET and IGBT are used as resonant switches.

Editat Iunie 28, 2018 de Vizitator