Surse SMPS rezonante/cvasirezonante

[Vizitator]

Sa-l stapanesti sanatos !

Mi se pare prea mare pauza.

EDIT: eu am pus mereu un set de 3 oscilograme: aprox la rezonanta, sub si peste cu un procent oarecare:

Editat Mai 6, 2017 de Vizitator

[maxente]

Timpul mort ar fi pe la 0,8uS. O sa incerc sa il mai reduc sau o sa mai jonglez putin pe la frecventa

Editat Mai 6, 2017 de maxente

[Marian]

Vezi ca ti-am lasat un pm...

[Vizitator]

Acela nu e timp mort ci pauza rezultata din diferenta intre frecv de comanda si cea de rezonanta. Trebuie sa maresti frecventa.

[maxente]

Sonda de curent prima data am avut-o in secundar pusa.

Acum am pus-o in primar.

Daca maresc frecventa arata urat curentu

Editat Mai 6, 2017 de maxente

[Vizitator]

Pai tu ai transformat-o din nou in LLC si asa sunt formele acolo:

[iop95]

Cum adica a transformat-o in LLC? Nu era LLC?

Tot timpul a fost LLC, in diverse regimuri de functionare.

 

Daca mai mariti un pic frecventa, pana aproape de rezonanta, caderea de tensiune cu sarcina ar trebui sa fie si mai mica.

[Vizitator]

 

Series resonant converters

The circuit diagram of an SRC is shown in Fig. 1.20. The DC

characteristic of the SRC is shown in Fig. 1.21. The operating

region is on the right side of resonant frequency f0 owing to

preferred ZVS operation.

It can be seen from the operating region that at light load,

the switching frequency needs to increase to a very high value

to keep the output voltage regulated. Theoretically, the SRC

will lose voltage regulation capability at a no load

condition. This is a problem for SRC.

At 300V input, the converter is working close to resonant

frequency. As the input voltage increases, the converter is

working at a higher frequency, away from the resonant

frequency. This means more and more energy is circulating in

the resonant tank instead of being transferred to output.

On the other hand, when converters operate far from the

resonant frequency, the turn-off current increases

significantly due to large phase shift between excitation

voltage and current of the resonant tank. The switching loss

will be high.

With the above analysis, we can see that SRC is not a good

candidate for dc-dc converters with holdup time requirement.

The major problems are: light-load regulation, high

circulating energy and high turn-off current at nominal input

voltage.

LLC:

LLC resonant converters, illustrated in Fig. 1.26, have been

studied for a long time. In 1990, A.K.S. Bhat proposed LLC

resonant converter [C.50]. However, the LLC converter was

designed similar as a series resonant converter. Thus, its

superior characteristics were not fully utilized. For a while,

the LLC resonant converters were almost neglected. However, in

2002, B. Yang and F.C. Lee revealed the advantages of LLC

resonant converters [C.51]. Since then, LLC resonant

converters have drawn a lot of attention [C.51]–[C.59].

Based on the LLC resonant tank, different topologies, such as

half-bridge and three-level structures, are utilized for

different applications [C.51]-[C.59]. Two-phase LLCs are

proposed in [C.57]. Variable frequency control is the major

control method. A digitally controlled LLC resonant converter

is also reported in [C.58]. Optimal designs of LLC resonant

converters are discussed in [C.52] and [C.56].

The voltage gain of the LLC resonant converter is drawn in

Fig. 1.27. With variable frequency control, the voltage gain

of LLC resonant converter can be controlled as boost mode or

buck mode. During the holdup time, the LLC resonant converter

can operate in boost mode. Thus, high voltage gain is

achieved. Meanwhile, at the nominal condition, the LLC

resonant converter operates very close to the resonant

frequency, which is the best operation point to accomplish

high efficiency. In addition, voltage gains of different Q

converge at the series resonant point. The LLC resonant tank

parameters can be optimized to achieve high efficiency for a

wide load range. As a result, holdup time extension capability

is accomplished without sacrificing the efficiency at the

nominal condition. The LLC resonant converter is considered as

one of the most desirable topologies for wide input voltage

range.

The advantages of LLC resonant converters are:

ZVS capability from the zero load to the full load and low

turn-off current for primary side switches, so switching loss

is low;

Zero-current-switching (ZCS) is achieved for secondary side

rectifiers and low voltage stress;

High voltage gain capability, which is suitable for holdup

time operation, and means that bulky capacitors can be reduced

considerably.

[iop95]

N-am inteles ce vreti sa aratati cu descrierea postata.

Daca inainte, cu bobina separata era LLC (deci in niciun caz SRC), acum cu inductanta de scapari pe post de bobina de rezonanta cum ar putea fi "transformata" in LLC.

 

Si acum raportul Lp/Lr este f mare si caracteristica f aplatizata...poate fi ok pentru operare la frecv fixa.

Daca inductanta de scapari a ramas la 22.7micro, cu 220nF frecv de rezonanta este la 69.85k.

Operand la 56.5k, pentru sarcini mai mari de 5A o sa iasa din ZVS.

[maxente]

In ultimu experiment am modificat putin trafu si inductanta de pierderi nu mai e de 22uH, este de 41uH iar capacitatea serie este de 2x68nF care masurata imi da 120nF. Frecventa de lucru a oscilatorului este de 56khz.

In pozele de mai jos e curentul si tensiunea direct in primarul trafului ETD49

Prima poza e fara sarcina

 

 

Cum am mai zis, daca incep sa maresc frecventa oscilatorului, incepe curentul sa capete incet forma din poza de mai jos

Daca micsorez frecventa, curentul isi pastreaza forma curbata, dar pauza aia din mijloc semnalata de @miticamy in postul #631 se lateste tot mai mult. Practic cum e acum la frecventa de 56khz curentul arata cel mai ''sinusoidal''

Editat Mai 9, 2017 de maxente

[sesebe]

Maxente, vezi ca in meniul canalului poti seta gainul sondei si poti sa schimbi exprimarea in amperi.

[maxente]

Deocamdata fiind un traf de curent facut pe genunchi, nu m-a interesat valoarea curentului. M-a interesat mai mult forma lui. Oricum, multumesc de pont, mai am de butonat prin setarile osciloscopului pana mai invat una alta

 

Revin cu niste poze la forma tensiunii pe capetele condensatorului serie cu traful ETD49. Cu galben este la condensator si cu mov e curentul prin traf

Prima este fara sarcina

Editat Mai 9, 2017 de maxente

[Vizitator]

Am zis mai demult ca la urmatoarea SMPS voi face filmari.

Am mai modificat o sursa de Yamaha, transformata dupa nevoile (puterea) clientului, aveti filmare cu formele de curent.

 

[Blacksmith]

Nustiu care e secretul tau, dar imi place ce le faci !

 

PS: De ce joaca sinusoida aia asa pe osciloscop ?

 

PS2: Poti pune o oscilograma cu tensiunea pe iesire a unei surse d-asta rezonanta de o faci tu ? Dar oscul dat pe AC si la cea mai mica treapta de tensiune. Adica as fi interesat sa vad daca mai sint mizerii pe tensiune cum e la cele hard swiching...

[Vizitator]

O sa fac miine, deja sint la job...

Asa joaca ea, si la smps mele face la fel.

Secretul meu este experienta sau mai bine zis experimentarile facute dealungul timpului.

In tot ceea ce fac, niciodata nu am calculat nimic...

Editat Mai 11, 2017 de Vizitator