[introduction] carborundum (SiC) power parts of an apparatus has been applied extensively at server power source, store can the domain such as inverter of systematic He Guangfu. Some closer year come, automobile industry drove carborundum to the change of electric power drive (SiC) applied growth, also make design an engineer to pay close attention to the advantage of this technology more, widen its use a field.

Carborundum (SiC) power parts of an apparatus has been applied extensively at server power source, store can the domain such as inverter of systematic He Guangfu. Some closer year come, automobile industry drove carborundum to the change of electric power drive (SiC) applied growth, also make design an engineer to pay close attention to the advantage of this technology more, widen its use a field.

Choose technology of parts of an apparatus

No matter use a field how, design of every power source is in order to answer a few same fundamental questions of proceed: How much is inputting voltage, output voltage and output electric current respectively? Next, the performance standard that design personnel wants to consider their strive to come true in end item. Current, power source designs personnel to be able to use a variety of parts of an apparatus to satisfy these standards, include nitrogen to change gallium (GaN) , carborundum (SiC) mix all sorts of is based on silicon (Si) technology, be like bar of MOSFET, insulation ambipolar transistor (IGBT) with super knot (SJ) parts of an apparatus (graph 1) .

Graph 1: These technologies have respective advantage and the most applicable application field

Press when rated puncture report under 400 V, and when the operation that design requirement leads with having opposite low frequency under the power of 1 KW, silicon (Si) it is a right choice normally. Frequency of need tall switch waits in production USB charger in order to reduce magnetic component size compact model when application, nitrogen changes gallium (GaN) it is an admirable choice. The rated voltage interpose that exceeds condition of 1 KW, low frequency to fall in power comes at 600 V 1, below the circumstance of 700 V, IGBT but with carborundum (SiC) the consideration is used together. Nevertheless, to taller switch frequency or higher power density, carborundum (SiC) it is optimal choice.

The center of the choice

In the graph 1 in, the central place that forms between many choices is located in the voltage of medium on the high side and switch frequency. However, carborundum (SiC) efficient the choice that makes its become a be convinced making a person, because the balance to cost of stock detailed account and operation cost may be a critical factor.

Wolfspeed carborundum (SiC) parts of an apparatus is had extremely low guide electrify block, this is meant guide a loss is small and efficiency is tall. In this respect, with silicon (Si) change gallium with nitrogen (GaN) compare (graph 2) , carborundum (SiC) in all application all excel is other technology. Character of this material oneself makes the wave motion that guides electrify block follows temperature small, and nitrogen changes gallium (GaN) with silicon (Si) the rating that RDS(ON) issues than room temperature increases 2.5 times or more.

Graph 2: Wolfspeed carborundum (SiC) the low RDS(ON that parts of an apparatus can maintain stable inside very wide temperature range)

Implement PFC technology change

Develop from simple bridge-type commutator and commutator of contemporary power source comes, this kind of commutator needs only ” big farad capacitor ” come flowing dc output. Addition passive power factor is corrective (PFC) the LC filter that level contains frequency of frequency of a labour normally. The application that this kind of method applies to the relatively low power that did not ask strictly to efficiency and dimension (graph 3) .

Graph 3: Complete bridge commutator from simple not having PFC develops the basic PFC that do not have the bridge

Nowadays, in most switch power source, step up converter serves as active PFC to use after diode commutate bridge, a few its switch frequency is taller than labour frequency frequency quantitative class, because this can use smaller inductor and capacitor. According to specific applying, carborundum is used in active PFC circuit (SiC) diode replaces silicon (Si) base diode but effect of aux will be able to rises two to 3 percent.

On the other hand, it is OK to increase switch frequency increase switch frequency 200 KHz from 80 KHz contractible over all dimension or raise power density to amount to 60% . Generally speaking, raise switch frequency to conduce to the dimension of contractible inductor, and reduce the cupreous loss of inductor.

However, raise 400 KHz from 200 KHz when frequency when, cupreous loss tends smooth, and loss of inductor magnetism core increases continuously. Its are accrual decreases successively as a result, measure is narrow 10% to 15% , power loss increases 10% to 15% . Must narrow to those the application of dimension, this is an eclectic plan that can accept probably.

Want to raise efficiency level 90% above, must new scale circuit, take out diode the bridge. For take out diode, a kind of method is move inductor to input end to communication, replace two bottom diode in bridge-type circuit with two MOSFET. Left switch is in voltage of half weeks of promotion, the switch of right is in lose voltage of half weeks of promotion.

The challenge that faces basically without bridge circuit place is, node of tall frequency switch sheds even best friend the input directly, and photograph of dc ground connection is inputted to communication is floating. This meeting brings about any parasitism capacitance to become directly in all modular EMI. The common method that solves this one problem is do not have bridge double Boost through using or be called come true partly without the bridge (graph 4, left) .

Graph 4: Do not have solution of bridge double Boost quite (left) and use carborundum (SiC) the form of complete bridge gradual progress of implementation namely totem pole develop attacks (right)

Attack in this kind of develop in the structure, two diode of wrong lower part removed issue of float ground connection, and the direct link that fractionation inductor eliminated switch node and alternating current source, solved thereby in all modular EMI problem. Although can use silicon (Si) MOSFET, but their highest efficiency is 95% to 96% , and cover an area of an area bigger, need two inductor, then cost of total stock detailed account may be higher.

Totem pole develop attacks

Totem pole develop attacks is not to have the equipment that develop of bridge double Boost attacks to choose plan, its name originates transistor the means of mutual pile (graph 4, right) . If plan institute is shown, totem pole is OK version of MOSFET of make it complete bridge, OK also make it does not have bridge version, namely on the right side of the MOSFET of arm of low frequency bridge is replaced for diode.

If be in,guide continuously a mode (the job below CCM) condition, the biggest challenge that blow on the face of totem pole pictures faces is the carry on one’s shoulder of retrorse extensive telegram in reply that comes from MOSFET body diode. In the course that changes high-pressured side switch from low-pressure side switch, two MOSFET cannot guide at the same time, body diode must guide inside dead band time. Silicon (Si) restore character to reduce its efficiency reversely (graph 5) .

Graph 5: Carborundum (SiC) with silicon (Si) body diode restores to compare reversely

In design of power source of all hard switch, must guide when body diode when connecting, metropolis generation recovers loss reversely. Carborundum (SiC) carry without minority stream child, because this restores electric current reversely,be almost 0.

And silicon (Si) the loss of MOSFET wants tower above class of a few amounts. This is silicon (Si) the account that parts of an apparatus cannot use in totem pole.

Is complete bridge totem pole still mixture totem pole?

The totem pole that carries synchronous commutate is the implementation means with highest efficiency. Although it is OK,silicon is used in arm of low frequency bridge (Si) MOSFET, but only all 4 carborundum (SiC) MOSFET came true two-way move, for example, in the application of join intelligence electrified wire netting, need to make a few balance in respect of complexity and cost of stock detailed account.

Include server power supply inside most cost is sensitive model application is used do not have the bridge or ” mix ” totem pole develop attacks, the PIN diode with low price is used on arm of low frequency bridge (graph 6) . Its advantage is uses component measure least, and the carborundum of C3M of 650V compression grade as Wolfspeed (SiC) of MOSFET roll out, it is a kind of implementation kind that has cost effectiveness, compare with complete bridge photograph, light laden loss of efficiency is less than 0.5% .

Graph 6: Use carborundum (SiC) of MOSFET and diode ” mix ” totem pole develop attacks

However, if the graph is shown 7 times, want the latent capacity that develops develop of totem pole PFC adequately to attack, realize prep above the peak value efficiency of 99% , use all 4 carborundum (SiC) the PFC of complete bridge totem pole of MOSFET can eliminate diode to press fall, realize highest efficiency and power density thereby.

Graph 7: Complete carborundum of have the aid of (SiC) the PFC of complete bridge totem pole of MOSFET

Wolfspeed CRD-03600AD065E-L 3.6 KW consults the design had proved this. Should consult the design incorporated stock detailed account, principle layout of graph, circuit board, demonstrate guideline of file, application to wait, can get in order to download. It uses Wolfspeed newest compact, thin model TOLL encloses MOSFET of Ω of 650 V 45 M, implementation efficiency is more than 99% , and power density achieves 92W/in3.

This kind is based on carborundum (SiC) totem pole design can be communication – dc changeover is offerred as far as possible tall efficiency, make the engineer can be designed satisfy or exceed the strictest efficiency to ask (like 80+ titanium standard) system.

If need to undertake emulation to your design, can you use online SpeedFit? Design emulator or SpeedVal Kit? Modular evaluate platform, latter is systematic performance in board evaluate offerred an agile compose to build module. If have doubt, apply online discussion in our power please the connection of with Wolfspeed carborundum power expert on platform, or the part such as the documentation that browses our website to go up, tool and support.

The article reprints from: Qorvo semiconductor

 

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