[introduction]In car, industry and inverter application, grow increasingly to the requirement of efficiency raising below level of higher output power. And in electric car (EV) domain, through increasing electric machinery drive efficiency is mixed accelerate batteries to charge speed, this kind is optimized lengthen add boat course of development to expanding function is mixed crucial. To industry, improving efficiency is to reduce the whole world to the sources of energy is used up and increase can need duratively, because this is the efficiency benefit of technology of dc small electrified wire netting mainly currently. In green but field of second birth energy, efficient can promote what Guang Fufa report, waterpower and wind-force generate electricity to use, so that from inside finite rich utmost gets the sources of energy.

In car, industry and inverter application, grow increasingly to the requirement of efficiency raising below level of higher output power. And in electric car (EV) domain, through increasing electric machinery drive efficiency is mixed accelerate batteries to charge speed, this kind is optimized lengthen add boat course of development to expanding function is mixed crucial. To industry, improving efficiency is to reduce the whole world to the sources of energy is used up and increase can need duratively, because this is the efficiency benefit of technology of dc small electrified wire netting mainly currently. In green but field of second birth energy, efficient can promote what Guang Fufa report, waterpower and wind-force generate electricity to use, so that from inside finite rich utmost gets the sources of energy.

To achieve goal of this one basic efficiency, industry of electric power electron is in to raise switch frequency and voltage to transfer, still try to balance cost and function and reduce total size at the same time (graph 1) . However, implementation transforms this kind need is compositive next generation semiconductor device, release unoccupied place SiC of the power MOSFET of new version and broadband and GaN regularly.

This brought a challenge to design engineer: Below the setting that progresses continuously in technology of switch power transistor, how can just assure power drive product won’t outdated, use these new generation technologies below the situation that does not need to be redesigned ceaselessly thereby?

Graph 1: Switch frequency is taller, solution size is smaller, the choice of technology of canal of Dan Jing body depends on output power and bear cost of be confined to.

It is with typical power source design requirement exemple: Electric car needs solution of a kind of efficient, compact charger of advanced three-phase batteries. Introduce two-way power drive, answer on two direction at the same time likewise effective: Communication turns to flow with dc pass on continuously. Communication side should have active power factor to control (PFC) , dc side should have low switch loss, the batteries that is as high as 800 VDC with voltage wraps join. This design needs to move below tall switch frequency, in order to reduce the dimension of inductance component and weight.

The graph is shown 2 times for a kind of possible solution, combined three-phase PFC, complete bridge among them two-way LLC and active commutator. This solution needs 14 power transistor, compare to realize optimal sex value, can mix use MOSFET, SiC and practicable GaN parts of an apparatus.

Graph 2: The likelihood that charger of batteries of two-way and electric car designs solution.

All power transistor needs to use alone grid driver, high side transistor (Q1, Q3, Q5, Q7, Q9, Q11 and Q13) still need electric segregation. If grid driver has alone Out+ and Out- to cite a base, can be in guide connect and close cycle to use different grid resistor to optimize switch character. In addition, still can choose to keep apart Vpos and Vneg to guide in order to be in during understanding cycle enhance transistor adequately, during closing cycle, undertake discharging to grid capacitance quickly. Negative ” close ” the error that because source pole inductance is caused,voltage still can eliminate guides, raise switch dependability thereby [about negative grid driving voltage (also apply to low side switch) the labor of demand, the white paper that consults be offerred in RECOM website please ” use IGBT and SIC MOSFET will design reliable and durable transistor circuit ” ] . This is problem place: The transistor of different switch technique and different version, its are the biggest grid driving voltage is endless and identical (graph 3) .

Graph 3: Transistor grid driving voltage because technology and difference of version reason existence.

Be aimed at + 15/-9 V is asymmetrical the IGBT of power source voltage and optimized grid driver design, will negative to only 1 V surplus arrives absolutely the biggest the generation that is restricted to be worth or SiC of the 2nd generation create severe pressure, and be over devoid law is compatible transistor of the 3rd acting SiC. Need transfers to exist in the 2nd generation or the design of the 3rd acting SiC from generation SiC similar problem: + what voltage of 20 V the right path will is equal to or exceed new generation is absolutely the biggest be restricted to be worth, bring about appear prematurely breakdown.

Current trend is, new-style power transistor will be in every generation to increase completely below n of inferior grid driving voltage or be over total depletion, but n of optimal grid driving voltage still is met because of iteration of manufacturer, development He Jing body provides a kind and differ somewhat.  Because keep apart voltage of grid driver power source (Vpos and Vneg) by segregation transformer or segregation DC/DC converter are offerred, although grid driver itself applies to all transistor type, but the solution that the choice of transistor of every kinds of power needs to differ. Although use,this is meant make the transistor of switch of 2 class supplier with compatible foot, need possibly also to undertake to keeping apart power source grand design is changed.

But process designing segregation is asymmetrical power source can satisfy this kind of requirement, be aimed at different transistor option in order to support grid driver circuit (the new generation transistor that the likelihood includes to had be notted release) undertake optimizing.

RECOM released this kind of product: RxxC2T25S. This is a SMD DC/DC converter that uses SOIC to enclose, contain compositive segregation transformer (graph 4) . Through changing the resistance in circuit of feedback voltage divider, can install output alone to be in + 2.5 V comes + 22.5 V and – 2.5 V comes – inside the limits of 22.5 V, this is meant should combine output to be in only 18 to 25 V limits inside, solution of a kind of power source can be offerred + 15/-9, + 20/-5, + 18/-4, + 15/-3 or combination of any other output voltage. Personnel of this support design is passed change BoM resistance (is not PCB design) , relaxed between one class and supplier of transistor of 2 class power switch. This also is meant, if roll out,have + 14.5/-3.5 V is optimal of grid driving voltage brand-new generation power transistor, criterion this solution enough satisfies prospective requirement. Finally, output voltage can adjust independently, n of voltage of this special to going to grid drive adjacent and absolutely maximum in order to obtain as far as possible tall switch efficiency is crucial.

Graph 4: Use the segregation DC/DC converter that SOIC encloses, have programmable asymmetrical stabilized voltage output.

Raise kilowatt level as power level, the environment all round grid driver and grid driver power source asks to become more severe exacting. Although the switch loss of technology of advanced WBG power transistor is inferior, but temperature of predicting environment job is higher. The hard switch of tall voltage can produce very tall Dv/dt to change rate, because of this good CMTI (in all immunity to interference of modular transient state) , low segregation capacitance and tall segregation are spent crucial to making sure switch is stable and reliable.

The limits of environmental job temperature of RxxC2T25S is – 40 ℃ comes + 100 ℃ (1.5 W is laden) , highest + 125 ℃ (0.6 W is laden) , especially CMTI is S of μ of ± 150 KV/ , segregation capacitance is 3.5 PF and 3 KVAC/1 only minute segregation (rated repeat peak value voltage to be ± 1200 VDC) . Output still provides comprehensive safeguard, can prevent short circuit, overload and too lukewarm breakdown.

Owe press Suo Dinggong to be able to be meant, after input voltage and output voltage are only stable, just can activation DC-OK cites a base, because this should bring a foot to be able to connect those who receive grid driver to go up make can cite a base, be in steady state in order to ensure from first switch cycle begins (graph 5) .

Graph 5: The solution of driver of comprehensive segregation grid of use RxxC2T25S. R1-R4 setting outputs voltage.

Anyhow, rxxC2T25S is to design personnel to expect long already solution. The SMD component of a hard usage, apply to keep apart grid driver only and design, have all technology function of contented expectation, and can choose output voltage freely, can use existing solution and prospective design to achieve the biggest efficiency thereby.

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