CN100499161C - Metal-insulating-graphitized carbon field effect transistor - Google Patents

Abstract

The invention relates to a voltage controlled high-power switch tube, belonging to power electronic device, called MICFET for short. It substitutes graphitized carbon fiber (or thermal decomposition carbon film) for semiconductor to make conductive channels. It has characters of easy control, quick switch action, high-voltage resistance, very small switch-on resistance and high working temperature, especially applied to power electronic system.

Description

Metal-insulation-graphitized carbon field effect transistor

The present invention is a kind of voltage-controlled high-power switch tube, belongs to power electronic device, the English MICFET that is called for short.The same on the principle with present widely used semiconductor field MOSFET, all be to utilize grid electrostatic field pinch off conducting channel, different is that the present invention adopts graphitized carbon fibre (or thermal decomposition carbon film) to replace semiconductor, makes conducting channel.Therefore, it has easy to control, and switch motion is fast, and is high pressure resistant, and conducting resistance is very little, the characteristics that working temperature is high.Being particularly suitable for power electronic system uses.

Come out so far from first transistor of the fifties in last century, successively invented thyristor SCR, turn-off thyristor GTO, high power transistor GTR, power field effect pipe VMOSFET, insulated door gated transistors IGBT, power electronic device such as MOS control thyristor MCT.They have created countless miracles in field of power electronics, for the mankind make a great contribution.But because they all are to make basic material with semiconductor.See that at present all there is the contradiction between the high withstand voltage and high current capacity in the high power device that nearly all semiconductor is done.Especially power semiconductor always has the conduction voltage drop of 1～3V (if be 100A by electric current, then to consume hundreds of VA in vain, also will add radiator), big like this conduction loss, except that reducing energy utilization efficiency, also limited the application of semiconductor power device in the demanding field of loss.

Thinking of the present invention and purpose are to make conducting channel with the resistivity graphitized carbon fibre more much lower than semiconductor, and have structurally done ingenious arrangement, make grid still can utilize electrostatic field pinch off electric conduction of carbon fiber raceway groove.Make conduction voltage drop than low 2～3 orders of magnitude of semiconductor device, simultaneously high back-pressure and the big little novel electric power electric device of electric current contradiction.

The present invention is that a kind of of Yang Jinyu " metal-insulation-metal field effect transistor " invention (01106729.2) specializes and improvement.Its structure such as figure one, wherein 1 is graphitized carbon fibre (conducting channel), its upper end connects together and makes anode A, and the lower end connects together and makes negative electrode K.2 is that insulation film is (as SiC, Al ₂O ₃, Ta ₂O ₅, pottery).3 is the metallic film grid, is divided into G ₁And G ₂Two groups, each group also connects, and is connected to outer lead respectively.Figure two, are fundamental diagram behind the external control circuit.A, G among the figure ₁, G ₂, K partly is the equivalent electric circuit of carbon fiber field effect transistor; E _a, E _gBe respectively high pressure positive supply and grid control negative supply; R _LBe plate-load, D ₁Be voltage-stabiliser tube, its voltage stabilizing value and E _gEquate; C is an electric capacity; R ₁, R ₂Be resistance, R ₁Resistance is less, and R ₂Resistance (is used for keeping D greatly ₁Electric current of voltage regulation); K ₁, K ₂, K ₃Be double-pole three throw switch.

We illustrate its operation principles in conjunction with figure two: work as K switch ₁, K ₂, K ₃When putting the on position, grid G ₁, G ₂Last voltage all is zero, field effect transistor conducting this moment.The electric current that conduction voltage drop equals to flow through carbon fiber multiply by the resistance of carbon fiber itself.We know that the resistivity of single crystal graphite is 4 * 10 ^-5Ω Cm, graphitized carbon fibre look producer's difference probably 10 ^-4About the Ω Cm.The semi-conducting material of this numeric ratio power device will hang down 2～3 orders of magnitude.Simultaneously, negative supply Eg is through K ₃-R ₁-A-K path makes the voltage on the capacitor C be charged to the Eg value.Work as K switch ₁, K ₂, K ₃When putting the Off position, the voltage on negative supply Eg and the capacitor C is immediately to grid G ₂And G ₁The electric capacity charging.Make Ug ₂K=Ug ₁A=-Eg.According to the principle of negative electric field repulsion negatron, by grid G ₁, G ₂Electron number in the regional carbon fiber of that is surrounded will greatly reduce, when negative voltage Eg is enough high, and this regional free electron light of will being ostracised, G _1.G ₂Institute's area surrounded becomes insulation layer (being that the field effect pipe ends), simultaneously Uak=+Ea.When ending, voltage-stabiliser tube D ₁, by Ea-R _L-R ₂Path is kept voltage stabilizing, keeps the voltage on the electric capacity, thereby continues to keep the field effect transistor cut-off state.

Characteristic of the present invention is discussed below

(1) benefit of being brought by graphitized fibre: (1) resistivity is littler than semi-conducting material, so conduction voltage drop can be than low 2～3 orders of magnitude of semiconductor device; (2) single electron conduction (not having PN junction), control circuit is simple, so switching speed is fast; (3) the carbon fiber chemical stability is good, and is not oxidized under 500 ℃ in air.Behind the deielectric-coating such as parcel SiC, performance is more stable, so working temperature is much higher than silicon semiconductor device; (4) thermal conductivity of carbon fiber is higher, is convenient to heat radiation.The shape of carbon fiber is suitable for obtaining excellent contact, and the ability of bigger anti-surge current is arranged; (5) carbon fiber is easy to obtain, and valency is also cheap than silicon single crystal.

(2) by the benefit of bringing on the structure: (1) whole field effect transistor by no several monofilament carbon fiber field effect transistor elementary cells compose in parallel-or claim the multiple fibre cluster.Therefore, with the parallel connection of several same model field effect transistor, be the thing that follows a well mapped-out plan to enlarge electric current; (2) in the manufacturing mainly with technologies such as vapour depositions, much more simple than semiconductor technology, do not need the ultra-clean factory building yet, manufacturing cost is lower than semiconductor certainly; (3) in Yang Jinyu (01106729.2) invention, the method that overcomes high back-pressure is the series connection with several MIMFET field effect transistor elementary cells, and the series connection number is many more, and back-pressure is high more.Several elementary cells in the middle of the present invention removes are only stayed two elementary cells in two (near A and K), increase reverse voltage with regard to lengthening figure one dotted portion.Say by principle, ending of two field effect transistor in two has transient process, be that the grid negative electricity is pressed with a uphill process, under the grid region in the carbon fiber free electron process that reduces is also arranged gradually, the resistance of whole carbon fiber constantly rises thereupon, voltage more and more higher (quickening siphons away whole free electron in the carbon fiber) between anode A and the negative electrode K; When minus gate voltage rises to peak, the anode positive voltage will siphon away all free electrons in the whole carbon fiber, and MICFET just ends.This is desirable state.In fact owing to many disadvantages in the manufacture process, in carbon fiber, also there is a small amount of free electron.The purpose of our lengthening figure one dotted portion has two.The first prevents the epidermis high pressure between anode-grid and cathode creepage (each root carbon fiber appearance all has the dielectric parcel fortunately, adds follow-up vacuum resin pickup technology again).It two is to increase in the motion process collision probability with carbon atom to the residual free electron of only a few.Reduce velocity of electrons, in order to avoid the destruction that high-velocity electrons cause.(even have puncture also can only burn indivedual several carbon filaments, and can not burn out entire device, can in aging of product process, solve).As seen, along with the lengthening of figure one dotted portion, the also corresponding increase of the conducting resistance of carbon fiber (but because carbon fiber resistance rate is littler than semiconductor, so the absolute value of its resistance increases also not quite).(5) can consider with parcel Al ₂O ₃Aluminum fiber replace figure one dotted portion, conducting resistance can be lower like this.

(3) characteristic of driving (control) circuit: (1) voltage control mode, driving power is little, and speed is fast; (2) work as K ₁, K ₂, K ₃Switch adopts after the photoelectricity coupling isolating switch, and carbon fiber is up and down between two field effect transistor at two ends and just finished electrical isolation between whole field effect transistor and the photoelectricity driver; (3) unique deficiency of this drive circuit: need a negative supply Eg; (4) can make power model to above-mentioned part, use more convenient.

Claims (2)

1, a kind of fet power device is characterized in that:

A, fet power device adopt metal-insulation-graphitized carbon MICFET structure, and wherein graphitized carbon is its conducting channel;

B, for graphitized carbon, in multiple fibre cluster field effect transistor, adopt carbon fiber to make conducting channel; In multi-layer stacks condenser type field effect transistor, adopt the thermal decomposition carbon film to make conducting channel;

C, in the MICFET overall structure, only respectively do a MICFET elementary cell at the two ends of graphitized carbon conducting channel, middle one section is still the graphitized carbon raceway groove, is requiring the especially little application scenario of conducting resistance, interlude is with parcel AL ₂O ₃The aluminum fiber bundle substitute carbon fiber bundle.

2, a kind of drive circuit of MICFET device

By voltage-stabiliser tube D ₁, capacitor C, resistance R ₁R ₂, double-pole three throw switch K ₁K ₂K ₃, high voltage source Ea, load resistance R _LReach negative supply Eg and form, it is characterized in that:

A, upper end MICFET are A-G _t-K and lower end MICFET are A-G ₂-K is separately-driven, though with two K switch that MICFET is connected up and down ₁K ₂K ₃Action links, but is mutually insulated on electric;

B, work as K switch ₁K ₂K ₃When adopting photoelectric coupling switch, carbon fiber is up and down between two field effect transistor at two ends and just finished electrical isolation between whole field effect transistor and the photoelectric controller;

The grid G of c, lower end MICFET ₂, when ON through K switch ₂Ground connection; During OFF, G ₂Through K switch ₃Be connected to the negative pole of power supply Eg, its plus earth;

The grid G of d, upper end MICFET ₁, when ON through K switch ₁Ground connection; During OFF, G ₁Through K switch ₁Be connected to D ₁C point in parallel, D ₁The voltage stabilizing value identical with Eg, this parallel connection point also is connected to resistance R ₂And resistance R ₁, R ₂Other end ground connection, R ₁The other end is connected to K ₃The ON point, and D ₁Another of C point in parallel is connected to anode A;

Also be connected to load resistance R between e, anode A and the high voltage source Ea _L

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