CN2143385Y - Improved and high reliable EFT converter - Google Patents

Abstract

The utility model provides an improved and high reliable EFT converter, which relates to the passive inversion technique in the electric field. The utility model is widely used for occasions with uninterrupted power supply, AC frequency speed control, etc. The utility model is mainly characterized in that the gate electrode of a power tube is connected in series with two resistors, then the gate electrode is connected with a trigger signal source, one of the resistors is connected in parallel with a diode, the conducting direction of the diode is back on to the gate electrode, so the logical control that the utility model is switched on after switched off is realized, and the overvoltage and the overcurrent of a main circuit are reduced. Circuits are simplified, and the reliability is enhanced.

Description

Improved and high reliable EFT converter

The utility model relates to the passive inverter technology in the electric field.Be widely used in occasions such as new energy resources system, uninterruption power source, ac variable frequency speed regulation.

Inverter is the technology that is full of vitality most in the contemporary electric field.In traditional inverter, be (i.e. two the power device conductings simultaneously that prevent that two power devices of same brachium pontis " lead directly to " in the main circuit, cause short circuit), be provided with a kind of being called in the circuit: the logic control of " closing the conducting of having no progeny earlier ", other adds complicated pushing unit.Its basic control idea is: two any moment of power tube of same brachium pontis do not allow conducting simultaneously.Open a certain power tube, must turn-off the other power tube on the same brachium pontis earlier, otherwise just cause " leading directly to " to damage power tube.In the frequency changer circuit of routine,, also to add a kind of delay function in order to prevent " leading directly to " short circuit of main circuit--after turn-offing a power tube, just also will allow another power tube conducting on the same brachium pontis through one section time-delay.Because the potential change between each power tube of last brachium pontis (as T4, T6, T2 among Fig. 3) grid of inverter is big, so the grid-control power supply of last each power tube of brachium pontis all uses special-purpose insulating power supply, photoelectrical coupler and additional steepness circuit in the custom circuit.Like this, not only make circuit become complicated, and reduced the reliability of inverter.Existing both at home and abroad manufacturer is the reliability that guarantees inverter of the high reliability by electronic device, but cost is very high.

The purpose of this utility model is: utilize the intrinsic characteristics of field effect transistor and derivation device thereof, realize the logic control of " closing the conducting of having no progeny earlier " with simple method.And select circuit parameter rightly, eliminate " overvoltage ", " overcurrent " phenomenon in the custom circuit.Simplify frequency changer circuit significantly, improve its reliability, reduce production costs.

The utility model is realized by the following technical solutions: inverter of the present utility model is the simplification inverter that utilizes power field effect pipe and derivation device (IGBT) thereof etc. to be designed to.Its technical spirit is: utilize the grid of power field effect pipe and the parasitic junction capacitance between the source electrode and power controlling is little, reaction speed is fast characteristics, use a spot of electronic devices and components can constitute the inverter of high reliability.Promptly with power field effect pipe and derive from the grid of device and the parasitic junction capacitance between the source electrode as the have no progeny delay capacitor of conducting of the elder generation pass of inverter, to simplify inverter circuit significantly.Realize two main power tube interlockings of same brachium pontis in the inverter circuit with the small-power field effect transistor.The charging resistor Ri of the parasitic junction capacitance between main power tube grid, the source electrode is greater than its discharge resistance Ri ', to play the effect of eliminating overvoltage, overcurrent.Physical circuit is seen Fig. 1, it is characterized in that: connect among the gate control signal source Uin of brachium pontis power field effect pipe under the inverter main circuit two resistance (Fig. 1) R4, R5, and R5 two ends parallel diode D1, the conducting direction of diode is the grid of power tube dorsad.And satisfy following relation: R5 〉=R4.

The gate control signal of bridge power tube is by small-power field effect transistor T7(Fig. 1 on the inverter) provide after the following brachium pontis gate control signal Uin paraphase with correspondence, it is characterized in that: the shared signal Uin of gate control signal of the gate control signal of T7 and following brachium pontis.Meet grid-control power supply U2 behind two resistance R 1 of grid series connection of last brachium pontis power tube, the R2; The mid point N of two resistance connects the drain electrode of small-power field effect transistor T7, and R2＞R1.

As shown in Figure 4, the junction capacitance Co of a parasitism is arranged between power field effect pipe and derivation its grid of device and the source electrode, this parasitic junction capacitance Co has considerable influence to opening with shutoff.When on off state uses, because the output resistance Ri of trigger signal source and the time constant that parasitic junction capacitance Co has constituted a RiCo.When adding gate control signal is timing, and capacitor C o both end voltage (that is grid voltage) connects exponential function and rises, and has only after grid voltage has reached cut-in voltage, and power tube just begins conducting.After this, along with the rising of grid voltage, power tube enters saturation conduction from the amplification region.Power tube is bigger in the amplification region power consumption, should reduce the time that is in the amplification region as far as possible.Therefore, all emphasize what is called " the strong triggering " on the physical data, promptly reduce the output resistance of trigger as much as possible, thereby reduce to discharge and recharge time constant.The strong triggering improving the switching speed of power tube reduces the switch consumption and plays a good role, but also brought the shortcoming of two aspects: the one, increased the complexity of circuit, and reduced the reliability of circuit; The 2nd, owing to the strong switching speed that has improved power tube that triggers, bring bigger main circuit di/dt and du/dt thus, thereby produce " overvoltage " and " overcurrent ".In order to reduce " overvoltage " and " overcurrent ", have to take the corresponding protection measure again, more increased the complexity of circuit.

The utility model utilizes the parasitic junction capacitance Co of power field effect pipe dexterously, and selects the discharge resistance Ri ' of parasitic junction capacitance rightly, thereby makes that the discharge time constant of parasitic junction capacitance is less, and power tube can be turn-offed quickly.Select the charging resistor Ri of parasitic junction capacitance rightly, make the charge constant of parasitic capacitance bigger.When triggering signal is timing,, make voltage (grid voltage) on the parasitic junction capacitance Co reach the just conducting of cut-in voltage of power tube because the existence of charge constant will wait a period of time.Two power tubes that so just guaranteed the same brachium pontis of inverter have one handing-over period, two not conductings of power tube in this section handing-over time, thus realized the have no progeny requirement of conducting of first pass.

Find through serious analysis: the energy that power tube is whenever opened once and consumed is relevant with triggering power.But the switch of power tube consumption the more important thing is that except that outside the Pass having with triggering power the switch consumption is directly proportional with switching frequency.The frequency application scope of power field effect pipe is very wide, can use the hundreds of kilohertz.When power frequency was used, because frequency is very low, so the switch consumption was very little; Saved " the strong triggering " and can not cause that the efficient of main circuit reduces.Saved " the strong triggering " like this, also just removed " overvoltage " of main circuit, the disadvantage of " overcurrent "; Can save overvoltage, overcurrent protection in the circuit, improve the reliability of circuit more.Obtained the effect that serves multiple.

The utility model is described in further detail below in conjunction with drawings and Examples

Fig. 1 is a single-phase inverter circuit diagram of the present utility model

Fig. 2 is the single-phase inverter circuit diagram that the utility model adds auxiliary grid-control power supply

Fig. 3 is that the utility model is used for threephase asynchronous frequency conversion speed-adjusting system circuit diagram

Fig. 4 is a power field effect pipe parasitic junction capacitance schematic diagram.

With Fig. 3 is example, and among the figure: E is a DC power supply.C1 is a power filtering capacitor, and C2, C3 are the auxiliary grid power filtering capacitors.T1, T2, T3, T4, T5, T6 are the main power field effect pipes of inverter, and T7, T8, T9 are auxiliary commutation small-power field effect transistor.D1, D2 are auxiliary grid-control power rectifier pipes, and D3, D4, D5 close the conducting diode of having no progeny earlier.DW1, DW2, DW3, DW4, DW5, DW6 are protection field effect transistor voltage-stabiliser tubes.Y represents voltage controlled oscillator.H represents ring distributor.M represents pulse width modulator.A, B, C represent the output of inverter, that is when being used for AC speed regulating, the end of incoming cables of threephase asynchronous winding.Ri is the charging resistor of parasitic junction capacitance, and Ri ' is the discharge resistance of parasitic junction capacitance.Last brachium pontis, Ri ≈ R4+R10 ≈ R6+R11 ≈ R2+R12, Ri ' ≈ R4 ≈ R6 ≈ R2; Following brachium pontis, Ri ≈ R1+R19 ≈ R3+R20 ≈ R5+R21, Ri ' ≈ R1 ≈ R3 ≈ R5.

Embodiment 1: shown in Figure 1, and be the simplest single-phase inverter of the present utility model, the power field effect pipe T2 among the figure is by the frequency variation signal Uin control break-make of input.Frequency variation signal Uin is that pulsewidth is 180 ° a square wave, and when input signal was zero, auxiliary small-power field effect transistor T7 and main power field effect pipe T2 turn-offed; Bridge master power field effect pipe T1 provides grid voltage and saturation conduction by voltage U 2 through resistance R 1, R2 on this moment.Uin becomes timing by zero when the input frequency variation signal, auxiliary at first conducting of small-power field effect transistor T7 (small-power field effect transistor reaction speed is fast).Because the conducting of T7, the current potential that N is ordered drop to zero by E rapidly.Because R1 very little (hundreds of Europe is following) causes the grid source parasitic capacitance Co of brachium pontis T1 pipe to discharge rapidly, promptly the grid voltage of T1 descends rapidly and turn-offs fast; Meanwhile, although though frequency variation signal Uin for just, the resistance of the gate series resistance R4+R5 of T2 pipe is bigger, so the charge constant of the grid source parasitic capacitance of T2 pipe is also big slightly.Like this, just guaranteed after last brachium pontis power tube T1 turn-offs, again by the time down the parasitic junction capacitance Co of brachium pontis power tube T2 be charged to after the cut-in voltage just open-minded; Small-power field effect transistor T7 has played the interlocked usefulness of two field effect transistor T1, T2 up and down.Like this, just realized the logic control of traditional " closing the conducting of having no progeny earlier ".Evidence scope planted agent's time spent of tens kilo hertzs, can limit the switch consumption of power tube in allowed limits.

The grid-control power supply U2 that goes up brachium pontis power field effect pipe T1 among Fig. 1 is provided by bootstrap voltage mode.Be that the grid-control power supply is to constitute half-wave rectifying circuit by elements such as main power source E, rectifying tube D2 and filter capacitor C3.Its process is as follows: during brachium pontis power field effect pipe T2 conducting instantly, to capacitor C 3 chargings, C3 both end voltage U2 is approximately equal to supply voltage E to positive supply E through diode D2, and with this grid-control power supply as last brachium pontis power tube T1.Voltage U 2 is far above the permission grid voltage of T1 pipe, for guaranteeing not overvoltage of grid, voltage stabilizing didoe DW1 in parallel between the grid source electrode of T1 pipe.Because grid-control power supply U2 is higher, the parasitic junction capacitance Co charging of T1 pipe is very fast, and for guaranteeing the charging time-delay, charging resistor R2 wherein specially obtains bigger than normal, and is calculated as follows: R ₂=R ₅E/Eg.E is the highest DC power supply voltage of main circuit in the formula, and Eg is the highest grid voltage of power tube T1.By this formula calculate R2, the conducting time-delay of T1, T2 two pipes is close.Power consumption among the R2 is also less at this moment.

In the higher inverter of voltage,, can adopt independent grid-control power supply for reducing power consumption.Be embodiment 2 of the present utility model, as shown in Figure 2.

Embodiment 3: Fig. 3 is the inverter basic circuit diagram that is applicable to that the threephase asynchronous speed governing is used.Field effect transistor T1, T2, T3, T4, T5, T6 are the main power tubes of inverter, and T7, T8, T9 are auxiliary commutation small-power field effect transistor.Two pipe utmost point D1, D2 and resistance R 13 and capacitor C 2, C3 form spontaneous last brachium pontis power tube T2, the shared grid-control power supply of T4, T6.The production process of this grid-control power supply is as follows: when the effect pipe T1 conducting of home court, positive supply E charges to capacitor C3 through D1, R13, T1.When being responsible for the T4 conducting, the voltage of capacitor C3 charges to C2 through D2, T4, R13.Several all after dates, the C2 both end voltage rises to supply voltage E, and with this as the shared grid-control power supply of last brachium pontis power field effect pipe.

DC power supply E can be obtained by AC rectification.In order to improve the power factor of rectification circuit, available diode rectification, DC power supply E is constant substantially amount like this.For realizing the permanent flux regulator (being the f/v=constant) of AC asynchronous motor, be provided with voltage controlled oscillator (Y), ring distributor (H) and pulse width modulator (M) etc.As speed setting potentiometer R18 during in zero-bit, voltage controlled oscillator (Y) failure of oscillation, pulse width modulator (M) is output as full zero state.Following brachium pontis power field effect pipe T1, T3, T5 and auxiliary little field effect transistor T7, T8, T9 are in off state.Meanwhile, power field effect pipe T2, the T4 of last brachium pontis, T6 are in conducting state.But because the field effect transistor of following brachium pontis is all turn-offed, whole main circuit opens circuit entirely, and the output terminals A of inverter, B, C(are the end of incoming cables of three phase windings of asynchronous motor) last no-voltage.When speed setting potentiometer R18 left zero-bit, voltage controlled oscillator (Y) then changed its output frequency f according to the size of speed setting with being directly proportional.。Ring distributor (H) is with the frequency f of voltage controlled oscillator (Y) output.Be separated into the square-wave signal of 120 ° of three-phase mutual deviations, square-wave signal is: 180 ° for just, and 180 ° is zero.This 180 ° square wave and pulse width modulated wave and control corresponding field effect transistor T1, T3, T5, T7, T8, T9 behind the door.The duty ratio of pulse width modulator (M) is directly proportional with its input voltage.Regulate the circuit parameter of voltage controlled oscillator (Y) and pulse width modulator (M) rightly, when motor reached rated speed, the output duty cycle of pulse width modulator (M) was 1.Like this, voltage in speed-change process on the motor windings and frequency just can keep the relation (being the f/v=constant) of ratio, have realized the permanent magnetic field control of three phase converter to threephase asynchronous.

More than several circuit that exemplify are inverters with field effect transistor, but this utility model also is useful for and field effect transistor insulation bar power tube (routine IGBT etc.) inverter roughly the same.

Claims (2)

1, a kind of inverter that is made of power field effect pipe electronic components such as (IGBT) is characterized in that:

A. two resistance R 4 of series connection, R5 among the gate control signal source Uin of brachium pontis power tube under the main circuit, R5 two ends parallel diode D1 wherein, the conducting direction of diode is the grid of power tube dorsad, resistance R 5 〉=R4;

B. the gate control signal of going up the brachium pontis power tube is by providing after the following brachium pontis gate control signal Uin paraphase of small-power field effect transistor T7 with correspondence.Meet grid-control power supply U2 behind two resistance R 1 of grid series connection of last brachium pontis power tube, the R2, the mid point N of two resistance meets the drain electrode of small-power field effect transistor T7, wherein R2＞R1.

2, by the described inverter of claim 1, it is characterized in that: the grid-control power supply U2 that goes up the brachium pontis power tube is made of half-wave rectifying circuits such as main power source E, rectifying tube D2 and filter capacitor C3.

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