CN101588132A

CN101588132A - AC chopper and chopping method thereof

Info

Publication number: CN101588132A
Application number: CNA2008101672104A
Authority: CN
Inventors: 徐雅梅
Original assignee: BEIJING BOWANG TIANCHENG SCI-TECH DEVELOPMENT Co Ltd
Current assignee: BEIJING BOWANG TIANCHENG SCI-TECH DEVELOPMENT Co Ltd
Priority date: 2007-11-28
Filing date: 2008-10-15
Publication date: 2009-11-25

Abstract

The invention provides an AC chopper and a chopping method thereof. The chopper is connected between an AC power source and a load, and comprises a switch group, an inductor, a current polarity detector and a switch-control logic unit, wherein the switch group comprises a plurality of switches and is connected with the AC power source; one end of the inductor is connected with the switch group, and the other end of the inductor is connected with the load; the current polarity detector is connected between the inductor and the load and is used to detect the direction of current output to the load by the chopper at the moment of switching switch states; and the switch-control logic unit receives current-direction signals sent by the current polarity detector and sends different control time-sequence signals to a plurality of switches according to the current-direction signals so as to control the turn-on sequence of the switches and convert the inductor mutually between a follow-current state and a charged state. As the method is based on current polarity but not voltage polarity to perform detection, input-voltage short circuit does not exist at any moment. In addition, the method detects current polarity only at the moment of switching switch states, and is a non-continuous detection method, thus systems are not easy to oscillate.

Description

A kind of AC chopper and chopping method thereof

Technical field

The present invention relates to AC converter, particularly utilize switching mode to realize the AC chopper and the chopping method thereof of power transfer.

Background technology

The phase control rectifier technology replaces electromagnetism class voltage-regulating technique in many occasions as the AC voltage adjusting technology of a comparative maturity, obtains extensive use.But the phase control rectifier technology has many unsurmountable defectives, as is subjected to the abundant and serious mains by harmonics electric current pollution of low power factor that trigger angle influences, slow dynamic responding speed, output low-order harmonic etc.AC chopper based on the DC chopper simple topology becomes a new research focus in recent years.AC chopping control voltage regulation technology has the power factor that only depends on load, fast dynamic responding speed, wide linear voltage regulation scope and input and output and is easy to filtering and advantage such as sineization highly, can be applicable to fields such as high-power, quick pressure regulation.

Fig. 1 is a kind of circuit diagram of existing chopper, and S1, S2 are full control switching devices, can open at any time and turn-off.Inductance L ₀Be energy storage device, M is load.When this chopper circuit was applied to the DC/DC conversion, input voltage and output current polarity did not all change.During circuit working, at first the S1 switch is disconnected closes, and the S2 switch turn-offs simultaneously, and the input power supply passes through switch S 1 to L ₀Charging, i _LIncrease exponentially.The S1 switch turn-offs then, and the S2 switch is disconnected simultaneously closes inductance L ₀In electric current by switch S 2 afterflows, i _LBeing exponential curve descends.Energy storage inductor L ₀Big more, current i _LFluctuation more little.In the DC/DC conversion, in order to simplify circuit, as shown in Figure 2, switch S 2 also can be a diode D, and the negative electrode of diode is received switch S 1 and energy storage inductor L ₀Between, the anode of diode connects the negative electrode of input voltage.Like this, switch S 1 is being turn-offed L ₀During charging, diode reverse biased does not have electric current to flow through diode.When S1 turn-offs, diode forward biasing, L ₀In electric current pass through diode continuousing flow.DC chopper circuit when work key waveforms as shown in Figure 3.

DC chopper is operated in the quadrant of input voltage and output current.When chopper is applied to the AC/AC conversion, need be operated in four quadrants of input voltage and output current, the switch of use must be two-way, and this just needs more complicated topological structure and method of controlling switch.In the research of AC chopper, do a lot of work, and produced a lot of AC chopping control topologys.Circuit topology shown in Figure 4 is exactly a kind of more welcome AC chopper topology.The pressure regulation of AC chopper is to liking alternating voltage, and in order all to modulate at the positive and negative half-wave of voltage, switch must be two-way.Among Fig. 4, S1, S2, S3, S4 are single-way switch, and they adopt IGBT and diode to form, and diode is parallel between the collector and emitter of IGBT, and the negative electrode of diode is connected with the collector electrode of IGBT, and we claim that this end is the negative electrode of switch; The anode of diode is connected with the emitter of IGBT, and we claim that this end is the anode of switch.So, switch just can be controlled current lead-through and the shutoff from the negative electrode to the anode direction, and switch from the anode to the cathode direction because diode in parallel, electric current is in the conducting all the time of this direction, so claim that they are single-way switch.Among Fig. 4, S1 and the S4 bidirectional switch T1 that partners, S2 and the S3 bidirectional switch T2 that partners.Wherein the anode of switch S 1 links to each other with negative electrode to switch S 2; The anode of switch S 4 links to each other with the negative electrode of switch S 3; The negative electrode of switch S 1 and switch S 4 connects input voltage source, and a termination of inductance is to the anode of switch S 1, and the anode of the other end of inductance and switch S 4 is the chopper output.When S1 and S4 conducting, when S2, S3 turn-offed, the input power supply was to induction charging, and circuit reduction figure is shown in Fig. 5 a.When S2, S3 conducting, when S1 and S4 turn-off, inductance afterflow discharge, circuit reduction figure is shown in Fig. 5 b.When we adopt certain switch control strategy, when inductance in the circuit is periodically switched, just realized chopper control between induction charging state and afterflow state to input voltage.Switch among Fig. 4 can obtain by transistor device and diode combinations in practice, and a diode is connected in parallel between transistorized source electrode and the drain electrode, and the polar orientation of diode is with transistorized opposite.Here we use IGBT to describe as switch, but the transistor that also can use other kinds is as switch.

Inductance in the chopper need be opened T2 when turn-offing T1 when being transformed into the afterflow state from charged state.But, owing to stored a large amount of electric charges in the power transistor, when a control voltage makes a transistor when making another transistor turns simultaneously, the electric current that is implemented in the transistor that ends can continue for some time again, transistor conducting simultaneously will take place like this and make the situation of short circuit, can cause switch to damage.In order to prevent the generation of this situation, when Fig. 5 a state directly forwards Fig. 5 b state to, need to insert that chien shih T1, T2 turn-off when a bit of, be called as " Dead Time " during this period of time.Yet it also is a problem that T1, T2 turn-off simultaneously.Afterflow in the inductance L 0 is obstructed, can produce the peak voltage that switch is damaged, generally pass through buffer or clamped network with the peak voltage clamp, what bring therefrom is excessive clamp power loss, this loss is along with the linear growth of increasing of switching frequency, and along with the exponential type that increases to of voltage and current increases.Therefore, during this method only is applicable to, small-power resistive load AC voltage adjusting field.

In patent publication No. is the patent of CN1967994A a kind of similar AC chopper topology has been discussed, this method can avoid inserting Dead Time, but has used more power device in the circuit, has increased the loss of system.

In addition, in " Novel topologies of AC chopper " literary composition, introduced a kind of similar AC chopper topology.This method can well solve the problem in the afterflow of Dead Time inductance, need not to add buffer or voltage clamping circuit in the circuit.We describe this method in conjunction with Fig. 4.In the method, according to the polarity of input supply voltage, take following switching strategy: at the input supply voltage positive half period, switch S 3, S4 conducting always, switch S 1, S2 modulate conducting by the pwm signal of a certain fixed duty cycle, and wherein when a switch opens, another then turn-offs; At the negative half-cycle of input supply voltage, switching mode in contrast.In this method of controlling switch, current circuit exists all the time.Therefore do not need to add buffer or voltage clamping circuit, in the input supply voltage positive half period, circuit has three kinds of mode of operations: active mode, Dead Time pattern, afterflow pattern.Concrete introduction about these several mode of operations please refer to original text.

Patent publication No. is that the patent of CN1410855A is used the chopper switches control strategy that similarly detects based on input voltage polarity with said method.

Yet this switching strategy that detects based on input supply voltage polarity also exists the some shortcomings part.In actual applications, when particularly being applied in quick pressure regulation field, the waveform of input voltage can be subjected to voltage flicker and influence of harmonic and produce bigger distortion, as shown in Figure 6.In addition, for fear of the interference of harmonic wave to voltage detector, before detecting voltage, need tested voltage is carried out filtering, the output of polarity of voltage detector will produce a filtering delay-time like this, polarity of voltage detector itself also has time-delay simultaneously, therefore the output of polarity of voltage detector will produce an inevitably time-delay, shown in the t among Fig. 6.Time-delay t can cause the detection mistake of polarity of voltage.Therefore, in actual applications, the detection of voltage over zero is not a thing easily, is easy to produce polarity of voltage and detects mistake.When polarity of voltage detected mistake, input voltage will form short circuit, as shown in Figure 7.And, in the above-mentioned AC chopper topology that detects based on input voltage polarity, at any time all the polarity with input voltage is relevant for the state of switch, need constantly input voltage polarity to be fed back among non-linear of circuit, voltage is easy to cause the vibration of system in the fluctuation of zero crossing.Fig. 8 has shown the feedback controling mode of this switching strategy.

Summary of the invention

The object of the present invention is to provide a kind of AC chopper and chopping method thereof based on discrete current detecting, owing to there is not input-voltage short circuit to exist at any time, and the mode of operation of switch and input supply voltage are irrelevant, therefore are applicable to the occasion that the quality of importing power supply is not had high requirement.

To achieve these goals, the present invention proposes following technical scheme:

At first be a kind of AC chopper:

1, a kind of AC chopper is connected between AC power and the load, comprising:

Switches set comprises a plurality of switches, is connected with described AC power;

Inductance, the one end is connected with described switches set, and the other end is connected with described load;

The current polarity detector is connected between described inductance and the described load, is used for detecting the sense of current that described chopper is exported to described load in the moment of described switch switching state, i.e. the inductive current direction;

The switch control logic unit, receive the current direction signal that described current polarity detector is sent, and send different control timing signals to a plurality of switches of described switches set according to described current direction signal, to control the conducting order of described a plurality of switches, make described inductance between afterflow state and charged state, change mutually.

2, wherein switches set comprises bidirectional switch T1 and bidirectional switch T2, described AC power, described bidirectional switch T1, described inductance and described load constitute first loop, during the then described first loop conducting of described bidirectional switch T1 conducting, described power supply is to described induction charging; And described bidirectional switch T2, described inductance and described load constitute second loop, and during the then described second loop conducting of described bidirectional switch T2 conducting, described inductance is in the afterflow state; Described first loop and described second loop have at least one to be conducting.

3, wherein switches set comprises the first single-way switch S1, the second single-way switch S2, the 3rd single-way switch S3 and the 4th single-way switch S4; Described bidirectional switch T1 comprises the first single-way switch S1 and the 4th single-way switch S4, and described bidirectional switch T2 comprises the second single-way switch S2 and the 3rd single-way switch S3; Wherein the anode of S1 links to each other with the negative electrode of S2, and the anode of S2 links to each other with the anode of S3, and the negative electrode of S3 links to each other with the anode of S4; Wherein each single-way switch comprises transistor device parallel with one another and diode respectively, described diode is parallel between the described transistorized collector and emitter, the negative electrode of described diode is connected with described transistor collector, and this end is the negative electrode of described switch; The anode of described diode is connected with described emitter, and this end is the anode of switch.

4, wherein transistor is bipolar junction transistor, IGBT, metal-oxide-semiconductor field effect t transistor, magnetron or gate cutout.

5, wherein the switch control logic unit comprises following pattern to the control of described a plurality of switches:

When described current polarity detector detects described chopper output current polarity is timing, and the afterflow state of described inductance and the current polarity of charged state are also for just, and the switching mode conversion sequence is as follows:

The 1st pattern: the described second loop conducting, described inductance is in the afterflow state;

The 2nd pattern: still keep the described second loop conducting, described inductance is in the afterflow state;

The 3rd pattern: when the input supply voltage ui of described AC power＞0, have only the second loop conducting, described inductance is in the afterflow state; When ui＜0, first loop and all conductings of second loop, described inductance is in afterflow and charging and deposits state;

The 4th pattern: have only the described first loop conducting, described inductance is in charged state;

The 5th pattern: keep having only the described first loop conducting, described inductance is in charged state;

When described current polarity detector detects described chopper output current polarity when negative, also for negative, the switching mode conversion sequence is as follows for the afterflow state of described inductance and the current polarity of charged state:

The 6th pattern: the described second loop conducting, described inductance is in the afterflow state;

The 7th pattern: still keep the described second loop conducting, described inductance is in the afterflow state;

The 8th pattern: when the input supply voltage ui of described AC power＜0, have only the second loop conducting, described inductance is in the afterflow state; When ui＞0, described first loop and all conductings of second loop, described inductance is in afterflow and charging and deposits state;

The 9th pattern: have only the described first loop conducting, described inductance is in charged state;

The 10th pattern: keep having only the described first loop conducting, described inductance is in charged state.

6, wherein pattern further comprises:

The 1st pattern: switch S 1, S4 turn-off, S2, S3 conducting, and the described second loop conducting, described inductance is in the afterflow state;

The 2nd pattern: S1, S4, S3 turn-off, and the described second loop conducting is still kept in the S2 conducting, and described inductance is in the afterflow state;

The 3rd pattern: S1, S3 turn-off, and S2, S4 conducting when the input supply voltage ui of described AC power＞0, have only the second loop conducting, and described inductance is in the afterflow state; When ui＜0, first loop and all conductings of second loop, described inductance is in afterflow and charging and deposits state;

The 4th pattern: S1, S2, S3 turn-off, and the S4 conducting has only the described first loop conducting, and described inductance is in charged state;

The 5th pattern: S2, S3 turn-off, and S1, S4 conducting keep having only the described first loop conducting, and described inductance is in charged state;

The 6th pattern: switch S 1, S4 turn-off, S2, S3 conducting, and the described second loop conducting, described inductance is in the afterflow state;

The 7th pattern: S1, S4, S2 turn-off, and the described second loop conducting is still kept in the S3 conducting, and described inductance is in the afterflow state;

The 8th pattern: S2, S4 turn-off, and S1, S3 conducting when the input supply voltage ui of described AC power＜0, have only the second loop conducting, and described inductance is in the afterflow state; When ui＞0, described first loop and all conductings of second loop, described inductance is in afterflow and charging and deposits state;

The 9th pattern: S2, S3, S4 turn-off, and the S1 conducting has only the described first loop conducting, and described inductance is in charged state;

The 10th pattern: S2, S3 turn-off, and S1, S4 conducting keep having only the described first loop conducting, and described inductance is in charged state.

7, wherein described switch is controlled by pulse-width signal in the switch control logic unit.

8, wherein said switches set comprises two IGBT half-bridge modules, and an IGBT half-bridge module comprises that switch S 1 and switch S 2, the two IGBT half-bridges comprise switch S 3 and switch S 4;

Each IGBT half-bridge module connects a two IGBT drive plate respectively, each described pair of IGBT drive plate receive the described pulse-width signal of a pair of complementation and in corresponding IGBT half-bridge module two switches send respectively and comprise conducting or the drive signal of turn-offing, wherein be provided with a Dead Time between each conducting or the cut-off signals;

Have one section delay time t1 between the described pulse-width signal of described two IGBT half-bridge modules, t1 is greater than described Dead Time.

9, wherein t1 is the twice of described Dead Time.

10, AC chopper also comprises two overload protecting circuits, is used to protect described a plurality of switch not to be subjected to the destruction of peak voltage; One of them overload protecting circuit is connected in parallel between the anode of the negative electrode of the first single-way switch S1 and the second single-way switch S2; Another overload protecting circuit is connected in parallel between the anode of the negative electrode of the 4th single-way switch S4 and the 3rd single-way switch S3; Each overload protecting circuit comprises a diode and active voltage clamp circuit.

Secondly, the invention allows for a kind of AC chopping method:

11, a kind of AC chopping method is applicable to above-mentioned AC chopper, may further comprise the steps:

Described current polarity detector detects the sense of current that described chopper is exported to described load in the moment of described switch switching state, i.e. the inductive current direction;

Described switch control logic unit receives described current direction signal, and sends different control timing signals according to described current direction signal to a plurality of switches of described switches set;

Described a plurality of switch is according to described control timing signal and conducting or shutoff, makes the conversion mutually between afterflow state and charged state of described inductance.

12, during the wherein said first loop conducting, described power supply is to described induction charging; And during the described second loop conducting, described inductance is in the afterflow state; Described first loop and described second loop have at least one to be conducting.

13, wherein said switch control logic unit comprises following pattern to the control of described a plurality of switches:

When described current polarity detection method detects described chopping method output current polarity is timing, and the afterflow state of described inductance and the current polarity of charged state are also for just, and the switching mode conversion sequence is as follows:

When described current polarity detection method detects described chopping method output current polarity when negative, also for negative, the switching mode conversion sequence is as follows for the afterflow state of described inductance and the current polarity of charged state:

14, wherein pattern further comprises:

The 10th pattern: S1, S4 conducting, S2, S3 turn-off, and keep having only the described first loop conducting, and described inductance is in charged state.

15, wherein described switch is controlled by pulse-width signal in the switch control logic unit.

16, wherein the AC chopping method is two IGBT half-bridge modules with described group of switches, and an IGBT half-bridge module comprises that switch S 1 and switch S 2, the two IGBT half-bridges comprise switch S 3 and switch S 4;

17, wherein t1 is the twice of described Dead Time.

18, this AC chopping method adopts two overload protecting circuits to protect described a plurality of switch not to be subjected to the destruction of peak voltage; One of them overload protecting circuit is connected in parallel between the anode of the negative electrode of the first single-way switch S1 and the second single-way switch S2; Another overload protecting circuit is connected in parallel between the anode of the negative electrode of the 4th single-way switch S4 and the 3rd single-way switch S3; Each overload protecting circuit comprises a diode and active voltage reed position circuit.

Chopper of the present invention and control method thereof are compared with existing control method, a large amount of advantages is arranged: 1, because method of controlling switch of the present invention is based on the current polarity detection, rather than detect based on polarity of voltage, therefore there is not the input-voltage short circuit to exist at any time; 2, only detecting current polarity constantly at the switch switching state, is a kind of detection method of noncontinuity, and system is not easy to produce vibration.3, therefore the mode of operation of switch and input supply independent do not need the input power quality is had higher requirements.The ability that 4, overload protection is arranged, circuit can quit work safely during system overload.5, use power device seldom in the circuit, reduced the loss of system.

Description of drawings

Fig. 1 is existing chopper circuit schematic diagram.

Fig. 2 is that existing DC chopper is simplified circuit theory diagrams.

Fig. 3 is existing DC chopper key job waveform schematic diagram.

Fig. 4 is the schematic diagram of another kind of existing AC chopper.

Fig. 5 is existing AC chopper induction charging and afterflow view.

Fig. 6 is the existing actual input voltage waveform schematic diagram of chopper.

Fig. 7 is the schematic diagram of a kind of existing switch control strategy when producing input-voltage short circuit under certain conditions.

Fig. 8 is a kind of system's control schematic diagram of existing switch control strategy based on input voltage polarity.

Fig. 9 is the structural representation of AC chopper of the present invention.

Figure 10 a～Figure 10 e is that AC chopper of the present invention is timing in output current polarity, the working state schematic representation of switch.

Figure 10 f～Figure 10 j is an AC chopper of the present invention in output current polarity when negative, the working state schematic representation of switch.

Figure 11 a is that AC chopper of the present invention is timing in output current polarity, control time sequences of switches figure.

Figure 11 b is an AC chopper of the present invention in output current polarity when negative, control time sequences of switches figure.

Figure 12 is the schematic diagram of the embodiment of AC chopper switch control logic of the present invention.

Current direction schematic diagram when Figure 13 is an AC chopper overload protection of the present invention.

Figure 14 is an active voltage clamper schematic diagram among the embodiment of AC chopper of the present invention.

Embodiment

Followingly AC chopper of the present invention and chopping method thereof are elaborated with reference to accompanying drawing.What at first must state is; though the present invention is illustrated with the following examples; but can not be with the embodiment interpretation that limits the invention; structure such as switches set; also can adopt the switch of other other quantity of form to realize; as long as can reach the purpose of proof load power supply, all should fall into protection scope of the present invention with the group shutoff of current detection signal control switch or conducting.

Fig. 9 is the structural representation of AC chopper of the present invention.Among the figure, AC power AC is used for to load 5 power supplies.AC chopper of the present invention is connected between AC power AC and the load 5, comprising:

Switches set comprises first switch S 1, second switch S2, the 3rd switch S 3, the 4th switch S 4, is respectively unidirectional solid switchgear, and switch S 1-S4 is combined by transistor device and diode parallel connection respectively.Transistor wherein can be such as BJT (bipolar junction transistor), IGBT, or MOSFE T (metal-oxide-semiconductor field effect t) transistor, or even thyratron transistor such as MET (magnetron〉or GTO (gate cutout).Between the input A, the B that between first switch S 1 and the 4th switch S 4 are this AC chopper, be connected with AC power AC.In a preferred embodiment, S1, S2, S3, S4 adopt IGBT and diode to form respectively, and diode is parallel between the collector and emitter of IGBT, and the negative electrode of diode is connected with the collector electrode of IGBT, and we claim that this end is the negative electrode of switch; The anode of diode is connected with the emitter of IGBT, and we claim that this end is the anode of switch.As shown in Figure 9, wherein the anode of switch S 1 links to each other with negative electrode to switch S 2; The anode of switch S 4 links to each other with the negative electrode of switch S 3; The negative electrode of switch S 1 and switch S 4 connects input voltage source.So, switch just can be controlled current lead-through and the shutoff from the negative electrode to the anode direction, and switch from the anode to the cathode direction because diode in parallel, electric current is in the conducting all the time of this direction, so claim that they are single-way switch.

Inductor L is connected with switches set, is responsible for accepting the charging of AC power AC and to load 5 discharges.One termination of inductance is to the anode of switch S 1, and the other end of inductance serves as the output C of chopper, and load 5 is connected with the C point.Inductor L can be operated in charging or afterflow state (the afterflow state is the state of power remove to load 5 discharges) according to switch S 1-S4 different conducting or cut-off state.The operating state of inductor L and the conducting of switches set or end between relation see aftermentioned for details.

Current polarity detector 6, be connected between inductance L and the load 5, making can be from AC chopper output C sampling of the present invention, be used to detect the sense of current that chopper outputs to load 5, of particular note, current polarity detector 6 of the present invention, only detect the sense of current that described chopper is exported to described load 5 constantly at the switch switching state, being the sense of current of inductance L, is a kind of detection method of noncontinuity, makes whole system be not easy to produce vibration like this.

Switch control logic unit 7, the current direction signal that received current polarity detector 6 is sent generates different control timing signals then, is used for the conducting of control switch device S1-S4 or by order, sees aftermentioned for details.

When overload protecting circuit 8,9, this overload protecting circuit are used on switch issuable destructive high voltage, prevent that electric current from producing destructive peak voltage on switch module.Overload protecting circuit 8 connects between the anode of the negative electrode that is parallel to switch S 1 and switch S 2, and overload protecting circuit 9 is parallel between the anode of the negative electrode of switch S 4 and switch S 3.

It more than is the circuit structure of AC chopper of the present invention, chopper will be powered continuously to load 5, on the meaning of this function, Fig. 4 that switches set among Fig. 9 of the present invention can still be similar to prior art is divided into two groups with switching device S1-S4 like that: S1 and the S4 bidirectional switch T1 that partners, S2 and the S3 bidirectional switch T2 that partners.So, AC power AC, bidirectional switch T1, inductance L and load 5 just might constitute first loop, and during the first loop conducting, power supply is to induction charging; And bidirectional switch T2, inductance L and load 5 just might constitute second loop, and during the second loop conducting, inductance is in the afterflow state; Each loop all can provide electric current to load 5; In order to provide continuous power supply, regardless of the conducting of switching device S1-S4 or by order, AC chopper of the present invention will guarantee that all at least two loops is conducting to load 5.

Below describe the running in the AC chopper of the present invention in detail.Under most of situation, when the switch switching state in the inductance electric current just the polarity of chopper output current can not change, only near current zero-crossing point, make an exception, and be very faint at current zero-crossing point place electric current, even current polarity produces change when switch switches like this, also can not influence the operate as normal of system.After inductance entered charging or afterflow state, the polarity of chopper output current and the state of switch were irrelevant.Therefore, when switch state, inductance can be regarded as a current source that polarity is constant.Below in conjunction with Figure 10 a-Figure 10 j and Figure 11 a, when Figure 11 b illustrates the switching of switch, the transfer process of inductance L between charging and afterflow state.Wherein switch conducting when high level among Figure 11 a and Figure 11 b is turn-offed during low level.S1 and the S4 bidirectional switch T1 that partners wherein, S2 and the S3 bidirectional switch T2 that partners, for simplicity, T1 and T2 no longer mark in Figure 10 a-Figure 10 j; First loop noted earlier is the bigger loop among Figure 10 a-Figure 10 j, and second loop is the less loop among Figure 10 a-Figure 10 j.

When current polarity detector 6 detects chopper output current polarity is timing, and the switching mode conversion sequence is as follows, is transformed into the complete cycle that charging is transformed into afterflow again so that inductance is finished from afterflow:

The 1st pattern: shown in Figure 10 a, switch S 1, S4 turn-off, S2, S3 conducting, and switching signal is corresponding to the time slot a among Figure 11 a, and inductance is in the afterflow state.At this moment, the current i in the inductance 1 along direction shown in it in second loop flow.

The 2nd pattern: shown in Figure 10 b, S1, S4, S3 turn-off, the S2 conducting, and switching signal is corresponding to the time slot b among Figure 11 a, and this moment, electric current was still kept preceding state.

The 3rd pattern: shown in Figure 10 c, S1, S3 turn-off, S2, S4 conducting, and switching signal is corresponding to the time slot c among Figure 11 a, and at this moment electric current can have two loops.When input supply voltage ui＞0, have only i1 to be present in second loop; When ui＜0, because there are two electric currents of i1, i2 simultaneously in the biasing of the diode forward among S1 conducting in first loop and second loop.

The 4th pattern: shown in Figure 10 d, S1, S2, S3 turn-off, the S4 conducting, and switching signal is corresponding to the time slot d among Figure 11 a, and at this moment only there is current i 1 in circuit in first loop, and power supply is to induction charging;

The 5th pattern: shown in Figure 10 e, S2, S3 turn-off, S1, S4 conducting, and switching signal is corresponding to the time slot e among Figure 11 a, and it is constant that electric current keeps preceding state in the circuit.So far, inductance has been finished the conversion from the afterflow to the charged state.

Sum up said process, when chopper output current polarity for just, inductance is from the afterflow state exchange to charged state the time, switch is according to the order alteration switch state of a → b → c → d → e among Figure 11 a.And when chopper output current polarity for just, inductance is when being transformed into the afterflow state from charged state, switch is according to the order alteration switch state of e → d → c → b → a among Figure 11 a.Like this, be timing in chopper output current polarity, inductance has just been finished from afterflow and has been transformed into the complete cycle that charging is transformed into afterflow again.

When current polarity detector 6 detects chopper output current polarity when negative, the switching mode conversion sequence is as follows, is transformed into the complete cycle that charging is transformed into afterflow again so that inductance is finished from afterflow:

The 6th pattern: shown in Figure 10 f, switch S 1, S4 turn-off, S2, S3 conducting, and switching signal is corresponding to the time slot f among Figure 11 b, and inductance is in the afterflow state.At this moment, the current i in the inductance 1 is prolonged direction shown in it in second loop flow.

The 7th pattern: shown in Figure 10 g, S1, S4, S2 turn-off, the S3 conducting, and switching signal is corresponding to the time slot g among Figure 11 b, and this moment, electric current was still kept preceding state.

The 8th pattern: shown in Figure 10 h, S2, S4 turn-off, S1, S3 conducting, and switching signal is corresponding to the time slot h among Figure 11 b, and at this moment electric current can have two loops.When input supply voltage ui＜0, have only i1 to exist; When ui＞0, because there are two electric currents of i1, i2 simultaneously in the biasing of the diode forward among S4 conducting.

The 9th pattern: shown in Figure 10 i, S2, S3, S4 turn-off, the S1 conducting, and switching signal is corresponding to the time slot i among Figure 11 b, and at this moment only there is current i 1 in circuit, and power supply begins to induction charging;

The 10th pattern: shown in Figure 10 j, S1, S4 conducting, S2, S3 turn-off, and switching signal is corresponding to the time slot j among Figure 11 b, and it is constant that electric current keeps preceding state in the circuit.At this moment, inductance is transformed into charged state.So far, inductance is finished from the afterflow state exchange to charged state.

Sum up said process, when chopper output current polarity for negative, inductance is from the afterflow state exchange to charged state the time, switch is according to the order alteration switch state of f → g → h → i → j among Figure 11 b.And work as chopper output current polarity for negative, and inductance is when being transformed into the afterflow state from charged state, and switch is according to the order alteration switch state of j → i → h → g → f among Figure 11 b.Like this, when negative, inductance has just been finished from afterflow and has been transformed into the complete cycle that charging is transformed into afterflow again in chopper output current polarity.

Below by a preferred embodiment of the present invention chopper of the present invention and chopping method thereof are further elaborated, wherein the transistor among switch S 1, S2, S3, the S4 adopts IGBT.

In the preferred embodiment, as shown in Figure 9, what switch S 1, S2, S3, S4 used is two IGBT half-bridge modules, drive by two two IGBT drive plates respectively, the signal of drive plate is generated by switch control logic, and one of them IGBT half-bridge module comprises switch S 1 and switch S 2, and the anode of S1 links to each other with the negative electrode of S2, another IGBT half-bridge module comprises switch S 3 and switch S 4, and the anode of S4 links to each other with the negative electrode of S3.When S1, S4 conducting, when S2, S3 turn-offed, inductance was in charged state; When S1, S4 shutoff, when S2, S3 conducting, inductance is in the afterflow state.A pair of IGBT in the IGBT half-bridge module is driven by two IGBT drive plates.Two IGBT drive plates are accepted the pwm signal that switch control logic produces, two IGBT conductings on IGBT half-bridge of moving control or shutoff.Owing to the conducting simultaneously of two IGBT on the IGBT half-bridge, that is to say the conducting simultaneously of switch S 1 and switch S 2, switch S 3 and switch S 4 conducting simultaneously, the IGBT drive plate can insert one section Dead Time in the centre when accepting another IGBT conducting of an IGBT shutoff of pwm signal driving rear drive.This Dead Time does not need to add in pwm signal, is produced automatically by drive plate.

The switching sequence of analyzing switch among Figure 11 as can be seen, when each inductance is changed between charged state and afterflow state, two of an IGBT half-bridge switch elder generation switching states always, the then switch of another IGBT half-bridge module switching state again.Any moment, the not conducting simultaneously of two switches in each IGBT half-bridge module, after a switch switched to off state by conducting state, through one section Dead Time, another switch switched to conducting state by off state.In Figure 11 a and Figure 11 b, time slot d and time slot g are the Dead Times between S1 and the S2, and time slot b and time slot i are the Dead Times between S3 and the S4.When the switch on IGBT half-bridge of pwm signal control of a pair of complementation (phase place is opposite), can on the IGBT drive plate, Dead Time be set, the situation of two switches conducting simultaneously can not take place.Therefore, can use the two IGBT drive plates of pwm signal input of a pair of complementation to drive two switches on the IGBT half-bridge module.The sequential chart of the switching signal among Figure 11 can be simplified like this, what wherein the drive plate of switch S 1, S2 used is the signal of a pair of complementation, and what the drive plate of switch S 3, S4 used is the signal of a pair of complementation.So-called complementary signal, when promptly a switching signal was high level on IGBT half-bridge, another switching signal was a low level.Two switches on IGBT half-bridge insert Dead Time by drive circuit when change over switch state mutually, make one of them switch turn-off earlier, through behind the Dead Time, and the conducting again of another switch.So only switch S 1 in IGBT half-bridge of needs analysis and the switch switching sequence between the switch S 4 in another IGBT half-bridge can draw the logical relation between load current direction and the switching signal.Figure 11 a has shown that load current polarity is timing, the relation between the pwm signal of each switching signal and input.Figure 11 b has shown when load current polarity is negative, the relation between the pwm signal of each switching signal and input.The signal that is applied on switch S 1, S2, S3, the S4 is produced by logical circuit by the pwm signal that controller or additive method produce, and can analyze each switching signal and the logical relation of importing between the pwm signal according to Figure 11 a and Figure 11 b.As can be seen, switch S 1 and S2 are two switches on the IGBT half-bridge in Figure 12, and they are by the signal controlling of a pair of complementation, and the Dead Time between the switch is time slot d and g among the t2 figure; Switch S 3 and S4 are two switches on another IGBT half-bridge, and they are by the signal controlling of a pair of complementation, and the Dead Time between the switch is middle time slot b and i.Control signal on switch S 1, S2, S3, the S4 can be obtained by following method: with pwm signal time-delay a period of time t1 of input, this time is greater than the Dead Time when two switches switch on the IGBT half-bridge, the twice that can get Dead Time.It is identical so just to obtain two duty ratios, but between have two pwm signals of time-delay t1, we claim phase place the preceding pwm signal be " preceding phase " signal, phase place after pwm signal be " back phase " signal.Shown in Figure 12 a, when load current polarity is timing, the control signal on the switch S 1 can obtain like this: when " preceding phase " when signal is high level, applies " back phase " signal on the S1; When " preceding phase " when signal is low level, applies " preceding phase " signal on the S1.Shown in Figure 12 b, when load current polarity when negative, the control signal on the switch S 1 can obtain like this: when " preceding phase " when signal is high level, apply " preceding phase " signal on the S1; When " preceding phase " when signal is low level, applies " back phase " signal on the S1.Simultaneously as can be seen, when applying the high level signal conducting on the S1, the switch S 2 on the same IGBT half-bridge can be closed earlier in the drawings, through S1 conducting again behind the Dead Time.In like manner, can derive the signal that applies on the switch S 4, and obtain table 1.

Table 1

" preceding phase " signal	Inductive current polarity	The signal that applies on the switch S 1	The signal that applies on the switch S 4
" preceding phase " signal	Inductive current polarity	The signal that applies on the switch S 1	The signal that applies on the switch S 4	High level (1)	+(1)	" back phase " (0)	" preceding phase " (1)
Low level (0)	+(1)	" preceding phase " (1)	" back phase " (0)	High level (1)	+(1)	" back phase " (0)	" preceding phase " (1)
Low level (0)	+(1)	" preceding phase " (1)	" back phase " (0)	High level (1)	-(0)	" preceding phase " (1)	" back phase " (0)
Low level (0)	-(0)	" back phase " (0)	" preceding phase " (1)	High level (1)	-(0)	" preceding phase " (1)	" back phase " (0)

As can be seen from Table 1, the control signal that applies on the switch S 1 is " preceding phase " signal or " back phase " signal, the signal deciding that obtains after the polar signal distance by " preceding phase " pwm signal and inductive current, when the signal behind the XOR is low level, apply " back phase " signal on the S1, when the signal behind the XOR is high level, apply " preceding phase " signal on the S1.The control signal that applies on the switch S 4 is that " preceding phase " signal or " back phase " signal are then opposite with signal on the switch S 1, when the signal that obtains after the polar signal distance by " preceding phase " pwm signal and inductive current is high level, apply " preceding phase " signal on the S4, when the signal behind the XOR is high level, apply " back phase " signal on the S4.Like this, switch control logic is just very simple.In conjunction with Figure 12 switch control logic is narrated.At first, the pwm signal of a certain duty ratio is sent into switch control logic, will obtain " preceding phase " pwm signal and " back mutually " pwm signal after the pwm signal time-delay, and oppositely obtain their complementary signal.The signal that " preceding phase " pwm signal and current polarity signal distance obtain is sent into selector, select when selecting signal to select when selecting signal with " back phase " pwm signal power controlling switch S 1 for low level with " preceding phase " pwm signal power controlling switch S 1 for high level.The signal that " preceding phase " pwm signal and current polarity signal distance obtain is again through sending into selector behind the reverser, select when selecting signal to select when selecting signal with " back phase " pwm signal power controlling switch S 4 for low level with " preceding phase " pwm signal power controlling switch S 4 for high level.The pwm signal of switch S 2 uses simultaneously and S1 complementation, power switch S3 uses the pwm signal with the S4 complementation.Dead Time during two switch switching states on IGBT half-bridge is inserted by two IGBT drive plates, does not need control logic to produce.

In addition, in some cases, may produce destructive high voltage on the switch.Such as, when system overload, it is very big that the electric current among the L can become.At this moment, all IGBT modules can be because of overcurrent protection shutoff automatically, and the electric current in the inductance can not produce destructive peak voltage owing to there is the loop on switch module.Perhaps, current polarity has taken place and has detected mistake in the moment that electric current is bigger in inductance, also can cause electric current to lose the loop.The operation principle of the overload protecting circuit of this chopper is described below in conjunction with Figure 13.In order to prevent that the electric current in the inductance from not having the loop and produce destructive peak voltage on switch module, the instinct invention is provided with the overload protecting circuit unit, comprises two overload protecting circuits.One of them overload protecting circuit is connected in parallel between the anode of the negative electrode of the first single-way switch S1 and the second single-way switch S2; Another overload protecting circuit is connected in parallel between the anode of the negative electrode of the 4th single-way switch S4 and the 3rd single-way switch S3, is used to protect described switch not to be subjected to the destruction of peak voltage.Current path during two overload protecting circuit work is shown in Figure 13 arrow.

Overload protecting circuit is composed in series by a diode and active voltage clamp circuit; be connected in parallel on the disjunct two ends of switch on the IGBT half-bridge then; wherein the anode of diode links to each other with the negative electrode of a switch; the negative electrode of diode links to each other with the input of active voltage clamp circuit, and the output of active voltage clamp circuit connects the anode of another switch.During the chopper operate as normal, there is not electric current to pass through the active voltage clamper.When the electric current in the inductance lost the loop in chopper circuit, the electric current in the inductance was absorbed by the active voltage clamper by loop i1 and i2, prevented that electric current from producing destructive peak voltage on switch module.Active voltage clamper circuit structure as shown in figure 14, current i is charged to capacitor C, when Uc greater than protection during voltage, the Q conducting, electric capacity discharges by resistance R.When Uc less than protection during voltage, Q ends, i continues electric capacity is charged.Like this, just be cushioned device when the electric current in the inductance loses the loop in chopper circuit and sponged, reached the purpose of protection switch.

Certainly, Figure 13 and 14 is embodiments of the invention, and the present invention can also adopt the overload protection arrangement of other kinds and structure.

Because the characteristics of switch control strategy of the present invention are based on chopper output current polarity, the control method of switch is and the chopper output current, and just current polarity is relevant in the load, and irrelevant with input voltage polarity.When the inductance in the circuit is changed,, adopt different switch switchover policy according to the difference of load current polarity between charging and these two states of afterflow.After inductance entered charging or afterflow state, the state of switch and the polarity of load current were irrelevant, and it is just passable only need to detect primary current polarity before each switch switches, and does not need current polarity is carried out continuous detection.Because the energy storage effect of inductance, and the time from the induction charging state exchange to inductance afterflow state is relative and the PWM cycle is very little (actual in 1%).The variation of electric current in the circuit state transfer process is far smaller than the variation of whole PWM in the cycle.If the variation of whole PWM periodic current is 100A, the variation of switch switching slot time current is less than 1A so.Therefore, in the most of the time, can think inductance between charging and afterflow state in very little a period of time of changing, the polarity of electric current is constant in the inductance.Only at the near zero-crossing point of electric current, when inductance was changed between charging and afterflow state, current polarity just might change, and caused wrong switch control strategy.But near current zero-crossing point, the electric current in the load is very little, can not produce destructive peak voltage on switch.Therefore, this method that detects based on load current polarity is reliable.Owing to the noncontinuity of its current detecting, also reduced the possibility of system's generation feedback oscillation.

Overload protecting circuit among the present invention when the current polarity detection makes a mistake at system overload or under the very big situation of electric current, can not be damaged by protection switch.

Owing to only when switch switches, detect electric current, not to carry out continuously, therefore, when zero passage detection, be not easy to cause vibration, can be applied to high pressure field, EMI.

Though the present invention reference specific embodiment wherein is described, those skilled in the art still can carry out a lot of accommodations, improves or the like.Only otherwise exceed spirit of the present invention, all should be within the scope of the invention.

Claims

1, a kind of AC chopper is connected between AC power and the load, comprising:

It is characterized in that described AC chopper also comprises:

2, AC chopper as claimed in claim 1, it is characterized in that, described switches set comprises bidirectional switch T1 and bidirectional switch T2, described AC power, described bidirectional switch T1, described inductance and described load constitute first loop, during the then described first loop conducting of described bidirectional switch T1 conducting, described power supply is to described induction charging; And described bidirectional switch T2, described inductance and described load constitute second loop, and during the then described second loop conducting of described bidirectional switch T2 conducting, described inductance is in the afterflow state; Described first loop and described second loop have at least one to be conducting.

3, AC chopper as claimed in claim 2 is characterized in that, described switches set comprises the first single-way switch S1, the second single-way switch S2, the 3rd single-way switch S3 and the 4th single-way switch S4; Described bidirectional switch T1 comprises the first single-way switch S1 and the 4th single-way switch S4, and described bidirectional switch T2 comprises the second single-way switch S2 and the 3rd single-way switch S3; Wherein the anode of S1 links to each other with the negative electrode of S2, and the anode of S2 links to each other with the anode of S3, and the negative electrode of S3 links to each other with the anode of S4; Wherein each single-way switch comprises transistor device parallel with one another and diode respectively, described diode is parallel between the described transistorized collector and emitter, the negative electrode of described diode is connected with described transistor collector, and this end is the negative electrode of described switch; The anode of described diode is connected with described emitter, and this end is the anode of switch.

4, AC chopper as claimed in claim 3 is characterized in that, described transistor is bipolar junction transistor, IGBT, metal-oxide-semiconductor field effect t transistor, magnetron or gate cutout.

As claim 2 or 3 described AC chopper, it is characterized in that 5, described switch control logic unit comprises following pattern to the control of described a plurality of switches:

6, AC chopper as claimed in claim 5 is characterized in that, described pattern further comprises:

As claim 1 or 6 described AC chopper, it is characterized in that 7, described switch is controlled by pulse-width signal in described switch control logic unit.

8, AC chopper as claimed in claim 7 is characterized in that,

Described switches set comprises two IGBT half-bridge modules, and an IGBT half-bridge module comprises that switch S 1 and switch S 2, the two IGBT half-bridges comprise switch S 3 and switch S 4;

9, AC chopper as claimed in claim 8 is characterized in that, t1 is the twice of described Dead Time.

10, as claim 3,4 or 5 described AC chopper, it is characterized in that, also comprise two overload protecting circuits, be used to protect described a plurality of switch not to be subjected to the destruction of peak voltage; One of them overload protecting circuit is connected in parallel between the anode of the negative electrode of the first single-way switch S1 and the second single-way switch S2; Another overload protecting circuit is connected in parallel between the anode of the negative electrode of the 4th single-way switch S4 and the 3rd single-way switch S3; Each overload protecting circuit comprises a diode and active voltage clamp circuit.

11, a kind of AC chopping method is applicable to the described AC chopper as claim 1-10, it is characterized in that, may further comprise the steps:

12, AC chopping method as claimed in claim 11 is characterized in that, during the described first loop conducting, described power supply is to described induction charging; And during the described second loop conducting, described inductance is in the afterflow state; Described first loop and described second loop have at least one to be conducting.

13, as claim 11 or 12 described AC chopping methods, it is characterized in that described switch control logic unit comprises following pattern to the control of described a plurality of switches:

14, AC chopping method as claimed in claim 13 is characterized in that, described pattern further comprises:

15, as claim 11,12,13 or 14 described AC chopping methods, it is characterized in that described switch is controlled by pulse-width signal in described switch control logic unit.

16, AC chopping method as claimed in claim 15 is characterized in that,

With described group of switches is two IGBT half-bridge modules, and an IGBT half-bridge module comprises that switch S 1 and switch S 2, the two IGBT half-bridges comprise switch S 3 and switch S 4;

17, AC chopping method as claimed in claim 16 is characterized in that, t1 is the twice of described Dead Time.

18, as claim 11,12,13,14,15,16 or 17 described AC chopping methods, it is characterized in that, adopt two overload protecting circuits to protect described a plurality of switch not to be subjected to the destruction of peak voltage; One of them overload protecting circuit is connected in parallel between the anode of the negative electrode of the first single-way switch S1 and the second single-way switch S2; Another overload protecting circuit is connected in parallel between the anode of the negative electrode of the 4th single-way switch S4 and the 3rd single-way switch S3; Each overload protecting circuit comprises a diode and active voltage clamp circuit.