Invention content
In view of this, the present invention provides a kind of leadage circuit and LED drive circuit, to be opened in offer controllable silicon dimmerWhile opening the firing current of moment, reduces loss when controllable silicon dimmer is opened, improve the efficiency of LED drive circuit.
In a first aspect, providing a kind of leadage circuit, it is applied to the LED drive circuit with controllable silicon dimmer, it is described to let outElectric discharge road includes：
It releases module, is configured as connecting with the DC bus of LED drive circuit, and controlled bus current of releasing；And
Controller, the module that is configured as when the controllable silicon dimmer is opened releasing described in control make leakage current withChange with the waveform of busbar voltage, to accelerate the rate of decay of the busbar voltage oscillation.
Further, the leakage current is not less than the controllable silicon dimmer in the busbar voltage attenuation processLatching current, and be gradually reduced with the reduction of the oscillation amplitude of the busbar voltage.
Further, module of releasing described in the controller control generates the leakage current of predetermined time.
Further, the predetermined time is more than the die-away time of busbar voltage oscillation.
Further, the controller includes：
Antihunt circuit is configured as carrying out sampling generation reference signal to the waveform of the busbar voltage；
Current control circuit is configured as according to module of releasing described in the reference signal and current sampling signal outputSignal is controlled, the current sampling signal is for characterizing the leakage current.
Further, the antihunt circuit has scheduled time constant to adjust the reference signal.
Further, the controller further includes：
Bleeder circuit is configured as carrying out voltage of the partial pressure generation for characterizing the busbar voltage to the busbar voltageSampled signal；
The antihunt circuit is additionally configured to export the reference signal according to the waveform of the voltage sampling signal.
Further, the antihunt circuit includes：
Resistance；And
Capacitance, it is in series with a resistor to be connected between busbar and ground terminal；Or
The antihunt circuit includes：
Resistance；And
Capacitance, it is in series with a resistor to be connected between the output and ground of the bleeder circuit.
Further, the module of releasing includes：
Transistor is configured as when the controllable silicon dimmer is opened, and is given birth to according to the concussion waveform of the busbar voltageAt the leakage current；
And
Sampling element is configured as sampling the leakage current to generate current sampling signal.
Second aspect provides a kind of LED drive circuit, including：
Controllable silicon dimmer is connected to alternating current input power supplying；
Rectification circuit is connect with the controllable silicon dimmer, and busbar voltage is exported to DC bus；
LED circuit control module is configured as the electric current that LED load is flowed through in control；And
Leadage circuit as described above.
The technical solution of the embodiment of the present invention follows busbar electric by controlling leakage current when controllable silicon dimmer is openedThe waveform of pressure changes so that the rate of decay of busbar voltage oscillation is accelerated, to provide controllable silicon dimmer unlatchingWhile the firing current of moment, loss when controllable silicon dimmer is opened is reduced, the efficiency of LED drive circuit is improved.
Specific implementation mode
Below based on embodiment, present invention is described, but the present invention is not restricted to these embodiments.UnderText to the present invention datail description in, it is detailed to describe some specific detail sections.Do not have for a person skilled in the artThe description of these detail sections can also understand the present invention completely.In order to avoid obscuring the essence of the present invention, well known method, mistakeThere is no narrations in detail for journey, flow, element and circuit.
In addition, it should be understood by one skilled in the art that provided herein attached drawing be provided to explanation purpose, andWhat attached drawing was not necessarily drawn to scale.
It will also be appreciated that in the following description, " circuit " refer to passed through by least one element or sub-circuit it is electricalThe galvanic circle that connection or electromagnetism connect and compose.It " is connected when claiming element or another element of circuit " being connected to " or element/circuit" between two nodes when, it can be directly coupled or connected another element or may exist intermediary element, element itBetween connection can be physically, in logic or its combination.On the contrary, when claiming element " being directly coupled to " or " directly connectingBe connected to " another element when, it is meant that the two be not present intermediary element.
Unless the context clearly requires otherwise, "include", "comprise" otherwise throughout the specification and claims etc. are similarWord should be construed as the meaning for including rather than exclusive or exhaustive meaning；That is, being containing for " including but not limited to "Justice.
In the description of the present invention, it is to be understood that, term " first ", " second " etc. are used for description purposes only, withoutIt can be interpreted as indicating or implying relative importance.In addition, in the description of the present invention, unless otherwise indicated, the meaning of " multiple "It is two or more.
Fig. 1 is the circuit diagram of the LED drive circuit of the embodiment of the present invention.As shown in Figure 1, LED drive circuit includesControllable silicon dimmer TRIAC, rectification circuit 11, leadage circuit 12 and LED circuit control module 13.Controllable silicon dimmer TRIACIt is connected between ac input end mouth and rectification circuit 11.Rectification circuit 11 is connect with controllable silicon dimmer, can for that will pass throughAlternating current after control silicon light modulator TRIAC copped waves is converted to direct current and is output to DC bus BUS.LED circuit control module 13It is configured as the electric current that LED load is flowed through in control.
Leadage circuit 12 is connect with DC bus BUS, is configured as controlling busbar of releasing when controllable silicon dimmer is openedElectric current, and control leakage current and the waveform of busbar voltage is followed to change, to accelerate the rate of decay of busbar voltage oscillation.
Preferably, leadage circuit 12 be additionally configured to control leakage current be not less than in the busbar voltage attenuation processThe latching current of the controllable silicon dimmer, and be gradually reduced with the reduction of the oscillation amplitude of busbar voltage, to ensureReduce the loss of circuit under conditions of controllable silicon dimmer TRIAC conductings.
Preferably, leadage circuit 12 generates the leakage current of predetermined time when controllable silicon dimmer TRIAC is opened.Into oneStep ground, leadage circuit 12 release bus current predetermined time be more than busbar voltage oscillation die-away time.This is not only maintainedThe conducting electric current of controllable silicon dimmer TRIAC also effectively prevents controllable silicon dimmer TRIAC and is touched in the abnormal of open stageHair (for example, when maintaining the conducting electric current of controllable silicon dimmer TRIAC inadequate, causes controllable silicon dimmer TRIAC to be constantly inRebooting status), it is ensured that the stability of circuit.
It should be understood that the leadage circuit in the present embodiment acts only on controllable silicon dimmer TRIAC open stages, with prevent canAbnormal triggerings of the silicon light modulator TRIAC in open stage is controlled, the driving electricity of LED load is dropped to less than in busbar voltage VBUSOther leadage circuits are also needed to when pressure to release.
In conclusion the present embodiment follows shaking for busbar voltage when controllable silicon dimmer is opened by controlling leakage currentSwing waveform variation so that the rate of decay of busbar voltage oscillation is accelerated, to provide controllable silicon dimmer unlatching momentWhile firing current, loss when controllable silicon dimmer is opened is reduced, the efficiency of LED drive circuit is improved.
Fig. 2 is the circuit diagram of the LED drive circuit of first embodiment of the invention.As shown in Fig. 2, LED drive circuitIncluding controllable silicon dimmer TRIAC, rectification circuit 21, leadage circuit 22 and LED circuit control module 23.Controllable silicon dimmerTRIAC is connected between ac input end mouth and rectification circuit 21.Rectification circuit 21 is connect with controllable silicon dimmer, for will be throughThe alternating current crossed after controllable silicon dimmer TRIAC copped waves is converted to direct current and is output to DC bus BUS.LED circuit controls mouldBlock 23 is configured as the electric current that LED load is flowed through in control.
In the present embodiment, as shown in Fig. 2, leadage circuit 22 includes release module 221 and controller 222.It releases module221 are configured as connecting with the DC bus of LED drive circuit, and release controllable silicon dimmer TRIAC open stages are controlledBus current.Controller 222 is configured as releasing module 221 so that letting out in the control of controllable silicon dimmer TRIAC open stagesDischarge stream Ibld follows the waveform of busbar voltage VBUS to change, to accelerate the decaying speed of the busbar voltage VBUS oscillationsDegree.
Wherein, module of releasing 221 includes transistor Q and sampling element R3.Transistor Q is configured as in controllable silicon dimmerTRIAC open when it is controlled conducting with bus current of releasing, and after the predetermined time controlled shutdown to reduce circuit loss.Sampling memberPart R3 is configured as sampling leakage current Ibld to generate the current sampling signal Vbld for characterizing leakage current Ibld.Ying LiSolution, the present embodiment sampling resistor is as sampling element, but other elements that can be carried out to leakage current can be applied toIn the present embodiment.
Controller 222 includes antihunt circuit a, bleeder circuit b and current control circuit cl.Bleeder circuit b is connected to LED drivesBetween the DC bus and ground terminal of dynamic circuit, including resistance R1 and resistance R2.Bleeder circuit b is configured as to busbar voltageVBUS carries out voltage sampling signal SVbus of the partial pressure generation for characterizing busbar voltage VBUS.Antihunt circuit a is connected to partial pressure electricityBetween the output and ground of road b, for generating reference signal Vref according to voltage sampling signal SVbus.In the present embodimentIn, antihunt circuit a is the RC first differential circuits being made of resistance R and capacitance C, for the oscillation wave according to busbar voltage VBUSShape generates reference signal Vref.It should be understood that other can realize that the circuit structure of above-mentioned effect can be applied to the present embodimentIn.Current control circuit cl is used to generate the control for module 221 of releasing according to reference signal Vref and current sampling signal VbldSignal VG.In a preferred embodiment, difference amplifier can be used in current control circuit.It should be understood that other can be realThe circuit structure of existing above-mentioned effect can be applied in the present embodiment.
When controllable silicon dimmer TRIAC is opened, will produce between the inductance and capacitance in controllable silicon dimmer TRIAC humorousIt shakes, this input voltage that controllable silicon dimmer can be caused to be supplied to LED drive circuit generates more high-frequency oscillation.NamelyIt says, when controllable silicon dimmer TRIAC is opened, busbar voltage VBUS can be vibrated with relatively high frequency.
In the present embodiment, busbar voltage VBUS is divided by bleeder circuit b to generate characterization busbar voltageThe voltage sampling signal SVbus of VBUS.It is readily appreciated that, the frequency of oscillation of voltage sampling signal SVbus is with busbar voltage VBUS'sFrequency of oscillation keeps equal.And sampling is carried out to the waveform of voltage sampling signal SVbus by antihunt circuit a and generates benchmarkSignal Vref.Then module 221 of releasing is controlled by the variation of reference signal Vref to release to bus current.
When busbar voltage VBUS changes (voltage sampling signal SVbus corresponds to proportional variation), the electricity in antihunt circuit aHold C to be charged rapidly (or electric discharge), reference signal Vref is proportional to the time rate of change of busbar voltage VBUS.Also, according toThe reference signal Vref and current sampling signal Vbld control signal VG generated follow reference signal Vref to change.Therefore, it releasesThe control signal VG of module 221 follows the waveform of busbar voltage VBUS to change, and in turn, leakage current Ibld follows busbar electricThe waveform variation of VBUS is pressed, this makes the oscillatory extinction speed of busbar voltage VBUS accelerate.Therefore, in the present embodimentLED drive circuit can accelerate the rate of decay of busbar voltage oscillation in silicon-controlled unlatching.
Since reference signal Vref is proportional to the time rate of change of busbar voltage VBUS, when busbar voltage VBUS vibrates widthWhen the gradual decaying of value (namely the time rate of change of busbar voltage VBUS reduces), reference signal Vref is also gradually reduced therewith, fromAnd the control signal VG for module 221 of releasing is gradually reduced, leakage current Ibld is gradually reduced.Therefore, leakage current Ibld withThe reduction of the oscillation amplitude of busbar voltage VBUS and be gradually reduced.This makes LED circuit provide controllable silicon dimmer unlatchingWhile the firing current of moment, loss when controllable silicon dimmer is opened is reduced, the efficiency of LED drive circuit is improved.It is readily appreciated that, when busbar voltage VBUS vibrates very little, the time rate of change of busbar voltage VBUS is approximately 0, leakage currentIbld is also approximately at 0.
Preferably, leadage circuit 22 generates the leakage current of predetermined time when controllable silicon dimmer TRIAC is opened.Into oneStep ground, leadage circuit 22 release bus current predetermined time be more than busbar voltage oscillation die-away time.This is not only maintainedThe conducting electric current of controllable silicon dimmer TRIAC also effectively prevents controllable silicon dimmer TRIAC and is touched in the abnormal of open stageHair, it is ensured that the stability of circuit.
Preferably, antihunt circuit a has scheduled time constant with the rate of decay (the RC single orders of control bus voltage VBUSTimeconstantτ=R*C of differential).It is readily appreciated that, the time constant of antihunt circuit a is bigger, the rate of decay of reference signal VrefIt is faster.But when time constant is excessive, the amplitude of reference signal Vref decaying is excessive (namely reference signal Vref is smaller),So that the oscillation amplitude of leakage current Ibld is larger (namely leakage current Ibld is smaller), LED drive circuit may be such thatInput current is less than the latching current of controllable silicon dimmer TRIAC conductings and then leads to the abnormal passes controllable silicon dimmer TRIACDisconnected problem.Therefore, the time constant that rational antihunt circuit is arranged is vital.
In conclusion the present embodiment follows shaking for busbar voltage when controllable silicon dimmer is opened by controlling leakage currentSwing waveform variation so that the rate of decay of busbar voltage oscillation is accelerated, to provide controllable silicon dimmer unlatching momentWhile firing current, loss when controllable silicon dimmer is opened is reduced, the efficiency of LED drive circuit is improved.
Fig. 3 is the circuit diagram of the LED drive circuit of second embodiment of the invention.As shown in figure 3, LED drive circuitIncluding controllable silicon dimmer TRIAC, rectification circuit 31, leadage circuit 32 and LED circuit control module 33.Controllable silicon dimmerTRIAC is connected between ac input end mouth and rectification circuit 31.Rectification circuit 31 is connect with controllable silicon dimmer, for will be throughThe alternating current crossed after controllable silicon dimmer TRIAC copped waves is converted to direct current and is output to DC bus BUS.LED circuit controls mouldBlock 33 is configured as the electric current that LED load is flowed through in control.
In the present embodiment, as shown in figure 3, leadage circuit 32 includes release module 321 and controller 322.Wherein, it releasesModule 321 includes transistor Q ' and sampling element R4.Transistor Q ' is configured as controlled when controllable silicon dimmer TRIAC is openedConducting with bus current of releasing, and after the predetermined time controlled shutdown to reduce circuit loss.Sampling element R4 is configured as adoptingSample leakage current Ibld ' is to generate the current sampling signal Vbld ' for characterizing leakage current Ibld '.It should be understood that the present embodimentSampling resistor is as sampling element, but other elements that can be carried out to leakage current can be applied in the present embodiment.
Controller 322 includes antihunt circuit c and current control circuit cl1.Antihunt circuit c be connected to DC bus BUS andBetween ground terminal, for generating reference signal Vref ' according to busbar voltage VBUS.In the present embodiment, antihunt circuit c is by electricityThe RC first differential circuits for hindering R ' and capacitance C ' compositions, for generating reference signal according to the waveform of busbar voltage VBUSVref’.It should be understood that other can realize that the circuit structure of above-mentioned effect can be applied in the present embodiment.Current control electricityRoad cl1 is used to generate the control signal VG ' for module 321 of releasing according to reference signal Vref ' and current sampling signal Vbld '.When controllable silicon dimmer TRIAC is opened, resonance is will produce between the inductance and capacitance in controllable silicon dimmer TRIAC, this can leadThe input voltage that controllable silicon dimmer is supplied to LED drive circuit is caused to generate more high-frequency oscillation.That is, canWhen controlling the TRIAC unlatchings of silicon light modulator, busbar voltage VBUS can be vibrated with relatively high frequency.
In the present embodiment, sampling is carried out to the waveform of busbar voltage VBUS by antihunt circuit c and generates benchmark letterNumber Vref '.Then module 321 of releasing is controlled by the variation of reference signal Vref ' to release to bus current.
When busbar voltage VBUS changes, the capacitance C ' in antihunt circuit c is charged rapidly (or electric discharge), reference signalVref ' is proportional to the time rate of change of busbar voltage VBUS.Also, according to reference signal Vref ' and current sampling signalThe control signal VG ' that Vbld ' is generated follows reference signal Vref ' to change.Therefore, the control signal VG ' of module of releasing 321 is followedThe waveform of busbar voltage VBUS changes, and in turn, leakage current Ibld ' follows the waveform of busbar voltage VBUS to change,This makes the oscillatory extinction of busbar voltage VBUS accelerate.Therefore, the energy in silicon-controlled unlatching of the LED drive circuit in the present embodimentEnough accelerate the rate of decay of busbar voltage oscillation.
Since reference signal Vref ' is proportional to the time rate of change of busbar voltage VBUS, when busbar voltage VBUS vibratesAmplitude gradually decay the time rate of change of busbar voltage VBUS (namely reduce) when, reference signal Vref ' is also gradually reduced therewith,It is gradually reduced to the control signal VG ' for module 321 of releasing, leakage current Ibld ' is gradually reduced.Therefore, leakage current Ibld 'It is gradually reduced with the reduction of the oscillation amplitude of busbar voltage VBUS.This makes LED circuit provide controllable silicon dimmerWhile opening the firing current of moment, loss when controllable silicon dimmer is opened is reduced, the effect of LED drive circuit is improvedRate.It is readily appreciated that, when busbar voltage VBUS vibrates very little, the time rate of change of busbar voltage VBUS is approximately 0, leakage currentIbld ' is also approximately at 0.
Preferably, leadage circuit 32 generates the leakage current of predetermined time when controllable silicon dimmer TRIAC is opened.Into oneStep ground, leadage circuit 32 release bus current predetermined time be more than busbar voltage oscillation die-away time.This is not only maintainedThe conducting electric current of controllable silicon dimmer TRIAC also effectively prevents controllable silicon dimmer TRIAC and is touched in the abnormal of open stageHair, it is ensured that the stability of circuit.
Preferably, antihunt circuit c has scheduled time constant with the rate of decay (the RC single orders of control bus voltage VBUSTimeconstantτ=R*C of differential).It is readily appreciated that, the time constant of antihunt circuit c is bigger, the decaying speed of reference signal Vref 'Degree is faster.But when time constant is excessive, the amplitude of reference signal Vref ' decaying it is excessive (namely reference signal Vref ' compared withIt is small) so that the oscillation amplitude of leakage current Ibld ' is larger (namely leakage current Ibld ' is smaller), may be such that LED drivesThe input current of circuit is less than the latching current of controllable silicon dimmer TRIAC conductings and then leads to controllable silicon dimmer TRIAC notThe problem of normal turn-off.Therefore, the time constant that rational antihunt circuit is arranged is vital.
In conclusion the present embodiment follows shaking for busbar voltage when controllable silicon dimmer is opened by controlling leakage currentSwing waveform variation so that the rate of decay of busbar voltage oscillation is accelerated, to provide controllable silicon dimmer unlatching momentWhile firing current, loss when controllable silicon dimmer is opened is reduced, the efficiency of LED drive circuit is improved.
Fig. 4 is the working waveform figure of the LED drive circuit of the prior art.Fig. 5 is the LED drive circuit of the embodiment of the present inventionWorking waveform figure.As shown in figure 4, traditional LED drive circuit is not provided with antihunt circuit.At the t1 ' moment, controllable silicon dimmerIt opens, module of releasing provides fixed leakage current Ibld1 (electric current of similar square wave) and releases the regular hour (t1 '-t2 ').Open stage due to busbar voltage in controllable silicon dimmer generates oscillation, in order to avoid there is controllable silicon dimmer shutdownOr the case where abnormal contact, the leakage current Ibld1 of module of releasing need a larger value and needing maintain one section compared withThe long time.Which results in LED drive circuits to have larger loss, reduces the efficiency of LED drive circuit.
And in the present embodiment, as shown in figure 5, the time rate of change of reference signal Vref and busbar voltage VBUS at thanExample so that leakage current Ibld follows the waveform of busbar voltage VBUS to change, and then accelerates busbar voltage VBUS oscillationsThe rate of decay so that leakage current Ibld is gradually reduced with the reduction of the oscillation amplitude of busbar voltage VBUS.ThisSo that LED drive circuit reduces controllable silicon light modulation while providing the firing current of controllable silicon dimmer unlatching momentLoss when device is opened, improves the efficiency of LED drive circuit.
The foregoing is merely the preferred embodiment of the present invention, are not intended to restrict the invention, for those skilled in the artFor, the present invention can have various modifications and changes.It is all within spirit and principles of the present invention made by any modification, equivalentReplace, improve etc., it should all be included in the protection scope of the present invention.