CN105392234B - Multipath current-sharing output LED (Light-Emitting Diode) driving power supply and dimming method - Google Patents

Abstract

The invention relates to a multipath current-sharing output LED (Light-Emitting Diode) driving power supply and a dimming method. The driving power supply comprises a switching network module, an LCL-nT type resonance network, a rectification network and a load unit, which are orderly connected with each other; the switching network comprises a first bridge arm and a second bridge arm which are connected in parallel, wherein the second bridge arm is used as a phase shift bridge arm and used for realizing wide-range lighting control; and the load unit comprises n paths of current-sharing output LED loads. The multipath current-sharing output LED driving power supply and the dimming method provided by the invention can realize constant and balanced output current under multiple paths of different LED lamp voltages, and have the characteristics of being simple in circuit structure, good in constant-current characteristic and high in current sharing accuracy, etc.

Description

A kind of LED drive power and light-dimming method of multi-path flow equalizing output

Technical field

The present invention relates to LED drive power field, the LED drive power of particularly a kind of multi-path flow equalizing output and light modulation side Method.

Background technology

LED as forth generation electric light source, due to having the advantages that long service life, light efficiency be high, energy-saving and environmental protection are progressively subject to The favor of people, becomes the focus of lighting field.And the LED driver of high efficient and reliable is then to ensure LED steady operations Key.Because LED has nonlinear C-V characteristic and negative temperature characteristic coefficient feature, therefore LED generally adopts constant current Drive to ensure the constant of its luminosity.

It is the requirement generally needs for meeting illumination while lighting plurality of LEDs because single LEDs power is less.This is accomplished by Plurality of LEDs is combined using series-parallel connection method.To ensure that LED luminance is consistent, simplest method is exactly by these LED strips Join and be used as load, during using this structure, although circuit structure is simple, and without equal flow problem, but as one of LED Whole circuit is will result in during damage cannot work, and when power output is larger, the voltage of output also can be very high, be unfavorable for protecting The safety of card circuit.Therefore the LED larger for power generally adopts the series-parallel mixed structure of LED multi-path, using this knot Structure easily realizes high-power output, and reliability is also higher.But the characteristic and conduction voltage drop due to LED negative temperature coefficients is discrete Property, even if the pressure drop respectively on string LED is equal, the electric current in each LED strip also has larger difference, causes the luminous strong of each paths of LEDs Degree is different, or even produces excessively stream, it is therefore desirable to realize flowing through the equilibrium of each LED strip electric current using measure is flowed.Flow measure Generally active stream and passive two kinds of stream.All there is relatively independent current constant control in active current share scheme, each branch road Circuit, therefore stream effect is good, however it is necessary that using more components and parts, relatively costly, control circuit is also relatively complicated. Passive current share scheme is to realize the equal of multiple-channel output using passive devices such as electric capacity, transformer (coupling inductance), magnetic amplifiers Stream, simple with circuit structure, cost is relatively low, the advantages of efficiency is higher.

It is also more and more extensive to the needs of LED dimmer applications with promoting the use of for LED.LED light modulations can save energy Source, adjusts spatial vision effect, while the service life of LED can also be extended, improves the reliability of LED.

The content of the invention

In view of this, the purpose of the present invention is to propose to the LED drive power and light-dimming method of a kind of output of multi-path flow equalizing, electricity Line structure is simple, and constant-current characteristics is good, flows high precision, while realizing the smooth brightness adjustment control to LED.

The circuit of the present invention is realized using below scheme：A kind of LED drive power of multi-path flow equalizing output, including phase successively Switching network module even, LCL-nT type resonant networks, commutated network and LED load unit；Wherein described switching network bag Two the first bridge arms being in parallel and the second bridge arm are included, wherein the second bridge arm is used as phase shift bridge arm, to realize that wide scope is dimmed Control, the load unit includes that the LED load of output is flowed on n roads.

Further, the LCL-nT types resonant network includes capacitance C_s1, capacitance C_s2, resonant inductance L_r1, it is humorous Shake inductance L_r2, resonant capacitance C_rAnd n inductance L_k1To L_kn；The capacitance C_s1One end, capacitance C_s2One end It is respectively connecting to the midpoint of two bridge arms in the switching network, the capacitance C_s1The other end, capacitance C_s2It is another One end is respectively connecting to the resonant inductance L_r1One end, resonant inductance L_r2One end, the resonant inductance L_r1The other end, Resonant inductance L_r2The other end is connected and is connected to the resonant capacitance C_rOne end, the resonant capacitance C_rThe other end connection One of parallel connected end of two bridge arms, the n inductance L into the switching network_k1To L_knRespectively with n transformer string It is connected in parallel on the resonant capacitance C after connection respectively_rTwo ends.

Further, the commutated network includes 2n commutation diode, and the anode of the 2n commutation diode is distinguished Same Name of Ends, different name end with n transformer secondary of the LCL-nT types resonant network is connected, wherein with n-th transformer Two connected commutation diodes of secondary are D_n1、D_n2；Connect respectively after the rectified diode rectification of secondary of the n transformer It is connected to the load of n paths of LEDs.

It is preferred that when circuit works in constant current frequency, the current effective value in the n paths of LEDs load is：

Wherein, U_dcIt is the virtual value of input direct voltage, L_r1=L_r2=L_r, C_s1=C_s2=C_s, L_k1=L_k2 ==L_kn=L_k, n₁、n₂The respectively n transformer primary secondary number of turn.

The light-dimming method of the present invention adopts below scheme：A kind of LED of multi-path flow equalizing output as described above drives electricity The light-dimming method in source specifically includes following steps：

Step S1：Obtain the asynchronous ac equivalent circuit figure of two-phase sequential, including two branch roads in parallel, tie point bag Include the equivalent source of series connectionCapacitance C_s1, resonant inductance L_r1, equivalent source of second branch road including series connectionEvery straight Electric capacity C_s2, resonant inductance L_r2；Two branch roads in parallel and the resonant capacitance C_rParallel connection, the resonant capacitance C_rOne end with L_k1To L_knEquivalent inductance L_kOne end be connected, the resonant capacitance C_rThe other end be connected with one end of equivalent load Z, it is described Equivalent inductance L_kThe other end be connected with the other end of equivalent load Z；

Step S2：IfWherein U_mFor LCL-nT type resonant network input voltage fundametal compoments Amplitude, and

Step S3：The electric current obtained in equivalent load Z is：

The virtual value for obtaining output current is：

Wherein, A for only with the capacitance C_s1, capacitance C_s2, equivalent sourceEquivalent sourceResonance electricity Sense L_r1, resonant inductance L_r2, resonant capacitance C_r, equivalent inductance L_kRelevant parameter；

Step S4：Change the phase shift bridge arm phase place, i.e., change in [0, π]Size so that the output current of circuit I_oFrom the smooth change to zero is fully loaded with, that is, cause the smooth light modulation of circuit realiration gamut.

Compared with prior art, the present invention has following beneficial effect：

1st, to propose the LCL-nT type multi-path flow equalizings that are in parallel of one kind two for high-power LED illumination application scenario defeated for the present invention The controlled resonant converter topological structure for going out, it is possible to achieve on multichannel difference LED voltage Xia Ge roads output current it is constant with it is balanced, With the features such as circuit structure is simple, constant-current characteristics is good and flows high precision.

2nd, the present invention is in parallel on the basis of LCL-nT type controlled resonant converters two, it is proposed that a kind of phase shift brightness adjustment control plan Slightly, using two be in parallel in bridge arm one dim bridge arm as phase shift, adjust conversion by changing the phase shifting angle of two bridge arms The output current of device, realizes the smooth brightness adjustment control to LED, has the advantages that light modulation precision height, dimming scope width.

Description of the drawings

Fig. 1 is the schematic block circuit diagram of the present invention.

Fig. 2 is the work wave schematic diagram of each state of converter of the present invention.

Fig. 3 is the LCL-nT type controlled resonant converter ac equivalent circuits of the present invention.

Fig. 4 is the relation curve of output current and operating frequency when present invention load is different.

Fig. 5 is n roads transformers connected in parallel equivalent circuit of the present invention.

Fig. 6 is the asynchronous ac equivalent circuit figure of two-phase sequential of the present invention.

Fig. 7 is the present inventionOutput current I during change_oChange curve.

Specific embodiment

Below in conjunction with the accompanying drawings and embodiment the present invention will be further described.

As shown in figure 1, a kind of LED drive power of multi-path flow equalizing output is present embodiments provided, including what is be sequentially connected Switching network module, LCL-nT type resonant networks, commutated network and LED load unit；Wherein described switching network includes two The first bridge arm being in parallel and the second bridge arm, wherein the second bridge arm is used as phase shift bridge arm, to realize wide scope brightness adjustment control, The load unit includes that the LED load of output is flowed on n roads.

In the present embodiment, the LCL-nT types resonant network includes capacitance C_s1, capacitance C_s2, resonant inductance L_r1, resonant inductance L_r2, resonant capacitance C_rAnd n inductance L_k1To L_kn；The capacitance C_s1One end, capacitance C_s2 One end be respectively connecting to the midpoint of two bridge arms in the switching network, the capacitance C_s1The other end, capacitance C_s2The other end be respectively connecting to the resonant inductance L_r1One end, resonant inductance L_r2One end, the resonant inductance L_r1It is another One end, resonant inductance L_r2The other end is connected and is connected to the resonant capacitance C_rOne end, the resonant capacitance C_rIt is another End is connected to one of parallel connected end of two bridge arms in the switching network, the n inductance L_k1To L_knRespectively with n change The resonant capacitance C is connected in parallel on respectively after depressor series connection_rTwo ends.

In the present embodiment, the commutated network includes 2n commutation diode, the anode of the 2n commutation diode Same Name of Ends respectively with n transformer secondary of the LCL-nT types resonant network, different name end are connected, wherein with n-th transformation Two connected commutation diodes of the secondary of device are D_n1、D_n2；Divide after the rectified diode rectification of secondary of the n transformer It is not connected to the load of n paths of LEDs.

Particularly, in the present embodiment, when in converter two be in parallel bridge arm drive signal it is identical when, work wave is such as Shown in Fig. 2.The course of work is divided into 6 states, as follows to each state analysis：U in figure_gsIt is defeated for the two LCL-nT type multichannels that are in parallel Go out the driving voltage waveform of controlled resonant converter, be made up of the complementary signal of a pair of Dead Time fixations, drive signal Q1 is upper pipe The drive waveforms of S1, drive signal Q2 is the drive waveforms of down tube S2；u_DS2For the half-bridge midpoint voltage of inversion module, i.e. down tube S2 drain electrodes, the voltage of source electrode；i_dTo flow through the electric current of switching tube, wherein i_d1To flow through the electric current of upper pipe S1, i_d2To flow through down tube The electric current of S2；i_LrTo flow through resonant inductance L_rElectric current；i_DTo flow through the electric current of secondary side diode, wherein i_Dn1To flow through two poles Pipe D_n1Electric current, i_Dn2To flow through diode D_n2Electric current；i_TpTo flow through the electric current of transformer primary side.Below to each working condition It is analyzed：

1)t₀＜ t ＜ t₁：T=t₀When, switching tube S2 conductings, capacitance C_sThe voltage at two ends is added in the defeated of resonant tank Enter end.Within very short a period of time after S2 conductings, resonant inductance L_rElectric current complete reversely；Flow through inductance L_kElectric current i_LKWith Flow through the electric current i of transformer primary side_TpDirection do not change, secondary commutation diode D_n2Conducting, D_n1Cut-off；This stage by In i_LKThe rate of decay compare i_TpIt is slow, so the electric current i on magnetizing inductance_mGradually increase, and work as i_TpWhen being reduced to zero, i_mIncrease To maximum, circuit enters next stage.

2)t₁＜ t ＜ t₂：T=t₁When, primary side current of transformer i_TpDrop to 0 and start reversely, the electric current of transformer secondary Therewith reversely, commutation diode D_n2Turn off because bearing back-pressure, D_n1Turn on therewith, realize direct current output, and electric current therein by Maximum is gradually risen to, this stage switch network is still that S2 is in on-state, is continued by C_sThe voltage at two ends is provided to resonant tank Voltage；The i in this stage_LK、i_TpIt is gradually reduced in the presence of backward voltage, in t₂Moment intersects at a point, i.e. i_mReduce To zero, now circuit enters next stage.

3)t₂＜ t ＜ t₃：T=t₂When, switching tube S2 shut-offs, resonant inductance L_rOn electric current i_LrDirection is constant, switching tube S2 On electric current i_d2Direction is constant, the electric current i on S1_d1Reversely, the parasitic capacitance for illustrating S2 is started to charge up, and the parasitic capacitance of S1 is opened Begin to discharge, after a period of time, the terminal voltage of S2 rises to maximum V_d, i.e., the terminal voltage of S1 parasitic capacitances is by resonance current i_LrInstead To being charged to zero, and i_LrNow it is less than 0, therefore i_d1To flow through the electric current of the parasitic diode of S1, therefore S1 realizes no-voltage It is open-minded；

4)t₃＜ t ＜ t₄：T=t₃When, switching tube S1 is open-minded, and input voltage is added in the input of resonant tank, resonant inductance L_rElectric current i_LrWith the electric current i on switching tube S1_d1Direction changes within a very short time.Now i_LKAnd i_TpDirection still For reverse, so the rectifier bridge of secondary is still D_n1Conducting；Due to i_TpThe speed for reversely reducing faster, so static exciter Electric current i_mContinue to inversely increase, work as i_TpWhen being reversely reduced to zero, i_mReverse maximum is increased to, circuit enters next stage.

5)t₄＜ t ＜ t₅：T=t₄When, switching tube S1 continues to turn on, primary side current of transformer i_TpIncrease to 0 and start anti- To the electric current of transformer secondary is reverse therewith, commutation diode D_n1Shut-off, D_n2It is open-minded, and electric current therein gradually rises up to most Big value；The i in this stage_LK、i_TpGradually increase in the presence of forward voltage, in t₅Moment intersects at a point, i.e. i_mIncrease To zero, now circuit enters next stage.

6)t₅＜ t ＜ t₆：T=t₅When, switching tube S1 shut-offs, resonant inductance L_rThe sense of current it is constant, the electricity of switching tube S1 Stream direction is constant, and reverse electric current occurs in S2, and the parasitic capacitance for showing S1 is started to charge up, and the parasitic capacitance of S2 starts to discharge, and one After the section time, the voltage at S2 two ends is by resonance current i_LrReverse charging is to zero, and i_LrNow it is more than 0, therefore i_d2To flow through S2's The electric current of body diode, is that S2 realizes that no-voltage opens the condition of creating.

t₁-t₆Be in parallel a complete cycle of LCL-T type multiple-channel output controlled resonant converters for two.

In this example, it is assumed that primary current only has fundametal compoment to transmit energy to secondary, ignore other harmonic components Effect, and C in resonant network_s1=C_s2=C_s, L_r1=L_r2=L_r、L_k1=L_k2==L_kn=L_k、L_m1=L_m2 ==L_mn=L_mAnd Z₁=Z₂==Z_n=Z, thus obtains the exchange of LCL-nT types resonant network Equivalent circuit is as shown in Figure 3.

In Fig. 3, U is the fundametal compoment virtual value of resonant tank input voltage, U_outIt is the equivalent output to transformer primary side The fundametal compoment virtual value of voltage, L_r、L_k、C_rRespectively resonant inductance and resonant capacitance, C_sFor capacitance, L_mFor static exciter Inductance, Z is load equivalent resistance, it is assumed that each road component parameters in parallel are consistent, then haveFormula In, n₁、n₂The respectively n transformer primary secondary number of turn, U_dcIt is the virtual value of input direct voltage.

The current effective value that can be obtained according to Fig. 3 in equivalent load Z/n is：

A=(X_Lr+X_Cs)(X_Lm+X_Lk+nX_Cr)+2X_Cr(X_Lm+X_Lk)

B=X_Lm[(X_Lr+X_Cs)(X_Lk+nX_Cr)+2X_LkX_Cr] (1)

Understand to work as A identically vanishing, when input voltage is fixed, size and the capacitance C of load current_s, resonant inductance L_r、L_kWith resonant capacitance C_rRelating to parameters, and with load size it is unrelated.Then have：

ω₀ ⁴(L_m+L_k)L_rC_rC_s-ω₀ ²[(L_m+L_k)(C_r+2C_S)+nL_rC_s]+n=0 (2)

When circuit works in constant current frequency, the current effective value in the n roads load is：

Wherein, U_dcIt is the virtual value of input direct voltage, L_r1=L_r2=L_r, C_s1=C_s2=C_s, L_k1=L_k2 ==L_kn=L_k, n₁、n₂The respectively n transformer primary secondary number of turn.

As shown in figure 4, when load resistance is respectively 10 Ω, when 20 Ω, 30 Ω, 40 Ω, 50 Ω, output current becomes with frequency The curve of change is as shown in Figure 4, it can be seen that at constant current operation frequency and its near a range of frequency band, load resistance from 10 Ω change to 50 Ω, and its output current is almost equal, and circuit is operated in the range of the band frequency, can realize that constant current drives.

In the present embodiment, equal properties of flow analysis is additionally provided, as shown in figure 5, be n roads Parallel opertation equivalent circuit, and Connection output loop equivalent inpnt voltage beAssume that equivalent output current maximum in the output of n roads isMinimum is equivalent defeated Going out electric current isMaximum stream error is ξ, the maximum unbalanced degree of load for δ (i.e. when load imbalance degree is maximum, Zb=δ Za, wherein δ >=1).

As Qu Ge roads resonant inductance L_k1、L_k2、…L_knIt is equal, each road static exciter inductance L_m1、L_m2、…L_mnIt is equal, When load impedance Z is not waited, minimum and maximum equivalent current is respectively in branch road：

Then the equal stream error of maximum output current is in each branch road

Can be obtained by formula (4), formula (5), formula (6)

Wherein, Z_bThe maximum equivalent load that can be allowed when meeting equal stream error for circuit.

From formula (7), the equal stream error of output current is only relevant with the unbalanced degree of load, and the unbalanced degree of load is got over Greatly, then the equal stream error of output current is bigger, but as long as choose being supported in setting range, exporting equal stream error just can control In the range of maximum stream error ξ.

The present embodiment additionally provides a kind of light-dimming method tool of the LED drive power of multi-path flow equalizing output as described above Body is comprised the following steps：

Step S1：The asynchronous ac equivalent circuit figure of two-phase sequential is obtained, as shown in fig. 6, including two branch roads in parallel, Tie point includes the equivalent source of series connectionCapacitance C_s1, resonant inductance L_r1, equivalent electric of second branch road including series connection SourceCapacitance C_s2, resonant inductance L_r2；Two branch roads in parallel and the resonant capacitance C_rParallel connection, the resonant capacitance C_rOne end and L_k1To L_knEquivalent inductance L_kOne end be connected, the resonant capacitance C_rThe other end and equivalent load Z one End is connected, equivalent inductance L_kThe other end be connected with the other end of equivalent load Z；

Step S2：IfWherein U_mFor LCL-nT type resonant network input voltage fundametal compoments Amplitude, and

Step S3：The electric current obtained in equivalent load Z is：

The virtual value for obtaining output current is：

Wherein, A for only with the capacitance C_s1, capacitance C_s2, equivalent sourceEquivalent sourceResonant inductance L_r1, resonant inductance L_r2, resonant capacitance C_r, equivalent inductance L_kRelevant parameter；

Step S4：Change the phase shift bridge arm phase place, i.e., change in [0, π]Size so that the output current of circuit I_oFrom the smooth change to zero is fully loaded with, that is, cause the smooth light modulation of circuit realiration gamut.Obtain output current value I and phase shifting angleBetween graph of relation, as shown in Figure 7.It can be seen that working asWhen changing between [0, π], output current I_o From being fully loaded with to zero change, and the change curve of electric current is substantially smooth, and circuit can realize the smooth light modulation of gamut.

The foregoing is only presently preferred embodiments of the present invention, all impartial changes done according to scope of the present invention patent with Modification, should all belong to the covering scope of the present invention.

Claims (4)

1. the LED drive power that a kind of multi-path flow equalizing is exported, it is characterised in that：Including the switching network module being sequentially connected, LCL-nT type resonant networks, commutated network and LED load unit；Wherein described switching network includes two the first bridges being in parallel Arm and the second bridge arm, wherein the second bridge arm is used as phase shift bridge arm, to realize wide scope brightness adjustment control, the load unit bag Include the LED load that output is flowed on n roads；

Wherein, the light-dimming method of the LED drive power of the multi-path flow equalizing output is comprised the following steps：

Step S1：The asynchronous ac equivalent circuit figure of two-phase sequential, including two branch roads in parallel are obtained, tie point includes string The equivalent source of connectionCapacitance C_s1, resonant inductance L_r1, equivalent source of second branch road including series connectionCapacitance C_s2, resonant inductance L_r2；Two branch roads in parallel and the resonant capacitance C_rParallel connection, the resonant capacitance C_rOne end and L_k1Extremely L_knEquivalent inductance L_kOne end be connected, the resonant capacitance C_rThe other end be connected with one end of equivalent load Z, it is described equivalent Inductance L_kThe other end be connected with the other end of equivalent load Z；

Step S2：IfWherein U_mFor the amplitude of LCL-nT type resonant network input voltage fundametal compoments, And

Step S3：The electric current obtained in equivalent load Z is：

The virtual value for obtaining output current is：

Wherein, A for only with the capacitance C_s1, capacitance C_s2, equivalent sourceEquivalent sourceResonant inductance L_r1、 Resonant inductance L_r2, resonant capacitance C_r, equivalent inductance L_kRelevant parameter；

Step S4：Change the phase shift bridge arm phase place, i.e., change in [0, π]Size so that output current I of circuit_oFrom completely Smooth change between zero is downloaded to, that is, causes the smooth light modulation of circuit realiration gamut.

2. the LED drive power that a kind of multi-path flow equalizing according to claim 1 is exported, it is characterised in that：The LCL-nT Type resonant network includes capacitance C_s1, capacitance C_s2, resonant inductance L_r1, resonant inductance L_r2, resonant capacitance C_rAnd n Inductance L_k1To L_kn；The capacitance C_s1One end, capacitance C_s2One end be respectively connecting to two in the switching network The midpoint of bridge arm, the capacitance C_s1The other end, capacitance C_s2The other end be respectively connecting to the resonant inductance L_r1 One end, resonant inductance L_r2One end, the resonant inductance L_r1The other end, resonant inductance L_r2The other end is connected and connects To the resonant capacitance C_rOne end, the resonant capacitance C_rThe other end be connected in the switching network two bridge arms its In a parallel connected end, the n inductance L_k1To L_knRespectively the resonant capacitance C is connected in parallel on respectively with after n transformer series_r Two ends.

3. the LED drive power that a kind of multi-path flow equalizing according to claim 1 is exported, it is characterised in that：The screens Network includes 2n commutation diode, and the anode of the 2n commutation diode is individual with the n of the LCL-nT types resonant network respectively The Same Name of Ends of transformer secondary, different name end are connected, wherein two commutation diodes being connected with the secondary of n-th transformer are D_n1、D_n2；The load of n paths of LEDs is respectively connecting to after the rectified diode rectification of secondary of the n transformer.

4. the LED drive power that the multi-path flow equalizing described in any one claim according to claim 1,2 or 3 is exported, It is characterized in that：When circuit works in constant current frequency, the current effective value in the n paths of LEDs load is：

$I_O=\left|\frac{8\left(\frac{n_1}{n_2}\right){\mathrm{\ω}}_0{C}_s{U}_{dc}}{{\mathrm{\π}}^2\[{{\mathrm{\ω}}_0}^4{L}_k{L}_r{C}_r{C}_s-{{\mathrm{\ω}}_0}^2(L_k{C}_r+2L_k{C}_s+{\mathrm{nL}}_r{C}_s)+n\]}\right|;$

Wherein, U_dcIt is the virtual value of input direct voltage, L_r1=L_r2=L_r, C_s1=C_s2=C_s, L_k1=L_k2== L_kn=L_k, n₁、n₂The respectively n transformer primary secondary number of turn.