CN114096042A - Multi-path constant-current output LED driving power supply based on variable Boost inductor - Google Patents

Multi-path constant-current output LED driving power supply based on variable Boost inductor Download PDF

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CN114096042A
CN114096042A CN202111246232.1A CN202111246232A CN114096042A CN 114096042 A CN114096042 A CN 114096042A CN 202111246232 A CN202111246232 A CN 202111246232A CN 114096042 A CN114096042 A CN 114096042A
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unit
current
constant current
constant
variable
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何青青
刘磊
邱名扬
周克亮
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Wuhan University of Technology WUT
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/39—Circuits containing inverter bridges
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4225—Arrangements for improving power factor of AC input using a non-isolated boost converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/34—Voltage stabilisation; Maintaining constant voltage
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/345—Current stabilisation; Maintaining constant current
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/355—Power factor correction [PFC]; Reactive power compensation
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/36—Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI]
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
    • Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Rectifiers (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a variable-Boost-inductance-based multi-path constant-current-output LED driving power supply, which comprises a Boost type PFC unit, a DC/DC unit and a control unit, wherein the Boost type PFC unit: method and apparatus for converting a constant AC input voltage to a constant DC busPressing; the DC/DC unit is used for converting the DC bus voltage into constant DC output; a control unit: the constant current source is used for collecting the output current of the AC/DC passive resonance constant current unit and controlling the variable inductor L in the Boost type PFC unitBTo achieve a constant output current. According to the invention, by controlling the magnitude of the Boost inductance value, the duty ratio and the frequency can be fixed, the control strategy is simplified, the circuit topology is simplified, and the high input power factor is automatically realized.

Description

Multi-path constant-current output LED driving power supply based on variable Boost inductor
Technical Field
The invention belongs to the technical field of LED lighting, and particularly relates to a multi-path constant-current output LED driving power supply based on a variable Boost inductor, which is used for controlling the constancy of the output current of the LED driving power supply.
Technical Field
Compared with the conventional illumination mode, the led (light emitting diode) illumination has the outstanding advantages of high efficiency, energy saving, no pollution, long service life, etc., and is regarded as a "fourth generation illumination light source", which has become a research hotspot in the illumination field in recent years, and has gradually been widely applied in the illumination fields of street illumination, tunnel illumination, landscape illumination, etc. In the LED lighting field, a two-stage LED driving power supply is often used to complete power conversion, and a preceding stage Power Factor Correction (PFC) unit rectifies a power frequency ac voltage to obtain a constant dc voltage and implements a power factor correction function; the post-stage DC/DC unit converts the constant direct current voltage into constant direct current output. The two-stage LED driving power supply needs two driving circuits and controllers (a power factor correction controller and a DC/DC controller), and in order to further simplify the structure, reduce components and reduce the cost, a single-stage LED driving power supply is provided by a student. For the control strategy, some scholars provide a modular open-loop multi-path resonant constant-current LED driving power supply which consists of a full-bridge inverter and a plurality of LCL-T resonant rectifiers. However, when the duty ratio of the switching tube is too small, the high-frequency alternating-current square wave contains a large amount of higher harmonics, an LCLC series-parallel resonant filter network needs to be added, and circuit topology components are added. Another scholars has proposed a rectifier bridge-free PFC topology network based on variable duty ratio, which requires input voltage zero-crossing detection and switching tube duty ratio conversion at the input voltage zero-crossing. However, at the time of duty cycle switching, the switching tube current may suddenly change, resulting in a large current spike.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a multi-path constant current output LED driving power supply based on a variable Boost inductor, solves the problem of complex circuit control mode, and can optimize a network structure, improve the efficiency and reduce the cost.
In order to achieve the purpose, the invention designs a multi-path constant current output LED driving power supply based on variable Boost inductance, which is characterized by comprising a Boost type PFC unit, a DC/DC unit and a control unit,
the Boost type PFC unit: for converting a constant AC input voltage to a constant DC bus voltage, comprising a variable inductance LBDiode D1And D2Switch tube S1And S2PFC output bus capacitor CB；
The DC/DC unit: the high-frequency DC/AC unit converts the constant direct-current bus voltage into high-frequency alternating-current square wave voltage, the high-frequency AC unit is electrically isolated by a transformer, and the AC/DC passive resonance constant-current unit converts the high-frequency alternating-current square wave voltage into constant direct current to be output to an LED load;
the control unit: the sampling circuit is used for sampling the output current of the AC/DC passive resonance constant current unit and controlling the variable inductor L in the Boost type PFC unitBTo achieve a constant output current.
Preferably, the AC/DC passive resonance constant current units are multiple and include passive elements, such as inductors, capacitors, and diodes, each passive resonance constant current unit drives a string of LEDs, and one passive resonance constant current unit is added for each path of LED output increase.
Preferably, a T-shaped transformer is adopted for electrical isolation between the high-frequency DC/AC unit and the AC/DC passive resonance constant current unit.
Preferably, the control unit collects a current feedback value of the AC/DC passive resonance constant current unit, generates an error signal after comparing the current feedback value with a reference current value, converts the error signal into a current control signal and outputs the current control signal to the variable inductor LB。
Preferably, the switching tube S1And S2The duty ratios of (a) and (b) are all fixed to 0.5. In order to ensure the stable operation of the system, the zero-crossing detection of the input voltage and the duty ratio switching are particularly important, the current of the switching tube is suddenly changed at the time of switching the duty ratio, the current peak is overlarge, and the phenomenon of tube burning due to the overlarge current of the switching tube caused by the direct switching of the duty ratio in the experimental process can be avoided. If the duty ratio can be fixed at 0.5, the problem of overlarge transient current of the switching tube caused by direct switching of the duty ratio can be avoided.
Preferably, the high frequency DC/AC part is composed of a full bridge or half bridge inverter network.
Preferably, the switching network switching tubes in the Boost type PFC unit and the DC/DC unit are of a triode, a MOSFET and/or an IGBT.
Preferably, the controller adopts a proportional controller, a PI controller or a PID controller. The controller obtains an error signal by comparing the reference signal and the feedback signal, which is applied to the controller. The controller generates a control signal for adjusting the dc bias current, and then the inductance value of the Boost inductor of the PFC unit may be adjusted by adjusting the dc bias current to adjust the output.
Preferably, the switching tube S1And S2When the duty ratio is fixed, the variable inductor L in the Boost type PFC unit is controlledBThe inductance value of (2) has a power factor correction function.
Compared with the prior art, the invention has the following beneficial effects:
1. and the variable Boost inductor is adopted for control, and the switching frequency and the duty ratio are fixed, so that the control strategy is simplified.
2. Because the variable Boost inductor is adopted for control, the switching duty ratio can be fixed to 0.5, and the problem of high harmonic content of high-frequency alternating current bus voltage caused by the duty ratio value limitation of a PFC unit is avoided; meanwhile, the LCLC series-parallel resonant filter network can be removed, so that the circuit topology is simplified.
3. The duty ratio is fixed at 0.5, zero-crossing detection of input voltage is not needed, and the problem of current peak caused by duty ratio switching at the zero-crossing point of the input voltage can be solved.
4. The output voltage UB of the PFC unit remains almost constant throughout the input/output variation.
5. Because the output voltage UB of the Boost type PFC unit is far larger than twice of the amplitude of the input voltage, the PFC unit works in a DCM mode, and therefore high input power factor can be automatically achieved.
6. In the invention, through reasonable parameter design, the switch tube can realize soft switching, thereby reducing the switching loss and improving the efficiency.
Drawings
Fig. 1 is an architecture diagram of a single-stage multi-channel constant current output LED driving power supply based on variable Boost inductance control.
Fig. 2 is a specific circuit topology of the architecture of fig. 1.
Fig. 3 is a schematic diagram derived from a single-stage full-bridge high-frequency resonant AC/AC converter topology.
Fig. 4 is an operation waveform of the single-stage full-bridge high-frequency resonant AC/AC converter in one power frequency period TL.
Fig. 5 is a schematic diagram of the operation principle of duty cycle switching when the input voltage is zero-crossing.
Fig. 6 is a simulation waveform when the input voltage is zero-crossing.
Fig. 7 is a diagram illustrating the relationship between the parameter m and the input power factor PF.
Fig. 8 is an operation waveform of the PFC unit of fig. 2 during a power frequency period of the input voltage.
Fig. 9 shows the structure and principle of the double E-type variable inductor.
Fig. 10 is a diagram of the variable inductor bias circuit and the relationship between the variable inductor LB and the dc current Ib.
Fig. 11 is a block diagram of a control scheme for controlling the main inductance value LB.
Fig. 12 is a graph of input voltage current for the circuit of fig. 2 operating under closed loop control.
Fig. 13 is a voltage-current experimental waveform of the switching tubes S1 and S2 measured when the input voltage is 99V, 110V, 121V respectively, when the circuit shown in fig. 2 operates under closed-loop control.
Fig. 14 is a waveform diagram of dynamic experiment of output voltage current when the circuit shown in fig. 2 is operated under closed-loop control and when the input voltage is changed. FIG. 14(a) is an experimental waveform with an input voltage of 99V; FIG. 14(b) is an experimental waveform with an input voltage of 121V; FIG. 14(c) is an experimental waveform when the input voltage jumps from 99V to 121V; fig. 14(d) shows experimental waveforms when the input voltage transits from 121V to 99V.
Fig. 15 is a waveform diagram of input and output dynamics when the circuit shown in fig. 2 is operated under closed-loop control to cause a load to jump and thereby change the output voltage. FIG. 15(a) is an experimental waveform when the main circuit output voltage jumps from 36V to 4V; FIG. 15(b) is an experimental waveform when the main circuit output voltage jumps from 4V to 36V; FIG. 15(c) is an experimental waveform when the transition from 36V to 4V is made from the output voltage; fig. 15(d) shows an experimental waveform when the channel output voltage transits from 4V to 36V.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
Referring to fig. 1, the invention designs a variable Boost inductor-based multi-path constant current output LED driving power supply, which can simplify a control strategy and a circuit topology, realize soft switching, automatically realize high input power factor, have high switching utilization rate, and output current with high precision. Taking the circuit structure of fig. 2 as an example, the invention includes a Boost type PFC unit, a DC/DC unit, and a control unit:
boost type PFC unit: the power factor correction circuit adopts a totem-pole Boost type PFC unit without a rectifier bridge for converting a constant alternating current input voltage into a constant direct current bus voltage, and comprises a variable inductor LBDiode D1And D2Switch tube S1And S2PFC outputBus capacitor CB. The topology structure of the PFC unit can be a topology with a rectifier bridge or a topology without the rectifier bridge.
DC/DC unit: the high-frequency DC/AC unit converts the constant direct-current bus voltage into high-frequency alternating-current square wave voltage, the high-frequency AC unit is electrically isolated through a T-shaped transformer, and the AC/DC passive resonance constant-current unit converts the high-frequency alternating-current square wave voltage into constant direct current to be output to an LED load. The high-frequency alternating-current bus voltage can be symmetrical or asymmetrical square waves, the DC/AC part is composed of a switch network and can be connected with an isolation transformer to realize input and output isolation, and the AC/DC part is composed of a passive element inductor, a capacitor and a diode.
The DC/AC part in the DC/DC unit can be composed of a full-bridge or half-bridge inverter network, and the AC/DC part is composed of a passive resonance constant current network and a rectifying module. The passive resonance constant current network can be composed of LCL-T, CLC-pi, CLC-T or LCL-pi, and the rectification module can be a half-wave rectification structure, a full-wave rectification structure, a bridge rectification structure and a voltage-multiplying rectification structure.
The AC/DC passive resonance constant current units are multiple and consist of passive element inductors, capacitors and diodes, each passive resonance constant current unit drives a string of LEDs, one passive resonance constant current unit is added for each path of added LED output, and each passive resonance constant current unit can be the same or different to adapt to the corresponding LED output.
And the switching tubes of the switching networks in the Boost type PFC unit and the DC/DC unit are triodes, MOSFETs and/or IGBTs.
A control unit: the sampling circuit is used for sampling the output current of the AC/DC passive resonance constant current unit and controlling the variable inductor L in the Boost type PFC unitBTo achieve a constant output current.
The control unit controls the Boost inductance value of the PFC unit through the sampling value and the controller, and constant output current is achieved. The control unit obtains an error signal by sampling the output signal, by comparing the reference signal with the output signal, and then applies it to the controller. The controller includes, but is not limited to, a proportional controller, a PI controller, a PID controller, and the like. The controller generates a control signal that is used to adjust the dc bias current. The direct current bias current generates direct current bias magnetic flux density in the magnetic core, the magnetic induction intensity of the whole inductor is adjusted, the magnetic permeability of the material is adjusted by changing the direct current working point around the B-H curve inflection point, the inductance value of the variable Boost inductor is adjusted to adjust the output current of the LED driving power supply, and therefore high-precision current is output. The control object of the present invention may be the output current of the DC/DC unit or may also be the output direct voltage signal of the PFC unit.
The principle of the invention for realizing constant current by controlling the inductor LB is shown in figure 3, the angular frequency omega of the LCL-T resonant networkoCorresponding normalized angular frequency ωnAnd the ratio of the two inductances gamma can be expressed as
Figure BDA0003321069210000061
Where f isSWRepresenting the switching frequency, ωSWRepresenting the switching angular frequency.
Setting omega n1, D is 0.5, only u is consideredacAnd uDmIn the case of the fundamental component, the output current IomAnd an output voltage UomIndependently, a constant current can be realized, which can be expressed as
Figure BDA0003321069210000062
Where N denotes the turns ratio of the transformer, with a value equal to N1/n2。
So that only the variable inductance L is adjustedBOf such a value that the storage capacitor voltage U isBIt is sufficient that they remain substantially unchanged. According to the formula (2), when the input and output voltages are changed, the inductance L is adjustedBMain output current I of main valueomIs controlled by closed loop and stores energy capacitor voltage UBMay remain substantially unchanged.
The inductance L is described belowBValue of and storage capacitor voltage UBThe relationship (2) of (c).
Available input active power PinIs composed of
Figure BDA0003321069210000071
Wherein
Figure BDA0003321069210000072
Equation (3) shows variable inductance LBValue and storage capacitor voltage UBThere is a one-to-one correspondence, and under the condition of disturbance change of input voltage, the inductance can be adjusted by adjusting the variable inductance LBOf such a value that the capacitor voltage UBRemain substantially unchanged; in the case of a change in the output power, the variable inductance L can also be adjustedBTo realize output IomThe purpose of this is constant. Then the current I is output according to the above equation (2)omCan be kept unchanged, thus realizing the function of constant current.
The duty ratio D is set to 0.5 in this embodiment.
The principle of the rectifier-bridge-free PFC duty ratio-variable control (the case of D change) and the duty ratio switching process will be described below according to the working principle of the rectifier-bridge-free push-pull output Boost type PFC unit.
As shown in fig. 3, the Boost-type PFC unit without rectifying bridge comprises an inductor LBDiode DR1And DR2Switch tube S1And S2And an energy storage capacitor CB(ii) a The full-bridge LC-LC series-parallel resonant DC/AC unit comprises an energy storage capacitor CBSwitch tube S1-S4LC-LC series-parallel resonant network and transformer T, wherein the resonant network is composed of series inductor LsAnd a series capacitor CsParallel inductor LpAnd a parallel capacitor CpAnd (4) forming. Voltage U of energy storage capacitorBIs not only the output voltage of PFC unit, but also the output of DC/AC unitVoltage input, switching tube S1、S2Multiplexing is performed.
FIG. 4 shows the single-stage full-bridge high-frequency resonant AC/AC converter in a power frequency period TLThe operating waveform in. At an input voltage uinIn the positive half period of (1), the switching tube S1、S2Complementary conducting, switching tube S3、S4Complementary conducting, switching tube S3Relative to the switching tube S1Phase-shifted by 180 DEG, diode DR2Turn-off, switch tube S1、S3Keeping the duty ratio D unchanged; at the input voltage uinDuring the negative half period of (1), the switching tube S1And S2、S3And S4Switch tube S in the same complementary conduction3Relative to the switching tube S1Phase-shifted by 180 DEG, diode DR1Turn-off, switch tube S2、S4Keeping the duty cycle D unchanged. Since the duty ratio D is not changed and the inductive current iLBInterrupted, iLBThe envelope line of the power factor correction circuit is a sine wave with the same frequency and phase as the input voltage, and the power factor correction function is realized. Voltage U of energy storage capacitorBBy a switching tube S1、S2、S3And S4Obtaining the input voltage u of the resonant network by full-bridge inversionRSince the switch tube shifts phase by 180 °, uRThe dc component in (1) is zero. The LC-LC series-parallel resonant network has good filtering characteristic and can input voltage uRFiltering out medium and high harmonic component, and outputting voltage upThe primary voltage of the transformer mainly comprises a fundamental component, and the Total Harmonic content (THD) of the primary voltage of the transformer can be lower than 5% through reasonable design. It is noted that uRThe waveform is symmetrical in positive and negative half cycles, the harmonic content is greatly reduced, and the high-frequency sinusoidal alternating-current output voltage u with constant frequency and amplitude can be obtained after the electric isolation is realized by the transformer Tac。
The working principle of duty cycle switching when the input voltage crosses zero is as shown in fig. 5, and since the duty cycle needs to be converted at the zero crossing of the input voltage, the zero crossing detection of the input voltage and the duty cycle switching are particularly important for ensuring the stable operation of the system. The switching tube current waveform obtained by PSIM simulation during direct duty cycle switching is shown in FIG. 6, and it is worth noting that at the time of duty cycle switching, the switching tube current is suddenly changed, the current peak is too large, and the phenomenon of tube burning occurs due to the fact that the direct switching of the duty cycle causes the switching tube current to be too large in the experimental process. Therefore, the duty ratio is fixed at 0.5 and is not changed, and the problem of overlarge transient current of the switching tube caused by direct switching of the duty ratio can be avoided.
In the invention, the variable inductance L in the Boost type PFC unit is controlledBThe inductance value of (2) has a power factor correction (PF) function.
When the PFC unit operates in DCM and the duty ratio D is not changed, the PFC unit can automatically implement the power factor correction function, so the condition of operating in DCM is derived first.
Let the input voltage be
uin＝UinmsinωLt (5)
Wherein, UinmIs the input voltage amplitude, omegaLIs the input voltage angular frequency.
According to the working principle of the converter, the duty ratio D is not changed, and the inductive current iLBThe rising rate of (A) is different with the change of the input voltage, which is U at the input voltageinmThe time reaches the maximum value; and due to the voltage U of the energy storage capacitorBUnchanged, its falling rate is U at input voltageinmThe time is minimal. Therefore, only when the input voltage is U, the input voltage is ensuredinmWhen the time converter works in a Critical connection mode (CRM), the work in DCM can be ensured in the whole 1/2 power frequency period, and at the moment, the inductive current works in a switching period TSWAverage value ofLBmaxShould be less than or equal to 1/2 of its peak current, i.e.
Figure BDA0003321069210000091
The inductor current i is shown in FIG. 4LBIn a switching period TSWThe average value of the inner waveform
Figure BDA0003321069210000092
Is composed of
Figure BDA0003321069210000093
Due to the inductance LBVolt-second balance in one switching period, thus
uin·D·TSW＝(UB-uin)·d'·TSW (8)
Further, the compounds represented by the formulae (5), (7) and (8) can be obtained
Figure BDA0003321069210000094
Wherein
Figure BDA0003321069210000095
From the equation (9), when the input voltage is UinmWhen the temperature of the water is higher than the set temperature,
Figure BDA0003321069210000096
to a maximum value ILBmaxThus, therefore, it is
Figure BDA0003321069210000097
The conditions for the PFC unit to work in DCM according to the formulas (6) and (11) are as follows
D≤1-m (12)
The input power factor PF of the PFC unit is calculated as follows. As can be seen from fig. 3, the ac side input current is the inductor current iLB. The input active power P can be obtained by the formulas (5) and (9)inIs composed of
Figure BDA0003321069210000101
Wherein
Figure BDA0003321069210000102
The effective value of the input current, i.e. the effective value of the inductive current I, can be obtained from the formula (9)LBIs composed of
Figure BDA0003321069210000103
Wherein
Figure BDA0003321069210000104
The input apparent power S can be obtained according to the formulas (5) and (15)inIs composed of
Figure BDA0003321069210000105
Wherein U isinIs the effective value of the input voltage.
The input power factor PF obtained from the equations (13) and (17) is
Figure BDA0003321069210000106
Since A, B are both functions of the parameter m, the PF size is only related to m, and thus the relationship is shown in FIG. 8. As can be seen from fig. 8, in order to satisfy the requirement of the energy star for the power factor greater than 0.9, m should be guaranteed to be less than 0.9.
The power factor PF is only related to m and if m is less than 0.9, it can be ensured that the power factor PF is greater than 0.9 to meet the energy star requirements.
Since D is 0.5, equation (4) can be derived as m ≦ 0.5, with m having a value much less than 0.9. Therefore, as long as the PFC unit satisfies the condition of operating in DCM, a high input power factor can be automatically achieved. In conjunction with equation (2), the condition of the PFC unit operating in DCM can be expressed as
m≤0.5→UB≥2Uinm (19)
Accordingly, the above boundary condition can be interpreted as: the PFC unit operates in the DCM mode and obtains a high input power factor as long as the output voltage of the PFC unit is greater than twice the magnitude of the input voltage.
It is therefore necessary to control the value of the design inductance so that the boundary conditions (19) are met to achieve the power factor correction function.
In this embodiment, the Boost-type PFC unit without the rectifier bridge operates in one power frequency period T of the input voltageLThe internal operating waveform is shown in FIG. 8, where Q1And Q2Indicating switch tube S1And S2The gate driving voltage of (1). As can be seen from the figure, the switching tube S1And S2And conducting complementarily. The duty cycle D is fixed at 0.5, which means that the switching tube S is switched1And S2Is always 0.5TSWWherein T isSWIs a switching cycle. At an input voltage uinIn the positive half-cycle of (2), diode D2Cut off in the reverse direction when switching tube S1When conducting, the inductor L is suppliedBMagnetizing; when switching tube S1When turned off, is stored in the inductor LBIs transmitted to the load. At an input voltage uinNegative half period of (D), diode D1Cut off in the reverse direction when switching tube S2When conducting, the inductor L is suppliedBMagnetizing; when switching tube S2When turned off, is stored in the inductor LBIs transmitted to the load. For the PFC unit, when the duty ratio D is fixed and the inductive current iLBDiscontinuous, inductive current iLBHas an envelope of a sine wave and is coupled to the input voltage uinIn phase, so that the power factor correction function can be automatically realized.
FIG. 9(a) shows a structure of a variable inductor using a double E-shaped core, in which a control winding is formed on a lateral leg of the double E-shaped core with N turnsDCAre connected. The main winding is arranged on the air gap middle strut of the magnetic core and has N turnsACThe winding of (a). By controlling the DC bias current I in the windingDCSize, generating DC bias magnetic flux density in the magnetic core, regulating the whole electricityThe magnetic induction intensity of the sensor is further adjusted by changing the dc operating point around the inflection point of the B-H curve, as shown in fig. 9 (B).
FIG. 10(a) shows a variable inductance or main winding inductance LBA bias circuit for providing a direct current. DC current auxiliary winding LbConnected current source IiGeneration, inductance LBThe change is made by changing the dc level of the magnetic flux density. Further, fig. 10(b) shows a variable inductance LBWith its direct bias current IbThe general relationship between, as can be seen, the variable inductor value LBAnd a direct current IbIn inverse proportion.
FIG. 11 shows a schematic diagram for controlling the main inductance LBA control scheme block diagram of (1). An error signal is first obtained by comparing a reference voltage and a feedback voltage and then applied to the PI controller. The PI controller generates a control signal that is used to adjust the dc bias current. Then, the inductance value of the variable inductor can be adjusted by adjusting the dc bias current to adjust the output current of the LED driving power supply.
Fig. 2 to 15 show experimental waveforms according to the present invention. The input and output and the parameter setting of each component are as follows: rated input voltage Uin＝110V，LB130 muH-556 muH, rated output current 0.7A, switching frequency 100kHZ, transformer turn ratio N-N1：n 22, inductance Lm175 muh, inductance Lam87 muH, capacitance Cm＝14nF。
FIG. 12 is a graph of input voltage current when the circuit is operating under closed loop control. As can be seen from FIG. 12, the inductor current iLBIn discontinuous mode, the envelope of inductor current iLB is a sine wave and is related to input voltage uinIn phase, consistent with the theoretical analysis. The current i is filtered by an LC input filterLBThe input power factor obtained by the experimental measurement after the higher harmonic wave in the medium is about 0.99, and the requirement of energy star is met.
FIG. 13 shows the switching tube S measured at 99V, 110V and 121V input voltages respectively when the circuit is under closed-loop control1And S2Voltage current experimental waveform of (2). Output power P at different input voltagesO75W time switch tube S1And S2The drain-source voltage and the switch tube current of (1) are shown in FIG. 12, in the switch tube S1And S2Before the arrival of the gate signal, current iS1And iS2Less than zero means that the antiparallel diode of the switching tube is conducting and thus the switching tube S1And S2Zero voltage conduction is achieved. In addition, the experimentally measured inductor current i is given in fig. 13LBFurther proving the Boost inductor current i from the figureLBAre discontinuous at different input voltages.
FIG. 14 is a waveform diagram of dynamic experimental output voltage current when the input voltage changes when the circuit is operated under closed-loop control. As can be seen from fig. 14(a) and 14(b), the output current I of the main circuit is closed-loop controlledom-preDoes not vary with the input voltage. PFC unit output voltage UBKeeping constant at about 380V, and outputting current I from the circuitos-preAlso remains constant. The dynamic experimental waveforms when the input voltage abruptly changes are shown in fig. 14(c) and 14(d), and in fig. 14(c), the input voltage uinFrom about 99VACRises to about 121VAC(ii) a In FIG. 14(d), the input voltage uinFrom about 121VACDown to about 99VAC. In both fig. 14(c) and 14(d), the output current I of the main circuitom-preCan be restored to the previous state in a short time, and therefore, the closed-loop control of the main circuit output current can be realized.
FIG. 15 is a waveform diagram of the input/output dynamics when the output voltage is varied by a load jump when the circuit is operating under closed loop control. FIG. 15(a) shows the output voltage U when the output voltage is from the circuitosWhen the main circuit output voltage is approximately 36V and is reduced to 4V, the corresponding main circuit load change is changed from 9 LEDs connected in series to 1 LED. Accordingly, FIG. 15(b) shows the output voltage U when the voltage is outputted from the circuitosExperimental waveforms measured when the main circuit output voltage rises from about 4V to 36V at approximately 36V. As can be seen from fig. 15(a) and 15(b), since the main road is closed-loop controlled,the output current of the main circuit can be recovered to the previous state in a short time, and the fluctuation of the output current of the auxiliary circuit is small, so that the precision requirement is met. FIG. 15(c) shows the output voltage U when main circuit is outputtingomThe output waveform of the slave output voltage decreasing from about 36V to about 4V when the output voltage is approximately equal to 36V, the corresponding slave load change is also from 9 LEDs connected in series to 1 LED, and FIG. 15(d) shows that when the output voltage of the master circuit U is equal to the output voltage of the master circuit UomAnd the output waveform of the slave output voltage rising from about 4V to about 36V when the voltage is approximately equal to 36V. Likewise, according to fig. 15(c) and 15(d), the output current of the master can be kept constant when the slave voltage changes, and the output current of the slave fluctuates less, satisfying the constant current accuracy requirement. In this way, closed-loop control of the main circuit output current is achieved, and the auxiliary circuit output current can be controlled at the main circuit voltage UomAnd a slave voltage UosMeets the constant current precision requirement in the whole variation range.
According to the analysis of the experimental waveform, the fixed duty ratio control strategy is simpler, the switching tubes can realize soft switching, the switching loss is reduced, high-precision current can be output, and the constant current output function is realized. Compared with the traditional multi-path constant-current LED driving power supply, the LED driving power supply has a simpler structure and has obvious advantages in terms of the number of elements and control.
The above examples of the present invention are merely illustrative of the present invention and are not intended to limit the embodiments of the present invention. Variations and modifications in other variations will occur to those skilled in the art upon reading the foregoing description. Not all embodiments are exhaustive. All obvious changes and modifications of the present invention are within the scope of the present invention.

Claims (10)

1. The utility model provides a multichannel constant current output LED drive power supply based on become Boost inductance which characterized in that: comprises a Boost type PFC unit, a DC/DC unit and a control unit,
the Boost type PFC unit: for converting a constant AC input voltage to a constant DC bus voltage, comprising a variable inductance LBDiode D1And D2Switch tube S1And S2PFC output bus capacitor CB；
The DC/DC unit: the high-frequency DC/AC unit converts the constant direct current bus voltage into high-frequency alternating current square wave voltage, the high-frequency alternating current square wave voltage is electrically isolated through a transformer, and the AC/DC passive resonance constant current unit converts the high-frequency alternating current square wave voltage into constant direct current output;
the control unit: the sampling circuit is used for sampling the output current of the AC/DC passive resonance constant current unit and controlling the variable inductor L in the Boost type PFC unitBTo achieve a constant output current.
2. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: the AC/DC passive resonance constant current units are multiple and consist of passive element inductors, capacitors and diodes, each passive resonance constant current unit drives a string of LEDs, and one passive resonance constant current unit is added when one path of LED output is added.
3. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: and the high-frequency DC/AC unit and the AC/DC passive resonance constant-current unit are electrically isolated by adopting a T-shaped transformer.
4. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: the control unit acquires a current feedback value of the AC/DC passive resonance constant current unit, generates an error signal after comparing the current feedback value with a reference current value, converts the error signal into a current control signal and outputs the current control signal to the variable inductor LB。
5. The variable Boost inductor-based multi-path constant current output LED driving power supply as claimed in claim 1Characterized in that: the switch tube S1And S2The duty ratios of (a) and (b) are all fixed to 0.5.
6. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: the high-frequency DC/AC part consists of a full-bridge or half-bridge inverter network.
7. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 2, characterized in that: the AC/DC passive resonance constant current unit comprises a passive resonance constant current network and a rectification module, the passive resonance constant current network structure comprises LCL-T, CLC-pi, CLC-T or LCL-pi, and the rectification module is a half-wave rectification, full-wave rectification, bridge rectification or voltage-doubling rectification structure.
8. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: and the switching tubes of the switching networks in the Boost type PFC unit and the DC/DC unit are triodes, MOSFETs and/or IGBTs.
9. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 1, characterized in that: the controller adopts a proportional controller, a PI controller or a PID controller.
10. The variable Boost inductor-based multi-path constant current output LED driving power supply according to claim 5, characterized in that: the switch tube S1And S2When the duty ratio is fixed, the variable inductor L in the Boost type PFC unit is controlledBThe inductance value of (2) has a power factor correction function.
CN202111246232.1A 2021-10-26 2021-10-26 Multi-path constant-current output LED driving power supply based on variable Boost inductor Pending CN114096042A (en)

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