CN110972355B - Two-channel LED driver based on resonant switch capacitor - Google Patents

Abstract

A two-channel LED driver based on a resonant switch capacitor belongs to the technical field of LED driving. The present invention is directed toIn the passive current-sharing technology driven by the LED, the complexity of a circuit is increased along with the increase of LED branches, and the current-sharing precision is influenced. The method comprises the following steps: the leading-out wires of the connection points of two bridge arms of a half-bridge circuit are connected with a switched capacitor C_rOne terminal of (1), switch capacitor C_rThe other end of the buffer inductor L is connected with_rOne end of (1), buffer inductance L_rAnother end of the diode D₁While connecting the diode D₂The anode of (1); leading-out wires of the connection points of the two bridge arms of the other half-bridge circuit are grounded; diode D₁One path of LED to be driven is connected between the anode and the grounding point; diode D₂The other path of LED to be driven is connected between the cathode of the LED and the grounding point; one path of LED to be driven and output capacitor C₀₁Parallel connection, another path of LED to be driven and output capacitor C₀₂And (4) connecting in parallel. The invention realizes the current sharing of the two branch LEDs based on the principle of capacitance charge balance, has simple circuit and small volume, and does not need additional control circuit.

Description

Two-channel LED driver based on resonant switch capacitor

Technical Field

The invention relates to a two-channel LED driver based on a resonant switched capacitor, and belongs to the technical field of LED driving.

Background

The LED has the advantages of small volume, high power density, long service life, no environmental pollution, pure light color, high working efficiency and the like, and has high luminous efficacy compared with the traditional incandescent lamp and other light sources. When the light with the same brightness is emitted, the power consumption of the incandescent lamp is several times that of the LED, and therefore, the LED has been widely used in various fields such as street lighting, indoor lighting, and LCD backlight light source.

With the continuous maturation of LED packaging technology, LEDs have shown a trend to replace fluorescent lighting. In most LED lighting occasions, a mode of combining LED lamp strings in parallel is adopted, and according to the characteristic of LED constant current driving, an LED driving current equalizing technology is widely concerned by researchers. At present, the following problems mainly exist:

1) the traditional active current sharing technology adopts active devices and can accurately control each path of current through feedback control, but circuit components of the scheme are more in number, a control circuit is more complex, the reliability is difficult to guarantee, meanwhile, due to the addition of the active devices, no matter linear devices or switching devices, extra loss is inevitably generated in the circuit, the system efficiency is reduced, and the system volume is increased.

2) In the current passive current sharing technology, based on a transformer or coupling inductor passive current sharing technology, current balancing of any LED branch circuit can be achieved, however, as the number of the needed transformers or coupling inductors is increased sharply, the complexity of a circuit is increased, the power density is low, the size is large, the reliability is reduced, and the current sharing precision is easily influenced by parameters of the transformers or the coupling inductors.

Disclosure of Invention

The invention provides a two-channel LED driver based on a resonant switch capacitor, aiming at the problems that in the existing passive current sharing technology driven by LEDs, the complexity of a circuit is increased along with the increase of LED branches, and the current sharing precision is influenced.

The invention relates to a two-channel LED driver based on a resonant switched capacitor, which comprises two half-bridge circuits and an input capacitor C_in1An input capacitor C_in2And a switch capacitor C_rBuffer inductor L_rDiode D₁Diode D₂An output capacitor C₀₁And an output capacitor C₀₂，

The two half-bridge circuits form a stack bridge and a power supply V_inConnected in parallel with an input capacitor C of one of the half-bridge circuits_in1Another half-bridge circuit connected in parallel with input capacitor C_in2；

The connection point of the two bridge arms of the half-bridge circuit is connected with the leadOutgoing line connection switch capacitor C_rOne terminal of (1), switch capacitor C_rThe other end of the buffer inductor L is connected with_rOne end of (1), buffer inductance L_rAnother end of the diode D₁While connecting the diode D₂The anode of (1);

leading-out wires of the connection points of the two bridge arms of the other half-bridge circuit are grounded;

diode D₁One path of LED to be driven is connected between the anode and the grounding point; diode D₂The other path of LED to be driven is connected between the cathode of the LED and the grounding point; one path of LED to be driven and output capacitor C₀₁Parallel connection, another path of LED to be driven and output capacitor C₀₂And (4) connecting in parallel.

According to the two-channel LED driver based on resonant switched capacitors of the present invention,

the drive signals of the two half-bridge circuits cause the two legs of each half-bridge circuit to conduct complementarily, and a dead zone exists between the complementary conductions.

According to the two-channel LED driver based on resonant switched capacitors of the present invention,

the half-bridge circuit comprises a switching tube S₁And a switching tube S₂The other half-bridge circuit comprises a switching tube S₃And a switching tube S₄(ii) a Switch tube S₁Duty ratio of 0.25, switching tube S₃Is 0.75, switching tube S₁And a switching tube S₃There is a phase difference of 180 °.

According to the two-channel LED driver based on resonant switched capacitors of the present invention,

all the switch tubes are NMOS tubes.

The invention has the beneficial effects that: the invention realizes the current sharing of the two branch circuits of the LED based on the principle of capacitance charge balance, has simple circuit and small volume, does not need an additional control circuit, and has the function of buffering the current by adopting a small resonance inductor (the chip inductor can meet the requirement). The driver works in a discontinuous conduction DCM mode, so that four switching tubes of two half-bridge circuits can obtain a zero-current switch ZCS, high working frequency and efficiency are achieved, the size of the driver can be reduced, the input cost is greatly reduced in the field of middle-low power LED illumination application, and the stress requirement on devices is avoided.

The invention uses two half-bridges to form a stacked bridge, and square wave voltage with the frequency 2 times of the switching frequency is generated between the middle points of the upper bridge arm and the lower bridge arm by controlling the switching mode of the stacked bridge, so that the switching frequency is half of the system working frequency, and the switching loss is reduced.

The driver is easy to expand, and can expand the LED array on the premise of not changing the number of the switching tubes, so that the multi-array LED driving is realized.

The driver circuit can ensure constant output voltage and current by open-loop operation, a closed loop does not need to be designed, and the cost and the complexity of the circuit are greatly reduced.

Drawings

FIG. 1 is a schematic circuit diagram of a resonant switched capacitor based two-channel LED driver according to the present invention;

FIG. 2 is a waveform illustrating the operation of the driver according to the present invention; in the figure V_g1-V_g4Are respectively a switch tube S₁-S₄Drive signal waveform of V_mindIs the stack bridge midpoint voltage, I_s1-I_s4Are respectively a switch tube S₁-S₄Icr and Vcr are current-voltage waveforms of the switched capacitor Cr, respectively;

FIG. 3 shows the driver of the present invention at t₀To t₁Mode 1 schematic of a time period;

FIG. 4 shows the driver of the present invention at t₁Modal 2 diagram of time of day;

FIG. 5 shows the driver of the present invention at t₂Modal 3 schematic at time;

FIG. 6 shows the driver of the present invention at t₃Modality 4 schematic diagram of the moment;

FIG. 7 shows a driver according to the present invention composed of₄Time until after half a resonance period, i.e. t₁Modality 5 schematic of the time;

FIG. 8 shows the driver of the present invention at t₃Modality 6 schematic of the time;

FIG. 9 is a schematic diagram of mode 7 of the actuator of the present invention, which is the same as mode 3;

FIG. 10 is a schematic diagram of mode 8 of the actuator of the present invention, which is the same as mode 4;

FIG. 11 is a simulated waveform diagram of the switching tube drive for two half-bridge circuits;

FIG. 12 is a diagram of a switched capacitor C_rVoltage and current simulation oscillograms of (1);

FIG. 13 is a waveform diagram illustrating soft switching simulation of the switching tube;

FIG. 14 is a graph of the voltage and current waveforms output by the present invention; v_co1Is the voltage of channel 1 (i.e. one path of LED to be driven), V_co2Is the voltage of channel 2 (i.e., the other to-be-driven LED); i is₀₁Is a channel 1 current, I₀₂Is channel 2 current; FIG. 15 is a diagram of a switched capacitor C_rVoltage and current prototype experimental oscillograms of (1);

FIG. 16 shows a switching tube S₁And a switching tube S₂The experimental oscillogram of the soft switch prototype;

FIG. 17 shows a switching tube S₃And a switching tube S₄The experimental oscillogram of the soft switch prototype;

figure 18 is a graph of the efficiency of the drive of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is further described with reference to the following drawings and specific examples, which are not intended to be limiting.

Concrete implementIn a first embodiment, referring to fig. 1, the present invention provides a two-channel LED driver based on a resonant switched capacitor, which is characterized in that the two-channel LED driver includes two half-bridge circuits and an input capacitor C_in1An input capacitor C_in2And a switch capacitor C_rBuffer inductor L_rDiode D₁Diode D₂An output capacitor C₀₁And an output capacitor C₀₂，

The two half-bridge circuits form a stack bridge and a power supply V_inConnected in parallel with an input capacitor C of one of the half-bridge circuits_in1Another half-bridge circuit connected in parallel with input capacitor C_in2；

The leading-out wires of the connection points of the two bridge arms of the half-bridge circuit are connected with a switched capacitor C_rOne terminal of (1), switch capacitor C_rThe other end of the buffer inductor L is connected with_rOne end of (1), buffer inductance L_rAnother end of the diode D₁While connecting the diode D₂The anode of (1);

leading-out wires of the connection points of the two bridge arms of the other half-bridge circuit are grounded;

diode D₁One path of LED to be driven is connected between the anode and the grounding point; diode D₂The other path of LED to be driven is connected between the cathode of the LED and the grounding point; one path of LED to be driven and output capacitor C₀₁Parallel connection, another path of LED to be driven and output capacitor C₀₂And (4) connecting in parallel.

The current sharing method and the current sharing device have the advantages that the current sharing technology of the switched capacitor is utilized, the current sharing of the two strings of LEDs to be driven can be realized under the condition that an active device is not needed, the structure is simple, the cost is low, and the expansion is easy.

The soft switch working state can be realized by using a small resonance inductor, a switching tube and a secondary rectifier diode, and the high-efficiency operation of the system is ensured.

Further, as shown in connection with fig. 2, the drive signals of the two half-bridge circuits make the two legs of each half-bridge circuit conduct complementarily, and there is a dead zone between the complementary conduction.

The embodiment utilizes the stacking bridge to control the switching sequence of the switching tubes, thereby ensuring the work efficiency of the systemThe frequency is twice the switching frequency, the switching loss is reduced, the system efficiency is improved, and the driving waveform is shown in figure 11, and visible V_mindIs twice the switching frequency.

Still further, as shown in fig. 2, the half-bridge circuit includes a switch S₁And a switching tube S₂The other half-bridge circuit comprises a switching tube S₃And a switching tube S₄(ii) a Switch tube S₁Duty ratio of 0.25, switching tube S₃Is 0.75, switching tube S₁And a switching tube S₃There is a phase difference of 180 °. That is, the switch tube S₁To S₄The duty ratios of (a) are 0.25, 0.75, 0.25 in sequence.

A schematic diagram of the present embodiment is shown in fig. 1. The stacked bridge is formed by two half-bridges, wherein both bridge arms in each half-bridge are complementarily conductive, i.e. S₁And S₂Complementary conduction, S₃And S₄Complementary conduction is realized, and a certain dead zone exists. As shown in fig. 2, the voltage V at the midpoint of the stacked bridge is made_mindThe square wave signal with twice switching frequency and half amplitude of input voltage is obtained, the system works at twice switching frequency, and due to frequency doubling, the switching loss of four switching tubes of the system is only the same as that of a half-bridge converter. Using switched capacitors C_rThe ampere-second balance principle is that two paths of LEDs to be driven can realize self-current sharing, an additional active control device is not needed, and the ampere-second balance LED driving circuit has the advantages of small size and high stability. Using a small buffer inductance L_rAnd each switching tube can realize ZCS.

Fig. 2 shows the main waveforms of the driver. In the waveform, V_g1、V_g2、V_g3And V_g4Are respectively a switch tube S₁、S₂、S₃And S₄The drive signal of (1). In one switching period, eight switching modes can be divided, and an equivalent circuit of each mode is shown in fig. 3 to 10, and the working state of each mode is described in detail below.

Mode 1: at t₀At any moment, switch tube S₁Start to conduct, in this mode, the switching tube S₁And S₃Conduction, S₂And S₄Turn-off, diode D₂On, the current flows as shown in FIG. 3, and the voltage across the switched capacitor Cr is positive, starting to control C_rCharging is carried out, C_rAnd L_rCarry out resonance, C_rThe voltage across the terminals begins to rise after half a resonant period, i.e. t₁At the moment, S flows₁And S₃The current of (1) falls to zero, this mode ends, S₁And S₃The zero current turn-off of (2) creates conditions. In the process, half of the energy is transferred to the output capacitor C₀₂And half of the energy in the corresponding LED string to be driven is stored in the switched capacitor C_rIn (1).

Mode 2: as shown in connection with fig. 4, at t₁At all times, flows through the switch tube S₁And S₃Is reduced to zero, at which time the output capacitor C is₀₁And C₀₂Respectively providing energy for the two strings of LEDs to be driven.

Modality 3: as shown in connection with fig. 5, at t₂At any moment, switch tube S₂Is conducted, in this mode, the switching tube S₂And S₃Conduction, S₁And S₄Turn off and store in the switched capacitor C_rEnergy in to the output capacitor C₀₁And supplying power to the corresponding LED strings to be driven. Another string of LEDs to be driven is composed of an output capacitor C₀₂Providing energy.

Modality 4: as shown in connection with fig. 6, at t₃At all times, flows through the switch tube S₂And S₃Is reduced to zero, at which time the output capacitor C is₀₁And C₀₂Respectively providing energy for the two strings of LEDs to be driven.

Mode 5: as shown in connection with fig. 7, at t₄At any moment, switch tube S₄Start to conduct, in this mode, the switching tube S₂And S₄Conduction, S₁And S₃Turn-off, diode D₂On, the current flows as shown in FIG. 7, and the voltage across the switched capacitor Cr is positive, starting to control C_rCharging is carried out, C_rAnd L_rCarry out resonance, C_rThe voltage across the terminals begins to rise after half a resonant period, i.e.t₁At the moment, S flows₁And S₃The current of (1) falls to zero, this mode ends, S₁And S₃The zero current turn-off of (2) creates conditions. In the process, half of the energy is transferred to the output capacitor C₀₂And half of the energy in the corresponding LED string to be driven is stored in the switched capacitor C_rIn (1).

Modality 6: as shown in connection with fig. 8, at t₃At all times, flows through the switch tube S₂And S₄Is reduced to zero, at which time the output capacitor C is₀₁And C₀₂Respectively providing energy for the two strings of LEDs to be driven.

Modality 7: as shown in fig. 9, this modality is the same as modality 3, and will not be described herein.

Modality 8: as shown in fig. 10, this modality is the same as modality 4, and will not be described herein.

As an example, all the switch transistors are NMOS transistors as shown in fig. 1.

In order to verify the effect and the theoretical correctness of the invention, a 130KHz/16W prototype is made. The main system parameters of the driver are shown in table 1, wherein the driver chip is Si8273, the control chip is TMS320F28027, and the indexes are as follows:

(1) input voltage: direct current 100V;

(2) output voltage: direct current 25V;

(3) output power: rated power is 16.3W;

(4) rated operating frequency: 130 KHz;

(5) efficiency: rated operating condition 92.64%;

TABLE 1 System parameters

Fig. 11 shows a driving simulation waveform diagram based on PSIM, and it can be seen that, in a given driving mode, the midpoint voltage of the stacked bridge is a square wave, the amplitude of the square wave is half of the input voltage, and the frequency of the square wave is twice of the switching frequency, so that the purpose of frequency doubling is achieved.

FIG. 12The PSIM-based switched capacitor voltage and current simulation oscillogram is provided, and can be seen in the buffer inductor L_rUnder the action of the switch capacitor, soft charging is realized.

Fig. 13 shows a waveform diagram of driving and current simulation of the switching tube based on PSIM, and it can be seen that ZCS is realized by four switching tubes, so that switching loss is reduced.

Fig. 14 shows experimental waveform diagrams of voltage and current prototype of the channel 1 and the channel 2, and it can be seen that the current mean values of the two channels are equal, and self-current sharing is realized.

FIG. 15 shows a waveform of a voltage-current prototype of a switched capacitor, which can be seen in the snubber inductor L_rUnder the action of the switch capacitor, soft charging is realized.

FIG. 16 shows a switching tube S₁，S₂The driving and resonant capacitor current experiment oscillogram shows that the switch tube S₁，S₂ZCS is achieved and switching losses are reduced.

FIG. 17 shows a switching tube S₃，S₄The driving and resonant capacitor current experiment oscillogram shows that the switch tube S₃，S₄ZCS is achieved and switching losses are reduced.

Fig. 18 shows the efficiency curves at different output powers, with the highest efficiency reaching 92.64%.

Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.

Claims (2)

1. A two-channel LED driver based on a resonant switched capacitor is characterized by comprising two half bridgesCircuit and input capacitor C_in1An input capacitor C_in2And a switch capacitor C_rBuffer inductor L_rDiode D₁Diode D₂An output capacitor C₀₁And an output capacitor C₀₂，

The two half-bridge circuits form a stack bridge and a power supply V_inConnected in parallel with an input capacitor C of one of the half-bridge circuits_in1Another half-bridge circuit connected in parallel with input capacitor C_in2；

The leading-out wires of the connection points of the two bridge arms of the half-bridge circuit are connected with a switched capacitor C_rOne terminal of (1), switch capacitor C_rThe other end of the buffer inductor L is connected with_rOne end of (1), buffer inductance L_rAnother end of the diode D₁While connecting the diode D₂The anode of (1);

leading-out wires of the connection points of the two bridge arms of the other half-bridge circuit are grounded;

diode D₁One path of LED to be driven is connected between the anode and the grounding point; diode D₂The other path of LED to be driven is connected between the cathode of the LED and the grounding point; one path of LED to be driven and output capacitor C₀₁Parallel connection, another path of LED to be driven and output capacitor C₀₂Parallel connection;

the driving signals of the two half-bridge circuits enable two bridge arms of each half-bridge circuit to be in complementary conduction, and a dead zone exists between the complementary conduction;

the half-bridge circuit comprises a switching tube S₁And a switching tube S₂The other half-bridge circuit comprises a switching tube S₃And a switching tube S₄(ii) a Switch tube S₁Duty ratio of 0.25, switching tube S₃Is 0.75, switching tube S₁And a switching tube S₃There is a phase difference of 180 °.

2. The resonant switched-capacitor based two-channel LED driver of claim 1,

all the switch tubes are NMOS tubes.

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