CN103118460B - Novel multi-path LED passive current-equalizing circuit and LED driving power source - Google Patents

Abstract

The invention relates to a novel multi-channel LED passive current equalizing circuit, including an LLC converter, characterized in that the LLC converter has first and second secondary side windings and first and second output current equalizing circuits, which can Realize four-way LED string current-sharing output; the proposed four-way passive current-sharing output strategy based on LLC converter can be expanded to any 2N-way current-sharing output at different output voltages, with simple circuit and good current-sharing effect, etc. advantage. The present invention further provides an LED driving power supply using the above-mentioned multi-channel LED passive current sharing circuit.

Description

A new multi-channel LED passive current sharing circuit and LED drive power supply

technical field

The invention relates to the technical field of LED current sharing, in particular to a novel multi-channel LED passive current sharing circuit and an LED driving power supply using the current sharing circuit. the

Background technique

In recent years, the current situation of energy shortage has made human beings increasingly aware of the importance of energy conservation and emission reduction. As a new type of lighting source, LED has the advantages of long life, energy saving and environmental protection, so it will definitely occupy a place in the future lighting field, and efficient and reliable LED driving power is the key to the rapid development of LED lighting. the

In practical applications, high-power LEDs often require the use of multiple LEDs in parallel. However, the different V-I characteristics of LEDs in different branches will lead to uneven currents. Therefore, it is necessary to study the current sharing strategy for multiple outputs. the

Contents of the invention

In view of the shortcomings of the existing passive current sharing strategy, such as poor current sharing accuracy in the case of more than four outputs or large circuit volume and loss due to the use of coupled inductors, the present invention proposes a new passive current sharing strategy. The method of capacitive current sharing is applied to the occasion of multiple outputs. the

The present invention adopts the following scheme to realize: a novel multi-channel LED passive current equalizing circuit, comprising an LLC converter, characterized in that the LLC converter has first and second secondary side windings and first and second sets of output equalizers stream circuit;

The first set of output current sharing circuits includes a first current sharing capacitor, the first end of the first current sharing capacitor is connected to the first output end of the first secondary winding, and the second end is connected to the first diode The anode of the first diode is connected to the cathode of the third diode, and the cathode of the first diode is connected to the anode of the first LED light string; the second output terminal of the first secondary winding is connected to the second output of the second diode The positive pole is connected to the negative pole of the fourth diode, the negative pole of the second diode is connected to the positive pole of the second LED light string; the negative pole of the first and second LED light strings is connected to the positive pole of the third diode , one end of the first capacitor and one end of the second capacitor are connected; the other end of the first capacitor is connected to the cathode of the first diode; the other end of the second capacitor is connected to the second diode negative connection of

The second set of output current sharing circuits includes a second current sharing capacitor, the first end of the second current sharing capacitor is connected to the first output end of the second secondary winding, and the second end is connected to the fifth diode The anode of the fifth diode is connected to the cathode of the seventh diode; the cathode of the fifth diode is connected to the anode of the third LED light string; the second output terminal of the second secondary winding is connected to the sixth diode The positive pole of the eighth diode is connected to the negative pole of the eighth diode; the negative pole of the sixth diode is connected to the positive pole of the fourth LED light string; the negative pole of the third LED light string is connected to one end of a third current sharing capacitor and the anode of the fourth diode; the cathode of the fourth LED light string is connected to the anode of the seventh diode, the anode of the eighth diode, the other end of the third current sharing capacitor, the third The anode of the diode is connected to one end of the third capacitor; the other end of the third capacitor is connected to the cathode of the fifth diode; one end of the fourth capacitor is connected to the cathode of the sixth diode, The other end is connected to the anode of the eighth diode.

In one embodiment of the present invention, it further includes a third secondary winding, a third set of output current sharing circuits, and a fourth current sharing capacitor; the fourth current sharing capacitor is arranged between the negative terminal of the fourth LED light string and the Between the anodes of the eighth diode; the third output current sharing circuit includes a fifth current sharing capacitor, the first end of the fifth current sharing capacitor is connected to the first output of the third secondary winding The second end is connected to the anode of the ninth diode and the cathode of the eleventh diode, and the cathode of the ninth diode is connected to the anode of the fifth LED light string; the third secondary side The second output end of the winding is connected to the anode of the tenth diode and the cathode of the twelfth diode, and the cathode of the tenth diode is connected to the anode of the sixth LED light string; the fifth, The negative terminals of the six LED light strings are connected to the anode of the twelfth diode, one end of the fifth capacitor, and one end of the sixth capacitor; the other end of the fifth capacitor is connected to the negative electrode of the ninth diode; The other end of the sixth capacitor is connected to the cathode of the tenth diode; the anode of the eleventh diode is connected to the cathode of the fourth LED light string. the

In an embodiment of the present invention, the secondary winding and the output current sharing circuit connected thereto can be expanded into 2N output current sharing circuits, where N is a natural number not less than 1. the

The present invention also provides an LED driving power supply adopting the above-mentioned multi-channel LED passive current equalizing circuit, which is characterized in that it includes: a sampling resistor connected in series with the negative terminal of the first LED light string, used To collect the operating current of the LED light string; the operating current is sent to an LLC control circuit through a voltage comparison and photoelectric isolation circuit, and the LLC control circuit controls the LLC conversion according to the comparison result of the voltage comparison and photoelectric isolation circuit machine work. the

In one embodiment of the present invention, it further includes a third secondary winding, a third set of output current sharing circuits, and a fourth current sharing capacitor; the fourth current sharing capacitor is arranged between the negative terminal of the fourth LED light string and the Between the anodes of the eighth diode; the third output current sharing circuit includes a fifth current sharing capacitor, the first end of the fifth current sharing capacitor is connected to the first output of the third secondary winding The second end is connected to the anode of the ninth diode and the cathode of the eleventh diode, and the cathode of the ninth diode is connected to the anode of the fifth LED light string; the third secondary side The second output end of the winding is connected to the anode of the tenth diode and the cathode of the twelfth diode, and the cathode of the tenth diode is connected to the anode of the sixth LED light string; the fifth, The negative terminals of the six LED light strings are connected to the anode of the twelfth diode, one end of the fifth capacitor, and one end of the sixth capacitor; the other end of the fifth capacitor is connected to the negative electrode of the ninth diode; The other end of the sixth capacitor is connected to the cathode of the tenth diode; the anode of the eleventh diode is connected to the cathode of the fourth LED light string. the

In an embodiment of the present invention, the secondary winding and the output current sharing circuit connected thereto can be expanded into 2N output current sharing circuits, where N is a natural number not less than 1. the

The invention utilizes the current equalizing capacitor to realize the current equalizing output of any 2N channels with different output voltages, and has the advantages of simple circuit, good current equalizing effect and the like. the

Description of drawings

Fig. 1 is a schematic diagram of circuit connection of an embodiment of the present invention. the

Fig. 2 is a schematic diagram of circuit connection of another embodiment of the present invention. the

Figures 3 to 6 are LLC resonant converters in Time conduction diagram.

Figure 7 to Figure 8 are the equivalent circuits of the converter operation. the

Fig. 9 is a schematic circuit diagram of a prototype of a four-way output LED driving power supply according to an embodiment of the present invention. the

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. the

As shown in Figure 1, this embodiment provides a new type of multi-channel LED passive current sharing circuit, including an LLC converter, which is characterized in that: the LLC converter has first and second secondary windings and first and second Group output current sharing circuit;

The first set of output current sharing circuits includes a first current sharing capacitor, the first end of the first current sharing capacitor is connected to the first output end of the first secondary winding, and the second end is connected to the first diode The anode of the first diode is connected to the cathode of the third diode, and the cathode of the first diode is connected to the anode of the first LED light string; the second output terminal of the first secondary winding is connected to the second output of the second diode The positive pole is connected to the negative pole of the fourth diode, the negative pole of the second diode is connected to the positive pole of the second LED light string; the negative pole of the first and second LED light strings is connected to the positive pole of the third diode , one end of the first capacitor and one end of the second capacitor are connected; the other end of the first capacitor is connected to the cathode of the first diode; the other end of the second capacitor is connected to the second diode negative connection of

The second set of output current sharing circuits includes a second current sharing capacitor, the first end of the second current sharing capacitor is connected to the first output end of the second secondary winding, and the second end is connected to the fifth diode The anode of the fifth diode is connected to the cathode of the seventh diode; the cathode of the fifth diode is connected to the anode of the third LED light string; the second output terminal of the second secondary winding is connected to the sixth diode The positive pole of the eighth diode is connected to the negative pole of the eighth diode; the negative pole of the sixth diode is connected to the positive pole of the fourth LED light string; the negative pole of the third LED light string is connected to one end of a third current sharing capacitor and the anode of the fourth diode; the cathode of the fourth LED light string is connected to the anode of the seventh diode, the anode of the eighth diode, the other end of the third current sharing capacitor, the third The anode of the diode is connected to one end of the third capacitor; the other end of the third capacitor is connected to the cathode of the fifth diode; one end of the fourth capacitor is connected to the cathode of the sixth diode, The other end is connected to the anode of the eighth diode.

Please refer to Fig. 2, in an embodiment of the present invention, it also includes a third secondary winding, a third set of output current sharing circuits, and a fourth current sharing capacitor; the fourth current sharing capacitor is arranged on the fourth LED lamp Between the negative terminal of the string and the positive pole of the eighth diode; the third output current sharing circuit includes a fifth current sharing capacitor, the first end of the fifth current sharing capacitor is connected to the third secondary side The first output end of the winding is connected, the second end is connected with the anode of the ninth diode and the cathode of the eleventh diode, and the cathode of the ninth diode is connected with the anode end of the fifth LED light string; The second output end of the third secondary winding is connected to the anode of the tenth diode and the cathode of the twelfth diode, and the cathode of the tenth diode is connected to the anode of the sixth LED light string; The negative ends of the fifth and sixth LED light strings are connected to the anode of the twelfth diode, one end of the fifth capacitor, and one end of the sixth capacitor; the other end of the fifth capacitor is connected to the ninth diode The other end of the sixth capacitor is connected to the cathode of the tenth diode; the anode of the eleventh diode is connected to the cathode of the fourth LED light string. the

In an embodiment of the present invention, the secondary winding and the output current sharing circuit connected thereto can be expanded into 2N output current sharing circuits, where N is a natural number not less than 1. the

In order to allow those skilled in the art to better understand the present invention, the working principle of the entire circuit will be further described below. the

Please refer to Figure 1. Groups I and II in Figure 1 each have two LED light strings, which are four-output passive current sharing circuits. The circuit is mainly composed of 3 parts: the LLC resonant link on the primary side of the transformer; the two output circuits of group I and group II using capacitor current sharing; and a current sharing capacitor used to balance the load current of group I and group II . In this way, the circuit can realize the automatic current sharing of the four outputs with only 3 capacitors. Please refer to Figure 2. In the figure, the current sharing capacitor C _b3 is responsible for the output current sharing of the first group and the second group, and the current sharing capacitor C _b4 is responsible for the output current sharing of the second group and the third group. In this way, the passive current sharing method It can also be extended to any 2N output occasions.

Please continue to refer to Figure 1, the circuit can work in continuous mode or discontinuous mode: continuous mode means that the secondary side diodes of group I and group II have all the time and only one group is in the conduction state; discontinuous mode means There is a dead zone when the two groups of diodes on the secondary side of Group I and Group II are turned on in turn, that is, both groups of diodes are in the off state. the

When the circuit operating frequency is higher than the resonant frequency When , there is always only , And the current sharing capacitor on the secondary side participates in the resonance. In this way, a switching cycle can be divided into 8 stages of working process. The present invention only analyzes 4 stages in half a switching cycle, and the conduction schematic diagrams of each stage are shown in Fig. 3 to Fig. 6 . The specific work process is analyzed as follows:

See Figure 3, Phase 1 ( ): Suppose time switch network upper tube The voltage across the parasitic capacitance is the resonant current reverse charge to zero, while At this time, it is less than 0, so the flow through The parasitic diode, at this time Zero-voltage turn-on can be achieved; in this stage, the primary winding of the transformer is clamped by the load voltage, so Does not participate in resonance and excitation current under forward voltage gradually increases, while the resonant current then increases sinusoidally and Compare Large, so the rectifier diodes D1, D4, D5, D8 are turned on. time Increase to 0, at this time the circuit work enters stage 2.

See Figure 4, Phase 2 ( ): time Zero voltage turn on. During this phase the excitation current and resonant current continue to grow and > , so the rectifier diodes D1, D4, D5, and D8 continue to maintain the conduction state, Does not participate in resonance. time, shutdown, the circuit operation enters phase 3.

See Figure 5, Phase 3 ( ): at this stage , are all turned off. Resonant current to the tube The parasitic capacitance of the charge, but also to the down tube discharge of the parasitic capacitance, so start to get smaller, but Still greater than the excitation current , so the rectifier diodes D1, D4, D5, and D8 continue to maintain the conduction state, and the excitation inductance is still excited by the forward voltage. Continue to increase linearly. time, = , the circuit operation enters phase 4.

See Figure 6, Phase 4 ( ):exist Resonant current after time less than excitation current , so the rectifier diodes D2, D3, D6, and D7 start to conduct. In this stage, the primary winding of the transformer is clamped by the load voltage, and the clamping voltage is the polarity of upper negative and lower positive, so the exciting current linearly decreases but still greater than . time, The voltage across the parasitic capacitance becomes zero, and the circuit operation enters stage 5.

Due to the symmetry of the positive and negative half-cycle work of the LLC resonant converter, the working states of stages 5 to 8 are similar to those of stages 1 to 4, and will not be analyzed here. the

According to the above analysis, it can be seen that a voltage waveform in which a positive voltage and a negative voltage alternately appear on the secondary winding of the transformer. suppose in - During the time, the voltage of the secondary winding is forward voltage, as shown in Figure 7, the flow path of the current in group I is , D1, , , D4 then flows back to the power supply, the current Give charge, give Discharge; the flow path of current in group Ⅱ is , D5, , , D8 and then flow back, the current Give charge, load Give Charge. Therefore:

(1)

exist - During the time, when the secondary winding voltage is negative voltage, as shown in Figure 8, the current flow path in Group I is D2, , D3, back voltage source, current Give Discharge; the flow path of current in group II is D6, , D7, flow back again, the current Give discharge while the load Give Charge. Therefore:

(2)

Because the charge and discharge charge of the capacitor in a steady state is balanced in one cycle, so:

(3)

And the current of each load is:

(4)

From formula (4-1) - formula (4-4) can get,

Thus there are:

(5)

connected in series to the negative end of the first LED light string to collect the operating current of the LED light string; the operating current is sent to an LLC control circuit through a voltage comparison and photoelectric isolation circuit, and the LLC control circuit is based on the The comparison result of the voltage comparison and the photoelectric isolation circuit controls the operation of the LLC converter. Similarly, the multi-channel LED passive current sharing circuit in the LED driving power supply can be expanded to 2N channels.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention. the

Claims (2)

1. the passive flow equalizing circuit of novel LED multi-path, comprises LLC converter, it is characterized in that: described LLC converter has first and second secondary winding and first and second group output current-sharing circuit,

Described first group of output current-sharing circuit comprises the first current-sharing electric capacity, the first end of this first current-sharing electric capacity is connected with the first output of described the first secondary winding, the positive pole of the second end and the first diode, the 3rd diode cathode connects, the negative pole of described the first diode is connected with the positive terminal of a LED lamp string, the second output of described the first secondary winding and the positive pole of the second diode, the negative pole of the 4th diode connects, the negative pole of described the second diode is connected with the positive terminal of the 2nd LED lamp string, described first, the negative pole end of two LED lamp strings and the 3rd diode cathode, one end of the first electric capacity, one end of the second electric capacity connects, the other end of described the first electric capacity is connected with the negative pole of described the first diode, the other end of described the second electric capacity is connected with the negative pole of described the second diode,

Described second group of output current-sharing circuit comprises the second current-sharing electric capacity, the first end of this second current-sharing electric capacity is connected with the first output of described the second secondary winding, the positive pole of the second end and the 5th diode, the negative pole of the 7th diode connects, the negative pole of described the 5th diode is connected with the positive terminal of the 3rd LED lamp string, the second output of described the second secondary winding and the positive pole of the 6th diode, the negative pole of the 8th diode connects, the negative pole of described the 6th diode is connected with the 4th LED lamp string positive terminal, the negative pole end of described the 3rd LED lamp string connects one the 3rd one end of current-sharing electric capacity and the positive pole of described the 4th diode, described the 4th negative pole end of LED lamp string and the positive pole of described the 7th diode, the 8th diode cathode, the other end of the 3rd current-sharing electric capacity, one end of anodal and the 3rd electric capacity of the 3rd diode connects, the other end of described the 3rd electric capacity is connected with the negative pole of described the 5th diode, one end of the 4th electric capacity is connected with the negative pole of described the 6th diode, the other end is connected with the positive pole of described the 8th diode,

Also comprise the 3rd secondary winding, the 3rd group of output current-sharing circuit and the 4th current-sharing electric capacity, described the 4th current-sharing electric capacity is located between the negative pole end of described the 4th LED lamp string and the positive pole of described the 8th diode, described the 3rd group of output current-sharing circuit comprises the 5th current-sharing electric capacity, the first end of the 5th current-sharing electric capacity is connected with the first output of described the 3rd secondary winding, the positive pole of the second end and the 9th diode, the 11 diode cathode connects, the negative pole of described the 9th diode is connected with the positive terminal of the 5th LED lamp string, the second output of described the 3rd secondary winding and the positive pole of the tenth diode, the negative pole of the 12 diode connects, the negative pole of described the tenth diode is connected with the positive terminal of the 6th LED lamp string, the described the 5th, the negative pole end of six LED lamp strings and the 12 diode cathode, one end of the 5th electric capacity, one end of the 6th electric capacity connects, the other end of described the 5th electric capacity is connected with the negative pole of described the 9th diode, the other end of described the 6th electric capacity is connected with the negative pole of described the tenth diode, the positive pole of described the 11 diode is connected with the negative pole end of described the 4th LED lamp string,

Described secondary winding and the output current-sharing circuit of connection thereof can be expanded into the output current-sharing of 2N road, and wherein, N is not less than 1 natural number.

2. adopt a LED driving power for the passive flow equalizing circuit of LED multi-path claimed in claim 1, it is characterized in that: comprising: a sampling resistor, this sampling resistor is serially connected with the negative pole end of a described LED lamp string, in order to gather the operating current of LED lamp string; Described operating current through a voltage ratio and photoelectric isolating circuit send to a LLC control circuit, this LLC control circuit according to described voltage ratio compared with and the comparative result of photoelectric isolating circuit control the work of described LLC converter.