KR101026392B1 - Led lighting drive circuit and method for compensating current error between a rows thereof - Google Patents

Abstract

PURPOSE: An LED driving circuit and a method for compensating current errors are provided to improve reliability of an LED lamp by compensating, controlling, and sensing the current errors. CONSTITUTION: A half-bridge inverter(10) converts input DC power into AC power. A first transformer(20) outputs the boosted or dropped AC power after the AC power is boosted or dropped. An electric wave rectifying unit(30) full wave-rectifies the AC power. An LED unit(40) includes a plurality of LEDs which are connected in parallel to be turned on with the DC power. A second transformer(50) transforms the supplied current into the voltage and outputs the sensed voltage. A feedback unit(60) compares the sensed voltage with a reference voltage and outputs the comparison result signal.

Description

LED LIGHTING DRIVE CIRCUIT AND LED LID HEAT COMPENSATION METHOD {LED LIGHTING DRIVE CIRCUIT AND METHOD FOR COMPENSATING CURRENT ERROR BETWEEN A ROWS THEREOF}

The present invention relates to an LED lighting driving circuit and a method for compensating LED hot current errors thereof, and more particularly, to an LED lighting driving circuit and a LED hot LED that compensate for a current error between LED columns due to a difference in LED voltage and current characteristics. The present invention relates to a current error compensation method.

In general, one LED element has a small capacity, and thus LEDs are connected in series and in parallel to emit a lot of light. Thus, when LEDs are used in parallel or in parallel, current errors occur for each LED column due to characteristic errors in voltage and current between the LEDs. The current error between the columns causes non-uniform distribution of heat between the LED rows, thereby reducing the reliability of the entire LED luminaire and preventing the uniformity of light of the LED luminaires.

Thus, the following techniques have been proposed in order to compensate for current errors.

1 to 3 is a configuration diagram showing a LED lighting driving circuit for compensating the conventional current error.

1 to 3, the conventional LED lighting driving circuit uses a linear regulator or a switching regulator in each column after inputting the DC voltage as shown in FIGS. 1 and 2 to compensate for the current error, or as shown in FIG. 3. The direct current balance transformer is connected directly to the LED row.

However, the method as shown in FIG. 1 using the linear regulator in each column takes voltage across both ends of the regulator by the voltage difference between the LED columns, resulting in a very poor efficiency, and does not correct an error in resistance for current sensing.

In the case of FIG. 2 using a switching regulator for each column, a configuration for configuring the switching regulator is complicated and an error of current due to an error of a sensing resistor occurs, especially when a small current flows through the LED.

In the case of using the current balanced transformer directly in the LED column and the input voltage in the form of square wave AC, as shown in FIG. 3, the LED conducts only a half cycle of the AC voltage. There is a high risk that the device is damaged by the reverse peak voltage of.

The present invention has been made in view of the above problems, to provide a LED lighting driving circuit and a LED hot current error compensation method for improving the reliability and quality of the overall LED lighting by compensating the hot current error. There is this.

Another object of the present invention is to provide an LED lighting driving circuit and a method for compensating LED hot current errors thereof, which can reduce hot current errors in a series-parallel connection of LEDs.

The objects of the present invention are not limited to the above-mentioned objects, and other objects which are not mentioned will be clearly understood by those skilled in the art from the following description.

LED lighting driving circuit according to an aspect of the present invention for achieving the above object, the half-bridge inverter is switched by the switching control signal to convert the input DC power to AC power; A first transformer for boosting or stepping down the AC power; A full-wave rectifying unit having a structure in which at least two columns each having a parallel structure are provided, the full-wave rectifying unit for full-wave rectifying AC power input from the first transformer to the LED units provided in each row; An LED unit having a parallel structure so as to be turned on by the DC power supply of the full-wave rectifying unit, and having a plurality of LEDs connected in series for at least two columns; When AC current by AC power supplied to each column flows to either the primary side or the secondary side of the second transformer, which is a current balancing transformer, the current supply principle makes the same as the other current, and then supplies the whole supply. A second transformer converting the current into a voltage and outputting the sensed voltage; And a feedback unit for comparing an error between the voltage sensed by the second transformer and the reference voltage and feeding back a switching control signal corresponding to the error according to the comparison result to the half bridge inverter.

Preferably, the feedback unit, the rectifier circuit for rectifying the AC voltage sensed by the second transformer to a DC voltage; An error amplifier configured to calculate an error between the rectified DC voltage and the reference voltage and to amplify an error signal corresponding to the calculated error; And a half bridge inverter controller configured to output a switching control signal to the half bridge inverter in consideration of an error signal.

Preferably, the feedback unit further includes a photo coupler for receiving an error signal from the error amplifier and transmitting the received error signal to a half bridge inverter controller.

Preferably, in the second transformer, windings of the primary side and the secondary side are wound with the same number of turns in opposite directions.

Preferably, the AC voltage of the half bridge inverter is adjusted by the resonance curve and the switching frequency of the resonance filter.

Preferably, the second transformer takes an average value of the currents on the primary side and the secondary side so that the currents on the primary side and the secondary side are equal.

LED hot current error compensation method of the LED lighting driving circuit according to another aspect of the present invention, in the hot current error compensation method of the LED lighting driving circuit described above, the half-bridge inverter is the AC power supply according to the initial DC frequency And converting the converted AC power into a full-wave rectifying unit which is transformed by the first transformer and provided in at least two columns having a parallel structure, and converted into DC power; LED unit provided in each column corresponding to the full-wave rectifying unit operating by receiving a full-wave rectified DC power from the full-wave rectifying unit; When the AC current by the AC power supplied to each column flows to either the primary side or the secondary side of the second transformer, the second transformer is made to have the same size as the current on the other side by the current balancing principle, Converting a current into a voltage to output a sensed AC voltage; And the feedback unit rectifies the sensed AC voltage into a DC voltage, compares an error with the reference voltage, and feeds back the switching control signal according to the comparison result to the half bridge inverter, and switches according to the switching control signal fed back by the half bridge inverter. Operating to output an AC power source.

Preferably, when an error occurs, the feedback unit determines that an error has occurred and outputs a switching control signal corresponding to the error occurrence.

The present invention by the above-described problem solving means to minimize the current error between the LED heat to flow a uniform current, evenly distribute the heat of the LED and evenly distributed light brightness to improve the reliability and quality of the LED lighting It can be effective.

1 to 3 is a block diagram showing a LED lighting driving circuit for compensating the conventional current error.
4 is a configuration diagram of an LED lighting driving circuit according to an embodiment of the present invention.
FIG. 5 is a configuration diagram showing a circuit of a half bridge inverter in FIG. 4. FIG.
FIG. 6 is a diagram for explaining a full wave rectifying portion and an LED portion in FIG. 4. FIG.
7 is a view for explaining the operation of the second transformer in FIG.
8 shows an equivalent circuit of the circuit of FIG.
FIG. 9 is an exemplary diagram for explaining a second transformer in FIG. 4; FIG.
FIG. 10 shows an equivalent circuit for one column of the equivalent circuit of FIG. 8. FIG.
FIG. 11 is a diagram for explaining a feedback section in FIG. 4; FIG.
FIG. 12 is an exemplary view illustrating an example in which a second transformer is extended to cascade in FIG. 4. FIG.
13 is a flowchart illustrating a method for compensating LED hot current error of an LED lighting driving circuit according to an exemplary embodiment of the present invention.

In the following description, specific details of the LED lighting driving circuit of the present invention are shown to provide a more general understanding of the present invention, but it is understood that the present invention can be easily carried out without these specific details and also by modification thereof. It will be apparent to those of ordinary skill in the art.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail, focusing on the parts necessary to understand the operation and action according to the present invention.

4 is a configuration diagram of the LED lighting driving circuit according to an embodiment of the present invention.

Referring to FIG. 4, the LED lighting driving circuit according to the present invention includes a half bridge inverter 10, a first transformer 20, a full wave rectifying unit 30, an LED unit 40, and a second transformer 50. ), The feedback unit 60 and the like.

First, the half-bridge inverter 10 receives a source power of DC and switches by a switching control signal to output AC power. At this time, the size of the AC power is controlled by the resonant curve and the switching frequency of the resonant filter.

The first transformer 20 receives AC power from the half-bridge inverter 10 to the primary side and boosts or steps down the AC voltage at a predetermined ratio and outputs the AC power to the secondary side.

The full-wave rectifying unit 30 has a structure in which each one is provided in at least two columns having a parallel structure, and full-wave rectified AC power input from the first transformer 20 to the LED unit 40 provided in each row. .

The LED unit 40 has a structure in which a plurality of LEDs are connected in series to each column so as to receive a full-wave rectified power from the full-wave rectifying unit 30 respectively provided in at least two columns having a parallel structure. Here, the operation between the columns of the LED unit 40 will be described in detail below.

When the second transformer 50 flows to either the primary side or the secondary side of the second transformer 50, which is a current balancing transformer, when the AC current by the AC power supplied to each column flows, the current on the other side is changed by the current balancing principle. After the size and the same as, after converting the total supplied current to the voltage and outputs the sensed voltage. Here, in the second transformer 50, windings of the primary side and the secondary side are wound with the same number of turns in opposite directions. Detailed description of the second transformer 50 will be described later.

The feedback unit 60 is provided with a rectifier circuit 61, an error amplifier 63, a photo coupler 65 and a half bridge inverter controller 67, and the voltage sensed by the second transformer 50 and the reference The error with the voltage is compared, and the switching control signal corresponding to the error according to the comparison result is fed back to the half bridge inverter 10. Here, the rectifier circuit 61 rectifies the AC voltage sensed by the second transformer 50 to a DC voltage. The error amplifier 63 calculates an error between the rectified DC voltage and the reference voltage, and after amplifying the error signal corresponding to the calculated error to the photo coupler 65 after constant amplification, the photo coupler 65 receives the error. The signal is transmitted to the half bridge inverter controller 67 to finally feed back a switching control signal corresponding to the error signal to the half bridge inverter 10. Detailed description thereof will be described later.

Referring to Figure 4 describes the operation and operation of the LED lighting driving circuit according to the present invention.

The half bridge inverter 10 receives a source power of DC and is converted into AC power by a switching operation by a switching control signal. At this time, the size of the AC power is controlled by the resonant curve and the switching frequency of the resonant filter.

The converted AC power supplies AC power to the full-wave rectifier 30 provided in each of at least two columns having a parallel structure. Then, the full-wave rectifying unit 30 provided in each column is supplied to the LED unit 40 after full-wave rectifying the AC power. The AC current by the AC power supplied to each column flows to either the primary side or the secondary side of the second transformer 50, which is a current balancing transformer, but the same as the other current due to the current balancing principle.

Thereafter, the second transformer 50 converts the total current supplied from the final stage into a voltage and outputs the sensed voltage to the error amplifier 63. Here, the rectifier circuit 61 is provided between the second transformer 50 and the error amplifier 63 before the voltage sensed by the error amplifier 63 is input. Thus, the rectifier circuit 61 converts the sensed voltage of the second transformer 50 into a DC voltage, senses an average value, and outputs the average value to the error amplifier 62.

Thereafter, the error amplifier 63 compares an error value between the sensed voltage received from the second transformer 50 and the reference voltage, and halves the error signal corresponding to the error generated as a result of the comparison through the photo coupler 65. Transfer to the bridge inverter controller 67.

Accordingly, the half bridge inverter controller 67 transmits a switching control signal corresponding to the half bridge inverter 10 so that the switching frequency of the half bridge inverter 10 can be changed in consideration of an error generated through the received error signal. To send.

As a result, the half bridge inverter 10 may supply a current corresponding to the switching frequency signal to the first transformer 20 side. Here, the current supplied to the first transformer 20 is adjusted in size by the changed switching frequency signal and the resonance filter so that a desired current can be supplied.

FIG. 5 is a configuration diagram illustrating a circuit of a half bridge inverter in FIG. 4.

Referring to FIG. 5, the half-bridge inverter 10 according to the present invention is an LLC resonant half-bridge inverter, and has a resonant filter such as 'A', and the switches SW1 and SW2 alternately switch with each other. The operation allows AC power to be output to the final output terminal Vout on the secondary side of the first transformer 20. At this time, as shown in Figure 5 it can be seen through the above description that the signal input to the switch SW1, SW2 is a switching control signal.

FIG. 6 is a diagram for explaining a full wave rectifying unit and an LED unit in FIG. 4.

Referring to FIG. 6, the full wave rectifying unit 30 and the LED unit 40 are illustrated. In general, since the switching frequency is high, the diodes D1_1, D1_2, D1_3 and D1_4 of the full wave rectifying unit 30 use FastRecovery or Shottkey diodes. .

The high switching frequency also allows capacitor C1 to use small values.

Since AC power is input, a current flows through D1_1 and D1_4 when the voltage is positive, and a current flows through D1_3 and D1_2 when the voltage is negative, which is smoothed through the capacitor C1 to provide a DC current to the LED unit 40. Will flow.

Next, the second transformer 50 of the current balance transformer will be described.

7 is a view for explaining the operation of the second transformer in FIG. In FIG. 7, only two columns are shown as the LED unit 40 to help understanding of the present invention.

Referring to FIG. 7, when the full-wave rectifying unit 30 and the LED unit 40 are represented by equivalent resistance, the same as that of FIG. 8, and the error of the current between the columns of the LED unit 40 is because the values of the equivalent resistance are different from each other. , A hot error means a situation where i1 and i2 of FIG. 7 are different.

That is, when there is no second transformer 50, Req1 and Req2 are different due to the LED characteristic error, i1 and i2 are different.

Operation of the second transformer 50 may be described semantically as shown in FIG. 9.

As shown in FIG. 9, since the windings of the second transformer 50 are wound in opposite directions, the direction of the magnetic flux generated by the current flowing in the primary and secondary sides of the second transformer 50 is reversed. do.

First, when the amount of current flowing in the primary and secondary is the same, the magnetic flux is equal to each other and the magnetic flux is canceled and eventually the second transformer 50 is operated as if there is no.

If the primary current is larger than the secondary side current, the magnetic flux on the primary side, which has a large amount of current, is transferred to the secondary side, so that the current on the primary side decreases, and the current on the secondary side increases, so that the primary and secondary currents increase. Equilibrium is achieved.

As shown in FIG. 10, the equivalent equation is again shown in one column in order to show how to equilibrate as an actual equation.

L1 and L2 of FIG. 8 represent inductances of the primary side and the secondary side, which are expressed as follows.

In Equation 1, M denotes mutual inductance of the second transformer, i1 denotes a current flowing in the primary side of the second transformer, and i2 denotes a current flowing in the secondary side of the second transformer.

At this time, if it is assumed that the leakage inductance is '0', mutual inductance M is equal to L1. If the number of turns of L1 and L2 is the same, L1 = L2 = M, and thus can be expressed as Equation 2 below.

After obtaining the equations on the secondary side, two equations are expressed as the following equation (3).

That is, if Req1 and Req2 are the same, the ratio of the current becomes 1, and if Req1 and Req2 are much larger than jwL, the ratio of the two currents approaches 1 regardless of the difference between Req1 and Req2.

FIG. 11 is a diagram for explaining a feedback unit in FIG. 4.

Referring to FIG. 11, the feedback unit 60 includes a rectifier circuit 61, an error amplifier 63, a photo coupler 65, and a half bridge inverter controller 67.

 When AC current flows through the LED unit 40, the sensing is sensed by the value of the voltage by Rsense.

Thereafter, the rectifier circuit 61 converts the DC voltage to sense an average value. This is input to the error amplifier 63, an error signal corresponding to the error generated in comparison with the reference voltage is input to the half-bridge inverter controller 67 through the photo coupler 65.

Then, the half bridge inverter controller 67 outputs the switching control signal corresponding to the error to the half bridge inverter 10 by the input error signal.

That is, the half bridge inverter controller 67 controls to change the switching frequency of the half bridge inverter 10 until the sensed voltage is equal to the reference voltage.

On the other hand, when the heat of the LED unit 40 increases, the second transformer 50 can be extended to the cascade connection as shown in FIG.

13 is a flowchart illustrating a method for compensating LED hot current error in an LED lighting driving circuit according to an exemplary embodiment of the present invention. LED hot current error compensation method of the LED lighting driving circuit according to Figure 13 should have the configuration of the LED lighting driving circuit described above.

Referring to FIG. 13, first, DC power is supplied to the half bridge inverter 10 (S1301), and the inverter is switched to an initially set frequency (S1303).

Thereafter, the half bridge inverter 10 converts the DC power to AC power (S1305), and outputs the AC power according to the gain determined by the resonant filter according to the initially set frequency to the primary side of the first transformer 20. (S1307).

Then, the first transformer 20 boosts and steps down the AC voltage input to the primary side at a specific ratio and outputs the secondary side (S1309), and the secondary voltage of the outputted first transformer 20 has at least a parallel structure. Input to the full-wave rectifier 30 provided in each of the two or more columns is converted into a DC power supply (S1311).

Accordingly, the LED unit 40 provided in each column corresponding to the full wave rectifying unit 30 is turned on by receiving the full-wave rectified DC power from the full wave rectifying unit 30 (S1313).

At this time, when the AC current by the AC power supplied to each heat flows to either the primary side or the secondary side of the second transformer 50, the second transformer 50 is the current and magnitude of the other side by the current balance principle. After the E is equal to, the total supplied current is converted into a voltage to output the sensed AC voltage (S1315). That is, the second transformer 50 takes an average value of currents on the primary side and the secondary side of the second transformer 50 so that the currents on the primary side and the secondary side are equal.

Thereafter, the feedback unit 60 rectifies the sensed AC voltage into a DC voltage (S1317), compares the error between the rectified DC voltage and the reference voltage, and converts the switching control signal according to the comparison result into the half bridge inverter 10. (S1319). That is, when an error occurs, the feedback unit 60 determines that an error has occurred and outputs a switching control signal corresponding to the error generation to the half bridge inverter 10.

As a result, the half bridge inverter 10 outputs AC power by switching according to the switching control signal fed back (S1321).

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

Claims (6)

A half bridge inverter switched by a switching control signal to convert an input DC power source into an AC power source;
A first transformer for boosting or stepping down the AC power;
A full-wave rectifying unit having a structure in which at least two columns each having a parallel structure are provided, the full-wave rectifying unit for full-wave rectifying AC power input from the first transformer to the LED units provided in each row;
An LED unit having a parallel structure so as to be turned on by the DC power supply of the full-wave rectifying unit, and having a plurality of LEDs connected in series for at least two columns;
When the current by the AC power supplied to each column flows to either the primary side or the secondary side, the current on the primary side and the secondary side are made equal by the current balancing principle, and then the entire supplied current is converted into voltage and sensed. A second transformer for outputting a voltage; And
A feedback unit for comparing an error between the voltage sensed by the second transformer and the reference voltage and feeding back a switching control signal corresponding to the error according to the comparison result to the half bridge inverter,
AC voltage of the half-bridge inverter is controlled by the resonance curve and the switching frequency of the resonant filter LED lighting drive circuit.
The method of claim 1, wherein the second transformer,
An LED lighting driving circuit, wherein the windings of the primary side and the secondary side are wound with the same number of turns in opposite directions.
delete The method of claim 1, wherein the second transformer,
An LED lighting driving circuit comprising the average of the currents on the primary side and the secondary side so that the currents on the primary side and the secondary side are equal.
In the method of compensating for the hot current error of the LED lighting driving circuit according to any one of claims 1, 2 or 4,
The half-bridge inverter converts the input DC power into AC power according to the initially set frequency, and the converted AC power is transformed by the first transformer and input to a full-wave rectifier provided in at least two columns of parallel structure, respectively. Transforming;
LED unit provided in each column corresponding to the full-wave rectifying unit operating by receiving a full-wave rectified DC power from the full-wave rectifying unit;
When the AC current by the AC power supplied to each column flows to either the primary side or the secondary side of the second transformer, the second transformer is made to have the same size as the current on the other side by the current balancing principle, Converting a current into a voltage to output a sensed AC voltage; And
The feedback unit rectifies the sensed AC voltage into a DC voltage, compares an error with a reference voltage, and feeds back a switching control signal according to the comparison result to the half bridge inverter, thereby switching according to the switching control signal fed back by the half bridge inverter. Outputting AC power,
AC voltage converted by the half-bridge inverter, the LED hot current error compensation method of the LED lighting drive circuit, characterized in that it is adjusted by the resonant curve and the switching frequency of the resonance filter.
The method of claim 5, wherein the feedback unit determines that an error has occurred and outputs a switching control signal corresponding to the occurrence of an error when an error occurs.

Images