JP2010050336A - Power supply apparatus for light-emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the efficiency of operating a light-emitting element and reduce the possibility of flicker, even when a rectifier circuit output is supplied to a drive circuit in pulsating flow waveforms. <P>SOLUTION: The power supply apparatus for light-emitting elements includes: a group of light-emitting elements composed of a plurality of light-emitting elements serially connected, an AC power supply, a rectifier circuit that rectifies the output of the AC power supply for conversion into pulsating flow waveforms, and a drive circuit that drives the group of light-emitting elements by keeping the effective value of current flowing through the group of light-emitting elements constant using the output current of the rectifier circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power supply device for light emitting elements such as an LED (Light Emitting Diode) element and an EL (Electro Luminescence) element, and more particularly to a power supply apparatus compatible with AC input.

  In a power supply device for a light-emitting element that supports AC input, the output circuit of the AC power supply is rectified by a rectifier circuit, and the pulsating waveform output from the rectifier circuit is smoothed so that it becomes DC by an electrolytic capacitor using a smoothing circuit. In general, the light emitting element is driven.

  However, the power supply device having the above configuration requires a large-capacity electrolytic capacitor used for the smoothing circuit, and the large-capacity electrolytic capacitor is large and tall, and thus it is difficult to reduce the thickness and size of the power supply device. There was a problem.

  As a technique for solving this problem, for example, in Patent Document 1, the output of a rectifier circuit is supplied to a drive circuit with a substantially pulsating waveform without being converted into direct current by a smoothing circuit and flows to an LED element. A technique for driving an LED element by controlling current is disclosed.

According to the technique disclosed in Patent Document 1, since the LED element can be driven even if a capacitor having a small capacity is used in the smoothing circuit, the power supply device can be configured without an electrolytic capacitor, and thus the power supply device can be made thinner and smaller. It becomes possible.
JP 2006-147933 A

  However, in the technique disclosed in Patent Document 1, a plurality of LED element groups are connected in parallel, and the drive circuit is a switch connected to each of the plurality of LED element groups according to the voltage value of the pulsating waveform. Is used to control the current flowing in the LED element.

  Therefore, depending on the voltage value of the pulsating waveform, there are LED elements that are hardly used, and there is a problem that the usage efficiency of the LED elements is poor.

  Moreover, since the number of LED elements to light changes, there exists a subject that a flicker may generate | occur | produce.

  Therefore, an object of the present invention is to improve the use efficiency of the light emitting element and reduce the possibility of flickering even when the output of the rectifier circuit is supplied to the drive circuit as a pulsating current waveform. An object of the present invention is to provide a power supply device for a light emitting element that can be used.

In order to achieve the above object, a power supply device for a light-emitting element of the present invention comprises:
One light emitting element group formed by connecting a plurality of light emitting elements in series;
AC power supply,
A rectifier circuit that rectifies the output of the AC power source and converts it into a pulsating waveform;
And a drive circuit that drives the light emitting element group with a constant effective value of the current flowing through the light emitting element group using the output current of the rectifier circuit.

  According to the power supply device for a light-emitting element of the present invention, the output of the rectifier circuit is supplied to the drive circuit with a substantially pulsating waveform, and flows to a light-emitting element group formed by connecting a plurality of light-emitting elements in series by the drive circuit. The light emitting element group is driven with a constant current effective value.

  Therefore, there is no need to convert the output of the rectifier circuit into direct current using a large-capacitance electrolytic capacitor, so that the power supply device can be reduced in thickness and size.

  Further, when the light emitting element group is driven, all the light emitting elements constituting the light emitting element group are turned on, so that the use efficiency of the light emitting elements can be improved and the number of light emitting elements to be turned on is not changed. The effect that the possibility of flickering can be reduced is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the following description, the power supply device for a light emitting element of the present invention will be described by taking an example in which the light emitting element to be driven is an LED element. However, the present invention is not limited to this, and the light emitting element to be driven is not limited to this. The present invention can also be applied to an EL element.

  FIG. 1 is a block diagram showing a configuration of a power supply device according to an embodiment of the present invention.

  Referring to FIG. 1, the power supply device according to the present embodiment includes an LED element group 10, an AC power supply 20, a rectifier circuit 30, a smoothing circuit 40, and a drive circuit 50.

  The LED element group 10 is formed by connecting a plurality of LED elements in series.

  The rectifier circuit 30 rectifies the output of the AC power source 20 and converts it into a pulsating waveform.

  The smoothing circuit 40 includes a smoothing capacitor 41 that smoothes the output current of the rectifier circuit 30.

  The drive circuit 50 drives the LED element group 10 by using the output current of the rectifier circuit 30 to make the effective value of the current flowing through the LED element group 10 constant.

  In the present embodiment, the output of the rectifier circuit 30 is supplied to the drive circuit 50 with a substantially pulsating waveform, and the drive circuit 50 causes the effective current flowing in the LED element group 10 formed by connecting a plurality of light emitting elements in series. The LED element group 10 is driven with a constant value.

  Therefore, since the smoothing circuit 40 does not need to convert the output of the rectifier circuit 30 into direct current, it is not necessary to use a large-capacity electrolytic capacitor for the smoothing capacitor 41, and a ceramic capacitor having a small capacity can be used. Miniaturization is possible. The rectifier circuit 30 can also be reduced in size, and the drive circuit 50 can also be reduced in size, as will be described in detail later.

  Therefore, the power supply device can be reduced in thickness and size.

  Further, when the LED element group 10 is driven, since all the LED elements constituting the LED element group 10 are lit, the use efficiency of the LED elements can be improved, and the number of LED elements to be lit remains unchanged. Therefore, the possibility of flickering can be reduced.

  The life of the power supply device usually depends on the life of the electrolytic capacitor. However, since the electrolytic capacitor is not used, the life can be extended.

  Further, since the capacitor capacity of the smoothing circuit 40 can be reduced, the power factor can be improved.

Example 1
FIG. 2 is a block diagram illustrating the configuration of the power supply device according to the first embodiment of the present invention.

  Referring to FIG. 2, the power supply device of the present embodiment embodies the drive circuit 50 of FIG. 1, and other configurations are the same as those of FIG. 1.

  That is, the drive circuit 50 of this embodiment includes a choke coil 51, a diode 52, a FET (Field Effect Transistor) 53, a resistor 54, a constant current control circuit 55, and a capacitor 56.

  The choke coil 51 is an element connected in series with the LED element group 10.

  The diode 52 is connected in parallel with the LED element group 10 and the choke coil 51, and is an element for causing the current generated by the back electromotive force of the choke coil 51 to be superimposed on the output current of the rectifier circuit 30 and to flow to the LED element group 10. is there.

  The FET 53 is a switching element whose drain terminal is connected to a connection point between the choke coil 51 and the diode 52 and makes the choke coil 51 and the diode 52 conductive.

  The resistor 54 is an element that is connected to the source terminal of the FET 53 and detects a current flowing through the LED element group 10.

  The constant current control circuit 55 inputs and detects the current flowing through the resistor 54 to the CS terminal, and based on the detected current, the gate voltage applied from the GATE terminal so that the current flowing through the LED element group 10 is constant. Is a circuit for turning on / off the FET 53 by controlling.

  The capacitor 56 is an element that is connected in parallel with the LED element group 10 and in series with the choke coil 51, and smoothes the current flowing through the LED element group 10.

  Among the above components, the diode 52, the FET 53, the resistor 54, and the constant current control circuit 55 can be miniaturized, and the choke coil 51 can be miniaturized by increasing the switching frequency. Further, since the capacitor 56 may have a low withstand voltage, the size can be reduced.

  Therefore, the drive circuit 50 can be reduced in size.

  Here, in the power supply device of this embodiment shown in FIG. 2, the waveform of the output voltage of the rectifier circuit 30 (rectified voltage waveform) when the LED element group 10 is driven using a ceramic capacitor having a small capacity as the smoothing capacitor 41. 3 and 4 show current waveforms (LED current waveforms) flowing through the LED element group 10.

  In the example of FIG. 3, the output power is smaller than the capacitor capacity of the smoothing capacitor 41. Therefore, a substantially direct current flows as the LED current.

  On the other hand, in the example of FIG. 4, the output power is larger than the capacitor capacity of the smoothing capacitor 41. Therefore, when the output voltage of the rectifier circuit 30 decreases, the energy of the smoothing capacitor 41 becomes insufficient, and the LED current decreases.

  However, the LED current at this time has a waveform close to a pulse with a period of 120 Hz or 100 Hz, and the LED element group 10 can be lit without flickering. Therefore, even if the capacity of the smoothing capacitor 41 is small, there is no problem visually. 10 can be driven.

  As described above, in this embodiment, even when a ceramic capacitor is used as the smoothing capacitor 41, the LED element group 10 can be driven without flickering. Miniaturization can be achieved.

  Also, the smoothing circuit 40 can be deleted.

In addition, it is possible to improve the use efficiency of the LED element, extend the life, and improve the power factor described above.
(Example 2)
FIG. 5 is a block diagram showing the configuration of the power supply device according to the second embodiment of the present invention.

  Referring to FIG. 5, the power supply device of this embodiment is obtained by omitting the capacitor 56 from the drive circuit 50 of the first embodiment shown in FIG. 2, and the other configuration is the same as that of FIG.

  Here, FIG. 6 shows a rectified voltage waveform and an LED current waveform when the LED element group 10 is driven using a ceramic capacitor having a small capacity as the smoothing capacitor 41 in the power supply device of the present embodiment shown in FIG.

  In the example of FIG. 6, the output power is larger than the capacitor capacity of the smoothing capacitor 41 as in the example of FIG. 4.

  In the present embodiment, unlike the first embodiment, since the current flowing through the LED element group 10 is not smoothed by the capacitor 56, the LED current is not constant.

  However, the LED current at this time is constant as an effective value, and flickering is not perceived by human eyes.

  Therefore, even if the capacity of the smoothing capacitor 41 is small, the LED element group 10 can be driven without problems visually, and by using a ceramic capacitor for the smoothing capacitor 41, the power supply device can be made thinner and smaller. be able to.

  Other effects are the same as those of the first embodiment.

It is a block diagram which shows the structure of the power supply device of one Embodiment of this invention. It is a block diagram which shows the structure of the power supply device of Example 1 of this invention. FIG. 3 is a diagram for explaining an example of an LED current flowing in an LED element group in the power supply device shown in FIG. 2. FIG. 3 is a diagram for explaining another example of an LED current flowing in an LED element group in the power supply device shown in FIG. 2. It is a block diagram which shows the structure of the power supply device of Example 2 of this invention. FIG. 6 is a diagram for explaining an example of an LED current flowing in an LED element group in the power supply device shown in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 LED element group 20 AC power supply 30 Rectifier circuit 40 Smoothing circuit 41 Smoothing capacitor 50 Drive circuit 51 Choke coil 52 Diode 53 FET
54 Resistance 55 Constant current control circuit 56 Capacitor

Claims (7)

One light emitting element group formed by connecting a plurality of light emitting elements in series;
AC power supply,
A rectifier circuit that rectifies the output of the AC power source and converts it into a pulsating waveform;
A power supply device for a light emitting element, comprising: a drive circuit that drives the light emitting element group by making an effective value of a current flowing through the light emitting element group constant using an output current of the rectifier circuit. In the power supply device for light emitting elements according to claim 1,
The drive circuit is
A coil connected in series with the light emitting element group;
A diode connected in parallel with the light emitting element group and the coil, and for causing a current generated by a counter electromotive force of the coil to be superimposed on an output current of the rectifier circuit and flowing through the light emitting element group;
A switching element connected to a connection point between the coil and the diode, and for conducting the coil and the diode;
A resistor for detecting a current flowing in the light emitting element group;
A constant current control circuit that detects a current flowing through the resistor and turns on / off the switching element so that an effective value of a current flowing through the light emitting element group is constant based on the detected current. A power supply device for a light-emitting element. In the power supply device for light emitting elements according to claim 2,
The drive circuit is
The power supply device for a light emitting element according to claim 2, further comprising a capacitor connected in parallel with the light emitting element group and in series with the coil, and smoothing a current flowing through the light emitting element group. In the power supply device for light emitting elements according to claim 3,
A power supply device for a light emitting element, wherein an output current of the rectifier circuit is directly input to the drive circuit. In the power supply device for light emitting elements of any one of Claim 1 to 3,
A power supply device for a light emitting element, further comprising a smoothing circuit for smoothing an output current of the rectifier circuit with a ceramic capacitor and inputting the smoothed current to the drive circuit. In the power supply device for light emitting elements of any one of Claim 1 to 5,
The power supply device for a light emitting element, wherein the light emitting element is an LED element. In the power supply device for light emitting elements of any one of Claim 1 to 5,
The light emitting element is an EL element, and a power supply device for the light emitting element.