KR20140090830A - THD correction circuit for lighting apparatus - Google Patents

Abstract

The present invention relates to a constant current circuit for a lighting device. Total harmonic distortion (THD) is improved by separating a lighting group into two groups, serially connecting a diode between two groups, connecting a first switch circuit to the top of a first lighting group and the bottom of the diode, in parallel, by adding two switch circuits, and connecting a second switch circuit to the top of the diode and the bottom of the second lighting group, in parallel. Lighting with constant brightness is performed from a half voltage.

Description

[0001] THD correction circuit for lighting apparatus [0002]

The present invention relates to a constant current circuit of a lighting apparatus, and more particularly, to a constant current circuit of a lighting apparatus, in which a diode is connected in series between two lighting apparatus groups and two switch circuits are added to improve THD (Total Harmonic Distortion) The present invention relates to a constant current circuit for improving the THD of a lighting apparatus.

The waveform of a typical AC power source shows the shape of a sine wave. When a diode and a capacitor are connected together like a power supply circuit, a current flows only at the end of a sine wave, so that the current waveform is not a sinusoidal wave but has a very narrow sine wave shape similar to a pulse wave. . THD represents the degree to which the current waveform is distorted from the sinusoidal wave compared to the original sinusoidal input voltage. The smaller the value, the closer to the sinusoidal wave without the harmonic.

In the case of lighting equipment including LEDs, it is advantageous in terms of electric efficiency to increase the driving voltage of the lighting device. However, when the voltage is increased, the current does not flow in the low voltage phase portion with respect to the AC power source, It falls out.

In case of lighting equipment, the THD level must be kept below a certain level to perform the original function. The standard is less than 30% under the UL (Underwriters Laboratories Standard) and CE mark (Confromity to European) standards. Therefore, since THD can not be achieved with a general circuit configuration, other techniques such as additional circuit configuration are required.

FIG. 1A is a circuit diagram of a lighting apparatus using a conventional AC input-DC output power source, and FIG. 1B is a graph illustrating a voltage flow in FIG. 1A.

In the case of a general power supply circuit requiring direct current as described above, especially a power supply circuit of an LED or a CFD, current consumption is not proportional to an input voltage when an AC power is input to a DC output in a power supply circuit The THD value becomes high. 1A, the AC power input from the AC input power source 10 is subjected to full-wave rectification through the input diode 11, supplies power to the illuminator base 12, and exits through the output diode 13.

At this time, the waveform of the AC power input to the illuminator base 12 appears in the form of a current waveform as shown in FIG. Theoretically, the waveform of the AC power source should appear in the form of a full wave rectified sine wave (A), but the actual current waveform will appear as a pulsed wave shape (B) due to the increased THD value.

FIG. 2A is a circuit diagram of another lighting apparatus using a conventional AC input-DC output power source to which a resistor is connected, and FIG. 2B is a graph showing the voltage flow in FIG. 2A. In FIG. 2, the flow of the AC power input from the AC input power supply 20 is the same as the flow of the AC power of FIG. 1A. However, in FIG. 2, a resistor 24 is connected in series between the input diode 21 and the illuminator base 22 to limit the current.

The waveform of the AC power input to the illuminator base 22 of FIG. 2A appears in the form of a current waveform as shown in FIG. 2B. The resistor 24 is connected between the input diode 21 and the illuminator base 22 to limit the current and thereby flow a current in the form of a pulsed wave D which is theoretically proportional to the full wave rectified sinusoidal waveform C However, it still does not have a waveform that meets THD limits.

As an additional circuit for improving the THD, the most commonly used method is a method of using a PFC (Power Factor Correction) circuit in a complementary manner. PFC, which is a general power factor and THD improvement method, includes capacitors, switching gears, and fuse type. Such a PFC circuit is ineffective in terms of efficiency, and is uneconomical due to the circuit terminals.

In order to control the size of the DC voltage of the AC power supply for the lighting system, a current controlled LED driving circuit using a switching mode power supply (SMPS) or a switching regulator is used. This is complicated circuit, difficult to design, Which is uneconomical.

Methods for solving such existing problems and improving the power factor and THD are disclosed in the patents 10-1064906 and 10-1160154.

In the case of the above-mentioned Japanese Patent No. 10-1064906, as the number of LEDs is increased, current is flowed while switching, which is effective in improvement of THD, but current does not flow uniformly in the LEDs. It can not be operated at the maximum rated value.

In the case of the above-mentioned Patent No. 10-1160154, the LED group is operated in two groups. Since only one of the upper and lower operation is operated a lot, the operation of both ends becomes uneven, It can not be operated at the maximum rating of the LED.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a lighting apparatus in which lighting apparatuses operating in an upper and a lower lighting unit operate in an almost uniform manner, A circuit for supplying a current close to a constant current is provided.

In order to accomplish the object of the present invention as described above,

In the constant current circuit of the lighting apparatus, a diode is connected in series between the first illumination group and the second illumination group, a first switch circuit is connected in parallel to the upper end of the first illumination group and the lower end of the diode, And the second switch circuit is connected in parallel to the lower end of the group to improve the THD.

In the above, the first switch circuit and the second switch circuit include a left section in which a relatively large first resistor and a second resistor are connected in series; A first transistor connected between the collector of the first transistor and the collector of the first transistor, and a third resistor connected in series between the collector of the first transistor and the third resistor; A second transistor connected to the emitter portion of the first transistor and the third resistor, and a fourth portion connected in series with the collector portion of the second transistor; And the left section, the center section, and the right section are connected in parallel.

In the above, it is preferable that the first transistor and the second transistor are formed of a BJT, a FET, or a semiconductor device performing the same operation.

In this case, a resistor may be further connected in parallel between the collector and the emitter of the second transistor.

According to the present invention, it is possible to safely control by supplying the same current to the entire lighting group and switching the current to be equal to or more than the predetermined power so as to exhibit the same brightness, and it is possible to achieve economical THD It has an effect.

FIG. 1A is a circuit diagram of a conventional lighting device using an AC input-DC output power source. FIG.
FIG. 1B is a graph showing the voltage flow in FIG. 1A. FIG.
2A is a circuit diagram of a lighting apparatus using a conventional AC input-DC output power source to which a resistor is connected;
FIG. 2B is a graph showing the voltage flow in FIG. 2A. FIG.
FIG. 3A is a circuit diagram of a lighting device constructed by applying the THD improved constant current circuit of the present invention. FIG.
FIG. 3B is a graph showing the voltage flow in FIG. 3A. FIG.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. The following description is provided to assist the understanding and implementation of the present invention, but the present invention is not limited thereto. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit of the invention as set forth in the following claims.

3A shows an illuminator circuit constructed by applying the THD improved constant current circuit of the present invention. The AC power input from the AC input power source 100 is supplied to the THD improved constant current circuit 1000 through the input diode 110 I go in. The driving voltage is applied to the upper switch group 200 while the current is limited through the entry resistance 120. At this time, it is determined that the first transistor 210 is driven by the first resistor 201 having a relatively high resistance value And the resistance ratio of the second resistor 202. Therefore, when the waveform of the driving voltage is a low voltage portion, the first transistor 210 does not operate. When the first transistor 210 does not operate, the second transistor 220 operates to turn on the fourth resistor 204 The current is supplied to the lower illumination unit 250 and the current is supplied to the lower illumination unit 250 through the third resistor 203 when the first transistor 210 operates.

The configuration of the lower switch group 300 is the same as that of the upper switch group 200 and supplies current to the upper illumination unit 350. At this time, the collision of the two switch groups 200 and 300 is applied by the control diode 400 as a reverse voltage so that the lighting units 250 and 350 of the two groups operate at half voltage. And then flows through the illumination unit 350 and the control diode 400 to the lower illumination unit 250 to form a serial flow.

FIG. 3B is a graph showing the flow of voltages input to the two groups of illumination units 250 and 350 of FIG. 3A. It can be seen that the portion of the actual pulse waveform F is widened to approach the theoretical rectified sine wave shape F to improve the THD.

Hereinafter, the overall flow of the present invention will be described with reference to FIGS. 3A and 3B. 3A, the voltage input through the input resistor 120 supplies a current to the lower illumination unit 250 through the upper switch circuit 200 and the lower switch circuit 300 supplies current to the upper illumination unit 350 . The first resistor 201 and the second resistor 202 of the upper switch circuit 200 and the fifth resistor 301 and the sixth resistor 302 of the lower switch circuit 300 are connected to each other through a resistor 203 The first resistor 201, the second resistor 202 and the fifth resistor 301 and the sixth resistor 302 of the lower switch circuit 300 are connected in parallel to each other, The first transistor 210 of the upper switch circuit 200 and the third transistor 310 of the lower switch circuit 300 do not operate because no current flows through the series connected portion, 4 transistor 320 operates to supply current to the lower illumination unit 250 through the fourth resistor 204 in the case of the upper switch circuit 200 and the eighth resistor 304 of the lower switch circuit 300 to the upper illumination unit 250. [ (350) so that current can be supplied to the upper illuminating unit (350). When the first transistor 210 and the third transistor 310 operate in an increased magnitude of the driving voltage, the upper switch circuit 200 supplies current to the lower illumination unit 250 through the third resistor 203, The seventh resistor 303 of the switch circuit 300 is connected to the upper illuminating unit 350 so that current can be supplied to the upper illuminating unit 350. Since the voltage across the two switch circuits 200 and 300 is applied as a reverse voltage by the control diode 400, the upper and lower illumination units 250 and 350 are driven from half the voltage, When the driving voltage is the maximum, the upper and lower tier row names 250 and 350 of FIG. 3A operate in series and thus form the maximum voltage f2 period of FIG. 3B. When the voltage decreases, The switches 200 and 300 operate in the reverse order to the above-described operation mode to form the voltage drop switch voltage f3 of FIG. 3B.

10, 20, 100: AC input power source
11, 21, 110: input diodes 12, 22, 250, 350:
24, 120: Input resistance 200: Upper switch group
201: first resistor 202: second resistor
203: third resistor 204: fourth resistor
210: first transistor 220: second transistor
300: lower switch group 301: fifth resistor
302: sixth resistor 303: seventh resistor
304: eighth resistor 310: third transistor
320: fourth transistor 400: control diode
1000: THD improved constant current circuit

Claims (4)

In a constant current circuit of a lighting apparatus,
A diode connected in series between the first illumination group and the second illumination group;
A first switch circuit connected in parallel with the upper end of the first lighting group and the lower end of the diode;
And a second switch circuit connected in parallel with the diode top and the lower end of the second lighting group. The method according to claim 1,
The first switch circuit and the second switch circuit may include a first section having a relatively large first resistance and a second section having a second resistance connected in series; A first transistor connected between the collector of the first transistor and the collector of the first transistor, and a third resistor connected in series between the collector of the first transistor and the third resistor; A second transistor connected to the emitter of the first transistor and a collector of the second transistor, and a fourth resistor connected in series between the collector and the emitter of the first transistor, and the left, middle, Wherein the lighting circuit is connected in parallel. 3. The method of claim 2,
Wherein the first transistor and the second transistor are composed of a BJT, a FET, and a semiconductor device performing the same operation. 3. The method of claim 2,
And a resistor is connected in parallel between the collector and the emitter of the second transistor.

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