KR102504278B1 - A Converter Circuit for LED Lamps Having Power Factor Correction Function with Dimming Function - Google Patents

Abstract

The present invention is intended to provide an LED lamp converter circuit having a power factor correction function in dimming, which has a power factor correction function in dimming, wherein dimming control and power factor control in dimming adopt a 2-stage method, and additionally, a power factor improvement unit consisting of a capacitor and a switching element at an input terminal is added such that power factor control can be achieved partly by a power factor control chip and largely by changing a composite capacitor. Accordingly, dimming control and power factor correction are possibly performed in the entire converter system in a harmonious manner without being biased to one side. Furthermore, the present invention is intended to provide an LED lamp converter circuit having a power factor correction function in dimming, which has a feedback control function that takes into account a dimming level specified through an interface and the current load status.

Description

A Converter Circuit for LED Lamps Having Power Factor Correction Function with Dimming Function}

The present invention relates to a converter circuit for an LED lamp, and more particularly to a converter circuit for an LED lamp having an additional power factor correction function when dimming to a low output.

LED, which is widely used as a light source for lighting fixtures, has various advantages such as high illuminance, low power consumption, semi-permanent lifespan, eco-friendly and emotional lighting, and has recently become a popular light source for lighting fixtures.

On the other hand, in order to light the LED, a converter, which is a power supply device that receives commercial power and converts it into the rated power required for lighting, is required. A converter with a regulating function, ie a dimming function, is used.

On the other hand, one of the factors that determine the quality of a lighting device is the power factor of the converter. The power factor is the difference between the active power (actually used power) in an AC circuit and the apparent power (total power supplied from the power source). ), it is a ratio that indicates how effectively the voltage and current actually applied to the lighting device worked. As the power factor is higher, the difference between apparent power and active power disappears, so power waste can be minimized.

However, when the brightness of a lighting device is adjusted using a converter having a dimming function, it is unavoidable that the power factor is lowered due to a phase shift and mismatch of the time constant due to a change in the switching frequency of the PWM IC due to a change in input stage current. , Since the power factor reduction phenomenon of the converter leads to a decrease in power efficiency, when the brightness of the lighting device is adjusted using the converter, more power than necessary is consumed.

That is, among converters for LED lighting, the dimming converter adjusts the brightness by controlling the current of the LED load. At 100% output, the power factor (PF) is maintained, but when the brightness is reduced by controlling the output current, the power factor (PF) is lowered. At this time, in general, the power factor (PF) of the LED lighting must exceed a certain level, but when the output is lowered, the power factor is also lowered (for example, when the output is lowered to about 20%, the power factor (PF) is lowered to 0.7 to 0.6 or less), and power loss increases. . Therefore, it was necessary to develop a converter with a good power factor (PF) even at low output in a dimming converter for LED lighting.

As a first prior art for improving the power factor well together with the dimming function, there is something such as Korean Patent No. 1455146 (high efficiency LED dimming converter).

As shown in FIG. 1, the first prior art includes an EMI filter 10, a rectifier 20, a power factor improving PWM unit 30, a transformer T1, a DC unit 40, a feedback unit 50, Components such as the driving power supply unit 60, the dimming control unit 70, and the dimming interface unit 80 are roughly classified.

The power factor improving unit PWM unit 30 includes a switching element Q1 that turns on and off the transformer T1 and switches it, a control unit U1 that controls switching of the switching element Q1, and the control unit U1. ) Detecting the voltage waveform of the start resistors (R2, R24) and the capacitor (C9) and the output pulsating current power supply of the rectifying unit (20) providing the starting voltage for the initial driving and providing the voltage to the control unit (U1) parts (R1, R23, R3, C6), the auxiliary coil (t1) wound on the primary side of the transformer (T1) and coupled with magnetic flux, and the voltage induced in the auxiliary coil (t1) is converted to a constant voltage to be used as a driving power source. The current induced by the switching of the transformer T1 from the driving power supply units D12, R28, Q3, C14, C12, R21, ZD1, Q3 that is converted and provided to the control unit U1, and the auxiliary coil t1. The current sensing unit R13 detects, in particular, the zero point at which the strength of the current becomes 0, and provides it to the control unit U1, and limits the strength of the counter-electromotive force induced in the primary side of the transformer T1 according to switching. and snubbers (D9, R12, C11) for protection, and peripheral elements (R5, 7, 8, 9, 10, 11, 14, C8, etc.) connected to drive the control unit U1.

The driving power supply units D12, R28, Q3, C14, C12, R21, ZD1, and Q3 maintain a stable driving voltage even in low light dimming, so that the power factor correction PWM unit 30 operates stably even at low light levels.

The control unit U1 controls the switching of the switching element Q1 so that the waveform of the current induced in the transformer T1 matches the waveform of the voltage output from the rectifying unit 20, that is, voltage The power factor is improved by making the overcurrent in phase.

More specifically, the control unit U1, at an intermediate point in time when the intensity of the voltage in the voltage waveform of the output pulsating current power supply of the rectifying unit 20 detected by the voltage sensing units R1, R23, R3, and C6 is high, The switching element (Q1) is switched on and off with a low frequency, and the switching element (Q1) is switched on and off with a relatively high frequency at the beginning and end when the strength of the voltage is weak, so that the current induced in the transformer (T1) every moment according to the switching The power factor is improved by ensuring that the current waveform of the average value connecting them has the same period and shape as the voltage waveform.

And, on the output side of the DC unit 40, a resistor R18 as a voltage sensing unit for sensing the voltage supplied to the LED, which is a load, and resistors R30 and R31 as a current sensing unit for sensing the current supplied to the LED, A dimming power supply unit 90 providing a reference voltage for dimming is connected.

The resistor R18 as the voltage sensing unit provides the voltage sensed through the first terminal to the dimming control unit 70, and the resistor R31 as the current sensing unit supplies the sensed current through the fourth terminal to the dimming control unit 70. The dimming power supply unit 90 supplies the reference voltage for dimming to the dimming control unit 70 and the dimming interface unit 80 through terminals 5 and 5', respectively.

The dimming power supply unit 90 provides a reference voltage for dimming, that is, a maximum voltage within a range of a dimming command signal for changing the illuminance of the LED. For example, when the dimming command signal has a range of 0 to 10 volts, a maximum voltage of 10 volts becomes a reference voltage for dimming and is provided to the dimming control unit 70 and the dimming interface unit 80. This reference voltage prevents the dimming command signal received and recognized by the dimming interface unit 80 and the dimming control unit 70 from exceeding 10 volts even when a dimming command signal is input from the outside at a level greater than or equal to the reference voltage.

The dimming power supply unit 90 is composed of resistors R41, R42, and R26, a capacitor C26, and a variable regulator U3, and from the output voltage of the DC unit 40 through the resistor R22 to the resistors R41 and R42. A reference voltage of 10 volts is created by the ratio.

The dimming interface unit 80 provides a dimming command signal to the dimming control unit 70 while preventing the dimming command signal input from the outside from affecting the dimming control unit 70, and when the input dimming command signal is equal to or less than a minimum reference value. A light off signal is provided to the dimming control unit 70 to turn off the light.

However, in the case of the first prior art, the control unit U1 controls the switching of the switching element Q1 so that the waveform of the current induced in the transformer T1 is the voltage output from the rectifying unit 20. Since the power factor is improved by matching the shape of the waveform, that is, by making the voltage and current be in phase, it is not easy to accurately match the zero point in a high-frequency circuit where the frequency is gradually increased to be in phase. There are limits.

On the other hand, as a second prior art for improving the power factor well together with the dimming function, there is something such as Korean Patent No. 2033953 (Apparatus and Method for Improving Power Factor of Converter for LED Lighting).

The second prior art is as shown in FIG. 2, and the power factor improvement device 100 of the converter for LED lighting according to the second prior art includes an electromagnetic compatibility (EMC) filter module 110, a bridge rectification module 120, a first transformer 130, a second transformer 140, a pulse width modulation (PWM) switching control module 150, a switching module 160, a smoothing circuit module 170, voltage sensing module 180 and a transformer connection control module 190.

The power factor improvement device 100 of the second prior art converter for LED lighting continuously senses the voltage of the DC output signal directly input to the load so that the power factor does not decrease depending on the load and is maintained above a certain level. It can be configured so that

The power factor correction device 100 of the LED lighting converter turns on/off the parallel connection of the first transformer 130 and the second transformer 140 according to the voltage value of the DC output signal, thereby reducing the reactance of the entire transformer By changing the (reactance), it can be configured to adjust the power factor.

That is, the voltage detection module 180 detects the voltage of the DC output signal output from the smoothing circuit module 130, and the transformer connection control module 190 is parallel to each other according to the voltage detected by the voltage detection module 180. The parallel connection of the connected first transformer 130 and the second transformer 140 is turned on/off, and the transformer connection control module 190 controls the DC voltage signal detected by the voltage detection module 180. When the duty ratio is lowered to a predetermined ratio or less, the connection of the first transformer 130 and the second transformer 140 is turned on/off to maintain the duty ratio at or above the predetermined ratio. can

More specifically, by turning on / off the connection of the first transformer 130 and the second transformer 140, a pair of reactance of the first transformer 130 and the second transformer 140 ( reactance) is varied and the power factor is compensated so that a certain power factor or more may be maintained.

However, in the case of the second prior art, in order to adjust the power factor by changing the reactance of the transformer, it takes up a relatively large space and requires the use of an expensive inductor, which is not preferable in terms of economy, and the process of actual productization Several constraints can occur spatially in .

Subsequently, as a third prior art for improving the power factor well together with the dimming function, Korean Patent No. 2333323 (LED module power supply converter having a dimming function with improved power factor at low output), as shown in FIGS. 3 and 4 same as bar

As shown in FIG. 2, the converter for supplying LED module power having a dimming function with improved power factor at low output according to the third prior art includes a safety and EMI filter unit 100, a primary rectifier unit 200, and a snubber circuit unit. (300), controller unit 400, switching unit 500, transformer 600, power factor improvement circuit unit 700, surge voltage prevention unit 800, secondary rectification unit 900, constant current and dimming control unit 1000 ), a dimming sensor power supply unit 1100, a PWM dimming signal input unit 1200, and an EMI filter unit 1300.

In order to improve the power factor, the power factor improving circuit unit 700 needs to partially compensate the external RC network for stabilizing the loop compensation terminal (COMP). If this external RC network is fixed, the power factor may deteriorate when there is a change in the input current or output current. To improve the power factor, connect the power factor to an external condenser (C5) for stabilization of the loop compensation terminal (CMP) of the driver IC (U1). The enhancement circuit needs to be compensated, but if this external condenser (C5) is fixed, the power factor may deteriorate when there is a change in input current or output current.

For such power factor improvement, that is, power factor improvement, three resistors (R4, R5, R6) and a load resistor (R2) configured between the primary rectifier 200 and the controller unit 400 in series propagate commercial power An appropriate voltage level to make a signal source for rectifying and compensating the loop compensation terminal (CMP) is to adjust the voltage by the resistance distribution of the resistor (R4), resistor (R5), resistor (R6) and the load resistor (R2), and the capacitor ( C3) supplies only the AC signal source from the regulated signal source to the loop compensation terminal (CMP). Outside the loop compensation terminal (CMP), a damper (DAMPER) circuit consisting of a capacitor (C4) and a resistor (R9) is added as an RC network to properly respond to rapid voltage level changes of the loop compensation terminal (CMP).

4, one end is connected to R6 among the three resistors (R4, R5, R6) serially connected between the primary rectifier 200 and the controller unit 400 and connected in series. The load resistor R2 configures the full-wave rectifier 710 to full-wave rectify the commercial power supply and adjust the voltage level by dividing the resistance to properly drive the CMP circuit. Among them, the other end of the load resistor R2 is full-wave rectified, It plays a role in supplying the lowered voltage signal to the CMP stage of the driver IC (U1). Since only the full-wave rectification AC signal source is required, a capacitor (C3) is used between the CMP terminal of the driver IC (U1) and the load resistor (R2) to supply it to the CMP terminal.

As the CMP stage of the driver IC (U1), the effect can be obtained only with a capacitor (C3) of appropriate capacity, but there are cases where it does not respond to rapid voltage level changes. A damper circuit 730 was additionally configured as C4 and C5). For example, it is possible to solve the problem that the power factor (PF) or total harmonic distortion (THD) is different when the CMP voltage is lowered at a high level and increased at a lower level at a specific output.

On the other hand, the CMP terminal 740 of the driver IC (U1), when there is no power factor (PF) enhancement circuit unit 700, the CMP terminal operates at DC voltage by an internal DC bias and an external condenser, and when 100% output current is DC If the output current is 20% at 18Vdc, it is lowered to DC 11Vdc, and the power factor (PF) is also lowered accordingly.

However, when there is a power factor (PF) enhancing circuit unit 700, the CMP terminal selectively changes the CMP terminal voltage level upward by the signal introduced through the condenser 720 to the DC voltage caused by the internal DC bias and the external condenser. and, due to the signal level of the CMP stage, the fixed sawtooth wave inside the LED driver IC (U1) is compared and controlled with the voltage of the CMP pin, and the internal driving circuit operates so that an appropriate output can be output through internal logic control, so the power factor is improved. .

However, similar to the first prior art, the third prior art also improves the power factor by the time constants or parameters of the fixed elements connected to the terminals by the PWM control driver IC, so when the degree of dimming greatly changes, the power factor There are bound to be limits to improvement.

Finally, Korean Patent No. 2350568 (Power Factor Correction Type Dimming Converter) as a fourth prior art for improving power factor well together with a dimming function will be described with reference to FIGS. 4 and 5 .

Hereinafter, the power factor correction type dimming converter according to the fourth prior art will be described with reference to FIGS. 5 and 6, the power factor correction type dimming converter 10 according to the fourth prior art has an AC input unit 102 ), a voltage conversion unit 104, a dimming circuit unit 106, a reactance control unit 108, and a dimming control unit 110.

The AC input unit 102 filters the AC voltage input from the external power source 20 and outputs the filtered AC voltage through a bridge diode.

The voltage conversion unit 104 converts the DC high voltage output from the AC input unit 102 into a DC low voltage and outputs it.

The dimming circuit unit 106 adjusts the brightness of the lighting device 22 based on the DC low voltage output from the voltage converter 104 . The dimming circuit unit 106 may adjust the brightness of the lighting device 22 based on a dimming control signal supplied from the dimming controller 110 .

The reactance control unit 108 adjusts the capacitance value of the capacitor included in the voltage converter 104 according to the capacitance control signal. The reactance control unit 108 receives a capacitance control signal from the dimming control unit 110 .

The dimming controller 110 outputs a capacitance control signal corresponding to a dimming value input from the outside.

In the fourth prior art, the dimming value represents the brightness of the lighting device 22 and may be input by a user or any other device. For example, the dimming value may be any one value from 10 to 100%, or any one value from 1 to 10 or 1 to 5. The minimum value of the dimming value may correspond to the minimum brightness of the lighting device 22 , and the maximum value of the dimming value may correspond to the maximum brightness of the lighting device 22 . Intervals and maximum/minimum values of each dimming value may be set differently according to embodiments.

The lighting device 22 is a lighting device using an LED element as a light source.

The dimming control unit 110 supplies a dimming control signal corresponding to the dimming value to the dimming circuit unit 106 so that the brightness of the lighting device 22 matches the dimming value input from the outside. Accordingly, the dimming circuit unit 106 adjusts the brightness of the lighting device 22 to correspond to the dimming value based on the dimming control signal.

Maintaining the power factor of the power factor correction type dimming converter 10 close to 1 depends on designing the capacitance value of the circuit of the voltage converter 104 to be resonant with respect to the switching frequency of the switching element included in the voltage converter 104. .

In the converter 10 according to the fourth prior art, the switching frequency of the switching element included in the voltage converter 104 decreases as the dimming value increases, and the switching frequency increases as the dimming value decreases ( 10) is.

Referring to FIG. 7 , the voltage converter 104 of the power factor correction type dimming converter 10 according to the fourth prior art includes a transformer 122, a switching element 124, a plurality of capacitors C1, C2, C3, C4).

In FIG. 7 , the transformer 122 includes a primary coil L1 and a secondary coil L2 wound around an iron core.

The switching element 124 is connected to one end of the primary side coil L1. The switching element 124 is switched, that is, repeatedly turned on/off according to a predetermined switching frequency.

A number of capacitors (C1, C2, C3, C4) are connected in parallel with each other. Although four capacitors C1, C2, C3, and C4 are shown in FIG. 7, the number of capacitors included in the voltage converter 104 may vary. Also, capacitance values of the respective capacitors C1, C2, C3, and C4 may be set differently.

The reactance adjusting unit 108 includes a plurality of transistors connected to respective capacitors. For example, in FIG. 7, the reactance adjuster 108 includes a first transistor Q1 connected to a first capacitor C1, a second capacitor C2, a third capacitor C3, and a fourth capacitor C4, respectively. It includes two transistors Q2, a third transistor Q3, and a fourth transistor Q4.

In addition, the reactance controller 108 includes a plurality of logic devices 131, 132, and 133 connected between the dimming controller 110 and the transistors.

The dimming controller 110 outputs a capacitance control signal corresponding to a dimming value input from the outside. For example, the dimming controller 110 may output a digital signal corresponding to the magnitude of a dimming value input from the outside. The on/off states of the first transistor Q1 , the second transistor Q2 , the third transistor Q3 , and the fourth transistor Q4 may be respectively controlled by the capacitance control signal output from the dimming control unit 110 . there is. As the first transistor Q1, the second transistor Q2, the third transistor Q3, and the fourth transistor Q4 are turned on or off, respectively, the first capacitor C1, the second capacitor C2, and the third transistor Q4 are turned on or off. Combined capacitance values of the capacitor C3 and the fourth capacitor C4 may be adjusted.

Based on the capacitance control signal output by the reactance control unit 108, the capacitance correction value Ci decreases as the dimming value decreases, and the capacitance correction value Ci increases as the dimming value increases. ) is controlled to increase. Accordingly, as the dimming value decreases, the switching frequency of the switching element 124 increases, and at the same time, the capacitance value of the voltage converter 104, that is, the combined capacitance value of the plurality of capacitors C1, C2, C3, and C4 decreases. . Therefore, the converter 10 according to the fourth prior art, that is, a converter in which the switching frequency of the switching element included in the voltage converter 104 decreases as the dimming value increases, and the switching frequency increases as the dimming value decreases. Even if the dimming value of (10) changes, there is an effect that the power factor of the converter 10 is always maintained at a value equal to or higher than a certain value.

However, the fourth prior art is a '1-stage' circuit rather than a '2-stage' circuit. and other auxiliary circuits (FET, diode, capacitor, resistor, etc.), the circuit itself is simple, but it is a form in which a smoothing electrolytic capacitor is not used on the primary side of the transformer, so it illuminates when the power supply is unstable. This method is mainly used for small-capacity (less than 50W) products for low-priced indoor use. That is, since the fourth prior art is a one-stage method, it is a form that can only be implemented in a form of gradually reducing the dimming step by using several capacitors on the input side, and in the case of the fourth prior art, the power factor Even after correction, it is possible to achieve about 0.915PF at 50% load, but at 40% load, it is 0.888PF and less than 0.9PF, that is, between 40 and 50%, there is a problem that the 0.9PF standard required by the KS standard collapses. In addition, it is a form of complex configuration for changing the reactance value using several capacitors (or coils) and changing the C value (or L value) to perform power factor correction, which also has various limitations (cost due to capacitors at the input stage). It is a technology that has a new problem of disharmony of the entire system due to a problem, a load problem, or an overheating problem.

Korean Patent No. 1455146 (High Efficiency LED Dimming Converter) Korean Patent No. 2033953 (Apparatus and method for improving power factor of converter for LED lighting) Korean Patent No. 2333323 (LED module power supply converter with dimming function with improved power factor at low output) Korean Patent No. 2350568 (Power factor correction type dimming converter)

The present invention, as a countermeasure against the problems of the first to fourth prior art, has a power factor correction function during dimming, but also uses a two-stage method for dimming control and power factor control during dimming, and furthermore, a capacitor and a switching element at the input stage By adding a power factor correction unit consisting of, power factor control is performed partly by the power factor control chip and largely by changing the synthesized capacitor, enabling dimming control and power factor correction as the entire converter system harmoniously so as not to be biased to either side. It is to provide a converter circuit for an LED lamp having a power factor correction function during dimming.

In addition, the converter circuit for LED lamps having a power factor correction function during dimming of the present invention has a feedback control function considering the dimming level specified through the interface and the current load state, while having a power factor correction function during dimming Converter for LED lamps to provide a circuit.

Additionally, the converter circuit for an LED lamp having a power factor correction function during dimming of the present invention is to provide a converter circuit for an LED lamp having a power factor correction function while controlling dimming even when the internal temperature is abnormally overheated.

The converter circuit for an LED lamp having a power factor correction function during dimming of the present invention for achieving the above object includes a power supply unit 100 that safely supplies commercial AC power by filtering it; a rectifier 200 for rectifying the AC power filtered by the power supply unit; a switching converter unit 400 performing frequency modulation while inverting the DC power rectified by the rectification unit 200; a power factor correction circuit unit 300 for correcting the power factor of the DC power rectified by the rectification unit 200; A transformer (T1) for receiving the DC power rectified by the rectifying unit and converting it to the voltage level of the lighting unit of the LED lamp while inverting and correcting the power factor by the power factor correction circuit unit 300 and the switching converter unit 400; A synchronous rectification circuit unit 500 for converting the AC suitably transformed in the secondary side of the transformer T1 into DC; A power output unit 600 for smoothing and filtering the ripple current of the rectifier circuit unit 500 and supplying stable DC power to the LED; a feedback control unit 700 that senses output current and voltage from the power output unit 600 and outputs a dimming control signal to the switching converter unit 400 for feedback control; a dimming/power factor control unit 800 that applies a dimming level outside the converter circuit and generates a power factor improvement control signal under a low dimming condition according to the dimming level; and a power factor improving unit 900 that improves the power factor in low dimming by changing the reactance of the output terminal of the rectifying unit 200 in a low dimming condition in response to the power factor improvement control signal from the dimming/power factor control unit 800; It is characterized by comprising a.

Preferably, the power output unit 600 includes a sensing unit for sensing secondary side voltage and current, and in the feedback control unit 700, the switching converter unit 400 is controlled by the voltage and current sensed by the sensing unit. ), it is characterized in that feedback control is performed with constant current and constant voltage by switching at a higher frequency than the frequency at high output for low output.

Also preferably, the feedback control unit 700 senses the current at both ends P6 and P9 of the sensing resistor SH3 of the sensing circuit unit 630 of the power output unit 600 to generate a current sensing signal. A current feedback unit 710 and a voltage feedback unit 720 for generating a voltage sensing signal by sensing the output voltage of the output terminal P2 of the smoothing circuit unit 610 of the power output unit 600 through a voltage dividing resistor; It is characterized in that it consists of a dimming control signal generator 740 for generating a dimming control signal to the switching converter 400 according to the levels of the current sensing signal and the voltage sensing signal.

Also preferably, the dimming/power factor control unit 800 detects a dimming interface unit 810 that provides a dimming level outside the converter circuit and a dimming level input from the dimming interface unit 810 to improve the power factor. It is characterized in that it consists of a dimming level detection unit 820 that controls the unit 900.

More preferably, when a voltage corresponding to a dimming level below the reference value is input through the input terminals (DIM+, DIM-) of the dimming interface unit 810, the current feedback unit 710 of the feedback control unit 700 also receives a voltage. The reference voltage of the voltage corresponding to the dimming level below the reference value is applied, and the output to the LED lighting unit (not shown) is dimmed by the switching of the switching converter unit 400, and at the same time, on the one hand, the dimming level While the voltage corresponding to the dimming level below the reference value is also applied to the detection unit 820, a signal for switching the switching element Q8 of the capacitor CX4 for adjusting the reactance of the power factor improving unit 900 is generated in low light dimming. It is characterized by doing.

More preferably, control between the current feedback unit 710 and the switching converter unit 400 is performed by the first photocoupler PC1, and the dimming level detection unit 820 and the power factor improving unit 900 ) is characterized in that the control between them is performed by the second photocoupler (PC2).

Most preferably, the power factor correction unit 900 emits light from the light emitting diode PC2A of the second photocoupler PC2, and the second photocoupler PC2 of the power factor correction unit 900 in low light dimming. Since the light receiving unit PC2B of is turned on, the switching element Q8 is turned off and the reactance adjustment capacitor CX4 is opened, resulting in a reduced combined capacitance value.

According to the converter circuit for LED lamps having a power factor correction function during dimming according to the present invention, a plurality of power factor control methods are performed in parallel, partially by a power factor control chip, largely by changing a composite capacitor, so that power factor control is performed, Dimming control and power factor correction are possible as a whole system of converters harmoniously so as not to be biased to one side.

In addition, according to the converter circuit for LED lamps having a power factor correction function during dimming of the present invention, while having a feedback control function considering the dimming level specified through the interface and the current load state, for LED lamps having a power factor correction function during dimming A converter circuit is provided.

Additionally, according to the converter circuit for an LED lamp having a power factor correction function during dimming of the present invention, it is possible to provide a converter circuit for an LED lamp having a power factor correction function while controlling dimming even when the internal temperature is abnormally overheated.

In addition to the above objects and effects, other objects and advantages of the present invention will become apparent through detailed description of the embodiments with reference to the accompanying drawings.

1 is a circuit diagram of a high-efficiency LED dimming converter according to a first prior art.
Figure 2 is a block diagram of a power factor improvement device of a converter for LED lighting according to a second prior art.
Figure 3 is a circuit diagram for explaining a converter for supplying power to an LED module having a dimming function with improved power factor at low output according to a third prior art.
Figure 4 is a diagram for explaining in detail the power factor enhancement circuit in the LED module power supply converter having a dimming function with improved power factor at low output shown in FIG.
5 is a block diagram showing the configuration of a power factor correction type dimming converter according to a fourth prior art;
6 is a block diagram showing the configuration of a voltage conversion unit and a reactance adjusting unit of a converter according to a fourth prior art;
7 is a block diagram of a converter circuit for an LED lamp according to an optimal embodiment of the present invention.
8 is a detailed circuit diagram of the input terminal of FIG. 7;
9 is a detailed circuit diagram of the output stage of FIG. 7;
10 is a detailed circuit diagram of the dimming/power factor control unit of FIG. 7;

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

(Example)

First, a converter circuit for a high-voltage and high-frequency LED lamp according to an optimal embodiment of the present invention will be described with reference to FIGS. 7 to 10 .

7 is a block diagram of a converter circuit for an LED lamp according to an optimal embodiment of the present invention, FIG. 8 is a detailed circuit diagram of an input terminal of FIG. 7, FIG. 9 is a detailed circuit diagram of an output terminal of FIG. 7, and FIG. It is a detailed circuit diagram of the dimming/power factor control unit of FIG. 7 .

First, the converter circuit for the LED lamp of the best embodiment of the present invention, as shown in Figure 7, a power supply consisting of a fuse, a line filter, a varistor and a capacitor that safely supplies commercial AC power by filtering it, a power supply unit 100; a rectifier 200 for rectifying the AC power filtered by the power supply unit; a switching converter unit 400 performing frequency modulation while inverting the DC power rectified by the rectification unit 200; a power factor correction circuit unit 300 for correcting the power factor of the DC power rectified by the rectification unit 200; A transformer (T1) for receiving the DC power rectified by the rectifying unit and converting it to the voltage level of the lighting unit of the LED lamp while inverting and correcting the power factor by the power factor correction circuit unit 300 and the switching converter unit 400; A synchronous rectification circuit unit 500 for converting the AC suitably transformed in the secondary side of the transformer T1 into DC; A power output unit 600 for smoothing and filtering the ripple current of the rectifier circuit unit 500 and supplying stable DC power to the LED; a feedback control unit 700 that senses output current and voltage from the power output unit 600 and outputs a dimming control signal to the switching converter unit 400 for feedback control; a dimming/power factor control unit 800 that applies a dimming level outside the converter circuit and generates a power factor improvement control signal under a low dimming condition according to the dimming level; and a power factor improving unit 900 that improves the power factor in low dimming by changing the reactance of the output terminal of the rectifying unit 200 in a low dimming condition in response to the power factor improvement control signal from the dimming/power factor control unit 800; made including

Hereinafter, each component will be described in more detail with reference to FIGS. 7 and 8. The power factor correction circuit unit 300 is composed of a Power Factor Controller (PFC) (U1), which is an IC for a power factor controller, and its peripheral circuits. As such, additionally, the start RC circuit (R13 to R15, C9) of the PFC (U1), the pulsating current voltage detection circuit (R37 to R40, C14) output from the rectifier, the choke transformer (L1), the first switching for power factor correction Circuits such as element Q1 and peripheral circuits, NTC (TH1) and snubber circuits (R22 to R24, R141 to R143, C5), coupling resistors (R25 to R27) to the switching converter unit 400 may be further included. there is.

At this time, in the power supply terminal (Vcc) of the power factor correction circuit unit 300, a first auxiliary power supply unit 350 composed of an auxiliary coil L1-1 coupled with magnetic flux to the choke transformer L1 and capacitors C4 and C5, etc. ) is preferably connected.

The switching converter unit 400 is composed of a PFM (U2), which is an LC resonance type switching converter controller IC, switching elements (Q2, Q3) and their peripheral circuits, the PFM (Pulse Frequency Modulator) (U2) It is oscillated by the second and third switching elements (Q2, Q3) and the primary coil (T1-1) and the capacitor (C8) that are alternately switched at a frequency controlled by, such an oscillated AC power is a transformer ( T1), in particular, to the STBY terminal (No. 5) of the PFM (U2), the state of the load (LED) is changed by the control signal of the feedback control unit 700 to the light receiving unit PC1B of the first photocoupler PC1. ), it oscillates at a higher frequency when dimming control is desired with low output.

At this time, a second auxiliary power supply unit 450 composed of auxiliary coils L1-5 coupled with magnetic flux to the transformer T1 and a capacitor C7 is connected to the power terminal Vcc of the switching converter unit 400. it is desirable to be

Continuing to refer to FIGS. 7 and 9 , the rectifier circuit unit 500 is inductively coupled to the second and third coils T1-2 and T1-3 on the secondary side of the transformer T1 and to them. It consists of the 20th and 21st switching elements Q20 and Q21 coupled to each other, and a synchronous rectifier controller U4 that controls them. The output voltage rectified by the rectifier controller U4 is the power output unit of the next stage ( 600) is output.

The power output unit 600 passes through a smoothing circuit 610 composed of smoothing capacitors C31 to C33 and an EMI filter 620 composed of a line filter LF5 for blocking high frequencies, so that a stabilized DC voltage is generated. It is output to the LED lighting part.

At this time, a sensing circuit unit 630 for sensing the secondary side voltage is provided on one side of the smoothing circuit unit 610 and a separate sensing unit for sensing the output voltage is provided at the output terminal of the smoothing circuit unit 610, and a feedback control unit in the next stage is provided. In 700, by outputting a feedback signal to the switching converter unit 400 by the voltage and current sensed by the power output unit 600, by performing switching at a higher frequency than the frequency at high output for low output , feedback control is performed with constant current and constant voltage.

Regarding this, in more detail with reference to FIGS. 8 and 9, the voltage feedback unit 720 for sensing the output voltage of the output terminal P2 of the smoothing circuit unit 610 through a voltage dividing resistor is an amplifier (eg, LM258A) The output voltage is sent to the sensing voltage input terminal (terminal No. 2) of (U3). Thus, the reference voltage of the reference voltage input terminal (terminal No. 3) is compared and amplified with the reference voltage (voltage divided by the voltage dividing resistors (R64 and R65) of Vcc), and the amplified voltage is output to terminal No. 1.

Similarly, the current feedback unit 710, in order to sense the current of both ends (P6, P9) of the sensing resistor (SH3) of the sensing circuit unit 630, the potential corresponding to the reference current (potential of P5) It is sent to terminal 5 of the amplifier (U3), and the potential of the P6 point is sensed by the current feedback unit 710 and the sensing current is sent to terminal 6, and the potential difference between them is inverted and amplified to amplify. The voltage is output to the 7th terminal. The current feedback unit 710 will be described in detail later.

The driving power (Vcc) of the feedback control unit 700 is supplied by a third auxiliary power supply unit 750 composed of the tertiary-side fourth coil T1-4 of the transformer T1 and capacitors C49 and C50. Now, the cathode side of the light emitting diode PC1A of the first photocoupler PC1 of the dimming control signal generator 740, the anode side of which is connected to the Vcc, is the first and second backflow prevention diodes D25, D27) and coupling resistors are connected to the 7th and 1st terminals of the amplifier (U3). Therefore, during normal operation of the converter circuit, the 7th pin of the amplifier U3 is close to Vcc, so that the first anti-backflow diode D25 is not energized and the second anti-backflow diode D27 is energized, so that the constant voltage It operates in the mode, and when a specific voltage is applied to the sensing resistor SH3 of the sensing circuit unit 630, the voltage at the 7th terminal drops further from Vcc (for example, to 'Vcc/2'), so that the first photo port The voltage applied to the resistor R77 on the cathode side of the light emitting diode PC1A of the coupler PC1 is greater, so that the current flows through the first anti-backflow diode D25, thereby operating in the constant current mode. After all, according to the potential level of the light emitting diode PC1A of the first photocoupler PC1, whether the light receiving unit PC1B of the first photocoupler PC1 of the switching converter unit 400 is under a light load or a heavy load. is feedback controlled, and the switching converter unit 400 performs dimming control to change the load output by changing the resonant switching frequency accordingly.

Now, referring primarily to FIG. 10 and auxiliaryly referring to FIGS. 7 to 9 , the dimming/power factor control unit 800 includes a dimming interface unit 810 for providing a dimming level outside the converter circuit and a dimming interface unit. It is composed of a dimming level detection unit 820 that detects the dimming level input from 810 and controls the power factor improving unit 900. When inputs a dimming value from 0 to 100% (here, 0 to 10Vdc), the corresponding voltage is output to the CS terminal of the dimming board 813 via the filter 812. For reference, when 10V is input through the input terminals (DIM+, DIM-), 10V is also output to the CS terminal, so in this case, full operation is performed with 100% brightness.

However, when 1.5V is input through the input terminals (DIM+, DIM-), 1.5V is also output to the CS terminal, so in this case, 1.5V is also applied to the CS terminal of the current feedback unit 710 of FIG. 9, Therefore, the voltage difference between the voltage of the CS terminal (P3) of the current feedback unit 710 and the voltage of the P9 point of the smoothing circuit unit 610 is divided and appears at the P5 point (the detailed reference voltage adjustment is the adjustment of the variable resistor VR1). ), eventually, the output to the LED lighting unit is dimmed to 15% brightness by the switching of the transformer output, the first photocoupler (PC1), and the switching converter unit (400: see FIG. 8), and on the other hand Since a voltage corresponding to 1.5V is also applied to the non-inverting input terminal of the comparator U5 of the dimming level detection unit 820 (assuming that a reference transfer of 2V is set to the inverting input terminal of the comparator U5), the comparator Since the output of is 'Low', the light emitting diode (PC2A) of the second photocoupler (PC2) emits light, and the second power factor improving unit (900: see FIG. 8) in low illumination (less than 20%) dimming. Since the light receiving unit PC2B of the photocoupler PC2 is turned on, the eighth switching element Q8 is eventually turned off and the combined capacitance value is reduced from (CX3+CX4) to (CX3), and the power factor is 0.9 or more even in low light dimming. can be maintained as

Now, finally, the current feedback unit 710 will be described in detail and the entire operation of the present invention will be described in detail.

In a state where the converter circuit for LED lamps having a power factor correction function during dimming according to the present invention operates in 100% full operation mode, for example, the dimming level is set through the input terminals (DIM+, DIM-) of the dimming interface unit 810. When 5V is input (see FIG. 10), 5V is also raised at the CS terminal of FIG. The divided voltage of the other synthesized voltage divider resistor (Req = R84//VR1 + R67//R71) is applied to the P5 terminal, and this voltage divider is the reference voltage of the current amplification unit of the amplifier (U3) of the feedback control unit (700) 5 times. applied to the terminal.

Now, the terminal voltage of the output terminal (P6) of the sensing circuit unit 630 as a sensing current signal is applied to terminal 6 as a current amplification unit sensing voltage of the amplifier (U3) of the feedback control unit 700, and the output Since 'Low' is output to the terminal (pin 7), the first photocouplers (PC1A, PC1B) of the dimming control signal generator 740 operate, and the switching converter unit (with an intermediate frequency for dimming control corresponding to 5V) As the PFM (U2) operates so that 400) oscillates, 50% dimming control is eventually performed on the LED lighting unit. However, at this time, the second photocoupler (PC2) of the dimming level detection unit 820 of FIG. 10 is higher than the reference voltage (2V), so it does not operate yet, and thus the eighth switching of the power factor improving unit 900 of FIG. 8 Since the element Q8 continues to be in the 'On' state, it is maintained at a relatively high first capacitance value (CX3 + CX4) for heavy load, and the power factor control is performed by the power factor correction circuit unit 300 including the PFC (U1) is regulated by

On the other hand, when the dimming level is input as 1.5V through the input terminals (DIM+, DIM-) of the dimming interface unit 810 (see FIG. 10), 1.5V is also displayed on the CS terminal of FIG. 9, and the CS terminal (P3) The divided voltage of one side voltage divider resistor (R58) and the other side synthetic voltage divider resistor (Req = R84//VR1 + R67//R71) for 1.5V of and the voltage of the P9 connection point of the sensing circuit part 63 is applied to the P5 terminal, This divided voltage is applied to terminal 5 as a reference voltage of the current amplification unit of the amplifier U3 of the feedback control unit 700.

Now, the terminal voltage of the output terminal (P6) of the sensing circuit unit 630 as a sensing current signal is applied to terminal 6 as a current amplification unit sensing voltage of the amplifier (U3) of the feedback control unit 700, and the output Since 'Low' is output to the terminal (pin 7), the first photocouplers (PC1A, PC1B) of the dimming control signal generator 740 operate, and the switching converter unit (with an intermediate frequency for dimming control corresponding to 5V) As the PFM (U2) operates so that 400) oscillates, 50% dimming control is eventually performed on the LED lighting unit. However, at this time, the second photocoupler PC2 of the dimming level detector 820 of FIG. 10 does not yet operate because the dimming level value (5V) is higher than the reference voltage (2V), and thus the power factor improving unit of FIG. 8 Since the eighth switching element (Q8) of (900) continues to be in the 'On' state, it is maintained at a relatively high first capacitance value (CX3 + CX4) for heavy load, and detailed power factor control is performed by PFC (U1 ) It is controlled by the power factor correction circuit unit 300 including.

By the way, when the dimming level is input as 1.5V through the input terminals (DIM+, DIM-) of the dimming interface unit 810, 1.5V is also output to the CS terminal. Therefore, in this case, the current feedback unit 710 of FIG. 9 1.5V is also applied to the CS terminal of , and therefore, the voltage difference between the voltage of the CS terminal (P3) of the current feedback unit 710 and the voltage of the P9 point of the smoothing circuit unit 610 is divided to correspond to 1.5V at the P5 point. Voltage appears, and eventually, the output to the LED lighting unit is dimmed to 15% brightness by switching of the transformer output, the first photocoupler (PC1), and the switching converter unit (400: see FIG. 8), while at the same time , since a voltage corresponding to 1.5V is also applied to the non-inverting input terminal of the comparator U5 of the dimming level detection unit 820, assuming that a reference transfer of 2V is set to the inverting input terminal of the comparator U5, the Since the output of the comparator becomes 'Low', the light emitting diode (PC2A) of the second photocoupler (PC2) emits light, and the first power factor improving unit (900: see FIG. 8) in low light (less than 20%) dimming. 2 Since the light receiving part PC2B of the photocoupler PC2 is turned on, the eighth switching element Q8 is eventually turned off and the combined capacitance value is reduced from (CX3+CX4) to (CX3), and the power factor continues even in low light dimming. can be maintained above 0.9.

That is, the present invention, unlike the 1-stage (STAGE) method of the fourth prior art, is a 2-stage (STAGE) method, a power factor correction circuit composed of an active PFC (U1) and its peripheral devices ( 300), a PWM or PFM (U2) and a switching converter unit 400 consisting of its peripherals. Since it operates to boost the pulsating wave in the rectified state above the peak value of the input AC voltage, it has the advantage of maximizing active power (power factor correction close to 1) by allowing current to flow in all phases of the AC input voltage. , PWM or PFM (U2) is a type of circuit that modulates the pulse width or frequency, regardless of whether it is insulated or non-insulated, and steps it down to a low voltage for driving LEDs. In the case of a light load, in particular, by adding a power factor improving unit 900, it is an excellent technology to achieve a power factor of 0.9 or more without flicker and EMI problems even at a light load. [Table 1] shows the above The power factor (PF) value at each load amount according to the optimal embodiment of the present invention is not considered. can indicate

power factor Dimming voltage (V) One 2 3 4 5 6 7 8 9 10 load (%) 10 20 30 40 50 60 70 80 90 100 Power factor (PF) - 0.9 0.91 0.93 0.95 0.95 0.96 0.97 0.975 0.98

Finally, with reference to FIG. 9, the overheating control function of the present invention will be described. For example, when external dimming is 100%, that is, when the voltage of the CS terminal (P3) is 10V, overheating of the converter circuit (for example, 80 ℃ or more) PTC type thermistor of the current feedback unit 710 (Positive Temperature Coefficient Thermistor) When (THS1) is open, the resistance between the contact point P4 on one side of the thermistor THS1 and the CS terminal P3 increases from (R67//R71) to (R71), and P9 of the sensing circuit part 63 The one-side voltage divider resistance between the connection point and P5 remains as (R58), but the other side synthetic voltage divider resistance of the sensing circuit part 63 is (Req = R84//VR1 + R67//R71) to (Req' = R84//VR1 + R71), so the divided voltage of the P5 contact point (ie, the reference voltage of the 5th pin of the amplifier U3) decreases. Therefore, as the voltage of pin 5, which is the output voltage of the amplifier U3, is changed from "High" to "Low," the first port of the first dimming control signal generator 740 is changed despite the 100% dimming condition. As the couplers (PC1A, PC1B) operate, the PFM (U2) operates so that the switching converter unit 400 oscillates at the intermediate frequency for dimming control, and eventually dimming control that lowers the output current to the LED lighting unit is performed This will protect the entire circuit.

Of course, when the temperature drops and the thermistor THS1 of the current feedback unit 710 is returned to its original position, naturally, the dimming control is stopped and 100% full operation is returned.

In the above, the present invention has been described according to one embodiment of the present invention, but as in the case of three or more lighting units, those skilled in the art to which the present invention pertains within the scope of the technical spirit of the present invention. It is natural that changes and modifications in .

(First prior art) (FIG. 1)
10: EMI filter 20: rectifier
30: power factor correction PWM unit 40: DC unit
50: feedback unit 60: driving power supply unit
70: dimming control unit 80: dimming interface unit
T1: Trans
(Second prior art) (FIG. 2)
110: EMC filter module 120: bridge rectification module
130: first transformer 140: second transformer
150: PWM switching control module 160: switching module
170: smoothing circuit module 180: voltage sensing module
190: transformer connection control module
(Third prior art) (Figs. 3 and 4)
100: safety and EMI filter unit 200: primary rectification unit
300: snubber circuit part 400: controller part
500: switching unit 600: transformer
700: power factor improving circuit unit 800: surge voltage prevention unit
900: secondary rectification unit 1000: constant current and dimming control unit
1100: power supply unit for dimming sensor 1200: PWM dimming signal input unit
1300: EMI filter unit
710: full-wave rectifier 720: condenser
730: Damper circuit 740: CMP terminal
(4th prior art) (Figs. 5 and 6)
10: power factor correction type dimming converter 102: AC input unit
104: voltage conversion unit 106: dimming circuit unit
108: reactance control unit 110: dimming control unit
20: external power supply 22: lighting device
(the present invention) (Figs. 7 to 11)
100: power supply unit 200: rectification unit
300: power factor correction circuit unit 350: first auxiliary power supply unit
400: switching converter unit 450: second auxiliary power unit
500: rectifier circuit unit 600: power output unit
610: smoothing circuit part 620: filter part
700: feedback control unit 710: current feedback unit
720: voltage feedback unit 730: amplification unit
740: dimming control signal generator 750: third auxiliary power supply
800: dimming/power factor control unit 810: dimming interface unit
820: dimming level detection unit 900: power factor improvement unit

Claims (7)

A converter circuit for an LED lamp having a power factor correction function during dimming,
A power supply unit 100 that receives commercial AC power, filters it, and supplies it safely;
a rectifier 200 for rectifying the AC power filtered by the power supply unit;
a switching converter unit 400 performing frequency modulation while inverting the DC power rectified by the rectification unit 200;
a power factor correction circuit unit 300 for correcting the power factor of the DC power rectified by the rectification unit 200;
A transformer (T1) for receiving the DC power rectified by the rectifying unit and converting it to the voltage level of the lighting unit of the LED lamp while inverting and correcting the power factor by the power factor correction circuit unit 300 and the switching converter unit 400;
A synchronous rectification circuit unit 500 for converting the AC suitably transformed in the secondary side of the transformer T1 into DC;
A power output unit 600 for smoothing and filtering the ripple current of the rectifier circuit unit 500 and supplying stable DC power to the LED;
a feedback control unit 700 that senses output current and voltage from the power output unit 600 and outputs a dimming control signal to the switching converter unit 400 for feedback control;
a dimming/power factor control unit 800 that applies a dimming level outside the converter circuit and generates a power factor improvement control signal under a low dimming condition according to the dimming level; and
a power factor improving unit (900) for improving the power factor in low dimming by changing a reactance of an output terminal of the rectifying unit (200) in a low dimming condition in response to the power factor improvement control signal from the dimming/power factor control unit (800);
It is made including,
The dimming/power factor control unit 800 detects a dimming interface unit 810 that provides a dimming level outside the converter circuit and a dimming level input from the dimming interface unit 810 to operate the power factor improving unit 900. It consists of a dimming level detection unit 820 that controls,
When a voltage corresponding to a dimming level below the reference value is input through the input terminals (DIM+, DIM-) of the dimming interface unit 810,
The reference voltage of the voltage corresponding to the dimming level below the reference value is also applied to the current feedback unit 710 of the feedback control unit 700, and the output to the LED lighting unit is dimmed by switching of the switching converter unit 400, and at the same time,
On the other hand, while a voltage corresponding to a dimming level lower than the reference value is applied to the dimming level detection unit 820, the switching element Q8 of the capacitor CX4 for adjusting the reactance of the power factor improving unit 900 in low light dimming is applied. A converter circuit for an LED lamp having a power factor correction function during dimming, characterized in that it operates so that a switching signal is issued. According to claim 1,
In the power output unit 600, a sensing unit for sensing secondary side voltage and current is provided,
In the feedback control unit 700, by outputting a feedback signal to the switching converter unit 400 by the voltage and current sensed by the sensing unit, switching is performed at a higher frequency than the frequency at high output for low output , A converter circuit for an LED lamp having a power factor correction function during dimming, characterized in that feedback control is performed with constant current and constant voltage. According to claim 1,
The feedback control unit 700,
A current feedback unit 710 for generating a current sensing signal by sensing the current at both terminals P6 and P9 of the sensing resistor SH3 of the sensing circuit unit 630 of the power output unit 600;
a voltage feedback unit 720 for generating a voltage sensing signal by sensing the output voltage of the output terminal P2 of the smoothing circuit unit 610 of the power output unit 600 through a voltage dividing resistor;
A converter for LED lamps having a power factor correction function during dimming, characterized in that composed of a dimming control signal generator 740 for generating a dimming control signal to the switching converter unit 400 according to the levels of the current sensing signal and the voltage sensing signal. Circuit. delete delete According to claim 1,
Control between the current feedback unit 710 and the switching converter unit 400 is performed by a first photocoupler PC1,
A converter circuit for an LED lamp having a power factor correction function during dimming, characterized in that the control between the dimming level detection unit 820 and the power factor improving unit 900 is performed by the second photocoupler (PC2). According to claim 6,
The power factor improving unit 900 is a light receiving unit PC2B of the second photocoupler PC2 of the power factor improving unit 900 in low light dimming while the light emitting diode PC2A of the second photocoupler PC2 emits light. Since is turned on, the switching element (Q8) is turned off and the reactance adjustment capacitor (CX4) is opened, resulting in a combined capacitance value that is lowered.

Images