TW201448666A - LED lamp - Google Patents

Abstract

The present invention discloses an LED lamp. By incorporating LED long strings in parallel and a capacitor, the LED lamp can remain high power factor (PF) and perform more uniform brightness without AC frequency flickering.

Description

LED light fixture

The invention relates to an LED lamp, in particular to an LED lamp with high power effect, uniform brightness and good color rendering.

The high-voltage LED long string has the advantages of low price, no electromagnetic interference (EMI) and simple structure, and is increasingly adopted by the public. However, the long drive mode of high voltage LEDs still has many shortcomings that need to be improved.

In U.S. Patent No. 7,081,722, a multi-segment switch is used to drive a long string of high voltage LEDs to accommodate high and low input voltages, but the methods described in the above patents, such as the drive current is a constant current, or by the drive current increasing with the input voltage, In order to improve the power factor (PF), there are defects in the actual application, and there is room for improvement. In Fig. 1, (A) shows the waveform of the input AC voltage after bridge rectification; (B) shows that the LED current increases with the increase of the input voltage in order to increase the PF; (C) shows the LED constant current output wave. Types (D) and (E) show the LED light-emitting modes of (B) and (C), respectively. As can be seen from the figure, the brightness of long strings of conventional high voltage LEDs is proportional to the input voltage. Moreover, in the period (I) when the input voltage is lower than the starting voltage VF of the LED string closest to the power source, the entire string of LEDs does not emit light due to no current flowing, forming a dark block. In addition, the LED string is sequentially illuminated as the input voltage rises, so that the overall brightness is in phase with the input voltage, commonly known as AC ripple or stroboscopic, which can cause eye fatigue and discomfort.

Supertex, a US semiconductor manufacturer, has released a product to reduce the proportion of the entire lamp that does not emit light by reducing the minimum on-voltage of the LED segment. However, when the input voltage is lower than the minimum on-voltage, it still causes darkness.

Therefore, it is necessary to develop a high-voltage driving LED architecture with high power factor, low cost, high efficiency, reduced dark block ratio, no AC ripple, high color rendering effect, and total brightness does not change with input voltage.

The object of the present invention is to provide an LED lamp which can greatly reduce the AC ripple and maintain a high color rendering effect under the condition of maintaining high power.

The control circuit of the present invention is not limited to an integrated circuit, and may be an entire circuit control architecture or device.

The LED lamp of the present invention may include: a first LED long string, a second LED long string, and a capacitor. The first LED is long in an input voltage period, and the period during which the input voltage is lower than the start potential VF of the long string of the first LED is not (I). The second LED long string is electrically connected in parallel with the first LED, and during the period (I), the period in which the second LED does not emit light is (II), but (I) is greater than (II). The capacitor is electrically connected in parallel with the long length of the second LED such that the first LED long string and the second LED long string are at least partially optically complementary.

The LED lamp of the present invention may further include: a first LED long string, a second LED long string, and a capacitor. The first LED is long in an input voltage period, and the period during which the input voltage is lower than the start potential VF of the long string of the first LED is not (I). The second LED long string is electrically connected in parallel with the first LED long string, and the period in which the second LED long string does not emit light is (II), but (I) and (II) do not overlap. The capacitor is electrically connected in parallel with the long length of the second LED such that the first LED long string and the second LED long string are optically complementary.

Alternatively, the LED lamp of the present invention may include: a first LED long string, a second LED long string, and a capacitor. When the input voltage is the highest, the first LED long string has the highest brightness and the highest power consumption. The long length of the second LED is lower due to the long string of the first LED. The capacitor is electrically connected in parallel with the second LED. Thereby, when the input voltage is lower than the lowest starting potential VF of the long string of the first LED, the long string of the second LED can continue to emit light. Preferably, when the input voltage is the lowest, the long length of the second LED string is the highest and the power consumption is the highest.

The above LED lamp preferably includes at least one diode electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected in series to the second LED long string.

Alternatively, the LED lamp of the present invention comprises: a first LED long string, a second LED long string electrically connected in parallel with the second LED, a capacitor electrically connected in parallel with the first LED, and at least one diode . The diode is electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected in series to the second LED long string, when the input voltage is lower than the capacitor voltage The current can still flow into the long string of the first LED.

Preferably, in the luminaire of the present invention, the first LED long string and the second LED long series are thermally connected to the same heat sink.

20, 20'‧‧‧ input voltage sampling circuit

30‧‧‧Constant power calculation circuit

40‧‧‧Voltage reversal circuit

51, 51'‧‧‧ master servant controller

70‧‧‧The first LED long string

70’‧‧‧Second LED long string

902, 902'‧‧‧ Bridge Rectifier

903‧‧‧Half-bridge rectifier

D1‧‧‧Reverse withstand voltage diode

C2‧‧‧ storage capacitor

R2, R3‧‧‧ resistance

Figure 1 shows the relationship between the current and illuminating waveforms of a conventional LED luminaire and the input voltage waveform.

Fig. 2 is a view showing a driving circuit of the LED lamp of the present invention.

Fig. 3 is a view showing the illuminating wave pattern of the LED lamp of Fig. 2.

Fig. 4 is a view showing a driving circuit of another LED lamp of the present invention.

Fig. 5 is a view showing the illuminating wave pattern of the LED lamp of Fig. 4.

Fig. 6 shows the total luminance of the long LED strings of the second LED at different times.

Fig. 7 shows an example of a combination of a long LED string and related components.

Figure 8 shows a schematic diagram of adding X capacitance and setting the storage capacitor in the long string of LEDs.

The LED lamp referred to in the present invention is a single lamp comprising at least two long strings of LEDs connected in parallel, and may be in the form of a bulb, a light bar, a lamp tube, etc., but is not limited thereto. A single luminaire usually has a heat sink (also known as a heat sink or heat sink). Each LED long string may comprise a single or a plurality of LED strings in series, each of which may be uniformly on/off or segmented. Each LED string can include a single or a plurality of series and/or parallel LEDs.

Figure 2 is a block diagram showing one of the preferred embodiments of the LED lamp of the present invention. The output of the bridge rectifier 902 is connected to the current input terminals of the first LED long string 70 and the second LED long string 70' in parallel. In this embodiment, the first LED long string and the second LED long string respectively comprise a plurality of LED strings in series, which are controlled by respective current switches in parallel. The current switch can be a conventional constant current controller consisting of an operational amplifier and an N-type high voltage component.

The long length of the first LED has a high power factor characteristic, similar to the conventional multi-segment control LED, so the luminance of the light increases with the input voltage. When the input voltage is lower than the lowest starting voltage of the first LED string, the long string of LEDs flows due to no current, causing a dark block of the entire lamp. In addition, the long strings of LEDs are sequentially illuminated as the input voltage rises, resulting in an AC ripple as shown in Figure 1 (D). The average voltage of the long string of the first LED is V1, flat The average current is I1, and the ideal output power of the first LED long string is P1=V1×I1.

Since the two LED long strings are connected to the same bridge rectifier 902, a reverse voltage diode D1 is disposed between the second LED long string and the output of the bridge rectifier 902, and the output terminal of the withstand voltage diode D1 is A storage capacitor C2 is connected in parallel between the long input terminals of the LED. As the storage capacitor C2 is charged and discharged, the current switch can sequentially turn on the corresponding LED string. Because the second LED has a long series-parallel capacitor C2, the input current is not proportional to the input voltage, and there is no high power factor. However, during the period when the input voltage is lower than the capacitor voltage, the capacitor C2 can continuously supply the long string of electric energy of the LED, which not only improves the luminous efficiency, but also makes the brightness of the overall LED relatively stable.

The average current flowing through the long string of the second LED is I2, and the average voltage is the voltage V2 of the capacitor C2, and the output power of the second LED long string is P2=V2×I2. As shown in Fig. 3, the broken line is the voltage of the long string of the first LED, and the solid line is the voltage of the long string of the second LED, V2 > V1. If the current flowing through the long string of the first LED is the same as the current of the long string of the second LED, P2>P1, and the luminance of the long string of the second LED is better than that of the first LED. As can be seen from the figure, in the period (I) in which the long length of the first LED does not emit light, the period (II) in which the second LED does not emit light is small, so the long string of the second LED can compensate for the long string of the first LED. Part of the dark area, or a long string with the first LED is partially optically complementary, reducing the time the fixture does not illuminate.

In the long string of the second LED, the multi-segment current switch is connected in parallel with the LED. Therefore, during the discharge of the capacitor, the multi-segment switch can fluctuate with the voltage of the input capacitor, and find the best corresponding number of LED strings, and continuously emit light.

Figure 4 shows the architecture of another preferred embodiment of the present invention. The difference from the first embodiment is that the current switches of the first LED long string 70 and the second LED long string 70' are respectively connected to the respective master/slave controllers 51, 51', and the appropriate ones can be selected. The LED string is turned on or off to correspond to its input voltage. Every small string of electricity The output of the flow control switch automatically detects the voltage at the terminal. When the input voltage of the long string of LEDs increases from zero potential to the highest potential, and the terminal voltage reaches the set voltage, the current switch current of the main servant is lowered, and the LED strings are sequentially illuminated.

In this embodiment, the first LED long string 70 has high power factor characteristics and is designed for constant power. The input voltage sampling circuit 20 samples the divided voltage between the resistors R2 and R3 and is calculated by the constant power calculating circuit 30 . The calculation result is transmitted to the main servant controller 51, and the current of each LED string can be adjusted to make the output power of the long string of the first LED approach a fixed value.

An input voltage sampling circuit 20' and a voltage inversion calculation circuit 40 are disposed between the main servo controller 51' of the second LED long string 70' and the output terminal of the bridge rectifier 902. After the input voltage sampling circuit 20' is sampled between the resistors R2 and R3, it is calculated by the voltage inversion calculation circuit 40, and each of the LED strings is set to a constant current by the constant current controller. And the higher the input voltage, the lower the brightness, and the lower the input voltage, the higher the brightness.

The output of the constant current controller is connected in parallel to the corresponding LED string, and a voltage detector is connected to detect the voltage of the output terminal. If the detected voltage is higher than a certain set value, the LED string will be activated and the constant current switch of the higher potential LED string will be turned off. Therefore, when the output voltage of the bridge rectifier increases, the controller circuit can lower the output current of the LED string; when the output voltage of the bridge rectifier decreases, the controller circuit can increase the output current of the LED string. Figure 5 shows the illuminating waveform of this architecture, where (A) is the output voltage waveform of the bridge rectifier, (B) is the brightness of the long string of the first LED, and (C) is the brightness of the long string of the second LED. . If the first LED long string and the second LED long string are packaged in the same light emitting package or in the lamp, the brightness of the overall LED lamp is close to constant brightness as shown by (D). In this embodiment, the first LED does not emit a long string. The period (I) does not overlap with the period (II) in which the second LED does not emit a long string, so the second LED long string can theoretically completely compensate for the dark area of the long string of the first LED, or is long with the first LED. Completely optically complementary.

In other embodiments, in order to improve the accuracy of the constant light, the brightness change of the long string of the first LED can be actually measured, and then the brightness of the long string of the second LED is adjusted to make the brightness of the two pairs complement each other. For example, if the first LED long string with high power is a luminance/time function, then the second LED long string is the inverse function of the first string luminance/time. In this way, the sum of the brightness of the long strings of the two LEDs does not change with time, closer to the ideal constant light source.

Alternatively, the second LED long string is driven in a constant current manner to overcome the problem that the entire LED is dark when the first LED long string cannot be lit. As shown in Fig. 6, (A) is the output voltage waveform of the bridge rectifier, (B) is the brightness of the long string of the first LED with high power, and (C) is the second LED continuously driven by the constant current. The long string of brightness, (D) is the total brightness of (B) and (C), although the brightness change is not improved, the dark area can be eliminated. (E) is the brightness of the long string of the second LED driven by the constant current only in the dark area, and (F) is the total brightness of (B) and (E), except that the dark area is almost completely eliminated, the brightness can be more uniform.

In addition, in order to improve color rendering, a long string of red high voltage LEDs may be connected in parallel with the capacitor output end of the second LED string to form three high voltage LED long string architectures. The control mode of this architecture is similar to that of the second LED long string, but it drives the long string of red LEDs with different currents to reinforce the original color rendering. The driving current of the long string of the red LED can be constant current or adjusted with the brightness of the white light, and the output current can be proportional to the input voltage, inversely proportional or irrelevant.

In the present invention, the coupling structure of the LED long string and the AC power source is not limited to the above embodiment. Figure 7 shows the other coupling methods. The dashed boxes represent the LED string and switch combination. In the figure, (A) includes two parallel voltage withstand reverse diodes D1, D1' and storage capacitors C2, C2', but one of the withstand voltage reverse diodes D1 connects two parallel LED long strings. . (B) comprising two parallel bridge rectifiers 902, 902', each connected to a long string of LEDs, one of which is connected in parallel with the storage capacitor C2, and does not need to be connected to the withstand voltage reverse diode D1; The difference from (B) is that the bridge rectifier connected to the capacitor C2 is a half-bridge rectifier 903 of the center tap structure.

In the present invention, the size of the capacitor and the position of the parallel connection are also not limited to the above embodiment. Figure 8 shows the other coupling modes. In (A), the storage capacitor C2 connected to the withstand voltage reverse diode D1 has a larger capacitance value, and the capacitor C3 that is not connected to the withstand voltage reverse diode (commonly known as X capacitor) is small (about <0.2uF); (B) shows that capacitor C2 can be set in the long string 70' of the LED, the current output of any LED string, the reverse voltage diode D1 is set Between the capacitor C2 and the current output of the LED string. The reverse voltage diode D1 can also be changed to an LED or other component that prevents current from being reversed.

The data is actually measured in the architecture of Figure 4. The specifications of the first and second LED long strings, such as the wattage number (lm/W), electrical characteristics such as the on-voltage, are the same. The first LED long string 70 has a total of 12 LED strings with high power factor (PF) characteristics.

The second LED long string 70' has a total of 6 LED strings, wherein the first LED string comprises 10 LEDs in series, and each of the second to sixth LED strings comprises 3 LEDs in series, corresponding to the current switch. Segmentation control. The turn-on voltage of each of the LEDs is Vf = 3V, and the turn-on voltage of each of the second to sixth LED strings is about 9V. This design allows the number of LED strings to be activated to be dynamically corrected with the instantaneous capacitor voltage, ensuring that the capacitor voltage is greater than the minimum VF total voltage, and there is no luminescence.

The fast digital camera is used to observe and record the overall LED long string illumination brightness, and adjust the LED output current so that the total brightness does not change with time and is close to a constant value.

If there is only a long string of the first LED, the power factor (PF) is about 0.96. If the first LED long string is combined with the second LED long string, the power factor (PF) is still greater than 0.7.

Making the second LED long string into a constant current output can solve the original problem of the dark block, as shown in Figure 6. Alternatively, changing the long LED of the second LED to a red LED can increase its color rendering.

In summary, the present invention integrates two different high-voltage LED long strings, and still has high power factor characteristics in electrical properties, and the entire LED lamp can emit light when the input voltage is zero, and the light does not follow the fluctuation of the input voltage. Changed with a constant illuminating effect.

In the present invention, the number and connection method of the withstand voltage reverse diode and the storage capacitor are not particularly limited, and may depend on the number of LEDs and the number of LEDs required. It is within the scope of the invention to provide a long string of suitable electrical energy for the LED.

The effects and advantages of the present invention can be summarized from the above description including:

1. By simply combining LED long strings, the problem of dark areas can be solved effectively and economically.

2. After the LED string is combined, it still has a high power effect.

3. Not only achieve constant power output, but also maintain constant brightness output.

70‧‧‧The first LED long string

70’‧‧‧Second LED long string

902‧‧‧Bridge rectifier

D1‧‧‧Reverse withstand voltage diode

C2‧‧‧ storage capacitor

Claims (12)

An LED lamp comprising: a first LED long string, in an input voltage cycle, the period of time when the input voltage is lower than the start potential VF of the first LED long string is not (I); a second LED is long a string, electrically connected in parallel with the first LED, and in the period (I), the period in which the second LED does not emit light is (II), but (I) is greater than (II); and a capacitor, and The second LED is electrically connected in parallel so that the first LED long string and the second LED long string are at least partially optically complementary. The LED lamp of claim 1, further comprising: at least one diode electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected to the The second LED is long. The LED lamp of claim 1, wherein the first LED long string and the second LED long string are thermally connected to the same heat sink. An LED lamp comprising: a first LED long string, in an input voltage cycle, the period of time when the input voltage is lower than the start potential VF of the first LED long string is not (I); a second LED is long The string is electrically connected in parallel with the long length of the first LED, and the period in which the second LED does not emit light is (II), but (I) and (II) do not overlap; and a capacitor is long with the second LED Electrically paralleling, the first LED long string and the second LED long string are optically complementary. The LED lamp of claim 4, further comprising: at least one diode electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected in series to the second LED Long strings. The LED lamp of claim 4, wherein the first LED long string and the second LED Long strings of heat are connected to the same heat sink. An LED lamp comprising: a first LED long string, when the input voltage is the highest, the brightness is the highest, and the power consumption is the highest; a second LED long string is a lower power factor relative to the first LED long string; and a capacitor, The second LED is electrically connected in parallel with the second LED; thereby, when the input voltage is lower than the lowest starting potential VF of the long string of the first LED, the long string of the second LED can continue to emit light. For the LED lamp of claim 7, when the input voltage is the lowest, the second LED has the highest brightness and the highest power consumption. The LED lamp of claim 7, further comprising: at least one diode electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected in series to the second LED Long strings. The LED lamp of claim 7, wherein the first LED long string and the second LED long string are thermally connected to the same heat sink. An LED lamp comprising: a first LED long string; a second LED long string electrically connected in parallel with the first LED; a capacitor connected in parallel with the second LED; and at least one diode Body, electrically coupled between the first LED long string and the second LED long string, and the output end of the diode is electrically connected in series to the second LED long string, when the input voltage is lower than the capacitor voltage, the current Still can flow into the long string of the first LED. The LED lamp of claim 11, wherein the first LED long string and the second LED long string are thermally connected to the same heat sink.