Method for controlling LED lighting and lighting device using same

Abstract

In a method for controlling LED lighting for lighting an LED string which is driven by a full-wave rectified pulsating current and in which a plurality of LEDs are connected in series from a power supply end serving as a proximal end side to a distal end side, a first power supply point is provided on the proximal end side, a second power supply point is provided at an LED connection point where the number of the LEDs connected in series from the proximal end side is larger than the number of the LEDs counted from the distal end side, a first LED lighting control operation is performed to light the LEDs connected from the second power supply point toward the distal end side according to the magnitude of an instantaneous value while a pulsating instantaneous voltage is low and, after all the LEDs from the second power supply point to the farthest-end LED are lit, a second LED lighting control operation is performed to light the LEDs from the proximal-end-side first power supply point to the farthest-end LED, the number of which is equal to or more than the number of the LEDs from the second power supply point to the farthest-end LED, according to the instantaneous value of the pulsating current. In the method for controlling LED lighting, the first lighting control operation and the second lighting control operation are performed in reverse order when the instantaneous value of the pulsating voltage shifts from increase to decrease.

Description

Method for Controlling LED Lighting and Lighting Device Using the Same

[0001] The present invention relates to a method for controlling LED lighting that uses a pulsating current obtained by full-wave rectifying alternating current to light an LED without using a direct current power supply, and a lighting device using the same.

[0002] LED lighting has the characteristics of long life and low power consumption compared to conventional lighting fixtures such as fluorescent lamps and incandescent bulbs. Therefore, as a lighting device that replaces fluorescent lamps and incandescent bulbs to improve the living environment through energy conservation and thus prevent global warming, it is rapidly spreading in various fields.

[0003] However, many LED lights use a direct current power supply that outputs a constant voltage to operate long-life LEDs. Generally, in a direct current power supply, after rectifying and smoothing the input alternating current and then converting it to a high frequency, it goes through step-down, rectification, and smoothing to obtain the desired direct current voltage, and negative feedback control is used to obtain a stable direct current voltage. In addition, a large-capacity electrolytic capacitor is used for smoothing after rectification, and multiple capacitors may be used. By the way, when calculating the life of a direct current power supply, the electrolytic capacitor used has the characteristic that its life is halved for every 10°C increase in ambient temperature. Therefore, it is necessary to consider the life and failure of the electrolytic capacitor as well as the failure and life of other components used in the direct current power supply. At present, even when using long-life LEDs, the life of the lighting device as a whole is determined by the life and failure rate of the direct current power supply used in the device.

[0004] In addition, a direct current power supply uses many components to reduce harmonic waves generated when rectifying and smoothing the input alternating current, radiated noise generated due to high-frequency operation inside the power supply, etc. Although it is a means by which a small and stable direct current can be easily obtained, the extension of the life of the direct current power supply, the simplification of the method for reducing harmonic waves and unnecessary radiated noise, etc. are still unsolved problems since the emergence of LED lighting. Therefore, solutions for solving the above problems of conventional LED lighting have been explored.

[0005] Therefore, in order to maximize the inherently long lifespan characteristics of LEDs, LED lighting technology has been disclosed that utilizes pulsating current obtained by full-wave rectification of AC to light the LEDs without using a DC power supply (see, for example, Patent Document 1).

[0006] Japanese Patent Publication No. 5486698 describes the conventional AC-driven LED drive control method, cited as reference document 1 above, with reference to drawings. Figure 5 is an example of a circuit diagram for explaining this conventional AC-driven LED drive control method, and Figure 6 shows the LED lighting state according to this circuit diagram (Figure 5). Referring to these, the conventional AC-driven LED drive control method will be explained below. In order to facilitate understanding of the present invention, including this figure and other drawings, the number of LEDs is exemplarily set to 10 and the AC voltage fluctuation to ±10% in this explanation, prioritizing the simplification of the text for clarity of the drawings. However, it should be emphasized that even with a relatively low AC voltage of 100V, the peak value is approximately 141V, so in actual LED lighting, roughly 50 to 60 LEDs are required, and the number of LEDs will differ depending on the AC voltage. However, if dozens of LEDs are shown in the drawing, the drawing will become complicated and difficult to understand. Therefore, in the explanation of this invention, the number of LEDs in the drawing will be 10 as an example, and the operation will be explained in the following numbered order. 1. Even if the pulsating voltage is low and two LEDs do not light up, SW1 to SW6 remain closed. The pulsating voltage gradually rises, and LEDs 1 and 2 light up. At this point, the pulsating voltage is low and LEDs 3 to 10 cannot light up. Continue this operation as long as the pulsating voltage is low and LEDs 1 to 4 are not lit, and move to the next operation when the pulsating voltage rises and LEDs 1 to 4 can light up. 2. When the pulsating voltage rises further and it becomes possible to light up four LEDs, open SW1. SW2 remains closed, so LEDs 1 to 4 light up, but the pulsating voltage is still low and LEDs 5 to 10 do not light up. 1. Continue this operation as long as the pulsating voltage is low and LEDs 1-6 are not lit. When the pulsating voltage rises and LEDs 1-6 can be lit, proceed to the next operation. If LEDs 1-4 cannot be kept lit, return the switches to their original positions and return to the previous operation. 3. When the pulsating voltage rises further and all six LEDs can be lit, open SW2. SW3 remains closed, so LEDs 1-6 light up. The pulsating voltage is low and LEDs 7-10 do not light up. Continue this operation as long as the pulsating voltage is low and LEDs 1-8 are not lit. When the pulsating voltage rises and LEDs 1-8 can be lit, proceed to the next operation. If LEDs 1-6 can no longer be kept lit, return the switches to their original positions and return to the previous operation.4. When the pulsating voltage rises further and it becomes possible to light up 8 LEDs, open SW3. SW4 remains closed, so LEDs 1-8 light up. The pulsating voltage is low, so LEDs 9-10 do not light up. Continue this operation as long as the pulsating voltage is low and LEDs 1-9 are not lit. When the pulsating voltage rises and LEDs 1-9 become able to light up, move to the next operation. Also, when it becomes impossible to keep LEDs 1-8 lit, return the SWs to their original positions and return to the previous operation. 5. When the pulsating voltage rises further and it becomes possible to light up 9 LEDs, open SW4. SW5 remains closed, so LEDs 1-9 light up. The pulsating voltage is low, so LED 10 does not light up. Continue this operation as long as the pulsating voltage is low and LEDs 1-10 are not lit. When the pulsating voltage rises and LEDs 1-10 become able to light up, move to the next operation. Also, when it becomes impossible to keep LEDs 1-9 lit, return the SWs to their original positions and return to the previous operation. 6. When the pulsating voltage rises further and all 10 LEDs can light up, SW5 is opened. Since SW6 remains closed, all LEDs 1 through 10 light up. The operation of lighting LEDs 1 through 10 continues, but when it becomes impossible to light LEDs 1 through 10, the switches are returned to their original positions and the operation returns to the previous state.

[0007] Furthermore, once the maximum number of LEDs that can be lit with the current has been reached, the current will begin to decrease, and thereafter, the reverse of the previous operation should be performed.

[0008] Figure 6 is an explanatory diagram showing the LED lighting state when the LED driving control method using the AC drive method based on the drawing in Figure 5 is implemented. In this explanatory diagram, the pulsating voltage is explained using the operation from the start of the voltage rise after the voltage has dropped completely as an example. The SW state is maintained unless otherwise instructed. The specific procedure for opening and closing the switches is shown for when the opening and closing operations of each SW (switch) shown in Figure 5 are performed according to the procedures 1 to 7.

[0009] Conventional AC-driven LED lighting supplies power to the LEDs from a fixed point and increases or decreases the number of lit LEDs according to the pulsating instantaneous voltage. Therefore, when the pulsating instantaneous voltage is high, the number of lit LEDs increases, and when the pulsating instantaneous voltage is low, the number of lit LEDs decreases. Consequently, LEDs close to the power supply point remain lit even when the AC voltage drops, but LEDs farther from the power supply point gradually turn off starting from the furthest LED as the voltage drops, and this extinguishing is visible to the naked eye.

[0010] This will be explained based on the diagram of the lighting state of conventional AC-driven LED lighting. Figure 6 is a diagram showing the LED lighting state according to voltage fluctuations when all 10 LEDs are lit when the AC voltage is at its maximum using the conventional AC driving method. This driving method aims to help understand the technology of controlling the lighting of LEDs with the pulsating current obtained by full-wave rectifying the AC input. As for the specific procedure for opening and closing the switches, the diagram shows the state after opening and closing each SW (switch) shown in Figure 5 according to the procedures 1 to 7 described above.

[0011] Regarding the drawings, Figure 6(a) on the left shows the state when the voltage rises (see the peak shown by the solid line representing the pulsating current at nominal voltage + 10%). At the peak shown by the solid line at nominal voltage + 10%, it can be seen that all of LEDs 1 to 10, which are exemplified for the explanation of the present invention, are lit.

[0012] Furthermore, Figure 6(b) in the middle shows the state at standard voltage (see the peak portion indicated by the solid line representing the pulsating current at nominal voltage ±0%). At the peak portion of the solid line indicating nominal voltage ±0%, it can be seen that LEDs 1 to 9, which are exemplified for the explanation of the present invention, are lit, while LED 10 is off.

[0013] Furthermore, Figure 6(c) on the right shows the state when the voltage drops (see the peak shown by the solid line representing the pulsating current at nominal voltage -10%). At the peak shown by the solid line at nominal voltage -10%, it can be seen that LEDs 1 to 8, which are exemplified for the explanation of the present invention, are lit, while LEDs 9 and 10 are off.

[0014] Therefore, in order to avoid a situation where some of the LEDs in the LED lighting are visibly turned off, conventional LED lighting control methods have been employed that ensure all LEDs remain lit even when the AC voltage drops (that is, regardless of the supply voltage in Figure 6, which is a diagram illustrating the problem of the present invention, only eight LEDs are installed and all LEDs 1 to 8 are lit).

[0015] The problem with adopting this control method is that it requires controlling the LED lighting to match the lowest pulsating voltage. As a result, the voltage difference between the currently operating AC supply voltage and the lowest AC supply voltage cannot contribute to light emission and becomes a loss. Therefore, improving lighting efficiency and reducing the losses required to achieve this is inherently difficult.

[0016] The above problems can be explained in more detail as follows: In conventional AC-driven LED lighting, as mentioned above, the number of LEDs that light up starting from the power supply point increases when the peak voltage of the pulsating current is high, and decreases when it is low. Therefore, LEDs close to the power supply point remain lit even when the peak voltage of the pulsating current decreases, but LEDs further away gradually become lit for shorter periods as the peak voltage of the pulsating current decreases, and eventually turn off.

[0017] As the AC voltage drops, the LEDs sequentially turn off starting from the furthest end of the power supply point, and this can be visually confirmed. Therefore, conventional AC-driven LED lighting was designed so that all LEDs would light up even when the input AC voltage was at its lowest, thus eliminating LEDs that would not light up during voltage drops.

[0018] This is to eliminate non-illuminating LEDs when the supply voltage drops within the nominal fluctuation range, preventing the LED lighting from being mistaken for a malfunction. For the reasons above, even if the AC voltage is higher than the lower limit of the nominal fluctuation range, the difference between the lower limit and the current supply voltage cannot be utilized and becomes a loss, not contributing to light emission.

[0019] Therefore, conventional AC-driven systems have the difficult problem of not being able to improve lighting efficiency, and the portion that is lost cannot be used to improve efficiency.

[0020] The object of the present invention is to provide an LED lighting control method that utilizes pulsating current obtained by full-wave rectification of AC without using a DC power supply to light the LEDs, which has an extremely long product life, excellent luminous efficiency, and makes efficient use of power energy, and by lighting all LEDs even when there are voltage fluctuations, it is possible to reduce the losses of LED lighting and improve efficiency compared to conventional methods, as well as to provide an LED lighting control method and lighting device using the same.

[0021] To solve the above-mentioned problems, the LED lighting control method according to claim 1 of the present invention is an LED lighting control method that is driven by a full-wave rectified pulsating current and has an LED lighting control function for lighting an LED row in which a plurality of LEDs are connected in series between the power supply end on the near end and the far end, the power supply end on the farthest end, wherein a first power supply point is provided on the near end, and a second power supply point is provided at a connection point between LEDs such that the number of LEDs connected in series from the near end is equal to or greater than the number of LEDs connected in series from the far end, a first LED lighting control operation is performed in which the LEDs connected from the second power supply point toward the far end are lit in accordance with the magnitude of the instantaneous value while the instantaneous voltage of the pulsating current is low, a second LED lighting control operation is performed in which the LEDs connected toward the far end from the first power supply point on the near end to the farthest end are lit in accordance with the instantaneous value of the pulsating current, with the number of LEDs lit in accordance with the instantaneous value of the pulsating current being equal to or greater than the number of LEDs lit in the first LED lighting control operation, The first and second LED lighting control operations are performed in reverse order following the second LED lighting control operation, as the instantaneous value of the pulsating current decreases from the peak value of the pulsating current voltage.

[0022] Furthermore, the LED lighting control method according to claim 2 of the present invention is characterized in that, in the LED lighting control method described in claim 1, at least one of the LEDs connected in series is not composed of a single LED but of multiple LEDs connected in parallel. Furthermore, the LED lighting control method according to claim 3 of the present invention is characterized in that, in the LED lighting control method described in claim 1, an on / off switch for isolation is provided between the second power supply point and the LED connected closest thereto, and the on / off switch is opened during the first lighting control operation and closed during the second lighting control operation.

[0023] Furthermore, the LED lighting control method according to claim 4 of the present invention is characterized in that, in the LED lighting control method described in claim 3, instead of providing the on / off switch, it is provided with a diode that performs an equivalent role to the on / off switch.

[0024] Furthermore, the LED lighting control method according to claim 5 of the present invention is a lighting device equipped with the control method described in any one of claims 1 to 4.

[0025] According to the present invention, a method for controlling LED lighting that utilizes pulsating current obtained by full-wave rectification of AC without using a DC power supply to light the LEDs is provided, which results in an extremely long product life, excellent luminous efficiency, and efficient use of power energy, and by lighting all LEDs even during voltage fluctuations, it is possible to provide an LED lighting control method and a lighting device using the same that can reduce losses in LED lighting and improve efficiency compared to conventional methods.

[0026] This is a diagram of the LED lighting control circuit that constitutes the basic configuration of the present invention. This is a characteristic diagram illustrating the LED lighting control method according to the present invention. This is a diagram of the LED lighting control circuit according to the first embodiment of the present invention. This is a diagram of the LED lighting control circuit according to the second embodiment of the present invention. This is a conventional LED lighting control circuit diagram. This is a characteristic diagram illustrating a conventional LED lighting control method.

[0027] The following describes the essential basic configuration features of the LED lighting control method according to the present invention (hereinafter referred to as the "new AC drive method" as appropriate). This explanation will utilize the circuit diagram in Figure 1 and the characteristic diagram in Figure 2 to facilitate understanding. Figure 1 is a schematic diagram of the circuit realizing the new AC drive method according to the present invention, and a schematic diagram of an LED lighting device using this circuit. Figure 2 is an explanatory diagram showing the LED lighting state using the new AC drive method based on the schematic configuration shown in Figure 1.

[0028] The new AC drive method according to the present invention has two main features: firstly, it dynamically changes the lighting area of ​​the LED array in response to the instantaneous voltage of the pulsating current; secondly, while conventional AC drive methods only light up the LED section when the instantaneous voltage of the pulsating current obtained by full-wave rectifying the supplied AC voltage is high, the new AC drive method according to the present invention lights up the LEDs even when the instantaneous voltage is low; and secondly, it is a driving method that lights up all LEDs within the same pulsating current cycle even if the AC voltage fluctuates within a predetermined range. Furthermore, by utilizing the AC voltage fluctuations that could not be used in the past to contribute to LED lighting, this new AC drive method achieves a significant improvement in lighting efficiency and a reduction in losses compared to conventional AC drive methods used in LED lighting control.

[0029] In conventional AC driving methods, all LED rows are lit when the AC voltage is at the lower limit of its fluctuation range. As a result, the current and its peak value are limited to the value at the lower limit of the AC voltage and do not flow beyond that. Even if the supplied AC voltage increases, the current waveform plateaus. However, in the new AC driving method of the present invention, the waveform plateaus until the instantaneous voltage determined by the lighting of all LEDs is eliminated. This results in a current waveform that approximates the input voltage waveform, and even during voltage fluctuations, the current waveform approximates a sinusoidal wave in accordance with the voltage fluctuations, making it possible to achieve further harmonic reduction.

[0030] The following describes the conceptual diagram of the operation of the new AC drive method of the present invention. Figure 1 is a schematic configuration diagram for realizing a specific lighting control method of the new AC drive method according to the present invention. In order to facilitate understanding of the present invention, the LEDs depicted in the drawings, as in Figures 3 to 5, are shown as an example, with 10 LEDs connected in series, which is fewer than the actual number of LEDs, and switches for realizing the functions of the present invention are shown placed in predetermined locations.

[0031] Furthermore, the control function unit is shown as a block diagram, and the specific and illustrative configuration of this control function will be described in the first and second embodiments described later.

[0032] Next, an example of the procedure for a specific lighting control method of the new AC drive method according to the present invention will be explained in accordance with the configuration in Figure 1. In the following explanation, the operation will be explained using the pulsating current instantaneous voltage from the start of the voltage rise after the voltage has dropped as an example. In the following explanation, the SW state will remain as is unless instructed otherwise, but opening and closing the SW may be optional if there is no effect on anything else. The switching of each switch shown in Figure 1 will be performed using the switching procedure unique to the present invention. Specifically, in the configuration shown in Figure 1, the LEDs will be driven in the following procedure from item 1 to item 7. 1. While the pulsating current instantaneous voltage is low and the two LEDs have not yet lit up, close PSW01, open PSW02, close SW1, and open the other switches. The pulsating current instantaneous voltage will gradually rise, and eventually LEDs 7 and 8 will light up. 2. When the pulsating current instantaneous voltage rises further and reaches a voltage that can light up all four LEDs, open SW1 and close SW2. Furthermore, for the other switches, PSW01 remains closed, PSW02 remains open, and SW3 and SW14-16 remain open. This operation continues as long as the instantaneous voltage of the pulsating current is low and LEDs 1-6 are not lit. When the instantaneous voltage of the pulsating current rises and LEDs 1-6 can be lit, the next operation is performed. If LEDs 1-4 cannot be kept lit, the SWs are returned to their original positions and the operation returns to the previous state. 3. When the instantaneous voltage of the pulsating current rises further and reaches a voltage that can light all six LEDs, SW2 is opened, SW3 is closed, PSW01 is opened, and PSW02 is closed. Furthermore, for the other switches, SW1 remains open, and SW14-16 remain open. 4. When the instantaneous voltage of the pulsating current is low and LEDs 1-8 are not lit, this operation continues. When the instantaneous voltage of the pulsating current rises and LEDs 1-8 can be lit, the operation moves to the next step. If LEDs 1-6 cannot be kept lit, the switches are returned to their original positions and the operation returns to the previous state. 4. When the instantaneous voltage of the pulsating current rises further and reaches a voltage that can light up all eight LEDs, SW3 is opened and SW14 is closed. As for the other switches, PSW01 remains open, PSW02 remains closed, SW1-2 remains open, and SW15-16 remains open.1. Continue this operation as long as the instantaneous voltage of the pulsating current is low and LEDs 1-9 are not lit. When the instantaneous voltage of the pulsating current rises and LEDs 1-9 can be lit, proceed to the next operation. If LEDs 1-8 cannot be kept lit, return the switches to their original positions and return to the previous operation. 5. When the instantaneous voltage of the pulsating current rises further and reaches a voltage that can light up all nine LEDs, open SW14 and close SW15. Also, for the other switches, PSW01 remains open, PSW02 remains closed, SW1-3 remains open, and SW16 remains open. Continue this operation as long as the instantaneous voltage of the pulsating current is low and LEDs 1-10 are not lit. When the pulsating current voltage rises and LEDs 1-10 can be lit, proceed to the next operation. Also, if LEDs 1-9 cannot be kept lit, return the switches to their original positions and return to the previous operation. 6. When the instantaneous voltage of the pulsating current rises further and it becomes possible to light up all 10 LEDs, open SW15 and close SW16. This will light up all LEDs from LED1 to LED10. The other switches will remain as follows: PSW01 will remain open, PSW02 will remain closed, and SW1-3 and SW14-15 will remain open. Continue this operation as long as LEDs 1-10 are lit. 7. From this point onward, as the instantaneous voltage of the pulsating current will begin to drop after reaching its peak value, perform the reverse operation.

[0033] Furthermore, as a special note regarding the operation explanations from 1 to 7, PSW02 is provided for the purpose of separating LEDs 6 and 7 when PSW01 is closed and preventing reverse voltage application to LED 6. It should be noted that if the forward voltage drop of the diode is within an acceptable range, it can be replaced with a diode. Figure 2 is a diagram of the LED lighting status according to voltage fluctuations when considering the new AC drive method of the present invention so that all 10 LEDs light up when the AC voltage is at its maximum. It is a diagram intended to help understand the technology of controlling the lighting of LEDs with the pulsating current obtained by full-wave rectifying the AC input. Figure 2(a) on the left shows the state when the AC input voltage is at its maximum (nominal voltage + 10%), Figure 2(b) in the middle shows the state when the AC input voltage is at its standard (nominal voltage ± 0%), and Figure 2(c) on the right shows the state when the AC input voltage is at its minimum (nominal voltage - 10%).

[0034] According to this diagram, the new AC drive method, when designed considering an AC voltage fluctuation range of, for example, ±10%, can light up all LEDs within the same pulsating waveform even when the voltage rises or falls. This demonstrates that by utilizing the voltage fluctuation section that was previously unusable, a significant efficiency improvement (for example, about 10%) can be achieved.

[0035] Next, a specific and illustrative detailed description of the new AC drive method according to the present invention will be presented as the first and second embodiments. First, the first embodiment will be described. The first embodiment is a method of implementing the new AC drive method according to the present invention using digital control. Figure 3 is a diagram that shows the control details of the new AC drive method according to this first embodiment in more detail than Figure 1. The details of the control will be described below.

[0036] The drive control unit is equipped with an ADC for voltage measurement. The ADC for voltage measurement has the function of converting analog input signals into digital signals (i.e., Analog to Digital Converter), and will be referred to simply as "ADC" below.

[0037] In the present invention illustrated in this first embodiment (hereinafter simply referred to as "the present invention"), the ADC has the function of converting two analog input signals, In1 and In2, into digital signals. The ADC then selects one of In1 and In2 according to the instructions of the MCU (described later), converts the selected analog signal into a digital signal, and reports its value to the MCU.

[0038] Furthermore, the drive control unit is equipped with a DAC for setting the current value. The DAC has the function of converting a digital input signal into an analog voltage signal (i.e., a Digital to Analog Converter), and will be referred to simply as "DAC" below.

[0039] Furthermore, the drive control unit is equipped with a microcontroller unit (hereinafter simply referred to as "MCU"), which controls the lighting of all LEDs. More specifically, an ADC for voltage measurement is used to collect the instantaneous voltage of the pulsating current, and the necessary switches are instructed to open and close via the switch control unit. At the same time, a DAC for current value setting is used to control the gate voltage of the metal oxide field-effect transistor (hereinafter simply referred to as "MOS") MOS1, thereby controlling the current value ID flowing through MOS1 to be within a predetermined range.

[0040] Furthermore, the drive control unit controls the opening and closing of all switches via the switch control unit according to instructions from the MCU. The switches have a PSW1 that controls the power supply point of the LEDs, and a function to open and close switches CSW14, CSW26, CSW3, and CSW5, which are connected to multiple lead ends drawn from multiple locations in the LED row, in order to drive a preset number of LEDs according to the instantaneous voltage of the pulsating current, and connect to the drain of the drive MOS1.

[0041] Furthermore, as mentioned above, the drive control unit controls the current ID flowing through MOS1 by controlling the gate voltage applied to MOS1. To explain in a little more detail, the MCU measures the voltage across resistor RD with the ADC and calculates the current value ID by dividing the obtained value by the value of RD. The MCU compares the calculated ID with a target value held within the MCU. If the difference is within a predetermined range, the DAC setting remains as it is. If the difference is small and outside the predetermined range, the DAC setting value is increased by a predetermined value. If the difference is large and outside the predetermined range, the DAC setting value is decreased by a predetermined value. This operation allows the MCU to manipulate the gate voltage of MOS1 and control the current (ID) flowing through MOS1 to be within the set range.

[0042] Please note that Figure 3 is merely an explanatory diagram of the operation overview of the new AC drive method according to the present invention, and therefore does not show components necessary for stable operation, such as resistors and capacitors. This diagram is merely an illustrative diagram intended to facilitate understanding of the invention and does not guarantee stable operation or explain standards for performance, function, etc.

[0043] Next, the operation of the new AC drive method using digital control according to the second embodiment of the present invention described above will be explained. Specifically, the operation is started in the following procedure. (Operation 1) Prior to the start of LED lighting control, the MCU first makes the necessary settings to enable operation. Next, the MCU makes the necessary settings for the surrounding parts. Specifically, this includes instructing the switch control unit to open all switches, setting the output of the DAC for current value setting to bring the current of MOS1 within the allowable value according to the pre-set information, initializing the ADC for voltage measurement and reacquiring voltage information if necessary, etc. Needless to say, if any other operation is deemed necessary, it will not be interfered with. Also, if it is clear that the operation will have no effect on anything else, the corresponding switch does not need to perform the instructed operation, and the same applies thereafter. (Operation 2) Next, the MCU prepares for LED lighting control. First, it detects the start of the rising edge of the pulsating voltage. This involves using a voltage measuring ADC to measure In1 (pulsating voltage) (more precisely, the instantaneous voltage of the pulsating current), and then measuring the voltage value of In2 (the voltage generated across resistor RD due to the ID of MOS1). When the value of In1 exceeds a preset range and it is confirmed that In1 continues to decrease or increase, it is determined that the instantaneous voltage of the pulsating current has begun to rise or fall. This determination of rising or falling instantaneous voltage of the pulsating current will be carried out in the same manner from now on, and will be referred to as the rise and fall of the pulsating current. It should also be added that the measurement of In1 and In2 is performed continuously without instruction. This operation continues until it is detected that the instantaneous voltage of the pulsating current has begun to rise and the measured pulsating current voltage In1 has reached a voltage equal to or greater than the preset lighting voltage (reference voltage 2) of LEDs 7-8. (Operation 3) The MCU closes PSW1 and CSW14 to light up LEDs 7-8, then compares the terminal voltage In2 of RD with the value of (set current value for LEDs 7-8) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, it increases the output of the current value setting DAC by a preset value; if it is higher, it decreases it by a preset value. This operation is repeated to control the current of LEDs 7-8 so that it remains within the set range. If upper and lower limits are set for the gate voltage applied to MOS1 or the output voltage of the current value setting DAC, those conditions will also be followed.Furthermore, the instantaneous voltage value In1 of the pulsating current when the voltage value of resistor RD generated by current ID of MOS1 settles within the set range, and the DAC instruction value at that time, are reflected as actual values ​​in the reference values, etc. (Other methods may be possible, but in this invention, they are simply reflected.) Then, if the measured pulsating current voltage In1 is less than the preset lighting voltage (reference voltage 4) of LEDs 7 to 10, this operation continues, if In1 exceeds reference voltage 4, the operation moves to the next step, and if In1 falls below reference voltage 2, the operation returns to the previous step. (Operation 4) The MCU opens CSW14 and closes CSW26 in order to light up LEDs 7 to 10. PSW1 is then closed. Next, the terminal voltage In2 of RD is compared with the value of (set current value for LEDs 7-10) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, the output of the current value setting DAC is increased by a preset value; if it is higher, it is decreased by a preset value. This operation is repeated to control the current of LEDs 7-10 so that it remains within the set range. If upper and lower limits are set for the gate voltage applied to MOS1 or the output voltage of the current value setting DAC, those conditions will also be followed. The pulsating voltage value In1 and the DAC instruction value at the time In2, i.e., the voltage value of resistor RD generated by the current value ID of MOS1, settle within the set range, and these values ​​are reflected in the reference values, etc., as actual driving values ​​for LEDs 7-10. This operation continues as long as the measured pulsating voltage In1 does not reach the preset lighting voltage (reference voltage 6) for LEDs 1-6. When In1 exceeds the reference voltage 6, the operation moves to the next step, and when In1 falls below the reference voltage value 4, the operation returns to the previous step. (Operation 5) The MCU opens CSW26 and PSW1 and closes CSW3 to light up LEDs 1 to 6. It should be noted that in this explanation, a diode is installed between LED 6 and LED 7 and functions as a substitute for the switch PSW02 function shown in Figure 1. Next, the terminal voltage In2 of RD is compared with the value of (set current value to flow through LEDs 1 to 6) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, the output of the current value setting DAC is increased by a preset value; if it is higher, it is decreased by a preset value. This operation is repeated to control the current of LEDs 1 to 6 to stay within the set range. If there are upper or lower limits set for the gate voltage applied to MOS1 or the output voltage of the current value setting DAC, those conditions will also be followed.Furthermore, the pulsating voltage value In1 and the DAC instruction value at the time when the voltage value of resistor RD generated by In2, i.e., the current value ID of MOS1, settles within the set range are reflected in the reference voltage, etc., as actual driving values ​​for LEDs 1 to 6. This operation continues as long as the measured pulsating voltage In1 does not reach the preset lighting voltage (reference voltage 8) for LEDs 1 to 8. When In1 exceeds the reference voltage 8, the operation moves to the next step, and when the reference voltage value falls below 6, the operation returns to the previous step. (Operation 6) The MCU opens CSW3 and closes CSW14 to light up LEDs 1 to 8. Next, the terminal voltage In2 of RD is compared with the value of (set current value to flow through LEDs 1 to 8) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, the output of the current value setting DAC is increased by a preset value; if it is higher, it is decreased by a preset value. This operation is repeated to control the current of LEDs 1 to 8 so that it falls within the set range. Furthermore, if upper or lower limits are set for the gate voltage applied to MOS1 or the output voltage of the DAC used for setting the current value, those conditions will also be followed. In addition, the pulsating voltage value In1 and the DAC instruction value at the time when the voltage value of resistor RD generated by In2, i.e., the current value ID of MOS1, settles within the set range will be reflected in the reference voltage value, etc., as the actual driving value of LED1 to LED8. Then, this operation will continue as long as the measured pulsating voltage In1 does not reach the preset lighting voltage (reference voltage 9) for LED1 to LED9, and when In1 exceeds the reference voltage 9, the next operation will proceed, and when the reference voltage value falls below 8, the operation will return to the previous operation. (Operation 7) The MCU opens CSW14 and closes CSW5 in order to light up LED1 to LED9. Next, the terminal voltage In2 of RD is compared with the value of (set current value to flow through LEDs 1-9) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, the output of the current value setting DAC is increased by a preset value; if it is higher, it is decreased by a preset value. This operation is repeated to control the current of LEDs 1-9 so that it remains within the set range. If upper or lower limits are set for the gate voltage applied to MOS1 or the output voltage of the current value setting DAC, those conditions will also be followed. Furthermore, the pulsating voltage value In1 and the DAC instruction value at the time In2, i.e., the voltage value of resistor RD generated by the current value ID of MOS1, settle within the set range, and these values ​​are reflected in the reference voltage value, etc., as actual data from when LEDs 1-9 were driven.Then, this operation continues as long as the measured pulsating voltage In1 does not reach the preset lighting voltage (reference voltage 10) for LEDs 1 to 10. When In1 exceeds the reference voltage 10, the next operation begins, and when the reference voltage falls below 9, the operation returns to the previous operation. (Operation 8) The MCU opens CSW5 and closes CSW26 to light up LEDs 1 to 10. Next, the terminal voltage In2 of RD is compared with the value of (set current value to flow through LEDs 1 to 10) × (resistance value of RD). If the value of In2 is lower than the aforementioned value, the output of the current value setting DAC is increased by a preset value; if it is higher, the output is decreased by a preset value. This operation is repeated to control the current of LEDs 1 to 10 so that it is within the set range. If upper or lower limits are set for the gate applied voltage of MOS1 or the output voltage of the current value setting DAC, those conditions will also be followed. Furthermore, the pulsating voltage value In1 and the DAC instruction value at the time when the voltage value across resistor RD, which is generated by the current value ID of MOS1, settles within the set range, are reflected in the reference voltage value, etc., as actual data from when LEDs 1 to 10 were driven. This operation continues as long as the measured pulsating voltage In1 is equal to or greater than the preset lighting voltage (reference voltage 10) for LEDs 1 to 10, and returns to the previous operation when the reference voltage value falls below 10.

[0044] As is clear from the above description, in the conventional LED lighting method that does not use the technology of the present invention, the power supply points of the LEDs were fixed, and the number of lit LEDs was increased or decreased according to the instantaneous voltage of the pulsating current. Therefore, the LED section that lights up when the instantaneous voltage is low also lights up when the AC voltage drops, but the part that lights up when the instantaneous voltage is high has a gradually shorter lighting time and eventually turns off when the AC voltage drops, and it was even possible to visually identify that it had turned off. That is, in the conventional AC drive, when the AC voltage is at the lower limit of the fluctuation range, all LED columns are lit, so the current flowing and its peak value are the maximum values at the lower limit of the AC voltage, and no more current flows, and the current waveform flattens out. Therefore, when the AC voltage drops, it appears as if only some of the LEDs have turned off. This phenomenon is very likely to be recognized as if there is a failure in some of the LEDs and some of the LEDs do not light up. To avoid this, it was necessary to consider that all LEDs would light up even at the lower limit of the fluctuation range of the AC voltage so that all LEDs would light up when the AC voltage drops. Therefore, as a trade-off, the fluctuating part of the AC voltage cannot be used for LED lighting, and there is also a problem of a decrease in the use efficiency of the AC input energy and an increase in losses.

[0045] However, according to the new AC drive method of the present invention, the lighting area of the LED column is dynamically changed according to the instantaneous voltage of the pulsating current, and the LED section that conventionally only lights up when the instantaneous voltage is high is also lit when the instantaneous voltage is low, so that all LEDs can be lit within the same pulsating current cycle even when the AD voltage fluctuates within a predetermined range. That is, in the new AC drive method of the present invention, there is no flattening of the waveform until the instantaneous voltage determined by all LED lighting is reached, and it is possible to realize a current waveform approximated to the input voltage waveform, and it is also possible to approximate to a current waveform approximated to a sine wave even when the voltage fluctuates, so that further harmonic reduction can be realized. That is, by the new AC drive method of this method, by also contributing the fluctuating part of the AC voltage that could not be used conventionally to LED lighting, a significant improvement in efficiency and reduction in losses have been achieved compared to the conventional method.

[0046] Next, a second embodiment of the new AC driving method according to the present invention will be described. The second embodiment is the content when the new AC driving method according to the present invention is realized by analog-digital hybrid control. FIG. 4 is a drawing that shows the content of the control unit of the new AC driving method according to this second embodiment in more detail than FIG. 1. For the sake of facilitating and simplifying the explanation and the drawing, the LEDs illustrated are fewer than the actual number of LEDs, and for example, 10 LEDs are used for the explanation. Hereinafter, the details of the control will be described.

[0047] The second embodiment is composed of constant current sources I1 to I6, switches OP1 to OP6 that control their operations, switches PSW01 and PSW02 for controlling the power supply locations of the LEDs, resistors Ri1 to Ri6 for detecting the currents flowing through the respective constant current sources, and a constant current source control unit that controls these, and LEDs. The constant current source control unit has the following functions.

[0048] The constant current control unit controls the constant current sources I1 to I6 using the switches OP1 to OP6, and controls the power supply locations according to the instantaneous voltage of the pulsating current using the switches PSW01 and PSW02. Further, the constant current control unit recognizes whether each constant current source is operating by detecting the voltage generated at both ends of the resistors Ri1 to Ri6 connected to the respective constant current sources I1 to I6.

[0049] In FIG. 4 used for the explanation of this second embodiment, the switch PSW02 is used for the explanation. However, since the purpose of PSW02 is to separate between LEDs 6 and 7 when PSW01 is closed and to prevent reverse voltage application to LED6, it is pointed out that if the forward voltage drop of the diode is within the allowable range, PSW02 can be replaced with a diode.

[0050] Also, in this figure, an example using a switch for suppressing the operation of the constant current source is described. Suppressing the operation of the constant current source will not change the operation whether the suppression function is included in the constant current source or a switch function is provided separately from the constant current source. However, the inventor of the present invention considered that it is easier to understand by explaining the functions separately as individual operations, so the above functions are explained separately.

[0051] Next, a new AC drive method for the mixed analog-digital control system according to the second embodiment of the present invention described above will be explained. Specifically, the LED lighting control is started (Start) in the following procedure. (Operation 1) Immediately after power-on, the constant current source control unit closes switch PSW01 and switches OP01 to OP03 to enable the operation of constant current sources I1 to I3, while PSW02 and switches OP04 to OP06 are opened, suppressing the operation of constant current sources I4 to 6. In reality, the start of operation rarely occurs when the pulsating current rises. In most cases, operations are performed sequentially in order of operation number up to the operation number corresponding to the instantaneous voltage of the input pulsating current, and at the same time, the LEDs are also lit while a series of operations up to the operation number corresponding to the instantaneous voltage are performed. However, explaining the operation would be very complicated, so here we will explain the control content assuming that the constant current control unit starts operating the moment the pulsating current voltage begins to rise. (Operation 2) While the instantaneous voltage of the pulsating current is low and LEDs 7-8 do not light up, the constant current control unit closes switches OP1-3, and maintains the current state of the other switches (OP4-6 are open, PSW01 is closed, and PSW02 is open). The instantaneous voltage of the pulsating current gradually rises and when constant current source I1 starts operating, LEDs 7 and 8 light up, but constant current sources I2-3 remain in an operational state. The constant current control unit knows that constant current source I1 has started operating when a voltage of I1 × Ri1 is generated across resistor Ri1. Similarly, the constant current control unit knows when I2-I6 have started operating. This operation continues as long as the instantaneous voltage of the pulsating current rises further but constant current source I2 has not yet started operating and LEDs 7-10 do not light up, and then moves to the next operation when constant current source I2 starts operating. If constant current source I2 does not operate, and the current of constant current source I1 decreases or stops operating, the system determines that the instantaneous voltage of the pulsating current has decreased and maintains the current state until the pulsating current voltage rises again and LED lighting control becomes possible. (Operation 3) When the instantaneous voltage of the pulsating current rises, constant current source I2 starts operating and LEDs 7-10 light up. The constant current control unit knows that constant current source I2 has started operating and opens switch OP1 to suppress the operation of constant current source I1. Constant current source I3 remains in an operational state. The other switches maintain their current state (OP2-3 are closed, I2 is operational, I3 is operational, OP4-6 are open, suppressing the operation of constant current sources I4-I6, PSW01 is closed, PSW02 is open).The operation continues as long as the instantaneous voltage of the pulsating current does not yet start up and LEDs 1-6 do not light up, even though the instantaneous voltage of the pulsating current has risen further. Once the instantaneous voltage of the constant current source I3 starts up, the operation moves to the next step. If the instantaneous voltage of the constant current source I2 does not start up and the current of the constant current source I2 decreases or stops working, the system determines that the instantaneous voltage of the pulsating current has decreased, returns the switches to their state before the start of this operation, and returns to the previous step. (Operation 4) The instantaneous voltage of the pulsating current rises and the instantaneous voltage of the constant current source I3 starts up and LEDs 1-6 light up. The constant current control unit knows that the constant current source I3 has started up and opens switch OP2 to suppress the operation of the constant current source I2. It also opens switch PSW01 and closes PSW02 and switches OP4-6 to make the constant current sources I4-6 operational. The other switches remain in their current state (OP1 is open to suppress the operation of constant current source I1). The operation continues as long as the instantaneous voltage of the pulsating current does not rise further but the constant current source I4 has not yet started operating and LEDs 1-8 have not yet lit up. Once the constant current source I4 starts operating, the operation moves to the next step. If the constant current source I4 does not start operating, and the current of the constant current source I3 decreases or stops operating, the system determines that the instantaneous voltage of the pulsating current has decreased, returns the switches to their state before the start of this operation, and returns to the previous step. (Operation 5) The instantaneous voltage of the pulsating current rises, the constant current source I4 starts operating, and LEDs 1-8 light up. The constant current control unit knows that the constant current source I4 has started operating and opens switch OP3 to suppress the operation of constant current source I3. Constant current sources I5-I6 remain in an operational state. The other switches remain in their current state (OP1-2 are open to stop constant current sources I1-I2, OP5-6 are closed, PSW01 is open, and PSW02 is closed). The operation continues as long as the instantaneous voltage of the pulsating current does not yet start to operate and LEDs 1-9 do not light up, even though the instantaneous voltage of the pulsating current has risen further. When the instantaneous voltage of the constant current source I5 starts to operate, the operation moves to the next step. If the instantaneous voltage of the constant current source I4 does not start to operate, and the current of the constant current source I4 decreases or stops operating, the system determines that the instantaneous voltage of the pulsating current has decreased, returns the switches to their state before the start of this operation, and returns to the previous step. (Operation 6) The instantaneous voltage of the pulsating current rises, the instantaneous voltage of the constant current source I5 starts to operate, and LEDs 1-9 light up. The constant current control unit knows that the constant current source I5 has started to operate and opens switch OP4 to suppress the operation of the constant current source I4. The constant current source I6 remains in an operational state.The other switches remain in their current state (OP1-3 are open, stopping constant current sources I1-I3; OP5-6 are closed, PSW01 is open, and PSW02 is closed). This operation continues as long as the instantaneous voltage of the pulsating current does not yet start operating due to the constant current source I6 not starting up and LEDs 1-10 not lighting up. When the constant current source I6 starts operating, the operation moves to the next step. If the constant current source I6 does not start up, and the current of the constant current source I5 decreases or stops operating, the system determines that the instantaneous voltage of the pulsating current has decreased, returns the switches to their state before the start of this operation, and then returns to the previous step. (Operation 7) The instantaneous voltage of the pulsating current increases, the constant current source I6 starts operating, and LEDs 1-10 light up. The constant current control unit knows that the constant current source I6 has started operating and opens switch OP5 to suppress the operation of the constant current source I5. The other switches remain in their current state (OP1-5 are open, stopping constant current sources I1-I5; OP6 is closed, PSW01 is open, and PSW02 is closed). This operation continues as long as the instantaneous voltage of the pulsating current does not rise further but the constant current source I6 has not yet started operating and LEDs 1-10 have not lit up. When the constant current source I6 starts operating, the operation moves to the next step. This operation continues as long as the instantaneous voltage of the pulsating current is high and the constant current source I6 is operating. When the current of the constant current source I6 decreases or it stops operating, it is determined that the instantaneous voltage of the pulsating current has decreased, and the switches are returned to their state before the start of this operation, and then the operation returns to the previous step. From the specific descriptions of the various embodiments shown above, it can be easily understood that the contents of (1) to (5) below are sufficiently explained as the excellent technical idea of ​​the present invention.(1) The LED lighting control method according to the present invention is an LED lighting control method that is driven by a full-wave rectified pulsating current and has an LED lighting control function that lights up an LED row in which a plurality of LEDs are connected in series between the power supply end on the near end and the far end, the power supply end on the near end has a first power supply point and a second power supply point is provided at a connection point between LEDs in which the number of LEDs connected in series from the near end is equal to or greater than the number of LEDs connected in series from the far end, and while the instantaneous voltage of the pulsating current is low, the LEDs connected from the second power supply point toward the far end have the power supply The gist of the invention is to perform a first LED lighting control operation in which LEDs are lit according to the magnitude of the value, and after all LEDs from the second power supply point to the furthest LED have been lit, a second LED lighting control operation is performed in which more LEDs than the number of LEDs lit in the first LED lighting control operation are lit from the first power supply point on the near end to the furthest LED according to the instantaneous value of the pulsating current, and following the second LED lighting control operation, the first and second lighting control operations are performed in reverse order as the instantaneous value of the pulsating current decreases from the peak value of the pulsating current voltage. (2) Preferably, of the LEDs connected in series, at least one LED is not composed of a single LED but of multiple LEDs connected in parallel. (3) Preferably, an on / off switch for isolation is provided between the second power supply point and the LED connected closest to it, and it is preferable to control this on / off switch to open during the first lighting control operation and to close during the second lighting control operation. (4) Preferably, instead of providing the on / off switch, a diode that performs an equivalent function to the on / off switch may be provided. (5) A lighting device having the constituent requirements of (1) to (4) in this way can exhibit remarkable effects not seen in conventional lighting devices. Specifically, it is possible to fully enjoy the advantages of the LED driving method, which involves full-wave rectifying the AC power supply to create a pulsating current and using it to light the LED without smoothing. In other words, the inventors of this invention would like to emphasize that the present invention has the distinctive advantage of being able to utilize the energy of the AC power supply to the maximum extent without waste without using a large-capacity capacitor.

[0052] It should be noted that the circuit block diagrams and voltage / current (power) characteristic diagrams shown in the above-described embodiments and their modifications are merely examples, and it goes without saying that the structure, materials, circuit configuration, etc., can be appropriately modified within the scope that allows the effects of the present invention to be realized. Industrial application fields

[0053] The industrial application field of this invention relates to a control method for LED lighting that utilizes pulsating current obtained by full-wave rectification of alternating current in order to light an LED without using a DC power supply, and to any lighting device using this method.

Claims

1. An LED lighting control method that is driven by a full-wave rectified pulsating current and has an LED lighting control function for lighting an LED array in which multiple LEDs are connected in series between the power supply end on the near end and the far end, wherein a first power supply point is provided on the near end, and a second power supply point is provided at a connection point between LEDs such that the number of LEDs connected in series from the near end is equal to or greater than the number of LEDs connected in series from the far end, a first LED lighting control operation is performed in which LEDs connected from the second power supply point toward the far end are lit in accordance with the magnitude of the instantaneous value while the instantaneous voltage of the pulsating current is low, a second LED lighting control operation is performed in which LEDs equal to or greater than the number of LEDs lit in the first LED lighting control operation are lit in accordance with the instantaneous value of the pulsating current from the first power supply point on the near end to the farthest end, An LED lighting control method characterized in that, following the second LED lighting control operation, the first and second lighting control operations are performed in reverse order as the instantaneous value of the pulsating current decreases from the peak value of the pulsating current voltage.

2. The LED lighting control method according to claim 1, characterized in that at least one of the LEDs connected in series is not composed of a single LED but is composed of multiple LEDs connected in parallel.

3. The LED lighting control method according to claim 1, characterized in that an on / off switch for isolation is provided between the second power supply point and the LED closest to it, and the on / off switch is opened during the first lighting control operation and closed during the second lighting control operation.

4. The LED lighting control method according to claim 3, characterized in that instead of having the on / off switch, it is provided with a diode that performs an equivalent function to the on / off switch.

5. A lighting device comprising the control method described in any one of claims 1 to 4.

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