LED power supply control device and control method thereof

Abstract

An LED power supply control device capable of precisely controlling tiny currents supplies power to an LED load. The device comprises a conversion circuit, a control unit, a current adjustment unit, and a capacitor bank. The current adjustment unit detects a current feedback signal associated with the output current of the conversion circuit and, based on a comparison between the current feedback signal and a preset current condition, determines whether to control the capacitor bank to adjust its capacitance. The control unit then adjusts the switching frequency of the conversion circuit based on the capacitance value. The present invention also relates to a control method for the LED power supply control device.

Description

Technical Field

[0001] The present invention relates to an LED power supply control device and a control method thereof, and more particularly to an LED power supply control device and a control method thereof capable of precisely controlling tiny currents. Background Art

[0002] As light-emitting diodes (LEDs) become increasingly common and their manufacturing costs continue to decline, LED lighting applications are becoming increasingly widespread. Consequently, the demand for LED power supply controllers, which supply power to the LEDs, is also rapidly increasing. LED lighting systems typically include an LED power supply controller and an LED load comprising light-emitting diodes. The LED power supply controller supplies power to the LED load, causing it to emit light.

[0003] To meet the control requirements of varying LED lighting brightness (i.e., load current), conventional LED power supply control devices adjust the output current by adjusting the on and off times of the power switch in their internal conversion circuit. For example, the power switch is controlled to remain on while simultaneously monitoring the output current of the LED power supply control device. When the output current gradually rises to a preset limit due to the continuous conduction of the power switch and reaches a predetermined limit, the power switch is controlled to be turned off and a capacitor coupled to a control unit that provides a control signal to the power switch is charged. When the capacitor is charged to a predetermined specific voltage, the control unit correspondingly controls the power switch to be turned on, entering the next control cycle. Furthermore, the capacitance of the capacitor affects the length of the capacitor charging time and also affects the off time of the control signal. For example, the larger the capacitance of the capacitor, the longer it takes for the capacitor to charge to the predetermined specific voltage, which correspondingly prolongs the off time of the control signal. This reduces the switching frequency of the power switch, thereby causing the power supply control device to output a lower current. However, when the LED load current demand is extremely low (for example, but not limited to, less than 10mA), relying solely on the aforementioned single capacitor, the capacitor's charging time is limited by its capacitance, which in turn limits the lower limit of the power switch switching frequency. Consequently, conventional LED power supply control devices are unable to provide output currents lower than the preset minimum output current specification, and thus cannot meet the requirements for precise control in response to changes in the LED load current demand under extremely low output current conditions.

[0004] Therefore, how to design an LED power supply control device and its control method with the ability to accurately control tiny currents, while being able to provide a tiny output current lower than the preset minimum output current specification and still respond to the current demand changes of the LED load, is a major research topic that the inventors of the present disclosure want to conduct. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides an LED power supply control device with the ability to accurately control tiny currents to overcome the problems of the prior art. The LED power supply control device supplies power to the LED load, and the LED power supply control device includes a conversion circuit, a control unit, a current adjustment unit and a capacitor group. The conversion circuit is coupled to the LED load and receives an input voltage. The control unit is coupled to the conversion circuit to control the conversion circuit to convert the input voltage into an output voltage, so that the conversion circuit provides an output voltage and an output current to the LED load. The current adjustment unit is coupled to the conversion circuit to detect a current adjustment feedback signal related to the output current. The capacitor group is coupled to the control unit and the current adjustment unit. The current adjustment unit determines whether to control the capacitor group to adjust the capacitance value based on the comparison result between the current adjustment feedback signal and the current preset condition, and the control unit adjusts the switching frequency of the conversion circuit based on the capacitance value.

[0006] In order to solve the above problems, the present invention provides a control method for an LED power supply control device to overcome the problems of the prior art. The micro-current precise control method is used to control the LED power supply control device to supply power to the LED load. The micro-current precise control method includes the following steps: (a) controlling the LED power supply control device to convert the input voltage into the output voltage, and providing the output voltage and output current to the LED load. (b) obtaining a current adjustment feedback signal related to the output current, and comparing the current adjustment feedback signal with the current preset condition to obtain a comparison result. (c) adjusting the capacitance value of the capacitor group in the LED power supply control device according to the comparison result, and adjusting the switching frequency of the LED power supply control device according to the capacitance value to adjust the output current.

[0007] The main purpose and technical effect of the present invention is to determine whether to control the capacitor group to adjust the capacitance value based on the current preset conditions and the output current through the current adjustment unit, so as to adjust the capacitance value so that the control unit correspondingly adjusts the switching frequency of the conversion circuit switch, thereby achieving the technical effect of being able to respond to changes in the current demand of the LED load while being able to provide a tiny output current lower than the preset minimum output current specification.

[0008] In order to further understand the technologies, means and technical effects adopted by the present invention to achieve the intended objectives, please refer to the following detailed description of the present invention and the accompanying drawings. It is believed that the objectives, features and characteristics of the present invention can be understood in depth and in detail. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a circuit diagram of the LED power supply control system of the present invention;

[0010] Figure 2ADetailed circuit diagram of the first embodiment of the LED power supply control system of the present invention;

[0011] Figure 2B A detailed circuit diagram of a second embodiment of the LED power supply control system of the present invention;

[0012] Figure 3A A method flow chart of a method for accurately controlling a small current of an LED power supply control device according to the present invention; and

[0013] Figure 3B This is a flow chart of the capacitance value adjustment method of the present invention.

[0014] Description of reference numerals:

[0015] A, A'...LED control system

[0016] 100…LED power supply control device

[0017] 1…Conversion circuit

[0018] Q…Power switch

[0019] 12…Output path

[0020] 2…Control unit

[0021] Vc…Charging voltage

[0022] 3…Current adjustment unit

[0023] 4…capacitor bank

[0024] R…resistance

[0025] Ca…capacitor

[0026] 42…Switched capacitor bank

[0027] SW…switch

[0028] Ci…Current adjustment capacitor

[0029] 200...LED load

[0030] Vi…Input voltage

[0031] Vo…output voltage

[0032] Io…output current

[0033] Sc_Q…control signal

[0034] Sif1…current feedback signal

[0035] Sif2…current adjustment feedback signal

[0036] Sc, Sc1~Scn…capacitor adjustment signal

[0037] Si…current preset signal

[0038] C…capacitance value

[0039] Li…current preset conditions

[0040] Vi1~Vin…Threshold DETAILED DESCRIPTION

[0041] The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings:

[0042] See also Figure 1 This is a circuit diagram of an LED power control system according to the present invention. LED power control system A includes an LED power control device 100 and an LED load 200. The LED power control device 100 provides power to the LED load 200. The LED power control device includes a conversion circuit 1, a control unit 2, a current adjustment unit 3, and a capacitor bank 4. The conversion circuit 1 is coupled to the LED load 200 via an output path 12. The control unit 2 is coupled to the conversion circuit 1 and provides a control signal Sc_Q based on a current feedback signal Sif1 associated with the output current Io. This control signal controls the conversion circuit 1 to convert the input voltage Vi into an output voltage Vo to power the LED load 200. Conversely, the conversion circuit 1 also provides an output current Io to the LED load 200 via the output path 12, providing a power output corresponding to the load size. The current adjustment unit 3 is coupled to the output terminal of the conversion circuit 1 and detects a current adjustment feedback signal Sif2 associated with the output current Io on the output path 12. The capacitor bank 4 couples the control unit 2 and the current adjustment unit 3 and has a capacitance value C. It is worth mentioning that in one embodiment of the present invention, the current feedback signal Sif1 and the current adjustment feedback signal Sif2 fed back by the output path 12 can be obtained by, for example but not limited to, a conventional feedback circuit (not shown), which will not be elaborated herein.

[0043] Specifically, the control unit 2 receives a current feedback signal Sif1 associated with the output current Io and provides a corresponding control signal based on the current feedback signal Sif1 to adjust and stabilize the current value of the output current Io. For example, but not limited to, the control unit 2 can adjust and stabilize the current value of the output current Io by adjusting the on and off time of the power switch (not shown) inside the conversion circuit 1 based on the current feedback signal Sif1. The capacitance value C of the capacitor bank 4 affects the time when the control unit 2 charges the capacitor bank 4, which in turn affects the control unit 2 adjusting the off time of the power switch (not shown) inside the conversion circuit 1, thereby adjusting the output current Io of the conversion circuit. Among them, the current adjustment unit 3 compares the current adjustment feedback signal Sif2 corresponding to the output current Io based on the current preset condition Li provided internally or externally, and determines whether to provide the capacitance adjustment signal Sc to control the capacitor bank 4 to adjust the capacitance value C based on the comparison result.

[0044] Furthermore, the unadjusted capacitance value C of the capacitor bank 4 limits the maximum charging time that the control unit 2 can use to charge the capacitor bank 4. This maximum charging time is associated with the maximum off-time of the control signal Sc_Q (i.e., the capacitance value C limits the maximum off-time of the control signal Sc_Q), thereby limiting the minimum switching frequency of the power switch and, consequently, the minimum current value that the LED power supply control device 100 can provide. Consequently, when the LED load 200 has an extremely low current demand, less than the aforementioned minimum current value, the LED power supply control device 100 will be unable to provide the corresponding extremely low output current. Therefore, the primary purpose and technical effect of the present invention is to determine whether to control the capacitor bank 4 to adjust the capacitance value C based on a comparison between the preset current condition Li and the current adjustment feedback signal Sif2 associated with the output current Io by the current adjustment unit 3. By adjusting the capacitance value C, the LED power supply control device 100 can overcome the existing minimum output current limitation and further reduce the output current Io, thereby achieving precise control to meet the extremely low current demand of the LED load 200. It is worth mentioning that in one embodiment of the present invention, the control unit 2 and the current adjustment unit 3 can be integrated circuit chips, programmable microcontrollers or other chips or microcircuit components, or control circuits composed of electronic components.

[0045] See also Figure 2A This is a detailed circuit diagram of the first embodiment of the LED control system of the present invention, and is also shown in FIG. Figure 1In one embodiment of the present invention, the conversion circuit 1 is a buck converter including a power switch Q, but is not limited thereto. Any switching conversion circuit (such as, but not limited to, a flyback converter) that can control the LED load 200 should be included in the scope of this embodiment. The capacitor group 4 includes at least one capacitor Ca (one is shown in this embodiment) and at least one switched capacitor group 42, and the switched capacitor group 42 includes a switch SW and a current adjustment capacitor Ci connected in series with the switch SW. The capacitor Ca is coupled to the control unit 2. The switched capacitor group 42 is connected in parallel with the capacitor Ca, and the current adjustment unit 3 determines whether to provide the capacitor adjustment signal Sc1~Scn to turn on the switch SW based on the comparison result of the current preset condition Li and the current adjustment feedback signal Sif2 associated with the output current Io, so as to adjust the capacitance value C of the capacitor group 4 by controlling whether the capacitor Ca and the current adjustment capacitor Ci are connected in parallel.

[0046] Furthermore, the current preset condition Li can be at least one threshold value Vi1-Vin, and the number of threshold values ​​is less than or equal to the number of switches SW. The current adjustment unit 3 determines whether to turn on the corresponding switch SW based on whether the current adjustment feedback signal Sif2 corresponding to the output current Io is less than or equal to the threshold values ​​Vi1-Vin, thereby adjusting the number of capacitors Ca and current adjustment capacitors Ci connected in parallel to adjust the capacitance value C. For example, the current preset condition Li includes two threshold values ​​Vi1 and Vi2 (assuming they correspond to 10mA and 5mA, respectively), the number of capacitors Ca is two, the number of current adjustment capacitors Ci is four, and the number of switches SW is four. The four switches SW are respectively coupled to the current adjustment capacitors Ci, and two capacitors Ca are connected in parallel to the control unit 2. When the current adjustment feedback signal Sif2 corresponding to the output current Io is less than or equal to the threshold value Vi1 (corresponding to 10mA), the current adjustment unit 3 provides capacitance adjustment signals Sc1 and Sc2 to turn on the two switches SW, so that the two current adjustment capacitors Ci coupled to the switches SW are connected in parallel to the capacitors Ca (i.e., four capacitors are connected in parallel). In this way, the capacitance value C can be increased. The same is true when the output current Io is less than or equal to the current threshold Vi2 (corresponding to 5 mA), which will not be described in detail here.

[0047] Specifically, the control unit 2 adjusts the switching frequency of the control signal Sc_Q based on the charging time of the capacitor bank 4, thereby adjusting the magnitude of the output current Io. When the current adjustment feedback signal Sif2 corresponding to the output current Io is less than or equal to the thresholds Vi1-Vin, the current adjustment unit 3 turns on the switch SW corresponding to the thresholds Vi1-Vin, increasing the capacitance C. This correspondingly prolongs the charging time of the capacitor bank 4 controlled by the control unit 2, thereby lengthening the off time of the control signal Sc_Q provided by the control unit 2. This in turn reduces the switching frequency of the overall power switch, enabling the LED power supply control device 100 to provide a lower output current Io than before the capacitance C is adjusted. Conversely, the capacitance C is reduced, resulting in a higher output current Io. This solves the aforementioned problem of being unable to provide an output current Io that meets the extremely low current requirements of the LED load 200.

[0048] See also Figure 2A The capacitor bank 4 is also coupled to the output terminal of the conversion circuit 1 via a resistor R to receive the output voltage Vo. The charging time for the capacitor bank 4 can be calculated using the resistance of the resistor R and the capacitance C of the capacitor bank 4 (depending on the actual condition of the capacitor Ca and the current adjustment capacitor Ci being connected in parallel). The control unit 2 may include a discharge circuit or a switch circuit for discharging the capacitor bank 4. The charging time t can be expressed as:

[0049]

[0050] VOFT is a preset specific voltage used for comparison with the charging voltage of capacitor bank 4 during charging. When current feedback signal Sif1 reaches a preset current control upper limit (not shown) within control unit 2, control unit 2 adjusts control signal Sc_Q to enter the off-time to turn off power switch Q and simultaneously begins controlling the charging of capacitor bank 4. When the charging voltage of capacitor bank 4 rises to VOFT (for example, but not limited to 1V), control unit 2 ends the off-time of control signal Sc_Q, enters the next control cycle, and adjusts control signal Sc_Q to enter the on-time to turn on power switch Q.

[0051] In this way, the change of the capacitance value C can be adjusted by whether the capacitor Ca is connected in parallel with the current adjustment capacitor Ci, affecting the upper limit of the off time of the control signal S_Q provided by the control unit 2, thereby reaching the lower limit of the switching frequency of the power switch Q. When the capacitance value C becomes larger, the charging time can be prolonged, so that the off time of the control signal Sc_Q is prolonged, thereby causing the switching frequency of the power switch Q to be lowered to provide a smaller output current Io. On the other hand, the current preset condition Li can be pre-set in the current adjustment unit 3, and the current adjustment unit 3 uses the internal current preset condition Li to control the switch SW. Alternatively, the current preset condition Li can also be the same as Figure 2A As shown, the external circuit 300 provides a current preset signal Si to the current adjustment unit 3, so that the current adjustment unit 3 obtains a corresponding current preset condition Li according to the current preset signal Si.

[0052] by Figure 2A For example, the current preset condition Li sets the threshold Vin to correspond to 10mA, and the capacitance C of the capacitor Ca is 470pF, and the capacitance C of the current adjustment capacitor Ci is 330pF. When the output current Io is greater than 10mA, the current adjustment unit 3 provides a capacitance adjustment signal Sc1 corresponding to the threshold Vin to control the switch SW to be non-conductive, so that the capacitance C of the capacitor group 4 is 470pF. When the output current Io is less than or equal to 10mA, the current adjustment unit 3 provides a capacitance adjustment signal Sc1 corresponding to the current threshold Vin to control the switch SW to be conductive, so that the capacitance C of the capacitor group 4 is 470pF plus 330pF. In this way, the capacitance C can be increased, so that the control unit 2 can further reduce the switching frequency to provide a lower output current Io.

[0053] See also Figure 2B This is a detailed circuit diagram of the second embodiment of the LED control system of the present invention, and is also shown in FIG. Figure 1 . Figure 2B The LED control system A' of the embodiment Figure 2A The difference between the LED control system A and the control system A is that the capacitor bank 4 is not coupled to the output terminal of the conversion circuit 1 to receive the output voltage Vo. Instead, the control unit 2 internally provides a charging voltage Vc for charging the capacitor bank 4. The charging voltage Vc is used to charge the capacitor bank 4 through the resistor R, thereby generating a charging time (the control unit 2 may include a discharge circuit or a switch circuit for discharging the capacitor bank 4). In a preferred embodiment, the charging voltage Vc can be the operating voltage Vcc received by the control unit 2 itself. The charging time can be calculated using the resistance value of the resistor R and the capacitance value C of the capacitor bank 4 (depending on the connection of the capacitor Ca and the current adjustment capacitor Ci in parallel) using the aforementioned formula.

[0054] See also Figure 3A This is a flow chart of the method for accurately controlling a small current of an LED power supply control device of the present invention, and is also referred to in conjunction with Figures 1-2B. The micro-current precise control method mainly controls the LED power supply control device 100 to supply power to the LED load 200. The micro-current precise control method includes: first, controlling the LED power supply control device to convert the input voltage into the output voltage, and providing the output voltage and output current to the LED load (S100). A preferred embodiment is to use the control unit 2 to control the conversion circuit 1 to convert the input voltage Vi into the output voltage Vo, so as to provide the output voltage Vo and the output current Io through the output path 12 to power the LED load 200. Then, a current adjustment feedback signal associated with the output current is obtained, and the current adjustment feedback signal is compared with the current preset condition to obtain a comparison result (S120). A preferred embodiment is to use the current adjustment unit 3 to detect the current adjustment feedback signal Sif2 associated with the output current Io on the output path 12, and compare it with the current preset condition Li stored internally or provided externally to obtain a comparison result.

[0055] Then, the capacitance value is adjusted according to the comparison result, and the switching frequency of the LED power supply control device 100 is adjusted according to the capacitance value to adjust the output current (S140). A preferred embodiment is to use the comparison result obtained by the current adjustment unit 3 to control the capacitor group 4 to adjust the capacitance value C, so that the control unit 2 adjusts the switching frequency of the power switch Q inside the conversion circuit 1 according to the capacitance value C to adjust the output current Io of the conversion circuit 1. Among them, the control unit 2 adjusts the switching frequency of the control signal Sc_Q according to the charging time of charging the capacitor group 4, thereby adjusting the magnitude of the output current Io. A preferred embodiment can be to use the output voltage Vo to charge the capacitor group 4 through the resistor R to generate the charging time. Alternatively, the charging voltage Vc provided by the control unit 2 is used to charge the capacitor group 4 through the resistor R to generate the charging time. It is worth mentioning that the above steps do not limit the order of implementation. The order of the steps can be changed or the steps can be performed in parallel. As long as the order of implementation that can achieve the main technical effects of the present invention is achieved, it should be included in the scope of this embodiment.

[0056] See also Figure 3B This is a flow chart of the capacitance value adjustment method of the present invention, and is also referred to in conjunction with Figures 1 to 3A. The current preset condition Li can be at least one threshold value Vi1~Vin, and the capacitance value adjustment method includes: first, adjusting the capacitance value by controlling whether a plurality of capacitors in the capacitor group are connected in parallel (S200). A preferred embodiment is that the capacitor group 4 includes at least one capacitor Ca and at least one switch capacitor group 42, and the switch capacitor group 42 includes a switch SW and a current adjustment capacitor Ci connected in series with the switch SW. The current adjustment unit 3 determines whether to provide a control signal Sc1~Scn to turn on the switch SW based on the comparison result of the current preset condition Li and the current adjustment feedback signal Sif2 associated with the output current Io, so as to adjust the capacitance value C by controlling whether the capacitor Ca and the current adjustment capacitor Ci are connected in parallel. Then, whether to control the capacitors to be connected in parallel is determined based on whether the current adjustment feedback signal is less than or equal to at least one threshold (S220). In a preferred embodiment, the current adjustment unit 3 determines whether to turn on the corresponding switch SW according to whether the current adjustment feedback signal Sif2 corresponding to the output current Io is less than or equal to the threshold Vi1-Vin, so as to adjust the number of capacitors Ca and the current adjustment capacitor Ci in parallel and adjust the capacitance value C.

[0057] Then, when the current adjustment feedback signal is less than or equal to at least one threshold value, the control capacitors are connected in parallel to increase the capacitance value of the capacitor group (S240). Finally, when the current adjustment feedback signal is greater than at least one threshold value, the control capacitors are not connected in parallel to reduce the capacitance value of the capacitor group (S260). Among them, adjusting the capacitance value C of the capacitor group 4 mainly affects the turn-off time of the control signal Sc_Q of the control conversion circuit 1 (that is, the time to turn off the power switch Q), thereby affecting the switching frequency of the power switch Q. The above-mentioned steps (S240) and (S260) can be referred to the example implementation method. Figure 2A , I will not elaborate on it here.

[0058] However, the above description is only a detailed description and drawings of the preferred specific embodiments of the present invention, and the features of the present invention are not limited thereto and are not intended to limit the present invention. The full scope of the present invention should be based on the claims. All embodiments that are consistent with the concepts of the claims of the present invention and similar variations thereof should be included in the scope of the present invention. Any changes or modifications that can be easily thought of by any person skilled in the art within the field of the present invention can be covered by the claims of this disclosure.

Claims

1. An LED power supply control device capable of precisely controlling a tiny current, for supplying power to an LED load, the LED power supply control device comprising: a conversion circuit coupled to the LED load and receiving an input voltage; a control unit coupled to the conversion circuit, for controlling the conversion circuit to convert the input voltage into an output voltage, so that the conversion circuit provides the output voltage and an output current to the LED load; a current adjustment unit, coupled to the conversion circuit, for detecting a current adjustment feedback signal associated with the output current; and a capacitor group, coupling the control unit and the current adjustment unit; The current adjustment unit determines whether to adjust a capacitance value of the capacitor group according to a comparison result between the current adjustment feedback signal and a current preset condition, and the control unit adjusts a switching frequency of the conversion circuit according to the capacitance value.

2. The LED power supply control device according to claim 1, wherein the capacitor bank comprises: at least one capacitor coupled to the control unit; and At least one switched capacitor group connected in parallel with the at least one capacitor, the at least one switched capacitor group comprising a switch coupled to the current adjustment unit and a current adjustment capacitor connected in series with the switch; The current adjustment unit determines whether to turn on the switch according to the comparison result.

3. The LED power control device according to claim 2 , wherein the current preset condition is at least a threshold, and the current adjustment unit determines whether to turn on the switch of the at least one switched capacitor group corresponding to the at least one threshold according to whether the current adjustment feedback signal is less than or equal to the at least one threshold.

4. The LED power supply control device of claim 3 , wherein the current adjustment unit turns on the switch of the at least one capacitor switch group to increase the capacitance value when the current adjustment feedback signal is less than or equal to the at least one threshold value, and turns off the switch of the at least one switched capacitor group to decrease the capacitance value when the output current is greater than the at least one threshold value. 5 . The LED power control device as claimed in claim 1 , wherein the control unit adjusts the switching frequency according to a charging time of the capacitor bank, and the charging time is related to a value of the capacitor. 6 . The LED power control device as claimed in claim 5 , wherein the capacitor bank is coupled to a charging voltage provided by the control unit via a resistor, and the control unit generates the charging time by controlling the charging voltage to charge the capacitor bank via the resistor. 7 . The LED power control device as claimed in claim 5 , wherein the capacitor group is coupled to the output voltage via a resistor, and the control unit generates the charging time by controlling the output voltage to charge the capacitor group via the resistor. 8 . The LED power control device as claimed in claim 1 , wherein the control unit provides a control signal to the conversion circuit, and the control unit adjusts an off time of the control signal according to the capacitance value to adjust the switching frequency.

9. A method for controlling an LED power supply control device to supply power to an LED load, the method comprising the following steps: Controlling the LED power control device to convert an input voltage into an output voltage, and providing the output voltage and an output current to the LED load; Obtaining a current adjustment feedback signal associated with the output current, and comparing the current adjustment feedback signal with a current preset condition to obtain a comparison result; and A capacitance value of a capacitor group in the LED power control device is adjusted according to the comparison result, and a switching frequency of the LED power control device is adjusted according to the capacitance value to adjust the output current.

10. The control method according to claim 9, further comprising the following steps: The capacitance value is adjusted by controlling whether a plurality of capacitors in a capacitor group are connected in parallel.

11. The control method according to claim 10, wherein the current preset condition is at least a threshold, and the current precise control method further comprises the following steps: When the current adjustment feedback signal is less than or equal to the at least one threshold, controlling the capacitors to be connected in parallel to increase the capacitance value; and When the current adjustment feedback signal is greater than the at least one threshold, the capacitors are controlled not to be connected in parallel so as to reduce the capacitance value.

12. The control method according to claim 10, further comprising the steps of: The switching frequency is adjusted according to a charging time of the capacitor group, and the charging time is related to the size of the capacitance value.

13. The control method according to claim 12, further comprising the steps of: A charging voltage or the output voltage is provided to charge the capacitor group to generate the charging time.

14. The control method according to claim 9, further comprising the steps of: An off time of a control signal of the LED power control device is adjusted according to the capacitance value to adjust the switching frequency.

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