Accelerated start-up dimmable LED driver circuit

Abstract

The application provides an adjustable light LED drive circuit with accelerated starting, which comprises an energy storage device connected in parallel to the positive and negative electrodes of an LED load; a main power circuit electrically connected to both ends of the energy storage device to form a loop and configured to generate an output current for charging the energy storage device, wherein the main power circuit is provided with a first load resistor for adjusting the output current; and a starting time compensation circuit having a second load resistor and configured to control the first load resistor and the second load resistor to be connected in parallel to increase the peak value of the output current when the LED drive circuit starts, and cut off the first load resistor and the second load resistor to restore the output current when the voltage between the two ends of the energy storage device reaches a preset voltage value. The application increases the peak value of the output current in a period of the starting process, thereby increasing the charging current of the energy storage device, accelerating the starting time of the LED load, and improving the product experience of users.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technology, specifically to a dimmable LED driver circuit that accelerates startup. Background Technology

[0002] In dimming products, there are strict requirements for startup time. Because the output of the driver circuit contains a large-capacity electrolytic capacitor, the output current is lower at low dimming levels, resulting in a longer charging time for the electrolytic capacitor. This inevitably leads to a longer startup time and a poorer user experience. Summary of the Invention

[0003] To address the aforementioned technical problems, this application provides a dimmable LED driver circuit for accelerated startup, thereby improving the startup speed of LED loads.

[0004] This application proposes a dimmable LED driver circuit for accelerated startup, comprising:

[0005] Energy storage devices are connected in parallel to the positive and negative terminals of the LED load;

[0006] The main power circuit is electrically connected to both ends of the energy storage device to form a loop and is configured to generate an output current to charge the energy storage device. The main power circuit is provided with a first load resistor for adjusting the output current.

[0007] The startup time compensation circuit has a second load resistor and is configured to control the first load resistor and the second load resistor to be connected in parallel to increase the peak value of the output current when the LED driver circuit is started, and to disconnect the first load resistor and the second load resistor to restore the output current when the voltage across the energy storage device reaches a preset voltage value.

[0008] Preferably, the startup time compensation circuit further includes a first switching transistor and a second switching transistor, wherein:

[0009] The first switching transistor is configured to turn on when the LED driving circuit is started, so as to turn on the circuit containing the second load resistor, thereby controlling the first load resistor and the second load resistor to be connected in parallel;

[0010] The second switch is configured to turn on when the voltage across the energy storage device reaches the preset voltage value, thereby turning off the first switch and disconnecting the first load resistor from the second load resistor.

[0011] Preferably, the start-up time compensation circuit further includes an RC charging circuit, wherein:

[0012] The first switching transistor is turned on via power supply VCC;

[0013] The second switch is turned on by the RC charging circuit.

[0014] Preferably, when the voltage across the energy storage device reaches the preset voltage value, the charging voltage of the RC charging circuit reaches the turn-on voltage of the second switch.

[0015] Preferably, the preset voltage value is lower than the start-up voltage of the LED load.

[0016] Preferably, both the first switch and the second switch are NMOS transistors.

[0017] Preferably, the input terminal of the RC charging circuit is connected to the power supply VCC, and the output terminal is connected to the gate (G) of the second switching transistor; the gate (G) of the first switching transistor is electrically connected to both the drain (D) of the second switching transistor and the power supply VCC; the source (S) of both the first and second switching transistors is connected to signal ground; the drain (D) of the first switching transistor is connected to the second load resistor; and the second load resistor and the first load resistor are connected to the same node in the main power circuit.

[0018] Preferably, the energy storage device is an electrolytic capacitor.

[0019] Preferably, it further includes a dimming circuit, which includes a signal conversion chip and an optocoupler, wherein:

[0020] The signal conversion chip is configured to convert an external DIM signal into a PWM signal;

[0021] The optocoupler is configured to output isolation of the PWM signal;

[0022] The main power circuit is also configured to adjust the current flowing through the LED load according to the PWM signal to adjust the brightness of the LED load.

[0023] Preferred options also include:

[0024] The rectifier circuit is configured to rectify the input AC voltage into DC voltage;

[0025] A filter circuit, connected between the output terminal of the rectifier circuit and the input terminal of the main power circuit, is configured to filter the DC voltage.

[0026] The main power circuit is also configured to transform the DC voltage into the DC voltage required by the LED load.

[0027] This application proposes a dimmable LED driver circuit for accelerated startup. By adding a startup time compensation circuit to the main power circuit, when the LED driver circuit starts up, the first load resistor and the second load resistor are connected in parallel to reduce the resistance in the circuit. This increases the peak value of the output current of the main power circuit during the startup period, allowing the voltage across the energy storage device to reach the startup voltage of the LED load more quickly, thereby accelerating the startup time. Before the voltage across the LED load reaches the startup voltage, the first and second load resistors are disconnected, restoring the output current of the main power circuit. This application increases the charging current of the energy storage device by increasing the peak value of the output current of the main power circuit during the startup process, thus accelerating the startup time of the LED load and improving the user's product experience. Attached Figure Description

[0028] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of this application. Other embodiments and many anticipated advantages of these embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0029] Figure 1 This is an architectural diagram of a dimmable LED driver circuit for accelerated startup according to an embodiment of this application;

[0030] Figure 2 This is a partial circuit diagram of a dimmable LED driver circuit for accelerated startup according to a specific embodiment of this application;

[0031] Figure 3 This is a circuit diagram of a startup time compensation circuit according to a specific embodiment of this application;

[0032] Figure 4 This is a circuit diagram of a dimming circuit according to a specific embodiment of this application.

[0033] The meanings of the numbers in the diagram are as follows: 1. Rectifier circuit; 2. Filter circuit; 3. Main power circuit; 31. First load resistor; 4. Start-up time compensation circuit; 41. Second load resistor; 42. Switching circuit; 43. RC charging circuit; 5. Dimming circuit; 6. Energy storage device. Detailed Implementation

[0034] In the following detailed description, reference is made to the accompanying drawings, which form part of the detailed description and illustrate illustrative specific embodiments in which the present application may be practiced. In this regard, directional terms such as “top,” “bottom,” “left,” “right,” “up,” “down,” etc., are used with reference to the orientation of the described figures. Because components of the embodiments can be positioned in several different orientations, directional terms are used for illustrative purposes and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present application is defined by the appended claims.

[0035] Furthermore, it should be understood that in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by electrical or electromagnetic connections. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to another element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0036] This application proposes a dimmable LED driver circuit for accelerated startup. Figure 1 A schematic diagram of an accelerated startup dimmable LED driver circuit according to an embodiment of this application is shown, such as... Figure 1 As shown, the drive circuit includes a rectifier circuit 1, a filter circuit 2, a main power circuit 3, a start-up time compensation circuit 4, a dimming circuit 5, and an energy storage device 6.

[0037] The rectifier circuit 1 receives an AC voltage at its input terminal and rectifies it into a DC voltage. The filter circuit 2 connects to the output terminal of the rectifier circuit 1 and filters this DC voltage. One input terminal of the main power circuit 3 connects to the output terminal of the filter circuit 2, transforming the DC voltage to the DC voltage required by the LED load and filtering the transformed DC voltage. The energy storage device 6 is connected between the output terminal of the main power circuit 3 and the positive and negative terminals of the LED load, charging it with the output current provided by the main power circuit 3. Once the starting voltage of the LED load is reached, it supplies power to the LED load. (Start-up time...) The input of the compensation circuit 4 is connected to the power supply VCC, and the output is connected to one of the inputs of the main power circuit 3. It is used to increase the peak value of the output current of the main power circuit 3 during a certain period of the LED load startup process, thereby increasing the charging current of the energy storage device 6, so that the energy storage device 6 can reach the startup voltage of the LED load more quickly, thereby speeding up the startup time of the LED load. The input of the dimming circuit 5 is a DIM dimming signal, and the output is connected to one of the inputs of the main power circuit 3. It is used to convert the DIM dimming signal into a PWM signal, thereby controlling the main power circuit 3 to adjust the current flowing through the LED load to adjust the brightness of the LED load.

[0038] Figure 2 A partial circuit diagram of a dimmable LED driver circuit for accelerated startup according to a specific embodiment of this application is shown, as follows: Figure 2 As shown, rectifier circuit 1 includes a rectifier bridge BD1, and filter circuit 2 includes resistor R12, inductor L1, and capacitors C3 and C4. Main power circuit 3 consists of a DC-DC transformer chip U2 and its peripheral circuitry; in this embodiment, U2 is a step-down chip. A first load resistor 31 is connected to the node where the main power circuit 3 generates the output current Isen. The first load resistor 31 includes resistors R23 and R24 connected in parallel and is used to adjust the magnitude of the output current. In this embodiment, energy storage device 6 uses electrolytic capacitors; two electrolytic capacitors, EC4 and EC5, are connected in parallel between the output terminal of the main power circuit 3 and the positive and negative terminals of the LED load.

[0039] Figure 3 A circuit diagram of a startup time compensation circuit according to a specific embodiment of this application is shown, as follows: Figure 3As shown, the startup time compensation circuit 4 includes a second load resistor 41, a switching circuit 42, and an RC charging circuit 43. The switching circuit 42 includes a first switch Q6 and a second switch Q5. The first switch Q6 is turned on via the power supply VCC and is configured to conduct during the startup of the entire LED driver circuit, thus turning on the circuit containing the second load resistor 41. This causes the first load resistor 31 and the second load resistor 41 to be connected in parallel, thereby reducing the resistance value in the main power circuit 3 and increasing the peak value of the output current of the main power circuit 3. The second switch Q5 is turned on via the RC charging circuit 43 and is configured to conduct when the voltage across the energy storage device 6 reaches a preset voltage value, turning off the first switch Q6. This disconnects the first load resistor 31 and the second load resistor 41, restoring the resistance value in the main power circuit 3 and allowing the output current of the main power circuit 3 to return to its normal value to charge the energy storage device 6.

[0040] In this embodiment, the preset voltage value is less than the starting voltage of the LED load.

[0041] In this embodiment, both the first switch Q6 and the second switch Q5 are NMOS transistors.

[0042] In this embodiment, when the voltage across the energy storage device 6 reaches the preset voltage value, the charging voltage of the RC charging circuit 43 reaches the turn-on voltage of the second switch Q5. At this time, the state changes of the first switch Q6 and the second switch Q5 are: Q6 turns on, Q5 turns off → Q6 turns off, Q5 turns on.

[0043] Specifically, the RC charging circuit 43 includes a diode D11, a resistor R51, and a capacitor C2 connected in sequence between the power supply VCC and the signal ground. One end of the resistor R51 and the capacitor C2 are connected to the gate (G) of the second switch Q5. The drain (D) of the second switch Q5 is electrically connected to the gate (G) of the first switch Q6 and the power supply VCC. The source (S) of the second switch Q5 and the first switch Q6 are connected to the signal ground. The second load resistor 41 includes resistors R54-R57 connected in parallel. One end of the second load resistor 41 is connected to the Isen node of the main power circuit 3, and the other end is connected to the drain (D) of the first switch Q6.

[0044] In a preferred embodiment, a resistor R52 is connected between the power supply VCC and the drain of the second switching transistor Q5, and a resistor R53 is connected between the gate of the first switching transistor Q6 and the signal ground. Resistors R52 and R53 divide the power supply VCC, and resistor R52 ensures that when the gate voltage of the first switching transistor Q6 is pulled low, the power supply VCC will not be pulled low.

[0045] As can be seen from the circuit above, initially, since the power supply VCC charges the RC charging circuit 43, the voltage across capacitor C2 has not yet reached the turn-on voltage of the gate (G) of the second switching transistor Q6, so the second switching transistor Q6 is turned off. Meanwhile, the power supply VCC directly supplies power to the gate (G) of the first switching transistor. Because the voltage value of the power supply VCC is higher than the turn-on voltage of the gate (G) of the first switching transistor Q5, the first switching transistor Q5 turns on initially. The source (S) to drain (D) of the first switching transistor Q5 is connected, and the loop containing the second load resistor 41 is completed. The second load resistor 41 and the first load resistor 31 form a parallel relationship. The resistance value in the main power circuit 3 decreases, and the peak value of the output current of the main power circuit 3 increases. Consequently, the charging current of the main power circuit 3 to the energy storage device 6 increases, and the time it takes for the voltage across the energy storage device 6 to reach the starting voltage of the LED load increases, thus accelerating the start-up of the LED load.

[0046] When the charging voltage across the RC charging circuit 43 reaches the turn-on voltage of the gate of the second switch Q6, the second switch Q6 starts to conduct. At the same time, the second switch Q6 pulls down the gate voltage of the first switch Q5, and the first switch Q5 changes from the conducting state to the turning off state. The second load resistor 41 is disconnected from the first load resistor 31. At this time, the power supply VCC will not be pulled down due to the presence of resistor R52. Meanwhile, the resistance value of the main power circuit 3 returns to its previous value, and the peak value of the output current of the main power circuit 3 returns to its previous value.

[0047] Therefore, the function of the second load resistor 41 is to increase the peak value of the output current of the main power circuit 3, the switching circuit 42 is used to connect and disconnect the second load resistor 41 and the first load resistor 31, and the function of the RC charging circuit 43 is to change the time during which the output current of the main power circuit 3 is maintained at its peak value. Thus, the formula for calculating the LED load start-up time can be obtained:

[0048] t = RC * ln[(V1 - V0) / (V1 - Vt)]

[0049] Where R is the resistance value of resistor R51, C is the capacitance value of capacitor C2, V1 is the charging voltage of RC charging circuit 43, V0 is the initial voltage across capacitor C2, and Vt is the real-time voltage across capacitor C2.

[0050] It can be seen that the start-up time of the LED load can be changed by changing the values ​​of R51 and C2.

[0051] Figure 4 A circuit diagram of a dimming circuit according to a specific embodiment of this application is shown, as follows: Figure 4As shown, the dimming circuit 5 consists of a signal conversion chip U4, an optocoupler U3, and their peripheral circuitry. The signal conversion chip U4 receives the DIM dimming signal at its input and outputs a PWM signal. The optocoupler U3 isolates the PWM signal and inputs it to the PWM node of the main power circuit 3, specifically the PWM pin of U2 in the main power circuit 3. After the LED load starts, the dimming circuit 5 outputs a PWM signal. U2 in the main power circuit 3 adjusts the current flowing through the LED load according to this PWM signal, thereby adjusting the brightness of the LED load.

[0052] This application proposes a dimmable LED driver circuit for accelerated startup. By adding a startup time compensation circuit 4 to the main power circuit 3, when the entire LED driver circuit begins charging, the first load resistor 31 and the second load resistor 41 are connected in parallel to reduce the resistance in the circuit. This increases the peak value of the output current of the main power circuit 3 during the startup period, causing the voltage across the energy storage device 6 to reach the startup voltage of the LED load more quickly, thereby accelerating the startup time. Before the voltage across the LED load (across the energy storage device 6) reaches the startup voltage, the first load resistor 31 and the second load resistor 41 are disconnected, thus restoring the output current of the main power circuit 3. This application increases the charging current of the energy storage device 6 by increasing the peak value of the output current of the main power circuit 3 during the startup process, thereby accelerating the startup time of the LED load and improving the user's product experience.

[0053] It is obvious that those skilled in the art can make various modifications and alterations to the embodiments of this application without departing from the spirit and scope of this application. In this way, this application also aims to cover such modifications and alterations if they fall within the scope of the claims and their equivalents. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are described in mutually different dependent claims does not indicate that a combination of these measures cannot be used for profit. Any reference numerals in the claims should not be considered limiting in scope.

Claims

1. A dimmable LED driver circuit for accelerated startup, characterized in that, include: Energy storage devices are connected in parallel to the positive and negative terminals of the LED load; The main power circuit is electrically connected to both ends of the energy storage device to form a loop and is configured to generate an output current to charge the energy storage device. The main power circuit is provided with a first load resistor for adjusting the output current. A startup time compensation circuit, having a second load resistor, is configured to control the first load resistor and the second load resistor to be connected in parallel to increase the peak value of the output current when the LED driver circuit is started, and to disconnect the first load resistor and the second load resistor to restore the output current when the voltage across the energy storage device reaches a preset voltage value. The startup time compensation circuit further includes a first switching transistor and a second switching transistor, wherein: The first switching transistor is configured to turn on when the LED driving circuit is started, so as to turn on the circuit containing the second load resistor, thereby controlling the first load resistor and the second load resistor to be connected in parallel; The second switch is configured to turn on when the voltage across the energy storage device reaches the preset voltage value, so as to turn off the first switch and thereby disconnect the first load resistor and the second load resistor. The startup time compensation circuit also includes an RC charging circuit, wherein: The first switching transistor is turned on via power supply VCC; The second switch is turned on via the RC charging circuit; It also includes a dimming circuit, which comprises a signal conversion chip and an optocoupler, wherein: The signal conversion chip is configured to convert an external DIM signal into a PWM signal; The optocoupler is configured to output isolation of the PWM signal; The main power circuit is also configured to adjust the current flowing through the LED load according to the PWM signal to adjust the brightness of the LED load.

2. The driving circuit according to claim 1, characterized in that, When the voltage across the energy storage device reaches the preset voltage value, the charging voltage of the RC charging circuit reaches the turn-on voltage of the second switch.

3. The driving circuit according to claim 2, characterized in that, The preset voltage value is lower than the start-up voltage of the LED load.

4. The driving circuit according to claim 1, characterized in that, Both the first and second switching transistors are NMOS transistors.

5. The driving circuit according to claim 4, characterized in that, The input terminal of the RC charging circuit is connected to the power supply VCC, and the output terminal is connected to the gate (G) of the second switching transistor. The gate (G) of the first switching transistor is electrically connected to both the drain (D) of the second switching transistor and the power supply VCC. The source (S) of both the first and second switching transistors is connected to signal ground. The drain (D) of the first switching transistor is connected to the second load resistor. The second load resistor and the first load resistor are connected to the same node in the main power circuit.

6. The driving circuit according to claim 1, characterized in that, The energy storage device is an electrolytic capacitor.

7. The driving circuit according to claim 1, characterized in that, Also includes: The rectifier circuit is configured to rectify the input AC voltage into DC voltage; A filter circuit, connected between the output terminal of the rectifier circuit and the input terminal of the main power circuit, is configured to filter the DC voltage. The main power circuit is also configured to transform the DC voltage into the DC voltage required by the LED load.

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