Control circuit, LED driver and control method

Abstract

The present invention provides a control circuit, an LED driver and a control method. The controller is configured to output a modulation signal to a dimmable chip when a DC input is detected, and the dimmable chip drives the switch of a transformer or a converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, an EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved.

Description

Technical Field

[0001] Embodiments of the present disclosure relate generally to the field of electrical devices, and more particularly to control circuits, LED drivers, and control methods. Background Art

[0002] This section introduces aspects that may be helpful for a better understanding of the present disclosure. Therefore, the statements in this section should be read in this light, and should not be understood as an admission that what is in the prior art is or is not in the prior art.

[0003] In the lighting field, more and more products need to pass EMI (electromagnetic interference) tests with DC (direct current) emergency input, but the switching frequency is too constant to pass the EMI test.

[0004] To solve this problem, for example, for products using dimmable chips, an EMI filter including multiple inductors can be added to the input of the product. Summary of the invention

[0005] The inventors of the present disclosure have found that an EMI filter including a plurality of inductors is large in size and high in cost.

[0006] In general, embodiments of the present disclosure provide a control circuit, an LED driver, and a control method. In the embodiment, the controller is configured to output a modulation signal to a dimmable chip when a DC input is detected, and the dimmable chip drives a switch of a transformer or a converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, an EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved.

[0007] In a first aspect, a control circuit is provided, comprising: a dimmable chip configured to drive a switch of a transformer or a converter; and a controller configured to output a modulation signal to the dimmable chip when a DC input is detected, and the dimmable chip drives the switch according to the modulation signal.

[0008] In one embodiment, when a DC input is detected, a modulation signal is output to the DIM pin of the dimmable chip.

[0009] In one embodiment, the modulation signal is a periodic modulation signal.

[0010] In one embodiment, the modulation signal is a PWM signal.

[0011] In one embodiment, the switch is a high frequency switch, and the switch includes two transistors.

[0012] In one embodiment, the controller is configured to not output a modulation signal to the dimmable chip when an AC input is detected.

[0013] In one embodiment, the dimmable chip is further configured to adjust the output current of the transformer or converter.

[0014] In one embodiment, the controller is a microcontroller unit (MCU).

[0015] In a second embodiment, an LED driver is provided, the LED driver comprising: the control circuit according to the first embodiment.

[0016] In one embodiment, the LED driver further comprises a transformer or converter configured to transfer energy to the output controlled by the switch.

[0017] In one embodiment, the LED driver further comprises: a detection circuit configured to detect whether the input of the LED driver is a DC input or an AC input.

[0018] In a third embodiment, a control method of an LED driver is provided, the control method comprising: when a DC input is detected, a controller outputs a modulation signal to a dimmable chip; and the dimmable chip drives a switch of a transformer or a converter according to the modulation signal.

[0019] In one embodiment, the modulation signal is a periodic modulation signal.

[0020] In one embodiment, the modulation signal is a PWM signal.

[0021] According to various embodiments of the present disclosure, the controller is configured to output a modulation signal to the dimmable light chip when a DC input is detected, and the dimmable light chip drives the switch of the transformer or converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, the EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] By way of example, the above and other aspects, features and benefits of various embodiments of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to represent similar or equivalent elements. The accompanying drawings are shown to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale, wherein:

[0023] Figure 1 is a diagram of a control circuit having an embodiment of the present disclosure;

[0024] Figure 2 is a diagram of an LED driver having an embodiment of the present disclosure;

[0025] Figure 3 is a circuit diagram of an LED driver having an embodiment of the present disclosure;

[0026] Figure 4 is a flow chart of a control method of an LED driver having an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] The present disclosure will now be discussed with reference to several exemplary embodiments. It should be understood that the purpose of discussing these embodiments is only to enable those skilled in the art to better understand the present disclosure and thus implement the present disclosure, rather than to propose any limitation on the scope of the present disclosure.

[0028] As used herein, the terms "first" and "second" refer to different elements. Unless the context clearly indicates otherwise, the singular forms "one" and "a kind of" are intended to also include plural forms. As used herein, the terms "include", "comprise", "have" and / or "contain" specify the presence of the features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. The term "based on" should be understood as "based at least in part". The terms "one embodiment" and "embodiment" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". Other explicit and implicit definitions may be included below.

[0029] First embodiment

[0030] In a first embodiment, a control circuit is provided.

[0031] Figure 1 is a diagram of a control circuit having an embodiment of the present disclosure. Figure 1 As shown, the control circuit 100 includes:

[0032] A dimmable chip 110 configured to drive a switch of a transformer or a converter; and

[0033] The controller 120 is configured to output a modulation signal to the dimmable chip when a DC input is detected.

[0034] In one embodiment, the dimmable chip 110 drives the switch through a driving signal. For example, the driving signal is output by the TX1 and TX2 pins of the dimmable chip 110 .

[0035] In one embodiment, the control circuit 100 may be applied to any product including a dimmable chip, such as an LED driver.

[0036] The LED driver may include a transformer or a converter.

[0037] In one embodiment, a transformer or converter delivers energy to an output that is controlled by a switch.

[0038] In one embodiment, the switch is a high frequency switch. For example, the switch includes two transistors, such as field effect transistors (FETs).

[0039] In one embodiment, the LED driver can be dimmed using a PWM (pulse width modulation) signal or an analog signal via the dimmable chip 110. That is, the dimmable chip 110 is further configured to adjust the output current of the transformer or converter according to the PWM signal or the analog signal.

[0040] In one embodiment, the dimmable chip 110 may be any type of dimmable chip, such as RED2821.

[0041] In one embodiment, the controller 120 outputs a modulation signal to the dimmable chip 110 according to the detection signal.

[0042] For example, when a DC input is detected, the controller 120 outputs a modulation signal to the dimmable chip 110. And when an AC input is detected, the controller 120 does not output a modulation signal to the dimmable chip 110. The DC input or the AC input is a power supply input or a mains supply input.

[0043] For example, when a DC input is detected, a modulation signal is output to the DIM pin of the dimmable chip.

[0044] For example, when a DC input of the LED driver is detected, the pin of the controller 120 is not pulled down and the controller 120 outputs a modulation signal. Alternatively, when a DC input of the LED driver is detected, the pin of the controller 120 is pulled down and the controller 120 outputs a modulation signal.

[0045] In one embodiment, any detection method may be used to detect whether the input to the LED driver is a DC input or an AC input.

[0046] For example, AC current can pass through a capacitor, while DC current can be isolated by a capacitor. This characteristic of the capacitor can be applied to detect whether the input of the LED driver is a DC input or an AC input.

[0047] When AC is input, the path including the capacitor is turned on and the optocoupler connected to the path is turned on, and a low level is provided to the pin of the controller 120. In other words, the pin of the controller 120 is pulled down, and the controller 120 does not output a modulation signal to the dimmable light chip 110.

[0048] When DC is input, the path including the capacitor is disconnected and the optocoupler is disconnected, and a low level is not provided to the pin of the controller 120. In other words, the pin of the controller 120 is not pulled down, and the controller 120 outputs a modulation signal to the dimmable chip 110.

[0049] In one embodiment, the controller 120 is configured to receive a signal from the dimming interface, and the modulation signal depends on the signal from the dimming interface and whether a DC input is detected. That is, the controller 120 combines the signal from the dimming interface and the detection signal and outputs the modulation signal to the dimmable chip 110.

[0050] In one embodiment, the dimmable chip 110 drives the switch according to the modulation signal.

[0051] In one embodiment, the modulation signal is a pulse modulation signal or an amplitude modulation signal. For example, the modulation signal is a PWM (pulse width modulation) signal or a pulse duration modulation signal or an analog signal, such as an analog signal voltage level.

[0052] The parameters of the PWM signal or analog signal can be set according to actual requirements.

[0053] For example, the frequency of the PWM signal may be set to 100 Hz to 100 kHz.

[0054] For example, the duty cycle of the PWM signal or analog signal can be adjusted according to the output current requirement.

[0055] When a PWM signal or an analog signal is input to the DIM pin of the dimmable chip 110, the TX1 and TX2 pins of the dimmable chip 110 may output a driving signal to the switch at a high level of the PWM signal, while the TX1 and TX2 pins may not output a driving signal to the switch at a low level of the PWM signal. Therefore, the switch is driven according to the PWM signal. Therefore, due to the change in the switching frequency of the converter or transformer, the EMI test can be passed.

[0056] In one embodiment, the controller is a microcontroller unit (MCU).

[0057] In one embodiment, other configurations and functions of the control circuit may be similar to those in the related art, and more details of these components shall not be further described herein.

[0058] As can be seen from the above embodiment, the controller is configured to output a modulation signal to the dimmable chip when a DC input is detected, and the dimmable chip drives the switch of the transformer or converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, the EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved.

[0059] Second embodiment

[0060] In a second embodiment, an LED driver is provided.

[0061] Figure 2 is a diagram of an LED driver having an embodiment of the present disclosure.

[0062] like Figure 2 As shown, the LED driver 10 comprises:

[0063] A control circuit 100, which is configured to drive at least one switch according to a modulation signal, and whose structure and function are the same as those described in the first embodiment, which shall not be further described herein;

[0064] A detection circuit 200, the detection circuit is configured to detect whether the input of the LED driver is a DC input or an AC input;

[0065] A dimming interface 600 configured to receive a dimming signal and control an output current or output power of the LED driver 10;

[0066] A converter or transformer 300 is configured to transfer energy to an output controlled by a switch.

[0067] In one embodiment, the LED driver 10 may further include a filter circuit 400 and a rectifier circuit 500 , the construction and function of which may be similar to those in the related art, and more details of these components shall not be further described herein.

[0068] In one embodiment, the LED driver 10 can be used to drive the LED 20 as an output load. The LED driver 10 can control the current, voltage or power supplied to the LED 20 according to the dimming signal received by the dimming interface 600. The control circuit 100 can combine the two signals received from the detection circuit 200 and the dimming interface 600, and can drive the switch according to the combination of the two signals.

[0069] Figure 3 is a circuit diagram of an LED driver having an embodiment of the present disclosure.

[0070] like Figure 3 As shown, a dimmable chip RED2821 as an example of an integrated control chip for an LED driver and a microcontroller unit MCU constitute a control circuit 100 .

[0071] When AC is input, a path including the capacitor C1 is turned on and the optocoupler connected to the path is turned on, and a low level is provided to the pin of the MCU 120. And the MCU does not output a PWM signal or an analog signal to the DIM pin of the dimmable chip RED2821, and the TX1 and TX2 pins of the dimmable chip RED2821 output a driving signal to the switch composed of transistors Q1 and Q2, and the switch works.

[0072] When DC is input, the path including the capacitor C1 is disconnected and the optocoupler is disconnected, and a low level is not provided to the pin of the MCU. Then, the MCU outputs a PWM signal or an analog signal to the DIM pin of the dimmable chip RED2821 according to the signal (DIM+ and DIM-) from the dimming interface. The dimming interface 600 is preferably designed to receive a dimming control signal, such as a 1V-10V dimming signal. When a PWM signal or an analog signal is input to the DIM pin of the dimmable chip 110, the TX1 and TX2 pins of the dimmable chip RED2821 output a drive signal to the switch with a high level of the PWM signal or the analog signal, while the TX1 and TX2 pins do not output a drive signal to the switch with a low level of the PWM signal or the analog signal. Therefore, the switch is driven and works according to the PWM signal or the analog signal.

[0073] In one embodiment, other configurations and functions of the LED driver may be similar to those in the related art, and more details of these components shall not be further described herein.

[0074] As can be seen from the above embodiment, the controller is configured to output a modulation signal to the dimmable chip when a DC input is detected, and the dimmable chip drives the switch of the transformer or converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, the EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved.

[0075] Third embodiment

[0076] In a third embodiment, a control method of an LED driver is provided, which corresponds to the control circuit described in the first embodiment.

[0077] Figure 4 FIG. 1 is a flow chart of a control method of an LED driver according to an embodiment of the present disclosure. Figure 4 As shown, the method includes:

[0078] Step 401: When a DC input is detected, the controller outputs a modulation signal to the dimmable chip; and

[0079] Step 402: The dimmable chip drives a switch of a transformer or a converter according to a modulation signal.

[0080] In one embodiment, the modulation signal is a pulse modulation signal or an amplitude modulation signal. For example, the modulation signal is a PWM signal or an analog signal.

[0081] In one embodiment, for the specific implementation of the above steps, reference may be made to the contents described in the first embodiment, which shall not be further described herein.

[0082] As can be seen from the above embodiment, the controller is configured to output a modulation signal to the dimmable chip when a DC input is detected, and the dimmable chip drives the switch of the transformer or converter according to the modulation signal. Therefore, due to the change in the switching frequency of the converter or transformer, the EMI test can be passed, and an EMI filter including a plurality of inductors is not required, and a compact size and low cost are achieved.

[0083] Generally speaking, although the operations are shown in a specific order, this situation should not be understood as requiring such operations to be performed in the specific order shown or in a sequential order or requiring all the operations shown to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these specific implementation details should not be understood as limitations on the scope of the present disclosure, but should be understood as descriptions of features that may be specific to a specific embodiment. Certain feature parts described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various feature parts described in the context of a single embodiment may also be implemented in multiple embodiments individually or in the form of any suitable sub-combination.

[0084] Although the present disclosure is described in language specific to structural features and / or method actions, it should be understood that the present disclosure defined by the appended claims is not necessarily limited to the specific features or actions described above. Instead, the specific features and actions described above are disclosed as exemplary forms of implementing the claims.

Claims

1. A control circuit, comprising: A dimmable chip, wherein the dimmable chip is configured to drive a switch of a transformer or a converter; and a controller configured to output a modulation signal to the dimmable chip when a DC input is detected, and not output the modulation signal to the dimmable chip when an AC input is detected, The dimmable chip drives the switch according to the modulation signal, The controller is configured to receive a signal from a dimming interface, combine the signal from the dimming interface and a detection signal indicating whether a DC input is detected, and output the modulation signal to the dimmable chip. The control circuit does not have an EMI filter including a plurality of inductors.

2. The control circuit according to claim 1, wherein: When a DC input is detected, the modulation signal is output to the DIM pin of the dimmable chip.

3. The control circuit according to claim 1, wherein: The modulation signal is a pulse modulation signal or an amplitude modulation signal.

4. The control circuit according to claim 3, wherein: The modulation signal is a PWM signal or an analog signal.

5. The control circuit according to claim 1, wherein: The switch is a high frequency switch, And the switch includes two transistors.

6. The control circuit according to claim 1, wherein: The dimmable chip is further configured to adjust an output current of the transformer or the converter.

7. The control circuit according to claim 1, wherein: The controller is a microcontroller unit (MCU).

8. An LED driver, comprising: A control circuit according to any one of claims 1 to 7.

9. The LED driver according to claim 8, wherein: The LED driver further comprises: A dimming interface is configured to receive a dimming signal and control an output current or an output power of the LED driver.

10. The LED driver according to claim 8 or 9, wherein: The LED driver further comprises: a transformer or converter configured to transfer energy to an output controlled by the switch; and A detection circuit is configured to detect whether the input of the LED driver is a DC input or an AC input.

11. A control method for an LED driver, the control method comprising: When a DC input is detected, the controller outputs a modulation signal to the dimmable chip, and when an AC input is detected, the controller does not output the modulation signal to the dimmable chip, The dimmable chip drives the switch of the transformer or converter according to the modulation signal. The method further comprises: The controller receives a signal from the dimming interface, combines the signal from the dimming interface with a detection signal indicating whether a DC input is detected, and outputs the modulation signal to the dimmable chip. The control circuit of the LED driver does not have an EMI filter including a plurality of inductors.

12. The control method according to claim 11, wherein: The modulation signal is a pulse modulation signal or an amplitude modulation signal.

13. The control method according to claim 11 or 12, wherein: The modulation signal is a PWM signal or an analog signal.

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