WO2022032632A1

WO2022032632A1 - Control circuit, led driver and control method

Info

Publication number: WO2022032632A1
Application number: PCT/CN2020/109141
Authority: WO
Inventors: Qiuxiang MAO; Shuanghong Wang; Shengdie Lin
Original assignee: Tridonic Gmbh & Co Kg
Priority date: 2020-08-14
Filing date: 2020-08-14
Publication date: 2022-02-17
Also published as: GB202300803D0; CN116250376A; GB2611942A

Abstract

A control circuit, an LED driver and a control method. A controller 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 convertor according to the modulation signal. Thus, the EMI test can be passed due to changes of switch frequency of the converter or the transformer and the EMI filter including multiple inductors is not needed, and compact size and low cost are achieved.

Description

CONTROL CIRCUIT, LED DRIVER AND CONTROL METHOD

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of electrical apparatus, and more particularly to a control circuit, an LED driver and a control method.

BACKGROUND

This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

In the field of lighting field, more and more products need to pass EMI (electromagnetic interference) test at DC (direct current) emergency input, but the switch frequency is too constant to pass the EMI test.

To solve this problem, for example, for a product using a dimmable chip, a EMI filter including multiple inductors may be added to an input end of the product.

SUMMARY

Inventors of this disclosure found that the size of the EMI filter including multiple inductors is big and the cost is high.

In general, embodiments of the present disclosure provide a control circuit, an LED driver and a control method. In the embodiments, a controller 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 convertor according to the modulation signal. Thus, the EMI test can be passed due to changes of switch frequency of the converter or the transformer and the EMI filter including multiple inductors is not needed, and compact size and low cost are achieved.

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

In an embodiment, the modulation signal is outputted to a DIM pin of the dimmable chip when a DC input is detected.

In an embodiment, the modulation signal is a periodic modulation signal.

In an embodiment, the modulation signal is a PWM signal.

In an embodiment, the switch is a high frequency switch, and the switch comprises two transistors.

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

In an embodiment, the dimmable chip is further configured to adjust output current of the transformer or the convertor.

In an embodiment, the controller is a microcontroller unit (MCU) .

In a second embodiment, there is provided an LED driver, including: the control circuit according to the first embodiment.

In an embodiment, the LED driver further comprising: a transformer or a convertor configured to transfer energy to an output end controlled by the switch.

In an embodiment, the LED driver further comprising: a detection circuit configured to detect whether an input of the LED driver is a DC input or an AC input.

In a third embodiment, there is provided control method of an LED driver, including: a controller outputs 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 convertor according to the modulation signal.

In an embodiment, the modulation signal is a periodic modulation signal.

In an embodiment, the modulation signal is a PWM signal.

According to various embodiments of the present disclosure, a controller 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 convertor according to the modulation signal. Thus, the EMI test can be passed due to changes of switch frequency of the converter or the transformer and the EMI filter including multiple inductors is not needed, and compact size and low cost are achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and benefits of various embodiments of the disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:

Fig. 1 is a diagram of a control circuit with an embodiment of the present disclosure;

Fig. 2 is a diagram of an LED driver with an embodiment of the present disclosure;

Fig. 3 is a circuit diagram of the LED driver with an embodiment of the present disclosure;

Fig. 4 is a flowchart of the control method of an LED driver with an embodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure will now be discussed with reference to several example embodiments. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure.

As used herein, the terms “first” and “second” refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises, ” “comprising, ” “has, ” “having, ” “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on. ” The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ” Other definitions, explicit and implicit, may be included below.

First embodiment

A control circuit is provided in a first embodiment.

Fig. 1 is a diagram of a control circuit with an embodiment of the present disclosure. As shown in Fig. 1, a control circuit 100 includes:

a dimmable chip 110 configured to drive a switch of a transformer or a convertor; and

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

In an embodiment, the dimmable chip 110 drives the switch by a driving signal. For example, the driving signal is outputted by TX1 and TX2 pins of the dimmable chip 110.

In an embodiment, the control circuit 100 may be applied in any product includes a dimmable chip, such as an LED driver.

The LED driver may include a transformer or a convertor.

In an embodiment, the transformer or the convertor transfer energy to an output end controlled by the switch.

In an embodiment, the switch is a high frequency switch. For example, the switch comprises two transistors, such as field effect transistors (FETs) .

In an embodiment, the LED driver may be dimmable with a PWM (Pulse Width Modulation) signal or an analog signal via the dimmable chip 110. That is to say, the dimmable chip 110 is further configured to adjust output current of the transformer or the convertor according to the PWM signal or the analog signal.

In an embodiment, the dimmable chip 110 may be any type of dimmable chip, such as RED2821.

In an embodiment, the controller 120 outputs a modulation signal to the dimmable chip 110 according a detection signal.

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

For example, the modulation signal is outputted to a DIM pin of the dimmable chip when a DC input is detected.

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 the modulation signal. Alternatively, when a DC input of the LED driver is detected, a pin of the controller 120 is pulled down and the controller 120 outputs the modulation signal.

In an embodiment, any detection method may be used for detecting whether an input of the LED driver is a DC input or an AC input.

For example, the AC current may pass a capacitor while the DC current may be isolated by the capacitor, this character of the capacitor may be applied to detect whether an input of the LED driver is a DC input or an AC input.

When an AC is inputted, a pass including the capacitor is on and an optocoupler connected to the pass is on, and a low level is provided to a pin of the controller 120. In other words, the pin of controller 120 is pulled down and the controller 120 dose not output the modulation signal to the dimmable chip 110.

When a DC is inputted, a pass including the capacitor is off and the optocoupler is off, and a low level is not provided to a pin of the controller 120. In other words, the pin of controller 120 is not pulled down and the controller 120 outputs the modulation signal to the dimmable chip 110.

In an embodiment, the controller 120 is configured to receive a signal from a dimming interface and the modulation signal is depending on the signal from a dimming interface and whether a DC input is detected. That is to say, the controller 120 combines the signal from a dimming interface and the detection signal, and outputs the modulation signal to the dimmable chip 110.

In an embodiment, the dimmable chip 110 drives the switch according to the modulation signal.

In an 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, e.g. an analog signal voltage level.

The parameters of the PWM signal or the analog signal may be set according to actual requirements.

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

For example, the duty cycle of the PWM signal or the analog signal may be adjusted according to the requirements for output current.

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

In an embodiment, the controller is a microcontroller unit (MCU) .

In an embodiment, other constructions and functions of the control circuit may be similar to those in the related art, and more details of these parts shall not be described herein any further.

As can be seen from the above embodiments, a controller 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 convertor according to the modulation signal. Thus, the EMI test can be passed due to changes of switch frequency of the converter or the transformer and the EMI filter including multiple inductors is not needed, and compact size and low cost are achieved.

Second embodiment

An LED driver is provided in a second embodiment.

Fig. 2 is a diagram of an LED driver with an embodiment of the present disclosure.

As shown in Fig. 2, an LED driver 10 includes:

a control circuit 100 configured to drive at least one switch according to a modulation signal, a structure and functions of which being identical to those described in the first embodiment, which shall not be described herein any further;

a detection circuit 200 configured to detect whether an input of the LED driver is a DC input or an AC input;

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

a converter or a transformer 300 configured to transfer energy to an output end controlled by the switch.

In an embodiment, the LED driver 10 may further include a filter circuit 400 and a rectification circuit 500, whose constructions and functions may be similar to those in the related art, and more details of these parts shall not be described herein any further.

In an embodiment, the LED driver 10 may be used to drive an LED 20 as output load. The LED driver 10 may control the current, voltage or power supplied to the LED 20 depending on the dimming signal received by the dimming interface 600. The control circuit 100 may combine both signals received from the detection circuit 200 and the dimming interface 600 and may drive a switch according to the combination of both signals.

Fig. 3 is a circuit diagram of the LED driver with an embodiment of the present disclosure.

As shown in Fig. 3, the dimmable chip RED2821 as one example of an integrated control chip for a LED driver and the microcontroller unit MCU constitutes the control circuit 100.

When an AC is inputted, a pass including the capacitor C1 is on and an optocoupler connected to the pass is on, and a low level is provided to a 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, the TX1 and TX2 pins of the dimmable chip RED2821 output the driving signal to the switch, which is constituted by the transistors Q1 and Q2, and the switch works.

When a DC is inputted, the path including the capacitor C1 is off and the optocoupler is off, 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 a signal from the dimming interface (DIM+ and DIM-) . The dimming interface 600 is preferably designed to receive dimming control signals, e.g. 1-10 V dimming signals. When the PWM signal or the analog signal inputted into the DIM pin of the dimmable chip 110, the TX1 and TX2 pins of the dimmable chip RED2821 output the driving signal to the switch at a high level of the PWM signal or the analog signal, while the TX1 and TX2 pins do not output the driving signal to the switch at a low level of the PWM signal or the analog signal. Thus the switch is driven and works according to the PWM signal or the analog signal.

In an embodiment, other constructions and functions of the LED driver may be similar to those in the related art, and more details of these parts shall not be described herein any further.

Third embodiment

A control method of an LED driver is provided in a third embodiment, corresponding to the control circuit described in the first Embodiment.

Fig. 4 is a flowchart of the control method of an LED driver with an embodiment of the present disclosure. As shown in Fig. 4, the method includes:

Step 401: a controller outputs a modulation signal to a dimmable chip when a DC input is detected; and

Step 402: the dimmable chip drives a switch of a transformer or a convertor according to the modulation signal.

In an 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.

In an embodiment, reference may be made to what is described in the first embodiment for particular implementations of the above steps, which shall not be described herein any further.

Generally, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A control circuit, comprising:

a dimmable chip configured to drive a switch of a transformer or a convertor; and

a controller configured to output a modulation signal to the dimmable chip when a DC input is detected,

the dimmable chip drives the switch according to the modulation signal.
The control circuit according to claim 1, wherein,

the controller is configured to receive a signal from a dimming interface and the modulation signal is depending on the signal from a dimming interface and whether a DC input is detected.
The control circuit according to claim 1 or 2, wherein,

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

the modulation signal is a pulse modulation signal or an amplitude modulation signal.
The control circuit according to claim 4, wherein,

the modulation signal is a PWM signal or an analog signal.
The control circuit according to claim 1, wherein,

the switch is a high frequency switch,

and the switch comprises two transistors.
The control circuit according to claim 1, wherein,

the controller is configured not to output the modulation signal to the dimmable chip when an AC input is detected.
The control circuit according to claim 1, wherein,

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

the controller is a microcontroller unit (MCU) .
An LED driver, comprising:

the control circuit according to any one of claims 1-9.
The LED driver according to claim 10, wherein, the LED driver further comprising:

a dimming interface configured to receive a dimming signal and to control the output current or output power of the LED driver.
The LED driver according to claim 10 or 11, wherein, the LED driver further comprising:

a transformer or a convertor configured to transfer energy to an output end controlled by the switch; and

a detection circuit configured to detect whether an input of the LED driver is a DC input or an AC input.
A control method of an LED driver, comprising:

a controller outputs 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 convertor according to the modulation signal.
The control method according to claim 13, wherein,

the modulation signal is a pulse modulation signal or an amplitude modulation signal.
The control method according to claim 13 or 14, wherein,

the modulation signal is a PWM signal or an analog signal.