WO2022170580A1

WO2022170580A1 - Method and device of detecting open load for dimmable constant voltage driver

Info

Publication number: WO2022170580A1
Application number: PCT/CN2021/076569
Authority: WO
Inventors: Xinhai Li; Zongjie WU; Kun Xiong
Original assignee: Tridonic Gmbh & Co Kg
Priority date: 2021-02-10
Filing date: 2021-02-10
Publication date: 2022-08-18
Also published as: GB202311409D0; GB2617992A

Abstract

A method and device of detecting open load for a dimmable constant voltage driver, and a dimmable constant voltage driver. A voltage on a switch for dimming at a dimming condition is detected and a detection signal is obtained, the open load condition could be determined according to the detection signal. The reason is that when current flows through a load the load would act as a pull up element at a dimming condition, and a voltage could be detected. Therefore, the shunt resistor or the current sensing transformer is not needed, and a low cost and high efficiency could be achieved for open load detection.

Description

METHOD AND DEVICE OF DETECTING OPEN LOAD FOR DIMMABLE CONSTANT VOLTAGE DRIVER

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of electrical apparatus, and more particularly to a method and device of detecting open load for a dimmable constant voltage driver, and a dimmable constant voltage driver.

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.

Nowadays, dimmable drivers are widely used in illuminating fields. With a dimmable driver, the luminescent intensity of an illuminating device may be adjusted in a wide range.

For a dimmable constant voltage driver, a constant voltage is provided for a load on the output of the driver at a dimming level.

Open load detection is used for determining whether there is a load on the output of the driver. An existing method of detecting open load is measuring output current.

One popular solution is using a shunt resistor to measure the output current. Another popular solution is using a current sensing transformer to measure the output current.

SUMMARY

Inventors of this disclosure found that the power loss could be very high because dimmable constant voltage products normally output low voltages and high current for the solution using the shunt resistor, and the material cost is high and more PCB space is needed for the solution using the current sensing transformer.

In general, embodiments of the present disclosure provide a method and device of detecting open load for a dimmable constant voltage driver, and a dimmable constant voltage driver. In the embodiments, a voltage on a switch for dimming at a dimming condition is detected and a detection signal is obtained, the open load condition could be determined according to the detection signal. The reason is that when current flows through a load the load would act as a pull up element at a dimming condition, and a voltage could be detected. Therefore, the shunt resistor or the current sensing transformer is not needed, and a low cost and high efficiency could be achieved for open load detection.

In a first aspect, there is provided a method of detecting open load for a dimmable constant voltage driver, including: detecting a voltage on a switch for dimming at a dimming condition to obtain a detection signal; and determining an open load condition according to the detection signal.

In an embodiment, the determining an open load condition according to the detection signal comprises: it is determined that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and it is determined that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.

In an embodiment, the periodic signal is a PWM (Pulse Width Modulation) signal.

In an embodiment, the switch is a switching MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) .

In an embodiment, the method further includes: transferring the detection signal to a primary side of the dimmable constant voltage driver.

In an embodiment, the detection signal is transferred to the primary side via an opto-coupler.

In an embodiment, the method further includes: detecting a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and determining an open load condition according to a detected power or current.

In an embodiment, the switch is connected to the output of the dimmable constant voltage driver.

In a second aspect, there is provided a device of detecting open load for a dimmable constant voltage driver, including: a first detection unit configured to detect a voltage on a switch for dimming at a dimming condition to obtain a detection signal; and a first determining unit configured to determine an open load condition according to the detection signal.

In an embodiment, the first determining unit determines that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and determines that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.

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

In an embodiment, the switch is a switching MOSFET.

In an embodiment, the device further includes: a transferring unit configured to transfer the detection signal to a primary side of the dimmable constant voltage driver.

In an embodiment, a second detection unit configured to detect a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and a second determining unit configured to detect an open load condition according to a detected power or current.

In an embodiment, the switch is connected to the output of the dimmable constant voltage driver

In a third aspect, there is provided a dimmable constant voltage driver, including: the device according to the second aspect.

In an embodiment, the dimmable constant voltage driver is a LED driver

According to various embodiments of the present disclosure, a voltage on a switch for dimming at a dimming condition is detected and a detection signal is obtained, the open load condition could be determined according to the detection signal. The reason is that when current flows through a load the load would act as a pull up element at a dimming condition, and a voltage could be detected. Therefore, the shunt resistor or the current sensing transformer is not needed, and a low cost and high efficiency could be achieved for open load detection.

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 flowchart of a method of detecting open load for a dimmable constant voltage driver with an embodiment of the present disclosure;

Fig. 2 is a block diagram of a dimmable constant voltage product with an embodiment of the present disclosure;

Fig. 3 is a diagram of the detection signal when there is a load with an embodiment of the present disclosure;

Fig. 4 is a diagram of the detection signal when there is no load with an embodiment of the present disclosure;

Fig. 5 is a circuit diagram of the dimmable constant voltage product with an embodiment of the present disclosure;

Fig. 6 is a diagram of a device of detecting open load for a dimmable constant voltage 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 method of detecting open load for a dimmable constant voltage driver is provided in a first embodiment.

Fig. 1 is a flowchart of a method of detecting open load for a dimmable constant voltage driver with an embodiment of the present disclosure. As shown in Fig. 1, the method includes:

Step 101: determining whether the dimmable constant voltage driver is at a dimming condition; proceeding to step 102 when the determination result is “yes” , and proceeding to step 105 when the determination result is “no” ;

Step 102: detecting a voltage on a switch for dimming at a dimming condition to obtain a detection signal;

Step 103: transferring the detection signal to a primary side of the dimmable constant voltage driver;

Step 104: determining an open load condition according to the detection signal;

Step 105: detecting a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and

Step 106: determining an open load condition according to a detected power or current.

In an embodiment, the dimmable constant voltage (CV) driver may be any type of dimmable constant voltage drivers. For example, the dimmable constant voltage driver is a LED driver. That is to say, the load which an output of the dimmable constant voltage driver connected to is a LED.

Fig. 2 is a block diagram of a dimmable constant voltage product with an embodiment of the present disclosure. As shown in Fig. 2, a dimmable constant voltage product 10 includes a dimmable constant voltage driver 200 and a LED 300.

The dimmable constant voltage driver 200 drives the LED 300 with a dimming signal. The dimmable constant voltage driver 200 includes a device 201 of detecting open load, a controller 202, a converter 203, a PWM dimmer 204 and a switch 205. The converter 203 is configured to provide current for the LED 300.

The controller 202 outputs a PWM signal to the PWM dimmer 204, and the PWM dimmer 204 may adjust the output current of the converter 203 with the PWM signal, so as to realize the dimming of the illuminating device 202. A dimming level is related to a duty ratio of the PWM signal.

For example, the dimming level is high when the duty ratio of the PWM signal is high and the dimming level is low when the duty ratio of the PWM signal is low.

The switch 205 is connected to the output of the dimmable constant voltage driver 200 and the LED 300. The LED 300 is at a dimming condition when the switch 205 is turned on, and the LED 300 is not at a dimming condition when the switch 205 is turned off.

For example, the converter 203 may be a switched converter clocked at high frequency, such as a resonant half-bridge converter. Alternatively, the converter may be an isolated converter, such as a flyback converter. Furthermore, the converter may be a non-isolated converter, such as a boost converter, buck converter or buck-boost converter.

For example, the controller 202 is a MCU (Microcontroller Unit) .

For example, the switch is a switching MOSFET.

In step 101, whether the dimmable constant voltage driver is at a dimming condition may be determined by detecting a PWM signal. For example, the PWM signal is shown in Fig. 5. When the PWM signal is detected, the dimmable constant voltage driver is at a dimming condition, and when the PWM signal is not detected, the dimmable constant voltage driver is at no dimming condition.

In step 102, a voltage on a switch for dimming at a dimming condition is detected. As shown in Fig. 2, the detection signal is obtained on the switch 206 by the device 201. Any existing method may be used for detecting the voltage.

In step 104, the open load condition is determined according to the detection signal.

In an embodiment, it is determined that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and it is determined that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.

For example, the periodic signal is a PWM signal when a PWM signal acts as a dimming signal.

Fig. 3 is a diagram of the detection signal when there is a load with an embodiment of the present disclosure. Fig. 4 is a diagram of the detection signal when there is no load with an embodiment of the present disclosure. As shown in Fig. 3, when there is a load on the output of the dimmable constant voltage driver, the detection signal is a PWM signal, and when there is no load on the output of the dimmable constant voltage driver, the detection signal is always low.

In an embodiment, step 103 is optional. In other words, the detection signal may be detected on the switch for dimming, or the detection signal may be transferred to the primary side and detected on the primary side.

In an embodiment, in step 103, the detection signal is transferred to the primary side via an opto-coupler.

In an embodiment, step 105 and step 106 are optional. In step 105, any existing method may be used for detecting the power or current on the primary side and determining the open load condition according to the detected power or current.

Fig. 5 is a circuit diagram of the dimmable constant voltage product with an embodiment of the present disclosure. As shown in Fig. 5, a switching MOSFET M180 acts as the switch for dimming, the detection signal is detected on the MOSFET M180. Furthermore, the detection signal may be transferred to the primary side of the dimmable constant voltage driver. As shown in Fig. 5, the detection signal is transferred to the primary side of the dimmable constant voltage driver via an opto-coupler U90.

As can be seen from the above embodiments, a voltage on a switch for dimming at a dimming condition is detected and a detection signal is obtained, the open load condition could be determined according to the detection signal. The reason is that when current flows through a load the load would act as a pull up element at a dimming condition, and a voltage could be detected. Therefore, the shunt resistor or the current sensing transformer is not needed, and a low cost and high efficiency could be achieved for open load detection.

Second embodiment

A device of device of detecting open load for a dimmable constant voltage driver is provided in a second embodiment. The device is corresponding to the method described in the first embodiment.

As shown in Fig. 6, the device 201 of detecting open load for a dimmable constant voltage driver includes:

a first detection unit 601 configured to detect a voltage on a switch for dimming at a dimming condition to obtain a detection signal; and

a first determining unit 602 configured to determine an open load condition according to the detection signal.

In an embodiment, the first determining unit 602 determines that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and determines that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.

For example, the periodic signal is a PWM signal.

For example, the switch is a switching MOSFET.

In an embodiment, the device 201 may further include:

a transferring unit 603 configured to transfer the detection signal to a primary side of the dimmable constant voltage driver.

For example, the detection signal is transferred to the primary side via an opto-coupler.

In an embodiment, the device 201 may further include:

a second detection unit 604 configured to detect a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and

a second determining unit 605 configured to detect an open load condition according to a detected power or current.

In an embodiment, functions of the adjusting unit 301, first determining unit 302 and second determining unit 303 may be corresponding to the steps of the method in the first embodiment, and shall not be described herein any further.

Third embodiment

A dimmable constant voltage driver is provided in a third embodiment.

In an embodiment, the driver may be any type of dimmable constant voltage drivers. For example, the driver is a LED driver.

As shown in Fig. 2, the dimmable constant voltage driver 200 includes a device 201 of detecting open load, a controller 202, a converter 203, a PWM dimmer 204 and a switch 205. Reference may be made to Embodiment 1 for specific implementation of the dimmable constant voltage driver 200, and repeated parts thereof 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 method of detecting open load for a dimmable constant voltage driver, comprising:

detecting a voltage on a switch for dimming at a dimming condition to obtain a detection signal; and

determining an open load condition according to the detection signal.
The method according to claim 1, wherein, the determining an open load condition according to the detection signal comprises:

it is determined that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and

it is determined that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.
The method according to claim 2, wherein,

the periodic signal is a PWM signal.
The method according to claim 1, wherein,

the switch is a switching MOSFET.
The method according to claim 1, wherein, the method further comprises:

transferring the detection signal to a primary side of the dimmable constant voltage driver.
The method according to claim 5, wherein,

the detection signal is transferred to the primary side via an opto-coupler.
The method according to claim 1, wherein, the method further comprises:

detecting a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and

determining an open load condition according to a detected power or current.
The method according to any one of claims 1-7, wherein,

the switch is connected to the output of the dimmable constant voltage driver.
A device of detecting open load for dimmable constant voltage driver, comprising:

a first detection unit configured to detect a voltage on a switch for dimming at a dimming condition to obtain a detection signal; and

a first determining unit configured to determine an open load condition according to the detection signal.
The device according to claim 9, wherein,

the first determining unit determines that there is a load on the output of the dimmable constant voltage driver when the detection signal is a periodic signal; and determines that there is no load on the output of the dimmable constant voltage driver when the detection signal is always low.
The device according to claim 10, wherein,

the periodic signal is a PWM signal.
The device according to claim 9, wherein,

the switch is a switching MOSFET.
The device according to claim 9, wherein, the device further comprises:

a transferring unit configured to transfer the detection signal to a primary side of the dimmable constant voltage driver.
The device according to claim 13, wherein,

the detection signal is transferred to the primary side via an opto-coupler.
The device according to claim 9, wherein, the device further comprises:

a second detection unit configured to detect a power or current on a primary side of the dimmable constant voltage driver at no dimming condition; and

a second determining unit configured to detect an open load condition according to a detected power or current.
The device according to any one of claims 9-15, wherein,

the switch is connected to the output of the dimmable constant voltage driver.
A dimmable constant voltage driver, comprising:

the device according to any one of claims 9-16.
The driver according to claim 17, wherein,

the dimmable constant voltage driver is a LED driver.