Description:FIELD OF THE INVENTION
[0001] The present invention relates to the field of semiconductor architecture and circuit design, and more particularly, the present invention relates to the Multi-function linear LED driver.
BACKGROUND FOR THE INVENTION:
[0002] The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known, or part of the common general knowledge in any jurisdiction as of the priority date of the application. The details provided herein the background if belongs to any publication is taken only as a reference for describing the problems, in general terminologies or principles or both of science and technology in the associated prior art.
[0003] The LED driver market is highly cost sensitive. The conventional LED driver uses three external resistors (current sense resistor – RCS, OTP resistor RTH and OVP resistor – RD) as shown in Figure 1 (COVENTIONAL). Moreover, the conventional low cost LED driver doesn’t include any smart feature which is included only in the premium LED drivers.
[0004] In light of the foregoing, there is a need for a multi-function linear LED driver that overcomes problems prevalent in the prior art. The LED driver of the present invention can reconfigure to design multiple variants of LED bulb. The additional features in the proposed bulb are designed without increasing the cost of the chip.
OBJECTS OF THE INVENTION:
[0005] Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows.
[0006] The principal object of the present invention is to overcome the disadvantages of the prior art by providing the Multi-function linear LED driver.
[0007] Another object of the present invention is to provide the Multi-function linear LED driver, wherein the LED driver allows implementation of multiple variants of LED bulb without making any change in the IC.
[0008] Another object of the present invention is to provide the Multi-function linear LED driver, wherein the controller inside the chip eliminates the need of external OTP (over temperature protection), OVP (over voltage protection) and CS (current sense) resistors hence reducing the system cost and size.
[0009] Another object of the present invention is to provide the Multi-function linear LED driver, wherein the accurate on-chip current sensing circuit not only eliminates the external current resistors but also improves efficiency by saving I2R loss which occurs in the external series current sense resistor.
[0010] Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY OF THE INVENTION:
[0011] The present invention provides a multi-function linear LED driver.
[0012] The proposed LED driver integrates over temperature protection (OTP), current sensing (CS) and line voltage derating (VD) feature fully on-chip which saves 3 external resistors leading to cost and space savings. The proposed LED driver also includes dimming features which allows the LED driver to be configured for the following multiple variants of bulb:
- Regular mode- LED Driver is configured to operate as 9W LED Bulb
- LED Bulb with Nigh Lamp Mode: Same bulb can be used as night lamp and provides significant cost savings (night bulb, holder, switch and wire) to the customer.
- Remote Controlled LED Bulb: Provides low-cost alternative to WiFi controlled LED bulbs.
- Automatic Brightness Control: Can be interfaced with ambient light sensor (ALS) for automatic brightness control based on ambient light.
- LED Light with Motion Detector: Can be interfaced with motion detector to turn ON/OFF the light.
[0013] The main invention is the multi-functionality and circuits to achieve the same. The proposed LED driver can be configured as below:
VDIM OPERATING MODE DESCRIPTION
Open (NC) or 5V Regular The driver is configured in fixed brightness (9W) mode
V0-V2
(For e.g. V0=0.5V and V2=4.5V) Dimming
(used with remote, ambient light sensing and motion sensor) The driver current (LED brightness) is function of VDIM
V0-GND Night Lamp Feature The driver is configured to enable the night lamp mode
BRIEF DESCRIPTION OF DRAWINGS:
[0014] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
[0015] Figure-1: Conventional LED Driver;
[0016] Figure-2: Proposed LED Driver of the present invention;
[0017] Figure-3: Architecture of the Proposed LED driver IC;
[0018] Figure -4: Line voltage Derating;
[0019] Figure -5: Over Temperature Protection (OTP);
[0020] Figure -6: Analog Dimming;
[0021] Figure -7: PWM Dimming;
[0022] Figure -8: Remote controlled smart LED Bulb operation;
[0023] Figure -9: LED Bulb with Ambient Light Sensing and Motion Detector;
[0024] Figure -10: LED Bulb with Night Lamp Mode.
DETAILED DESCRIPTION OF DRAWINGS:
[0025] While the present invention is described herein by way of example using embodiments and illustrative drawings, those skilled in the art will recognize that the invention is not limited to the embodiments of drawing or drawings described and are not intended to represent the scale of the various components. Further, some components that may form a part of the invention may not be illustrated in certain figures, for ease of illustration, and such omissions do not limit the embodiments outlined in any way. It should be understood that the drawings and the detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the present invention as defined by the appended claim.
[0026] As used throughout this description, the word "may" is used in a permissive sense (i.e. meaning having the potential to), rather than the mandatory sense, (i.e. meaning must). Further, the words "a" or "a" mean "at least one” and the word “plurality” means “one or more” unless otherwise mentioned. Furthermore, the terminology and phraseology used herein are solely used for descriptive purposes and should not be construed as limiting in scope. Language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited, and is not intended to exclude other additives, components, integers, or steps. Likewise, the term "comprising" is considered synonymous with the terms "including" or "containing" for applicable legal purposes. Any discussion of documents, acts, materials, devices, articles, and the like are included in the specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention.
[0027] In this disclosure, whenever a composition or an element or a group of elements is preceded with the transitional phrase “comprising”, it is understood that we also contemplate the same composition, element, or group of elements with transitional phrases “consisting of”, “consisting”, “selected from the group of consisting of, “including”, or “is” preceding the recitation of the composition, element or group of elements and vice versa.
[0028] The present invention is described hereinafter by various embodiments with reference to the accompanying drawing, wherein reference numerals used in the accompanying drawing correspond to the like elements throughout the description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only and are not intended to limit the scope of the claims. In addition, several materials are identified as suitable for various facets of the implementations. These materials are to be treated as exemplary and are not intended to limit the scope of the invention.
[0029] The present invention provides a multi-function linear LED driver.
[0030] The proposed LED driver integrates over temperature protection (OTP), current sensing (CS) and line voltage derating (VD) feature fully on-chip which saves 3 external resistors leading to cost and space savings. The proposed LED driver also includes dimming features which allows the LED driver to be configured for the following multiple variants of bulb:
- LED Bulb with Nigh Lamp Mode: Same bulb can be used as night lamp and provides significant cost savings (night bulb, holder, switch and wire) to the customer.
- Remote Controlled LED Bulb: Provides low-cost alternative to WiFi controlled LED bulbs.
- Automatic Brightness Control: Can be interfaced with ambient light sensor (ALS) for automatic brightness control based on ambient light.
- LED Light with Motion Detector: Can be interfaced with motion detector to turn ON/OFF the light.
[0031] Figure 3 discloses architecture of the Proposed LED driver IC. The proposed LED driver uses internal current sensing and to regulate the LED current which eliminates the requirement of an external current sense resistor. Unlike the conventional technique which controls the gate voltage of High voltage (700V) FETs to regulate the LED current and makes it impossible to implement on-chip current sensing, the proposed LED driver uses 700V FET as cascode to limit the supply of current source (VSOURCE) to 6V which allows 6V transistors to be used for the LED sink current (ILED). The supply voltage of 6V is generated internally using a high voltage linear regulator.
[0032] Figure 4 discloses a Line voltage Derating. The Internal line voltage derating protects 700V FETs by reducing the LED current when peak line voltage crosses 350V (~250V RMS).
[0033] Figure 5 discloses Over Temperature Protection (OTP). The OTP protects the LED driver from getting overheated by reducing the LED current at a pre-defined temperature threshold (for example 120°C) and LEDs are turned OFF if temperature exceeds 150°C.
[0034] Figure 6 and Figure 7 disclose Analog Dimming and PWM Dimming respectively. If dimming feature is used then DIM pin is applied with an analog signal of 0.5V. A small hysteresis around 0.5V can be added to prevent the driver from oscillating between dimming and night lamp modes. LED driver enters dimming mode if min. voltage of 0.5V is detected at DIM pin and led current can be increased/decreased linearly with VDIM. ILED is set to max. (40mA) when VDIM=4.5V. In case dimming feature is not used, DIM pin can be either connected to ground or left floating.
Operating Modes of the Proposed LED driver IC:
[0035] Based on voltage at the DIM pin, the proposed LED driver can be configured in one of the following three modes:
VDIM OPERATING MODE DESCRIPTION
Open (NC) or 5V Regular The driver is configured in fixed brightness (9W) mode
V0-V2 Dimming
(used with remote, ambient light sensing and motion sensor) The driver current (LED brightness) is function of VDIM
V0-GND Night Lamp Feature The driver is configured to enable the night lamp mode
Use Cases of Operating Modes:
[0036] Figure 8 disclose a Remote controlled smart LED Bulb operation. Since most of the smart LED bulbs available in the market are based on WiFi and mobile app are expensive and target high tier market, the proposed LED drivers enables the implementation of inexpensive remote controlled LED bulb for mid and low tier market. Though WiFi bulbs offer rich features of brightness and color controls which makes it 5-6x expensive compared to a regular bulb, the proposed LED bulb offers only most commonly used ON/OFF and brightness control features using a RF remote with minimum cost overhead (cost of RF Tx/Rx).
[0037] Figure 9 discloses LED Bulb with Ambient Light Sensing and Motion Detector. The LED bulb with motion detector is used to save energy by automatically turning OFF the LED bulb when there is no motion. The DIM pin of proposed LED driver can be interfaced with on-board motion detector and implement the same. The Automatic Brightness Control is interfaced with ambient light sensor (ALS) for automatic brightness control based on ambient light.
[0038] Figure 10 discloses a LED Bulb with Night Lamp Mode. The night mode feature allows the proposed LED bulb to use the same bulb as night lamp. The features saves cost overhead of an additional night bulb (usually 0.5W).
[0039] The disclosure has been described with reference to the accompanying embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein.
[0040] The foregoing description of the specific embodiments so fully revealed the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein. , Claims:We Claim:
1) A multi-function linear LED driver, the multi-function linear LED driver comprising:
- an integrated circuit (IC) having an on-chip over-temperature protection (OTP) circuit, on-chip current sensing (CS) circuit, and on-chip line voltage derating (VD) circuit;
- wherein said on-chip OTP circuit, CS circuit, and VD circuit eliminate the need for external OTP, CS and OVP resistors, thereby reducing system cost and size; and
- wherein the LED driver is configurable to operate in multiple modes including regular mode, dimming mode, and night lamp mode based on a control voltage (VDIM) applied to a DIM pin.
2) The multi-function linear LED driver as claimed in claim 1, wherein the LED driver is configured to operate in regular mode when said VDIM is either open-circuited or set to a voltage of about 5V, thereby providing a fixed brightness output.
3) The multi-function linear LED driver as claimed in claim 1, wherein the LED driver is configured to operate in dimming mode when said VDIM is maintained between about 0.5V and 4.5V, such that the LED current and brightness are varied linearly with the applied VDIM.
4) The multi-function linear LED driver as claimed in claim 1, wherein the LED driver is configured to operate in night lamp mode when said VDIM is connected to ground, thereby reducing LED brightness for low-light operation.
5) The multi-function linear LED driver as claimed in claim 1, wherein the on-chip current sensing circuit regulates LED current without the use of an external current sensing resistor, thereby reducing I²R losses and improving efficiency.
6) The multi-function linear LED driver as claimed in claim 1, wherein the reference current of the on-chip current sensing circuit is fixed during design for a desired LED current by leaving pin no. 6 (NC/CS) floating; wherein by connecting an external resistor at pin no. 6 (NC/CS), the user can control the LED current.
7) The multi-function linear LED driver as claimed in claim 1, wherein the on-chip line voltage derating circuit reduces LED current when peak line voltage exceeds about 350V, thereby protecting high-voltage switching elements in the driver.
8) The multi-function linear LED driver as claimed in claim 1, wherein the on-chip OTP circuit (102) reduces LED current when a pre-defined temperature threshold, such as 120°C, is reached, and turns OFF the LEDs when temperature exceeds about 150°C.
9) The multi-function linear LED driver as claimed in claim 1, wherein the DIM pin is adapted to interface with one or more external control modules selected from the group comprising of:
- a remote-control receiver for ON/OFF and brightness control;
- an ambient light sensor for automatic brightness adjustment;
- a night lamp mode that allows the LED bulb to be use as the same bulb as a night lamp; and
- a motion detector for automatic ON/OFF operation based on motion detection.
10) The multi-function linear LED driver as claimed in claim 1, wherein the LED driver is adaptable to form multiple variants of LED bulbs including a regular LED bulb, a remote-controlled LED bulb, an ambient light-sensing LED bulb, a motion-sensing LED bulb, and an LED bulb with night lamp mode, without modification to the IC design.