FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
“SYSTEM AND METHOD FOR CONTROLLING SPEED OF A DIRECT CURRENT (DC) FAN”
We, Bajaj Electricals Limited, an Indian National, of 45/47, Veer Nariman Road, Fort, Mumbai- 400001, Maharashtra, India.
The following specification particularly describes the invention and the manner in which it is to be performed

FIELD OF THE INVENTION
The present disclosure relates to a system and method for controlling speed of a direct current (DC) fan. More particularly, the present disclosure relates to the system and method with improved efficiency for controlling the speed of the direct current (DC) fan.
BACKGROUND OF THE INVENTION
Brushless direct current (BLDC) fans are known to be operated by a direct current (DC) electric motor. It is commonly known that a BLDC fan also employs an electric control system for controllably operating the electric DC motor, for controllably operating the BLDC fan. Specifically, the electric control system is responsible for controlling a speed of DC electric motor, for consecutively controlling a speed of the DC fan.
Conventionally, the electric control system includes a combination of a wall-mounted regulator, a bulk capacitor, a rectifier, a voltage sensing optocoupler, a motor driver, and a microcontroller. The wall-mounted regulator is electrically connected to and receives a base AC power supply from a main power supply. The wall-mounted regulator outputs a main AC power supply. The bulk capacitor is electrically connected in series with the wall-mounted regulator. The bulk capacitor receives the main AC power supply from the wall-mounted regulator, perform a differential voltage drop on the main power supply, and thus output a reduced AC power supply. The rectifier is electrically connected in series with the bulk capacitor, and is adapted to convert the reduced AC power supply to a reduced DC power supply. The voltage sensing optocoupler and the motor driver is electrically connected in series with the rectifier, such that each of the voltage sensing optocoupler and the motor driver receive the reduced DC power supply therefrom. Further, the voltage sensing optocoupler senses a voltage of the reduced DC power supply, and output an analog signal to the motor driver based on the sensed voltage of the reduced DC power supply. The motor driver is also

connected in series with the voltage sensing optocoupler. The motor driver is adapted to receive the analog signal from the voltage sensing optocoupler and the reduced DC power supply from the rectifier, manipulate the reduced DC power supply based on the analog signal to output a controlled output DC power supply, and thus operate the DC motor at a speed based on the output DC power supply. Notably, in order to change the speed of the DC motor, a position of the wall-mounted regulator is adjusted. This causes a change (drop/increase) in the voltage of the reduced DC power supply from the rectifier sensed by the voltage sensing optocoupler, and thus change (drop/increase) in value of the analog signal generated by the voltage sensing optocoupler to the motor driver, and thus finally changing the corresponding value of the output DC power supply and thus the speed of the DC motor.
It may be noted that in the aforementioned embodiment of the electric control system, the value of the speed of the DC motor is controlled based on the analog signal generated by the voltage sensing optocoupler. This may lead to error or less precise control of the speed of the DC motor, due to improper or incorrect analog signal been generated by the voltage sensing optocoupler, leading to inefficient and imprecise control of the speed of the DC motor. Additionally, the bulk capacitor and the voltage sensing optocoupler, further increases a cost of the electric control system for controlling the speed of the DC motor of the DC fan.
Accordingly, there is a well felt need of an improved and less costlier speed control system for controlling the speed of the DC motor of the DC fan. Particularly, it is required to provide a speed control system for controlling the speed of the DC motor of the DC fan, capable of performing functions efficiently and precisely, without use of the bulk capacitor and the voltage sensing optocoupler.

SUMMARY OF THE INVENTION
One aspect of the present disclosure relates to a system for controlling the speed of a DC fan. The system comprises a fan controller module comprising: a voltage sensing module; a control module in electrical communication with the voltage sensing module; and a motor driver. The control module comprises: a storage unit; a transceiver unit in electrical communication with the voltage sensing module; a determination unit; a comparison unit; and a signalling unit, wherein the storage unit, the transceiver unit, the determination unit, the comparison unit, and the signalling unit are in electrical communication with each other. The motor driver is in electrical communication with the signalling unit of the control module, and is adapted to receive an output signal from the signalling unit of the control module to rotate a fan motor of the DC fan.
Another aspect of the present disclosure is that the voltage sensing module is adapted to detect the voltage of an incoming power supply, and generate an analog output signal.
Another aspect of the present disclosure is that the storage unit of the control module is adapted to store at least a first predetermined voltage (x) value, and at least a second predetermined speed (y) value, the at least first predetermined voltage (x) value is mapped to the at least second predetermined speed (y) value. Another aspect of the present disclosure is that the transceiver unit of the control module is adapted to receive the analog output signal, from the voltage sensing module.
Another aspect of the present disclosure is that the determination unit of the control module is adapted to determine the voltage of the analog output signal received by the transceiver unit.
Another aspect of the present disclosure is that the comparison unit of the control module is adapted to compare the voltage of the analog output signal determined by the determination unit of the control module, with at least the first predetermined voltage (x) value, and identify a predetermined speed (y)

value.
Another aspect of the present disclosure is that the signalling unit is adapted to
generate at least an output signal based on the identified predetermined speed
(y) value.
Another aspect of the present disclosure is that a relationship between the at
least first predetermined voltage (x) value and the at least second predetermined
speed (y) value is defined by such that a and b are
constants.
Another aspect of the present disclosure is that the system for controlling the
speed of the DC fan further comprises at least one voltage varying module and at
least an AC/DC convertor module, such that the AC/DC converter module is in
electrical communication with at least one voltage varying module.
Another aspect of the present disclosure is that the at least one voltage varying
module is adapted to receive a main AC power supply, and generate at least an
output AC power supply; and the at least one AC/DC converter module adapted
to convert the received output AC power supply of the at least one voltage
varying module to the incoming DC power supply, such that either of the output
AC power supply and the incoming DC power supply are the incoming power
supply.
Another aspect of the present invention is that the fan motor runs at a voltage
ranging from 20V to 28V.
Another aspect of the present disclosure relates to a method for controlling the
speed of a DC ceiling fan. The method comprising: sensing a voltage of a power
supply, and generate an analog output signal; receiving the analog output
signal; determining the voltage of the analog output signal; and comparing the
voltage of the analog output signal with at least the first predetermined voltage
(x) value, and identify a predetermined speed (y) value; generating at least an
output signal based on the identified predetermined speed (y) value; and

receiving the output signal to rotate a fan motor of the DC fan at the identified predetermined speed (y) value.
Yet another aspect of the present disclosure is that a relationship between the at least first predetermined voltage (x) value and the at least second predetermined
speed (y) value is defined by
Yet another aspect of the present disclosure is that the method for controlling the speed of the DC ceiling fan further comprises supplying a main AC power supply to at least one voltage adjusting unit to generate an output AC power supply; and supplying the output AC power supply to at least one AC/DC converter to generate the incoming DC power supply, wherein either of the output AC power supply and the incoming DC power supply are the incoming power supply.
BRIEF DESCRIPTION OF DRAWINGS
The present invention, both as to its organization and manner of operation,
together with further objects and advantages, may best be understood by
reference to the following description, taken in connection with the
accompanying drawings. These and other details of the present invention will be
described in connection with the accompanying drawings, which are furnished
only by way of illustration and not in limitation of the invention, and in which
drawings:
The present invention, which is in the stage of development and testing provides
exactly such a system. The invention is described with reference to the appended
figures where:
Figure 1 is a schematic representation of a block diagram of a system for
controlling speed of a DC motor of a DC fan, in accordance with one embodiment
of the present disclosure.
Figure 2 is a flowchart of a method of controlling speed of a DC motor of a DC
fan, in accordance with another embodiment of the present disclosure.

Figure 3 shows a tabulated comparison of data corresponding to various parameters to indicate a relationship between a first predetermined voltage (x) value and a second predetermined speed (y) value of the DC motor of the DC fan, in accordance with the concepts of the present disclosure.
Figure 4 shows a graph illustrating the relationship between the first predetermined voltage (x) value and the second predetermined speed (y) value, in accordance with the concepts of the present disclosure.
DETAILED DESCRIPTION OF THE TECHNOLOGY
In the following description, for the purposes of explanation, various specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent, however, that embodiments of the present invention may be practiced without these specific details. Several features described hereafter can each be used independently of one another or with any combination of other features. An individual feature may not address any of the problems discussed above or might address only one of the problems discussed above. Some of the problems discussed above might not be fully addressed by any of the features described herein. Example embodiments of the present invention are described below, as illustrated in various drawings in which like reference numerals refer to the same parts throughout the different drawings.
The present disclosure generally relates to a system and method for controlling speed of a direct current (DC) fan. The DC fan, also known as brushless direct current (BLDC) fan, is a conventionally known fan comprising of a central member carrying a DC motor, and multiple blades extending outwardly from the central member, such that the DC motor is powered by direct current (DC) power supply, to rotate the central member along with the multiple blades for generating an airflow. Notably, a speed of DC fan is dependent on a speed of DC motor. Accordingly, the system and method, as disclosed in the present disclosure, is focused towards the system and method for controlling speed of

the DC motor (and thus DC fan). For ease in reference and understanding, the DC motor is interchangeably referred to as a DC fan motor, hereinafter. It is commonly known that the fan motor runs at a very low voltage ranging from 20V to 28V. Therefore, it is required to precisely control the electric supply to the DC fan motor, to control the speed of the DC fan motor.
Figure 1 is a schematic representation of a block diagram of a system for controlling speed of the DC motor [140] (and thus the DC fan). The system includes at least one voltage varying module [150], at least an AC-DC converter module [160], and a fan controller module [100]. It may be noted that the at least one voltage varying module [150], the at least an AC-DC converter module [160], and the fan controller module [100] are electrically connected sequentially in series with each other, to supply controlled electric power to the DC fan motor [140] for its operation. In particular, the at least one AC-DC converter module [160] is electrically connected in series to the at least one voltage varying module [150], while the fan controller module [100] is electrically connected in series to the at least one AC-DC converter module [160], and further the DC fan motor [140] is electrically connected in series to the fan controller module [100], such that the at least one voltage varying module [150], the at least an AC-DC converter module [160], and the fan controller module [100], in combination with each other, control the supply of electric power and thus speed of the DC fan motor [140]. Details of the arrangement of the system for controlling speed of the DC fan motor [140] will be explained hereinafter.
The voltage varying module [150] is a commonly known wall-mounted regulator device capable of varying an electric power supply. The voltage varying module [150] is electrically connected to a main power supply. The voltage varying module [150] is adapted to receive a main alternating current (AC) power supply, and generate an output AC power supply. The voltage varying module [150] may embody any wall-mounted regulator device of any power capacity, which is capable of varying an electric power supply. In particular, the voltage varying

module [150] includes multiple steps/settings, such that the voltage varying module [150] alters a voltage of the output AC power supply at different steps/settings. Examples of the voltage varying module [150] may include, but is not limited to, a 50 W regulator, an 80 W regulator, and/or a 100 W regulator. The at least an AC-DC converter module [160] is a commonly known rectifier device capable of converting an alternating current (AC) power supply to direct current (DC) power supply. The at least an AC-DC converter module [160] is series electrical communication to the voltage varying module [150]. The at least an AC-DC converter module [160] is adapted to convert the received output AC power supply of the at least one voltage varying module (150) to an incoming DC power supply. The voltage of the incoming DC power supply is dependent on the voltage of the received output AC power supply. Therefore, adjustment of the steps/settings of the voltage varying module [150], causes adjustment of the voltage of the received output AC power supply and thus adjustment of the voltage of the incoming DC power supply.
The fan controller module [100] is a module installed on a printed circuit board (PCB), which receives the incoming DC power supply from the at least an AC-DC converter module [160], and accordingly controllably rotate the DC fan motor [140]. The fan controller module [100] is in series electrical communication to the at least an AC-DC converter module [160]. The fan controller module [100] is adapted to controllably rotate the DC fan motor [140], such that a speed of rotation of the DC fan motor [140] is dependent on a voltage of the input power supply. The fan controller module [100] includes a voltage sensing module [110], a motor driver [130], and a control module [120], which in conjunction with each other, are capable of controllably rotating the DC fan motor [140]. It may be noted that each of the voltage sensing module [110], the motor driver [130], and the control module [120], may be formed on either same PCB, or separate PCBs and electrically connected together. The voltage sensing module [110] is an interconnected arrangement of electronic

components. The voltage sensing module [110] is electrically connected in series to the at least an AC-DC converter module [160]. The voltage sensing module [110] is adapted to detect the voltage of the incoming power supply at the AC-DC converter module [160]. Further, the voltage sensing module [110] is adapted to generate an analog output signal based on the voltage of the incoming power supply. In a preferred embodiment, the voltage sensing module [110] detects the voltage of the incoming DC power supply at the AC-DC converter module [160], to generate analog output signal based on the voltage of the incoming DC power supply. Alternately, the voltage sensing module [110] detects the voltage of the output AC power supply at the AC-DC converter module [160], to generate analog output signal based on the voltage of the output AC power supply. The control module [120] is a microcontroller or a microprocessor that controls operation of the fan controller module [100]. Particularly, the control module [120] is adapted to perform the method of the present disclosure, as disclosed later in details. Particularly, the control module [120] is adapted to: receive the analog output signal from the voltage sensing module [110]; determine the voltage of the analog output signal of voltage sensing module; compare the voltage of the analog output signal with at least the first predetermined voltage (x) value and thus identify a predetermined speed value (y); and finally generate at least an output signal based on the identified predetermined speed value (y). The motor driver [130] is commonly known circuit that is electrically connected to the AC-DC converter module [160] to receive the incoming DC power supply, and is electrically connected to the control module [120] to receive the output signal, and thus rotate the DC fan motor [140] based on the output signal received thereof. The motor driver [130] rotates the DC fan motor based on the output signal received from control module [120]. This output signal can be of I2C, analog voltage or digital data or PWM.
Details of the control module [120] will be explained in details hereinafter. The control module [120] is a microcontroller, or a microprocessor, or a combination

of interconnected electronic components, capable of performing a method of controlling the speed of DC fan motor [140] based on the incoming power supply. In the present disclosure, the control module [120] includes a storage unit [110], a transceiver unit [123], a determination unit [125], a comparison unit [127], and a signalling unit [129], wherein the storage unit [110], the transceiver unit [123], the determination unit [125], the comparison unit [127], and the signalling unit [129] are interconnected with each other. In the present disclosure, each of the storage unit [110], the transceiver unit [123], the determination unit [125], the comparison unit [127], and the signalling unit [129], are modules integrated within the microcontroller/microprocessor. The storage unit [121] of the control module [120] is adapted to store at least a first predetermined voltage (x) value, and at least a second predetermined speed (y) value, such that the at least first predetermined voltage (x) value is mapped to the at least second predetermined speed (y) value. A relationship between the at least first predetermined voltage (x) value and the at least second
predetermined speed (y) value is defined by wherein a and
b are constants. Notably, the storage unit [121] stores the at least a first predetermined voltage (x) value, and corresponding the at least a second predetermined speed (y) value, based on pretesting performed on the system during initialization stage, wherein the system was supplied with different input electric power supply to determine corresponding different speeds. The results
outputted a relationship formula of wherein a and b are
constants, and correspondingly a list of the at least a first predetermined voltage (x) value and the at least a second predetermined speed (y) value, are prepared and stored in the storage unit [121].
Furthermore, the transceiver unit [123] of the control module [120] receives the analog output signal from the voltage sensing module [110]. The determination unit [125] of the control module [120] determines the voltage of the analog

output signal of voltage sensing module [110] received by the transceiver unit [123]. The comparison unit [127] of the control module [120] compares the voltage of the analog output voltage of voltage sensing module determined by the determination unit of the control module [120] with the at least the first predetermined voltage (x) value, and identify a predetermined speed (y) value. In particular, the comparison unit [127] compares the voltage of the analog output signal with the at least the first predetermined voltage (x) value of the list; identifies one of the at least the first predetermined voltage (x) value that closely matches with the voltage of the analog output signal, and identifies the corresponding speed value as the predetermined speed (y) value. The signalling unit [129] further generates at least an output signal based on the identified predetermined speed (y) value, which is received by the motor driver [130] to rotate the DC fan motor [140] at the speed based on the output signal received thereof.
Figure 2 shows a flowchart of the method [200] for controlling the speed of the DC fan motor [140] and thus the DC ceiling fan. The method initiates at step 202. At step 202, the incoming DC power supply is supplied to the fan control module [100]. In particular, at step 202, the voltage varying module [150] supplies a main AC power supply to at least one voltage varying unit (150) to generate an output AC power supply. Further, the at least one AC/DC converter (160) supplies the output AC power supply to generate the incoming DC power supply. Notably, a voltage of the incoming DC power supply is dependent on steps/settings of the voltage varying module [150]. The method then proceeds to step 204. At step 204, the voltage sensing module (110) senses the voltage of the incoming power supply, and generate an analog output signal. The method then proceeds to step 206.
At step 206, the transceiver unit (123) of the control module (120), receives the analog output signal of the voltage sensing module (110). The method then proceeds to step 208.

At step 208, the determination unit (125) of the control module (120), determines the voltage of the analog output signal of the voltage sensing module (110). The method then proceeds to step 210.
At step 210, the comparison unit (127) of the control module (120), compares the voltage of the analog output signal with at least the first predetermined voltage (x) value, and identify a predetermined speed (y) value. The method then proceeds to step 212. A relationship between the at least first predetermined voltage (x) value and the at least second predetermined speed (y) value is
defined by wherein a and b are constants.
At step 212, the signalling unit of the control module (120), generates at least an output signal based on the identified predetermined speed (y) value. The method then proceeds to step 214.
At step 214, the motor driver (130) receives the output signal to rotate a fan motor (140) of the DC fan based on the output signal.
EXAMPLE
Figure 3 shows a tabulated comparison of data corresponding to various parameters to indicate a relationship between a first predetermined voltage (x) value and at least a predetermined speed (y) value, in accordance with the concepts of the present disclosure. Figure 4 shows a graph illustrating the relationship between the first predetermined voltage (x) value and the second predetermined speed (y) value, in accordance with the concepts of the present disclosure. Figure 3 and 4 are to be viewed in conjunction with each other, in order to properly understand the example given hereunder. An exemplary of the present invention has been given hereunder, wherein the relationship of the predetermined voltage (x) value and the predetermined speed (y) value is determined, in accordance with the method disclosed in the present disclosure. The table shows four columns, wherein the input supply voltage is in volts (V),

ADC counts is the first predetermined voltage (x) value determined by the determination unit [125] of the control module [120], the speed command is the second predetermined speed (y) value of the fan motor [140] identified by the comparison unit [127], and power corresponds to the rated power of the DC fan regulator (known at the time of the experiment).
An experiment on DC fan regulators with different rated powers was conducted, and the ADC value as disclosed in Figure 3, when applied as the predetermined
voltage (x) value to the formula provided the
predetermined speed (y) value corresponding to the speed command as disclosed in Figure 3. For example, when the predetermined voltage (x) value (ADC counts (x)) determined by the determination unit [125] of the control module [120] is 440, the predetermined speed (y) value is determined as
which is approx.. 450. Similarly, when the predetermined
voltage (x) value (ADC counts (x)) determined by the determination unit [125] of the control module [120] is 432, the predetermined speed (y) value is
determined as which is approx.. 427. In another
example, when the predetermined voltage (x) value (ADC counts (x)) determined by the determination unit [125] of the control module [120] is 395, the
predetermined speed (y) value is determined as
which is approx. 425. It may be noted that the aforementioned values of predetermined voltage (x) value (ADC counts (x)) and the predetermined speed (y) value (speed command (y)) are exemplary, and various other such examples can be referred to from the tabulation shown in Figure 3. Further, such examples can be envisioned from the graph, as shown in figure 4. Therefore, the speed value (y) is appropriately determined by the system, disclosed in the present invention. While the preferred embodiments of the present invention have been described

hereinabove, it should be understood that various changes, adaptations, and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims. It will be obvious to a person skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive.
List of Components:
100 - Fan Controller Module
110 - Voltage Sensing Module
120 - Control Module
121 - Storage Unit 123 – Transceiver Unit 125 - Determination Unit 127 – Comparison Unit

129 – Signalling Unit
130 - Motor Driver 140 - Fan Motor
150 - Voltage Varying Module 160 - AC/DC Converter Module

I/We Claim:
1. A system for controlling the speed of a DC fan, the system comprising a
fan controller module [100], said module [100] comprising:
(a) a voltage sensing module [110];
(b) a control module [120] in electrical communication with the voltage sensing module [110], the control module [120] comprising:
a. a storage unit [121];
b. a transceiver unit [123] in electrical communication with
the voltage sensing module [110];
c. a determination unit [125];
d. a comparison unit [127]; and
e. a signalling unit [129], wherein the storage unit [121], the
transceiver unit [123], the determination unit [125], the
comparison unit [127], and the signalling unit [129] are in
electrical communication with each other; and
(c) a motor driver [130] in electrical communication with the
signalling unit [129] of the control module [120], and adapted to
receive an output signal from the signalling unit [129] of the
control module [120] to rotate a fan motor [140] of the DC fan
based on the output signal.
2. The system as claimed in claim 1, wherein the voltage sensing module [110] is adapted to detect the voltage of an incoming power supply, and generate an analog output signal.
3. The system as claimed in claim 1, wherein the storage unit [121] of the control module [120] is adapted to store at least a first predetermined voltage (x) value, and at least a second predetermined speed (y) value, the at least first predetermined voltage (x) value is mapped to the at least

second predetermined speed (y) value.
4. The system as claimed in claims 1 and 2, wherein the transceiver unit [123] of the control module [120] is adapted to receive the analog output signal, from the voltage sensing module [110].
5. The system as claimed in claims 1 and 2, wherein the determination unit [125] of the control module [120] is adapted to determine the voltage of the analog output signal received by the transceiver unit [123].
6. The system as claimed in claims 1, 3, and 5, wherein the comparison unit [127] of the control module [120] is adapted to compare the voltage of the analog output signal determined by the determination unit of the control module [120], with at least the first predetermined voltage (x) value, and identify a predetermined speed (y) value.
7. The system as claimed in claim 1 and 6, wherein the signalling unit [129] is adapted to generate at least an output signal based on the identified predetermined speed (y) value.
8. The system as claimed in claim 3, wherein a relationship between the at least first predetermined voltage (x) value and the at least second
predetermined speed (y) value is defined by such
that a and b are constants.
9. The system as claimed in claim 1, further comprising:
(a) at least one voltage varying module [150]; and
(b) at least an AC/DC converter module [160] in electrical communication with the at least one voltage varying module [150].
10. The system as claimed in claim 9, wherein the at least one voltage varying
module [150] is adapted to receive a main AC power supply, and generate
at least an output AC power supply; and the at least one AC/DC converter
module [160] adapted to convert the received output AC power supply of

the at least one voltage varying module [150] to the incoming DC power supply, such that either of the output AC power supply and the incoming DC power supply are the incoming power supply.
11. The system as claimed in claim 1, wherein the fan motor [140] runs at a voltage ranging from 20V to 28V.
12. A method for controlling the speed of a DC ceiling fan, the method comprising:

a) sensing by a voltage sensing module [110], a voltage of an incoming power supply, and generate an analog output signal;
b) receiving by a transceiver unit [123] of a control module [120], the analog output signal;
c) determining by a determination unit [125] of the control module [120], the voltage of the analog output signal; and
d) comparing by a comparison unit [127] of the control module [120], the voltage of the analog output signal with at least the first predetermined voltage (x) value, and identify a predetermined speed (y) value;
e) generating by a signalling unit of the control module [120], at least an output signal based on the identified predetermined speed (y) value; and
f) receiving by a motor driver [130] the output signal, to rotate a fan motor [140] of the DC fan based on the output signal.
13. The method as claimed in claim 12, wherein a relationship between the
at least first predetermined voltage (x) value and the at least second
predetermined speed (y) value is defined by
14. The method as claimed in claim 12, further comprises:
supplying a main AC power supply to at least one voltage adjusting unit [150] to generate an output AC power supply; and

supplying the output AC power supply to at least one AC/DC converter [160] to generate the incoming DC power supply, wherein either of the output AC power supply and the incoming DC power supply are the incoming power supply.