Claims:WE CLAIM:
1. A speed control system for BLDC motor based fan using capacitive step-type fan regulator [115], comprising:
a power supply with integrated power factor correction (PFC) [101 – 107];
a BLDC motor without embedded rotor position sensors [201 – 205];
an Electromagnetic interference (EMI) filter [100];
a six transistor inverter stage [114];
a capacitive step type fan regulator [115];
a microcontroller [111];
an internal control switch [110]; and
a capacitive load [108],
characterized in that the position of the capacitive step type fan regulator [115] is determined real-time as break or sag by the preprogrammed firmware logic in the microcontroller [111], by monitoring the signature of a divided down rectified voltage [109],
wherein position of the capacitive step type fan regulator [115] is identified as break when the divided down rectified voltage [109] is in the range of 0V to 0.3V and
wherein position of the capacitive step type fan regulator [115] is identified as sag when the difference in average of divided down rectified voltage [109] in a pre-determined time window in real time [116] and the previous time window value [117] is in the range of 0.3V to 3.6V.

2. The speed control system for BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 1, wherein the capacitive step-type fan regulator [115] comprises switches [S] and capacitors [Cr], and the switches [S] is a break-before-make type (BBM) switch or make-before-break type (MBB) switch.

3. The system for BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 1, wherein the microcontroller [111] is 8-bit controller embedded in the motor [201 – 205] body.

4. The system for BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 1, wherein the capacitive step-type fan regulator [115] is selected from four-step capacitive fan regulator (4 positions) or five-step capacitive fan regulator (5 positions).

5. The system for BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 1, wherein the microcontroller [111] controls the internal control switch [110] to connect and disconnect the capacitive load [108].

6. The system for BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 1, wherein the difference between the average peak of the divided down rectified voltage [109] with and without the capacitive load [108] connected depending on the capacitive step type fan regulator [115] impedance.

7. A method to control speed of BLDC motor based fan using capacitive step-type fan regulator [115], comprises of steps:
monitoring the change in signature of a divided down rectified voltage [109] by a microcontroller [111] embedded in a BLDC motor [201 – 205] body,
determining average value of the divided down rectified voltage [109];
detecting change in the capacitive step type fan regulator [115] as break, when the average value of divided down rectified voltage [109] is in the range of 0V to 0.3V;
detecting change in the capacitive step type fan regulator [115] as sag, when the difference between the average of divided down rectified voltage [109] continuously for a pre-determined time window in real time [116] and the previous time window [117] is in the range of 0.3V to 3.6V;
increasing the sample count [118] by 1;
detecting change in the capacitive step type fan regulator [115] when the range of increased value of sample count [118] is between 1 to 20; and
computing the difference between the average peak of the divided down rectified voltage [109] with and without the capacitive load [108] connected which in turn corresponds to the capacitive step type fan regulator [115] step position,
wherein the microcontroller [111] controls the internal control switch [110] to connect and disconnect the capacitive load [108] and the difference between the average peak of the divided down rectified voltage [109] with and without the capacitive load [108] depends on capacitive step type fan regulator [115] impedance and corresponds to the regulator step position.

8. The method to control speed of BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 7, wherein the speed is determined by the microcontroller [111] based on capacitive step type fan regulator [115] impedance change by monitoring the divided down rectified voltage [109].

9. The method to control speed of BLDC motor based fan using capacitive step-type fan regulator [115] as claimed in claim 7, wherein the regulator position is determined from the average peak of divided down rectified voltage [109] with the internal control switch [110] in OFF position. , Description:FIELD OF INVENTION
The present invention relates to a speed control system and method for a sensor less BLDC motor-based ceiling fan which uses capacitive step-type fan regulator. More particularly the present invention related to speed control system that controls the BLDC motor-based ceiling fan speed based on signature in voltage waveform when universal capacitive step type fan regulator position changes in real time.

BACKGROUND OF INVENTION
Ceiling fans are extensively used in homes to provide air circulation. Especially in tropical countries, the uses of ceiling fans are very vide and it is necessary that the fens are provided with proper regulators/switches to optimize energy consumption. Ceiling fans offer cooling functional features which are usually operated by one or more pull chains and/or by a remote control. Such cooling feature typically includes several speeds: high, medium, low and off.

The cooling features such that speed controls of the ceiling fans are typically operated by pull chains. Operating and/or controlling the speed of the ceiling fan by pull chains have its disadvantages. Although the pull chains are often labeled to clarify which pull chains provides which function; these labels are not readily visible and consumers are often confused as to which pull chain provides the desired function. Moreover, consumers often get confused and frustrated when manipulating the pull chains to achieve the desired fan speed resulting in multiple consecutive unnecessary actuations of the pull chains. Additionally, because the ceiling fan is secured to the ceiling and suspended there from, the pull chains are often difficult for users to reach depending on the height of the user, the height of the ceiling fan suspension, or both.

Ceiling fans may also be controlled by remote control operation. Such remote control operation includes using a remote controller to transmit wireless signals to the ceiling fan. The user commands the desired speed by pressing a button on the IR based remote transmitter unit which is commonly known as remote control. When the button is pressed, the IR transmitter transmits bursts of digital signal (1’s and 0’s) carrying the address and data. The IR receiver at fan end receives the bursts, demodulates it and then sends it to a microcontroller. The software in the microcontroller decodes the information and changes the speed of the fan according to the valid user command from the remote control. This is akin to the operation in several remote-controlled household appliances such as TV, music system etc. However, in public places in general and hospitals, large offices, schools and colleges in particular, remote control can be inconvenient for obvious reason.
Accordingly, it will be advantageous to provide a system to control the speed of a BLDC motor-based ceiling fan using wall mounted universal capacitive step type fan regulator.

OBJECTS OF INVENTION
One or more of the problems of the conventional prior art may be overcome by various embodiments of the present invention.

The primary object of the present invention is to provide a speed control system for a BLDC motor based ceiling fan using wall mounted universal capacitive step-type fan regulator.

It is another object of the present invention, wherein the control logic is implemented by programming the microcontroller of the electronic controller embedded in the motor body.

It is another object of the present invention, wherein the microcontroller monitors the signature of a divided down rectified voltage and finds break or sag in the divided down rectified voltage to detect change in the capacitive step type fan regulator position.

It is another object of the present invention, wherein firmware is preprogrammed to computes the difference between the average peak of the divided down rectified voltage with and without the capacitive load connected which corresponding to the capacitive step type fan regulator step position.

It is another object of the present invention, wherein the difference between the average peaks of the divided down rectified voltage with and without the capacitive load connected is calculated depending on the capacitive step type fan regulator impedance.

It is another object of the present invention, wherein the microcontroller controls the internal control switch to connect and disconnect the capacitive load.

It is another object of the present invention, wherein the capacitive step-type fan regulator is four-step capacitive fan regulator (4 positions) or five-step capacitive fan regulator (5 positions).

It is another object of the present invention, wherein the switches in the capacitive step-type fan regulator are break-before-make type (BBM) switch or make-before-break type (MBB) switch.

SUMMARY OF INVENTION
Thus according to the embodiment of the present invention there is provided a speed control system for BLDC motor based fan using capacitive step-type fan regulator, comprising a power supply with integrated power factor correction (PFC); a BLDC motor without embedded rotor position sensors; an Electromagnetic interference (EMI) filter; a six transistor inverter stage; a capacitive step type fan regulator; a microcontroller; an internal control switch and a capacitive load.

It is another aspect of the present invention, wherein the position of the capacitive step type fan regulator is determined real-time as break or sag by the preprogrammed firmware logic in the microcontroller, by monitoring the signature of a divided down rectified voltage.

It is another aspect of the present invention, wherein the position of the capacitive step type fan regulator is identified as break when the divided down rectified voltage is in the range of 0V to 0.3V.

It is another aspect of the present invention, wherein the position of the capacitive step type fan regulator is identified as sag when the difference in average of divided down rectified voltage in a pre-determined time window in real time and the previous time window value is in the range of 0.3V to 3.6V.

It is another aspect of the present invention, wherein the capacitive step-type fan regulator comprises switches and capacitors, and the switches is a break-before-make type (BBM) switch or make-before-break type (MBB) switch.

It is another aspect of the present invention, wherein the microcontroller is 8-bit controller embedded in the motor body.

It is another aspect of the present invention, wherein the capacitive step-type fan regulator is selected from four-step capacitive fan regulator (4 positions) or five-step capacitive fan regulator (5 positions).

It is another aspect of the present invention, wherein the microcontroller controls the internal control switch to connect and disconnect the capacitive load.

It is another aspect of the present invention, wherein the difference between the average peak of the divided down rectified voltage with and without the capacitive load connected depending on the capacitive step type fan regulator impedance.

According to another embodiment of the present invention there is provided method to control speed of BLDC motor based fan using capacitive step-type fan regulator, comprises of steps monitoring the change in signature of a divided down rectified voltage by a microcontroller embedded in a BLDC motor body, determining average value of the divided down rectified voltage, detecting change in the capacitive step type fan regulator as break, when the average value of divided down rectified voltage is in the range of 0V to 0.3V, detecting change in the capacitive step type fan regulator as sag, when the difference between the average of divided down rectified voltage continuously for a pre-determined time window in real time and the previous time window is in the range of 0.3V to 3.6V, increasing the sample count by 1, detecting change in the capacitive step type fan regulator when the range of increased value of sample count is between 1 to 20, and computing the difference between the average peak of the divided down rectified voltage with and without the capacitive load connected which in turn corresponds to the capacitive step type fan regulator step position, wherein the microcontroller controls the internal control switch to connect and disconnect the capacitive load and the difference between the average peak of the divided down rectified voltage with and without the capacitive load depends on capacitive step type fan regulator impedance and corresponds to the regulator step position.

It is another aspect of the present invention, wherein the speed is determined by the microcontroller based on capacitive step type fan regulator impedance change by monitoring the divided down rectified voltage.

It is another aspect of the present invention, wherein the regulator position is determined from the average peak of divided down rectified voltage with the internal control switch in OFF position.

BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1: illustrates the circuit diagram of a speed control system for BLDC motor based fan using wall mounted universal capacitive step type fan regulator according to the present invention.
Figure 2: illustrates a Sensorless BLDC motor based ceiling fan connected with external five-step capacitive fan regulator according to the present invention.
Figure 3: illustrates a Sensorless BLDC motor based ceiling fan connected with external four-step capacitive fan regulator according to the present invention.
Figure 4: illustrates the flowchart of the method to detection of fan regulator position change according to the present invention.
Figure 5: illustrates the flowchart of the method to determination of the fan regulator position according to the present invention.
Figure 6: illustrates a screenshot of the divided down rectified voltage waveform, which is captured during the detection of Break-Before-Make(BBM) type fan regulator position, according to the present invention.
Figure 7: illustrates a screenshot of the divided down rectified voltage waveform, which is captured during the detection of Make-Before-Break(MBB) type fan regulator position, according to the present invention.
Figure 8: illustrates a screenshot of the divided down rectified voltage waveform with the capacitor connected and without the capacitor connected, which is captured during the determination of fan regulator position, according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES
The present invention provides a speed control system for a BLDC motor based ceiling fan using wall mounted universal capacitive step-type fan regulator [115]. According to the present invention, the speed control system comprises an AC-DC power supply with integrated power factor correction (PFC) [101 – 107], an Electromagnetic interference (EMI) filter [100], a six transistor inverter stage [114], a capacitive step type fan regulator [115], a microcontroller [111], an internal control switch [110], a capacitive load [108] and a BLDC motor without embedded rotor position sensors [201 – 205] as shown in Figure 1.

The microcontroller [111] placed in an electronic controller embedded in a BLDC motor [201 – 205] body and firmware algorithm is loaded in it. The capacitive step-type fan regulator [115] is normally fitted on the wall of the room where the ceiling fan is fitted. Referring Figure 2 - 3, the capacitive step-type fan regulator [115] having 4 step type or 5 step type. It is one of the aspects of the present invention, the capacitive step type fan regulator [115] is a four-step capacitive fan regulator, in which the fan speed is set to 1st, 2nd, 3rd and 4th to control the speed of the fan in 4steps. It is another aspect of the present invention, the capacitive step type fan regulator [115] is a five-step capacitive fan regulator, in which the fan speed is set to 1st, 2nd, 3rd, 4th and 5th to control the speed of the fan in 5 steps. The capacitive step-type fan regulator [115] consists of switches [S] and capacitors [Cr]. The switches [S] in the capacitive step-type fan regulator [115] are break-before-make type (BBM) switch or make-before-break type (MBB) switch. The capacitive step-type fan regulator [115] supports above said two types of switches so it is called as Universal capacitive step type fan regulator [115].

The present invention is to use a low cost and wall mountable capacitive step type fan regulator [115] (4 positions or 5 positions) to control the speed of the fan. In each step, the capacitive step type fan regulator [115] interposes a difference in impedance between the mains supply and the fan. Whenever the user changes the capacitive step type fan regulator [115] knob from one position to another there is a change in the impedance interposed and the microcontroller [111] detects this change. The change is then interpreted and processed by the microcontroller [111] appropriately and corresponding speed is set.

To set the fan speed according to the capacitive step type fan regulator [115] step position is selected by the user, the control is done in the firmware loaded in the microcontroller [111]. This control logic is implemented by programming the 8-bit microcontroller of the electronic controller embedded in the motor [201 – 205] body. The microcontroller [111] monitors the signature of a divided down rectified voltage [109] for,
1) Detection of capacitive step type fan regulator [115] position change and
2) Identification of the position of capacitive step type fan regulator [115]

The logic shown in figure 4 is implemented by the microcontroller [111] to detect the change in position of the capacitive step type fan regulator [115]. When the capacitive step type fan regulator [115] knob / step position changes, there is a change in the signature of the divided down rectified voltage [109] due to a break or sag in the AC supply caused by the Break-Before-Make(BBM) or Make-Before-Break(MBB) type of capacitive step type fan regulator [115] respectively. The position of the capacitive step type fan regulator [115] is determined real-time as break or sag by the preprogrammed firmware logic in the microcontroller [111], by monitoring the signature of a divided down rectified voltage [109].

The microcontroller [111] monitors the signature of a divided down rectified voltage [109]. If the average value of divided down rectified voltage [109] is within the range of 0V to 0.3V then the ‘transition’ or ‘change’ in the capacitive step type fan regulator [115] position is detected. This change is considered as the ‘break’ in divided down rectified voltage [109] as shown in the screenshot of figure 6.

If the average value of divided down rectified voltage [109] is above the range of 0V to 0.3V then the microcontroller [111] continues to compute the average of divided down rectified voltage [109] waveform for a fixed time (window) and compares the average of divided down rectified voltage [109] in a pre-determined time window in real time value [116] (Wn) with previous time window value [117] (Wn-1). If the difference between the window values (Wn and Wn-1) is within the range of 0.3V to 3.6V, then the ‘transition’ or ‘change’ in position is detected. This change is considered as the ‘sag’ in the divided down rectified voltage [109] as shown in the screenshot of figure 7. When the sag is detected in the divided down rectified voltage [109], then the microcontroller [111] increase the sample count [118] by 1. If the increased value of sample count [118] is within the range of 1 to 20, then the ‘transition’ or ‘change’ in the capacitive step type fan regulator [115] position is detected.

Once the microcontroller [111] detects that the capacitive step type fan regulator [115] position has changed, it then implements the logic illustrated in figure 5 to determine the position of capacitive step type fan regulator [115]. To identify the capacitive step type fan regulator [115] position, the microcontroller [111] switches OFF the motor by turning OFF the internal control switch [110] and calculates the average peak of the divided down rectified voltage [109] without the capacitive load [108] connected. Then the microcontroller [111] turns ON the internal control switch [110] and calculates the average peak of the divided down rectified voltage [109] with the capacitive load [108] connected. The screen shot of the divided down rectified voltage [109] waveform with and without the capacitive load [108] connected is shown in figure 8.

The microcontroller [111] then compares the average peak of the divided down rectified voltage [109] with the capacitive load [108] connected and the average peak of the divided down rectified voltage [109] without the capacitive load [108] connected. The difference between the two average peak values changes depending on the capacitive step type fan regulator [115] impedance which in turn corresponds to the capacitive step type fan regulator [115] step position. Thus, based on the difference in value, the microcontroller [111] determines the capacitive step type fan regulator [115] step position. The speed of the BLDC motor based ceiling fan is set by the microcontroller [111] based on the determined capacitive step type fan regulator [115] step position.

Advantages of the present invention
The present invention is a reliable and cost-effective system to control the speed of a BLDC motor-based ceiling fan using wall mounted universal capacitive step type fan regulator, which is independent of type of regulator and manufacturer of regulator.
It provides solution to both the models of regulators. i.e break-before- make type (BBM) or make-before-break type (MBB).
Eliminates the need for an external infrared remote-control unit and an infrared remote receiver
The present invention extended to other types of domestic and industrial fans such as table fans, air circulator fans and other fans which are based on electronically commutated motors.

Although, the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.