4. DESCRIPTION
Technical Field of the Invention
The disclosure relates generally to a brushless DC motor inverter controller, more particularly to the 3 phase firing control of a BLDC motor.
Background of the Invention
The brushless DC (BLDC) motor is becoming increasingly popular in sectors such as automotive (particularly electric vehicles (EV)), HVAC, white goods and industrial because it does away with the mechanical commutator used in traditional motors, replacing it with an electronic device that improves the reliability and durability of the unit. A BLDC motor is known as a "synchronous" type because the magnetic field generated by the stator and the rotor revolve at the same frequency. One benefit of this arrangement is that BLDC motors do not experience the "slip" typical of induction motors.
The stator of a BLDC motor comprises steel laminations, slotted axially to accommodate an even number of windings along the inner periphery (Figure 1). While the BLDC motor stator resembles that of an induction motor, the windings are distributed differently wherein the rotor od BLDC motor is constructed from permanent magnets with two-to-eight N-S pole pairs. More magnet pairs increase torque and smooth out so-called torque ripple, evening the power delivery from the motor. The downside is a more complex control system, increased cost, and lower maximum speed.
Hall effect sensors are often used in motor control applications. Hall sensors are used to detect the location of the rotor during rotation by detecting a change in the magnetic field caused by rotation of the rotor. In a typical motor control system using Hall sensors to detect rotor position with respect to the stator, Hall sensors are attached along the stator at equally spaced angular locations. The firing angle of the current BLDC motors is about 120 degrees and the firing is done in two phases i.e., two stator coils are energised for the continuous rotation of the motor which has some disadvantages like low efficiency, and loss of speed.

Therefore, there is a need to develop a controlling method of a BLDC motor with better characteristics by firing the coils instantly for more than two phases to improve the overall efficiency of a given BLDC motor.
Brief Summary of the Invention
According to an aspect of the invention, a method of three phase firing of a BLDC motor with a firing angle of 120 degrees is disclosed wherein the motor comprises a microcontroller of 5 V, hall sensors, six step commutation process, drive integrated circuits, fly back converter, comparator, regulator, MOSFETS and pot to control the duty cycle.
According to an aspect of the invention, wherein the stator coils of the 3- phase BLDC motor are energized instantly in all the three phases with a firing angle of 120 degrees during the six step commutation process.
According to an aspect of the invention, the input voltage is amplified/stepped down to 12V for the working of the MOSFETS through the fly back converter and the comparator compares the the error signals to required signals in order to prevent the excessive current inputs.
According to an aspect of the invention, the drive integrated circuits amplify the voltage from 5 to 12V for the functioning of the MOSFETS which act as switches for the inverter/3 phase conduction operation during the six stage commutation process.
According to an aspect of the invention, six step flux directions are obtained for driving the motor with 120-degree conducting control by firing all the three phases. Mode switching shifts the flux direction to the alternate mode thereby pulling the rotor for its continuous rotation.

According to an aspect of the invention, pulse width modulation (PWM) is implemented using microcontroller equipped with dedicated PWM hardware for getting the required analog results from ADC with digital means.
Brief Description of the Drawings
Example embodiments of the present invention are illustrated by accompanying drawings, wherein.
FIG. 1 illustrates the circuit diagram of the proposed motor with 3 coil firing at 120 degrees according to the embodiment of the invention.
FIG. 2 illustrates the flow chart describing the step by step process of the BLDC motor according to the embodiment of the invention.
Detailed Description of the Invention
The following description is merely exemplary in nature and is not intended to limit the present invention, applications, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Referring to the drawings, wherein like reference numerals designate identical or corresponding systems, preferred embodiments of the present invention are described.
FIG. 1 illustrates the circuit diagram of the proposed motor 100 with 3 coil firing in three phases at a firing angle of 120 degrees each according to the embodiment of the invention. As shown in FIG. 1, the BLDC motor with 3 coil firing at a firing angle of 120 degrees in a six step commutation process is disclosed, wherein the BLDC motor 100 comprises a microcontroller 102 of 5V to control and generate firing algorithms, hall sensors 118 to determine position of the rotor, six step

commutation process to instantly energize stator coils for firing the motor 100 in 2 phases at the angle of 180 degrees, a plurality of drive integrated circuits 106-108 to amplify the voltage from 5 to 12V, a fly back converter 112 to step down the voltage to 12V for the working of the MOSFETS 110, a comparator 114 to compare/analyze the error signals to required signals for preventing the excessive current inputs, a regulator 104 regulates the voltage from 12V to 5V which is supplied to the microcontroller 102, a plurality of MOSFETS 110 to operate during the commutation process and a pot 116 to control the duty cycle. When the motor is turned ON, the hall sensors 118 inside the motor 100 detects the rotor position and send the information to the microcontroller 102. The microcontroller 102 AT Mega 328p-AU then generates the algorithm according to the hall sensor 118 signals and runs the six step commutation process where the 2 coils of the motor are magnetized with the firing angle of 180 degrees. The stator coils are instantly energized by firing the motor in 2 phases during the six-step commutation process with six different pulses outputs fed to the MOSFETS 110 of the motor. The voltage is amplified from 5 to 12V for the functioning of the MOSFETS 110 that act as switches for the 3-phase conduction operation with the use of drive integrated circuits 106-108 which are three in total. The fly back converter 112 regulates and supplies the required voltage to both microcontroller 102 which is 5V as well as 12V for drive integrated circuits 106-108 uniformly and similarly regulator 104 regulates the supply voltage of 12V from the drive integrated circuits (IC's) 106-108to 5V required for the functioning of microcontroller. The MOSFETS of the motor act as switches and runs the motor according to the various pulse outputs that are generated by the microcontroller 102 throughout the six step commutation process. The comparator 114 compares the signals received throughout the process and cuts-off the power supply in case of excessive power flow by sending the error signals to the microcontroller 102 and the commutation process is terminated ensuring the safety of the circuit and motor 100.
FIG. 2 illustrates the flow chart describing the step by step process of the BLDC motor according to the embodiment of the invention. As shown in FIG.2, initially the analog to digital conversion ports (ADC Ports) 220 are activated when the motor is turned ON. The hall sensors 218 inside the motor determines the position of the rotor and determines when and how the stator coils are to be energized. This information is processed by the microcontroller (AT Mega 32U-MU). The input to the microcontroller 202 is 5 V. The microcontroller 202 controls which two of the switches in

the three-phase inverter must be closed to positively or negatively energize the two active coils with the help of the algorithm that will be generated by the controller 202 in real-time. The motor revolutions per minute (RPM) is set by the pot with reference to the hall sensor signals 218 and ADC inputs.
The conduction process is carried out through the six stage commutation process, wherein all the three stator coils of the 3- phase BLDC motor are instantly energized in 3 phases at a conventional firing angle of 120 degrees. The coils for the 3 phase motor are U, V, and W. The passing of a current through a coil generates a magnetic field. For three coils, there are three paths through which the current is passed namely phase U (current into coil U), phase V (into coil V), and phase W. Initially at phase U, the magnetic flux is generated during conduction process. Since all three coils are interconnected through a single lead wire from each and it is not possible to generate phase U in isolation. Now, when current passes through coils U and W, the flux generated at each coil is the resultant flux result of the combined magnetic fields from U and W. This large flux will cause the inner rotor to turn until the S and N poles of the rotor permanent magnet are aligned. Rotation is maintained by continually switching the flux so that the permanent magnet is constantly chasing the rotating magnetic field induced by the coils. In other words, energizing of U, V, and W is continually switched so that the resultant flux keeps moving, producing a rotating field that continually pulls on the rotor magnet. The inverter control is done by the MOSFETS that act as switches according to the inputs of the microcontroller in response to the hall sensor signals. The operating voltage of MOSFETS are of 12V. The Fly back converter amplifies/steps down the voltage required to the MOSFETS.
With 120-degree conducting control, there are only six step flux directions for driving the motor. Considering the modes, switching from Mode 1 to 2 moves the resultant flux direction to next mode, pulling the rotor along accordingly. Switching from Mode 2 to 3 shifts the flux direction another, again pulling the rotor. Repeating this process generates a continuous rotation.

From a reading of the description above of the preferred embodiments of the present invention, modifications and variations thereto may occur to those skilled in the art. Therefore, the scope of the present invention is to be limited only by the claims of this invention

Claims I/We Claim
1. An improved design (100) for controlling a BLDC motor by a 3-coil firing at an angle of
120 degrees, wherein the motor (100) 2comprises:
a microcontroller (102) of 5V to control and generate firing algorithms;
hall sensors (118) to determine position of the rotor;
six step commutation process to instantly energize stator coils for firing the motor
(100) in 3 phases at the angle of 120 degrees;
a plurality of drive integrated circuits (106-108) to amplify the voltage from 5 to
12 V;
a fly back converter (112) to step down the voltage to 12V for the working of the
MOSFETS;
a comparator (114) to compare/analyze the error signals to required signals for
preventing the excessive current inputs;
a regulator (104) regulates the voltage from 12V to 5V which is supplied to the
microcontroller;
a plurality of MOSFETS (110) to operate during the commutation process and
a pot to control the duty cycle.
2. The design (100) as claimed in claim 1, wherein the microcontroller AT Mega 32U-MU (102) generates the algorithm with respect to the position of rotor coils determined by the hall effect sensors (118) inside the motor.
3. The design (100) as claimed in claim 1, wherein the hall sensors (118) detect the position of the rotor during the operation and gives information to the microcontroller (102) for the generation of necessary algorithm.
4. The design (100) as claimed in claim 1, wherein all the stator coils are instantly energized on firing the motor in 3 phases with the firing angle of 120 degrees using the six-step

commutation process with six different pulses outputs and fed to the MOSFETS (110) of the motor.
5. The design (100) as claimed in claim 1, wherein the drive integrated circuits (106-108) amplify the voltage from 5 to 12V for the functioning of the MOSFETS (110) that act as switches for the 3-phase conduction operation.
6. The design (100) as claimed in claim 1, wherein the fly back converter (112) regulates and supplies the required voltage to both microcontroller as well as drive integrated circuits (106-108) uniformly.
7. The design (100) as claimed in claim 1, wherein the comparator (114) compares the signals received throughout the process and cuts-off the power supply in case of excessive power flow by sending the error signals to the microcontroller (102) which then stops the commutation process.
8. The design (100) as claimed in claim 1, wherein the regulator (104) regulates the supply voltage of 12V from the drive integrated circuits (IC's) (106-108) to 5V required for the functioning of microcontroller (102).
9. The design (100) as claimed in claim 1, wherein the MOSFETS (110) act as switches to
run the motor at various speeds corresponding to the hall sensor (118) signals.
10. The design (100) as claimed in claim 1, wherein the speeds of the motor can be adjusted
as per the user by controlling the duty cycle of the device using pot (116)which is basically
a knob like structure.

11. The design (100) as claimed in claim 1, wherein the 120-degree firing of all the coils in three phases/coils with the proposed six step commutation process improves the efficiency up to 95 % and reduces any kind of losses in drive.