FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A control unit for a single phase BLDC motor
INVENTORS
Nirody Jaishankar, A-1 Nandanvan, Opposite Ambaji Dham, MG Road, Mulund, Mumbai 400080, Maharashtra, India and Shenoy Purushotham Talachery, Crompton Greaves Ltd, Advanced Motor Design and Technology Center, CG Global R&D Centre, Kanjur Marg (East), Mumbai 400042, Maharashtra, India, both Indian nationals
APPLICANTS
CROMPTON GREAVES LIMITED, CG House, Dr Annie Besant Road, Worli, Mumbai 400030, Maharashtra, India, an Indian company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

' FIELD OF THE INVENTION
This invention relates to a control unit for a single phase BLDC motor.
BACKGROUND OF THE INVENTION
BLDC (Brushless Direct Current) motors are generally single phase or three phase motors and are associated with single phase controller and three phase controller, respectively for controlling their operation. Both the single phase and three phase controllers are connected to a power section which in turn is connected to the phase winding(s) of the single phase or three phase motor. In a single phase motor, the input of the controller is connected to a Hall sensor and the output of the controller is coupled to the single phase stator winding of the motor through the power section. For energisation of the stator winding by the controller in the correct direction it is necessary to sense the rotor position. The rotor position is sensed by the Hall sensor which generates an output signal which is applied to the input pin of the controller. Based on the signal applied to the input pin of the controller, the controller generates two sets of valid output signals according to the truth table which is created on the basis of a single input to the controller. These signals are used by the power section to energize the single stator winding of the motor and run the motor. In a three phase motor, the rotor position is sensed by three Hall sensors. The output signals of the three hall sensors are applied to three input pins of the three phase controller. Based on the signals applied to the three input pins of the controller, the controller generates six sets of valid output signals according to the truth table which is created on the basis of three inputs to the controller. These signals are used by the power section to energize the three stator windings of the


' motor in the correct direction and run the motor. As stated earlier six sets of valid output signals are required in a three phase motor for excitation of the three phase stator windings, whereas two sets of valid output signals are required in a single phase motor for excitation of the single phase stator winding. The controller of a single phase motor generates the required two sets of valid output signals from a single input signal received from the hall sensor, whereas the controller of a three phase motor generates the required six sets of valid output signals from the three input signals received from the three hall sensors. Because of this, the circuit configurations of the controller of a single phase motor and the controller of a three phase motor are distinct and different and single phase and three phase BLDC controllers cannot be interchanged and used. Therefore, manufacturers of single phase and three phase motors necessarily have to maintain separate inventories for the components of the respective controllers. This is expensive, time consuming and cumbersome. Manufacture of separate and independent circuit configurations of single phase and three phase controllers is also expensive and time consuming.
OBJECTS OF THE INVENTION
An object of the invention is to provide a control unit for a single phase BLDC motor, which control unit is versatile, reliable, simple in construction and cost effective.
An object of the invention is to provide a control unit for a single phase BLDC motor, which control unit eliminates the need of separate inventories in respect of single phase and three phase controllers.


DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a control unit for a single phase BLDC motor, the control unit comprising a three phase controller and a logic inverter circuit, the input of the logic inverter circuit being connected to the output of a Hall sensor and output of the logic inverter circuit being connected to two input pins of the three phase controller, the output of the Hall sensor being further connected to a third input pin of the three phase controller, the output of the three phase controller being connected to the single phase winding of the motor through a power section.
The following is a detailed description of the invention with reference to Fig 1 of the accompanying drawings, which is a block diagram of the control unit for a single phase BLDC motor according to an embodiment of the invention. As illustrated in Fig 1, the control unit 1 for a single phase BLDC motor (not shown) comprises a three phase controller 2 and a logic inverter circuit 3. The input of the logic inverter circuit is connected to the output of a Hall sensor 4. The output of the logic inverter circuit is connected to two input pins (not marked) of the three phase controller. The output of the Hall sensor is further connected to a third input pin (not marked) of the three phase controller. The output of the three phase controller is connected to the single phase winding (not shown) of the motor through a power section 5. The logic inverter circuit may comprise a logic gate or a combination of discrete transistor(s) and resistor(s). The three phase controller is a microcontroller or an integrated circuit such as ASIC (Application Specific Integrated Circuit). During operation of the motor, the Hall sensor


senses the position of the rotor and outputs a signal. The output signal of the Hall sensor is applied to the input of the logic inverter circuit and to the respective input pin of the three phase controller. The logic inverter circuit generates an output signal which is applied to the respective two input pins of the three phase controller. The output signal generated by the logic inverter circuit is an inversion of the signal from the Hall sensor. Based on the three signals at the three input pins of the three phase controller, the controller generates six sets of output signals according to the truth table created on the basis of the three inputs to the controller. However, only two sets of valid signals are required for energising the single stator winding of the BLDC motor. Because the two inputs to the controller are inversion of the sensor signal, only two sets of the six sets of signals generated by the three phase controller are valid. The two sets of valid signals are used by the power section to energize the single stator winding in the correct direction for running the motor.
According to the invention the circuit configuration of the three phase controller as used in the control unit of a single phase BLDC motor remain the same as that of the circuit configuration of the three phase controller of a three phase BLDC motor, except for the logic inverter circuit. Therefore, manufacturers of single phase and three phase motors need not maintain separate inventories for the components of the respective controllers. As a result inventory of the components is reduced so also the cost. There is versatility in the construction of the controllers and their construction is simplified, their cost is reduced and their construction time is also reduced. The reliability of the controllers is also maintained.


We Claim
1. A control unit for a single phase BLDC motor, the control unit comprising a three phase controller and a logic inverter circuit, the input of the logic inverter circuit being connected to the output of a Hall sensor and output of the logic inverter circuit being connected to two input pins of the three phase controller, the output of the Hall sensor being further connected to a third input pin of the three phase controller, the output of the three phase controller being connected to the single phase winding of the motor through a power section.
2. The control unit as claimed in claim 1, wherein the logic inverter circuit comprises a logic gate or a combination of discrete transistor(s) and resistor(s).
3. The control unit as claimed in claim 1 or 2, wherein the three phase controller is a microcontroller or an integrated circuit such as ASIC (Application Specific Integrated Circuit).





ABSTRACT
A control unit (1) for a single phase BLDC motor (not shown). The control unit comprises a three phase controller (2) and a logic inverter circuit (3). The input of the logic inverter circuit is connected to the output of a Hall sensor (4) and output of the logic inverter circuit is connected to two input pins (not marked) of the three phase controller. The output of the Hall sensor is further connected to a third input pin (not marked) of the three phase controller. The output of the three phase controller is connected to the single phase winding (not shown) of the motor through a power section (5) (Fig 1).