KR0182012B1 - A commutation circuit of a bldc. motor - Google Patents

Abstract

The present invention relates to a current circuit of a brushless DC motor, and receives a back electromotive force detector (10) for detecting and outputting back electromotive force during motor operation, and a voltage of a peak value and a neutral point of the back electromotive force signal output from the back electromotive force detector (10). And a reference voltage generator 40 generating and outputting first and second reference voltages for generating a current signal, and outputting the first and second reference voltage signals output from the reference voltage generator 40 and the counter electromotive force detector. It is composed of a current signal generator 50 for receiving a counter electromotive force to generate a current signal for determining the switching order for driving the motor, so that the sensorless drive circuit of a brushless DC motor can be implemented with simple hardware and easy to control It relates to the current circuit of a brushless DC motor.

Description

Current circuit of brushless dc motor

1 is a conceptual diagram showing a driving circuit of a conventional brushless DC motor,

2 is a block diagram showing a current circuit in a sensorless driving circuit of a conventional brushless DC motor,

3 is a circuit diagram showing each delay generator implemented by an Al filter in the current circuit of a conventional brushless DC motor,

4 is a block diagram showing a current circuit in the sensorless driving circuit of the brushless DC motor according to the embodiment of the present invention,

5 is a waveform diagram illustrating a generation section of a current signal generated from a current circuit of a brushless DC motor according to an embodiment of the present invention.

6 is a state table showing the state of each current signal for each current signal generation section shown in FIG.

7 is a circuit diagram illustrating a reference voltage generator in a current circuit of a brushless DC motor according to an embodiment of the present invention.

8 is a circuit diagram illustrating a current signal generator in a current circuit of a brushless DC motor according to an embodiment of the present invention.

9 is a waveform diagram showing the operation of the current circuit of the brushless DC motor according to the embodiment of the present invention.

The present invention relates to a current circuit of a brushless DC motor, and more particularly, to a current circuit of a brushless DC motor configured to be simple and easy to control in a sensorless driving circuit of a brushless DC motor. .

Recently, brushless direct current (BLDC) motors are mainly used for small precision motors used in the electronics industry. However, in order to drive such a brushless DC motor, it is necessary to detect the position of the magnetic pole of the rotor. Thus, in order to detect the position of the magnetic pole of the rotor, a magnetic pole detection sensor such as a Hall sensor has been mainly adopted.

However, a stimulus detection sensor such as a hall sensor has problems such as raising the cost of the entire system and increasing the defective rate during product production. Therefore, in recent years, a sensorless driving method that detects and drives back electromotive force generated in a motor without using a sensor in detecting a position of a magnetic pole has been adopted.

Hereinafter, a commutation circuit of a brushless DC motor in a conventional sensorless driving method will be described with reference to the accompanying drawings.

FIG. 2 is a block diagram showing a current circuit in a sensorless driving circuit of a conventional brushless DC motor, and FIG. 3 is a respective delay implemented by RC delay elements in the conventional current circuit shown in FIG. A circuit diagram showing a generator.

As shown in FIG. 2, the configuration of the current circuit in the sensorless drive circuit of a conventional brushless DC motor includes a back EMF detector 10 for detecting and outputting back EMF during motor operation; An angle delay generator (20) for delaying a constant angle (θd) from a zero-cross point of the counter electromotive force signal output from the counter electromotive force detector (10); It consists of a current signal generator 30 for generating a current signal for determining the switching order for driving the motor through the signal output from each of the delay generators 20.

In the current circuit of such a conventional brushless DC motor, each delay generator 20 which delays a constant angle [theta] d from the zero-cross point of the back EMF signal is usually used with a digital counter or as shown in FIG. You will use a filter.

Here, when using a digital counter, the value (Test) set in the counter is (the total number of pulses in one cycle) / 360 ° × θd (degree). There is a problem of becoming complicated. In addition, in the case of using the RC delay element, it is difficult to select the resistors R and the capacitors C, add cost, and lower the reliability of the entire system. In addition, even if the speed of the motor changes, the delayed angle θd does not change, and thus there is a problem in that the optimal current cannot be performed.

Accordingly, an object of the present invention is to provide a current circuit of a brushless DC motor which is simple and easy to control in a sensorless driving circuit of a brushless DC motor.

The configuration of the present invention for achieving the above object comprises a back electromotive force detector for detecting and outputting back electromotive force during motor operation; A reference voltage generator which receives the maximum value of the counter electromotive force signal output from the counter electromotive force detector and a voltage of a neutral point, and generates and outputs first and second reference voltages for generating a current signal; And a current signal generator configured to receive the first and second reference voltage signals output from the reference voltage generator and the counter electromotive force output from the counter electromotive force detector to generate a current signal for determining a switching order for driving the motor. The reference voltage generator includes: a first operator configured to receive the maximum value of the counter electromotive force and the neutral point voltage output from the counter electromotive force detector, and subtract the neutral point voltage from the maximum value of the counter electromotive force; A second operator which determines a switching point for the current by multiplying an output signal of the first operator by a sine function to an angle to be delayed; A third operator for generating a first reference voltage by adding the neutral point voltage to an output signal of the second operator; And a fourth operator for generating a second reference voltage by subtracting the output signal of the second operator from the neutral point voltage.

The current signal generator is configured to receive a counter electromotive force output from the counter electromotive force generator as a non-inverting input, and to receive a first reference voltage output from the reference voltage generator as an inverting input, respectively, so as to up-level switching the motor driving circuit. Three comparators for generating a signal; Three comparators for receiving the counter electromotive force output from the counter electromotive force generator as an inverting input and receiving the second reference voltage output from the reference voltage generator as the non-inverting input, respectively, and generating a low-level switching signal of the motor driving circuit. have.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention in detail.

4 is a block diagram showing a current circuit in a sensorless driving circuit of a brushless DC motor according to an embodiment of the present invention, and FIG. 7 is a reference voltage in a current circuit of a brushless DC motor according to an embodiment of the present invention. 8 is a circuit diagram showing a generator, and FIG. 8 is a circuit diagram showing a current signal generator in a current circuit of a brushless DC motor according to an embodiment of the present invention.

As shown in FIG. 4, the configuration of the current circuit of the brushless DC motor according to the embodiment of the present invention includes a back electromotive force detector 10 for detecting and outputting back electromotive force during motor operation; A reference voltage generator 40 which receives the maximum value of the counter electromotive force signal output from the counter electromotive force detector 10 and the voltage of the neutral point, and generates and outputs first and second reference voltages for generating a current signal; A current signal generator 50 that receives the first and second reference voltage signals output from the reference voltage generator 40 and the counter electromotive force output from the counter electromotive force detector, and generates a current signal for determining a switching order for driving the motor Consists of

As shown in FIG. 7, the configuration of the reference voltage generator 40 receives the maximum value Va_emf_max of the counter electromotive force and the voltage Vn of the neutral point from the counter electromotive force detector 10 and receives the maximum value of the counter electromotive force ( A first operator 41 which subtracts the neutral point voltage Vn from Va_emf_max; A second operator 42 which multiplies an output signal of the first operator 41 by a sine function θd of an angle to be delayed to determine a switching point for the current; A third operator (43) for generating the first reference voltage (Vref1) by adding the neutral point voltage (Vn) to the output signal of the second operator (42); The fourth operator 44 generates a second reference voltage Vref2 by subtracting the output signal of the second operator 42 from the neutral point voltage Vn.

As illustrated in FIG. 8, the configuration of the current signal generator 50 receives the counter electromotive force Va_emf, Vb_emf, and Vc_emf output from the counter electromotive force generator 10 as a non-inverting input (+), respectively, and the reference. Three comparisons 51 for receiving the first reference voltage Vref1 output from the voltage generator 40 as the inverting input (-), respectively, to generate the up-level switching signals Sa, Sb, and Sc of the motor driving circuit. 53, 55); The reverse electromotive force Va_emf, Vb_emf, and Vc_emf output from the counter electromotive force generator 10 are respectively received as inverting inputs (-), and the second reference voltage Vref2 output from the reference voltage generator 40 is respectively non-inverted input ( It is composed of three comparators 52, 54, 56 which generate the low-level switching signals Sa, Sb, Sc of the motor driving circuit.

The operation of the current circuit of the brushless DC motor according to the embodiment of the present invention made as described above is as follows.

First, FIG. 1 is a conceptual diagram showing a driving circuit of a conventional brushless DC motor, in which up-level switching signals Sa, Sb, and Sc are low-level switching signals. It is shown that the switching order for driving the motor is determined by.

5 is a waveform diagram illustrating a generation section of a current signal generated from a current circuit of a brushless DC motor according to an embodiment of the present invention.

The magnitude of the counter electromotive force shown in FIG. 5 is summarized as follows.

(Va_emf: back electromotive force of A phase, Vb_emf: back electromotive force of B phase, Vc_emf: back electromotive force of C phase, Vn: voltage of neutral point)

Next, the relationship between the entire switching process for the motor current and the counter electromotive force Va ', Vb', and Vc 'will be described.

First, as shown in FIG. 5, in section I, the phase A switching signal Sa of the motor driving circuit is turned on at the point P1 where Va 'and Vc' meet, and Va 'and Vb' meet. At point P2 the switching signal Sa is off. Here, when the angle from the zero-cross point of the counter electromotive force to the intersection point P1 is θd, the switching point for the current is present at (Va-Vn) × sinθd.

The phase-A switching signal Sa is turned on and off based on the switching points Va-Vn × sinθd for current. Similarly, the B-phase switching signal Sb is turned on and off based on (Vb-Vn) x sinθd and the C-phase switching signal Sc is turned on and off based on (Vc-Vn) xsinθd.

The state of each current signal for each current signal generation section is shown in detail in the state table shown in FIG.

Next, a process of generating a commutation signal will be described.

First, since only the counter electromotive force Va ', Vb', Vc 'is output level is small, the switching signal ( ) Cannot be created. Therefore, the original counter electromotive force Va_emf, Vb_emf, and Vc_emf0 are used as inputs of the comparator. )

FIG. 7 illustrates a process of generating two reference voltages Vref1 and Vref2 for generating a current signal using the maximum value Va_emf_max of the A-phase back EMF and the neutral point voltage Vn. The magnitudes of the two reference voltages Vref1 and Vref2 generated through the above process may be expressed as follows.

If the above method is also applied to the B and C phases of the motor, reference voltages for each phase can be generated, and as shown in FIG. The current can be performed by using a comparator to delay a certain angle from the zero-cross point of back EMF and then generate a current signal.

9 is a waveform diagram illustrating the operation of a current circuit of a brushless DC motor according to an exemplary embodiment of the present invention. The current after delaying a constant electric angle θd from the zero-cross point of counter electromotive force by using two reference voltages is shown in FIG. The process of carrying current through a signal is shown.

Therefore, the effect of the current circuit of the brushless DC motor according to the embodiment of the present invention operating as described above is to implement a simple hardware in the sensorless drive circuit of the brushless DC motor to facilitate control.

Claims (2)

A counter electromotive force detector 10 which detects and outputs a counter electromotive force during motor operation; A reference voltage generator 40 which receives the maximum value of the counter electromotive force signal output from the counter electromotive force detector 10 and the voltage of the neutral point, and generates and outputs first and second reference voltages for generating a current signal; A current signal generator 50 that receives the first and second reference voltage signals output from the reference voltage generator 40 and the counter electromotive force output from the counter electromotive force detector, and generates a current signal for determining a switching order for driving the motor The reference voltage generator 40 includes a first operator 41 which receives the maximum value of the counter electromotive force and the neutral point voltage output from the counter electromotive force detector 20 and subtracts the neutral point voltage from the maximum value of the counter electromotive force; A second operator 42 which multiplies an output signal of the first operator 41 by a sine function θd of an angle to be delayed to determine a switching point for the current; A third operator (43) for generating a first reference voltage (Vref1) by adding the neutral point voltage to the output signal of the second operator (42); And a fourth operator (44) for generating a second reference voltage (Vref2) by subtracting the output signal of the second operator (42) from the neutral point voltage. The reference voltage generator 40 of claim 1, wherein the current signal generator 50 receives back electromotive force Va_emf, Vb_emf, and Vc_emf output from the back electromotive force generator 10 as a non-inverting input (+), respectively. Each of the first reference voltages Vref1 output from the inverting input (-) is received, and the up-level switching signal of the motor driving circuit ( Three comparators 51, 53, and 55 for generating < RTI ID = 0.0 > The reverse electromotive force Va_emf, Vb_emf, and Vc_emf output from the counter electromotive force generator 10 are respectively received as inverting inputs (-), and the second reference voltage Vref2 output from the reference voltage generator 40 is respectively non-inverted input ( Low-level switching signal of the motor drive circuit Current circuit of a brushless DC motor, characterized in that consisting of three comparators (52, 54, 56) for generating a.