KR0177991B1 - A commutating triggering circuit of sensorless bldc motor - Google Patents

Abstract

The present invention discloses a current timing determining circuit of a sensorless brushless direct current motor. The circuit comprises zero cross signal generating means for inputting a three-phase back electromotive force signal of the motor to generate a zero cross signal, zero cross signal generating means for generating a pulse at an edge of the zero cross signal, and a coefficient in response to the pulse. Counting means for shifting, and storing means for shifting and storing the value counted by said counting means one bit lower, and comparing the value counted by said counting means with a value stored in said storing means. Comparing means for generating a current timing signal, and switching signal generating means for generating switching signals for flowing a three-phase current to the motor by inputting the current timing signal and the three-phase back electromotive force signal of the motor. It is. Therefore, finding the current timing using the counter recalculates the timing each time a switching occurs, so that the optimum current timing can always be found.

Description

Current Timing Circuit of Sensorless Brushless DC Motor

1 is a block diagram of a current timing determining circuit of a sensorless brushless DC motor of the present invention.

2A to 2G are each sub-output waveform diagram of the block diagram shown in FIG.

3A and 3B are for explaining the operation of the n-bit counter and n-bit latch shown in FIG.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to brushless direct current motors, and more particularly, to a current timing determining circuit of a sensorless brushless direct current motor capable of finding the optimal current timing of a sensorless brushless direct current motor.

Most of the small precision motors used in the electronics industry are brushless DC motors. However, in order to start a brushless DC motor, a magnetic pole detection sensor for detecting the position of the rotor is required. In recent years, many sensorless starting methods have been used which start using a back electromotive force generated when the motor is rotated without attaching a magnetic pole detection sensor. Brushless DC motor has the advantages that the motor characteristics are similar to the DC motor, it is easy to control, there is no brush compared to the DC motor, the structure is simple and maintenance of the motor is not necessary. In brushless DC motors, a current is performed by using a brush in a DC motor using a semiconductor device to perform current by turning on and off a switch connected to the motor. When starting a brushless DC motor, it is important to select a good time to perform the current action. In case of starting the sensorless type, it is necessary to use the counter electromotive force to determine the time of the current. The present invention invented a method of finding the timing of current by operating a digital counter by using a counter electromotive force as an input.

Conventionally, an external device is attached, and a method of finding the timing of distorting the counter electromotive force of a motor and using the current is used. In this case, the external device value is fixed, so that a value that is well applied at both low and high speeds is selected. Was not possible. In other words, in the related art, a method of attaching a resistor or a capacitor to the outside to delay the counter electromotive force so as to perform a current action in the zero corose of the delayed counter electromotive area is used. However, this method is difficult to select the values of resistors and capacitors, and the delay degree does not change well even when the motor accelerates from low speed to high speed.

Accordingly, an object of the present invention is to provide a current timing determining circuit of a sensorless brushless direct current motor capable of finding an optimal current timing.

The current timing determination time of the sensorless brushless DC motor of the present invention for achieving the above object is a zero cross signal generating means for generating a zero cross signal by inputting a three-phase back EMF signal of the motor, the edge of the zero cross signal A pulse generating means for generating a pulse, a counting means for counting in response to said pulse, a storage means for shifting and storing the value counted by said counting means one bit lower in response to said pulse, said counting means Means for generating a current timing signal when the value counted by the means compares with a value stored in the storage means, and inputs the current timing signal and the three-phase back EMF signal of the motor to generate a three-phase current. It consists of a switching signal generating means for generating switching signals to flow to.

Referring to the accompanying drawings, a current timing determining circuit of the sensorless brushless DC motor of the present invention will be described.

1 is a block diagram of a current timing determining circuit of a sensorless brushless DC motor of the present invention, wherein a zero cross signal generating circuit 10, a counter signal generating circuit 12, an n bit counter 14, and a 1 bit shift register are shown. (16), n-bit latch 18, comparator 20, and switching signal generation circuit 22. As shown in FIG.

The zero cross signal generation circuit 10 inputs three-phase back EMF signals Va-emf, Vb-emf, and Vc-emf of the motor to generate a zero corse signal. The counter signal generation circuit 12 generates a pulse at the edge of the zero cross signal. This signal is a counter signal. The n bit counter 14 starts or ends the counting operation in response to the counter signal. The zero cross signal causes six zero crosses in one cycle and six pulses. When the counting start signal of the n-bit counter 14 is applied, counting is started, and this operation continues counting until the back electromotive force of the motor crosses zero cross again and a stop signal is generated. When the counter electromotive force of the motor passes through the zero cross, and the stop signal is applied from the n-bit counter 14, the n-bit counter 14 stops counting. The one-bit shift register 16 shifts and stores the counted value one bit lower. The n bit latch 18 stores the value shifted by the 1 bit shift register 16, where the n bit counter 14 starts counting again. The data stored in the latch is a reference for determining the next current period. The comparator 20 generates a current timing signal when the newly started count value and the value of the bit latch 18 stored in the previous period are the same, and this timing becomes the midpoint of the zero cross. At this point, the switch can be turned on and off to perform current. The switching signal generation circuit 22 inputs the current timing and the counter electromotive force of the motor, so that the switching signals Sa (+) and Sa (-) of the three-phase switch flowing three-phase currents Ia, Ib, and Ic to the motor. , Sb (+), Sb (-), Sc (+), Sc (-)). Here, (+) is a switch connected to the power supply side, (-) means a switch connected to the ground terminal.

2A-G are waveform diagrams of the sub-outputs of the block diagram shown in FIG. 1, and FIG. 2A is a waveform of three-phase back EMF (Va-emf, Vb-emf, Vc-emf), and 2b, c, and d are motors. The waveforms of the currents Ia, Ib, and Ic applied to each phase are shown in FIG. 2E, the waveform of the current timing of the motor, FIG. 2F, the waveform of the zero cross signal, and FIG. 3G, the waveform of the counter signal.

The back electromotive force signals Va-emf, Vb-emf, and Vc-emf of the motor are 120 degrees in phase difference and the same in magnitude. Current action, ie switching, occurs when the counter electromotive force of each phase motor meets, and this point is the midpoint of the zero cross of the back electromotive force of the motor. If the current action is not made at an appropriate time, the applied current is not used to efficiently torque, and the acceleration is slowed down due to heat loss. The zero cross signal generation circuit 10 inputs the back electromotive force signals Va-emf, Vb-emf, and Vc-emf shown in FIG. 2A to generate the zero cross signal shown in FIG. 2F. The counter signal generation circuit 12 generates the pulse shown in Fig. 2f at the edge of the zero cross signal. Six zero crosses occur in one cycle, and six pulses are generated. This pulse is also applied to the clock of the n-bit latch 18 to shift and store the value of the n-bit counter 14 counted in the previous period to one bit lower. At the same time that the 1-bit shifted value of the n-bit counter 14 is stored in the n-bit latch 18, the n-bit counter 14 counts again. The n-bit comparator 20 generates a pulse called a current period as shown in FIG. 2f if the newly started count value and the latch value stored in the previous period are the same. The point where the pulse of the current phase is generated becomes the midpoint of the zero cross point of the motor. At this point, the switching signal generation circuit 22 turns the switch on and off to perform current.

3A and 3B illustrate the operation of the n-bit counter and the n-bit latch shown in FIG. 1, and FIG. 3A shows a signal counted by the n-bit counter 14 in the Nth cycle. 1 bit shifted and stored in the n-bit latch 18 lower. At the same time as it is stored in the n-bit latch 18, the counter 14 starts the (N + 1) th count again. If the value of the counter 14 started in the (N + 1) th period is compared with the value of the latch stored in the Nth period, a current timing signal is generated. 3b shows the operation of the (N + 1) th cycle.

Therefore, the current timing determination circuit of the sensorless brushless DC motor of the present invention uses a counter to find the current timing, and each time a switching occurs, the timing is recalculated so that the optimum current timing can always be found. have.

Claims (2)

Zero cross signal generating means for inputting a three-phase back electromotive force signal of the motor to generate a zero cross signal, pulse generating means for generating a pulse at the edge of the zero cross signal, counting means for counting in response to the pulse, Storage means for shifting and storing the value counted by said counting means one bit lower in response to said pulse, the current timing when the value counted by said counting means compares with the value stored in said storage means Comparison means for generating a signal, and switching signal generating means for inputting the current timing signal and the three-phase back electromotive force signal of the motor to generate switching signals for flowing a three-phase current to the motor. Current timing determination circuit of sensorless brushless DC motors. 2. The current timing determining circuit of a sensorless brushless direct current motor according to claim 1, wherein the current timing signal is generated at an intermediate point of the zero cross signal.