CN201383788Y

CN201383788Y - Simple BEMF zero-crossing detection circuit of brushless direct current motor

Info

Publication number: CN201383788Y
Application number: CN200920300760U
Authority: CN
Inventors: 刘瑜; 林亮; 方曙光
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-02-21
Filing date: 2009-02-21
Publication date: 2010-01-13
Anticipated expiration: 2019-02-21

Abstract

The utility model relates to a simple BEMF (back electromotive force) zero-crossing detection circuit of a brushless direct current motor, which comprises a singlechip used for executing the detection algorithms and a BEMF detection circuit, wherein the BEMF detection circuit comprises a voltage comparator, a BEMF sampling resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6 and a filtering capacitor C1; the resistor R5, the resistor R6 and the filtering capacitor C1 compose a voltage sampling circuit used for collecting the driving voltage of the motor, and the voltage sampling circuit is connected with the out-phase terminal of the voltage comparator; and the output terminal of the voltage comparator is connected with the interrupting interface of the singlechip. Furthermore, a resistor R7 is arranged at the in-phase terminal of the voltage comparator, and is grounded, therefore the detection circuit is applicable to the wide voltage range. The detection circuit has the benefits that simple hardware and different resistance coefficient ratios are adopted, so that the circuit is applicable to various voltage ranges, the detection precision of the BEMF is ensured, the measuring precision of the rotor position of the electric motor is improved, and a better phase changing time is obtained.

Description

A kind of simple back electromotive force zero-crossing detection circuit of brushless direct current motor

Technical field

The utility model belongs to the Driving technique field of brshless DC motor.

Background technology

The no sensing Driving technique of brshless DC motor obtains using very widely because of the technical advantage of himself, such as the motor-driven of direct current compressor, and the motor-driven of electric motor car etc.The control of the rotating speed of brshless DC motor is by driving voltage is regulated, and comes the power supply of switch motor to realize according to the position of rotor.Because there are the corresponding relation of determining in the rotor-position of brshless DC motor and back electromotive force,, just need not the rotor-position sensing element if therefore determine the rotor-position of brshless DC motor by detecting counter electromotive force of motor.But back electromotive force can not directly detect, and can only obtain indirectly by detecting phase voltage.Such as, when A, B switch on mutually, detect the C phase voltage, when the C phase voltage equal driving voltage 1/2 the time, be defined as the zero crossing of back electromotive force.Voltage detecting need convert voltage analog to single-chip microcomputer manipulable digital quantity by digital to analog converter.Therefore, the no sensing Driving technique of common brshless DC motor often adopts relatively more expensive single-chip microcomputer, has multi-channel A C translation interface.Like this, tend to bring expensive result to final products.

Summary of the invention

To the present invention seeks to adopt hardware simplicity in order reducing cost, to realize that back electromotive force zero-crossing detects, accurately motor rotor position obtains accurate commutation point, thereby realizes the no transducer control effect of more stable brshless DC motor.

The technical scheme that its technical problem that solves the utility model adopts is:

A kind of simple back electromotive force zero-crossing detection circuit of brushless direct current motor, comprise single-chip microcomputer and the counter electromotive force detection circuit of carrying out detection algorithm, described counter electromotive force detection circuit, comprise voltage comparator, the resistance R 1 that connects the A phase, the resistance R 2 that connects the B phase, the resistance R 3 of connection C phase is with described resistance R 1, resistance R 2, the resistance R 4 that resistance R 3 connects, described resistance R 4 connects the in-phase end of described voltage comparator, resistance R 5 and resistance R 6, and filter capacitor C1 forms voltage sampling circuit, gather motor driven voltage, and connect the end of oppisite phase of described voltage comparator, the output of described voltage comparator connects the middle fracture of described single-chip microcomputer.

Described single-chip microcomputer is opened external interrupt, sets interrupt service routine.Described interrupt service routine comprises and calculates commutation half period T _HLF, judge commutation half period T _HLFWhether greater than minimum commutation half period T _HLFmin, calculate commutation t constantly _CMTnextSpecific as follows: as, to trigger described interrupt service routine when described voltage comparator generation level conversion; Described interrupt service routine is at first with current interruption moment t _ZERODeduct the last time commutation moment t of described motor _CMT, obtain commutation half period T _HLF, i.e. T _HLF=t _ZERO-t _CMT, judge commutation half period T then _HLFWhether greater than minimum commutation half period T _HLFminIf, T _HLF＞T _HLFmin, the current interruption of described interrupt service routine record is t constantly _ZERO, and from current interruption moment t _ZEROPostpone commutation half period T _HLF, determine the commutation point t of described motor _CMTnext, i.e. t _CMTnext=t _ZERO+ T _HLFOn the contrary, then do not do any processing, withdraw from interrupt service routine.

Resistance R 7 can be set, described resistance R 7 other end ground connection at the in-phase end of described voltage comparator; Described resistance R 4, resistance R 5, resistance R 6, resistance R 7, maintenance proportionate relationship R7/ (R4+R7)==R6/ (R5+R6)/2.

The beneficial effects of the utility model mainly show: 1, circuit structure is simple, and cost is low; 2, the back electromotive force zero-crossing accuracy of detection effectively improves; 3, suitable voltage range is wide.

Description of drawings

Fig. 1 is the schematic diagram of the back electromotive force zero-crossing detection circuit of brushless DC motor without sensor;

Fig. 2 is the schematic diagram that increases the back electromotive force zero-crossing detection circuit of pull down resistor;

Fig. 3 is the signal graph of back electromotive force;

Fig. 4 is the interrupt service routine flow chart.

Embodiment

Below in conjunction with accompanying drawing the utility model is further described.

With reference to Fig. 1, Fig. 2, Fig. 3, Fig. 4, a kind of simple back electromotive force zero-crossing detection circuit of brushless direct current motor and method comprise single-chip microcomputer 1 and the counter electromotive force detection circuit of carrying out detection algorithm.

Counter electromotive force detection circuit, comprise voltage comparator 2, the resistance R 1 that connects the A phase, the resistance R 2 that connects the B phase, the resistance R 3 of connection C phase, described resistance R 1, resistance R 2, resistance R 3 other ends link together, and connect resistance R 4, and described resistance R 4 other ends connect the in-phase end of described voltage comparator 2.Described resistance R 1, resistance R 2, resistance R 3 play the effect of the back electromotive force of sampling motor 3, and connect the in-phase end of described voltage comparator 2 later on by resistance R 4 current limlitings.

Resistance R 5 and resistance R 6, and filter capacitor C1 composition voltage sampling circuit are gathered motor driven voltage, and are connected the end of oppisite phase of described voltage comparator 2.Resistance R 5 and resistance R 6 adopt 1: 1 ratio setting, can guarantee that the later magnitude of voltage of dividing potential drop is 1/2 of motor driven voltage VDC.

The output of described voltage comparator 2 connects the middle fracture of described single-chip microcomputer 2.In described motor 3 rotation processes, the voltage of end of oppisite phase remains on 1/2 of motor driven voltage VDC, and the back-emf voltage of in-phase end is the AC signal with the VDC/2 average, so in the time of back-emf voltage process VDC/2 average, when being the back electromotive force zero passage, the output of described voltage comparator 2 produces a level conversion: become low level from high level, perhaps become high level from low level.

Described single-chip microcomputer 2 setting programs are opened external interrupt; When level conversion takes place described voltage comparator 2, trigger interrupt service routine.Described interrupt service routine comprises and calculates commutation half period (T _HLF) 4, judge commutation half period (T _HLF) whether greater than minimum commutation half period (T _HLFmin) 5, calculate commutation (t constantly _CMTnext) 6.Specific as follows: as, to trigger described interrupt service routine when level conversion takes place described voltage comparator 2; Described interrupt service routine is at first with current interruption moment t _ZERODeduct the last time commutation moment t of described motor 3 _CMT, obtain commutation half period T _HLF, i.e. T _HLF=t _ZERO-t _CMT, judge commutation half period T then _HLFWhether greater than minimum commutation half period T _HLFminIf, T _HLF＞T _HLFmin, the current interruption of described interrupt service routine record is t constantly _ZERO, and from current interruption moment t _ZEROPostpone commutation half period T _HLF, determine the commutation point t of described motor 3 _CMTnext, i.e. t _CMTnext=t _ZERO+ T _HLFOn the contrary, then do not do any processing, withdraw from interrupt service routine.

As can be seen from Figure 3, after described motor 3 carries out commutation, there is the demagnetization process of certain hour, this period can be triggered two even a plurality of external interrupt, and these two interruptions can not be reacted correct back electromotive force zero-crossing, therefore need judge in interrupt service routine.

Further, resistance R 7 can be set at the in-phase end of described voltage comparator 2, described resistance R 7 other end ground connection.The setting of resistance R 7 can increase the suitable voltage range of this circuit.At first, the withstand voltage scope when magnitude of voltage VDC surpasses voltage comparator 2 then needs to be provided with resistance R 7.Secondly, need to keep resistance ratio R7/ (R4+R7) to equal R6/ (R5+R6)/2.

Claims

1. simple back electromotive force zero-crossing detection circuit of brushless direct current motor, comprise single-chip microcomputer (1) and the counter electromotive force detection circuit of carrying out detection algorithm, it is characterized in that: described counter electromotive force detection circuit, comprise voltage comparator (2), the resistance R 1 that connects the A phase, the resistance R 2 that connects the B phase, the resistance R 3 that connects the C phase, with described resistance R 1, resistance R 2, the resistance R 4 that resistance R 3 connects, described resistance R 4 connects the in-phase end of described voltage comparator (2), resistance R 5 and resistance R 6, and filter capacitor C1 forms voltage sampling circuit, gather motor driven voltage, and connect the end of oppisite phase of described voltage comparator (2), the output of described voltage comparator (2) connects fracture in the described single-chip microcomputer (2).

2. a kind of simple back electromotive force zero-crossing detection circuit of brushless direct current motor as claimed in claim 1 is characterized in that: described single-chip microcomputer (2) is opened external interrupt, sets interrupt service routine.

3. a kind of simple back electromotive force zero-crossing detection circuit of brushless direct current motor as claimed in claim 1 is characterized in that: can resistance R 7 be set at the in-phase end of described voltage comparator (2), described resistance R 7 other end ground connection; Described resistance R 4, resistance R 5, resistance R 6, resistance R 7, maintenance proportionate relationship R7/ (R4+R7)==R6/ (R5+R6)/2.