Impedance detection method of DC brushless controller power tube

Abstract

The invention discloses an impedance detection method for a power tube of a direct-current brushless controller, the direct-current brushless controller is connected with and controls a three-phase bridge type inverter circuit composed of six MOS (Metal Oxide Semiconductor) tubes, the three-phase output ends A, B and C of the three-phase bridge type inverter circuit are respectively connected with the three-phase input end of a brushless motor, and the method comprises the following steps: firstly, establishing a resistance network; and respectively calculating the impedance of the upper MOS tube and the lower MOS tube of the three-phase bridge type inverter by using the bus voltage and the resistance network. According to the invention, the resistance measurement of the upper and lower MOS tubes is realized by using the existing back electromotive force circuit, and whether the MOS tubes are good or bad is distinguished by judging the resistance. According to the invention, the impedance measurement of the upper and lower bridge power MOS tubes is realized by using the existing brushless motor control circuit, the program is easy to realize, and the impedance judgment of the power MOS can be realized only by using the ADC and judging the threshold value of the ADC.

Description

Technical Field

[0001] The invention relates to the field of motor control, and in particular to an impedance detection method for a power tube of a direct current brushless controller. Background Art

[0002] Brushless motors generally use DC brushless controllers to control the inverter circuit composed of MOS and other power tubes. Once the MOS tube is damaged, continuing to work may have serious consequences. After the MOS tube is damaged, the impedance presented is different, and the existing overcurrent or fuse may not be able to play a good protective role. Therefore, before starting the control, measuring the impedance of the MOS tube is an important means to ensure safe operation.

[0003] The existing impedance measurement of MOS tubes in the control circuit of a brushless DC controller generally requires the addition of peripheral devices or instruments, which increases costs and complicates the process. Summary of the invention

[0004] The purpose of the present invention is to provide an impedance detection method for a power tube of a brushless DC controller, which utilizes an existing back electromotive force circuit to measure the resistance of upper and lower MOS tubes, and distinguishes whether the MOS tube is good or bad by judging the resistance value.

[0005] The technical solution of the present invention is:

[0006] The impedance detection method of the power tube of the DC brushless controller is that the DC brushless controller is connected to control a three-phase bridge inverter circuit composed of 6 MOS tubes, and the three-phase output terminals A, B, and C of the three-phase bridge inverter circuit are respectively connected to the three-phase input terminals of the brushless motor. The method first establishes a resistor network:

[0007] The output end of phase A is connected to ground through resistors RA1 and RA2 connected in series;

[0008] The output end of phase B is connected to ground through resistors RB1 and RB2 connected in series;

[0009] The output end of phase C is connected to ground through resistors RC1 and RC2 connected in series;

[0010] Among them, RA1=RB1=RC1, RA2=RB2=RC2;

[0011] Through chip ADC sampling, the impedance of the upper and lower MOS tubes of the three-phase bridge inverter circuit is calculated respectively using the bus voltage and the resistance network.

[0012] Preferably, when the brushless motor is not started, the ABC three-phase output terminals are equivalent to wire connections; assuming that the MOS tube has impedance, R MOS express.

[0013] Preferably, the method of calculating the impedance of the upper and lower MOS tubes of the three-phase bridge inverter circuit respectively by chip ADC sampling and using the bus voltage and the resistance network includes:

[0014] S1. Assume that the ADC reference voltage is Vref and the accuracy is Acy;

[0015] S2, its ADC formula is:

[0016] S3. Calculate V CC Voltage value:

[0017]

[0018] Right now

[0019]

[0020] Where V ADC is the bus ADC sampling value, and the rest are constants;

[0021] S4, use Ea, Eb, and Ec to represent the intermediate voltages of the three-phase ABC series resistors respectively.

[0022] Since RA1=RB1=RC1, RA2=RB2=RC2, so Ea=Eb=Ec, use Ea for calculation:

[0023]

[0024] V E Bring it into Ea formula;

[0025] S5. Calculate the ADC value of Ea:

[0026]

[0027] Bring it in

[0028]

[0029] Where V ADC Except for , the rest are constants, and the constant terms are replaced by K;

[0030] S6, resistance value judgment:

[0031] When setting a corresponding R MOS When the resistance value is ADC Judgment threshold; R MOS With E ADC Inversely proportional, R MOS The smaller the E ADC The larger the value, the software only needs to judge as follows:

[0032] Current Sample E ADC >(Current sampling V ADC *K), which means that the current MOS tube impedance is lower than the set value.

[0033] Preferably, the detection method further comprises: setting any one of Eb and Ec as output, whose output voltage is Vdd, Ea as ADC input, setting the lower bridge impedance to R MOS ;

[0034] Formula derivation:

[0035]

[0036]

[0037] Substitute the formula into it,

[0038]

[0039] Among them, all terms are constants, and R is set MOS value, the corresponding E ADC Judgment threshold, R MOS With E ADC Proportional to R MOS The smaller the E ADC The smaller the value, the smaller the ADC If it is less than the judgment threshold, it means that the MOS tube impedance is lower than the set value.

[0040] The advantages of the present invention are:

[0041] 1. The impedance detection method of the power tube of the brushless DC controller of the present invention does not need to add a circuit, and the MOS tube can be measured without turning on. The impedance of the upper and lower MOS tubes can be calculated respectively by sampling the chip ADC and using the bus voltage and the resistance network.

[0042] 2. The present invention utilizes the existing brushless motor control circuit to realize the impedance measurement of the upper and lower bridge power MOS tubes. The program is simple to implement. It only needs to use ADC to determine the impedance of the power MOS by judging its threshold value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0044] Figure 1 It is the overall block diagram of the control circuit of the brushless DC controller;

[0045] Figure 2 This is a simplified circuit diagram for upper bridge detection;

[0046] Figure 3This is a simplified circuit diagram for lower bridge detection. DETAILED DESCRIPTION

[0047] like Figure 1 As shown, the impedance detection method of the power tube of the DC brushless controller of the present invention, the DC brushless controller is connected to control the three-phase bridge inverter circuit composed of 6 MOS tubes Q1-Q6, and the three-phase output terminals A, B, and C of the three-phase bridge inverter circuit are respectively connected to the three-phase input terminals of the brushless motor. The method first establishes a resistor network:

[0048] The output end of phase A is connected to ground through resistors RA1 and RA2 connected in series;

[0049] The output end of phase B is connected to ground through resistors RB1 and RB2 connected in series;

[0050] The output end of phase C is connected to ground through resistors RC1 and RC2 connected in series;

[0051] Among them, RA1=RB1=RC1, RA2=RB2=RC2;

[0052] Use Ea, Eb, and Ec to represent the intermediate voltages of the three ABC three-phase series resistances, so Ea, Eb, and Ec;

[0053] The busbar is connected to the ground through resistors RV1 and RV2 connected in series; the voltage between resistors RV1 and RV2 is represented by VDC;

[0054] The present invention calculates the impedances of the upper and lower MOS tubes of the three-phase bridge inverter circuit respectively by using chip ADC sampling and bus voltage and a resistance network.

[0055] When the brushless motor is not started, the ABC three-phase output terminals are equivalent to wire connections; assuming that the MOS tube has impedance, R MOS According to the above, the circuit can be simplified as follows Figure 2 shown.

[0056] The method of calculating the impedance of the upper and lower MOS tubes of the three-phase bridge inverter circuit by sampling the chip ADC and using the bus voltage and the resistance network includes:

[0057] S1. Assume that the ADC reference voltage is Vref and the accuracy is Acy;

[0058] S2, its ADC formula is:

[0059] S3. Calculate V CC Voltage value:

[0060]

[0061] Right now

[0062]

[0063] Where V ADC is the bus ADC sampling value, and the rest are constants;

[0064] S4, use Ea, Eb, and Ec to represent the intermediate voltages of the three-phase ABC series resistors respectively.

[0065] Since RA1=RB1=RC1, RA2=RB2=RC2, so Ea=Eb=Ec, use Ea for calculation:

[0066]

[0067] V E Bring it into Ea formula;

[0068] S5. Calculate the ADC value of Ea:

[0069]

[0070] Bring it in

[0071]

[0072] Where V ADC Except for , the rest are constants, and the constant terms are replaced by K;

[0073] S6, resistance value judgment:

[0074] When setting a corresponding R MOS When the resistance value is ADC Judgment threshold; R MOS With E ADC Inversely proportional, R MOS The smaller the E ADC The larger the value, the software only needs to judge as follows:

[0075] The current sampling EADC>(current sampling VADC*K) means that the current MOS tube impedance is lower than the set value.

[0076] The above is the judgment on the bridge and the derivation of the formula.

[0077] The following introduces the judgment of the bridge and the derivation of the formula.

[0078] S1, set any one of Eb and Ec as output, its output voltage is Vdd, Ea is ADC input, set the lower bridge impedance to R MOS ;

[0079] S2 formula derivation:

[0080]

[0081] Substitute the formula into it,

[0082]

[0083] In the formula, all terms are constants, and R is set MOS value, the corresponding E ADC Judgment threshold, R MOS With E ADC Proportional to R MOS The smaller the E ADC The smaller the value is. So we only need to judge the current sampling E ADC If it is less than the judgment threshold, it means that the MOS tube impedance is lower than the set value.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any modifications made according to the spirit of the main technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for detecting the impedance of a power tube of a brushless DC controller, wherein the brushless DC controller is connected to control a three-phase bridge inverter circuit composed of six MOS tubes, and the three-phase output terminals A, B, and C of the three-phase bridge inverter circuit are respectively connected to the three-phase input terminals of a brushless motor, characterized in that: First, create the resistor network: The output end of phase A is connected to ground through resistors RA1 and RA2 connected in series; The output end of phase B is connected to ground through resistors RB1 and RB2 connected in series; The output end of phase C is connected to ground through resistors RC1 and RC2 connected in series; Among them, RA1=RB1=RC1, RA2=RB2=RC2; Through chip ADC sampling, the impedance of the upper and lower MOS tubes of the three-phase bridge inverter circuit is calculated respectively using the bus voltage and the resistance network.

2. The impedance detection method of the power tube of the brushless DC controller according to claim 1, characterized in that: When the brushless motor is not started, the ABC three-phase output terminals are equivalent to wire connections; assuming that the MOS tube has impedance, R MOS express.

3. The impedance detection method of the power tube of the brushless DC controller according to claim 2, characterized in that: The method of calculating the impedance of the upper and lower MOS tubes of the three-phase bridge inverter circuit by sampling the chip ADC and using the bus voltage and the resistance network includes: S1. Assume that the ADC reference voltage is Vref and the accuracy is Acy; S2, its ADC formula is: S3. Calculate V CC Voltage value: Right now Where V ADC is the bus ADC sampling value, and the rest are constants; S4, use Ea, Eb, and Ec to represent the intermediate voltages of the three-phase ABC series resistors respectively. Since RA1=RB1=RC1, RA2=RB2=RC2, so Ea=Eb=Ec, use Ea for calculation: V E Bring it into Ea formula; S5. Calculate the ADC value of Ea: Bring it in Where V ADC Except for , the rest are constants, and the constant terms are replaced by K; S6, resistance value judgment: When setting a corresponding R MOS When the resistance value is ADC Judgment threshold; R MOS With E ADC Inversely proportional, R MOS The smaller the E ADC The larger the value, the software only needs to judge as follows: Current Sample E ADC >(Current sampling V ADC *K), which means that the current MOS tube impedance is lower than the set value.

4. The impedance detection method of the power tube of the brushless DC controller according to claim 3, characterized in that: Also includes: Set any one of Eb and Ec as output, and its output voltage is Vdd, Ea is ADC input, and the lower bridge impedance is R MOS ; Formula derivation: Substitute the formula into it, Among them, all terms are constants, and R is set MOS value, you can generate the corresponding E ADC Judgment threshold, R MOS With E ADC Proportional to R MOS The smaller the E ADC The smaller the value, the smaller the ADC If it is less than the judgment threshold, it means that the MOS tube impedance is lower than the set value.

Images