Using the HT45RM03 and HT45B0C to Control a 3-phase Brushless DC Motor

Transcription

1 Using the HT45RM03 and HT45B0C to Control a 3-phase Brushless DC Motor D/N: HA0117E Introduction The important application for this example is directed towards 3-phase Brushless DC motors. These motors have internal positioning sensors. The operating voltage is 36V DC and uses an MCU to generate PWM signals for the three phase brushless motor. Three phase Brushless DC motors offer the advantage of high efficiency, low noise, long life etc. with popular applications are in areas such as electric vehicles. This example uses the HT45RM03 together with the HT45B0C to drive three phase brushless DC motors. The HT45RM03 is the main controller device while the HT45B0C is an NMOS driver. Functional and Characteristic Description Working voltage 36V MCU direct PWM output driver Over-current protection Adjustable speed 1

2 Hardware Block Diagram Using the HT45RM03 and HT45B0C to Control a 3-phase Brushless DC Motor This example uses the HT45RM03 MCU device as the main controller. The main circuit blocks are: power supply circuit, driver rotation interface, power driver circuit, protection circuit and control circuit etc. DC 36V DC 5VDC 15V Power 電源回路 Circuit VR DC 5V HT45RM03 PC0 PC1 PC2 PC3 PC4 PC5 NMOSNMOS Gate Driver HT45B0C Motor current 電機電流采樣電路 sampling signal 3 Phase BLDC Run/Stop Key pa4/int0a pa5/int0b pa6/int0c HALL C HALL B HALL A Hardware Block Diagram Functional Description Power Supply Circuit The 36V power supply provides the three phase brushless motor with power, additionally by using LM317, 7815 and 7805 devices power is supplied to the HT45RM03 and the other peripheral circuits. Driver Rotation Interface The driver rotation interface is an MCU controlled circuit and power driver circuit interface. The circuit uses the HT45B0C as the driver rotation interface. Power Driver Circuit There are 6 NMOS power drive circuits to drive the three phase brushless motor. This example uses 6 N-type Mosfet transistors to form a three phase half bridge drive circuit, which can be used for driving three phase brushless motors. 2

3 Protection Circuit This example has protection circuits for over-current, which is used to protect the three phase brushless motor. The circuit uses the HT45RM03 internal operational amplifier and comparator in its implementation. Control Circuit By using an adjustable resistor the speed of the motor can be setup. When the VR voltage is between 0.4V and 3.4V, pressing the Run/Stop key will start the motor. Pressing the Run/Stop key again will stop the motor. The HT45RM03 uses hall sensors for feedback signals to determine at which point the relevant pair of N-FETs should be turned on. 3

4 Application Circuit Using the HT45RM03 and HT45B0C to Control a 3-phase Brushless DC Motor ` 4

5 H/W Operating Principle Over-current Protection Circuit The present application over-current protection circuit uses the HT45RM03 internal operational amplifier/comparator. The motor current signal is first amplified (PA0/OPVINP, PB3/OPVINN, PB2/OPOUT) and then converted using the MCU AD converter, after which the comparator is used (PA1/CVINP, PA2/CVINN, PA3/COUT) to implement the current protection function. HT45B0C Application Circuit The HT45B0C is an MCU used to control the power drive circuit interface. It is not only used as a voltage level converter interface, but also as a bridge protection circuit, to prevent the NMOS power devices from burning out due to wrong switching. 5

6 HT45B0C Characteristics: Provides 3 high drive and 3 low drive mosfet drivers Low drive supply range 9V ~ 20V High driver output maximum voltage 80V Low Voltage Protection The HT45B0C input/output truth table is shown below: 6

7 Power Driver Circuit The Power Driving circuit is formed of 6 NMOS devices, type 60nf06. For anti-clockwise motor rotation the hall sensor corresponding output signal order is For anti-clockwise motor rotation, the NMOS device condition with respect to the hall sensor signals is shown in the following table: Hall sensor(sa,sb,sc) NMOS condition 000 Q5, Q4 on 001 Q1, Q4 on 011 Q1, Q6 on 111 Q3, Q6 on 110 Q3, Q2 on 100 Q5, Q2 on * the hall sensor corresponding output signal order is defined by the motor specification. 7

8 S/W Flowchart Main Flowchart Start WDT Overflow? Initialise RAM Initialize Special Register Cancel Comparator Offset Voltage Cancel OP Offset Voltage Get Velometer Voltage Get Current Value Event3 Process Speed Controller Main Program Description Initialise the RAM and I/O etc special function registers Calibrate the operational amplifier/comparator GetVelometerVoltage: VR voltage detect program GetCurrent Value: Brushless motor current measurement program Event3Process: Includes run/stop switch detection and calculation of pwm values from the VR SpeedControler: Brushless motor voltage adjustment program 8

9 VR Voltage Measurement Flowchart Get Velometer Voltage 1 R_AN0ConvertNO>=2? R_Temp0=R_VelometerVolTm p/4 R_VelometerVolTmp[n]< = R_VelometerVolTmp[0]? R_Temp0 > C_VelometerMin? R_VelometerTmp[n]<=>R_V elometertmp[0] R_Temp0 > C_VolometerMax? MMOV R_Temp0, C_VolometerMax R_VelometerVolTmp[1] > R_VelometerVolTmp[n]? CLR F_VelometerRotated R_VelometerVolTmp<=>R_Vel ometervoltmp[1] MMOV R_VelometerVol, R_Temp0 set F_VelometerRotated R_AN0ConvertNO >= 4? L_ExitGetVelometerVoltage R_VelometerVolTmp[n]< = R_VelometerVolTmp[2]? R_VelometerVolTmp[n]<=>R_ VelometerVolTmp[2] R_VelometerVolTmp[3] > R_VelometerVolTmp[n]? R_VelometerVolTmp[n]<=>R_ R_VelometerVolTmp[3] R_AN0ConvertNO = 8? 1 L_Exit GetVelometerVoltage 9

10 GetCurrentValue Flowchart Get Current Value 1 R_AN4ConvertNO>=2? R_Temp0=R_CurrentValue/4 R_CurrentValue[n]< = R_CurrentValue[0]? R_Temp0 > C_Current16A? R_CurrentValue[n]<=>R_Cur rentvalue[0] clr F_OverCurrent clr R_OverCurrentTime set F_OverCurrent R_CurrentValue[1] > R_CurrentValue[n]? R_CurrentValue<=>R_Current Value[1] R_Current10A<= C_Current10Ae? clr F_LimitCurrent F_LimitCurrent = 0? R_OverCurrentTime >= C_OverCurrentTime? R_AN4ConvertNO >= 4? set F_LimitCurrent clr R_OverCurrentTime R_CurrentValue[n]< = R_CurrentValue[2]? L_ExitGetCurrentValue R_CurrentValue[n]<=>R_Curre ntvalue[2] R_CurrentValue[3] > R_CurrentValue[n]? R_CurrentValue[n]<=>R_Curre ntvalue[3] R_AN4ConvertNO = 8? 1 L_ExitGetCurrentValue 10

11 Event3 Process Flowchart L_Event3Process P_RunUp = 0? clr R_KeyPrDebounce R_KeyPrDebounce = C_KeyPrDebounce? inc R_KeyPrDebounce R_KeyPrDebounce = C_KeyPrDebounce? clr F_RunStop or set F_RunStop R_VelometerVol = 0? L_CaulatePwm clr R_TargetPwm[0] clr R_TargetPwm[1] ExitEvent3Process 11

12 SpeedControler Flowchart L_Speed Controler F_Run Stop=1? call SBR_Stop Motor F_VelometerRotated = 0? call SBR_Stop Motor call SBR_Start Motor F_Start Motor = 0? jmp L_Limit Current Protector F_Limit Current = 0? R_SpeedUp Time = 0? L_SpeedUp R_Pwm < R_Target Pwm? R_Pwm > R_Target Pwm? L_Speed Down L_Exit Speed Controler 12