SPWM波指的是占空比呈正弦規律變化的PWM波,生成方式是在定時器中斷中調整PWM波的占空比。
對於互補的兩路SPWM波,一路為低電平 ‘0’ 時,另一路為高電平 ‘1’,即兩路是互補的。
對於STM32F7,使用高級定時器TIM1可以方便地生成互補SPWM波。步驟如下:
1、確定載波周期 Tc,也即是每個SPWM波的周期。對於逆變電路,常采用20kHz,也即 Tc = 50us;
2、確定基波周期 Tb,此處取50Hz,即 Tb = 20ms;
3、計算取點數N,Tb / Tc = 20ms/50us = 4000;半個周期內則為 N = 2000點;
4、計算占空比,Di = sin(i*pi / N), i = 1, 2, 3, ..., N;
5、確定最大最小占空比,例如最小占空比 Dmin = 0,最大占空比Dmax = 100%;
6、計算並修改定時器的比較值。將占空比為0%時,定時器的比較值設置為Cmin = 0;將占空比為100%時,定時器的比較值設為Cmax = 5399;則每中斷一次,占空比的值設為 Cmax*Di,直接在中斷里完成計算。
根據以上計算,可以修改最小占空比和最大占空比,也可以修改基波與載波頻率。
以下是具體定時器配置與中斷服務函數程序,基於STM32F767IGBT:
//使用高級定時器 1 完成 //Update--2019.6.3 //sin_k = TIM1_ARR / 200.0 * (float)(spwm_max_duty - spwm_min_duty ) ; //正弦波的比例系數,一個簡單的數學代換 //sin_b = TIM1_ARR / 200.0 * (float)(spwm_max_duty + spwm_min_duty ) ; //正弦波的截距 #include "timer1.h" #include "led.h" #include "math.h" TIM_HandleTypeDef TIM1_Handler; //定時器句柄 TIM_OC_InitTypeDef TIM1_CH1Handler; //定時器3通道4句柄 TIM_BreakDeadTimeConfigTypeDef BreakDeadTime_Config; #define PWM_GPIO GPIOA #define PWM_PIN1 GPIO_PIN_8 #define PWM_PIN2 GPIO_PIN_7 #define TIM1_ARR 5399 //SPWM波相關計算 //sin_points -- 一個周期內中斷計算的正弦點數,20KHz載波,Tc = 50us,基波周期 Tb = 50us * sin_points //Tb = 20Hz = 50ms = 50,000us, sin_points = 1000 //Tb = 100Hz = 10ms = 10,000us , sin_points = 200 //(-sin_k + sin_b ) / TIM1_ARR = spwm_min_duty % //( sin_k + sin_b ) / TIM1_ARR = spwm_max_duty %,反解出 sin_k, sin_b // sin_k = TIM1_ARR / 200.0 * (float)(spwm_max_duty - spwm_min_duty ) // sin_b = TIM1_ARR / 200.0 * (float)(spwm_max_duty + spwm_min_duty ) uint8_t spwm_min_duty = 10; //SPWM波最小占空比 uint8_t spwm_max_duty = 90; //SPWM波最大占空比 uint16_t count = 0; uint16_t sin_points = 200; uint16_t cc1_value; //比較寄存器 1的值,修改改變占空比 float sin_k,sin_b; //TIM1 PWM部分初始化 //PWM輸出初始化 //arr:自動重裝值 //psc:時鍾預分頻數 void TIM1_PWM_Init(u16 arr,u16 psc) { //時鍾配置 TIM1_Handler.Instance = TIM1; //定時器3 TIM1_Handler.Init.Prescaler = psc; //定時器分頻 TIM1_Handler.Init.CounterMode=TIM_COUNTERMODE_UP;//向上計數模式 TIM1_Handler.Init.Period=arr; //自動重裝載值 TIM1_Handler.Init.ClockDivision=TIM_CLOCKDIVISION_DIV1; HAL_TIM_PWM_Init(&TIM1_Handler); //初始化PWM,會調用HAL_TIM_PWM_Init(*) //PWM配置 TIM1_CH1Handler.OCMode=TIM_OCMODE_PWM1; //模式選擇PWM1 TIM1_CH1Handler.Pulse=arr/2; //設置比較值,此值用來確定占空比,默認比較值為自動重裝載值的一半,即占空比為50% TIM1_CH1Handler.OCPolarity = TIM_OCPOLARITY_HIGH;//輸出比較極性為高 TIM1_CH1Handler.OCNPolarity = TIM_OCPOLARITY_HIGH; TIM1_CH1Handler.OCIdleState = TIM_OCIDLESTATE_SET; TIM1_CH1Handler.OCNIdleState = TIM_OCIDLESTATE_SET; HAL_TIM_PWM_ConfigChannel(&TIM1_Handler,&TIM1_CH1Handler,TIM_CHANNEL_1);//配置TIM1通道1 //死區時間配置 //https://blog.csdn.net/DZRYWYBL/article/details/82527889 BreakDeadTime_Config.OffStateRunMode = TIM_OSSR_DISABLE; BreakDeadTime_Config.OffStateIDLEMode = TIM_OSSI_DISABLE; BreakDeadTime_Config.LockLevel = TIM_LOCKLEVEL_OFF; BreakDeadTime_Config.DeadTime = 0X00; //0x00~0xFF,當設置為0xFF時,50us周期,約有4.68us死區時間;0x0F約有100ns死區時間 BreakDeadTime_Config.BreakState = TIM_BREAK_DISABLE; BreakDeadTime_Config.BreakPolarity = TIM_BREAKPOLARITY_HIGH; BreakDeadTime_Config.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE; HAL_TIMEx_ConfigBreakDeadTime(&TIM1_Handler, &BreakDeadTime_Config); //中斷配置 HAL_NVIC_SetPriority(TIM1_CC_IRQn,1,3); //設置中斷優先級,搶占優先級1,子優先級3 HAL_NVIC_EnableIRQ(TIM1_CC_IRQn); //開啟ITM3中斷 //開啟PWM並使能中斷 HAL_TIM_PWM_Start_IT(&TIM1_Handler, TIM_CHANNEL_1); //開啟PWM輸出並使能中斷 HAL_TIMEx_PWMN_Start(&TIM1_Handler, TIM_CHANNEL_1); //打開互補通道 } //定時器底層驅動,時鍾使能,引腳配置 //此函數會被HAL_TIM_PWM_Init()調用 //htim:定時器句柄 void HAL_TIM_PWM_MspInit(TIM_HandleTypeDef *htim) { GPIO_InitTypeDef GPIO_Initure; __HAL_RCC_TIM1_CLK_ENABLE(); //使能定時器3 __HAL_RCC_GPIOA_CLK_ENABLE(); __HAL_RCC_GPIOB_CLK_ENABLE(); GPIO_Initure.Pin=PWM_PIN1 | PWM_PIN2; //PWM Pin GPIO_Initure.Mode=GPIO_MODE_AF_PP; //復用推完輸出 GPIO_Initure.Pull=GPIO_PULLUP; //上拉 GPIO_Initure.Speed=GPIO_SPEED_HIGH; //高速 GPIO_Initure.Alternate=GPIO_AF1_TIM1; //PA8復用為TIM1_CH1 HAL_GPIO_Init(PWM_GPIO,&GPIO_Initure); } //設置TIM通道4的占空比 //compare:比較值 void TIM_SetTIM1Compare1(u32 compare) { TIM1->CCR1=compare; } //定時器1中斷服務函數 void TIM1_CC_IRQHandler(void) //注意名稱與通用計時器不同,多了 CC { HAL_TIM_IRQHandler(&TIM1_Handler); } //定時器1中斷服務函數調用 void HAL_TIM_OC_DelayElapsedCallback(TIM_HandleTypeDef *htim) { if(htim==(&TIM1_Handler)) { count ++; if(count == sin_points) count = 0; sin_k = TIM1_ARR / 200.0 * (float)(spwm_max_duty - spwm_min_duty ) ; //正弦波的比例系數,一個簡單的數學代換//更正為相減 sin_b = TIM1_ARR / 200.0 * (float)(spwm_max_duty + spwm_min_duty ) ; //正弦波的截距//更正為相加 cc1_value = (uint16_t) (sin_k * sin( (double)count * 6.28318 / (double)sin_points) + sin_b); //正弦值計算,得到SPWM波占空比 TIM_SetTIM1Compare1(cc1_value); } }
主函數配置為
TIM1_PWM_Init(5400-1,2-1); //216M / (5400 * 2 ) = 20K