如何计算产生SPWM所需要的占空比

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1. /** @author Mei Jilin 
2.     @date   2013/9/2 
3.     @brief  加入生成SPWM部分 
4. **/  
5. #include "timer.h"  
6. #include "led.h"  
7. static uint16_t CCR3_Val = 1800;  
8. static uint16_t PrescalerValue = 0;  
9.   
10. /*PWM输出配置说明，*/  
11. /* - Prescaler = (TIM3CLK / TIM3 counter clock) - 1 选择TIMER工作在36MHZ 
12.  
13.     The TIM3 is running at 36 MHz: TIM3 Frequency = TIM3 counter clock/(ARR + 1) 
14.                                                   = 36 MHz / 3600 = 10 KHz 
15.     TIM3 Channel1 duty cycle = (TIM3_CCR1/ TIM3_ARR)* 100 */  
16.     /*转换周期10K*/  
17. void PWM_Init(void)  
18. {  
19.     TIM_TimeBaseInitTypeDef     TIM_TimeBaseStructure;  
20.     TIM_OCInitTypeDef           TIM_OCInitStructure;  
21.     GPIO_InitTypeDef            GPIO_InitStructure;  
22.     NVIC_InitTypeDef NVIC_InitStructure;      
23.         /* TIM3 clock enable */  
24.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE);  
25.   
26.     /* GPIOA and GPIOB clock enable */  
27.     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOB|  
28.                              RCC_APB2Periph_AFIO, ENABLE);  
29.     /* GPIOA Configuration:TIM3 Channel1, 2, 3 and 4 as alternate function push-pull */  
30.     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8;  
31.     GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  
32.     GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;  
33.     GPIO_Init(GPIOA, &GPIO_InitStructure);  
34.       
35.     GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;      //TIM1_CH1N  
36.     GPIO_Init(GPIOB, &GPIO_InitStructure);  
37.       
38.      /* Compute the prescaler value */  
39.     PrescalerValue = (uint16_t) (SystemCoreClock / 36000000) - 1; //TIMER2 - 36MHZ  
40.     /* Time base configuration */  
41.     TIM_TimeBaseStructure.TIM_Period = 3600;                    /*TIM3_ARR = 2879,12.5Khz*/  
42.     TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;  
43.     TIM_TimeBaseStructure.TIM_ClockDivision = 0;  
44.     TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  
45.     TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;  
46.     TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure);  
47.   
48.     /* Channel 1, 2,3 and 4 Configuration in PWM mode */  
49.     TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;  
50.     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;  
51.     TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable; //关闭互补输出  
52.     TIM_OCInitStructure.TIM_Pulse = CCR3_Val;  
53.     TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;  
54.     TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;  
55.     TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;  
56.     TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Set;  
57.     TIM_OC1Init(TIM1, &TIM_OCInitStructure);  
58.       
59.     TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable); //这句的功能是让改变CCR2之后马上有效      
60.     TIM_ITConfig(TIM1, TIM_IT_CC1, ENABLE);  
61.     NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1);  
62.     NVIC_InitStructure.NVIC_IRQChannel = TIM1_CC_IRQn;  
63.     NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;  
64.     NVIC_InitStructure.NVIC_IRQChannelSubPriority = 6;  
65.     NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;  
66.     NVIC_Init(&NVIC_InitStructure);      
67.           
68.     TIM_Cmd(TIM1, ENABLE);    
69.     /* TIM1 Main Output Enable */  
70.     TIM_CtrlPWMOutputs(TIM1, ENABLE);   //TIM1需要加上这句,貌似低级定时器不需要  
71. }  
72. uint16_t Duty[] = {1800,1856,1912,1968,2023,2078,2131,2183,2233,2282,2329,2373,2416,2456,2493,  
73.     2528,2559,2588,2614,2636,2655,2671,2684,2692,2698,2699,2698,2692,2684,2671,2655,2636,2614,  
74.     2588,2559,2528,2493,2456,2416,2373,2329,2282,2233,2183,2131,2078,2023,1968,1912,1856,1800,  
75.     1743,1687,1631,1576,1521,1468,1416,1366,1317,1270,1226,1183,1143,1106,1071,1040,1011,985,  
76.     963,944,928,915,907,901,900,901,907,915,928,944,963,985,1011,1040,1071,1106,1143,1183,1226,  
77.     1270,1317,1366,1416,1468,1521,1576,1631,1687,1743,1799,1799};  
78. uint16_t count = 0;  
79. uint16_t num = sizeof(Duty)/(sizeof(Duty[0]));  
80. void TIM1_CC_IRQHandler(void)  
81. {  
82.   if (TIM_GetITStatus(TIM1, TIM_IT_CC1) != RESET)  
83.   {  
84.     TIM1->SR = (uint16_t)~TIM_IT_CC1;  
85.     TIM1->CCR1 = Duty[count];  
86.     count++;  
87.     if(count==num)  
88.     {  
89.         count=0;  
90.     }  
91.   }  
92. }  

在上一篇文章里粘贴了STM32产生SPWM的代码，我在编写这些代码时最大的问题就是如何得到占空比，就是代码中的数组 Duty[]。他的思想就是对正弦波采样，在采样点出用PWM的占空比来代替正弦波在该点的数值。最容易想到就是用定时器的ARR值乘以sin(2*pi*f*t)，就可以得到对应的寄存器CCR值。但是CCR值不能为负，所以要把sin(2*pi*f*t)变为

A*sin(2*pi*f*t)+B的形式，取A=B=0.5；那么计算公式为ARR*（0.5*sin(2*pi*f*t)+0.5)，上传一个C++写的exe文件，可以帮助产生Duty[]数组.

http://download.csdn.NET/detail/mjlsuccess/6205567

软件使用vs2010编写的可能在有些电脑上无法运行，如果你装有VS2010,我可以把原工程发给你

转载于http://blog.youkuaiyun.com/mjlsuccess/article/details/11019805

自己思考：10KZ为载波（锯齿波）的频率，最终输入给电机为100HZ正弦波，则载波比为100，也就是100个数据，同时ccr不能为负值，故进行抬升，原本应该为0-1800，进行抬升1800的0.5倍