2015全国大学生电子设计大赛校选---spwm波形发生器理论
来源:互联网 发布:赌场 知乎 编辑:程序博客网 时间:2024/05/21 18:08
SPWM(Sinusoidal PWM)法是一种比较成熟的,目前使用较广泛的PWM法。前面提到的采样控制理论中的一个重要结论:冲量相等而形状不同的窄脉冲加在具有惯性的环节上时,其效果基本相同。SPWM法就是以该结论为理论基础,用脉冲宽度按正弦规律变化而和正弦波等效的PWM波形即SPWM波形控制逆变电路中开关器件的通断,使其输出的脉冲电压的面积与所希望输出的正弦波在相应区间内的面积相等,通过改变调制波的频率和幅值则可调节逆变电路输出电压的频率和幅值。
实现SPWM方法有:等面积法 硬件调制法 软件生成法 自然采样法 规则采样法 低次谐波消去法 梯形波与三角波比较法
以下是软件实现方法
-
#include "timer.h" #include "led.h" static uint16_t CCR3_Val = 1800; static uint16_t PrescalerValue = 0; void PWM_Init(void) { TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure; TIM_OCInitTypeDef TIM_OCInitStructure; GPIO_InitTypeDef GPIO_InitStructure; NVIC_InitTypeDef NVIC_InitStructure; RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE); RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA|RCC_APB2Periph_GPIOB| RCC_APB2Periph_AFIO, ENABLE); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_Init(GPIOA, &GPIO_InitStructure); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13; GPIO_Init(GPIOB, &GPIO_InitStructure); PrescalerValue = (uint16_t) (SystemCoreClock / 36000000) - 1; TIM_TimeBaseStructure.TIM_Period = 3600; TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue; TIM_TimeBaseStructure.TIM_ClockDivision = 0; TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; TIM_TimeBaseStructure.TIM_RepetitionCounter = 0; TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable; TIM_OCInitStructure.TIM_Pulse = CCR3_Val; TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High; TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set; TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCIdleState_Set; TIM_OC1Init(TIM1, &TIM_OCInitStructure); TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable); TIM_ITConfig(TIM1, TIM_IT_CC1, ENABLE); NVIC_PriorityGroupConfig(NVIC_PriorityGroup_1); NVIC_InitStructure.NVIC_IRQChannel = TIM1_CC_IRQn; NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0; NVIC_InitStructure.NVIC_IRQChannelSubPriority = 6; NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; NVIC_Init(&NVIC_InitStructure); TIM_Cmd(TIM1, ENABLE); TIM_CtrlPWMOutputs(TIM1, ENABLE); } uint16_t Duty[] = {1800,1856,1912,1968,2023,2078,2131,2183,2233,2282,2329,2373,2416,2456,2493, 2528,2559,2588,2614,2636,2655,2671,2684,2692,2698,2699,2698,2692,2684,2671,2655,2636,2614, 2588,2559,2528,2493,2456,2416,2373,2329,2282,2233,2183,2131,2078,2023,1968,1912,1856,1800, 1743,1687,1631,1576,1521,1468,1416,1366,1317,1270,1226,1183,1143,1106,1071,1040,1011,985, 963,944,928,915,907,901,900,901,907,915,928,944,963,985,1011,1040,1071,1106,1143,1183,1226, 1270,1317,1366,1416,1468,1521,1576,1631,1687,1743,1799,1799}; uint16_t count = 0; uint16_t num = sizeof(Duty)/(sizeof(Duty[0])); void TIM1_CC_IRQHandler(void) { if (TIM_GetITStatus(TIM1, TIM_IT_CC1) != RESET) { TIM1->SR = (uint16_t)~TIM_IT_CC1; TIM1->CCR1 = Duty[count]; count++; if(count==num) { count=0; } } } 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.
0 0