PWM波形出错，不知道哪里的问题有一段高电平

Question

（stm32f4）PWM+DMA驱动ws2812时，总是有一段波形是高电平导致灯条颜色不受控，不是关闭pwm的问题，尝试过TIM_ForcedOCxConfig这个函数，使用这个函数之前也试过拉低引脚，并不起作用。并且这段高电平在PWM有波之前就已经出现了。也出现过类似这样的波形：
(高电平之前的波正常，这段高电平之后的也正常，目前的情况是灯会串色，按复位键之后会变色)

GPIO_InitTypeDef GPIO_InitStructure;
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_OCInitTypeDef TIM_OCInitStructure;
DMA_InitTypeDef DMA_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2,ENABLE);      //TIM2时钟使能    
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);     //使能PORTB时钟    
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1,ENABLE);//DMA1时钟使能

GPIO_PinAFConfig(GPIOB,GPIO_PinSource10,GPIO_AF_TIM2);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;           //GPIOB10
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;        //复用功能
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;    //速度100MHz
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;   
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_DOWN;       
GPIO_Init(GPIOB,&GPIO_InitStructure);              //初始化PB10
  
TIM_TimeBaseStructure.TIM_Prescaler= 1-1;  //定时器分频
TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up; //向上计数模式
TIM_TimeBaseStructure.TIM_Period= 105 - 1; 
TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1; 

TIM_TimeBaseInit(TIM2,&TIM_TimeBaseStructure);//初始化定时器2

//初始化TIM2 Channel3 PWM模式     
TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //选择定时器模式:TIM脉冲宽度调制模式2
 TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //输出极性:TIM输出比较极性低
TIM_OC3Init(TIM2, &TIM_OCInitStructure);  //根据指定的参数初始化外设TIM2 OC3

TIM_ARRPreloadConfig(TIM2,ENABLE);//ARPE使能
 
TIM_OC3PreloadConfig(TIM2, TIM_OCPreload_Enable);  //使能TIM2在CCR3上的预装载寄存器

DMA_DeInit(DMA1_Stream1);
    
DMA_InitStructure.DMA_Channel = DMA_Channel_3;  //通道选择

DMA_InitStructure.DMA_PeripheralBaseAddr = ((uint32_t)(&(TIM2->CCR3)));//DMA外设地址
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)headPixelBuffer;//DMA 存储器0地址
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;//存储器到外设模式
DMA_InitStructure.DMA_BufferSize = HEADPIXELNUM * GRBLen;//数据传输量
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;//外设非增量模式
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;//存储器增量模式
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Word;//外设数据宽度:32位
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Word;//存储器数据宽度:32位
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;// 使用模式 普通
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_Full;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;//存储器突发单次传输
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;//外设突发单次传输
DMA_Init(DMA1_Stream1, &DMA_InitStructure);//初始化DMA Stream

TIM_ForcedOC3Config(TIM3, TIM_ForcedAction_InActive);//将PWM输出强制为低

该函数设置完灯色后调用
TIM_SelectOCxM(TIM2, TIM_Channel_3, TIM_OCMode_PWM1);
TIM_CCxCmd(TIM2, TIM_Channel_3, TIM_CCx_Enable);
TIM_Cmd(TIM2, ENABLE);
DMA_SetCurrDataCounter(DMA1_Stream1, (uint16_t)(HEADPIXELNUM * GRBLen));
TIM_DMACmd(TIM2, TIM_DMA_Update, ENABLE);
DMA_Cmd(DMA1_Stream1, ENABLE);

while(!DMA_GetFlagStatus(DMA1_Stream1 ,DMA_FLAG_TCIF1));    

TIM_ForcedOC3Config(TIM2, TIM_ForcedAction_InActive);//将PWM输出强制为低
DMA_Cmd(DMA1_Stream1, DISABLE);
DMA_ClearFlag(DMA1_Stream1, DMA_FLAG_TCIF1);    
TIM_Cmd(TIM2, DISABLE);