我初始化了   IO 时钟设置 和通道设置不打开定时器就直接工作了 ，关也没法关，我输出PWM 用在红外线发射管上的大神帮帮！！！
  GPIO_InitTypeDef GPIO_InitStructure;
  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
  TIM_OCInitTypeDef  TIM_OCInitStructure;
  uint16_t PrescalerValue = 0;

  RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL ;
  GPIO_Init(GPIOA, &GPIO_InitStructure);
        GPIO_ResetBits(GPIOA,GPIO_Pin_1);

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource1, GPIO_AF_TIM2);
        PrescalerValue = (uint16_t) ( SystemCoreClock/2/ 20000000) - 1;
  /* Time base configuration */
  TIM_TimeBaseStructure.TIM_Period = 525;
  TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);

  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 332;//1/3  175
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OC2Init(TIM2, &TIM_OCInitStructure);
  TIM_OC2PreloadConfig(TIM2, TIM_OCPreload_Enable);

TIM_Cmd(TIM2, DISABLE);