stm32f103 timer1 PWM输出频率1HZ需要等待一百多秒才出波形，10HZ等十几秒出波形，100hz很快出波形，请问是怎么回事
代码如下：

void timer1_pwm_init(uint16_t arr,uint16_t psc)
{
        GPIO_InitTypeDef GPIO_InitStructure;
        TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
        TIM_OCInitTypeDef  TIM_OCInitStructure;
       

        RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM1, ENABLE); //使能TIMx外设
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);  //使能GPIOA外设时钟使能
        RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

  //设置该引脚为复用输出功能,输出TIM1 CH1的PWM脉冲波形
        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8|GPIO_Pin_11; //TIM1_CH1
        GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //复用功能输出
        GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
        GPIO_Init(GPIOA, &GPIO_InitStructure); //初始化GPIO

        TIM_TimeBaseStructure.TIM_Period = arr; //设置自动重装载周期值
        TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置预分频值 不分频
        TIM_TimeBaseStructure.TIM_ClockDivision = 0; //设置时钟分割:TDTS = Tck_tim
        TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式
        TIM_TimeBaseInit(TIM1, &TIM_TimeBaseStructure); //根据指定的参数初始化TIMx
       
         
        TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1; //CH1 PWM2模式       
        TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //比较输出使能
        TIM_OCInitStructure.TIM_Pulse = 0; //设置待装入捕获比较寄存器的脉冲值
        TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_Low; //OC1 低电平有效
//        TIM_OC1Init(TIM1, &TIM_OCInitStructure);  //根据指定的参数初始化外设TIMx
    TIM_OC4Init(TIM1, &TIM_OCInitStructure);

//        TIM_OC1PreloadConfig(TIM1, TIM_OCPreload_Enable);  //CH1 预装载使能
        TIM_OC4PreloadConfig(TIM1, TIM_OCPreload_Enable);

        TIM_ARRPreloadConfig(TIM1, ENABLE); //使能TIMx在ARR上的预装载寄存器
       
        TIM_CtrlPWMOutputs(TIM1,ENABLE);        //MOE 主输出使能,高级定时器必须开启这个
       
        TIM_Cmd(TIM1, ENABLE);  //使能TIMx

}

int main(void)
{
    timer1_pwm_init(7199,99);
   TIM_SetCompare4(TIM1,4500);

   while(1)
  {

  };
}