为什么出来的是50HZ
void TIM3_PWM_Init(void)
{  

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
TIM_OCInitTypeDef  TIM_OCInitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);   //TIM14时钟使能    
TIM_TimeBaseStructure.TIM_Period=10000-1;   //自动重装载值
TIM_TimeBaseStructure.TIM_Prescaler=168-1;  //定时器分频
TIM_TimeBaseStructure.TIM_CounterMode=TIM_CounterMode_Up; //向上计数模式
TIM_TimeBaseStructure.TIM_ClockDivision=TIM_CKD_DIV1; 

TIM_TimeBaseInit(TIM3,&TIM_TimeBaseStructure);//初始化定时器14

//初始化TIM14 Channel1 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_OC1Init(TIM3, &TIM_OCInitStructure);
TIM_OC2Init(TIM3, &TIM_OCInitStructure);
TIM_OC3Init(TIM3, &TIM_OCInitStructure);
TIM_OC4Init(TIM3, &TIM_OCInitStructure);
  
TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);
TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM3, ENABLE);

TIM_Cmd(TIM3, ENABLE);
   
}