STM32普通定时器配置PWM的问题

oid TIM3_Init(void)

{

TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

TIM_OCInitTypeDef  TIM_OCInitStructure;

/* PWM信号电平跳变值 */

//    u16 CCR1= 36000;

//    u16 CCR2= 36000;

/*PCLK1经过2倍频后作为TIM3的时钟源等于72MHz*/

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);

/* Time base configuration */

TIM_TimeBaseStructure.TIM_Period =1599;                                     //计数周期1600

TIM_TimeBaseStructure.TIM_Prescaler = 1;                                    //设置预分频：预分频=2，即为72/3=24MHz

TIM_TimeBaseStructure.TIM_ClockDivision = 0;                                //设置时钟分频系数：不分频

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;                 //向上计数溢出模式

TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);

/* PWM1 Mode configuration: Channel1 */

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;                           //配置为PWM模式1

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse =600;                                       //设置跳变值，当计数器计数到这个值时，电平发生跳变

TIM_OCInitStructure.TIM_OCPolarity =TIM_OCPolarity_Low;                    //当定时器计数值小于CCR1时为高电平

TIM_OC1Init(TIM3, &TIM_OCInitStructure);                                    //使能通道1

TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);

/* PWM1 Mode configuration: Channel2 */

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OCInitStructure.TIM_Pulse = 300;                                       //设置通道2的电平跳变值，输出另外一个占空比的PWM

TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;                    //当定时器计数值小于CCR2时为低电平

TIM_OC2Init(TIM3, &TIM_OCInitStructure);                                    //使能通道2

TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);

TIM_ARRPreloadConfig(TIM3, ENABLE);                                         //使能TIM3重载寄存器ARR

/* TIM3 enable counter */

TIM_Cmd(TIM3, ENABLE);

Delay_8ms();

TIM_Cmd(TIM3, DISABLE);

}