void TIM3_PWM_Init(u16 arr,u16 psc)
{  
    GPIO_InitTypeDef GPIO_InitStructure;
    TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;
    TIM_OCInitTypeDef  TIM_OCInitStructure;
   

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);    //ʹÄܶ¨Ê±Æ÷3ʱÖÓ
     RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB  | RCC_APB2Periph_AFIO, ENABLE);  //ʹÄÜGPIOÍâÉèºÍAFIO¸´Óù¦ÄÜÄ£¿éʱÖÓ
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC,ENABLE);
    GPIO_PinRemapConfig(GPIO_PartialRemap_TIM3, ENABLE); //Timer3²¿·ÖÖØÓ³Éä  TIM3_CH2->B5   

   //ÉèÖøÃÒý½ÅΪ¸´ÓÃÊä³ö¹¦ÄÜ,Êä³öTIM3 CH2µ&#196WMÂö³å²¨ÐΠ   GPIOB.5
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; //TIM_CH2
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //¸´ÓÃÍÆÍìÊä³ö
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);//³õʼ»¯GPIO

        GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4; //TIM_CH1
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //¸´ÓÃÍÆÍìÊä³ö
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStructure);//³õʼ»¯GPIO
   
   
            GPIO_InitStructure.GPIO_Pin = GPIO_Pin_8|9; //TIM_CH1
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;  //¸´ÓÃÍÆÍìÊä³ö
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOC, &GPIO_InitStructure);//³õʼ»¯GPIO
   
   //³õʼ»¯TIM3
    TIM_TimeBaseStructure.TIM_Period = arr; //ÉèÖÃÔÚÏÂÒ»¸ö¸üÐÂʼþ×°Èë»î¶¯µÄ×Ô¶¯ÖØ×°ÔؼĴæÆ÷ÖÜÆÚµÄÖµ
    TIM_TimeBaseStructure.TIM_Prescaler =psc; //ÉèÖÃÓÃÀ´×÷ΪTIMxʱÖÓƵÂʳýÊýµÄÔ¤·ÖƵֵ
    TIM_TimeBaseStructure.TIM_ClockDivision = 0; //ÉèÖÃʱÖÓ·Ö¸î:TDTS = Tck_tim
    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIMÏòÉϼÆÊýģʽ
    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure); //¸ù¾ÝTIM_TimeBaseInitStructÖÐÖ¸¶¨µÄ²ÎÊý³õʼ»¯TIMxµÄʱ¼ä»ùÊýµ¥Î»
   
    //³õʼ»¯TIM3 Channel2 PWMģʽ     
    TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //Ñ¡Ôñ¶¨Ê±Æ÷ģʽ:TIMÂö³å¿í¶Èµ÷ÖÆģʽ2
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //±È½ÏÊä³öʹÄÜ
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //Êä³ö¼«ÐÔ:TIMÊä³ö±È½Ï¼«ÐÔ¸ß
    TIM_OC2Init(TIM3, &TIM_OCInitStructure);  //¸ù¾ÝTÖ¸¶¨µÄ²ÎÊý³õʼ»¯ÍâÉèTIM3 OC2

    TIM_OC2PreloadConfig(TIM3, TIM_OCPreload_Enable);  //ʹÄÜTIM3ÔÚCCR2ÉϵÄԤװÔؼĴæÆ÷

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //Ñ¡Ôñ¶¨Ê±Æ÷ģʽ:TIMÂö³å¿í¶Èµ÷ÖÆģʽ2
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //±È½ÏÊä³öʹÄÜ
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //Êä³ö¼«ÐÔ:TIMÊä³ö±È½Ï¼«ÐÔ¸ß
    TIM_OC1Init(TIM3, &TIM_OCInitStructure);  //¸ù¾ÝTÖ¸¶¨µÄ²ÎÊý³õʼ»¯ÍâÉèTIM3 OC2

    TIM_OC1PreloadConfig(TIM3, TIM_OCPreload_Enable);  //ʹÄÜTIM3ÔÚCCR2ÉϵÄԤװÔؼĴæÆ÷
   
         TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //Ñ¡Ôñ¶¨Ê±Æ÷ģʽ:TIMÂö³å¿í¶Èµ÷ÖÆģʽ2
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //±È½ÏÊä³öʹÄÜ
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //Êä³ö¼«ÐÔ:TIMÊä³ö±È½Ï¼«ÐÔ¸ß
    TIM_OC3Init(TIM3, &TIM_OCInitStructure);  //¸ù¾ÝTÖ¸¶¨µÄ²ÎÊý³õʼ»¯ÍâÉèTIM3 OC2

    TIM_OC3PreloadConfig(TIM3, TIM_OCPreload_Enable);  //ʹÄÜTIM3ÔÚCCR2ÉϵÄԤװÔؼĴæÆ÷
   
             TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM2; //Ñ¡Ôñ¶¨Ê±Æ÷ģʽ:TIMÂö³å¿í¶Èµ÷ÖÆģʽ2
     TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable; //±È½ÏÊä³öʹÄÜ
    TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High; //Êä³ö¼«ÐÔ:TIMÊä³ö±È½Ï¼«ÐÔ¸ß
    TIM_OC4Init(TIM3, &TIM_OCInitStructure);  //¸ù¾ÝTÖ¸¶¨µÄ²ÎÊý³õʼ»¯ÍâÉèTIM3 OC2

    TIM_OC4PreloadConfig(TIM3, TIM_OCPreload_Enable);  //ʹÄÜTIM3ÔÚCCR2ÉϵÄԤװÔؼĴæÆ÷
   
    TIM_Cmd(TIM3, ENABLE);  //ʹÄÜTIM3

}

主函数

while(1)
{   
   
    TIM_SetCompare2(TIM3,17501);
    TIM_SetCompare1(TIM3,17800);
            TIM_SetCompare3(TIM3,17501);   
    TIM_SetCompare4(TIM3,17501);
   
    }     
}