关于timer16路pwm输出极性的问题

在做bldc驱动上希望用p+nmos也就是comos模式驱动，可以利用同步整流减少续流损耗，但在实现的过程中对于mos管和STM32对于pwm波形极性的设置不甚明白，希望高手指点一二，不胜感激。
6路pwm输出设置：
/* Channel 1, 2,3 and 4 Configuration in PWM mode */
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_PWM1;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM_OCInitStructure.TIM_Pulse = ps;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;
  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Set;
  TIM_OC1Init(TIM1, &TIM_OCInitStructure);

  /* Automatic Output enable, Break, dead time and lock configuration*/
  TIM_BDTRInitStructure.TIM_OSSRState = TIM_OSSRState_Enable;
  TIM_BDTRInitStructure.TIM_OSSIState = TIM_OSSIState_Enable;
  TIM_BDTRInitStructure.TIM_LOCKLevel = TIM_LOCKLevel_OFF;
  TIM_BDTRInitStructure.TIM_DeadTime = 1;
  TIM_BDTRInitStructure.TIM_Break = TIM_Break_Enable;
  TIM_BDTRInitStructure.TIM_BreakPolarity = TIM_BreakPolarity_Low;
  TIM_BDTRInitStructure.TIM_AutomaticOutput = TIM_AutomaticOutput_Enable;
  TIM_BDTRConfig(TIM1, &TIM_BDTRInitStructure);


6步换相操作：

if (step == 1)
  {
   /* Next step: Step 2 Configuration ---------------------------- */

   /*  Channel1 configuration */
   // TIM_SelectOCxM(TIM1, TIM_Channel_1, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Enable);
#if 0   
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);
   /**OC1N=CC1NP,CC1NP=0下桥臂关*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif

   /*  Channel2 configuration */
   // TIM_SelectOCxM(TIM1, TIM_Channel_2, TIM_OCMode_PWM1 );
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=1下桥臂开*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_Low);

   /*  Channel3 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=0下桥臂关*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_High);
   step++;
  }
  else if (step == 2)
  {
   /* Next step: Step 3 Configuration ---------------------------- */

   /*  Channel1 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Disable);
#if 0   
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);
   /**OC1N=CC1NP,CC1NP=0下桥臂关*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif

   /*  Channel2 configuration */
   //  TIM_SelectOCxM(TIM1, TIM_Channel_2, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Disable);   
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=1下桥臂开*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_Low);
#endif   

   /*  Channel3 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_3, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Enable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=0下桥臂关*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif   
   step++;
  }
  else if (step == 3)
  {
   /* Next step: Step 4 Configuration ---------------------------- */

   /*  Channel1 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_1, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);
   /*OC1N=CC1NP,CC1NP=1下桥臂开*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_Low);

   /*  Channel2 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=0下桥臂关*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_High);

   /*  Channel3 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_3, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Enable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=0下桥臂关*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif  
   step++;
  }
  else if (step == 4)
  {
   /* Next step: Step 5 Configuration ---------------------------- */

   /*  Channel1 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_1, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Disable);
   /*下桥臂常开*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_Low);
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);

   /*  Channel2 configuration */
   //  TIM_SelectOCxM(TIM1, TIM_Channel_2, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Enable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=0下桥臂关*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif

   /*  Channel3 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Disable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=0下桥臂关*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif  
   step++;
  }
  else if (step == 5)
  {
   /* Next step: Step 6 Configuration ---------------------------- */

   /*  Channel1 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);
   /**OC1N=CC1NP,CC1NP=0下桥臂关*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_High);

   /*  Channel2 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_2, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Enable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=0下桥臂常关*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif

   /*  Channel3 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_3, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=1下桥臂开*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_Low);  
   step++;
  }
  else
  {
   /* Next step: Step 1 Configuration ---------------------------- */
   /*  Channel1 configuration */
   //   TIM_SelectOCxM(TIM1, TIM_Channel_1, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_1, TIM_CCx_Enable);
#if 0   
   TIM_CCxNCmd(TIM1, TIM_Channel_1, TIM_CCxN_Disable);
   /**OC1N=CC1NP,CC1NP=0下桥臂关*/
   TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif

   /*  Channel2 configuration */
   TIM_CCxCmd(TIM1, TIM_Channel_2, TIM_CCx_Disable);
#if 0
   TIM_CCxNCmd(TIM1, TIM_Channel_2, TIM_CCxN_Disable);
   /*OC2N=CC2NP,CC2NP=0下桥臂关*/
   TIM_OC2NPolarityConfig(TIM1, TIM_OCNPolarity_High);
#endif   

   /*  Channel3 configuration */
   //    TIM_SelectOCxM(TIM1, TIM_Channel_3, TIM_OCMode_PWM1);
   TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Disable);
   TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);
   /*OC3N=CC3NP,CC3NP=1下桥臂开*/
   TIM_OC3NPolarityConfig(TIM1, TIM_OCNPolarity_Low);  
   step = 1;

请问其中：
1.同步整流是怎么实现的？
2.  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Reset;  
TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Set;
这四句分别实现什么功能？
3.TIM_OC1NPolarityConfig(TIM1, TIM_OCNPolarity_High);
该句是为了设置pwm互补通道的输出极性，这里面的high和low分别代表什么意思？是输出1和0的意思吗，还是输出1导通和0导通？
4.对于pmos管和nmos管导通原理自然不一样，是相反的，在程序里怎么体现呢？打比方来讲对于3通道：
TIM_CCxCmd(TIM1, TIM_Channel_3, TIM_CCx_Disable);
TIM_CCxNCmd(TIM1, TIM_Channel_3, TIM_CCxN_Disable);

若上桥为pmos，下桥为nmos，上述2句是不是导通其中的一桥，而另一桥关断？那哪个导通哪个关断呢？关于这个极性的设置好头大啊，望大神不吝详细指点一二！