STM32 timer--general timer output with dead zone complementary PWM

Function: Use a common timer to output 2 complementary PWMs with adjustable frequency, adjustable duty cycle and adjustable dead zone.

Principle: As shown in the figure below, the counting mode is the center alignment mode

It can be seen that the CH3 high level interval is centered when the counter counts to 4 and extends to both sides.

As for CH4, since its output polarity is opposite, it extends to both sides with 0 as the center.

CCR3 becomes smaller and the duty cycle increases

CCR4 becomes larger, and the duty cycle increases

The sum of CCR3 and CCR4 is ARR

Note that in this mode the counter count period = ARR, which is different from the PWM mode: count period = ARR + 1

Refer to the following figure in the STM32 reference manual:

Therefore, the code and calculation formula are sorted out as follows:

void TIM3_PWMShiftInit(void)  

{  

    float Duty = 0;

    u16 ARR = 0, PSC = 0, CH3Ccr = 0, CH4Ccr = 0, DT = 0;

    u32 Frequency = 0;

    TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;  

    GPIO_InitTypeDef GPIO_InitStruct;  

    TIM_OCInitTypeDef TIM_OCInitStruct;

    Frequence = 125000; //Frequency, unit: Hz

    Duty = 0.5; //Duty cycle

    DT = 1000; //Dead time, unit: ns

    //Center alignment mode, only when CNT counts to CCR flips once, the frequency is halved compared to PWM mode, and ARR does not need to be -1

    ARR = 36000000/(PSC+1)/Frequence; //Set to 125KHz

    CH3Ccr = ARR*Duty - DT/2/((PSC+1)*13.89f); //TIM 72M, one cycle is about 13.89ns

    CH4Ccr = ARR - CH3Ccr; //CH4 and CH3 are ARR

    /************************TIM3 GPIO configuration************************ *****/  

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);  

    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;  

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_0|GPIO_Pin_1;  

    GPIO_InitStruct.GPIO_Speed ​​= GPIO_Speed_50MHz;  

    GPIO_Init(GPIOB,&GPIO_InitStruct);    

    /**********************Initialize TimBase structure****************************/  

    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3,ENABLE);

    TIM_TimeBaseInitStruct.TIM_ClockDivision = TIM_CKD_DIV1;  

    TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_CenterAligned1;  

    TIM_TimeBaseInitStruct.TIM_Period = ARR;         

    TIM_TimeBaseInitStruct.TIM_Prescaler = PSC;       

    TIM_TimeBaseInit(TIM3, &TIM_TimeBaseInitStruct);  

    TIM_TimeBaseInit(TIM1, &TIM_TimeBaseInitStruct);  

    /**********************Initialize TIM3 OC structure****************************/  

    TIM_OCInitStruct.TIM_OCMode = TIM_OCMode_PWM2;  

    TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_Low;  

    TIM_OCInitStruct.TIM_OutputState = TIM_OutputState_Enable;  

    TIM_OCInitStruct.TIM_Pulse = CH3Ccr;            

    TIM_OC3Init(TIM3,&TIM_OCInitStruct);                                                       

    TIM_OCInitStruct.TIM_Pulse = CH4Ccr;  

    TIM_OCInitStruct.TIM_OCPolarity = TIM_OCPolarity_High;

    TIM_OC4Init(TIM3,&TIM_OCInitStruct);  

    TIM_Cmd(TIM3, ENABLE);

}  

The oscilloscope waveform is as follows:

The program sets the frequency to 125K, the duty cycle to 50%, and the dead time to 1000ns. The waveform displayed by the oscilloscope is consistent with this.

Change the frequency to 125K, duty cycle to 25%, dead time to 500ns, and the waveform is as follows:

At 125K, the duration of high level with 25% duty cycle should be 2us, minus the dead zone of 0.5us = 1.5us,

From the figure above, we can see that the high level duration is about 1.5us, which is in line with the program setting.