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CHN1 and CHN1N collision - is it posible ?

Question asked by karakaya.mehmet on Jun 7, 2014
Latest reply on Jun 10, 2014 by karakaya.mehmet
hello dear forum

I designed an inverter for vibration tank ( photo below )
it is simply an H bridge with 500 V 20 A mosfets
the frequency and duty is variable with STM32F103
the vibrator worked for 5 minutes and one of the H-mosfet blow up
the L-mosfet  also show 0 resistance so it is also fried

I added ( 100 nF 1 KOhm in series snubber )  paralel to DS of every mosfet

I suspect that there was a collision of CHN1 and CHN1N

please look at my code and comment if there is posibility of collision ( turn ON at the same time )

Or is there a snubber ( hardware design ) problem ? ( no software problem )

thank you

PWM_init(){
...............
  
  TIM_TimeBaseStructure.TIM_Prescaler = 99;
  TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
  TIM_TimeBaseStructure.TIM_Period = 14400;
  TIM_TimeBaseStructure.TIM_ClockDivision = 0;
  TIM_TimeBaseStructure.TIM_RepetitionCounter = 0;
  
  TIM_TimeBaseInit(TIM8, &TIM_TimeBaseStructure);
  
  TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Timing;
  TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;
  TIM_OCInitStructure.TIM_OutputNState = TIM_OutputNState_Enable;
  TIM_OCInitStructure.TIM_Pulse = 1000;
  TIM_OCInitStructure.TIM_OCPolarity = TIM_OCPolarity_High;
  TIM_OCInitStructure.TIM_OCNPolarity = TIM_OCNPolarity_High;
  TIM_OCInitStructure.TIM_OCIdleState = TIM_OCIdleState_Set;
  TIM_OCInitStructure.TIM_OCNIdleState = TIM_OCNIdleState_Set;
  
  TIM_OC1Init(TIM8, &TIM_OCInitStructure);
  TIM_OC2Init(TIM8, &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 = 120;
  TIM_BDTRInitStructure.TIM_Break = TIM_Break_Disable;//Enable;
  TIM_BDTRInitStructure.TIM_BreakPolarity = TIM_BreakPolarity_Low;
  TIM_BDTRInitStructure.TIM_AutomaticOutput = TIM_AutomaticOutput_Disable;
  
  TIM_BDTRConfig(TIM8, &TIM_BDTRInitStructure);
  
  TIM_CCPreloadControl(TIM8, DISABLE);
  TIM_ARRPreloadConfig(TIM8, ENABLE);
  TIM_ITConfig(TIM8, TIM_IT_Update , ENABLE);
  
  TIM_Cmd(TIM8, ENABLE);
  TIM_CtrlPWMOutputs(TIM8, ENABLE);
}
------------------
main(){
.........................
while(1){
        Delay(2000);
// freq varies between 25 and 106 Hz and puls varies between %10 and %90
//freqpot and pulspot are ADC channels connectted to potantiometers
  
        freqdisp=freqpotantiometer/5+250;
        freq=2*freqdisp  ;duty=90-pulspotantiometer/51;
        period=7200000L/freq;puls=(period/100)*duty;
  
// I want you comment especially on below bit of code 
// if the compare value is changed inbetween a PWM period 
// is there a posibility of CHN1 and CHN1N being ON at the same time 
// the ARR value is buffered but the compare registers are not as far as I know  
  
        if ((freqold!=freq)||(pulsold!=puls)){
        TIM_SetCompare1(TIM8, puls);
        TIM_SetCompare2(TIM8, puls);
        TIM_SetAutoreload(TIM8,period);  }
        freqold=freq;pulsold=puls;  
............
}
-----------------
void TIM8_UP_IRQHandler(void){
    TIM_ClearFlag(TIM8, TIM_FLAG_Update);
    TIM_ClearITPendingBit(TIM8, TIM_IT_Update);
    tim8tog++;
    if (tim8tog&0x1) {
    TIM_SelectOCxM(TIM8, TIM_Channel_1, TIM_OCMode_PWM2);
    TIM_CCxCmd(TIM8, TIM_Channel_1, TIM_CCx_Enable);
    TIM_CCxNCmd(TIM8, TIM_Channel_1, TIM_CCxN_Disable);
  
    TIM_SelectOCxM(TIM8, TIM_Channel_2, TIM_OCMode_PWM2);
    TIM_CCxCmd(TIM8, TIM_Channel_2, TIM_CCx_Disable);
    TIM_CCxNCmd(TIM8, TIM_Channel_2, TIM_CCxN_Enable); }
    else {
    TIM_SelectOCxM(TIM8, TIM_Channel_2, TIM_OCMode_PWM2);
    TIM_CCxCmd(TIM8, TIM_Channel_2, TIM_CCx_Enable);
    TIM_CCxNCmd(TIM8, TIM_Channel_2, TIM_CCxN_Disable);
  
    TIM_SelectOCxM(TIM8, TIM_Channel_1, TIM_OCMode_PWM2);
    TIM_CCxCmd(TIM8, TIM_Channel_1, TIM_CCx_Disable);
    TIM_CCxNCmd(TIM8, TIM_Channel_1, TIM_CCxN_Enable); }  


ecc.jpg

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