I want to use a MOSFET (say IRLZ44n) to control 12V DC motor using Arduino's PWM. Since I posses limited knowledge of electronics I did some research on MOSFETs and need help to better understand it.
1. I want to calculate switching time of MOSFET. By using equations like Q = CV and Q = It and assuming Arduino provides gate current of 20mA @5V, switching times can be found by looking at value of charges in datasheet. But is it really that simple. Based on the graph shown below, it seems like the turn on time depends on Vgs, which is changing with time. If this is true, can we use I = C*dv/dt to calculate turn on time? If yes, what will be value of capacitances?
2. Since the mosfet is driven by Arduino's PWM how to ensure that charging and discharging time is less than PWM is switching frequency (say 490Hz operating at 50% duty cycle)? How to calculate switching losses and how can I minimize it?
3. Based on the graph shown below, saturation region is where current stops increasing. Also, according to wikipedia, MOSFET is in saturation region if Vds> (VgsVth). How is this possible if Vds falls to zero when Vgs is applied? Also, When i look at the graph of Ids vs Vds, I cannot understand why Ids rises with Vds, when clearly it should as shown in Gate charge curve. Am i reading the graph of Ids vs Vds incorrectly? What am I missing?
4. From the perspective of performance i.e. switching time and losses, when using PWM where should the operating point of MOSFET be? Linear/Ohmic or Saturation?
1. I want to calculate switching time of MOSFET. By using equations like Q = CV and Q = It and assuming Arduino provides gate current of 20mA @5V, switching times can be found by looking at value of charges in datasheet. But is it really that simple. Based on the graph shown below, it seems like the turn on time depends on Vgs, which is changing with time. If this is true, can we use I = C*dv/dt to calculate turn on time? If yes, what will be value of capacitances?
2. Since the mosfet is driven by Arduino's PWM how to ensure that charging and discharging time is less than PWM is switching frequency (say 490Hz operating at 50% duty cycle)? How to calculate switching losses and how can I minimize it?
3. Based on the graph shown below, saturation region is where current stops increasing. Also, according to wikipedia, MOSFET is in saturation region if Vds> (VgsVth). How is this possible if Vds falls to zero when Vgs is applied? Also, When i look at the graph of Ids vs Vds, I cannot understand why Ids rises with Vds, when clearly it should as shown in Gate charge curve. Am i reading the graph of Ids vs Vds incorrectly? What am I missing?
4. From the perspective of performance i.e. switching time and losses, when using PWM where should the operating point of MOSFET be? Linear/Ohmic or Saturation?
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