I am tring to generate a square wave of 100KHz and 200 volts peak to peak across a resistor via H- bridge. The current could go upto 30A.
I am looking into two following ways to drive the NMOS ( four NMOS transistors ) H - bridge.
a. Using H bridge Drivers HIP4081A. I tried to look for the replacement of HIP4081A but only found A4940 from Allegro microsystems which a little slower than the HIP part regarding rise and fall time. According to my understanding the Driver chip has to charge the input capacitance of the transistors. I am planning to use NMOS transistor (IRF540).
So, according to HIP 4081A data sheet trise = 10nsec at C= 1000pF and if power supply = 50Volts (60% of 50V = 30volts) , So, I calculated (1000pF x 30V) / 10nsec = 3 Amp.
The gate to source charging capacitance of IRF540 is 14nC; So, the charging time would be
(14nC x 30 V) / 3 = 140nsecs. Are my calculations accurate and in right direction?
b. I calculated the same things using A4940 and found the following results
(1000pF x 30V) / 35nsec = 857 mA
(14nC x 30V) / (857mA) = 490nsec.
Which proves that the A4940 is a slower part. But how will it effect the voltage waveform across the resistive load. I meant to say what would be the difference between the two waveforms generated by two different driver chips.
Is there true replacement part available for HIP4081A. The reason for finding the replacement for HIP4081A are
a. What if Intersil discontinue this part in the future. b. May be there is a cheapaer part available than HIP4081A.
- The second method is to use four NPN transitors to drive two PMOS transistors (High side) and two NMOS (Low Side) transistors. Microcontroller will provide the PWM pulses to control the 2N2222 transistors. You can find the diagram at the following link.
I am thinking of using 2N2222A to drive two (IRF540N) but unable to find the PMOS equivalent of IRF540 N. Any suggestions!! Do I need them of the same ratings?
Please also suggest that H - bridge driver approach is the better approach or the NPN transistors driving the PMOS and NMOS transistors is the good approach. I heard that the NPN driving the PMOS and NMOS is the most efficient way, if yes than how?
Would 2N222 be able to charge the MOSFETS quickly as HIP4081A. What parameters should I consider before I choose the microcontroller.
This is not a home work. :)