I am using IR2184 FET Driver and datasheet tells that HO is in phase with IN and so LO is not in phase that is inverted. So, circuits in previous posts are wrong. Here is my new circuit.
Is this correct.
HO and LO will be complementary. So, can be used in synchronous buck converters where switch 1 and switch works Syncronously.
Common sense tell that switch 1 and switch 2 should not be ON at the same time because then switch 2 will short the +ve bus to GND.
Datasheet of IR2184 is not clear. Unlike other FET drivers it has only one input and two outputs namely HO and LO and I guess they have to be complementary to drive a push-pull circuit.
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By referring the book Power Electronics - Circuits, Devices and Applications, 3rd Ed., by Muhammed H Rashid, page nos. 191 to 193 I have done these calculations for my buck converter.
PWM frequency 20 KHz
Input Voltage to Buck Converter is Vs = 15V
Required Output Voltage is Va = 5V
Load Current is 3A
pk-pk ripple current of Inductor = 0.01A
pk-pk output ripple voltage is choosen as 10 mV
L = 5(12 - 5) / (0.01 * 20000 * 12) = 35 / 2400 = 14.6 mH
15 mH is a standard value and we can use it
So, doing the reverse calculation to find out PWM
f = 5(12 - 5) / (0.01 * 15 * 10^(-3) * 12) = 19444.44 Hz = 19.444 KHz
C = 0.01 / (8 * 0.01 * 19444) = 6.43 uF
we can choose 6.8 uF 16V Electrolytic
doing the calculations again
pk-pk ripple voltage = 0.01 / (8 * 19444 * 6.8 * 10^(-6)) = 9.5 mV
Tpwm = 1/F = (0.01 * 15 * 10^(-3) * 12) / (5 * (12 - 5)) = 0.0018 / 35 = 51.42 us
F = 1/T = 19444.47 same as calculated earlier
Now, how to calculate duty ?
D = Ton / (Ton + Toff)
If I choose 20% duty
then 20% of 255 (pwm duty varied from 0 to 255 in mikroC PWM Library) is 55
55 is the duty value
Ton = 20% of 51.42 us = 10.284 us ON and
Toff = 51.42 us - 10.284 us = 41.136 us
Are these calculations correct ?
So, Can I use 6.8 uF 16V and 15 mH 6A Ferrite Core ?
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Problem is in Inductors. the mH 4A or above Inductors are like transformer package.
If I choose uH inductors then f becomes MHz.
What to do ?
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This is the new calculation I did. It is correct and only good for Proteus simulation.
Input Voltage to Buck Converter is Vs = 15V
Required Output Voltage is Va = 5V
Load Current is 3A
pk-pk ripple current of Inductor = 0.01A
pk-pk output ripple voltage is choosen as 10 mV
L = 5(15 - 5) / (0.01 * 20000 * 15) = 35 / 2400 = 14.6 mH
15 mH is a standard value and we can use it
So, doing the reverse calculation to find out PWM frequency
f = 5(15 - 5) / (0.01 * 15 * 10^(-3) * 15) = 22222.22 Hz = 22.22 KHz
C = 0.01 / (8 * 0.01 * 22222) = 5.625 uF
we can choose 5.6 uF 16V Electrolytic
doing the calculations again
pk-pk ripple voltage = 0.01 / (8 * 19444 * 5.6 * 10^(-6)) = 10.044 mV
//Tpwm = 1/F = (0.01 * 15 * 10^(-3) * 15) / (5 * (12 - 5)) = 0.0018 / 35 = 51.42 us
//F = 1/T = 19444.47 same as calculated earlier
Tpwm = 1/F = 1/22222 = 45 us
20% duty means 0.2 * 255 (duty value is between 0 and 255 in mikroC PWM library)
duty value = 51
20% of 45 us = 9 us
Ton = 9 us
and
Toff = 45 us - 9 us = 36 us
D = Ton/(Ton + Toff) = 9 us / 45 us = 0.2 = 20%