Choosing Bootstrap Capacitor and Diode

24volt battery goes up to 30v max and you can use 40V fets with lower rds on like IRF1404. 60V is not a good idea beacause of more than 2 times rds on.

Don't forget low esr caps on your dc link closest to the fets.( 4*470uf/35V rubycon ZLH or similar is fine)

about diode and capacitor it depends on your design. if the duty cycles reaches to 100% for a long time calculte the cap from I.t=V.

I=Qc*f+Icc = total current of the driver at the frequency f and gate charge of Qc.

t=the time that dut cycle=100%

c=Capacitor in farad.

if you can limit the duty cyle to something like 95% then you can generally use a small cap like 1uF.

about the diode don't worry, use a 1n4148+ 10ohm in series.

Hi, I want to ask about if when I drive my motor in regenerative braking, will the 40V mosfet suitable for my design? 

Will you recommend me the mosfet driver that is suitable to drive the 40V mosfet? 

From my reading of regenerative braking circuits, I have design a 2 quadrant DC motor driver using mosfet. When mosfet 1 is on, it will act as buck converter to drive the DC motor. When mosfet 2 is on, it will act as boost converter to regen back the current to charge the battery.

I have try to find a suitable mosfet driver, which where I came to the half bridge bootstrap mosfet driver. I am beginner in using mosfet driver to drive DC motor. Can you guide me on this matter? (My title is about Regenerative Braking)

40 is enough because you must limit the brake power to limit the current to 50A for example and bus voltage to 30v.(for 12cell PB batt)

A 40v mosfet has a break down voltage around 45 to 55 volt and for 30v system its enough.

There are to many drivers for this voltages from Ti,IRF,onsemi,fairchild.

for instance check IR2113 .Its a half bridge driver with independent hi and lo inputs  and shotdown pin and check IR2184 for non independent type with dead time.

there to many app notes in IRF.com and other websites.

Hi, Okay! Thanks a lot.

One last question, what is the differences between half bridge driver with independent hi and lo inputs and with dependent driver...

Is it for independent, the hi and lo output can be control separately, means that, I can choose to on hi or lo output when I need it.

Is it for dependent, the hi and lo output is depends on each other, which is, when I on hi output, the lo will be off, and vice versa....

I have check the IRF.com....it has many app notes...I will take my time to read it.

Regards,

Ronald

Yes you got it.

In some application like two switch forward or fly back we need two switch turn on at the sane time in this case we need independent type.

For normal half bridge driving simultanous turn on should be avoided and we need a dead time between hi and lo and we go with dependednt...

Thank you very much. I will try to build out the circuits. 

Hi,

I have a new problem...I need advice on choosing power diode for my boost converter.

During the regenerative braking, the current will feed back to the battery. How large a power diode rating should I get?

Can you recommend me a power diode product?

You don't need any diode. 

Mosfets -inherently - have internal body diodes and also they are two way switch when they are ON and will by pass the body diodes when they are ON.

So the drop voltage will decrease and the efficiency will rise.(synchronous rectification)

Ok.

Now I am facing the problem of calculating the boostrap capacitor value...

By referencing the application notes an978 , the formula is as below

Following are the the values of the parameters that I was able to find:

• Qg, Gate charge of High Side FET = 196nC.
• I(qbs), Quiescent current for high side driver circuitry = 230uA.
• Q(ls), Level shift charge required per cycle = 5nC
• Frequency of Operation = 15kHz
• Vcc, Supply Voltage, 12V
• Forward voltage drop across bootstrap diode = 1.3V

The following are the values that I do not know how to start with,

• Voltage drop across low side FET, V(ls) = (unknown)
• Vmin, minimum voltage between Vb and Vs  = (unknown) --> guessing value maybe is 12V

I am going to use Battery of 24V, mosfet driver of IR2110 , and the mosfet IRF1404 (40V) as per recommended.

Can mind to help me in this problem? Thanks a lot.

Don't make it difficult!

Just put a 10uf/25v and a 100nf closest to the driver.(or just  one 1uf multilayer)

irf1404 and ir2110  will work from 8 to 20v so its not complicated. for best performance put 1N5817(or19...) for boot diode and 2.2 to 10 ohm resistor in series.

12v supply is fine and choose f=22khz for noisless operation.

Trust me , it will work. just read the application notes for best PCB layout and correct grounding for ir2110 and power stage.

Okay. Sorry for misleading, as I am beginner in this gate drive design.

Thanks for the help. I am appreciate it. Will look out the application notes as suggested.

Hi,

I have built out the circuit and tested running on my DC motor.

I have faced a problem where when I output 100% duty cycle or (99.99%) of duty cycle, my DC motor cannot run smoothly. I have try to check on the gate voltage, it seems that when duty cycle is 99.99%, the supply to the gate of the mosfet is unstable.

Is this problem related to the boostrap capacitor? I have tried to change 10uF into 100uF, its also the same.