Are Diodes Necessary in a H bridge circuit for motor braking?

Hie i am trying to build a mosfet motor driver using the schematic sourced from a fellow forum member. The schematic is the attachment i uploaded below. Do i need protection diodes for motor braking as indicated by those red squares and are they facing the right way? Thank you.

The website i sourced this schematic is:

MOSFETs come with built in power diodes, its part of the structure of all power MOSFETs.

Sometimes people add external schottky diodes which have a lower forward voltage to reduce losses, but usually using synchronous rectification is a bigger win.

This is nothing to do with braking, diodes are required because the load is inductive.

For regenerative braking you need to control the H-bridge over all 4 quadrants using PWM and sense the supply current, and you need a power supply that can actually store energy (battery or supercaps). Otherwise you will need power-dump resistors and probably a diode to isolate them.

With a straight-forward H-bridge powered from batteries, and PWM control in fast-decay mode you'll get regenerative braking automatically on reducing drive level. If you have full synchronous rectification for fast-decay mode (switching two FETs, not just one), you'll save wasting energy in the diodes.

Do i need protection diodes for motor braking

How big is the motor? Inductance? Maybe the Internal Intrinsic Body Diodes will work, maybe not. You need to do some research here ...

are they facing the right way?

Yes, they point same way as the Internal Intrinsic Body Diodes inside the MOSFET.

A super safe way ... http://hephaestusaudio.com/media/2008/11/mosfet-body-diode.pdf

Use (ultra) fast recovery diodes - not your ordinary diode. Many design criteria to consider: Volts, Amps, Inductance, Recovery Time, Dead Time, etc Now the real question is which Part Number?

Investigate a snubber across the motor, too. This is not a question with a simple yes / no answer. google "fast recovery diode h-bridge mosfet"

I found the answer i was looking for on the web. it turns out that another chip i was looking at has a logic that prevents "shoot through" and provides electronic brake to the motor without blowing up the circuit or shorting the battery.

Here is a link to the tutorial: http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge

tawandapro: Hie i am trying to build a mosfet motor driver using the schematic sourced from a fellow forum member. The schematic is the attachment i uploaded below. Do i need protection diodes for motor braking as indicated by those red squares and are they facing the right way? Thank you.

The website i sourced this schematic is: http://tahmidmc.blogspot.sg/2013/01/using-high-low-side-driver-ir2110-with.html

I have tried to use the same schematic but i don't have good results, How you inject the PWM signal in the IR2110? thanks

The bootstrap capacitors (C1, C5) in that circuit are very large and there is no current limiting
resistor in the bootstrap path, which is distinctly odd.

The resistors R3,4,7,8 are entirely redundant, the gate driver chip handles everything to do with
shutdown. I can see that these have motivated increasing the bootstrap caps to much larger values
than normal. The website that circuit came from has some unconvincing explanation of why those
resistors are there (*), but I’ve never seen or used that before, it seems to be some protection scheme
for high voltage use.

Standard bootstrap caps are about 10 to 20 times the total gate capacitance. You can add 10 ohms
or so in series with the bootstrap diodes to reduce current pulses through the diodes to a sensible
level.

Make sure the decoupling for the IR2110 itself is 10x or more than the bootstrap caps.

All 12V decoupling ceramic. Careful attention to ground plane / layout is needed (the output traces
and bootstrap components that swing at high dV/dt should not be over a ground plane, note.)

(*) I think the originator was using a high voltage bridge without powering up the 12V before the main
high voltage supply - that is always likely to lead to failure - in fact with high power circuitry a soft-switch
is normally used to prevent massive inrush currents to high voltage decoupling electrolytics.

mrsummitville: Use (ultra) fast recovery diodes - not your ordinary diode.

Why would you imagine you need to do that?