# Electrical – Issues about driving a high current DC Motor using an H-bridge

dc motorh-bridge

Nowadays, we're trying to replicate a 24V 40A H-bridge as shown in the link:

``````Component   Value/Part#
MOSFETS     STP80NF55-08 (80A 55V)
Half Bridge Driver  IR2109

DC to DC converter  VBSD1-S24-S12-SIP (24V to 12V)
Regulator   78L05 (5V)
Inverters   SN74HC14N
Optoisolator    4N270545K
C_B     0.1 uF
R_G     4.7 Ω
R_PD    2.2 kΩ
``````

Our layout:

Before we start, we comprehend the basic principles of the H bridge. In this design, we have trouble in providing 5V into 4N27 optocoupler and 12V into IR2109 Gate Driver. The voltage converter VBSD1-s24-s12 sparks and burns each trial and we measure 24V voltage applied to IR2109. While this procedure, the motor could not move at all.

• Near to VBSD1 converter, we use polar capacitors instead of
nonpolar ones as the datasheet of it. This is true or not?
• What can we measure to control this circuit?
• What can be the reasons behind the converter burn?

Note: The ground terminal is the left hand side of the copper traces

your circuit seems fine , but it doesn't contain a current limiting protection . and you might be driving the motor directly without ramping the PWM . So my guess what is happening is that the motor is accelerating and decelerating quickly causing High voltage spikes on the 24v bus . by the way if your 24v is from a bench power supply then it can cause a disaster , it should be battery or batteries in parallel to power supply to absorb the regeneration energy .

Another aspect is the DC DC converter choice , 1W might not be enough and isolation is not needed since you are using a bootstrap driver . So use a 7812 instead it will work flawlessly.

So my proposed solution :

1. Use Battery for 24v supply

2. use a TVS on 24v bus to absorb the transients

3. Ramp the PWM every 1 ms 1% for example , to accelerate/decelerate slowly to prevent spikes from happening

4. Use a small 1A to 2A dc motor to test the system , check the signals with oscilloscope , if every thing works fine , install the big motor .

general note: NEVER put the oscilloscope ground pin on the Vs terminal when trying to measure the high side transistor gate . instead measure the High side gate signal with respect to ground ( it will be around 36v).