Is there any special PCB use for Power Electronic.?

Question

Hi everyone, I am HK from INTI College Penang, Malaysia. Recently I had work on a DC Motor Controller using HIP4081A as the driver and IRF3205 as the MOSFET. The rating is 100A continuous current working with 24V of DC Motor and the maximum voltage over the board is ~30V. I had managed to create the PCB and the working DC Motor Controller but the problem is the device might fail if my H-bridge direction switching is done frequently. It fail in the way that the controller no longer working anymore or the upper left side MOSFETs are all fried or the driver are fried. Do i need to supply all the on board IC or devices with an external supply or can i used the battery supply directly from the motor and step it down using regulator to supply the chips? Will that cause the failure of the device?

Answer 1

you should have a separate power supply for the load and control voltages. when you are switching it a higher speed (i assume you are shooting for 01k-15khz) the loading and unloading of the MOSFETs is probably causing an oscillation in the DC supply. i would do the following:

- widen you traces or tint the traces with solder to increase current carrying capabilities and reduce the resistance.

-upgrade the power supply. a separate control voltage is recommended, but there is no reason the voltage cant be cleaned up. 78xx voltage regulators do not handle fluctuations well (this is why 2 can not be hooked in series). use a large cap and a toroid coil to clean the power before it is regulated. add additional filters before it is used by the board.

- put a limiting resistor in series with the MOSFET. this will reduce the current draw, i know it only need Vgs to turn on, but you are apparently having trouble with power draw. a small RL will reduce the power and EMP surge felt by the MOSFET. remember, current is the instantaneous change in voltage. if you are turning it on very fast you are sending it a lot of current. a cap in series with the MOSFET could also help. i am not sure which is better. both probably would not be a great idea. the MOSFET has an internal capacitance so adding a RL should give all the timing control you need.

also read what i wrote to "amaldonadojr85" on the HIP4081A. i assume he is a classmate of yours.

http://answers.yahoo.com/question/index;...

best of luck! i will be watching this question so give me an update. also, will optocouplers help isolate the MOSFETS from the HIP4081A?   am not aware of you current draw. they might be useful. then again, this DIP was designed to run MOSFETs directly...

Answer 2

In motor controllers that I have seen, DC to DC converters have been used to supply the low voltage control circuits from higher voltage DC. A small inverter circuit is powered from the higher voltage DC and creates AC at 1000 Hz or so. The 1000 Hz AC is the primary voltage for a toroid transformer with several secondary windings. The secondary windings feed DC supplies at various voltage levels. The low level DC supplies are isolated from the higher voltage level and some may need to be isolated from each other.