# Simulating a load dump circuit [duplicate]

I am trying to build automotive load dump circuitry to bench test my inverter design. I would like to know if anyone has any experience building something like this. I need to create a 172V spike that stays for 400ms.

• Out of curiosity, why 172V for 400ms? I have seen in a couple of places that 60V for 5ms is a typical design point for automotive load dumps. – Dan Laks Sep 23 '14 at 0:04
• This is the requirement for the automotive application we are working on . – EE_Ami Sep 23 '14 at 0:23
• I was planning to charge up a big inductor and then open the switch to dump all that energy into my board. I was checking to see if someone already has built something like this up. – EE_Ami Sep 23 '14 at 0:25
• How much current? I can rub a balloon on my wool sweater and get kV's that last for seconds. – George Herold Sep 23 '14 at 1:10

Here OP is talking about ISO 7637 PULSE 5a, which is simulated version of load dump situation in automotive.

Specification of pulse 5a 12V(two wheeler) and 24V(4 wheeler) are shown below:

As it shows maximum of 174V can be produced for 400 ms in case a load dump situation occurs in the vehicle. And if load dump occurs all the electronics circuits will be fried if not protected.

Now,

The worst instances of surge voltage are generated when the battery is disconnected when the engine is in operation, and the alternator is supplying current to the power line of the vehicle.

To test the circuits whether they comply with ISO 7637 PULSE 5a, it needs to be tested with Pulse 5a generator, like the one shown here.

Pulse 5a Protection

There are couple of good documents on internet about protection from Pulse 5a, and a suggestion 5KP series diodes are suggested to use, and some times two diodes in parallel are also used for protection.

• This is not an answer. You've described everything that the OP already knows, but you've failed to answer the question about how to generate/simulate the required pulse. – Dave Tweed Sep 23 '14 at 12:40
• @DaveTweed: I have mentioned about pulse generator using the link of noiseken. noiseken.com/modules/products/index.php?content_id=202 – AKR Sep 23 '14 at 14:58