Driving Peltier with VNH5019A-E

steven239955_stm1_st · ‎2015-01-13

Posted on January 13, 2015 at 20:37

I am having trouble driving a peltier device with the VNH5019. The channel config. in the scope pictures is as follows:

1. Vin to H-bridge2. PWM logic in3. A leg out4. B leg out

GoodDrive.bmp shows what's supposed to happen. When the 50% 10kHz PWM pulses on 12 V is applied to the peltier, which should draw up to 12 A. But sometimes it turns out like in BadDrive.bmp where the peltier drive is cutoff prematurely, and then the next several PWM cycles are skipped. It seems to depend on the exact instance of the H-Bridge used, peltier used, or temperature gradient of the peltier; i.e. I think something is just right on the edge of working.

I put a 27 uH inductor on both legs, and the situation improved a little as in L.bmp. Not sure what the problem is. Any thoughts or ideas would be much appreciated.

#vnh5019

Brugus · ‎2015-01-15

Posted on January 15, 2015 at 17:05

Mr. Van Buskirk,

Few questions about the application:

1. Temperature: is the PCB copper area connected to the tab of the device, designed to avoid the thermal shutdown under the working condition you described?

2. Did you check output current amplitude by using a current probe?

3. Pin 12: is this pins NC? Check the application schematic diagram reported in figure #5 in the datasheet

Best regards,

Marco Brugora

steven239955_stm1_st · ‎2015-01-15

Posted on January 16, 2015 at 02:00

Marco, We actually just figured this out today. The problem is being caused by ~200ns voltage spikes on the INA and INB lines during switching. Apparently it is just enough to trigger both lines to be read high and the output then is set to ''Brake to Vcc''.

jsoman00 · ‎2015-02-10

Posted on February 10, 2015 at 12:46

Hi, Mr. Van Buskirk,Marco Brugora.

I have trouble with vnh5019a-e.

I also use it for peltier devices.

The trouble is that when it flows near 9A currents, then vnh5019 is shutdown.

I don't know why.

It doesn't look like thermal shutdown.

When I reset the Vcc, it works.

Do you guys have any idea on it?

Thank you.

Brugus · ‎2015-02-12

Posted on February 12, 2015 at 10:09

I suggest to check the input signals (waveforms). What is the PWM frequency and the voltage supply level?

Could you share the schematic diagram?

Best Regards,

Marco Brugora.