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Original question:

PWM Polarity Inverting Circuit for TEC module using DRV8432 in parallel full bridge mode

DRV8432: DRV8432 in parallel full bridge mode to drive Peltier Module for heating and cooling - using EVAL8432 and own design

sai77
Prodigy 110 points

Part Number: DRV8432

Hi,

I'm using DRV8432-EVAL module in PFB(parallel Full Bridge) Mode to drive Peltier module rating 24V/12A.

I have worked on My own designed DRV8432 PCB in PFB mode. myschematic design also attached here.

The board is working good PVDD=12V driving 4A current.Peltier-Driver-DRV8432-schematic.pdf

if voltage is changed to PVDD=15V trying to drive 6A current and IC 8432 and heat sink are getting too hot and  finally driving 1.8A of current showing  5V(30% DC) on output though the PWM is 98% (DC).

Mode: PFB

PWM Freq : 40Khz

1 . Peltier - heating 

PWMA - 98% Duty Cycle

PWMB -1% DC

2.  Peltier - cooling

PWMA -1% DC

PWMB - 98% Duty Cycle

Why cause this? How to solve this problem?

Thanks 

Regards

Sai

  • 0
    TI__Guru** 114905 points
    Hi Sai,

    Have you checked the /OTW and /FAULT pins to determine if the device is overheating and shutting down?

    Changing from 4A to 6A increases the power by ~2.25x. Is your heat sink large enough?
  • 0 in reply to Rick Duncan
    Prodigy 110 points

    hi Rick,

    Thanks for the quick reply.

    I am using EVAL module and the heatsink has given along with it.
    sometimes there is no indication on /OTW and /FAULT pins but suddenly current and Voltage came down ..

    example:

    If my application draws 6A@15V ,
    but it is showing 1.8A current and 5V accrros output pins(accross TEC module) though the PWM is 98% DC @15V.  -

    are the Capacitors charged or not??

    Here Peltier is for both heating and cooling - so I am trying to switch from heating to cooling mode means swaping the polarity of PWM A and  B  instantly.

    Please clarify whether any delay is required at the switching time...

    Why cause this? 


    Regards,
    Sai

  • 0 in reply to sai77
    TI__Guru** 114905 points
    Hi Sai,

    Were any changes made to the DRV8432EVM? If so, what changes were made?

    Can you provide scope captures of the outputs when the current suddenly changes. This will help identify why the current is changing.
  • 0 in reply to Rick Duncan
    Prodigy 110 points

    Hi Rick,

    No changes have made to the DRV8432EVM. just Added extra circuitry for current measurement- ACS712-20A. Circuitry is as shown below.

    The scope captures of the outputs with load, without load @14V and 15V.

    1. Ringing without load

    2. output at14V                                                                         3. output @15V

     

    Data of Peltier Heating and Cooling Swapping the PWM channels.

    DRV8432 - Peltier Heating -Cooling-Current-Data.xls

    Is Any short through happening while changing the direction at higher currents??

    @15V it is not drawing exact current and IC is also getting hot.  Sometimes /OTW, /FAULT showing the error.

    Regards

    sai

  • 0 in reply to sai77
    Prodigy 110 points

    Please reply. 

  • 0 in reply to sai77
    TI__Guru** 114905 points
    Hi Sai,

    Where is Channel 1 and Channel 2 connected in the scope captures?

    It would be beneficial to see the signals OUT_A, OUT_B, OUT_C, and OUT_D (prior to the inductor).