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BQ24450: Power transistor heated while battery as a source to load

Prashant Chavan6
Intellectual 320 points
Part Number: BQ24450

Dear All,

I have faced these issue..

1) Pass transistor 2N3055 getting heated when battery act as source to load with 7A and 24V And simultaneously Charging is going on. 

2) When Battery as Source to load and Charging of battery is not going on

 - is the reverse voltage come across IC ??

- And IN pin of IC will get floating and Stat1 and STAT2 LED's were not blinking properly, 

- Can we fix this floating status of IN pin??? And HOW??

I have attached schematic here, PFA.......

Thanks,

Prashantsch of bq24450 (1).PDF

  • 0
    TI__Guru* 75656 points
    Hello
    During condition 1,battery source to load and charging:
    1.) What is current at Vin and voltage across 2N3055?

    Condition 2, battery source to load and no charging:
    1.) Do you see heating in this condition?
    2.) The input supply has been removed and Vin is floating?
  • 0 in reply to Bill Johns
    Intellectual 320 points
    Hi Bill Johns,
    Thanks for reply, During condition 1 -battery source to load and charging:
    1)-> Current at Vin was 2.48A and Vin = 28V, Load current was about 7 to 8A
    And Power transistor 2N3055 having Pd= 115W , DC collector current 15A and VCE(Sat)=1.1V
    Heating temp. above 80 degree celcius.

    Condition 2, battery source to load and no charging:
    1)-> NO , 2N3055 was not heating when charging was stopped and Battery connected to Load
    2)-> I have done parallel connection from battery ,one is to the load and other is from Charging ckt. to battery
    So voltage at IN pin was about 12 to 16V when battery voltage from 24V to 18V
    And the moment Battery voltage below 18V , STAT indication getting confused between ON/OFF