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Original question:

BQ24630: PG PIN blinking, charge very low

BQ24630: Problem with a Pneumatic power source, PG pin blinking, cannot charge

Kangmin Xu
Prodigy 100 points
Part Number: BQ24630

We design a 24V charging System using BQ24630, ACSET and ISET1 is adjustable through MCU. Battery is 19.2V LiFePO4.

When the system powered by 24V AC to DC, 2.5A power adapter, everything works perfectly. It can charge the system based on ACSET and ISET1 values.

We also want to charge the system using a pneumatic generator as a backup power source when AC adapter is not available.

We use this one.  It provides 24V with max 500 mA at 7 bar input air supply. Two pneumatic generators can provides 1000mA, we tested these setup using a load tester, it works fine. It can output 1000mA as advertised.

In our charging circuit, We use a 100uF capacitor at the input of the pneumatic generator to stabilize the voltage.

We tested using two pneumatic generators, system load 300mA, BQ24630 can pick up the power source and charge the battery at around 600mA rate.

However, when the system load increases to 600mA, BQ24630 cannot pick up the power source, and PG pin is blinking. 

I tried to use a higher capacitor like 470uF or 1000uF, not seems to work. 

I attach the schematic, waveform of PG pin and power supply of pneumatic generators. C1 to C3 are power supply capacitors.

Could you suggest a voltage stabilizing circuit that can smooth out the voltage and let BQ24630 to pick up the power source easily?

What's the requirement of Power supply?

Wave form: Yellow is pneumatic power source, light blue is PG pin. Normal operating, this is when system load is low, less than 300mA. Charging ok.

PG pin Blinking, cannot charge. this is when system load is 600mA, 

  • 0
    TI__Mastermind 24075 points

    Hi Kangmin,

       When you turn on the 600mA load, the load on your adapter to provide both the system load, as well as the battery charge current causes the input adapter to drop its voltage to try and maintain the load (power conservation). This is most likely causing your charger to enter in and out of SLEEP mode. You can verify by observing VCC, SRN, PG and PH node, as you will observe VCC droop to SRN (battery voltage) causing the converter to be disabled. 

  • 0 in reply to Kedar Manishankar
    Prodigy 100 points

    Yes, I know, that's why I set ACSET to 1000mA to limit the max current draw from the supply. 

    When load is 300mA, battery is charging at around 600mA. (This is working)

    When load is 600mA, battery should be charging around 300mA, but it's not charging, only cycling. 

  • 0 in reply to Kangmin Xu
    TI__Mastermind 24075 points

    Hi Kangmin,

       There is a CC limit on your supply itself as well. This is why the 2.5A adapter works right? Capture the signals mentioned above so we can verify what is happening during the cyclic charge and no charge.

  • 0 in reply to Kedar Manishankar
    Prodigy 100 points

    Will do. I can get above signals on Wednesday.

    If it's the supply issue, what's your suggestion? 

    Add more supplies in parallel? Each one will output 500mA, so maybe 3 to 4 supply should provide sufficient power for 600mA system load.

  • 0 in reply to Kangmin Xu
    TI__Mastermind 24075 points

    Hi Kangmin,

       Choosing adapter type based off of load and charge current requirements is more system level and up to the engineer designing. That would be a good next step once we see the test results verifying if we are entering in and out of SLEEP. I would verify that adding supply in parallel works in lab.