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bq51013 Power Dissipation

Kei Sato73562
Expert 2310 points
Other Parts Discussed in Thread: BQ51013

Please teach the calculating formula of the Power Dissipation.

bq51013 Power Dissipation is Rectifying circuit loss+ LDO loss?

Even an electricity loss of LDO exceeds a permission loss at 400mA.

  • 0
    TI__Guru* 75806 points

     

    To improve efficiency and provide good load transient response voltage into the LDO (V-RECT) will change with output current.  This will result in a change in efficiency as load changes, improving as load increases.

    Also below 225mA the synchronous rectifier is operating in a half synchronous mode, but improving as load increases.

    Figure 5 in data sheet will give the overall efficiency ( both LDO and Rectifier) as a function of output power.  

    Figure 4 in the data sheet provides rectifier efficiency as a function of output power.

    Below is a breakdown of LDO voltage drop as a function of output current.

     

    LDO input voltage (V-Rect)  / LDO Voltage drop:

    Less than 100mA – 7.08V / 2.08V

    100mA to 200mA – 6.28V / 1.28V

    200mA to 400mA – 5.53V / 0.53V

    Greater than 400mA – 5.11V / 0.11V

     

    In the case of an output current of 500A at 5V or 2.5W.

    Rectifier efficiency is about 95% for a loss of 125mW (5% * 2.5W), see figure 4

    LDO at that current will have a 0.11V drop for a loss of 55mW (0.11V * 0.5A).

    Total loss is 180mW, this indicates an overall efficiency of about 93%.

    Figure 5 indicates a total efficiency of about 93% at 2.5W

    Best Regards

    Bill