Battery Management, LED Driver ICs

Hi!

I’m hoping you can help me...

I am looking to develop a new bike light, but need help determining which components to use. The choices are overwhelming!

I realize that you are primarily an IC company, but I wanted to give you the full spec, so you can get a feel for what I am trying to do. Any recommendations as to components would be highly appreciated!!!

I have a 6V/40mA solar panel, which I am currently using to charge a single 3.7V/1200mAh Li-Ion battery. The panel works great, but I have no battery management, overcharge protection, etc. Then, I am looking to drive one or more LEDs that can provide a great combination of brightness/lumens/mcds with long battery life. Finally, an LED Drivers is needed to provide power management for High, Low & Flashing settings.

Block Diagram:

6V/40mA solar panel

          |

Battery Management IC (needed)

          |

3.7V/1200mAh Li-Ion Battery

          |

LED Driver IC (needed)

          |

LEDs (needed)

Please let me know if there is any other information I can provide.

Thanks!

Rob.

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  • 0
    •  Analog Employees 
    on Apr 13, 2013 1:44 AM over 7 years ago

    Great!  I'm glad were both thinking the same thing.  So here's how I would do it with the ADD5205:

    NOTES:

    1.  Connect nSHDN to 1.5 - 6.0 V to enable the ADD5205.  This is also where an oscillator would be connected for blinking. 

    2.  Connect a PWM signal to the PWM pin to turn the LEDs on.  So if you didn't want to use the NMOS on the ISET pin.  You could instead apply a PWM duty cycle here and the ADD5205 would scale (dim) the LED current as a percentage of the duty cycle. 

         If a PWM signal is not used for dimming, then connect nSHDN to PWM.

    3.  Change ISET resistors (R1 and R2) to set the LED current:

         ILED (mA) = 2600 / RSET (kohm) * 2 (because 2 current sinks are connected together)

    4.  When the gate of N1 is high, then Rset=R1||R2.  When N1 gate is low, then Rset=R2.  So R2 sets your dimming current and R1||R2 sets your full scale current. 

    The ADD5205 will boost the input voltage up to the required voltage to drive the LEDs.  So Vout will be greater than Vin.  And if the Vf of the LEDs, or the input voltage, or the LED current changes, then the ADD5205 automatically compensates to deliver the optimal voltage.  And if you want to add (or subtract) LEDs in the future, everything stays the same (no schematic changes). 

    Here's a picture of what the demo board looks like (so you can get an idea of the size of the solution):

Reply
  • 0
    •  Analog Employees 
    on Apr 13, 2013 1:44 AM over 7 years ago

    Great!  I'm glad were both thinking the same thing.  So here's how I would do it with the ADD5205:

    NOTES:

    1.  Connect nSHDN to 1.5 - 6.0 V to enable the ADD5205.  This is also where an oscillator would be connected for blinking. 

    2.  Connect a PWM signal to the PWM pin to turn the LEDs on.  So if you didn't want to use the NMOS on the ISET pin.  You could instead apply a PWM duty cycle here and the ADD5205 would scale (dim) the LED current as a percentage of the duty cycle. 

         If a PWM signal is not used for dimming, then connect nSHDN to PWM.

    3.  Change ISET resistors (R1 and R2) to set the LED current:

         ILED (mA) = 2600 / RSET (kohm) * 2 (because 2 current sinks are connected together)

    4.  When the gate of N1 is high, then Rset=R1||R2.  When N1 gate is low, then Rset=R2.  So R2 sets your dimming current and R1||R2 sets your full scale current. 

    The ADD5205 will boost the input voltage up to the required voltage to drive the LEDs.  So Vout will be greater than Vin.  And if the Vf of the LEDs, or the input voltage, or the LED current changes, then the ADD5205 automatically compensates to deliver the optimal voltage.  And if you want to add (or subtract) LEDs in the future, everything stays the same (no schematic changes). 

    Here's a picture of what the demo board looks like (so you can get an idea of the size of the solution):

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