This is a design circuit for converter that using for a very practical LM2623A ratio adaptive circuit to drive a digital camera motor. It produces 5 volts from input voltages ranging between 1.8 and 4.5 volts. This is the figure of the circuit;
The duty cycle is not shown, but it varies from about 86% at 1.8 volts in to 71% at 4.5 volts in. Maintaining the 86% duty cycle at 4.5 volts would reduce the efficiency and increase the ripple. Maintaining the 70% duty cycle at 1.8 volts would significantly reduce the output capability. Several camera manufacturers are already requiring 1.8 to 4.5 volt operation from all the power supplies. The 1.8 to 4.5 voltage standard allows a manufacturer to build his product and let the user select disposable Alkalines, Ni-MH or Li-Ion at the point of purchase.
[Schematic circuit source: National Semiconductor Notes]
The duty cycle is not shown, but it varies from about 86% at 1.8 volts in to 71% at 4.5 volts in. Maintaining the 86% duty cycle at 4.5 volts would reduce the efficiency and increase the ripple. Maintaining the 70% duty cycle at 1.8 volts would significantly reduce the output capability. Several camera manufacturers are already requiring 1.8 to 4.5 volt operation from all the power supplies. The 1.8 to 4.5 voltage standard allows a manufacturer to build his product and let the user select disposable Alkalines, Ni-MH or Li-Ion at the point of purchase.
[Schematic circuit source: National Semiconductor Notes]
Cool chip
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