Using Lead-acid Battery as Power Source for Walkman

The dry lead-acid battery has an output voltage of 6V and a capacity of 0.5Ah. In terms of its size and capacity, it is very suitable for powering a tape player. Since most tape players are powered by two AA batteries, a step-down DC-DC converter as shown in the attached figure needs to be connected between the battery and the player.

The converter has an input voltage of 33V to 16.5V, an output voltage of 3.3V, and a maximum output current of 3A. When the output current is 1A, the conversion efficiency is over 94%, and the static power consumption of the device is only 80μA.

T1 uses a 5A, 60V MOSFET; D1 uses a 3A Schottky diode; L1 uses a magnetic core inductor that can pass SA current, which requires the wire diameter of the inductor to be thick enough, and it is best to use multiple strands of wire. Other components are selected as indicated in the figure.

It is necessary to explain the role of resistor R1. This resistor is crucial to suppress the output ripple of this converter: if the peak current flowing through T1 is too large, the signal is input through pin 6 of IC1, and IC1 turns off T1, which effectively suppresses the peak current and reduces EMI.