3V Power Supply For Portable Radios

Posted on Nov 8, 2012

Most small portable radios require a 3-V supply, which is normally provided by two AA or AAA batteries

3V Power Supply For Portable Radios
Click here to download the full size of the above Circuit.

. Because rechargeable batteries are an option with many of these radios, most of them are fitted with a charger socket. When such radios are used in a stationary condition (e.g., in the kitchen or in the office), it is useful (and economical) to use the mains-operated supply described here. The supply is small enough to be fitted inside the radio or in a mains adapter case (less than transformer). Voltage regulator IC1 is adjusted for an output of 3 V by resistors RI and R2, which are decoupled by C2. Capacitor C3 provides additional filtering. Diode D1 indicates whether the unit has been connected to the mains. The diode also provides the load necessary for the regulator to function properly; in its absence, the secondary voltage of the transformer might become too high when the unit is not loaded. The transformer should be a short-circuit-proof miniature type, which is rated at 12 V and 4.5 VA. The secondary voltage is slightly higher than needed for a radio, but this reserve is useful when the unit is used with a cassette or CD player. It is advisable to check the output voltage of the unit when it is switched on for the first time before connecting it to a radio or cassette player.

Leave Comment

characters left:

New Circuits



Popular Circuits

19 LED Clock circuit
High frequency crystal oscillator
Design and simulation study of anti exciting type switching power supply of single-end
The embedded microcontroller MC68HC912B32 background debugs the mode to design
electronic liquid detector circuit
LED Thermometer
PIC16F630 14 Pin FLASH Based 8 Bit CMOS Microcontrollers
DMX PC Keyboard Interface circuit