Thrifty Voltage Regulator


Posted on Feb 5, 2014

One of the drawbacks of a three-pin voltage regulator is that the input voltage needs to be 2. 5 3 V higher than the output voltage. This makes these integrated regulators unsuitable for battery power supplies. If, for instance, the output voltage is 5 V, a 9 V battery could be discharged to 7. 5 V or thereabouts only. On top of this, most of thes


Thrifty Voltage Regulator
Click here to download the full size of the above Circuit.

e regulators draw a current of about 2 mA. Special low-drop versions sometimes offer a solution, but they are not ideal either. The regulator described here is rather thriftier: it draws a current of only 300 µA and the difference between its input and output is only 100 200 mV In the circuit diagram, T1 is arranged as a series regulator, which means that the difference between input voltage and output voltage is limited to the transistor`s saturation potential. Therefore, a 9 V battery can be discharged to about 5 V, which is quite an improvement on the situation with an integrated regulator. Diodes D1-D2-D3, or a suitable zener diode (D4), in conjunction with R5 and P1, form a variable reference voltage source, which is used as the (output-dependent) base potential of T3. If the output voltage drops below a desired level, the base potential of T3 also drops. The transistor then conducts less hard and its collector voltage rises. The base voltage of T2 also rises, so that T1 is driven harder. This results in the near-instantaneous restoration of the output voltage. The design of the reference voltage source is clearly of paramount importance. The current through the LEDs or the zener diode is of the order of only 100 µA. This means that thedrop across a 5. 1 V zener diode is only 4. 3 V and across each LED, only about 1. 43 V. For a wanted output voltage of 4. 8 V, the three LEDs proved very effective, whereas the zener...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Digital-frequency-doubler
    The UC3825BN as DC/DC Converter Central Processor Circuit Schematic and Datasheet
    3A Switching Power Supply
    variable power supply with l200
    High Voltage Converter: 90V From 1.5V
    Feeding CB and Ham radio audio into the aux circuit
    Metal detector 8
    A LOW-BATTERY ALARM FOR 13.6 VOLT LEAD-ACID BATTERIES
    electronic chime
    Homemade subwoofer playback system 01
    Milliammeter table circuit composed of resistance
    Single-ended Class A amplifier circuit diagram of 6N1 + 6P3P



    Top