Base reach-through active series voltage regulator

Abstract

The pass transistor of this series regulator supplies current at a regulated voltage only sightly below its unregulated supply voltage. The driver transistor, driven by the feedback loop, is supplied from a higher voltage source. During periods when the pass transistor cannot supply the load because its source voltage is too low, the driver transistor supplies the load through the base-emitter junction of the pass transistor without affecting the regulation.

What is claimed is: 
     
       1. A direct current voltage regulator for providing .Iadd.a load current at .Iaddend.a regulated voltage to an output terminal comprising a first source of direct current having a voltage that may drop below said regulated voltage, a pass transistor having its collector connected to said first source and its emitter connected to said output terminal, a second source of direct current having a voltage that remains above said regulated voltage, a driver transistor having its .[.collector-emitter path.]. .Iadd.collector and emitter .Iaddend.connected .Iadd.in a low impedance path .Iaddend.between said second source and the base of said pass transistor, and feedback means connected between said output terminal and said driver transistor for driving said driver transistor in response to the voltage at said output terminal .[.whereby during periods when said first source voltage is below said regulated voltage.]., said driver transistor .[.supplies.]. .Iadd.operating to supply said load .Iaddend.current .Iadd.at said regulated voltage .Iaddend.to said output terminal through the base-emitter junction of said pass transistor  .[.to maintain.]. .Iadd.during periods when said first source voltage is lower than .Iaddend.said regulated voltage. 
     
     
       2. A direct current voltage regulator as in claim 1 wherein said first and second direct current sources are derived from a common alternating current source. 
     
     
       3. A direct current voltage regulator as in claim 1 wherein the polarity of said driver transistor is opposite to the polarity of said pass transistor. 
     
     
       4. A direct current voltage regulator as in claim 3 wherein said feedback means includes a source of reference potential, means for sensing the voltage at said output terminal, comparing means for producing an error signal proportional to the difference between said regulated voltage and said reference potential and amplifying means for driving said driver transistor in proportion to said error signal. 
     
     
       5. A direct current voltage regulator as in claim 2 including a third DC source derived from said common AC source connected to said feedback means for providing the energy to drive said driver transistor, and current limiting means connected between said feedback means and said driver transistor whereby said feedback means are prevented from supplying current to said output terminal through the base-emitter junction of said driver transistor.