Startup circuit for self-supplied voltage regulator

A startup circuit for a self-supplied voltage regulator, comprising:

• a voltage regulator to regulate an output voltage, where said output voltage is derived from a power supply voltage, said voltage regulator coupled to a startup circuit, where an amplifier means of said voltage regulator produces said output voltage;
• said startup circuit to initiate a startup by having a current applied to an input of said startup circuit which causes said power supply to bring up said output voltage at an output node, thereby starting operation of said amplifier means, where said startup circuit switches off when said amplifier means pulls up said output voltage to a desired final output voltage;
• a comparator of said startup circuit to compare an output current capability of said voltage regulator with a startup current of said startup circuit plus output currents of said voltage regulator, where said comparator switches off said startup circuit when said output current capability is higher than said startup current plus said output currents of said voltage regulator;
• and
• scaling circuits comprising current mirrors to scale down currents of said startup circuit.

A startup circuit for a self-supplied voltage regulator, comprising:

• a voltage regulator to regulate an output voltage of said voltage regulator, said voltage regulator further comprising:
• an amplifier means for amplifying a differential input voltage to produce said output voltage at an output node (Vout) and to further provide control voltages as inputs to a startup circuit, where said amplifier means will start its operation once said output voltage rises;
• a first pmos transistor its input coupled to a first of said control voltages to receive a steering current;
• first current mirror means, its input coupled to said first pmos transistor to mirror the current of said first pmos transistor;
• and
• second current mirror means coupled between the output of said first current mirror means and an external power supply (VDD), where the output of said second current mirror means couples to said output node (Vout) to provide a source of current and a rising voltage to said output node (Vout);
• said startup circuit for initiating and terminating the startup of said voltage regulator, said startup circuit further comprising:
• third current mirror means having an external input (ibstart) to provide a current derived from said external power supply, where said third current mirror means provides signals at its output for said initiation of said startup and further to terminate the startup of said voltage regulator;
• a current comparator to effect a current comparison between an output current capability of said voltage regulator and its output current including the current used by said startup circuit, where when said output current of said startup circuit predominates, said startup circuit initiates said startup of said voltage regulator, and when said output current capability of said voltage regulator predominates, said startup circuit terminates said startup of said voltage regulator;
• a second pmos transistor coupled to said output node (Vout), its input coupled to a first of said control voltages to provide a current for current mirroring;
• fourth current mirror means, its input coupled to said second pmos transistor, said fourth current mirror means to provide at its output, at a node Ns, a mirrored current;
• and
• a third pmos transistor, a sense transistor, its input coupled to a second of said control voltages to steer said third pmos transistor, said third pmos transistor coupled between said output node (Vout) and said node Ns, to measure said output current capability of said voltage regulator.

A method of providing a startup circuit for a self-supplied voltage regulator, comprising the steps of:

• a) providing a voltage regulator with an amplifier to produce an output voltage;
• b) coupling a startup circuit to said voltage regulator and applying a current to an input of said startup circuit, thereby turning on said startup circuit;
• c) causing said output voltage of said voltage regulator to rise thereby starting operation of said amplifier;
• and
• d) switching off said startup circuit when said amplifier pulls its output voltage up to the desired final output voltage based on a compare circuit to compare the output current capability of said voltage regulator with the output current of said voltage regulator including the current of said startup circuit.