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Regulating current output from a buck converter without external current sensing

  • US 8,680,836 B2
  • Filed: 03/15/2012
  • Issued: 03/25/2014
  • Est. Priority Date: 09/29/2008
  • Status: Active Grant
First Claim
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1. A method comprising:

  • generating a reference current, wherein a switching regulator includes an inductor, a power switch and a bootstrap capacitor, wherein the power switch has a source, a drain and a gate and is integrated into an integrated circuit, and wherein an inductor current flows through the inductor during an on time of the power switch;

    generating a sense current whose magnitude is proportional to the inductor current flowing through the power switch during the on time, wherein the sense current is generated without sensing a current external to the integrated circuit, wherein the sense current increases during the on time, and wherein during the on time the bootstrap capacitor supplies a voltage to the gate of the power switch;

    maintaining an output voltage of the switching regulator at a predetermined voltage level when an output current of the switching regulator is less than a predetermined current level;

    maintaining the output current at the predetermined current level when the output voltage is less than the predetermined voltage level, wherein the output current reaches the predetermined current level when a current error voltage reaches a steady state; and

    determining a trip time at which the increasing sense current equals the reference current, wherein output current is maintained at a predetermined current level such that, when the output current equals the predetermined current level, a first time period before the trip time during which the sense current is less than the reference current is a fixed proportion of a second time period after the trip time during which the sense current is greater than the reference current.

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