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SERIES REGULATOR WITH OVER CURRENT PROTECTION CIRCUIT

  • US 20090273323A1
  • Filed: 07/16/2009
  • Published: 11/05/2009
  • Est. Priority Date: 09/13/2007
  • Status: Active Grant
First Claim
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1. A series regulator with an over current protection circuit, wherein the series regulator receives an input voltage at an input power supply terminal and generates an output voltage and an output current at an output terminal, the series regulator comprising:

  • a differential amplifier having an inverting input that receives a reference voltage, a non-inverting input, and a differential amplifier output;

    an output transistor connected between the input power supply terminal and the output terminal, wherein a control electrode of the output transistor is connected to the differential amplifier output;

    a current sense transistor having a source electrode connected to the input power supply terminal, and a control electrode connected to the differential amplifier output, wherein the conductivity of the current sense transistor is dependent on the conductivity of the output transistor;

    a current limiting transistor connected between the input power supply terminal and the differential amplifier output;

    an attenuator circuit connected between the output terminal and a power supply reference terminal, the attenuator circuit having an attenuator output connected to the non-inverting input of the differential amplifier, the attenuator output providing a voltage signal proportional to the output voltage at the output terminal;

    a first constant current source connected to the input power supply terminal;

    a second constant current source connected to the power supply reference terminal;

    a differential transistor pair comprising a first differential transistor with a control electrode coupled to a drain electrode of the current sense transistor, the first differential transistor coupling the current sense transistor to the second constant current source, the differential transistor pair comprising a second differential transistor with a control electrode coupled to the output terminal, the second differential transistor coupling an output of the first constant current source to the second constant current source; and

    a current to voltage converter coupling the output of first constant current source to the power supply reference terminal, the current to voltage converter having a converter output coupled to a control electrode of the current limiting transistor,wherein, in operation, the current sense transistor controls the conductivity of the second differential transistor thereby varying a control current supplied from the first constant current source to the current to voltage converter, and wherein when the control current matches a limiting threshold value, a voltage control signal at the converter output controls the current limiting transistor to thereby limit maximum current flow through the output transistor.

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