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Current feedback method, current feedback circuit, driving circuit and switching power supply thereof

  • US 9,246,384 B2
  • Filed: 10/28/2014
  • Issued: 01/26/2016
  • Est. Priority Date: 10/31/2013
  • Status: Active Grant
First Claim
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1. A current feedback circuit, comprising:

  • a) a first current mirror circuit having an input terminal coupled to a source of a main power transistor of a switching power supply, and a control terminal configured to receive a pulse-width modulation (PWM) control signal, said first current mirror circuit being configured to generate a first mirror current;

    b) said first current mirror circuit and said main power transistor being on such that an output sampling current flows through said first current mirror circuit and said main power transistor when said PWM control signal is active;

    c) a second current mirror circuit configured to generate an output feedback current that is in a predetermined direct proportion with said output sampling current, and is generated in accordance with said first mirror current;

    d) a current follower with input terminals coupled to a charging and discharging circuit and said first current mirror circuit, and an output terminal coupled to a current detection pin, wherein said current follower comprises an operational amplifier having input terminals coupled to input and output terminals of said first current mirror circuit, and a first transistor having a gate coupled to an output terminal of said operation amplifier, a source coupled to an inverting input terminal of said operational amplifier, and a drain coupled to said current detection pin; and

    e) a first switch circuit coupled between said charging and discharging circuit and an input terminal of said operational amplifier, wherein said first switch circuit is off when said PWM control signal is inactive.

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