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Start-up circuit for flyback converter having secondary pulse width modulation

  • US 6,456,511 B1
  • Filed: 06/29/2000
  • Issued: 09/24/2002
  • Est. Priority Date: 02/17/2000
  • Status: Expired due to Fees
First Claim
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1. A switching power supply for translating alternating current of a voltage source within a standard range of voltage supply mains into regulated power supplying a load, the regulated power being electrically isolated from the voltage supply mains, the power supply comprising:

  • first rectifier means for rectifying the alternating current into a first rectified current, when connected to the voltage supply mains, and having a positive output node and a return node, a series network including a primary winding of a first energy storing transformer means and a controlled electronic switching means connected across the positive output node and the return node, the first energy storing transformer means also having at least one secondary winding electrically isolated from the primary winding, the controlled electronic switching means having a control electrode, first network means connected to the control electrode, second rectifier means connected to the secondary winding for rectifying alternating energy stored in the first energy storing transformer means into a first secondary voltage, first capacitor means connected to store said first secondary voltage during an initial startup interval, control circuit means operated by the first secondary voltage and responsive to a control signal responsive to power supplied to the load for generating and putting out control pulses following the initial startup interval, and an isolation circuit for transferring the control pulses to the control electrode for controlling duty cycle of the controlled electronic switching means in relation to the control signal.

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