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

A technology for controlling electrodes and controlling circuit devices, which can be used in conversion equipment with intermediate conversion to AC, adjustment of electrical variables, control/regulation systems, etc., and can solve problems such as additional cost and complexity.

Inactive Publication Date: 2003-03-19
TE CONNECTIVITY CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Other concerns and disadvantages include the added cost and complexity of providing an effective start-up circuit

Method used

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

Examples

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Embodiment Construction

[0032] See figure 2 The switching power supply 100 according to the principles of the present invention includes a transformer 73 having a primary winding 91 on the primary side 102 and two secondary windings 92 and 93 on the secondary side 104. The primary side 102 includes a switching transistor 75, preferably an N-channel enhancement type metal oxide silicon field effect transistor (MOSFET), having a drain connected to one side of the primary winding 91 and a source connected to the primary side ground loop. The transistor 75 includes an insulated gate, which has a capacitor 74, is connected to a positive DC bus extending from the output of the full-wave rectifier 71, has a resistor 78 and a Zener diode 79, and is connected to a primary side ground loop. The capacitor 74 provides an initial charging current to the gate, and the resistor 78 enables the capacitor 74 to be charged during startup. The Zener diode 79 clamps the gate voltage to a safe value.

[0033] The secondary s...

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PUM

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Abstract

An output isolated, switching power supply (100) has a transformer (73) with a primary (91) and two secondaries (92, 93), and electronic switch (75) in series with the primary, a first rectifier (87) and filter (88) on the first secondary (93) to provide bias power during both startup and operating modes, and a second rectifier (80) and filter (82) on the second secondary (92) to provide regulated output power. A resistor-capacitor network (78, 74) on the primary side provides an initial operating condition, such as a single control pulse, to the electronic switch which causes sufficient energy to be transferred through the first secondary to supply sufficient startup energy to operate a current control integrated circuit (89) on the secondary side in a staged fashion. After the initial operating condition, the current control integrated circuit generates and applies a control signal to the electronic switch through an isolation circuit (77) to cause the electronic switch to turn on and off in controlled fashion in order to deliver regulated power to the output of the supply. The low voltage, secondary side, current control integrated circuit provides a further aspect of the present invention.

Description

Technical field [0001] The invention relates to a switching power supply. More specifically, the present invention relates to a transformer-based flyback converter, which uses secondary pulse width modulation control and has a primary side starting circuit powered by a voltage provided by the secondary side. Background technique [0002] The present invention relates to an electronic switching power supply, which has a high input voltage and is used in low power situations, such as an offline battery charging circuit, which requires a self-contained bias power supply provided by an AC power line on the input side. For safety reasons, it is necessary to provide electrical insulation between the input power line and the output power of the switching power converter. In switching power supply converters powered by AC power lines, output insulation is generally achieved by providing a transformer between the input side and the output side of the converter. High-voltage switching elem...

Claims

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Application Information

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IPC IPC(8): H02M3/28H02M1/00H02M1/36H02M3/335
CPCH02M1/36H02M3/33523H02M3/335
Inventor C·王
Owner TE CONNECTIVITY CORP
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