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LLC soft start by operation mode switching

A resonant mode, working cycle technology, applied in the direction of conversion equipment with intermediate conversion to AC, high-efficiency power electronic conversion, output power conversion devices, etc., can solve the problem of excessive instantaneous current or inrush current, power MOSFET stop running, Problems such as inoperability of power MOSFET

Active Publication Date: 2015-05-20
TEXAS INSTR INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the LLC converter starts to charge the discharged output capacitor, the instantaneous or inrush current drawn through the power MOSFET may be too large and cause the power MOSFET to stop operating
Gradually charging the output capacitor during start-up of the LLC converter prevents the power MOSFET from becoming inoperable

Method used

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  • LLC soft start by operation mode switching
  • LLC soft start by operation mode switching
  • LLC soft start by operation mode switching

Examples

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Embodiment Construction

[0017] The drawings and description generally disclose example embodiments of LLC converters. To sum up, the LLC converter includes a switching circuit, a resonant circuit, a rectifier circuit and a load. During start-up, especially when the output capacitor is being discharged, inrush current can be drawn by the power switches in the switching circuit. To limit this inrush current, the LLC converter starts in PWM mode first. The signal driving the power switch is a PWM (Pulse Width Modulation) signal, which has a fixed period and a variable duty cycle. Using the PWM signal to drive the power switch gradually charges the output capacitor, protecting the power switch from inrush current.

[0018] When the output voltage is charged to a predetermined voltage close to the output voltage set point (the output capacitor is fully charged at this time), the signal driving the switches in the switching circuit will change to a resonant mode signal with variable period and fixed duty...

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PUM

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Abstract

An embodiment of the invention provides a method of reducing surge current in an LLC converter. The LLC converter comprises a switching circuit having a first switch and a second switch, a resonant circuit, and a rectification circuit. During start up of the LLC converter, first and second signals having a fixed period and a variable duty cycle are applied to the first and second switches respectively. When a predetermined voltage on a load configured to be coupled to the rectification circuit is reached, the first and second signals are changed to signals having a variable period and a fixed duty cycle.

Description

technical field [0001] The present invention relates to DC / DC converters, and more particularly to LLC DC / DC converters. Background technique [0002] DC / DC (direct current / direct current) converters are found in many electronic devices. For example, DC / DC converters are commonly found in PDAs (Personal Digital Assistants), cellular phones, and laptop computers. These electronic devices typically contain several sub-circuits that have different voltage level requirements than those supplied by the battery or external power source. A DC / DC converter converts DC power from one voltage level to another to meet the voltage levels required by sub-circuits. [0003] One way to provide DC / DC conversion is through the use of linear regulators. However, for devices such as laptop computers and cellular phones, linear regulators may dissipate too much heat. [0004] A DC / DC converter converts one DC voltage to another DC voltage by temporarily storing input energy and then releasi...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02M3/28H02M1/32
CPCH02M1/36Y02B70/10H02M3/33571H02M3/01
Inventor 孙博胜罗宇伟钟·叶
Owner TEXAS INSTR INC