Rectifying Bridge Control Circuit Inrush Current Management
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Solution Overview
Problem
Existing AC/DC converter architectures face challenges in minimizing stand-by power consumption and limiting inrush current peaks during startup, particularly in systems using rectifying bridges.
Innovation Solution
The proposed solution involves an AC/DC converter design with a rectifying bridge connected to controllable switching elements or rectifying elements, controlled by a microcontroller using a PNP or NPN transistor switch, which injects and extracts gate current to manage the inrush current and reduce stand-by losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a rectifying bridge is used to convert AC voltage to DC voltage, then the converter can deliver the required DC output, but stand-by power consumption increases
Solution Approach 1:
The patent applies phase-angle control to change the conduction angle of the rectifying bridge elements, thereby regulating the output power while minimizing stand-by losses. By controlling the firing angle of the thyristors or triacs, the converter can operate at reduced power levels during stand-by mode without maintaining full conduction, thus reducing energy consumption while still delivering required power when needed.
2Device complexity
If the converter starts up without current limiting, then the startup process is simple, but inrush current peaks occur that can damage components
Solution Approach 1:
The patent implements a soft-start mechanism that progressively increases the conduction angle from a limited initial value to the full operating range. During startup, the control circuit initially restricts the firing angle to prevent excessive inrush current, then gradually increases it over a predetermined time period. This preliminary current limiting action prevents component damage while maintaining relatively simple control circuitry using basic timing and angle control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively decreases stand-by losses and limits inrush current peaks by controlling the switching elements in phase angle, eliminating the need for resistive elements and simplifying the control circuitry, thereby improving the efficiency and reliability of the converter.
Implementation Method 1
a PNP or NPN transistor switch, which injects and extracts gate current to manage the inrush current and reduce stand-by losses
Implementation Method 2
a rectifying bridge having input terminals respectively connected to the first and second terminals; and having either: output terminals respectively coupled by a controllable switching element to the third terminal and connected to the fourth terminal
Data Source
AI summary
An AC/DC converter includes a first terminal and a second terminal to receive an AC voltage and a third terminal and a fourth terminal to deliver a DC voltage. A rectifying bridge is provided in the converter. A controllable switching or rectifying element has a control terminal configured to receive a control current. A first switch is coupled between a supply voltage and the control terminal to inject the control current. A second switch is coupled between the control terminal and a reference voltage to extract the control current. The first and second switches are selectively actuated by a control circuit.