Bridge Converter Pre-Charging to Suppress Capacitor Inrush Current
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Solution Overview
Problem
Existing bridge circuits in motor drive devices face issues with excessive current flow during switching, potentially damaging electronic components and reducing their durability and lifetime.
Innovation Solution
A converter device with a bridge rectification circuit and capacitors connected in parallel, using a changeover switch element and control unit to manage voltage control, including pulse width modulation (PWM) and boost control to suppress inrush currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the changeover switch element is turned on during operation of the bridge circuit, then voltage control can be switched between low-voltage and high-voltage modes, but excessive current may flow through the capacitor, potentially damaging electronic components and reducing their durability and lifetime
Solution Approach 1:
The control unit performs preliminary action by controlling the switching elements to boost the capacitor voltage to a predetermined level before turning on the changeover switch element. This preliminary voltage boosting prevents excessive current flow when the switch is activated, thereby protecting electronic components while enabling voltage control versatility.
2Speed
If the switching element is turned on without preliminary voltage boosting, then the device can respond quickly to voltage control demands, but inrush current may damage the capacitor and other electronic components
Solution Approach 1:
The control unit executes preliminary voltage boosting through switching elements before activating the changeover switch element. This preliminary action eliminates inrush current by ensuring the capacitor is pre-charged to the appropriate voltage level, thereby preventing component damage while maintaining rapid response capability.
Solution Approach 2:
The control unit applies preliminary anti-action by counteracting the potential inrush current through proactive voltage boosting. By preparing the capacitor voltage in advance, the system prevents the harmful inrush current effect before it can occur, protecting components while enabling fast switching response.
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
The solution effectively suppresses inrush currents, preventing damage to electronic components and ensuring safe operation of the converter device.
Implementation Method 1
a bridge rectification circuit that rectifies AC power supplied from an AC power supply
Implementation Method 2
a plurality of capacitors connected in parallel with an output side of the bridge rectification circuit and connected in series with each other
Implementation Method 3
the control unit performs pulse width modulation (PWM) control of the changeover switch element
Data Source
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AI summary
Provided is a converter device in which a rush current flowing to a capacitor when a changeover switch element is turned on can be suppressed. A converter device (10) comprises: a bridge rectification circuit (5) comprising an AC power supply (2), a first arm part (arm 1) provided with a first switching element (Tr1), and a second arm part (arm 2) provided with a second switching element (Tr2); a plurality of series-connected capacitors (C1, C2) connected in parallel with the bridge rectification circuit (5); a changeover switch element (SW1) for switching the path of current flowing through the bridge rectification circuit (5) and the plurality of capacitors; and a control unit (24) for controlling on/off of the first switching element (Tr1)and the second switching element (Tr2) on the basis of a boost control signal generated using a carrier frequency having a frequency higher than the frequency of the AC voltage of the AC power supply (2), thereby boosting the output voltage and then switching the changeover switch element on.