DC/DC Converter Leg Control for Stable Symmetric Output Voltage
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Solution Overview
Problem
Existing DC/DC converters face issues with asymmetric output terminal potentials leading to increased complexity and potential resonant current flow, which destabilizes output voltage.
Innovation Solution
A power conversion device with a DC/DC conversion unit and a control unit that includes independent current control units for each leg, using current and voltage detection to stabilize output voltage and suppress common mode current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a half-bridge circuit is used for DC/DC conversion, then the circuit structure is simpler, but the output terminal potentials are asymmetric with respect to ground potential, requiring additional prevention measures and increasing device complexity
Solution Approach 1:
The patent divides the single DC/DC conversion unit into two independent legs (positive leg and negative leg), each with its own semiconductor switching elements and control units. This segmentation allows independent control of each leg to achieve symmetric output potentials while maintaining the benefits of a distributed architecture that improves reliability.
Solution Approach 2:
The patent intentionally creates asymmetric control strategies for the positive and negative legs. The positive leg uses one control method while the negative leg uses a different control method, specifically designed to counterbalance each other and achieve symmetric output potentials with respect to ground, thereby solving the asymmetry problem of half-bridge circuits.
2Reliability
If a full-bridge circuit is used for DC output voltage, then the output terminal potentials are symmetric with respect to ground potential, but resonant current may flow through the passive filter causing output voltage oscillation
Solution Approach 1:
The patent employs feedback control mechanisms where detection units monitor the output potentials and currents, and control units adjust the switching of semiconductor elements based on this feedback. This closed-loop control suppresses resonant current by detecting oscillations and counteracting them, preventing output voltage oscillation while maintaining symmetric potentials.
Solution Approach 2:
The patent dynamically changes operating parameters such as switching frequencies and duty ratios of the semiconductor elements to avoid resonant frequencies of the passive filter. By adjusting these parameters in real-time, the system prevents resonant current flow while maintaining stable symmetric output voltages.
3Reliability
If common mode current flows to stabilize potentials with respect to ground, then output voltage stability is improved, but resonant current flows through the passive filter causing oscillation
Solution Approach 1:
The patent extracts and separately controls the common mode current component from the overall current. By using independent control units for each leg and detection units to monitor current distribution, the system identifies and suppresses the common mode current component that would otherwise cause resonant oscillation, while maintaining the beneficial potential stabilization effect.
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 device provides stabilized DC voltage by suppressing common mode current, reducing resonant current, and improving efficiency in power distribution systems.
Implementation Method 1
an output filter including a first magnetic energy storage element on a positive side, a second magnetic energy storage element on a negative side
Implementation Method 2
a first electric energy storage element and a second electric energy storage element connected in series between the positive side and the negative side
Implementation Method 3
a first current detection unit for detecting current flowing through an output end of the positive leg, a second current detection unit for detecting current flowing through an output end of the negative leg; and a voltage detection unit for detecting voltage between the positive side and the negative side
Data Source
AI summary
A power conversion device according to the present disclosure includes: a DC/DC conversion unit including positive and negative legs composed of semiconductor switching elements connected in series, an output filter having magnetic energy storage elements connected to output ends of the legs and first and second electric energy storage elements connected in series and having a neutral point, first and second current detection units, and a voltage detection unit; and a control unit composed of a single output voltage control unit which outputs a current command value, and first and second current control units which generate gate signals on the basis of the current command value and detection current values, to control ON/OFF operations of the semiconductor switching elements, independently of each other.