DC/DC Converter Secondary Side Reflux Circuit Surge Suppression
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Solution Overview
Problem
Conventional DC/DC converters face inefficiencies and size constraints due to surge voltage suppression methods, where the clamping voltage is dependent on load voltage and snubber circuit resistance, leading to increased losses and heat-related issues when load voltage varies.
Innovation Solution
A DC/DC converter design incorporating a secondary side reflux circuit that diverts load current during transformer primary side voltage absence, reducing reflux current through the rectifier circuit and enabling Zero Volt Switching (ZVS) feasibility while suppressing surge generation using soft switching methods without a snubber circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a snubber circuit is provided to suppress surge voltage, then the surge voltage is clamped and rectifier circuit elements are protected, but the clamping voltage becomes highly dependent on load voltage and snubber resistance, causing increased losses when load voltage varies
Solution Approach 1:
The patent extracts and eliminates the snubber circuit from the system by implementing a secondary side reflux circuit that diverts load current during transformer primary side voltage absence. This removes the source of energy losses while maintaining surge suppression functionality through alternative means.
Solution Approach 2:
The patent introduces a secondary side reflux circuit as an intermediary mechanism that mediates between the transformer and rectifier circuit. This reflux circuit diverts load current during periods when primary side voltage is absent, preventing direct surge interaction with the rectifier circuit and eliminating the need for snubber-based clamping.
2Reliability
If the resistance value of the snubber circuit is reduced to ensure efficient surge absorption when load voltage is high, then surge voltage is absorbed efficiently, but loss generated by the resistor increases particularly when load voltage is low
Solution Approach 1:
The patent removes the snubber circuit entirely from the system, replacing it with a secondary side reflux circuit that achieves surge suppression without the energy losses inherent in resistive clamping mechanisms. This eliminates the fundamental trade-off between suppression efficiency and energy loss.
Solution Approach 2:
The patent changes the operational parameters by implementing soft switching methods that operate at zero voltage switching (ZVS) conditions. This fundamentally alters how surge suppression is achieved, moving from resistive clamping to controlled switching that minimizes energy dissipation while maintaining suppression effectiveness.
3Reliability
If conventional surge suppression methods are used with load voltage variation, then surge voltage is clamped, but heat-related problems occur and device size increases
Solution Approach 1:
The patent extracts and removes the heat-generating snubber circuit from the system. By implementing a secondary side reflux circuit with soft switching, the solution eliminates the resistive heating problem while maintaining surge suppression functionality.
Solution Approach 2:
The secondary side reflux circuit acts as an intermediary that prevents direct energy dissipation as heat. By diverting load current during primary voltage absence and using soft switching transitions, the system suppresses surges without the thermal losses associated with traditional snubber circuits.
4Reliability
If a snubber circuit is provided to protect rectifier circuit elements, then overvoltage protection is achieved, but the device complexity increases
Solution Approach 1:
The patent merges the surge suppression function with the existing transformer and rectifier circuit operations. The secondary side reflux circuit integrates with the transformer primary side voltage cycles, utilizing the same magnetic coupling and switching mechanisms already present in the system, thereby avoiding additional complexity.
Solution Approach 2:
The secondary side reflux circuit serves multiple functions: it suppresses surge voltage, enables soft switching operation, and improves overall system efficiency. By consolidating these functions into a single integrated mechanism rather than adding separate protective circuits, the patent reduces overall device complexity while enhancing performance.
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 improves efficiency and reduces the size of the DC/DC converter while effectively suppressing surge generation due to recovery currents, maintaining ZVS feasibility and minimizing losses in semiconductor switching elements.
Implementation Method 1
a primary side and a secondary side are insulated by a transformer
Implementation Method 2
positive and negative rectangular wave-shaped pulse trains transmitted from a primary side to a secondary side via a transformer are converted into rectangular wave-shaped pulse trains of an identical polarity by being rectified using a rectifier circuit
Implementation Method 3
the surge voltage is stored in the capacitor
Data Source
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Figure 2
Figure 3A
AI summary
This invention is concerning a secondary side reflux circuit having a series circuit that is formed by connecting a secondary side reflux diode and a reflux reactor in series, the secondary side reflux circuit being provided on a secondary side of a DC/DC converter that subjects DC power from a DC power supply to DC/DC conversion and outputs the converted power to a load connected in series to a smoothing reactor connected to an output side of a rectifier circuit having a plurality of rectifying semiconductor switching elements. During a period in which a voltage from the DC power supply is not applied to a primary side of a transformer, the secondary side reflux circuit diverts a load current flowing through a load so as to return the load current to the load.