Self-Excited DC/DC Converter Phase-Shift Control for Stable Output
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Solution Overview
Problem
Existing self-excited oscillator circuits face issues with waveform abnormalities and increased FET loss due to reactive current in parallel resonance units, leading to a narrow range of application and instability in output voltage.
Innovation Solution
A circuit configuration involving a primary-side and secondary-side circuit with self-excited oscillator circuits, including power transmission coils, resonant capacitors, switching elements, feedback coils, and a phase shift filter, which stabilizes output voltage by controlling the inductance of primary-side control coils based on secondary-side current, thereby decoupling from self-excited oscillation conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gate bias of FET is raised or lowered to control output voltage, then output voltage control is achieved, but FET enters unsaturated operation causing waveform abnormality and increased FET loss
Solution Approach 1:
The patent introduces a resonant circuit as an intermediary between the FET and the load. The resonant circuit, comprising a resonant capacitor and parallel resonance unit, absorbs the reactive current that would otherwise cause FET loss. This mediator allows the FET to operate in its saturated region while still achieving output voltage control through the resonant circuit's impedance characteristics.
Solution Approach 2:
The patent changes the operating parameters of the resonant circuit, specifically introducing a parallel resonance unit with specific capacitance and inductance values. By adjusting the resonance frequency and impedance of this circuit, the system achieves output voltage control without requiring the FET to leave its saturated operation region, thereby maintaining low FET loss.
2Power
If reactive current increases in parallel resonance unit, then output voltage adjustment is possible, but waveform abnormality occurs deviating from self-excited oscillation conditions
Solution Approach 1:
The patent employs feedback mechanisms where the resonant circuit's oscillation frequency and amplitude are fed back to control the FET gating signal. This feedback loop ensures that even when reactive current varies for output voltage adjustment, the system maintains the necessary conditions for self-excited oscillation, preventing waveform abnormalities.
Solution Approach 2:
The patent creates a dynamic system where the resonant circuit parameters can adjust in real-time to maintain oscillation conditions. The system dynamically balances the reactive current in the parallel resonance unit with the feedback control mechanism, allowing output voltage adjustment while continuously maintaining stable self-excited oscillation waveforms.
3Device complexity
If simple circuit configuration is used, then device complexity is reduced, but output voltage stabilization becomes difficult without control IC
Solution Approach 1:
The patent implements a self-service mechanism where the resonant circuit automatically stabilizes the output voltage through its inherent resonance characteristics. The parallel resonance unit and feedback mechanism work together to self-regulate the output voltage without requiring external control ICs, thereby achieving both circuit simplicity and voltage stabilization reliability.
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 configuration allows for stable output voltage stabilization with a simple circuit design, reducing FET loss and expanding the application range by controlling reactive current and phase shift, ensuring consistent voltage delivery.
Implementation Method 1
a first feedback coil magnetically coupled to the first power transmission coil and connected to each control electrode of the first pair of switching elements
Implementation Method 2
a first resonant capacitor constituting a resonant circuit together with the first power transmission coil
Implementation Method 3
a primary-side control coil magnetically coupled to the secondary-side control coil and having a characteristic that an inductance of the primary-side control coil changes depending on a current flowing through the secondary-side control coil
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An output stabilization circuit (1) includes: a primary-side circuit (2) including first and second self-excited oscillator circuits (10, 20) connected to a direct-current power supply (BT); and a secondary-side circuit (3), wherein the first and second self-excited oscillator circuits include power transmission coils (N11, N12, N21, N22), resonant capacitors (C11, C21), switching element pairs (Q11, Q12, Q21, Q22), and feedback coils (Nf1, Nf2), the second self-excited oscillator circuit (20) further includes a phase shift filter (F20), the phase shift filter (F20) includes a primary-side control coil (Lf21) that is magnetically coupled to a secondary-side control coil (Lc31) included in the secondary-side circuit (3) and that has a characteristic that an inductance changes depending on a current flowing through the secondary-side control coil.