Self-Excited DC/DC Converter Phase-Shift Control for Stable Output
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Solution Overview
Problem
Self-excited oscillator circuits face issues with waveform abnormalities and increased FET loss due to reactive current in parallel resonance units, limiting their application range and stability of output voltage.
Innovation Solution
A circuit configuration involving a primary-side circuit with two self-excited oscillator circuits and a secondary-side circuit, utilizing power transmission coils, resonant capacitors, switching elements, feedback coils, and a phase shift filter to stabilize output voltage by controlling current magnitude and phase shift based on output voltage, without relying on control ICs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a self-excited oscillator circuit is used to simplify the circuit configuration, then the device complexity is reduced, but the output voltage stability deteriorates
Solution Approach 1:
The patent introduces a feedback mechanism where the output voltage is detected and fed back to the control electrode of the switching element through a feedback coil. This feedback loop enables automatic regulation of the output voltage by adjusting the switching element's operation based on the detected output level, thereby stabilizing the output without requiring complex external control circuits.
Solution Approach 2:
The self-excited oscillator circuit inherently generates its own oscillation signal through the resonant circuit and feedback coil, eliminating the need for external control ICs or separate oscillation generation circuits. The circuit serves itself by using the output voltage detection and feedback to automatically regulate its own operation, achieving voltage stabilization through self-service mechanisms.
2Reliability
If gate bias of FET is adjusted to control output voltage, then the output voltage stability is improved, but the FET loss increases due to reactive current
Solution Approach 1:
The patent changes the control parameter from gate bias voltage adjustment to phase-shifted pulse width modulation. By controlling the switching element with phase-shifted pulses that are synchronized with the resonant oscillation, the circuit achieves voltage regulation while maintaining the FET in optimal switching mode, thereby reducing reactive current and minimizing FET loss compared to continuous gate bias adjustment.
Solution Approach 2:
The control electrode receives periodic phase-shifted pulses that are synchronized with the resonant oscillation frequency. This periodic action allows the switching element to operate in discrete switching states rather than continuous analog control, reducing the time the FET spends in high-loss transition regions and minimizing reactive current flow through the parallel resonance unit.
3Reliability
If gate bias is raised or lowered to control output, then output voltage control is achieved, but waveform abnormality occurs deviating from self-excited oscillation conditions
Solution Approach 1:
The circuit preliminarily establishes the resonant oscillation conditions through the resonant circuit (inductor and capacitor) before output control is needed. The self-excited oscillator is designed to naturally generate stable sinusoidal waves at the resonant frequency, and the subsequent control actions are designed to maintain rather than disrupt these pre-established oscillation conditions, preventing waveform abnormalities.
Solution Approach 2:
The feedback coil detects the output voltage waveform and feeds this information back to the control electrode. This feedback mechanism continuously monitors the waveform quality and adjusts the switching element's operation to maintain proper self-excited oscillation conditions, preventing waveform abnormalities by correcting deviations in real-time based on the detected output state.
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 effectively stabilizes output voltage with a simple circuit design, reducing FET loss and waveform abnormalities, thereby expanding the application range of self-excited oscillator circuits.
Implementation Method 1
a feedback coil magnetically coupled to the 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
Data Source
AI summary
An output stabilization circuit includes: a primary-side circuit including first and second self-excited oscillator circuits connected to a direct-current power supply; and a secondary-side circuit, wherein the first and second self-excited oscillator circuits include power transmission coils, resonant capacitors, switching element pairs, and feedback coils, the second self-excited oscillator circuit further includes a phase shift filter, the phase shift filter includes a primary-side control coil that is magnetically coupled to a secondary-side control coil included in the secondary-side circuit and that has a characteristic that an inductance changes depending on a current flowing through the secondary-side control coil.