Full-Bridge Resonant Converter Control Using Primary Charge Feedback
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Solution Overview
Problem
Conventional full-bridge series resonant converters with dual-loop control have limited bandwidth, resulting in poor dynamic response and inability to eliminate ripples in output voltage and current due to the use of a Rogowski coil on the secondary side for current sensing.
Innovation Solution
A resonant converter design that uses a current sensor on the primary side to generate a current differential signal, which is then double integrated to obtain an electric charge signal, allowing for control of primary switches based on input and output voltages to improve dynamic response and eliminate ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual-loop control with variable-frequency modulation is used, then voltage and current control is achieved, but bandwidth is small and dynamic response is poor
Solution Approach 1:
The patent changes the control parameter from variable-frequency modulation to fixed-frequency pulse width modulation. By fixing the switching frequency and modulating the pulse width based on the charge signal, the system achieves wider bandwidth and better dynamic response while maintaining effective voltage and current control through the full-bridge switch circuit.
2Measurement precision
If Rogowski coil is disposed on secondary side for current sensing, then current differential signal is obtained, but dynamic response is limited and ripples cannot be eliminated
Solution Approach 1:
Instead of sensing current on the secondary side as in conventional designs, the patent inverts the sensing location to the primary side using a current sensor. The sensor measures primary current, and through double integration to obtain charge information, this primary-side sensing approach enables better dynamic response and ripple elimination while maintaining accurate current measurement capability.
3Reliability
If conventional average current control is used, then output current is regulated, but output voltage and current ripples persist
Solution Approach 1:
The patent implements a feedback mechanism where the charge signal obtained from double integration of the primary current is fed back to control the full-bridge switch circuit. This charge-based feedback control enables the system to regulate both output voltage and current while effectively reducing ripples, as the charge signal provides real-time information about the energy transfer 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
The solution significantly enhances the dynamic response of the resonant converter, increasing its bandwidth and eliminating output voltage and current ripples, resulting in a much improved performance compared to conventional systems.
Implementation Method 1
When a current flowing through the resonant inductor passes through the current sensor, the current sensor generates a current differential signal correspondingly
Implementation Method 2
The resonant circuit is electrically connected to the full-bridge switch circuit and includes a resonant inductor
Data Source
Figure 1
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AI summary
A resonant converter (1) including a full-bridge switch circuit (11), a resonant circuit (12), a transformer (T), a rectifier circuit (13), a current sensor (14) and a controller (15) is provided. The full-bridge switch circuit (11) includes switches (Q1, Q2, Q3, Q4). The resonant circuit (12) is electrically connected to the full-bridge switch circuit (11) and includes a resonant inductor (Lr). The transformer (T) includes primary and secondary windings, and the primary winding is electrically connected to the resonant circuit (12). The rectifier circuit (13) is electrically connected to the secondary winding. The current sensor (14) is electrically connected to the resonant circuit (12). When a current (Ir) flowing through the resonant inductor (Lr) passes through the current sensor (14), the current sensor (14) generates a current differential signal correspondingly. The controller (15) performs double integration on the current differential signal to acquire an electric charge signal (Qcr) and controls operation of the switches of the full-bridge switch circuit (11) according to the electric charge signal (Qcr) and the input and output voltages (Vin, Vo) of the resonant converter (1).