Charging Device Boundary Mode Control Parasitic Resonance
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Solution Overview
Problem
Existing charging devices face inefficiencies in charging time and switching frequency due to swing current phenomena and the need for detecting resistors, particularly in continuous and discontinuous conduction modes, which affect charging efficiency and smoothness.
Innovation Solution
A charging device with boundary mode control, incorporating a transformer, power switch, detection circuit, and PWM controller, where the detection circuit detects parasitic capacitance resonance to provide a detection signal for boundary mode control, allowing for efficient switching and minimizing swing currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuous conduction mode (CCM) control is used, then charging efficiency is improved and charging time is reduced, but a detecting resistor connected to the secondary-side winding is necessary, increasing device complexity
Solution Approach 1:
The patent extracts the current detection function from the secondary-side circuit and relocates it to the primary-side circuit by detecting the resonance of parasitic capacitance of the power switch. This eliminates the need for a detecting resistor on the secondary side and the corresponding PWM control chip pin, thereby reducing device complexity while maintaining charging efficiency.
2Productivity
If continuous conduction mode (CCM) control is used, then charging efficiency is improved, but swing current phenomenon occurs in primary-side current, increasing fault risk
Solution Approach 1:
The patent converts the harmful swing current phenomenon into a useful detection signal. By detecting the resonance of parasitic capacitance of the power switch, which occurs naturally during the swing current period, the system can identify the appropriate timing to turn on the power switch. This transforms the harmful swing current into a beneficial timing reference, eliminating the need for secondary-side current detection and reducing fault risks.
3Device complexity
If discontinuous conduction mode (DCM) control is used, then device complexity is reduced by eliminating detecting resistor, but charging time increases and charging efficiency decreases
Solution Approach 1:
The patent implements a dynamic control strategy where the power switch is turned on based on real-time detection of parasitic capacitance resonance. This dynamic timing adjustment allows the system to operate in a boundary mode between CCM and DCM, achieving fast charging performance similar to CCM while eliminating the need for secondary-side current detection, thus resolving the contradiction between device complexity and charging efficiency.
4Device complexity
If discontinuous conduction mode (DCM) control is used, then blank time increases causing longer charging time, but detecting resistor is eliminated
Solution Approach 1:
The patent introduces a feedback mechanism where the detection circuit continuously monitors the resonance of parasitic capacitance of the power switch and provides feedback signals to the control circuit. This feedback enables precise timing control of the power switch turn-on moment, minimizing or eliminating the blank time period. The system dynamically adjusts the switching timing based on real-time circuit conditions, achieving fast charging without requiring secondary-side current detection.
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 solution eliminates the need for secondary-side current detection, reduces swing currents, achieves high charging efficiency with short charging time, and maintains smooth average charging current, even at higher output voltages, while using a smaller input capacitor.
Implementation Method 1
the detection circuit is used for detecting the resonance of parasitic capacitance of the power switch to provide a detection signal for boundary mode control
Data Source
AI summary
A charging device with boundary mode control is disclosed. The charging device includes a transformer, a power switch, a detection circuit and a pulse-width modulation (PWM) controller. The power switch is electrically connected to one end of a primary-side winding of the transformer. The detection circuit is electrically connected to the primary-side winding and the power switch. The detection circuit detects the resonance of the parasitic capacitance of the power switch, thereby generating a detection signal for boundary mode control. The PWM controller generates a pulse-width modulation signal for driving the power switch, and turns on the power switch according to the detection signal.