H-Bridge Transformer Voltage Control for Compact Power Adapters
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Solution Overview
Problem
Power adapters designed for electronic devices face challenges in efficiently managing high voltage due to the physical size requirements of high-voltage components needed for power factor correction, which can interfere with other design considerations.
Innovation Solution
The use of an H-bridge transformer with a center-tapped secondary coil and a controller that adjusts the voltage across the primary coil by controlling switches, allowing for efficient voltage management and reducing the need for large high-voltage components through strategic switching and inductor placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power factor correction circuit steps-up the input voltage to a higher voltage, then the voltage handling capability is improved, but the physical size of high-voltage components increases
Solution Approach 1:
The patent changes the operating parameters of the transformer by controlling the voltage across the primary coil through an H-bridge circuit. By adjusting the RMS voltage and frequency of the primary coil voltage, the transformer can achieve the required voltage transformation ratio without requiring excessive turns ratios, thereby reducing the physical size of high-voltage components while maintaining voltage handling capability.
Solution Approach 2:
The patent employs dynamic control of the H-bridge switches to adjust the voltage and frequency applied to the primary coil in real-time. This dynamic operation allows the transformer to operate at optimal points across varying load conditions, enabling compact design by avoiding oversized components that would be required for static, worst-case design scenarios.
2Reliability
If high-voltage components are used to safely handle stepped-up voltage, then the voltage safety is improved, but the adapter volume increases
Solution Approach 1:
The H-bridge circuit serves multiple functions: it controls the voltage magnitude, adjusts the frequency, and enables bidirectional power flow capability. This multi-functionality allows a single circuit topology to achieve voltage safety through controlled operation while avoiding the need for separate, additional high-voltage isolation components that would increase adapter volume.
Solution Approach 2:
By dynamically changing the voltage and frequency parameters applied to the transformer primary, the system can maintain safe operating conditions across varying loads. The controller adjusts these parameters to keep the transformer operating within safe flux density limits, eliminating the need for oversized magnetic components designed for worst-case scenarios.
3Power
If the voltage across the primary coil is increased to improve power factor correction, then the power factor improvement is improved, but the transformer core flux increases
Solution Approach 1:
The patent incorporates feedback control where the controller monitors the operating conditions and adjusts the H-bridge switch timing and duty cycle accordingly. This feedback mechanism ensures that the voltage and frequency applied to the primary coil are optimized to maintain unity power factor while preventing transformer core flux from exceeding safe limits, thus resolving the contradiction between power factor improvement and core flux control.
Solution Approach 2:
The H-bridge circuit operates by applying periodic voltage pulses to the transformer primary at a frequency higher than the line frequency. By controlling the duty cycle and frequency of these periodic pulses, the system can achieve power factor correction through resonant operation while maintaining the transformer core flux within safe operating boundaries through precise timing control.
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 approach enables compact power adapter designs that effectively handle high voltages while minimizing the physical footprint of high-voltage components, improving efficiency and adaptability to varying power demands.
Implementation Method 1
the PFC circuit steps-up the input voltage to a higher voltage
Data Source
AI summary
An adapter for electrical power that includes a rectifier coupled to a transformer with a primary coil and a secondary coil. The secondary coil includes a first end tap, a second end tap, and a center tap. A first switch is coupled between the first end tap and a primary side ground. A second switch is coupled between the second end tap and the primary side ground. A controller is coupled to the first switch and to the second switch so that during one or more intervals, the first switch and the second switch are alternately open and closed a predetermined number of times, wherein the initial switch closed each interval alternates between the first switch and the second switch, and after the predetermined number of times, both the first switch and the second switch are opened for a predetermined time period.