Battery Charger Transformer Terminal Reduction via Full-Bridge Topology
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Solution Overview
Problem
The existing battery chargers for electric vehicles have a large size due to the secondary windings of the transformer requiring six terminals, leading to increased insulation distance and size, especially for the secondary winding connected to the main battery with high voltage and low current, which complicates the charging circuit design.
Innovation Solution
A battery charger design that uses a transformer with a primary winding and two secondary windings, where the secondary-side circuit is configured as a full-bridge circuit with parallel-connected bodies including switching and rectifying units, allowing the charger to perform both charging operations with reduced terminal count and size, eliminating the need for center taps and minimizing the transformer's size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the transformer has secondary windings with center taps to enable both charging operations, then the charging functionality is improved, but the number of terminals increases to six, leading to increased size
Solution Approach 1:
The patent applies universality by making the secondary-side circuit perform multiple functions: it can operate as a rectifier circuit during AC charging and as an inverter circuit during DC charging. This multi-functionality eliminates the need for separate circuits and center taps, reducing the transformer terminal count from six to four while maintaining both charging capabilities
Solution Approach 2:
The patent applies inversion by reversing the traditional approach: instead of using the transformer's secondary windings to directly provide both AC and DC outputs with center taps, the invention uses a single secondary winding with switching elements that can configure the circuit topology to achieve rectification or inversion as needed. This inverts the conventional design paradigm and reduces terminal requirements
2Reliability
If the distance between terminals of the secondary winding is increased for insulation purposes, then the insulation performance is improved, but the size of the secondary winding and overall charger increases
Solution Approach 1:
The patent applies parameter changes by modifying the circuit topology and switching configuration to reduce voltage stress on individual insulation points. By using active switching elements and reconfigurable circuit paths, the effective voltage differences across insulation barriers are reduced, allowing for smaller terminal spacing while maintaining insulation reliability
3Volume of stationary object
If the number of terminals of the transformer is reduced, then the size is reduced, but the circuit design complexity increases
Solution Approach 1:
The patent applies merging by combining the rectifier circuit and inverter circuit into a single secondary-side circuit with shared components. The switching elements and reactive components serve dual purposes in both charging modes, reducing the total component count and interconnection complexity despite the increased functional requirements
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 reduces the overall size of the battery charger by minimizing the transformer's size, as the full-bridge circuit configuration reduces the number of terminals and components, while maintaining functionality for charging both the main and sub-batteries.
Implementation Method 1
a transformer including a primary winding, a first secondary winding, and a second secondary winding
Implementation Method 2
an operation to rectify an AC voltage induced in the first secondary winding and supply the rectified voltage to the main battery
Implementation Method 3
an operation to convert a DC voltage from the main battery into an AC voltage and supply the AC voltage resulting from the conversion to the first secondary winding
Data Source
AI summary
A battery charger (1000) non-concurrently performing a first operation to charge a main battery (MBA) and a sub-battery (SBA) by using an external power supply (AC), and a second operation to charge the sub-battery by using the main battery, including: a power supply circuit (1); a transformer (3); a secondary-side circuit (4) rectifying a voltage induced in a winding (302) and supplying the voltage to the main battery in a first time period for the first operation, and converting a DC voltage from the main battery into an AC voltage and supplying the AC voltage to the winding in a second time period for the second operation; a conduction angle adjustment circuit (7); and a control circuit (10), the secondary-side circuit being a full-bridge circuit including parallel-connected arms each including parallel-connected bodies connected in series, the parallel-connected bodies each including a switching unit and a rectifying unit connected in parallel.