Single-Stage On-Board Charger With PFC and Battery Charge Control
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Solution Overview
Problem
The existing two-stage isolated on-board chargers require a large number of power components, increasing the overall cost, and there is a need to enable a single-stage isolated on-board charger to function as a two-stage charger efficiently with Power Factor Correction (PFC) and control battery-side voltage or current.
Innovation Solution
A method and structure for a single-stage isolated on-board charger that includes a controllable bridge-type AC/AC and AC/DC conversion circuits connected through a transformer, with phase-shift control to achieve soft-switching and PFC functionality by regulating grid-side current based on battery-side voltage and grid-side voltage phases, reducing the number of components and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a two-stage isolated on-board charger structure is used, then the PFC function and battery-side voltage/current control are achieved, but the number of power components increases and overall cost increases
Solution Approach 1:
The patent merges the PFC circuit and isolated DC/DC conversion circuit into a single-stage integrated structure. The AC/AC conversion circuit performs both PFC and isolation functions while the AC/DC conversion circuit handles battery charging, reducing the number of power components while maintaining both PFC capability and battery control functionality.
Solution Approach 2:
The AC/AC conversion circuit is designed to perform multiple functions simultaneously: power factor correction, electrical isolation, and voltage regulation. This multi-functional design allows the single-stage charger to achieve the same capabilities as the two-stage charger with fewer components.
2Device complexity
If a single-stage isolated on-board charger structure is used, then the number of power components and overall cost are reduced, but the PFC function and battery-side voltage/current control capability are compromised
Solution Approach 1:
The patent combines the PFC and DC/DC functions into an integrated single-stage architecture where the AC/AC conversion circuit handles both PFC and isolation, and the AC/DC conversion circuit manages battery charging, thereby maintaining full functionality with reduced component count.
Solution Approach 2:
The patent implements feedback control mechanisms where the controller regulates the AC/AC and AC/DC conversion circuits based on sampled battery-side voltage and grid-side current parameters. This feedback ensures that the single-stage charger maintains accurate PFC performance and battery voltage/current control comparable to two-stage designs.
3Loss of energy
If phase-shift control is implemented in the single-stage charger, then soft-switching is achieved and efficiency is improved, but control complexity increases
Solution Approach 1:
The patent employs dynamic phase-shift control where the phase difference between switching signals of the AC/AC and AC/DC conversion circuits is continuously adjusted based on operating conditions. This dynamic adjustment enables soft-switching across varying load and line conditions, minimizing switching losses while the controller manages the complexity through coordinated phase 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
The single-stage charger achieves PFC function and controls battery-side voltage/current, reduces component count, lowers costs, and enhances efficiency while maintaining soft-switching capabilities.
Implementation Method 1
A transformer side of a controllable bridge-type AC/AC conversion circuit is connected to an alternating-current side of a controllable bridge-type AC/DC conversion circuit through a transformer
Data Source
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AI summary
An on-board charger control method, wherein a transformer side of an AC/AC conversion circuit (30) is connected to an alternating current side of an AC/DC conversion circuit (40) by means of a transformer (10), so that an on-board charger is of a single-stage structure; in a stable state, an instantaneous sampling value of a grid-side current is equal to an instantaneous reference value thereof, and the instantaneous reference value of the grid-side current is determined by means of the phase of an instantaneous sampling value of a grid-side voltage and a reference peak value of the grid-side current, so that the on-board charger has a PFC function; a battery-side charging power is indirectly controlled by means of controlling the grid-side current, so that the on-board charger has a battery-side voltage and current control function; phase shift control on the two conversion circuits enables power devices in the two conversion circuits to achieve soft switching, and the single-stage structure allows currents to flow through fewer devices, thus improving efficiency; and therefore, by using the single-stage structure, the present invention efficiently achieves the PFC function and the battery-side voltage and current control function of two-stage isolated on-board chargers. Further disclosed is an on-board charger.