Synchronous Rectification Battery Charger Anti-Reflection Protection
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Solution Overview
Problem
Existing synchronous rectification type battery charging circuits fail to effectively cut off the anti-reflection switch tube and charging main circuit in time when the input voltage falls, leading to potential damage from reflected current, especially when charging multiple battery cells in series, due to inefficiencies and reliability issues in current methods.
Innovation Solution
A protection circuit is introduced that detects the input voltage and outputs control signals to cut off or turn on the anti-reflection switch tube and charging main circuit based on a predetermined threshold value, ensuring timely disconnection and preventing voltage and current reflection, thereby protecting the charging circuit and battery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is inserted serially to prevent battery voltage reflection, then reliability is improved, but efficiency deteriorates due to large positive voltage drop
Solution Approach 1:
The patent changes the electrical parameter (voltage drop) by replacing the diode with a MOSFET operated in linear region as an active switch. This active switch can be controlled to have very low on-resistance, reducing the voltage drop from typical diode levels (0.7V) to millivolt levels, thereby maintaining protection functionality while dramatically reducing energy loss.
Solution Approach 2:
The patent substitutes the passive diode protection mechanism with an active MOSFET-based protection circuit that uses electrical control signals. Instead of relying on the diode's inherent unidirectional conduction property, the system uses an electronically controlled switch that can be rapidly activated/deactivated, providing more efficient and controllable protection.
2Loss of energy
If a MOSFET is added in parallel to the anti-reflection diode to improve efficiency, then energy loss is reduced, but device complexity increases and miniaturization becomes difficult due to heating
Solution Approach 1:
The patent merges the protection function with the existing synchronous rectification MOSFETs (Q1, Q2) by using them as the anti-reflection switches. Instead of adding separate protection components, the control circuit leverages the already-present power MOSFETs, eliminating the need for additional parallel MOSFETs and reducing overall device complexity while maintaining low energy loss.
Solution Approach 2:
The patent makes the synchronous rectification MOSFETs serve dual functions: synchronous rectification during normal charging operation and anti-reflection protection during input voltage failure. This multi-functionality eliminates the need for dedicated protection components, simplifying the circuit structure and reducing thermal issues.
3Adaptability or versatility
If voltage comparison method is used to control cutting off, then adaptability is improved, but reliability deteriorates due to voltage ripple and sampling delay
Solution Approach 1:
The patent implements preliminary action by monitoring the input voltage and triggering protection before the actual voltage reflection damage occurs. The control circuit detects input voltage abnormalities and proactively activates the anti-reflection MOSFETs to block reflected current, preventing damage before it happens rather than reacting after detection.
Solution Approach 2:
The patent employs feedback control where the control circuit continuously monitors the input voltage status and the state of synchronous rectification, adjusting the switching state of anti-reflection MOSFETs accordingly. This closed-loop feedback ensures reliable timely protection while adapting to different operating conditions.
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 enables real-time detection and timely cutting off of the charging circuit, preventing damage and maintaining high efficiency, reliability, and miniaturization of the charging circuit, even when charging multiple batteries.
Implementation Method 1
a protection circuit, connected to the voltage input, for outputting an indicating signal for representing whether an operation of preventing charging voltage from reflecting is not performed or is performed, according to a value of an input voltage of the synchronous rectification type battery charging circuit
Data Source
AI summary
The present invention discloses a synchronous rectification type battery charging circuit, comprising: a charging main circuit for charging a battery; an anti-reflection switch tube, connected between a voltage input of the synchronous rectification type battery charging circuit and the charging main circuit; and a control logic and driving circuit, for controlling turning-on and cutting-off of the charging main circuit and the anti-reflection switch tube, characterized in that the synchronous rectification type battery charging circuit further including a protection circuit which outputs to the control logic and driving circuit an indicating signal for representing turning-on or cutting-off of the charging main circuit and the anti-reflection switch tube, according to a value of an input voltage of the synchronous rectification type battery charging circuit.