Battery Charger Zero-Crossing Control with Dynamic Reference
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Solution Overview
Problem
Conventional battery chargers for motorcycles face difficulties in performing zero-crossing control during sudden load changes, particularly when the battery voltage is high, as the load imbalance among phases can prevent detection of zero-crossings, leading to ineffective control.
Innovation Solution
A battery charger design that includes rectifiers, switches, a zero-crossing detector, and a detection reference changer, where the detection reference changer adjusts the zero-crossing detection reference by supplying an offset voltage or changing the reference voltage to ensure accurate detection even during sudden load changes, allowing for proper zero-crossing control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If synchronous switching control in units of three phases is used to suppress load imbalance, then phase balance is improved, but zero-crossing control still cannot be sufficiently achieved during sudden load changes
Solution Approach 1:
The patent changes the detection reference parameter dynamically based on battery voltage levels. When battery voltage is high (above threshold), a first detection reference is used that allows zero-crossing detection even when AC output swings only in positive voltage region. When battery voltage is low (below threshold), a second detection reference is used for normal operation. This parameter adaptation resolves the contradiction by making the detection system flexible enough to handle sudden load changes while maintaining phase balance control.
2Ease of operation
If conventional zero-crossing detection is used, then normal operation is maintained, but zero-crossing cannot be detected when AC output swings only in positive voltage region
Solution Approach 1:
The patent makes the detection reference dynamic rather than fixed. The detection reference changes based on battery voltage conditions, allowing the system to adapt between normal operation mode and sudden load change mode. This dynamic adjustment enables zero-crossing detection to work in both normal AC output conditions and abnormal positive-voltage-only swinging conditions, resolving the contradiction between ease of operation and measurement precision.
3Device complexity
If detection reference is fixed, then system complexity is reduced, but zero-crossing detection fails under sudden load changes
Solution Approach 1:
The patent prepares multiple detection reference values in advance (first detection reference for high battery voltage, second detection reference for low battery voltage) and selects the appropriate one based on real-time battery voltage monitoring. This preliminary preparation of multiple references with conditional selection enables reliable zero-crossing detection under varying load conditions without requiring complex real-time calculation or adjustment mechanisms, thus resolving the contradiction between device complexity and reliability.
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 the battery charger to effectively perform zero-crossing control even under conditions of sudden load changes, ensuring stable and efficient charging by adjusting the detection reference to account for rising AC outputs in the positive voltage region.
Implementation Method 1
the zero-crossing detector is configured to compare each of the AC voltages with a reference voltage to detect the zero-crossings
Implementation Method 2
The detection reference changer may include a voltage generator configured to generate an offset voltage that is a predetermined negative voltage
Data Source
AI summary
A battery charger includes a plurality of rectifier, a plurality of switches respectively for the plurality of rectifier elements, a zero-crossing detector, a switch controller, and a detection reference changer. The plurality of rectifier elements rectify AC voltages of three phases output from a power generator. The plurality of rectifier elements, in an off-state, causes the plurality of rectifier elements to rectify the AC voltages to charge a battery. The plurality of rectifier elements, in an on-state, causes the AC voltages to be short-circuited to a negative side of the battery. The zero-crossing detector detects zero-crossings of the AC voltages. The switch controller outputs, based on the zero crossings, a gate signal for turning on and off the plurality of switches. The detection reference changer changes a reference for the zero-crossing detector to detect the zero crossings.