EV Charger Current Control Under Low Input Voltage
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Solution Overview
Problem
Slow chargers for electric vehicles face issues when input voltage drops below a certain threshold, leading to unpredictable problems, reduced efficiency, and user dissatisfaction, as they often interrupt charging operations.
Innovation Solution
A charger with a sensing unit and controller that implements a first monitoring mode to reduce current using PWM when input voltage is below a reference value, and a second monitoring mode to further reduce current if the voltage remains low, with a lower limit, and increases current when voltage returns to or exceeds the reference value, utilizing a Schmitt trigger circuit for voltage sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the charger interrupts charging operation when input voltage is low, then the charger and electric vehicle are protected from damage, but charging efficiency is greatly reduced and user satisfaction decreases
Solution Approach 1:
The charger dynamically adjusts the charging current based on the detected input voltage level. When voltage is low, the controller automatically reduces current magnitude while maintaining continuous charging operation, rather than interrupting service. This dynamic adaptation allows the system to operate safely across a range of voltage conditions while preserving charging functionality and user satisfaction.
Solution Approach 2:
The system changes the operating parameters (current magnitude) in response to voltage conditions. By monitoring input voltage and adjusting current output accordingly, the charger maintains reliable operation under varying voltage conditions without interrupting charging, thus protecting equipment while sustaining productivity.
2Productivity
If the charger continues charging at low voltage without interruption, then charging efficiency is maintained, but unpredictable problems may occur for the electric vehicle, charger, and charging infrastructure
Solution Approach 1:
The charger incorporates a sensing unit that continuously monitors input voltage and feeds this information back to the controller. Based on the feedback signal, the controller adjusts the charging current magnitude appropriately. This closed-loop feedback mechanism ensures the system responds adaptively to voltage conditions, maintaining safety while preserving charging operation.
Solution Approach 2:
The system dynamically adjusts current magnitude based on real-time voltage monitoring. When low voltage is detected, the controller automatically reduces current to safe levels, preventing equipment damage while maintaining continuous charging operation. This dynamic response ensures both reliability and productivity are preserved.
3Reliability
If the charger reduces current magnitude when input voltage is low, then system safety is maintained, but charging time increases
Solution Approach 1:
Instead of completely interrupting charging operation, the system applies partial action by reducing current magnitude to a lower safe level. This partial reduction maintains protective safety measures while preserving continuous charging functionality, thereby minimizing the time loss compared to full interruption and restart cycles.
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
Prevents damage to the charger and electric vehicle, maintains charging efficiency, and notifies authorities of abnormalities, ensuring safe and uninterrupted charging even at low input voltages.
Implementation Method 1
a sensing unit provided at the charger, configured to sense an input voltage input to the charger
Implementation Method 2
the controller controls magnitude of the current flowing to the electric vehicle by a pulse width modulation (PWM) method
Implementation Method 3
the sensing unit further includes a voltage sensor for sensing the magnitude of the input voltage, in which a Schmitt trigger circuit is applied
Data Source
AI summary
The present disclosure relates to a charger for preventing problems that may occur in a charger, an electric vehicle, and a charging infrastructure without interrupting charging of the charger when a voltage input to the charger is a low voltage, and includes a sensing unit provided at the charger, configured to sense an input voltage input to the charger; and a controller provided at the charger, configured to perform a first monitoring mode in which the charger is controlled to reduce current flowing to the electric vehicle when the input voltage sensed at the sensing unit is lower than a reference value which is lower than a rated voltage by a preset magnitude.