Mild Hybrid Charging System Preventing Super Capacitor Reverse Charge
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Solution Overview
Problem
In mild hybrid vehicle charging systems, the super capacitor can be reverse charged from the battery due to self-discharge, especially when the charging voltage of the super capacitor is lower than the battery voltage, leading to high current flows and inefficiencies during system assembly.
Innovation Solution
A charging system for mild hybrid vehicles that includes a non-insulated buck type DC-DC converter with a switching element without a body diode, a circuit interruption transistor, a relay, or a forwardly biased diode to prevent energy from flowing from the battery to the super capacitor, thereby preventing reverse charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-insulated buck type DC-DC converter is used in a mild hybrid vehicle charging system, then device complexity is reduced and ease of manufacture is improved, but the super capacitor can be reverse charged from the battery when its voltage is lower, causing high current flows and energy loss
Solution Approach 1:
A body diode is introduced as an intermediary component in the DC-DC converter circuit. The body diode is connected in parallel with the switching element and acts as a mediator to prevent reverse charging by blocking current flow from the battery to the super capacitor when the super capacitor voltage is lower than the battery voltage, thus eliminating the need for complex insulation structures while preventing energy loss.
Solution Approach 2:
The body diode provides preliminary protection against reverse charging by being pre-configured in the circuit to automatically block harmful current flow. When the super capacitor voltage drops below battery voltage, the body diode immediately prevents current from flowing backward, thereby preemptively stopping the reverse charging process before it can cause significant energy loss or damage.
2Ease of manufacture
If the super capacitor voltage is lower than battery voltage during system assembly, then the system can be assembled and operated, but reverse charging occurs causing high current flows that reduce reliability
Solution Approach 1:
The body diode serves as a protective intermediary that allows system assembly and operation to proceed normally while simultaneously preventing harmful reverse charging currents. The diode is integrated into the converter circuit in a way that does not interfere with normal charging operations but automatically activates to block reverse current when voltage conditions warrant, thus maintaining reliability without compromising ease of assembly.
Solution Approach 2:
The body diode provides self-service protection by automatically detecting voltage conditions and blocking reverse current without requiring external control or intervention. The diode's inherent electrical properties cause it to naturally conduct in the forward direction and block in the reverse direction, providing automatic protection that enhances reliability while requiring no additional control systems or complex assembly procedures.
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 reverse charging of the super capacitor from the battery, reducing inefficiencies and ensuring stable voltage levels, especially during initial system assembly when the super capacitor's voltage is lowest.
Implementation Method 1
a non-insulated buck type DC-DC converter with a switching element without a body diode, a circuit interruption transistor, a relay, or a forwardly biased diode to prevent energy from flowing from the battery to the super capacitor
Implementation Method 2
a switching element without a body diode, a circuit interruption transistor
Implementation Method 3
a forwardly biased diode to prevent energy from flowing from the battery to the super capacitor
Data Source
AI summary
A charging system for a hybrid vehicle which prevents a super capacitor from being reverse charged. In the illustrative charging system a DC-DC converter is connected to the inverter and configured to receive the DC electricity from the inverter and drop voltage. A battery is configured to receive the DC electricity from the DC-DC converter and to be charged by the DC electricity. Finally, a means for preventing reverse charging is mounted on a path between the super capacitor and the battery and is configured to prevent energy from flowing from the battery to the super capacitor.