Heater Control Unit Diode Network for Transient Oscillation Management
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Solution Overview
Problem
Existing heater control units (HCUs) for exhaust aftertreatment systems face challenges in efficiently accommodating high inductances in electrical wiring harnesses, leading to transient voltage and current oscillations when switching the heater on and off, which can result in inefficiencies and potential component damage.
Innovation Solution
The proposed HCU design includes a switch responsive to control signals, coupled with capacitors and diodes to manage current flow through different paths, enabling efficient current flow when on and blocking it when off, thereby mitigating oscillations and optimizing energy dissipation during the off state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HCU switches off the heater, then the heater stops heating, but transient voltage and current oscillations occur due to energy stored in the wiring harness inductance
Solution Approach 1:
A diode is introduced as an intermediary component to manage the transient energy dissipation path. The diode enables controlled current flow in one direction during switch-off, allowing the stored inductive energy to dissipate safely through a designated path rather than causing harmful oscillations throughout the circuit.
Solution Approach 2:
The harmful transient oscillations caused by wiring harness inductance are converted into a beneficial controlled dissipation process. By providing a dedicated path with a diode, the previously harmful energy release is transformed into a controlled and manageable event that protects the HCU and other components.
2Reliability
If capacitors are added to accommodate transient current oscillations, then the HCU can handle the oscillations, but the device complexity increases
Solution Approach 1:
The function of handling transient oscillations is extracted from the main HCU switching circuit and assigned to a separate, dedicated dissipation path. This separation allows the main HCU to focus on its primary switching function while the extracted transient management function is handled independently by the diode and associated components.
Solution Approach 2:
Rather than making the entire HCU circuit more complex, the transient management capability is applied locally where needed - specifically in the transient dissipation path. The diode and associated components are strategically placed only where transient energy needs to be managed, leaving the rest of the circuit simple and efficient.
3Object-generated harmful factors
If the wiring harness inductance is reduced, then transient oscillations are minimized, but the wiring harness design becomes more difficult and costly
Solution Approach 1:
The system provides its own transient management capability through the integrated diode and capacitor network, making the wiring harness design independent of transient suppression requirements. The wiring harness can be designed for simplicity and cost-effectiveness without needing to minimize inductance, as the transient management is handled by the self-contained dissipation path in the HCU.
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
This configuration reduces transient current oscillations, minimizes RMS current, and allows for efficient manufacturing, enhancing the performance and reliability of the HCU by effectively managing energy storage and discharge in the wiring harness.
Implementation Method 1
a first diode coupled in series with the one or more capacitors, the series-coupled first diode and one or more capacitors configured to provide current flow about a second path between the first and second wiring harness sections, wherein when the switch is in the off state the first diode enables current flow about the second path through the one or more capacitors in a first direction, and blocks current flow about the second path through the one or more capacitors in a second direction opposite the first direction
Implementation Method 2
The HCU may include capacitors to help accommodate the transient current oscillations
Implementation Method 3
The wiring harness sections used to couple the battery, HCU and heater in aftertreatment systems of these types may have relatively high inductances (e.g., between 4 μH and 10 μH). The HCU may be configured to accommodate transient voltage and current oscillations produced by energy stored in the wiring harness sections when the HCU is switched off.
Data Source
AI summary
A heater control unit and wiring harness for coupling a battery to an exhaust after treatment system of an internal combustion engine. The heater control unit is configured with one or more capacitors and diodes to accommodate transient oscillating current flows that may be caused by energy stored in the wiring harness when the heater control unit switches between on and off states.