Simulated Battery Cell Protection Circuit Using MOSFET Short-Circuit
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Solution Overview
Problem
In hardware-in-the-loop test systems, simulated battery cells can experience impermissibly high cell voltages and power losses due to overloads or malfunctions, leading to potential damage and complex circuitry requirements for protection.
Innovation Solution
A protective circuit for simulated battery cells, featuring a MOSFET connected to the output, a capacitor to charge the MOSFET gate, and a threshold voltage detection device to control the MOSFET's operation, allowing for short-circuiting when overvoltage is detected and releasing when safe, thereby preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard overload shutdown procedure is applied to a power source, then protection against overloads is achieved, but it cannot be applied to a power sink and would require significantly more complex circuitry to open an overloaded battery cell
Solution Approach 1:
Instead of opening the circuit to protect against overloads (standard approach for power sources), the patent applies the opposite approach for power sinks: it short-circuits the overloaded battery cell through the MOSFET. This inversion of the protection mechanism allows effective protection while maintaining relatively simple circuitry, as the MOSFET-based short-circuit approach is less complex than circuitry required to safely open an overloaded cell.
2Loss of energy
If the gate electrode is released when capacitor voltage drops, then the MOSFET stops conducting, but releasing too late causes the MOSFET to transition into a partially conductive state resulting in high power dissipation
Solution Approach 1:
The patent uses a threshold voltage detection device that monitors the capacitor voltage and releases the gate electrode when the voltage drops below a predetermined threshold. This preliminary action ensures the MOSFET is turned off before it transitions into a partially conductive state that would cause high power dissipation. The threshold-based triggering provides timely protection while preventing energy loss.
3Reliability
If multiple battery cells are protected individually, then each cell is protected from overvoltage, but the overall system complexity increases
Solution Approach 1:
The patent describes a protection circuit that can be applied to multiple battery cells in series, where a single MOSFET can short-circuit multiple cells simultaneously. The overvoltage detection device monitors the combined voltage of multiple cells and triggers the protection mechanism for the entire group. This multi-functional approach provides cell-level protection while reducing overall system complexity compared to individually protecting each cell.
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
Effectively protects the simulator from consequential damage by short-circuiting the battery cell during overvoltage events, reducing the complexity and risk of damage associated with traditional circuitry solutions.
Implementation Method 1
a capacitor (3) connected to a gate electrode (7) of the at least one MOSFET (2), wherein the overvoltage detection device (4) is configured to charge the capacitor (3) with the output voltage when an overvoltage limit of the output voltage is exceeded
Data Source
Figure 1
AI summary
The invention relates to a protection circuit for a simulated battery cell (1) comprising the simulated battery cell (1) with an output (6) having an output voltage, at least one MOSFET (2) connected to the output (6) of the simulated battery cell (1) for short-circuiting the same, a capacitor (3) connected to a gate electrode (7) of the at least one MOSFET (2), an overvoltage detection device (4) configured to charge the capacitor (3) with the output voltage when an overvoltage limit of the output voltage is exceeded, and a threshold voltage detection device (5) configured to release the gate electrode (7) when a voltage on the capacitor (3) falls below a threshold value.