Battery Loss Handling Circuit for Reverse Battery Protection
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Solution Overview
Problem
Existing electric power systems face challenges in protecting loads from reverse battery connections, which can cause damage due to negative input voltages and reverse currents, and exhibit unpredictable behavior during battery loss events due to repeated enabling and disabling of transistors.
Innovation Solution
A controller circuit comprising a voltage subtractor, gate control circuit, and discharge circuit is used to manage transistor states, emulating an ideal diode to block negative voltages and currents, and includes a discharge circuit to stabilize transistor behavior during battery loss events by removing charge from parasitic capacitances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection system uses a transistor to block reverse battery connection, then the load is protected from negative input voltage, but the transistor exhibits repeated enabling and disabling during battery loss events causing unpredictable behavior
Solution Approach 1:
The patent extracts the problematic parasitic capacitance from the transistor's normal operation by providing an external discharge path. The discharge circuit removes charge accumulated in the parasitic capacitance between the transistor's gate and source/drain terminals, preventing this stored charge from causing false triggering and state instability during battery loss events.
Solution Approach 2:
The discharge circuit provides preliminary anti-action by proactively removing charge from the parasitic capacitance before it can cause unwanted transistor enabling. By continuously or periodically discharging the parasitic capacitance, the system prevents the harmful effect of charge accumulation that would otherwise lead to repeated enabling/disabling cycles.
2Duration of action of moving object
If the protection system blocks reverse current to allow load side additional time to operate, then the load operation time is extended, but the system becomes more complex
Solution Approach 1:
The discharge circuit serves multiple functions: it stabilizes the transistor state during battery loss events, prevents false enabling, and enables the transistor to reliably block reverse current. By making the discharge circuit a integral part of the protection system, the patent achieves multi-functionality without proportionally increasing complexity.
3Object-affected harmful factors
If the transistor is used to isolate the load from negative voltage, then the load is protected from damage, but charge accumulates in parasitic capacitances causing unpredictable transistor behavior
Solution Approach 1:
The discharge circuit acts as an intermediary between the transistor's parasitic capacitance and the rest of the circuit. It provides a controlled path for charge removal, mediating the interaction between the stored charge and the transistor operation to prevent unpredictable behavior while maintaining the protective isolation function.
Data Source
AI summary
In some examples, a controller circuit comprises: a voltage subtractor circuit having a subtractor output and first and second subtractor inputs, in which the first subtractor input is adapted to be coupled to a first current terminal of a transistor, the second subtractor input is adapted to be coupled to a second current terminal of the transistor; a gate control circuit having a gate control input and a gate control output, the gate control input coupled to the subtractor output, the gate control output adapted to be coupled to a gate of the transistor; and a discharge circuit having a discharge circuit input and a discharge circuit output, the discharge circuit input coupled to the gate control circuit, the discharge circuit output adapted to be coupled to the first current terminal of the transistor.