Bi-directional Over-voltage Protection Circuit with Back-to-back MOSFETs
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Solution Overview
Problem
Existing over-voltage protection circuits impose limitations on power sources when supplying voltage to accessory power supplies, and are not time and cost efficient in their implementation.
Innovation Solution
A bi-directional over-voltage protection circuit with a voltage regulator and lockout circuit, coupled with a multi-transistor switching circuit and control circuits, allows for bidirectional current flow control, enabling efficient voltage regulation and accessory power supply management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a prior art over-voltage protection circuit with body diode is used, then the circuit can protect against over-voltage conditions, but the circuit places limitations on the power source when supplying voltage to accessory power supplies
Solution Approach 1:
The patent inverts the traditional body diode configuration by using back-to-back connected field effect transistors with their body diodes oriented in opposite directions. This inversion allows current to flow bidirectionally while maintaining over-voltage protection, thereby enabling the power source to supply voltage to accessory power supplies without limitations while preserving the reliability of over-voltage protection.
2Power
If accessory power supply is added to shunt current, then voltage available to over-voltage output increases, but device complexity increases
Solution Approach 1:
The patent merges the accessory power supply function with the over-voltage protection circuit by integrating the accessory power supply as an additional current path within the same circuit architecture. The back-to-back field effect transistors serve dual purposes: protecting against over-voltage while enabling the accessory power supply to shunt current and increase voltage available to the output, thereby achieving power enhancement without proportionally increasing device complexity.
3Ease of operation
If field effect transistor with body diode is used, then current flow can be controlled, but reverse current flow is limited by body diode forward bias
Solution Approach 1:
The patent applies the inversion principle by connecting field effect transistors in back-to-back configuration with body diodes oriented in opposite directions. This arrangement eliminates the unidirectional current limitation of a single body diode, enabling full bidirectional current flow control while maintaining ease of operation through gate drive circuit control of the transistor switches.
4Reliability
If gate drive circuit biases transistor to conduct only when voltage exceeds threshold, then over-voltage protection is maintained, but current flow is restricted during normal operation
Solution Approach 1:
The patent employs dynamic control through gate drive circuits that adjust the biasing of each field effect transistor based on real-time voltage conditions. The transistors are biased to conduct when voltage exceeds thresholds for over-voltage protection, while allowing efficient current flow during normal operation. The dynamic gating mechanism maintains reliability by enabling protection when needed while maximizing productivity by minimizing resistance during normal current flow.
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
The bi-directional over-voltage protection circuit allows for a greater input voltage swing, enabling current flow when necessary and effectively blocking current flow when required, thus optimizing power supply to both charging and accessory devices without limiting the power source.
Implementation Method 1
Field effect transistor 30 has a body diode 32
Data Source
AI summary
A bi-directional over-voltage protection circuit and a method for blocking current flow therein. The bi-directional over-voltage protection circuit comprises a regulator coupled to a lockout circuit, wherein the regulator and the lockout circuit are coupled for receiving an input signal and are coupled to a charging control circuit. A reverse path control circuit has an input coupled for receiving a control signal and an output coupled to the charging control circuit. A multi-transistor switching circuit is coupled to the forward control circuit. Preferably, the gate of each n-channel MOSFET is coupled to the charging control circuit, the drains are coupled together, and the source of one of the n-channel MOSFETS is coupled to an input and the source of the other n-channel MOSFET is coupled to an output of the bi-directional over-voltage protection circuit.