Voltage-to-Current Driver Circuit Suppressing Current Spikes
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Solution Overview
Problem
Voltage to current converters used to control LED strings face issues with current spikes during switching, leading to junction breakdown and malfunction, such as dimming and flickering, due to high voltage stress on NMOS transistors.
Innovation Solution
A control circuit that switches a transistor between current-conducting and current-blocking modes using a first and second current branch, diverting current from the first branch to the second branch quickly to suppress spikes and prevent junction breakdown, while maintaining a voltage bias greater than the breakdown threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transistor is used to control current through LED strings with high voltage supply, then the current control capability is improved, but the transistor junctions are subjected to voltage stress that can cause breakdown and malfunction
Solution Approach 1:
The current control path is divided into two separate branches: a first current branch for normal current conduction and a second current branch for voltage stress diversion. This segmentation allows the transistor to operate reliably by routing different current paths through different branches, preventing junction breakdown while maintaining current control capability.
Solution Approach 2:
A control circuit acts as an intermediary between the high voltage supply and the transistor, dynamically switching between the first and second current branches. This intermediary controls the timing and path of current flow, ensuring that voltage stress is diverted away from the transistor junctions while maintaining proper LED string operation.
2Speed
If current switching is performed rapidly to suppress current spikes, then the response speed is improved, but the complexity of the control circuit increases
Solution Approach 1:
The second current branch is pre-configured as a voltage stress diversion path before voltage stress occurs. The control circuit is designed to detect and respond to voltage stress conditions by switching to the pre-prepared second branch, enabling rapid response without requiring complex real-time calculation or control algorithms.
Solution Approach 2:
The control circuit dynamically switches between the first and second current branches based on real-time operating conditions. This dynamic switching allows the system to adapt to varying voltage and current conditions, suppressing current spikes and preventing junction breakdown while maintaining relatively simple circuit architecture through straightforward switching logic.
Data Source
AI summary
Various aspects of the present disclosure include a controlled current path having a load that draws current from the controlled current path. In response to a modulating voltage signal, current is controlled through the load which causes a transistor circuit, including a transistor, to switch between two current modes. Switching will subject the transistor to voltage stresses due to current in the controlled current path spiking towards a breakdown threshold of the transistor. In response to a first aspect of the modulating voltage signal and in one of the current modes, the current in the controlled current path is directed through the first current branch. In response to a second aspect of the modulating voltage signal and in the other current mode, the current in the controlled current path is diverted from the first current branch to a second current branch.