LED Driver Circuit Using Time-Varying Offset to Prevent Current Spikes
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Solution Overview
Problem
Single stage driver designs for LED lighting face challenges in avoiding input current spikes, which reduce power factor and total harmonic distortion, often requiring larger and more expensive components to mitigate these issues.
Innovation Solution
A driving circuit that uses a time-varying offset to modulate the regulated current, ensuring the voltage across the energy storage component remains above the supply voltage, thereby preventing input current spikes without increasing component size or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stage driver topology is used to reduce cost, then device complexity and component cost are reduced, but input current spikes occur which reduce power factor and increase total harmonic distortion
Solution Approach 1:
The patent applies dynamics by making the reference current time-varying instead of fixed. The reference current is modulated with a time-varying offset signal that synchronizes with the input voltage ripple frequency, allowing the driver to dynamically adjust the energy storage capacitor discharge rate to prevent voltage drops below input voltage, thereby eliminating current spikes while maintaining single-stage topology
Solution Approach 2:
The patent changes the parameter of reference current from a static value to a time-varying signal. By modulating the reference current with an offset that varies at the input ripple frequency, the control parameter adapts to the instantaneous voltage conditions, preventing uncontrolled capacitor charging currents while maintaining cost-effective single-stage architecture
2Object-generated harmful factors
If component values are selected to remove current spikes, then input current quality improves, but system efficiency decreases and component size and cost increase
Solution Approach 1:
Instead of changing physical component values, the patent changes the electrical parameter of reference current to be time-varying. This software-based control approach eliminates current spikes through intelligent modulation without requiring larger inductors or capacitors, thereby maintaining high system efficiency while improving input current quality
3Device complexity
If a fixed reference current is used for output current control, then control simplicity is maintained, but voltage across energy storage component drops below supply voltage causing current spikes
Solution Approach 1:
The patent transitions from a static fixed reference current to a dynamic time-varying reference current that is modulated at the input ripple frequency. This dynamic adjustment allows the control circuit to maintain simplicity in structure while adapting the reference current magnitude to prevent the energy storage capacitor voltage from dropping below the supply voltage, thereby eliminating current spikes
Data Source
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AI summary
A driving circuit comprises a switch mode power converter circuit to convert a supply voltage (e.g. rectified mains), including an energy storage component and a main control switch. The energy storage component discharges to provide a regulated DC current to an output load upon the switching of the main control switch. A time-varying offset is used to modulate the regulated current thereby controlling the voltage across the energy storage component. In this way, the voltage across the energy storage component is maintained above the supply voltage with a safety margin, and this is used to prevent input current spikes and hence prevent an efficiency reduction of the driver circuit.