Inductor Current Detection Circuit for LED Driver Power Factor Correction
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Solution Overview
Problem
Conventional LED drivers face challenges in achieving power factor correction and high current control precision, leading to low input power factor and high harmonic components, especially when driving LED lighting which is sensitive to current rather than voltage.
Innovation Solution
An inductor current detection circuit is implemented in a switching mode power supply under discontinuous conduction mode, comprising a voltage detection circuit, a voltage holding circuit, and a comparison circuit to generate a zero-crossing signal representing the inductor current ending time, allowing for precise control of the power switch and achieving high power factor correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional power supplies are used to power LED, then the system is simple, but power factor correction cannot be achieved and input power factor is low with increased harmonic components
Solution Approach 1:
The patent introduces an intermediary inductor current detection circuit that includes a voltage detection circuit, voltage holding circuit, and comparison circuit. This intermediary component detects the inductor current indirectly through voltage sampling and generates zero-crossing signals, enabling power factor correction without requiring direct complex current measurement hardware.
Solution Approach 2:
The patent replaces direct mechanical/electrical current measurement with a voltage-based detection system. By sampling the drain-source voltage of the power switch and processing it through holding and comparison circuits, the system substitutes a simpler voltage measurement approach for direct current measurement, achieving power factor correction while maintaining system simplicity.
2Measurement precision
If inductor current detection is implemented in discontinuous conduction mode, then current control precision is improved, but device complexity increases
Solution Approach 1:
The patent creates a copy of the inductor current information through voltage sampling. The voltage detection circuit captures the drain-source voltage which correlates with inductor current, and the voltage holding circuit maintains this sampled voltage. This copying approach allows precise current detection without directly measuring the inductor current, reducing the complexity of the detection circuit while maintaining measurement precision.
Solution Approach 2:
The voltage detection circuit serves multiple functions: it detects the inductor current information, generates zero-crossing signals for control, and provides feedback for power factor correction. By making the detection circuit multi-functional, the patent reduces the need for separate dedicated components, thereby improving current control precision without proportionally increasing device complexity.
3Loss of energy
If zero-crossing detection is used to control power switch timing, then switching losses are reduced, but measurement and detection difficulty increases
Solution Approach 1:
The patent inverts the detection approach by not directly measuring the inductor current to detect zero-crossing points. Instead, it measures the drain-source voltage of the power switch, which exhibits characteristic voltage patterns during discontinuous conduction mode. The voltage holding circuit holds the sampled voltage, and the comparison circuit detects when this held voltage crosses zero, indirectly identifying the inductor current ending time. This inversion simplifies the measurement process while maintaining accurate zero-crossing detection for reduced switching losses.
Data Source
AI summary
The present invention pertains to an inductor current detection circuit in a switching mode power supply, and a light-emitting diode (LED) driver thereof. In one embodiment, an inductor current detection circuit configured in a switching mode power supply under discontinuous conduction mode, can include: (i) a voltage detection circuit configured to generate a sampling voltage based on a drain-source voltage of a power switch in the switching mode power supply; (ii) a voltage holding circuit configured to receive the sampling voltage, and to generate a holding voltage through a sampling and holding operation; and (iii) a comparison circuit configured to compare the sampling voltage against the holding voltage, and to generate a zero-crossing signal when the sampling voltage is less than the holding voltage, where the zero-crossing signal is configured to represent an inductor current ending time of the switching mode power supply.