Zero-Crossing Detection Circuit for Transformer-Free LED Load Sensing
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Solution Overview
Problem
Current LED driving circuits are complex, bulky, and costly due to their reliance on transformers for load detection, making them inefficient for functional aspects like output over-load and over-voltage protection.
Innovation Solution
A circuit and method that includes a load power supply circuit with a diode and inductor connected in series, a voltage-dividing resistor, and a zero-crossing detection circuit to rapidly detect current zero-crossing points and load voltage, using a transistor switch to control load voltage and a zero-crossing detection circuit to determine when diode current crosses zero, allowing for efficient detection with a simple and cost-effective design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used for load detection in LED driving circuits, then the detection function is achieved, but the circuit becomes complex, bulky, and costly
Solution Approach 1:
The patent extracts the load detection function from the transformer and implements it separately using a voltage-dividing resistor connected to the LED string. This allows the transformer to be eliminated while maintaining the protection function, directly resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent creates a simplified copy of the load detection mechanism by using a voltage-dividing resistor that mimics the transformer's ability to detect load conditions. This copy provides the same protection function without the complexity of the original transformer-based approach.
2Reliability
If a transformer is used for load detection, then protection function is provided, but the circuit volume increases
Solution Approach 1:
The load detection function is extracted from the transformer and implemented using compact voltage-dividing resistors and detection circuits, dramatically reducing the circuit volume while maintaining protection functionality.
3Reliability
If a transformer is used for load detection, then detection is achieved, but the cost increases
Solution Approach 1:
The patent replaces the expensive transformer with inexpensive voltage-dividing resistors and simple detection circuits. These cheaper components achieve the same detection capability, directly reducing manufacturing cost while maintaining reliability.
4Productivity
If conventional circuits are used, then basic function is provided, but detection speed is slow
Solution Approach 1:
The voltage-dividing resistor is pre-configured in the circuit to continuously monitor voltage conditions. When an over-voltage or over-load condition occurs, the detection circuit immediately detects the changed voltage division ratio and triggers protection, achieving fast detection without complex processing.
Data Source
AI summary
A circuit and a method for detecting a current zero-crossing point, and a circuit and method for detecting a load voltage are disclosed. The circuit for detecting current zero-crossing point includes: a load power supply circuit, a voltage-dividing resistor, a transistor switch, a zero-crossing detection circuit; the load power supply circuit includes: a load, a diode, and a transformer; one end of a primary winding of the transformer is connected with the operating voltage input terminal, the other end of the primary winding of the transformer is connected with a first end of the transistor switch and a first end of the voltage-dividing resistor, a second end of the voltage-dividing resistor and a second end of the transistor switch are connected with the ground, the load voltage is controlled by the transistor switch.