Capacitive Voltage Divider for LED Operating Device AC Detection
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Solution Overview
Problem
Existing operating devices for lamps, particularly LEDs, face inefficiencies due to the permanent connection and power losses associated with ohmic voltage dividers used to differentiate between AC and DC voltage supplies.
Innovation Solution
A monitoring circuit employing a capacitive voltage divider with a diode at its midpoint and an actively controlled discharge path is used to detect AC voltage, reducing power losses by minimizing permanent active current consumption and enabling efficient switching between AC and DC voltage supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an ohmic voltage divider is used to detect AC voltage, then the detection function is achieved, but permanent power losses occur and the base load increases
Solution Approach 1:
The patent changes the fundamental parameter of the voltage divider from ohmic (resistive) to capacitive. This transformation allows the monitoring circuit to draw current only during charging phases rather than continuously, eliminating permanent power losses while maintaining AC voltage detection capability. The capacitive reactance varies with frequency, enabling detection without continuous power consumption.
Solution Approach 2:
The capacitive voltage divider operates by charging and discharging periodically with each AC voltage cycle. The monitoring capacitor charges during positive half-cycles and discharges during negative half-cycles, creating a periodic action pattern. This periodic charging/discharging enables AC detection while consuming power only intermittently, resolving the contradiction between detection functionality and continuous power loss.
2Measurement precision
If an ohmic voltage divider is permanently connected to the network, then AC voltage detection is enabled, but the base load increases
Solution Approach 1:
The monitoring circuit uses periodic charging and discharging of the capacitive voltage divider in synchronization with AC voltage cycles. The capacitor charges during positive half-cycles and discharges during negative half-cycles, creating a periodic action pattern. This periodic charging/discharging enables AC detection while consuming power only intermittently, resolving the contradiction between detection functionality and continuous power loss.
Solution Approach 2:
The capacitive voltage divider is designed to charge itself from the AC voltage source during positive half-cycles and automatically discharge during negative half-cycles through the monitoring capacitor. This self-service mechanism eliminates the need for continuous external power supply or active components, reducing base load while maintaining detection capability.
3Loss of energy
If a capacitive voltage divider is used instead of ohmic, then power losses are reduced, but the circuit complexity increases
Solution Approach 1:
The patent extracts the resistive elements from the voltage divider and replaces them entirely with capacitive elements. This extraction of the ohmic component eliminates continuous power losses while the capacitive structure provides the necessary voltage division and detection function. The simplified capacitive structure actually reduces component count compared to complex ohmic designs with multiple resistors and active elements.
Solution Approach 2:
The monitoring capacitor acts as an intermediary element that bridges the AC voltage source and the detection circuitry. It temporarily stores energy during charging phases and releases it during discharging phases, mediating the power flow and enabling detection without continuous power consumption. This intermediary capacitor simplifies the overall circuit by replacing complex resistance-based monitoring mechanisms.
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
This solution allows for efficient detection of AC voltage without permanent power losses, enabling seamless switching to reduced power operation when AC voltage fails, thus optimizing energy usage and extending the lifespan of emergency energy sources.
Implementation Method 1
a capacitive voltage divider which is arranged between one of the two inputs of the rectifier and ground and a further diode is arranged at the midpoint of the capacitive voltage divider which charges a capacitor when the voltage at the midpoint of the capacitive voltage divider exceeds the voltage at the monitoring capacitor
Data Source
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AI summary
Operating device (1) for operating illuminants, especially LEDs, comprising connections (P1, P2) for drawing power from a power supply network (20), a downstream network filter (C1, L3, L4) and a rectifier (14) having a monitoring circuit for identifying whether an alternative voltage is applied to the connections (P1, P2) for drawing power or not, said monitoring circuit comprising a capacitive voltage divider (C6, C3) which is interposed between one of the two inputs of the rectifier (14) and ground.