LED Driver Device Zero Crossing Detection Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing LED driver circuits face challenges in compatibility with various dimmer devices, particularly phase-cut dimmers, due to differences in input characteristics, leading to inefficiencies and power losses, and fail to maintain high power factor and low cost requirements.
Innovation Solution
A driver device with a controllable switch and measurement path using a high resistance resistor to detect zero crossings, allowing precise impedance adjustment and phase-cut voltage measurement without influencing the dimmer's timing circuit, enabling compatibility with different dimmers and maintaining high power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a current sensor with measurement resistors is used to detect zero crossing, then zero crossing detection is achieved, but power factor is reduced due to high power loss in measurement resistors
Solution Approach 1:
The patent introduces a capacitor as an intermediary element in parallel with the measurement resistor. This capacitor provides an alternative current path that bypasses the power-consuming measurement resistor during normal operation, while still allowing the measurement resistor to detect zero crossings when needed. The capacitor charges and discharges in conjunction with the measurement resistor, creating a timing circuit that enables zero crossing detection without continuous power dissipation.
Solution Approach 2:
The measurement circuit operates periodically rather than continuously. The capacitor charges during specific phases and discharges during others, with the measurement resistor only actively detecting zero crossings at specific moments in the AC cycle. This periodic operation significantly reduces average power loss compared to continuous measurement resistor operation.
2Adaptability or versatility
If a low load impedance path is provided for dimmer timing circuit, then compatibility with phase-cut dimmers is achieved, but power loss increases especially at low power operation
Solution Approach 1:
The patent implements a dynamic impedance switching mechanism using a controllable switch (such as a MOSFET or triac) that changes the load impedance based on operating conditions. During dimmer compatibility phases, the switch provides a low impedance path for the timing circuit. During normal LED operation, the switch transitions to a high impedance state, minimizing power loss. This dynamic adaptation allows the circuit to maintain dimmer compatibility while reducing continuous power consumption.
Solution Approach 2:
The circuit dynamically changes electrical parameters (impedance, current path) based on operational mode. The controllable switch alters the circuit configuration to provide different impedance levels: low impedance when dimmer timing current is needed, and high impedance during normal operation. This parameter switching enables the circuit to satisfy both dimmer compatibility requirements and power efficiency goals.
3Measurement precision
If measurement resistors are used in the current path, then current measurement is possible, but the measurement unit influences the current provided to LEDs and reduces power factor
Solution Approach 1:
The patent divides the circuit into separate functional paths: a measurement path containing the measurement resistor and capacitor for detection purposes, and a main current path for LED operation. The measurement path is segmented off from the main power path using switches and timing control, allowing current measurement without the measurement components continuously influencing the LED current. This segmentation isolates the measurement function from the power delivery function.
Solution Approach 2:
The capacitor acts as an intermediary that decouples the measurement resistor from the main current path. During measurement phases, the capacitor allows the measurement resistor to sense current or voltage without being in series with the LED current path. This intermediary element enables measurement while preventing the measurement resistor from continuously influencing LED operation and degrading power factor.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
The present invention relates to a driver device (30)for driving a load (32), in particular an LED unit (32) having one or more LEDs, comprising input terminals (45) for receiving an input voltage (V14) from an external power source (12) for powering the load (32), a current path (46) including a controllable switch (50) for connecting the input terminals (45) to each other, a measurement path (48) including a resistor (56, 58, 84, 86) connecting the input terminals (45) to each other for providing an alternating voltage corresponding to the input voltage (V14) and including a measuring device (64, 70) for measuring the alternating voltage(V15) at the measurement path (48), and a controller (54, 62) for controlling the controllable switch (50) on the basis of the measured alternating voltage.