LED Operating Circuit with Transformer Saturation Detection
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Solution Overview
Problem
Existing operating circuits for LEDs struggle to maintain constant current and power, leading to fluctuations in light spectrum due to high-frequency switching, which affects brightness control and color constancy.
Innovation Solution
The proposed solution involves a control unit that selects switch-on and switch-off times for a switch clocked by a transformer with a primary winding series-connected with the LED, using a secondary winding and measuring element to determine when the transformer is no longer saturated, allowing for precise current regulation and measurement with minimal ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If high-frequency switching is used to regulate LED current, then brightness control is achieved, but current ripple increases causing light spectrum fluctuations
Solution Approach 1:
The patent applies periodic PWM switching to regulate LED brightness while using a large output capacitor to smooth the current ripple. The capacitor charges during switch-on and discharges during switch-off, providing a low-impedance path that reduces current fluctuations and maintains stable light spectrum despite high-frequency switching operation.
Solution Approach 2:
The output capacitor acts as an intermediary element between the switching regulator and the LED load. It absorbs the high-frequency current ripple generated by PWM switching and provides a stable current to the LED, thereby decoupling the brightness control mechanism from the light spectrum stability requirement.
2Measurement precision
If complex measuring circuits are used to measure LED current during switch-off phase, then current measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent uses the existing output capacitor and LED circuitry to indirectly measure current during the switch-off phase. By monitoring the voltage across the capacitor or the current through the LED during this phase, the system obtains accurate current information without requiring separate complex measuring circuits, leveraging the natural operation of existing components for measurement purposes.
3Stability of the object's composition
If switch is turned on when current is zero to minimize ripple, then current stability is improved, but switching frequency control becomes more difficult
Solution Approach 1:
The patent implements feedback control by monitoring the output capacitor voltage or LED current and using this information to determine the optimal switching timing. The control unit adjusts the switch-on moment based on real-time current conditions, ensuring the switch operates when current is minimal while maintaining precise control over switching frequency through closed-loop regulation.
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 approach ensures a stable current through the LED, reducing ripple and maintaining constant LED power, thereby enhancing brightness control and color constancy by allowing flexible operation with varying numbers of LEDs and adaptive response to changes in load.
Implementation Method 1
a transformer with a primary winding series-connected with the LED, using a secondary winding and measuring element to determine when the transformer is no longer saturated
Implementation Method 2
a coil and a switch clocked by a control unit, with energy being temporarily stored in the coil when the switch is closed, which is discharged via the LED when the switch opens
Data Source
Figure 1a~1b
Figure 2a~3a
Figure 3b~4
AI summary
The invention relates to a method for operating at least one LED by means of a switched-mode regulator circuit to which a DC voltage or a rectified AC voltage is supplied and which provides a supply voltage for at least one LED by means of a coil (L1) and a switch (S1) that is clocked by a control/regulation unit (SR). When the switch (S1) is activated, power is temporarily stored in the coil (L1) and is discharged through a diode (D1) and through at least one LED when the switch (S1) is deactivated and the current flows through the LED through a first power storage element which is coupled to a second power storage element. The first power storage element just reaches its maximum capability of storing power due to the current (iLED) flowing through the LED. A rising current is supplied to the second power storage element such that the time can be detected when the first power storage element recovers its capability of storing power due to the current flowing through the second power storage element.