LED Operating Circuit Voltage Measurement Compensation
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Solution Overview
Problem
Existing LED operating circuits using switching regulators face measurement errors due to temperature- and operating-point-dependent voltage errors caused by the envelope demodulator, leading to significant inaccuracies in detecting the LED voltage.
Innovation Solution
A compensation circuit is introduced, comprising a second diode to counteract the offset voltage introduced by the first diode, along with an operational amplifier and capacitors to reduce harmonics and electromagnetic interference, ensuring accurate voltage detection across the LED path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an envelope demodulator is used to detect the voltage across the LED path, then the LED voltage can be measured indirectly, but temperature- and operating-point-dependent voltage errors occur leading to significant measurement inaccuracies
Solution Approach 1:
The patent introduces a compensation circuit that actively counteracts the temperature- and operating-point-dependent voltage errors by adjusting the detection parameters. The compensation circuit modifies the detection voltage to compensate for the diode's forward voltage drop variations, thereby maintaining accurate LED voltage measurement across different operating conditions and temperatures.
2Ease of operation
If a diode is used in the envelope demodulator, then the high-frequency voltage can be rectified, but an offset voltage is introduced that causes detection errors
Solution Approach 1:
The patent introduces a compensation diode as an intermediary element that mirrors the voltage drop characteristics of the rectification diode. By connecting this compensation diode in parallel with the envelope demodulator's diode, the voltage offset introduced by the rectification diode is compensated, allowing accurate envelope detection while maintaining the rectification function.
3Productivity
If the switch is clocked to achieve efficient power conversion, then the converter operates at high frequency, but harmonics and electromagnetic interference are generated
Solution Approach 1:
The patent uses a compensation diode connected in parallel with the envelope demodulator to act as an intermediary that filters out high-frequency switching components. This compensation circuit allows the main converter to operate at high frequency for efficient power conversion while the compensation diode absorbs or cancels the harmful harmonics and electromagnetic interference generated during switching.
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
The compensation circuit effectively mitigates temperature- and operating-point-dependent voltage errors, enhancing the accuracy of LED voltage measurement and reducing measurement errors, thereby improving the reliability of the LED operating circuit.
Implementation Method 1
a transformer T1 having a primary winding L BUCK and a secondary winding L2 coupled to one another
Implementation Method 2
An envelope demodulator comprising a diode D1, a capacitor C1 and a resistor R DISCHG is connected in series with this resistor R CHG
Implementation Method 3
The parallel connection of the capacitor C1 and the resistor R DISCHG forms a low-pass filter to remove the high-frequency signal
Implementation Method 4
an operational amplifier, at the positive input of which the output voltage of the envelope curve demodulator is present and at the negative input of which the second diode is connected
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to an operating circuit for an LED series, having: a converter, particularly a DC-DC converter, having a controllable switch (S1) and an inductor (LBUCK) for converting an input voltage (Vin) fed to the operating circuit into a supply voltage for the LED series; - a control unit (SR) for driving the switch (S1); - a secondary-side inductor (L2) coupled to the inductor (LBUCK); - an envelope curve demodulator (30) for detecting the envelope curve of the voltage (V'LED) present at the secondary-side inductor (L2); and - a compensating circuit (31) for compensating an error caused by the envelope curve demodulator (30) relating to the detection of the envelope curve.