Switching Converter Variable Coefficient Circuit Offset Error Reduction
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Solution Overview
Problem
Existing switching converters for LED light sources face significant offset errors, particularly in regions where the drive current is small, leading to inaccuracies in stabilizing the target current, which is exacerbated in applications with a wide dynamic range of drive currents.
Innovation Solution
A control circuit for switching converters that includes a coefficient circuit capable of switching coefficients based on the current range of the drive current, generating current detection and setting signals to maintain a high range and reduce offset error influence, comprising a first and second coefficient circuit with variable gain amplifiers and voltage dividing circuits, and a pulse modulator with current limit and zero current detection to adjust the drive pulse duty ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed coefficient is used in the control circuit, then the circuit structure is simple, but offset errors significantly affect current stabilization accuracy in small current regions
Solution Approach 1:
The patent applies the dynamics principle by making the coefficient variable rather than fixed. The control circuit switches between a first coefficient and a second coefficient based on the drive current range, allowing the system to adapt to different operating conditions. This dynamic adjustment reduces offset errors in small current regions while maintaining circuit functionality across the full current range.
Solution Approach 2:
The patent implements parameter changes by modifying the coefficient value based on the drive current range. When the drive current is in a small range, a different coefficient is selected compared to when the drive current is in a large range. This parameter change allows the system to optimize measurement precision across different operating conditions without requiring a completely complex circuit redesign.
2Measurement precision
If a variable coefficient is switched based on current range, then offset error influence is reduced, but the control circuit complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the drive current range into multiple regions (small current range and large current range). Each region has its own optimized coefficient, allowing the system to handle different current levels with appropriate precision. This segmentation reduces offset errors by ensuring each segment uses a coefficient optimized for its specific range.
Solution Approach 2:
The control circuit dynamically switches between coefficients based on the detected current range. This dynamic behavior allows the system to maintain high measurement precision across the full operating range while managing complexity through systematic switching logic rather than requiring entirely separate circuits for each range.
3Adaptability or versatility
If the drive current range is wide, then the converter is more versatile, but offset errors become more significant and affect dimming precision
Solution Approach 1:
The patent makes the coefficient dynamic based on the drive current range, allowing the system to maintain versatility across a wide current range while preserving dimming precision. By switching coefficients according to the current range, the system can handle both large and small currents accurately, ensuring that offset errors do not degrade dimming precision even when operating across a wide dynamic range.
Solution Approach 2:
The system changes the coefficient parameter based on the operating current range, enabling it to maintain high dimming precision across the full versatile range. This parameter adaptation ensures that whether the converter is operating at high or low current levels, the appropriate coefficient is applied to minimize offset errors and maintain accurate dimming control.
Data Source
AI summary
A CS terminal receives a detection voltage VCS corresponding to voltage drop across a detection resistor RCS provided on a path of a drive current ILED or an inductor current IL. An ADIM terminal receives an analog dimming voltage VADIM indicating a target amount of the drive current ILED. A coefficient circuit multiplies at least one of the detection voltage VCS and the analog dimming voltage VADIM by a variable coefficient and generates a current detection signal IS and a current setting signal IREF. A pulse modulator generates a drive pulse SDRV whose duty ratio is adjusted such that the current detection signal IS approaches the current setting signal IREF. A driver drives a switching transistor M according to the drive pulse SDRV.