Digital Error Amplifier for LED Driver Ripple Filtering

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Solution Overview

Problem

Conventional LED constant-current driving circuits with buck topology face challenges in filtering out 50 Hz/60 Hz voltage ripples, requiring large compensation capacitors that cannot be integrated and are susceptible to electrical leakage, making it difficult to implement a simple peripheral circuit.

Innovation Solution

An error amplification apparatus with a pulse generating circuit and a counting unit that generates a loop control signal by counting pulses, digitizing the compensation voltage to filter out AC ripples, allowing for reduced capacitance and integration of the compensation capacitor within an IC, and eliminating moisture-related issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large compensation capacitor is used to filter out 50 Hz/60 Hz voltage ripples, then the filtering effect is improved, but the device complexity and integration difficulty increase

Engineering Contradiction:

Improvefiltering effectVSAvoidintegration difficulty

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the conventional analog error amplifier with a digital error amplifier that uses a counter to generate the compensation voltage. The counter counts pulses from the pulse generating circuit and outputs a digital compensation voltage, substituting the mechanical/analog capacitor-based filtering system with a digital counting and pulse generation system. This digital approach eliminates the need for large external compensation capacitors while achieving the same filtering effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If a large compensation capacitor is used to filter out AC ripples, then the filtering effect is improved, but the electrical leakage due to moisture increases

Engineering Contradiction:

Improvefiltering effectVSAvoidelectrical leakage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the analog error amplifier with a digital error amplifier that uses a counter to generate the compensation voltage. The counter counts pulses from the pulse generating circuit and outputs a digital compensation voltage, substituting the mechanical/analog capacitor-based filtering system with a digital counting and pulse generation system. This digital approach eliminates the need for large external compensation capacitors while achieving the same filtering effect.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If a large compensation capacitor is implemented outside the chip, then the filtering effect is improved, but the peripheral circuit complexity increases

Engineering Contradiction:

Improvefiltering effectVSAvoidperipheral circuit

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the error amplifier function with a pulse generating circuit and a counter. The pulse generating circuit generates first and second pulses based on the output voltage of the error amplifier, and the counter counts these pulses to generate the loop control signal. This integration combines multiple functions into a unified digital circuit block that can be implemented within the IC, eliminating the need for external compensation capacitors and reducing peripheral circuit complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS10425002B2Error amplification apparatus and driving circuit including the same

Publication Date: 2019.09.24 HANGZHOU SILAN MICROELECTRONICS CO LTD

AI summary

The disclosure relates to an error amplification apparatus and a driving circuit including the error amplification apparatus. In the error amplification apparatus according to the disclosure, a pulse generating circuit generates a first pulse and a second pulse in accordance with an output voltage of an error amplification unit, a counting unit being coupled to the pulse generating circuit counts the first pulse and the second pulse, and generates a loop control signal representing a compensation voltage based on the count. The disclosure utilizes the counting unit to digitize the compensation voltage, and the counter value can reflect the compensation voltage, so that the variation of the loop control signal in the AC cycle of 50 Hz or 60 Hz is controlled to be little, thereby filtering out the ripple of AC of 50 Hz or 60 Hz. In this manner, the capacitance of the compensation capacitor is reduced so that the compensation capacitor can be integrated inside the IC chip, thereby simplifying the peripheral design, and eliminating the influence on the loop by the electrical leakage current due to moisture.