LED Driver Circuit with Current Mirror Sensing
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Solution Overview
Problem
Existing light emitting element driving apparatuses consume excessive power in sensing resistors and suffer from low power factor and high total harmonic distortion when controlling serially connected LEDs.
Innovation Solution
A light emitting element driving apparatus that includes a rectifying unit, a switching unit, an amplifying unit, a sensing resistor, and a current sensing circuit to control the LEDs, along with a power factor correction unit using a capacitor and voltage regulator to manage AC signals and reduce power consumption and harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing resistor is used to control serially connected LEDs, then the LED current can be regulated, but excessive power is consumed in the sensing resistor
Solution Approach 1:
The patent introduces a current sensing circuit that uses a small sensing resistor in conjunction with operational amplifiers to create a virtual ground configuration. This intermediary circuit allows precise current measurement through the sensing resistor while the op-amps compensate for voltage drops, enabling accurate LED current regulation with minimal power consumption in the sensing resistor itself.
Solution Approach 2:
The patent replaces the direct resistive control method with an electronic control system using operational amplifiers and feedback circuits. Instead of relying solely on the sensing resistor to control current, the system uses electronic amplification and feedback to achieve precise current regulation, significantly reducing the power burden on the sensing resistor.
2Adaptability or versatility
If AC voltage is rectified to control LEDs, then the LEDs can be driven from AC power source, but power factor is low and total harmonic distortion is high
Solution Approach 1:
The patent incorporates a power factor correction circuit that pre-processes the AC voltage before rectification. This preliminary action includes adding series capacitors and using active correction techniques to compensate for the reactive power and harmonic currents that will be generated during rectification, thereby improving power factor and reducing total harmonic distortion before the main power conversion occurs.
Solution Approach 2:
The patent employs feedback control in the power factor correction circuit, where the current and voltage are continuously monitored and the correction circuit adjusts its output to maintain optimal power factor. The feedback mechanism detects harmonic distortion and actively compensates for it, ensuring low power factor and minimal harmonic distortion throughout operation.
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 apparatus effectively reduces power consumption in sensing resistors, improves power factor, and minimizes total harmonic distortion, enhancing the efficiency and performance of LED control systems.
Implementation Method 1
a rectifying unit configured to provide a rectified signal to the light emitting unit according to a result of rectifying an alternating current (AC) signal
Implementation Method 2
a sensing resistor connected between the second node and an electrical ground
Implementation Method 3
a current sensing circuit configured to generate mirrored current by mirroring current supplied from the first node
Implementation Method 4
an amplifying unit configured to amplify each of reference voltages having different levels and a voltage of a second node
Data Source
AI summary
Disclosed herein is a light emitting element driving apparatus for controlling a light emitting unit including serially connected light emitting element arrays. The apparatus includes a rectifying unit configured to provide a rectified signal to the light emitting unit according to a result of rectifying an alternating current (AC) signal, a switching unit configured to selectively connect output terminals of the light emitting element arrays to a first node, an amplifying unit configured to amplify each of reference voltages having different levels and a voltage of a second node and to generate first amplified signals controlling the switching unit according to an amplification result, a sensing resistor connected between the second node and an electrical ground, and a current sensing circuit configured to generate mirrored current by mirroring current supplied from the first node and to provide the mirrored current to the second node.