LED Driver Circuit with Full Bridge Rectifier and Constant Current Sink
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Solution Overview
Problem
Conventional LED driver circuits face challenges in accurately controlling the brightness of LEDs due to variations in household power consumption, leading to insufficient current supply and difficulty in maintaining consistent luminance.
Innovation Solution
An LED driver circuit comprising a full bridge rectifier and a constant current sink circuit, where the constant current sink is an Integrated Circuit (IC) coupled to the full bridge rectifier, ensures a pure DC constant current is supplied to the LEDs, enhancing the working duty during AC input periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limit resistor is added to the full bridge rectifier, then the diodes are protected from over current damage, but the LEDs are operated under insufficient current supplied conditions and it is difficult to control the brightness accurately
Solution Approach 1:
The patent changes the circuit configuration by adding a capacitor in parallel with the current limit resistor. This parameter change allows the circuit to maintain diode protection while enabling accurate brightness control through PWM signal modulation, resolving the contradiction between reliability and measurement precision
Solution Approach 2:
The patent introduces a capacitor as an intermediary element between the current limit resistor and the LEDs. This capacitor smooths the current waveform and works with the PWM controller to provide precise brightness control while maintaining the protective function of the current limit resistor
2Reliability
If the resistance R of the current limit resistor is selected based on maximum voltage Vpeak, then the diodes are protected, but the LEDs receive insufficient current when VRMS varies under household power consumption influence
Solution Approach 1:
The patent makes the circuit dynamic by introducing a PWM controller that adjusts the duty cycle based on feedback from the sensing resistor. This dynamic adjustment ensures adequate current supply to LEDs while maintaining diode protection, resolving the contradiction between reliability and productivity
Solution Approach 2:
The patent implements a feedback mechanism using a sensing resistor connected to the PWM controller. The controller monitors the current through the LEDs and adjusts the duty cycle accordingly, ensuring both diode protection and adequate current supply under varying household power conditions
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 solution guarantees consistent current flow to LEDs, providing desired luminance and overcoming the limitations of conventional driver circuits by ensuring pure DC current and increased working duty during AC input periods.
Implementation Method 1
The AC to DC rectification is performed by use of the full bridge rectifier. The diodes D31 and D21 conduct the positive half period current, and the diodes D41 and D11 conduct the negative half period current.
Implementation Method 2
a first capacitor, a second capacitor and a third capacitor are respectively coupled between a first connecting point and a second connecting point, a third connecting point and a fourth connecting point, and a fifth connecting point and a sixth connecting point
Data Source
AI summary
An LED driver circuit that sinks pure DC current through LEDs. According to the invention, a constant current sink circuit is coupled to a full bridge rectifier. The full bridge rectifier includes at least a first bridge arm, a second bridge arm, a third bridge arm and a fourth bridge arm. The first bridge arm and the fourth bridge arm are connected in parallel with the third bridge arm and the second bridge arm in opposite directions, respectively. The connection of the first bridge arm and the third bridge arm and the connection of the second bridge arm and the fourth bridge arm are connected in series. Each of the bridge arms may consist of at least one LED. The constant current sink circuit is used for sinking pure DC current. The LEDs can be driven by pure constant current and can provide desired luminance.