LED Driver Bleeder Circuit PWM Noise Cancellation
Solution Overview
Problem
Conventional phase-controlled dimming circuits for LEDs often malfunction due to foreign noise or interference, leading to flicker or flash, and result in high power loss when trying to maintain a conducting state with a bleeder current.
Innovation Solution
An LED driving circuit with a bleeder circuit that includes a bleeder resistance and switch connected in series, receiving a high frequency pulse signal to flow a bleeder current with a high frequency pulse form, which cancels out interfering currents and maintains constant current flow to the LED without significant power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bleeder current is caused to flow to maintain the conducting state of the dimming circuit, then the reliability of the dimming circuit is improved, but the power loss and temperature increase significantly
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation (PWM) to control the bleeder switch, causing the bleeder current to flow only during specific periods when needed to maintain TRIAC conduction. This pulsed operation rather than continuous current flow reduces average power loss while ensuring the TRIAC remains in conducting state during the required time intervals.
Solution Approach 2:
The patent changes the parameter of bleeder current from continuous to pulsed by controlling the bleeder switch with PWM signals. This parameter change allows the system to maintain the necessary holding current for TRIAC operation only when needed, rather than maintaining a continuous current, thereby reducing overall power consumption and heat generation in the bleeder circuit.
2Ease of operation
If a phase-controlled dimming circuit using TRIAC is used for LED illumination, then the ease of operation is improved, but foreign noise or interference causes malfunction and flicker
Solution Approach 1:
The patent employs feedback mechanisms where the controller monitors the conducting angle of the TRIAC and adjusts the PWM duty cycle accordingly. This feedback control ensures that the bleeder current is applied at the correct timing and duration to maintain stable TRIAC conduction, preventing malfunction and flicker while preserving the ease of phase-controlled dimming operation.
Solution Approach 2:
The patent introduces a bleeder switch as an intermediary component controlled by PWM signals. This switch acts as a mediator between the control circuit and the TRIAC, enabling precise control of the bleeder current to maintain TRIAC conduction stability without directly interfering with the phase-controlled dimming operation, thus reducing noise-induced malfunction.
3Loss of energy
If the current flowing in the TRIAC is reduced due to high LED efficiency, then the energy efficiency is improved, but the dimming circuit malfunctions due to foreign noise or interference
Solution Approach 1:
The patent applies preliminary action by proactively supplying bleeder current through the controlled bleeder switch before the TRIAC might become unstable due to low load current. This preventive measure ensures the TRIAC remains in a stable conducting state throughout the dimming operation, preventing noise-induced malfunction while allowing the LED to operate at high efficiency with minimal current.
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 effectively reduces or prevents malfunctions caused by noise interference while minimizing power loss and temperature increase, ensuring stable LED operation.
Implementation Method 1
a rectifier circuit that rectifies an alternating-current voltage output from the dimming circuit
Implementation Method 2
a smoothing circuit that smoothes the direct current voltage output from the rectifier circuit
Implementation Method 3
The high frequency pulse signal is input to the bleeder switch so that a bleeder current having a high frequency pulse form flows in the bleeder resistance
Data Source
AI summary
An LED driving circuit includes a dimming circuit that controls a conducting angle of an alternating current supplied from a power supply to phase-control a current to be supplied to an LED, a rectifier circuit that rectifies an alternating-current voltage output from the dimming circuit, a smoothing circuit that smoothes a direct current voltage output from the rectifier circuit, a switching device that is connected with the LED in series; a constant current control circuit that outputs a high frequency pulse signal to the switching device to control the switching device, and a bleeder circuit that is provided between an output terminal of the rectifier circuit and a ground and that has a bleeder resistance and a bleeder switch connected in series. The high frequency pulse signal is input to the bleeder switch so that a bleeder current having a high frequency pulse form flows in the bleeder resistance.