Linear Power Supply Smart Bulb Driver Circuit
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Solution Overview
Problem
Existing smart light bulbs face challenges in achieving a power factor higher than 0.7 while maintaining a flicker percentage less than 30%, and they often require high input capacitance, which contradicts the need for low EMI emission and high thermal performance, especially when using linear power supplies.
Innovation Solution
The implementation of a linear power supply design that eliminates input capacitance and uses only output capacitance for flicker control, combined with parallel-connected linear current regulators to distribute thermal load and an EMI filter to manage PWM noise, ensuring a power factor greater than 0.7 and flicker percentage less than 30%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high input capacitance is used to maintain flicker percentage less than 30%, then flicker control is improved, but EMI emission increases and thermal performance deteriorates
Solution Approach 1:
The patent removes the input capacitance component from the power supply circuit entirely. Instead of using high input capacitance to control flicker, the invention places capacitance only at the output side of the linear power supply, extracting the harmful EMI-generating element while maintaining flicker control through alternative means (output capacitance and linear regulator design).
Solution Approach 2:
The linear power supply circuit acts as an intermediary between the AC input and LED output, using its inherent filtering characteristics and the output capacitance to smooth current delivery without requiring large input capacitance. The linear regulator intermediate stage converts and stabilizes the input voltage before reaching the LEDs, eliminating the need for high input capacitance.
2Manufacturing precision
If high input capacitance is used to maintain flicker percentage less than 30%, then flicker control is improved, but thermal performance deteriorates
Solution Approach 1:
The patent removes the input capacitance component that would generate excessive heat through continuous charging and discharging cycles. By eliminating this component and using only output capacitance for flicker control, the overall thermal load in the circuit is reduced, improving thermal performance.
Solution Approach 2:
The linear power supply uses simpler, lower-cost components with lower thermal profiles compared to complex switching power supply components. The design accepts some energy dissipation as heat in the linear regulator but uses smaller overall component sizes that generate less cumulative thermal load.
3Ease of manufacture
If linear power supply is used to reduce cost and improve thermal performance, then manufacturing cost is reduced, but achieving power factor greater than 0.7 becomes difficult
Solution Approach 1:
The patent modifies the operating parameters of the linear power supply circuit, specifically the capacitance values and their placement, to optimize the power factor. By carefully selecting output capacitance values and positioning them strategically, the circuit achieves improved power factor (greater than 0.7) while maintaining the simplicity and low cost of linear power supply architecture.
4Object-generated harmful factors
If EMI filter is added to manage PWM noise, then EMI emission is reduced, but device complexity increases
Solution Approach 1:
The patent combines the EMI filtering function with existing circuit components rather than adding separate dedicated EMI filter components. The output capacitance and inductance elements serve dual purposes: both as power storage/transfer elements and as EMI filtering elements, thereby reducing overall device complexity while still managing PWM noise effectively.
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
This approach results in a low-cost, low-standby-power smart bulb that meets CEC Title 21 Tier 2 standards with improved thermal performance and effective EMI filtering, enabling wireless control through PWM signals.
Implementation Method 1
The LED power supply circuit includes at least one linear current regulator... in which the circuits when integrated into a smart bulb can provide a low standby power, low EMI emission, low cost, low flicker percentage, and a high-power factor
Implementation Method 2
The output side of the driver circuit includes an output smoothing capacitor for controlling flicker percentage
Implementation Method 3
The driver circuit further includes an electromagnetic interference (EMI) filter in the input side of the driver circuit. The electromagnetic interference (EMI) filter can be present between the bridge rectifier of the power input circuit and the light emitting diode (LED) power supply circuit
Implementation Method 4
a light engine including light emitting diodes (LEDs)
Data Source
AI summary
A driver circuit that includes an input side including a power input circuit and an output side including a light emitting diode (LED) output current circuit. The output side of the driver circuit includes an output smoothing capacitor for controlling flicker percentage. A light emitting diode (LED) power supply circuit is present between the input side and the output side for controlling current from the AC power input circuit to the light emitting diode (LED) output current circuit. The LED power supply circuit includes at least two linear current regulators that are connected in parallel. The circuit also includes a controller circuit including a controller for signaling the light emitting diode (LED) power supply to control current to the light emitting diode (LED) output current circuit to provide a lighting characteristic.