LED Control Circuit Reference Voltage Scaling
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Solution Overview
Problem
Existing control circuits for LED illumination systems face inefficiencies due to reduced power factor and reduced efficiency when the AC power supply voltage varies, causing the reference voltage to be clamped by the Zener diode, which prevents effective control of the switching element and results in suboptimal light emission intensity.
Innovation Solution
A control circuit with a reference voltage generating unit that includes a transistor-based voltage dividing circuit, where the resistance between the source and drain changes with the rectified voltage, allowing the reference voltage to adapt and prevent clamping by the Zener diode, enabling effective comparison and control of the switching element to maintain optimal light emission intensity across varying AC power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Zener diode is used to generate reference voltage in the control circuit, then the reference voltage is stabilized at the Zener voltage, but when the rectified voltage exceeds the Zener voltage, the reference voltage becomes clamped and cannot follow the rectified voltage waveform, reducing power factor and efficiency
Solution Approach 1:
The patent changes the parameter of the reference voltage generating circuit by replacing the fixed Zener diode voltage clamp with a transistor-based voltage divider circuit. The transistor's resistance between source and drain changes dynamically according to the rectified voltage, allowing the reference voltage to scale proportionally with the rectified voltage rather than being clamped at a fixed value. This resolves the contradiction by maintaining reference voltage stability through proportional scaling while avoiding clamping effects that reduce power factor.
Solution Approach 2:
The patent introduces dynamics into the reference voltage generation by using a transistor whose resistance varies with the rectified voltage. This creates a dynamic voltage divider where the reference voltage automatically adjusts its magnitude based on the instantaneous rectified voltage level. This dynamic adaptation eliminates the static clamping problem of Zener diodes while maintaining stable proportional reference voltage throughout the AC cycle, thereby improving power factor.
2Stability of the object's composition
If the reference voltage is clamped by the Zener diode, then the reference voltage remains constant, but the control of the switching element cannot be executed according to the waveform of the rectified voltage, reducing system efficiency
Solution Approach 1:
The patent changes the reference voltage parameter from a constant clamped value to a dynamically scaled value that maintains a constant proportion to the rectified voltage. The transistor-based voltage divider ensures the reference voltage remains stable relative to the rectified voltage waveform, allowing proper timing control of the switching element throughout the entire AC cycle, thereby eliminating energy loss from improper switching control.
3Power
If the voltage of the AC power supply increases, then more power is available for the LED, but the reference voltage becomes clamped at the Zener voltage, preventing effective control and reducing efficiency
Solution Approach 1:
The patent introduces dynamic scaling of the reference voltage through the transistor-based voltage divider. When AC power supply voltage increases and rectified voltage rises above the former Zener clamp level, the transistor's varying resistance allows the reference voltage to scale proportionally rather than being clamped. This maintains effective control efficiency across the full range of available power, allowing the system to utilize increased power input without losing control precision.
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 ensures that the reference voltage dynamically adjusts with the rectified voltage, preventing clamping and maintaining efficient control of the switching element, thereby improving the power factor and efficiency of the system while allowing for consistent light emission intensity adjustment.
Implementation Method 1
a transistor Q1 whose resistance value between a source and a drain changes according to the voltage rectified by the rectifying unit 30
Implementation Method 2
a rectifying unit 30 that full-wave rectifies an AC power supply
Implementation Method 3
a choke coil 14, a regenerative diode 16... the regenerative diode 16 which regenerates the energy stored in the choke coil 14
Data Source
AI summary
A control circuit of a light-emitting element comprises a rectifying unit (30) which full-wave rectifies an alternating current power supply, a switching element (38), a reference voltage generating unit (40) which generates a reference voltage (Vref), and a comparator (42) which receives a voltage (Srec) rectified by the rectifying unit (30), compares a comparative voltage (Vcmp) corresponding to a current flowing to an LED (102) and the reference voltage (Vref), and controls switching of the switching element (38) according to a comparison result, wherein the reference voltage generating unit (40) comprises a voltage dividing circuit having a transistor (Q1) in which a resistance value between a source and a drain is changed according to the voltage rectified by the rectifying unit (30), and outputs, using the voltage dividing circuit, the reference voltage (Vref) according to the voltage (Srec) rectified by the rectifying unit (30).