LED Driving Circuit Three-Stage Dimming via Max On-Time Pin
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Solution Overview
Problem
Existing LED lamp driving circuits with three-stage dimming control require high-cost constant current control chips with switching action pins, limiting design flexibility and increasing costs due to the need for specialized components.
Innovation Solution
A driving circuit for LED lamps that uses alternating voltage input terminals and a constant current control chip with a maximum on-time pin, along with a variable control resistor and switching transistors to adjust resistance values, eliminating the need for switching action pins DET1 and DET2, thereby reducing costs and enhancing design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a constant current control chip with switching action pins DET1 and DET2 is used to achieve three-stage dimming control, then the dimming control function is realized, but the chip cost increases and design flexibility decreases
Solution Approach 1:
The patent extracts the dimming control function from the constant current control chip by utilizing its existing maximum on-time pin, rather than requiring specialized switching action pins. This separates the core current control function from the dimming control function, allowing standard chips to be used for dimming applications.
Solution Approach 2:
The maximum on-time pin of the constant current control chip is made multi-functional by using it for both current control and dimming control. This allows a single standard chip to perform multiple functions without requiring specialized pins or higher-cost components.
2Adaptability or versatility
If switching action pins DET1 and DET2 are required on the constant current control chip, then three-stage dimming can be achieved, but the chip cost increases
Solution Approach 1:
The patent uses inexpensive external resistors connected to the maximum on-time pin to achieve dimming control, replacing the need for expensive specialized chips. These simple passive components are much cheaper than modifying or selecting high-cost constant current control chips with specialized pins.
Solution Approach 2:
The patent changes the control parameter from switching action pins to the maximum on-time pin resistance value. By varying the resistance connected to the maximum on-time pin, different current levels are achieved, enabling dimming control through parameter adjustment rather than specialized hardware.
3Adaptability or versatility
If a constant current control chip with switching action pins is used, then three-stage dimming control is achieved, but the circuit design space is reduced
Solution Approach 1:
The patent introduces dynamic resistance selection through switching transistors that connect different resistors to the maximum on-time pin based on control signals. This dynamic configuration allows flexible dimming control without requiring fixed specialized pins, expanding circuit design possibilities.
Solution Approach 2:
The patent introduces external resistors and switching transistors as intermediary components between the control signals and the constant current control chip. These intermediaries translate control requirements into resistance values connected to the maximum on-time pin, providing design flexibility without modifying the chip itself.
Data Source
AI summary
Disclosed is a driving circuit for a Light Emitting Diode (LED) lamp, the LED lamp containing the driving circuit and a method for operating the driving circuit. The driving circuit includes: three alternating voltage input terminals, including two alternating voltage input terminals for receiving an alternating voltage and one common terminal, the two alternating voltage input terminals are controlled so that at least one alternating voltage input terminal receives the alternating voltage from a power supply; a constant current control circuit receiving the alternating voltage through at least one alternating voltage input terminal and outputting a constant direct current to an LED load, the constant current control circuit includes a constant current control chip having a maximum on-time pin; and a three-stage dimming detection control circuit including a variable control resistor for three-stage dimming control, and is controlled by the alternating voltage received by at least one alternating voltage input terminal so that the variable control resistor is connected to the maximum on-time pin with different resistance values, and the constant current control chip outputs three different current levels according to a resistance value of the connected variable control resistor.