LED Power Supply Circuit for Continuous Control Operation
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Solution Overview
Problem
Existing power supply circuits for LED lighting fail to ensure continuous operation of control circuits during protective activities, as power is often cut off when overvoltage, overcurrent, or overheating is detected, disrupting the protection mechanism.
Innovation Solution
A power supply circuit utilizing a first PNP transistor and a second NPN transistor, coupled in a specific configuration to provide power to the control circuit from the middle tap of serial LEDs, ensuring uninterrupted operation by switching the current loop when protective actions are triggered.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power supply is cut off to protect LED light sources during overvoltage, overcurrent or overheat conditions, then protection activity is triggered, but voltage of control circuit drops and protecting activity cannot be triggered any longer
Solution Approach 1:
The power supply is segmented into two independent paths: one path supplies power to LED light sources through the control switch, and another path supplies power to control circuit through the PNP transistor and NPN transistor network. This segmentation allows the control circuit to remain powered even when the main power path is cut off for protection.
Solution Approach 2:
The PNP transistor and NPN transistor act as intermediary components that enable the control circuit to receive power from the first group of LED light sources through a voltage divider network, rather than directly from the main power input that may be cut off during protection events.
2Reliability
If additional switch power supply is employed to supply power to control circuit separately, then control circuit can still be supplied with power unceasingly when protecting activity is triggered, but device complexity increases and efficiency decreases
Solution Approach 1:
The PNP transistor and NPN transistor network serves multiple functions: it powers the control circuit during normal operation, maintains control circuit power during protection events, and provides automatic switching between power sources. This eliminates the need for separate switch power supply circuits.
Solution Approach 2:
The power supply for control circuit is merged with the LED light source power path by using the first group of LED light sources as the power source for control circuit through the transistor network, rather than using a completely separate power supply system.
3Ease of manufacture
If voltage regulator is supplied directly from driver output voltage, then cost is reduced, but efficiency is too low due to high voltage
Solution Approach 1:
A resistor network (R1, R2, R3) acts as an intermediary voltage divider between the high-voltage LED power path and the control circuit power input, providing appropriate voltage levels without requiring expensive high-voltage regulators while maintaining reasonable efficiency.
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 configuration allows efficient energy usage during normal operation and ensures the control circuit remains powered during protective activities, preventing voltage cutoff and maintaining continuous operation.
Implementation Method 1
a first PNP transistor whose collector is coupled to a power input of the control circuit, emitter is coupled to a first node between a first group of LED light sources and a second group of LED light sources upstream the control switch, and a base is coupled to a second node between the control switch and the second group of LED light sources, such that when the control switch controls the current path to close, the first PNP transistor is on and when the control switch controls the current path to open, the first PNP transistor is off
Implementation Method 2
a second NPN transistor whose base is coupled to the emitter of the first PNP transistor, emitter is coupled to the power input of the control circuit, and collector is coupled to power input of the plurality of LED light sources
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The application discloses a power supply circuit for control circuit of LED lighting, the LED lighting comprising a plurality of LED light sources connected in series and a control switch for controlling on and off of current path of the LED light sources. The power supply circuit is characterized in that it comprises a first PNP transistor whose collector is coupled to power input of the control circuit, emitter is coupled to a first node between a first group of LED light sources and a second group of LED light sources upstream the control switch, and base is coupled to a second node between the control switch and the second group of LED light sources, such that when the control switch controls the current path to close, the first PNP transistor is on and when the control switch controls the current path to open, the first PNP transistor is off; a second NPN transistor whose base is coupled to emitter of the first PNP transistor, emitter is coupled to the power input of the control circuit, and collector is coupled to power input of the plurality of LED light sources. The application further relates to LED lighting comprising the power supply circuit.