LED Driver Circuit Reducing Switch Power Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current LED drivers designed for a specific mains input voltage are costly when adapted for a wide range of input voltages, such as 120V to 277V, due to high power losses in self-oscillation converters like RCC-based buck converters.
Innovation Solution
A driver circuit using a flyback ringing choke switch mode power converter with a sub-circuit that includes a ramp circuit and voltage follower to provide a linearly increasing driving current to the main switch, reducing power loss by controlling the base current of the main transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a typical self-oscillation converter is used with a wide input voltage range, then the driver can operate with different mains voltages, but the power loss in driving the switch becomes higher
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor through a resistor before the main switch is activated. This preliminary charging action ensures that when the switch closes, the voltage across the capacitor is already at an appropriate level, preventing excessive inrush current and reducing power loss. The capacitor is charged in advance during a pre-charge phase, so that the main switching operation occurs under optimized conditions.
Solution Approach 2:
The patent implements dynamics by using a capacitor that charges dynamically through a resistor, creating a time-varying voltage profile. The capacitor voltage transitions from zero to a steady value following an exponential charging curve, allowing the circuit to adapt its characteristics over time. This dynamic behavior enables the circuit to handle wide input voltage ranges while controlling power loss through the natural RC time constant.
2Power
If excessive current/voltage is provided by the oscillated element, then the switch can be driven, but the power loss increases
Solution Approach 1:
The patent applies parameter changes by modifying the voltage parameter across the capacitor through resistive charging. Instead of applying full voltage immediately, the voltage parameter is gradually changed from 0V to the supply voltage through the RC charging process. This controlled parameter change reduces the instantaneous power demand while maintaining the necessary driving capability for the switch, thereby reducing overall power loss.
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 reduces power loss and maintains efficiency across a wide range of input voltages, making the LED driver more cost-effective and efficient.
Implementation Method 1
a first capacitor adapted to be charged by said supply voltage so as to be with a linearly increasing voltage
Implementation Method 2
a voltage follower connected to said first capacitor and adapted for providing a linearly increasing driving voltage that follows a linearly increasing voltage on said first capacitor
Implementation Method 3
a voltage to current conversion unit between said voltage follower and the control terminal of the main switch, for providing the control terminal of the main switch with a linearly increasing driving current that depends on the linearly increasing driving voltage
Implementation Method 4
a primary winding in series with the collector-emitter of the main transistor; a secondary winding which forms an inductor of a flyback output stage
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention provides a driver circuit for driving an LED arrangement which uses a switch mode power converter, for example a flyback ringing choke converter, which comprises a main switch (e.g. bipolar transistor) and a sub-circuit for generating a current for the control terminal of the main switch. The sub-circuit in some examples makes use of an auxiliary winding as a voltage supply, and further comprises a ramp circuit for generating a ramp voltage from the voltage supply and a voltage follower, such as a control transistor, connected between the voltage supply and the control input of the main switch. By ramping up the current of the main switch, the losses arising as a result of the current flowing to the control input of the main switch are reduced. One set of examples makes use of a flyback ringing choke converter, which enables low cost implementation and good efficiency. The driver is able to receive a wide range of input voltages, by ensuring that the power loss is kept low. In particular, by ramping up the control current of the main switch, the losses arising as a result of the current flowing are reduced.