Tapped-Inductor LED Converter With Non-Complementary Synchronous Rectification
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Solution Overview
Problem
Existing LED drivers with tapped-inductor boost topology experience high conduction losses due to output diodes, and synchronous topologies disrupt boundary conduction mode operation.
Innovation Solution
A power converter with a rectifying switch and control circuit that maintains boundary conduction mode operation while reducing conduction losses by using a non-complementary duty cycle signal for the rectifying switch, preserving efficiency at lower output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tapped-inductor boost topology with output diode is used, then the converter operates in boundary conduction mode with simple control, but high conduction losses occur due to the output diode
Solution Approach 1:
The patent changes the operating parameters by introducing a synchronous rectifying switch that operates with a non-complementary duty cycle signal. This allows the rectifying switch to conduct during specific intervals that preserve the boundary conduction mode characteristics while reducing the voltage drop across the rectification path, thereby reducing conduction losses without disrupting the BCM operation
2Loss of energy
If a synchronous tapped-inductor boost topology with rectifying switch is used, then conduction losses are reduced, but boundary conduction mode operation is disrupted
Solution Approach 1:
The patent implements dynamic control of the rectifying switch using a non-complementary duty cycle signal that adapts to the operating conditions. The rectifying switch is turned on and off at specific timing intervals that are not simply complementary to the main switch, allowing the system to maintain boundary conduction mode while achieving synchronous rectification benefits. This dynamic timing control preserves the natural BCM characteristics
3Loss of energy
If a rectifying switch with complementary duty cycle signal is used, then conduction losses are reduced, but the anode potential does not fall to zero and current flows from load to source
Solution Approach 1:
The patent applies preliminary action by controlling the rectifying switch to turn off before the main switch turns on, using a non-complementary duty cycle timing. This preliminary turn-off prevents the anode potential from remaining at output voltage level during the main switch conduction period, thereby preventing reverse current flow from load to source while still achieving synchronous rectification during the appropriate intervals
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
Improves efficiency at lower output voltages, particularly at higher powers, enabling cost savings through reduced cell count or increased rated output power.
Implementation Method 1
a tapped inductance and a rectifying circuit, arranged in series between an input potential and an output potential of the converter
Implementation Method 2
The rectifying circuit comprises a rectifying switch. The converter further comprises a Schottky diode arranged in parallel with the rectifying switch
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
Disclosed is a power converter (1) for at least one LED (2). The converter (1) comprises a tapped inductance (101, Lmag, N1, N2) and a rectifying circuit (102), arranged in series between an input potential (Vin) and an output potential (Vout) of the converter (1). The rectifying circuit (102) comprises a rectifying switch (Ssynch). The converter (1) further comprises a regulating switch (103, S), arranged between a tap of the tapped inductance (101, Lmag, N1, N2) and a ground potential of the converter (1). The converter (1) further comprises a first sensing circuit (104), configured to sense a voltage being indicative of a common potential (Vzx) of the tapped inductance (101, Lmag, N1, N2) and the rectifying circuit (102) relative to the ground potential of the converter (1). The converter (1) further comprises a second sensing circuit (106), configured to sense a voltage being indicative of a measurement value (Iin,meas) of an input current (Iin) of the converter (1). The converter (1) further comprises a control circuit (107), configured to regulate an input current of the converter (1) in accordance with a regulating duty cycle signal (D) for the regulating switch (103, S); generate the regulating duty cycle signal (D) for the regulating switch (103, S) in accordance with the common potential (Vzx) and the input current (Iin) of the converter (1); and generate a rectifying duty cycle signal (DR) for the rectifying switch (SR) in accordance with and being non-complementary to the regulating duty cycle signal (D). This provides an efficiency improvement especially for low output voltages.