Light emitting diode driving circuit

Abstract

A light emitting diode driving circuit comprises a conversion circuit and a control circuit, wherein the conversion circuit receives a power supply signal to provide an output current to drive the light emitting diode, and consists of a switch element and a current detection element as well as inductance. A principle of a 90-degree phase difference between a resonance current and a voltage in a resonance circuit theory is employed, so the control circuit can determine a wave hollow point of two end voltage of the switch element according to the inductance current detected by the current detecting element and resonance signals of the two end voltage of the switch element after the inductance current decreased to zero; the switch element is controlled to switch between connection and cut-off via the wave hollow point of the two end voltage of the switch element, so absolute wave hollow point switch can be achieved and power loss and electromagnetic interference signal strength can be reduced during switch.

Description

technical field [0001] The invention relates to a driving circuit, in particular to a light emitting diode driving circuit with valley switching effect. Background technique [0002] Light-emitting diodes are components driven by low-voltage DC. Generally, in general lighting applications, a switching converter is often used as a driving circuit. [0003] refer to figure 1 , figure 2 and image 3 , a general switching converter such as figure 1 The step-down converter (Buck Converter) shown, such as figure 2 The buck-boost converter (Buck-Boost Converter) shown, and if image 3 In the shown flyback converter (Flyback Converter), the switching of the switching element 11 is used to achieve the effect of adjusting the output voltage / current. However, at the moment of switching of the switching element 11, switching loss (Switching Loss) and Electromagnetic Interference (EMI for short) and other issues. [0004] In recent years, in the study of reducing switching loss ...

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Problems solved by technology

[0007] Depend on Figure 4 It can be seen that due to the observed voltage V AUX The position of the trough point is variable, so the preset voltage V ref cannot track the observed voltage V well AUX trough point, but can only be switched in the second half cycle of resonance, and cannot achieve absolute trough switching

[0008] refer to image 3 and Figure 5 , Figure 5 shown as image 3 The schematic diagram of the switching waveform of the negative voltage comparison method corresponding to the flyback converter circuit of Figure 5 As can be seen in, the predetermined voltage V ref still cannot track the observed voltage V well AUX trough point, can not achieve absolute trough switching

[0009] Furthermore, by figure 1 , figure 2 ,and image 3 As can be seen in the prior art, in order to detect the observed voltage V AUX The auxiliary winding 12 and the voltage dividing resistor 13 must be added, and a corresponding pin must be added to the control circuit 14 to receive the observed voltage V AUX for subsequent comparisons, which increases system circuit component count and results in higher cost

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