led backlight short circuit protection circuit

Abstract

The invention discloses an LED (light emitting diode) backlight short-circuit protection circuit, which comprises a first triode Q1, a second triode Q2 and a third triode Q3, wherein an emitting electrode of the first triode Q1 is connected to an LED load, a collector electrode of the first triode Q1 is grounded through a resistor R1 and a resistor R4 which are connected in parallel, the junction point of the resistor R1 and the resistor R4 is connected with a base electrode of the second triode Q2, and the base electrode is connected with a collector electrode of the third triode Q3 through a resistor R2; a collector electrode of the second triode Q2 is connected with a short-circuit protection end, and an emitting electrode is grounded; a base electrode of the third triode Q3 is connected with a control signal end through a resistor R3, and an emitting electrode is grounded; a constant output current is provided for the LED load by outputting high level to the control signal end, and the constant output current is not provided for the LED load by outputting low level to the control signal end; the short-circuit protection end and the control signal end are both connected onto a single-chip microcomputer; when the LED load is in short circuit, the second triode Q2 is connected, so that the short-circuit protection end outputs the low level, when the single-chip microcomputer detects that the short-circuit protection end is low-level, the low level is outputted to the control signal end, and the isolation protection can be realized.

Description

technical field [0001] The invention relates to the field of switching power supply circuits, and more particularly relates to an LED backlight short-circuit protection circuit. Background technique [0002] At present, in the application industry of switching power supply, especially in the application field of LED backlight TV, the mainstream constant current solution is mostly using BOOST boost circuit, that is, the front stage FLYBACK (or other architecture) outputs 12V (for power amplifier) ​​plus 24V (or other voltage levels), and then 24V again uses the second-stage BOOST constant current boost method, the structure diagram is as follows figure 1 Shown: After the AC input passes through the EMI filter circuit and bridge rectifier successively, and then passes through the pre-stage AC-DC voltage regulator circuit to output 12V voltage and 24V, and then the output 24V is first boosted and then BOOSTed to a constant current through a dedicated IC The working mode provid...

AI Technical Summary

Problems solved by technology

[0003] The solution is mature and highly reliable, but the price is too expensive to be widely used

Moreover, the existing LED backlight constant current scheme has no short-circuit protection, and there is no automatic isolation protection in the event of a short-circuit of the LED load, resulting in damage to the entire circuit element due to over-power consumption

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