CN201927998U

CN201927998U - Short circuit protection circuit for LED backlight lamp strings

Info

Publication number: CN201927998U
Application number: CN2010206252925U
Authority: CN
Inventors: 梁盛贤; 崔义团; 乔景明
Original assignee: Konka Group Co Ltd
Current assignee: Konka Group Co Ltd
Priority date: 2010-11-25
Filing date: 2010-11-25
Publication date: 2011-08-10
Anticipated expiration: 2020-11-25

Abstract

The utility model discloses a short circuit protection circuit for LED backlight lamp strings, which aims to resolve the technical problem that a constant-current module is required to be protected and economic loss is required to be reduced during LED short circuit damage. The technical scheme for resolving the technical problem includes that the short circuit protection circuit for LED backlight lamp strings comprises more than two groups of LED lamp strings, constant-current modules and a power supply module, the power supply module is respectively connected with the LED lamp strings, and each group of the LED lamp strings is connected with the corresponding constant-current module. The short circuit protection circuit is characterized in that two ends of the constant-current module of each group of LED lamp strings are connected with protection circuit modules, and the protection circuit modules are connected with the power supply module. When the short circuit protection circuit is compared with the prior art, the protection circuit modules and the power supply module are added in the constant-current modules in the LED backlight lamp strings, the constant-current modules driven by LEDs can be protected when LEDs on the LED lamp strings are in short circuit fault, and accordingly repair cost and economic loss are reduced.

Description

LED-backlit lamp string short-circuit protection circuit

Technical field

The utility model relates to a kind of backlight circuit of LED-backlit LCD TV, particularly a kind of LED-backlit lamp string short-circuit protection circuit.

Background technology

The backlight circuit of LED-backlit liquid crystal TV set generally all has the LED lamp string more than 2 or 2 at present.As shown in Figure 1, because LED brightness and current related so the LED-backlit drive circuit all has constant flow module, is given all LED lamp power supplies by a supply module, every LED lamp all with a constant flow module polyphone, the effect by constant flow module makes the current constant that flows through every LED lamp string.

When many LED lamps are series-parallel, be short-circuit condition if there are several LEDs to damage on wherein a certain, then the voltage that bears on the constant flow module of contacting on that root lamp string will raise, might surpass the voltage that constant flow module can bear, cause damaging constant flow module, and because the constant current effect of constant flow module, the electric current on the constant flow module is constant, the thermal losses of constant flow module as a result increases, and might burn out constant flow module.Circuit with Fig. 1 is an example, every lamp string all is connected in series by n LED, because the conduction voltage drop of each LED is all fixed, thus the voltage at every lamp string two ends be directly proportional with the LED quantity of polyphone, when not having the LED damage, VL1=VL2, Vc1=Vc2, Vc1+VL1=Vc2+VL2=Vo is when the 1st lamp string has the LED short circuit to damage, VL1 can diminish, again since the 2nd LED lamp string do not damage, so Vc2 and VL2 are constant, and Vo=Vc2+VL2, so Vo is constant, Vc1=Vo-VL1, Vo is constant, and VL1 diminishes, the result is that Vc1 becomes greatly, and promptly the voltage at constant flow module 1 two ends increases.Because the amount that Vc1 increases is directly proportional with the number that LED damages, when the LED damage was a lot of, Vc1 might cause constant flow module 1 to damage above the voltage that constant flow module 1 can bear.And after the voltage at constant flow module 1 two ends increases; because the effect of constant current; the electric current that constant flow module 1 is flow through is constant; so constant flow module 1 heating power own can increase; might cause constant flow module 1 to burn out, under the situation that has the LED short circuit to damage, prior art fails constant flow module is protected; constant flow module damages easily, causes economic loss.

Summary of the invention

The purpose of this utility model provides a kind of LED-backlit lamp string short-circuit protection circuit, and the technical problem that solve is a protection constant flow module when the LED short circuit damages, reduces economic loss.

For solving the problems of the technologies described above; the utility model is by the following technical solutions: a kind of LED-backlit lamp string short-circuit protection circuit; comprise two groups of above LED lamp string, constant flow module and supply modules; described supply module connects LED lamp string respectively; each group LED lamp string connects a constant flow module respectively; it is characterized in that: the two ends of the constant flow module of described each group LED lamp string are connected with the protective circuit module, and described protective circuit module connects supply module.

Protective circuit module of the present utility model is by the first divider resistance R1H; the second divider resistance R1L; voltage U 1; reference voltage Vref and protection executive circuit are formed; the described first divider resistance R1H connects with the second divider resistance R1L; the output head grounding of the second divider resistance R1L; the end of the first divider resistance R1H is connected with the two ends of the constant flow module of one group of LED lamp string; the described first divider resistance R1H connects with the second divider resistance R1L; the normal phase input end that connects voltage comparator U1 at the output of the first divider resistance R1H; the input of the second divider resistance R1L is connected with the normal phase input end of voltage comparator U1; the reverse input end of voltage comparator U1 connects reference voltage Vref, and the output of described voltage comparator U1 connects supply module through the protection executive circuit.

Protection executive circuit of the present utility model is made up of triode Q1, first resistance R 2 and second resistance R 3; the base stage of described triode Q1 is connected with voltage comparator U1 through first resistance R 2; grounded emitter, collector electrode are connected with the power supply pin Vcc of the control chip of supply module after the 3rd resistance R 3.

The utility model compared with prior art; add protective circuit module and supply module in the constant flow module of employing in LED-backlit lamp string; the constant flow module that can protect LED to drive when short trouble appears in the LED on LED lamp string, thus maintenance cost and economic loss reduced.

Description of drawings

Fig. 1 is the circuit theory diagrams of prior art.

Fig. 2 is circuit theory diagrams of the present utility model.

Fig. 3 is the circuit theory diagrams of the utility model protection executive circuit.

Embodiment

The utility model will be further described below in conjunction with drawings and Examples.

As shown in Figure 2; LED-backlit lamp string short-circuit protection circuit of the present utility model; comprise two groups of above LED lamp strings; constant flow module and supply module; described supply module connects LED lamp string respectively; each group LED lamp string connects a constant flow module respectively; the two ends of the constant flow module of each group LED lamp string (as VL1) connect the protective circuit module; the protective circuit module is by the first divider resistance R1H; the second divider resistance R1L; voltage U 1; reference voltage Vref and protection executive circuit are formed; wherein; the first divider resistance R1H connects with the second divider resistance R1L; the end of the first divider resistance R1H is connected with the two ends of the constant flow module of one group of LED lamp string; the first divider resistance R1H connects with the second divider resistance R1L; the normal phase input end that connects voltage comparator U1 at the output of the first divider resistance R1H; the input of the second divider resistance R1L is connected with the normal phase input end of voltage comparator U1; the reverse input end of voltage comparator U1 connects reference voltage Vref, and the output of voltage comparator U1 connects supply module through the protection executive circuit.VL1 is an example with LED lamp string; the first divider resistance R1H of protective circuit module connects with the second divider resistance R1L; the end of the first divider resistance R1H is connected with the two ends of the constant flow module 1 of LED lamp string VL1; the first divider resistance R1H connects with the second divider resistance R1L; the normal phase input end that connects voltage comparator U1 at the output of the first divider resistance R1H; the input of the second divider resistance R1L is connected with the normal phase input end of voltage comparator U1; the reverse input end of voltage comparator U1 connects reference voltage Vref; the output of described voltage comparator U1 connects supply module through the protection executive circuit; this protection executive circuit is by the triode Q1 of NPN type; first resistance R 2 and second resistance R 3 are formed; the base stage of described triode Q1 is connected with voltage comparator U1 through first resistance R 2; grounded emitter, collector electrode is connected with the power supply pin Vcc of the control chip of supply module through second resistance R 3.

When U1 output high level, triode Q1 saturation conduction, the power supply pin voltage of the control chip of supply module is dragged down, and control chip quits work, and causes supply module to stop the power supply of LED lamp, and constant flow module is protected.

When the voltage at constant flow module 1 two ends is higher; this partial pressure value is greater than Vref; relatively export high level; the protection executive circuit detects this high level; just, supply module is quit work, the LED disappearance of powering to supply module output protection signal; the loss of voltage at constant flow module two ends has been protected constant flow module.On each constant flow module, all add this overvoltage crowbar, just can protect all constant flow modules.

The magnitude of voltage of Vref can be provided with according to actual needs, but can not be higher than the withstand voltage upper limit of constant flow module.

Claims

1. LED-backlit lamp string short-circuit protection circuit; comprise two groups of above LED lamp string, constant flow module and supply modules; described supply module connects LED lamp string respectively; each group LED lamp string connects a constant flow module respectively; it is characterized in that: the two ends of the constant flow module of described each group LED lamp string are connected with the protective circuit module, and described protective circuit module connects supply module.

2. LED-backlit lamp string short-circuit protection circuit according to claim 1; it is characterized in that: described protective circuit module is by the first divider resistance R1H; the second divider resistance R1L; voltage U 1; reference voltage Vref and protection executive circuit are formed; the described first divider resistance R1H connects with the second divider resistance R1L; the output head grounding of the second divider resistance R1L; the end of the first divider resistance R1H is connected with the two ends of the constant flow module of one group of LED lamp string; the described first divider resistance R1H connects with the second divider resistance R1L; the normal phase input end that connects voltage comparator U1 at the output of the first divider resistance R1H; the input of the second divider resistance R1L is connected with the normal phase input end of voltage comparator U1; the reverse input end of voltage comparator U1 connects reference voltage Vref, and the output of described voltage comparator U1 connects supply module through the protection executive circuit.

3. LED-backlit lamp string short-circuit protection circuit according to claim 2; it is characterized in that: described protection executive circuit is made up of triode Q1, first resistance R 2 and second resistance R 3; the base stage of described triode Q1 is connected with voltage comparator U1 through first resistance R 2; grounded emitter, collector electrode are connected with the power supply pin Vcc of the control chip of supply module after the 3rd resistance R 3.