KR101080135B1 - Open Lamp Protection Circuit and Method Using The Same - Google Patents

Abstract

The present invention relates to an open lamp detection of a display device, and more particularly, to an open lamp detection circuit and a detection method for detecting an open lamp of a display device for driving a plurality of lamps to maintain system stability.

The present invention forms a current transformer having a primary to tertiary winding between the inverter and the lamp for an effective response to the open lamp in the display device for driving a plurality of lamps, and through the primary and secondary windings of the current transformer Detects the voltage induced in the tertiary winding according to the self-balancing state of the primary and secondary windings, and compares it with the comparison reference voltage to determine whether the lamp is open. If the above lamp is open, shut down the system to protect the remaining lamps and keep the system stable.

Description

Open Lamp Protection Circuit and Method {Open Lamp Protection Circuit and Method Using The Same}

1 is a schematic illustration of a typical direct backlight assembly;

2 is a block diagram conceptually illustrating an open lamp sensing circuit in accordance with the present invention;

3 is an exemplary configuration of an organic voltage detector and a determiner to explain an open lamp detection circuit according to the present invention.

<Code Description of Main Parts of Drawing>

200: induced voltage detection unit 210: determination unit

220: ENA control unit 230: ENA output unit

The present invention relates to an open lamp detection of a display device, and more particularly, to an open lamp detection circuit and a detection method for detecting an open lamp of a display device for driving a plurality of lamps to maintain system stability.

Among the various display devices, liquid crystal display devices (LCDs), which have advantages such as light weight, thinness, and low power consumption driving, have been widely used due to their wide range of application, and these liquid crystal display devices have been actively developed. It is widely used in audio and video equipment.

In general, a liquid crystal display device is manufactured in a form in which a liquid crystal layer is interposed between two substrates including an electric field forming electrode, and the alignment angle of the liquid crystal is changed by an electric field formed between the two substrates, The transmittance of is controlled to represent the desired image.

On the other hand, such a liquid crystal display device is a light-receiving device that displays an image by adjusting the amount of light irradiated from the outside requires a light source, that is, a backlight assembly for irradiating light to the liquid crystal panel.

The backlight assembly is classified into an edge type and a direct type according to the position of the light source with respect to the display surface. Among these, the direct type backlight assembly has a large light utilization rate, is easy to handle, and there is no limitation on the size of the display surface. It is widely used in liquid crystal display devices.

In addition, the backlight lamp configured in the backlight assembly is typically configured using a plurality of cold cathode fluorescent lamps (CCFL) or an external electrode fluorescent lamp (EEFL), and uses a single voltage supply. In parallel, a parallel drive inverter system for driving a plurality of lamps is generally used.

1 is a view schematically showing a general direct backlight assembly.

As illustrated, the direct type backlight assembly 100 includes a plurality of lamps 110, first and second inverters 120 and 130 for driving the plurality of lamps 110, and a plurality of lamps ( 110 is connected to and driven in parallel with the first and second inverters 120 and 130.

At this time, the first and second inverters (120, 130) is composed of a transformer (Transformer) as a main element, the current limiting capacitor (Cs) for controlling the current output to the lamp 110 is provided respectively In addition, the low-voltage alternating current power input is converted into high-voltage alternating current power enough to drive the lamp 110 and supplied to both electrodes of the lamp 110.

Meanwhile, when the lamp 110 is opened, excessive voltage is applied to the remaining lamps 110, which causes problems such as deterioration of the life of the lamp 110 and damage of the lamp 110, thereby detecting the system. Should be shut down to maintain stabilization.

At this time, it is possible to determine whether the lamp 110 is opened by an electrical signal, but the change rate is small when the lamp 110 is in a normal state and in an abnormal state, which is difficult to use.

More specifically, if 20 lamps are connected in parallel, the total impedance of the lamp is the impedance / lamp number of one lamp, and the impedance of one lamp is usually about 200㏀, so it is 10㏀ in the normal state, In the case of 10.5㏀.

As such, the rate of change between steady state and abnormal state is only 5%, which is the initial starting state of the lamp, environmental test condition (0 ~ 60 ℃), input voltage (24 ± 10%), dimming (Minmm, Max ~) Since the effect of the condition exceeds the change of 5%, it is difficult to shut down the system by using an electrical signal.

As a result, the OVP function may be used at present, but the OVP function may not respond to an open situation of each lamp because the power shutdown function does not work until a plurality of lamps are opened.

Therefore, an object of the present invention is to improve the disadvantage of the open lamp detection circuit, and for this purpose, a current transformer having first to third coils is formed between the transformer and the lamp of the inverter, and the balance of the primary and secondary coils is formed. By determining whether the lamp is open by comparing the voltage induced in the tertiary coil with the reference voltage according to the state, it is possible to effectively sense the open state of each lamp to shut down the system.

The open lamp detection circuit according to the present invention for the above object and the ENA output unit for outputting a power enable signal; Organic voltage sensing unit comprising a primary and secondary windings for driving the n and m lamps, respectively, and a current transformer having a tertiary winding in which voltage is induced according to a self-balancing state of the primary and secondary windings. Wow; A determination unit which receives the detected voltage from the induced voltage detection unit and a comparison reference voltage and determines whether the lamp is open; And an ENA controller configured to receive a power enable signal from the ENA output unit and to control an output of the power enable signal according to a cutoff control signal input from the determination unit.

At this time, the sum of n and m is equal to the total number of the lamps.

N or m is 1;

The turns ratio of the primary and secondary windings is m: n.

When there is no open lamp, the induced voltage detector outputs a voltage close to 0 [V], and when there is an open lamp, a value larger than the output voltage when there is no open lamp is output.

The primary and secondary windings have the same inductance value per unit length.

The determining unit includes a rectifying unit and a smoothing unit for converting AC power into a DC power source, and a comparing unit which receives the DC power source and compares it with the comparison reference voltage to determine whether the lamp is opened.

The induced voltage output from the induced voltage detector is proportional to the number of turns of the tertiary winding.

The comparison reference voltage is smaller than the sensing voltage output from the induced voltage detector when the one lamp is opened and is greater than 0 [V].

One or two of the induced voltage detector and the determiner are configured according to the driving method of the lamp.

The open lamp detection method according to the present invention for the above object comprises the steps of: outputting a power enable signal from the ENA output unit; Sensing a voltage induced in the tertiary winding according to a self-balancing state of the primary and secondary windings in the induced voltage sensing unit; Receiving the sensed voltage and the comparison reference voltage, determining whether the lamp is open, and outputting a cutoff control signal; And receiving the cutoff control signal from the ENA controller to control an output of a power enable signal.

In this case, the method further includes converting the voltage induced in the tertiary winding into a DC power source.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram conceptually illustrating an open lamp detection circuit according to the present invention.

As shown, the open lamp detection circuit according to the present invention includes an ENA output unit, an ENA control unit, an induced voltage detection unit, and a determination unit.

ENA output unit 230 outputs a power enable signal (ENA) instructing the operation of the system, the enable signal (ENA) is a continuous power to the system to the driver (not shown) that supplies power to the system This signal indicates.

The ENA control unit 220 receives the power enable signal ENA from the ENA signal output unit 230 and outputs an external output of the power enable signal ENA by the cutoff control signal S of the determination unit 220. When the output of the power enable signal ENA is cut off by the ENA controller 220, the power supply to each component of the system is stopped and the system is shut down.

The induced voltage sensing unit 200 is formed between an inverter and a plurality of lamps, and is composed of a current transformer having primary to tertiary windings and tertiary according to the self-balancing state of the primary and secondary windings. The voltage induced in the winding is supplied to the determination unit 210.

At this time, the primary to tertiary windings are formed as coils having the same inductance value per unit length.

The determination unit 210 receives the induced voltage from the induced voltage sensing unit 200 and compares the induced voltage with a reference voltage to determine whether the lamp is open, and supplies the cutoff control signal S to the ENA controller 220. .

On the other hand, the open lamp detection circuit according to the present invention is applicable to both the method of driving the lamp with one power supply voltage, the method of driving with two power supply voltages of different phases, and the method of driving with two power supply voltages In this case, the open lamp detection circuit, precisely the induced voltage detection unit and the determination unit may be configured in only one power supply unit, but it is preferable to configure each of the two power supply units.

Hereinafter, a case in which an open lamp detection circuit (organic voltage detection unit and determination unit) is configured in each of two power supply units, which are the most preferable methods, will be described as an embodiment.

3 is an exemplary view illustrating an organic voltage sensing unit and a determination unit for explaining an open lamp detection circuit according to the present invention. The circuit configuration of the illustrated determination unit may be freely changed without departing from the technical spirit as an example.

As shown, a plurality of lamps and first and second inverters 332 and 334 for supplying power to both electrodes of the lamps are formed, and between the first and second inverters 332 and 334 and the lamps. The organic voltage sensing unit 300 is formed at the second side, and the determination unit 310 is formed to receive the output (detected voltage) of the organic voltage sensing unit 300.

As described above, the organic voltage sensing unit 300 is composed of a current transformer having primary to tertiary windings 302, 304, and 306, and is formed of primary and secondary windings 302 and 304. The voltage induced in the tertiary winding 306 is supplied to the determination unit 310 according to the self equilibrium state.

N lamps are connected and driven in the primary winding 302 of the current transformer, and m lamps (the total number of lamps-the number of lamps connected to the primary winding) are connected to the secondary winding 304. And driven, the lamp is not connected to the tertiary winding 306 and used as an output terminal of the organic voltage sensing unit 300.

At this time, it is most preferable that n or m is 1, that is, one lamp is connected to the primary side or the secondary side, and the other lamp is connected to the secondary side or the primary side to drive.

On the other hand, the winding ratio of the primary and secondary windings 302, 304 is set based on the normal state (no open lamp), and the current and the number of turns flowing in the primary winding 302 are I1 and N1. If the current flowing through the secondary winding 304 and the number of turns are referred to as I2 and N2, the turns ratio N1: N2 is as follows.

There are n and m lamps connected to the primary and secondary windings 302 and 304, respectively, and because each lamp has the same resistance, the same current I flows through each lamp. Therefore, the current of nI flows through the primary winding 302 connected to the n lamps, and the current of mI flows through the secondary winding 304 to which the m lamps are connected.

At this time, since the current and the number of turns of the primary and secondary windings 302 and 304 have a relationship of I2 / I1 = N1 / N2, mI / nI = N1 / N2, whereby N1: N2 = m: n. That is, the turns ratio of the primary and secondary windings 302 and 304 should be set to be m: n.

On the other hand, voltage e3 = (Δφ / Δt) * N3 [V] induced in the tertiary winding 306 of the current transformer is N3, the number of turns of the tertiary winding 306, and Δφ is the magnetic flux density change amount.

Further, Δφ = | φ1-φ2 | = | (L1 * I1)-(L2 * I2) |, where L1 and L2 are the inductance values of the primary and secondary windings 302 and 304, respectively, and the primary and secondary windings 302, 304) has the same inductance value per unit length, so that L1 and L2 may be replaced with the number of turns N1 and N2. Thus Δφ = | φ1-φ2 | = | (N1 * I1)-(N2 * I2) |, where N1 and N2 are m and n, respectively, so the equation above is Δφ = | φ1-φ2 | = | (m * I1)-(n * I2) |

In summary, the number of lamps connected to the primary and secondary windings 302 and 304 is n: m, the current ratio is nI: mI, the winding ratio is m: n, and is induced in the tertiary winding. The voltage e3 = (| (m * I1)-(n * I2) | / Δt) * N3 [V].

Because of this, in steady state e3 = | (m * nI)-(n * mI) | = 0, and in an abnormal state (lamp open), e3 = | (m * I1 ')-(n * I2') | and (m * I1 ') ≠ (n * I2'), so e3 ≠ 0 Becomes

At this time, I1 'and I2' are currents flowing in the primary and secondary windings 302 and 304 when the lamp is opened, respectively.

As an example for understanding, if the total number of lamps is 10, one lamp is connected to the primary winding 302 of the current transformer and nine lamps are connected to the secondary winding 304, that is, n = 1, The case where m = 9 is demonstrated.

Since one lamp is connected to the primary winding 302 and nine lamps to the secondary winding 304, n: m = 1: 9, and thus the winding ratio is N1: N2 = 9: 1.

In the steady state, the current flowing in the primary and secondary windings 302 and 304 becomes I1 = 1I and I2 = 9I, respectively, and the induced voltage e3 = | (9 * 1I)-(1 * 9I) | = | 9I-9I | Since = 0, no voltage is induced in the tertiary winding 306.

In an abnormal state, more specifically, when the lamp connected to the secondary winding 304 is opened, the current I2 flowing in the secondary winding 304 to which the open lamp is connected is reduced, and the open lamp is not connected. The current I1 flowing in the primary winding 302 which is not (no open ramp) is increased.

At this time, the increase value of I1 and the decrease value of I2 are the same, that is, the sum of I1 and I2 is the same as the sum of I1 and I2 in the steady state, and for convenience of explanation, I1 = 1.3I and I2 = 8.7 Assume that it is reduced to I.

Therefore, in an abnormal state e3 = | (9 * 1.3I) * (1 * 8.7I) | * N3, and | 11.7I-8.7I | = 2I ≠ 0, voltage is induced in the tertiary winding 306, and the voltage induced in the tertiary winding 306 as shown in the formula is proportional to the number of turns of the tertiary winding 306, that is, N3 Induction, it is possible to adjust the output (output voltage) of the sense voltage.

The determination unit 310 may be largely divided into a rectifier 312, a smoothing unit 314, and a comparator 316, and the rectifying unit and the smoothing units 312 and 314 may be detected from the induced voltage detector 300. Voltage, more precisely, rectifies and smoothes AC power to DC power, and receives the rectified and smoothed power (DC power) from the comparator to compare the reference voltage (Vref) to judge whether the lamp is open. do.

As shown in the drawing, the rectifier 312 includes first and second diodes D1 and D2 connected in parallel, and the smoothing unit 314 is connected in series with the first resistor R1 and the first resistor R1. The second resistor R2 and the capacitor C are connected in parallel to each other, and the sensing voltage is rectified and smoothed by DC through the rectifier 312 and the smoother 314.

The comparator 316 receives a comparison reference voltage Vref and a sense voltage (a sense voltage converted into a DC power supply) and outputs a cutoff control signal S. The comparator OP-Amp is a comparator. It is composed.

As shown, a reference voltage Vref is input to the inverting input terminal (-) of the operational amplifier OP-Amp, a sense voltage is input to the non-inverting input terminal (+), and a high signal is detected when the sensing voltage is high. (Signal for interrupting the power supply enable signal) is output, and a low signal (a signal for holding the power supply enable signal) is outputted when the comparison reference voltage Vref is high.

On the other hand, in case of theoretically steady state, the detection voltage is 0 [V]. Therefore, the reference voltage (Vref) should be set to 0 [V]. Even if the sense voltage is not 0 [V], a slightly higher voltage is sensed.

Therefore, in consideration of this, the reference voltage (Vref) should be set slightly higher than 0 [V].

At this time, it is possible to adjust the sensed voltage output to N3 (third winding number), so you need to set the reference voltage (Vref) in consideration of this.

For example, if N3 is set so that the sense voltage outputted when one lamp is opened is about 5 [V], the reference voltage should be set to 5 [V]> Vref> 0 [V].

As described above, the open lamp detection circuit according to the present invention detects the voltage induced in the tertiary winding 306 through the current transformer having the primary to tertiary windings 302, 304, 306, and sensed voltage The determination unit 310 compares the comparison with the reference voltage Vref to determine whether the lamp is open, and accordingly supplies the cutoff control signal S to the ENA control unit 220 of FIG. 2 to shut down the system.

As described above, the open lamp detection circuit according to the present invention is formed between the inverter and the lamp, and determines whether the lamp is opened by determining whether the lamp is open by a voltage sensed using a current transformer having primary to third windings. By detecting excessive voltage applied to the surrounding lamp of the open lamp, problems such as lamp life deterioration and lamp breakage are improved.

In addition, when one of the lamps is opened, the system shuts down, protecting the remaining lamps and maintaining system stabilization.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

As described above, the open lamp sensing circuit according to the present invention forms a current transformer having primary to third windings between the inverter and the lamp, drives the lamp with the primary and secondary windings, and the magnetic field of the primary and secondary windings. By determining whether the lamp is open by comparing the voltage induced in the tertiary winding with the comparison reference voltage according to the equilibrium state, the system is shut down in response to the open condition of each lamp to protect the remaining lamps and to maintain stability of the system. It works.

Claims (12)

An ENA output unit for outputting a power enable signal; An organic voltage sensing unit including a primary and a secondary winding to which n and m lamps are connected, and a current transformer having a tertiary winding in which voltage is induced according to a self-balancing state of the primary and secondary windings; ; A determination unit which receives the detected voltage from the induced voltage detection unit and a comparison reference voltage and determines whether the lamp is open; An ENA controller which receives a power enable signal from the ENA output unit and controls the output of the power enable signal according to a cutoff control signal input from the determination unit; Open lamp detection circuit comprising a. The method of claim 1, Wherein the sum of n and m is equal to the total number of lamps. The method of claim 1, The open lamp detection circuit of the n or m is 1. The method of claim 1, The winding ratio of the primary and secondary windings is m: n open lamp detection circuit. The method of claim 1, The zero voltage detection unit outputs a voltage of 0 [V] when there is no open lamp, and when there is an open lamp, a value greater than a voltage output when there is no open lamp. The method of claim 1, The first and second windings have an open ramp sensing circuit having the same inductance value per unit length. The method of claim 1, And the determination unit includes a rectifying unit and a smoothing unit for converting an AC signal into a DC signal, and a comparing unit receiving the DC signal and comparing the DC reference signal to determine whether the lamp is open. The method of claim 1, And an induced voltage output from the induced voltage detector is proportional to the number of turns of the tertiary winding. The method of claim 1, The comparison reference voltage is less than the detection voltage output from the induced voltage detector when the one lamp is open, the open lamp detection circuit is greater than 0 [V]. The method of claim 1, And one or two of the induced voltage detector and the determiner according to the driving method of the lamp. An ENA output unit for outputting a power enable signal; An organic voltage sensing unit including a primary and a secondary winding to which n and m lamps are connected, and a current transformer having a tertiary winding in which voltage is induced according to a self-balancing state of the primary and secondary windings; ; A determination unit which receives the detected voltage from the induced voltage detection unit and a comparison reference voltage and determines whether the lamp is open; In the open lamp detection method of the open sensing circuit comprising an ENA control unit for receiving a power enable signal from the ENA output unit, and controlling the output of the power enable signal in accordance with the cutoff control signal input from the determination unit, Outputting a power enable signal from the ENA output unit; Sensing a voltage induced in the tertiary winding according to a self-balancing state of the primary and secondary windings by the induced voltage sensing unit; Receiving the sensed voltage and the comparison reference voltage, determining whether the lamp is open, and outputting a cutoff control signal; Controlling the output of a power enable signal by receiving the cutoff control signal from the ENA controller; Open lamp detection method comprising a. The method of claim 11, And converting the voltage induced in the third winding into a DC signal.

Images