KR100857239B1 - Error prevention circuit in back light driver - Google Patents

Abstract

A malfunction prevention circuit of a backlight driving control device is provided to reset a microcomputer and protect a circuit safely in an abnormal state by detecting a variation of a checked voltage. A malfunction prevention circuit of a backlight driving control device includes a microcomputer(100), an amplifying transistor(Q1), a first AC filter capacitor(C1), a first FET(Field Effect Transistor)(Q2), a second AC filter capacitor(C3), a second FET(Q3), and a regulator(200). The microcomputer outputs a first state voltage in a normal state, and outputs a second state voltage in an abnormal state. The amplifying transistor amplifies the first state voltage and the second state voltage of the microcomputer to a predetermined level. The first AC filter capacitor passes an AC component of the first and second state voltages amplified by the amplifying transistor. The first FET is controlled by a voltage outputted from the first AC filter capacitor, and switches a predetermined constant voltage. The second AC filter capacitor passes an AC component of the constant voltage based on a switching state of the first FET. The second FET is controlled in response to an output of the second AC filter capacitor, and switches the constant voltage. The regulator controls a supply state of a driving power of the microcomputer in response to an input of the constant voltage according to the switching of the second FET.

Description

Error prevention circuit in back light driver

1 is a malfunction prevention circuit diagram of a backlight driving control apparatus according to an embodiment of the present invention;

2 is an output waveform diagram of a microcomputer in a steady state;

3 is an output waveform diagram of a microcomputer in an abnormal state.

<Description of the code used in the main part of the drawing>

100: microcomputer 200: regulator

VCC: Constant Voltage Q1: Amplifying Transistor

Q2, Q3: FET C1, C3: AC Filter Capacitor

C2: smoothing capacitor D1: reverse bias diode

R4, R9: high pass filter resistor R5: discharge resistor

The present invention relates to a LED drive control device for a backlight used in the LCD.

Typically, a microcomputer (hereinafter, abbreviated as "microcomputer") is employed as the LED driving control device for backlight used in LCD. This microcomputer is much more susceptible to external input noise (eg static electricity) than conventional analog circuit components. When noise is input into an actual LED driving controller, the microcomputer is often latched or malfunctions.

Micom's malfunction can lead to abnormal operation of the device or undesirable effects such as failure or damage of internal components.

Therefore, there is an urgent need for a circuit for quickly detecting a malfunction of the microcomputer and forcibly resetting the microcomputer in the event of a malfunction.

The present invention provides a malfunction preventing circuit of a backlight driving control apparatus for detecting an operating state of a microcomputer.

The present invention provides a malfunction preventing circuit of a backlight driving control device for quickly restoring an abnormal state of a microcomputer to a normal state.

The present invention provides a microcomputer for outputting a first state voltage in a normal state and a second state voltage in an abnormal state; An amplifier transistor configured to amplify the first state voltage and the second state voltage of the microcomputer to a predetermined level; A first AC filter capacitor configured to pass AC components of the first state voltage and the second state voltage amplified by the amplifying transistor; A first FET controlled on / off by a voltage output from the first AC filter capacitor to switch a predetermined constant voltage; A second AC filter capacitor configured to pass an AC component of the constant voltage according to a switching state of the first FET; A second FET controlled on / off according to an output of the second AC filter capacitor to switch the constant voltage; And a regulator configured to control a supply state of driving power of the microcomputer in response to whether the constant voltage is input according to the switching of the second FET.

In one embodiment of the present invention, the first state voltage is a square wave check voltage.

The second state voltage is a check voltage of a high or low state.

The apparatus may further include a reverse bias preventing diode installed in the first AC filter capacitor to forward bias the AC voltage output from the first AC filter capacitor.

In addition, the regulator supplies a driving voltage to the microcomputer when the input voltage is high, and blocks the driving voltage supplied to the microcomputer when the input voltage is low.

In addition, the voltage amplifier may further include a voltage divider connected to the emitter and the base of the amplifying transistor to divide the square wave flowing from the microcomputer to a predetermined level.

The display device may further include a first resistor for the high pass filter connected to the first AC filter capacitor to form a closed loop and flowing a current.

In addition, it may further include a smoothing capacitor to smooth the output of the first AC filter capacitor.

The display device may further include a second resistor connected to the smoothing capacitor in parallel to discharge the voltage charged in the smoothing capacitor.

In addition, it may further include a third resistor for the high-pass filter connected to the second AC filter capacitor to form a closed loop to flow a current.

Hereinafter, exemplary embodiment (s) of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description there are shown a number of specific details, such as components of the specific circuit, which are provided only to help a more general understanding of the present invention that the present invention may be practiced without these specific details. It is self-evident to those of ordinary knowledge in Esau. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a malfunction prevention circuit diagram of a backlight driving control apparatus according to an embodiment of the present invention, FIG. 2 is an output waveform diagram of a microcomputer in a normal state, and FIG. 3 is an output waveform diagram of a microcomputer in an abnormal state. .

In the malfunction prevention circuit of the backlight driving control apparatus according to the exemplary embodiment of the present invention, as shown in FIG. 1, the microcomputer 100 outputs a square wave in a normal state, and applies a constant voltage (high or low) in an abnormal state. Output to check terminal.

The amplifying transistor Q1 is connected to the check terminal of the microcomputer 100 so that the base is connected to the check terminal to amplify the check signal output to the check terminal to a predetermined level, and the emitter is connected to the AC filter capacitor C1 and the constant voltage VCC. The collector is grounded. The resistor R3 for transmitting the constant voltage to the emitter of the amplifying transistor Q1 and the resistor R2 between the base and the collector divide the square wave voltage of the microcomputer 100 to a predetermined level to turn the amplifying transistor Q1 on / off. To be off. When the square wave is in the "high" state, the base voltage of the amplifying transistor Q1 is equal to or higher than the emitter, and the amplifying transistor Q1 is turned off. When the square wave is in the "low" state, the base of the amplifying transistor Q1 is turned off. The voltage becomes " low " and the amplifying transistor Q1 is turned on.

The AC filter capacitor C1 is connected to the emitter of the amplifying transistor Q1 to pass the AC component of the check signal amplified by the amplifying transistor Q1.

The high pass filter resistor R4 forms a closed loop connected to ground to form an electric potential difference so that the AC filter capacitor C1 can pass a current, and serves as a high pass filter. It passes the AC signal which changes periodically, and the peak voltage increases and decreases according to the filter setting.

The reverse bias preventing diode D1 is configured to prevent the AC filter capacitor C1 and the smoothing capacitor (C1) from being passed to the ground through the AC filter capacitor C1 and the amplifying transistor Q1 when the smoothing capacitor C2 of the rear stage is discharged. C2) is connected in the forward direction.

The discharge resistor R5 serves to discharge the charging voltage of the smoothing capacitor C2, and if there is no voltage supply from the AC filter capacitor C1, the voltage charged to the smoothing capacitor C2 is forced by the discharge resistor R5. Discharge.

The smoothing capacitor C2 smoothes an AC component transmitted from the reverse bias preventing diode D1 to discharge a predetermined level of voltage.

The FET Q2 is connected to the smoothing capacitor C2 with the gate connected to the smoothing capacitor C2 so that the on / off state is controlled by the voltage discharged from the smoothing capacitor C2, the drain is the constant voltage VCC and the AC filter capacitor ( Simultaneous connection to C3).

AC filter capacitor C3 is connected to the drain of FET Q2 to pass the AC component of constant voltage VCC switched by FET Q2.

The high pass filter resistor R9 forms a closed loop connected to ground to form a potential difference so that the AC filter capacitor C3 can pass a current, and serves as a high pass filter. It allows the AC signal to change temporarily, and the peak voltage increases and decreases according to the filter setting.

The gate is connected to the capacitor C3, the source is grounded, and the drain is connected to the constant voltage VCC and the regulator 200 so that the FET Q3 is switched by an AC component delivered from the AC filter capacitor C3.

The regulator 200 determines whether to supply power to the microcomputer 100 according to the constant voltage switched by the FET Q3.

Here, the resistor R1 is a voltage drop resistor that prevents a short between the microcomputer 100 and the amplifying transistor Q1.

Resistor R6 is the gate protection resistor of FET Q2.

The resistor R7 is a voltage drop resistor that protects the constant voltage VCC and the ground from being broken when the FET Q2 is operated.

The resistor R8 is a voltage drop resistor for dropping the voltage applied to the gate of the FET Q3.

The resistor R10 is a voltage drop resistor that protects the constant voltage VCC and the ground from being broken when the FET Q3 is operated.

That is, when the microcomputer 100 is in the normal state, as shown in FIG. 2, the check voltage of the square wave is output from the check terminal. The check voltage of the square wave is amplified to a predetermined level through the amplifying transistor Q1 and transferred to the AC filter capacitor C1. The AC filter capacitor C1 uses the characteristic of passing when the input voltage is AC, and transmits the output of the square wave to the reverse bias diode D1 for the rear stage.

The square wave check voltage passing through the reverse bias preventing diode D1 is smoothed to the constant voltage state in the smoothing capacitor C2, and is supplied to the gate of the FET Q2 to turn on the FET Q2.

When the FET Q2 is turned on, no voltage difference occurs between the AC filter capacitor C3 so that the AC filter capacitor C3 remains open, so that the gate of the FET Q3 is turned low. To be turned off.

Accordingly, the constant voltage VCC is supplied to the regulator 200, and the regulator 200 supplies a predetermined driving voltage to the microcomputer 100 by the constant voltage VCC supplied at all times.

Meanwhile, when the microcomputer 100 is in an abnormal state, as shown in FIG. 3, the check terminal outputs a check voltage in a constant voltage (high or low) state. The check voltage in the constant voltage state is amplified to a predetermined level through the amplifying transistor Q1 and transferred to the AC filter capacitor C1. Since no voltage variation occurs at both ends of the AC filter capacitor C1, the AC filter capacitor C1 is in an open state. Therefore, no voltage is transmitted to the reverse bias preventing diode D1. Therefore, no voltage is applied to the smoothing capacitor C2, and the gate of the FET Q2 is kept low and the FET Q2 is turned off.

When the FET Q2 is turned off, the constant voltage VCC is supplied to the AC filter capacitor C3, and a voltage difference is generated at both ends of the AC filter capacitor C3. Accordingly, a predetermined voltage is applied to the gate of the FET Q3. To temporarily turn on FET Q3.

When the FET Q3 is turned on, the constant voltage VCC is passed to the ground through the FET Q3, so that the voltage supplied to the regulator 200 is temporarily cut off. Therefore, the regulator 200 cuts off the voltage supplied to the microcomputer 100, and the microcomputer 100 is reset.

Thereafter, after a predetermined time has elapsed, the voltage of the AC filter capacitor C3 is discharged by the resistor R9 so that there is no voltage difference across the AC filter capacitor C3, the FET Q3 is turned off again, and the regulator ( 200 again supplies the normal voltage to the microcomputer 100.

Therefore, the circuit may be safely protected by automatically detecting an abnormal state of the microcomputer 100 and forcibly resetting the microcomputer 100.

As described above, although the specific embodiment (s) have been described in the detailed description of the present invention, various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiment (s), but should be defined by the appended claims and equivalents thereof.

The present invention can detect the change in the check voltage according to the abnormal state of the microcomputer to reset the microcomputer when the abnormal state, the microcomputer automatically returns to normal, and can safely protect the circuit.

Claims (10)

A microcomputer outputting a first state voltage in a normal state and a second state voltage in an abnormal state; An amplifier transistor configured to amplify the first state voltage and the second state voltage of the microcomputer to a predetermined level; A first AC filter capacitor configured to pass AC components of the first state voltage and the second state voltage amplified by the amplifying transistor; A first FET controlled on / off by a voltage output from the first AC filter capacitor to switch a predetermined constant voltage; A second AC filter capacitor configured to pass an AC component of the constant voltage according to a switching state of the first FET; A second FET controlled on / off according to an output of the second AC filter capacitor to switch the constant voltage; And And a regulator configured to control a supply state of the driving power of the microcomputer in response to whether the constant voltage is input according to the switching of the second FET. The method of claim 1, The first state voltage is, Malfunction prevention circuit of backlight drive control device which is square wave check voltage. The method of claim 1, The second state voltage is, Malfunction prevention circuit of backlight drive control device which is check voltage of high or low state. The method of claim 1, And a reverse bias prevention diode installed in the first AC filter capacitor to forward bias the AC voltage output from the first AC filter capacitor. The method of claim 1, The regulator, Supply a driving voltage to the microcomputer when the input voltage is high, A malfunction preventing circuit of a backlight driving control device which cuts off a driving voltage supplied to the microcomputer when the input voltage is low. The method of claim 1, And a voltage divider connected to the emitter and the base of the amplifying transistor, respectively, to divide a square wave flowing from the microcomputer to a predetermined level. The method of claim 1, And a first resistor for a high pass filter connected to the first AC filter capacitor to form a closed loop and allowing a current to flow. The method of claim 1, And a smoothing capacitor that smoothes the output of the first AC filter capacitor. The method of claim 8, And a second resistor connected to the smoothing capacitor in parallel and discharging the voltage charged in the smoothing capacitor. The method of claim 1, And a third resistor for a high pass filter connected to the second AC filter capacitor to form a closed loop to flow a current.

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