KR20110017491A - Current driving circuit and led driving circut for using the same - Google Patents

Abstract

PURPOSE: A current driving circuit and an LED driving circuit for using the same are provided to flow exact amount of current into an LED assembly by allowing a current having the offset voltage compensation current of an amplifier into the LED assembly. CONSTITUTION: An LED driver circuit(100) comprises an LED assembly(140), a high voltage generating unit(110), a current drive circuit part(130), and a PWM controller(120). The high voltage generating unit boosts voltage and transmit it to the LED assembly. An input signal is converted into an output signal through the current drive circuit and is fedback to an input terminal.

Description

CURRENT DRIVING CIRCUIT AND LED DRIVING CIRCUT FOR USING THE SAME}

The present invention relates to a current driving circuit and an LED driving circuit using the same, and more particularly, to a current driving circuit for stably supplying current to a plurality of light emitting diodes and an LED driving circuit using the same.

Cold Cathode Fluorescent Lamp (CCFL) was used as a light emitting device. However, in the case of CCFL, the response speed is about 15ms and color reproducibility is low. In addition, the use of mercury can lead to environmental hazards. Recently, however, light emitting diodes (LEDs) have attracted attention as environmentally friendly materials.

In addition, the light emitting diodes are environmentally friendly due to less mercury use and power consumption compared to CCFLs, fast response speed, and excellent color reproducibility. In addition, since the brightness and color temperature of the backlight may be arbitrarily adjusted by adjusting the amount of light of the light emitting diodes emitting red, green, and blue colors, the amount of light of the backlight may be adjusted according to an image displayed on the display device.

The driving device for lighting the light emitting diode includes an LED assembly formed by connecting a plurality of diodes. Since the optical characteristics of the light emitting diode are determined by the current flowing through the light emitting diode, it is preferable to adjust the voltages of both ends of the light emitting diode.

1 is a view showing a current driving circuit for supplying current to the LED driving circuit according to the prior art. Referring to FIG. 1, the current driving circuit includes a first transistor T1 and a feedback unit 10.

The first transistor T1 has a first electrode connected to an LED assembly (not shown) in which a plurality of light emitting diodes are connected in series, and the second electrode is connected to a resistor R _SET . The output terminal of the amplifier 11 is connected to the gate.

The feedback unit 10 includes an amplifier 11 and a resistor R _SET , and the amplifier 11 receives a reference voltage V _REF to a positive terminal and a resistor R _SET to a negative terminal. The formed voltage is fed back and delivered.

In the current driving circuit configured as described above, the voltage formed on the resistor R _SET under the control of the feedback unit 10 is defined as a voltage equal to the reference voltage V _REF . Therefore, the current flowing through the LED assembly is theoretically represented by Equation 1 below.

I _LED = V _REF / R _SET

(I _LED is the current flowing through the LED assembly, V _REF is the reference voltage, and R _SET is the magnitude of the resistance formed in the feedback part.)

However, since the offset voltage Vos is present in the amplifier 11, the current flowing through the LED assembly is expressed by Equation 2 below.

I _LED = (V _REF -Vos) / R _SET

(I _LED is the current flowing through the LED assembly, V _REF is the reference voltage, R _SET is the size of the resistor formed in the feedback section, and Vos is the offset voltage of the amplifier.)

Therefore, there is a problem that an error due to the offset voltage of the amplifier occurs in the current flowing through the LED assembly.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a current driving circuit and an LED driving circuit using the same, by allowing a current corresponding to an offset voltage of an amplifier to flow through the LED assembly, so that an accurate current flows through the LED assembly.

In addition, the technical problem to be achieved by the present invention is to drive a current corresponding to the offset voltage of the amplifier to the LED assembly so that the correct current flows to the LED assembly to enable accurate and fine dimming control and LED using the same It is to provide a driving circuit.

In order to achieve the above object, a first aspect of the present invention provides an LED assembly including a plurality of light emitting diodes; A high voltage generator for boosting an input voltage to apply a high voltage to the LED assembly; A current driving circuit for controlling a current flowing in the LED assembly; And a PWM control unit for controlling the high voltage generation unit, wherein the current driving circuit changes an output signal by changing an input signal input to an input terminal, and feeds back the output signal to output a voltage at a time when a predetermined voltage is detected. The present invention provides an LED driving circuit that fixes an offset voltage by fixing an input signal input to an input terminal.

In order to achieve the above object, the second aspect of the present invention, the first switching element for causing a current to flow from the first electrode to the second electrode corresponding to the voltage applied to the gate; A first amplifier for applying a predetermined voltage to the gate of the first switching element, a resistor formed between the first node to which the second electrode of the first switching element is connected and ground, and the negative of the first amplifier A first switch for switching between a terminal and the first node, a second switch for switching between an output terminal of the first amplifier and a gate of the first switching element, and a negative terminal of the first amplifier An amplifier comprising a third switch for switching an input of the fourth switch and a fourth switch for switching between an output terminal of the first amplifier and a controller; A voltage D / A converter for generating the lowest voltage from the lowest voltage; And sequentially outputting the highest voltage from the lowest voltage in the voltage D / A converter, and detecting an offset voltage of the first amplifier so that an offset voltage is transferred from the voltage D / A converter to a positive terminal of the first amplifier. It provides a current drive circuit comprising the control unit to deliver a compensated voltage.

According to the current driving circuit and the LED driving circuit using the same according to the present invention, by allowing a current compensated for the offset voltage value of the amplifier to flow through the LED assembly, a more accurate amount of current can flow through the LED assembly.

In addition, according to the present invention, more accurate dimming control is possible by allowing a current to be compensated for the offset voltage value of the amplifier to flow through the LED assembly.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

2 is a structural diagram showing the structure of the LED driving circuit according to the present invention. Referring to FIG. 2, the LED driving circuit 100 includes an LED assembly 140, a high voltage generation unit 110, a PWM control unit 120, and a current driving circuit unit 130.

The LED assembly 140 has a plurality of light emitting diode rows in which a plurality of light emitting diodes are connected in series are arranged in parallel. Then, light is emitted in response to the current flowing through each LED row. The light emitting diodes emit red, green, and blue light, and can adjust luminance of red, green, and blue, respectively.

The high voltage generator 110 receives the input voltage Vin and boosts the voltage to the LED assembly 140. The coil L, the diode D, the transistor T3, the gate driver 110a, and the booster controller 110b and capacitor C2. The high voltage generation unit 110 causes a change in the current flowing through the coil L by the turn-on / turn-off operation of the transistor T3 to generate a high voltage by the electromotive force generated in the coil L. Then, the current is output in one direction by the diode D. The current output through the diode D is applied to the LED assembly 140 at a high voltage through the capacitor C2. The current output through the diode D1 is fed back to control the booster controller 110b by the first resistor r1 and the second resistor r2. The booster controller 111b receives the pulse width modulated signal by the PWM controller 120 to drive the gate driver 110a to adjust the turn-on / turn-off time of the switching device to adjust the magnitude of the electromotive force generated in the coil L. It can be adjusted.

The PWM controller 120 generates a pulse width modulated signal V _PWM and transmits the generated pulse width modulated signal V _PWM to the high voltage generator 110. The high voltage generation unit 110 receiving the pulse width modulation signal V _PWM boosts the input voltage Vin. In addition, the PWM controller 120 may transmit the pulse width modulation signal V _PWM to the current driver circuit 130.

The current driver circuit unit 130 includes a plurality of current driver circuits 130a... 130j, and a light emitting diode column of the LED assembly 140 is connected to each of the current driver circuits 130a. . In addition, the amount of current flowing through the LED assembly 140 is determined by each of the current driving circuits 130a... 130j to adjust the amount of light emitted from the LED assembly 140. In addition, the current driver circuit unit 130 may receive a pulse width modulation signal (V _PWM ) from the PWM controller 120 to control the connection relationship between the LED assembly 140 and the current driver circuits 130a ... 130j. .

3 is a structural diagram showing a first embodiment of the current driving circuit employed in the LED driving circuit according to the present invention. Referring to FIG. 3, the current driving circuit 130a includes a first switching element M1a, a voltage D / A converter 132a, a controller 133a, and an amplifier 135a. In addition, the first switching device M1a may be implemented as a transistor, and the transistor includes a source electrode, a drain electrode, and a gate electrode. In addition, a source electrode and a drain electrode can be called a 1st electrode and a 2nd electrode.

The first switching device M1a controls the current flowing from the first electrode to the second electrode in response to the voltage applied to the gate. The first electrode of the first switching device M1a is connected to the LED array 140, the second electrode is connected to the first node N1a, and the gate is connected to the second switch S2a of the amplifier 135a. Connected.

The voltage D / A converter 132a sequentially outputs the highest voltage at the lowest voltage and supplies it to the amplifier 135a.

The controller 133a detects the change in the output voltage of the amplifier 135a to determine the offset voltage of the amplifier 135a and then outputs a voltage corresponding to the offset voltage in the voltage D / A converter 132a. .

The amplifier 135a receives a resistor R _SET1 connected between the ground and the first node N1, a reference voltage V _REF to a positive terminal, and a voltage formed by the resistor R _SET1 to a negative terminal. The first amplifier (131a) receiving the transmission, the first switch (S1a) for switching between the negative terminal of the first amplifier 131a and the first node (N1a), the output terminal and the first switching of the first amplifier (131a) A second switch S2a for switching between gates of the element M1a, a third switch for switching between a reference voltage input terminal VREF to which the reference voltage V _REF is input and a negative terminal of the first amplifier 131a (S3a), the fourth switch (S4a) for switching between the output terminal of the first amplifier (131a) and the control unit (133a).

In the current driving circuit 130a configured as described above, first, the first switch S1a and the second switch S2a are turned off, and the third switch S3a and the fourth switch S4a are kept on. . Therefore, the reference voltage V _REF is transmitted to the negative terminal of the first amplifier 131a and the voltage of the output terminal of the first amplifier 131a is transferred to the controller 133a. At this time, since the first switch S1a and the second switch S2a are off, input of the voltage of the first node N1a to the negative terminal of the first amplifier 131a is blocked and the first amplifier 131a is blocked. The output voltage of the first switching element M1a is blocked from being transferred to the gate.

The voltage D / A converter 132a sequentially transfers the highest voltage at the lowest voltage to the positive terminal of the first amplifier 131a. In the first amplifier 131a, the first amplifier is driven by the high open loop gain of the first amplifier 131a at a moment when the difference between the voltages input to the negative and positive terminals becomes the offset voltage of the first amplifier 131a. The output of 131a is changed from the low state to the high state. At this time, the controller 133a senses a change in the output voltage of the first amplifier 131a and the amplifier in the voltage D / A converter 132a at the moment when the output of the first amplifier 131a changes from a low state to a high state. The voltage input to the positive terminal of 131a is grasped. The identified voltage is recognized as the offset voltage of the first amplifier 131a.

When the first switch S1a and the second switch S2a are turned on, and the third switch S3a and the fourth switch S4a are turned off, the positive terminal of the first amplifier 131a is turned on. The voltage output from the voltage D / A converter 132a is transferred and the voltage of the first node N1a is transferred to the negative terminal of the first amplifier 131a. The voltage of the output terminal of the first amplifier 131a is transferred to the gate of the first switching element M1a. In this case, the voltage output from the voltage D / A converter 132a is a voltage obtained by adding up the reference voltage V _REF and the offset voltage of the first amplifier 131a determined by the controller 133a. Accordingly, the gate of the first switching device M1a is applied with a voltage reflecting the offset voltage of the first amplifier M1a, thereby reducing the driving error of the current flowing from the source of the first switching device M1a to the drain direction.

4 is a structural diagram showing a second embodiment of the current driving circuit employed in the LED driving circuit according to the present invention. Referring to FIG. 4, the current driving circuit 130b includes a first switching element M1b, an amplifier 141, a voltage D / A converter 132b, a controller 135b, and a mirror unit 142. do. The first switching device M1b may be implemented as a transistor, and the transistor includes a source electrode, a drain electrode, and a gate electrode. In addition, a source electrode and a drain electrode can be called a 1st electrode and a 2nd electrode.

The first switching device M1b allows a driving current to flow in the LED array by flowing a current from the first electrode to the second electrode corresponding to the voltage applied to the gate. The first electrode of the first switching device M1b is connected to the LED array, the second electrode is connected to the first node N1b, and the gate is connected to the second switch S2b of the amplifier 141. The first electrode and the second electrode of the first switching element M1b correspond to the source electrode and the drain electrode.

The amplifier 141 allows a current to flow through the first switching device M1b by applying a predetermined voltage to the gate of the first switching device M1b. The amplifier 141 receives a resistor R _SET2 connected between the ground and the first node N1b and receives a predetermined voltage from the voltage D / A converter 132b to the positive terminal and receives the resistor to the negative terminal. The first amplifier 131b receiving the voltage formed by R _SET2 , the first switch S1b for switching between the negative terminal of the first amplifier 131b and the first node N1b, and the first amplifier ( A third switch (S2b) for switching between the output terminal of the 131b and the first switching device (M1b), the third switch for switching between the negative terminal of the voltage D / A converter 132b and the first amplifier (131b) ( S4b) and a fourth switch S4b for switching between the output terminal of the first amplifier 131b and the controller 135b.

In addition, the voltage D / A converter 132b includes a resistor string 133b and a decoder 134b. The resistor string 133b is connected between the first reference voltage and the second reference voltage and a plurality of resistors are connected in series. Here, the first reference voltage corresponds to a voltage generated in the resistor string 133b by a current flowing from the first electrode to the second electrode of the third switching element M3b, and the second reference voltage corresponds to ground. The first reference voltage and the second reference voltage are divided by the plurality of resistors to generate the lowest voltage to the highest voltage. The decoder 134b selects a voltage from the lowest voltage to the highest voltage generated by the resistor string 133b by a switching operation and transfers the same to the positive terminal of the first amplifier 131b.

The control unit 135b sequentially inputs the highest voltage from the lowest voltage to the positive terminal of the first amplifier 131b in the voltage D / A converter 132b. Then, the voltage of the output terminal of the first amplifier 131b is sensed to determine the offset voltage of the first amplifier 131b.

The mirror unit 142 applies a predetermined voltage to the voltage D / A converter 132b to output a predetermined voltage from the amplifier 141 so that a current can flow to the LED array. The mirror unit 142 includes a second switching element M2b in which a first electrode is connected to a first driving power supply VDD, and a second electrode and a gate are connected to a second node N2b, and the first electrode is a first driving device. The third switching device M3b connected to the power supply VDD, the second electrode connected to the resistor string 133b, and the gate connected to the gate of the second switching device M2b, and the reference voltage _VREF as a positive terminal. A fourth switching for applying current from the first electrode to the second electrode by applying the output voltages of the second amplifier 142b and the second amplifier 142b to which the feedback is transmitted and the feedback voltage is transmitted to the negative terminal. A resistor R for feeding a predetermined voltage back to the negative terminal of the second amplifier 142b by the current flowing through the first and second electrodes of the element M4b and the fourth switching element M4b. Include.

In the current driving circuit configured as described above, first, when a predetermined voltage is applied to the gate of the fourth switching element M4b by the second amplifier 142b, the second electrode at the first electrode of the fourth switching element M4b is applied. The driving current flows in the direction. The current flows from the first electrode to the second electrode of the second switching device M2b by the flow of the driving current, and the third switching device M3b having the gate connected to the second switching device M2b in common. Current flows in the direction of the second electrode from the first electrode. At this time, the current flowing from the first electrode of the third switching element M3b to the second electrode direction is determined by the ratio (1: M) of the channel region of the second switching element M2b and the third switching element M3b. The current flowing from the first electrode to the second electrode of the third switching device M3b may flow larger than the current flowing from the first electrode to the second electrode of the second switching device M2b. Therefore, a large current can be driven with a small current.

In addition, a current flowing from the first electrode to the second electrode of the third switching device M3b is applied to the resistor string 133b to form a voltage. The voltage applied to the resistor string 133b is divided by the respective resistors of the resistor string 133b to generate the highest voltage from the lowest voltage. Then, by the operation of the decoder 134b, the lowest voltage and the highest voltage are sequentially input to the positive terminal of the first amplifier 131b. Then, the voltage corresponding to the offset voltage of the first amplifier 131b is grasped from the input voltage. In addition, the resistor string 133b and the third switch S3b are connected, and the voltage divided by the resistor string 133b transferred through the third switch S3b is input to the positive terminal of the first amplifier 131b. It is the same voltage as the reference voltage.

In addition, the current driver 141 is driven as described in the description of FIG. 3 so that the voltage reflecting the offset voltage of the first amplifier 131b is applied to the gate of the first switching device M1b.

While preferred embodiments of the present invention have been described using specific terms, such descriptions are for illustrative purposes only and it is understood that various changes and modifications may be made without departing from the spirit and scope of the following claims. It must be broken.

1 is a view showing a current driving circuit for supplying current to the LED driving circuit according to the prior art.

2 is a structural diagram showing the structure of the LED driving circuit according to the present invention.

3 is a structural diagram showing a first embodiment of the current driving circuit employed in the LED driving circuit according to the present invention.

4 is a structural diagram showing a second embodiment of the current driving circuit employed in the LED driving circuit according to the present invention.

Claims (11)

An LED assembly comprising a plurality of light emitting diodes; A high voltage generator for boosting an input voltage to apply a high voltage to the LED assembly; A current driving circuit for controlling a current flowing in the LED assembly; And Including a PWM control unit for controlling the high voltage generation unit, The current driving circuit An LED driving circuit for compensating an offset voltage by changing an input signal input to an input terminal to change an output signal, and feeding back the output signal to fix a voltage at a time when a predetermined voltage is sensed as an input signal input to the input terminal. The method of claim 1, The current drive circuit A first switching device connected to the LED assembly, a second electrode connected to the first node, and a current flowing through the LED assembly in response to a voltage applied to the gate; A first amplifier configured to apply a predetermined voltage to a gate of the first switching device to allow a current to flow in the first switching device, and a first switch to switch between a negative terminal of the first amplifier and the first node And a second switch for switching between an output terminal of the first amplifier and a gate of the first switching element, a third switch for switching an input of a reference voltage to a negative terminal of the first amplifier, and the first switch. An amplifier including a fourth switch for switching between an output terminal of the amplifier and a controller; A voltage D / A converter for generating the lowest voltage from the lowest voltage; And The voltage D / A converter sequentially outputs the highest voltage from the lowest voltage, senses the offset voltage of the first amplifier, and reflects the offset voltage to the positive terminal of the first amplifier in the voltage D / A converter. LED driving circuit comprising the control unit for transmitting a voltage. The method of claim 2, When the first switch and the second switch are in an off state and the third switch and the fourth switch are in an on state, the reference voltage is transmitted to a negative terminal of the first amplifier and a positive terminal is higher than the reference voltage. High voltage is applied sequentially, And the first amplifier applies a predetermined voltage to the gate of the first switching element when the first switch and the second switch are on and the third switch and the fourth switch are off. The method of claim 2, And a mirror unit configured to generate a large current using a small current, wherein the voltage D / A converter generates the reference voltage by a driving current generated in the mirror unit. The method of claim 4, wherein The voltage D / A converter And a decoder for sequentially providing a resistor string for generating the highest voltage from the lowest voltage by the driving current and the highest voltage from the lowest voltage to the positive terminal of the first amplifier. The method of claim 5, The mirror unit A second switching element having a first electrode connected to a driving power supply and a second electrode and a gate connected to a second node; A third switching element having a first electrode connected to a driving power source, a second electrode connected to the resistance column, and a gate connected to the second node; A fourth switching element having a first electrode connected to the second node and a second electrode connected to ground through a resistor; And And a second amplifier receiving the reference voltage through a positive terminal and receiving a voltage formed by the resistor at a negative terminal and applying a predetermined voltage to a gate of the fourth switching device. A first switching element configured to allow a current to flow from the first electrode to the second electrode in response to a voltage applied to the gate; A first amplifier for applying a predetermined voltage to the gate of the first switching element, a resistor formed between the first node to which the second electrode of the first switching element is connected and ground, and the negative of the first amplifier A first switch for switching between a terminal and the first node, a second switch for switching between an output terminal of the first amplifier and a gate of the first switching element, and a negative terminal of the first amplifier An amplifier comprising a third switch for switching an input of the fourth switch and a fourth switch for switching between an output terminal of the first amplifier and a controller; A voltage D / A converter for generating the lowest voltage from the lowest voltage; And The voltage D / A converter sequentially outputs the lowest voltage from the lowest voltage, senses the offset voltage of the first amplifier, and compensates the offset voltage from the voltage D / A converter to the positive terminal of the first amplifier. And a control unit for transferring the supplied voltage. The method of claim 7, wherein When the first switch and the second switch are in an off state and the third switch and the fourth switch are in an on state, the reference voltage is transmitted to a negative terminal of the first amplifier and a positive terminal is higher than the reference voltage. High voltage is applied sequentially, And the first amplifier applies a predetermined voltage to a gate of the first switching element when the first switch and the second switch are on and the third switch and the fourth switch are off. The method of claim 7, wherein And a mirror unit configured to generate a large current using a small current, wherein the voltage D / A converter generates the reference voltage by a driving current generated in the mirror unit. The method of claim 9, The voltage D / A converter And a decoder for sequentially providing a resistor string for generating the highest voltage from the lowest voltage by the driving current and the highest voltage from the lowest voltage to the positive terminal of the first amplifier. 11. The method of claim 10, The mirror unit A second switching element having a first electrode connected to a driving power supply and a second electrode and a gate connected to a second node; A third switching element having a first electrode connected to a driving power source, a second electrode connected to the resistance column, and a gate connected to the second node; A fourth switching element having a first electrode connected to the second node and a second electrode connected to ground through a resistor; And And a second amplifier receiving the reference voltage through a positive terminal and receiving a voltage formed by the resistor at a negative terminal and applying a predetermined voltage to a gate of the fourth switching device.

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