KR20160057744A - Apparatus for driving light emitting diode with key scan function - Google Patents

Abstract

The present invention provides an apparatus for driving a light emitting diode (LED) with a key scan function. The apparatus for driving a light emitting diode with a key scan function drives an LED matrix by providing a first voltage and a second voltage to a first power line and a second power line based on LED driving information stored in a system control unit, and scans a key matrix by providing the first voltage to the first power line. The apparatus includes a control unit providing a first control signal and a second control signal for suppressing parasitic capacitance of the LED matrix for an idle period of the LED matrix and the key matrix; and a parasitic capacitance suppressing unit suppressing a charge and discharge path by the parasitic capacitance by providing the first voltage and the second voltage to the first power line and the second power line in response to the first and second control signals. Thus, by suppressing the charge and discharge path that may occur by the parasitic capacitance within the LED matrix by previous charging and discharging, an unintended LED can be prevented from being emitted.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an LED driving device having a key scan function,

The present invention relates to an LED driving apparatus, and more particularly, to an LED driving apparatus having a key scanning function.

An input device in which a plurality of keys are arranged is widely used in electronic products. When a user presses a key placed on the input device, a specific command is input to the electronic product.

Such a key input device uses a method of scanning a key on / off in a microprocessor. The key scanning method utilizes the fact that a predetermined electric signal is generated only by touching a part of a body (a finger or the like) without pressing or turning a switch or a knob.

The input device of the above-described key scanning method is employed in various electronic products, and may include a key matrix of a k x j array corresponding to the number of keys required for system control. The key scan method determines whether a key is pressed by applying a high potential to a column of the key matrix and detecting a potential change of a row.

An LED driving apparatus having a key scan function includes a key matrix and an LED matrix. The LED driving apparatus includes a key matrix controller for determining whether a user presses a key by scanning the key matrix, .

However, in an LED driving apparatus having a key scan function, an unintended LED may emit light due to parasitic capacitance in the LED matrix.

The parasitic capacitance existing in the LED matrix can be charged in the key scan process and the charge / discharge path can be formed in the LED matrix by the charged parasitic capacitance.

The charge reversal path caused by the parasitic capacitance can cause the LEDs not corresponding to the LED drive information to emit light.

That is, the LED driving apparatus having a key scan function according to the related art has a problem in that an unintended LED can emit light due to a parasitic capacitance parasitized in the LED matrix.

It is an object of the present invention to provide an LED driving apparatus having a key scan function capable of suppressing a charge / discharge path due to a parasitic capacitance parasitic in an LED matrix, thereby preventing unintentional LED light emission.

It is another object of the present invention to provide an LED driving apparatus having a key scan function capable of stably operating an LED matrix drive and a key matrix scan.

The LED driving apparatus having a key scan function according to the present invention drives the LED matrix by providing first and second voltages to first and second power supply lines corresponding to LED drive information of a system control unit, Wherein the first and second voltages are applied to the first and second voltage lines to scan the key matrix, wherein the first and second voltages are applied to the LED matrix and the idle period of the key matrix in order to suppress the parasitic capacitance of the LED matrix. A control unit for providing a control signal; And a parasitic capacitance suppression unit for suppressing a charge / discharge path due to the parasitic capacitance by providing the second voltage and the first voltage to the first and second power supply lines corresponding to the first and second control signals do.

An LED driving apparatus having a key scan function according to the present invention includes: first and second driving units for driving an LED matrix in response to first and second driving signals; A parasitic capacitance suppressing unit for suppressing a charge / discharge path due to the parasitic capacitance of the LED matrix corresponding to the first and second control signals; And providing the first and second driving signals to the first and second driving units in an LED driving period and providing the first driving signal to the first driving unit during a key scanning period, And a controller for providing the first and second control signals in a idle period between the LED drive period and the key scan period.

As described above, the present invention can prevent the unintended LED from emitting light by suppressing the charging / discharging path which may be caused by the parasitic capacitance parasitic in the LED matrix through the preceding charging / discharging.

In addition, the present invention suppresses charge / discharge paths due to the parasitic capacitance in the dormant time, so that it can be operated stably without affecting the operation of the matrix matrix driving and the key matrix scan.

1 is a block diagram illustrating an LED driving apparatus having a key scan function according to an embodiment of the present invention.
2 is a diagram illustrating another embodiment of an LED driving apparatus having a key scan function according to the present invention.
Figs. 3 and 4 show 8-segment and 14-segment to be employed in the LED matrix of Figs. 1 and 2. Fig.
5 is a diagram for explaining an operation of an LED driving apparatus having a key scan function according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the terminology used herein is for the purpose of description and should not be interpreted as limiting the scope of the present invention.

The embodiments described in the present specification and the configurations shown in the drawings are preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention and thus various equivalents and modifications Can be.

1 is a block diagram illustrating an LED driving apparatus having a key scan function according to an embodiment of the present invention. For example, a common cathode type LED matrix 30 is applied.

1, an LED driving apparatus 10 having a key scan function according to the present embodiment includes an interface 13, a display memory 14, a control unit 11, a clock generator 16, first and second Driving units SW1 and SW2, parasitic capacitance suppression units SW3 and SW4, and a key detection unit 12. [

The interface 13 supports bidirectional communication between the system control unit 40 and the LED driving apparatus 10. [ The system control unit 40 may be a microcomputer (MCU) such as a washing machine, a refrigerator, a kimchi storage, and an air conditioner. The interface 13 provides the key detection signal Key_value output from the key detection unit 12 to the system control unit 40 and outputs the LED drive information corresponding to the key detection signal Key_value output from the system control unit 40 To the display memory unit (14).

The display memory unit 14 stores the LED drive information provided from the system control unit 40 via the interface 13. [

The clock generator 16 generates a reference clock signal corresponding to the oscillation signal of the oscillator 15 and provides the reference clock signal to the controller 11. The reference clock signal may be used to operate the embodiment on a segment-by-segment basis. For example, it can be used for an LED drive period, a key scan period, and an idle period.

Herein, the LED driving period may be set as a period in which the controller 11 drives the LED matrix 30 in correspondence with the LED driving information, and the key scanning period may be set in the column of the key matrix 20 as an LED matrix 30 may be set as a period for determining whether or not a key is pressed by a potential change appearing in rows of the key matrix 20 by sequentially applying a power source voltage VDD that drives the key matrix 20, The interval between the LED matrix driving period and the key scanning period and the key matrix 20 between the LED driving period and the key scanning period are stopped.

The first and second driving units SW1 and SW2 receive the first and second driving signals SG [1: n] and GR [1: m] provided from the control unit 11 in the LED matrix 30 The power source voltage VDD is supplied to the first power line L1 connected to the LED anode terminals and the ground voltage VSS is supplied to the second power line L2 connected to the LED cathode terminals. That is, the first and second driving units SW1 and SW2 form an LED driving current path corresponding to the first and second driving signals SG [1: n] and GR [1: m] . For example, the first driving unit SW1 may include a plurality of first PMOS [1: n], and the second driving unit SW2 may include a plurality of first NMOS [1: m].

Here, when the LED matrix 30 is a common cathode type, the first power line L1 is connected to the anode terminal of the LEDs in the LED matrix 30, and the second power line L2 is connected to the anode of the LEDs And can be connected to a common cathode terminal (see FIG. 1). At this time, the external resistor RB may be provided between the first power supply line L1 and the anode terminal of the LEDs to drive the LED.

When the LED matrix 30 is a common anode type, the first power line L1 may be connected to the common anode terminal of the LEDs, and the second power line L2 may be connected to the cathode terminal of the LEDs. (See FIG. 2). At this time, the external resistor RB may be provided between the second power supply line L2 and the cathode terminal of the LEDs to drive the LED.

The external resistor RB may be set to a value for driving the LED matrix 30 with a target current, and may be provided in each column of the LED matrix.

The parasitic capacitance suppression units SW3 and SW4 are connected to the ground voltage VSS to the first and second power supply lines L1 and L2 corresponding to the first and second control signals CS1 and CS2 provided from the control unit 11, And a power supply voltage (VDD) are supplied to precharge and charge the parasitic capacitance.

The parasitic capacitance suppression units SW3 and SW4 include a preceding discharging unit SW3 for discharging the first power supply line L1 to the ground voltage VSS in response to the first control signal CS1, And a precharging unit SW4 for precharging the second power supply line L2 to the power supply voltage corresponding to the second power supply line CS2.

That is, when the precharge unit SW3 is activated in response to the first control signal CS1, a discharge path is formed to discharge the parasitic capacitance CP1, and the precharging unit SW4 corresponds to the second control signal CS2 The charge path is formed and the parasitic capacitance CP2 is charged. For example, the preceding discharging unit SW3 may be composed of a plurality of second NMOSs [1: n], and the precharging unit SW4 may be composed of a plurality of second PMOSs [1: m].

The parasitic capacitance suppression units SW3 and SW4 may correspond to the first and second control signals CS1 and CS2 that are activated in the idle period between the LED matrix driving period and the LED matrix driving period and the key matrix scan period It is possible to prevent unintended LEDs from being emitted by the parasitic capacitances CP1 and CP2 of the LED matrix 30 without affecting the operation of the LED matrix driving and the key matrix scan.

The control unit 11 outputs the first and second driving signals SG [1: n] and GR [1: m] corresponding to the LED driving information stored in the display memory 14 to the first and second To the driving units SW1 and SW2 to control the driving of the LED matrix 30 and to provide the first driving signal SG [1: n] to the first driving unit SW1 during the key scanning period, ).

The control unit 11 generates first and second control signals CS1 and CS2 for suppressing the parasitic capacitances CP1 and CP2 of the LED matrix 30 in the idle periods of the LED matrix 30 and the key matrix 20, ) To the parasitic capacity suppression units SW3 and SW4. That is, the control unit 11 outputs the first and second driving signals SG [1: n] and GR [1: m] during the LED driving period, n], and outputs the first and second control signals CS1 and CS2 in the idle period.

The key detection unit 12 detects the potentials appearing in the rows of the key matrix 20 when the power source voltage VDD is sequentially applied to the columns of the key matrix 20 by the first driving unit SW1 And provides the key detection signal (Key_value) to the system control unit 40 via the interface 13. The system control unit 40 determines whether or not the key is pressed.

The system control unit 40 processes the key detection signal Key_value as a command input by the user and provides the LED drive information corresponding to the key detection signal Key_value to the display memory 14 via the interface 13. [ The controller 11 then outputs the first and second drive signals SG [1: n] and GR [1: m] corresponding to the LED drive information stored in the display memory 14 to the first and second drivers SW1, and SW2 to control the driving of the LED matrix 30.

2 is a diagram illustrating another embodiment of an LED driving apparatus having a key scan function according to the present invention.

2, an LED driving apparatus 10 having a key scan function according to the present embodiment includes an interface 13, a display memory 14, a control unit 11, a clock generator 16, first and second Driving units SW1 and SW2, parasitic capacitance suppression units SW3 and SW4, and a key detection unit 12. [

In this embodiment, a common anode type LED matrix 30 is applied, which is the same as the configuration of Fig. The power supply voltage VDD is supplied to the grid terminals GRID [1: m] by the first drive signal GR [1: m] while applying the common anode type and the second drive signal SG [ The control section 11, the first and second driving sections SW1 and SW2 and the parasitic capacity suppression sections SW3 and SW4 (SW1 and SW2) are connected to the segment terminals SEG [1: n] ), And detailed description of the redundant configuration is omitted.

The control unit 11 outputs first and second driving signals GR [1: m] and SG [1: n] corresponding to the LED driving information stored in the display memory 14 to the first and second And supplies the first drive signal GR [1: m] to the first drive unit SW1 during the key scan interval to provide the first drive signal SW [1: m] to the first drive unit SW1 to scan the key matrix 20 . The control unit 11 generates first and second control signals CS1 and CS2 for suppressing the parasitic capacitances CP1 and CP2 of the LED matrix 30 in the idle periods of the LED matrix 30 and the key matrix 20, ) To the parasitic capacity suppression units SW3 and SW4.

The first and second driving units SW1 and SW2 are connected to the first and second driving signals GR [1: m] and SG [1: n] provided from the control unit 11 in the LED matrix 30 The power supply voltage VDD is supplied to the first power supply line L1 connected to the common anode terminals and the ground voltage VSS is supplied to the second power supply line L2 connected to the LED cathode terminals. That is, the first and second driving units SW1 and SW2 form an LED driving current path corresponding to the first and second driving signals GR [1: m] and SG [1: n] .

The parasitic capacitance suppression units SW3 and SW4 are connected to the ground voltage VSS to the first and second power supply lines L1 and L2 corresponding to the first and second control signals CS1 and CS2 provided from the control unit 11, And a power supply voltage (VDD) are supplied to precharge and charge the parasitic capacitance. The parasitic capacitance suppression units SW3 and SW4 are activated in the idle period between the LED matrix driving period and the LED matrix driving period and the key matrix scan period and are controlled by the parasitic capacitances CP1 and CP2 of the LED matrix 30 Thereby preventing the LED from emitting light. As described above, the embodiment of FIG. 2 can solve the problems of the prior art like the embodiment in which the common cathode type LED of FIG. 1 is applied.

Figs. 3 and 4 show 8-segment and 14-segment to be employed in the LED matrix of Figs. 1 and 2. Fig. Specifically, FIG. 3A shows the 8-segment, FIG. 3B shows the 8-segment of the common cathode type, and FIG. 3C shows the 8-segment of the common anode type. 4 (a) shows a 14-segment, (b) shows a 14-segment of a common cathode type, and FIG. 4 (c) shows a 14-segment of a common anode type.

In the LED display panel applied to electronic appliances, the number of LEDs varies according to the number of segments, and is classified into a common anode type and a common cathode type according to the configuration method of the panel. In the LED drive device having the key scan function according to the present embodiment 10 can be applied to both the common cathode type or common anode type LED display panel of 8-segment and 14-segment.

5 is a diagram for explaining an operation of an LED driving apparatus having a key scan function according to the present invention.

1 and 5, an LED driving apparatus 10 having a key scanning function according to the present invention receives LED driving information from the system control unit 40, and outputs LED driving information corresponding to LED driving information in an LED driving period 30, performs a key scan during a key scan interval, and controls the parasitic capacitances CP1, CP2 of the LED matrix 30 in a rest period.

First, the operation of the LED driving period will be described as follows. The display memory 14 of the LED drive device 10 stores the LED drive information supplied from the system control unit 40 via the interface 13. [

The control unit 11 generates the first and second driving signals SG [1: n] and GR [1: m] corresponding to the LED driving information stored in the display memory 14 in the LED driving period, And supplies the first and second driving signals SG [1: n] and GR [1: m] to the first and second driving units SW1 and SW2.

The first driving unit SW1 transfers the power source voltage VDD to the first power source line L1 in response to the first driving signal SG [1: n], and the second driving unit SW2 transmits the second driving signal (VSS) to the second power supply line (L2) corresponding to the first power supply line (GR [1: m]). For example, the grid terminals GRID [1: m] are sequentially activated with a predetermined time unit T, and the first drive signals GRID [1: m] On / off is determined by specifying an LED to emit light in accordance with the control signal SG [1: n].

Then an LED drive current path is formed between the segment terminal SEG [1: n] connected to the first power supply line L1 and the grid terminal GRID [1: m] connected to the second power supply line L2 , LEDs corresponding to the LED drive information emit light by the LED drive current path formation.

The ON / OFF timing operation of the first and second driving units SW1 and SW2 is performed in response to a clock signal having a constant frequency (1 / T) generated by the clock generator 16 corresponding to the oscillation signal of the oscillator 15 Can be done.

Next, the operation of the key scan period will be described as follows.

The control unit 11 provides the first driving signal SG [1: n] to the first driving unit SW1 during the key scan interval, and the first driving unit SW1 supplies the first driving signal SG [1: n] The power supply voltage VDD is sequentially applied to the columns of the key matrix 20 through the first power supply line L1.

At this time, the key detector 12 determines whether or not the key is pressed by the potential change appearing in the rows of the key matrix 20, and transmits the key detection signal Key_value to the system controller 40 through the interface 13, .

The system control unit 40 processes the key detection signal Key_value as a command input by the user and provides the LED drive information corresponding to the key detection signal Key_value to the display memory 14 through the interface 13 . Then, the controller 11 supplies the first and second driving signals SG [1: n] and GR [1: m] corresponding to the LED driving information stored in the display memory 14 to the first And the second driving units SW1 and SW2 to control the driving of the LED matrix 30.

Next, the operation of the idle period will be described as follows.

The control unit 11 outputs the first and second control signals CS1 and CS2 in the idle period between the LED driving period (1 to 4, see FIG. 5) and the LED driving period and the key scanning period And supplies it to the capacity control units SW3 and SW4.

The leading discharging unit SW3 of the parasitic capacity suppressing units SW3 and SW4 supplies the ground voltage VSS to the first power supply line L1 in correspondence with the first control signal CS1 provided from the control unit 11 . That is, when the precharge unit SW3 is activated in response to the first control signal CS1, the parasitic capacitance CP1 is precharged by the discharge path formed between the first power supply line L1 and the ground voltage VSS .

The precharging unit SW4 of the parasitic capacity suppression units SW3 and SW4 supplies the power supply voltage VDD to the second power supply line L2 corresponding to the second control signal CS2 provided from the control unit 11 do. That is, when the precharge unit SW4 is activated in response to the second control signal CS2, the precharge unit SW4 precharges the parasitic capacitance CP2 by the charge path formed between the second power supply line L1 and the power supply voltage VDD.

The parasitic capacitance suppression units SW3 and SW4 that are driven as described above are activated and driven in the idle period between the LED driving period and the LED driving period and the key scanning period. Therefore, it is possible to prevent the LEDs from emitting light by the parasitic capacitances CP1 and CP2 without affecting the driving of the LED matrix 30 and the scanning of the key matrix 20.

As described above, according to the present invention, unintentional LEDs are prevented from emitting light by suppressing charge / discharge paths that may occur due to parasitic capacitance parasitic in the LED matrix.

In addition, the present invention suppresses charge / discharge paths due to parasitic capacitance in the idle period, and thus operates stably without affecting the operation of the LED matrix drive and the key matrix scan.

10: LED driving device 11:
12: key detection unit 13: interface
14: display memory 15: oscillator
16: clock generator 20: key matrix
30: LED matrix 40: system controller
SW1: first drive unit SW2: second drive unit
SW3: preceding discharge SW4:
CP1, CP2: parasitic capacitance

Claims (10)

The first and second power lines are supplied with the first and second voltages corresponding to the LED driving information of the system control unit to drive the LED matrix and the first voltage is supplied to the first power line to scan the key matrix In the LED drive device,
A control unit for providing first and second control signals for suppressing the parasitic capacitance of the LED matrix in the idle period of the LED matrix and the key matrix; And
A parasitic capacitance suppressing part for suppressing a charge / discharge path due to the parasitic capacitance by providing the second voltage and the first voltage to the first and second power supply lines corresponding to the first and second control signals;
And a key scan function. The plasma display apparatus according to claim 1, wherein the parasitic capacitance suppressing portion
A preceding discharging portion forming a precedent discharge path between the first power supply line and the second voltage in response to the first control signal; And
A precharge unit that forms a precharge path between the second power supply line and the first voltage corresponding to the second control signal;
And a key scan function. 3. The method of claim 2,
Wherein the first power supply line is connected to an anode terminal of the LED matrix and the second power supply line is connected to a common cathode terminal, the second voltage is a ground voltage, and the first voltage is a power supply voltage. An LED drive device having a scan function. 3. The method of claim 2,
Wherein the first power supply line is connected to a common anode terminal of the LED matrix and the second power supply line is connected to a cathode terminal, the second voltage is a ground voltage, and the first voltage is a power supply voltage. An LED driving device having a key scan function. The method according to claim 1,
An oscillator for generating and outputting an oscillation signal; And
And a clock generator for outputting a clock signal corresponding to the oscillation signal,
Wherein the control unit provides the first and second control signals to the parasitic capacitance suppression unit in the idle period in response to the clock signal. The method according to claim 1,
A key detection unit detecting a key depression of the key matrix and outputting a key detection signal; And
An interface for transmitting the key detection signal to the system control unit and for transmitting LED drive information provided from the system control unit to the display memory;
And a key scan function. The method according to claim 6,
And a display memory for storing the LED driving information transmitted through the interface and providing the LED driving information to the control unit,
Wherein the controller has a key scan function for controlling the LED matrix to be driven corresponding to the LED drive information. First and second driving units driving the LED matrix in response to the first and second driving signals;
A parasitic capacitance suppressing unit for suppressing a charge / discharge path due to the parasitic capacitance of the LED matrix corresponding to the first and second control signals; And
Wherein the first and second driving signals are supplied to the first and second driving units during a driving period of the LED driving unit and the first driving signals are supplied to the first driving unit during a key scanning period, A control unit for providing the first and second control signals during idle periods between the driving period and the key scanning period;
And a key scan function. 9. The semiconductor memory device according to claim 8, wherein the parasitic capacitance suppressing portion
A preceding discharging unit for discharging the first power line connected to the anode terminal of the LED matrix to a ground voltage in response to the first control signal; And
A precharging unit for precharging a second power supply line connected to the cathode terminal of the LED matrix in response to the second control signal to a power supply voltage;
And a key scan function. 9. The method of claim 8,
An oscillator for generating and outputting an oscillation signal; And
And a clock generator for outputting a clock signal corresponding to the oscillation signal,
Wherein the LED drive period, the key scan period, and the idle period are previously set corresponding to the clock signal.

Images