TWI442816B - Light source system and method for driving light emitting diodes in order to promote esd capability - Google Patents

Description

Light source system and LED driver for improving electrostatic discharge capability law

The present invention relates to a light source system, and more particularly to a light source system and a driving method for a light emitting diode.

In recent years, with the rapid development of semiconductor technology, portable electronic products and flat panel display products have also emerged. Among the many types of flat panel displays, liquid crystal displays (LCDs) have become the mainstream of display products based on their low voltage operation, no radiation scattering, light weight and small size. In general, since the liquid crystal display panel itself does not have self-luminous characteristics, it is necessary to place a backlight module under the liquid crystal display panel to provide a (back) light source required for the liquid crystal display panel.

The conventional backlight modules can be roughly divided into two types, one is a backlight module composed of a cold cathode fluorescent lamp (CCFL), and the other is a light emitting diode (LED). A backlight module is formed. Among them, since the light-emitting diode backlight module can improve the color gamut of the liquid crystal display, most of the panel manufacturers today replace the cold cathode tube backlight module with the light-emitting diode backlight module.

The light-emitting diode backlight module has a plurality of sets of LED strings arranged side by side, and each of the light-emitting diode strings is composed of a plurality of light-emitting diodes connected in series. In practice, each light pole The body string operates under a DC output voltage and is illuminated by the drive of the driver IC. However, since each of the light-emitting diode strings is connected to the driving wafer through a connector, it is easier to produce a failed electrostatic discharge test result when performing an ESD test.

In order to solve such a problem, a transient voltage suppression diode (TVS diode) may be additionally added between each LED string and the outside of the driving chip to improve the electrostatic discharge test result. Success rate and protection against electrostatic discharge. However, the disadvantage is that in response to the demand for large-sized panels today, the total number of LED strings disposed in the LED backlight module is increased, so that the additional transient voltage suppression diodes are required. The more will be, which will increase the production cost.

In view of this, the present invention provides a light source system and a light emitting diode driving method, thereby effectively improving the problems described in the prior art.

An embodiment of the invention provides a light source system including a light emitting diode module and a driving unit. The light emitting diode module has at least one light emitting diode string, and the light emitting diode string is operated under a DC output voltage. The driving unit is coupled to the LED module to provide the DC output voltage. The driving unit further drives the light emitting diode string according to a setting signal, and determines whether to provide an electrostatic discharge path in response to the voltage drop of the light emitting diode string and a predetermined reference voltage.

In an embodiment of the invention, the drive unit includes a buck-boost line, a driver, and an electrostatic discharge unit. The buck-boost line is coupled to the anode of the LED string for receiving a DC input voltage, and boosting or stepping down the DC input voltage to generate the DC output voltage. The driver is coupled between the cathode of the LED string and the ground potential for driving the LED string according to the setting signal, and accordingly providing a feedback signal to the buck-boost line, thereby The buck-boost line is caused to react to the feedback signal to adjust the DC output voltage. The electrostatic discharge unit is coupled to the cathode of the LED string for comparing the voltage drop of the LED string with the preset reference voltage to determine whether to provide the ESD path.

Another embodiment of the present invention provides a method for driving a light emitting diode suitable for driving at least one LED string, comprising: providing a DC output voltage to the LED string; driving the device according to a setting signal Determining whether to provide an electrostatic discharge path by comparing a voltage drop of the light emitting diode string with a preset reference voltage.

In an embodiment of the invention, when the voltage drop of the LED string is compared to be greater than the preset reference voltage, the electrostatic discharge path is provided. On the contrary, when the voltage drop of the LED string is compared to be less than the preset reference voltage, the supply of the ESD path is stopped.

Based on the above, the present invention mainly provides an electrostatic discharge unit having a comparison function directly in a driving unit (which can be regarded as a driving wafer) for driving a light emitting diode string, thereby providing an electrostatic discharge path when an electrostatic discharge event occurs. Quickly venting electrostatic discharges caused by electrostatic discharge events Current. In this way, since the electrostatic discharge unit having the comparison function can be directly disposed in the driving wafer, the overall manufacturing cost can be reduced not only in the conventional method (that is, the method of additionally adding the transient voltage suppression diode). And can also achieve the protection of electrostatic discharge.

It is to be understood that the foregoing general description and claims

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the exemplary embodiments embodiments In addition, wherever possible, the same reference numerals in the drawings

FIG. 1 is a schematic diagram of a light source system 10 according to an embodiment of the invention. Referring to FIG. 1 , the light source system 10 of the present embodiment may be an LED backlight module suitable for use in a liquid crystal display system (LCD system), but is not limited thereto, and includes illumination. A diode module 101 and a driving unit 103 are provided. The LED module 101 has at least one LED string LED which is formed by connecting a plurality of LEDs in series, and the LED string LED is operated in a DC output. The DC output voltage is Vout.

The driving unit 103 is coupled to the LED module 101 for providing a DC output voltage Vout to the LED string LED. In addition, the drive unit 103 can be further based on the system side (such as a timing controller, but is not limited Here, the setting signal ST is provided to generate a pulsation current signal to drive the LED string LED, and reacts to the voltage drop VDN of the LED string LED. A comparison of the predetermined reference voltage Verf determines whether an ESD path is provided to vent the ESD current caused by the ESD event.

In the embodiment, the driving unit 103 can be a driver IC, and includes a boost-buck circuit 105, a driver 107, and an electrostatic discharge unit (ESD unit) 109. The buck-boost line 105 is coupled to an anode of the LED array LED for receiving a DC input voltage Vin and boosting or stepping down the DC input voltage Vin (boost/ Buck processing) produces a DC output voltage Vout. That is, when the DC input voltage Vin is smaller than the operating voltage required for the LED string LED, the buck-boost line 105 boosts the DC input voltage Vin to generate and provide a suitable DC output voltage Vout for illumination. The diode string LED; conversely, when the DC input voltage Vin is greater than the operating voltage required for the LED string LED, the buck-boost line 105 steps down the DC input voltage Vin to generate and provide a suitable DC The output voltage Vout is given to the LED string LED.

The driver 107 is coupled between the cathode Cd of the LED string and the ground potential for being provided by the system end (for example, but not limited to the timing controller). The supplied setting signal ST correspondingly generates a pulsating current signal to drive the LED string LED to emit light, and accordingly provides a feedback signal FB to the buck-boost line 105, so that the buck-boost line 105 reacts to the feedback Signal FB to adjust DC output voltage Vout. More specifically, the buck-boost line 105 can be reacted to the feedback signal FB to control/adjust the magnitude of the DC output voltage Vout provided by it, for example, by pulse width modulation (PWM), thereby providing the supplied DC output voltage. Vout can be consistent with the expected setting signal ST.

The electrostatic discharge unit 109 is coupled to the cathode Cd of the LED string of the LED to compare the voltage drop VDN of the LED string with the preset reference voltage Vref, thereby determining whether to provide an ESD path. More specifically, FIG. 2 is a schematic diagram of an electrostatic discharge unit 109 according to an embodiment of the present invention. Referring to FIG. 1 and FIG. 2 together, the electrostatic discharge unit 109 includes a comparator CMP and a switch SW. The comparator CMP is configured to compare the voltage drop VDN of the LED string and the preset reference voltage Vref to output the first comparison signal CS1 or the second comparison signal CS2.

In addition, the switch SW is coupled to the comparator CMP for determining whether to conduct to form an electrostatic discharge path in response to the first comparison signal CS1 or the second comparison signal CS2 outputted by the comparator CMP. Moreover, the switch SW can be implemented by an N-type transistor, such as an N-type metal oxide semiconductor (NMOS) transistor, but is not limited thereto, so the switch SW is hereinafter referred to as an N-type transistor. SW. Wherein, the gate of the N-type transistor SW is coupled to the output end of the comparator CMP, and the N-type transistor SW The source is coupled to the ground potential, and the drain of the N-type transistor SW is coupled to the cathode Cd of the LED string LED.

In this embodiment, when the comparator CMP compares the voltage drop VDN of the LED string LED to be less than the preset reference voltage Vref, the comparator CMP outputs the first comparison signal CS1 (eg, a logic low level). As a result, the N-type transistor (switch) SW will turn off in response to the first comparison signal CS1. In addition, when the comparator CMP compares the voltage drop VDN of the LED string LED to be greater than the preset reference voltage Vref, the comparator CMP outputs a second comparison signal CS2 (eg, a logic high level). As a result, the N-type transistor (switch) SW will turn on in response to the second comparison signal CS2.

More specifically, during the operation of the light source system 10, when no electrostatic discharge event occurs, the voltage drop VDN of the LED string LED is not greatly affected by the electrostatic discharge event, so this is The voltage drop VDN of the LED string LED will be less than the preset reference voltage Vref. Therefore, the comparator CMP outputs a first comparison signal CS1 having a logic low level to cause the N-type transistor (switch) SW to be turned off. On the other hand, during the operation of the light source system 10, when an electrostatic discharge event occurs, the voltage drop VDN of the LED string LED is greatly increased due to the electrostatic discharge event, so the light emitting diode The voltage drop VDN of the body string LED will be greater than the preset reference voltage Vref. Therefore, the comparator CMP outputs a second comparison signal CS2 having a logic high level to cause the N-type transistor (switch) SW to be turned on.

It can be seen that during the operation of the light source system 10, when there is an electrostatic discharge When an event occurs, the comparator CMP causes the N-type transistor (switch) SW to conduct to form/provide an electrostatic discharge path, thereby rapidly venting the electrostatic discharge current ESD_I caused by the electrostatic discharge event to the ground potential. In this way, the internal components (not shown) of the driver 107 can be protected, thereby enabling an external electrostatic discharge protection component (I/O) that is generally designed to be input (I/O) of the driving unit 103 (ie, driving the wafer) (not shown). Show) together to achieve protection against electrostatic discharge. In addition, since the electrostatic discharge unit 109 can be directly disposed in the driving wafer, the manufacturing cost can be greatly reduced as compared with the conventional method (that is, the method of additionally adding the transient voltage suppressing diode).

Based on the disclosure/teaching of the above embodiments, FIG. 3 is a flowchart of a method for driving a light emitting diode according to an embodiment of the present invention. Referring to FIG. 3, the LED driving method of the embodiment is adapted to drive at least one LED string, and includes: providing a DC output voltage to the LED string (Step S301); driving according to the setting signal a light emitting diode string (step S303); and determining whether to provide an electrostatic discharge path by comparing a voltage drop of the light emitting diode string with a preset reference voltage (step S305).

In this embodiment, when comparing the voltage drop of the LED string is greater than the preset reference voltage, it indicates that an electrostatic discharge event occurs, so that an electrostatic discharge path is required to vent the static electricity caused by the electrostatic discharge event. Discharge current; conversely, when comparing the voltage drop of the LED string is less than the preset reference voltage, it means that there is no electrostatic discharge event, so it will be necessary to stop providing the ESD path to avoid affecting the LED string. drive.

In summary, the present invention mainly provides an electrostatic discharge unit with a comparison function directly in a driving wafer for driving a light emitting diode string, thereby providing an electrostatic discharge path for rapid venting when an electrostatic discharge event occurs. Electrostatic discharge current caused by an electrostatic discharge event. In this way, since the electrostatic discharge unit having the comparison function can be directly disposed in the driving wafer, the overall manufacturing cost can be reduced not only in the conventional method (that is, the method of additionally adding the transient voltage suppression diode). And can also achieve the protection of electrostatic discharge. In addition, any means of designing, fabricating, or otherwise disposing an electrostatic discharge unit having a comparative function directly in the drive wafer to achieve electrostatic discharge protection is within the scope of the present invention.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims. In addition, any of the objects or advantages or features of the present invention are not required to be achieved by any embodiment or application of the invention. In addition, the abstract sections and headings are only used to assist in the search of patent documents and are not intended to limit the scope of the invention.

10‧‧‧Light source system

101‧‧‧Lighting diode module

103‧‧‧Drive unit

105‧‧‧Floating and lowering lines

107‧‧‧ drive

109‧‧‧Electrostatic discharge unit

LED‧‧‧Light diode string

CMP‧‧‧ comparator

SW (N-type transistor) ‧ ‧ switch

Vin‧‧‧DC input voltage

Vout‧‧‧DC output voltage

ST‧‧‧Set signal

FB‧‧‧ feedback signal

Voltage drop of VDN‧‧‧Light-emitting diode strings

Vref‧‧‧Preset reference voltage

CS1‧‧‧ first comparison signal

CS2‧‧‧Second comparison signal

Ad‧‧‧Anodes of LED strings

Cd‧‧‧ cathode of light-emitting diode string

ESD_I‧‧‧ Electrostatic discharge current

S301~S305‧‧‧ Steps of the flow chart of the LED driving method according to an embodiment of the present invention

The following drawings are a part of the specification of the invention, and illustrate the embodiments of the invention

1 is a flow chart of a light source system 10 in accordance with an embodiment of the present invention.

FIG. 2 is a schematic diagram of an electrostatic discharge unit 109 according to an embodiment of the invention.

3 is a flow chart of a method for driving a light emitting diode according to an embodiment of the invention.

10‧‧‧Light source system

101‧‧‧Lighting diode module

103‧‧‧Drive unit

105‧‧‧Floating and lowering lines

107‧‧‧ drive

109‧‧‧Electrostatic discharge unit

LED‧‧‧Light diode string

Vin‧‧‧DC input voltage

Vout‧‧‧DC output voltage

ST‧‧‧Set signal

FB‧‧‧ feedback signal

Voltage drop of VDN‧‧‧Light-emitting diode strings

Vref‧‧‧Preset reference voltage

Ad‧‧‧Anodes of LED strings

Cd‧‧‧ cathode of light-emitting diode string

Claims (8)

A light source system comprising: a light emitting diode module having at least one light emitting diode string, wherein the light emitting diode string is operated under a DC output voltage; and a driving unit coupled to the light emitting diode a module for providing the DC output voltage, wherein the driving unit further drives the LED string according to a set signal, and is responsive to a voltage drop of the LED string and a predetermined reference voltage Determining whether to provide an electrostatic discharge path, wherein the driving unit comprises: a buck-boost line coupled to the anode of the LED string for receiving a DC input voltage, and boosting or lowering the DC input voltage The DC output voltage is generated after the pressure processing; a driver is coupled between the cathode of the LED string and a ground potential for driving the LED string according to the setting signal, and accordingly a feedback signal is applied to the buck-boost line such that the buck-boost line reacts to the feedback signal to adjust the DC output voltage; and an ESD unit is coupled to the LED Cathode string, for comparing the voltage drop with the predetermined reference voltage, so as to determine whether the electrostatic discharge path. The light source system of claim 1, wherein the electrostatic discharge unit comprises: a comparator for comparing the voltage drop with the predetermined reference voltage, thereby outputting a first comparison signal or a second comparison signal. And a switch coupled to the comparator for reacting to the first or second The comparison signal determines whether or not to conduct to form the electrostatic discharge path. The light source system of claim 2, wherein when the comparator compares the voltage drop to be less than the predetermined reference voltage, the comparator outputs the first comparison signal; and when the comparator compares the When the voltage drop is greater than the preset reference voltage, the comparator outputs the second comparison signal. The light source system of claim 3, wherein the switch is turned off in response to the first comparison signal; and the switch is turned on in response to the second comparison signal. The light source system of claim 4, wherein the switch is an N-type transistor, wherein a gate of the N-type transistor is coupled to an output of the comparator, a source of the N-type transistor The drain of the N-type transistor is coupled to the cathode of the LED string. The light source system of claim 1, wherein the light source system is at least one light emitting diode backlight module. An LED driving method is suitable for driving at least one set of LED strings, and the LED driving method comprises: providing a DC output voltage to the LED string, wherein the step comprises receiving the DC Inputting a voltage, and boosting or stepping down the DC input voltage to generate the DC output voltage; driving the LED string according to a set signal, wherein the step includes providing a feedback signal to perform When the DC input voltage is boosted or stepped down, the feedback signal is reflected to adjust the DC output voltage; Determining whether to provide an electrostatic discharge path by comparing a voltage drop of the LED string with a predetermined reference voltage, wherein the step includes comparing the voltage drop with the preset reference voltage to determine whether to provide the static electricity Discharge path. The method of driving a light emitting diode according to claim 7, wherein when the voltage drop is greater than the predetermined reference voltage, the electrostatic discharge path is provided; and when the voltage drop is compared to the preset When the voltage is referenced, the supply of the electrostatic discharge path is stopped.