CN101500361B - Light emitting diode driving device and driving method thereof - Google Patents

Abstract

The invention discloses a light emitting diode driving device and a driving method thereof. The light emitting diode driving device comprises a duty ratio setting unit, a direct current setting unit, a control unit and a light emitting diode driving circuit. The duty ratio setting unit is used for outputting a duty ratio setting signal. The DC setting unit is used for outputting a DC setting signal. The control unit is used for receiving the duty ratio setting signal and the direct current setting signal and outputting a direct current control signal and a duty ratio control signal according to the duty ratio setting signal and the direct current setting signal. The LED driving circuit is used for driving at least one LED according to the direct current control signal and the duty ratio control signal. The invention can effectively adjust the current value and the duty ratio of the driving current of the light-emitting diode, improves the working efficiency of the LED and accurately controls the average conducting current of the LED.

Description

Light emitting diode driving device and driving method thereof

technical field

The present invention relates to a light emitting diode driving device and a driving method thereof, more precisely, to a light emitting diode driving device and a driving method thereof applied to a panel.

Background technique

Due to good characteristics such as low power consumption and low operating temperature, light emitting diodes (Light Emitting Diode, LED) have been widely used at present.

For example, most small and medium-sized panels use 3 to 10 LEDs, which are connected in series as the backlight source, and even the backlight of the keyboard of a mobile phone or a Personal Digital Assistant (PDA) is mostly a backlight. The use of LEDs as auxiliary lighting, coupled with the European Union's requirements for mercury-free, so the newer generation of LED drive technology is quite expected by the market.

Most of the portable products are designed with a dimming function for the backlight of the panel, that is to say, in the case of no AC power supply, standby mode, etc., the brightness of the backlight will be adjusted to reduce power consumption and prolong battery life. However, the current LED driving method has the following disadvantages:

1. The LED drive current is a fixed value, which cannot be adjusted automatically according to the usage conditions. Since the intensity of the light-emitting diodes is controlled by the magnitude of the current flowing through the light-emitting diodes, the driving method with a fixed current value limits the convenience of its use.

2. The driving current is fixed to the current at the maximum brightness, and the current at the maximum brightness is used at non-maximum brightness, which will cause the LED to act in a lower efficiency area. To sum up, the current LED driving method has its defects, and a better LED driving method is expected by the industry.

Contents of the invention

The invention provides a light emitting diode driving device and a driving method thereof, which can better drive the light emitting diode by adjusting the current value and duty cycle of the light emitting diode driving current.

An embodiment of the LED driving device of the present invention includes a duty cycle setting unit, a DC setting unit, a control unit and a LED driving circuit. The duty ratio setting unit is used for outputting a duty ratio setting signal. The DC setting unit is used for outputting a DC setting signal. The control unit is used for receiving the duty cycle setting signal and the DC setting signal, and outputting a DC control signal and a duty cycle control signal according to the duty cycle setting signal and the DC setting signal. The LED driving circuit is used for driving at least one LED according to the DC control signal and the duty ratio control signal.

An embodiment of the light emitting diode driving method of the present invention, the driving method includes: providing a first driving current for driving a light emitting diode in a first time period, the first driving current has a first duty ratio and a first current value; and providing a second driving current for driving a light emitting diode in a second time period following the first time period, the second driving current has a second duty cycle and a first Two current values, wherein the first current value is not equal to the second current value and the first duty cycle is not equal to the second duty cycle.

An embodiment of the method for driving a light emitting diode of the present invention, the driving method includes: providing a duty ratio setting signal; providing a DC setting signal; receiving the duty ratio setting signal and the DC setting signal to a A control unit; outputting a direct current control signal and a duty cycle control signal to a light emitting diode drive circuit through the control unit; and driving at least one light emitting diode according to the direct current control signal and the duty cycle control signal.

The invention can effectively adjust the current value and the duty cycle of the light-emitting diode driving current, so that the working efficiency of the LED is improved and the average conduction current of the LED can be accurately controlled.

The foregoing has outlined rather broadly the technical features and advantages of the present invention to enable a better understanding of the following detailed description of the invention. Additional features and advantages will be described hereinafter which form the subject of the claims of the invention. Those skilled in the art should appreciate that the concepts and specific embodiments disclosed below can be used to modify or design other structures or processes to achieve the same purpose as the present invention. Those of ordinary skill in the art should also realize that such equivalent constructions cannot depart from the spirit and scope of the invention as defined by the appended claims.

Description of drawings

By referring to the foregoing description and the following drawings, the technical features and advantages of the present invention can be fully understood.

FIG. 1 illustrates a system block diagram of a light emitting diode driving device according to an embodiment of the present invention;

FIG. 2A and FIG. 2B respectively illustrate waveform diagrams received and output by the control unit in the LED driving device according to an embodiment of the present invention; and

FIG. 3 illustrates a system block diagram of a control unit in an LED driving device according to an embodiment of the present invention.

Wherein, the reference signs are explained as follows:

100 LED driver

102 LEDs

104 Duty cycle setting unit

106 DC setting unit

108 control unit

110 LED drive circuit

302 Duty cycle and current operation unit

308 Current order setting unit

Detailed ways

Please refer to FIG. 1 , which illustrates a system block diagram of an LED driving device according to an embodiment of the present invention. The LED driving device 100 is used to drive the LED 102 , wherein the LED driving device 100 includes a duty cycle setting unit 104 , a DC setting unit 106 , a control unit 108 and a LED driving circuit 110 . The duty ratio setting unit 104 is used to output a duty ratio setting signal to the control unit 108 and the DC setting unit 106 is used to output a DC setting signal to the control unit 108; The duty ratio setting signal and the DC setting signal output a DC control signal and a duty ratio control signal to the LED driving circuit 110, and the LED driving circuit 110 then receives the DC control signal and the duty ratio The control signal drives the LED.

Please refer to Figure 2A and Figure 2B. Fig. 2A illustrates the waveform diagram received by the control unit in the light-emitting diode driving device according to an embodiment of the present invention; the duty ratio setting signal can be a pulse width modulation (PWM) signal, voltage, digital Signals, etc., the embodiment here takes the pulse width on-period signal as an example; FIG. 2B illustrates a waveform diagram output by the control unit in the LED driving device according to an embodiment of the present invention. In this waveform diagram, the setting order of the output current is 4, that is, the output current can be the maximum output current Imax, 0.75 times the maximum output current 0.75Imax, 0.5 times the maximum output current 0.5Imax, or 0.25 times the maximum output Current 0.25Imax. In the diagram, the horizontal axis represents the time axis, and the vertical axis represents the magnitude of the current. Please refer to Fig. 2A first, in the time period T1, the duty ratio input from the duty ratio setting unit 104 to the control unit 108 is 100%, and the maximum current input from the DC setting unit 106 to the control unit 104 is IMAX; T2, the duty ratio input from the duty ratio setting unit 104 to the control unit 108 is 75%, and the maximum current from the DC setting unit 106 to the control unit 104 is IMAX; in the time period T3, from the duty ratio setting The duty cycle of unit 104 input control unit 108 is 85%, and the maximum current from direct current setting unit 106 input control unit 104 is IMAX; The duty cycle is 50%, and the maximum current input from the direct current setting unit 106 to the control unit 104 is IMAX; in the time period T5, the duty cycle from the duty cycle setting unit 104 to the control unit 108 is 30%, and from The maximum current input by the DC setting unit 106 to the control unit 104 is IMAX. Please continue to refer to FIG. 2B, in the time period T1', the duty ratio output from the control unit 108 to the LED driving unit 110 is 100%, and the current is IMAX; in the time period T2', the output from the control unit 108 to the LED driver The duty ratio of the unit 110 is 100%, and the current is 0.75IMAX; in the time period T3', the duty ratio output from the control unit 108 to the LED driving unit 110 is 85%, and the current is IMAX; in the time period T4', The duty ratio output from the control unit 108 to the LED driving unit 110 is 100%, and the current is 0.5IMAX; in the time period T5′, the duty ratio output from the control unit 108 to the LED driving unit 110 is 60%, and the current It is 0.5IMAX. It should be noted that the duty ratio and current received by the control unit 108 and the output duty ratio and current may be equal or different. For example, the duty cycle and current received by the control unit 108 in the time period T2 are 75% and IMAX, respectively, and the duty cycle and current output by the control unit 108 in the time period T2' are 100% and 0.75IMAX are different. The duty ratio and current received by the control unit 108 and the output duty ratio and current satisfy the following relationship:

Received duty cycle * received current = output duty cycle * output current ----- equation (1)

By adjusting the duty cycle of the output and the output current to satisfy the equation (1), the LED can be adaptively operated in a region of higher working efficiency. The present invention can improve the working efficiency of the LED by matching the DC drive and the pulse width conduction period drive; in addition, the efficiency can be improved by adjusting the DC setting, and the flow can be precisely controlled by adjusting the pulse width conduction period. The average current of the LED.

Please refer to Figure 3. FIG. 3 is a system block diagram illustrating the control unit 108 in the LED driving device according to an embodiment of the present invention. The control unit 108 includes a current order setting unit 308 for determining a current order; a duty cycle and current calculation unit 302 for setting the current order according to the maximum current value determined by the DC setting unit 106 The current order determined by the constant unit 308 and the duty cycle setting signal transmitted by the duty cycle setting unit 104 output a DC control signal and a duty cycle control signal. The current order setting unit can arbitrarily set the current order according to actual needs. Taking the 4th current order (1-4) as an example, the operation of the duty cycle and current operation unit 302 is described. When the duty ratio represented by the received duty ratio setting signal is 0≤duty ratio≤25, the current order is set to 1, and the DC control signal is set to 1 ^* maximum current value IMAX/4 ; When the duty cycle represented by the received duty cycle setting signal is 25<duty cycle≤50, the current order is set to 2, and the DC control signal is set to 2 ^* maximum current value IMAX/4 = maximum current value IMAX/2; when the duty ratio represented by the received duty ratio setting signal is 50<duty ratio≤75, the current order is set to 3, and the DC control signal is set to 3 ^* maximum current value IMAX/4; when the received duty cycle setting signal represents a duty cycle of 75<duty cycle≤100, the current order is set to 4, and the DC control signal is set to The maximum current value IMAX. For example, when the duty cycle represented by the received duty cycle setting signal is 80%, the current order is 4, and the DC control signal is 4 ^* maximum current value IMAX/4=maximum current value IMAX, according to the equation (1) The available duty cycle control signal is 80%. For example, when the duty cycle setting signal represented by the received duty cycle setting signal is 25%, the current order is 1, and the DC control signal is 1 ^* Imax/4=0.25Imax, according to the equation (1 ) The available duty cycle control signal is 100%. Although the current order is 4 as an example for illustration, the current order can be set according to actual needs, and is not limited thereto.

Next, please refer to FIG. 1 and FIG. 2B at the same time. During the time period T2' and T3', the light emitting diode driving device 100 provides a first driving current for driving the light emitting diode 102 in the time period T2', the first driving current has a duty ratio of 100% and a current value of 0.75IMAX ; Next, the light-emitting diode driving device 100 provides a second driving current for driving the light-emitting diode 102 in a time period T3' following the time period T2', the second driving current has a duty cycle of 80% and a current value IMAX; during the time periods T2' and T3', the duty ratio of the first driving current is greater than that of the second driving current; and the current value of the first driving current is smaller than the current value of the second driving current.

During the period T3' and T4', the LED driving device 100 provides a second driving current for driving the LED 102 in the time period T3', the second driving current has a duty cycle of 80% and a current value IMAX; Next, the light emitting diode driving device 100 provides a third driving current for driving the light emitting diode 102 in a time period T4' following the time period T3', the third driving current has a duty ratio of 100% and a current value of 0.5 IMAX; during the time periods T3' and T4', the duty cycle of the second driving current is smaller than the duty cycle of the third driving current; and the current value of the second driving current is greater than the current value of the third driving current.

By means of the above-mentioned light-emitting diode driving device and its driving method, the current value and duty cycle of the light-emitting diode driving current can be effectively adjusted, so that the working efficiency of the LED can be improved and the average conduction current of the LED can be precisely controlled, which is a preferred option. A driving device and a driving method of a light emitting diode.

The technical contents and technical features of the present invention have been disclosed above, but those of ordinary skill in the art should understand that without departing from the spirit and scope of the present invention defined by the appended claims, the teachings and disclosures of the present invention can be made various replacements and grooming. For example, many of the processes disclosed above could be performed differently or replaced by other processes, or a combination of both.

Claims (10)

1. A light-emitting diode driving device, comprising: a duty ratio setting unit, used to output a duty ratio setting signal; a DC setting unit for outputting a DC setting signal; a control unit for receiving the duty cycle setting signal and the DC setting signal, and outputting a DC control signal and a duty cycle control signal according to the duty cycle setting signal and the DC setting signal; and a light emitting diode driving circuit, used for driving at least one light emitting diode according to the direct current control signal and the duty cycle control signal; The DC setting signal is used to set the maximum current value output by the control unit; Among them, the control unit further includes: a current order setting unit for determining a current order; and A duty ratio and current computing unit is used to output the DC control signal and the duty ratio control signal according to the maximum current value and the current order. 2. The LED driving device as claimed in claim 1, wherein the duty cycle setting signal includes information of a duty cycle of the current received by the control unit. 3. The LED driving device according to claim 1, wherein the product of the duty cycle represented by the duty cycle control signal and the DC control signal is equal to the duty cycle represented by the duty cycle setting signal and the The product of the DC setting signal. 4. A light-emitting diode driving method, comprising: providing a duty ratio setting signal; Provide a DC setting signal; receiving the duty cycle setting signal and the DC setting signal to a control unit, and using the DC setting signal to set the maximum current value output by the control unit; providing a current order; Outputting a DC control signal and a duty cycle control signal to a light emitting diode drive circuit through the control unit according to the maximum current value and the current order; and driving at least one light emitting diode according to the DC control signal and the duty cycle control signal; Wherein, a first driving current is provided during a first time period to drive the light emitting diode, and the first driving current has a first duty ratio and a first current value; and providing a second driving current for driving the LED during a second time period following the first time period, the second driving current has a second duty cycle and a second current value, wherein the first A current value is not equal to the second current value and the first duty cycle is not equal to the second duty cycle. 5. The LED driving method as claimed in claim 4, wherein the first current value is greater than the second current value. 6. The LED driving method as claimed in claim 4, wherein the first current value is smaller than the second current value. 7. The LED driving method as claimed in claim 4, wherein the first duty ratio is smaller than the second duty ratio. 8. The LED driving method as claimed in claim 6, wherein the first duty cycle is greater than the second duty cycle. 9. A method of driving a light emitting diode, comprising: providing a duty ratio setting signal; Provide a DC setting signal; receiving the duty cycle setting signal and the DC setting signal to a control unit, and using the DC setting signal to set the maximum current value output by the control unit; providing a current order; Outputting a DC control signal and a duty cycle control signal to a light emitting diode drive circuit through the control unit according to the maximum current value and the current order; and At least one LED is driven according to the DC control signal and the duty ratio control signal. 10. The LED driving method according to claim 9, wherein the step of driving at least the LED further comprises: providing a first driving current for driving the LED during a first time period; and A second driving current is provided in a second time period following the first time period to drive the LED.

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