TW201507543A - Light emitting apparatus and current controlling method thereof - Google Patents

Abstract

A light emitting apparatus includes a first light emitting unit, a first switching unit, a second light emitting unit, a second switching unit and a current controlling unit. The first light emitting unit has at least one LED and a first current through the first light emitting unit. The first switching unit is series connected with the first light emitting unit forming a first conducting path. The second light emitting unit has at least one LED and a second current through the second light emitting unit. The second switching unit is series connected with the second light emitting unit forming a second conducting path. The second conducting path is parallel connected to the first conducting path. The current controlling unit is electrically connected with the first switching unit and the second switching unit. The current controlling unit controls a first duty cycle of the first switching unit and a second duty cycle of the second switching unit according to a first current value of the first current and a second current value of the second current respectively. The present invention also discloses a current controlling method.

Description

Light emitting device and current control method thereof

The present invention relates to a light emitting device and a current control method therefor.

With the development of semiconductor process technology, light emitting diodes (LEDs) are commonly used in human life, such as lighting devices, which can make lighting devices more economical than traditional halogen or tungsten lamps. Electricity, for example, applied to advertising billboards, can make advertising billboards more attractive at night.

During the process of the LED, the directional bias of each of the LEDs produced is not exactly the same due to the difference in materials or process conditions. When these light-emitting diodes are connected in series to form a plurality of light-emitting diode strings connected in parallel, the luminance of each of the light-emitting diode strings will be inconsistent. In the prior art, in order to solve the above problem, each of the LED strings is connected in series with a transistor switch controlled by a current control unit, and the current control unit performs constant current control by The voltage difference between the drain and the source of each transistor switch is controlled to make the brightness of each of the light emitting diode strings uniform.

For example, a light-emitting device includes three light-emitting diodes connected in series and in parallel, each light-emitting diode string includes a transistor switch, and the light-emitting diode strings respectively have a total forward bias voltage of VF1, VF2, and VF3. When a voltage VDC is supplied to the LED strings, the power control unit controls voltage differences VDS1, VDS2, and VDS3 between the drains and the sources of the respective transistor switches corresponding to the LED strings. Let VDC=VF1+VDS1=VF2+VDS2=VF3+VDS3. However, since the total forward bias of each of the LED strings is different, each of the transistor switches generates excess waste heat, which not only causes waste of energy, but also increases the heat dissipation area of the circuit board, thereby causing the size of the circuit board. Increased and material costs also increase.

Therefore, how to provide a light-emitting device having uniform brightness and saving energy consumption has become one of important issues.

In view of the above problems, it is an object of the present invention to provide a light-emitting device which has uniform brightness and which can reduce energy consumption.

To achieve the above object, a light emitting device according to the present invention includes a first light emitting unit, a first switching unit, a second light emitting unit, a second switching unit, and a current control unit. The first light emitting unit has at least one light emitting diode and a first current flowing through one of the first light emitting units. The first switching unit is connected in series to the first lighting unit and forms a first conduction path. The second light emitting unit has at least one light emitting diode and a second current flowing through one of the second light emitting units. The second switching unit is connected in series to the second lighting unit, and forms a second conduction path, and the second conduction path is connected in parallel with the first conduction path. The current control unit electrically connects the first switch unit and the second switch unit, and controls one of the first duty cycles of the first switch unit according to one of the first current value and the second current value of the second current And a second duty cycle of the second switching unit.

In one embodiment, the light emitting diode system is an inorganic light emitting diode or an organic light emitting diode.

In an embodiment, when the first current value is less than the second current value, the current control unit controls the first duty cycle of the first switching unit to be greater than the second duty cycle of the second switching unit, when the first current value is greater than the second current The current control unit controls the first duty cycle of the first switching unit to be less than the second duty cycle of the second switching unit.

In an embodiment, when the first switching unit is turned on, the first lighting unit is illuminated, and when the second switching unit is turned on, the second lighting unit is illuminated.

In an embodiment, the average currents of the first lighting unit and the second lighting unit are substantially equal.

In an embodiment, a third lighting unit and a third switching unit are further included. The third light emitting unit has at least one light emitting diode and a third current flowing through the third light emitting unit, the third switching unit is connected in series to the third light emitting unit, and forms a third conductive path, and the third The conduction path is connected in parallel with the first conduction path and the second conduction path, wherein the current control unit is electrically connected to the third switching unit, and controls the third duty cycle of the third switching unit according to the third current value of the third current. .

In one embodiment, the first light emitting unit and the second light emitting unit respectively comprise a plurality of light emitting diodes, and the light emitting diode systems in the first light emitting unit are connected in series with each other, and the light emitting two in the second light emitting unit The pole systems are connected in series.

In one embodiment, the current control unit controls the first duty cycle of the first switching unit and the second duty cycle of the second switching unit in a pulse width modulation manner.

In an embodiment, the brightness of the first lighting unit and the second lighting unit are substantially the same.

In one embodiment, the product of the first duty cycle of the first lighting unit and the current is substantially the same as the product of the second duty cycle of the second lighting unit and the current.

The present invention further includes a current control method, which is coupled to a light-emitting device, the light-emitting device comprising a first light-emitting unit, a first switch unit, a second light-emitting unit, a second switch unit, and a current control unit, wherein An illuminating unit has at least one illuminating diode, the first switching unit is connected in series with the first illuminating unit, and forms a first conducting path, the second illuminating unit has at least one illuminating diode, and the second illuminating unit and the first illuminating unit The second switch unit is connected in series with the second light-emitting unit, and forms a second conductive path. The second conductive path is connected in parallel with the first conductive path. The current control method includes: the current control unit measures the flow through the first light-emitting unit. a first current and a second current of the second light emitting unit; adjusting a common driving voltage such that a first current value of the first current is equal to a predetermined current value, and wherein the second current value is greater than the predetermined current a value; the current control unit controls the first switching unit to have a first duty cycle, and the second switch unit has a second Period for the first product of the first current value and the duty cycle is equal to the product of the second current value and the second duty cycle.

In one embodiment, the step of adjusting the common drive voltage refers to increasing the common drive voltage such that the first current value is equal to the predetermined current value and the second current value is greater than the predetermined current value.

In an embodiment, the light emitting device further includes a third light emitting unit and a third switch unit, wherein the third light emitting unit has at least one light emitting diode and flows through the third light emitting unit. a third current value, the third switching unit is connected in series to the third lighting unit, and forms a third conduction path, and the third conduction path is connected in parallel with the first conduction path and the second conduction path, and the current control method comprises: a current control unit Measuring a third current value flowing through one of the third lighting units; adjusting the common driving voltage such that one of the third current values is greater than the predetermined current value; and the current control unit controls the third switching unit to have a third duty cycle The product of the first current value and the first duty cycle is equal to the product of the second current value and the second duty cycle, and is also equal to the product of the third current value and the third duty cycle.

In an embodiment, when the first switching unit is turned on, the first lighting unit is illuminated, and when the second switching unit is turned on, the second lighting unit is illuminated.

In one embodiment, the first light emitting unit and the second light emitting unit respectively comprise a plurality of light emitting diodes, and the light emitting diode systems in the first light emitting unit are connected in series with each other, and the light emitting two in the second light emitting unit The pole systems are connected in series.

In one embodiment, the third light emitting unit includes a plurality of light emitting diodes, and the light emitting diode systems in the third light emitting unit are connected in series with each other.

In one embodiment, the current control unit controls the first duty cycle of the first switching unit and the second duty cycle of the second switching unit in a pulse width modulation manner.

In an embodiment, the brightness of the first lighting unit and the second lighting unit are substantially the same.

According to the present invention, in a light-emitting device and a current control method thereof, a current control unit controls a first duty cycle of the first switching unit and a second duty cycle of the second switching unit to flow through the first light-emitting unit. The average currents of the unit and the second light-emitting unit are substantially equal, so that the brightness of the first light-emitting unit and the second light-emitting unit are substantially the same, and waste heat generated by the first switch unit and the second switch unit can be reduced, thereby not only saving energy consumption. It is also possible to reduce the board area required for heat dissipation, thereby reducing the cost of materials.

1, 1a‧‧‧Lighting device

11‧‧‧First lighting unit

12‧‧‧second lighting unit

13‧‧‧3rd lighting unit

C‧‧‧Current Control Unit

D1a~D1c, D2a~D2c, D3a~D3c‧‧‧Light Emitting Diode

P1‧‧‧First conduction path

P2‧‧‧second conduction path

P3‧‧‧ third conduction path

I1‧‧‧first current value

I2‧‧‧second current value

I3‧‧‧ third current value

Iset‧‧‧Predetermined current value

Step flow of current control method for S1~S6‧‧‧ illuminating device

SW1‧‧‧ first switch unit

SW2‧‧‧Second switch unit

SW3‧‧‧ third switch unit

T1‧‧‧ first work cycle

T2‧‧‧ second work cycle

T3‧‧‧ third work cycle

V‧‧‧Common drive voltage

1 is a schematic view of a light emitting device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of the duty cycle of each switch unit.

3 is a schematic view of a light emitting device according to a second embodiment of the present invention.

Figure 4 is a schematic diagram of the duty cycle of each switching unit.

FIG. 5 is a schematic flow chart of a current control method according to the present invention.

FIG. 6 is a schematic flow chart of another current control method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light-emitting device and a current control method thereof according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements will be described with the same reference numerals.

Please refer to FIG. 1, which is a schematic diagram of a light emitting device according to a first embodiment of the present invention. The illuminating device 1 includes a first illuminating unit 11 and a first switching unit SW1. The first illuminating unit 11 and the first switching unit SW1 are connected in series to form a first conducting path P1, a second illuminating unit 12 and a second switching unit. SW2, the second lighting unit 12 and the second switching unit SW2 are connected in series to form a second conduction path P2 and a current control unit C. The light-emitting device 1 can be a lighting device, a backlight of the liquid crystal display device, an advertising billboard, or an LED display device or the like.

The first light-emitting unit 11 has at least one light-emitting diodes D1a-D1c. Here, three are taken as an example. It should be noted that in different embodiments, the number of light-emitting diodes can be designed according to actual needs, for example, Can be one, two or more. The light-emitting diodes D1a to D1c may be, for example but not limited to, an inorganic light-emitting diode or an organic light-emitting diode.

In the present embodiment, the LEDs D1a to D1c are connected in series, and the first illumination unit 11 has a first forward bias voltage V1 and a first current flowing through the first illumination unit 11. . The light-emitting diodes D1a-D1c each have a forward bias, for example, the forward bias of the light-emitting diode D1a is V1a, the forward bias of the light-emitting diode D1b is V1b, and the light-emitting diode D1c The forward bias is V1c. Therefore, the first forward bias voltage V1 is equal to the sum of the forward biases of the light-emitting diodes D1a to D1c, that is, V1 = V1a + V1b + V1c. It should be noted that the LEDs D1a~D1c may have different forward bias voltages V1a~V1c corresponding to the LEDs D1a~D1c due to different process conditions or materials. The first current of a forward bias voltage V1 is different. In addition, in other embodiments, the connection manner of the light emitting diodes of the first light emitting unit 11 may include serial connection or parallel connection, or Both include series connection and parallel connection.

The first switching unit SW1 is connected in series to one end of the first lighting unit 11. In detail, the first switch unit SW1 can be, for example, a transistor switch, one end of which is electrically connected to the first light-emitting unit 11 to form a first conductive path P1, and the other end of which is electrically connected to the current control unit C, and In this embodiment, the first switching unit SW1 is controlled by the current control unit C, and when the first switching unit SW1 is turned on, the first lighting unit 11 is illuminated to emit light.

The second light-emitting unit 12 is connected in series with the second switch unit SW2 to form a second conductive path P2. The first conductive path P1 is connected in parallel with the second conductive path P2, and the second light-emitting unit 12 has at least one light-emitting diode D2a. D2c, here are three examples, it should be noted that in different embodiments, the number of light-emitting diodes can be designed according to actual needs, for example, one, two or more, and second The number of the light emitting diodes of the light emitting unit may be the same as or different from the number of the light emitting diodes of the first light emitting unit, and the number is the same as an example. The light-emitting diodes D2a to D2c may be, for example but not limited to, an inorganic light-emitting diode or an organic light-emitting diode.

In the present embodiment, the LEDs D2a to D2c are connected in series, and the second illumination unit 12 has a second forward bias voltage V2 and a second current flowing through the second illumination unit 12. . The light-emitting diodes D2a-D2c each have a forward bias, for example, the forward bias of the light-emitting diode D2a is V2a, the forward bias of the light-emitting diode D2b is V2b, and the light-emitting diode D2c The forward bias is V2c. Therefore, the second forward bias voltage V2 is equal to the sum of the forward biases of the light-emitting diodes D2a to D2c, that is, V2 = V2a + V2b + V2c. It should be noted that the LEDs D2a~D2c may have different forward bias voltages V2a~V2c corresponding to the LEDs D2a~D2c due to different process conditions or material relationships. The second current of the second forward bias voltage V2 is different, and the second forward bias voltage V2 may also be different from the first forward bias voltage V1. In addition, in other embodiments, the connection manner of the LEDs of the second illumination unit 12 may include serial connection or parallel connection, or both serial connection and parallel connection.

The second switching unit SW2 is connected in series to one end of the second lighting unit 12. In detail, the second switch unit SW2 can be, for example, a transistor switch, one end of which is electrically connected to the second light emitting unit 12, and the other end of which is electrically connected to the current control unit C, and in this embodiment, the second The switch unit SW2 is controlled by the current control unit C, and when the second switch unit SW2 is turned on At the same time, the second light emitting unit 12 is turned on to emit light.

The current control unit C can be, for example but not limited to, a microcontroller unit (MCU) electrically connected to the first switching unit SW1 and the second switching unit SW2, and the current control unit C controls the first switching unit SW1, respectively. And the second switching unit SW2 is turned on or off. In detail, after the current control unit C adjusts the common driving voltage, the first current value I1 of the first lighting unit and the second current value I2 of the second lighting unit respectively control the first working period T1 of the first switching unit SW1. (first duty cycle) and a second duty cycle T2 of the second switching unit SW2, wherein the current control unit C can control the first, for example but not limited to, pulse width modulation (PWM) The switch unit 11 and the second switch unit 12.

Please refer to FIG. 2 below to further explain the operation of the current control unit C.

Please refer to FIG. 2 , which is a schematic diagram of the on-time of the first switching unit SW1 and the second switching unit SW2. As shown in FIG. 2 , in the embodiment, the second forward bias voltage V2 corresponding to the second light emitting unit 12 is smaller than the first forward bias voltage V1 corresponding to the first light emitting unit 11 . Before the regulation of the duty cycle is performed, since the second forward bias voltage V2 is smaller than the first forward bias voltage V1, when the first switching unit SW1 and the second switching unit SW2 are both turned on, the second light emitting unit 12 flows. The second current system may be greater than the first current flowing through the first lighting unit 11. The brightness of the light-emitting diodes D1a to D1c and D2a to D2c is proportional to the current value passed, so the average brightness of the first light-emitting unit 11 is smaller than the average brightness of the second light-emitting unit 12.

In order to make the average brightness of the first light-emitting unit 11 and the second light-emitting unit 12 substantially the same, the current control unit C can change the first current and the second current by adjusting the common driving voltage V, and add the first control. The first duty cycle (on-time of one unit time) of the switch unit SW1 and the second duty cycle of the second switch unit SW2 are such that the average current flowing through the first light-emitting unit 11 and the second light-emitting unit 12 is substantially equal. Furthermore, the product of the first duty cycle T1 of the first lighting unit 11 and the first current value I1 is substantially the same as the product of the second duty cycle T2 of the second lighting unit 12 and the second current value I2. That is, as shown in FIG. 2, the areas indicated by the two different patterns are equal in unit time. It should be noted that in order to make the illustration clearer, the area marked by the two patterns is located in different unit time to avoid In the case of avoiding overlap, the area indicated by the two patterns may be partially overlapped and located in the same unit time.

In other words, when the first forward bias voltage V1 is smaller than the second forward bias voltage V2, the current value I1 flowing through the first light emitting unit 11 is greater than the current value I2 flowing through the second light emitting unit 12, and the current control unit C controls The duty cycle T1 of the first switching unit SW1 is smaller than the duty cycle T2 of the second switching unit SW2; when the first forward bias voltage V1 is greater than the second forward bias voltage V2, the current value I1 flowing through the first lighting unit 11 is The current control unit C controls the first duty cycle T1 of the first switching unit SW1 to be greater than the second duty cycle T2 of the second switching unit SW2, which is smaller than the current value I2 flowing through the second lighting unit 12. Here, the first forward bias voltage V1 is greater than the second forward bias voltage V2, and the first current value I1 flowing through the first light emitting unit 11 is smaller than the second current value I2 flowing through the second light emitting unit 12 For example, the first duty cycle T1 of the first switching unit SW1 in FIG. 2 is greater than the second duty cycle T2 of the second switching unit SW2.

For example, when the current value I1 flowing through the first light emitting unit 11 is 0.8 times the current value I2 flowing through the second light emitting unit 12 (ie, I1=0.8*I2), the current control unit C controls the first switch. The first duty cycle T1 of the unit SW1 is 1.25 times of the second duty cycle T2 of the second switching unit SW2 (ie, T1=1.25*T2), so that I1*T1=I2*T2, thereby reaching the first lighting unit 11 and The purpose of the average luminance (average luminous intensity) of one unit time of the second light-emitting unit 12 is the same, wherein the units of the respective current values are the same, and here the ampere (A) is taken as an example, not a limitation. It should be noted that the first working period T1 and the second working period T2 may be cumulative sums in one unit time, that is, the first working period T1 and the second working period T2 may be the sum of the plurality of small working periods respectively. , for example, the sum of the time in a frame.

It should be noted that the illuminating device 1 of the present invention may have a plurality of current control units C corresponding to respective predetermined current values, and the current control unit C controls the plurality of illuminating units. The current control unit C can change the corresponding predetermined current value according to actual product application requirements, so that the light-emitting units corresponding to the different current control units C can have different predetermined current values.

Please refer to FIG. 3, which is a schematic diagram of a light emitting device according to a second embodiment of the present invention. The illuminating device 1a is substantially the same as the illuminating device 1 except that the illuminating device 1a further includes a third illuminating unit 13 and a third switching unit SW3, and the third illuminating unit 13 and The third switching unit SW3 is connected in series to form a third conduction path P3.

The third conductive path P3 is connected in parallel with the first conductive path P1 and the second conductive path P2, and the third light-emitting unit 13 has at least one light-emitting diode D3a-D3c. In a different embodiment, the number of the light emitting diodes may be designed according to actual needs, for example, one, two or more, and the number of the light emitting diodes of the third light emitting unit and the first light emitting unit, The number of the light emitting diodes of the second light emitting unit may be the same or different, and the number is the same as an example. The light-emitting diodes D3a to D3c may be, for example but not limited to, an inorganic light-emitting diode or an organic light-emitting diode.

In the present embodiment, the LEDs D3a to D3c are connected in series, and the third illumination unit 13 has a third forward bias voltage V3 and a third current flowing through the third illumination unit 13. . The light-emitting diodes D3a-D3c each have a forward bias, for example, the forward bias of the light-emitting diode D3a is V3a, the forward bias of the light-emitting diode D3b is V3b, and the light-emitting diode D3c The forward bias is V3c. Therefore, the third forward bias voltage V3 is equal to the sum of the forward biases of the light-emitting diodes D3a to D3c, that is, V3 = V3a + V3b + V3c. It should be noted that the LEDs D3a~D3c may have different forward bias voltages V3a~V3c corresponding to the LEDs D3a~D3c due to different process conditions or material relationships, and the third pass may be the same. The bias voltage V3 may also be different from the first forward bias voltage V1 and the second forward bias voltage V2. In addition, in other embodiments, the connection manner of the LEDs of the third lighting unit 13 may include serial connection or parallel connection, or both serial connection and parallel connection.

The third switching unit SW3 is connected in series to one end of the third lighting unit 13. In detail, the third switch unit SW3 can be, for example, a transistor switch, one end of which is electrically connected to the third light emitting unit 13 and the other end of which is electrically connected to the current control unit C, and in this embodiment, the third The switching unit SW3 is controlled by the current control unit C, and when the third switching unit SW3 is turned on, the third lighting unit 13 is turned on to emit light.

The current control unit C controls the first switching unit SW1, the second switching unit SW2, and the third switching unit SW3 to be turned on and off, so that the first current value I1 flowing through the first lighting unit 11 and the first switching unit SW1 are The product of one duty cycle T1, the product of the second current value I2 flowing through the second light emitting unit 12 and the second duty cycle T2 of the second switching unit SW2, and the third current value I3 flowing through the third light emitting unit 13 and the first Third work of three switch unit SW3 The product of the period T3 is substantially equal. In other words, it can be expressed as I1*T1=I2*T2=I3*T3, that is, as shown in FIG. 4, the areas indicated by the three different patterns are equal. It should be noted that, in order to make the illustration clearer, the areas marked by the three patterns are located in different unit time to avoid confusion when overlapping. In fact, the areas indicated by the three patterns may overlap and be in the same part. Unit time. Here, the first forward bias voltage V1 is greater than the second forward bias voltage V2, the second forward bias voltage V2 is greater than the third forward bias voltage V3, and the first current value I1 flowing through the first light emitting unit 11 For example, the current value I2 flowing through the second light emitting unit 12 is smaller, and the second current value I2 flowing through the second light emitting unit 12 is smaller than the third current value I3 flowing through the third light emitting unit 13.

Please refer to FIG. 5, which is a schematic flowchart of the current control method of the present invention. The current control method is a light-emitting device, the components included in the light-emitting device and the connection relationship thereof. The current control method of the embodiment includes the following steps: the current control unit measures the flow through the first light-emitting unit. a current and a second current (S1) of the second lighting unit, adjusting a common driving voltage, the first current value of the first current is equal to a predetermined current value, and the second current is greater than a predetermined one The current value (S2) and the current control unit control the first switching unit to have a first duty cycle, and control the second switching unit to have a second duty cycle such that the product of the first current value and the first duty cycle is equal to the second current The product of the value and the second duty cycle (S3).

In step S1, when both the first switching unit SW1 and the second switching unit SW2 are turned on, the current control unit C measures the first current flowing through the first lighting unit 11 and the second current flowing through the second lighting unit 12. And comparing with a predetermined current value Iset to confirm the magnitude relationship between the adjusted first current value I1, the second current value I2 and the predetermined current value Iset. The current control unit C can measure the first current and the second current each time the first light emitting unit 11 and the second light emitting unit 12 are lit, and continue the subsequent duty cycle regulation.

In step S2, the common driving voltage V refers to the total voltage of the first driving unit 11 and the second lighting unit 12 being driven together, and the first current and the second current are changed by adjusting the common driving voltage V. For example, when at least one of the first current or the second current measured by the equivalent is lower than the predetermined current value Iset, the common driving voltage V is increased, so that both the first current and the second current start to increase until the first current The first current value I1 is equal to the predetermined current value Iset, and the second current value I2 of the second current is greater than the predetermined current value Iset.

In step S3, the brightness of the light-emitting unit is determined by the magnitude of the current. Therefore, in order to make the average brightness of all the light-emitting units substantially the same, pulse width modulation (PWM) is used to control the operation of each light-emitting unit. Cycle (on time per unit time). For example, please match with FIG. 1 and FIG. 2, after the measurement, the first current system is smaller than the second current, and the first current is less than the predetermined current value Iset, so the common driving voltage V is adjusted, so that Both the current and the second current become larger until the first current value I1 is equal to the predetermined current value Iset and the second current value I2 is greater than the predetermined current value Iset. Next, the current control unit C controls the second duty cycle T2 corresponding to the second switching unit SW2 by using the first duty cycle T1 corresponding to the first switching unit SW1 as 100%. The product of the first current value I1 and the first duty cycle T1 is made equal to the product of the second current value I2 and the second duty cycle T2.

It should be noted that, in the current control method of the embodiment, when the common driving voltage V is adjusted, and the first current or the second current measured by the equivalent is greater than the predetermined current value Iset, the common driving voltage V may also be reduced. The at least one current value is made equal to the predetermined current value Iset, and the other current value is greater than the predetermined current value Iset.

Referring to FIG. 3 and FIG. 6 simultaneously, a light-emitting device 1a according to a second embodiment of the present invention is different from the light-emitting device of the first embodiment in that the light-emitting device 1a further includes a third light-emitting unit 13 and a third The switching unit SW3, the current control method of the light-emitting device 1a comprises the following steps: the current control unit measures a first current flowing through one of the first lighting units, a second current of the second lighting unit, and a third of the third lighting unit a current (S4); adjusting a common driving voltage such that one of the first currents is equal to a predetermined current value, one of the second currents is greater than a predetermined current value, and the third current is a third current The value is greater than the predetermined current value (S5); and the current control unit controls the first switching unit to have a first duty cycle, the second switching unit has a second duty cycle, and the third switching unit has a third duty cycle. The product of the first current value and the first duty cycle is equal to the product of the second current value and the second duty cycle, and is also equal to the product of the third current value and the third duty cycle (S6).

Since the third lighting unit 13 and the third switching unit SW3 are added, in step S4, unlike step S1 of the foregoing embodiment, when the third switching unit SW3 is turned on, the current control unit C measures through the third. The third current of the light-emitting unit 13 is compared with a predetermined current value Iset to confirm the magnitude relationship between the third current value I3 of the third current and the predetermined current value Iset.

Step S5 is different from step S2 of the foregoing embodiment in that the first current, the second current, and the third current are changed by adjusting the common driving voltage V in step S5. For example, when at least one of the first current, the second current, or the third current measured by the equivalent is lower than the predetermined current value Iset, the common driving voltage V is increased, so that the first current, the second current, and the third current are both The increase is started until the first current value I1 is equal to the predetermined current value Iset, and the second current value I2 and the third current value I3 are both greater than the predetermined current value Iset.

Step S6 is different from step S3 of the foregoing embodiment. In step S6, the current control unit C controls the third corresponding to the third switching unit SW3 by using the first duty cycle T1 corresponding to the first switching unit SW1 as 100%. Work cycle T3. The product of the first current value I1 and the first duty cycle T1 is made equal to the product of the second current value I2 and the second duty cycle T2, and is also equal to the product of the third current value I3 and the third duty cycle T3.

According to the above aspect of the present invention, in a light-emitting device and a current control method thereof, a current control unit controls a first duty cycle of the first switching unit and a second duty cycle of the second switching unit to flow through the first lighting unit and The average currents of the second light-emitting units are substantially equal, so that the brightness of the first light-emitting unit and the second light-emitting unit are substantially the same, and the waste heat generated by the first switch unit and the second switch unit can be reduced, thereby not only saving energy consumption, but also Reduce board space required for heat dissipation, which in turn reduces material costs.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1‧‧‧Lighting device

11‧‧‧First lighting unit

12‧‧‧second lighting unit

C‧‧‧Current Control Unit

D1a~D1c, D2a~D2c‧‧‧Light Emitting Diodes

P1‧‧‧First conduction path

P2‧‧‧second conduction path

SW1‧‧‧ first switch unit

SW2‧‧‧Second switch unit

V‧‧‧Common drive voltage

Claims (18)

A light-emitting device includes: a first light-emitting unit having at least one light-emitting diode and a first current flowing through the first light-emitting unit; a first switch unit connected in series to the first light-emitting unit, and forming a a first conductive path; a second light emitting unit having at least one light emitting diode and a second current flowing through the second light emitting unit; a second switching unit connected in series to the second light emitting unit, and forming a first a second conduction path, the second conduction path is connected in parallel with the first conduction path; and a current control unit electrically connecting the first switching unit and the second switching unit, and according to the first current value of the first current And a second current value of the second current, respectively controlling a first duty cycle of the first switching unit and one second duty cycle of the second switching unit. The light-emitting device of claim 1, wherein the light-emitting diode system is an inorganic light-emitting diode or an organic light-emitting diode. The illuminating device of claim 1, wherein the current control unit controls the first working period of the first switching unit to be greater than the second switching unit when the first current value is less than the second current value During the second duty cycle, when the first current value is greater than the second current value, the current control unit controls the first duty cycle of the first switching unit to be less than the second duty cycle of the second switching unit. The illuminating device of claim 1, wherein the first switching unit lights up the first lighting unit, and when the second switching unit is turned on, illuminates the second lighting unit. The illuminating device of claim 1, wherein the average current of the first illuminating unit and the second illuminating unit is substantially equal. The illuminating device of claim 1, further comprising: a third illuminating unit having at least one illuminating diode and flowing through the third a third current of the light emitting unit; and a third switching unit connected in series to the third light emitting unit, and forming a third conductive path, the third conductive path is connected in parallel with the first conductive path and the second conductive path The current control unit is electrically coupled to the third switching unit, and controls a third duty cycle of the third switching unit according to a third current value of the third current. The illuminating device of claim 1, wherein the first illuminating unit and the second illuminating unit respectively comprise a plurality of illuminating diodes, wherein the illuminating diode systems in the first illuminating unit are connected in series The light emitting diode systems in the second light emitting unit are connected in series with each other. The illuminating device of claim 1, wherein the current control unit controls the first duty cycle of the first switching unit and the second operation of the second switching unit in a pulse width modulation manner cycle. The illuminating device of claim 1, wherein the brightness of the first illuminating unit and the second illuminating unit are substantially the same. The illuminating device of claim 1, wherein the product of the duty cycle of the first illuminating unit and the current is substantially the same as the product of the duty cycle and the current of the second illuminating unit. A current control method for a light-emitting device is coupled to a light-emitting device, the light-emitting device comprising a first light-emitting unit, a first switch unit, a second light-emitting unit, a second switch unit, and a current control unit, wherein the current control unit The first illuminating unit has at least one illuminating diode, the first illuminating unit is connected in series with the first illuminating unit, and forms a first conducting path, the second illuminating unit has at least one illuminating diode, the second illuminating unit The unit is connected in parallel with the first lighting unit, the second switching unit is connected in series with the second lighting unit, and forms a second conduction path. The second conduction path is connected in parallel with the first conduction path. The current control method includes: The current control unit measures a first current flowing through one of the first lighting units and a second current of the second lighting unit; Adjusting a common driving voltage such that a first current value of the first current is equal to a predetermined current value, and a second current value of the second current is greater than the predetermined current value; and the current control unit controls the first switch The unit has a first duty cycle, and the second switch unit is controlled to have a second duty cycle, such that the product of the first current value and the first duty cycle is equal to the product of the second current value and the second duty cycle . The current control method according to claim 11, wherein the step of adjusting the common driving voltage refers to increasing the common driving voltage so that the first current value is equal to the predetermined current value, and the second current The value is greater than the predetermined current value. The current control method of claim 11, wherein the illuminating device further comprises a third illuminating unit and a third switching unit, the third illuminating unit having at least one illuminating diode and flowing through the a third current value of the third light-emitting unit, the third switch unit is connected in series to the third light-emitting unit, and forms a third conductive path, and the third conductive path is connected in parallel with the first conductive path and the second conductive path The current control method includes: the current control unit measuring a third current flowing through one of the third lighting units; adjusting the common driving voltage such that a third current value of the third current is greater than the predetermined current value; The current control unit controls the third switching unit to have a third duty cycle, such that the product of the first current value and the first duty cycle is equal to the product of the second current value and the second duty cycle, and is equal to the first The product of the three current values and the third duty cycle. The current control method of claim 11, wherein the first switching unit is turned on to illuminate the first lighting unit, and the second switching unit is turned on to illuminate the second lighting unit. The current control method of claim 11, wherein the first light emitting unit and the second light emitting unit respectively comprise a plurality of light emitting diodes The light-emitting diode systems in the first light-emitting unit are connected in series with each other, and the light-emitting diode systems in the second light-emitting unit are connected in series with each other. The current control method of claim 13, wherein the third light emitting unit comprises a plurality of light emitting diodes, and the light emitting diode systems in the third light emitting unit are connected in series with each other. The current control method of claim 11, wherein the current control unit controls the first duty cycle of the first switching unit and the second of the second switching unit in a pulse width modulation manner Working period. The current control method of claim 11, wherein the brightness of the first light emitting unit and the second light emitting unit are substantially the same.