WO2014090640A1

WO2014090640A1 - Current compensation device and lighting apparatus with the same

Info

Publication number: WO2014090640A1
Application number: PCT/EP2013/075420
Authority: WO
Inventors: Xiongqiang HE; Xuewei Dai; Wuqiang LIAO; Xin FAN
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2012-12-12
Filing date: 2013-12-03
Publication date: 2014-06-19
Anticipated expiration: 2015-06-12
Also published as: CN203072200U

Abstract

There is provided a current compensation device of a lighting apparatus for controlling ON/OFF of a current control switch unit in the lighting apparatus based on a sensing voltage sensed by a voltage sensing unit in the lighting apparatus and an OFF duration of the current control switch unit, characterized by including: a mapping unit which maps an ON/OFF state of at least one lighting switch unit in the lighting apparatus to ON/OFF data corresponding to an ON/OFF condition of the current control switch unit; a control unit which obtains the ON/OFF data from the mapping unit when the ON/OFF state of any of the at least one lighting switch unit changes; and a current compensation driving unit which generates a driving signal according to the sensing voltage and the ON/OFF data to control ON/OFF of the current control switch unit.

Description

CURRENT COMPENSATION DEVICE AND LIGHTING APPARATUS WITH THE SAME

FIELD

[ 0001] The present disclosure relates to the technical field of a lighting apparatus, and in particular to a current compensation device and a lighting apparatus with the same.

BACKGROUND

[ 0002 ] This section provides background information related to the present disclosure which is not necessarily prior art.

[ 0003] Color temperature is a characteristic of visible light that has important applications in lighting field and the like. The color temperature of a light source is the tempera^¬ ture of an ideal black body radiator that radiates light of comparable hue to that of the light source. Different color temperatures will result in different influences on human emotions or feelings. And, lighting with different color tem^¬ perature may be needed in different occasions. When a color temperature of a lighting apparatus is controlled, an average current flowing through lighting units of the lighting apparatus will vary as the lighting units are switched in and by- passed, thereby resulting in an unwanted color temperature of the lighting apparatus.

SUMMARY

[ 0004 ] This section provides a general summary of the present disclosure, and is not a comprehensive disclosure of its full scope or all of its features.

[ 0005] Some embodiments of the present disclosure provide a current compensation device and a lighting apparatus with the same which can have good response to dynamic load, to ensure consistency of an average current flowing through lighting units of the lighting apparatus, thereby obtaining a desir^¬ able lighting effect of the lighting apparatus.

[ 0006] According to an aspect of the present disclosure, there is provided a current compensation device of a lighting appa- ratus for controlling ON/OFF of a current control switch unit in the lighting apparatus based on a sensing voltage sensed by a voltage sensing unit in the lighting apparatus and an OFF duration of the current control switch unit, characterized by including: a mapping unit which maps an ON/OFF state of at least one lighting switch unit in the lighting appara^¬ tus to ON/OFF data corresponding to an ON/OFF condition of the current control switch unit; a control unit which obtains the ON/OFF data from the mapping unit when the ON/OFF state of any of the at least one lighting switch unit changes; and a current compensation driving unit which generates a driving signal according to the sensing voltage and the ON/OFF data to control ON/OFF of the current control switch unit.

[ 0007 ] Preferably, the ON/OFF data may be ON data corresponding to an ON condition of the current control switch unit, and the current compensation driving unit may include: a conver^¬ sion unit which converts the ON data into a variable refer^¬ ence voltage; a comparison unit which compares the variable reference voltage with the sensing voltage to output a com^¬ parison signal; a constant OFF duration generation unit which outputs a constant OFF duration denotation signal; and a latch and driving unit which generates the driving signal based on the comparison signal and the constant OFF duration denotation signal. [ 0008] Preferably, the conversion unit may include a conversion resistor and a conversion capacitor, one terminal of the conversion resistor is connected to the control unit, another terminal of the conversion resistor is connected to the one terminal of the conversion capacitor, and another terminal of the conversion capacitor is grounded.

[ 0009] Preferably, the comparison unit may include a first op amplifier, the sensing voltage is connected to a positive in^¬ put terminal of the first op amplifier, and a node between the conversion resistor and the conversion capacitor is connected to a negative input terminal of the first op ampli^¬ fier .

[ 0010] Preferably, the constant OFF duration generation unit may output the constant OFF duration denotation signal based on a constant OFF duration set by the control unit.

[ 0011] Preferably, the constant OFF duration generation unit may output the constant OFF duration denotation signal based on the driving signal generated by the current compensation driving unit, and the constant OFF duration generation unit may include: a timing circuit which is connected between a power supply voltage and a grounding and includes a timing resistor and a timing capacitor connected in series, wherein a terminal of the timing resistor is connected to the power supply voltage, and a terminal of the timing capacitor is grounded; a discharge circuit which includes a discharge tri- ode, a collector of the discharge triode is connected to a node between the timing resistor and the timing capacitor in the timing circuit, an emitter of the discharge triode is grounded, and a base of the discharge triode is controlled by the driving signal generated by the current compensation driving unit; and a comparison circuit which includes a sec^¬ ond op amplifier, the node between the timing resistor and the timing capacitor in the timing circuit is connected to a positive input terminal of the second op amplifier, and a comparison reference voltage is connected to a negative input terminal of the second op amplifier.

[ 0012 ] Preferably, the latch and driving unit may include: a latch circuit which includes a SR latch, the comparison sig^¬ nal is connected to a R input terminal of the SR latch, and the constant OFF duration denotation signal is connected to a S input terminal of the SR latch; and a driving circuit, an input terminal of which is connected to a Q output terminal of the SR latch.

[ 0013] Preferably, the ON/OFF data may be OFF data correspond^¬ ing to an OFF duration of the current control switch unit, and the current compensation driving unit may include: a tim^¬ ing unit which outputs a variable OFF duration denotation signal based on the OFF data; a comparison unit which com^¬ pares a constant reference voltage with the sensing voltage to input a comparison signal; and a latch and driving unit which generates the driving signal based on the comparison signal and the variable OFF duration denotation signal. [ 0014 ] Preferably, the comparison unit may include an op ampli^¬ fier, the sensing voltage is connected to a positive input terminal of the op amplifier, and a constant reference volt^¬ age is connected to a negative input terminal of the op am^¬ plifier . [ 0015] Preferably, the latch and driving unit may include: a latch circuit which includes a SR latch, the comparison signal is connected to a R input terminal of the SR latch, the variable OFF duration denotation signal is connected to a S input terminal of the SR latch, and a Q output terminal of the SR latch outputs an enable signal to the timing unit; and a driving circuit, an input terminal of which is connected to a Q output terminal of the SR latch. [ 0016] According to another aspect of the present disclosure, there is provided a lighting apparatus including: a power supply unit; a plurality of lighting units connected in se^¬ ries with each other powered by the power supply unit; at least one lighting switch unit, each of which is connected in parallel with corresponding one of the plurality of lighting units; an energy storage unit which is connected in series to the plurality of lighting units; a current control switch unit which is connected in series to the energy storage unit; an unidirectional current conduction unit which is connected in parallel with the plurality of lighting units and the en^¬ ergy storage unit; and a voltage sensing unit which is con^¬ nected in series to the current control switch unit to sense a sensing voltage corresponding to a current flowing through the plurality of lighting units when the current control switch unit is turned on, characterized in that the lighting apparatus further includes a current compensation device ac^¬ cording to the present disclosure which controls ON/OFF of the current control switch unit based on the sensing voltage and an OFF duration of the current control switch unit.

[ 0017 ] Preferably, the driving signal generated by the current compensation driving unit may be a switching signal.

[ 0018] Preferably, the control unit may provide a control sig^¬ nal to each lighting switch unit to control ON/OFF of each lighting switch unit.

[ 0019] Preferably, the control signal may be a PWM (Pulse Width Modulation) signal, and the control unit may control the lighting effect of the lighting apparatus through the control signal . [ 0020] Preferably, each of the plurality of lighting units may include one LED (Light Emitting Diode) or a plurality of LEDs connected in series. [ 0021] Preferably, the lighting switch unit may include a switch device.

[ 0022 ] Preferably, the energy storage unit may include an in^¬ ductor . [ 0023] Preferably, the current control switch unit may include a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) device .

[ 0024 ] Preferably, the unidirectional current conduction unit may include a diode, an anode of the diode is connected to the energy storage unit, and a cathode of the diode is con^¬ nected to the power supply unit.

[ 0025] Preferably, the voltage sensing unit may include a sens^¬ ing resistor.

[ 0026] The current compensation device and a lighting apparatus with the same according to the present disclosure may map the ON/OFF state of the lighting switch unit to the ON/OFF data corresponding to an ON/OFF condition of the current control switch unit and generate the driving signal based on the ON/OFF data to control ON/OFF of the current control switch unit. Therefore, the lighting apparatus can have good re^¬ sponse to dynamic load, to ensure consistency of an average current flowing through lighting units of the lighting apparatus, thereby obtaining a desirable lighting effect of the lighting apparatus. [ 0027 ] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illus^¬ tration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS 028] The drawings described herein are for illustrative pur^¬ poses only of selected embodiments and not all possible im^¬ plementations, and are not intended to limit the scope of the present disclosure. In the drawings:

Figure 1 is a circuit structural diagram of a lighting apparatus known by the inventors of the present disclosure;

Figure 2 is a timing chart of signals in the lighting apparatus shown in Figure 1 ; Figure 3 is a graph of an average current flowing through lighting units in the lighting apparatus shown in Figure 1 versus load voltage;

Figure 4 is a circuit structural diagram of a lighting apparatus with a current compensation circuit known by the inventors of the present disclosure;

Figure 5 is a block diagram of a schematic structure of a lighting apparatus according to an embodiment of the pre^¬ sent disclosure;

Figure 6 is a circuit structural diagram of a lighting apparatus according to the embodiment of the present disclo^¬ sure ;

Figure 7 is an example of a lookup table in the light^¬ ing apparatus according to the embodiment of the present dis^¬ closure shown in Figure 6; Figure 8 is a timing chart of signals in the lighting apparatus according to the embodiment of the present disclo^¬ sure shown in Figure 6; and

Figure 9 is a circuit structural diagram of a lighting apparatus according to a specific embodiment of the present disclosure. [ 0029] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, how- ever, that the description herein of specific embodiments is not intended to limit the present disclosure to the particu^¬ lar forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives fal^¬ ling within the spirit and scope of the present disclosure. Note that corresponding reference numerals indicate corre^¬ sponding parts throughout the several views of the drawings.

DESCRIPTION OF EMBODIMENTS

[ 0030] Examples of the present disclosure will now be described more fully with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses .

[ 0031] Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be em^¬ ployed, that example embodiments may be embodied in many dif^¬ ferent forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well- known technologies are not described in detail.

[ 0032 ] As shown in Figure 1, a lighting apparatus 100 known by the inventors of the present disclosure may include a plural- ity of lighting units 111, 112, and 113 connected in series, which are powered by an input voltage Vin. Each of the light^¬ ing units 111, 112, and 113 may include one LED or a plural^¬ ity of LEDs connected in series. The number of the LEDs in- eluded in respective lighting units may be same or may be different .

[ 0033] A MOSFET device Q2 is connected in parallel with the lighting unit 111, and a MOSFET device Q3 is connected in parallel with the lighting unit 112. Specifically, a drain and source of the MOSFET device Q2 are connected to both ter^¬ minals of the lighting unit 111, respectively, and a drain and source of the MOSFET device Q3 are connected to both ter^¬ minals of the lighting unit 112, respectively. Additionally, a gate of the MOSFET device Q2 is controlled by a PWM signal Q2_PWM, and a gate of the MOSFET device Q3 is controlled by a PWM signal Q3_PWM.

[ 0034 ] Each of the lighting units 111, 112, and 113 may have respective color temperature. The color temperature of LED refers to the color of the light emitted by the LED, which is generally classified into three types of warm white (2700k- 4500k), pure white (4500k-6500k) , and cool white (6500k or more) . LED with different color temperature may be selected as necessary. After a LED is selected, the color temperature of the selected LED is unchanged. When the color temperature of the LED lighting device needs to be changed, it is neces^¬ sary to provide at least two LED lighting units with different color temperatures. Herein, it is assumed that the light^¬ ing unit 111 has a first color temperature such as warm white, the lighting unit 112 has a second color temperature as pure white, and the lighting unit 113 has a third color temperature as cool white.

[ 0035] When the PWM signal Q2_PWM is of a low level such that the MOSFET device Q2 is turned off, the lighting unit 111 is switched in and emits a light with the first color tempera^¬ ture. On the other hand, when the PWM signal Q2_PWM is of a high level such that the MOSFET device Q2 is turned on, the lighting unit 111 is bypassed and therefore emits no light. Thus, the intensity of the light with the first color tem^¬ perature may be controlled through the duty ratio of the PWM signal Q2_PWM.

[ 0036] Correspondingly, when the PWM signal Q3_PWM is of a low level such that the MOSFET device Q3 is turned off, the lighting unit 112 is switched in and emits a light with the second color temperature. On the other hand, when the PWM signal Q3_PWM is of a high level such that the MOSFET device Q3 is turned on, the lighting unit 112 is bypassed and there^¬ fore emits no light. Thus, the intensity of the light with the second color temperature may be controlled through the duty ratio of the PWM signal Q3_PWM.

[ 0037 ] When the intensity varying light with the first color temperature, the intensity varying light with the second color temperature, and the intensity constant light with the third color temperature are mixed in a desirable proportion, a desirable color temperature of the lighting apparatus 100 will be achieved.

[ 0038] In Figure 1, an inductor LI for energy storage, a MOSFET device Ql for controlling a current I_L1 flowing through the lighting units, and a resistor Rs for sensing the current

I_L1 are connected in series to the lighting units 111, 112, and 113 in order. Specifically, one terminal of the inductor LI is connected to the lighting unit 113, and the other ter^¬ minal thereof is connected to a drain of the MOSFET device Ql . A source of the MOSFET device Ql is connected to one ter^¬ minal of the resistor Rs, and the other terminal of the re^¬ sistor Rs is grounded. [ 0039] Additionally, it is noted that a diode Dl is connected in parallel with the lighting units 111, 112, and 113 and the inductor LI. Specifically, an anode of the diode Dl is con^¬ nected to the inductor LI, and a cathode thereof is connected to the lighting unit 111.

[ 0040] When the MOSFET device Ql is turned on, the input volt^¬ age Vin powers the lighting units 111, 112, and 113, the in^¬ ductor LI stores energy, and the diode Dl is turned off. On the other hand, when the MOSFET device Ql is turned off, the diode Dl is turned on, and the inductor LI releases energy to power the lighting units 111, 112, and 113. It is understood by those skilled in the art that the current I_L1 flowing through the lighting units will fluctuate with turning on and off of the MOSFET device Ql . However, a desirable color tem- perature of the lighting apparatus 100 may be achieved as long as an average value Io of the current I_L1 remains un^¬ changed .

[ 0041] Control of the MOSFET device Ql will be described in de^¬ tail below. As shown in Figure 1, when the MOSFET device Ql is turned on, the current I_L1 flows through the resistor Rs, and therefore a sensing voltage Vsense is obtained. The sens^¬ ing voltage Vsense corresponds to the current I_L1 when the MOSFET device Ql is turned on.

[ 0042 ] The sensing voltage Vsense is input to a positive input terminal of an op amplifier XI in a control module 120. Addi^¬ tionally, a reference voltage Vref is input to a negative in^¬ put terminal of the op amplifier XI. The reference voltage Vref is obtained from a voltage dividing circuit including resistors Rl and R2 connected in series between a power sup- ply voltage Vcc and grounding, and therefore is constant.

[ 0043] The op amplifier XI outputs a result of comparison of the sensing voltage Vsense with the reference voltage Vref to a signal generator 121 in the control module 120. The signal generator 121 generates a buck PWM signal BUCK_PWM based on the signal input by the op amplifier XI. The signal BUCK_PWM is input to a gate of the MOSFET device Ql via a driver 130, thereby controlling ON/OFF of the MOSFET device Ql .

[ 0044 ] The operational principle of the lighting apparatus 100 will be further described in combination with Figure 2 below. Firstly, it is assumed that the signal Q2_PWM is always of a low level and the duty ratio of the signal Q3_PWM is limited to be 50% to simplify the analysis. Thus, the MOSFET device Q2 is always turned off, and the lighting unit 111 is always switched in.

[ 0045] During the period of tl, the signal Q3_PWM is of a low level, and therefore the MOSFET device Q3 is turned off and the lighting unit 112 is switched in. At this time, an output voltage Vout of the lighting units is the sum of voltages across the lighting units 111, 112, and 113.

[ 0046] During the period of t2, the signal Q3_PWM is of a high level, and therefore the MOSFET device Q3 is turned on and the lighting unit 112 is bypassed. At this time, the output voltage Vout of the lighting units is the sum of voltages across the lighting units 111 and 113. Compared to that dur^¬ ing the period of tl, the output voltage Vout decreases dur^¬ ing the period of t2. [ 0047 ] The effect of changing in the output voltage Vout on the average current Io flowing through the lighting units will be further described below. With reference to Figures 1 and 2, at the initial time, the signal BUCK_PWM is of a high level, and the MOSFET device Ql is ON. At this time, the lighting units are powered by the input voltage Vin, the inductor LI begins to store energy, and the current I_L1 begins to in^¬ crease . [ 0048] As the current I_L1 increases, the sensing voltage

Vsense also increases. When the sensing voltage Vsense ex^¬ ceeds the reference voltage Vref, the op amplifier XI outputs a high level. The signal generator 121 which receives the in- put signal with high level from the op amplifier XI generates the signal BUCK_PWM with low level. The signal BUCK_PWM with low level is input to the gate of the MOSFET device Ql via the driver 130, resulting in OFF of the MOSFET device Ql .

[ 0049] When the MOSFET device Ql is OFF, the diode Dl is ON. At this time, the inductor LI begins to release energy and power the lighting units, and the current I_L1 begins to decrease.

[ 0050] Next, when the cycle of the signal BUCK_PWM terminates, the signal BUCK_PWM changes to be the high level again, and the MOSFET device Ql is ON again. Thus, the current I_L1 in- creases again until the sensing voltage Vsense exceeds the reference voltage Vref. It can be realized that a peak value Ipk of the current I_L1 is decided by the reference voltage Vref. In other words, the peak current Ipk will remain unchanged if the reference voltage Vref is constant. [ 0051] In Figure 2, it is assumed that the difference between the maximum and the minimum of the current I_L1 is denoted as ΔΙ and the average current Io is in the middle of the maximum and the minimum of the current I_L1. Whereby the following formula 1) may be obtained:

[ 0052 ] Further, those skilled in the art may readily obtain the formula (2) as follows:

(V. - V ) .

AI V in out / D

(2)

[ 0053] where Fs denotes the frequency of the signal BUCK PWM, L denotes the inductance of the inductor LI, and D denotes the duty ratio of the signal BUCK_PWM.

[ 0054 ] Furthermore, those skilled in the art may obtain the formula (3) as follows:

[ 0055] In accordance with the formulas (l)-(3) as above, a graph of the average current Io versus the load output volt^¬ age Vout as shown in Figure 3 may be obtained.

[ 0056] As can be seen from the combination of Figures 2 and 3, the output current lout (i.e., the average current Io flowing through the lighting units) increases as the output voltage Vout decreases. In this case, it is necessary to compensate for the output current lout, so that the output current lout always remains consistent to obtain the desirable color tem- perature of the lighting apparatus 100.

[ 0057 ] As shown in Figure 4, a lighting apparatus 200 with a current compensation circuit known by the inventors of the present disclosure provides an example in which the output current lout is compensated for. The difference of the light- ing apparatus 200 shown in Figure 4 from the lighting appara^¬ tus 100 shown in Figure 1 lies in that the lighting apparatus 200 provides a circuit consisting of resistors Rc2 and Rc3 and MOSFET devices Qc2 and Qc3 for compensating for the output current lout. [ 0058] Specifically, as shown in Figure 4, one terminal of the resistor Rc2 is connected to a node between the resistors Rl and R2, another terminal thereof is connected to a drain of the MOSFET device Qc2, and a source of the MOSFET device Qc2 is grounded. One terminal of the resistor Rc3 is connected to the node between the resistors Rl and R2, another terminal thereof is connected to a drain of the MOSFET device Qc3, and a source of the MOSFET device Qc3 is grounded.

[ 0059] A gate of the MOSFET device Qc2 is controlled by the signal Q2_PWM. Thus, when the signal Q2_PWM is of a low level, the MOSFET devices Q2 and Qc2 are both OFF. The light^¬ ing unit 111 is switched in, and the resistor Rc2 has no in^¬ fluence on the reference voltage Vref. On the other hand, when the signal Q2_PWM is of a high level, the MOSFET devices Q2 and Qc2 are both ON. The lighting unit 111 is bypassed, the output voltage Vout is caused to decrease, and therefore the output current lout has a tendency of increasing (see Figures 2 and 3) . At the same time, since the MOSFET device Qc2 is ON, the resistors Rc2 and R2 are connected in paral^¬ lel, resulting in decreasing of the reference voltage Vref. As described above, the peak value Ipk of the current I_L1 is decided by the reference voltage Vref. It is understood by those skilled in the art that the peak value Ipk of the cur^¬ rent I_L1 decreases as the reference voltage Vref decreases. As can be seen from Figure 2, while the output current lout has a tendency of increasing, the output current lout has a tendency of decreasing if the peak value Ipk of the current I_L1 decreases. In a case where the resistance values of the resistors Rl, R2, and Rc2 are set appropriately, the output current lout at a time when the signal Q2_PWM is of the high level may be caused to maintain consistent with the output current lout at a time when the signal Q2_PWM is of the low level .

[ 0060] Likewise, a gate of the MOSFET device Qc3 is controlled by the signal Q3_PWM. Thus, when the signal Q3_PWM is of a low level, the MOSFET devices Q3 and Qc3 are both OFF. On the other hand, when the signal Q3_PWM is of a high level, the MOSFET devices Q3 and Qc3 are both ON. In a case where the resistance values of the resistors Rl, R2, and Rc3 are set appropriately, the output current lout at a time when the signal Q3_PWM is of the high level may be caused to maintain consistent with the output current lout at a time when the signal Q3_PWM is of the low level. [ 0061] Thus, the lighting apparatus 200 shown in Figure 4 may compensate for the output current lout, so that the output current lout is capable of always maintaining consistent in a case that the load varies dynamically.

[ 0062 ] However, it is noted that the lighting apparatus 200 shown in Figure 4 can only provide four compensations for the output current lout, i.e., compensations for switching in of the lighting unit 111, bypassing of the lighting unit 111, switching in of the lighting unit 112, and bypassing of the lighting unit 112. If the load variations of the lighting units in the lighting apparatus exceeds the four situations, for example, if three or more lighting units are required to be controlled for switching in or bypassing, at least six compensations for the output current lout should be provided, which is difficult to be realized by employing resistor array only.

[ 0063] In accordance with the formulas (l)-(3) as above, the inventors of the present disclosure has appreciated that the following formula (4) may be obtained:

Iout=Ipk-0.5 (Vin-Vout) *Ton/L=Ipk-0.5*Vout*Toff/L (4) [ 0064 ] where Ton denotes a high level duration within a cycle of the signal BUCK_ PWM (i.e., the ON duration of the MOSFET device Ql), and Toff denotes a low level duration within a cycle of the signal BUCK_ PWM (i.e., the OFF duration of the MOSFET device Ql) . [ 0065] In the lighting apparatus for which the present disclo^¬ sure may apply, the input voltage Vin the inductance L are generally constant values, and the load output voltage Vout keeps changing. Additionally, it is noted that the ON dura^¬ tion Ton is related to the peak current Ipk.

[ 0066] As can be seen from the formula (4), in a case that the output voltage Vout changes, if it intends to cause the out- put current lout to always maintain consistent, one of the following two methods may be adopted:

[ 0067 ] 1) changing the OFF duration Toff correspondingly according to the output voltage Vout, and keeping the other pa^¬ rameters unchanged; or

[ 0068] 2) changing the peak current Ipk correspondingly according to the output voltage Vout, and keeping the other parame^¬ ters unchanged.

[ 0069] In other words, it is possible to cause the output cur^¬ rent lout to always maintain consistent by changing the

ON/OFF condition of the MOSFET device Ql correspondingly according to the output voltage Vout.

[ 0070] As shown in Figure 5, a lighting apparatus 300 according to a specific embodiment of the present disclosure may in^¬ clude a power supply unit 310, lighting units 321, 322, and 323, lighting switch units 331,332, and 333, an energy storage unit 340, an unidirectional current conduction unit 350, a current control switch unit 360, a voltage sensing unit 370, and a current compensation unit 380. It is appreciated by those skilled in the art that the numbers of the lighting units and the lighting switch units shown in Figure 5 are only illustrative, and the number of the lighting switch units may less than that of the lighting units.

[ 0071] The lighting units 321, 322, and 323 are connected in series with each other, and are powered by the power supply unit 310. The lighting switch units 331, 332, and 333 are connected in parallel with the lighting units 321, 322, and 323, respectively. The energy storage unit 340 is connected in series to the lighting units 321, 322, and 323, and the current control switch unit 360 is connected in series to the energy storage unit 340. The unidirectional current conduc^¬ tion unit 350 is connected in parallel with the lighting units 321, 322, and 323 and the energy storage unit 340, thereby forming a current loop. The voltage sensing unit 370 is connected in series to the current control switch unit 360, to sense a sensing voltage corresponding to a current flowing through the lighting units when the current control switch unit 360 is ON. The current compensation device 380 may control ON/OFF of the current control switch unit 360 based on the sensing voltage.

[ 0072 ] Specifically, the current compensation device 380 may include a mapping unit 381, a control unit 382, and a current compensation driving unit 383. The mapping unit 381 maps an ON/OFF state of the lighting switch units 331, 332, and 333 to ON/OFF data corresponding to an ON/OFF condition of the current control switch unit 360. The ON/OFF condition men^¬ tioned herein includes the ON condition of the current con- trol switch unit 360 and the OFF duration of the current con^¬ trol switch unit 360. When the ON/OFF state of any of the lighting switch units 331, 332, and 333 changes, the control unit 382 obtains the ON/OFF data from the mapping unit 381. The current compensation driving unit 383 generates a driving signal according to the sensing voltage and the ON/OFF data to control ON/OFF of the current control switch unit 360.

[ 0073] In the lighting apparatus 300 shown in Figure 5, the

ON/OFF state of the lighting switch units 331, 332, and 333 may be mapped to the ON/OFF data corresponding to an ON/OFF condition of the current control switch unit 360, and the driving signal may be generated based on the ON/OFF data to control ON/OFF of the current control switch unit 360. There^¬ fore, the lighting apparatus 300 can have good response to dynamic load, to ensure consistency of an average current flowing through the lighting units 321, 322, and 323 of the lighting apparatus 300, thereby obtaining a desirable color temperature of the lighting apparatus 300. [ 0074 ] The present teachings are suitable for incorporation in many different types of lighting apparatus. Further, the pre^¬ sent disclosure is not limited to controlling of the color temperature, but may be applied to various applications in which lighting effects are controlled. For exemplary pur- poses, descriptions are made below, taking a LED lighting ap^¬ paratus in combination with controlling of the color temperature as an example.

[ 0075] With reference to Figure 6, a lighting apparatus 400 ac^¬ cording to a specific embodiment of the present disclosure may include a plurality of lighting units 421, 422, and 423 connected in series with each other, which are powered by a DC (Direct Current) power supply 410. The plurality of light^¬ ing units 421, 422, and 423 correspond to the lighting units 321, 322, and 323 shown in Figure 5, and the DC power supply 410 corresponds to the power supply unit 310 shown in Figure 5.

[ 0076] Each lighting unit may have respective color tempera^¬ ture. Each of the lighting units 421, 422, and 423 may in^¬ clude one LED or a plurality of LEDs connected in series. The number of the LEDs included in respective lighting units may be same or may be different.

[ 0077 ] Switch devices such as MOSFET devices 431, 432, and 433 corresponding to the lighting switch units 331, 332, and 333 shown in Figure 5 are connected in parallel with the lighting units 421, 422, and 423, respectively.

[ 0078] An inductor 440, a MOSFET device 460, and a resistor 470 shown in Figure 6 correspond to the energy storage unit 340, the current control switch unit 360, and the voltage sensing unit 370, respectively, shown in Figure 5, which are con^¬ nected in series to the lighting units 421, 422, and 423 in order . [ 0079] Additionally, a diode 450 corresponding to the unidirec^¬ tional current conduction unit 350 shown in Figure 5 is con^¬ nected in parallel with the lighting units 421, 422, and 423 and the inductor 440.

[ 0080] The connection manner of respective devices as described above is similar to that shown in Figures 1 and 4, and there^¬ fore will not be repeated herein.

[ 0081] A current compensation device 480 shown in Figure 6 cor^¬ responds to the current compensation device 380 shown in Fig^¬ ure 5. The current compensation device 480 may include at least part of a lookup table 481, a CPU (Central Processing Unit) 482, a TOFF timer 483, a reference voltage generator 484, a comparator 485, a SR latch 486, and a driver 487.

[ 0082 ] The operational principle of the current compensation device 480 will be described in detail below. As described above, in a case that the output voltage Vout of the lighting units 421, 422, and 423 changes, if it intends to cause the output current lout of the lighting units 421, 422, and 423 to always maintain consistent, one may change the OFF dura^¬ tion Toff of the MOSFET device 460 correspondingly according to the output voltage Vout while keeping the other parameters unchanged, or may change the peak current Ipk of the output current correspondingly according to the output voltage Vout while keeping the other parameters unchanged. Descriptions will be made below for the former case firstly. [ 0083] When the output current lout is caused to always main^¬ tain consistent by changing the OFF duration Toff of the MOSFET device 460, the ON/OFF data for mapping is OFF data corresponding to the OFF duration Toff. The lookup table 481 shown in Figure 6 corresponds to the mapping unit 381 shown in Figure 5. The lookup table 481 may be implemented by a register, a memory and the like, for example. The lookup ta- ble 481 may indicate a relationship between the ON/OFF state of the MOSFET devices 431, 432, and 433 and the OFF duration Toff, as shown in Figure 7. It is understood that the spe^¬ cific data for the OFF duration Toff corresponding to the ON/OFF state of the MOSFET devices 431, 432, and 433 is il- lustrative and can be calculated in advance to be stored in the lookup table 481.

[ 0084 ] In the example shown in Figure 7, the first column de^¬ notes the ON/OFF state of the MOSFET devices 431, 432, and 433, and the second column denotes the corresponding OFF du- ration Toff of the MOSFET device 460. Stringl, String2, and String3 denote switching in of the lighting units 421, 422, and 423, respectively. Data for the first row is taken as an example. Stringl+String2+String3 denotes that the lighting units 421, 422, and 423 are all switched in. At this time, the OFF duration Toff of the MOSFET device 460 is set to 131.

[ 0085] When the lighting units 421, 422, and 423 are all

switched in, the CPU 482 corresponding to the control unit 382 shown in Figure 5 obtains the value of 131 for the OFF data from the lookup table 481, i.e., the OFF duration Toff of the MOSFET device 460.

[ 0086] The CPU 482 transmits the OFF data to the TOFF timer

483. The TOFF timer 483 may output a variable OFF duration denotation signal based on the OFF data. For example, the TOFF timer 483 may perform decrement count upon receiving the value of 131 for the OFF data. As the value for the OFF data is decreased to be zero, the TOFF timer 483 may output a high level as the variable OFF duration denotation signal. [ 0087 ] Meanwhile, the comparator 485 may compare a constant reference voltage with the sensing voltage sensed via the re^¬ sistor 470 to input a comparison signal. It is noted that the constant reference voltage may be implemented in the manner shown in Figure 1 instead of by means of the reference volt^¬ age generator 484.

[ 0088] Specifically, the comparator 485 may be an op amplifier.

The sensing voltage Vsense is connected to a positive input terminal of the op amplifier 485, and the constant reference voltage is connected to a negative input terminal of the op amplifier 485.

[ 0089] Further, the comparison signal output by the comparator 485 and the variable OFF duration denotation signal output by the TOFF timer 483 are connected to R and S input terminals of the SR latch 486, respectively. Furthermore, a Q output terminal of the SR latch 486 outputs an enable signal EN to the TOFF timer 483, and a Q output terminal thereof is con^¬ nected to an input terminal of the driver 487, so that the driver 487 outputs a driving signal to drive ON/OFF of the MOSFET device 460. This driving signal may be a switching signal such as a PWM signal.

[ 0090] At the initial time, when the ON/OFF state of the light^¬ ing switch units 431, 432, and 433 changes, the CPU 482 ob^¬ tains the OFF data from the lookup table 481 and transmits the OFF data to the TOFF timer 483. At this time, it is as^¬ sumed that the MOSFET device 460 is in an ON state. The sens^¬ ing voltage Vsense increases with time. When Vsense exceeds the constant reference voltage, the comparator 485 outputs a comparison signal with high level. This comparison signal sets the Q output terminal to 0 and sets the Q output termi^¬ nal to 1. Thus, the driver 487 outputs a driving signal with low level, causing the MOSFET device 460 to be OFF. At the same time, the Q output terminal inputs the enable signal EN to the TOFF timer 483, causing the TOFF timer 483 to start timing .

[ 0091] As the TOFF timer 483 accomplishes the timing for the OFF data, the variable OFF duration denotation signal is in- put to the S input terminal of the SR latch 486. This vari^¬ able OFF duration denotation signal sets the Q output terminal to 1 and sets the Q output terminal to 0. Thus, the driver 487 outputs a driving signal with high level, causing the MOSFET device 460 to be ON again. At the same time, the output terminal disables the TOFF timer 483 for timing.

[ 0092 ] As shown in Figure 8, when the ON/OFF state of the lighting switch units 431, 432, and 433 changes, the OFF du^¬ ration Toff of the MOSFET device 460 are changed correspond^¬ ingly while the other parameters are kept unchanged. Thus, while the peak current Ipk of the output current keeps un^¬ changed, the duration and amplitude of decreasing of the out put current change, and therefore it is still possible to cause the average current of the output current to maintain consistent . [ 0093] With reference to Figure 9, description will be made be low for the case where the output current lout is caused to always maintain consistent by changing the peak current Ipk of the output current. The circuit structure of a lighting apparatus 400' shown in Figure 9 is similar to that of the lighting apparatus 400 shown in Figure 6, and descriptions for the same parts thereof will not be repeated herein.

[ 0094 ] When the output current lout is caused to always main^¬ tain consistent by changing the peak current Ipk of the out^¬ put current, the ON/OFF data for mapping is ON data corre- sponding to the peak current Ipk. When the ON/OFF state of the lighting switch units 431, 432, and 433 changes, the CPU 482 obtains the ON data from the lookup table 481. [ 0095] The CPU 482 transmits the ON data to a conversion unit to convert the ON data into a reference voltage Vref. In Fig^¬ ure 9, the conversion unit includes a conversion resistor Rref and a conversion capacitor Cref. One terminal of the conversion resistor Rref is connected to the CPU 482, another terminal of the conversion resistor Rref is connected to the one terminal of the conversion capacitor Cref, and another terminal of the conversion capacitor Cref is grounded.

[ 0096] Meanwhile, the comparator 485 may compare the variable reference voltage Vref with the sensing voltage Vsense sensed via the resistor 470 to input a comparison signal.

[ 0097 ] Specifically, the comparator 485 may be an op amplifier.

The sensing voltage Vsense is connected to a positive input terminal of the op amplifier 485, and the reference voltage Vref is connected to a negative input terminal of the op am^¬ plifier 485.

[ 0098] Additionally, a constant OFF duration generation unit 483' corresponding to the TOFF timer 483 shown in Figure 6 may output a constant OFF duration denotation signal based on the driving signal PWM_MOS generated by the driver 487.

[ 0099] Specifically, the constant OFF duration generation unit 483' may include a timing circuit which is connected between a power supply voltage (e.g., 5V) and a grounding, a dis^¬ charge circuit, and a comparison circuit. The timing circuit includes a timing resistor R' and a timing capacitor C connected in series. A terminal of the timing resistor R' is connected to the power supply voltage, and a terminal of the timing capacitor C is grounded. The discharge circuit in^¬ cludes a discharge triode Q' . A collector of the discharge triode Q' is connected to a node between the timing resistor R' and the timing capacitor C , an emitter of the discharge triode Q' is grounded, and a base of the discharge triode Q' is controlled by the driving signal PWM_MOS . The comparison circuit includes an op amplifier X' . The node between the timing resistor R' and the timing capacitor C is connected to a positive input terminal of the op amplifier X' , and a comparison reference voltage (e.g., 2.5V) is connected to a negative input terminal of the op amplifier X' .

[ 00100] Further, the comparison signal output by the comparator 485 and the constant OFF duration denotation signal output by the constant OFF duration generation unit 483' are connected to R and S input terminals of the SR latch 486, respectively. Furthermore, a Q output terminal of the SR latch 486 is con^¬ nected to an input terminal of the driver 487, so that the driver 487 outputs the driving signal PWM_MOS to drive ON/OFF of the MOSFET device 460. [ 00101] At the initial time, when the ON/OFF state of the light^¬ ing switch units 431, 432, and 433 changes, the CPU 482 ob^¬ tains the ON data from the lookup table 481 and transmits the ON data to the conversion resistor Rref in the conversion unit in a manner of PWM signal, thereby obtaining the refer- ence voltage Vref corresponding to the ON data. This refer^¬ ence voltage Vref decides the magnitude of the peak current Ipk. At this time, it is assumed that the MOSFET device 460 is in an ON state. The sensing voltage Vsense increases with time. When Vsense exceeds the reference voltage Vref, the comparator 485 outputs a comparison signal with high level.

This comparison signal sets the Q output terminal to 0. Thus, the driver 487 outputs a driving signal PWM_MOS with low level, causing the MOSFET device 460 to be OFF.

[ 00102 ] At the same time, the driving signal PWM_MOS with low level causes the discharge triode Q' to be OFF, so that the timing capacitor C starts charging. When a certain charging time elapses, the voltage at the positive input terminal of the op amplifier X' will be higher than the reference volt- age. At this time, the op amplifier X' outputs a comparison signal with high level as the constant OFF duration denota^¬ tion signal.

[ 00103] The constant OFF duration denotation signal is input to the S input terminal of the SR latch 486. This constant OFF duration denotation signal sets the Q output terminal to 1. Thus, the driver 487 outputs a driving signal PWM_MOS with high level, causing the MOSFET device 460 to be ON again. At the same time, the driving signal PWM_MOS with high level causes the discharge triode Q' to be ON, thereby releasing the charge accumulated in the timing capacitor C . Therefore, the voltage at the positive input terminal of the op ampli^¬ fier X' will be lower than the reference voltage. At this time, the op amplifier X' outputs a comparison signal with low level, which has no influence on the SR latch 486.

[ 00104 ] As described above, the output current lout may be

caused to always maintain consistent either by changing the OFF duration Toff of the MOSFET device 460 or by changing the peak current Ipk of the output current. Since the ON/OFF data is stored in the lookup table and can be acquired readily, provision of compensation for the output current lout for each case can be facilitated even if the load variations of the lighting units in the lighting apparatus exceeds the four situations as described above. [ 00105] Additionally, in Figures 6 and 9, the MOSFET devices

431, 432, and 433 are driven by drivers 491, 492, and 493, respectively, which in turns are controlled by the CPU 482. In other words, the CPU 482 may provide a control signal to the MOSFET devices 431, 432, and 433 to control ON/OFF of MOSFET devices 431, 432, and 433. The control signal may be a PWM signal and may be determined by the user in advance. The CPU 482 may control the lighting effect of the lighting appa^¬ ratus through the control signal. [ 00106] It can be appreciated by those skilled in the art that, if a CPU for providing the control signal exists in the prior art lighting apparatus, the existing CPU can be employed to provide the ON/OFF data corresponding to the ON/OFF condition of the current control switch unit without additional cir^¬ cuit. Accordingly, the cost for the lighting apparatus may be reduced .

[ 00107 ] Further, the constant OFF duration generation unit 483' composed of respective specific devices is provided in Figure 9. However, the present disclosure has not specific limita^¬ tion thereto. For example, the constant OFF duration genera^¬ tion unit may also be realized by the TOFF timer 483 shown in Figure 6. In this case, the CPU 482 may set a constant OFF duration, and transmit constant OFF data corresponding to the set constant OFF duration to the TOFF timer 483. The TOFF timer 483 which is the constant OFF duration generation unit may output the constant OFF duration denotation signal based on the constant OFF duration set by the CPU 482.

The particular embodiments disclosed above are illustrative only, as the disclosure may be modified and practiced in dif^¬ ferent but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Further^¬ more, no limitations are intended to the details of construc^¬ tion or design herein shown, other than as described in the claims below. It is therefore evident that the particular em^¬ bodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the disclosure.

Claims

A current compensation device of a lighting apparatus for controlling ON/OFF of a current control switch unit in the lighting apparatus based on a sensing voltage sensed by a voltage sensing unit in the lighting appara^¬ tus and an OFF duration of the current control switch unit, characterized by comprising:

a mapping unit which maps an ON/OFF state of at least one lighting switch unit in the lighting apparatus to ON/OFF data corresponding to an ON/OFF condition of the current control switch unit; a control unit which obtains the ON/OFF data from the mapping unit when the ON/OFF state of any of the at least one lighting switch unit changes; and

a current compensation driving unit which generates a driving signal according to the sensing voltage and the ON/OFF data to control ON/OFF of the current control switch unit.

The current compensation device according to claim 1, wherein the ON/OFF data is ON data corresponding to an ON condition of the current control switch unit, and the current compensation driving unit includes: a conversion unit which converts the ON data into a variable reference voltage; a comparison unit which compares the variable refer^¬ ence voltage with the sensing voltage to output a com^¬ parison signal;

a constant OFF duration generation unit which outputs a constant OFF duration denotation signal; and a latch and driving unit which generates the driving signal based on the comparison signal and the constant OFF duration denotation signal.

The current compensation device according to claim 2, wherein the conversion unit includes a conversion resistor and a conversion capacitor, one terminal of the conversion resistor being connected to the control unit, an^¬ other terminal of the conversion resistor being connected to the one terminal of the conversion capacitor, and an^¬ other terminal of the conversion capacitor being

grounded .

The current compensation device according to claim 3, wherein the comparison unit includes a first op ampli^¬ fier, the sensing voltage being connected to a positive input terminal of the first op amplifier, and a node be^¬ tween the conversion resistor and the conversion capacitor being connected to a negative input terminal of the first op amplifier.

The current compensation device according to claim 2, wherein the constant OFF duration generation unit outputs the constant OFF duration denotation signal based on a constant OFF duration set by the control unit.

The current compensation device according to claim 2, wherein the constant OFF duration generation unit outputs the constant OFF duration denotation signal based on the driving signal generated by the current compensation driving unit, and the constant OFF duration generation unit includes: a timing circuit which is connected between a power sup^¬ ply voltage and a grounding and includes a timing resis^¬ tor and a timing capacitor connected in series, wherein a terminal of the timing resistor is connected to the power supply voltage, and a terminal of the timing capacitor is grounded; a discharge circuit which includes a discharge triode, a collector of the discharge triode being connected to a node between the timing resistor and the timing capacitor in the timing circuit, an emitter of the discharge triode being grounded, and a base of the discharge triode being controlled by the driving signal generated by the current compensation driving unit; and a comparison circuit which includes a second op ampli^¬ fier, the node between the timing resistor and the timing capacitor in the timing circuit being connected to a positive input terminal of the second op amplifier, and a comparison reference voltage being connected to a nega^¬ tive input terminal of the second op amplifier.

The current compensation device according to claim 2, wherein the latch and driving unit includes:

a latch circuit which includes a SR latch, the comparison signal being connected to a R input terminal of the SR latch, and the constant OFF duration denotation signal being connected to a S input terminal of the SR latch; and a driving circuit, an input terminal of which is con^¬ nected to a Q output terminal of the SR latch.

The current compensation device according to claim 1, wherein the ON/OFF data is OFF data corresponding to an OFF duration of the current control switch unit, and the current compensation driving unit includes: a timing unit which outputs a variable OFF duration de^¬ notation signal based on the OFF data; a comparison unit which compares a constant reference voltage with the sensing voltage to input a comparison signal; and a latch and driving unit which generates the driving signal based on the comparison signal and the variable OFF duration denotation signal.

The current compensation device according to claim 8, wherein the comparison unit includes an op amplifier, the sensing voltage being connected to a positive input ter^¬ minal of the op amplifier, and a constant reference volt^¬ age being connected to a negative input terminal of the op amplifier.

The current compensation device according to claim 8, wherein the latch and driving unit includes:

a latch circuit which includes a SR latch, the comparison signal being connected to a R input terminal of the SR latch, the variable OFF duration denotation signal being connected to a S input terminal of the SR latch, and a Q output terminal of the SR latch outputting an enable signal to the timing unit; and a driving circuit, an input terminal of which is con^¬ nected to a Q output terminal of the SR latch.

A lighting apparatus comprising: a power supply unit; a plurality of lighting units connected in series with each other powered by the power supply unit;

at least one lighting switch unit, each of which is connected in parallel with corresponding one of the plural^¬ ity of lighting units; an energy storage unit which is connected in series to the plurality of lighting units; a current control switch unit which is connected in se^¬ ries to the energy storage unit; an unidirectional current conduction unit which is con^¬ nected in parallel with the plurality of lighting units and the energy storage unit; and a voltage sensing unit which is connected in series to the current control switch unit to sense a sensing volt^¬ age corresponding to a current flowing through the plurality of lighting units when the current control switch unit is turned on, characterized in that the lighting apparatus further com- prises:

a current compensation device according to any of claims 1-10 which controls ON/OFF of the current control switch unit based on the sensing voltage and an OFF duration of the current control switch unit.

12. The lighting apparatus according to claim 11, wherein the driving signal generated by the current compensation driving unit is a switching signal.

13. The lighting apparatus according to claim 11, wherein the control unit provides a control signal to each lighting switch unit to control ON/OFF of each lighting switch unit .

14. The lighting apparatus according to claim 13, wherein the control signal is a Pulse Width Modulation signal, and the control unit controls the lighting effect of the lighting apparatus through the control signal.

15. The lighting apparatus according to claim 11, wherein

each of the plurality of lighting units includes one LED or a plurality LEDs connected in series.

16. The lighting apparatus according to claim 11, wherein the lighting switch unit includes a switch device.

17. The lighting apparatus according to claim 11, wherein the energy storage unit includes an inductor.

18. The lighting apparatus according to claim 11, wherein the current control switch unit includes a MOSFET device.

19. The lighting apparatus according to claim 11, wherein the unidirectional current conduction unit includes a diode, an anode of the diode being connected to the energy stor^¬ age unit, and a cathode of the diode being connected to the power supply unit.

20. The lighting apparatus according to claim 11, wherein the voltage sensing unit includes a sensing resistor.