TWI407835B - Led circuit having led driving circuit and operation method of the same - Google Patents

Abstract

A LED circuit is provided. The LED circuit comprises LED channels and a LED driving circuit. The LED driving circuit comprises: a current mirror, a dc-to-dc converter and current sink modules each connected between one of the LED channels and an output load to lock the voltage at the output load at a level of a setting voltage. The current mirror comprises an input branch to generate an input setting current according to a variable setting load and an output branch to generate an output setting current to further generate a variable reference voltage and the setting voltage. A control module of the dc-to-dc converter generates a driving voltage according the variable reference voltage and a feedback voltage to control a gate of the power MOS of the dc-to-dc converter to further control the operation of the LED channels. A LED circuit operation method is disclosed herein as well.

Description

Light-emitting diode circuit with light-emitting diode driving circuit and operating method thereof

The present disclosure relates to a circuit structure and a method of operating the same, and more particularly to a light emitting diode circuit having a light emitting diode driving circuit and a method of operating the same.

Compared to traditional light bulb lighting tools, light emitting diodes (LEDs) are estimated to be four times more efficient than conventional light bulbs. Moreover, the light-emitting diode does not have a conventional light bulb containing toxic mercury, and has a longer service life than the light bulb. Under various factors, the light-emitting diode has become the latest mainstream technology of modern lighting technology.

The current extraction circuit is often used in a string of light-emitting diodes in a light-emitting diode circuit to provide a mechanism for steady current regulation. When the feedback voltage associated with the output voltage of one of the LED strings is used to compare with a fixed reference voltage to achieve the feedback control mechanism, the voltage of the output voltage is often Maintained near the size of the reference voltage. When the operation mode of the LED string is changed and the current of the LED string is reduced, the heat generated by the current extraction circuit is not due to the presence of a fixed reference voltage, and the current does not decrease due to the current becoming smaller. In the low current mode of operation, it causes additional power loss.

Therefore, how to design a light-emitting diode circuit with a light-emitting diode driving circuit and a method for operating the same to overcome the above problems is an urgent problem to be solved in the industry.

Therefore, one aspect of the present disclosure is to provide a light emitting diode (LED) driving circuit for driving a plurality of light emitting diodes, the LED driving circuit comprising: A plurality of current capture modules, current mirrors, and DC to DC converters. The current capture module is respectively connected to one of the LED strings and the output load to latch the voltage of the output load to the set voltage level. The current mirror contains: an input branch and an output branch. The input branch generates an input set current based on the variable set load. The output branch generates an output set current, and the output branch includes a first load connected in series and a second load to generate a variable reference voltage and a set voltage according to the output set current, respectively. The DC-to-DC converter includes a control module and a power amplifier connected to the LED string, wherein the control module is configured to feed back according to the variable reference voltage and one of the plurality of outputs of the self-luminous diode string The voltage generates a drive voltage to control the gate of the power amplifier to further control the operation of the LED string.

According to an embodiment of the present disclosure, when the resistance of the variable set load is changed to change the input set current, and further, the output set current is changed according to the input set current, the variable reference voltage is varied.

According to another embodiment of the present disclosure, each current extraction module includes: a switch MOS transistor and an operational amplifier. The switch MOS transistor is connected to one of the LED strings and the output load. The operational amplifier includes: a positive input terminal, a negative input terminal, and an output terminal. The positive input receives the set voltage. The negative input is connected to the output load and the MOS transistor is switched to latch the voltage of the output load to a set voltage level. The output is connected to the gate of the switch MOS transistor.

According to still another embodiment of the present disclosure, the current ratio between the output current and the LED current of each of the LED current strings is the same as the resistance ratio between the second load and the output load.

According to still another embodiment of the present disclosure, the first load is a resistor or a diode.

According to the disclosure, there is an embodiment in which the DC-to-DC converter further includes: an inductor, a diode, and a capacitor. The inductor couples the supply voltage to the first end. The diode is connected between the first end and the LED string. The capacitor is connected to the LED string, wherein the power amplifier is substantially connected to the first end to charge and discharge the capacitor according to the driving voltage. The anode of the diode is connected to the first end, and the cathode of the diode is connected to the capacitor.

Another aspect of the present disclosure is to provide a light emitting diode circuit comprising: a plurality of light emitting diode strings and a light emitting diode driving circuit. The LED driving circuit comprises: a plurality of current capturing modules, a current mirror and a DC to DC converter. The current capture module is respectively connected to one of the LED strings and the output load to latch the voltage of the output load to the set voltage level. The current mirror contains: an input branch and an output branch. The input branch generates an input set current based on the variable set load. The output branch generates an output set current, and the output branch includes a first load connected in series and a second load to generate a variable reference voltage and a set voltage according to the output set current, respectively. The DC-to-DC converter includes a control module and a power amplifier connected to the LED string, wherein the control module is configured to feed back according to the variable reference voltage and one of the plurality of outputs of the self-luminous diode string The voltage generates a drive voltage to control the gate of the power amplifier to further control the operation of the LED string.

According to an embodiment of the present disclosure, when the resistance of the variable set load is changed to change the input set current, and further, the output set current is changed according to the input set current, the variable reference voltage is varied.

According to another embodiment of the present disclosure, each current extraction module includes: a switch MOS transistor and an operational amplifier. The switch MOS transistor is connected to one of the LED strings and one of the output loads. The operational amplifier includes: a positive input terminal, a negative input terminal, and an output terminal. The positive input receives the set voltage. The negative input is connected to the output load and the MOS transistor is switched to latch the voltage of the output load to a set voltage level. The output is connected to the gate of the switch MOS transistor.

According to still another embodiment of the present disclosure, the current ratio between the output current and the LED current of each of the LED current strings is the same as the resistance ratio between the second load and the output load.

According to still another embodiment of the present disclosure, the first load is a resistor or a diode.

According to the disclosure, there is an embodiment in which the DC-to-DC converter further includes: an inductor, a diode, and a capacitor. The inductor couples the supply voltage to the first end. The diode is connected between the first end and the LED string. The capacitor is connected to the LED string, wherein the power amplifier is substantially connected to the first end to charge and discharge the capacitor according to the driving voltage. The anode of the diode is connected to the first end, and the cathode of the diode is connected to the capacitor.

A further aspect of the present disclosure is to provide a method for operating a light-emitting diode circuit, which is applied to a light-emitting diode circuit, the light-emitting diode circuit includes a plurality of light-emitting diode strings, and the operation method of the light-emitting diode circuit includes The following steps. Generating an input set current according to a variable setting load on an input branch of the current mirror; generating an output set current according to an input set current at an output branch of the current mirror, wherein the output branch includes a first load and a second load connected in series to respectively output Setting a current to generate a variable reference voltage and setting a voltage; latching a voltage connected to an output load of one of the LED strings to a set voltage level; and receiving a variable reference by a control module of the LED circuit The voltage and the feedback voltage of one of the plurality of outputs of the self-luminous diode string are used to control the gate of the power amplifier to further control the operation of the LED string.

According to another embodiment of the present disclosure, the operation method of the LED circuit further includes the steps of: changing the resistance of the variable set load to change the input set current; and changing the output set current according to the input set current to make the variable The reference voltage changes.

According to still another embodiment of the present disclosure, the current ratio between the output current and the LED current of each of the LED current strings is the same as the resistance ratio between the second load and the output load.

The advantage of applying the disclosure is to establish a variable reference voltage that can be changed with the operation mode by setting the load and the current mirror to dynamically adjust the feedback control mechanism when switching to different operation modes. Operation, to achieve the effect of reducing power consumption, and easily achieve the above purposes.

Please refer to Figure 1. FIG. 1 is a schematic diagram of a light-emitting diode circuit 1 in an embodiment of the present disclosure. The light-emitting diode circuit 1 includes a plurality of light-emitting diode strings 10 and a light-emitting diode driving circuit. The LED driving circuit comprises: a plurality of current capturing modules 12 (shown in a block in FIG. 1), a DC to DC converter, and a current mirror 16.

The DC to DC converter includes an inductor 140, a diode 142, a capacitor 144, a control module 146, and a power amplifier 148.

The inductor 140 is used to couple the supply voltage Vp to the first terminal P. The diode 142 is connected between the first end P and the LED string 10. The anode end of the diode 142 is connected to the first end P, and the cathode end of the diode 142 is connected to the capacitor 144 and the LED string 10. It should be noted that the number of strings of the light-emitting diode strings 10 and the number of light-emitting diodes included in each of the light-emitting diode strings are adjusted in different embodiments as appropriate.

In one embodiment, the control module 146 includes an error amplifier and a bandwidth modulator (not shown), wherein the error amplifier is based on a reference voltage Vr and a feedback related to the voltages of the LED strings 10 The voltage Vfb produces a comparison result. The wave width modulator further generates a driving voltage Vd according to the comparison result and an oscillation signal. When the drive voltage Vd is high, the power amplifier 148 will be turned on. When the drive voltage Vd is low, the power amplifier 148 will be turned off. The power amplifier 148 can thus switch between on and off to charge and discharge the capacitor 144. The charging and discharging process of the capacitor 144 allows the LED string 10 to be turned on or off.

The current extraction modules 12 are respectively connected to one of the LED strings 10 to provide a voltage stabilization or current stabilization mechanism. Please also refer to Figure 2. FIG. 2 is a schematic diagram of the current mirror 16, the two LED arrays 100 and 102, and the two current extraction modules 120 and 122 of FIG. 1 according to an embodiment of the disclosure.

The current extraction module 120 is connected between the LED array 100 and the output load 20. The current extraction module 122 is connected between the LED string 102 and the output load 22. Please refer to Figure 3 at the same time. FIG. 3 is a more detailed diagram of the current extraction module 120 and the output load 20. The current extraction module 120 includes an operational amplifier 30 and a switching MOS transistor 32. The switching MOS transistor 32 is connected to the corresponding LED string 100 and the output load 20. The operational amplifier 30 has a positive input (labeled +), a negative input (labeled -), and an output. The positive input terminal is used to receive the set voltage Vset. The negative input terminal is coupled to the output load 20 and the switching MOS transistor 32 to latch the voltage of the output load 20, i.e., the voltage labeled N at the third level, to the set voltage level Vset. The output of operational amplifier 30 is coupled to the gate of switching MOS transistor 32.

Current mirror 16 includes an input branch 160 and an output branch 162. The input branch 160 generates an input set current Iset1 in accordance with the variable set load 161. In other words, the variable set load 161 can be a variable resistor so that the user can change the magnitude of the input set current Iset1 by adjusting its resistance. Since it is in the form of a current mirror 16, the output branch 162 can generate an output set current Iset2 in accordance with the input set current Iset1.

Output branch 162 includes a first load 163 and a second load 165 that are in series. In this embodiment, the first load 163 and the second load 165 are both resistors. In an embodiment, the first load 163 can also be a diode to obtain a voltage difference at both ends thereof. Therefore, two voltages can be generated on the first load 163 and the second load 165 according to the output set current Iset2.

The voltage generated on the second load 165 is used as the aforementioned set voltage Vset and transmitted to the positive input terminals of the operational amplifiers of the current capture modules 120 and 122 to provide a voltage latching mechanism. Due to the voltage latching mechanism, the output set current Iset2 and the LED current of each of the LED strings (such as the LED current Id shown in FIGS. 2 and 3) have a current ratio. The ratio of resistances between the second load 165 and the output load 20 is the same. For example, when the resistance of the output load 20 is R1 and the resistance of the second load 165 is 200*R1, the current ratio between the output set current Iset2 and the LED current Id is also 200.

The voltage on the first load 163 is then used as a variable reference voltage Vr for transmission to the control module 146 depicted in FIG. Therefore, the control module 146 generates the driving voltage Vd substantially according to the variable reference voltage Vr and the feedback voltage Vfb. It should be noted that the feedback voltage Vfb is generated according to the output end of one of the LED strings 10, such as the output terminal O of the LED string 100. In one embodiment, the feedback voltage Vfb can be selected from the voltages of the outputs via a minimum selection mechanism.

Therefore, when the resistance value of the variable setting load 161 is changed so that the input setting current Iset1 is changed, the output setting current Iset2 will be changed according to the input setting current Iset1. The changed set current Iset2 will further vary the variable reference voltage Vr and the light-emitting diode current Id.

In one example, in the initial mode of operation, the LED current Id is 40 milliamps and the variable reference voltage Vr is 0.8 volts. When the operation mode of the LED circuit 1 is changed due to the variable setting load 161 being adjusted to a small value, further reducing the LED current Id to 20 mA, such as the control module 146 is still fixed. The reference voltage realizes the feedback mechanism, and the current capture module will lock the output voltage of the LED string to a fixed reference voltage value (ie, 0.8V) due to the feedback mechanism, and cannot reduce the light-emitting diode The adjustment of the bulk current Id greatly reduces its power consumption.

If the control module 146 adopts the variable reference voltage Vr in the above embodiment, the feedback control mechanism will be changed when the operating mode is changed (eg, the LED current Id is changed from 40 mA to 20 mA). The change of the load 161 is set, and the variable reference voltage Vr is adjusted to a smaller value. Therefore, the output voltage of the LED string will be latched at a lower voltage value (such as 0.6 volts) as the operating mode changes, so that the power can be greatly reduced.

For example, in the original mode of operation, the feedback control mechanism causes the output voltage of the LED string to be latched at 0.8 volts, and the power consumption will be 0.8 volts*40 milliamps. If a fixed reference voltage is used, the power consumption of the changed operating mode will be 0.8 volts * 20 milliamps. On the other hand, if a variable reference voltage is used, the power consumption of the changed operating mode will drop to 0.6 volts * 20 milliamps. When the current extraction module connected to all the LED strings in the LED circuit greatly reduces the power consumption due to the design of the variable reference voltage, the power consumption of the overall LED circuit is reduced. Very impressive.

It should be noted that in the second figure, two LED strings are taken as an example. In essence, the number of LED strings can be adjusted differently in different situations.

Please refer to Figure 4. FIG. 4 is a flow chart of a method for operating a light emitting diode circuit according to an embodiment of the disclosure. The operation method of the light emitting diode circuit can be applied to the light emitting diode circuit 1 as shown in FIG. The operation method of the LED circuit comprises the following steps (it should be understood that the steps mentioned in the embodiment can be adjusted according to actual needs, except for the order in which the sequence is specifically stated, or even simultaneously or partially Simultaneous execution).

In step 401, an input set current Iset1 is generated in the input branch 160 of the current mirror 16 according to the variable set load 161. Next, in step 402, an output set current Iset2 is generated according to the input set current Iset1 at the output branch 162 of the current mirror 16, wherein the output branch 162 includes the first load 163 and the second load 165 connected in series to generate the current set current Iset2, respectively. The variable reference voltage Vr and the set voltage Vset. In step 403, the voltage of the output load connected to one of the LED strings 10 is latched to the set voltage level Vset. In step 404, the control module 146 of the LED circuit 1 receives the variable reference voltage Vr and the feedback voltage Vfb of one of the plurality of output terminals of the self-luminous diode string 10 to control the power amplifier 148. The gate is used to further control the operation of the LED string 10.

The advantage of applying the disclosure is to establish a variable reference voltage that can be changed with the operation mode by setting the load and the current mirror to dynamically adjust the operation of the feedback control mechanism when switching to different operation modes. , to achieve the effect of reducing power consumption.

The present disclosure has been disclosed in the above embodiments, but it is not intended to limit the disclosure, and any person skilled in the art can make various changes and refinements without departing from the spirit and scope of the disclosure. The scope of protection of the disclosure is subject to the definition of the scope of the patent application.

1. . . Light-emitting diode circuit

10. . . Complex LED string

100, 102. . . Light-emitting diode string

12. . . Complex current capture module

120, 122. . . Current capture module

140. . . inductance

142. . . Dipole

144. . . capacitance

146. . . Control module

148. . . Power amplifier

16. . . Current mirror

160. . . Input branch

161. . . Variable setting load

162. . . Output branch

163. . . First load

165. . . Second load

20, 22. . . Output load

30. . . Operational Amplifier

32. . . Switched gold oxide semi-transistor

401-404. . . step

The above and other objects, features, advantages and embodiments of the present disclosure will become more apparent and understood.

1 is a schematic diagram of a light emitting diode circuit in an embodiment of the present disclosure;

2 is a schematic diagram of a current mirror, two LED strings, and two current capturing modules in FIG. 1 according to an embodiment of the disclosure;

3 is a more detailed schematic diagram of the current capture module and the output load in FIG. 2 in an embodiment of the present disclosure;

FIG. 4 is a flow chart of a method for operating a light emitting diode circuit according to an embodiment of the disclosure.

100, 102. . . Light-emitting diode string

120, 122. . . Current capture module

16. . . Current mirror

160. . . Input branch

161. . . Variable setting load

162. . . Output branch

163. . . First load

165. . . Second load

20, 22. . . Output load

Claims (17)

A light emitting diode (LED) driving circuit for driving a plurality of light emitting diodes, the LED driving circuit comprising: a plurality of current capturing modules respectively connected to the light emitting diodes One of the LED strings and an output load to latch the voltage of the output load to a set voltage level; a current mirror comprising: an input branch for generating an input according to a variable set load Setting a current; and an output branch for generating an output set current, the output branch comprising a first load connected in series and a second load to generate a variable reference voltage and the set voltage according to the output set current respectively And a DC converter comprising a control module and a power amplifier connected to the LED strings, wherein the control module is configured to use the variable reference voltage and the light emitting diodes Retrieving a voltage from one of a plurality of output terminals of the string to generate a driving voltage to control the gate of the power amplifier to further control the light emitting The operation of the polar body string. The illuminating diode driving circuit of claim 1, wherein when the resistance of the variable setting load is changed to change the input setting current, and further, the output setting current is changed according to the input setting current, The variable reference voltage changes. The illuminating diode driving circuit of claim 1, wherein each of the current sourcing modules comprises: a switching MOS transistor connected to one of the illuminating diode strings and the output load; An operational amplifier comprising: a positive input terminal for receiving the set voltage; a negative input terminal coupled to the output load and the switch MOS transistor to latch a voltage of the output load to the set voltage level And an output connected to the gate of the MOS transistor. The illuminating diode driving circuit of claim 1, wherein the output setting current and a current ratio between one of the LED currents of each of the LED current strings, and the second load and the output One of the resistors has the same resistance ratio. The illuminating diode driving circuit of claim 1, wherein the first load is a resistor or a diode. The illuminating diode driving circuit of claim 1, wherein the DC to DC converter further comprises: an inductor coupling a supply voltage to a first end; a diode connected to the first end and The capacitors are connected to the LED strings, wherein the power amplifier is substantially connected to the first terminal to charge and discharge the capacitor according to the driving voltage. The illuminating diode driving circuit of claim 6, wherein an anode of the diode is connected to the first end, and a cathode of the diode is connected to the capacitor. An LED circuit includes: a plurality of LED strings; and a LED driving circuit comprising: a plurality of current capturing modules respectively connected to one of the LED strings and one of the LED strings Outputting a load to latch the voltage of the output load to a set voltage level; a current mirror comprising: an input branch for generating an input set current according to a variable set load; and an output branch for Generating an output set current, the output branch including one of the first load and a second load in series to generate a variable reference voltage and the set voltage according to the output set current, respectively; and flowing to the DC converter, including a control module and a power amplifier connected to the LED strings, wherein the control module is configured to use the variable reference voltage and one of a plurality of outputs from the LED strings A feedback voltage generates a drive voltage to control the gate of the power amplifier to further control the operation of the LED strings. The illuminating diode circuit of claim 8, wherein when the resistance of one of the variable set loads is changed to cause the input set current to change, and further the output set current is changed according to the input set current, the variable The reference voltage changes. The illuminating diode circuit of claim 8, wherein each of the current sourcing modules comprises: a switching MOS transistor connected to one of the illuminating diode strings and one of the output loads And an operational amplifier comprising: a positive input terminal for receiving the set voltage; a negative input terminal coupled to the output load and the switch MOS transistor to latch the output load voltage to the setting a voltage level; and an output connected to the gate of the MOS transistor. The illuminating diode circuit of claim 8, wherein the output setting current and a current ratio between the LED currents of each of the LED current strings, and the second load and the output load One of the resistance ratios is the same. The illuminating diode circuit of claim 8, wherein the first load is a resistor or a diode. The illuminating diode circuit of claim 8, wherein the DC to DC converter further comprises: an inductor coupling a supply voltage to a first end; a diode connected to the first end and the first end And a capacitor connected to the LED string, wherein the power amplifier is substantially connected to the first end to charge and discharge the capacitor according to the driving voltage. The illuminating diode circuit of claim 8, wherein an anode end of the diode is connected to the first end, and a cathode end of the diode is connected to the capacitor. A method for operating a light-emitting diode circuit is applied to a light-emitting diode circuit, the light-emitting diode circuit comprising a plurality of light-emitting diode strings, and the method for operating the light-emitting diode circuit comprises the following steps: according to a variable setting Loaded on an input branch of a current mirror to generate an input set current; according to the input set current, an output branch of the current mirror generates an output set current, wherein the output branch includes one of the first load and a second a load to generate a variable reference voltage and the set voltage according to the output set current; respectively, latching a voltage connected to one of the output strings of the light emitting diode strings to a set voltage level; A control module of the LED circuit receives the variable reference voltage and returns a voltage from one of a plurality of output terminals of the LED strings to control a gate of a power amplifier to Further controlling the operation of the strings of the LEDs. The operating method of the LED circuit of claim 15, further comprising the steps of: changing a resistance of the variable setting load to cause the input setting current to change; and changing the output setting current according to the input setting current, In order to make the variable reference voltage change. The method of operating a light-emitting diode circuit according to claim 15, wherein the output set current and a current ratio between one of the light-emitting diode currents of each of the light-emitting diode current strings, and the second load and the One of the resistance ratios between the output loads is the same.