TWI492664B - Power foldback linear led driving circuit - Google Patents

Description

Power foldback linear light emitting diode driving circuit

The invention relates to a light emitting diode driving circuit, in particular to a power folding type linear light emitting diode driving circuit.

In recent years, environmental awareness has grown rapidly, and countries have advocated environmental protection policies such as energy conservation and carbon reduction. One example is the reduction of the power consumed by lighting fixtures. At present, the most popular energy-saving lamps are Light Emitting Diode (LED) lighting. Because of its energy saving, environmental protection, long life and durability, it is gradually replacing traditional lamps and gradually expanding to Various applications.

The light-emitting diode has similar electrical characteristics to the conventional conventional rectifier diode, and is driven by a low voltage, which is a unidirectional conductive element, so a DC drive must be used. The "Fig. 1" shows the architecture of a typical driver circuit. The mains V _{ac is} used as the power source. Since the mains is usually AC, the AC voltage of the full-wave voltage is first converted into a half-wave rectified voltage through the bridge rectifier 20, and then supplied to the LED driving circuit 21 to output the driving voltage. Or drive current to drive the LEDs 22 to emit light.

However, the light-emitting diode has traditionally operated at a fixed current. As shown in FIG. 2, the on-voltage and the on-current of the light-emitting diode at V _ac1 are V _LED1 and I _LED1 , respectively, and are turned on at V _ac2 . The voltage and the on-current are V _LED2 and I _LED2 , respectively, and the output power is also P _out1 (=V _LED1 *I _LED1 *Ton1/T) becomes P _out2 (=V _LED2 *I _LED2 *Ton2/T). When the input AC voltage V _ac is increased from V _ac1 to V _ac2 , the on-period is thus increased from Ton1 to Ton2. As can be seen from the graph and the above relationship, when the voltage fluctuation is increased, the conduction period is also It becomes larger, so the output power P _out2 will also be greater than the output power P _out1 . It can be seen that when the input AC voltage V _ac changes, the equivalent output power of the LED is not fixed, causing the brightness of the LED to change. The long-term operation will cause the temperature of the LED substrate to rise, and the driving circuit will also rise due to the AC voltage. High, LED substrate temperature rises and the temperature is getting higher and higher, which is the disadvantage of the application of the AC voltage fixed current on the conventional linear drive light-emitting diode.

In summary, there is a need for a protection circuit that allows the operating temperature of the driver circuit. The degree is constant to avoid overheating of the LED or the drive circuit.

In view of the above problems, the present invention provides a power foldback type linear light emitting diode driving circuit, which has the function of decreasing the driving current as the AC voltage V _ac increases, so that the light emitting diode or the driving circuit is operated at a constant temperature state. And work in a secure environment to solve the problems encountered in the prior art.

A power foldback linear light emitting diode according to an embodiment of the invention The body drive circuit includes a temperature sensor, a first voltage current conversion circuit, a first subtractor, a second voltage current conversion circuit, a third voltage current conversion circuit, and a first load circuit. Wherein the temperature sensor responds to a sensing temperature to generate a reference voltage, and when the sensing temperature increases, the reference voltage changes with the sensing temperature; the first voltage current converting circuit responds to the temperature control voltage, thereby generating a first output voltage; the first subtractor is electrically coupled to the temperature sensor and the first voltage current conversion circuit, and the first subtractor subtracts the reference voltage from the first output voltage, The second voltage current conversion circuit is responsive to the second output voltage, and is converted into the second current output; the third voltage current conversion circuit is electrically coupled to the fourth voltage current conversion circuit, and responds to the first a second reference voltage, generating a third current output; and the first load circuit is electrically coupled to the second voltage current conversion circuit, thereby determining a first equivalent resistance for controlling the second current magnitude, wherein, when the second When the reference voltage is a predetermined value, the third current is subtracted from the second current to generate a set voltage Vset, and finally a set current ILED is generated by the voltage current conversion circuit to be driven to the light emitting diode.

According to the power folding type linear light emitting diode driving circuit of the present invention, when When the fluctuation of the current voltage is increased, the temperature of the LED substrate and the operating temperature of the driving circuit are increased, and the temperature protection is continued until the driving circuit is set, and then the driving current is adjusted, which is a linear down-conversion, and the slope of the down-regulation can be first. The equivalent resistance of the load circuit is determined such that the operating temperature of the light-emitting diode or the drive circuit is constant. Therefore, it is possible to effectively prevent the LED or the driving circuit from being overheated and burned.

The above description of the contents of the present invention and the following embodiments are described. The spirit and principles of the present invention are set forth and explained, and a further explanation of the scope of the patent application of the present invention is provided.

10‧‧‧Power foldback linear light emitting diode drive circuit

11‧‧‧Temperature Sensor

12‧‧‧First voltage current conversion circuit

13‧‧‧First subtractor

14‧‧‧Second voltage current conversion circuit

15‧‧‧ Third voltage current conversion circuit

16‧‧‧First load circuit

17‧‧‧fourth voltage current conversion circuit

20‧‧‧Bridge rectifier circuit

21‧‧‧Lighting diode drive circuit

22‧‧‧Lighting diode

21‧‧‧Second current generation circuit

22‧‧‧Comparative circuit

23‧‧‧ Third current generation circuit

24‧‧‧Second load circuit

25‧‧‧ Fifth voltage current conversion circuit

26‧‧‧second subtractor

110‧‧‧Input branch

111‧‧‧First operational amplifier

112‧‧‧Output branch

121‧‧‧Second comparator

122‧‧‧ third comparator

130‧‧‧Input branch

131‧‧‧4th operational amplifier

132‧‧‧Output branch

141‧‧‧First load

142‧‧‧second load

152‧‧‧ fifth operational amplifier

Fig. 1 is a schematic view showing the structure of a prior art light emitting diode circuit.

Fig. 2 is a waveform diagram of a prior art light emitting diode.

FIG. 3 is a block diagram of a power foldback linear light emitting diode driving circuit disclosed in the present invention.

Figure 4 is a power foldback linear light emitting diode disclosed in the present invention. The current reduction waveform of the drive circuit.

FIG. 5 is a block diagram showing another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

FIG. 6 is a first time-down waveform diagram of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

FIG. 7 is a waveform diagram of a current reduction waveform of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

Figure 8 is a circuit diagram of a second current generating circuit of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

FIG. 9 is a circuit diagram of a comparison circuit of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

FIG. 10 is a circuit diagram of a third current generating circuit of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

Figure 11 is a circuit diagram of a second load circuit of another embodiment of the power foldback type linear light emitting diode driving circuit disclosed in the present invention.

Figure 12 is a circuit diagram of a fifth voltage-current conversion circuit of another embodiment of the power foldback type linear light-emitting diode driving circuit disclosed in the present invention.

The detailed features and advantages of the present invention are set forth in the Detailed Description of the Detailed Description of the <RTIgt; </ RTI> <RTIgt; </ RTI> </ RTI> </ RTI> <RTIgt; Anyone familiar with the relevant artisan The objects and advantages associated with the present invention are readily understood. The following examples are intended to describe the present invention in further detail, but are not intended to limit the scope of the invention.

Please refer to FIG. 3, which is a block diagram of the power foldback linear light emitting diode driving circuit of the present invention. The power foldback type linear light emitting diode driving circuit 10 includes a temperature sensor 11, a first voltage current converting circuit 12, a first subtractor 13, a second voltage current converting circuit 14, and a third voltage current converting. The circuit 15, a first load circuit 16 and a fourth voltage current conversion circuit 17. The first voltage-current conversion circuit 12 is electrically coupled to the temperature sensor 11 and coupled to the first subtractor 13 to generate a second output voltage V _out2 . The first subtractor 13 is electrically coupled to the second voltage current. The conversion circuit 14 is configured to be electrically coupled to the third voltage current conversion circuit 15 and the first load circuit 16 respectively, and the second voltage current conversion circuit 14 is configured to use the second output voltage V _out2 according to the first load. The equivalent resistance of the circuit changes the output current. Finally, the third voltage current conversion circuit 15 is electrically coupled to the fourth voltage current conversion circuit 17.

The temperature sensor 11 responds to a sensing temperature, wherein the sensing temperature is the temperature of the light emitting diode or the driving circuit, _thereby generating a reference voltage V _ref1 , and when the sensing temperature changes, the reference voltage V _ref1 follows the sense When the temperature is changed, for example, when the sensed temperature is raised, the reference voltage V _{ref1 is} decreased, and the reference voltage V _ref1 and the temperature are negatively changed. The first voltage-current conversion circuit 12 responds to the temperature-controlled voltage V _TB to generate a first output voltage V _out1 which is set to a fixed voltage. The first subtractor 13 is electrically coupled to the temperature sensor 11 and the first voltage current conversion circuit 12, and the first subtractor 13 performs a subtraction operation on the reference voltage V _ref1 and the first output voltage V _out1 to generate a first Two output voltages V _out2 .

The second voltage-current conversion circuit 14 is responsive to the second output voltage V _out2 for conversion to a second current I _out2 output. The third voltage-current conversion circuit 15 is electrically coupled to the fourth voltage-current conversion circuit 17 and is responsive to a second reference voltage V _ref2 for conversion to a third current I _out3 output, and finally converted to generate a set voltage V. _Set . The first load circuit 16 includes a plurality of resistors. The first load circuit 16 is electrically coupled to the second voltage current conversion circuit 14 for controlling the magnitude of the second current I _out2 . When the reference voltage V _ref2 is a predetermined value, The third current I _{out3 is subtracted} from the second current I _out2 . The fourth voltage-current conversion circuit 17, in response to a set voltage V _set, and then generates a set current I _LED current via a fourth voltage conversion circuit. Finally, the output end of the power foldback linear light emitting diode driving circuit 10 is connected to the light emitting diode to drive the light emitting diode to emit light.

As shown in Fig. 4, when the input AC voltage V _ac changes to V _ac2 , as described above, a current _regulation is performed so that the operating temperature of the driving circuit is continuously maintained as a protection circuit.

Please refer to FIG. 5, which is an embodiment of the power foldback type linear light emitting diode driving circuit 10 of the present invention. As shown in the figure, the driving circuit further includes a comparing circuit 22, a second current generating circuit 21, a third current generating circuit 23, a second load circuit 24, a third voltage current converting circuit 15, and a fourth The voltage-current conversion circuit 17, a fifth voltage-current conversion circuit 25, and a second subtractor 26. The second subtractor 26 is electrically coupled to the comparison circuit 22 and the fifth voltage current conversion circuit 25. The second subtractor 26 is responsive to a third reference voltage V _ref3 and the first input voltage V _in1 , and is subtracted to reduce the voltage. The output current of the LED is electrically coupled to the comparison circuit 22 and the fifth voltage current conversion circuit 25, and the second subtractor 26 and the comparison circuit 22 receive a first input voltage V _in1 And operate. The comparison circuit 22 and the fifth voltage current conversion circuit 25 are electrically coupled to the second load circuit 24, respectively. The second load circuit 24 determines an equivalent resistance according to the fourth comparison voltage of the comparison circuit 22 and the fifth comparison voltage.

When the first input voltage V _{in1 is} increased greater than the third reference voltage V _ref3 , the first input voltage V _in1 and the third reference voltage V _ref3 are calculated by the second subtractor 26 to generate a first voltage V ₁ , the first voltage Used as a reference for downgrade. Responding to the first voltage and the switching current determined by the equivalent resistance of the load circuit, the fifth voltage current conversion circuit 25 processes the set voltage _{Vset of the} third voltage current conversion circuit 15, that is, the first time down, to output After the voltage is lowered, the voltage after the voltage reduction is converted into a driving current by the fourth voltage current converting circuit 17 to provide a light emitting diode. Through the above mechanism, as indicated by the dashed line of the I _{LED 2'} curve of "Fig. 6", it represents the current dropped so that the output power P _out1 at the voltage V _ac1 is equal to the output power P _out2 at the voltage V _ac2 . Therefore, the output power of the light-emitting diode remains unchanged, thereby avoiding the problem of LED brightness variation caused by AC voltage fluctuation.

Please continue to refer to "Figure 5," comparing circuit 22 receives a reference voltage V _ref4 fourth and fifth reference voltage V _ref5. After the comparison circuit 22 respectively, and the fourth reference voltage V _ref4 fifth reference voltage V _ref5 with a first input voltage V _in1 comparison, according to the fourth comparator output voltage V _out4 and the fifth comparison voltage _V out5.

As shown in Fig. 7, when the input AC voltage V _ac is increased from V _ac2 to V _ac3 , the output drive current is first _adjusted by the above first time, but the output power is not equal after being adjusted. It is necessary to change the slope of the current to replenish the output current to indirectly pull up the current so that the output power P _out2 at V _ac2 is equal to the output power P _out3 at V _ac3 , so that the output power of the LED can be maintained continuously. This control mode can achieve better single-sided AC voltage line adjustment rate, and solve the problem of LED brightness change caused by the wide range of wide-side AC voltage variation range of the conventional linear drive light-emitting diode, and can also maintain the same high power. Factor.

The second load circuit 24 is electrically coupled to the comparison circuit 22, and the load circuit 24 is responsive to the fourth comparison voltage V _out4 or the fifth comparison voltage V _out5 output by the comparison circuit 22, _thereby determining a second equivalent resistance and outputting a conversion current. . The load circuit 24 performs current replenishment based on the determined equivalent resistance, wherein the magnitude of the current can be determined by the equivalent resistance determined by the load circuit 24. The fifth voltage-current conversion circuit 25 responds to the first voltage outputted by the second subtractor 26 and the switching current of the second load circuit 24, and responds to a set voltage of a third voltage-current conversion circuit 15 to output a voltage-lowering voltage; Finally, the fourth voltage-current conversion circuit 17 converts the voltage-down voltage into a drive current.

The second subtractor 26 includes a second current generating circuit 21 and a third current generating circuit 23. Referring to FIG. 8 , it is a detailed circuit diagram of the second current generating circuit disclosed in the present invention. As shown, the second current generating circuit 21 includes a first operational amplifier 111, an input branch 110, and an output branch 112. The input branch 110 includes a first transistor M ₁ and the output branch 112 includes a second transistor M ₂ . The output terminal of the first operational amplifier 111 is coupled to the gate terminal of a third transistor M ₃ , and the negative input terminal of the first operational amplifier 111 is coupled to the source terminal of the third transistor M ₃ . The 汲 terminal of the third transistor M ₃ is connected to the 汲 terminal of the first transistor M ₁ . A first operational amplifier 111 to respond to a third reference voltage V _ref3, according to generate a third output voltage V _out3 and electrically coupled to the input branch 110. The input branch 110 generates a first input set current I _{in1 in} response to the third output voltage V _out3 . Due to the form of the second current generating circuit 21, the output branch 112 can map the first input set current I _{in1 of the} input branch 110 to generate a third output set current I _out3 for the third current generating circuit 23.

Please refer to FIG. 9 for a detailed circuit diagram of the comparison circuit disclosed in the present invention. As shown, the comparison circuit 22 includes a second comparator 121 and a third comparator 122. The second comparator 121 is responsive to the fourth reference voltage V _ref4 and the first input voltage V _in1 , and generates a fourth output voltage V _out4 at the output end. The output end of the second comparator 121 is electrically coupled to the second load circuit 24 . An eighth transistor 141 is used to control the eighth transistor 141 switch. The third comparator 122 is responsive to the fifth reference voltage V _ref5 and the first input voltage V _in1 , and generates a fifth output voltage V _out5 at the output end. The output of the third comparator 122 is electrically coupled to the second load circuit 24 . A plurality of ninth transistors 142 are used to control a plurality of ninth transistors 142 switches.

Please refer to FIG. 10, which is a detailed circuit diagram of the third current generating circuit 23 disclosed in the present invention. As shown, the third current generating circuit 23 includes a fourth operational amplifier 131, an input branch 130, and an output branch 132. The input branch 130 includes a fourth transistor M ₄ and the output branch 132 includes a fifth transistor M ₅ . The output terminal of the fourth operational amplifier 131 is coupled to the gate terminal of a sixth transistor M ₆ , and the negative input terminal of the fourth operational amplifier 131 is coupled to the source terminal of the sixth transistor M ₆ . The 汲 terminal of the sixth transistor M ₆ is connected to the 汲 terminal of the fourth transistor M ₄ . The fourth operational amplifier 131 is responsive to the first input voltage V _in1 to generate a sixth output voltage V _out6 and is provided to the input branch 130. The input branch 130 generates a second input set current I _{in2 in} response to the sixth output voltage V _out6 . Due to the form of the third current generating circuit 23, the output branch 132 can map the second input set current I _{in2 of the} input branch 130 to generate a fourth output set current I _out4 to the fifth voltage current converting circuit 25.

Please refer to FIG. 11 for a detailed circuit diagram of the load circuit 24 disclosed in the present invention. The second load circuit 24 includes a first load 141 and a second load 142. A first load 141 comprises an eighth transistor M ₈ and the first resistor R1 and a plurality of eighth connecting the transistor M _8, wherein the eighth transistor M ₈ of the switch by a fourth output voltage V 22 outputted from the comparison circuit _out4 control. The second load 142 includes a plurality of ninth transistors M ₉ and a plurality of second resistors R2 connected to the ninth transistor M ₉ , wherein the switches of the plurality of second transistors 144 are controlled by the fifth output voltage V _out5 . When the input AC voltage V _ac changes to V _ac3 , the eighth transistor M ₈ and the plurality of ninth transistor M ₉ switches are controlled by the output of the comparison circuit 22 to turn on the first resistor R1 and the first The second resistor R2 generates different series-parallel combinations to determine an equivalent resistance and output a switching current. The equivalent resistance determines the magnitude of the output current and produces an approximate current replenishment function. A third resistor R3 is connected between the second load circuit 24 and the fifth voltage current conversion circuit 25.

Finally, please refer to FIG. 12, which is a detailed circuit diagram of the fifth voltage-current conversion circuit 25 disclosed in the present invention. The fifth voltage-current conversion circuit 25 includes a seventh transistor M ₇ and a fifth operational amplifier 152. The output end of the seventh transistor M ₇ is electrically coupled to the second load circuit 24 . Fifth operational amplifier 152 is electrically coupled to the third current generating circuit 23 and second load circuit 24, and an output terminal electrically coupled to the gate of the transistor M seventh electrode _7, for controlling the seventh transistor M ₇ Current. The current I _L flowing through the seventh transistor M ₇ can be determined by the second current generating circuit 21 and the third current generating circuit 23 and the second load circuit 24.

According to the power foldback type linear light emitting diode driving circuit of the present invention, when the operating temperature exceeds the set temperature protection, the driving current of the light emitting diode is linearly adjusted, so that the operating temperature of the light emitting diode or the driving circuit is constant. In this way, the LED or the driving circuit can be effectively prevented from being overheated and burned.

Although the present invention has been disclosed above in the foregoing embodiments, it is not intended to limit the invention. It is within the scope of the invention to be modified and modified without departing from the spirit and scope of the invention. Please refer to the attached patent application for the scope of protection defined by the present invention.

10‧‧‧Power foldback linear light emitting diode drive circuit

11‧‧‧Temperature Sensor

12‧‧‧First voltage current conversion circuit

13‧‧‧First subtractor

14‧‧‧Second voltage current conversion circuit

15‧‧‧ Third voltage current conversion circuit

16‧‧‧First load circuit

17‧‧‧fourth voltage current conversion circuit

Claims (11)

A power foldback linear light emitting diode driving circuit includes: a temperature sensor that generates a reference voltage in response to a sensing temperature; and a first voltage current converting circuit that responds to a temperature control voltage to generate a first output voltage; a first subtractor electrically coupled to the temperature sensor and the first voltage current conversion circuit, the first subtractor subtracting the reference voltage and the first output voltage To generate a second output voltage; a second voltage current conversion circuit, corresponding to the second output voltage, according to which is converted into a second current output; a third voltage current conversion circuit, electrically coupled to a fourth voltage current conversion a circuit, in response to a second reference voltage, generating a third current output; and a first load circuit including a plurality of resistors electrically coupled to the second voltage current conversion circuit, the first load circuit having an equivalent a resistor, the equivalent resistor is used to control the second current magnitude, wherein when the reference voltage is a predetermined value, the third current is subtracted from the second current. The power foldback type linear light emitting diode driving circuit of claim 1, further comprising: a second subtractor, responsive to a first reference voltage and a first input voltage, and operating to generate a first voltage; a comparison circuit, receiving a fourth reference voltage and a fifth reference voltage, and comparing the fourth reference voltage and the fifth reference voltage with the first input voltage, thereby outputting the fourth comparison voltage and the a fifth comparison voltage; a second load circuit electrically coupled to the comparison circuit for responsive to the fourth comparison voltage and the fifth comparison voltage to determine an equivalent resistance, the equivalent resistance determining a conversion current And a fifth voltage-current conversion circuit that responds to the first voltage of the second subtractor output and The switching current of the equivalent resistance of the second load circuit is processed by a set voltage of a third voltage current converting circuit to output a voltage drop voltage; and a fourth voltage current converting circuit converts the voltage drop into one Drive current. The power foldback type linear light emitting diode driving circuit of claim 2, wherein the second subtractor comprises a second current generating circuit, the second current generating circuit comprising: a first operational amplifier, responding to a third a reference voltage, according to which a third output voltage is generated; an input branch, one end coupled to the first operational amplifier, the input branch back to the third output voltage to generate a first input set current; and an output branch to map the first An input set current is generated to generate a first output set current. The power foldback type linear light emitting diode driving circuit of claim 3, wherein the input branch comprises a first transistor and a third transistor. The power foldback linear light emitting diode driving circuit of claim 3, wherein the output branch comprises a second transistor. The power foldback type linear light emitting diode driving circuit of claim 2, wherein the comparing circuit comprises: a second comparator, corresponding to the fourth reference voltage and the first input voltage, generating a fourth at the output end An output voltage, the second comparator is electrically coupled to one of the eighth transistors of the second load circuit; and a third comparator that returns a fifth reference voltage and the first input voltage to generate an output at the output end The fifth output voltage is electrically coupled to the plurality of ninth transistors in the second load circuit. The power foldback type linear light emitting diode driving circuit of claim 2, wherein the second subtractor comprises a third current generating circuit, the third current generating circuit comprising: a fourth operational amplifier, which is first Input voltage, according to which a sixth output voltage is generated; An input branch, one end coupled to the comparison circuit, the input branch back to the sixth output voltage to generate a second input set current; and an output branch to map the second input set current for generating the second output set current The second output setting current flows through a resistor to generate the first voltage. The power foldback type linear light emitting diode driving circuit of claim 7, wherein the input branch comprises a fourth transistor and a sixth transistor. The power foldback linear light emitting diode driving circuit of claim 7, wherein the output branch comprises a fifth transistor. The power-return type linear light-emitting diode driving circuit of claim 2, wherein the fifth voltage-current converting circuit comprises: a seventh transistor, the output end is electrically coupled to the second load circuit; and a fifth The operational amplifier is electrically coupled to the third current generating circuit and the second load circuit, and the output end is electrically coupled to the gate of the seventh transistor for controlling the current of the seventh transistor. The power-return type linear light-emitting diode driving circuit of claim 2, wherein the second load circuit comprises: a third resistor; a first load comprising an eighth transistor and a plurality of the first a first resistor connected to the crystal, wherein the switch of the eighth transistor is controlled by the fourth output voltage; and a second load comprising a plurality of ninth transistors and a plurality of second connected to the ninth transistor And a resistor, wherein the switches of the plurality of ninth transistors are controlled by the fifth output voltage.