TWI445440B - Driving circuit - Google Patents

Description

Drive circuit

The invention relates to a driving circuit, in particular to a driving circuit with a constant voltage and steady current function.

At present, the world's annual energy accounts for 14% of electricity, and in the proportion of electricity use, the proportion of lighting is as high as 22%. Therefore, under the current trend of global energy conservation and carbon reduction, the influence of lighting plays an important role.

Today's common lighting sources are dominated by incandescent and fluorescent lamps. Although the incandescent lamp has low cost, it has the disadvantages of high energy consumption, low luminous efficiency and high heat generation, and does not conform to the current trend of global energy saving and carbon reduction. The fluorescent tube is made of glass and has sockets at both ends to connect the power supply and fix the position of the fluorescent tube. Unlike incandescent lamps, the fluorescent tube must be provided with a ballast (also known as a "stabilizer") that, in conjunction with the starter, produces an instantaneous high voltage that ionizes the gas to illuminate the fluorescent lamp. The advantages of fluorescent lamps are low cost and good luminous efficiency. But this product is also accompanied by some usage problems, such as: flashing, warming up, etc. The flashing frequency of the fluorescent lamp is related to the frequency of the driving voltage. Although it is not easy for the human eye to directly detect the flickering of the fluorescent lamp, these flickers may cause a fan effect in some environments, which may cause limitations and influences on some application environments. The warm-up of the fluorescent lamp causes a change in brightness at the beginning of the lighting and after a period of use. Therefore, the characteristics of long life, high luminous efficiency, and fast brightness of the light-emitting diode are regarded as the main sources of illumination and illumination for the next generation.

Light-emitting diodes can be used in a wide range of lighting applications, including indoor lighting, outdoor lighting, advertising signs, and backlight modules for electronic products. In the above application fields, the high cost and heat dissipation problems of the backlighting of the LED backlight are rapidly improving, and the overall penetration rate will continue to increase rapidly in the future. With the replacement of the current illumination source by the light-emitting diodes, how to appropriately drive the light-emitting diode as a light source and provide appropriate protection, so that the light-emitting diode can exert its characteristics and improve the safety of use has become today Important topic.

In order to enable the illuminating diode to provide stable illuminating, corresponding to different driving modes, the present invention enables the illuminating diode to provide stable illuminating by means of current control and voltage feedback. In order to avoid any circuit problems that may be encountered in the use of the LED driving circuit, the present invention additionally provides a protection function to occur in a problem sufficient to affect the normal operation of the circuit, and to provide protection against further damage of the circuit.

To achieve the above object, the present invention provides a driving circuit including a power supply circuit, a transistor switching unit, and a feedback control circuit. A power supply circuit is used to provide a power to drive a load. The transistor switch unit has at least one load coupling end for coupling a load to adjust a current flowing through the load. The feedback control circuit controls the amount of power provided by the power supply circuit according to the potential of the at least one load coupling end. The feedback control circuit includes an error amplifying circuit and a feedback control switch. The error amplifying circuit generates an error amplification signal according to the potential of the at least one load coupling end, and the feedback control switch is coupled to one output end of the error amplifying circuit. Switching between a conductive state and an off state according to a dimming signal.

The invention also provides another driving circuit comprising a power supply circuit, a transistor switching unit and a feedback control circuit. A power supply circuit is used to provide a power to drive a load. The transistor switch unit has at least one load coupling end for coupling a load to adjust a current flowing through the load. The feedback control circuit controls the amount of power provided by the power supply circuit according to the potential of the at least one load coupling end. The feedback control circuit includes a feedback signal generating circuit and a feedback control switch, and the feedback signal generating circuit is coupled to the transistor switching unit through the feedback control switch to generate a potential according to the potential of the at least one load coupling end. The feedback control switch is coupled to the feedback signal generation circuit to switch between a conduction state and an off state according to a dimming signal.

In an embodiment of the present invention, the feedback control circuit determines whether any of the potentials of the load coupling terminals are lower than a first predetermined potential value or higher than a second potential when the feedback control switch is in an on state. When the value is, the control circuit stops the power supply circuit to supply power to protect the driving circuit.

The above summary and the following detailed description are exemplary in order to further illustrate the scope of the claims. Other objects and advantages of the present invention will be described in the following description and drawings.

Referring to the first figure, there is shown a circuit diagram of a driving circuit according to a first preferred embodiment of the present invention. The driving circuit includes a feedback control circuit 100, a transistor switching unit 170, and a power supply circuit 160 for driving a load 150. In this embodiment, the load 150 is a light emitting diode module having a plurality of light emitting diodes connected in series. The power supply circuit 160 is coupled to an input power source Vin to convert (eg, boost or step down) the power of the input power source Vin according to a control signal Sc to output an output voltage Vout to drive the LED of the load 150. Group glow. In the present embodiment, the power supply circuit 160 is a DC-DC converter circuit including an inductor L, a transistor switch SW, a rectifying diode D, and an output capacitor C. One end of the inductor L is coupled to the input power source Vin, the other end is coupled to one end of the transistor switch SW, and the other end of the transistor switch SW is grounded. One end of the output capacitor C is coupled to the connection point of the inductor L and the transistor switch SW through the rectifying diode D, and the other end is grounded. The transistor switch unit 170 is a current control circuit coupled to the load 150 to regulate the magnitude of the current flowing through the load 150. The transistor switch unit 170 includes a transistor switch 174 and a current control circuit 172. The transistor switch has a current feedback terminal, a control terminal and a load coupling end, wherein the current feedback terminal is coupled to a current detecting resistor Ri, the load coupling end is coupled to the load 150, and the control terminal is coupled to the current control circuit. The output of 172. The current control circuit 172 is an amplifier that receives a reference voltage Vi non-invertedly, and the inverting terminal is coupled to the current feedback terminal of the transistor switch 174 to control the transistor switch according to the potential of the current feedback terminal and the reference voltage Vi. The state of 174 controls the equivalent resistance of transistor switch 174, thereby regulating the amount of current flowing through transistor switch 174. The current control circuit 172 simultaneously receives a dimming signal DIM. When the dimming signal DIM represents "ON" (which represents the LED of the load 150), the current control circuit 172 regulates the flow through the transistor switch 174 as described above. The current is sized, and when the dimming signal DIM represents "OFF" (representing that the LED module of the load 150 stops emitting light), the transistor switch 174 is turned off.

The feedback control circuit 100 is coupled to the load coupling end of the transistor switch 174 of the transistor switch unit 170 to receive the feedback signal FB representing one of the voltage across the transistor switch unit 170, that is, according to the potential of the load coupling end. The amount of power provided by the power supply circuit 160. The feedback control circuit 100 includes a duty cycle control circuit 110, an error amplification circuit 102, a compensation circuit 104, and a feedback control switch 106. The error amplifying circuit 102 generates an error amplification signal according to the feedback signal FB and a reference voltage signal Vr to the compensation circuit 104 for generating a feedback processing signal Ser. The feedback control switch 106 is coupled between the output compensation circuit 104 of the error amplifying circuit 102 and switches between an on state and an off state according to a dimming signal. When the dimming signal DIM represents "ON", the feedback control switch 106 is in an on state to transmit an error amplification signal to the compensation circuit to generate a feedback processing signal Ser. When the dimming signal DIM represents "OFF", the feedback control switch 106 is in an off state to stop transmitting the error amplification signal to the compensation circuit, so that the capacitor 116 maintains the level of the feedback processing signal Ser. The duty cycle control circuit 110 includes a pulse width modulator 120 and a driving unit 130. The pulse width modulator 120 can be a comparator, the inverting terminal receives a ramp signal, and the non-inverting terminal is coupled to the compensation circuit 104 to receive the feedback processing signal Ser, and accordingly generates a pulse width modulation signal S2. To the drive unit 130. The driving unit 130 receives the dimming signal DIM and the pulse width modulation signal S2. When the dimming signal DIM represents "ON", the driving unit 130 generates a control signal Sc according to the pulse width modulation signal S2 to control the on and off of the transistor switch SW in the power supply circuit 160 to adjust the power supply circuit 160 to provide power. size. When the dimming signal DIM represents "OFF", the driving unit 130 controls the power supply circuit 160 to stop supplying power.

Longitudinally, when the dimming signal DIM represents "OFF", the transistor switch 174 in the transistor switch unit 170 is turned off to stop the load 150 from flowing current and avoid continuously consuming the power stored in the output capacitor C. At this time, the power supply circuit 160 stops supplying power, so that the output voltage Vout maintains the voltage at the time of stable operation. In addition, the feedback control switch 106 in the feedback control circuit 100 is in the off state at this time, so that the potential of the feedback processing signal Ser is maintained at the potential of the stable operation. When the dimming signal DIM is turned to represent "ON", the load 150 can immediately flow through the current during steady operation, and the driving unit 130 can immediately provide the control signal Sc with a stable duty cycle (Duty Cycle). Compared with the conventional LED driving circuit, the driving circuit of the invention can return to a stable state more quickly during the dimming process, and the dimming is more accurate.

2 is a schematic circuit diagram of a light emitting diode driving circuit according to a second preferred embodiment of the present invention. Comparing the embodiment and the embodiment shown in the first figure, the main difference is that an error amplifying circuit 102, a compensation circuit 104 and a feedback control switch 106 in the feedback control circuit 100 are replaced by a feedback signal generating circuit. described as follows.

The feedback control circuit 100 includes a duty cycle control circuit 110, a feedback control unit 112, a feedback control switch 106, and a feedback signal generation circuit. The feedback signal generation circuit includes a charging unit, a discharge unit, and a Capacitor 116. The charging unit has a first current source I1 and a charging switch 114. The first current source I1 is coupled to the capacitor 116 through the charging switch 114 to provide a charging current to charge the capacitor 116. The discharge unit has a second current source I2 coupled to the capacitor 116 to provide a discharge current to discharge the capacitor 116. In this embodiment, the feedback control unit 112 is a comparator, and the non-inverting terminal receives a reference voltage signal Vr, and the inverting terminal receives the feedback signal FB to control the turning on and off of the charging switch 114 accordingly. The feedback control switch 106 is coupled to the capacitor 116 to the first current source I1 and the second current source I2, and is switched between an on state and an off state according to a dimming signal DIM. When the dimming signal DIM represents "ON", the feedback control switch 106 is in an on state, so that the first current source I1 and the second current source I2 can discharge and charge the capacitor 116, so that the potential of the capacitor 116 is based on the feedback signal FB. Adjust to generate a feedback processing signal Ser. When the dimming signal DIM represents "OFF", the feedback control switch 106 is in an off state to stop the first current source I1 and the second current source I2 to the capacitor 116, so that the capacitor 116 maintains the potential of the feedback processing signal Ser at this time.

Therefore, the driving circuit of the present embodiment can maintain the level of the feedback processing signal Ser when the dimming signal DIM stands for "OFF" as in the driving circuit shown in the first figure, and the dimming signal DIM is converted to "ON". At this time, the drive unit 130 can immediately provide the control signal Sc with a stable duty cycle. Therefore, the driving circuit of this embodiment also has the advantage of precise dimming.

In addition to the DC-to-DC boost converter circuit in the above embodiment, the drive circuit of the present invention may have other power supply circuits having a DC voltage output function, such as a flyback conversion circuit, a forward conversion circuit, and the like. The following is a description of the forward conversion circuit.

Referring to the third figure, there is shown a circuit diagram of a driving circuit according to a third preferred embodiment of the present invention. The LED driving circuit includes a feedback control circuit 200, a transistor switching unit 270, and a power supply circuit 260 for driving a LED module 250. The light emitting diode module 250 has a plurality of light emitting diode strings and the light emitting diode strings are connected in parallel with each other. The power supply circuit 260 is coupled to an AC input power source VAC through a bridge rectifier BD to convert the power of the AC input power source VAC according to a control signal Sc to drive the LED module 250 to emit light. In the present embodiment, the power supply circuit 260 is a forward conversion circuit including a transformer T, a transistor switch SW, rectifying diodes D1, D2, and an output capacitor C. One end of the primary side of the transformer T is coupled to the flow input power supply VAC, the other end is coupled to one end of the transistor switch SW, and the other end of the transistor switch SW is grounded through a current detecting resistor. One end of the output capacitor C is coupled to the secondary side of the transformer T through the rectifying diodes D1 and D2 and is grounded at the other end.

In order to ensure that any of the light-emitting diodes in the light-emitting diode module 250 is The plurality of load coupling terminals DS1~DSN of the transistor switch unit 270 are coupled to the plurality of light-emitting diode strings in the LED module 250 to make a plurality of light-emitting diodes The current of the polar body string is stabilized at a predetermined current value. In this embodiment, each of the plurality of load coupling terminals DS1 DSDSN is coupled to a current control circuit. The current control circuit includes a transistor switch and a current control circuit as in the foregoing embodiment. In actual implementation, the transistor switching unit 270 can use a current mirror or other current source with a transistor as a control, and is not limited to the circuit proposed in this embodiment. Since the driving voltage required for each string of light-emitting diodes to flow through a predetermined current value is not the same, the voltage levels of the plurality of load coupling terminals DS1 to DSN are different. In order to enable the load coupling terminals DS1~DSN of the transistor switch unit 270 to operate normally, the current flowing through can be controlled to a predetermined current value, and the position of the load coupling terminals DS1~DSN must be maintained at a first predetermined schedule. Potential value. To this end, the present invention can add a first extreme voltage detecting circuit 240, coupled to a plurality of load coupling terminals DS1~DSN, and generate a first feedback signal FB1 according to the lowest potential between the load coupling terminals DS1~DSN. . The first extreme voltage detecting circuit 240 can include a plurality of diodes, wherein the negative ends are respectively coupled to the plurality of load coupling terminals DS1 DSDSN, and the positive ends thereof are connected to each other and coupled to a driving power source through a resistor. VCC. In this way, the diode corresponding to the load coupling end having the lowest potential can be turned on, and the voltage across the other diodes is insufficient to be turned on, so that the potential of the first feedback signal FB1 is the load coupling end. The lowest potential plus the forward bias of the diode. In addition, the reference voltages Vi1~ViN received by the current control circuit in the transistor switch unit 270 may be different to correspond to the LEDs of different current driving requirements. Of course, the reference voltages Vi1~ViN may also be the same, so that the light emitting diodes Any of the light-emitting diodes in the body module 250 flow through the same current.

The feedback control circuit 200 includes a duty cycle control circuit 210 and a feedback signal generation circuit. The feedback signal generating circuit includes a feedback control unit 212, and the feedback control unit 212 can be a comparator. The non-inverting terminal receives a first reference voltage signal Vr1, and the inverting terminal receives the first feedback signal FB1. And the signal formed by the third reference voltage signal Vr3, that is, the level of the third reference voltage signal Vr3 minus the level of the first feedback signal FB1, wherein the third reference voltage signal Vr3 is higher than the first reference The voltage signal Vr1 is at the level. When any of the levels of the load coupling terminals DS1 DSDSN is lower than the first predetermined potential value, the level of the signal received by the inverting terminal of the feedback control unit 212 is lower than the first reference voltage signal Vr1. The bit feedback control unit 212 generates a feedback processing signal Ser. The duty cycle control circuit 210 includes an SR flip-flop 224 and a driving unit 230. The reset terminal R of the SR flip-flop 224 receives a periodic pulse signal, and the set terminal S receives the feedback processing signal Ser. Therefore, when the feedback control unit 212 generates the feedback processing signal Ser, the SR flip-flop 224 is triggered to generate the pulse width modulation signal S2 from the output terminal Q to the driving unit 230. The driving unit 230 receives a dimming signal DIM and a pulse width modulation signal S2, and the transistor switching unit 270 also receives the dimming signal DIM. When the dimming signal DIM represents "ON", the driving unit 230 generates a control signal Sc according to the pulse width modulation signal S2 to control the on and off of the transistor switch SW in the power supply circuit 260 to adjust the AC input power source VAC to provide power to The power supply circuit 260 provides the magnitude of the power, and the transistor switch unit 270 also causes the power supply circuit 260 to supply power to the LED module 250 to drive its illumination. When the dimming signal DIM represents "OFF", the driving unit 230 controls the power supply circuit 260 to stop the AC input power VAC from supplying power to the power supply circuit 260, and the transistor switching unit 270 also stops the power supply circuit 260 from supplying power to the light emitting diode 260. The polar body module 250. In order to avoid any possible misjudgment of the feedback control circuit 200 by receiving the first feedback signal FB1, the feedback signal generation circuit may further include a feedback control switch 205 coupled to the first extreme voltage detection circuit. The 240 and feedback control unit 212 is turned off when the dimming signal DIM stands for "OFF". Because the level of the third reference voltage signal Vr3 is subtracted from the level of the first feedback signal FB1, the feedback control unit 212 will not output the feedback processing signal Ser.

Since the transistor in the transistor switching unit 270 has a withstand voltage limit, when the potential of any of the load coupling terminals DS1 to DSN is higher than the withstand voltage value, the transistor switching unit 270 is damaged. For example, when any of the LED arrays in the LED module 250 is open, the feedback control circuit 200 continuously increases the output voltage of the power supply circuit 260 in an attempt to raise the potential of the corresponding load coupling terminal to a predetermined voltage value. At this time, the potential of the load coupling end corresponding to the other LED strings is too high; or, when a part of the LEDs in the LED string is short-circuited, the short-circuited LED crosses on the string. The voltage drop causes the potential of the load coupling terminal corresponding to the LED string to be too high. To avoid the above problem, a second extreme voltage detecting circuit 245 can be added, coupled to the plurality of load coupling terminals DS1 DSDSN, and a second feedback signal FB2 is generated according to the highest potential between the load coupling terminals DS1 DSDSN. . The voltage detecting circuit 245 can include a plurality of diodes, wherein the positive ends are respectively coupled to the plurality of load coupling terminals DS1 DSDSN, and the negative terminals thereof are connected to each other and grounded through a resistor. The feedback control circuit 200 further includes an overvoltage comparator 208. The non-inverting terminal receives the second feedback signal FB2, and the inverting terminal receives a second reference voltage signal Vr2. When the potential of the second feedback signal FB2 is higher than the second reference voltage signal Vr2, the overvoltage comparator 208 will output an overvoltage protection signal OVP.

In addition, when the circuit is in normal operation, the potentials of the plurality of load coupling terminals DS1 to DSN can be maintained at or above a predetermined voltage value. When the potential of any of the load coupling ends is lower than the predetermined voltage value and cannot rise back to the predetermined voltage value, it represents a circuit abnormality. However, when the circuit is started or dimmed, the potential of the plurality of load coupling terminals DS1 to DSN will be temporarily lower than the predetermined voltage value. In order to avoid misjudgment and eliminate the above circuit abnormality, a timing circuit 203 can be coupled to the feedback control unit 212 when the first feedback signal FB1 continues to be lower than the first reference voltage signal Vr1 for a predetermined time. At the time of the cycle, that is, when the feedback control unit 212 continues to output the high level for a predetermined period of time, the timer circuit 203 outputs an under-low protection signal S1. Of course, the timing circuit 203 can further receive an activation signal or a dimming signal to determine the timing of the timing start according to the activation signal or the dimming signal, wherein the activation signal is a signal indicating that the driving circuit starts to start. Since the power supply capability of the power supply circuit varies with the design of different circuits, the length of the predetermined time period required may be different. In order to cooperate with various circuit designs, if the feedback control circuit 200 of the present invention is a single integrated circuit, an additional set foot can be added, and the predetermined time period can be set by an external resistor or capacitor (not shown).

The feedback control circuit 200 further includes a protection unit 235 coupled to the timing circuit 203, the overvoltage comparator 208, and the driving unit 230. When receiving any of the overvoltage protection signal OVP and the low protection signal S1, a protection signal Prot is controlled to drive the driving unit 230 to stop generating the control signal Sc to achieve the protection function. In addition, the protection unit 235 can further receive the current detection signal Ise generated by the current detecting resistor. When the current detection signal Ise continues to be low for more than a predetermined time, the circuit representing the input end of the power supply circuit 260 is open, and the protection unit 235 can also output the protection signal Prot to control the driving unit 230 to stop generating the control signal Sc. Or when the current detection signal Ise exceeds an overcurrent protection value, the circuit representing the input end of the power supply circuit 260 is short-circuited. At this time, the protection unit 235 can output an error signal Fault to notify the circuit of the previous stage to stop supplying power to the light-emitting diode. The pole drive circuit prevents more components from being damaged by short circuits.

Please refer to the fourth figure, which is a circuit diagram of a light emitting diode driving circuit according to a fourth preferred embodiment of the present invention. Comparing the embodiment shown in this embodiment and the third figure, the main difference is that the power supply circuit 260 is a flyback conversion circuit, and the feedback control mode of the feedback control circuit 200 is also different, as explained below.

The power supply circuit 260 is coupled to an AC input power source VAC through a bridge rectifier BD to convert the power of the AC input power source VAC according to a control signal Sc to drive the LED module 250 to emit light. In the present embodiment, the power supply circuit 260 is a flyback conversion circuit including a transformer T, a transistor switch SW, a rectifying diode D, and an output capacitor C. One end of the primary side of the transformer T is coupled to the flow input power supply VAC, the other end is coupled to one end of the transistor switch SW, and the other end of the transistor switch SW is grounded through a current detecting resistor. One end of the output capacitor C is coupled to the secondary side of the transformer T through the rectifying diode D and the other end is grounded.

The feedback control circuit 200 includes a duty cycle control circuit 210 and a feedback signal generation circuit. The feedback signal generating circuit includes a feedback control unit 212, a charging unit, a discharging unit and a capacitor 216 to generate a feedback processing signal Ser. The charging unit has a first current source I1, a third current source I3, and a third switch 217. The first current source I1 is coupled to the capacitor 216 to provide a basic charging current to charge the capacitor 216, and the third current source I3 is coupled to the capacitor 216 through the third switch 217 to provide a charging current to charge the capacitor 216. The discharge unit has a second current source I2 and a second switch 215. The second current source I2 is coupled to the capacitor 216 through the second switch 215 to provide a discharge current to discharge the capacitor 216. The current of the first current source I1 is smaller than the current of the second current source I2 and the third current source I3. The feedback control unit 212 can be a comparator whose inverting terminal receives a first reference voltage signal Vr1, and the non-inverting terminal receives the first feedback signal FB1 to control the on and off of the second switch 215 accordingly. When the level of the first feedback signal FB1 is lower than the level of the first reference voltage signal Vr1, the feedback control unit 212 outputs a low level signal to turn off the second switch 215. At this time, the first current source I1 charges the capacitor 216 to increase the voltage of the capacitor 216. When the level of the first feedback signal FB1 is higher than the level of the first reference voltage signal Vr1, the feedback control unit 212 outputs a high level signal to turn on the second switch 215, so that the second current source I2 discharges the capacitor 216. The first current source I1 simultaneously charges the capacitor 216. Since the current of the first current source I1 is smaller than the current of the second current source I2, the voltage of the capacitor 216 will decrease. The duty cycle control circuit 210 includes a pulse width modulator 220 and a drive unit 230. The pulse width modulator 220 includes a comparator 222 and an SR flip-flop 224. The non-inverting terminal of the comparator 222 is coupled to the capacitor 216 to receive the feedback processing signal Ser, and the inverting terminal receives the current detecting signal Ise. The set terminal S of the SR flip-flop 224 receives one of the periodic clock signals, and the reset terminal R is coupled to the comparator 222. When the SR flip-flop 224 receives the clock signal at the set terminal S, a pulse width modulation signal S2 is generated from the output terminal Q to the driving unit 230. The driving unit 230 receives the pulse width modulation signal S2 and a dimming signal DIM to generate a control signal Sc to turn on the transistor switch SW of the power supply circuit 260. When the current flowing through the primary side of the transformer T rises so that the level of the current detecting signal Ise is higher than the voltage level of the capacitor 216, the comparator 222 outputs a signal of the high level to reset the SR flip-flop 224. The driving unit 230 stops generating the control signal Sc. At this time, the transistor switch SW of the power supply circuit 260 is turned off, and the energy stored in the transformer T is transmitted to the secondary side of the power supply circuit 260 to provide electric power to drive the LED module 250. Glowing.

In order to start the circuit or during the dimming process, the voltage of the capacitor 216 may rise rapidly to increase the transient response speed of the feedback control circuit 200. The feedback control circuit 200 controls the third switch 217 through the transient boost circuit 204. The transient boosting circuit 204 receives the start signal EN and the dimming signal DIM. When receiving the start signal EN dimming signal DIM is converted from "OFF" to "ON", the high level signal is output to turn on the third switch 217. When the third current source I3 and the first current source I1 simultaneously charge the capacitor 216, the voltage of the capacitor 216 rises rapidly. The transient boosting circuit 204 can set a predetermined length of time or turn off the third switch 217 according to the first feedback signal FB1, that is, the third switch 217 will be turned off after a fixed time; or when the load coupling end of the transistor switching unit 270 The third switch 217 is turned off when the lowest level in DS1~DSN reaches a predetermined level. The feedback control switch 206 is coupled between the capacitor 216 and the charging unit and the discharge unit. When the dimming signal DIM represents “OFF”, the feedback control switch 206 is in an off state to maintain the feedback processing generated by the capacitor 216. The signal is the standard of Ser.

In addition, in the overvoltage comparator 208 in this embodiment, the non-inverting terminal receives a third feedback signal FB3 instead of the second feedback signal FB2 in the embodiment shown in FIG. The third feedback signal FB3 is generated by a voltage detecting circuit 275 detecting the output voltage of the power supply circuit 260. When the output voltage of the power supply circuit 260 is higher than a predetermined protection value and the level of the third feedback signal FB3 is higher than the second reference voltage signal Vr2, the overvoltage comparator 208 outputs the overvoltage protection signal OVP. The protection unit 235 outputs a protection signal Prot to control the driving unit 230 to stop outputting the control signal Sc.

As described above, the present invention fully complies with the three requirements of the patent: novelty, advancement, and industrial applicability. The invention has been described above in terms of the preferred embodiments, and it should be understood by those skilled in the art that the present invention is not intended to limit the scope of the invention. It should be noted that variations and permutations equivalent to those of the embodiments are intended to be included within the scope of the present invention. Therefore, the scope of the invention is defined by the scope of the following claims.

100,200‧‧‧ feedback control circuit

102‧‧‧Error Amplifying Circuit

104‧‧‧Compensation circuit

106‧‧‧Feedback control switch

110, 210‧‧‧ work cycle control circuit

112, 212‧‧ ‧ feedback control unit

114‧‧‧Charge switch

116‧‧‧ Capacitance

120, 220‧‧‧ pulse width modulator

130‧‧‧ drive unit

150‧‧‧load

160, 260‧‧‧ power supply circuit

170, 270‧‧‧Crystal Switch Unit

172‧‧‧ Current Control Circuit

174‧‧‧Transistor Switch

203‧‧‧Timekeeping Circuit

208‧‧‧Overvoltage comparator

215‧‧‧second switch

217‧‧‧ third switch

222‧‧‧ comparator

224‧‧‧SR forward and reverse

230‧‧‧ drive unit

235‧‧‧protection unit

245‧‧‧Second extreme voltage detection circuit

240‧‧‧First extreme voltage detection circuit

250‧‧‧Lighting diode module

BD‧‧ ‧bridge rectifier

C‧‧‧ output capacitor

D, D1, D2‧‧‧ Rectifier

DIM‧‧‧ dimming signal

DS1~DSN‧‧‧Load coupling

Fault‧‧‧Error Signal

FB‧‧‧ feedback signal

FB1‧‧‧ first feedback signal

FB2‧‧‧ second feedback signal

FB3‧‧‧ third feedback signal

I1‧‧‧ first current source

I2‧‧‧second current source

I3‧‧‧ third current source

Ise‧‧‧ current detection signal

L‧‧‧Inductance

Prot‧‧‧ protection signal

OVP‧‧‧Overvoltage protection signal

Q‧‧‧output

R‧‧‧Reset

Ri‧‧‧current detection resistor

S‧‧‧Setting end

S1‧‧‧Low protection signal

S2‧‧‧ pulse width modulation signal

Sc‧‧‧ control signal

Ser‧‧‧Reply processing signal

SW‧‧•Chip switch

Vr‧‧‧ reference voltage signal

VAC‧‧‧AC input power

VCC‧‧‧ drive power supply

Vi‧‧‧reference voltage

Vin‧‧‧Input power supply

Vi1~ViN‧‧‧reference voltage

Vout‧‧‧ output voltage

Vr1‧‧‧ first reference voltage signal

Vr2‧‧‧ second reference voltage signal

Vr3‧‧‧ third reference voltage signal

T‧‧‧Transformer

The first figure is a circuit diagram of a driving circuit in accordance with a first preferred embodiment of the present invention.

The second figure is a circuit diagram of a driving circuit according to a second preferred embodiment of the present invention.

The third figure is a circuit diagram of a driving circuit in accordance with a third preferred embodiment of the present invention.

The fourth figure is a circuit diagram of a driving circuit according to a fourth preferred embodiment of the present invention.

100. . . Feedback control circuit

102. . . Error amplifier circuit

104. . . Compensation circuit

106. . . Feedback control switch

110. . . Work cycle control circuit

120. . . Pulse width modulator

130. . . Drive unit

150. . . load

160. . . Power supply circuit

170. . . Transistor switch unit

172. . . Current control circuit

174. . . Transistor switch

Vin. . . Input power

Sc. . . Control signal

Vout. . . The output voltage

L. . . inductance

SW. . . Transistor switch

D. . . Rectifier diode

C. . . Output capacitor

Ri. . . Current detecting resistor

Vi. . . Reference voltage

DIM‧‧‧ dimming signal

FB‧‧‧ feedback signal

Vr‧‧‧ reference voltage signal

Ser‧‧‧Reply processing signal

S2‧‧‧ pulse width modulation signal

Claims (11)

A driving circuit comprising: a power supply circuit for providing a power to drive a load; and a transistor switching unit having at least one load coupling end for coupling the load to adjust flow through a current of one of the loads; and a feedback control circuit for controlling the magnitude of the power provided by the power supply circuit according to the potential of the at least one load coupling end; wherein the feedback control circuit includes an error amplification circuit and a return a control switch, the error amplifying circuit generates an error amplification signal according to the potential of the at least one load coupling end, and the feedback control switch is coupled to the output end of the error amplifying circuit according to a dimming signal in a conducting state and Switch between an off state. The driving circuit of claim 1, wherein the transistor switching unit has a plurality of transistor switches and a plurality of current control circuits, each of the transistor switches having a control terminal, a current feedback terminal, and the The load coupling end, each current control circuit controls the state of the corresponding transistor switch according to the potential of the current feedback terminal corresponding to the transistor switch to control the current flowing through the corresponding transistor switch. The driving circuit of claim 1 or 2, wherein the feedback control circuit further comprises a compensation circuit for storing the error amplification signal to generate a feedback processing signal, wherein the feedback control switch is in the The error amplification signal is transmitted to the compensation circuit when the conduction state is in the off state, and the error amplification signal is stopped from being transmitted to the compensation circuit. The driving circuit of claim 3, wherein the feedback control circuit further comprises a duty cycle control circuit for controlling the power supply circuit to convert power of an input power source to provide the power according to the feedback processing signal. The duty cycle control circuit stops the power supply circuit from performing power conversion when the feedback control switch is in the off state. The driving circuit of claim 2, wherein the plurality of current control circuits further cut off the plurality of transistor switches according to a dimming signal. The driving circuit of claim 2, wherein the feedback control circuit determines whether any of the potentials of the load coupling ends are lower than the first predetermined when the feedback control switch is in the conducting state When the potential value is higher than the second potential value, if yes, the feedback control circuit stops the power supply circuit from performing power conversion on the power of an input power source. A driving circuit comprising: a power supply circuit for providing a power to drive a load; and a transistor switching unit having at least one load coupling end for coupling the load to adjust flow through And a feedback control circuit for controlling a power supply provided by the power supply circuit according to the potential of the at least one load coupling end; wherein the feedback control circuit includes a feedback signal generation circuit and a feedback control circuit, the feedback signal generation circuit is coupled to the transistor switch unit through the feedback control switch to generate a feedback processing signal according to the potential of the at least one load coupling end, the feedback control switch coupling The feedback signal generating circuit is switched between an on state and an off state according to a dimming signal. The driving circuit of claim 7, wherein the transistor switching unit has a plurality of transistor switches and a plurality of current control circuits, each of the transistor switches having a control terminal, a current feedback terminal, and the The load coupling end, each of the current control circuits controls a state of the corresponding transistor switch according to a potential of the current feedback terminal corresponding to the transistor switch to control a current flowing through the corresponding transistor switch. The driving circuit of claim 8, wherein the feedback control circuit The circuit further includes a duty cycle control circuit for controlling the power supply circuit to convert power of an input power source to provide the power according to the feedback processing signal, wherein the duty cycle control circuit is in the off state when the feedback control switch is in the off state The power supply circuit is stopped for power conversion. The driving circuit of claim 8, wherein the plurality of current control circuits further cut off the plurality of transistor switches according to a dimming signal. The driving circuit of claim 8, wherein the feedback control circuit determines whether any of the potentials of the load coupling ends are lower than the first predetermined when the feedback control switch is in the conducting state When the potential value is higher than the second potential value, if yes, the feedback control circuit stops the power supply circuit from performing power conversion on the power of an input power source.