TWI731368B - Light source driving apparatus and current adjusting method thereof - Google Patents

Abstract

A light source driving apparatus including a primary side and a secondary side is provided. The light source driving apparatus includes an isolated current sensing circuit, a dimming circuit, an independent voltage source, and a feedback circuit. The isolated current sensing circuit is coupled to the secondary side, and samples an output current of the light source driving apparatus by electromagnetic coupling to generate a current sensing signal. The dimming circuit receives a dimming input signal, and provides a reference controlled-current signal according to the dimming input signal and based on an operating voltage. The independent voltage source is configured to generate the operating voltage. Based on the operating voltage, the feedback circuit provides a feedback signal according to the current sensing signal and the reference controlled-current signal for adjusting the output current of the light source driving apparatus.

Description

Light source driving device and current adjustment method thereof

The present invention relates to a light source driving device, in particular to a light source driving device with adjustable output current.

With the development of lighting technology, light-emitting devices with dimming functions have been widely used in daily life to meet the lighting needs of different application scenarios. The light emitting device is usually equipped with a driving circuit for dimming operation. For example, when the light emitting element of the light emitting device is a light emitting diode (LED), the current output to the LED can be adjusted through the LED driving circuit to control the brightness of the LED.

When the conventional LED driving circuit performs a dimming operation, it usually uses a secondary-side resistor sampling current control method to adjust the brightness of the LED. However, when the dimming signal is low, for example, the dimming ratio is 1%, the current sampling through the secondary-side resistor will cause the sampling signal to be too low, which makes the LED driving circuit unable to accurately control the constant current output.

In addition, based on the regulations (IEC 61347-1: 2015, 3 ^rd edition), the dimming signal must be isolated from the output end of the LED drive circuit (that is, isolated from the secondary side signal), so the conventional LED drive circuit usually Two independent voltage sources must be set up, and the dimming output signal is provided to the current feedback circuit end through the optocoupler, thereby achieving the purpose of signal isolation and current feedback.

On the other hand, when using an LED driving circuit to perform three-in-one dimming, the conventional three-in-one dimming method usually sets the dimming frequency of the pulse width modulation (PWM) signal within a specific range Therefore, due to the different design of the frequency of the PWM signal in the conventional LED driving circuit, it is sometimes necessary to select a high-response optocoupler to achieve a more complete dimming output signal, thereby achieving lower PWM signal distortion (duty). loss).

The invention provides a light source driving device and a current adjustment method thereof, which can accurately control the output of a constant current under a low dimming current.

An embodiment of the present invention provides a light source driving device having a primary side and a secondary side. The light source driving device includes an isolated current detection circuit, a dimming circuit, an independent voltage source, and a feedback circuit. The isolated current detection circuit is coupled to the secondary side, and uses electromagnetic coupling to sample the output current of the light source driving device to generate a current detection signal. The dimming circuit receives the dimming input signal, and provides a reference current control signal based on the operating voltage and according to the dimming input signal. The independent voltage source generates the operating voltage. The feedback circuit is coupled between the isolated current detection circuit and the primary side of the light source driving device, and the feedback circuit is coupled to the independent voltage source and the dimming circuit. The feedback circuit performs a feedback operation based on the operating voltage, and provides a feedback signal based on the current detection signal and the reference current control signal. The light source driving device adjusts the output current of the light source driving device according to the feedback signal.

Another embodiment of the present invention provides a current adjustment method of a light source driving device. The current adjustment method includes: sampling the output current of the light source driving device through electromagnetic coupling to generate a current detection signal; receiving a dimming input signal, and providing a reference current control signal according to the dimming input signal based on the operating voltage; The operating voltage is generated by an independent voltage source; and the feedback operation is performed based on the operating voltage, and the feedback signal is provided according to the current detection signal and the reference current control signal to adjust the output current of the light source driving device.

Based on the foregoing, in the embodiments of the present invention, the light source driving device can achieve the signal isolation effect required by regulations by arranging an isolated current detection circuit and a single independent voltage source. In addition, the output current of the light source driving device is sampled through the isolated current detection circuit, and the output of constant current can be accurately controlled under low dimming current. Furthermore, since the feedback circuit and the dimming circuit in the light source driving device only need to operate through a single independent voltage source, the light source driving device of the present invention does not need to be provided with two sets of independent voltage sources.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

100, 200A, 200B, 200C, 200D: light source driving device

101: primary side

102: secondary side

110, 210: Isolated current detection circuit

120, 220: dimming circuit

130, 230: independent voltage source

140, 240: feedback circuit

201: AC power

221: dimming control circuit

222, 232: Voltage divider circuit

231: auxiliary power supply

241: first comparator

242: second comparator

243: Optical coupling element

2431: LED

2432: optical coupling transistor

250: voltage conversion circuit

251: Pulse Width Modulation Signal Controller

252: voltage converter

260: signal processing circuit

270: Rectifier circuit

280: Light-emitting element

C1: Input

C2: output

CCR: Reference current control signal

CVR: Reference voltage control signal

Dim: dimming input signal

D1: The first diode

D2: The second diode

FB: Feedback signal

Iout: output current

NA1: Primary side auxiliary coil

NA2: Secondary side auxiliary coil

NP: Primary side coil

NS: Secondary side coil

PWM: Pulse width modulation signal

R1~R6: resistance

SGND: Ground voltage level

SI: Current detection signal

SV: Voltage detection signal

S310, S320, S330, S340: method steps

T: Transformer

VCC: Operating voltage

VCS: Voltage adjustment signal

Vin: input voltage

Vout: output voltage

FIG. 1 is a circuit block diagram of a light source driving device according to an embodiment of the invention.

2A to 2D respectively show circuit block diagrams of light source driving devices according to different embodiments of the present invention.

FIG. 3 is a schematic flowchart of a current adjustment method of a light source driving device according to an embodiment of the present invention.

FIG. 1 is a circuit block diagram of a light source driving device 100 according to an embodiment of the invention. As shown in FIG. 1, the light source driving device 100 has a primary side 101 and a secondary side 102. The light source driving device 100 can receive an input voltage Vin, and convert the input voltage Vin into an output current Iout and an output voltage Vout, so as to serve as a driving power source for a back-end light emitting device (not shown). In order to achieve the purpose of dimming control, the light source driving device 100 of FIG. 1 may include an isolated current detection circuit 110, a dimming circuit 120, an independent voltage source 130, and a feedback circuit 140.

As shown in FIG. 1, the isolated current detection circuit 110 is coupled to the secondary side 102 of the light source driving device 100. The isolated current detection circuit 110 can sample the output current Iout of the light source driving device 100 through electromagnetic coupling to generate the current detection signal SI. For example, the isolated current detection circuit 110 may be a current transformer, and the current transformer may sense the output current Iout of the light source driving device 100 through electromagnetic coupling to generate the current detection signal SI.

Please refer to FIG. 1 again, the dimming circuit 120 can receive the dimming input signal Dim, and based on the operating voltage VCC, to provide according to the dimming input signal Dim Refer to the current control signal CCR. In other words, the dimming circuit 120 only needs to use a single power source (operating voltage VCC) to provide the reference current control signal CCR according to the dimming input signal Dim. In some embodiments, the dimming input signal Dim can be a DC voltage signal or a pulse width modulation signal, and the dimming circuit 120 can generate the reference current control signal CCR by changing the magnitude of the DC voltage or the duty cycle of the pulse wave.

The independent voltage source 130 can be used to generate the operating voltage VCC. The feedback circuit 140 is coupled between the isolated current detection circuit 110 and the primary side 101 of the light source driving device 100, and the feedback circuit 140 is coupled to the independent voltage source 130 and the dimming circuit 120.

For example, the feedback circuit 140 can use the operating voltage VCC as a power source, and receive the current detection signal SI provided by the isolated current detection circuit 110 and the reference current control signal CCR provided by the dimming circuit 120. The feedback circuit 140 can provide the feedback signal FB according to the current detection signal SI and the reference current control signal CCR. The light source driving device 100 can adjust the output current Iout of the light source driving device 100 according to the feedback signal FB.

In the embodiment of FIG. 1, the current detection signal SI is sampled through the isolation method of the isolated current detection circuit 110, and the dimming circuit 120 operates according to the operating voltage VCC generated by the independent voltage source 130, so the present invention There is no need to provide another set of isolated voltage sources to achieve the effect of isolating the dimming circuit 120 and the secondary side 102 of the light source driving device 100 from each other, which meets the requirements of laws and regulations. In addition, through the design of FIG. 1, the dimming circuit 120 does not need to be provided with an additional isolation element (such as an optocoupler) to provide the reference current control signal CCR to the feedback circuit 140, so the cost reduction effect can be achieved. Furthermore, due to the feedback circuit in the light source driving device 100 The dimming circuit 140 and the dimming circuit 120 only need to operate through a single independent voltage source 130, so the light source driving device 100 of the present invention does not need to be separately provided with two sets of isolated voltage sources.

Incidentally, the current detection signal SI obtained by the isolated current detection circuit 110 can maintain a higher resolution even at a lower dimming signal for feedback control. For example: assuming that the output current Iout of the light source driving device 100 is 2.8A, the control voltage that can be generated through the conversion of the current transformer and the sampling resistor is 2.8V. Therefore, when the dimming signal is low, for example, the dimming ratio is 1%, the current transformer can still provide a 28mV sampling signal (much greater than the offset offset voltage specification of a general operational amplifier), so an isolated current detection circuit is used 110 current sampling can achieve low dimming accuracy.

2A to 2D respectively show circuit block diagrams of light source driving devices 200A to 200D according to different embodiments of the present invention. As shown in FIG. 2A, the light source driving device 200A can receive the power provided by the AC power supply 201 and convert the power into the output current Iout to drive the light-emitting element 280. The light source driving device 200A includes a transformer T, an isolated current detection circuit 210, a dimming circuit 220, an independent voltage source 230, a feedback circuit 240, a voltage conversion circuit 250, a signal processing circuit 260, and a rectifier circuit 270.

The signal processing circuit 260 is coupled between the AC power source 201 and the voltage conversion circuit 250. The signal processing circuit 260 can perform processing such as rectification and filtering or power factor correction on the AC signal provided by the AC power supply 201 to generate a DC signal. The voltage conversion circuit 250 can convert the DC signal provided by the signal processing circuit 260 into a voltage adjustment signal VCS according to the received feedback signal FB. Voltage adjustment signal The VCS may be a voltage signal adjusted by the pulse width modulation signal PWM.

For example, the voltage conversion circuit 250 of FIG. 2A may include a pulse width modulation signal controller 251 and a voltage converter 252. The PWM signal controller 251 is coupled to the feedback circuit 240. The pulse width modulation signal controller 251 can generate the pulse width modulation signal PWM according to the feedback signal FB. The voltage converter 252 is coupled to the pulse width modulation signal controller 251 to receive the pulse width modulation signal PWM. The voltage converter 252 can provide the voltage adjustment signal VCS according to the pulse width modulation signal PWM, and transmit the voltage adjustment signal VCS to the transformer T. In this way, the transformer T can adjust the output current Iout of the light source driving device 200A according to the voltage adjustment signal VCS.

The transformer T includes a primary side coil NP and a secondary side coil NS. The primary side coil NP is coupled to the voltage conversion circuit 250, and the secondary side coil NS is coupled to the isolated current detection circuit 210 via the rectifier circuit 270. The secondary winding NS of the transformer T generates an induced current corresponding to the voltage adjustment signal VCS on the primary winding NP, and the induced current can be rectified and filtered by the rectifier circuit 270 to generate the output current Iout. Furthermore, the voltage adjustment signal VCS is the voltage across the primary winding NP of the transformer T, that is, the potential difference between the two ends of the primary winding NP of the transformer T.

In the embodiment of FIG. 2A, the transformer T further includes a primary side auxiliary winding NA1 and a secondary side auxiliary winding NA2. The primary auxiliary coil NA1 is coupled to the auxiliary power supply 231, and the secondary auxiliary coil NA2 is coupled to the independent voltage source 230. The auxiliary power source 231 can supply power to the pulse width modulation signal controller 251, and the independent voltage source 230 can supply the operating voltage VCC to the dimming circuit 220 and the feedback circuit 240.

The isolated current detection circuit 210 can sample the output current Iout of the light source driving device 200A through electromagnetic coupling to generate the current detection signal SI. For example, the isolated current detection circuit 210 may be a current transformer, and the current transformer may sense the output current on the output terminal of the rectifier circuit 270 through electromagnetic coupling to generate the current detection signal SI.

The dimming circuit 220 can receive the dimming input signal Dim, and provide the reference current control signal CCR according to the dimming input signal Dim. In this embodiment, the dimming circuit 220 includes a dimming control circuit 221 and a voltage divider circuit 222. The dimming control circuit 221 in the dimming circuit 220 can be a three-in-one dimming circuit (that is, 0~10V DC dimming/PWM dimming/variable resistance dimming), digital addressable lighting interface (digital addressable lighting) interface, DALI) circuit or Internet of things (IoT) dimming circuit.

The dimming control circuit 221 can convert the dimming input signal Dim into the reference current control signal CCR according to different types of dimming control interfaces. The input end of the dimming control circuit 221 can receive the dimming input signal Dim. In some embodiments, the dimming input signal Dim may be a DC voltage signal or a pulse width modulation signal.

The input terminal C1 and the output terminal C2 of the dimming control circuit 221 are respectively coupled to the operating voltage VCC and the voltage divider circuit 222. A resistor R1 is connected between the input terminal C1 and the output terminal C2 of the dimming control circuit 221. The voltage divider circuit 222 includes a resistor R2 and a resistor R3. The first terminal of the resistor R2 is coupled to the output terminal C2. The first end of the resistor R3 is coupled to the second end of the resistor R2, and the second end of the resistor R3 is coupled to the ground voltage level SGND. The dimming circuit 220 can be provided by dividing the operating voltage VCC on the resistor R3 Refer to the current control signal CCR. In addition, the resistance values of the resistor R2 and the resistor R3 can be determined according to design requirements. The resistor R2 and the resistor R3 can have the same resistance value or different resistance values, which is not limited by the present invention.

Please refer to FIG. 2A again, the feedback circuit 240 includes a first comparator 241 and an optical coupling element 243. The first comparator 241 is coupled to the isolated current detection circuit 210 and the dimming circuit 220 to receive the current detection signal SI and the reference current control signal CCR. The first comparator 241 can compare the current detection signal SI with the reference current control signal CCR to generate a first comparison signal.

In FIG. 2A, the light coupling element 243 includes a light-emitting diode 2431 and a light coupling transistor 2432. The first terminal of the light emitting diode 2431 is coupled to the operating voltage VCC via the resistor R6, and the second terminal of the light emitting diode 2431 is coupled to the output terminal of the first comparator 241. The first terminal and the second terminal of the optical coupling transistor 2432 are coupled to the voltage conversion circuit 250. The optical coupling element 243 can provide the feedback signal FB to the voltage conversion circuit 250 according to the first comparison signal generated by the first comparator 241. For example, the light-emitting diode 2431 in the optical coupling element 243 can generate a corresponding optical signal based on the first comparison signal. The optical coupling transistor 2432 can receive the light signal of the light emitting diode 2431 to generate the feedback signal FB.

The voltage conversion circuit 250 can provide a voltage adjustment signal VCS according to the feedback signal FB, so that the transformer T transmits the voltage adjustment signal VCS to adjust the output current Iout of the light source driving device 200A. For example, when the current detection signal SI is less than the reference current control signal CCR, the first comparator 241 can notify the optical coupling element 243 to generate a feedback signal FB that increases the output current Iout. When the current detection signal When SI is greater than the reference current control signal CCR, the first comparator 241 can notify the optical coupling element 243 to generate a feedback signal FB that reduces the output current Iout.

On the other hand, in the embodiments of FIGS. 2B to 2D, the feedback circuit 240 can also be used to indirectly determine the output voltage level of the light-emitting element 280. Please refer to FIG. 2B. In the light source driving device 200B of FIG. 2B, the independent voltage source 230 is also coupled to the voltage divider circuit 232, and the feedback circuit 240 further includes a second comparator 242 and a first diode D1. With the second diode D2. The independent voltage source 230 of FIG. 2B can provide the voltage detection signal SV through the voltage divider circuit 232. The second comparator 242 in FIG. 2B is coupled to the voltage divider circuit 232 to receive the voltage detection signal SV.

For example, the independent voltage source 230 of FIG. 2B may be coupled to a voltage divider circuit 232 composed of resistors R4 and R5, and provide the voltage detection signal SV by dividing the operating voltage VCC on the resistor R5. In the voltage divider circuit 232, the first end of the resistor R4 is coupled to the operating voltage VCC, the second end of the resistor R4 is coupled to the first end of the resistor R5, and the second end of the resistor R5 is coupled to the ground voltage level SGND. In addition, the resistance values of the resistor R4 and the resistor R5 can be determined according to design requirements. The resistor R4 and the resistor R5 can have the same resistance value or different resistance values, which is not limited by the present invention.

The second comparator 242 of FIG. 2B can compare the voltage detection signal SV with the reference voltage control signal CVR to generate a second comparison signal. In FIG. 2B, the second comparison signal generated by the second comparator 242 can be used to detect the voltage of the light-emitting element 280, and achieve a feedback control operation for the voltage of the light-emitting element 280 according to design requirements. For example, when the voltage detection signal SV is less than the reference voltage control signal CVR, the second comparator 242 can notify the optical coupling element 243 to adjust the feedback signal FB to increase the output voltage. When the voltage detection signal SV is greater than the reference voltage control signal CVR, the second comparator 242 can notify the optical coupling element 243 to adjust the feedback signal FB to reduce the output voltage.

It should be noted that, in the embodiment of FIG. 2B, the first comparator 241 and the second comparator 242 are respectively coupled to the optical coupling element 243 via the first diode D1 and the second diode D2. In other embodiments, the first comparator 241 or the second comparator 242 can also be directly coupled to the optical coupling element 243. For example, as shown in FIG. 2C, the first comparator 241 can be coupled to the optical coupling element 243 via the first diode D1, and the second comparator 242 is directly coupled to the optical coupling element 243. In the embodiment of FIG. 2D, the first comparator 241 may be directly coupled to the optical coupling element 243, and the second comparator 242 is coupled to the optical coupling element 243 via the second diode D2.

Incidentally, in the embodiments of FIGS. 2A to 2D, the independent voltage source 230, the feedback circuit 240, and the dimming circuit 220 in the light source driving device 200A~200D can be arranged on the same circuit board, and the dimming circuit The dimming control circuit 221 in 220 can be designed into different types of interface cards. Therefore, the present invention only needs to replace the interface card of the dimming circuit 220 to achieve the effect of quickly switching between different dimming control interfaces.

FIG. 3 is a schematic flowchart of a current adjustment method of a light source driving device according to an embodiment of the present invention. 1 and 3, in step S310, the isolated current detection circuit 110 can sample the output current Iout of the light source driving device 100 through electromagnetic coupling, thereby generating a current detection signal SI. In step S320, the dimming circuit 120 may receive the dimming input signal Dim, and based on the operating voltage VCC and dimming input signal Dim provide the reference current control signal CCR. In other words, the dimming circuit 120 only needs to use a single power supply (operating voltage VCC) to provide the reference current control signal CCR according to the dimming input signal Dim.

In step S330, the light source driving device 100 can generate the operating voltage VCC by a single independent voltage source 130. In step S340, the feedback circuit 140 may perform a feedback operation based on the operating voltage VCC. In other words, the feedback circuit 140 can use the operating voltage VCC as a power source in step S340, and provide the feedback signal FB according to the current detection signal SI and the reference current control signal CCR.

In this way, the light source driving device 100 can adjust the output current Iout of the light source driving device 100 according to the feedback signal FB. The implementation details of step S310 to step S340 can be deduced by analogy with reference to the relevant description of the embodiment shown in FIG. 1, and therefore will not be repeated.

In summary, in the embodiments of the present invention, the light source driving device can achieve the signal isolation effect required by regulations by arranging an isolated current detection circuit and a single independent voltage source. In addition, the output current of the light source driving device is sampled through the isolated current detection circuit, and the output of constant current can be accurately controlled under low dimming current. Furthermore, since the independent voltage source, feedback circuit and dimming circuit in the light source driving device can be set on the same circuit board, only the interface card of the dimming circuit needs to be replaced, and different dimming can be quickly switched. Control the function of the interface.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the relevant technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention When the scope of the attached patent application is defined, it shall prevail.

100: Light source drive device

101: primary side

102: secondary side

110: Isolated current detection circuit

120: dimming circuit

130: Independent voltage source

140: feedback circuit

CCR: Reference current control signal

Dim: dimming input signal

FB: Feedback signal

Iout: output current

SI: Current detection signal

VCC: Operating voltage

Vin: input voltage

Vout: output voltage

Claims (16)

A light source driving device has a primary side and a secondary side, comprising: an isolated current detection circuit coupled to the secondary side, wherein the isolated current detection circuit drives the light source through electromagnetic coupling An output current of the device is sampled to generate a current detection signal; a dimming circuit receives a dimming input signal and an operating voltage, and provides a reference current control signal according to the dimming input signal and the operating voltage An independent voltage source that generates the operating voltage; and a feedback circuit coupled between the isolated current detection circuit and the primary side of the light source driving device, and the feedback circuit is coupled to the independent voltage Source and the dimming circuit, wherein the feedback circuit receives the operating voltage, the current detection signal and the reference current control signal to perform a feedback operation, and provides a feedback operation based on the current detection signal and the reference current control signal A feedback signal, wherein the light source driving device adjusts the output current of the light source driving device according to the feedback signal. The light source driving device described in item 1 of the scope of patent application further includes: a transformer including a primary side coil and a secondary side coil, wherein the primary side coil is coupled to the primary side of the light source driving device, The secondary side coil is coupled to the isolated current detection circuit; and A voltage conversion circuit coupled to the feedback circuit and the primary side coil of the transformer, wherein the voltage conversion circuit provides a voltage adjustment signal according to the feedback signal, and the transformer adjusts the light source drive according to the voltage adjustment signal The output current of the device. According to the light source driving device described in claim 2, wherein the voltage conversion circuit includes: a pulse width modulation signal controller, coupled to the feedback circuit, and generates a pulse width modulation signal according to the feedback signal And a voltage converter, coupled to the pulse width modulation signal controller and the primary side coil of the transformer, according to the pulse width modulation signal to provide the voltage adjustment signal. The light source driving device described in item 3 of the scope of patent application, wherein the transformer further includes a primary side auxiliary coil and a secondary side auxiliary coil, wherein an auxiliary power source is coupled to the primary side auxiliary coil to supply power to the Pulse width modulation signal controller, the secondary side auxiliary coil is coupled to the independent voltage source. According to the light source driving device described in claim 1, wherein the independent voltage source provides a voltage detection signal through a first voltage divider circuit, and the feedback circuit is controlled according to the current detection signal and the reference current Signal and the voltage detection signal to provide the feedback signal. The light source driving device described in claim 1, wherein the dimming circuit provides the reference current control signal to the feedback circuit. According to the light source driving device described in claim 1, wherein the dimming circuit has an input terminal and an output terminal, the input terminal is coupled to the operating voltage, and the output terminal is coupled to a second voltage divider circuit. According to the light source driving device described in item 7 of the scope of patent application, a first resistor is connected between the input terminal and the output terminal of the dimming circuit. According to the light source driving device described in claim 8, wherein the second voltage divider circuit includes: a second resistor, wherein the first end of the second resistor is coupled to the output terminal; and a third resistor, The first end of the third resistor is coupled to the second end of the second resistor, and the second end of the third resistor is coupled to a ground voltage level. In the light source driving device described in item 1 of the scope of patent application, the isolated current detection circuit is a current transformer. According to the light source driving device described in claim 1, wherein the feedback circuit includes: a first comparator coupled to the isolated current detection circuit and the dimming circuit to receive the current detection signal and The reference current control signal, wherein the first comparator compares the current detection signal with the reference current control signal to generate a first comparison signal; and an optical coupling element coupled to the first comparator, wherein The optical coupling element provides the feedback signal according to the first comparison signal. According to the light source driving device described in item 5 of the scope of patent application, the feedback circuit includes: A first comparator is coupled to the isolated current detection circuit and the dimming circuit to receive the current detection signal and the reference current control signal, wherein the first comparator is the current detection signal and the reference The current control signal is compared to generate a first comparison signal; a second comparator is coupled to the first voltage divider circuit to receive the voltage detection signal, wherein the second comparator detects the voltage signal Compare with a reference voltage control signal to generate a second comparison signal; and an optical coupling element coupled to the first comparator and the second comparator, wherein the optical coupling element is based on the first comparison signal and the The second comparison signal provides the feedback signal. According to the light source driving device described in claim 12, the first comparator or the second comparator is directly coupled to the light coupling element. According to the light source driving device described in claim 12, the first comparator and the second comparator are respectively coupled to the light coupling element via a first diode and a second diode. The light source driving device according to claim 14, wherein the light coupling element includes: a light emitting diode, wherein the first end of the light emitting diode is coupled to the operating voltage, and the first end of the light emitting diode is coupled to the operating voltage. Two ends are coupled to the anode of the first diode and the anode of the second diode; and an optical coupling transistor, wherein the first end and the second end of the optical coupling transistor are coupled to the voltage conversion Circuit. A light source driving device is used to drive a light-emitting element, and has a primary side and a secondary side, comprising: an isolated current detection circuit coupled to the secondary side, wherein the isolated current detection circuit An output current of the light source driving device is sampled through electromagnetic coupling to generate a current detection signal; a dimming circuit receives a dimming input signal and an operating voltage to provide a dimming input signal Reference current control signal; an independent voltage source that generates the operating voltage, and the independent voltage source and the light-emitting element are isolated from each other; and a feedback circuit coupled to the isolated current detection circuit and the light source driving device Between the primary side, and the feedback circuit is coupled to the independent voltage source and the dimming circuit, wherein the feedback circuit receives the operating voltage, the current detection signal and the reference current control signal to perform a feedback operation , And provide a feedback signal according to the current detection signal and the reference current control signal, wherein the light source driving device adjusts the output current of the light source driving device according to the feedback signal.

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