TWI578847B - A system for providing an output current to one or more light emitting diodes - Google Patents

Description

System for providing output current to one or more light emitting diodes

The present invention relates to the field of circuits, and more particularly to a system for providing an output current to one or more light emitting diodes.

At present, the lighting technology of Light Emitting Diode (LED) has become increasingly mature. LEDs are widely used in the field of lighting to replace traditional incandescent lamps due to their high luminous efficiency and long service life. However, when an LED is used in place of an incandescent lamp, since the LED driving circuit generally does not have an overvoltage protection function or the overvoltage protection accuracy is not high, the LED driving circuit is easily damaged or cannot be efficiently utilized. In order to achieve high-precision overvoltage protection, it is necessary to add complicated peripheral circuits in the LED driving circuit, which is high in cost and on the other hand, the printed circuit is large in size and cannot be directly placed in the lamp head interface.

In view of one or more of the problems described above, the present invention provides a novel system for providing an output current to one or more light emitting diodes, and control for providing an output to one or more light emitting diodes The method of current output voltage of the system.

A system for providing an output current to one or more light emitting diodes in accordance with an embodiment of the invention includes a switch control element configured to generate a control signal based on information associated with the sensed signal, the demagnetization signal, and the reference signal And controlling, by the control signal, a cutoff and a conduction of a system power switch, wherein the system power switch is connected to a first diode terminal of the diode and a first inductor terminal of the inductor, the diode The body further includes a second diode terminal, the inductor further includes a second inductor terminal, and the one or more light emitting diodes are connected in parallel with the output capacitor at the second diode terminal and the Second inductor terminal The sensing signal is generated by sensing a current flowing through the system power switch, the demagnetization signal is generated by sensing a current flowing through the inductor, and the reference signal is a predetermined signal .

A method of controlling an output voltage of a system for providing an output current to one or more light emitting diodes in accordance with an embodiment of the present invention includes generating a control signal that characterizes whether the one or more light emitting diodes are in an active state Outputting a voltage detection signal; comparing a voltage indicated by the output voltage detection signal with a voltage indicated by the reference signal, and determining, according to the comparison result, whether an output voltage of the system is higher than a predetermined voltage value; a high output voltage of the system In the event of a predetermined voltage value, the system power switch in the system is turned off using the control signal.

A system for providing an output current to one or more light emitting diodes according to an embodiment of the present invention, and a method of controlling an output voltage of a system for supplying an output current to one or more light emitting diodes can provide high precision Overvoltage protection.

100, 200‧‧‧ system

1068, D1‧‧‧ diode

102, 202‧‧‧ AC rectifying components

VOUT‧‧‧ output voltage

104‧‧‧Controller components

COUT‧‧‧ output capacitor

106, 208‧‧‧ Current output components

204‧‧‧Resistor voltage dividing element

VAC‧‧‧AC input voltage

206‧‧‧Switch control components

VBULK‧‧‧ DC voltage

202-1‧‧‧First rectifying element terminal

GATE‧‧‧ terminal

202-2‧‧‧Second rectifier component terminal

1062‧‧‧System Power Switch

202-3‧‧‧3rd rectifying element terminal

1064‧‧‧Inductors

202-4‧‧‧4th rectifying element terminal

1066‧‧‧Sensor Resistors

VIN‧‧‧First control element terminal

204-1‧‧‧First voltage divider terminal

GATE‧‧ (second control element) terminal

204-2‧‧‧Second voltage divider terminal

CS‧‧‧ (third control element) terminal

204-3‧‧‧ Third voltage divider terminal

GND‧‧‧4th control element terminal

208-1‧‧‧First output component terminal

VDD‧‧‧ fifth control element terminal

208-2‧‧‧second output component terminal

R1, R2, R3‧‧‧ resistors

208-3‧‧‧third output component terminal

VOUT_OVP‧‧‧critical OVP voltage

208-4‧‧‧fourth output component terminal

VVIN‧‧‧ voltage signal

208-5‧‧‧5th output component terminal

L1‧‧‧Inductors

RS‧‧‧Sense Resistors

VCS‧‧‧ voltage value

Demagnetization time of TDemag‧‧‧Inductor L1

GM1‧‧‧First Transconductance Amplifier

C, C1‧‧‧ capacitor

GM2‧‧‧Second Transconductance Amplifier

COMP1‧‧‧ comparator

K1‧‧‧ switch

I_source, I_sink‧‧‧ current

Vth_ovp‧‧‧OVP threshold voltage

Vramp‧‧‧ voltage (voltage detection signal)

I _PK ‧‧‧Maximum current I _L flowing through inductor L1

The maximum value of the output voltage VOUT between the two outputs of the VOUT_PK‧‧ current output element 208

TON‧‧‧System Power Switch 1062 Metal Oxide Semiconductor Field Effect Crystal (MOSFET) is in the on state for the duration

TOFF‧‧‧ is the duration of the system power switch 1062 metal oxide semiconductor field effect transistor (MOSFET) in the off state

The invention can be better understood from the following description of specific embodiments of the invention, in which: FIG. 1 is a conventional system for providing an output current to one or more light-emitting diodes (BUCK circuit) FIG. 2 is a circuit diagram of a system for providing an output current to one or more light emitting diodes according to an embodiment of the present invention; and FIG. 3 is an operational waveform diagram of the system circuit shown in FIG. 2; Figure 4 is a circuit diagram of an Over Voltage Protection (OVP) module in the system circuit shown in Figure 2.

Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth However, it will be apparent to those skilled in the art that the present invention may be practiced without some of the details. The following description of the embodiments is merely provided to provide a better understanding of the invention. The present invention is in no way limited to any specific configurations and algorithms presented below, but without departing from the spirit and scope of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessary obscuring the invention.

In order to keep the brightness of the LED constant, a substantially constant current is typically supplied to the LED. Figure 1 is a circuit diagram of a conventional system (BUCK circuit) for providing an output current to one or more light emitting diodes.

As shown in FIG. 1, a system 100 for providing an output current to one or more light emitting diodes includes an AC rectifying element 102, a controller element 104, and a current output element 106. Specifically, when one or more LEDs are connected between the two terminals of the AC rectifying element 102: the AC rectifying element 102 receives the AC input voltage V _AC and converts the AC input voltage V _AC into a DC voltage V _BULK to Current is supplied to one or more LEDs. The controller component 104 outputs a control signal to the system power switch 1062 in the current output component 106 through the GATE terminal to control the turn-on and turn-off of the system power switch 1062 to regulate the current flowing through one or more LEDs (or output current) ). When system power switch 1062 is turned on, the current flowing through inductor 1064 in current output element 106 is sensed by sense resistor 1066 in current output element 106, causing the current sense signal to pass CS through controller element 104. The terminal is received. In response, controller component 104 generates a control signal based on the current sense signal to control the turn-on and turn-off of system power switch 1062. When the system power switch 1062 is turned off, a current loop is formed between the inductor 1064, the diode 1068, and one or more LEDs connected between the two output terminals of the current output element 106 in the current output element 106. .

In the system shown in Fig. 1, when the LED is disconnected from between the two output terminals of the current output element 106 (i.e., when the two outputs are open) or the LED fails to operate, two of the current output elements 106 The output voltage V _OUT between the outputs is too high (eg, equal to or greater than the nominal voltage of the output capacitor C _OUT connected between the two outputs of the current output element 106), resulting in the current output element 106 The output capacitor C _{OUT is} easily damaged.

Therefore, it is necessary to provide overvoltage protection for the open circuit of the two output terminals of the current output element 106 in the system shown in Fig. 1 (i.e., the output capacitor C _OUT in the protection current output element 106 is not _affected by the LED current. The output voltage V _OUT between the two outputs of the current output element 106 when the two outputs of the output element 106 are disconnected is equal to or greater than its rated voltage and is damaged). However, in the system shown in FIG. 1, the controller component 104 cannot directly measure the output voltage V _OUT between the two output terminals of the current output component 106, and thus cannot accurately control the two outputs of the current output component 106. The output voltage when the terminal is open.

In order to solve one or more problems present in the system shown in FIG. 1, an output current for supplying one or more light emitting diodes according to an embodiment of the present invention, which is described in detail below with reference to FIGS. 2-4, is proposed. system.

2 is a circuit diagram of a system for providing an output current to one or more light emitting diodes in accordance with an embodiment of the present invention. As shown in FIG. 2, system 200 for providing an output current to one or more light emitting diodes includes an AC rectifying element 202, a resistive dividing element 204, a switching control element 206, and a current output element 208. The AC rectifying element 202 includes first, second, third, and fourth rectifying element terminals 202-1, 202-2, 202-3, and 202-4. The resistor divider element 204 includes first, second, and third voltage divider component terminals 204-1, 204-2, 204-3. The switch control element 206 includes first, second, third, fourth, and fifth control element terminals VIN, GATE, CS, GND, VDD. Current output component 208 includes first, second, third, fourth, and fifth output component terminals 208-1, 208-2, 208-3, 208-4, 208-5.

As shown in Fig. 2, the first and second rectifying element terminals 202-1, 202-2 of the AC rectifying element 202 are respectively connected to both ends of an alternating current power source, and the third and fourth rectifying element terminals 202-3, 202- 4 is connected to the first and second voltage dividing element terminals 204-1, 204-2 of the resistor dividing element 204, respectively. The third voltage dividing element terminal 204-3 of the resistance dividing element 204 is connected to the first control element terminal VIN of the switching control element 206. The second control element terminal GATE of the switch control element 206 is connected to the second output element terminal 208-2 of the current output element 208, and the third control element terminal CS is connected to the third output element terminal 208-3 of the current output element 208, The fourth control element terminal GND is grounded, and the fifth control element terminal VDD is connected to the first voltage dividing element terminal 204-1 of the resistance dividing element 204 via the resistor R3 and is grounded via the capacitor C1. The first output element terminal 208-1 of the current output element 208 is connected to the first voltage dividing element terminal 204-1 of the resistance dividing element 204, and the fourth output element terminal 208-4 is grounded. An output capacitor C _OUT in current output component 208 is coupled in parallel with one or more LEDs between first output component terminal 208-1 and fifth output component terminal 208-5 of current output component 208 (first output component terminal 208) The -1 and fifth output element terminals 208-5 are the two outputs of the current output element 208).

In the system shown in FIG. 2, the AC rectifying element 202 receives the AC input voltage V _AC and rectifies the AC input voltage V _AC to a DC voltage V _BULK to provide current to one or more LEDs. The resistor divider element 204 divides the DC voltage V _BULK through resistors R1 and R2 to generate a voltage signal V _VIN that enters the switch control element 206. The voltage signal V _VIN obtained by dividing the DC voltage V _BULK by the resistor dividing element 204 enters the voltage via the third voltage dividing element terminal 204-3 of the resistor dividing element 204 and the first control element terminal VIN of the switching control element 206. Control element 206. The voltage control component 206 outputs a control signal to the system power switch 1062 MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET) in the current output component 208 through the second control component terminal GATE to control the system. Power switch 1062 MOSFET turn-on and turn-off. When the system power switch 1062 MOSFET is turned on, the current flowing through the inductor L1 in the current output element 208 is sensed by the sense resistor RS in the current output element 208, such that the current sense signal is passed by the switch control element 206. The three control element terminals CS are received. In response, switch control component 206 generates a control signal as one of a plurality of base signals to control the turn-on and turn-off of system power switch 1062 MOSFET. When the system power switch 1062 MOSFET is turned off, a current loop is formed between the inductor L1, the diode D1 in the current output element 208, and one or more LEDs connected between the two outputs of the current output element 208. .

Specifically, as shown in FIG. 2, the gate of the system power switch 1062 MOSFET serves as the second output element terminal 208-2 of the current output element 208; the drain of the system power switch 1062 MOSFET and the first diode of the diode D1 The terminal is connected to the first inductor terminal of the inductor L1; the second diode terminal of the diode D1 serves as the first output element terminal 208-1 of the current output element 208; and the collector of the system power switch 1062 MOSFET serves as the current output element a third output element terminal 208-3 of 208 and grounded via a sense resistor RS; a second inductor terminal of inductor L1 as a fifth output element terminal 208-5 of current output element 208; one or more LEDs The output capacitor C _{OUT is} connected in parallel between the first output element terminal 208-1 and the fifth output element terminal 208-5 of the current output element 208.

As shown in FIG. 2, the switch control component 206 includes an overvoltage protection module, a Pulse Width Modulation (PWM) signal generation module, a gate drive module, a demagnetization detection module, and a current sensing module. And a reference signal generation module. The overvoltage protection module is based on a voltage signal V _VIN from the resistor divider component 204, a demagnetization signal from the demagnetization detection module, a modulation signal from a pulse width modulation (PWM) signal generation module, and a reference signal. The reference signal of the generating module generates an overvoltage protection signal, and the demagnetization detecting module generates a demagnetization signal based on a current or voltage signal related to the demagnetization condition of the inductor L1 in the current output component 208, and the current sensing module is based on the current output component. The current sensing signal obtained by the sensing resistor RS in 208 generates a sensing current related signal, and the pulse width modulation (PWM) signal generating module generates a modulation based on the overvoltage protection signal, the demagnetization signal, and the sensing current related signal. The signal, the gate drive module generates a drive signal based on the modulation signal for driving the turn-on and turn-off of the system power switch 1062 MOSFET in the current output component 208.

Specifically, in the present embodiment, the basic principle of the pulse width modulation (PWM) signal generating module to generate the modulated signal is as follows: when one or more LEDs are connected between the two outputs of the current output element 106 and are normal In operation, the pulse width modulation (PWM) signal generation module generates a modulation signal based on the demagnetization signal and the sense current related signal for controlling the cutoff and conduction of the system power switch 1062 MOSFET in the current output component 208, thereby regulating the flow. Current through one or more LEDs (eg, when the demagnetization signal indicates the end of demagnetization, the pulse width modulation (PWM) signal generation module changes the modulation signal from low to high; when the sense current related signal indicates When the sense current reaches the set value, the pulse width modulation (PWM) signal generation module changes the modulation signal from a high level to a low level; the demagnetization signal and the sense current related signal alternately control the pulse width modulation (PWM) The signal generation module generates a modulation signal); when the LED is disconnected from the two output terminals of the current output element 106 or the LED fails, the pulse width modulation (PWM) signal generation module is generated based on the overvoltage protection module Overvoltage protection Signal generating modulated signal, system power switch for controlling the current output of 1062MOSFET element 208 in an off state, so that the current output element is the output voltage V _OUT between the two output terminals 208 is not higher than the rated voltage of the output capacitor Cout (ie, the protection output capacitor Cout is not damaged). In this embodiment, the modulated signal generated by the pulse width modulation (PWM) signal generation module is actually a control signal for the system power switch 1062 MOSFET.

Fig. 3 is a diagram showing the operation waveforms in the system circuit shown in Fig. 2. In Fig. 3, the pulse width modulation (PWM) waveform is the output waveform of the pulse width modulation (PWM) signal generation module (ie, the waveform of the modulation signal), and the GATE waveform is the output waveform of the gate drive module ( That is, the waveform of the drive signal), the I _L waveform is the current waveform flowing through the inductor L1, and the Demag waveform is the output waveform of the demagnetization detection module (that is, the waveform of the demagnetization signal). T _ON is the duration in which the system power switch 1062 MOSFET is in an on state (ie, the on time of the system power switch 1062 MOSFET), and T _OFF is the duration in which the system power switch 1062 is in an off state (ie, the off time of the system power switch 1062 MOSFET), T _Demag is the demagnetization time of inductor L1, and T _{Demag is} less than T _OFF .

In the system shown in FIG. 2, when the output voltage of the second control element terminal GATE of the switch control element 206 is at a high level (ie, the GATE waveform in FIG. 3 is logic high), the current output element 208 is The system power switch 1062 MOSFET is turned on, and the current flowing through the inductor L1 in the current output element 208 rises linearly (the current value flowing through the inductor L1 can be obtained according to the formula (1), where t is the current flowing through the inductor L1. time). In the current output element 208, the current flowing through the inductor L1 flows through the sense resistor RS to ground through the system power switch 1062 MOSFET, and the voltage value generated on the sense resistor RS (ie, at the switch control element 206) The voltage value V _CS ) sensed at the three control element terminals CS can be derived from equation (2). When V _CS reaches the set value or t reaches the set value T _ON , the output voltage of the second control element terminal GATE of the switch control element 206 becomes a low level (ie, the GATE waveform in FIG. 3 becomes a logic low), System power switch 1062 MOSFET) in current output element 208 is turned off. At this time, the inductor L1 in the current output element 208 is demagnetized by the diode D1 and one or more LEDs, and after the T _Demag time, the demagnetization ends, and the current flowing through the inductor L1 becomes zero. The switch control element 206 can determine the demagnetization start and end points of the inductor L1 by detecting the current flowing through the inductor L1 in the current output element 208, thereby obtaining a demagnetization time T _demag (demagnetization can be obtained according to formula (3) Time, where I _PK is the maximum value of the current I _L flowing through the inductor L1, and V _{OUT_PK} is the maximum value of the output voltage V _OUT between the two outputs of the current output element 208). In addition, since the circuit system shown in FIG. 2 is essentially an improvement to the BUCK circuit, the output voltage V _OUT between the two output terminals of the current output element 208 and the DC voltage V _BULK output by the AC rectifying element 202 are The relationship between the two is shown in equation (4).

That is, based on the DC voltage V _BULK output from the AC rectifying element 202, the on-time T _{ON of the} system power switch 1062 MOSFET, and the demagnetization time T _{Denag of the} inductor L1, the output voltage V _OUT can be calculated using Equation (4).

Figure 4 is the overvoltage protection (OVP) in the system circuit shown in Figure 2. The circuit diagram of the module. As shown in FIG. 4, the overvoltage protection module includes a first transconductance amplifier GM1, a second transconductance amplifier GM2, a switch K1, a reset unit, a capacitor C, and a comparator COMP1. Wherein, the first transconductance amplifier GM1 is connected between the first control element terminal VIN of the switch control element 206 and the first switch terminal of the switch K1, and the second transconductance amplifier GM2 is connected to the second switch terminal of the switch K1 and the overvoltage Between the reference signal generating modules outside the protection module, the reset unit is connected between the second switch terminal of the switch K1 and the demagnetization detecting module outside the overvoltage protection module, and the capacitor C is connected to the second switch of the switch K1. Between the terminal and the ground, the comparator COMP1 is connected between the second switch terminal of the switch K1 and a pulse width modulation (PWM) signal generating module external to the overvoltage protection module.

As shown in FIG. 4, the DC voltage V _BULK obtained by rectifying the AC input voltage V _AC by the AC rectifying element 202 is divided by the resistors R1 and R2 in the resistor divider element 204, thereby generating the switch control element 206. a voltage signal at the control element terminal VIN; a modulation signal output by the pulse width modulation (PWM) generation module (ie, the pulse width modulation (PWM waveform) in FIG. 3 is high level (ie, system power) When the switch 1062 is turned on, the switch K1 is turned on, and the voltage signal at the first control element terminal VIN of the switch control element 206 generates an I_source current to charge the capacitor C through the first transconductance amplifier GM1, and the OVP threshold from the reference signal generation module. The voltage Vth_ovp generates an I_sink current to discharge the capacitor C through the second transconductance amplifier GM2; if I_source>I_sink, the voltage Vramp on the capacitor C rises; in the pulse width modulation (PWM) generation module outputs a control signal (ie, 3) The pulse width modulation (PWM) waveform is low (ie, the system power switch 1062 MOSFET is turned off and the inductor L1 is demagnetized). The switch K1 is turned off. At this time, only the reference signal from the reference signal generation module is used. Vth_ovp generates an I_sink current through the second transconductance amplifier GM2 to discharge the capacitor C, and the voltage Vramp on the capacitor C drops.

After each demagnetization of the inductor L1 is completed, the comparator COMP1 compares the Vramp voltage with the OVP threshold voltage Vth_ovp to determine whether overvoltage protection (OVP) needs to be triggered (eg, if Vramp is higher than Vth_ovp, OVP is triggered). After each comparison, the voltage Vramp on the capacitor C is forcibly reset to Vth_ovp by the reset unit.

Here, at the first control element terminal VIN of the switch control element 206 The voltage signal can be derived from equation (5).

When the output voltage V _OUT between the two output terminals of the current output element 208 is at the critical OVP voltage (V _{OUT — OVDC} ), the capacitor C is charged during the _ON time in each cycle of charging and discharging the inductor L1. The voltage is equal to the discharge voltage of capacitor C during the demagnetization time (as shown in equation (6)): Combining equations (4) through (6), equation (7) can be derived:

As can be seen from the above, Vramp and Vth_ovp are compared by the end of the demagnetization of the inductor L1 in each cycle of charging and discharging the inductor L1, and the OVP is triggered when Vramp is higher than Vth_ovp (ie, the switch control element 206 is immediately turned off). The output of the second control element terminal GATE can realize high-precision overvoltage protection. Here, the critical OVP voltage V _{OUT —} OVP may be the rated voltage of the output capacitor Cout in the current output element 206, and the required R1 and R2 ratios may be pre-calculated according to the critical OVP voltage V _{OUT —} OVP and the OVP threshold voltage V _{th — ovp} .

It can be seen that there is disclosed an output voltage control method comprising: generating an output voltage detection signal (ie, Vramp) using a control signal characterizing whether one or more LEDs are in an active state; and outputting a voltage and reference indicated by the output voltage detection signal The voltage indicated by the signal (ie, Vth_ovp) is compared, and it is judged according to the comparison result whether the output voltage is higher than a predetermined voltage value; and when the output voltage is higher than the predetermined voltage value, the system is turned off by using the control signal (ie, the above-mentioned modulation signal) Power switch 1062 (ie, the MOSFET described above).

Those skilled in the art will appreciate that there are many more alternative embodiments and improvements that can be used to implement the embodiments of the present invention, and that the above-described embodiments and examples are merely illustrative of one or more embodiments. Therefore, the scope of the invention is limited only by the appended claims.

200‧‧‧ system

D1‧‧‧ diode

202‧‧‧AC rectifier components

COUT‧‧‧ output capacitor

208‧‧‧current output components

204‧‧‧Resistor voltage dividing element

VAC‧‧‧AC input voltage

206‧‧‧Switch control components

VBULK‧‧‧ DC voltage

204-1‧‧‧First voltage divider terminal

202-1‧‧‧First rectifying element terminal

204-2‧‧‧Second voltage divider terminal

202-2‧‧‧Second rectifier component terminal

204-3‧‧‧ Third voltage divider terminal

202-3‧‧‧3rd rectifying element terminal

208-1‧‧‧First output component terminal

202-4‧‧‧4th rectifying element terminal

208-2‧‧‧second output component terminal

VIN‧‧‧First control element terminal

208-3‧‧‧third output component terminal

GATE‧‧ (second control element) terminal

208-4‧‧‧fourth output component terminal

CS‧‧‧ (third control element) terminal

208-5‧‧‧5th output component terminal

GND‧‧‧4th control element terminal

RS‧‧‧Sense Resistors

VDD‧‧‧ fifth control element terminal

R1, R2, R3‧‧‧ resistors

VVIN‧‧‧ voltage signal

L1‧‧‧Inductors

C1‧‧‧ capacitor

1062‧‧‧System Power Switch

The maximum value of the output voltage VOUT between the two outputs of the VOUT_PK‧‧ current output element 208

TON‧‧‧System Power Switch 1062 Metal Oxide Semiconductor Field Effect Crystal (MOSFET) is in the on state for the duration

TOFF‧‧‧ is the duration of the system power switch 1062 metal oxide semiconductor field effect transistor (MOSFET) in the off state

Claims (9)

A system for providing an output current to one or more light emitting diodes, comprising: a switch control element configured to generate a control signal based on information associated with the sensed signal, the demagnetization signal, and the reference signal, and utilizing Determining a control signal to control off and on of a system power switch, wherein the system power switch is coupled to a first diode terminal of the diode and a first inductor terminal of the inductor, the diode further comprising a diode terminal, the inductor further includes a second inductor terminal, and the one or more light emitting diodes are connected in parallel with the output capacitor at the second diode terminal and the second inductor Between the terminals, the sensing signal is generated by sensing a current flowing through the system power switch, the demagnetization signal is generated by sensing a current flowing through the inductor, and the reference signal is Scheduled signal. The system of claim 1, wherein the switch control element is further configured to generate a modulation signal based on information associated with the sensing signal and the demagnetization signal, and in the one Or the plurality of light emitting diodes are connected between the second diode terminal and the second inductor terminal, and when the operating state is in an operating state, the modulation signal is used as the control signal to control the system power switch Turning on and off, and generating the control signal based on information associated with the demagnetization signal, the reference signal, and the modulation signal, and from the second one or more of the one or more light emitting diodes The turn-on and turn-off of the system power switch is controlled according to the control signal when the diode terminal and the second inductor terminal are disconnected or when a fault occurs. The system of claim 1, further comprising: an AC rectifying element configured to rectify an AC signal from the AC power source to generate a rectified voltage signal; the resistor divider element configured to be The rectified voltage signal is divided to generate an input signal into the switch control element, wherein The AC rectifying element includes first, second, third, and fourth rectifying element terminals, and the first and second rectifying element terminals are respectively connected to two ends of the alternating current power source, the third and fourth The rectifying element terminals are respectively connected to the first and second voltage dividing element terminals of the resistance dividing element, wherein the fourth rectifying element terminal is further connected to the ground, and the resistance dividing element further comprises a third voltage dividing element terminal The third voltage dividing element terminal supplies the input signal to the switch control element. The system of claim 2, wherein the switch control element comprises a switch, a first transconductance amplifier, a second transconductance amplifier, a comparator, a capacitor, and a reset unit, wherein the switch is turned on Controlled by the control signal, the first transconductance amplifier generates a first current for inputting the input signal of the switch control element from the outside during charging of the switch to charge the capacitor. The second transconductance amplifier generates a second current for discharging the capacitor by using the reference signal during the on-time of the switch and the demagnetization period indicated by the demagnetization signal, the comparator being Demagnetizing the signal indicating the current voltage on the capacitor and the voltage indicated by the reference signal at the end of the demagnetization, and generating the control signal according to the comparison result, the reset unit completing the current on the capacitor at the comparator When the voltage is compared with the voltage indicated by the reference signal, the current voltage on the capacitor is forcibly reset to the reference The voltage indicated by the signal. The system of claim 4, wherein the switch control element generates the means for turning off the system power switch when a current voltage on the capacitor is higher than a voltage indicated by the reference signal control signal. The system of claim 5, wherein the voltage indicated by the reference signal is no greater than a product of a voltage pre-set for the output capacitance and a scaling factor dependent on a circuit configuration of the system. A method of controlling an output voltage of a system for providing an output current to one or more light emitting diodes, comprising: Generating an output voltage detection signal by using a control signal characterizing whether the one or more light emitting diodes are in an active state; comparing a voltage indicated by the output voltage detection signal with a voltage indicated by the reference signal, and determining, according to the comparison result Whether the output voltage of the system is above a predetermined voltage value; in the event that the output voltage of the system is above the predetermined voltage value, the system power switch in the system is turned off using the control signal. The method of claim 7, wherein the control signal is generated based on information associated with the sensing signal, the demagnetization signal, and the reference signal, the sensing signal being through the sensing stream Generated by the current of the system power switch, the demagnetization signal is generated by sensing a current flowing through an inductor connected in series with the one or more light emitting diodes. The method of claim 7, wherein the reference signal indicates a voltage that is no greater than a product of an internal reference voltage and a scaling factor that depends on a circuit configuration of the system.