CN107529254B

CN107529254B - Switching device, and applicable LED driving system and driving method

Info

Publication number: CN107529254B
Application number: CN201710922929.3A
Authority: CN
Inventors: 郜小茹; 孙顺根
Original assignee: Shanghai Bright Power Semiconductor Co Ltd
Current assignee: Shanghai Bright Power Semiconductor Co Ltd
Priority date: 2017-09-30
Filing date: 2017-09-30
Publication date: 2024-01-26
Anticipated expiration: 2037-09-30
Also published as: CN107529254A

Abstract

The application provides a switching device, an LED driving system and a driving method, wherein the switching device comprises a switching unit and a controller; the controller is connected with a switch unit, wherein the switch unit is used for being connected between an input source and a resonance device, and comprises: the detection unit is used for acquiring a first electric signal for reflecting current change in the resonance device and acquiring a second electric signal for reflecting voltage change provided by an input source from the switching unit, outputting the first detection signal when detecting the opening moment of the switching unit set based on the first electric signal, and outputting the second detection signal when detecting the turning-on moment of the switching unit set based on the second electric signal; the control unit is connected with the detection unit and is used for controlling the connection or disconnection of the connected switch unit based on the received first detection signal and the second detection signal. The power output efficiency of the driving system is effectively improved.

Description

Switching device, and applicable LED driving system and driving method

Technical Field

The present disclosure relates to the field of LED driving, and in particular, to a switching device, and an LED driving system and driving method suitable for the switching device.

Background

The LED (light emitting diode) has various characteristics such as low operating voltage, low operating current, good impact resistance and shock resistance, high reliability, long service life, easy dimming, etc., and is widely used in various fields such as lighting, devices, display, indication, etc. However, LED devices have nearly severe requirements for driving power sources, for example, in order to ensure that LEDs reflect corresponding characteristics in applications, LED driving power sources need to have very high requirements in terms of efficiency conversion, effective power, constant current precision, power lifetime, electromagnetic compatibility, and the like.

In order to supply a constant current power supply with a high power factor to an LED load, an LED driving power supply adopts a driving manner of outputting a constant current by oscillation of a resonance device. The current common LED driving power supply includes, according to different operation modes of the resonant device: a switching device based on BCM (critical continuous current operation mode), a switching device based on DCM (discontinuous current operation mode), or the like. These switching devices are connected to the resonant device through peripheral circuits and are directed to providing a constant current output conforming to a high power factor index by effectively utilizing resonance through detection of the resonant device.

In fact, an increase in power factor can be achieved by improving the switching device while the skilled person wishes to minimize the losses and size of the switching device using semiconductor integration techniques. As a result, studies on switching devices are increasingly intensive. As shown in fig. 1, which depicts a simplified schematic of a circuit of an LED driving system, an electrical signal in a resonant device is collected between a switching device 911 and the resonant device 912 through sampling resistors RFBL and RFBH, and the switching device 911 based on gate driving is controlled to be turned on and off by detecting a valley of the electrical signal. In the switching devices of the above-mentioned type, since the oscillation period of the resonance device is not necessarily associated with the power supply fluctuation period, the power output efficiency of the entire driving system is not high.

Disclosure of Invention

The application provides a switching device, an LED driving system and a driving method which are applicable to the switching device and are used for solving the problem of low power output efficiency of the driving system.

To achieve the above and other objects, the present application provides in a first aspect a controller for connecting a switching unit for connection between an input source and a resonance device, comprising: a detection unit configured to acquire a first electric signal for reflecting a change in current in the resonance device and acquire a second electric signal for reflecting a change in voltage supplied from an input source from the switching unit, output the first detection signal when an off timing of the switching unit set based on the first electric signal is detected, and output the second detection signal when an on timing of the switching unit set based on a change in the second electric signal is detected; and the control unit is connected with the detection unit and is used for controlling the connected switch unit to be turned on or turned off based on the received first detection signal and the received second detection signal.

In certain embodiments of the first aspect, the detection unit comprises: the demagnetization start detection module is connected between the sampling end of the switch unit and the control unit, and is used for starting magnetization timing based on a first electric signal acquired from the sampling end when the switch unit is detected to be turned on, and outputting a first detection signal when the magnetization timing is finished.

In certain implementations of the first aspect, the demagnetization start detection module includes: a reference voltage generating circuit for determining a voltage corresponding to an average output current of the resonant device by detecting the first electric signal, and determining a reference voltage based on the determined voltage; the signal generation circuit is connected with the control unit and is used for generating a slope electric signal when the switch unit is detected to be conducted; and the comparison circuit is connected with the reference voltage generation circuit and the signal generation circuit, and is used for comparing the voltage of the ramp electric signal with the reference voltage and outputting a first detection signal when the voltage of the ramp electric signal reaches the reference voltage.

In certain embodiments of the first aspect, the reference voltage generating circuit includes a transconductance integrator having a first input terminal connected to the sampling terminal, a second input terminal connected to a reference voltage source, and an output terminal for connecting to an external low pass filter unit.

In certain embodiments of the first aspect, the signal generating circuit comprises a ramp signal generator having a control terminal connected to the control unit and an output terminal connected to the comparison circuit.

In certain embodiments of the first aspect, the detection unit comprises: the demagnetizing end detection module is connected between the driving end of the switch unit and the control unit, and is used for comparing a second electric signal acquired from the driving end with a preset valley voltage threshold value, and outputting a second detection signal when the voltage of the second electric signal reaches the valley voltage threshold value.

In certain implementations of the first aspect, the valley voltage threshold is a threshold voltage set based on parasitic capacitance release in the switching unit.

In certain implementations of the first aspect, the control unit includes: a control module for outputting a switch control signal for turning on the switching unit based on the received first detection signal and outputting a switch control signal for turning off the switching unit based on the received second detection signal; and the driving module is connected with the control module and is used for converting the received switch control signals into corresponding switch driving signals so as to drive the connected switch units.

In certain implementations of the first aspect, the controller further comprises: and the delay unit is used for maintaining the disconnection state for a delay time when the switch unit is detected to be disconnected.

In certain implementations of the first aspect, the detection unit obtains a first electrical signal from a source of the switching unit and a second electrical signal from a gate of the switching unit.

The present application provides in a second aspect a switching device comprising: a switching unit for connection between the input source and the resonant device; and a controller as described in any one of the above, connected to the switching unit, for performing on-off control of the switching unit by detecting the first and second electric signals flowing through the switching unit.

In certain embodiments of the second aspect, the switching unit comprises a gate-driven based power tube; the controller obtains a first electrical signal from a source electrode of the power tube and a second electrical signal from a gate electrode of the power tube.

The present application provides in a third aspect an LED driving system comprising: the alternating current-direct current conversion device is used for converting alternating current into direct current and outputting the direct current; a resonant device for providing constant current power to the LED load based on the controlled oscillation; a switching device as described above, connected to the path between the ac/dc conversion device and the resonance device, for controlling the path to be turned on or off based on the acquired first and second electric signals; the first electric signal is used for reflecting current change in the resonance device, and the second electric signal is used for reflecting voltage change provided by the input source.

In certain embodiments of the third aspect, the switching device further comprises a low-pass filter unit connected to the detection unit in the switching device.

The present application provides in a fourth aspect a switch control method, including: acquiring a first electric signal and a second electric signal flowing through a switch unit; a change in medium pressure; setting an off time of a switching unit based on the first electric signal, and turning off the switching unit when the off time is reached; and setting a turn-on timing of the switching unit based on the change of the second electric signal, and turning on the switching unit when the turn-on timing is reached.

In certain embodiments of the fourth aspect, the manner of setting the off-time of the switching unit based on the first electrical signal includes: starting to time the duration that a slope voltage reaches a reference voltage when the switching unit is detected to be conducted, and controlling the switching unit to be disconnected at the moment that the slope voltage reaches the reference voltage; wherein the reference voltage is a voltage obtained by detecting the first electric signal.

In certain embodiments of the fourth aspect, the manner of setting the on-time of the switching unit based on the change in the second electrical signal includes: comparing the second electric signal with a preset valley voltage threshold, and determining the turn-on time of the switch unit when the voltage of the second electric signal reaches the valley voltage threshold.

In certain implementations of the fourth aspect, the valley voltage threshold is a threshold voltage set based on parasitic capacitance release in the switching cell.

In certain embodiments of the fourth aspect, the method further comprises the step of maintaining the off state of the switching unit for a delay period when the switching unit is detected to be off.

The present application provides in a fifth aspect an LED driving method, including: controlling the on and off of the switching device by using the steps provided by the switching control method; and controlling the oscillation process of the resonance device based on the on and off of the switching device so as to drive the LED load to work.

The present application provides in a sixth aspect an LED control chip comprising: a controller as claimed in any one of the preceding claims, for controlling the switching unit to be turned on or off by detecting first and second electrical signals flowing through the connected switching unit.

In certain embodiments of the sixth aspect, the LED control chip further comprises the switching unit.

According to the switching device, the LED driving system and the driving method, the first electric signal used for reflecting the current change in the resonant device is collected from the sampling end of the switching unit, the second electric signal used for reflecting the voltage change provided by the input source is collected from the driving end of the switching unit, and the oscillating process of the resonant device is controlled by detecting the first electric signal and the second electric signal, so that the waveform change of the input source can be utilized to the maximum extent, and the driving circuit with high power factor can be provided for a high-power load.

Drawings

Fig. 1 is a simplified schematic diagram of a related art LED driving system in an embodiment.

Fig. 2 is a simplified circuit schematic of a switching unit in one embodiment of a switching device according to the present application.

Fig. 3 is a schematic structural diagram of a controller in an embodiment of a switching device according to the present application.

Fig. 4 is a schematic circuit diagram of a demagnetization initiating detection module in an embodiment of the switching apparatus of the present application.

FIG. 5 is a waveform diagram of each end of RAMP, COMP and off_pulse of FIG. 4.

Fig. 6 is a waveform diagram of the electrical signals at each end of the circuit of the switching device according to the present application under the variation of Vin signal provided by the input source.

Fig. 7 is a schematic diagram of a simplified circuit configuration of a demagnetization end detection module in an embodiment of the switching apparatus of the present application.

Fig. 8 is a schematic structural view of a switching device according to another embodiment of the present application.

Fig. 9 is a schematic structural view of a switching device according to another embodiment of the present application.

Fig. 10 is a waveform diagram of each end of the structure of fig. 9 including a delay control signal.

FIG. 11 is a schematic diagram of a chip package of an LED control chip according to an embodiment of the present application.

Fig. 12 is a schematic diagram of a chip package of an LED control chip according to another embodiment of the present application.

Fig. 13 is a simplified circuit schematic of an LED system of the present application in one embodiment.

FIG. 14 is a flow chart of a switch control method according to an embodiment of the present application.

Note that, in fig. 6 and 10, vin is an envelope waveform of the voltage signal output by the input source.

Detailed Description

Other advantages and effects of the present application will become apparent to those skilled in the art from the present disclosure, when the following description of the embodiments is taken in conjunction with the accompanying drawings. The present application may be embodied or carried out in other specific embodiments, and the details of the present application may be modified or changed from various points of view and applications without departing from the spirit of the present application.

It should be noted that, the structures, proportions, sizes and the like shown in the drawings attached to the present specification are used for understanding and reading only in conjunction with the disclosure of the present specification, and are not intended to limit the applicable limitations of the present application, so that any structural modification, change of proportion or adjustment of size is not technically significant, and all fall within the scope of the technical disclosure of the present application without affecting the efficacy and achievement of the present application. Also, the terms such as "upper," "lower," "left," "right," "middle," and "a" and the like recited in the present specification are merely for descriptive purposes and are not intended to limit the scope of the present application to which they may be applied, but rather to modify or adapt the relative relationship without materially altering the technical context.

The controller of fig. 1 is capable of adjusting the oscillation process of the resonant device, but the constant current voltage output by the resonant device has poor stability because it is not necessarily related to the input current fluctuation period. Accordingly, the present application provides a switching device, a switching control method, and an applicable LED drive.

It should be noted that the technical scheme of the switching device provided by the application is not only used in an LED driving system, but also can be applied to other circuit systems including switching devices, such as instruments and meters, medical equipment, air purifying equipment, and the like. Wherein the switching device may be integrated as a chip or packaged by an electronic device on a carrier such as a PCB board.

The switching device can control the oscillation process of the resonant device by controlling the power supply to the resonant device, wherein the switching device comprises a controller and a switching unit. The switching unit is connected to a power supply line of the resonance device to be controlled to turn on or off the line. The controller is used for controlling the on-off of the switch unit.

Wherein the switching unit comprises a controlled switching device. The number of controlled switching devices may be one or more. The controlled switching device can be a power tube based on grid drive or be formed by cascading a plurality of power tubes. For example, referring to fig. 2, a simplified circuit structure of the switch unit is shown. The power tube Q1 is a gate drive, the gate of which is connected to the output end of the controller 11, the source is connected to the resonant device 3, and the drain is connected to the input source 2. Wherein, the input source 2 comprises commercial power and an alternating current-direct current conversion device.

In order to more effectively utilize the power supplied by the input source to drive the load, please refer to fig. 3, which is a schematic diagram of the structural framework of the controller in one embodiment provided in the present application. The controller comprises a detection unit 111 and a control unit 112.

The detection unit 111 is configured to acquire a first electric signal for reflecting a change in current in the resonance device 3 and a second electric signal for reflecting a change in current supplied from the input source 2 from the switching unit 12, output the first detection signal when detecting an off timing of the switching unit 12 set based on the first electric signal, and output the second detection signal when detecting an on timing of the switching unit 12 set based on a change in the second electric signal.

The detection unit 111 can acquire the first and second electrical signals by detecting the connection nodes of the switching unit 12 and the resonator device 3, and the switching unit 12 and the input source 2, respectively. In some embodiments, the detection unit 111 connects the sampling end of the switching unit 12 and the driving end of the power tube in the switching unit 12, so as to obtain the first electrical signal and the second electrical signal respectively. For example, as shown in fig. 2, the controller 11 is connected to the source of the power transistor Q1 in the switching unit 12 to obtain a first electrical signal, and the controller 11 is connected to the gate of the power transistor Q1 in the switching unit 12 to obtain a second electrical signal.

The first electric signal is taken from a sampling end of the switch unit connected with the resonance device, so that the first electric signal reflects current or voltage change in the resonance device. The controller may control the switching unit to be turned off based on the first electrical signal. The controller and the resonance device are connected through a sampling circuit, and the sampling circuit comprises a sampling resistor. In some embodiments, the controller is internally provided with a sampling resistor, one end of the sampling resistor is connected with the sampling end, or the resonant device is internally provided with the sampling resistor, the sampling end of the controller is connected with the sampling resistor, or the sampling end of the controller is connected with the resonant device through an external sampling resistor.

In addition, since the switch unit is connected to the input source, a second electric signal reflecting the voltage variation provided by the input source can be obtained from the switch unit. Taking a switching unit including a power tube as an example, since parasitic capacitance is provided between drain gates of the power tube, a voltage change of an input source is reflected on a gate as a driving end by the parasitic capacitance. The second electrical signal on the acquisition gate can also reflect the voltage or current change provided by the input source.

The detection unit can be independently provided with detection conditions for detecting the opening and closing time of the switch, and the switch unit is controlled to be opened or closed when corresponding conditions are met. The detection unit may also detect only one of the electrical signals based on the current on-state or off-state of the switching unit. For example, during a period when the switching unit is in an on state, the detecting unit detects only the first electric signal so as to output the first detection signal. For example, during the off state of the switching unit, the detecting unit detects only the second electrical signal so as to output the second detection signal.

In some embodiments, the detection units both detect each electrical signal acquired individually and cooperate with each other to facilitate accurate control of the switching unit.

The detection unit comprises a demagnetization start detection module, is connected between a sampling end of the switch unit and the control unit, and is used for starting magnetization timing based on a first electric signal acquired from the sampling end when the switch unit is detected to be turned on, and outputting a first detection signal when the magnetization timing is finished.

Referring to fig. 4, a simplified circuit diagram of the demagnetization start detection module in an embodiment is shown, where the demagnetization start detection module includes: a reference voltage generation circuit 412.

The reference voltage generating circuit 412 is connected to the sampling terminal CS, and is configured to determine a reference voltage by detecting. Wherein the reference voltage generation circuit 412 comprises a transconductance integrator. The transconductance integrator obtains the reference voltage by amplifying and integrating an error between the first electrical signal and a reference voltage threshold.

For example, the transconductance integrator in the reference voltage generating circuit 412 has a first input terminal connected to the sampling terminal CS, a second input terminal connected to a reference voltage source, and an output terminal COMP outputting the reference voltage. Wherein, because the first electric signal is basically linear, the output reference voltage is basically stable. The output end is also used for being connected with an external low-pass filtering unit so that the output reference voltage Vcomp is stable.

For example, as shown in fig. 4, the negative input terminal (i.e., the first input terminal) of the transconductance integrator Gm is connected to the source (i.e., the sampling terminal CS) of the power transistor Q2, the positive input terminal (i.e., the second input terminal) of Gm is connected to a reference voltage source to always receive the voltage VREF, and the output terminal COMP outputs the reference voltage Vcomp. Wherein the reference voltage source may be integrated with the switching device or connected through a chip pin.

As shown in fig. 4, the demagnetization start detection module further includes a signal generation circuit 411 and a comparison circuit 415.

Wherein, the signal generating circuit 411 is connected to the control unit 413, and is configured to generate a ramp electric signal when it is detected that the switch unit 42 is turned on. Here, the control terminal of the signal generating circuit 411 may be connected between the control unit 412 and the switching unit 42, for example, connected to the driving terminal (GATE terminal) of the power tube, so as to receive a control signal for turning on the switching unit 42. For example, the signal generating circuit 411 includes a power tube A1 (not shown), a driving end of the power tube A1 is connected to a driving end of the power tube Q1, and when the power tube A1 receives the on control signal, the ramp signal generator in the signal generating circuit 411 is controlled to generate the ramp signal. The ramp signal generator may be a circuit including a capacitor, and starts to count from the time when the switch unit 42 is turned on by using a time period required for charging the capacitor, and the capacitor voltage rises linearly during charging and is output to the comparison circuit. The output end of the RAMP signal generator outputs a RAMP signal to the comparison circuit.

The comparison circuit 415 is connected to the reference voltage generation circuit 412 and the signal generation circuit 411, and is configured to compare the voltage of the ramp electric signal with the reference voltage, and output a first detection signal when the voltage of the ramp electric signal reaches the reference voltage.

Taking fig. 4 as an example, please refer to fig. 5, which shows waveforms of the ends of RAMP, COMP and off_pulse (output signal of the comparison circuit). A RAMP signal (RAMP signal) in a signal generating circuit is supplied to a positive input terminal of a comparing circuit, and Vcomp or a divided voltage based on Vcomp is supplied to a negative input terminal of the comparing circuit. In the example of fig. 4, the high level output from the off_pulse end of the comparison circuit 415 is a first detection signal, which indicates that the Vramp voltage has reached the Vcomp voltage (or the divided voltage of Vcomp). The control unit 413 outputs a control signal to turn off the switching unit based on the received first detection signal.

The signal generating circuit further comprises a bleeder circuit (not shown). The control terminal of the bleeder circuit may be shared with the output terminal of the ramp signal generator. For example, the bleeder circuit includes a controlled switch (e.g., power transistor A2) connected to ground and in parallel with a capacitor in the ramp generator, where power transistor A2 is turned on and off in opposite directions to power transistor A1. The control unit outputs a control signal for turning off the switching unit based on the received first detection signal to a control terminal of the signal generating circuit. Such as the gate of power tube A2. When receiving the disconnected control signal, the power tube A2 is conducted and discharges charges charged by a capacitor in the ramp signal generator, so that the Vramp voltage output by the ramp signal generator is reduced, when Vramp is smaller than Vcomp voltage (or the divided voltage of Vcomp), the off_pulse signal voltage output by the comparison circuit is changed from high level to low level, and the control unit still controls the switch unit to keep the disconnected state because the control unit does not receive the second detection signal.

For controlling the switch unit to be turned on, the detection unit comprises: the demagnetizing end detection module is connected between the driving end of the switch unit and the control unit, and is used for comparing a second electric signal acquired from the driving end with a preset valley voltage threshold value, and outputting a second detection signal when the voltage of the second electric signal reaches the valley voltage threshold value. Wherein the valley voltage threshold may be slightly above or slightly below the ground voltage. For a switching cell comprising a semiconductor device, such as a switching cell comprising a power transistor, the parasitic capacitance is charged or discharged when the voltage in the switching cell changes. The demagnetization end detection module can determine the conduction time of the switch unit by detecting a downward detection peak generated by discharging of the parasitic capacitance in the second electric signal. Correspondingly, the valley voltage threshold is a threshold voltage set based on parasitic capacitance release in the switch unit.

Referring to fig. 6, a schematic diagram of a downward peak waveform generated in the second electrical signal GATE by discharging the parasitic capacitor with a short period of time when the input source voltage is changed from high to low is shown. The demagnetization end detection module compares whether the received second electric signal reaches the valley voltage threshold or not, if yes, the second detection signal is output, and otherwise, the second detection signal is not output. For example, please refer to fig. 7, which shows a simplified circuit diagram of the demagnetization end detection module in the switching apparatus. The demagnetization end detection module comprises a comparator 512, wherein a negative input end of the comparator 512 is connected with a GATE end of the power tube Q1 to receive the second electric signal, and a positive input end of the comparator is connected with a reference voltage source to maintain a valley voltage threshold zcd _ref. Referring to fig. 6 and 7, during the on period of the switching unit 52, the gate voltage of the power transistor Q1 is high, the voltage of the second electrical signal is always higher than the valley voltage threshold zcd _ref, and the comparator always outputs a low level. When the Vin voltage provided by the input source 2 is changed from high to low, the parasitic capacitance between the gates and the drains of the power transistors discharges, so that the gate voltage continues to be detected during the initial transient period of decreasing to low level with Vin, so as to generate the detected peak, at this time, the comparator 512 compares the voltage of the second electric signal with the threshold ZCD _ref of the valley voltage and outputs a second detection signal with ZCD being the pulse signal (or high level). The control unit 513 controls the switching unit 52 to be turned on according to the second detection signal.

The control unit is used for outputting a control signal for driving the switch unit to the second driving end based on the received first detection signal and the second detection signal.

When the control unit receives a first detection signal indicating a demagnetization starting time, an off control signal is output to a second driving end connected with the switch unit, and when the control unit receives a second detection signal indicating a demagnetization ending time, an on control signal is output to the switch unit. The control signal for turning on and off may be a pulse signal or an enable signal. For example, as shown in fig. 2 and 3, the switching unit 12 includes a power tube Q1, and the control signal is an enable signal, that is, a continuous level signal, and is input from a driving end (Gate end) of the power tube Q1. When the control signal is at a low level, the voltage difference between the gate and the source of the power tube Q1 does not meet the on voltage, and the drain and the source of the power tube Q1 are disconnected, so that the switching unit 12 does not provide power and outputs. When the control signal is at a high level, the drain-source electrode of the power tube Q1 is turned on, and the current provided by the input source 2 is delivered to the resonance device 3 through the switching unit.

Here, the control unit may be composed of a circuit including a logic device including, but not limited to: analog logic devices and digital logic devices. Wherein the analog logic device is a device for processing analog electrical signals, including but not limited to: comparators, AND gates, OR gates, etc.; the digital logic device is used for processing the device of the digital signal represented by the pulse signal, which includes but is not limited to: flip-flops, gates, latches, selectors, etc. The control unit receives the first detection signal and the second detection signal through two ports respectively, performs logic processing on the received signals by utilizing a logic configuration table, and outputs a control signal for switching on or switching off based on a processing result.

In some embodiments, the control unit includes a control module and a drive module.

The control module is connected with the detection unit and is used for outputting a switch control signal for enabling the switch unit to be disconnected based on the received first detection signal and outputting a switch control signal for enabling the switch unit to be conducted based on the received second detection signal.

In this regard, please refer to fig. 8, which shows a schematic structural diagram of a switching device in yet another embodiment. The control module 613 includes two input terminals, one of which is connected to the demagnetization start detection module 611 and is configured to receive a first detection signal; the other input terminal is connected to the demagnetization end detection module 612, and is configured to receive a second detection signal. The control module 613 is a logic circuit configured based on the waveform and signal combination of the first detection signal and the second detection signal. For example, as shown in fig. 8, the control module 613 includes a trigger, and a reset terminal (R terminal) of the trigger may be connected to the demagnetization start detection module 611 and the demagnetization end detection module 612 directly or through a peripheral circuit of the trigger, so as to receive the first detection signal; the set end (S end) of the flip-flop may be connected to the detection unit directly or through a peripheral circuit of the flip-flop, for receiving the second detection signal. The first detection signal and the second detection signal are exemplified by pulse signals. When the R end receives the pulse signal and the S end is a low level signal, the trigger outputs an open switch control signal based on the logic combination in the trigger; when the S end receives the pulse signal and the R end is a low level signal, the trigger outputs a switch control signal which is conducted based on logic combination in the trigger. For the switching unit 62 including a power tube, the switching control signal needs to be output to the switching unit 62 through the driving module 614.

The driving module 614 is connected to the control module 613, as shown in fig. 8, for converting the received switch control signals into corresponding switch driving signals to drive the connected switching units 62. Here, the driving module 614 can be used to amplify the switch control signal and output a current with a certain driving capability to drive the power tube in the switch unit 62. The output end of the driving module 614 is connected to the gate of the power tube Q1 in the switching unit 62, so that the input source supplies energy to the resonant device after the power tube Q1 is turned on.

In some embodiments, since the input source is prone to voltage fluctuation during an instant after the input source changes from low level to high level, the corresponding second electric signal will also output voltage fluctuation, and the voltage fluctuation of the parasitic capacitance is superimposed by the fluctuating voltage, so that the demagnetization end detection module may generate the second detection signal by mistake. To prevent false triggering of the end of demagnetization detection module, the controller further comprises: and a delay unit.

The delay unit is used for maintaining the disconnection state in a delay time when the switch unit is detected to be disconnected.

For this purpose, the delay unit may be connected to the output of the detection module, or receive the first detection signal to determine that the switching unit is turned off, and start to time with a delay when the switching unit is detected to be turned off, and the control unit does not output the on control signal all the time during the time of the delay, and after the time of the delay is finished, the control unit turns on the switching unit based on the received second detection signal. The delay time of the delay unit is smaller than the time from the controller to the high reduction of the voltage provided by the input source after the switch unit is disconnected.

In some embodiments, the delay unit may be effective to an off control signal of the switching unit, latch the off control signal for a delay time period, and output a corresponding delay control signal to the detection unit. Correspondingly, the demagnetization end detection module does not output the second detection signal no matter whether the voltage of the second electric signal is reduced to the valley voltage threshold value or not in the duration period of the delay control signal until the delay control signal disappears.

In still other embodiments, referring to fig. 9, a schematic structural diagram of a switching device including a delay unit is shown. The delay unit 714 may be connected between the control module 713 and the driving module 715, and is effective with the off control signal output by the control module 713, and latches the off control signal for a delay time when the off control signal is received, where the latched delay control signal is output to the driving module, and the driving module 715 includes a logic circuit for not driving the switching unit to be turned on regardless of whether the control module outputs the on control signal during the duration of the delay control signal until the delay control signal disappears.

Taking fig. 9 as an example, the internal circuit of the switching device provided in the present application includes a CS sampling end, a COMP end, a ZCD end, an off_pulse end, and a GATE end, where the demagnetization start detection module 711 and the demagnetization end detection module 712 are respectively connected to the CS sampling end and the GATE end and are configured to receive the first electrical signal and the second electrical signal, and output a first detection signal and a second detection signal through the off_pulse end and the ZCD end, respectively; the control module 713 receives the first and second detection signals, respectively, and outputs a switch control signal; a driving module 715 is connected to the control module 713 for amplifying a switching control signal to drive a subsequent stage circuit. The switching unit 72 connected to and controlled by the controller includes, for example, a GATE-based (GATE-side) driving switching circuit.

Taking fig. 9 as an example, and referring to fig. 10, fig. 10 is a schematic diagram of waveforms at each end including a waveform of a delay control signal strong_pd. The operation of the switching device will now be described by taking the period T1 to T2 as an example. When the controller turns on the switch unit 72 (corresponding to time T1), the CS end generates an electric signal with increased voltage under the influence of magnetizing the resonant device 3, and the demagnetization start detection module 711 in the controller collects the first electric signal CS of the CS end and inputs the first electric signal CS to the reference voltage generation circuit, wherein the transconductance integrator in the reference voltage generation circuit amplifies and integrates the error voltage of the first electric signal CS and the voltage Vref, and then the error voltage is large, and the Vcomp voltage is output from the COMP end; meanwhile, the signal generating circuit in the demagnetization start detection module 711 starts to generate a ramp signal when the controller turns on the switching unit, and the voltage Vramp and the voltage Vcomp of the ramp signal are respectively output to the positive input terminal and the negative input terminal of the comparison circuit, and when the Vramp voltage reaches the Vcomp voltage, the output terminal (off_pulse terminal) of the comparison circuit outputs a high level (i.e., the first detection signal). Since the switching unit is turned ON, the voltage of the second electrical signal GATE received by the demagnetization end detection module 712 is always higher than the valley voltage threshold vzcd_ref, the output end (ZCD end) of the demagnetization end detection module 712 always outputs a low level during the ON period of the switching unit 72, and the control module 713 in the control unit outputs an off switch control signal (gate_on signal) from the output end (e.g., Q end) when the reset end (e.g., R end) receives a high level and the set end receives a low level, and the drive module 715 in the control unit outputs the gate_on signal from high to low to the GATE of the power transistor Q1 in the switching unit 72, so that the voltage of the GATE (GATE end) of the power transistor Q2 is reduced, thereby causing the power transistor Q1 to be turned off. The first electrical signal CS accordingly generates a waveform of reduced voltage in response to the discharging process of the electric energy of the resonance device (i.e., the demagnetizing process).

In the initial transient period of demagnetization, in order to prevent the input source Vin from generating jitter during the high level period, the delay unit 714 forces the driving module not to turn on the power tube Q1 based on the off control signal until the end of the delay timer.

During demagnetization, on the one hand, when the demagnetization initiation detection module 711 receives an OFF control signal of the gate of the power transistor Q2, wherein the signal generation circuit resets the RAMP signal so that the Vramp voltage of the RAMP terminal is lower than the Vcomp voltage, the off_pulse terminal outputs a low level to the reset terminal of the control unit. On the other hand, the second electric signal GATE generates a voltage change for probing down when a transient delay is generated after the switch unit 72 is turned off, and the demagnetization end detection module detects that the second electric signal GATE is lower than the valley voltage threshold vzcd_ref, so as to output a high level (i.e., a second detection signal). The control module 713 in the control unit outputs a switch control signal (gate_on signal from low to high) from the output terminal (e.g., Q terminal) when the reset terminal (e.g., R terminal) receives the low level and the set terminal receives the high level, and the driving module in the control unit amplifies the gate_on signal to the GATE (GATE terminal) of the power transistor Q2 in the drivable switching unit 72 and turns ON the power transistor Q1 through the power transistor Q2, so that the power supply path between the input source 2 and the resonant device 3 is turned ON, and the first electrical signal CS generates a waveform with a voltage rise according to the storage process (i.e., the magnetizing process) of the electrical energy of the resonant device 3. The controller repeats the magnetizing and demagnetizing processes so that the resonant device 3 supplies constant current power to the load.

Taking the example that the controller is configured in an LED driving system, the present application may provide an LED control chip including the controller. The LED control chip comprises pins connected with an external circuit. The controller may be packaged separately or with other circuits (such as a reference voltage source) in an LED control chip and externally connected to the switching unit. Referring to fig. 11, a schematic package diagram of an LED control chip in one embodiment is shown. The LED control chip includes a COMP pin, a CS pin, a GATE pin, a VCC pin, and a GND pin. The COMP pin is used for connecting a low-pass filtering unit, so that Vcomp in the controller is ensured to be basically stable. The CS pin is connected with the joint of the resonance device and the switch unit to acquire a first electric signal. The GATE pin is connected with a grid electrode of a power tube Q1 in the switch unit and is used for conducting and disconnecting control on the switch unit; the GATE pin also provides a second electrical signal. The VCC pin is connected with an external power supply or an external capacitor and used for supplying power to the LED control chip and providing stable voltage for a reference voltage source. The GND pin is used for grounding.

In some embodiments, the power transistor Q1 in the switching unit may be integrated in the LED control chip. Referring to fig. 12, a schematic package diagram of an LED control chip in yet another embodiment is shown. The LED control chip comprises a COMP pin, a CS pin, a VCC pin, a DRAIN pin and a GND pin. The COMP pin is used for connecting a low-pass filtering unit, so that Vcomp in the controller is ensured to be basically stable. The CS pin is connected with the joint of the resonance device and the switch unit to acquire a first electric signal. The VCC pin is connected with an external power supply or an external capacitor and is used for supplying power to the LED control chip and providing stable voltage for the reference voltage source; the VCC pin may also connect to the gate of the power transistor Q1 in the switching unit to provide a regulated voltage. The GND pin is used for grounding. The DRAIN pin is used for connecting an input source. The second electrical signal is collected by the GATE terminal of the chip internal power tube Q1.

The application also provides an LED driving system designed by adopting the switching device. Referring to fig. 13, a schematic structural diagram of the LED driving system in an embodiment is shown. The LED driving system includes: an ac/dc conversion device 81, a switching device 82, and a resonance device 83.

The ac/dc conversion device 81 is used for converting ac power into dc power. Wherein, the ac/dc conversion device 81 can be connected to the commercial power. The LED driving system can select parameters of all devices in the controller according to the voltage of the input source and the power frequency. The ac/dc conversion device 81 includes: a rectifier bridge circuit and a low pass filter circuit connected to the input source. For example, as shown in fig. 13, diodes D2, D3, D4, and D5 constitute a rectifier bridge circuit, and a low-pass filter circuit including a capacitor C1 is provided between an output terminal and a ground terminal of the rectifier bridge circuit.

The resonant device 83 is used to provide constant current power to the LED load based on controlled energy variation. The resonant device 83 includes an LC oscillator and its peripheral circuit including a sampling resistor connected to a sampling terminal of the switching device. The parameters of the inductance and the capacitance of the LC oscillator may be determined based on the mains frequency, the mains voltage, the output voltage and current specification, the magnetizing duration, and the demagnetizing duration. For example, in the critical continuous current operation mode, the magnetizing time of the resonant device 83 is kept substantially constant at a certain fixed mains voltage effective value and a fixed output voltage specification, so that the entire LED driving system has a high power factor in the critical continuous current operation mode.

The switching device 82 is connected to the ac/dc conversion device 81 and the resonance device 83, and is configured to control the on/off of the channel based on detecting the first electrical signal collected from the sampling end and the second electrical signal collected from the first driving end. For example, a simplified circuit diagram of the switching device can be seen in fig. 4, 5, 6, 7, 9, 11 and their corresponding description.

Taking fig. 13 as an example, the working process of the LED driving system for driving the LED load is as follows: the ac/dc conversion device 81 converts the mains supply into a quasi square wave and outputs the quasi square wave to the switching device 82, the switching device 82 is turned on and magnetizes the resonant device 83 at the beginning, and the switching device 82 collects a first electrical signal at the CS end of the power tube Q1 and a second electrical signal at the GATE end. The demagnetization starting detection module in the switching device 82 generates a ramp electric signal according to the on control signal of the switching device, and generates a reference voltage Vcomp corresponding to the ramp electric signal according to the first electric signal, and the demagnetization starting detection module performs magnetization timing based on a time period spent by the ramp electric signal rising from an initial voltage to the reference voltage Vcomp. The demagnetization end detection module in the switching device does not output the second detection signal according to the fact that the second electric signal is always larger than the valley voltage threshold Vzcd_ref. When the magnetization timing of the demagnetization starting detection module is finished, that is, vramp is greater than or equal to Vcomp, a first detection signal is output to a control unit in the switching device, and the control unit controls the switching unit in the switching device 82 to be turned off, so that the resonance device 82 starts the demagnetization operation. When the demagnetization operation starts, indicated by the off control signal in the switching device 82, the ramp signal is reset so that the demagnetization start detection module does not output the first detection signal; meanwhile, the GATE end voltage is detected to vzcd_ref, and when the demagnetization end detection module judges that the GATE end voltage is lower than vzcd_ref, the demagnetization end detection module outputs a second detection signal to the control unit, and the control unit controls the switch unit in the switch device to be conducted according to the second detection signal, so that the resonance device enters magnetizing operation.

The LED driving system further comprises a low-pass filtering unit which is connected with the detection unit in the switching device.

The low-pass filtering unit is a circuit comprising a capacitor, wherein the capacitor is connected with a demagnetization starting detection module in the detection unit. For example, as shown in fig. 13, the capacitor Ccomp in the low-pass filter unit is connected to the COMP terminal of the controller. The low-pass filtering unit is used for reducing the variation of the Vcomp voltage, so that the time spent by the RAMP signal rising from the initial value to the Vcomp voltage is basically kept unchanged, namely the magnetizing time is basically unchanged, and thus, the high power factor is obtained in the critical continuous current working mode.

The application also provides a switch control method. The switching control method may be performed by the switching device or by a device that may perform the steps of the switching control method.

Referring to fig. 14, a flowchart of the switch control method in one embodiment is shown. The switch control method comprises the following steps: steps S110, S120.

In step S110, a first electrical signal and a second electrical signal are acquired from the switching unit; the first electric signal is used for reflecting current change in the resonance device, and the second electric signal is used for reflecting voltage change provided by the input source.

Here, the current flowing through the resonance device may be detected from either end of a switching unit connected to the resonance device to obtain the first electrical signal. In some embodiments, the first electrical signal may be acquired from a sampling end of the switch unit connected to the resonant device. For example, a sampling end of the switching unit is connected to a circuit node between the resonance device and the switching unit through a sampling resistor to acquire the first electric signal. A sampling circuit can be arranged between the resonance device and the switch unit, and current or voltage change in the resonance device can be reflected by a first electric signal at one side of the sampling resistor. Wherein the sampling circuit comprises a sampling resistor. The sampling resistor can be built in the demagnetization detecting unit of the controller, or built in the resonance device, or positioned on a path between the demagnetization detecting unit and the resonance device.

The second electrical signal is collected from inside the switching unit. The driving end is a driving end of a switching device in the switching unit, for example, as shown in fig. 2, and the first driving end is a gate of the power tube Q1. When the voltage received by the drain electrode changes due to parasitic capacitance between the gate electrode and the drain electrode of the power tube Q1, the voltage of the second electric signal received by the gate electrode also changes and the voltage of the parasitic capacitance is superposed. Therefore, when the voltage provided by the input source changes, the voltage change with more obvious change can be obtained more easily by collecting the second electric signal of the grid electrode, and the switch unit can be controlled to be conducted more accurately, so that the purpose of matching the portrait process of the resonance device with the voltage change of the input source is achieved.

In step S120, an off time of a switching unit is set based on the first electrical signal, and the switching unit is turned off when the off time is reached; and setting a turn-on timing of the switching unit based on the change of the second electric signal, and turning on the switching unit when the turn-on timing is reached.

In this case, when it is detected that the switching device is on, it means that a current flows to the resonant device, and the inductance in the resonant device starts to magnetize, i.e., the moment when the switching device changes from the off state to the on state is the magnetization start moment of the resonant device. The switching device opening may be determined by detecting a switching control signal in the switching device or detecting a voltage of the first detection signal.

Wherein the step of setting the off-time of the switching unit based on the first electrical signal may be performed using the steps of: starting to time the duration that a slope voltage reaches a reference voltage when the switching unit is detected to be conducted, and controlling the switching unit to be disconnected at the moment that the slope voltage reaches the reference voltage; wherein the reference voltage is a voltage obtained by detecting the first electric signal.

Here, the ramp signal is sent to the comparison circuit to be compared with a reference voltage Vcomp, and the time period taken for the voltage Vramp of the ramp signal to rise from the initial value to the reference voltage Vcomp is the magnetizing time period of the resonant device. When Vramp rises to Vcomp, the set resonance device is magnetized to enter demagnetizing operation, so that the switching device is controlled to be turned off. For example, vramp and Vcomp are compared by a comparison circuit, and the switching device is controlled to be turned off when Vramp is equal to or greater than Vcomp.

Here, the Vcomp voltage is a voltage generated based on the first electrical signal input to a transconductance integrator. For example, the acquired first electric signal (CS electric signal) flowing through the resonance device is supplied to the reference voltage generation circuit to output the Vcomp voltage. For example, the reference voltage generating circuit includes a transconductance integrator, the positive input terminal of which receives a reference voltage Vref, and the negative input terminal of which receives the first electrical signal, and the transconductance integrator outputs a Vcomp voltage as the reference voltage. The reference voltage Vref is provided by a reference voltage source, which may be provided exclusively by the reference voltage Vref or may be obtained based on the divided voltage of the chip supply voltage VCC.

The step of setting the on-time of the switching unit based on the change of the second electrical signal may be performed using the steps of: comparing the second electric signal with a preset valley voltage threshold, and determining the turn-on time of the switch unit when the voltage of the second electric signal reaches the valley voltage threshold.

Here, as shown in fig. 9 and 10, the driving end in the switching device is affected by the conduction of the power tube Q1 during the magnetizing period of the resonant device (i.e., during the conduction period of the switching device), and the second electric signal maintains a low-high level. During the demagnetization period of the resonance device (namely, during the disconnection period of the switching device), the voltage waveform change of the shaped input power source Vin is detected, when the Vin makes a downward jump, the GATE end of the grid electrode of the power tube Q1 outputs a downward jump edge and goes down to the valley voltage threshold Vzcd_ref, and when the voltage of the second electric signal is smaller than or equal to the valley voltage threshold, the demagnetization ending moment is set and the switching device is controlled to be conducted.

For a switching device including a semiconductor device, as shown in fig. 9 and 10, the switching device using the power transistor Q1 as the switching device, the voltage fluctuation of the input source affects the voltage fluctuation of the gate of the power transistor Q1 during the initial moment of switching device off, thereby causing a dip change in the second electric signal, and in order to prevent the voltage corresponding to the dip change from triggering the switching device to be turned on by mistake, the method further includes the step of detecting the second electric signal when the switching device is turned off during the detection of the end of demagnetization.

When the switching device is turned off, the corresponding off control signal is latched for a delay time. And outputting a second detection signal no matter whether the voltage of the second electric signal is reduced to the valley voltage threshold value or not in the duration of the delay time duration until the delay time is ended. Wherein the delay time duration is less than the high level duration of the input source.

The switch control method is used for realizing on-off control of the switch device connected with the resonance device by setting the demagnetizing process of the external resonance device, so that continuous or intermittent oscillation of the resonance device is realized, and constant current power supply is provided for a load.

When the load connected with the resonance device is an LED load, the application further provides an LED driving method for realizing constant current power supply of the LED load. The LED driving method is used for a driving system for constant-current power supply of the LED load by using the resonance device.

According to the LED driving method, through executing the steps of a switch control method, when the demagnetization starting time is determined, a switch device connected with the resonance device is controlled to be disconnected, so that inductance in the resonance device enters demagnetization operation, and the resonance device outputs constant current power supply to an LED load. When the demagnetization end time is determined, the switching device can be controlled to be conducted, so that the inductor in the resonance device enters the magnetizing operation. The LED load is thus driven to operate based on the oscillating control of the resonant device by turning on and off the switching device.

Although the present invention has been described with respect to the preferred embodiments, it is not intended to limit the scope of the invention, and any person skilled in the art may make any possible variations and modifications to the technical solution of the present invention using the methods and technical matters disclosed above without departing from the spirit and scope of the present invention, so any simple modifications, equivalent variations and modifications to the above embodiments according to the technical matters of the present invention fall within the scope of the technical matters of the present invention.

Claims

1. A controller for connecting a switching unit for connection between an input source for providing direct current and a resonant device, comprising:

a detection unit configured to acquire a first electric signal for reflecting a change in current in the resonance device and acquire a second electric signal for reflecting a change in voltage supplied from an input source from the switching unit, output the first detection signal when an off timing of the switching unit set based on the first electric signal is detected, and output the second detection signal when an on timing of the switching unit set based on a change in the second electric signal is detected;

a control unit connected to the detection unit for outputting a switch control signal for turning off the switch unit based on the received first detection signal to control the switch unit to be turned off, and outputting a switch control signal for turning on the switch unit based on the received second detection signal to control the switch unit to be turned on;

the detection unit comprises a demagnetization start detection module and a demagnetization end detection module;

the demagnetization starting detection module is connected between the sampling end of the switch unit and the control unit, and is used for starting magnetization timing based on a first electric signal acquired from the sampling end when the switch unit is detected to be turned on, and outputting a first detection signal when the magnetization timing is finished;

The demagnetization start detection module comprises a reference voltage generation circuit, a signal generation circuit and a comparison circuit; the reference voltage generating circuit is used for determining a reference voltage by detecting the first electric signal; the signal generating circuit is connected with the control unit and is used for generating a slope electric signal when the switch unit is detected to be conducted; the comparison circuit is connected with the reference voltage generation circuit and the signal generation circuit, and is used for comparing the voltage of the ramp electric signal with the reference voltage and outputting a first detection signal when the voltage of the ramp electric signal reaches the reference voltage; determining a time when the voltage of the ramp electric signal reaches the reference voltage as an off time of the switching unit;

the demagnetization end detection module is connected between the driving end of the switch unit and the control unit, and is used for comparing a second electric signal acquired from the driving end with a preset valley voltage threshold value, outputting a second detection signal when the voltage of the second electric signal reaches the valley voltage threshold value, and determining the moment when the voltage of the second electric signal reaches the valley voltage threshold value as the conduction moment of the switch unit.

2. The controller of claim 1, wherein the reference voltage generation circuit comprises a transconductance integrator having a first input terminal connected to the sampling terminal, a second input terminal connected to a reference voltage source, and an output terminal outputting the reference voltage; the output end is also used for being connected with an external low-pass filtering unit.

3. The controller of claim 1, wherein the signal generation circuit comprises a ramp signal generator having a control terminal and an output terminal, the control terminal being coupled to the control unit, the output terminal being coupled to the comparison circuit.

4. The controller of claim 1, wherein the valley voltage threshold is a threshold voltage set based on parasitic capacitance release in the switching cell.

5. The controller according to claim 1, wherein the control unit comprises:

a control module for outputting a switch control signal for turning off the switching unit based on the received first detection signal and outputting a switch control signal for turning on the switching unit based on the received second detection signal;

And the driving module is connected with the control module and is used for converting the received switch control signals into corresponding switch driving signals so as to drive the connected switch units.

6. The controller according to claim 1, further comprising: and the delay unit is used for maintaining the disconnection state for a delay time when the switch unit is detected to be disconnected.

7. The controller of claim 1, wherein the detection unit obtains a first electrical signal from a source of the switching unit and a second electrical signal from a gate of the switching unit.

8. A switching device, comprising:

a switching unit for connection between the input source and the resonant device; and

a controller according to any one of claims 1 to 7, connected to the switching unit for off-controlling the switching unit by detecting a first electrical signal flowing through the switching unit and on-controlling the switching unit by detecting a second electrical signal flowing through the switching unit.

9. The switching device according to claim 8, wherein the switching unit includes a gate-driven-based power tube; the controller obtains a first electrical signal from a source electrode of the power tube and a second electrical signal from a gate electrode of the power tube.

10. An LED driving system, comprising:

the alternating current-direct current conversion device is used for converting alternating current into direct current and outputting the direct current;

a resonant device for providing constant current power to the LED load based on the controlled oscillation;

switching device according to any of claims 8-9, connected in a path between said ac-dc conversion means and resonance means for controlling said path to be switched on or off based on the acquired first and second electrical signals; wherein the first electrical signal is used to reflect the current change in the resonant device and the second electrical signal is used to reflect the voltage change provided by the input source.

11. The LED driving system according to claim 10, further comprising a low pass filter unit connected to the detection unit in the switching device.

12. A switch control method, characterized in that on or off of a switch unit is controlled using the controller according to any one of claims 1 to 7, the switch control method comprising:

acquiring a first electric signal and a second electric signal from a switch unit; the first electric signal is used for reflecting current change in the resonance device, and the second electric signal is used for reflecting voltage change provided by the input source;

Setting an off time of a switching unit based on the first electric signal, and turning off the switching unit when the off time is reached; and setting a turn-on timing of the switching unit based on the change of the second electric signal, and turning on the switching unit when the turn-on timing is reached.

13. The switching control method according to claim 12, wherein the manner of setting the off-time of the switching unit based on the first electric signal includes:

starting to time the duration that a slope voltage reaches a reference voltage when the switching unit is detected to be conducted, and controlling the switching unit to be disconnected at the moment that the slope voltage reaches the reference voltage; wherein the reference voltage is a voltage obtained by detecting the first electric signal.

14. The switching control method according to claim 12, wherein the manner of setting the on timing of the switching unit based on the change in the second electric signal includes: comparing the second electric signal with a preset valley voltage threshold, and determining the turn-on time of the switch unit when the voltage of the second electric signal reaches the valley voltage threshold.

15. The switching control method according to claim 14, wherein the valley voltage threshold is a threshold voltage set based on parasitic capacitance release in the switching unit.

16. The switch control method according to claim 12, further comprising the step of maintaining an off state of the switching unit for a delay period when the switching unit is detected to be off.

17. An LED driving method, comprising:

controlling the on and off of a switching device using steps provided by the switching control method according to any one of claims 12 to 16; and

and controlling the oscillation process of the resonance device based on the on and off of the switching device so as to drive the LED load to work.

18. An LED control chip, comprising:

a controller according to any one of claims 1-7, for controlling the switching unit to be turned off by detecting a first electrical signal flowing through a connected switching unit and to be turned on by detecting a second electrical signal flowing through a connected switching unit.

19. The LED control chip of claim 18, further comprising said switching unit.