A power failure detection circuit and LED lamp

Abstract

The present application belongs to the field of lighting technology, and relates to a power failure detection circuit and an LED lamp, which rectifies a power supply signal adjusted by a thyristor dimming switch circuit through a rectifier circuit to generate a rectified power supply signal; a constant current drive circuit generates a constant current drive signal and a power supply signal according to the rectified power supply signal, and adjusts the constant current drive signal according to a drive control signal; a voltage sampling circuit detects and samples the power supply signal to generate a voltage sampling signal; a control circuit compares the voltage sampling signal with a preset reference signal to generate a drive control signal; by changing the power failure detection point from before the rectifier circuit or after the rectifier circuit or the rear-stage circuit of the drive to the auxiliary power supply end of the constant current drive circuit, the power supply signal is detected and sampled, so as to compensate for the short-term low power failure caused by the low conduction angle during the thyristor phase-cut dimming, avoid the thyristor power failure misdetection at a low conduction angle, and improve the stability and reliability of the lighting load compatible with the thyristor dimming.

Description

Technical Field

[0001] The present application belongs to the field of lighting technology, and in particular relates to a power-off detection circuit and an LED lamp. Background Art

[0002] Thyristor, also known as thyristor, is an active switching element. It usually remains in a non-conducting state until it is triggered or "ignited" by a smaller control signal to make it conductive. Once ignited, it will remain conductive even if the trigger signal is removed. It can be cut off by adding a reverse voltage between its anode and cathode or reducing the current flowing through the thyristor diode to below a certain value. Since thyristors have the functions of current conversion / rectification, voltage regulation, frequency conversion and switching, they are widely used in automatic control, electromechanical fields, industrial electrical and household appliances, especially in Europe and the United States, where the dimmers used are all thyristor dimmers. Thyristor dimming is also the most widely used dimming method in LED dimming. It has the advantages of high adjustment accuracy and efficiency, small size, light weight, and easy remote control. Thyristor dimming uses phase control to achieve voltage regulation or dimming. It is a type of AC trigger circuit. The RC circuit in the thyristor dimming circuit is used to control the phase of the thyristor trigger signal. When the R value is small, the RC time constant is small, the phase shift of the trigger signal is small, the corresponding thyristor conduction angle is large, and the load obtains more power; when the R value is large, the RC time constant is large, the phase shift of the trigger signal is large, the corresponding thyristor conduction angle is small, and the load obtains less power. In the lighting power supply scheme, when it is necessary to detect power failure of the circuit, the traditional power failure detection scheme is to detect and obtain the power failure signal before the rectifier bridge, after the rectifier bridge, or in the secondary circuit, and then make the corresponding power failure action after the logic processing inside the chip. For lighting circuits compatible with thyristor dimming, the above power failure detection scheme is easy to cause false power failure detection when the thyristor is in a small conduction angle state, that is, when the conduction angle of the thyristor is less than or equal to a certain value.

[0003] Therefore, the conventional technical solution has the problem of abnormal power-off detection logic when the thyristor is in a low-power state with a small conduction angle. Summary of the invention

[0004] The purpose of the present application is to provide a power-off detection circuit and an LED lamp, aiming to solve the problem of abnormal power-off detection logic when the thyristor is in a low-power state with a small conduction angle in the traditional technical solution.

[0005] A first aspect of an embodiment of the present application provides a power failure detection circuit, which is connected to a thyristor dimming switch circuit and a lighting load, wherein the thyristor dimming switch circuit is connected to a power supply, and the power failure detection circuit includes:

[0006] a rectifier circuit connected to the thyristor dimming switch circuit and configured to rectify the power signal regulated by the thyristor dimming switch circuit to generate a rectified power signal;

[0007] a constant current drive circuit connected to the rectifier circuit and the lighting load, configured to generate a constant current drive signal and a power supply signal according to the rectifier power supply signal, and to adjust the constant current drive signal according to a drive control signal;

[0008] A voltage sampling circuit, connected to the constant current driving circuit, configured to detect and sample the power supply signal to generate the voltage sampling signal;

[0009] The control circuit is connected to the voltage sampling circuit and the constant current driving circuit, and is configured to compare the voltage sampling signal with a preset reference signal and generate the driving control signal according to the comparison result.

[0010] In one embodiment, the power failure detection circuit further includes:

[0011] The AC / DC voltage conversion circuit is connected to the rectifier circuit and the control circuit, and is configured to perform voltage conversion processing on the rectifier power supply signal to generate a first DC power.

[0012] In one embodiment, the power failure detection circuit further includes:

[0013] A first photoelectric isolation circuit is connected to the voltage sampling circuit and the control circuit and is configured to perform photoelectric isolation processing on the voltage sampling signal to generate an isolated sampling signal;

[0014] The control circuit is specifically configured to compare the isolated sampling signal with the preset reference signal, and generate the drive control signal according to the comparison result;

[0015] A second photoelectric isolation circuit is connected to the control circuit and the constant current drive circuit and is configured to perform photoelectric isolation processing on the drive control signal to generate an isolated drive control signal;

[0016] The constant current driving circuit is specifically configured to adjust the constant current driving signal according to the power supply signal and the isolation driving control signal.

[0017] In one embodiment, the power-off detection circuit includes a plurality of the constant current driving circuits; wherein each of the constant current driving circuits drives one lighting load correspondingly.

[0018] In one embodiment, the power-off detection circuit includes a plurality of the voltage sampling circuits; wherein the plurality of the constant current driving circuits are connected to the plurality of the voltage sampling circuits in a one-to-one correspondence.

[0019] In one embodiment, the driving control signal is one of a voltage signal and a pulse width modulation signal.

[0020] In one embodiment, the constant current driving circuit:

[0021] a transformer unit connected to the rectifier circuit and the lighting load, and configured to generate the constant current drive signal and the power supply signal according to the rectifier power supply signal;

[0022] The constant current driving unit is connected to the rectifier circuit, the voltage transformation unit, the voltage sampling circuit and the control circuit, and is configured to adjust the constant current driving signal according to the driving control signal.

[0023] In one embodiment, the constant current drive unit includes: a constant current drive chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a first diode, a first diode and a first capacitor; wherein the enable end of the constant current drive chip is connected to the first end of the first resistor, the dimming configuration end of the constant current drive chip is connected to the first end of the second resistor, the real-time clock end of the constant current drive chip is connected to the first end of the third resistor, the second end of the first resistor, the two ends of the second resistor and the second end of the third resistor are connected to the power supply ground, the drain end of the constant current drive chip and the anode of the first diode are connected to the The transformer unit is connected, the cathode of the first diode is connected to the first end of the sixth resistor, the second end of the sixth resistor is connected to the anode of the first diode, the first end of the fourth resistor and the first end of the first capacitor, the first end of the first capacitor is also connected to the voltage sampling circuit, the second end of the fourth resistor, the first end of the fifth resistor and the overvoltage detection end of the constant current drive chip are connected to the second photoelectric isolation circuit, the cathode of the first diode and the high voltage end of the constant current drive chip are connected to the rectifier circuit, and the second end of the fifth resistor, the second end of the first capacitor and the negative voltage end of the constant current drive chip are connected to the power ground.

[0024] In one embodiment, the control circuit includes: a microprocessor; wherein the first data input and output terminal of the microprocessor is connected to the first photoelectric isolation circuit, the second data input and output terminal of the microprocessor is connected to the second photoelectric isolation circuit, the power supply terminal of the microprocessor is connected to the first power supply terminal, and the ground terminal of the microprocessor is connected to the power ground.

[0025] A second aspect of the embodiments of the present application provides an LED lamp, wherein the LED lamp comprises a power-off detection circuit as described in any one of the above items.

[0026] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned power-off detection circuit and LED lamp, which rectifies the power signal adjusted by the thyristor dimming switch circuit through the rectifier circuit to generate a rectified power signal; the constant current drive circuit generates a constant current drive signal and a power supply signal according to the rectified power signal, and adjusts the constant current drive signal according to the drive control signal; the voltage sampling circuit detects the sampled power supply signal to generate a voltage sampling signal; the control circuit compares the voltage sampling signal with a preset reference signal, and generates a drive control signal according to the comparison result; by innovatively designing the power-off detection point from the front of the rectifier circuit or the back of the rectifier circuit or the rear stage circuit of the drive to the auxiliary power supply end of the constant current drive circuit, that is, the power supply signal end, the energy storage and discharge characteristics of the constant current drive circuit are used to compensate for the short-term power-off caused by the low conduction angle when the thyristor is phase-cut to dim, avoid the thyristor's power-off misdetection at a low conduction angle, and improve the stability and reliability of driving the lighting load to emit light in the lighting drive circuit compatible with thyristor dimming. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of a power-off detection circuit provided in an embodiment of the present application;

[0028] Figure 2 Another structural schematic diagram of a power failure detection circuit provided in an embodiment of the present application;

[0029] Figure 3 Another structural schematic diagram of a power failure detection circuit provided in an embodiment of the present application;

[0030] Figure 4 Another structural schematic diagram of a power failure detection circuit provided in an embodiment of the present application;

[0031] Figure 5 Another structural schematic diagram of a power failure detection circuit provided in an embodiment of the present application;

[0032] Figure 6 An exemplary circuit schematic diagram of a power-off detection circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0035] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0036] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0037] Figure 1 A schematic diagram of the structure of a power-off detection circuit provided in the first embodiment of the present application is shown. For the sake of convenience, only the part related to the present embodiment is shown, which is described in detail as follows:

[0038] A power failure detection circuit is connected to a thyristor dimming switch circuit 02 and a lighting load 100. The thyristor dimming switch circuit 02 is connected to a power supply 01. The power failure detection circuit includes: a rectifier circuit 11, a constant current drive circuit 12, a voltage sampling circuit 13 and a control circuit 14.

[0039] The rectifier circuit 11 is connected to the thyristor dimming switch circuit 02, and is configured to rectify the power signal adjusted by the thyristor dimming switch circuit 02 to generate a rectified power signal; the constant current drive circuit 12 is connected to the rectifier circuit 11 and the lighting load 100, and is configured to generate a constant current drive signal and a power supply signal according to the rectified power signal, and adjust the constant current drive signal according to the drive control signal; the voltage sampling circuit 13 is connected to the constant current drive circuit 12, and is configured to detect and sample the power supply signal to generate a voltage sampling signal; the control circuit 14 is connected to the voltage sampling circuit 13 and the constant current drive circuit 12, and is configured to compare the voltage sampling signal with a preset reference signal, and generate a drive control signal according to the comparison result.

[0040] In a specific implementation, the power supply 01 can be an AC power supply, providing AC power, such as 220V or 110V AC power. The thyristor dimming switch circuit 02 is connected to the AC power supply, and the current output to the subsequent circuit is adjusted by adjusting the conduction angle of the thyristor. The rectifier circuit 11 rectifies the power signal adjusted by the thyristor dimming switch circuit 02 to generate a rectified power signal, thereby converting the sinusoidal power signal into a rectified power signal without a negative half-cycle waveform. The constant current drive circuit 12 transforms the rectified power signal to generate a constant current drive signal and a power supply signal. The constant current drive signal is used to drive the lighting load 100 to emit light; the power supply signal is used to provide auxiliary power to the constant current drive circuit 12, and is also used to provide the voltage sampling circuit 13 with voltage detection sampling to generate a voltage sampling signal. The control circuit 14 compares the voltage sampling signal with a preset reference signal and generates a drive control signal according to the comparison result. The constant current drive circuit 12 also adjusts the constant current drive signal according to the drive control signal, thereby adjusting the constant current drive signal output to the lighting load 100.

[0041] Optionally, the preset reference signal is a preset voltage signal or a preset voltage change rate or a preset duration. For example, when the preset reference signal is a preset voltage signal, the control circuit 14 compares the voltage sampling signal with the preset voltage signal. If the comparison result is consistent, a drive control signal is generated; if it is inconsistent, no drive control signal is generated, or a drive control signal of another level is generated to control the constant current drive circuit 12 to adjust the constant current drive signal. By performing a power-off detection method in which a voltage detection is performed on the power supply signal output from the power supply signal end of the constant current driving circuit 12 to determine whether a power failure has occurred, the method of performing a power-off detection on the rectified power supply signal output after rectification or the power supply signal before rectification or the driving signal in the subsequent circuit of the driver is replaced. By utilizing the energy storage and discharge characteristics of the constant current driving circuit 12, it is possible to effectively compensate for a short power failure (for example, a power failure of 0 to 2s) that occurs when the thyristor is at a low conduction angle or the switch is falsely triggered, thereby avoiding the problem of power-off detection logic abnormality caused by the thyristor at a low conduction angle or the switch being falsely triggered, and outputting a stable and reliable constant current driving signal to drive the lighting load 100 to emit light, thereby improving the stability and reliability of driving the lighting load to emit light in a lighting driving circuit that is compatible with thyristor dimming.

[0042] Optionally, the constant current drive circuit 12 can be one or more of a buck circuit, a boost circuit, a buck-boost circuit, and a flyback circuit, and can generate a constant current drive signal based on the rectified power supply signal to drive the lighting load 100 to emit light, and at the same time generate a power supply signal to provide auxiliary power supply to the constant current drive circuit 12, and the power supply signal serves as a detection sampling object of the voltage sampling circuit 13.

[0043] The embodiment of the present application innovatively designs the power-off detection point from before the rectifier circuit or after the rectifier circuit or the subsequent circuit of the driver to the auxiliary power supply end (i.e., the power supply signal end) of the constant current drive circuit, and utilizes the energy storage and discharge characteristics of the constant current drive circuit to compensate for the brief power-off caused by the low conduction angle during thyristor phase-cut dimming, avoids false power-off detection of the thyristor at low conduction angles, improves the accuracy and reliability of power-off detection, and at the same time improves the stability and reliability of driving the lighting load to emit light in a lighting drive circuit compatible with thyristor dimming.

[0044] See also Figure 2 In one embodiment, the constant current driving circuit 12 includes: a voltage transformation unit 121 and a constant current driving unit 122 .

[0045] The transformer unit 121 is connected to the rectifier circuit 11 and the lighting load 100, and is configured to generate a constant current drive signal and a power supply signal according to the rectifier power supply signal; the constant current drive unit 122 is connected to the rectifier circuit 11, the transformer unit 121, the voltage sampling circuit 13 and the control circuit 14, and is configured to adjust the constant current drive signal according to the drive control signal.

[0046] In a specific implementation, optionally, the transformer unit 121 includes a transformer, and the rectifier power signal is converted into a voltage through the primary winding and the secondary winding of the transformer to generate a constant current drive signal; the rectifier power signal is converted into a voltage through the primary winding and the auxiliary winding of the transformer to generate a power supply signal. The constant current drive unit 122 includes a constant current drive chip, which can adjust the rectifier power signal on the primary winding of the transformer according to the drive control signal, thereby adjusting the constant current drive signal output by the secondary winding of the transformer to output a stable constant current drive signal, and stably and reliably drive the lighting load 100 to emit light.

[0047] Optionally, the drive control signal is one of a voltage signal and a pulse width modulation signal (ie, a PWM signal). The control circuit 14 generates a drive control signal according to the voltage sampling signal to control the constant current drive unit 122 to adjust the constant current drive signal output to the lighting load 100 .

[0048] When the thyristor is in a low conduction angle state or the switch is triggered by mistake, resulting in a short power failure (low power state), the energy storage and discharge characteristics of the primary winding and the auxiliary winding of the transformer are utilized. When a short power failure occurs, the power supply signal generated by the electromagnetic induction of the auxiliary winding of the transformer will not disappear immediately. The voltage sampling circuit 13 detects the sampled power supply signal to generate a voltage sampling signal. The control circuit 14 performs operations, analysis, and comparison on the voltage sampling signal to generate a drive control signal, that is, compares the voltage sampling signal with a preset reference signal, and generates a drive control signal according to the comparison result, thereby controlling the constant current drive unit 122 to respond to the constant current drive signal. The signal is adjusted, and then a stable constant current drive signal is output to drive the lighting load 100 to emit light instead of stopping the output of the constant current drive signal; and when the power-off time exceeds the time for releasing the electric energy of the transformer winding, the voltage sampling circuit 13 cannot detect the power supply signal, which can make the control circuit 14 generate a drive control signal to make the constant current drive unit 122 control the transformer unit 121 to stop outputting the constant current drive signal, so that when the thyristor is at a low conduction angle or the switch is triggered by mistake and a short power failure occurs, it is not judged as a circuit power failure and the power-off instruction is started, thereby avoiding the abnormality of the power-off detection and processing logic of the thyristor at a low conduction angle, and improving the accuracy and reliability of the power-off detection circuit.

[0049] See also Figure 3 In one embodiment, the power-off detection circuit includes a plurality of constant current driving circuits 12 ; wherein each constant current driving circuit 12 drives one lighting load 100 correspondingly.

[0050] In a specific implementation, there are multiple constant current drive circuits 12 in the optional power-off detection circuit. In specific applications, multiple constant current drive circuits 12 can be connected in parallel at the output end of the rectifier circuit 11 according to lighting requirements. For example, when there are two lighting loads 100, namely, a main lighting load and an auxiliary night light lighting load, two constant current drive circuits 12 are connected in parallel to output constant current drive signals to drive the main lighting load and the auxiliary night light lighting load to emit light.

[0051] Optionally, the power-off detection circuit includes a plurality of voltage sampling circuits 13 ; wherein the plurality of constant current driving circuits 12 are connected to the plurality of voltage sampling circuits 13 in a one-to-one correspondence.

[0052] In a specific implementation, when performing power-off detection, multiple voltage sampling circuits 13 can be set correspondingly according to multiple constant current driving circuits. The multiple voltage sampling circuits 13 respectively detect the signals (i.e., power supply signals) of the auxiliary power supply ends of the multiple constant current driving circuits 12 to generate multiple voltage sampling signals. The control circuit 14 performs operations, analyses, and comparisons on the multiple voltage sampling signals to generate multiple drive control signals to respectively control the multiple constant current driving circuits 12 to adjust the constant current driving signals output to the multiple lighting loads 100, thereby realizing power-off detection of the overall lighting driving circuit, avoiding false power-off detection caused by a short power-off when the thyristor is at a low conduction angle or the switch is falsely triggered, and improving the stability of driving the lighting load to perform luminous illumination.

[0053] See also Figure 4 In one embodiment, the power-off detection circuit further includes: an AC / DC voltage conversion circuit 15 .

[0054] The AC / DC voltage conversion circuit 15 is connected to the rectifier circuit 11 and the control circuit 14 and is configured to perform voltage conversion processing on the rectified power supply signal to generate a first DC power.

[0055] In a specific implementation, the AC / DC voltage conversion circuit 15 performs AC / DC voltage conversion and voltage stabilization on the rectified power supply signal output after rectification, and then outputs a first DC power with a constant voltage to power the control circuit 14 to meet the power demand of the control circuit 14 .

[0056] Optionally, the first direct current may also be output through a direct current power supply, for example, the first direct current may be provided by a battery power supply; or may be generated by a voltage conversion circuit performing voltage conversion and voltage stabilization on a power supply signal.

[0057] See also Figure 5 In one embodiment, the power-off detection circuit further includes: a first photoelectric isolation circuit 16 and a second photoelectric isolation circuit 17 .

[0058] The first photoelectric isolation circuit 16 is connected to the voltage sampling circuit 13 and the control circuit 14, and is configured to perform photoelectric isolation processing on the voltage sampling signal to generate an isolated sampling signal; the second photoelectric isolation circuit 17 is connected to the control circuit 14 and the constant current drive circuit 12, and is configured to perform photoelectric isolation processing on the drive control signal to generate an isolated drive control signal; the control circuit 14 is specifically configured to compare the isolated sampling signal with a preset reference signal and generate a drive control signal according to the comparison result; the constant current drive circuit 12 is specifically configured to adjust the constant current drive signal according to the isolated drive control signal.

[0059] In a specific implementation, the voltage sampling signal can be photoelectrically coupled and isolated by the first photoelectric isolation circuit 16, and the drive control signal can be photoelectrically isolated by the second photoelectric isolation circuit 17, so that in the drive circuit of the lighting load 100, the optical signal and the electrical signal do not interfere with each other, and each can work independently, thereby ensuring the normal operation of the power supply and the light source, improving the electrical insulation and anti-interference capabilities of the circuit, effectively protecting the circuit and the wires, and improving the safety and reliability of the power-off detection circuit.

[0060] Optionally, when the power-off detection circuit includes multiple constant current drive circuits 12 and multiple voltage sampling circuits 13, the power-off detection circuit also includes multiple first photoelectric isolation circuits 16 and multiple second photoelectric isolation circuits 17. Among them, the multiple first photoelectric isolation circuits 16 are connected to the multiple voltage sampling circuits 13 in a one-to-one correspondence, and are all connected to the control circuit 14; the multiple second photoelectric isolation circuits 17 are all connected to the control circuit 14, and are connected to the multiple constant current drive circuits 12 in a one-to-one correspondence; thereby, the multiple voltage sampling signals and the multiple drive control signals are respectively photoelectrically isolated, thereby reducing the electromagnetic interference in the power-off detection circuit, improving the safety and reliability of the power-off detection circuit, and also improving the anti-interference ability and safety and reliability of the lighting and lighting drive circuit.

[0061] See also Figure 6 In one embodiment, the constant current driving unit 122 includes: a constant current driving chip U1, a first resistor R3, a second resistor R4, a third resistor R5, a fourth resistor R9, a fifth resistor R10, a first diode D9 and a first capacitor C5; wherein, the enable terminal CS of the constant current driving chip U1 is connected to the first end of the first resistor R3, the dimming configuration terminal Tonmax of the constant current driving chip U1 is connected to the first end of the second resistor R4, the real-time clock terminal RTC of the constant current driving chip U1 is connected to the first end of the third resistor R5, the second end of the first resistor R3, the two ends of the second resistor R4 and the second end of the third resistor R5 are connected to the power ground, and the constant current driving chip The drain terminal DRAIN of U1 is connected to the transformer unit 121, the anode of the first diode D9, the first end of the fourth resistor R9 and the first end of the first capacitor C5 are connected to the transformer unit 121, the first end of the first capacitor C5 is also connected to the voltage sampling circuit 13, the second end of the fourth resistor R9, the first end of the fifth resistor R10 and the overvoltage detection end OVP of the constant current drive chip U1 are connected to the second photoelectric isolation circuit 17, the cathode of the first diode D9 and the high voltage end HV of the constant current drive chip U1 are connected to the rectifier circuit 11, and the second end of the fifth resistor R10, the second end of the first capacitor C5 and the negative voltage end VS of the constant current drive chip U1 are connected to the power ground.

[0062] In a specific implementation, the high voltage terminal HV of the constant current driver chip U1 is connected in series with the resistor R6 and then connected to the rectifier power signal output by the rectifier circuit 11. The anode of the first diode D9, the first end of the fourth resistor R9 and the first end of the first capacitor C5 together constitute the power supply signal terminal of the constant current driver unit 122, and output the power supply signal (VCC1) to the voltage sampling circuit 13, so that the voltage sampling circuit 13 can perform voltage detection sampling. The overvoltage detection terminal OVP of the constant current driver chip U1 inputs the isolated drive control signal (OVP1) output after the photoelectric coupling isolation processing, so that the constant current driver chip U1 adjusts the constant current drive signal output by the transformer unit 121. Optionally, the isolated drive control signal (OVP1) is a voltage signal.

[0063] In one embodiment, the isolated driving control signal may also be a PWM signal, and the constant current driving chip U1 adjusts the constant current driving signal output by the transformer unit 121 to the lighting load 100 according to the isolated driving control signal or the driving control signal in the form of a PWM signal.

[0064] In one embodiment, see Figure 6 The transformer unit 121 includes a transformer T1, and the transformer T1 includes a primary winding Na1, a secondary winding Nb1, and an auxiliary winding Nc1. A constant current drive signal is generated and output from the secondary winding Nb1 of the transformer T1, and a power supply signal is generated and output from the auxiliary winding Nc1 of the transformer T1. The drain terminal DRAIN of the constant current drive chip U1 is connected to the second end of the primary winding Na1 of the transformer T1, and the second end of the primary winding Na1 of the transformer T1 is the rectifier power signal input terminal of the transformer unit 121.

[0065] In a specific implementation, the power supply signal generated from the auxiliary winding Nc1 of the transformer T1 can be output to the constant current drive unit 122 after being protected against reverse connection and current limiting by the diode D8 and the resistor R11. The constant current drive chip U1 in the constant current drive unit 122 adjusts the voltage of the primary winding Na1 of the transformer T1 according to the drive control signal or the isolated drive control signal (OVP1), thereby adjusting the constant current drive signal output by the secondary winding Nb1 of the transformer T1.

[0066] In the embodiment of the present application, the power-off detection point is changed from before the rectifier bridge or after the rectifier bridge or the post-stage circuit of the driver to the auxiliary power supply end of the constant current driver chip U1, and the power supply signal (such as VCC1 and VCC2) is detected and sampled. The energy storage and discharge characteristics of the winding of the transformer T1 are utilized to compensate for the brief power-off caused by the low conduction angle during the thyristor phase-cut dimming, which can effectively avoid the false detection of power-off of the thyristor at a low conduction angle.

[0067] See also Figure 6In one embodiment, the control circuit 14 includes: a microprocessor U3; wherein, a first data input / output terminal P1.3 of the microprocessor U3 is connected to a first photoelectric isolation circuit 16, a second data input / output terminal P1.4 of the microprocessor U3 is connected to a second photoelectric isolation circuit 17, a power supply terminal VDD of the microprocessor U3 is connected to a first power supply terminal, and a ground terminal GND of the microprocessor U3 is connected to a power ground.

[0068] In a specific implementation, the first power supply terminal outputs the first direct current VDD. The microprocessor U3 may be a microcontroller unit (MCU) or a single chip computer with computing and analysis capabilities, and may perform computing, analysis and comparison on the voltage sampling signal to generate a driving control signal.

[0069] In one embodiment, the lighting circuit includes two lighting loads 100, wherein the first lighting load 100 is a main lighting LED (S1+ and S1-), corresponding to the first constant current drive circuit 12; the second lighting load 100 is a night light lighting LED (S2+ and S2-), corresponding to the second constant current drive circuit 12, and the two constant current drive circuits 12 have the same structure and the same working principle. The voltage sampling circuit 13 includes a sampling resistor, for example, the first voltage sampling circuit 13 uses a first sampling resistor R01, and the second voltage sampling circuit 13 uses a second sampling resistor R02, respectively detecting and sampling the power supply signal (VCC1) output by the first constant current drive circuit 12 and the power supply signal (VCC2) output by the second constant current drive circuit 12, and correspondingly generating a first voltage sampling signal and a second voltage sampling signal, and outputting them to the first data input and output terminal P1.3 of the microprocessor U3 and the third data input and output terminal P1.2 of the microprocessor U3 through the first photoelectric isolation circuit 16 connected thereto. The microprocessor U3 generates a first drive control signal and a second drive control signal according to the first voltage sampling signal and the second voltage sampling signal, respectively, and outputs them to the corresponding second photoelectric isolation circuit 17 through the second data input and output terminal P1.4 of the microprocessor U3 and the fourth data input and output terminal P1.5 of the microprocessor U3 for photoelectric isolation processing, thereby correspondingly outputting isolated drive control signals (OVP1 and OVP2) to the first constant current drive circuit 12 and the second constant current drive circuit 12, so as to adjust the constant current drive signals output to the main lighting LED (S1+ and S1-) and the night light lighting LED (S2+ and S2-), respectively.

[0070] In a specific implementation, optionally, the voltage sampling circuit 13 also includes a diode. For example, the first voltage sampling circuit 13 also includes a diode D16, and the second voltage sampling circuit 13 also includes a diode D17. The diode D16 and the diode D17 can rectify, stabilize, and prevent reverse connection of the power supply signal (VCC1 and VCC2), thereby improving the stability and reliability of the power-off detection circuit.

[0071] See also Figure 6 In one embodiment, the first photoelectric isolation circuit 16 includes a photocoupler U5; wherein the anode of the photocoupler U5 is connected to the voltage sampling circuit 13, the emitter of the photocoupler U5 is connected to the control circuit 14, and the cathode of the photocoupler U5 and the collector of the photocoupler U5 are connected to the power ground.

[0072] In a specific implementation, the anode of the photoelectric coupler U5 inputs a voltage sampling signal, and the emitter of the photoelectric coupler U5 outputs an isolated sampling signal. Optionally, the circuit structure of the second photoelectric isolation circuit 17 is the same as the circuit structure of the first photoelectric isolation circuit 16.

[0073] In one embodiment, the power-off detection circuit further includes: a filter circuit 18. The filter circuit 18 is connected to the rectifier circuit 11 and the constant current drive circuit 12, and is configured to filter and reduce noise on the rectifier power supply signal to filter out noise interference of the rectifier power supply signal, thereby improving the stability and reliability of the power-off detection circuit and driving the lighting load 100 to emit light.

[0074] In one embodiment, see Figure 6 , the filter circuit 18 includes an inductor L1, a resistor R1, a capacitor C1, a capacitor C2, a capacitor C3 and a resistor R2; wherein, the first end of the inductor L1, the first end of the resistor R1 and the first end of the capacitor C1 are connected to the rectifier circuit 11, the second end of the inductor L1, the second end of the resistor R1, the first end of the capacitor C2 and the first end of the capacitor C3 are connected to the constant current drive circuit 12, the first end of the capacitor C1, the second end of the capacitor C2 and the second end of the resistor R2 are connected to the power supply ground, and the first end of the resistor R2 is connected to the second end of the capacitor C3. In a specific implementation, the rectifier circuit 11 is connected in series with a diode D4 and then connected to the first end of the inductor L1, the first end of the resistor R1 and the first end of the capacitor C1. The filter circuit 18 can effectively filter and reduce noise on the rectifier power supply signal, thereby suppressing noise and preventing spike electromagnetic interference, so that a smooth and stable rectifier power supply signal is output to the constant current drive circuit 12. A diode D4 can also be connected in series between the rectifier circuit 11 and the filter circuit 18 to prevent reverse connection or prevent current backflow from causing damage to power supply components.

[0075] A second aspect of the present application provides an LED lamp, which includes the power-off detection circuit as described above.

[0076] In a specific implementation, the LED lamp can be applied to a lighting system with a thyristor dimming switch circuit 02 , and the user can control the switching and dimming of the LED lamp by adjusting the thyristor dimming switch circuit 02 .

[0077] The LED lamp of the embodiment of the present application can automatically compensate for the temporary power failure (low power state) caused by the low conduction angle during the thyristor phase-cut dimming, avoiding the problem of false detection of power failure of the thyristor at low conduction angle, so that the LED lamp has high stability and reliability in lighting.

[0078] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units, modules, and circuits is used as an example. In actual applications, the above-mentioned functions can be assigned to different functional units, modules, and circuits as needed, that is, the internal structure of the device can be divided into different functional units or modules or circuits to complete all or part of the functions described above. The functional units, modules, and circuits in the embodiments can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units, modules, and circuits are only for the convenience of distinguishing from each other, and are not used to limit the scope of protection of this application.

[0079] In the above embodiments, the description of each embodiment has its own emphasis. For the part not described or recorded in detail in one embodiment, reference can be made to the relevant description of other embodiments. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0080] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A power failure detection circuit connected to a thyristor dimming switch circuit and a lighting load, wherein the thyristor dimming switch circuit is connected to a power supply, characterized in that: The power-off detection circuit comprises: a rectifier circuit connected to the thyristor dimming switch circuit and configured to rectify the power signal regulated by the thyristor dimming switch circuit to generate a rectified power signal; a constant current drive circuit connected to the rectifier circuit and the lighting load, configured to generate a constant current drive signal and a power supply signal according to the rectifier power supply signal, and to adjust the constant current drive signal according to a drive control signal; A voltage sampling circuit, connected to the constant current driving circuit, configured to detect and sample the power supply signal to generate a voltage sampling signal; A control circuit is connected to the voltage sampling circuit and the constant current driving circuit, and is configured to compare the voltage sampling signal with a preset reference signal and generate the driving control signal according to the comparison result; wherein the control circuit compares the voltage sampling signal with the preset voltage signal, and if the comparison result is consistent, generates the driving control signal; if not consistent, does not generate the driving control signal, or generates a driving control signal of another level, so as to control the constant current driving circuit to adjust the constant current driving signal accordingly.

2. The power failure detection circuit according to claim 1, characterized in that: The power failure detection circuit further includes: The AC / DC voltage conversion circuit is connected to the rectifier circuit and the control circuit, and is configured to perform voltage conversion processing on the rectifier power supply signal to generate a first DC power.

3. The power failure detection circuit according to claim 1, characterized in that: The power failure detection circuit further includes: A first photoelectric isolation circuit is connected to the voltage sampling circuit and the control circuit and is configured to perform photoelectric isolation processing on the voltage sampling signal to generate an isolated sampling signal; The control circuit is specifically configured to compare the isolated sampling signal with the preset reference signal, and generate the drive control signal according to the comparison result; A second photoelectric isolation circuit is connected to the control circuit and the constant current drive circuit and is configured to perform photoelectric isolation processing on the drive control signal to generate an isolated drive control signal; The constant current driving circuit is specifically configured to adjust the constant current driving signal according to the isolated driving control signal.

4. The power failure detection circuit according to claim 1, characterized in that: The power-off detection circuit includes a plurality of constant current drive circuits; wherein each constant current drive circuit drives one lighting load correspondingly.

5. The power failure detection circuit according to claim 4, characterized in that: The power-off detection circuit includes a plurality of the voltage sampling circuits; wherein the plurality of the constant current driving circuits are connected to the plurality of the voltage sampling circuits in a one-to-one correspondence.

6. The power failure detection circuit according to claim 1, characterized in that: The driving control signal is one of a voltage signal and a pulse width modulation signal.

7. The power failure detection circuit according to claim 1, characterized in that: The constant current driving circuit comprises: a transformer unit connected to the rectifier circuit and the lighting load, and configured to generate the constant current drive signal and the power supply signal according to the rectifier power supply signal; The constant current driving unit is connected to the rectifier circuit, the voltage transformation unit, the voltage sampling circuit and the control circuit, and is configured to adjust the constant current driving signal according to the driving control signal.

8. The power failure detection circuit according to claim 7, characterized in that: The constant current drive unit includes: a constant current drive chip, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first diode and a first capacitor; wherein, the enable end of the constant current drive chip is connected to the first end of the first resistor, the dimming configuration end of the constant current drive chip is connected to the first end of the second resistor, the real-time clock end of the constant current drive chip is connected to the first end of the third resistor, the second end of the first resistor, the two ends of the second resistor and the second end of the third resistor are connected to the power ground, the drain end of the constant current drive chip, the anode of the first diode, the first end of the fourth resistor and the first end of the first capacitor are connected to the transformer unit, the first end of the first capacitor is also connected to the voltage sampling circuit, the second end of the fourth resistor, the first end of the fifth resistor and the overvoltage detection end of the constant current drive chip are connected to the second photoelectric isolation circuit, the cathode of the first diode and the high voltage end of the constant current drive chip are connected to the rectifier circuit, the second end of the fifth resistor, the second end of the first capacitor and the negative voltage end of the constant current drive chip are connected to the power ground.

9. The power-off detection circuit according to claim 3, characterized in that: The control circuit includes: a microprocessor; wherein the first data input and output terminal of the microprocessor is connected to the first photoelectric isolation circuit, the second data input and output terminal of the microprocessor is connected to the second photoelectric isolation circuit, the power supply terminal of the microprocessor is connected to the first power supply terminal, and the ground terminal of the microprocessor is connected to the power ground.

10. An LED lamp, characterized in that: The LED lamp comprises a power failure detection circuit as claimed in any one of claims 1 to 9.

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