A circuit for preventing dim light after lighting fixture is in standby or turned off

Abstract

The present invention relates to the field of lighting electronic circuits, and provides a circuit for preventing a lighting fixture from dimming after being in standby or shutting down, comprising a front-stage constant voltage circuit, a dimming prevention BUCK circuit and a lighting fixture, wherein the input end of the front-stage constant voltage circuit is connected to an external voltage, and the output end is connected to the input end of the dimming prevention BUCK circuit, and is used to provide a stable voltage input to the dimming prevention BUCK circuit of the rear stage, and the dimming prevention BUCK circuit comprises an inductive current isolation circuit and a BUCK constant current circuit, wherein the inductive current isolation circuit is arranged between the output end of the front-stage constant voltage circuit and the input end of the BUCK constant current circuit, and is used to prevent the inductive current generated by the front stage from flowing into the lighting fixture after being in standby or shutting down, and the output end of the BUCK constant current circuit is connected to the lighting fixture, and is used to supply a constant current to the lighting fixture, and drive the lighting fixture to emit a corresponding brightness; the present invention can prevent the lighting fixture from dimming when in standby or power-off state.

Description

Technical Field

[0001] The present invention relates to the field of lighting electronic circuits, and in particular to a circuit for preventing a lighting fixture from dimming after being in standby mode or turned off. Background Art

[0002] Compared with traditional lighting methods, LED has the characteristics of energy saving, environmental protection, long life, small size and easy operation. Therefore, it is deeply loved by the market and has been widely used. However, compared with traditional lighting, LED only needs a tiny amount of current to emit light. This characteristic means that after shutdown or standby, the tiny current induced by the external environment will cause the LED lamp to emit weak brightness, giving users the illusion that the lamp is not completely powered off, which in turn causes users to feel uncomfortable or unsafe. Summary of the invention

[0003] The problem solved by the present invention is how to provide a circuit to prevent a lamp from being dimly lit when in a standby or power-off state.

[0004] To solve the above-mentioned problem, the present invention provides a circuit for preventing a lighting fixture from dimming after being in standby or shutting down, comprising: a front-stage constant voltage circuit, a dimming prevention BUCK circuit and a lighting fixture, wherein the input end of the front-stage constant voltage circuit is connected to an external voltage, and the output end is connected to the input end of the dimming prevention BUCK circuit, for providing a stable voltage input to the dimming prevention BUCK circuit of the rear stage, the dimming prevention BUCK circuit comprises an inductive current isolation circuit and a BUCK constant current circuit, the inductive current isolation circuit is arranged between the output end of the front-stage constant voltage circuit and the input end of the BUCK constant current circuit, for preventing the inductive current generated by the front stage from flowing into the lighting fixture after being in standby or shutting down, and preventing the lighting fixture from dimming, the output end of the BUCK constant current circuit is connected to the lighting fixture, for supplying a constant current to the lighting fixture, and driving the lighting fixture to emit a corresponding brightness.

[0005] Furthermore, the front-stage constant voltage circuit includes a rectifier circuit, a filter circuit and a constant voltage regulation circuit. The input end of the rectifier circuit is connected to an external power supply, and the output end is connected to the input end of the constant voltage regulation circuit. The constant voltage regulation circuit provides a stable voltage input for the anti-micro-brightness BUCK circuit of the subsequent stage, and the filter circuit is used to filter the input and output power supplies of the constant voltage regulation circuit.

[0006] Furthermore, the BUCK constant current circuit includes a first lighting driver chip, a first MOS tube, a first diode, a first inductor and a first energy storage capacitor. The output end of the first lighting driver chip is connected to the gate of the first MOS tube, the source of the first MOS tube is connected to the negative output end of the previous constant voltage circuit, the drain of the first MOS tube is respectively connected to the anode of the first diode and the first end of the first inductor, the cathode of the first diode is respectively connected to the first end of the first energy storage capacitor and the positive electrode of the lighting fixture, and the second end of the first inductor is respectively connected to the second end of the first energy storage capacitor and the negative electrode of the lighting fixture.

[0007] Furthermore, the inductive current isolation circuit includes an isolation device and the first MOS tube, the isolation device is arranged between the positive input end of the previous constant voltage circuit and the BUCK constant current circuit, and the isolation device and the first MOS tube jointly cut off the external inductive current.

[0008] Furthermore, the isolating device is a second diode, an anode of the second diode is connected to the positive input terminal of the preceding constant voltage circuit, and a cathode of the second diode is connected to the positive electrode of the lighting fixture.

[0009] Furthermore, the BUCK constant current circuit also includes an adjusting resistor, a first end of the adjusting resistor is connected to the negative input end of the previous constant voltage circuit, and a second end of the adjusting resistor is respectively connected to the source of the first MOS tube and the feedback end of the first lighting driver chip, and adjusting the adjusting resistor is used to adjust the brightness of the lighting fixture.

[0010] Furthermore, the BUCK constant current circuit also includes a protection resistor, which is connected in parallel at both ends of the lighting fixture to play a role of voltage division protection.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] By setting up an anti-dim-brightness BUCK circuit, the induced current generated by the front stage can be prevented from flowing into the lighting fixture after the lighting is in standby or turned off, preventing the lighting fixture from dimming and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall principle structure of an embodiment of the present invention;

[0014] Figure 2 A schematic diagram of the principle structure of the existing lighting power supply according to an embodiment of the present invention;

[0015] Figure 3 The figure is a schematic diagram of the principle structure of the anti-faint light BUCK circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0017] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0018] In the description of this specification, the description with reference to the terms "embodiment", "one embodiment" and "one implementation" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or implementation are included in at least one embodiment or implementation of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or implementation. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or implementations in a suitable manner.

[0019] like Figure 1 As shown, the present invention provides a circuit for preventing a lighting fixture from dimming after being in standby or shutting down, comprising: a front-stage constant voltage circuit, a dimming prevention BUCK circuit and a lighting fixture, wherein the input end of the front-stage constant voltage circuit is connected to an external voltage, and the output end is connected to the input end of the dimming prevention BUCK circuit, for providing a stable voltage input to the dimming prevention BUCK circuit of the rear stage, the dimming prevention BUCK circuit comprises an inductive current isolation circuit and a BUCK constant current circuit, the inductive current isolation circuit is arranged between the output end of the front-stage constant voltage circuit and the input end of the BUCK constant current circuit, for preventing the inductive current generated by the front stage from flowing into the lighting fixture after being in standby or shutting down, and preventing the lighting fixture from dimming, the output end of the BUCK constant current circuit is connected to the lighting fixture, for supplying constant current to the lighting fixture, and driving the lighting fixture to emit a corresponding brightness.

[0020] It should be noted that since LEDs only need a tiny amount of current to emit light, this characteristic means that after being turned off or in standby mode, the tiny amount of current induced by the external environment will cause the LED lamp to emit a weak brightness;

[0021] The existing LED lighting power supply circuit can refer to Figure 2 , Figure 2In the figure, diodes D1-D4 are arranged at the live wire AC-L and the neutral wire AC-N of the external AC incoming line to form a rectifier bridge, which can convert the external input AC power into a DC power supply. The power chip IC, the power tube M1 and the transformer T1A form a constant voltage circuit for adjusting the voltage and forming the required constant voltage output for the output load of the subsequent stage. CL is the output load, that is, the distributed capacitance from the housing of the lamp to the ground. Capacitors C1, C2, and C3 are distributed filter capacitors between the power supplies. Capacitor C4 is the distributed capacitance of the transformer T1. Capacitors Y1-Y3 are Y capacitors between the power supply and the ground line PE. The invention is used to reduce electromagnetic interference and improve the quality of power supply. When the existing circuit is in standby or shutdown state, an induced current, i.e., a ghost current, will be generated, which makes the LED light slightly bright. The reason for the ghost current is that a potential difference is formed between AC-L and the earth. When a loop is formed, a leakage current, i.e., a ghost current, is generated. There is a distributed capacitor and a Y capacitor connected across the circuit and the device to form a loop. When a loop is formed between AC and the earth and there is a potential difference, a ghost current is generated. The size of the ghost current is affected by the potential difference and capacitance of the distributed capacitor to the earth. The larger the potential difference and the distributed capacitance, the larger the ghost current.

[0022] In this embodiment, Figure 2 As shown in the figure, the output of the front-stage constant voltage circuit is represented by VBUS+ and VBUS-, and the output of the anti-micro-brightness BUCK circuit to the lighting fixture is represented by LED+ and LED-. The anti-micro-brightness BUCK circuit prevents the occurrence of LED micro-brightness. The BUCK constant current circuit steps down the constant voltage of the front stage into a constant current output with a lower voltage. An induction current cut-off circuit is added on the basis of the BUCK to effectively cut off the external micro-current entering the LED lighting fixture through induction, thereby preventing the LED lighting fixture from being micro-bright after standby or shutdown; the lighting module emits a corresponding brightness after receiving the constant current of the BUCK, so as to meet the lighting needs of users.

[0023] In one embodiment of the present invention, the front-stage constant voltage circuit includes a rectifier circuit, a filter circuit and a constant voltage regulation circuit. The input end of the rectifier circuit is connected to an external power supply, and the output end is connected to the input end of the constant voltage regulation circuit. The constant voltage regulation circuit provides a stable voltage input for the anti-micro-brightness BUCK circuit of the subsequent stage, and the filter circuit is used to filter the input and output power supplies of the constant voltage regulation circuit.

[0024] It should be noted that the rectifier circuit converts the external AC power supply into a DC power supply, and the constant voltage regulation circuit provides a stable voltage input for the anti-fainting BUCK circuit of the subsequent stage.

[0025] In one embodiment of the present invention, the BUCK constant current circuit includes a first lighting driver chip, a first MOS tube, a first diode, a first inductor and a first energy storage capacitor, the output end of the first lighting driver chip is connected to the gate of the first MOS tube, the source of the first MOS tube is connected to the negative output end of the previous constant voltage circuit, the drain of the first MOS tube is respectively connected to the anode of the first diode and the first end of the first inductor, the cathode of the first diode is respectively connected to the first end of the first energy storage capacitor and the positive electrode of the lighting fixture, and the second end of the first inductor is respectively connected to the second end of the first energy storage capacitor and the negative electrode of the lighting fixture.

[0026] It should be noted that if Figure 3 As shown, the first inductor L1 and the first energy storage capacitor EC1 play the role of energy storage. When the first MOS tube Q1 is turned on, the first inductor L1 and the first energy storage capacitor EC1 store energy. When the first MOS tube Q1 is turned off, the first inductor L1 and the first energy storage capacitor EC1 form a discharge loop through the first diode D2 to form an output to the lighting fixture. The feedback end of the first lighting driver chip collects the current information of the lighting fixture loop, and then adjusts the PWM control signal output to the first MOS tube Q1, adjusts the on-off duration and frequency state of the first MOS tube Q1, and then controls the current output to the lighting fixture, thereby realizing constant current output to the lighting fixture.

[0027] In one embodiment of the present invention, the inductive current isolation circuit includes an isolation device and the first MOS tube, the isolation device is arranged between the positive input end of the previous constant voltage circuit and the BUCK constant current circuit, and the isolation device and the first MOS tube jointly cut off the external inductive current.

[0028] It should be noted that when the lamp is on standby or turned off, the first MOS tube Q1 is in a cut-off state, and the isolating device is arranged between the positive input end of the preceding constant voltage circuit and the BUCK constant current circuit. At this time, the current induced from the outside cannot form a loop through the isolating device, the LED lighting fixture, and the first MOS tube Q1, thereby achieving the purpose of isolating the induced current.

[0029] In one embodiment of the present invention, the isolating device is a second diode, an anode of the second diode is connected to the positive input terminal of the preceding constant voltage circuit, and a cathode of the second diode is connected to the positive electrode of the lighting fixture.

[0030] It should be noted that the isolating device may also be a thyristor, a relay or other electronic mechanical switching device. However, when a thyristor, a relay or other electronic mechanical switching device is used, a control circuit for the above-mentioned switching device needs to be provided to control the on and off of the above-mentioned switching device so as to cut off the induced current. In this embodiment, a reverse cut-off diode, i.e., a second diode D1, is used. The first MOS tube Q1 is an N-channel MOS tube having a built-in diode therein. The second diode D1 is used as the isolating device without adding other electronic components. The second diode D1 can cooperate with the first MOS tube Q1 to cut off the induced current flowing through the positive and negative outputs of the previous circuit in the shutdown and power-off state. The induced current flowing from VBUS+ and VBUS- of the upper circuit will be blocked by the first MOS tube Q1 and the second diode D1 respectively, and cannot pass through the second diode D1, the LED lighting fixture, and the first MOS tube Q1. The purpose of preventing dim light is achieved.

[0031] In one embodiment of the present invention, the BUCK constant current circuit also includes an adjusting resistor, a first end of the adjusting resistor is connected to the negative input end of the previous constant voltage circuit, a second end of the adjusting resistor is respectively connected to the source of the first MOS tube and the feedback end of the first lighting driver chip, and adjusting the adjusting resistor is used to adjust the brightness of the lighting fixture.

[0032] It should be noted that if Figure 3 As shown, when the lighting lamp is working, the regulating resistor R1 is in the current loop of the lighting fixture, and the current flowing through the regulating resistor R1 is the current flowing through the lighting fixture. The first end of the regulating resistor R1 is connected to the negative input end of the previous constant voltage circuit. The voltage at the feedback end of the first lighting driver chip is the voltage across the regulating resistor R1. The feedback end of the first lighting driver chip has a comparator inside. By comparing the collected voltage with the internal voltage, the PWM control signal output to the first MOS tube Q1 is adjusted to adjust the state of the first MOS tube Q1, thereby controlling the current of the lighting fixture to achieve constant current output. The regulating resistor R1 can adopt an adjustable resistor. After changing the resistance value of the regulating resistor R1, its terminal voltage will decrease. The voltage received at the feedback end of the first lighting driver chip decreases, which will change the PWM control signal, increase the loop current, increase the terminal voltage of the regulating resistor R1, and then achieve balance, and perform constant current output, thereby achieving a change in the current of the constant current output by changing the regulating resistor R1.

[0033] In one embodiment of the present invention, the BUCK constant current circuit further includes a protection resistor, which is connected in parallel at both ends of the lighting fixture to play a role of voltage division protection.

[0034] It should be noted that the protection resistor R2 is connected in parallel at both ends of the lighting fixture to divide the voltage of the lighting fixture, thereby protecting the lighting fixture.

[0035] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A circuit for preventing dim lighting after a lighting fixture is in standby or turned off, characterized in that: include: A front-stage constant voltage circuit, an anti-fainting BUCK circuit and a lighting fixture, wherein the input end of the front-stage constant voltage circuit is connected to an external voltage, and the output end is connected to the input end of the anti-fainting BUCK circuit, and is used to provide a stable voltage input to the anti-fainting BUCK circuit of the rear stage, and the anti-fainting BUCK circuit includes an inductive current isolation circuit and a BUCK constant current circuit, and the inductive current isolation circuit is arranged between the output end of the front-stage constant voltage circuit and the input end of the BUCK constant current circuit, and is used to prevent the inductive current generated by the front stage from flowing into the lighting fixture after standby or shutdown, so as to prevent the lighting fixture from appearing faintly bright, and the output end of the BUCK constant current circuit is connected to the lighting fixture, and is used to The BUCK constant current circuit comprises a first lighting driver chip, a first MOS tube, a first diode, a first inductor and a first energy storage capacitor, the output end of the first lighting driver chip is connected to the gate of the first MOS tube, the source of the first MOS tube is connected to the negative output end of the previous constant voltage circuit, the drain of the first MOS tube is respectively connected to the anode of the first diode and the first end of the first inductor, the cathode of the first diode is respectively connected to the first end of the first energy storage capacitor and the positive electrode of the lighting fixture, and the second end of the first inductor is respectively connected to the second end of the first energy storage capacitor and the negative electrode of the lighting fixture; The BUCK constant current circuit also includes an adjusting resistor, a first end of the adjusting resistor is connected to the negative input end of the previous constant voltage circuit, a second end of the adjusting resistor is respectively connected to the source of the first MOS tube and the feedback end of the first lighting driver chip, and the adjusting resistor is adjusted to adjust the brightness of the lighting fixture.

2. The circuit for preventing dim light after lighting fixture is in standby or turned off according to claim 1, characterized in that: The front-stage constant voltage circuit includes a rectifier circuit, a filter circuit and a constant voltage regulation circuit. The input end of the rectifier circuit is connected to an external power supply, and the output end is connected to the input end of the constant voltage regulation circuit. The constant voltage regulation circuit provides a stable voltage input for the anti-micro-brightness BUCK circuit of the subsequent stage, and the filter circuit is used to filter the input and output power supplies of the constant voltage regulation circuit.

3. The circuit for preventing dim light after lighting fixture is in standby or turned off according to claim 1, characterized in that: The inductive current blocking circuit includes a blocking device and the first MOS tube. The blocking device is arranged between the positive input end of the front-stage constant voltage circuit and the BUCK constant current circuit. The blocking device and the first MOS tube jointly cut off the external inductive current.

4. The circuit for preventing dim light after lighting fixture is in standby or turned off according to claim 3, characterized in that: The isolating device is a second diode, the anode of the second diode is connected to the positive input end of the front-stage constant voltage circuit, and the cathode of the second diode is connected to the positive electrode of the lighting fixture.

5. The circuit for preventing dim light after lighting fixture is in standby or turned off according to claim 1, characterized in that: The BUCK constant current circuit also includes a protection resistor, which is connected in parallel at both ends of the lighting fixture to play a role of voltage division protection.

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