LED lamp and power limiting circuit thereof

Abstract

The utility model provides a kind of LED lamp and its power limiting circuit, the power limiting circuit includes wireless control module, wireless control module is to first switching device output first control signal, and first switching device is used to control the current size flowing through lighting module;It further includes current detection circuit, and the current detection circuit includes single-chip microcontroller and second switching device, and single-chip microcontroller gathers the current size flowing through first switching device, and second control signal is output to second switching device to control the on-off of second switching device;The first end of second open device is connected to the control end of first switching device, and the second end of second switching device is grounded.The utility model further provides LED lamp with the above-mentioned circuit.The utility model can avoid that the current of LED lamp is too large and damage constant-voltage dimming circuit.

Description

Technical Field

[0001] This utility model relates to the technical field of LED lighting drive, specifically, to an LED lighting fixture and its power limiting circuit. Background Technology

[0002] LED lighting fixtures offer advantages such as energy efficiency, environmental friendliness, and long lifespan, and are widely used in various applications including home lighting and architectural decoration. An existing constant-voltage dimming LED lighting fixture circuit is as follows: Figure 1 As shown, the LED lamp is connected to a DC power supply, for example, Vin1 is the positive terminal and Vin2 is the negative terminal. The DC voltage supplies power to the wireless control module U1 through diode D1. The wireless control module U1 can be a Bluetooth module or a WIFI module, etc., and receives control signals sent by external control devices via wireless signals, such as signals to adjust the brightness and color temperature of the LED lamp.

[0003] The control pin of the wireless control module U1 outputs a PWM control signal to the field-effect transistor Q1 through resistor R3. The LED chip LED1, which serves as the lighting module, is connected in series with the field-effect transistor Q1. Therefore, the wireless control module U1 controls the current flowing through the LED chip LED1 by controlling the current in the field-effect transistor Q1. Currently, the brightness of the LED chip LED1 in LED lamps is typically controlled manually by the user. If the user sets the power of the LED lamp too high, it will cause the conduction angle of the field-effect transistor Q1 to be too large, resulting in excessive current flowing through the LED chip LED1. This will cause the power of the LED lamp to exceed the rated power of the constant voltage dimming circuit, potentially damaging the constant voltage dimming circuit.

[0004] Therefore, some existing LED lighting fixtures are equipped with an overcurrent protection unit. This unit detects the current flowing through the LED chip to determine if the LED fixture is in an overcurrent state, and thus whether the LED power is too high. However, existing LED lighting fixtures only adaptively adjust the current and do not effectively control the on / off state of the MOSFET. They fail to effectively protect the constant voltage dimming circuit and do not issue warning messages when the current is too high to inform users of the abnormal condition of the LED fixture, thus affecting the user experience. Summary of the Invention

[0005] The primary objective of this invention is to provide a power limiting circuit for LED lamps that can effectively protect LED lamps from overcurrent.

[0006] The second objective of this invention is to provide an LED lamp having the aforementioned power limiting circuit.

[0007] To achieve the first objective of this utility model, the power limiting circuit for the LED lamp provided by this utility model includes a wireless control module, which outputs a first control signal to a first switching device. The first switching device is used to control the magnitude of the current flowing through the lighting module. It also includes a current detection circuit, which includes a microcontroller and a second switching device. The microcontroller collects the magnitude of the current flowing through the first switching device and outputs a second control signal to the second switching device to control the on / off state of the second switching device. The first terminal of the second switching device is connected to the control terminal of the first switching device, and the second terminal of the second switching device is grounded.

[0008] As can be seen from the above solution, this utility model detects the current flowing through the first switching device using a microcontroller, which is essentially detecting the current flowing through the lighting module. Furthermore, the microcontroller can also control the on / off state of the second switching device. Since the first terminal of the second switching device is connected to the control terminal of the first switching device, the on / off state of the second switching device effectively controls the on / off state of the first switching device. Thus, when the microcontroller detects that the current flowing through the lighting module is too high, it can turn on the second switching device, thereby turning off the first switching device, thus preventing excessive current from flowing through the constant voltage dimming circuit and avoiding damage to it.

[0009] In a preferred embodiment, the second switching device includes a transistor, the control pin of the microcontroller is connected to the base of the transistor, the collector of the transistor is connected to the control terminal of the first switching device, and the emitter of the transistor is grounded.

[0010] It can be seen that by using a transistor as the second switching device, the control performance of the transistor makes the on / off control of the first switching device very flexible.

[0011] A further option is that the power limiting circuit also includes a current-limiting resistor connected in series with the first switching device.

[0012] Therefore, by setting a current-limiting resistor, excessive current flowing through the first switching device can be avoided to a certain extent, thereby protecting the constant voltage dimming circuit of the LED lamp.

[0013] A further approach is to connect the first end of the current-limiting resistor to the first switching device, and ground the second end of the current-limiting resistor.

[0014] A further approach is to have the microcontroller's sampling pin receive the signal output by the first switching device, and the sampling pin is also connected to a filter capacitor.

[0015] Therefore, the sampling pin of the microcontroller is also connected to a filter capacitor, which makes the current signal collected by the microcontroller more stable and avoids misjudgment caused by spikes in the current signal.

[0016] A further approach is to connect the microcontroller's indicator pin to an indicator device, preferably a light indicator or a sound indicator.

[0017] Therefore, by setting up light or sound indicators, alarms can be issued in a timely manner when LED lights malfunction, so that users are aware that the LED lights are in an abnormal state.

[0018] A further proposed solution is to use a field-effect transistor as the first switching device and a PWM signal as the first control signal.

[0019] To achieve the second objective mentioned above, the LED lamp provided by this utility model has a lighting module and the power limiting circuit of the LED lamp, wherein the lighting module is connected in series with the first switching device.

[0020] A preferred embodiment is that a unidirectional conducting device is provided between the positive terminal of the LED lamp power supply and the first switching device, with the positive terminal of the unidirectional conducting device connected to the first switching device and the negative terminal of the unidirectional conducting device connected to the positive terminal of the power supply.

[0021] Therefore, by setting a unidirectional conduction device, reverse current flow can be avoided, thereby preventing damage to LED lamps. Attached Figure Description

[0022] Figure 1 This is the circuit diagram of a power limiting circuit for an existing LED lamp.

[0023] Figure 2 This is an electrical schematic diagram of an embodiment of the power limiting circuit for LED lamps of this utility model.

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0025] This invention relates to a power limiting circuit for LED lamps, particularly those with constant voltage dimming circuits. This invention determines whether the LED lamp is operating at excessive power by detecting the current flowing through the lighting module, and takes overcurrent protection measures to prevent damage to the LED lamp when the power is too high.

[0026] See Figure 2In this embodiment, the LED light fixture is equipped with a wireless control module U11. The wireless control module U11 can be a Bluetooth or WIFI module, used to receive information sent by an external control terminal, such as displaying control information sent by the user via a smartphone. The wireless control module U11 is connected to a power supply. In this embodiment, the power supply can be a DC power supply, where Vin11 is the positive terminal of the power supply and Vin12 is the negative terminal. Therefore, Vin12 is grounded.

[0027] The control pin of the wireless control module U11 outputs a control signal to the field-effect transistor Q11, which serves as the first switching device, through resistor R13. Preferably, the gate of the field-effect transistor Q11, i.e., its control terminal, receives the first control signal output by the control pin of the wireless control module U11. The first control signal is a PWM signal. The wireless control module U11 controls the conduction time of the field-effect transistor Q11 by adjusting the duty cycle of the output PWM signal, thereby controlling the magnitude of the current flowing through the field-effect transistor Q11.

[0028] A diode D12, acting as a unidirectional conductor, is connected between the field-effect transistor Q11 and the positive terminal Vin11 of the power supply. The positive terminal of diode D12 is connected to the drain of the field-effect transistor Q11, and the negative terminal is connected to the positive terminal Vin11. This prevents current from flowing from the positive terminal Vin11 to the drain of the field-effect transistor Q11. Furthermore, the field-effect transistor Q11 is connected in series with an LED chip LED11, which serves as the lighting module. The positive terminal of LED11 is connected to the positive terminal Vin11, and the negative terminal is connected to the drain of the field-effect transistor Q11. Therefore, when the field-effect transistor Q11 is turned on, current can flow from the positive terminal Vin11 through LED11 to the field-effect transistor Q11. The source of the field-effect transistor Q11 is connected to the first terminal of a current-limiting resistor R14, and the second terminal of the current-limiting resistor R14 is grounded.

[0029] This embodiment also includes a current detection circuit. Specifically, the current detection circuit includes a microcontroller U1 and a transistor Q12 as a second switching device. The sampling pin of the microcontroller U12 is connected to the first end of a current-limiting resistor R14 through a resistor R11. The current flowing through the current-limiting resistor R4 forms a sampling voltage at the first end of the current-limiting resistor R14. The sampling pin of the microcontroller U12 collects the sampling voltage formed at the first end of the current-limiting resistor R14 through the resistor R11, thereby realizing the acquisition of the current flowing through the field-effect transistor Q11. In addition, the sampling pin of the microcontroller U12 is also connected to a filter capacitor C11. For example, the first end of the filter capacitor C11 is connected to the first end of the current-limiting resistor R14, and the second end of the filter capacitor C11 is grounded. The filter capacitor C11 can filter the sampling voltage, making the sampling voltage more stable and avoiding the interference of peaks in the sampling voltage to the detection of the microcontroller U12.

[0030] The control pin of microcontroller U12 is connected to the control terminal of transistor Q12, i.e., to the base of transistor Q12. The collector of transistor Q12 is connected to the first terminal of resistor R13, and the emitter of transistor Q12 is grounded. Therefore, transistor Q12 is connected between the control terminal of MOSFET Q11 and ground. Thus, when microcontroller U12 outputs the second control signal to turn on transistor Q12, the gate voltage of MOSFET Q11 is low, causing MOSFET Q11 to turn off. The PWM signal output by wireless control module U11 will not be able to drive MOSFET Q11 to conduct, resulting in no current flowing through the LED chip LED11.

[0031] Furthermore, the indicator pin of the microcontroller U12 is connected to an indicator device. In this embodiment, the indicator device is a light indicator device, specifically an LED chip LED12. When the microcontroller U12 outputs a second control signal to turn on the transistor Q12, it also outputs a signal through the indicator pin to make the LED chip LED12 light up, informing the user that the LED chip LED11 is currently not lighting up. Of course, in other embodiments, the indicator device can also be a sound indicator device, such as a speaker.

[0032] When the LED light is working, the positive terminal Vin11 of the power supply outputs DC current, which powers the wireless control module U11 and the microcontroller U12. The wireless control module U11 receives external control information and generates a corresponding PWM signal based on the external control information. The PWM signal is then output to the field-effect transistor Q11 to control the conduction time of Q11, thereby controlling the current of Q11. Additionally, the DC current output from the positive terminal Vin11 also flows through the LED chip LED11 and to the drain of the field-effect transistor Q11. However, due to the presence of diode D12, the current cannot flow from the positive terminal Vin11 through diode D12 to the field-effect transistor Q11.

[0033] After the field-effect transistor Q11 is turned on, the first terminal of the current-limiting resistor R14 forms a sampling voltage. The microcontroller U12 collects the sampling voltage and determines whether the current sampling voltage is too high. If the current sampling voltage does not exceed the preset threshold, it means that the current flowing through the field-effect transistor Q11 is not too large, that is, the current flowing through the LED chip LED11 is within the allowable range. At this time, the control pin of the microcontroller U12 outputs a low-level signal to the transistor Q12, the transistor Q12 is turned off, and the wireless control module U11 can control the operation of the field-effect transistor Q11 normally. Furthermore, the LED chip LED12 will not emit light.

[0034] If the current sampling voltage is too high, it indicates that the current flowing through the field-effect transistor Q11 is too large, meaning the current flowing through the LED chip LED11 exceeds the allowable range. At this time, the control pin of the microcontroller U12 outputs a high-level signal to the transistor Q12, turning it on. This grounds the gate of the field-effect transistor Q11, preventing the wireless control module U11 from controlling its operation. Consequently, the constant voltage dimming circuit will not function. Simultaneously, the indicator pin of the microcontroller U12 also outputs a high-level signal, causing the LED chip LED12 to illuminate, informing the user that the current in the LED chip LED11 is too high and a protective measure has been taken.

[0035] Once the power of LED chip LED11 returns to normal, meaning the sampling voltage collected by microcontroller U12 does not exceed the preset threshold, microcontroller U12 will control transistor Q12 to turn off. At this time, MOSFET Q11 will resume receiving the first control signal from wireless control module U11, and LED chip LED11 will resume normal operation. Furthermore, microcontroller U12 will also control LED chip LED12 to turn off, indicating that the constant voltage dimming circuit has resumed normal operation.

[0036] This invention uses a microcontroller to detect whether the current flowing through the lighting module is too high in order to determine whether the lighting module is overpowered. If the power is too high, the field-effect transistor Q11 will be cut off so that the current cannot flow through the lighting module, thereby protecting the constant voltage dimming circuit and preventing damage to the constant voltage dimming circuit.

[0037] Finally, it should be emphasized that the above are only preferred embodiments of the present utility model and are not intended to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A power limiting circuit for an LED lamp, comprising: A wireless control module, wherein the wireless control module outputs a first control signal to a first switching device, the first switching device being used to control the magnitude of the current flowing through the lighting module; The power limiting circuit is characterized by further comprising: A current detection circuit includes a microcontroller and a second switching device. The microcontroller collects the magnitude of the current flowing through the first switching device and outputs a second control signal to the second switching device to control the on / off state of the second switching device. The first terminal of the second switching device is connected to the control terminal of the first switching device, and the second terminal of the second switching device is grounded.

2. The power limiting circuit for LED lamps according to claim 1, characterized in that: The second switching device includes a transistor, the control pin of the microcontroller is connected to the base of the transistor, the collector of the transistor is connected to the control terminal of the first switching device, and the emitter of the transistor is grounded.

3. The power limiting circuit for LED lamps according to claim 1 or 2, characterized in that: The power limiting circuit also includes a current-limiting resistor connected in series with the first switching device.

4. The power limiting circuit for LED lamps according to claim 3, characterized in that: The first end of the current-limiting resistor is connected to the first switching device, and the second end of the current-limiting resistor is grounded.

5. The power limiting circuit for LED lamps according to claim 3, characterized in that: The sampling pin of the microcontroller receives the signal output by the first switching device, and the sampling pin is also connected to a filter capacitor.

6. The power limiting circuit for LED lamps according to claim 1 or 2, characterized in that: The indicator pin of the microcontroller is connected to an indicator device.

7. The power limiting circuit for LED lamps according to claim 6, characterized in that: The indicator device is a light indicator or a sound indicator.

8. The power limiting circuit for LED lamps according to claim 1 or 2, characterized in that: The first switching device is a field-effect transistor, and the first control signal is a PWM signal.

9. An LED lighting fixture, characterized in that, It includes a lighting module and a power limiting circuit for an LED luminaire as described in any one of claims 1 to 7, wherein the lighting module is connected in series with the first switching device.

10. The LED lamp according to claim 9, characterized in that: A unidirectional conducting device is provided between the positive terminal of the power supply of the LED lamp and the first switching device. The positive terminal of the unidirectional conducting device is connected to the first switching device, and the negative terminal of the unidirectional conducting device is connected to the positive terminal of the power supply.

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