Control circuit of lamp

Abstract

The invention provides a control circuit of a lamp, the resistance of the lamp changes along with the change of temperature, and the control circuit comprises a switching circuit and a preheating circuit; the preheating circuit is connected into the switching circuit; the preheating circuit is used for heating an initial resistor of the lamp to a working resistor; and the switching circuit is used for controlling the working state of the lamp. According to the application, the lamp is preheated, so that burnout caused by a current process when the lamp is started is avoided.

Description

Technical Field

[0001] This application relates to the field of lighting control technology, and more specifically, to a control circuit for a lamp. Background Technology

[0002] Most current lamps use tungsten filaments as the light-emitting component. Due to the metallic properties of tungsten filaments, their resistance changes with temperature. Commonly used lamps include incandescent lamps and halogen lamps. This property of changing resistance presents new challenges for lamp control.

[0003] For example, current halogen lamp control is based on a fixed switching frequency. Because the internal resistance of a halogen lamp is relatively small during cold starts, it generates a large current during startup, which can easily cause the lamp to burn out. Replacing it with a lamp with a lamp that has a larger internal resistance would increase costs. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a control circuit for a lamp to overcome the problems in the prior art.

[0005] In a first aspect, embodiments of this application provide a control circuit for a lamp, wherein the resistance of the lamp changes with temperature, and the control circuit includes: a switching circuit and a preheating circuit; the preheating circuit is connected to the switching circuit. The preheating circuit is used to heat the initial resistance of the lamp to the operating resistance. The switching circuit is used to control the working state of the lamp.

[0006] In some technical solutions of this application, the preheating circuit is used to increase the initial switching frequency of the switching circuit to the target switching frequency. The switching circuit is used to control the lamp to heat its initial resistance to its operating resistance at the target switching frequency.

[0007] In some technical solutions of this application, the control circuit mentioned above also includes a sampling resistor; The preheating circuit is used to heat the initial resistance of the lamp to the working resistance when the monitoring voltage of the sampling resistor is not within a preset voltage range.

[0008] In some technical solutions of this application, the preheating circuit mentioned above includes: a comparison module; The comparison module is used to compare the monitored voltage with a voltage threshold corresponding to a preset voltage range and output an enable signal.

[0009] In some technical solutions of this application, the control circuit includes: a trigger module; The trigger module is used to receive the enable signal and the target switching frequency, and output the target switching frequency when the enable signal is enabled.

[0010] In some technical solutions of this application, the control circuit includes: an oscillation module; The oscillation module is used to output the target switching frequency.

[0011] In some technical solutions of this application, the aforementioned switching circuit includes a MOSFET; The preheating circuit is used to control the switching of the MOS transistor to heat the initial resistance of the lamp.

[0012] In some technical solutions of this application, the aforementioned switching circuit includes a pulse width modulation module; The pulse width modulation module is used to receive the target switching frequency and the preset initial switching frequency output by the preheating circuit, and output a pulse voltage signal; wherein, the pulse voltage signal is used to control the switching of the MOS transistor.

[0013] In some technical solutions of this application, the above-mentioned switching circuit is used to control the lamp based on a target switching frequency when the lamp's resistance is the initial resistance; and to control the lamp based on the initial switching frequency when the lamp's resistance is the working resistance.

[0014] In some technical solutions of this application, the preheating circuit includes an oscillator, a comparator, and a trigger.

[0015] The technical solutions provided by the embodiments of this application may include the following beneficial effects: This application provides a control circuit for a lamp whose resistance changes with temperature. The control circuit includes a switching circuit and a preheating circuit. The preheating circuit is connected to the switching circuit. The preheating circuit is used to heat the initial resistance of the lamp to its operating resistance. The switching circuit is used to control the operating state of the lamp.

[0016] This application avoids burnout caused by the current flow during lamp startup by preheating the lamp.

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the control circuit for the first type of lamp provided in an embodiment of this application is shown; Figure 2 A schematic diagram of a control circuit in the prior art provided in the embodiments of this application is shown; Figure 3 A schematic diagram of the control circuit for the second type of lamp provided in an embodiment of this application is shown; Figure 4 A schematic diagram of a preheating circuit provided in an embodiment of this application is shown; Figure 5 This illustration shows a schematic diagram of the variation between the sampling resistor voltage and a preset power supply threshold provided in an embodiment of this application; Figure 6 A schematic diagram of the control circuit for the third type of lamp provided in an embodiment of this application is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in this application are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of this application. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this application illustrate operations implemented according to some embodiments of this application. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this application, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.

[0021] Furthermore, the described embodiments are merely some, not all, of the embodiments of this application. The components of the embodiments of this application described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0022] It should be noted that the term "comprising" will be used in the embodiments of this application to indicate the presence of the features declared thereafter, but does not exclude the addition of other features.

[0023] Most current lamps use tungsten filaments as the light-emitting component. Due to the metallic properties of tungsten filaments, their resistance changes with temperature. Commonly used lamps include incandescent lamps and halogen lamps. This property of changing resistance presents new challenges for lamp control.

[0024] For example, current halogen lamp control is based on a fixed switching frequency (specific circuits such as...). Figure 2 As shown in the image, because the internal resistance of a halogen lamp is relatively small during cold starts, it generates a large current during startup, which can easily cause the lamp to burn out. Replacing it with one having a larger internal resistance would increase costs.

[0025] Based on this, embodiments of this application provide a lamp control circuit, and some implementation methods of this application are described in detail below. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] Figure 1 This illustration shows a schematic diagram of a lamp control circuit provided in an embodiment of this application. It should be noted that in this embodiment, the resistance of the lamp or its light-emitting component changes with temperature; that is, when the light-emitting component is a metal filament, the filament can be a tungsten filament lamp. The control circuit in this embodiment is not applicable to lamps where the resistance of the lamp or its light-emitting component remains constant (or changes only slightly; a slight change can be measured by a specific resistance change threshold), such as fluorescent lamps, sodium lamps, and LED lamps.

[0027] For lamps whose light-emitting component resistance changes with temperature, this application provides a control circuit that includes a switching circuit 200 and a preheating circuit 100. The switching circuit 200 controls the lamp's operating state (on and off), and the preheating circuit 100 controls the lamp's resistance value to prevent the lamp from burning out due to low resistance (high current) when the lamp is turned on by the switching circuit 200.

[0028] In an optional implementation, due to the resistance characteristics of the lamp or light-emitting component (which change with temperature, generally increasing with rising temperature), the preheating circuit 100 in this embodiment controls the lamp resistance by increasing the lamp temperature, thereby increasing the lamp's resistance value. Various methods are used to increase the lamp temperature, such as heating. Considering safety and production costs, this embodiment adopts a method of increasing the lamp temperature by switching the lamp at a high frequency (relative to the initial switching frequency, which is the frequency used to control the lamp to operate normally).

[0029] Specifically, in this embodiment, the preheating circuit 100 increases the switching frequency of the switching circuit 200 from the initial switching frequency to the target switching frequency. The specific value of the target switching frequency can be set according to the initial resistance value of the lamp. For example, if the initial resistance value is large, the target switching frequency can be set smaller, and vice versa. After the preheating circuit 100 outputs the target switching frequency to the switching circuit 200, the switching circuit 200 controls the lamp to turn on and off at the target switching frequency. Each time the lamp is turned on and off, its temperature increases. When the lamp's temperature reaches a preset temperature threshold, the lamp's resistance reaches its operating resistance. Because the lamp's resistance increases, the input voltage remains constant, and the current flowing through the lamp is smaller than when the resistance is not increased, thus preventing the lamp from burning out.

[0030] In one optional implementation, the preheating circuit 100 has limitations on heating the lamp. For example, a lamp that has not been turned on for a long time needs to be heated when it is turned on; however, a lamp that has just been turned off (still in the working resistance state) does not need to be heated when it is turned on again. To avoid wasting the resources of the preheating circuit 100, this embodiment of the application needs to detect the lamp, and only when the preset heating requirements are met will the lamp be heated.

[0031] In determining the heating time, this embodiment of the application uses the current flowing through the lamp as the basis. Since the lamp's resistance changes, this embodiment employs a sampling resistor 300 in the control circuit, connected in series with the lamp, such as... Figure 3 As shown. By detecting that the current through the sampling resistor 300Ω equals the current through the lamp, the preset heating requirement can be specifically set as a current threshold. When the current through the lamp is greater than this current threshold, the lamp is heated until the current through the lamp is less than or equal to this current threshold.

[0032] Furthermore, since the resistance value of the sampling resistor 300 is fixed, the current detection of the sampling resistor 300 can be converted into the voltage detection of the sampling resistor 300. That is, the aforementioned preset heating requirement can be specifically set as a voltage threshold. When the voltage of the sampling resistor 300 is greater than the voltage threshold, the lamp is heated until the voltage of the sampling resistor 300 is less than the voltage threshold.

[0033] When comparing the voltage across the sampling resistor 300 with a preset voltage threshold, the preheating circuit 100 in this embodiment employs a comparison module, which receives the preset voltage threshold and the voltage across the sampling resistor. When the comparison module determines that the monitored voltage exceeds the voltage threshold range, the preheating circuit heats the lamp.

[0034] In an optional implementation, this embodiment of the application heats the lamp by using a high-frequency switching method on the switching circuit. Specifically, the preheating circuit 100 includes a trigger module and an oscillation module. The target switching frequency is generated by the oscillation module and controlled by the trigger module. When the trigger module receives an enable signal, it outputs the target switching frequency to the switching circuit 200. That is, in this embodiment, the switching circuit 200 controls the lamp in two ways: the first way is to control the lamp based on the initial switching frequency, and the second way is to control it based on the target switching frequency. In a specific scenario, the lamp is controlled based on the target switching frequency when it is turned on from the initial resistance until the initial resistance of the lamp rises to the working resistance, after which the lamp is controlled based on the initial switching frequency. Specifically, the switching circuit 200 includes a pulse width modulation module, which receives the initial switching frequency and the target switching frequency and outputs a pulse voltage signal. The pulse voltage signal is generated by adjusting the duty cycle based on the initial switching frequency or the target switching frequency.

[0035] In an alternative implementation, such as Figure 4 and Figure 5 As shown, the preheating circuit 100 includes an oscillator (OSC), a comparator (COMP), and an RS flip-flop. The clock signal of the target switching frequency output by the OSC is connected to the R terminal of the RS flip-flop. The COMP compares the voltage (IR) of the sampling resistor with the overcurrent protection voltage threshold (VOCP), and its output is connected to the S terminal of the RS flip-flop. The output of the RS flip-flop then leads to the control gate. A high or low level output from COMP controls whether the clock signal of the target switching frequency generated by the OSC is output to the gate. Specifically, when IR is greater than VOCP, COMP outputs a low level, causing the RS flip-flop to output the clock signal of the target switching frequency generated by the OSC to the control gate.

[0036] In an optional implementation, the control circuit in this application embodiment can be configured according to... Figure 6 The circuit is connected to the lamp as shown. Switching circuit 200 includes a PWM (Pulse Width Modulation) module, a filter capacitor, a MOSFET, and a sampling resistor. After the input voltage Vin is connected to the circuit, one end of the filter capacitor is connected first, and the other end of the filter capacitor is grounded. The filtered voltage is output to the drain of the MOSFET. The source of the MOSFET is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to one end of the load (lamp). The other end of the load is grounded. Preheating circuit 100 includes a high-frequency pulse generation circuit and a current filtering and monitoring circuit. Within the dashed box (preheating circuit 100), the output of the normal flashing frequency module (corresponding to the initial switching frequency) is connected to the PWM. The high-frequency pulse generation circuit and the current overcurrent detection circuit are interconnected, and the output of the high-frequency pulse generation circuit is connected to the PWM. The PWM output gate signal is connected to the gate of the MOSFET. The current overcurrent detection circuit is connected to the CS node between the sampling resistor and the source of the MOSFET. During operation, the "normal flashing frequency" dominates under normal conditions. The PWM generates a Gate signal based on this to control the MOSFET switch and adjust the power supply to the load. During preheating or overcurrent, the preheating circuit intervenes, and the high-frequency pulse generation circuit outputs a signal to cooperate. The overcurrent detection circuit monitors the voltage of the sampling resistor at the CS terminal. If an overcurrent occurs, the PWM output is adjusted to protect the circuit. Through the collaboration of various modules, the power supply control and protection of the load (light bulb) are achieved.

[0037] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In addition, the terms "first", "second", "third", etc. are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application. All should be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.

Claims

1. A control circuit for a lamp, characterized in that, The resistance of the lamp changes with temperature, and the control circuit includes a switching circuit and a preheating circuit; the preheating circuit is connected to the switching circuit. The preheating circuit is used to heat the initial resistance of the lamp to the operating resistance. The switching circuit is used to control the working state of the lamp.

2. The control circuit according to claim 1, characterized in that, The preheating circuit is used to increase the initial switching frequency of the switching circuit to the target switching frequency. The switching circuit is used to control the lamp to heat its initial resistance to its operating resistance at the target switching frequency.

3. The control circuit according to claim 1, characterized in that, The control circuit also includes a sampling resistor; The preheating circuit is used to heat the initial resistance of the lamp to the working resistance when the monitoring voltage of the sampling resistor is not within a preset voltage range.

4. The control circuit according to claim 3, characterized in that, The preheating circuit includes: a comparison module; The comparison module is used to compare the monitored voltage with a voltage threshold corresponding to a preset voltage range and output an enable signal.

5. The control circuit according to claim 4, characterized in that, The control circuit includes: a trigger module; The trigger module is used to receive the enable signal and the target switching frequency, and output the target switching frequency when the enable signal is enabled.

6. The control circuit according to claim 5, characterized in that, The control circuit includes: an oscillation module; The oscillation module is used to output the target switching frequency.

7. The control circuit according to claim 1, characterized in that, The switching circuit includes a MOSFET; The preheating circuit is used to control the switching of the MOS transistor to heat the initial resistance of the lamp.

8. The control circuit according to claim 7, characterized in that, The switching circuit includes a pulse width modulation module; The pulse width modulation module is used to receive the target switching frequency and the preset initial switching frequency output by the preheating circuit, and output a pulse voltage signal; wherein, the pulse voltage signal is used to control the switching of the MOS transistor.

9. The control circuit according to claim 1, characterized in that, The switching circuit is used to control the lamp based on a target switching frequency when the lamp's resistance is at its initial resistance, and to control the lamp based on an initial switching frequency when the lamp's resistance is its operating resistance.

10. The control circuit according to claim 1, characterized in that, The preheating circuit includes an oscillator, a comparator, and a trigger.

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