A control method for a lighting circuit, a control circuit and a lighting circuit

Abstract

The present invention discloses a control method, a control circuit and a lighting circuit of a lighting circuit. The lighting circuit comprises a linear adjustment tube. The load of the lighting circuit is an LED lamp. An AC input power source is rectified by a rectifier circuit to obtain a rectified voltage. The linear adjustment tube is connected in series with the LED lamp. The rectified voltage supplies power to the LED lamp. When the rectified voltage is greater than or equal to a first voltage, the linear adjustment tube is turned on and the current of the LED lamp is controlled to be a first current. Timing starts from when the LED lamp is turned on or when the current of the LED lamp is the first current. When the timing reaches a first time or when the rectified voltage is greater than or equal to a second voltage, the linear adjustment tube is controlled to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a control method for a lighting circuit, a control circuit and a lighting circuit. Background Art

[0002] With the development of LED lamp beads and lighting technology, linear LED lighting solutions have attracted more and more attention and research because of their low cost of electronic components, ease of full SMD production, and easy realization of modular lighting products with light engines. They also improve production efficiency and reduce labor costs. However, the application of traditional linear solutions has great limitations. They can only be applied within a specific input voltage range according to the load voltage. When the input voltage range is exceeded, the load current and power will change dramatically, seriously affecting the lighting effect or damaging the LED lamp beads. Therefore, how to make the output current in the linear solution unaffected by the input voltage and ensure that the output current or power is constant is an urgent problem to be solved. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a control method, a control circuit and a lighting circuit for solving the problem in the prior art that the output current is affected by the input voltage.

[0004] The technical solution of the present invention is to provide a control method for a lighting circuit, wherein the lighting circuit includes a linear adjustment tube, the load of the lighting circuit is an LED lamp, the AC input power is rectified by a rectifier circuit to obtain a rectified voltage, the linear adjustment tube is connected in series with the LED lamp, the rectified voltage supplies power to the LED lamp, when the rectified voltage is greater than or equal to a first voltage, the linear adjustment tube is turned on, and the current of the LED lamp is controlled to be a first current, timing starts from when the LED lamp is turned on or when the current of the LED lamp is the first current, when the timing reaches the first time, or when the rectified voltage is greater than or equal to a second voltage, the linear adjustment tube is controlled to be turned off, and the current of the LED lamp is zero, and in the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

[0005] Optionally, the first voltage is the forward conduction voltage drop of the LED lamp. When the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on after a delay of a second time. The timing starts from when the LED lamp is turned on or when the LED lamp current becomes the first current. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off.

[0006] As an option, the first time decreases as the peak value or effective value of the rectified voltage increases.

[0007] Optionally, when the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current decreases as the peak value or effective value of the rectified voltage increases.

[0008] Another technical solution of the present invention is to provide a control circuit of a lighting circuit, wherein the lighting circuit includes a linear adjustment tube, the load of the lighting circuit is an LED lamp, the AC input power is rectified by the rectifier circuit to obtain a rectified voltage, the linear adjustment tube is connected in series with the LED lamp, and the rectified voltage supplies power to the LED lamp. When the rectified voltage is greater than or equal to a first voltage, the control circuit controls the linear adjustment tube to be turned on, and controls the current of the LED lamp to be a first current. The timing starts from the time when the LED lamp is turned on or the time when the current of the LED lamp is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the control circuit controls the linear adjustment tube to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

[0009] Optionally, the control circuit includes a voltage sampling circuit, a current sampling circuit and a current control circuit. The voltage sampling circuit samples the rectified voltage to obtain a sampling voltage. The current sampling circuit samples the current of the LED lamp to obtain a sampling current signal. When the sampling voltage indicates that the rectified voltage is greater than or equal to a first voltage, the current control circuit controls the linear adjustment tube to be turned on, and controls the current of the LED lamp to be a first current according to the sampling current signal. The current control circuit starts timing from the time when the LED lamp is turned on or from the time when the LED lamp current is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the current control circuit controls the linear adjustment tube to be turned off.

[0010] Optionally, the first voltage is the forward conduction voltage drop of the LED lamp. When the sampled voltage indicates that the rectified voltage is greater than or equal to the first voltage, the current control circuit delays for a second time to control the linear adjustment tube to be turned on. The timing starts from the time when the LED lamp is turned on or from the time when the LED lamp current becomes the first current. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off.

[0011] As an option, the first time decreases as the peak value or effective value of the rectified voltage increases.

[0012] Optionally, when the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current decreases as the peak value or effective value of the rectified voltage increases.

[0013] Another technical solution of the present invention is to provide a lighting circuit.

[0014] Compared with the prior art, the circuit structure and method of the present invention have the following advantages: the output current is not affected by the input voltage, and the output current or power is ensured to be approximately constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a block diagram of the lighting circuit and control circuit of the present invention;

[0016] Figure 2 rectified voltage and output current waveforms according to an embodiment of the present invention;

[0017] Figure 3 The rectified voltage and output current waveforms of another embodiment of the present invention;

[0018] Figure 4 The rectified voltage and output current waveforms of another embodiment of the present invention;

[0019] Figure 5 This is a block diagram of another embodiment of the lighting circuit and control circuit thereof of the present invention. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, but the present invention is not limited to these embodiments. The present invention covers any substitution, modification, equivalent method and scheme made within the spirit and scope of the present invention.

[0021] In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without these detailed descriptions.

[0022] The present invention is described in more detail in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the accompanying drawings are all simplified and not in exact proportion, and are only used for the purpose of conveniently and clearly assisting in explaining the embodiments of the present invention.

[0023] The present invention provides a control method for a lighting circuit. Figure 1As shown, the lighting circuit includes a linear adjustment tube M01, the load of the lighting circuit is an LED lamp, the AC input power is rectified by the rectifier circuit to obtain a rectified voltage VREC, the linear adjustment tube M01 is connected in series with the LED lamp, and the rectified voltage VREC supplies power to the LED lamp. When the rectified voltage VREC is greater than or equal to a first voltage, the linear adjustment tube M01 is turned on, and the current of the LED lamp is controlled to be the first current. The timing starts from the time when the LED lamp is turned on or the time when the current of the LED lamp is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

[0024] Please refer to Figure 2 As shown, the rectified voltage and output current waveforms of an embodiment of the present invention are shown. When the rectified voltage VREC is greater than or equal to the first voltage, the linear adjustment tube M01 is turned on, and the current of the LED lamp is controlled to be the first current I1. The timing starts from when the LED lamp is turned on or when the current of the LED lamp is the first current I1. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

[0025] Please refer to Figure 3 FIG. 1 is a waveform of a rectified voltage and an output current of another embodiment of the present invention. When the rectified voltage VREC is greater than or equal to the first voltage V1, the linear adjustment tube M01 is turned on and controls the current of the LED lamp to be the first current I1. When the rectified voltage VREC is greater than or equal to the second voltage V2, the linear adjustment tube is turned off and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage VREC is greater than or equal to the first voltage V1, the linear adjustment tube is turned on again.

[0026] Please refer to Figure 4 As shown, it is the rectified voltage and output current waveform of another embodiment of the present invention, the first voltage is the forward conduction voltage drop VLED of the LED lamp, when the rectified voltage VREC is greater than or equal to the first voltage, the second time is delayed, the linear adjustment tube is turned on, the timing starts from the LED lamp being turned on or the LED lamp current being the first current, when the timing reaches the first time, the linear adjustment tube is controlled to be turned off. By delaying the second time, after the linear adjustment tube is turned on, the current on the LED lamp can reach the first current.

[0027] When the first time is a fixed value, the output power will not change with the input voltage. However, when the input voltage is high, the efficiency of the system will decrease. In some cases, in order to keep the input power constant, the first time is controlled to decrease with the increase of the peak value or effective value of the rectified voltage.

[0028] The first voltage is less than or equal to the forward conduction voltage drop of the LED lamp. When the linear adjustment tube is turned from off to on, when the first voltage is less than the forward conduction voltage drop of the LED lamp, the output current will not reach the first current, and when the rectified voltage is greater than the forward conduction voltage drop of the LED lamp, the output current can reach the first current. When the first voltage is greater than the forward conduction voltage drop of the LED lamp, when the linear adjustment tube is turned from off to on, when the first voltage is less than the forward conduction voltage drop of the LED lamp, the output current can reach the first current.

[0029] In one embodiment, when the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current I1 decreases as the peak value or effective value of the rectified voltage increases. Since the conversion efficiency under high input voltage is lower than that under low input voltage, the first current is set to decrease as the peak value or effective value of the rectified voltage increases, thereby achieving an effect of approximately constant input power.

[0030] Please refer to Figure 5 As shown, the lighting circuit further includes a first diode D10 and a first capacitor C10, the rectified voltage is connected to the LED lamp or the linear adjustment tube through the first diode D10, and the first capacitor C10 is connected in parallel with the LED lamp, thereby reducing the current ripple of the LED load and increasing the average current of the output LED.

[0031] The present invention also provides a control circuit for a lighting circuit, please refer to Figure 1 As shown, the lighting circuit includes a linear adjustment tube M01, and the load of the lighting circuit is an LED lamp. The AC input power is rectified by the rectifier circuit to obtain a rectified voltage VREC. The linear adjustment tube M01 is connected in series with the LED lamp, and the rectified voltage supplies power to the LED lamp. When the rectified voltage is greater than or equal to a first voltage, the control circuit controls the linear adjustment tube M01 to be turned on, and controls the current of the LED lamp to be the first current. The timing starts from the time when the LED lamp is turned on or the time when the LED lamp current is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the control circuit controls the linear adjustment tube to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again.

[0032] Please continue to refer to Figure 1As shown, in one embodiment, the control circuit includes a voltage sampling circuit 320, a current sampling circuit 330 and a current control circuit 310. The voltage sampling circuit 320 samples the rectified voltage VREC to obtain a sampled voltage V31. The current sampling circuit 330 samples the current of the LED lamp to obtain a sampled current signal V32. When the sampled voltage V31 indicates that the rectified voltage VREC is greater than or equal to a first voltage, the current control circuit controls the linear adjustment tube M01 to turn on, and controls the current of the LED lamp to be the first current according to the sampled current signal V32. The current control circuit starts timing from when the LED lamp is turned on or when the current of the LED lamp is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the current control circuit controls the linear adjustment tube to turn off.

[0033] In one embodiment, the first voltage is the forward conduction voltage drop of the LED lamp. When the sampled voltage indicates that the rectified voltage is greater than or equal to the first voltage, the current control circuit delays for a second time to control the linear adjustment tube to be turned on. The timing starts from when the LED lamp is turned on or when the LED lamp current is the first current. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off.

[0034] In one embodiment, the first time decreases as the peak value or effective value of the rectified voltage increases.

[0035] In one embodiment, the first voltage is less than or equal to a forward conduction voltage drop of the LED lamp.

[0036] In one embodiment, when the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current decreases as the peak value or effective value of the rectified voltage increases.

[0037] Please refer to Figure 5 As shown, the lighting circuit further includes a first diode D10 and a first capacitor C10, the rectified voltage is connected to the LED lamp or the linear adjustment tube through the first diode D10, and the first capacitor C10 is connected in parallel with the LED lamp, thereby reducing the current ripple of the LED load and increasing the average current of the output LED.

[0038] The invention also provides a lighting circuit.

[0039] In addition, although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated between the embodiments. For content that is not explicitly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0040] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A control method for a lighting circuit, wherein the lighting circuit comprises a linear adjustment tube, the load of the lighting circuit is an LED lamp, an AC input power source is rectified by a rectifier circuit to obtain a rectified voltage, the linear adjustment tube is connected in series with the LED lamp, the rectified voltage supplies power to the LED lamp, when the rectified voltage is greater than or equal to a first voltage, the linear adjustment tube is turned on, and the linear adjustment tube is controlled to work in a linear state to control the current of the LED lamp to be a first current, timing is started from when the LED lamp is turned on or when the current of the LED lamp is the first current, when the timing reaches a first time, or when the rectified voltage is greater than or equal to a second voltage, the linear adjustment tube is controlled to be turned off, and the current of the LED lamp is zero, and in the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again; wherein, When the timing reaches a first time, the linear adjustment tube is controlled to be turned off, and the first time decreases as the peak value or effective value of the rectified voltage increases; When the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current decreases as the peak value or effective value of the rectified voltage increases.

2. The method for controlling a lighting circuit according to claim 1, characterized in that: The first voltage is the forward conduction voltage drop of the LED lamp. When the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on after a delay of a second time. The timing starts from when the LED lamp is turned on or when the LED lamp current becomes the first current. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off.

3. A control circuit for a lighting circuit, the lighting circuit comprising a linear adjustment tube, the load of the lighting circuit being an LED lamp, the AC input power being rectified by a rectifier circuit to obtain a rectified voltage, the linear adjustment tube being connected in series with the LED lamp, the rectified voltage supplying power to the LED lamp, when the rectified voltage is greater than or equal to a first voltage, the control circuit controls the linear adjustment tube to be turned on, and controls the linear adjustment tube to operate in a linear state to control the current of the LED lamp to be a first current, and starts timing from when the LED lamp is turned on or when the current of the LED lamp is the first current. When the timing reaches a first time, or when the rectified voltage is greater than or equal to a second voltage, the control circuit controls the linear adjustment tube to be turned off, and the current of the LED lamp is zero. In the next half power frequency cycle, when the rectified voltage is greater than or equal to the first voltage, the linear adjustment tube is turned on again; wherein, When the timing reaches a first time, the linear adjustment tube is controlled to be turned off, and the first time decreases as the peak value or effective value of the rectified voltage increases; When the rectified voltage is greater than or equal to the second voltage, the linear adjustment tube is controlled to be turned off, and the first current decreases as the peak value or effective value of the rectified voltage increases.

4. The control circuit of the lighting circuit according to claim 3, characterized in that: The control circuit includes a voltage sampling circuit, a current sampling circuit and a current control circuit. The voltage sampling circuit samples the rectified voltage to obtain a sampling voltage. The current sampling circuit samples the current of the LED lamp to obtain a sampling current signal. When the sampling voltage indicates that the rectified voltage is greater than or equal to a first voltage, the current control circuit controls the linear adjustment tube to be turned on, and controls the current of the LED lamp to be a first current according to the sampling current signal. The current control circuit starts timing from the time when the LED lamp is turned on or from the time when the current of the LED lamp is the first current. When the timing reaches the first time, or when the rectified voltage is greater than or equal to the second voltage, the current control circuit controls the linear adjustment tube to be turned off.

5. The control circuit of the lighting circuit according to claim 4, characterized in that: The first voltage is the forward conduction voltage drop of the LED lamp. When the sampled voltage indicates that the rectified voltage is greater than or equal to the first voltage, the current control circuit delays for a second time to control the linear adjustment tube to be turned on. The timing starts from when the LED lamp is turned on or when the LED lamp current becomes the first current. When the timing reaches the first time, the linear adjustment tube is controlled to be turned off.

6. A lighting circuit, characterized in that: It comprises a control circuit as claimed in any one of claims 3 to 5, or adopts a control method as claimed in any one of claims 1 to 2.

Images