CN113194572A

CN113194572A - Low-harmonic linear constant-current LED lamp circuit

Info

Publication number: CN113194572A
Application number: CN202110338427.2A
Authority: CN
Inventors: 俞贤晓; 李斌; 吴国明
Original assignee: Yingtan Yankon Lighting Co ltd; Zhejiang Sunlight Illuminating Lamp Co ltd; Zhejiang Yankon Group Co Ltd
Current assignee: Yingtan Yankon Lighting Co ltd; Zhejiang Sunlight Illuminating Lamp Co ltd; Zhejiang Yankon Group Co Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2021-07-30

Abstract

The invention discloses a low-harmonic linear constant-current LED lamp circuit, which comprises a rectifying circuit, a voltage signal circuit, a first light-emitting module, a second light-emitting module, a constant-current linear circuit, a one-way conduction circuit, a constant-current switch circuit and a voltage sampling circuit, wherein a voltage control end of the constant-current linear circuit is provided with a voltage threshold value, the voltage control end of the constant-current linear circuit is used for controlling the conduction and cut-off states of a second output end of the constant-current linear circuit, and the constant-current linear circuit, the one-way conduction circuit, the constant-current switch circuit and the voltage sampling circuit are matched to enable the first light-emitting module to emit light independently and the second light-emitting module to emit light independently or enable the first light-emitting module and the second light-emitting module to emit light simultaneously; the low-frequency flash lamp has the advantages that the low-frequency flash lamp still can keep emitting light in a certain voltage range in which the alternating-current voltage of the mains supply is lower than the rated voltage, the phenomenon that the brightness of a light emitting surface is obviously uneven and the phenomenon of a dark space cannot occur, and the low-frequency flash function can be realized with lower cost.

Description

Low-harmonic linear constant-current LED lamp circuit

Technical Field

The invention relates to a linear constant current LED lamp circuit, in particular to a low-harmonic linear constant current LED lamp circuit.

Background

In the LED lighting industry, higher power LED lamps often have high power factor and low harmonic requirements. As the input current waveform of the LED lamp approaches a sine wave waveform, its harmonic wave becomes lower. Because linear constant current LED lamp circuit schemes often have the advantage of lower cost than switching power supply LED lamp circuit schemes, manufacturers prefer linear constant current LED lamp circuit schemes many times. The linear constant current LED lamp circuit meeting the low harmonic requirement usually adopts a three-stage linear constant current circuit scheme or a four-stage linear constant current circuit scheme. The working principle of the three-section linear constant current circuit scheme is similar to that of the four-section linear constant current circuit scheme, but the linear constant current LED lamp circuit adopting the three-section linear constant current circuit scheme is lower in cost and is a scheme which is preferentially adopted.

As shown in fig. 1, the conventional low-harmonic linear constant current LED lamp circuit generally includes a rectifier circuit, a voltage signal circuit, a first light emitting circuit, a second light emitting circuit, a third light emitting circuit and three-stage constant current circuits, the rectifier circuit has a first input terminal, a second input terminal, a positive output terminal and a negative output terminal, the rectifier circuit is used to convert an input sine wave ac voltage into a dc voltage composed of positive half cycles of two sine waves, the voltage signal circuit has an input terminal, an output terminal and a negative terminal, and the output terminal voltage is a voltage whose input terminal voltage is reduced according to a certain proportion, the output terminal voltage waveform is identical to the input terminal voltage waveform, the first light emitting circuit, the second light emitting circuit and the third light emitting circuit have a positive terminal and a negative terminal, and are formed by connecting the same number of LED light emitters or different numbers in series, and the performance of the LED light emitters is identical, the maximum instantaneous current value Imax of the three-section constant current circuit is set as Imax, the maximum instantaneous current value Imax is related to the voltage accessed by the current regulation end, and when the voltage of the current regulation end of the three-section constant current circuit changes according to the waveform of the positive half cycle of the sine wave, the maximum instantaneous current value Imax of the three-section constant current circuit also changes according to the waveform of the positive half cycle of the sine wave. The current magnitudes of the first output end, the second output end and the third output end of the three-stage constant current circuit have the following priority relation: when the current of the third output end is Imax, the first output end and the second output end are both cut off, the currents of the first output end and the second output end are both zero, and when the current of the third output end is zero, the maximum current of the second output end is Imax; when the current of the second output end is Imax, the first output end is cut off, the current of the first output end is zero, and when the current of the second output end and the current of the third output end are both zero, the maximum current of the first output end is Imax. The first input end and the second input end of the rectifying circuit are respectively connected with a live wire and a zero wire of a commercial power, the positive output end of the rectifying circuit is respectively connected with the positive electrode of the first light-emitting circuit and the input end of the voltage signal circuit, the output end of the voltage signal circuit is connected with the current regulating ends of the three sections of constant current circuits, the negative electrode of the first light-emitting circuit, the positive electrode of the second light-emitting circuit and the first output ends of the three sections of constant current circuits are connected, the negative electrode of the second light-emitting circuit, the positive electrode of the third light-emitting circuit and the second output ends of the three sections of constant current circuits are connected, and the negative electrode of the third light-emitting circuit and the third output ends of the three sections of constant current circuits are connected. The negative output end of the rectification circuit, the negative electrode of the voltage signal circuit and the negative electrode of the three sections of constant current circuits are connected.

In order to facilitate the explanation of the working principle of the low-harmonic linear constant current LED lamp circuit, the indexes of the low-harmonic linear constant current LED lamp circuit are idealized. Assuming that the voltage of a light emitting circuit composed of the LED light emitter when emitting light is V, when the voltage between the anode and the cathode of the light emitting circuit is less than V, the current flowing through the light emitting circuit is 0; when a current flows through the light emitting circuit, the voltage between the anode and the cathode is V. The voltage of the first light-emitting circuit, the voltage of the second light-emitting circuit and the voltage of the third light-emitting circuit during light emission are respectively set as V1, V2 and V3, the instantaneous value of the voltage output by the positive output end of the rectifying circuit is set as Vo, the absolute value of the voltage of the Vo and the absolute value of the instantaneous voltage of the mains supply are equal, the voltage of the Vo in one period changes to the positive half cycle of a sine wave, and the voltage value changes from 0 to the peak voltage of the mains supply and then to 0, regardless of the voltage drop of the rectifying circuit and the critical voltage of each output end of the three constant current circuits which meets the saturated conduction condition. When the rectifying circuit is connected with the alternating-current voltage of the mains supply and then outputs direct-current voltage, the voltage waveform output by the output end of the voltage signal circuit is the positive half-cycle waveform of a sine wave, and the magnitude of Imax of the three sections of constant-current circuits corresponds to the variation of Vo. If Va is V1, Vb is V1+ V2, and Vc is V1+ V2+ V3, in one period of Vo variation, when Vo is greater than or equal to 0 and less than Va, the current passing through the three-stage constant current circuit is zero, and none of the first light-emitting circuit, the second light-emitting circuit, and the third light-emitting circuit passes through the current and does not emit light; when Vo is larger than or equal to Va and smaller than Vb, the current of the first output end of the three sections of constant current circuits is Imax, the first light-emitting circuit emits light, and the second light-emitting circuit and the third light-emitting circuit do not have current and do not emit light; when Vo is larger than or equal to Vb and smaller than Vc, the current of the second output end of the three sections of constant current circuits is Imax, the current of the first output end is zero, the first light-emitting circuit and the second light-emitting circuit are connected in series to emit light, and the third light-emitting circuit does not emit light when no current passes through; when Vo is larger than or equal to Vc and smaller than or equal to the peak voltage of the commercial power, the current of the third output end of the three sections of constant current circuits is Imax, the currents of the first output end and the second output end are zero, and at the moment, the first light-emitting circuit, the second light-emitting circuit and the third light-emitting circuit are connected in series to emit light. If Va is 0, in the half sine wave voltage change of the alternating-current voltage of the commercial power, the voltage output by the output end between the positive output end and the negative output end of the rectification circuit is changed into the positive half cycle of the sine wave, the total current flowing through the three sections of constant-current circuits is equal to the maximum value Imax of the instantaneous current, and the change of the current magnitude corresponds to the positive half cycle of the sine wave. Therefore, the waveform of the mains current connected to the rectifying circuit is a sine wave, and theoretically, the harmonic wave of the current can reach 0, and because the change of the magnitude of the mains current connected to the rectifying circuit is consistent with the change of the magnitude of the voltage, the power factor can also reach 1 theoretically.

In practical application, the low-harmonic linear constant-current LED lamp circuit improves the luminous efficiency by reasonably selecting the values of Va, Vb and Vc on the premise of meeting the index requirements of high power factor and low harmonic. Currently, Va: vb: the ratio of Vc is approximately 1:2: 3. The low-harmonic linear constant-current LED lamp circuit is characterized in that: the light emitting time or the driving current of the first light emitting circuit is larger than that of the second light emitting circuit, and the light emitting time or the driving current of the second light emitting circuit is larger than that of the third light emitting circuit. Therefore, in the low-harmonic linear constant current LED lamp circuit, the phenomenon that the brightness of the LED luminous body of the first luminous circuit is greater than that of the LED luminous body of the second luminous circuit, and the brightness of the LED luminous body of the second luminous circuit is greater than that of the LED luminous body of the third luminous circuit occurs. When the ac mains voltage is lower than the rated voltage, the difference in brightness between the LED luminaries of the three lighting circuits becomes larger. When the low-harmonic linear constant-current LED lamp circuit is applied to a linear or panel type LED lamp, the phenomenon that the brightness of a light-emitting surface is obviously uneven can easily occur, and even the phenomenon that a dark area appears on the light-emitting surface because the third light-emitting circuit does not emit light can occur.

Disclosure of Invention

The invention aims to solve the technical problem of providing a low-harmonic linear constant current LED lamp circuit which can still keep light emitting within a certain voltage range that the alternating current voltage of a mains supply is lower than the rated voltage, and the phenomena of obvious uneven brightness of a light emitting surface and dark space can not occur.

The technical scheme adopted by the invention for solving the technical problems is as follows: a low-harmonic linear constant-current LED lamp circuit comprises a rectifying circuit, a voltage signal circuit, a first light-emitting module, a second light-emitting module and a constant-current linear circuit, wherein the rectifying circuit is provided with a first input end, a second input end, a positive output end and a negative output end, the rectifying circuit is used for converting a sine wave alternating-current voltage connected between the first input end and the second input end into a direct-current voltage consisting of positive half cycles of two sine waves and then outputting the direct-current voltage between the positive output end and the negative output end, the voltage signal circuit is provided with an input end, an output end and a negative electrode, the voltage of the output end is reduced according to a certain proportion, the voltage waveform of the output end is consistent with that of the input end, the first light-emitting module and the second light-emitting module are respectively provided with a positive electrode and a negative electrode, and the constant-current linear circuit is provided with a current adjusting end and a current adjusting end, The constant current circuit comprises a negative electrode, a first output end, a second output end and a voltage control end, wherein the maximum instantaneous current value of the constant current linear circuit is set as Imax, the Imax is the maximum value of the sum of the instantaneous currents of the first output end and the second output end of the constant current linear circuit, the magnitude of the Imax is related to the voltage connected to the current regulating end of the constant current linear circuit, when the voltage of the current regulating end of the constant current linear circuit changes according to the waveform of the positive half cycle of a sine wave, the maximum instantaneous current value Imax of the constant current linear circuit also changes according to the waveform of the positive half cycle of the sine wave, and the first output end and the second output end of the constant current linear circuit have the following priority relations: when the current of the second output end of the constant current linear circuit is Imax, the current of the first output end is zero, and when the current of the second output end of the constant current linear circuit is zero, the maximum current of the first output end is Imax; the voltage control end of the constant current linear circuit is provided with a voltage threshold value, the voltage control end of the constant current linear circuit is used for controlling the conduction and cut-off states of the second output end of the constant current linear circuit, when the voltage of the voltage control end of the constant current linear circuit is smaller than the voltage threshold value, the function of the constant current linear circuit is not influenced, when the voltage of the voltage control end of the constant current linear circuit is larger than or equal to the voltage threshold value, the second output end of the constant current linear circuit is in a cut-off loading state, and the maximum conduction current of the first output end of the constant current linear circuit is Imax; the low-harmonic linear constant current LED lamp circuit also comprises a unidirectional conduction circuit, a constant current switch circuit and a voltage sampling circuit, wherein the unidirectional conduction circuit is provided with an anode and a cathode, when the current direction is from the anode to the cathode of the unidirectional conduction circuit, the unidirectional conduction circuit is conducted, otherwise, the unidirectional conduction circuit is cut off, the constant current switch circuit is provided with a first end, a second end and a control end, the maximum conduction current is arranged between the first end and the second end of the constant current switch circuit, the control end and the second end of the constant current switch circuit are kept conducted, when the current between the control end and the second end of the constant current switch circuit is less than the maximum conduction current arranged between the first end and the second end, the first end and the second end are kept conducted, and when the current between the control end and the second end is more than or equal to the maximum conduction current arranged between the first end and the second end, the voltage sampling circuit is provided with an input end, an output end and a negative electrode, and the voltage of the output end of the voltage sampling circuit is the voltage of the input end of the voltage sampling circuit which is reduced according to a certain proportion; the first input end and the second input end of the rectifying circuit are respectively connected with a live wire and a zero wire of a commercial power, the positive output end of the rectifying circuit is respectively connected with the first end of the constant current switch circuit, the positive electrode of the second light-emitting module and the input end of the voltage signal circuit, the output end of the voltage signal circuit is connected with the current regulating end of the constant current linear circuit, the negative electrode of the first light-emitting module is connected with the first output end of the constant current linear circuit, the negative electrode of the second light-emitting module, the input end of the voltage sampling circuit, the positive electrode of the one-way conduction circuit and the second output end of the constant current linear circuit are connected, the second end of the constant current switch circuit is connected with the positive electrode of the first light-emitting module, and the control end of the constant current switch circuit is connected with the negative electrode of the one-way conduction circuit, the output end of the voltage sampling circuit is connected with the voltage control end of the constant current linear circuit, the negative output end of the rectifying circuit, the negative electrode of the voltage signal circuit and the negative electrode of the voltage sampling circuit are connected with the negative electrode of the constant current linear circuit, the voltage when the first light-emitting module emits light is smaller than the voltage when the second light-emitting module emits light, the current value when the first light-emitting module emits light alone is smaller than the current value when the second light-emitting module emits light alone, and the current value when the second light-emitting module emits light alone is smaller than the current values when the first light-emitting module and the second light-emitting module emit light simultaneously; in the voltage sampling circuit, when the voltage at the input end of the voltage sampling circuit is greater than or equal to the working voltage of the first light-emitting module, the voltage at the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit; when the voltage of the input end of the constant current linear circuit is smaller than the working voltage of the first light-emitting module, the voltage of the output end of the constant current linear circuit is smaller than the voltage threshold value of the voltage control end of the constant current linear circuit; setting the instantaneous value of the voltage output by the positive output end of the rectifying circuit as Vo, ideally (ignoring the voltage drop of the rectifying circuit, ignoring the critical voltage of each output end of the constant current linear circuit which meets the saturation conduction condition, ignoring the critical voltage of the first end and the second end of the current control switch which meets the saturation conduction condition), setting the absolute value of Vo and the instantaneous value of the alternating current voltage of the commercial power equal, setting the voltage variation of Vo in one period to change from 0 to the peak voltage of the commercial power and back to 0, setting the voltage when the first light-emitting module emits light as U1, setting the voltage when the second light-emitting module emits light as U2, and setting U1 to be less than U2, when the rectifying circuit is connected with the alternating current voltage of the commercial power, setting the output voltage between the positive output end and the negative output end as Vo, and when Vo is more than or equal to 0 and less than U1, the first light-emitting module and the second light-emitting module do not emit light, when Vo is greater than or equal to U1 and less than U2, the voltage and the current of the second output end of the constant current linear circuit are both 0, the first end and the second end of the constant current switch circuit are conducted, and the current of the first output end of the constant current linear circuit is Imax, so that the first light-emitting module singly emits light at the stage, the voltage Vo cannot drive the second light-emitting module to emit light, when Vo is greater than or equal to U2 and less than U1+ U2, the voltage of the second output end of the constant current linear circuit is less than U1, the voltage output by the output end of the voltage sampling circuit is less than the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a conducting state, and the current of the first output end of the constant current linear circuit is cut off at the moment, the current is 0, the second light emitting module emits light alone at this stage, the first light emitting module does not emit light, when Vo is greater than or equal to U1+ U2, the voltage of the second output end of the constant current linear circuit is greater than or equal to U1, the voltage output by the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in an off state, the first output end of the constant current linear circuit is on, and the current is Imax, because Imax at this time is greater than the maximum on-state current set at the first end and the second end of the constant current switch circuit, the current between the control end and the second end of the constant current switch circuit enables the first end and the second end to be off, at this stage, the first light emitting module and the second light emitting module emit light simultaneously, the currents flowing through the first light emitting module and the second light emitting module are equal.

The constant current switch circuit comprises a first integrated circuit and a first resistor, the first integrated circuit is a commonly-used three-terminal linear constant current chip with an output end, a negative electrode and a regulating end, the output end of the first integrated circuit is the first end of the constant current switch circuit, the negative electrode of the first integrated circuit is connected with one end of the first resistor, the connecting end of the first integrated circuit is the second end of the constant current switch circuit, the other end of the first resistor is connected with the regulating end of the first integrated circuit, and the connecting end of the first integrated circuit is the control end of the constant current switch circuit.

The voltage sampling circuit comprises a second resistor, a third resistor and a fourth resistor, wherein one end of the second resistor is the input end of the voltage sampling circuit, the other end of the second resistor is connected with one end of the third resistor, the other end of the third resistor is connected with one end of the fourth resistor, the connecting end of the third resistor is connected with the output end of the voltage sampling circuit, and the other end of the fourth resistor is the negative electrode of the voltage sampling circuit.

The voltage sampling circuit further comprises a first diode, the first diode is a rectifier diode, the first diode is used for improving the current continuity when the second light-emitting module emits light independently to turn to the first light-emitting module and the second light-emitting module emit light simultaneously, the anode of the first diode is connected with one end of the third resistor, and the cathode of the first diode is connected with the first output end of the constant current linear circuit.

The unidirectional conduction circuit is realized by adopting a rectifier diode, the anode of the rectifier diode is the anode of the unidirectional conduction circuit, and the cathode of the rectifier diode is the cathode of the unidirectional conduction circuit.

Compared with the prior art, the constant current linear circuit has the advantages that the maximum value of the instantaneous current of the constant current linear circuit is set to be Imax, the Imax is the maximum value of the sum of the instantaneous currents of the first output end and the second output end of the constant current linear circuit, the Imax is related to the voltage connected to the current adjusting end of the constant current linear circuit, when the voltage of the current adjusting end of the constant current linear circuit changes according to the waveform of the positive half cycle of the sine wave, the maximum value of the instantaneous current Imax of the constant current linear circuit also changes according to the waveform of the positive half cycle of the sine wave, and the first output end and the second output end of the constant current linear circuit have the following priority relations: when the current of the second output end of the constant current linear circuit is Imax, the current of the first output end is zero, and when the current of the second output end of the constant current linear circuit is zero, the maximum current of the first output end is Imax; the voltage control end of the constant current linear circuit is provided with a voltage threshold value, the voltage control end of the constant current linear circuit is used for controlling the conduction and cut-off states of the second output end of the constant current linear circuit, when the voltage of the voltage control end of the constant current linear circuit is smaller than the voltage threshold value, the function of the constant current linear circuit is not affected, when the voltage of the voltage control end of the constant current linear circuit is larger than or equal to the voltage threshold value, the second output end of the constant current linear circuit is in a cut-off loading state, and the maximum conduction current of the first output end of the constant current linear circuit is Imax; the low-harmonic linear constant current LED lamp circuit also comprises a unidirectional conduction circuit, a constant current switch circuit and a voltage sampling circuit, wherein the unidirectional conduction circuit is provided with a positive pole and a negative pole, when the current direction is from the positive pole to the negative pole of the unidirectional conduction circuit, the unidirectional conduction circuit is conducted, otherwise, the unidirectional conduction circuit is cut off, the constant current switch circuit is provided with a first end, a second end and a control end, the maximum conduction current is arranged between the first end and the second end of the constant current switch circuit, the control end and the second end of the constant current switch circuit are kept conducted, when the current between the control end and the second end of the constant current switch circuit is smaller than the maximum conduction current arranged between the first end and the second end of the constant current switch circuit, the first end and the second end of the constant current switch circuit are kept conducted, and when the current between the control end and the second end of the constant current switch circuit is larger than or equal to the maximum conduction current arranged between the first end and the second end of the constant current switch circuit, the first end and the second end of the constant current switch circuit are kept cut off, the voltage sampling circuit is provided with an input end, an output end and a negative electrode, and the voltage of the output end of the voltage sampling circuit is the voltage of the input end of the voltage sampling circuit which is reduced according to a certain proportion; the first input end and the second input end of the rectification circuit are respectively connected with a live wire and a zero wire of a commercial power, the positive output end of the rectification circuit is respectively connected with the first end of the constant current switch circuit, the positive electrode of the second light-emitting module and the input end of the voltage signal circuit, the output end of the voltage signal circuit is connected with the current regulation end of the constant current linear circuit, the negative electrode of the first light-emitting module is connected with the first output end of the constant current linear circuit, the negative electrode of the second light-emitting module, the input end of the voltage sampling circuit, the positive electrode of the one-way conduction circuit and the second output end of the constant current linear circuit are connected, the second end of the constant current switch circuit is connected with the positive electrode of the first light-emitting module, the control end of the constant current switch circuit is connected with the negative electrode of the one-way conduction circuit, the output end of the voltage sampling, The negative electrode of the voltage sampling circuit is connected with the negative electrode of the constant current linear circuit, the voltage of the first light-emitting module is lower than that of the second light-emitting module when the first light-emitting module emits light, the current value of the first light-emitting module when the first light-emitting module emits light independently is lower than that of the second light-emitting module when the second light-emitting module emits light independently, and the current value of the second light-emitting module when the second light-emitting module emits light independently is lower than that of the first light-emitting module and the second light-emitting module which emit light simultaneously; in the voltage sampling circuit, when the voltage at the input end of the voltage sampling circuit is greater than or equal to the working voltage of the first light-emitting module, the voltage at the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit; when the voltage of the input end of the constant current linear circuit is lower than the working voltage of the first light-emitting module, the voltage of the output end of the constant current linear circuit is lower than the voltage threshold value of the voltage control end of the constant current linear circuit; setting the instantaneous value of the voltage output by the positive output end of the rectifying circuit as Vo, in an ideal state (not counting the voltage drop of the rectifying circuit, neglecting the critical voltage of each output end of the constant current linear circuit which meets the saturation conduction condition, neglecting the critical voltage of the current control switch which meets the saturation conduction condition between the first end and the second end), the absolute value of Vo and the instantaneous value of the alternating current voltage of the mains supply are equal, the voltage change of Vo in one period is changed from 0 to the peak voltage of the mains supply and then returns to 0, the voltage when the first light-emitting module emits light is marked as U1, the voltage when the second light-emitting module emits light is marked as U2, U1 is less than U2, when the rectifying circuit is connected with the alternating current voltage of the mains supply, the output voltage between the positive output end and the negative output end is Vo, and when Vo is more than or equal to 0 and less than U1, the first light-emitting module and the second light-emitting module do not emit light, when Vo is greater than or equal to U1 and less than U2, the voltage and the current of the second output end of the constant current control circuit are both 0, the first end and the second end of the constant current switch circuit are connected, the current of the first output end of the constant current linear circuit is Imax, therefore, the first light emitting module emits light independently in the stage, the voltage Vo cannot drive the second light emitting module to emit light, when Vo is greater than or equal to U2 and less than U1+ U2, the voltage of the second output end of the constant current linear circuit is less than U1, the voltage output by the output end of the voltage sampling circuit is less than the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a conducting state, the current is Imax, at the moment, the first output end of the constant current linear circuit is cut off, the current is 0, the second light emitting module emits light independently in the stage, the first light emitting module does not emit light, when Vo is greater than or equal to U1+ U2, the voltage of the second output end of the constant current linear circuit is greater than or equal to U1, the voltage output by the output end of the voltage sampling circuit is more than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a cut-off state, the first output end of the constant current linear circuit is conducted, and the current is Imax, because Imax at the moment is larger than the maximum conduction current set by the first end and the second end of the constant current switch circuit, the current between the control end and the second end of the constant current switch circuit enables the first end and the second end to be cut off, the first light emitting module and the second light emitting module emit light at the same time, and the currents flowing through the first light emitting module and the second light emitting module are equal, so the light emitting characteristics of the first light emitting module and the second light emitting module of the low-harmonic linear constant current LED lamp circuit are as follows: when Vo is in a lower voltage interval, the first light emitting module emits light independently, then when Vo is in a higher voltage interval, the second light emitting module emits light independently, when Vo is in a highest voltage interval, the first light emitting module and the second light emitting module emit light simultaneously under the same current drive, if the voltage U1 when the first light emitting module emits light in the invention is equal to the voltage V1 when the first light emitting circuit in the existing low-harmonic linear constant current LED lamp circuit with three light emitting circuits (shown in FIG. 1) emits light, and U1+ U2 is equal to Vc, then the invention has similar power factor and harmonic index to the existing low-harmonic linear constant current LED lamp circuit with three light emitting circuits, namely the invention has higher power factor and harmonic index, if the second light emitting module in the invention is equal to the first light emitting circuit and the second light emitting circuit in the existing low-harmonic linear constant current LED lamp circuit with three light emitting circuits, the first light-emitting module is equal to a third light-emitting circuit in the existing low-harmonic linear constant-current LED lamp circuit with three light-emitting circuits, so that the currents of the first light-emitting circuit and the second light-emitting circuit in the invention are equal, the time for the first light-emitting circuit to independently emit light is eliminated, the time for the first light-emitting circuit to independently emit light is increased to be close to or equal to the current of the second light-emitting circuit, therefore, the low-harmonic linear constant-current LED lamp circuit of the invention has the advantages that the light-emitting uniformity is obviously superior to that of the existing low-harmonic linear constant-current LED lamp circuit with three light-emitting circuits, in addition, when the peak voltage of Vo is more than or equal to U2 and less than U1+ U2, the first light-emitting module and the second light-emitting module can both emit light, the invention eliminates the phenomenon that the third LED light-emitting circuit in the existing low-harmonic linear constant-current LED lamp circuit with three light-emitting circuits does not emit light in the voltage interval, is suitable for wide mains supply voltage range, can still keep emitting light in a certain voltage range in which the alternating-current voltage of the mains supply is lower than the rated voltage, and does not have the phenomenon of obvious uneven brightness of the light-emitting surface and the dark space phenomenon; in addition, the constant current linear circuit only needs two output ends of the first output end and the second output end, and one high-voltage output end is less than that of a currently commonly used three-section constant current circuit, so that the overall cost of the constant current linear circuit is equivalent to that of the existing low-harmonic linear constant current LED lamp circuit with three light-emitting circuits although a constant current switch circuit, a one-way conduction circuit and a voltage sampling circuit are added.

Drawings

FIG. 1 is a diagram of a prior art low harmonic linear constant current LED lamp circuit with three light emitting circuits;

FIG. 2 is a block diagram of a low harmonic linear constant current LED lamp circuit of the present invention;

FIG. 3 is a circuit diagram of a constant current switch circuit of the low harmonic linear constant current LED lamp circuit of the present invention;

fig. 4 is a circuit diagram of a unidirectional conducting circuit of the low harmonic linear constant current LED lamp circuit of the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Example (b): as shown in FIG. 2, a low-harmonic linear constant current LED lamp circuit comprises a rectifying circuit, a voltage signal circuit, a first light-emitting module, a second light-emitting module and a constant current linear circuit, wherein the rectifying circuit is provided with a first input end, a second input end, a positive output end and a negative output end, the rectifying circuit is used for converting a sine wave alternating current voltage connected between the first input end and the second input end into a direct current voltage consisting of positive half cycles of two sine waves and then outputting the direct current voltage between the positive output end and the negative output end, the voltage signal circuit is provided with an input end, an output end and a negative electrode, the voltage of the output end is reduced according to a certain proportion, the voltage waveform of the output end is consistent with that of the input end, the first light-emitting module and the second light-emitting module are respectively provided with a positive electrode and a negative electrode, and the constant current linear circuit is provided with a current adjusting end, a current output end, and a current output end of the constant current output end of the constant current circuit are respectively, and a current of the constant current output, and a current output is equal to the current output, and a voltage of the current output, and a voltage is equal to the current is equal to the voltage of the current is equal to the current, and the current is equal to the voltage of the current is equal to the current of the current, and the current is equal to the voltage of the current, and the voltage of the current is equal to the voltage of the voltage is equal to the voltage of the current of the constant current of the current, and the current is equal to the current of the voltage of the constant current is equal to the current of the constant current of the, The constant current linear circuit comprises a negative electrode, a first output end, a second output end and a voltage control end, wherein the maximum instantaneous current value of the constant current linear circuit is set to be Imax, the Imax is the maximum value of the sum of the instantaneous currents of the first output end and the second output end of the constant current linear circuit, the Imax is related to the voltage connected to the current regulation end of the constant current linear circuit, when the voltage of the current regulation end of the constant current linear circuit changes according to the waveform of a positive half cycle of a sine wave, the maximum instantaneous current value Imax of the constant current linear circuit also changes according to the waveform of the positive half cycle of the sine wave, and the first output end and the second output end of the constant current linear circuit have the following priority relations: when the current of the second output end of the constant current linear circuit is Imax, the current of the first output end is zero, and when the current of the second output end of the constant current linear circuit is zero, the maximum current of the first output end is Imax; the voltage control end of the constant current linear circuit is provided with a voltage threshold value, the voltage control end of the constant current linear circuit is used for controlling the conduction and cut-off states of the second output end of the constant current linear circuit, when the voltage of the voltage control end of the constant current linear circuit is smaller than the voltage threshold value, the function of the constant current linear circuit is not affected, when the voltage of the voltage control end of the constant current linear circuit is larger than or equal to the voltage threshold value, the second output end of the constant current linear circuit is in a cut-off loading state, and the maximum conduction current of the first output end of the constant current linear circuit is Imax; the low-harmonic linear constant current LED lamp circuit also comprises a unidirectional conduction circuit, a constant current switch circuit and a voltage sampling circuit, wherein the unidirectional conduction circuit is provided with a positive pole and a negative pole, when the current direction is from the positive pole to the negative pole of the unidirectional conduction circuit, the unidirectional conduction circuit is conducted, otherwise, the unidirectional conduction circuit is cut off, the constant current switch circuit is provided with a first end, a second end and a control end, the maximum conduction current is arranged between the first end and the second end of the constant current switch circuit, the control end and the second end of the constant current switch circuit are kept conducted, when the current between the control end and the second end of the constant current switch circuit is smaller than the maximum conduction current arranged between the first end and the second end of the constant current switch circuit, the first end and the second end of the constant current switch circuit are kept conducted, and when the current between the control end and the second end of the constant current switch circuit is larger than or equal to the maximum conduction current arranged between the first end and the second end of the constant current switch circuit, the first end and the second end of the constant current switch circuit are kept cut off, the voltage sampling circuit is provided with an input end, an output end and a negative electrode, and the voltage of the output end of the voltage sampling circuit is the voltage of the input end of the voltage sampling circuit which is reduced according to a certain proportion; the first input end and the second input end of the rectification circuit are respectively connected with a live wire and a zero wire of a commercial power, the positive output end of the rectification circuit is respectively connected with the first end of the constant current switch circuit, the positive electrode of the second light-emitting module and the input end of the voltage signal circuit, the output end of the voltage signal circuit is connected with the current regulation end of the constant current linear circuit, the negative electrode of the first light-emitting module is connected with the first output end of the constant current linear circuit, the negative electrode of the second light-emitting module, the input end of the voltage sampling circuit, the positive electrode of the one-way conduction circuit and the second output end of the constant current linear circuit are connected, the second end of the constant current switch circuit is connected with the positive electrode of the first light-emitting module, the control end of the constant current switch circuit is connected with the negative electrode of the one-way conduction circuit, the output end of the voltage sampling circuit is connected with the voltage control end of the constant current linear circuit, the negative output end of the rectification circuit, the negative electrode of the voltage signal circuit, the positive output end of the constant current switch circuit, the constant current switch circuit and the constant current switch circuit are connected with the control end of the constant current switch circuit, The negative electrode of the voltage sampling circuit is connected with the negative electrode of the constant current linear circuit, the voltage of the first light-emitting module is lower than that of the second light-emitting module when the first light-emitting module emits light, the current value of the first light-emitting module when the first light-emitting module emits light independently is lower than that of the second light-emitting module when the second light-emitting module emits light independently, and the current value of the second light-emitting module when the second light-emitting module emits light independently is lower than that of the first light-emitting module and the second light-emitting module which emit light simultaneously; in the voltage sampling circuit, when the voltage at the input end of the voltage sampling circuit is greater than or equal to the working voltage of the first light-emitting module, the voltage at the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit; when the voltage of the input end of the constant current linear circuit is lower than the working voltage of the first light-emitting module, the voltage of the output end of the constant current linear circuit is lower than the voltage threshold value of the voltage control end of the constant current linear circuit; setting the instantaneous value of the voltage output by the positive output end of the rectifying circuit as Vo, in an ideal state (not counting the voltage drop of the rectifying circuit, neglecting the critical voltage of each output end of the constant current linear circuit which meets the saturation conduction condition, neglecting the critical voltage of the current control switch which meets the saturation conduction condition between the first end and the second end), the absolute value of Vo and the instantaneous value of the alternating current voltage of the mains supply are equal, the voltage change of Vo in one period is changed from 0 to the peak voltage of the mains supply and then returns to 0, the voltage when the first light-emitting module emits light is marked as U1, the voltage when the second light-emitting module emits light is marked as U2, U1 is less than U2, when the rectifying circuit is connected with the alternating current voltage of the mains supply, the output voltage between the positive output end and the negative output end is Vo, and when Vo is more than or equal to 0 and less than U1, the first light-emitting module and the second light-emitting module do not emit light, when Vo is greater than or equal to U1 and less than U2, the voltage and the current of the second output end of the constant current control circuit are both 0, the first end and the second end of the constant current switch circuit are connected, the current of the first output end of the constant current linear circuit is Imax, therefore, the first light emitting module emits light independently in the stage, the voltage Vo cannot drive the second light emitting module to emit light, when Vo is greater than or equal to U2 and less than U1+ U2, the voltage of the second output end of the constant current linear circuit is less than U1, the voltage output by the output end of the voltage sampling circuit is less than the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a conducting state, the current is Imax, at the moment, the first output end of the constant current linear circuit is cut off, the current is 0, the second light emitting module emits light independently in the stage, the first light emitting module does not emit light, when Vo is greater than or equal to U1+ U2, the voltage of the second output end of the constant current linear circuit is greater than or equal to U1, the voltage output by the output end of the voltage sampling circuit is larger than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a cut-off state, the first output end of the constant current linear circuit is conducted, and the current is Imax.

As shown in fig. 3, in this embodiment, the constant current switch circuit includes a first integrated circuit U1 and a first resistor R1, the first integrated circuit U1 is a commonly-used three-terminal linear constant current chip having an output terminal, a negative terminal and a regulation terminal, the output terminal of the first integrated circuit U1 is the first terminal of the constant current switch circuit, the negative terminal of the first integrated circuit U1 is connected to one terminal of the first resistor R1, a connection terminal of the first integrated circuit U1 is the second terminal of the constant current switch circuit, and the other terminal of the first resistor R1 is connected to the regulation terminal of the first integrated circuit U1, and a connection terminal of the first resistor R3583 is the control terminal of the constant current switch circuit.

As shown in fig. 4, in this embodiment, the voltage sampling circuit includes a second resistor R2, a third resistor R3, and a fourth resistor R4, one end of the second resistor R2 is an input end of the voltage sampling circuit, the other end of the second resistor R2 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to one end of the fourth resistor R4, a connection end of the third resistor R3583 is an output end of the voltage sampling circuit, and the other end of the fourth resistor R4 is a negative electrode of the voltage sampling circuit. The voltage sampling circuit further comprises a first diode D1, the first diode D1 is a rectifier diode, the first diode D1 is used for improving the current continuity when the second light-emitting module emits light independently to the first light-emitting module and the second light-emitting module emit light simultaneously, the anode of the first diode D1 is connected with one end of a third resistor R3, and the cathode of the first diode D1 is connected with the first output end of the constant current linear circuit.

In this embodiment, the unidirectional conducting circuit is implemented by using a rectifying diode, an anode of the rectifying diode is an anode of the unidirectional conducting circuit, and a cathode of the rectifying diode is a cathode of the unidirectional conducting circuit.

Claims

1. A low-harmonic linear constant-current LED lamp circuit comprises a rectifying circuit, a voltage signal circuit, a first light-emitting module, a second light-emitting module and a constant-current linear circuit, wherein the rectifying circuit is provided with a first input end, a second input end, a positive output end and a negative output end, the rectifying circuit is used for converting a sine wave alternating-current voltage connected between the first input end and the second input end into a direct-current voltage consisting of positive half cycles of two sine waves and then outputting the direct-current voltage between the positive output end and the negative output end, the voltage signal circuit is provided with an input end, an output end and a negative electrode, the voltage of the output end is reduced according to a certain proportion, the voltage waveform of the output end is consistent with that of the input end, the first light-emitting module and the second light-emitting module are respectively provided with a positive electrode and a negative electrode, and the constant-current linear circuit is characterized by being provided with a current adjusting end, The constant current circuit comprises a negative electrode, a first output end, a second output end and a voltage control end, wherein the maximum instantaneous current value of the constant current linear circuit is set as Imax, the Imax is the maximum value of the sum of the instantaneous currents of the first output end and the second output end of the constant current linear circuit, the magnitude of the Imax is related to the voltage connected to the current regulating end of the constant current linear circuit, when the voltage of the current regulating end of the constant current linear circuit changes according to the waveform of the positive half cycle of a sine wave, the maximum instantaneous current value Imax of the constant current linear circuit also changes according to the waveform of the positive half cycle of the sine wave, and the first output end and the second output end of the constant current linear circuit have the following priority relations: when the current of the second output end of the constant current linear circuit is Imax, the current of the first output end is zero, and when the current of the second output end of the constant current linear circuit is zero, the maximum current of the first output end is Imax; the voltage control end of the constant current linear circuit is provided with a voltage threshold value, the voltage control end of the constant current linear circuit is used for controlling the conduction and cut-off states of the second output end of the constant current linear circuit, when the voltage of the voltage control end of the constant current linear circuit is smaller than the voltage threshold value, the function of the constant current linear circuit is not influenced, when the voltage of the voltage control end of the constant current linear circuit is larger than or equal to the voltage threshold value, the second output end of the constant current linear circuit is in a cut-off loading state, and the maximum conduction current of the first output end of the constant current linear circuit is Imax; the low-harmonic linear constant current LED lamp circuit also comprises a unidirectional conduction circuit, a constant current switch circuit and a voltage sampling circuit, wherein the unidirectional conduction circuit is provided with an anode and a cathode, when the current direction is from the anode to the cathode of the unidirectional conduction circuit, the unidirectional conduction circuit is conducted, otherwise, the unidirectional conduction circuit is cut off, the constant current switch circuit is provided with a first end, a second end and a control end, the maximum conduction current is arranged between the first end and the second end of the constant current switch circuit, the control end and the second end of the constant current switch circuit are kept conducted, when the current between the control end and the second end of the constant current switch circuit is less than the maximum conduction current arranged between the first end and the second end, the first end and the second end are kept conducted, and when the current between the control end and the second end is more than or equal to the maximum conduction current arranged between the first end and the second end, the voltage sampling circuit is provided with an input end, an output end and a negative electrode, and the voltage of the output end of the voltage sampling circuit is the voltage of the input end of the voltage sampling circuit which is reduced according to a certain proportion;

the first input end and the second input end of the rectifying circuit are respectively connected with a live wire and a zero wire of a commercial power, the positive output end of the rectifying circuit is respectively connected with the first end of the constant current switch circuit, the positive electrode of the second light-emitting module and the input end of the voltage signal circuit, the output end of the voltage signal circuit is connected with the current regulating end of the constant current linear circuit, the negative electrode of the first light-emitting module is connected with the first output end of the constant current linear circuit, the negative electrode of the second light-emitting module, the input end of the voltage sampling circuit, the positive electrode of the one-way conduction circuit and the second output end of the constant current linear circuit are connected, the second end of the constant current switch circuit is connected with the positive electrode of the first light-emitting module, and the control end of the constant current switch circuit is connected with the negative electrode of the one-way conduction circuit, the output end of the voltage sampling circuit is connected with the voltage control end of the constant current linear circuit, the negative output end of the rectifying circuit, the negative electrode of the voltage signal circuit and the negative electrode of the voltage sampling circuit are connected with the negative electrode of the constant current linear circuit, the voltage when the first light-emitting module emits light is smaller than the voltage when the second light-emitting module emits light, the current value when the first light-emitting module emits light alone is smaller than the current value when the second light-emitting module emits light alone, and the current value when the second light-emitting module emits light alone is smaller than the current values when the first light-emitting module and the second light-emitting module emit light simultaneously; in the voltage sampling circuit, when the voltage at the input end of the voltage sampling circuit is greater than or equal to the working voltage of the first light-emitting module, the voltage at the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit; when the voltage of the input end of the constant current linear circuit is smaller than the working voltage of the first light-emitting module, the voltage of the output end of the constant current linear circuit is smaller than the voltage threshold value of the voltage control end of the constant current linear circuit;

setting the instantaneous value of the voltage output by the positive output end of the rectifying circuit as Vo, ideally (ignoring the voltage drop of the rectifying circuit, ignoring the critical voltage of each output end of the constant current linear circuit which meets the saturation conduction condition, ignoring the critical voltage of the first end and the second end of the current control switch which meets the saturation conduction condition), setting the absolute value of Vo and the instantaneous value of the alternating current voltage of the commercial power equal, setting the voltage variation of Vo in one period to change from 0 to the peak voltage of the commercial power and back to 0, setting the voltage when the first light-emitting module emits light as U1, setting the voltage when the second light-emitting module emits light as U2, and setting U1 to be less than U2, when the rectifying circuit is connected with the alternating current voltage of the commercial power, setting the output voltage between the positive output end and the negative output end as Vo, and when Vo is more than or equal to 0 and less than U1, the first light-emitting module and the second light-emitting module do not emit light, when Vo is greater than or equal to U1 and less than U2, the voltage and the current of the second output end of the constant current linear circuit are both 0, the first end and the second end of the constant current switch circuit are conducted, and the current of the first output end of the constant current linear circuit is Imax, so that the first light-emitting module singly emits light at the stage, the voltage Vo cannot drive the second light-emitting module to emit light, when Vo is greater than or equal to U2 and less than U1+ U2, the voltage of the second output end of the constant current linear circuit is less than U1, the voltage output by the output end of the voltage sampling circuit is less than the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in a conducting state, and the current of the first output end of the constant current linear circuit is cut off at the moment, the current is 0, the second light emitting module emits light alone at this stage, the first light emitting module does not emit light, when Vo is greater than or equal to U1+ U2, the voltage of the second output end of the constant current linear circuit is greater than or equal to U1, the voltage output by the output end of the voltage sampling circuit is greater than or equal to the voltage threshold value of the voltage control end of the constant current linear circuit, the second output end of the constant current linear circuit is in an off state, the first output end of the constant current linear circuit is on, and the current is Imax, because Imax at this time is greater than the maximum on-state current set at the first end and the second end of the constant current switch circuit, the current between the control end and the second end of the constant current switch circuit enables the first end and the second end to be off, at this stage, the first light emitting module and the second light emitting module emit light simultaneously, the currents flowing through the first light emitting module and the second light emitting module are equal.

2. The linear constant current LED lamp circuit with low harmonic waves according to claim 1, wherein the constant current switch circuit comprises a first integrated circuit and a first resistor, the first integrated circuit is a commonly-used three-terminal linear constant current chip with an output terminal, a negative terminal and a regulating terminal, the output terminal of the first integrated circuit is the first terminal of the constant current switch circuit, the negative terminal of the first integrated circuit is connected with one terminal of the first resistor, the connecting terminal of the first integrated circuit is the second terminal of the constant current switch circuit, the other terminal of the first resistor is connected with the regulating terminal of the first integrated circuit, and the connecting terminal of the first resistor is the control terminal of the constant current switch circuit.

3. A low-harmonic linear constant current LED lamp circuit according to claim 1, wherein the voltage sampling circuit comprises a second resistor, a third resistor and a fourth resistor, one end of the second resistor is an input terminal of the voltage sampling circuit, the other end of the second resistor is connected to one end of the third resistor, the other end of the third resistor is connected to one end of the fourth resistor, a connection terminal of the third resistor is an output terminal of the voltage sampling circuit, and the other end of the fourth resistor is a negative terminal of the voltage sampling circuit.

4. A low-harmonic linear constant current LED lamp circuit as claimed in claim 3, wherein the voltage sampling circuit further comprises a first diode, the first diode is a rectifier diode, the first diode is used to improve the current continuity when the second light emitting module emits light alone to the first and second light emitting modules emit light simultaneously, the anode of the first diode is connected to one end of the third resistor, and the cathode of the first diode is connected to the first output terminal of the constant current linear circuit.

5. A low-harmonic linear constant-current LED lamp circuit according to claim 1, characterized in that the unidirectional conduction circuit is implemented by a rectifier diode, the anode of the rectifier diode is the anode of the unidirectional conduction circuit, and the cathode of the rectifier diode is the cathode of the unidirectional conduction circuit.