A three-segment linear LED constant current drive circuit

Abstract

The present invention provides a three-segment linear LED constant current driving circuit, comprising: a rectifier module, the output end of which is connected to a load branch; the load branch comprises a first group of LED light strings, a second group of LED light strings, a third group of LED light strings, a first constant current source, a first constant current resistor, a second constant current source, a second constant current resistor, a third constant current source and a third constant current resistor. The three-segment linear LED constant current driving circuit provided by the present invention, when the first group of LED light strings is lit, the first constant current source and the third constant current source jointly bear the voltage difference between the bus voltage and the first group of LED light strings, and when the first group of LED light strings and the second group of LED light strings are lit at the same time, the second constant current source and the third constant current source jointly bear the voltage difference between the bus voltage and the first group of LED light strings and the second group of LED light strings, under the same constant current source chip production process conditions, the voltage resistance performance of the product can be improved, and the reliability of the product can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of LED drive circuits, and in particular to a three-segment linear LED constant current drive circuit. Background Art

[0002] In the field of LED lighting applications, in order to reduce input current waveform distortion (THD) and improve power factor, the LED driver often uses a three-stage linear LED constant current drive circuit.

[0003] like Figure 1 As shown, an existing three-segment linear LED constant current driving circuit, the high-voltage output end of the rectifier module 1 is connected to the input end of the first group of LED light strings 2, the output end of the first group of LED light strings 2 is connected to the input end of the second group of LED light strings 3 and the input end of the first constant current source S1, the output end of the second group of LED light strings 3 is connected to the input end of the second constant current source S2 and the input end of the third group of LED light strings 4, the output end of the third group of LED light strings 4 is connected to the input end of the third constant current source S3, the output end of the third constant current source S3 is connected to the input end of the third constant current resistor Rs3 and the output end of the second constant current resistor Rs2, the output end of the third constant current resistor Rs3 is connected to the reference ground of the first constant current source S1, the second constant current source S2 and the third constant current source S3 and the low-voltage input end of the rectifier module 1, the input end of the second constant current resistor Rs2 is connected to the output end of the second constant current source S2 and the output end of the first constant current resistor Rs1, and the input end of the first constant current resistor Rs1 is connected to the output end of the first constant current source S1.

[0004] like Figure 1 In the circuit shown, when only the first group of LED light strings 2 is lit, the first constant current source S1 bears the voltage difference between the bus voltage and the first group of LED light strings 2; when only the first group of LED light strings 2 and the second group of LED light strings 3 are lit, the second constant current source S2 bears the voltage difference between the bus voltage and the first group of LED light strings 2 and the second group of LED light strings 3. In order to improve the power factor and increase the conduction phase angle of the input current of the LED light string, the voltage of the first string of LED lamp beads 2 and the second string of LED lamp beads 3 of the three-segment linear LED constant current drive circuit must not be too high; in the actual application of lamps, there are often some abnormal voltage fluctuations in the power grid, which also has higher requirements for product reliability; this also requires the power tube of the constant current control circuit corresponding to the three-segment linear constant current drive circuit to have higher voltage resistance.

[0005] In order to solve this problem, the existing three-segment linear LED constant current drive circuit adopts a higher chip withstand voltage process to solve the problem of higher voltage requirements for the power tube of the constant current control circuit in the application, but this also increases the chip area and makes it difficult to reduce the production cost; based on this problem, we improve the circuit. Summary of the invention

[0006] The main technical problem solved by the present invention is to provide a three-segment linear LED constant current driving circuit, which solves the problem that when the first group of LED light strings is currently lit, the first constant current source bears the voltage difference between the bus voltage and the first group of LED light strings. The present invention changes it to a circuit in which the first constant current source and the third constant current source jointly bear the voltage difference between the bus voltage and the first group of LED light strings.

[0007] In order to solve the above technical problems, a technical solution adopted by the present invention is to provide a three-segment linear LED constant current driving circuit, comprising:

[0008] Rectifier module, the input end is connected to the neutral line and live line of the mains, and the output end is connected to the load branch;

[0009] A load branch, comprising a first group of LED light strings, a second group of LED light strings, a third group of LED light strings, a first constant current source, a first constant current resistor, a second constant current source, a second constant current resistor, a third constant current source and a third constant current resistor;

[0010] The high-voltage output end of the rectifier module is connected to the positive input end of the first group of LED light strings, and the negative output end of the first group of LED light strings is respectively connected to the positive input end of the second group of LED light strings and the input end of the first constant current source; the negative output end of the second group of LED light strings is respectively connected to the positive input end of the third group of LED light strings and the input end of the second constant current source; the negative output end of the third group of LED light strings is respectively connected to the input end of the second constant current resistor, the output end of the second constant current source and the output end of the first constant current resistor; the output end of the second constant current resistor is respectively connected to the input end of the third constant current source, the reference ground of the first constant current source and the reference ground of the second constant current source; the input end of the first constant current resistor is connected to the output end of the first constant current source, the input end of the third constant current resistor is connected to the output end of the third constant current source, and its output end is respectively connected to the reference ground of the third constant current source and the negative output end of the rectifier module;

[0011] The first constant current source, the second constant current source and the third constant current source have the same constant current reference voltage value, and the resistance value of the second constant current resistor is greater than the resistance value of the third constant current resistor.

[0012] In one embodiment, the output waveform of the rectifier module is a pulsating DC wave after full-wave rectification of a sine wave, which is marked as Vin(θ). When the first group of LED light strings is forward-conducted, Vin(θ)≥VLED1. When the first group of LED light strings and the second group of LED light strings are turned on at the same time, Vin(θ)≥VLED2. When the first group of LED light strings, the second group of LED light strings and the third group of LED light strings are turned on at the same time, Vin(θ)≥VLED3.

[0013] When Vin(θ) < VLED1, the first constant current source, the second constant current source, and the third constant current source are in the off state; when VLED1 ≤ Vin(θ) < VLED2, the first constant current source and the third constant current source are turned on; when VLED2 ≤ Vin(θ) < VLED3, the first constant current source is turned off, and the second constant current source and the third constant current source are turned on; when VLED3 ≤ Vin(θ), the first constant current source and the second constant current source are turned off, and the third constant current source is turned on.

[0014] In one embodiment, the rectification module includes four rectifier diodes, and the four rectifier diodes form a rectifier bridge stack according to a bridge rectifier circuit.

[0015] The beneficial effects of the present invention are as follows:

[0016] (1) When the first group of LED lamp strings is lit, the first constant current source and the third constant current source jointly bear the voltage difference between the bus voltage and the voltage of the first group of LED lamp strings;

[0017] (2) When the first group of LED lamp strings and the second group of LED lamp strings are lit simultaneously, the second constant current source and the third constant current source jointly bear the voltage difference between the bus voltage and the voltages of the first group of LED lamp strings and the second group of LED lamp strings;

[0018] Thereby, the requirements for the withstand voltage capabilities of the first constant current source and the second constant current source are reduced. Under the conditions of the same constant current source chip production process, the withstand voltage performance of the entire circuit product can be improved, effectively improving the reliability of the product. Description of the Drawings

[0019] Figure 1 is a schematic circuit diagram of a three-stage linear LED constant current drive circuit of the prior art;

[0020] Figure 2 is a schematic circuit diagram of a three-stage linear LED constant current drive circuit of the present invention;

[0021] Figure 3 is a waveform diagram of the input voltage and input current of the three-stage linear LED constant current drive circuit of the present invention.

[0022] Description of the Drawings Figure 3 The ordinate of [] is a double coordinate, where one ordinate represents the output voltage Vin(θ) of the rectification module 1, and the other ordinate represents the output current Iin of the rectification module 1; wherein, the solid line represents the phase-amplitude change diagram of Vin(θ), and the dashed line represents the phase-amplitude change diagram of Iin. Detailed Embodiments

[0023] The technical solutions of the present invention will be described in detail below with reference to the drawings.

[0024] Please refer to Figure 2As shown, the three-segment linear LED constant current driving circuit of this embodiment includes:

[0025] Rectifier module 1, the input end is connected to the neutral line N and the live line L of the mains, and the output end is connected to the load branch;

[0026] The load branch includes a first group of LED light strings 2, a second group of LED light strings 3 and a third group of LED light strings 4, and the load branch also includes a first constant current branch, a second constant current branch and a third constant current branch; the first constant current branch includes a first constant current source S1 and a first constant current resistor Rs1, the second constant current branch includes a second constant current source S2 and a second constant current resistor Rs2, and the third constant current branch includes a third constant current source S3 and a third constant current resistor Rs3;

[0027] The high-voltage output end of the rectifier module 1 is connected to the positive input end of the first group of LED light strings 2, and the negative output end of the first group of LED light strings 2 is respectively connected to the positive input end of the second group of LED light strings 3 and the input end of the first constant current source S1; the negative output end of the second group of LED light strings 3 is respectively connected to the positive input end of the third group of LED light strings 4 and the input end of the second constant current source S2; the negative output end of the third group of LED light strings 4 is respectively connected to the input end of the second constant current resistor Rs2, the output end of the second constant current source S2 and the output end of the first constant current resistor Rs1; the output end of the second constant current resistor Rs2 is respectively connected to the input end of the third constant current source S3, the reference ground of the first constant current source S1 and the reference ground of the second constant current source S2; the input end of the first constant current resistor Rs1 is connected to the output end of the first constant current source S1, the input end of the third constant current resistor Rs3 is connected to the output end of the third constant current source S3, and its output end is respectively connected to the reference ground of the third constant current source S3 and the negative output end of the rectifier module 1;

[0028] The first constant current source S1, the second constant current source S2 and the third constant current source S3 have the same constant current reference voltage value, and the resistance value of the second constant current resistor Rs2 is greater than the resistance value of the third constant current resistor Rs3.

[0029] like Figure 2 and Figure 3As shown, specifically, the circuit working process is as follows. The rectification module 1 has an output waveform that is a pulsating DC wave after full-wave rectification of a sine wave, labeled as Vin(θ). Within a sine half-wave period, Vin(θ) gradually rises from 0 to reach the voltage threshold for the forward conduction of the first group of LED lamp strings 2, labeled as VLED1. In a specific application case, VLED1 is a constant value. As Vin(θ) continues to rise, it reaches the voltage threshold for the simultaneous conduction of the first group of LED lamp strings 2 and the second group of LED lamp strings 3, labeled as VLED2. In a specific application case, VLED2 is a constant value. As Vin(θ) continues to rise, it reaches the voltage threshold for the simultaneous conduction of the first group of LED lamp strings 2, the second group of LED lamp strings 3, and the third group of LED lamp strings 4, labeled as VLED3. In a specific application case, VLED3 is a constant value.

[0030] Furthermore, as Figure 3 shown, during the rising process of the output voltage Vin(θ) of the rectification module 1, when Vin(θ) < VLED1, all constant current sources are in the off state, and the current flowing through the LED lamp strings is zero. When Vin(θ) = VLED1, the first constant current source S1 and the third constant current source S3 conduct. The current outputs from the high-voltage output terminal of the rectification module 1, flows through the first group of LED lamp strings 2, the first constant current source S1, the first constant current resistor Rs1, the second constant current resistor Rs2, the third constant current source S3, the third constant current resistor Rs3, and finally inputs from the low-voltage terminal of the rectification module 1, which is the first current path. As Vin(θ) continues to rise, when Vin(θ) = VLED2, the first constant current source S1 disconnects, and the second constant current source S2 and the third constant current source S3 conduct. The current outputs from the high-voltage output terminal of the rectification module 1, flows through the first group of LED lamp strings 2, the second group of LED lamp strings 3, the second constant current source S2, the second constant current resistor Rs2, the third constant current source S3, the third constant current resistor Rs3, and finally inputs from the low-voltage terminal of the rectification module 1, which is the second current path. As Vin(θ) continues to rise, when Vin(θ) = VLED3, the first constant current source S1 and the second constant current source S2 disconnect, and the third constant current source S3 conducts. The current outputs from the high-voltage output terminal of the rectification module 1, flows through the first group of LED lamp strings 2, the second group of LED lamp strings 3, the third group of LED lamp strings 4, the second constant current resistor Rs2, the third constant current source S3, the third constant current resistor Rs3, and finally inputs from the low-voltage terminal of the rectification module 1, which is the third current path.

[0031] As Figure 3As shown, when Vin(θ) rises to the maximum value and starts to decline, the corresponding constant current sources will be turned off or on in the reverse order; when VLED2 ≤ Vin(θ) < VLED3, it is the second current path; when VLED1 ≤ Vin(θ) < VLED2, it is the first current path; when Vin(θ) < VLED1, all constant current sources are in the off state, and the current flowing through the LED string is zero.

[0032] For the specific circuit structure of the rectification module 1 Figure 2 As shown, in one embodiment, the rectification module 1 includes four rectifier diodes. The four rectifier diodes (D1, D2, D3, D4) form a rectifier bridge stack according to a bridge rectifier circuit. Of course, in a specific embodiment, the circuit structure of the rectification module 1 is not limited to Figure 2 As shown, as long as the function of the rectification module 1 in the present invention can be achieved, there is no limitation thereto, and all are within the protection scope of the present invention.

[0033] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structures made by using the specification and drawings of the present invention, directly or indirectly applied in other related technical fields, are similarly included in the patent protection scope of the present invention.

Claims

1. A three-segment linear LED constant current drive circuit, characterized in that: Comprising: A rectification module, with its input terminals connected to the neutral wire and the live wire of the mains power supply, and its output terminal connected to the load branch; The load branch includes a first group of LED lamp strings, a second group of LED lamp strings, a third group of LED lamp strings, a first constant current source, a first constant current resistor, a second constant current source, a second constant current resistor, a third constant current source, and a third constant current resistor; The high-voltage output terminal of the rectification module is connected to the positive input terminal of the first group of LED lamp strings. The negative output terminal of the first group of LED lamp strings is respectively connected to the positive input terminal of the second group of LED lamp strings and the input terminal of the first constant current source. The negative output terminal of the second group of LED lamp strings is respectively connected to the positive input terminal of the third group of LED lamp strings and the input terminal of the second constant current source. The negative output terminal of the third group of LED lamp strings is respectively connected to the input terminal of the second constant current resistor, the output terminal of the second constant current source, and the output terminal of the first constant current resistor. The output terminal of the second constant current resistor is respectively connected to the input terminal of the third constant current source, the reference ground of the first constant current source, and the reference ground of the second constant current source. The input terminal of the first constant current resistor is connected to the output terminal of the first constant current source. The input terminal of the third constant current resistor is connected to the output terminal of the third constant current source, and its output terminal is respectively connected to the reference ground of the third constant current source and the negative output terminal of the rectification module; The first constant current source, the second constant current source, and the third constant current source have the same constant current reference voltage value, and the resistance value of the second constant current resistor is greater than the resistance value of the third constant current resistor; The output waveform of the rectification module is a pulsating DC wave after full-wave rectification of a sine wave, marked as Vin(θ). When the first group of LED lamp strings conducts forwardly, Vin(θ)≥VLED1. When the first group of LED lamp strings and the second group of LED lamp strings conduct simultaneously, Vin(θ)≥VLED2. When the first group of LED lamp strings, the second group of LED lamp strings, and the third group of LED lamp strings conduct simultaneously, Vin(θ)≥VLED3. When Vin(θ)<VLED1, the first constant current source, the second constant current source, and the third constant current source are in the off state. When VLED1≤Vin(θ)<VLED2, the first constant current source and the third constant current source conduct. When VLED2≤Vin(θ)<VLED3, the first constant current source is disconnected, and the second constant current source and the third constant current source conduct. When VLED3≤Vin(θ), the first constant current source and the second constant current source are disconnected, and the third constant current source conducts.

2. The three-segment linear LED constant current driving circuit according to claim 1, characterized in that: The rectification module includes 4 rectifier diodes, and the 4 rectifier diodes form a rectifier bridge stack according to a bridge rectifier circuit.

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