A two-way light source color temperature adjustment circuit

Abstract

The present invention relates to the field of lighting technology, and in particular to a two-way light source color temperature adjustment circuit, wherein a two-way complementary color adjustment unit is used for an external color temperature control PWM signal, and when the signal is at a high level, a first current limiting color adjustment control unit is driven to conduct a first light source circuit, and if the signal is at a low level, a second current limiting color adjustment control unit is driven to conduct a second light source circuit; the two-way complementary color adjustment unit is also used for an external brightness control PWM signal, and its reference point is changed from a low-voltage side ground terminal GND to a high-voltage side ground terminal VS to generate a reference current; when the first current limiting color adjustment control unit or the second current limiting color adjustment control unit detects that the dimming current of the corresponding light source circuit is greater than the reference current, the first current limiting color adjustment control unit or the second current limiting color adjustment control unit drives a MOS tube Q1 or a MOS tube Q2 to clamp and suppress overshoot current; thereby achieving smooth color temperature adjustment, and suppressing overshoot current when the two light source circuits are switched, thereby maintaining the stability of color temperature adjustment.

Description

Technical Field

[0001] The invention relates to the technical field of lighting, in particular to a two-way light source color temperature adjustment circuit. Background Art

[0002] Color temperature switching of two light sources, that is, for example, a single light source is composed of multiple LED lamps connected in series. The color temperature switching of two LED lamps is usually achieved by controlling the brightness ratio of the two light sources through PWM signals to achieve color temperature switching and adjustment, which can achieve continuous adjustment of color temperature, thereby meeting lighting needs in different scenarios.

[0003] At present, the structure of the two-way light source color temperature switching circuit is: a color temperature switching circuit is set in the AC to DC constant current circuit, wherein the color temperature switching circuit is composed of a dual-way complementary color adjustment chip and its peripheral circuit. This color adjustment method divides the total current through two switches, and the resolution of color temperature adjustment can be made very high, especially at low brightness. The resolution of color temperature adjustment is also very high. Compared with the DC to DC constant current color adjustment circuit, when color temperature is adjusted at low brightness, the color temperature adjustment is smoother and the color temperature will not show obvious step-like changes.

[0004] However, the disadvantage of this circuit is that due to the voltage difference between the two LED lamps (light sources), when one high-voltage LED lamp is switched to another low-voltage LED lamp, an overshoot current will occur on the low-voltage LED lamp. The greater the voltage difference, the greater the overshoot current, which can easily cause the LED lamp to burn out, greatly affecting the reliability of the LED lamp (light source). The overshoot current will also destroy the smoothness of the color temperature adjustment, especially in mixed color temperature application scenarios, where noise will appear and the color temperature change will be uneven. Summary of the invention

[0005] In view of the above-mentioned defects, the purpose of the present invention is to provide a two-way light source color temperature adjustment circuit, which can achieve smooth color temperature adjustment while suppressing overshoot current when the two light source circuits are switched, thereby maintaining the stability of color temperature adjustment.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A two-way light source color temperature adjustment circuit, comprising an AC-to-DC constant current circuit, a first light source circuit and a second light source circuit, wherein the output end of the AC-to-DC constant current circuit is electrically connected to the first light source circuit and the second light source circuit respectively, and further comprising a first current limiting color adjustment control unit, a second current limiting color adjustment control unit, a dual-way complementary color adjustment unit, a MOS tube Q1, a sampling resistor R8, a MOS tube Q2 and a sampling resistor R9;

[0008] The cathode of the first light source circuit is electrically connected to the drain of the MOS tube Q1, the source of the MOS tube Q1, one end of the sampling resistor R8, and the cathode of the control end of the first current limiting color adjustment control unit are all electrically connected to the detection end of the first current limiting color adjustment control unit, the gate of the MOS tube Q1 is electrically connected to the anode of the control end of the first current limiting color adjustment control unit, and the other end of the sampling resistor R8 is connected to the high-voltage side ground end VS;

[0009] The cathode of the second light source circuit is electrically connected to the drain of the MOS tube Q2, the source of the MOS tube Q2, one end of the sampling resistor R9, and the cathode of the control end of the second current limiting color adjustment control unit are all electrically connected to the detection end of the second current limiting color adjustment control unit, the gate of the MOS tube Q2 is electrically connected to the anode of the control end of the second current limiting color adjustment control unit, and the other end of the sampling resistor R9 is connected to the high-voltage side ground end VS;

[0010] The input end of the first current limiting color adjustment control unit and the input end of the second current limiting color adjustment control unit are electrically connected to the first output end and the second output end of the two-way complementary color adjustment unit respectively, the current limiting reference end of the first current limiting color adjustment control unit and the current limiting reference end of the second current limiting color adjustment control unit are both electrically connected to the current limiting reference end of the two-way complementary color adjustment unit, the first input end of the two-way complementary color adjustment unit is externally connected to a brightness control PWM signal, and the second input end of the two-way complementary color adjustment unit is externally connected to a color temperature control PWM signal;

[0011] The dual-channel complementary color adjustment unit is used to externally connect the color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit is driven to turn on the first light source circuit; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit is driven to turn on the second light source circuit;

[0012] The dual-channel complementary color adjustment unit is also used to externally connect the brightness control PWM signal, change the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and generate a reference current; when the first current limiting color adjustment control unit detects that the dimming current of the first light source circuit is greater than the reference current, the first current limiting color adjustment control unit drives the MOS tube Q1 to clamp and suppress the overshoot current of the first light source circuit; or when the second current limiting color adjustment control unit detects that the dimming current of the second light source circuit is greater than the reference current, the second current limiting color adjustment control unit drives the MOS tube Q2 to clamp and suppress the overshoot current of the second light source circuit.

[0013] Furthermore, the circuit structures of the first current limiting color adjustment control unit and the second current limiting color adjustment control unit are the same;

[0014] The second current limiting color adjustment control unit comprises a switch circuit, a comparison circuit, a drive circuit and a detection circuit; the input end of the switch circuit is used as the input end of the second current limiting color adjustment control unit, the positive electrode of the output end of the drive circuit is used as the positive electrode of the control end of the second current limiting color adjustment control unit, the negative electrode of the output end of the drive circuit is used as the negative electrode of the control end of the second current limiting color adjustment control unit, the input end of the detection circuit is used as the detection end of the second current limiting color adjustment control unit, and the reference end of the comparison circuit is used as the current limiting reference end of the second current limiting color adjustment control unit;

[0015] The output end of the switch circuit is electrically connected to the input end of the drive circuit, the output end of the detection circuit is electrically connected to the input end of the comparison circuit, and the output end of the comparison circuit is electrically connected to the overcurrent feedback end of the drive circuit;

[0016] When the color temperature control PWM signal is at a high level, the switch circuit of the first current limiting color adjustment control unit is turned on, and the drive circuit of the first current limiting color adjustment control unit drives the MOS tube Q1 to work in the variable resistance area; when the color temperature control PWM signal is at a low level, the switch circuit of the second current limiting color adjustment control unit is turned on, and the drive circuit of the second current limiting color adjustment control unit drives the MOS tube Q2 to work in the variable resistance area;

[0017] The detection circuit collects the dimming current of the first light source circuit or the second light source circuit and transmits it to the comparison circuit; when the comparison circuit detects that the dimming current is greater than the reference current, the drive circuit drives the MOS tube Q1 or the MOS tube Q2 to operate in the saturation region.

[0018] Furthermore, the dual-channel complementary color-adjusting unit includes a resistor R1, a capacitor C2, a capacitor C7 and a dual-channel complementary color-adjusting chip U1; a reference current generating circuit is integrated inside the dual-channel complementary color-adjusting chip U1, an input end of the reference current generating circuit is used as a PWM-L end of the dual-channel complementary color-adjusting chip U1, and an output end of the reference current generating circuit is used as an OCP end of the dual-channel complementary color-adjusting chip U1;

[0019] The OUT1 end of the dual-channel complementary color-mixing chip U1 is used as the first output end of the dual-channel complementary color-mixing unit, the OUT2 end of the dual-channel complementary color-mixing chip U1 is used as the second output end of the dual-channel complementary color-mixing unit, the PWM-L end of the dual-channel complementary color-mixing chip U1 is used as the first input end of the dual-channel complementary color-mixing unit, the PWM end of the dual-channel complementary color-mixing chip U1 is used as the second input end of the dual-channel complementary color-mixing unit, and the OCP end of the dual-channel complementary color-mixing chip U1 is used as the current-limiting reference end of the dual-channel complementary color-mixing unit;

[0020] One end of the resistor R1 is connected to the VH power supply, the other end of the resistor R1 and one end of the capacitor C2 are electrically connected to the VH end of the dual-channel complementary color-adjusting chip U1, the other end of the capacitor C2 is connected to the high-voltage side ground terminal VS, one end of the capacitor C7 and the VCC end of the dual-channel complementary color-adjusting chip U1 are connected to the VCC power supply, and the other end of the capacitor C7 and the GND end of the dual-channel complementary color-adjusting chip U1 are connected to the low-voltage side ground terminal GND;

[0021] The dual-channel complementary color adjustment chip U1 is used to externally connect the color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit is driven to turn on the first light source circuit; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit is driven to turn on the second light source circuit;

[0022] The reference current generating circuit is used to externally connect the brightness control PWM signal, change the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and generate the reference current.

[0023] Furthermore, the reference current generating circuit includes a resistor R27, a MOS tube Q7, a resistor R28, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a transistor Q8, a comparator U1B and a voltage regulator U3; the gate of the MOS tube Q7 is used as an input end of the reference current generating circuit, and the output end of the comparator U1B is used as an output end of the reference current generating circuit;

[0024] The source of the MOS transistor Q7 is connected to the low-voltage side ground terminal GND, the drain of the MOS transistor Q7 and one end of the resistor R28 are electrically connected to one end of the resistor R22, the other end of the resistor R22 is electrically connected to the base of the transistor Q8, the emitter of the transistor Q8, the other end of the resistor R28 and one end of the resistor R27 are connected to the VH power supply, the collector of the transistor Q8 and one end of the resistor R23 are electrically connected to the positive input terminal of the comparator U1B, the negative input terminal of the comparator U1B and one end of the resistor R24 ​​are electrically connected to one end of the resistor R25, the other end of the resistor R24, the other end of the resistor R27, the cathode of the voltage regulator U3, and the reference electrode of the voltage regulator U3 are electrically connected to one end of the resistor R26, and the other end of the resistor R23, the other end of the resistor R25 and the other end of the resistor R26 are connected to the high-voltage side ground terminal VS.

[0025] Furthermore, the switch circuit includes a resistor R11, a resistor R13 and a MOS transistor Q6; one end of the resistor R11 is used as an input end of the switch circuit, and a drain of the MOS transistor Q6 is used as an output end of the switch circuit;

[0026] The other end of the resistor R11 and one end of the resistor R13 are both electrically connected to the gate of the MOS transistor Q6 , and the other end of the resistor R13 and the source of the MOS transistor Q6 are both connected to the high-voltage side ground terminal VS.

[0027] Further, the comparison circuit includes a comparator U3A, a capacitor C4, a capacitor C6, a resistor R15, a resistor R3 and a resistor R21; one end of the resistor R21 is used as a reference end of the comparison circuit, the negative input end of the comparator U3A is used as an input end of the comparison circuit, and one end of the resistor R3 is used as an output end of the comparison circuit;

[0028] The other end of the resistor R3 is electrically connected to the output end of the comparator U3A, the positive power supply end of the comparator U3A and one end of the capacitor C4 are both connected to the VH power supply, the other end of the capacitor C4 is connected to the high-voltage side ground end VS, the positive input end of the comparator U3A is electrically connected to one end of the resistor R15, the other end of the resistor R15 and the other end of the resistor R21 are both electrically connected to one end of the capacitor C6, and the other end of the capacitor C6 and the negative power supply end of the comparator U3A are both connected to the high-voltage side ground end VS.

[0029] Further, the driving circuit includes a resistor R6, a transistor Q4 and a resistor R7; one end of the resistor R6 is used as an input end of the driving circuit, the emitter of the transistor Q4 is used as an overcurrent feedback end of the driving circuit, one end of the resistor R7 is used as a positive output end of the driving circuit, and the other end of the resistor R7 is used as a negative output end of the driving circuit;

[0030] The other end of the resistor R6 is electrically connected to the base of the transistor Q4 , the emitter of the transistor Q4 is electrically connected to one end of the resistor R7 , and the collector of the transistor Q4 is electrically connected to the other end of the resistor R7 .

[0031] Further, the detection circuit includes a comparator U3B, a resistor R17 and a resistor R19; the output end of the comparator U3B is used as the output end of the detection circuit, and the positive input end of the comparator U3B is used as the input end of the detection circuit;

[0032] The output end of the comparator U3B is electrically connected to one end of the resistor R17, the negative input end of the comparator U3B and the other end of the resistor R17 are electrically connected to one end of the resistor R19, and the other end of the resistor R19 is connected to the high-voltage side ground terminal VS.

[0033] The technical solution provided by the present invention may include the following beneficial effects: The principle of color temperature adjustment is: after the dual-channel complementary color adjustment unit is externally connected to the color temperature control PWM signal (PWM-C), a pair of complementary PWM signals will be formed to control the first light source circuit and the second light source circuit respectively. Different color temperature effects will be presented according to the different times when the corresponding light source circuits are lit according to a pair of complementary PWM signals, thereby achieving color temperature adjustment.

[0034] When the first light source circuit and the second light source circuit are switched on, if the voltage difference is large, an overcurrent phenomenon will occur. The overcurrent suppression principle is: the overcurrent phenomenon is that the dimming current when the first light source circuit or the second light source circuit is lit is greater than the current output by the constant current source in the AC to DC constant current circuit. Therefore, the brightness control PWM signal (PWM-L) synchronized with the output current of the constant current source is used as the standard for judging whether there is an overcurrent, and the dual-channel complementary color adjustment unit is input to change the reference point of the brightness control PWM signal, that is, from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and finally generate a reference current; when the first current-limiting color adjustment control unit detects that the dimming current of the first light source circuit is greater than the reference current, the MOS tube Q1 is driven to clamp and suppress the overshoot current of the first light source circuit; or when the second current-limiting color adjustment control unit detects that the dimming current of the second light source circuit is greater than the reference current, the MOS tube Q2 is driven to clamp and suppress the overshoot current of the second light source circuit; and the duty cycle of the brightness control PWM signal can be limited to be proportional to the output current of the constant current source, and the reference current is set to match the output current of the constant current source.

[0035] In summary, the two-way light source color temperature adjustment circuit can achieve smooth color temperature adjustment while suppressing overshoot current when the two-way light source circuits are switched, thereby maintaining the stability of color temperature adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a schematic circuit diagram of a two-way light source color temperature adjustment circuit according to one embodiment of the present invention.

[0037] Figure 2 Yes Figure 1 A partial circuit diagram of a two-way light source color temperature adjustment circuit is shown.

[0038] Figure 3 Yes Figure 2 The internal circuit diagram of the dual-channel complementary color-adjusting chip U1 is shown.

[0039] Wherein: AC to DC constant current circuit 1, first light source circuit 2, second light source circuit 3, first current limiting color adjustment control unit 4, second current limiting color adjustment control unit 5, dual complementary color adjustment unit 6, MOS tube Q1, sampling resistor R8, MOS tube Q2, sampling resistor R9, switch circuit 51, comparison circuit 52, drive circuit 53, detection circuit 54, resistor R1, capacitor C2, capacitor C7, dual complementary color adjustment chip U1, reference current generation circuit 61, MOS tube Q7, resistor R28, resistor R22, resistor R23, resistor R24, resistor R25, resistor R26, transistor Q8, comparator U1B, voltage regulator U3, resistor R11, resistor R13, MOS tube Q6, comparator U3A, capacitor C4, capacitor C6, resistor R15, resistor R3, resistor R21, resistor R6, transistor Q4, resistor R7, comparator U3B, resistor R17, resistor R19. DETAILED DESCRIPTION

[0040] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0041] In the description of the embodiments of the present invention, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0043] Combine the following Figures 1 to 3 , describes a two-way light source color temperature adjustment circuit according to an embodiment of the present invention.

[0044] A two-way light source color temperature adjustment circuit includes an AC to DC constant current circuit 1, a first light source circuit 2 and a second light source circuit 3, wherein the output end of the AC to DC constant current circuit 1 is electrically connected to the first light source circuit 2 and the second light source circuit 3 respectively, and further includes a first current limiting color adjustment control unit 4, a second current limiting color adjustment control unit 5, a dual-way complementary color adjustment unit 6, a MOS tube Q1, a sampling resistor R8, a MOS tube Q2 and a sampling resistor R9;

[0045] The cathode of the first light source circuit 2 is electrically connected to the drain of the MOS tube Q1, the source of the MOS tube Q1, one end of the sampling resistor R8, and the cathode of the control end of the first current limiting color adjustment control unit 4 are all electrically connected to the detection end of the first current limiting color adjustment control unit 4, the gate of the MOS tube Q1 is electrically connected to the anode of the control end of the first current limiting color adjustment control unit 4, and the other end of the sampling resistor R8 is connected to the high-voltage side ground terminal VS;

[0046] The cathode of the second light source circuit 3 is electrically connected to the drain of the MOS tube Q2, the source of the MOS tube Q2, one end of the sampling resistor R9, and the cathode of the control end of the second current limiting color adjustment control unit 5 are all electrically connected to the detection end of the second current limiting color adjustment control unit 5, the gate of the MOS tube Q2 is electrically connected to the anode of the control end of the second current limiting color adjustment control unit 5, and the other end of the sampling resistor R9 is connected to the high-voltage side ground terminal VS;

[0047] The input end of the first current-limiting color-adjusting control unit 4 and the input end of the second current-limiting color-adjusting control unit 5 are electrically connected to the first output end and the second output end of the two-way complementary color-adjusting unit 6 respectively; the current-limiting reference end of the first current-limiting color-adjusting control unit 4 and the current-limiting reference end of the second current-limiting color-adjusting control unit 5 are electrically connected to the current-limiting reference end of the two-way complementary color-adjusting unit 6; the first input end of the two-way complementary color-adjusting unit 6 is externally connected to a brightness control PWM signal; the second input end of the two-way complementary color-adjusting unit 6 is externally connected to a color temperature control PWM signal;

[0048] The dual-channel complementary color adjustment unit 6 is used for external color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit 4 is driven to conduct the first light source circuit 2; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit 5 is driven to conduct the second light source circuit 3;

[0049] The dual-channel complementary color adjustment unit 6 is also used for an external brightness control PWM signal, changing the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS to generate a reference current; when the first current limiting color adjustment control unit 4 detects that the dimming current of the first light source circuit 2 is greater than the reference current, the first current limiting color adjustment control unit 4 drives the MOS tube Q1 to clamp and suppress the overshoot current of the first light source circuit 2; or when the second current limiting color adjustment control unit 5 detects that the dimming current of the second light source circuit 3 is greater than the reference current, the second current limiting color adjustment control unit 5 drives the MOS tube Q2 to clamp and suppress the overshoot current of the second light source circuit 3.

[0050] The present invention proposes a preferred embodiment of a two-way light source color temperature adjustment circuit, such as Figure 1 As shown, the principle of color temperature adjustment is: after the dual-channel complementary color adjustment unit 6 is externally connected to the color temperature control PWM signal (PWM-C), a pair of complementary PWM signals will be formed to control the first light source circuit 2 and the second light source circuit 3 respectively. Different time periods of lighting the corresponding light source circuits according to a pair of complementary PWM signals will present different color temperature effects, thereby realizing color temperature adjustment; for example, the first light source circuit 2 controls the cold white LED, and the second light source circuit 3 controls the warm white LED. The first light source circuit 2 is lit according to the high level of the color temperature control PWM signal (MOS tube Q1 is turned on), and the lighting time is a high level duty cycle. The second light source circuit 3 is lit according to the low level of the color temperature control PWM signal (MOS tube Q2 is turned on), and the lighting time is a low level duty cycle. Therefore, only one light source is lit at the same time. When the cold white LED is lit for a long time, the warm white LED is lit for a short time, and the overall light appears to be cold light. When the cold white LED is lit for a short time, the warm white LED is lit for a long time, and the overall light appears to be warm light.

[0051] When the first light source circuit 2 and the second light source circuit 3 are switched on, if the voltage difference is large, an overcurrent phenomenon will occur. The overcurrent suppression principle is: the overcurrent phenomenon is that the dimming current when the first light source circuit 2 or the second light source circuit 3 is lit is greater than the current output by the constant current source in the AC to DC constant current circuit 1. Therefore, the brightness control PWM signal (PWM-L) synchronized with the output current of the constant current source is used as the standard for judging whether there is an overcurrent, and the dual-channel complementary color adjustment unit 6 is input to change the reference point of the brightness control PWM signal, that is, from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and finally generate a reference current; when the first current limiting color adjustment control unit 4 detects that the dimming current of the first light source circuit 2 is greater than the reference current, the M is driven The OS tube Q1 clamps and suppresses the overshoot current of the first light source circuit 2; or when the second current limiting color adjustment control unit 5 detects that the dimming current of the second light source circuit 3 is greater than the reference current, the MOS tube Q2 is driven to clamp and suppress the overshoot current of the second light source circuit 3; and the duty cycle of the brightness control PWM signal can be limited to be proportional to the output current of the constant current source, and the reference current is set to match the output current of the constant current source. For example, when PWM-L is 100%, the output current is 1000mA, the overshoot current part is 100mA, and the reference current is 1100mA; when PWM-L is 50%, the output current is 500mA, the overshoot current part is 50mA, and the reference current is 550mA.

[0052] In summary, the two-way light source color temperature adjustment circuit can achieve smooth color temperature adjustment while suppressing overshoot current when the two-way light source circuits are switched, thereby maintaining the stability of color temperature adjustment.

[0053] Furthermore, the circuit structures of the first current limiting color adjustment control unit 4 and the second current limiting color adjustment control unit 5 are the same;

[0054] The second current limiting color adjustment control unit 5 includes a switch circuit 51, a comparison circuit 52, a drive circuit 53 and a detection circuit 54; the input end of the switch circuit 51 is used as the input end of the second current limiting color adjustment control unit 5, the positive electrode of the output end of the drive circuit 53 is used as the positive electrode of the control end of the second current limiting color adjustment control unit 5, the negative electrode of the output end of the drive circuit 53 is used as the negative electrode of the control end of the second current limiting color adjustment control unit 5, the input end of the detection circuit 54 is used as the detection end of the second current limiting color adjustment control unit 5, and the reference end of the comparison circuit 52 is used as the current limiting reference end of the second current limiting color adjustment control unit 5;

[0055] The output end of the switch circuit 51 is electrically connected to the input end of the drive circuit 53, the output end of the detection circuit 54 is electrically connected to the input end of the comparison circuit 52, and the output end of the comparison circuit 52 is electrically connected to the overcurrent feedback end of the drive circuit 53;

[0056] When the color temperature control PWM signal is at a high level, the switch circuit 51 of the first current limiting color adjustment control unit 4 is turned on, and the drive circuit 53 of the first current limiting color adjustment control unit 4 drives the MOS tube Q1 to work in the variable resistance area; when the color temperature control PWM signal is at a low level, the switch circuit 51 of the second current limiting color adjustment control unit 5 is turned on, and the drive circuit 53 of the second current limiting color adjustment control unit 5 drives the MOS tube Q2 to work in the variable resistance area;

[0057] The detection circuit 54 collects the dimming current of the first light source circuit 2 or the second light source circuit 3 and transmits it to the comparison circuit 52; when the comparison circuit 52 detects that the dimming current is greater than the reference current, the drive circuit 53 drives the MOS tube Q1 or the MOS tube Q2 to operate in the saturation region.

[0058] In this embodiment, the color temperature adjustment principle and overcurrent suppression principle of the first current limiting color adjustment control unit 4 and the second current limiting color adjustment control unit 5 are the same. Taking the second current limiting color adjustment control unit 5 as an example, Figure 2 As shown, it is composed of a switch circuit 51, a comparison circuit 52, a drive circuit 53 and a detection circuit 54, wherein the on-off of the switch circuit 51 determines the on-off of the light source circuit. For example, when the second light source circuit 3 is to be lit, the switch circuit 51 of the second current limiting color adjustment control unit 5 will be turned on, enabling the drive circuit 53 to drive the MOS tube Q2 to work in the variable resistance area; the detection circuit 54 is used to collect the dimming current of the light source circuit when the light source circuit is turned on; the comparison circuit 52 compares the dimming current with the reference current to determine whether the light source circuit has an overcurrent phenomenon, and feeds back The judgment result is given to the driving circuit 53. When overcurrent occurs, the driving circuit 53 is enabled to drive the MOS tube Q1 or the MOS tube Q2 to work in the saturation region to suppress the overshoot current. Because the MOS tube works in the saturation region, the electron concentration in the channel reaches saturation, and the drain current hardly increases with the increase of the drain-source voltage Vds, but tends to a stable value, so that the channel is pre-pinch-off at one end close to the drain. As Vds further increases, the pinch-off point moves toward the source, and finally forms a pinch-off region composed of a depletion layer, thereby clamping and suppressing the overshoot current.

[0059] Furthermore, the dual-channel complementary color-adjusting unit 6 includes a resistor R1, a capacitor C2, a capacitor C7 and a dual-channel complementary color-adjusting chip U1; a reference current generating circuit 61 is integrated inside the dual-channel complementary color-adjusting chip U1, and an input end of the reference current generating circuit 61 is used as a PWM-L end of the dual-channel complementary color-adjusting chip U1, and an output end of the reference current generating circuit 61 is used as an OCP end of the dual-channel complementary color-adjusting chip U1;

[0060] The OUT1 terminal of the two-way complementary color-adjusting chip U1 is used as the first output terminal of the two-way complementary color-adjusting unit 6, the OUT2 terminal of the two-way complementary color-adjusting chip U1 is used as the second output terminal of the two-way complementary color-adjusting unit 6, the PWM-L terminal of the two-way complementary color-adjusting chip U1 is used as the first input terminal of the two-way complementary color-adjusting unit 6, the PWM terminal of the two-way complementary color-adjusting chip U1 is used as the second input terminal of the two-way complementary color-adjusting unit 6, and the OCP terminal of the two-way complementary color-adjusting chip U1 is used as the current limiting reference terminal of the two-way complementary color-adjusting unit 6;

[0061] One end of the resistor R1 is connected to the VH power supply, the other end of the resistor R1 and one end of the capacitor C2 are electrically connected to the VH end of the dual-channel complementary color-adjusting chip U1, the other end of the capacitor C2 is connected to the high-voltage side ground terminal VS, one end of the capacitor C7 and the VCC end of the dual-channel complementary color-adjusting chip U1 are connected to the VCC power supply, and the other end of the capacitor C7 and the GND end of the dual-channel complementary color-adjusting chip U1 are connected to the low-voltage side ground terminal GND;

[0062] The dual-channel complementary color adjustment chip U1 is used for external color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit 4 is driven to conduct the first light source circuit 2; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit 5 is driven to conduct the second light source circuit 3;

[0063] The reference current generating circuit 61 is used for externally connecting a brightness control PWM signal, changing the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and generating a reference current.

[0064] In this embodiment, Figure 3 As shown in the figure, except for the reference current generating circuit 61, it is the internal integrated circuit structure of the existing dual-channel complementary color adjustment chip U1, such as the dual-channel complementary color adjustment chip U1 of model BP5929, which mainly realizes generating a pair of complementary PWM signals for color adjustment of two light source circuits according to the color temperature control PWM signal, and adds an integrated reference current generating circuit 61 for external brightness control PWM signal on the basis of the internal integrated circuit of the existing chip, and changes the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS to generate a reference current; thereby, a single chip realizes color temperature adjustment and outputs a reference current for overcurrent judgment.

[0065] Furthermore, the reference current generating circuit 61 includes a resistor R27, a MOS transistor Q7, a resistor R28, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a transistor Q8, a comparator U1B and a voltage regulator U3; the gate of the MOS transistor Q7 is used as an input end of the reference current generating circuit 61, and the output end of the comparator U1B is used as an output end of the reference current generating circuit 61;

[0066] The source of the MOS transistor Q7 is connected to the low-voltage side ground terminal GND, the drain of the MOS transistor Q7 and one end of the resistor R28 are electrically connected to one end of the resistor R22, the other end of the resistor R22 is electrically connected to the base of the transistor Q8, the emitter of the transistor Q8, the other end of the resistor R28 and one end of the resistor R27 are connected to the VH power supply, the collector of the transistor Q8 and one end of the resistor R23 are electrically connected to the positive input terminal of the comparator U1B, the negative input terminal of the comparator U1B and one end of the resistor R24 ​​are electrically connected to one end of the resistor R25, the other end of the resistor R24, the other end of the resistor R27, the cathode of the voltage regulator U3, and the reference electrode of the voltage regulator U3 are electrically connected to one end of the resistor R26, and the other end of the resistor R23, the other end of the resistor R25 and the other end of the resistor R26 are connected to the high-voltage side ground terminal VS.

[0067] In this embodiment, the voltage regulator U3 can be TL431, which is used to provide a stable voltage reference point at the reference pole, and then divide the voltage by resistors R24 and R25 to provide a reference voltage to the negative input terminal of the comparator U1B. When PWM-L is at a high level, the MOS tube Q7 is turned on, and the transistor Q8 is turned on, that is, the positive input terminal of the comparator U1B is a high voltage. When the voltage exceeds the reference voltage of the negative input terminal of the comparator U1B, the output terminal (that is, the OCP terminal) of the comparator U1B outputs a high level; when PWM-L is at a high level, the MOS tube Q7 is turned on, and the transistor Q8 is turned on, that is, the positive input terminal of the comparator U1B is a high voltage. When the voltage exceeds the reference voltage of the negative input terminal of the comparator U1B, the output terminal (that is, the OCP terminal) of the comparator U1B outputs a high level. When it is low level, MOS tube Q7 is turned off, transistor Q8 is turned off, that is, the positive input terminal of comparator U1B is a low voltage. When the voltage is less than the reference voltage of the negative input terminal of comparator U1B, the output terminal (that is, OCP terminal) of comparator U1B outputs a low level; that is, the output signal of OCP terminal and PWM-L are the same duty cycle signal, and the reference current generating circuit 61 only transmits the PWM-L signal based on the low voltage side ground terminal GND as the reference point to the OCP terminal based on the high voltage side ground terminal VS as the reference point, so as to change the reference point.

[0068] Furthermore, the switch circuit 51 includes a resistor R11, a resistor R13 and a MOS transistor Q6; one end of the resistor R11 is used as an input end of the switch circuit 51, and a drain of the MOS transistor Q6 is used as an output end of the switch circuit 51;

[0069] The other end of the resistor R11 and one end of the resistor R13 are both electrically connected to the gate of the MOS transistor Q6 , and the other end of the resistor R13 and the source of the MOS transistor Q6 are both connected to the high-voltage side ground terminal VS.

[0070] In this embodiment, the switch circuit 51 is composed of a resistor R11, a resistor R13 and a MOS transistor Q6. The MOS transistor Q6 can be turned on or off according to the PWM signal output from the OUT1 or OUT2 of the dual complementary color chip U1, thereby controlling whether to light up the light source circuit.

[0071] Furthermore, the comparison circuit 52 includes a comparator U3A, a capacitor C4, a capacitor C6, a resistor R15, a resistor R3 and a resistor R21; one end of the resistor R21 is used as a reference end of the comparison circuit 52, a negative input end of the comparator U3A is used as an input end of the comparison circuit 52, and one end of the resistor R3 is used as an output end of the comparison circuit 52;

[0072] The other end of the resistor R3 is electrically connected to the output end of the comparator U3A, the positive power supply end of the comparator U3A and one end of the capacitor C4 are both connected to the VH power supply, the other end of the capacitor C4 is connected to the high-voltage side ground terminal VS, the positive input end of the comparator U3A is electrically connected to one end of the resistor R15, the other end of the resistor R15 and the other end of the resistor R21 are both electrically connected to one end of the capacitor C6, and the other end of the capacitor C6 and the negative power supply end of the comparator U3A are both connected to the high-voltage side ground terminal VS.

[0073] In this embodiment, the comparison circuit 52 is composed of a comparator U3A, a capacitor C4, a capacitor C6, a resistor R15, a resistor R3 and a resistor R21, and can realize the reception and judgment of the dimming current and the reference current.

[0074] Furthermore, the driving circuit 53 includes a resistor R6, a transistor Q4 and a resistor R7; one end of the resistor R6 is used as an input end of the driving circuit 53, the emitter of the transistor Q4 is used as an overcurrent feedback end of the driving circuit 53, one end of the resistor R7 is used as a positive electrode of the output end of the driving circuit 53, and the other end of the resistor R7 is used as a negative electrode of the output end of the driving circuit 53;

[0075] The other end of the resistor R6 is electrically connected to the base of the transistor Q4 , the emitter of the transistor Q4 is electrically connected to one end of the resistor R7 , and the collector of the transistor Q4 is electrically connected to the other end of the resistor R7 .

[0076] In this embodiment, the driving circuit 53 is composed of a resistor R6, a transistor Q4 and a resistor R7. When the comparator U3A of the comparison unit 52 does not feed back an overcurrent signal (i.e., a high level), the gate-source voltage Vgs of the MOS tube Q1 or the MOS tube Q2 is driven to change accordingly when the color temperature is adjusted under the control of the MOS tube Q6 of the switch circuit 51, so as to light up the corresponding light source circuit; when the comparator U3A of the comparison unit 52 feeds back an overcurrent signal (i.e., a low level), the MOS tube Q1 or the MOS tube Q2 is driven to operate in the saturation region to clamp and suppress the overshoot current of the light source circuit.

[0077] Further, the detection circuit 54 includes a comparator U3B, a resistor R17 and a resistor R19; the output end of the comparator U3B is used as the output end of the detection circuit 54, and the positive input end of the comparator U3B is used as the input end of the detection circuit 54;

[0078] The output end of the comparator U3B is electrically connected to one end of the resistor R17, the negative input end of the comparator U3B and the other end of the resistor R17 are electrically connected to one end of the resistor R19, and the other end of the resistor R19 is connected to the high-voltage side ground terminal VS.

[0079] In this embodiment, the detection circuit 54 is a common-mode operational amplifier circuit composed of a comparator U3B, a resistor R17 and a resistor R19, which can collect and amplify the dimming current of the light source circuit and convert it into a voltage signal that can be recognized by the comparator U3A of the comparison unit 52, thereby realizing the collection function.

[0080] Other structures and operations of a two-way light source color temperature adjustment circuit according to an embodiment of the present invention are known to those skilled in the art and will not be described in detail here.

[0081] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0082] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A two-way light source color temperature adjustment circuit, comprising an AC to DC constant current circuit, a first light source circuit and a second light source circuit, wherein the output end of the AC to DC constant current circuit is electrically connected to the first light source circuit and the second light source circuit respectively, and characterized in that: It also includes a first current limiting color adjustment control unit, a second current limiting color adjustment control unit, a dual-channel complementary color adjustment unit, a MOS tube Q1, a sampling resistor R8, a MOS tube Q2 and a sampling resistor R9; The cathode of the first light source circuit is electrically connected to the drain of the MOS tube Q1, the source of the MOS tube Q1, one end of the sampling resistor R8, and the cathode of the control end of the first current limiting color adjustment control unit are all electrically connected to the detection end of the first current limiting color adjustment control unit, the gate of the MOS tube Q1 is electrically connected to the anode of the control end of the first current limiting color adjustment control unit, and the other end of the sampling resistor R8 is connected to the high-voltage side ground end VS; The cathode of the second light source circuit is electrically connected to the drain of the MOS tube Q2, the source of the MOS tube Q2, one end of the sampling resistor R9, and the cathode of the control end of the second current limiting color adjustment control unit are all electrically connected to the detection end of the second current limiting color adjustment control unit, the gate of the MOS tube Q2 is electrically connected to the anode of the control end of the second current limiting color adjustment control unit, and the other end of the sampling resistor R9 is connected to the high-voltage side ground end VS; The input end of the first current limiting color adjustment control unit and the input end of the second current limiting color adjustment control unit are electrically connected to the first output end and the second output end of the two-way complementary color adjustment unit respectively, the current limiting reference end of the first current limiting color adjustment control unit and the current limiting reference end of the second current limiting color adjustment control unit are both electrically connected to the current limiting reference end of the two-way complementary color adjustment unit, the first input end of the two-way complementary color adjustment unit is externally connected to a brightness control PWM signal, and the second input end of the two-way complementary color adjustment unit is externally connected to a color temperature control PWM signal; The dual-channel complementary color adjustment unit is used to externally connect the color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit is driven to turn on the first light source circuit; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit is driven to turn on the second light source circuit; The dual-channel complementary color adjustment unit is also used to externally connect the brightness control PWM signal, change the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and generate a reference current; when the first current limiting color adjustment control unit detects that the dimming current of the first light source circuit is greater than the reference current, the first current limiting color adjustment control unit drives the MOS tube Q1 to clamp and suppress the overshoot current of the first light source circuit; or when the second current limiting color adjustment control unit detects that the dimming current of the second light source circuit is greater than the reference current, the second current limiting color adjustment control unit drives the MOS tube Q2 to clamp and suppress the overshoot current of the second light source circuit.

2. The two-way light source color temperature adjustment circuit according to claim 1, characterized in that: The circuit structures of the first current limiting color adjusting control unit and the second current limiting color adjusting control unit are the same; The second current limiting color adjustment control unit comprises a switch circuit, a comparison circuit, a drive circuit and a detection circuit; the input end of the switch circuit is used as the input end of the second current limiting color adjustment control unit, the positive electrode of the output end of the drive circuit is used as the positive electrode of the control end of the second current limiting color adjustment control unit, the negative electrode of the output end of the drive circuit is used as the negative electrode of the control end of the second current limiting color adjustment control unit, the input end of the detection circuit is used as the detection end of the second current limiting color adjustment control unit, and the reference end of the comparison circuit is used as the current limiting reference end of the second current limiting color adjustment control unit; The output end of the switch circuit is electrically connected to the input end of the drive circuit, the output end of the detection circuit is electrically connected to the input end of the comparison circuit, and the output end of the comparison circuit is electrically connected to the overcurrent feedback end of the drive circuit; When the color temperature control PWM signal is at a high level, the switch circuit of the first current limiting color adjustment control unit is turned on, and the drive circuit of the first current limiting color adjustment control unit drives the MOS tube Q1 to work in the variable resistance area; when the color temperature control PWM signal is at a low level, the switch circuit of the second current limiting color adjustment control unit is turned on, and the drive circuit of the second current limiting color adjustment control unit drives the MOS tube Q2 to work in the variable resistance area; The detection circuit collects the dimming current of the first light source circuit or the second light source circuit and transmits it to the comparison circuit; when the comparison circuit detects that the dimming current is greater than the reference current, the drive circuit drives the MOS tube Q1 or the MOS tube Q2 to operate in the saturation region.

3. The two-way light source color temperature adjustment circuit according to claim 1, characterized in that: The dual-channel complementary color-adjusting unit includes a resistor R1, a capacitor C2, a capacitor C7 and a dual-channel complementary color-adjusting chip U1; a reference current generating circuit is integrated inside the dual-channel complementary color-adjusting chip U1, the input end of the reference current generating circuit is used as the PWM-L end of the dual-channel complementary color-adjusting chip U1, and the output end of the reference current generating circuit is used as the OCP end of the dual-channel complementary color-adjusting chip U1; The OUT1 end of the dual-channel complementary color-mixing chip U1 is used as the first output end of the dual-channel complementary color-mixing unit, the OUT2 end of the dual-channel complementary color-mixing chip U1 is used as the second output end of the dual-channel complementary color-mixing unit, the PWM-L end of the dual-channel complementary color-mixing chip U1 is used as the first input end of the dual-channel complementary color-mixing unit, the PWM end of the dual-channel complementary color-mixing chip U1 is used as the second input end of the dual-channel complementary color-mixing unit, and the OCP end of the dual-channel complementary color-mixing chip U1 is used as the current-limiting reference end of the dual-channel complementary color-mixing unit; One end of the resistor R1 is connected to the VH power supply, the other end of the resistor R1 and one end of the capacitor C2 are electrically connected to the VH end of the dual-channel complementary color-adjusting chip U1, the other end of the capacitor C2 is connected to the high-voltage side ground terminal VS, one end of the capacitor C7 and the VCC end of the dual-channel complementary color-adjusting chip U1 are connected to the VCC power supply, and the other end of the capacitor C7 and the GND end of the dual-channel complementary color-adjusting chip U1 are connected to the low-voltage side ground terminal GND; The dual-channel complementary color adjustment chip U1 is used to externally connect the color temperature control PWM signal; when the color temperature control PWM signal is at a high level, the first current limiting color adjustment control unit is driven to turn on the first light source circuit; when the color temperature control PWM signal is at a low level, the second current limiting color adjustment control unit is driven to turn on the second light source circuit; The reference current generating circuit is used to externally connect the brightness control PWM signal, change the reference point of the brightness control PWM signal from the low-voltage side ground terminal GND to the high-voltage side ground terminal VS, and generate the reference current.

4. The two-way light source color temperature adjustment circuit according to claim 3, characterized in that: The reference current generating circuit includes a resistor R27, a MOS transistor Q7, a resistor R28, a resistor R22, a resistor R23, a resistor R24, a resistor R25, a resistor R26, a transistor Q8, a comparator U1B and a voltage regulator U3; the gate of the MOS transistor Q7 is used as the input end of the reference current generating circuit, and the output end of the comparator U1B is used as the output end of the reference current generating circuit; The source of the MOS transistor Q7 is connected to the low-voltage side ground terminal GND, the drain of the MOS transistor Q7 and one end of the resistor R28 are electrically connected to one end of the resistor R22, the other end of the resistor R22 is electrically connected to the base of the transistor Q8, the emitter of the transistor Q8, the other end of the resistor R28 and one end of the resistor R27 are connected to the VH power supply, the collector of the transistor Q8 and one end of the resistor R23 are electrically connected to the positive input terminal of the comparator U1B, the negative input terminal of the comparator U1B and one end of the resistor R24 ​​are electrically connected to one end of the resistor R25, the other end of the resistor R24, the other end of the resistor R27, the cathode of the voltage regulator U3, and the reference electrode of the voltage regulator U3 are electrically connected to one end of the resistor R26, and the other end of the resistor R23, the other end of the resistor R25 and the other end of the resistor R26 are connected to the high-voltage side ground terminal VS.

5. The two-way light source color temperature adjustment circuit according to claim 2, characterized in that: The switch circuit includes a resistor R11, a resistor R13 and a MOS transistor Q6; one end of the resistor R11 is used as an input end of the switch circuit, and the drain of the MOS transistor Q6 is used as an output end of the switch circuit; The other end of the resistor R11 and one end of the resistor R13 are both electrically connected to the gate of the MOS transistor Q6 , and the other end of the resistor R13 and the source of the MOS transistor Q6 are both connected to the high-voltage side ground terminal VS.

6. A two-way light source color temperature adjustment circuit according to claim 2, characterized in that: The comparison circuit includes a comparator U3A, a capacitor C4, a capacitor C6, a resistor R15, a resistor R3 and a resistor R21; one end of the resistor R21 is used as a reference end of the comparison circuit, the negative input end of the comparator U3A is used as an input end of the comparison circuit, and one end of the resistor R3 is used as an output end of the comparison circuit; The other end of the resistor R3 is electrically connected to the output end of the comparator U3A, the positive power supply end of the comparator U3A and one end of the capacitor C4 are both connected to the VH power supply, the other end of the capacitor C4 is connected to the high-voltage side ground end VS, the positive input end of the comparator U3A is electrically connected to one end of the resistor R15, the other end of the resistor R15 and the other end of the resistor R21 are both electrically connected to one end of the capacitor C6, and the other end of the capacitor C6 and the negative power supply end of the comparator U3A are both connected to the high-voltage side ground end VS.

7. A two-way light source color temperature adjustment circuit according to claim 2, characterized in that: The driving circuit comprises a resistor R6, a transistor Q4 and a resistor R7; one end of the resistor R6 is used as an input end of the driving circuit, the emitter of the transistor Q4 is used as an overcurrent feedback end of the driving circuit, one end of the resistor R7 is used as a positive output end of the driving circuit, and the other end of the resistor R7 is used as a negative output end of the driving circuit; The other end of the resistor R6 is electrically connected to the base of the transistor Q4 , the emitter of the transistor Q4 is electrically connected to one end of the resistor R7 , and the collector of the transistor Q4 is electrically connected to the other end of the resistor R7 .

8. The two-way light source color temperature adjustment circuit according to claim 2, characterized in that: The detection circuit includes a comparator U3B, a resistor R17 and a resistor R19; the output end of the comparator U3B is used as the output end of the detection circuit, and the positive input end of the comparator U3B is used as the input end of the detection circuit; The output end of the comparator U3B is electrically connected to one end of the resistor R17, the negative input end of the comparator U3B and the other end of the resistor R17 are electrically connected to one end of the resistor R19, and the other end of the resistor R19 is connected to the high-voltage side ground terminal VS.

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