A lighting control circuit and chip

Abstract

The application discloses a kind of lighting control circuit and chip, it is applied to the lighting circuit being equipped with dimming switch tube and lighting module, lighting control circuit includes: comparison module, its first input end receives the first sampling voltage representing current through lighting module current, its second input end receives the second sampling voltage always greater than or equal to the first sampling voltage, its third input end receives the first threshold voltage compared with the first sampling voltage, its fourth input end receives the second threshold voltage compared with the second sampling voltage;Logic operation module is connected with the output end of comparison module, is configured as in intermittent current mode according to the output result of comparison module control dimming switch tube frequency.The application controls the on-off frequency of dimming switch tube based on comparison result to control the current flowing through lighting module, very good realization is controlled to intermittent current, realizes accurate dimming, and reduce the complexity of circuit, reduce power consumption.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to a lighting control circuit and chip. Background Art

[0002] Currently, LED lighting sources are increasingly being used in the lighting field due to their advantages such as small size, light weight, and fast response speed. In practical applications, LED lighting sources can typically adjust the brightness of the LED by adjusting the current flowing through the LED. The dimming depth is directly related to the performance of the LED lighting source. Conventional dimming methods generally include: PWM pulse width direct dimming, which adjusts the current flowing through the LED by inputting PWM signals with different duty cycles; and analog dimming, which adjusts the LED current by comparing the sampled voltage with a reference voltage. Both of these methods suffer from the inability to precisely control the LED current when deep dimming is required. To address this issue, existing technologies disclose deep dimming by simultaneously controlling the on-time and frequency of the switching tube in discontinuous current mode to achieve precise dimming. However, this method requires simultaneous calculation and control of the on-time and frequency, making its implementation complex and consuming high power. Summary of the Invention

[0003] In response to the deficiencies in the prior art, the present invention provides a lighting control circuit and chip that can accurately adjust the light while reducing circuit complexity and power consumption.

[0004] In a first aspect, the present invention provides a lighting control circuit, which is applied to a lighting circuit provided with a dimmer switch tube and a lighting module, the lighting control circuit comprising:

[0005] a comparison module, wherein a first input terminal receives a first sampled voltage representing a current flowing through the lighting module, a second input terminal receives a second sampled voltage that is always greater than or equal to the first sampled voltage, a third input terminal receives a first threshold voltage to be compared with the first sampled voltage, and a fourth input terminal receives a second threshold voltage to be compared with the second sampled voltage;

[0006] The logic operation module is connected to the output end of the comparison module and is configured to control the frequency of the dimming switch tube according to the output result of the comparison module in the discontinuous current mode.

[0007] Preferably, the comparison module includes a first comparison unit, a first input terminal of the first comparison unit receives the first sampling voltage, a second input terminal of the first comparison unit receives a first threshold voltage, and an output terminal of the first comparison unit is connected to the logic operation module.

[0008] Preferably, the comparison module further includes a second comparison unit, a first input terminal of the second comparison unit receives the second sampling voltage, a second input terminal of the second comparison unit receives a second threshold voltage, and an output terminal of the second comparison unit is connected to the logic operation module.

[0009] Preferably, the lighting control circuit further includes a resistor connected between the first input terminal of the first comparison unit and the first input terminal of the second comparison unit.

[0010] Preferably, the lighting control circuit further includes a compensation current module, which is connected to the first input end of the second comparison unit, and the compensation current module is configured to output a compensation current that is inversely proportional to the target dimming brightness of the lighting module to the first input end of the second comparison unit.

[0011] Preferably, the logic operation module includes a first logic unit, which is respectively connected to the output end of the comparison module and the dimming switch tube, and the first logic unit is configured to control the dimming switch tube to turn off when the first sampling voltage reaches a first threshold voltage and the second sampling voltage reaches a second threshold voltage.

[0012] Preferably, the logic operation module includes a second logic unit, which is respectively connected to the output end of the comparison module and the dimming switch tube, and the second logic unit is configured to control the dimming switch tube to be turned on when the first sampling voltage is less than a first threshold voltage or the second sampling voltage is less than a second threshold voltage.

[0013] Preferably, the logic operation module includes an AND gate logic unit, a first input end of the AND gate logic unit is connected to the output end of the first comparison unit, a second input end of the AND gate logic unit is connected to the output end of the second comparison unit, and an output end of the AND gate logic unit is connected to the dimming switch tube.

[0014] Preferably, the logic operation module is configured to control the on-time of the dimming switch tube to remain unchanged during the switching cycle of the dimming switch tube in the discontinuous current mode, and to control the on-time of the dimming switch tube to change in the critical current mode so that the lighting module reaches the target dimming brightness.

[0015] In a second aspect, the present invention provides a lighting control chip, comprising the lighting control circuit described in the first aspect.

[0016] The lighting control circuit and chip provided by the present invention control the on-off frequency of the dimming switch tube based on the comparison results to control the current flowing through the lighting module, effectively realize the control of intermittent current, achieve precise dimming, reduce the complexity of the circuit, and reduce power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0018] Figure 1 A schematic diagram of the structure of the lighting control circuit provided in this embodiment;

[0019] Figure 2 A circuit diagram of the lighting module provided in this embodiment;

[0020] Figure 3 Another structural diagram of the lighting control circuit provided in this embodiment;

[0021] Figure 4 Another structural diagram of the lighting control circuit provided in this embodiment;

[0022] Figure 5 Another structural diagram of the lighting control circuit provided in this embodiment;

[0023] Figure 6 A schematic structural diagram of the first logic unit provided in this embodiment;

[0024] Figure 7 A schematic diagram of the structure of the second logic unit provided in this embodiment;

[0025] Figure 8 A schematic diagram of the structure of the AND gate logic unit provided in this embodiment;

[0026] Figure 9 A first circuit diagram of the lighting control circuit provided in this embodiment;

[0027] Figure 10 A schematic diagram of the flipping time of the first comparator and the second comparator provided in this embodiment;

[0028] Figure 11 This is a second circuit diagram of the lighting control circuit provided in this embodiment. DETAILED DESCRIPTION

[0029] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, but cannot limit the protection scope of the present application.

[0030] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should be understood as the general meaning understood by the skilled person in the field to which the present application belongs.

[0031] A lighting control circuit 100 is applied to a lighting circuit provided with a lighting module 200 and a dimmer switch tube 300, referring to Figure 1 The lighting control circuit 100 includes a comparison module 11 and a logic operation module 12. Wherein, the first input end of the comparison module 11 receives a first sampling voltage Vcs1 representing the current flowing through the lighting module 200, the second input end of the comparison module 11 receives a second sampling voltage Vcs2 always greater than or equal to the first sampling voltage Vcs1, the third input end of the comparison module 11 receives a first threshold voltage VTH1 compared with the first sampling voltage Vcs1, and the fourth input end of the comparison module 11 receives a second threshold voltage VTH2 compared with the second sampling voltage Vcs2; the logic operation module 12 is connected with the output end of the comparison module 11, and is configured to control the frequency of the dimmer switch tube 300 according to the output result of the comparison module 11 in the discontinuous current mode.

[0032] In the present embodiment, referring to Figure 2 The lighting module 200 can include a light emitting diode unit 21, a first inductor 22 and a first freewheeling diode 23, the first end of the light emitting diode unit 21 is connected with a power supply and the first end of the first freewheeling diode 23 respectively, the second end of the light emitting diode unit 21 is connected with the first end of the first inductor 22, and the second end of the first inductor 22 is connected with the second end of the first freewheeling diode 23 and the dimmer switch tube 300 respectively. The first freewheeling diode 23 includes but is not limited to a transient voltage suppressor (TVS) tube. The first end of the light emitting diode unit 21 can be an anode, and the second end of the light emitting diode unit 21 can be a cathode. The first end of the first freewheeling diode 23 can be a cathode, and the second end of the first freewheeling diode 23 can be an anode. The light emitting diode unit 21 can include one or more LEDs.

[0033] The dimmer switch 300 can be an N-type field-effect transistor (FET), a P-type FET, or the like. In practical applications, the connection relationship between the logic operation module 12 and the dimmer switch 300 can be determined based on the type of the dimmer switch 300. In this embodiment, the dimmer switch 300 can be an N-type FET. A first terminal of the dimmer switch 300 is connected to the output terminal of the logic operation module 12, a second terminal of the dimmer switch 300 is connected to the second terminal of the first inductor 22, a third terminal of the dimmer switch 300 is connected to the first terminal of the third resistor 41, and a second terminal of the third resistor 41 is grounded. The first terminal of the dimmer switch 300 can be a gate, the second terminal of the dimmer switch 300 can be a drain, and the third terminal of the dimmer switch 300 can be a source.

[0034] In this embodiment, the first sampling voltage Vcs1 can be used to represent the current flowing through the lighting module 200. Figure 2 As shown, the first sampling voltage Vcs1 can control the source voltage of the dimming switch tube 300, and the source voltage can be used to represent the current flowing through the light emitting diode unit 21 in the lighting module 200. It should be noted that, as Figure 2 This is only one form of the first sampling voltage Vcs1 . Those skilled in the art should know that other methods may also be used to obtain the current representing the current flowing through the lighting module 200 .

[0035] It should be noted that the second sampling voltage Vcs2 should always be greater than or equal to the first sampling voltage Vcs1 . The first sampling voltage Vcs1 is compared with the first threshold voltage VTH1 , and the second sampling voltage Vcs2 is compared with the second threshold voltage VTH2 , and the comparison results are sent to the logic operation module 12 .

[0036] In this embodiment, there is no specific limitation on the usage and specific structure of the comparison module 11 , which only needs to meet the logic of controlling the dimming switch tube 300 .

[0037] In this embodiment, the logic operation module 12 may include, but is not limited to, a gate logic unit. The specific structure of the logic operation module 12 may be constructed using an AND gate, a NOT gate, a NAND gate, an OR gate, a NOR gate, an AND-OR gate, an XOR gate, and the like, as needed. The logic operation module 12 may also use analog circuits to perform various logic operations, or may use a combination of analog and digital circuits to perform various logic operations. The specific structure of the logic operation module 12 is not specifically limited herein.

[0038] In this embodiment, the dimming signal received by the lighting control circuit 100 is a PWM signal. The duty cycle of the dimming signal can be used to represent the Figure 2The brightness of the light-emitting diode unit 21 in the lighting module 200 shown is high or low. The larger the duty cycle, the higher the brightness of the light-emitting diode unit 21 needs to be controlled. At this time, the duty cycle of the PWM signal is positively correlated with the brightness (in other examples, the duty cycle of the PWM signal can also be negatively correlated with the brightness, which will not be repeated here). Relatively speaking, when the duty cycle of the dimming signal is small, the brightness of the light-emitting diode unit 21 is low. If the light-emitting diode unit 21 is still controlled to have current flowing through it at this time, the brightness of the light-emitting diode unit 21 will be high. Therefore, at this time, the lighting control circuit 100 operates in a discontinuous current mode, that is, in some time periods, the current flowing through the light-emitting diode unit 21 will be greater than zero, and in other time periods, the current flowing through the light-emitting diode unit 21 is zero. When the duty cycle of the dimming signal is large, the brightness of the light-emitting diode unit 21 is high. At this time, the lighting control circuit 100 operates in a critical current mode. At this time, it is necessary to control the light-emitting diode unit 21 to have current flowing through it at all times, thereby ensuring that the brightness of the light-emitting diode unit 21 is high.

[0039] In this embodiment, the comparison module 11 compares the first sampling voltage Vcs1 with the first threshold voltage VTH1, and compares the second sampling voltage Vcs2 with the second threshold voltage VTH2. The logic operation module 12 controls the on-off frequency of the dimming switch tube 300 based on the comparison results (i.e., the magnitude relationship between the first sampling voltage Vcs1 and the first threshold voltage VTH1, and the magnitude relationship between the second sampling voltage Vcs2 and the second threshold voltage VTH2) to control the current flowing through the lighting module 200, without having to control the on-time of the dimming switch tube 300. That is, in In the discontinuous current mode, regardless of the target dimming brightness of the LED unit 21, the duration of each conduction of the dimming switch tube 300 is fixed. In this embodiment, only the duration during which the current flowing through the LED unit 21 is zero needs to be changed. Thus, in the discontinuous current mode, under different target dimming brightnesses of the LED unit 21, there is no need to calculate the conduction time of the dimming switch tube 300 and the duration during which the current flowing through the LED unit 21 is zero in real time. This achieves discontinuous current control and precise dimming, while reducing the complexity of controlling the LED unit 21.

[0040] In this embodiment, the comparison module 11 may include a first comparison unit 111, see Figure 3 A first input terminal of the first comparison unit 111 receives the first sampling voltage Vcs1 , a second input terminal of the first comparison unit 111 receives the first threshold voltage VTH1 , and an output terminal of the first comparison unit 111 is connected to the logic operation module 12 .

[0041] For example, when the first sampling voltage Vcs1 is greater than or equal to the first threshold voltage VTH1, the first comparison unit 111 may output a high level; when the first sampling voltage Vcs1 is less than the first threshold voltage VTH1, the first comparison unit 111 may output a low level.

[0042] In this embodiment, the comparison module 11 may further include a second comparison unit 112, see Figure 3 A first input terminal of the second comparison unit 112 receives the second sampling voltage Vcs2 , a second input terminal of the second comparison unit 112 receives the second threshold voltage VTH2 , and an output terminal of the second comparison unit 112 is connected to the logic operation module 12 .

[0043] Similarly, for example, when the second sampling voltage Vcs2 is greater than or equal to the second threshold voltage VTH2, the second comparison unit 112 may output a high level; when the second sampling voltage Vcs2 is less than the second threshold voltage VTH2, the second comparison unit 112 may output a low level.

[0044] In this embodiment, the first comparison unit 111 and the second comparison unit 112 may be integrated into one integrated chip, or may be two independent comparators, which is not limited here.

[0045] In this embodiment, the lighting control circuit 100 may further include a resistor 13, see Figure 3 Resistor 13 is connected between the first input terminal of the first comparison unit 111 and the first input terminal of the second comparison unit 112. Resistor 13 may include a resistor unit, a sliding rheostat, etc., without limitation herein. In this embodiment, since the second sampling voltage Vcs2 is always greater than or equal to the first sampling voltage Vcs1, the current direction is from the first input terminal of the second comparison unit 112 to the first input terminal of the first comparison unit 111. Therefore, resistor 13 can act as a voltage booster to ensure that the second sampling voltage Vcs2 is always greater than or equal to the first sampling voltage Vcs1.

[0046] In order to more clearly describe the connection method of the first comparison unit 111, the second comparison unit 112 and the resistor 13, the following example is given:

[0047] See also Figure 4The first comparison unit 111 includes a first comparator 1111, the second comparison unit 112 includes a second comparator 1121, and the resistor 13 includes a first resistor 131. The first resistor 131 is connected between a first input terminal of the first comparator 1111 and a first input terminal of the second comparator 1121. The second input terminal of the first comparator 1111 receives a first threshold voltage VTH1, and the second input terminal of the second comparator 1121 receives a second threshold voltage VTH2. The output terminals of the first comparator 1111 and the second comparator 1121 are respectively connected to the logic operation module 12. The first input terminal of the first comparator 1111 and the first input terminal of the second comparator 1121 can be non-inverting input terminals, and the second input terminal of the first comparator 1111 and the second input terminal of the second comparator 1121 can be inverting input terminals.

[0048] See also Figure 5 The first comparison unit 111 includes a third comparator 1112, the second comparison unit 112 includes a fourth comparator 1122, and the resistor 13 includes a second resistor 132. The second resistor 132 is connected between a first input terminal of the third comparator 1112 and a first input terminal of the fourth comparator 1122. The second input terminal of the third comparator 1112 receives a first threshold voltage VTH1, and the second input terminal of the fourth comparator 1122 receives a second threshold voltage VTH2. The output terminals of the third comparator 1112 and the fourth comparator 1122 are respectively connected to the logic operation module 12. The first input terminal of the third comparator 1112 and the first input terminal of the fourth comparator 1122 can be inverting input terminals, and the second input terminal of the third comparator 1112 and the second input terminal of the fourth comparator 1122 can be non-inverting input terminals.

[0049] In this embodiment, the lighting control circuit 100 may further include a compensation current module 14. Figure 3 The compensation current module 14 is connected to the first input terminal of the second comparison unit 112 , and the compensation current module 14 is configured to output a compensation current inversely proportional to the target dimming brightness of the lighting module 200 to the first input terminal of the second comparison unit 112 .

[0050] In this embodiment, when the dimming signal is a PWM signal, the greater the duty cycle of the PWM signal, the higher the target dimming brightness of the lighting module 200 and the smaller the compensation current; the smaller the duty cycle of the PWM signal, the lower the target dimming brightness of the lighting module 200 and the larger the compensation current.

[0051] Specifically, when the target dimming brightness of the lighting module 200 is high (critical current mode), the control compensation current becomes smaller. Due to the presence of the resistor 13, when the first sampling voltage Vcs1 reaches the first threshold voltage VTH1, the second sampling voltage Vcs2 still does not reach the second threshold voltage VTH2. At this time, the dimming switch tube 300 is controlled to be turned on until the second sampling voltage Vcs2 also reaches the second threshold voltage VTH2, and the dimming switch tube 300 is controlled to be turned off. At this time, the larger the second threshold voltage VTH2, the higher the target dimming brightness of the lighting module 200.

[0052] When the target dimming brightness of the lighting module 200 is low (discontinuous current mode), the compensation current is increased. Due to the presence of resistor 13, when the second sampled voltage Vcs2 reaches the second threshold voltage VTH2, the first sampled voltage Vcs1 still has not reached the first threshold voltage VTH1. In this case, the dimmer switch 300 is turned on until the first sampled voltage Vcs1 also reaches the first threshold voltage VTH1, at which point the dimmer switch 300 is turned off. At this point, the larger the first threshold voltage VTH1, the higher the target dimming brightness of the lighting module 200. It should be noted that in this embodiment, the first threshold voltage VTH1 is a fixed value. That is, in discontinuous current mode, the target dimming brightness of the lighting module 200 is high or low, and the duration of each dimming switch 300 on-time is fixed. Low-brightness dimming is achieved by controlling only the duration of zero current flowing through the lighting module 200.

[0053] Furthermore, in this embodiment, the logic operation module 12 may include a first logic unit 121, see Figure 6 The first logic unit 121 is connected to the output end of the comparison module 11 and the dimming switch tube 300 respectively. The first logic unit 121 is configured to control the dimming switch tube 300 to turn off when the first sampling voltage Vcs1 reaches the first threshold voltage VTH1 and the second sampling voltage Vcs2 reaches the second threshold voltage VTH2.

[0054] In this embodiment, the logic operation module 12 includes a second logic unit 122, see Figure 7 The second logic unit 122 is connected to the output end of the comparison module 11 and the dimming switch tube 300 respectively. The second logic unit 122 is configured to control the dimming switch tube 300 to be turned on when the first sampling voltage Vcs1 is less than the first threshold voltage VTH1 or the second sampling voltage Vcs2 is less than the second threshold voltage VTH2.

[0055] In this embodiment, the logic operation module 12 includes an AND gate logic unit 123. Figure 8The first input end of the AND gate logic unit 123 is connected to the output end of the first comparison unit 111 , the second input end of the AND gate logic unit 123 is connected to the output end of the second comparison unit 112 , and the output end of the AND gate logic unit 123 is connected to the dimming switch tube 300 .

[0056] In this embodiment, the logic operation module 12 is configured to control the on-time of the dimming switch tube 300 to remain unchanged during the switching cycle of the dimming switch tube 300 in the discontinuous current mode, and to control the on-time of the dimming switch tube 300 to change in the critical current mode so that the lighting module 200 reaches the target dimming brightness.

[0057] The switching cycle can be considered the time period from the current on-time to the next on-time of the dimmer switch 300. In the discontinuous current mode, maintaining the on-time of the dimmer switch 300 during the switching cycle can be considered as: controlling the time period during which the current flowing through the LED unit 21 of the lighting module 200 is zero to change, thereby achieving brightness adjustment of the LED unit 21 of the lighting module 200, while maintaining the time period during which the current flowing through the LED unit 21 of the lighting module 200 gradually increases.

[0058] In order to more clearly describe the working mode and technical effects of the lighting control circuit 100, the following examples are given:

[0059] Example 1:

[0060] See also Figure 9 The first comparison unit 111 may be a first comparator 1111, the second comparison unit 112 may be a second comparator 1121, the resistor may include a first resistor 131, the compensation current module 14 may include a compensation current unit 141, and the logic operation module 12 may include a first NAND gate 1231. The first resistor 131 is connected between the first input terminal of the first comparator 1111 and the first input terminal of the second comparator 1121. The second input terminal of the first comparator 1111 receives a first threshold voltage VTH1, and the second input terminal of the second comparator 1121 receives a second threshold voltage VTH2. The output terminal of the first comparator 1111 and the output terminal of the second comparator 1121 are respectively connected to the first input terminal and the second input terminal of the first NAND gate 1231. The output terminal of the first NAND gate 1231 is connected to the first terminal of the dimming switch tube 300, and the second terminal of the dimming switch tube 300 is connected to the lighting module 200 (see FIG. 2 ). Figure 2). The first end of the compensation current unit 141 is connected to the power supply, and the second end of the compensation current unit 141 is connected to the first input end of the second comparator 1121. The first end of the first comparator 1111 is also connected to the first end of the third resistor 41, the second end of the third resistor 41 is grounded, and the first end of the third resistor 41 is also connected to the third end of the dimmer switch tube 300. The dimmer switch tube 300 can be an N-type field effect transistor, the first end of the dimmer switch tube 300 can be a gate, the second end of the dimmer switch tube 300 can be a drain, and the third end of the dimmer switch tube 300 can be a source. The first input end of the first comparator 1111 and the first input end of the second comparator 1121 can be non-inverting input ends, and the second input end of the first comparator 1111 and the second input end of the second comparator 1121 can be inverting input ends. The first sampling voltage Vcs1 is used to represent the current flowing through the third resistor 41. The larger the first sampling voltage Vcs1, the higher the brightness of the light-emitting diode unit 21.

[0061] In this embodiment, the lighting control circuit 100 includes two operating modes, namely a discontinuous current mode and a critical current mode. The compensation current of the compensation current unit 141 is I, and the first resistor 131 is R.

[0062] When the lighting control circuit 100 is in discontinuous current mode, the duty cycle of the PWM signal corresponding to the dimming signal is small, and the corresponding compensation current I is large. Since Vcs2 = Vcs1 + I × R, the second sampling voltage Vcs2 reaches the second threshold voltage VTH2 earlier than the first sampling voltage Vcs1 reaches the first threshold voltage VTH1. Consequently, the second comparator 1121 flips before the first comparator 1111, i.e., the second comparator 1121 outputs a high level earlier than the first comparator 1111. At this point, the second comparator 1121 outputs a high level, the first comparator 1111 outputs a low level, and the first NAND gate 1231 outputs a high level, turning on the N-type field-effect transistor (FET), causing the first sampling voltage Vcs1 to gradually rise. This gradually increases the current flowing through the LED unit 21 in the lighting module 200 until the first comparator 1111 also outputs a high level. When the first sampling voltage Vcs1 gradually rises to the first threshold voltage VTH1, the first comparator 1111 flips and outputs a high level. At this point, both the first comparator 1111 and the second comparator 1121 output a high level, and the first NAND gate 1231 outputs a low level, turning off the N-type field-effect transistor (FET), causing the first sampling voltage Vcs1 to gradually decrease. At this point, the current flowing through the LED unit 21 in the lighting module 200 gradually decreases from a peak current to zero. The peak current can be the current flowing through the LED unit 21 in the lighting module 200. A smaller duty cycle of the PWM signal corresponding to the dimming signal indicates a lower desired brightness of the LED unit 21, and a longer duration during which the current flowing through the LED unit 21 is zero.

[0063] In this embodiment, in discontinuous current mode, the brightness of the LED unit 21 in the lighting module 200 is controlled by controlling the frequency of the dimmer switch 300. Specifically, in discontinuous current mode, the duration of each on-state of the dimmer switch 300 remains constant (the period of time during which the current flowing through the LED unit 21 in the lighting module 200 gradually increases remains constant), while the period of time during which the current flowing through the LED unit 21 in the lighting module 200 is zero is varied, thereby achieving brightness adjustment of the LED unit 21 in the lighting module 200.

[0064] It should be noted that between the time period (T1) when the current flowing through the LED unit 21 in the lighting module 200 gradually increases and the time period (T3) when the current flowing through the LED unit 21 in the lighting module 200 is zero, there is also a time period (T2) when the current flowing through the LED unit 21 in the lighting module 200 gradually decreases, which is usually consistent with the time period when the current flowing through the LED unit 21 in the lighting module 200 gradually increases.

[0065] In the discontinuous current mode, Vcs1 = L·dIcs / dt. Since the peak value of the first sampling voltage Vcs1 is the fixed first threshold voltage VTH1, L is Figure 2 The first inductor 22 in the circuit 200 is connected to the first inductor 22, so the first sampling voltage Vcs1 and L are constant, and the peak value of Ics is the current flowing through the light-emitting diode unit 21 / the third resistor 41 when the first sampling voltage Vcs1 is at its peak value. Therefore, for the lighting control circuit 100 of the same lighting module 200, when the peak value of the first sampling voltage Vcs1 is the fixed first threshold voltage VTH1, the rising time T1 and the falling time T2 of the first sampling voltage Vcs1 or Ics are constant.

[0066] Moreover, in this embodiment, since the peak value of the first sampling voltage Vcs1 is the fixed first threshold voltage VTH1, the duration of T1 remains unchanged. That is, in the discontinuous current mode, the dimming depth is independent of the duration of T1. T1 is always in a fixed state, and only T3 needs to be controlled to change.

[0067] Therefore, it can be considered that when the lighting control circuit 100 is in the discontinuous current mode, the second sampling voltage Vcs2 will always be greater than the second threshold voltage VTH2, and the turn-off time of the dimming switch tube 300 is determined by the size relationship between the first sampling voltage Vcs1 and the first threshold voltage VTH1. It can be determined that at the same time, in this stage, the duration of T1 remains unchanged, and the duration of T3 is determined by the duty cycle of the PWM signal corresponding to the dimming signal, that is, the dimming depth is controlled by controlling the duration of T3.

[0068] The actual current flowing through the LED unit 21 / third resistor 41 is k·Ipeak·(T1+T2) / (T1+T2+T3), where k is a constant, Ipeak is the peak current flowing through the LED unit 21 / third resistor 41 at the moment the N-type field-effect transistor switches from the on state to the off state, T1 is the on-time (the period during which the current flowing through the LED unit 21 in the lighting module 200 gradually increases), T2 is the current fall-off time (the period during which the current flowing through the LED unit 21 in the lighting module 200 gradually decreases), and T3 is the dead time during which no current flows through the LED unit 21 / third resistor 41. It should be noted that a smaller actual current indicates a lower brightness of the LED unit 21. Therefore, when the duty cycle of the PWM signal corresponding to the dimming signal increases, the duration of T3 decreases, and the actual current increases, and vice versa. For the lighting control circuit 100 of the same lighting module 200, the above-mentioned k, Ipeak, T1, and T2 are fixed values. Therefore, a corresponding mapping relationship or linear proportional relationship can be set between the duty cycle of the PWM signal corresponding to the dimming signal and the dead time T3. For example, when the duty cycle is X1, the fixed dead time T3 is Y1. In this way, in the discontinuous current mode, the actual current flowing through the light-emitting diode unit 21 / the third resistor 41 can be controlled to correspond to the duty cycle of the PWM signal.

[0069] It can be seen from the above description that, based on the lighting control circuit 100 provided in this embodiment, in the discontinuous current mode, the requirement of dimming depth can be met by changing the duration of T3.

[0070] When the lighting control circuit 100 is in critical current mode, the duty cycle of the PWM signal corresponding to the dimming signal is large, and the corresponding compensation current I is small. Since Vcs2 = Vcs1 + I × R, the first sampling voltage Vcs1 reaches the first threshold voltage VTH1 earlier than the second sampling voltage Vcs2 reaches the second threshold voltage VTH2. Consequently, the first comparator 1111 flips before the second comparator 1121, i.e., the first comparator 1111 outputs a high level earlier than the second comparator 1121. At this point, the second comparator 1121 outputs a low level, and the first NAND gate 1231 outputs a high level, turning on the N-type field-effect transistor (FET), causing the first sampling voltage Vcs1 to gradually rise. This gradually increases the current flowing through the LED unit 21 in the lighting module 200 until the second comparator 1121 also outputs a high level. When the second sampling voltage Vcs2 gradually rises to the second threshold voltage VTH2, the second comparator 1121 flips and also outputs a high level. At this point, both the first comparator 1111 and the second comparator 1121 output a high level, and the first NAND gate 1231 outputs a low level, controlling the N-type field-effect transistor to turn off, causing the first sampling voltage Vcs1 to gradually decrease. At this time, the current flowing through the LED unit 21 in the lighting module 200 gradually decreases from the peak current until it reaches zero, and the N-type field-effect transistor is turned on again. The peak current can be the current flowing through the LED unit 21 in the lighting module 200 at the moment the dimmer switch 300 is turned off. Therefore, in the critical current mode, the duration of the zero current flowing through the LED unit 21 can be considered zero.

[0071] When the dimming depth reaches the maximum, the compensation current I is zero. At this time, the second sampling voltage Vcs2 is equal to the first sampling voltage Vcs1. When the first sampling voltage Vcs1 reaches the second threshold voltage VTH2, the second sampling voltage Vcs2 can synchronously reach the second threshold voltage VTH2 to control the N-type field effect transistor to turn off.

[0072] Specifically, in the critical current mode, the first comparator 1111 will flip earlier than the second comparator 1121. Regarding the flip time of the second comparator 1121: Figure 10 As shown, when the dimming depth gradually decreases from large to small, the peak value of the first sampling voltage Vcs1 also gradually decreases from the second threshold voltage VTH2 to the first threshold voltage VTH1, and the synchronous compensation current I also gradually increases. Based on the formula Vcs2=L·dI / dt, it can be seen that the time for the second sampling voltage Vcs2 to reach the second threshold voltage VTH2 will also increase accordingly, and therefore the time for the second comparator 1121 to flip will also be advanced.

[0073] That is, in the critical current mode, the first threshold voltage VT1 can be controlled to thereby control the on-time of the dimming switch tube 300 so as to achieve the target dimming brightness requirement.

[0074] As can be seen from the above description, when the second sampled voltage Vcs2 is greater than the second threshold voltage VTH2, the lighting control circuit 100 can be determined to be in discontinuous current mode. Furthermore, in this mode, the turn-off time of the dimmer switch 300 is determined by the magnitude relationship between the first sampled voltage Vcs1 and the first threshold voltage VTH1. When the first sampled voltage Vcs1 is greater than the first threshold voltage VTH1, the lighting control circuit 100 can be determined to be in critical current mode. Furthermore, in this mode, the turn-off time of the dimmer switch 300 is determined by the magnitude relationship between the second sampled voltage Vcs2 and the second threshold voltage VTH2. When the second sampled voltage Vcs2 reaches the second threshold voltage VTH2, the N-type field-effect transistor is controlled to turn off. The turn-off time (T2) is related to the current drop rate of the first inductor 22, that is, the N-type field-effect transistor is turned off until the current flowing through the first inductor 22 reaches zero.

[0075] It should be noted that in this embodiment, the compensation current I is not of the same order of magnitude as the actual current flowing through the LED unit 21 / the third resistor 41, and the compensation current I is much smaller than the actual current. Therefore, when this embodiment is adopted, the actual power consumption will also be lower.

[0076] In addition, in this embodiment, the durations of T1 and T2 may be the same.

[0077] Example 2:

[0078] See also Figure 11Compared to Example 1, this example differs in that the first comparison unit 111 includes a third comparator 1112, the second comparison unit 112 includes a fourth comparator 1122, the resistor 13 includes a second resistor 132, and the gate logic unit includes a first NOT gate 1232, a second NOT gate 1233, and a second NAND gate 1234. The second resistor 132 is connected between the first input of the third comparator 1112 and the first input of the fourth comparator 1122. The second input of the third comparator 1112 receives the first threshold voltage VTH1, and the second input of the fourth comparator 1122 receives the second threshold voltage VTH2. The outputs of the third comparator 1112 and the fourth comparator 1122 are connected to the inputs of the first NOT gate 1232 and the second NOT gate 1233, respectively. The outputs of the first NOT gate 1232 and the second NOT gate 1233 are connected to the inputs of the second NAND gate 1234, respectively. The output of the second NAND gate 1234 is connected to the dimmer switch 300. The first input terminal of the third comparator 1112 and the first input terminal of the fourth comparator 1122 may be inverting input terminals, and the second input terminal of the third comparator 1112 and the second input terminal of the fourth comparator 1122 may be non-inverting input terminals.

[0079] The working principle of this example is the same as that of Example 1 and will not be described here.

[0080] In this embodiment, only the duration of T3 needs to be calculated. At the same time, a resistor 13 and a compensation current I that is inversely proportional to the duty cycle of the PWM signal are cleverly set in the circuit. The on-off state of the N-type field-effect transistor is controlled by the comparison module 11, thereby controlling the current flowing through the lighting module 200, thereby achieving precise dimming, reducing the complexity of the circuit, and reducing power consumption.

[0081] Example 2:

[0082] A lighting control chip includes the lighting control circuit 100 of the first embodiment.

[0083] The products provided in the embodiments of the present invention are briefly described. For matters not mentioned in the embodiments, reference may be made to the corresponding contents in the aforementioned embodiments.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A lighting control circuit, characterized in that: Applicable to a lighting circuit provided with a dimmer switch tube and a lighting module, wherein the dimmer switch tube is an N-type field effect tube or a P-type field effect tube, and the lighting control circuit includes: a comparison module, wherein a first input terminal receives a first sampled voltage representing a current flowing through the lighting module, a second input terminal receives a second sampled voltage that is always greater than or equal to the first sampled voltage, a third input terminal receives a first threshold voltage to be compared with the first sampled voltage, and a fourth input terminal receives a second threshold voltage to be compared with the second sampled voltage; a logic operation module connected to the output end of the comparison module and configured to control the frequency of the dimming switch tube according to the output result of the comparison module in the discontinuous current mode; The comparison module includes a first comparison unit, a first input terminal of the first comparison unit receives the first sampling voltage, a second input terminal of the first comparison unit receives a first threshold voltage, and an output terminal of the first comparison unit is connected to the logic operation module; The comparison module further includes a second comparison unit, wherein a first input terminal of the second comparison unit receives the second sampling voltage, a second input terminal of the second comparison unit receives a second threshold voltage, and an output terminal of the second comparison unit is connected to the logic operation module; The lighting control circuit further includes a resistor connected between the first input terminal of the first comparison unit and the first input terminal of the second comparison unit; The lighting control circuit also includes a compensation current module, which is connected to the first input end of the second comparison unit and is configured to output a compensation current that is inversely proportional to the target dimming brightness of the lighting module to the first input end of the second comparison unit.

2. The lighting control circuit according to claim 1, characterized in that: The logic operation module includes a first logic unit, which is respectively connected to the output end of the comparison module and the dimming switch tube. The first logic unit is configured to control the dimming switch tube to turn off when the first sampling voltage reaches a first threshold voltage and the second sampling voltage reaches a second threshold voltage.

3. The lighting control circuit according to claim 1, characterized in that: The logic operation module includes a second logic unit, which is respectively connected to the output end of the comparison module and the dimming switch tube. The second logic unit is configured to control the dimming switch tube to turn on when the first sampling voltage is less than a first threshold voltage or the second sampling voltage is less than a second threshold voltage.

4. The lighting control circuit according to claim 1, characterized in that: The logic operation module includes an AND gate logic unit, a first input end of the AND gate logic unit is connected to the output end of the first comparison unit, a second input end of the AND gate logic unit is connected to the output end of the second comparison unit, and an output end of the AND gate logic unit is connected to the dimming switch tube.

5. The lighting control circuit according to claim 1, characterized in that: The logic operation module is configured to control the on-time of the dimming switch tube to remain unchanged during the switching cycle of the dimming switch tube in the discontinuous current mode, and to control the on-time of the dimming switch tube to change in the critical current mode so that the lighting module reaches the target dimming brightness.

6. A lighting control chip, characterized in that: The lighting control circuit comprises the lighting control circuit according to any one of claims 1 to 5.

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