A current control circuit

Abstract

The present invention provides a current control circuit, including a linear constant current circuit and an output voltage sampling module, wherein the linear constant current circuit includes a constant current driving module and active components and a control module respectively connected thereto, the control module controls the first reference voltage of the constant current driving module, and uses the constant current driving module to control the working state of the active components. The constant current driving module provides a constant current for the LED load; the output voltage sampling module is configured to sample the output voltage of the linear constant current circuit, and provide the sampled output voltage to the control module. If the lowest output voltage value of the output voltage provided to the control module within a preset period is less than a set value, the control module controls the first reference voltage of the constant current driving module to decrease, and the output current of the linear constant current circuit to decrease until the sampled lowest output voltage value of the linear constant current circuit is greater than the set value. This solution can solve the contradiction between the linear constant current flicker and the loss of the linear constant current circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of constant current driving, and in particular to a current control circuit. Background Art

[0002] At present, in order to save circuit costs and obtain high-quality flicker-free light, more and more LED lamps use linear constant current drive circuits. The use of linear constant current drive circuits can make the output current of the lamps almost ripple-free.

[0003] When actually designing linear constant current lamps, it is necessary to comprehensively consider factors such as the grid voltage range, no flicker, and the loss of the "linear constant current circuit". In order to make the loss of the linear constant current drive circuit as small as possible, the critical point voltage of the flicker should be designed to be as large as possible. However, this will cause flicker when the grid voltage is low. Therefore, how to effectively resolve this contradiction is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a current control circuit that overcomes the above problems or at least partially solves the above problems.

[0005] According to one aspect of the present invention, a current control circuit is provided, comprising a rectifier module, a capacitor element, a linear constant current circuit and an output voltage sampling module, wherein:

[0006] The rectifier module is connected to a capacitor element; one end of the capacitor element is connected to a linear constant current circuit, and the other end is connected to an LED load;

[0007] The linear constant current circuit comprises a constant current driving module and active elements and a control module respectively connected thereto, wherein the control module is configured to control a first reference voltage of the constant current driving module and use the constant current driving module to control the working state of the active element; the constant current driving module is configured to control the active element to be in an amplified state to provide a constant current for the LED load;

[0008] The output voltage sampling module is connected to the control module and the active element respectively, and is configured to sample the output voltage of the linear constant current circuit and provide the sampled output voltage to the control module;

[0009] Among them, if the lowest output voltage value of the output voltage provided by the output voltage sampling module to the control module within a preset period is less than the set value, the control module controls the first reference voltage of the constant current driving module to decrease, the constant current driving module controls the active element to be in an amplification state, and the output current of the linear constant current circuit decreases until the sampled lowest output voltage value of the linear constant current circuit is greater than the set value.

[0010] Optionally, the output voltage sampling module includes: a comparator, a first voltage-dividing resistor, and a second voltage-dividing resistor; wherein,

[0011] One end of the first voltage-dividing resistor is connected to the second voltage-dividing resistor, the other end is connected to the active element, and the other end of the second voltage-dividing resistor is grounded;

[0012] The comparator has a positive input terminal, a negative input terminal, and an output terminal, the positive input terminal is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the negative input terminal receives a second reference voltage, and the output terminal is connected to the control module;

[0013] The comparator is configured to sample the voltage obtained by dividing the output voltage of the linear constant current circuit on the second voltage-dividing resistor, and compare the sampled voltage value with the second reference voltage. If the sampled voltage value is less than the second reference voltage, the output end outputs a low level to the control module, and the control module controls the first reference voltage of the constant current driving module to decrease, and the output current of the linear constant current circuit decreases.

[0014] Optionally, the output voltage sampling module includes: a comparator, a first voltage-dividing resistor, and a second voltage-dividing resistor; wherein,

[0015] One end of the first voltage-dividing resistor is connected to the second voltage-dividing resistor, and the other end is connected to the active element, and the other end of the second voltage-dividing resistor is grounded;

[0016] The comparator has a positive input terminal, a negative input terminal, and an output terminal, wherein the negative input terminal is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the positive input terminal receives a second reference voltage, and the output terminal is connected to the control module;

[0017] The comparator is configured to sample the voltage obtained by dividing the output voltage of the linear constant current circuit on the second voltage-dividing resistor, and compare the sampled voltage value with the second reference voltage. If the sampled voltage value is less than the second reference voltage, the output end outputs a high level to the control module, and the control module controls the first reference voltage of the constant current driving module to decrease, and the output current of the linear constant current circuit decreases.

[0018] Optionally, the output voltage sampling module and the linear constant current circuit are integrated into the same IC chip;

[0019] The IC chip comprises an output pin and a ground pin, the output pin is connected to the LED load, and the ground pin is connected to a ground terminal.

[0020] Optionally, the output voltage sampling module is further configured to provide the sampled output voltage of the linear constant current circuit to the control module. If the output voltage provided to the control module is greater than a first preset voltage value, the control module controls the first reference voltage of the constant current driving module to decrease, and the constant current driving module controls the active element to operate in a cut-off state, the output voltage of the linear constant current circuit increases, and the LED load voltage decreases.

[0021] Optionally, the linear constant current circuit further includes:

[0022] An over-temperature protection circuit, connected to the control module, configured to detect the temperature of the IC chip where the linear constant current circuit is located;

[0023] If the over-temperature protection circuit detects that the temperature of the IC chip is higher than a preset temperature range, the control module is controlled to reduce the first reference voltage of the constant current driving module, and the output current of the linear constant current circuit is reduced until the temperature of the IC chip is within the preset temperature range;

[0024] If the over-temperature protection circuit detects that the temperature of the IC chip is lower than the preset temperature range, the control module is controlled to increase the first reference voltage of the constant current drive module until the output current of the linear constant current circuit increases to the preset maximum current, so that the temperature of the IC chip is within the preset temperature range.

[0025] Optionally, a sampling resistor is further included, and the linear constant current circuit further includes an output current sampling module connected to the sampling resistor, and the output current sampling module is also connected to the constant current driving module, the control module, and the active element respectively;

[0026] The sampling resistor is configured to convert the output current of the linear constant current circuit into a voltage value;

[0027] The output current sampling module is configured to sample the voltage value converted by the sampling resistor and provide it to the constant current driving module, and the constant current driving module obtains an output signal according to the received converted voltage value and the first reference voltage, and uses the output signal to control the active element to be in an amplified state, thereby providing a constant current for the LED load;

[0028] The output current sampling module is further configured to provide the sampled voltage value converted by the sampling resistor to the control module. If the voltage value provided to the control module is greater than a second preset voltage value, the control module controls the first reference voltage of the constant current driving module to decrease, the constant current driving module controls the active element to operate in a cut-off state, and the output current of the linear constant current circuit is reduced to zero.

[0029] Optionally, the sampling resistor is arranged inside the IC chip, one end of the sampling resistor is grounded, and the other end is connected to an active element.

[0030] Optionally, the sampling resistor is arranged outside the IC chip, and the IC chip further includes an enable pin. One end of the sampling resistor is grounded, and the other end is connected to the enable pin.

[0031] Optionally, the active element includes a triode or a field effect transistor;

[0032] If the active element is a field effect tube, the gate of the field effect tube is connected to the constant current driving module, the source is connected to the output current sampling module, and the drain is connected to the output voltage sampling module.

[0033] Optionally, the current control circuit further includes:

[0034] The internal power supply circuit is respectively connected to the control module, the constant current driving module, the active element, and the output voltage sampling module to supply power to the modules and elements connected thereto.

[0035] Optionally, the current control circuit further includes:

[0036] An internal power supply circuit is connected to the rectifier module, the control module, and the constant current drive module, respectively, and uses the direct current rectified by the rectifier module to power the modules connected thereto;

[0037] The IC chip also includes power pins, and the power pins are connected to the internal power circuit and the rectifier module respectively.

[0038] Optionally, the IC chip and the sampling resistor each include at least two, and the enable pin of each IC chip is connected to a corresponding sampling resistor;

[0039] The power pins of at least two IC chips are respectively connected to the rectifier module, the output pins are respectively connected to the LED load, and the ground pins are respectively connected to the ground terminal.

[0040] The embodiment of the present invention arranges an output voltage sampling module on the basis of a constant current driving circuit to timely sample the output voltage of the constant current driving circuit. When it is found that the output voltage of the constant current driving circuit is less than the set value in the preset period, the first reference voltage of the constant current driving module is timely reduced and the active element is controlled to be in an amplified state, thereby quickly reducing the output current of the linear constant current circuit, so that the output current is ripple-free, avoiding the flicker phenomenon of the lamp where the circuit is located, and realizing overcurrent protection of the circuit. Furthermore, while reducing the output current of the linear constant current circuit, the threshold voltage of the flicker is also reduced, thereby reducing the loss of the linear constant current circuit, thereby solving the contradiction between the linear constant current flicker and the loss of the linear constant current circuit within a larger voltage input range of the power grid.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below.

[0042] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0044] Figure 1a The structure diagram of the linear constant current circuit in the prior art is shown;

[0045] Figure 1b Shows Figure 1a Schematic diagram of the DC voltage waveform after rectification by the rectifier bridge in the linear constant current circuit;

[0046] Figure 1c Shows Figure 1a Schematic diagram of voltage waveform after capacitor filtering in the linear constant current circuit;

[0047] Figure 2a-2e Shows Figure 1a The output voltage waveform and output current waveform of the linear constant current circuit under different input voltages;

[0048] Figure 3 A schematic diagram showing the structure of a control circuit in one embodiment of the present invention is shown;

[0049] Figure 4a A schematic diagram of the internal structure of a detection circuit and a linear constant current circuit is shown;

[0050] Figure 4b Shows Figure 3 A schematic diagram of a circuit structure included in the output voltage sampling module in the illustrated embodiment;

[0051] Figure 4c Shows Figure 4b The waveform diagram of the sampling voltage and the reference voltage of the comparator in the embodiment shown;

[0052] Figure 4d Shows Figure 4b A waveform diagram of the output voltage of the comparator in the illustrated embodiment;

[0053] Figure 4e Shows Figure 3 Another schematic diagram of a circuit structure included in the output voltage sampling module in the illustrated embodiment;

[0054] Figure 4f Shows Figure 4e A waveform diagram of the output voltage of the comparator in the illustrated embodiment;

[0055] Figure 4g Shows Figure 4a A schematic diagram of the structure of the control circuit after the detection circuit and the linear constant current circuit are integrated into the same chip;

[0056] Figure 5 A schematic diagram showing the structure of a control circuit in another embodiment of the present invention is shown;

[0057] Figure 6a Another detection circuit and a linear constant current circuit are shown;

[0058] Figure 6b Shows Figure 6a A schematic diagram of the structure of the control circuit after the detection circuit and the linear constant current circuit are integrated into the same chip;

[0059] Figure 7 A schematic structural diagram of a control circuit in yet another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0061] Usually used in linear constant current drive Figure 1a The topology circuit shown in the figure, where "F" is a fuse. When the current flowing through the fuse exceeds a certain value, the fuse will blow to prevent the related circuits connected behind the fuse from generating overcurrent danger due to abnormal operation. "DB" is a rectifier bridge, which is used to rectify the AC voltage of the input power grid into a DC voltage. If there is no capacitor filtering, the DC voltage after the rectifier bridge rectification will fluctuate greatly (such as Figure 1b The voltage waveform shown in the figure is shown in the figure), so a capacitor "C" is added after the rectifier bridge to filter the DC voltage with large fluctuations into a DC voltage with small fluctuations. Figure 1c , the amplitude of voltage fluctuation △U=Umax-U, the amplitude depends on the capacity of capacitor "C" and the output current of "linear constant current circuit". When the output current remains unchanged, the larger the capacitance, the smaller the amplitude of voltage fluctuation, and vice versa. When the capacitance remains unchanged, the larger the output current, the larger the amplitude of voltage fluctuation, and vice versa. Figure 1a , "V LED " is the voltage drop of the LED load in series. Since the lamp is required to be flicker-free, "V LED ”≤“U”, if “V LED ”>“U”, that is, the voltage applied to the LED is fluctuating, and the current flowing through the LED is also fluctuating, and the light emitted by the LED will flicker. The “linear constant current circuit” is to keep the current flowing through the LED constant. It is generally composed of active components (such as triodes, field effect transistors, etc.), operational amplifier circuits and negative feedback sampling circuits. It is to control the active amplifier components to work in the amplification state to output the actual constant current. When “V LED ”≤“U”, the “linear constant current circuit” works in the amplification state, that is, the constant current state, and the LED will not flicker; when “V LED ">"U", the "linear constant current circuit" works in the state of mutual conversion between amplification and saturation, and the LED flickers; when "V LED ">"Umax", the "linear constant current circuit" works in saturation state, and the LED flickers more obviously. In addition, due to the "V D ”=“Umax”-“V LED ”, “V D ” is the voltage drop that the “linear constant current circuit” bears, so “V D The minimum value of " must be greater than the minimum operating voltage of the "linear constant current circuit" so that the LED will not flicker.

[0062] The voltage of power grids across the country is not constant. Some are lower than the rated voltage (AC220V), while others are higher than the rated voltage. In order to ensure that the linear constant current lamps have no flicker within the designed input voltage range, the minimum input voltage after rectification and filtering needs to be higher than the voltage "U" LED " is a little bigger, then the "linear constant current circuit" works in the constant current state, the voltage drop of the active component is the smallest, and since the current is constant, the loss of the active component is the smallest. However, if the input voltage increases, "U"-"V LED " will also increase, the voltage drop of active components will increase, and the loss of active components will also increase. Within the design input voltage range, the maximum input voltage will maximize the loss of active components.

[0063] The following example illustrates the linear constant current circuit loss: The capacity of the filter capacitor "C" is 4.7uF, V LED =240V@40mA, the output current of the "linear constant current circuit" is about 40mA.

[0064] See also Figure 2a , if the input voltage is AC207V, by analyzing "V D "The voltage waveform shows that "V D The average voltage drop is 32V, and the fluctuation amplitude is 50V. By analyzing the output current waveform of the "linear constant current circuit", it can be seen that the average value of the output current is 0.0384A, and the current waveform begins to have ripples. This is the critical point where the "linear constant current circuit" works in the amplification state and the state of mutual conversion between amplification and saturation. At this time, the "linear constant current circuit" loss P = 32 × 0.0384 = 1.23W.

[0065] See also Figure 2b If the input voltage is less than AC207V, the "linear constant current circuit" works in the state of mutual conversion between amplification and saturation. If the input voltage is AC180V, by analyzing "V D "The voltage waveform shows that "V D The average voltage drop is 7.49V, and the fluctuation amplitude is 12V. By analyzing the output current waveform of the "linear constant current circuit", it can be seen that the ripple of the current waveform is very large, and the average value of the output current is 0.0224A. At this time, the loss of the "linear constant current circuit" is P = 7.49 × 0.0224 = 0.17W.

[0066] See also Figure 2c If the input voltage is > AC207V, the "linear constant current circuit" works in the amplification state. If the input voltage is AC260V, by analyzing "V D "The voltage waveform shows that "V DThe average voltage drop is 106.5V, and the fluctuation amplitude is 53V. By analyzing the output current waveform of the "linear constant current circuit", it can be seen that the current waveform has no ripple, and its average value is 0.0383A. At this time, the loss of the "linear constant current circuit" is P = 106.5 × 0.0224 = 4.08W.

[0067] See also Figure 2d , when the capacity of the filter capacitor "C" and the relevant parameters of the LED remain unchanged, the output current of the "linear constant current circuit" is reduced to 0.0228A, and the input voltage is AC207V. By analyzing the "V D "The voltage waveform shows that "V D The average voltage drop is 34V, and the fluctuation amplitude is 64V. By analyzing the output current waveform of the "linear constant current circuit", it can be seen that the current has no ripple. At this time, the "linear constant current circuit" works in the amplification state, and the loss of the "linear constant current circuit" is P = 46.59 × 0.0228 = 1.06W.

[0068] See also Figure 2e , under the condition that the capacity of filter capacitor "C" and LED related parameters remain unchanged, if the input voltage is AC189V, by analyzing "V D "The voltage waveform shows that "V D The average voltage drop is 20.76V, and the amplitude of fluctuation is 32V. By analyzing the output current waveform of the "linear constant current circuit", it can be seen that the average value of the output current is 0.0229A, and the current waveform begins to have ripples. This is the critical point where the "linear constant current circuit" works in the amplification state and the state of mutual conversion between amplification and saturation. At this time, the "linear constant current circuit" loss P = 20.76 × 0.0229 = 0.48W.

[0069] Through the above analysis, we can know that Figure 2e Yes Figure 2a If the current flowing through the LED is reduced from 0.0384A to 0.0229A, the critical voltage of the strobe is also reduced from 207V to 189V. The main reason is that the voltage fluctuation amplitude across the capacitor "C" is reduced. According to the above explanation, "when the capacitance remains unchanged, the greater the output current, the greater the voltage fluctuation amplitude, and vice versa. Figure 2a and Figure 2d The comparison can prove that. Another reason is that the current flowing through the LED is reduced, "V LED "The voltage is also reduced, so reducing the current flowing through the LED can reduce the critical point voltage of the strobe.

[0070] When designing linear constant current lamps, it is necessary to comprehensively consider factors such as the grid voltage range, no flicker, and the loss of the "linear constant current circuit". In order to minimize the loss of the "linear constant current circuit", the critical point voltage of flicker should be designed to be as large as possible, but flicker will occur when the grid voltage is low. In order to solve this contradiction, the output current can be controlled by adding a detection circuit to the linear constant current circuit.

[0071] See also Figure 3 The embodiment of the present invention provides a control circuit, the control circuit includes a rectifier module (such as Figure 3 The rectifier bridge DB), capacitor element C, linear constant current circuit 1 and detection circuit 2, wherein the rectifier module is connected to the capacitor element C, one end of the capacitor element C is connected to the linear constant current circuit 1, and the other end is connected to the LED load, and the detection circuit 2 is connected to the linear constant current circuit 1. The rectifier module rectifies the external input AC power into DC power, and the capacitor element C filters the DC power from the rectifier module.

[0072] Detection circuit 2 can detect "V D ” voltage, when detecting “V D "When the lowest voltage point in a certain period is less than the set value, the output current of the linear constant current circuit 1 is controlled to decrease until the lowest voltage point of the detection circuit 2 is greater than the set value. In this way, when the grid voltage is low, although the output current of the linear constant current circuit 1 decreases and the luminous flux of the lamp decreases, the lamp will not flicker.

[0073] See also Figure 3 and Figure 4a The linear constant current circuit 1 implemented in the present invention includes a constant current driving module 11 and active components (such as Figure 4a MOS tube in the constant current driving module 11) and a control module 12, wherein the control module 12 is configured to control the first reference voltage of the constant current driving module 11, and use the constant current driving module 11 to control the working state of the active element; the constant current driving module 11 is configured to control the active element to be in an amplified state and provide a constant current for the LED load.

[0074] The detection circuit 2 includes an output voltage sampling module 21, which is connected to the control module 12 and the active element respectively, and is configured to sample the output voltage (ie, the OUT point voltage) of the linear constant current circuit 1 and provide the sampled output voltage to the control module 12.

[0075] If the output voltage provided by the output voltage sampling module 21 to the control module 12 has a minimum output voltage value within a preset period that is less than a set value, the control module 12 controls the first reference voltage of the constant current driving module 11 to decrease, and the constant current driving module 11 controls the active element to be in an amplifying state, and the output current of the linear constant current circuit decreases until the minimum output voltage value of the linear constant current circuit 1 sampled is greater than the set value. In this embodiment, the set value can be selected from the minimum value of the actual output voltage of the linear constant current circuit after setting the input voltage value as described above.

[0076] The preset period in this embodiment may be any period, for example, the preset period is T=1 / 50 Hz, T=1 / 100 Hz, etc., and the embodiment of the present invention does not make any specific limitation on this.

[0077] The embodiment of the present invention can quickly adjust the output current of the linear constant current circuit so that the output current is ripple-free, avoiding the flicker phenomenon of the lamp where the circuit is located, and also realizing overcurrent protection of the circuit. In one embodiment of the present invention, the rectifier module can rectify the external input AC power into DC power. In addition to using a rectifying bridge, other rectifier elements can also be used. Moreover, the active element can not only use MOS tubes, but also other active elements such as triodes. The embodiment of the present invention does not make specific limitations on this.

[0078] See also Figure 4a and Figure 4b In one embodiment of the present invention, the output voltage sampling module 21 may include: Figure 4b The comparator U, the first voltage-dividing resistor R1, and the second voltage-dividing resistor R2 are shown. One end of the first voltage-dividing resistor R1 is connected to the second voltage-dividing resistor R2, and the other end is connected to the active element (such as Figure 4a The linear constant current circuit output terminal OUT shown in the figure, and the other end of the second voltage dividing resistor R2 is grounded.

[0079] The comparator U has a positive input terminal (+), a negative input terminal (−), and an output terminal Vo. The positive input terminal is connected between the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2 , the negative input terminal receives the second reference voltage Vref1 , and the output terminal Vo is connected to the control module 12 .

[0080] In this embodiment, the comparator U can be configured to sample the output voltage of the linear constant current circuit and obtain the voltage divided on the second voltage-dividing resistor R2 (i.e., the voltage at the Vout point), and compare the sampled voltage value with the second reference voltage Vref1. If the comparison shows that the sampled voltage value is less than the second reference voltage Vref1, the output terminal Vo outputs a low-level signal to the control module 12. After receiving the low-level signal, the control module 12 controls the first reference voltage of the constant current driving module 11 to decrease, thereby reducing the output current of the linear constant current circuit.

[0081] In addition, if the comparator U finds that the sampled voltage value is greater than the second reference voltage Vref1 , the output terminal Vo outputs a high level signal to the control module 12 , and the amplitude of the high level signal is VCC.

[0082] In this embodiment, Figure 4c The waveform diagram of the voltage at the point Vout of the comparator U and the second reference voltage Vref1 is shown. The voltage at the point Vout is a fluctuating ripple voltage, and is smaller than Vref1 when the voltage at the point Vout is at the bottom. Figure 4d Shown is the voltage waveform output from the output terminal Vo.

[0083] See also Figure 4e In one embodiment of the present invention, relative to Figure 4b In the connection mode of the comparator U, the comparator U can also reverse its positive input terminal and negative input terminal. Specifically, the negative input terminal of the comparator U is connected between the first voltage-dividing resistor R1 and the second voltage-dividing resistor R2, the positive input terminal receives the second reference voltage Vref1, and the output terminal Vo is connected to the control module 12.

[0084] In this embodiment, the comparator U can also be configured to sample the output voltage of the linear constant current circuit and the voltage divided on the second voltage-dividing resistor R2, and compare the sampled voltage value with the second reference voltage Vref1. If the comparison shows that the sampled voltage value is less than the second reference voltage Vref1, the output terminal Vo outputs a high level to the control module 12, and the control module 12 controls the first reference voltage of the constant current driving module 11 to decrease, thereby reducing the output current of the linear constant current circuit. In this embodiment, Figure 4f Shown is the voltage waveform output from the output terminal Vo.

[0085] In the embodiment of the present invention, the linear constant current circuit output terminal OUT can also be directly connected to the positive input terminal of the comparator U, that is, the first voltage-dividing resistor R1 is omitted, and the voltage drop across the second voltage-dividing resistor R2 is the output voltage of the output terminal of the linear constant current circuit. In addition, in the embodiment of the present invention, the output voltage sampling module 21 can also use other circuits such as operational amplifiers to implement voltage sampling, and the embodiment of the present invention does not make specific limitations on this.

[0086] In one embodiment of the present invention, in order to facilitate production and processing, the output voltage sampling module 21 and the linear constant current circuit can also be integrated into the same IC chip, and the IC chip can fix the maximum output current. Figure 4g The effective pins of the IC chip include 2, namely the output pin and the ground pin. The output pin OUT (corresponding to Figure 4a The output end of the linear constant current circuit in the embodiment is connected to the LED load, and the ground pin GND is connected to the ground end.

[0087] In one embodiment of the present invention, the output voltage sampling module 21 can also be configured to provide the sampled output voltage of the linear constant current circuit to the control module 12. If the output voltage provided to the control module 12 is greater than the first preset voltage value, the control module 12 can control the first reference voltage of the constant current driving module 11 to be reduced to a specified voltage value. The constant current driving module 11 controls the active element to operate in a cut-off state, the output voltage of the linear constant current circuit increases, and the output voltage of the linear constant current circuit is consistent with the voltage across the capacitor C, and the LED load voltage is reduced, thereby achieving OVP (overvoltage protection) protection.

[0088] Continue to see Figure 4a In one embodiment of the present invention, the linear constant current circuit also includes an over-temperature protection circuit 13, which is connected to the control module 12. If the output voltage sampling module 21 and the linear constant current circuit are integrated in the same IC chip, the over-temperature protection circuit 13 can detect the temperature of the IC chip where the linear constant current circuit is located.

[0089] During the temperature detection process, the over-temperature protection circuit 13 generates heat due to the loss of the IC chip. Therefore, when the over-temperature protection circuit 13 detects that the temperature of the IC chip is higher than the preset temperature range, the control module 12 is controlled to reduce the first reference voltage of the constant current drive module 11, and the output current of the linear constant current circuit is reduced until the temperature of the IC chip is within the preset temperature range; when the over-temperature protection circuit 13 detects that the temperature of the IC chip is lower than the preset temperature range, the control module 12 is controlled to increase the first reference voltage of the constant current drive module 11, and the output current of the linear constant current circuit is increased until the output current of the linear constant current circuit increases to the preset maximum current value, so that the temperature of the IC chip is within the preset temperature range. Thus, the over-temperature protection circuit 13 can realize OCP (over current protection) protection.

[0090] Continue to see Figure 4a In one embodiment of the present invention, the current control circuit also includes a sampling resistor Rs, and the linear constant current circuit also includes an output current sampling module 14 connected to the sampling resistor Rs, and the output current sampling module 14 is also connected to the constant current driving module 11, the control module 12, and the active element respectively.

[0091] Since a voltage signal is generated after the output current of the linear constant current circuit flows through the sampling resistor Rs, the sampling resistor Rs can convert the output current of the linear constant current circuit into a voltage value.

[0092] The output current sampling module 14 is configured to sample the voltage value converted by the sampling resistor Rs and provide it to the constant current driving module 11. The constant current driving module 11 obtains an output signal based on the received converted voltage value and the first reference voltage. When the output signal is used to control the active element to be in an amplified state, a constant current is provided to the LED load.

[0093] The output current sampling module 14 is further configured to provide the sampled voltage value converted by the sampling resistor Rs to the control module 12. If the voltage value provided to the control module 12 is greater than the second preset voltage value, the control module 12 controls the first reference voltage of the constant current driving module 11 to be reduced to a specific voltage value, the constant current driving module 11 controls the active element to operate in a cut-off state, and the output current of the linear constant current circuit is reduced to zero, thereby achieving actual OCP protection.

[0094] like Figure 4a and Figure 4g As shown, in one embodiment of the present invention, the sampling resistor Rs may be disposed inside the IC chip, one end of the sampling resistor Rs is grounded, and the other end is connected to the active element.

[0095] See also Figure 5 In another embodiment of the present invention, in order to more conveniently replace the sampling resistor Rs and conveniently adjust the maximum output current, the sampling resistor Rs can also be set outside the IC chip. The IC chip also includes an enable pin CS. One end of the sampling resistor Rs is grounded, and the other end is connected to the enable pin CS.

[0096] Continue to see Figure 4a As mentioned above, active components can be triodes or field effect transistors (MOS tubes). Figure 4a The active element in the circuit is a field effect tube, the gate of the field effect tube is connected to the constant current driving module 11 , the source is connected to the output current sampling module 14 and the sampling resistor Rs, and the drain is connected to the output voltage sampling module 21 .

[0097] See also Figure 6a and Figure 6b In one embodiment of the present invention, the current control circuit may further include an internal power supply circuit 15, which is respectively connected to the control module 12, the constant current drive module 11, the active component, and the output voltage sampling module 21, and directly supplies power to the modules and components connected thereto. In addition, the internal power supply circuit 15 may also supply power to the modules or circuits not directly connected thereto, such as the over-temperature protection circuit 13 and the output current sampling module 14.

[0098] In another embodiment of the present invention, when the sampling resistor Rs is set outside the IC chip, the internal power supply circuit 15 can also be connected to the rectifier module, the control module 12, and the constant current drive module 11, respectively, and the DC power rectified by the rectifier module is used to power the modules connected thereto. In addition, the internal power supply circuit 15 can also power the modules or circuits that are not directly connected thereto, such as the over-temperature protection circuit 13, the output voltage sampling module 21, and the output current sampling module 14.

[0099] In this embodiment, the IC chip further includes a power pin Vin, which is connected to the internal power circuit 15 and the rectifier module (such as the rectifier bridge DB) respectively.

[0100] See also Figure 7 In one embodiment of the present invention, if the output current of the IC chip is insufficient or the temperature is too high, at least two IC chips can be used in parallel ( Figure 7 Two IC chips are shown connected in parallel, namely IC1 chip and IC2 chip).

[0101] In this embodiment, at least two sampling resistors ( Figure 7 Two sampling resistors are shown, namely, resistor Rs1 and resistor Rs2), and the enable pin CS of each IC chip is respectively connected to a corresponding sampling resistor. Figure 7 In the example, the enable pin CS of the IC1 chip is connected to the resistor Rs1, and the enable pin CS of the IC2 chip is connected to the resistor Rs2.

[0102] In addition, the power pins Vin of at least two IC chips are respectively connected to the rectifier bridge DB, the output pins OUT are respectively connected to the LED load, and the ground pins are respectively connected to the ground terminal.

[0103] According to any one of the above preferred embodiments or a combination of multiple preferred embodiments, the embodiments of the present invention can achieve the following beneficial effects:

[0104] By setting an output voltage sampling module on the basis of a constant current drive circuit to timely sample the output voltage of the constant current drive circuit, when it is found that the output voltage of the constant current drive circuit is less than the set value in the preset period, the first reference voltage of the constant current drive module is timely reduced and the active element is controlled to be turned off, thereby quickly reducing the output current of the linear constant current circuit, so that the output current is ripple-free, avoiding the flicker phenomenon of the lamp where the circuit is located, and realizing overcurrent protection of the circuit. Furthermore, while reducing the output current of the linear constant current circuit, the critical point voltage of the flicker is also reduced, thereby reducing the loss of the linear constant current circuit, thereby solving the contradiction between the linear constant current flicker and the loss of the linear constant current circuit within a larger voltage input range of the power grid.

[0105] 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 aforementioned embodiments, those skilled in the art should understand that within the spirit and principles of the present invention, the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not deviate from the protection scope of the present invention.

Claims

1. A current control circuit, characterized in that: It includes a rectifier module, a capacitor element, a linear constant current circuit and an output voltage sampling module, wherein: The rectifier module is connected to a capacitor element; one end of the capacitor element is connected to a linear constant current circuit, and the other end is connected to an LED load; The linear constant current circuit comprises a constant current driving module and active elements and a control module respectively connected thereto, wherein the control module is configured to control a first reference voltage of the constant current driving module and use the constant current driving module to control the working state of the active element; the constant current driving module is configured to control the active element to be in an amplified state to provide a constant current for the LED load; The output voltage sampling module is connected to the control module and the active element respectively, and is configured to sample the output voltage of the linear constant current circuit and provide the sampled output voltage to the control module; Wherein, if the lowest output voltage value of the output voltage provided by the output voltage sampling module to the control module within a preset period is less than the set value, the control module controls the first reference voltage of the constant current driving module to decrease, the constant current driving module controls the active element to be in an amplifying state, and the output current of the linear constant current circuit decreases until the lowest output voltage value of the linear constant current circuit sampled is greater than the set value, and the set value is the minimum value of the actual output voltage of the linear constant current circuit after the input voltage value is set; The output voltage sampling module comprises: a comparator, a first voltage-dividing resistor, and a second voltage-dividing resistor, wherein one end of the first voltage-dividing resistor is connected to the second voltage-dividing resistor, and the other end is connected to the active element, and the other end of the second voltage-dividing resistor is grounded; The comparator has a positive input terminal, a negative input terminal, and an output terminal, wherein the positive input terminal is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the negative input terminal receives a second reference voltage, and the output terminal is connected to the control module. The comparator is configured to sample the voltage obtained by dividing the output voltage of the linear constant current circuit on the second voltage-dividing resistor, and compare the sampled voltage value with the second reference voltage. If the sampled voltage value is less than the second reference voltage, the output terminal outputs a low level to the control module, and the control module controls the first reference voltage of the constant current driving module to decrease, and the output current of the linear constant current circuit decreases; or, The comparator has a positive input terminal, a negative input terminal, and an output terminal, the negative input terminal is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the positive input terminal receives a second reference voltage, and the output terminal is connected to the control module. The comparator is configured to sample the voltage obtained by dividing the output voltage of the linear constant current circuit on the second voltage-dividing resistor, and compare the sampled voltage value with the second reference voltage. If the sampled voltage value is less than the second reference voltage, the output terminal outputs a high level to the control module, and the control module controls the first reference voltage of the constant current driving module to decrease, and the output current of the linear constant current circuit decreases.

2. The current control circuit according to claim 1, characterized in that: The output voltage sampling module and the linear constant current circuit are integrated in the same IC chip; The IC chip comprises an output pin and a ground pin, the output pin is connected to the LED load, and the ground pin is connected to a ground terminal.

3. The current control circuit according to claim 2, characterized in that: The output voltage sampling module is further configured to provide the sampled output voltage of the linear constant current circuit to the control module. If the output voltage provided to the control module is greater than a first preset voltage value, the control module controls the first reference voltage of the constant current driving module to decrease, and the constant current driving module controls the active element to operate in a cut-off state, the output voltage of the linear constant current circuit increases, and the LED load voltage decreases.

4. The current control circuit according to claim 2, characterized in that: The linear constant current circuit also includes: An over-temperature protection circuit, connected to the control module, configured to detect the temperature of the IC chip where the linear constant current circuit is located; If the over-temperature protection circuit detects that the temperature of the IC chip is higher than a preset temperature range, the control module is controlled to reduce the first reference voltage of the constant current driving module, and the output current of the linear constant current circuit is reduced until the temperature of the IC chip is within the preset temperature range; If the over-temperature protection circuit detects that the temperature of the IC chip is lower than the preset temperature range, the control module is controlled to increase the first reference voltage of the constant current drive module, and the output current of the linear constant current circuit increases until the output current of the linear constant current circuit increases to the preset maximum current, so that the temperature of the IC chip is within the preset temperature range.

5. The current control circuit according to claim 2, characterized in that: It also includes a sampling resistor, and the linear constant current circuit also includes an output current sampling module connected to the sampling resistor, and the output current sampling module is also connected to the constant current driving module, the control module, and the active element respectively; The sampling resistor is configured to convert the output current of the linear constant current circuit into a voltage value; The output current sampling module is configured to sample the voltage value converted by the sampling resistor and provide it to the constant current driving module, and the constant current driving module obtains an output signal according to the received converted voltage value and the first reference voltage, and uses the output signal to control the active element to be in an amplified state, thereby providing a constant current for the LED load; The output current sampling module is further configured to provide the sampled voltage value converted by the sampling resistor to the control module. If the voltage value provided to the control module is greater than a second preset voltage value, the control module controls the first reference voltage of the constant current driving module to decrease, the constant current driving module controls the active element to operate in a cut-off state, and the output current of the linear constant current circuit is reduced to zero.

6. The current control circuit according to claim 5, characterized in that: The sampling resistor is arranged inside the IC chip, one end of the sampling resistor is grounded, and the other end is connected to an active element.

7. The current control circuit according to claim 5, characterized in that: The sampling resistor is arranged outside the IC chip. The IC chip further comprises an enable pin. One end of the sampling resistor is grounded, and the other end is connected to the enable pin.

8. The current control circuit according to claim 5, characterized in that: The active element includes a triode or a field effect transistor; If the active element is a field effect tube, the gate of the field effect tube is connected to the constant current driving module, the source is connected to the output current sampling module, and the drain is connected to the output voltage sampling module.

9. The current control circuit according to claim 3, characterized in that: The current control circuit further includes: The internal power supply circuit is respectively connected to the control module, the constant current driving module, the active element, and the output voltage sampling module to supply power to the modules and elements connected thereto.

10. The current control circuit according to claim 7, characterized in that: The current control circuit further includes: An internal power supply circuit is connected to the rectifier module, the control module, and the constant current drive module, respectively, and uses the direct current rectified by the rectifier module to power the modules connected thereto; The IC chip also includes power pins, and the power pins are connected to the internal power circuit and the rectifier module respectively.

11. The current control circuit according to claim 10, characterized in that: The IC chip and the sampling resistor each include at least two, and the enable pin of each IC chip is connected to a corresponding sampling resistor; The power pins of at least two IC chips are respectively connected to the rectifier module, the output pins are respectively connected to the LED load, and the ground pins are respectively connected to the ground terminal.

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