CN209824078U - Current control circuit - Google Patents
Current control circuit Download PDFInfo
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- CN209824078U CN209824078U CN201822175352.7U CN201822175352U CN209824078U CN 209824078 U CN209824078 U CN 209824078U CN 201822175352 U CN201822175352 U CN 201822175352U CN 209824078 U CN209824078 U CN 209824078U
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Abstract
The utility model provides a current control circuit, including linear constant current circuit and output voltage sampling module, wherein, linear constant current circuit includes constant current drive module and rather than the active element and the control module who is connected respectively, and the operating condition of active element is controlled to control module control constant current drive module's first reference voltage, utilization constant current drive module. The constant current driving module provides constant current for the LED load; the output voltage sampling module is configured to sample the output voltage of the linear constant current circuit, the sampled output voltage is provided for the control module, and if the lowest output voltage value of the output voltage provided for the control module in a preset period is smaller than a set value, the control module controls the first reference voltage of the constant current driving module to be reduced, and the output current of the linear constant current circuit is reduced until the lowest output voltage value of the sampled linear constant current circuit is larger than the set value. The scheme can solve the contradiction between the linear constant current stroboflash and the linear constant current circuit loss.
Description
Technical Field
The utility model relates to a constant current drive technical field especially relates to a current control circuit.
Background
At present, in order to save circuit cost and obtain high-quality non-stroboscopic light, more and more LED lamps adopt linear constant current driving circuits, and the output current of the lamps almost has no ripples by adopting the linear constant current driving circuits.
When a linear constant current lamp is actually designed, the voltage range of a power grid, no stroboflash, the loss of a linear constant current circuit and other factors need to be comprehensively considered, in order to enable the loss of the linear constant current driving circuit to be as small as possible, the stroboflash critical point voltage should be designed to be as large as possible, but the stroboflash can be caused to appear when the voltage of the power grid is lower, and therefore how to effectively solve the contradiction is the technical problem to be solved urgently at present.
SUMMERY OF THE UTILITY MODEL
In view of the above, the present invention has been made to provide a current control circuit that overcomes or at least partially solves the above problems.
According to an aspect of the present invention, there is provided a current control circuit, comprising a rectifying module, a capacitor element, a linear constant current circuit, and an output voltage sampling module, wherein,
the rectifying module is connected with the capacitor element; one end of the capacitor element is connected with the linear constant current circuit, and the other end of the capacitor element is connected with the LED load;
the linear constant current circuit comprises a constant current driving module, and an active element and a control module which are respectively connected with the constant current driving module, wherein the control module is configured to control a first reference voltage of the constant current driving module, and the constant current driving module is used for controlling the working state of the active element; the constant current driving module is configured to control the active element to be in an amplifying state and provide a constant current for the LED load;
the output voltage sampling module is respectively connected with the control module and the active element, and 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 by the output voltage sampling module to the control module in a preset period is smaller than a set value, the control module controls the first reference voltage of the constant current driving module to be reduced, 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 is reduced until the sampled lowest output voltage value of the linear constant current circuit is larger than the set value.
Optionally, the output voltage sampling module includes: the voltage divider comprises a comparator, a first voltage dividing resistor and a second voltage dividing resistor; wherein the content of the first and second substances,
one end of the first voltage-dividing resistor is connected with the second voltage-dividing resistor, the other end of the first voltage-dividing resistor is connected with the active element, and the other end of the second voltage-dividing resistor is grounded;
the comparator is provided with a positive input end, a negative input end and an output end, wherein the positive input end is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the negative input end receives a second reference voltage, and the output end is connected with the control module;
the comparator is configured to sample a voltage obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor, compare the sampled voltage value with the second reference voltage, and if the sampled voltage value is smaller than the second reference voltage, output a low level to the control module by an output end, wherein the control module controls the first reference voltage of the constant current driving module to be reduced, and the output current of the linear constant current circuit is reduced.
Optionally, the output voltage sampling module includes: the voltage divider comprises a comparator, a first voltage dividing resistor and a second voltage dividing resistor; wherein the content of the first and second substances,
one end of the first voltage-dividing resistor is connected with the second voltage-dividing resistor, the other end of the first voltage-dividing resistor is connected with the active element, and the other end of the second voltage-dividing resistor is grounded;
the comparator is provided with a positive input end, a negative input end and an output end, wherein the negative input end is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the positive input end receives a second reference voltage, and the output end is connected with the control module;
the comparator is configured to sample a voltage obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor, compare the sampled voltage value with the second reference voltage, and if the sampled voltage value is smaller than the second reference voltage, output a high level to the control module by an output end, wherein the control module controls the first reference voltage of the constant current driving module to be reduced, and the output current of the linear constant current circuit is reduced.
Optionally, 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 grounding pin, the output pin is connected with the LED load, and the grounding pin is connected with a grounding end.
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, and 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, 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.
Optionally, the linear constant current circuit further includes:
the over-temperature protection circuit is connected with the control module and is 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 in the preset temperature range;
and if the over-temperature protection circuit detects that the temperature of the IC chip is lower than the preset temperature range, controlling the control module to increase the first reference voltage of the constant current driving module until the output current of the linear constant current circuit is increased to a preset maximum current, so that the temperature of the IC chip is in the preset temperature range.
Optionally, the linear constant current circuit further comprises a sampling resistor, the linear constant current circuit further comprises an output current sampling module connected with the sampling resistor, and the output current sampling module is further connected with 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 the voltage value to the constant current driving module, the constant current driving module obtains an output signal according to the received converted voltage value and the first reference voltage, and the output signal is used for controlling the active element to be in an amplifying state and 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 be reduced, the constant current driving module controls the active element to work in a cut-off state, and the output current of the linear constant current circuit is reduced to zero.
Optionally, the sampling resistor is disposed inside the IC chip, and one end of the sampling resistor is grounded while the other end is connected to an active element.
Optionally, the sampling resistor is disposed outside the IC chip, the IC chip further includes an enable pin, one end of the sampling resistor is grounded, and the other end of the sampling resistor is connected to the enable pin.
Optionally, the active element comprises a triode or a field effect transistor;
if the active element adopts a field effect transistor, the grid electrode of the field effect transistor is connected with the constant current driving module, the source electrode of the field effect transistor is connected with the output current sampling module, and the drain electrode of the field effect transistor is connected with the output voltage sampling module.
Optionally, the current control circuit further comprises:
and the internal power circuit is respectively connected with the control module, the constant current driving module, the active element and the output voltage sampling module and supplies power to the modules and the elements connected with the internal power circuit.
Optionally, the current control circuit further comprises:
the internal power circuit is connected with the rectifying module, the control module and the constant current driving module respectively, and supplies power to the modules connected with the internal power circuit by using direct current rectified by the rectifying module;
the IC chip further comprises a power supply pin, and the power supply pin is connected with the internal power supply circuit and the rectification module respectively.
Optionally, the IC chip and the sampling resistor respectively include at least two, and an enable pin of each IC chip is correspondingly connected to one sampling resistor;
the power pins of at least two IC chips are respectively connected with the rectifying module, the output pins are respectively connected with the LED load, and the grounding pins are respectively connected with a ground end.
The embodiment of the utility model provides a through set up output voltage sampling module on constant current drive circuit's basis, in order to in time sample the output voltage to constant current drive circuit, when the output voltage of discovery constant current drive circuit is less than the setting value at the minimum output voltage value of presetting the cycle, the first reference voltage that reduces constant current drive module in time and control active component are the enlarged state, thereby reduce linear constant current circuit's output current fast, so that output current does not have the ripple, stroboscopic phenomenon has appeared in the lamps and lanterns of having avoided the circuit place, the overcurrent protection to the circuit has also been realized. Furthermore, the output current of the linear constant current circuit is reduced, and the stroboscopic critical point voltage is also reduced, so that the loss of the linear constant current circuit is reduced, and the contradiction between the linear constant current stroboscopic and the loss of the linear constant current circuit in a larger voltage input range of a power grid is solved.
The above description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented according to the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the present invention is given.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1a shows a schematic structure diagram of a linear constant current circuit in the prior art;
FIG. 1b is a schematic diagram showing the DC voltage waveform of the linear constant current circuit in FIG. 1a after rectification by a rectifier bridge;
FIG. 1c is a schematic diagram of a capacitor-filtered voltage waveform in the linear constant current circuit of FIG. 1 a;
FIGS. 2a-2e illustrate the output voltage and output current waveforms for the linear constant current circuit of FIG. 1a at different input voltages;
fig. 3 shows a schematic structural diagram of a control circuit in an embodiment of the present invention;
FIG. 4a shows a schematic diagram of the internal structure of a detection circuit and a linear constant current circuit;
FIG. 4b is a schematic diagram of a circuit structure included in the output voltage sampling module in the embodiment shown in FIG. 3;
FIG. 4c shows a waveform of the sampled voltage and the reference voltage of the comparator in the embodiment of FIG. 4 b;
FIG. 4d shows a waveform of the output voltage of the comparator in the embodiment shown in FIG. 4 b;
FIG. 4e is a schematic diagram of another circuit structure included in the output voltage sampling module in the embodiment shown in FIG. 3;
FIG. 4f shows a waveform of the output voltage of the comparator in the embodiment shown in FIG. 4 e;
FIG. 4g is a schematic structural diagram of a control circuit of the linear constant current circuit and the detection circuit of FIG. 4a integrated on the same chip;
fig. 5 shows a schematic diagram of a control circuit according to another embodiment of the present invention;
FIG. 6a shows an internal structural schematic of another detection circuit and linear constant current circuit;
fig. 6b is a schematic structural diagram of a control circuit after the detection circuit and the linear constant current circuit in fig. 6a are integrated on the same chip;
fig. 7 shows a schematic structural diagram of a control circuit in a further embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The topology circuit shown in fig. 1a is usually adopted in linear constant current driving, where "F" is a fuse, and when the current flowing through the fuse exceeds a certain value, the fuse will be blown out, so as to prevent the related circuits connected behind the fuse from generating overcurrent due to abnormal operation. "DB" is a rectifier bridge for rectifying an ac voltage input to the grid into a dc voltage. Without capacitive filtering, the dc voltage rectified by the rectifier bridge fluctuates significantly (e.g., voltage waveform shown in fig. 1 b), so that capacitive "C" filtering is added after the rectifier bridge to perform the functionThe DC voltage with large fluctuation is filtered into DC voltage with small fluctuation. As shown in fig. 1C, the amplitude Δ U of the voltage fluctuation is Umax-U, and depends on the capacity of the capacitor "C" and the magnitude of the output current of the "linear constant current circuit", and when the output current is kept constant, the larger the capacity of the capacitor is, the smaller the amplitude of the voltage fluctuation is, and vice versa, and when the capacity of the capacitor is kept constant, the larger the output current is, the larger the amplitude of the voltage fluctuation is, and vice versa. Continuing with FIG. 1a, "VLED"is the voltage drop added by the series LED loads, and since the lamp requires no stroboflash, it requires" V "forLED"≦" U "if" VLED">" U ", that is, the voltage applied to the LED fluctuates, the current flowing through the LED also fluctuates, and the light emitted from the LED strobes. The linear constant current circuit is used for keeping constant current flowing through an LED, generally comprises an active element (such as a triode, a field effect transistor and the like), an operational amplification circuit and a negative feedback sampling circuit, and is used for controlling the active amplification element to work in an amplification state to actually output constant current. When is "VLEDWhen the current is less than or equal to U, the linear constant current circuit works in an amplifying state, namely a constant current state, and the LED cannot generate stroboflash; when is "VLEDThe ">" U "and the" linear constant current circuit "work in a state of mutual conversion between amplification and saturation, and the LED generates stroboflash; when is "VLED">" Umax "and" linear constant current circuit "work in saturation state, and the stroboscopic of LED appears more obvious. In addition, due to "VD”＝“Umax”-“VLED”，“VD"is the voltage drop borne by the" linear constant current circuit ", thus" VDThe minimum value of the LED is larger than the minimum working voltage of the linear constant current circuit, and the LED can not generate stroboflash.
The voltage of the power grid is not constant across the country, some are lower than the rated voltage (AC220V) and some are higher than the rated voltage. In order to ensure that the lamps adopting linear constant current have no stroboflash within the designed input voltage range, the minimum input voltage rectification and filtration voltage U is required to be higher than VLEDWhen the linear constant current circuit works in a constant current state, the voltage drop of the active element is minimum, and the current is constant, so that the active element is in a constant current stateThe losses are minimal. However, if the input voltage increases, "U" - "VLEDThe "and thus the active element voltage drop increases and the active element losses also increase. The input voltage is maximized within a range of the design input voltage to maximize the loss of the active element.
The following illustrates linear constant current circuit losses as follows: the capacity of the filter capacitor "C" is 4.7uF, VLED 240V @40mA, and the output current of the "linear constant current circuit" is about 40 mA.
Referring to FIG. 2a, if the AC207V voltage is input, by analyzing "VD"the voltage waveform of" V "is knownDThe "average pressure drop is 32V and the amplitude of the fluctuation is 50V. As can be seen from the analysis of the output current waveform of the "linear constant current circuit", the average value of the output current is 0.0384A, and the current waveform starts to have ripples, which is a critical point of the "linear constant current circuit" operating in the amplification state and the state where the amplification and saturation are switched to each other, and when the "linear constant current circuit" has a loss P of 32 × 0.0384 of 1.23W.
Referring to fig. 2b, if the input voltage < AC207V, the "linear constant current circuit" operates in a state where amplification and saturation are switched to each other. With an input voltage of AC180V, by analyzing "VD"the voltage waveform of" V "is knownDThe "average pressure drop was 7.49V and the amplitude of the fluctuation was 12V. As can be seen from an analysis of the output current waveform of the "linear constant current circuit", the ripple of the current waveform is very large, and the average value of the output current is 0.0224A, and in this case, the loss P of the "linear constant current circuit" is 7.49 × 0.0224W.
Referring to fig. 2c, if the input voltage > AC207V, the "linear constant current circuit" operates in an amplified state. With an input voltage of AC260V, by analyzing "VD"the voltage waveform of" V "is knownDThe "average pressure drop was 106.5V and the amplitude of the fluctuation was 53V. When the output current waveform of the "linear constant current circuit" is analyzed, the current waveform has no ripple, and the average value is 0.0383a, so that the loss P of the "linear constant current circuit" is 106.5 × 0.0224, 4.08W.
Referring to fig. 2d, under the condition that the capacity of the filter capacitor "C" and the related parameters of the LED are not changed, the output current of the "linear constant current circuit" is reduced to 0.0228A, input voltage AC207V, by analysis of "VD"the voltage waveform of" V "is knownDThe "average pressure drop is 34V and the amplitude of the fluctuation is 64V. When the output current waveform of the linear constant current circuit is analyzed, the current has no ripple, and the linear constant current circuit works in an amplifying state, and the loss P of the linear constant current circuit is 46.59 multiplied by 0.0228 to 1.06W.
Referring to FIG. 2e, under the condition that the capacity of the filter capacitor "C" and the LED-related parameters are unchanged, if the input voltage AC189V, the "V" is analyzedD"the voltage waveform of" V "is knownDThe "average pressure drop is 20.76V and the amplitude of the fluctuation is 32V. As can be seen from the analysis of the output current waveform of the "linear constant current circuit", the average value of the output current is 0.0229A, and the current waveform starts to have ripples, which is a critical point of the "linear constant current circuit" operating in the amplification state and the state where the amplification and saturation are switched to each other, and the loss P of the "linear constant current circuit" is 20.76 × 0.0229 — 0.48W.
From the above analysis, it can be seen that fig. 2e shows that if the current flowing through the LED of fig. 2a is reduced from 0.0384A to 0.0229A, the critical point voltage of the strobe is also reduced from 207V to 189V, mainly because the voltage fluctuation amplitude across the capacitor "C" is reduced, and according to the above explanation, "when the capacitance of the capacitor is kept unchanged, the larger the output current is, the larger the voltage fluctuation amplitude is, and vice versa, the smaller the voltage fluctuation amplitude is, and it can be proved by comparing fig. 2a with fig. 2 d. There is also a reason why "V" is reduced due to the current flowing through the LEDLEDThe voltage of "is also reduced, thus reducing the current through the LED and lowering the critical point voltage of the strobe.
When designing a linear constant current lamp, factors such as the voltage range of a power grid, no stroboflash, no loss of a linear constant current circuit and the like need to be comprehensively considered. In order to minimize the loss of the linear constant current circuit, the critical point voltage of stroboflash is designed to be as large as possible, but stroboflash can occur when the power grid voltage is low, and in order to solve the contradiction, the output current can be controlled by adding a detection circuit in the linear constant current circuit.
Referring to fig. 3, the embodiment of the present invention provides a control circuit, the control circuit includes a rectifier module (such as the rectifier bridge DB of fig. 3), a capacitor C, a linear constant current circuit 1 and a detection circuit 2, wherein, the rectifier module connects the capacitor C, the capacitor C connects one end of the linear constant current circuit 1, the other end of the linear constant current circuit connects the LED load, and the detection circuit 2 is connected with the linear constant current circuit 1. The rectifying module rectifies the externally input alternating current into direct current, the capacitor element C filters the direct current from the rectifying module,
the detection circuit 2 can detect V in real timeD"voltage when detecting" VDWhen the lowest voltage point in a certain period is smaller than a set value, the output current of the linear constant current circuit 1 is controlled to be reduced until the lowest voltage point of the detection circuit 2 is larger than the set value. When the voltage of the power grid is lower, although the output current of the linear constant current circuit 1 is reduced, the luminous flux of the lamp is reduced, but the lamp does not have stroboflash.
Referring to fig. 3 and 4a, the linear constant current circuit 1 of the present invention includes a constant current driving module 11, and an active element (for example, a MOS transistor in fig. 4 a) and a control module 12 respectively connected to the constant current driving module 11, wherein the control module 12 is configured to control a first reference voltage of the constant current driving module 11, and control a working state of the active element by using the constant current driving module 11; and the constant current driving module 11 is configured to control the active element to be in an amplifying state and provide a constant current for the LED load.
The detection circuit 2 includes an output voltage sampling module 21, and the output voltage sampling module 21 is connected to the control module 12 and the active element, respectively, and is configured to sample the output voltage (i.e., the voltage at the OUT point) of the linear constant current circuit 1 and provide the sampled output voltage to the control module 12.
If the lowest output voltage value of the output voltage provided by the output voltage sampling module 21 to the control module 12 in the preset period is smaller than the set value, the control module 12 controls the first reference voltage of the constant current driving module 11 to decrease, the constant current driving module 11 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 1 is larger than the set value. In this embodiment, the setting value may be the minimum value of the actual output voltage of the linear constant current circuit after the input voltage value is set.
The preset period in this embodiment may be any period, for example, a period of T-1/50 Hz, T-1/100 Hz, etc. is set as the preset period, and the embodiment of the present invention does not specifically limit this period.
The embodiment of the utility model provides a can adjust the output current of linear constant current circuit fast to make output current do not have the ripple, stroboscopic phenomenon appears in the lamps and lanterns of having avoided the circuit place, also realized the overcurrent protection to the circuit. The utility model discloses an in the embodiment, rectifier module can be the direct current with the alternating current rectification of external input, and it can also adopt other rectifier element except can adopting the arrangement bridge to, active element not only can adopt the MOS pipe, can also adopt other active element such as triode, the embodiment of the utility model provides an it does not do specific injecing to this.
Referring to fig. 4a and 4b, in an embodiment of the present invention, the output voltage sampling module 21 may include a comparator U, a first voltage dividing resistor R1, and a second voltage dividing resistor R2 as shown in fig. 4 b. One end of the first voltage-dividing resistor R1 is connected to the second voltage-dividing resistor R2, the other end is connected to the active element (the output end OUT of the linear constant current circuit shown in fig. 4 a), and the other end of the second voltage-dividing resistor R2 is grounded.
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 a second reference voltage Vref1, and the output terminal Vo is connected to the control module 12.
In this embodiment, the comparator U may be configured to sample a voltage (i.e., a voltage at the Vout point) obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor R2, compare the sampled voltage value with the second reference voltage Vref1, and if the comparison result shows that the sampled voltage value is smaller than the second reference voltage Vref1, the output terminal Vo outputs a low level signal to the control module 12, and after the control module 12 receives the low level signal, the first reference voltage of the constant current driving module 11 is controlled to decrease, and thus the output current of the linear constant current circuit decreases.
In addition, if the comparator U compares 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.
In this embodiment, fig. 4c is a waveform diagram of the Vout point voltage of the comparator U and the second reference voltage Vref 1. The Vout point voltage is a fluctuating ripple voltage, and is less than Vref1 when the Vout point voltage is at the bottom of the valley. Fig. 4d shows the voltage waveform output by the output Vo.
Referring to fig. 4e, in an embodiment of the present invention, relative to the connection manner of the comparator U in fig. 4b, the comparator U may further connect the positive input terminal and the negative input terminal in reverse, 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.
In this embodiment, the comparator U may be further configured to sample a voltage obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor R2, compare the sampled voltage value with the second reference voltage Vref1, and if the comparison result shows that the sampled voltage value is smaller 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, so that the output current of the linear constant current circuit decreases. In this embodiment, FIG. 4f shows the voltage waveform output by the output Vo.
In the embodiment of the present invention, the linear constant current circuit output end OUT can also be directly connected to the positive input end of the comparator U, i.e. the first voltage dividing resistor R1 is omitted, and the voltage drop of the second voltage dividing resistor R2 is the output voltage of the linear constant current circuit output end. Furthermore, in the embodiment of the utility model provides an in, output voltage sampling module 21 can also adopt other circuits such as operational amplifier to realize voltage sampling, the embodiment of the utility model provides a do not do specific injecing to this.
The utility model discloses an in the embodiment, for the convenience production and processing, output voltage sampling module 21 and linear constant current circuit can also be integrated in same IC chip, and the biggest output current can be fixed to the IC chip. Referring to fig. 4g, the effective pins of the IC chip include 2 pins, i.e., an output pin OUT (i.e., corresponding to the output terminal of the linear constant current circuit in fig. 4 a) connected to the LED load and a ground pin GND connected to the ground terminal.
In an embodiment of the present invention, the output voltage sampling module 21 can be further configured to be configured to provide the output voltage of the sampled linear constant current circuit for the control module 12, if the output voltage provided to the control module 12 is greater than a 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 work in a cut-off state, the output voltage of the linear constant current circuit is increased, and the output voltage of the linear constant current circuit is consistent with the voltage at the two ends of the capacitor C, the LED load voltage is reduced, so as to realize OVP (overvoltage protection) protection.
Continuing to refer to fig. 4a, in an embodiment of the present invention, the linear constant current circuit further includes an over-temperature protection circuit 13, which is connected to the control module 12, and 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.
In the process of detecting the temperature, the over-temperature protection circuit 13 generates heat due to loss of the IC chip, so that 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 reduces the first reference voltage of the constant current driving module 11, and the output current of the linear constant current circuit is reduced until the temperature of the IC chip is in 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 increases the first reference voltage of the constant current driving module 11, and increases the output current of the linear constant current circuit until the output current of the linear constant current circuit increases to a 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.
Continuing to refer to fig. 4a, in an embodiment of the present invention, the current control circuit further includes a sampling resistor Rs, the linear constant current circuit further includes an output current sampling module 14 connected to the sampling resistor Rs, and the output current sampling module 14 is further connected to the constant current driving module 11, the control module 12, and the active element respectively.
Since the output current of the linear constant current circuit generates a voltage signal after flowing through the sampling resistor Rs, the sampling resistor Rs can convert the output current of the linear constant current circuit into a voltage value.
And the output current sampling module 14 is configured to sample the voltage value converted by the sampling resistor Rs and provide the voltage value to the constant current driving module 11, the constant current driving module 11 obtains an output signal according to the received converted voltage value and the first reference voltage, and when the active element is controlled to be in an amplification state by using the output signal, the constant current is provided for the LED load.
The output current sampling module 14 is further configured to provide the voltage value converted by the sampled sampling resistor Rs to the control module 12, and if the voltage value provided to the control module 12 is greater than a 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, so that the actual OCP protection is realized.
As shown in fig. 4a and 4g, in an 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 device.
Referring to fig. 5, in another embodiment of the present invention, the sampling resistor Rs is replaced for more convenience to adjust the maximum output current conveniently, the sampling resistor Rs can be set outside the IC chip, the IC chip further 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.
With continued reference to fig. 4a, it has been described that the active element may be a transistor or a field effect transistor (MOS transistor). The active element in fig. 4a is a field effect transistor, the gate of the field effect transistor 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.
Referring to fig. 6a and 6b, in an embodiment of the present invention, the current control circuit may further include an internal power circuit 15, and the internal power circuit 15 is connected to the control module 12, the constant current driving module 11, the active element, and the output voltage sampling module 21 respectively, and directly supplies power to the modules and elements connected thereto. The internal power supply circuit 15 may supply power to a module or a circuit not directly connected to the overheat protection circuit 13, the output current sampling module 14, or the like.
In another embodiment of the present invention, when the sampling resistor Rs is disposed outside the IC chip, the internal power circuit 15 can be further connected to the rectifier module, the control module 12, and the constant current driving module 11, respectively, and the dc power rectified by the rectifier module is used to supply power to the module connected thereto. The internal power supply circuit 15 may supply power to a module or a circuit that is not directly connected to the overheat protection circuit 13, the output voltage sampling module 21, the output current sampling module 14, or the like.
In this embodiment, the IC chip further includes a power pin Vin, and the power pin is connected to the internal power circuit 15 and the rectifying module (e.g., the rectifying bridge DB), respectively.
Referring to fig. 7, in an 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 may be used in parallel (fig. 7 shows that two IC chips are connected in parallel, i.e., an IC1 chip and an IC2 chip).
In this embodiment, at least two sampling resistors (fig. 7 shows two sampling resistors, namely, a resistor Rs1 and a resistor Rs1) are included, and the enable pin CS of each IC chip is respectively connected to one sampling resistor, in fig. 7, 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 Rs 2.
In addition, the power pins Vin of at least two IC chips are respectively connected to the rectifier bridge DB, the output pin OUT is respectively connected to the LED load, and the ground pin is respectively connected to the ground.
According to any one of the above preferred embodiments or a combination of a plurality of the above preferred embodiments, the embodiment of the present invention can achieve the following advantageous effects:
the output voltage sampling module is arranged on the basis of the constant current driving circuit to sample the output voltage of the constant current driving circuit in time, when the lowest output voltage value of the output voltage of the constant current driving circuit in a preset period is smaller than a set value, the first reference voltage of the constant current driving module is reduced in time and the active element is controlled to be turned off, so that the output current of the linear constant current circuit is reduced rapidly, the output current is free of ripples, the stroboscopic phenomenon of a lamp where the circuit is located is avoided, and the overcurrent protection of the circuit is also realized. Furthermore, the output current of the linear constant current circuit is reduced, and simultaneously, the stroboscopic critical point voltage is also reduced, so that the loss of the linear constant current circuit is reduced, and the contradiction between the linear constant current stroboscopic and the loss of the linear constant current circuit in a larger voltage input range of a power grid is solved.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments can be modified or some or all of the technical features can be equivalently replaced within the spirit and principles of the present invention; such modifications and substitutions do not depart from the scope of the present invention.
Claims (13)
1. A current control circuit is characterized by comprising a rectifying module, a capacitor element, a linear constant current circuit and an output voltage sampling module, wherein,
the rectifying module is connected with the capacitor element; one end of the capacitor element is connected with the linear constant current circuit, and the other end of the capacitor element is connected with the LED load;
the linear constant current circuit comprises a constant current driving module, and an active element and a control module which are respectively connected with the constant current driving module, wherein the control module is configured to control a first reference voltage of the constant current driving module, and the constant current driving module is used for controlling the working state of the active element; the constant current driving module is configured to control the active element to be in an amplifying state and provide a constant current for the LED load;
the output voltage sampling module is respectively connected with the control module and the active element, and 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 by the output voltage sampling module to the control module in a preset period is smaller than a set value, the control module controls the first reference voltage of the constant current driving module to be reduced, 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 is reduced until the sampled lowest output voltage value of the linear constant current circuit is larger than the set value.
2. The current control circuit of claim 1, wherein the output voltage sampling module comprises: the voltage divider comprises a comparator, a first voltage dividing resistor and a second voltage dividing resistor; wherein the content of the first and second substances,
one end of the first voltage-dividing resistor is connected with the second voltage-dividing resistor, the other end of the first voltage-dividing resistor is connected with the active element, and the other end of the second voltage-dividing resistor is grounded;
the comparator is provided with a positive input end, a negative input end and an output end, wherein the positive input end is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the negative input end receives a second reference voltage, and the output end is connected with the control module;
the comparator is configured to sample a voltage obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor, compare the sampled voltage value with the second reference voltage, and if the sampled voltage value is smaller than the second reference voltage, output a low level to the control module by an output end, wherein the control module controls the first reference voltage of the constant current driving module to be reduced, and the output current of the linear constant current circuit is reduced.
3. The current control circuit of claim 1, wherein the output voltage sampling module comprises: the voltage divider comprises a comparator, a first voltage dividing resistor and a second voltage dividing resistor; wherein the content of the first and second substances,
one end of the first voltage-dividing resistor is connected with the second voltage-dividing resistor, the other end of the first voltage-dividing resistor is connected with the active element, and the other end of the second voltage-dividing resistor is grounded;
the comparator is provided with a positive input end, a negative input end and an output end, wherein the negative input end is connected between the first voltage-dividing resistor and the second voltage-dividing resistor, the positive input end receives a second reference voltage, and the output end is connected with the control module;
the comparator is configured to sample a voltage obtained by dividing the output voltage of the linear constant current circuit by the second voltage dividing resistor, compare the sampled voltage value with the second reference voltage, and if the sampled voltage value is smaller than the second reference voltage, output a high level to the control module by an output end, wherein the control module controls the first reference voltage of the constant current driving module to be reduced, and the output current of the linear constant current circuit is reduced.
4. Current control circuit according to any of claims 1-3,
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 grounding pin, the output pin is connected with the LED load, and the grounding pin is connected with a grounding end.
5. The current control circuit of claim 4,
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 larger than a first preset voltage value, the control module controls the first reference voltage of the constant current driving module to be reduced, the constant current driving module controls the active element to work in a cut-off state, the output voltage of the linear constant current circuit is increased, and the LED load voltage is reduced.
6. The current control circuit of claim 4, wherein the linear constant current circuit further comprises:
the over-temperature protection circuit is connected with the control module and is 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 in 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 driving module, the output current of the linear constant current circuit is increased until the output current of the linear constant current circuit is increased to a preset maximum current, and the temperature of the IC chip is in the preset temperature range.
7. The current control circuit according to claim 4, further comprising a sampling resistor, wherein the linear constant current circuit further comprises an output current sampling module connected to the sampling resistor, and the output current sampling module is further 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 the voltage value to the constant current driving module, the constant current driving module obtains an output signal according to the received converted voltage value and the first reference voltage, and the output signal is used for controlling the active element to be in an amplifying state and 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 be reduced, the constant current driving module controls the active element to work in a cut-off state, and the output current of the linear constant current circuit is reduced to zero.
8. The current control circuit of claim 7,
the sampling resistor is arranged in the IC chip, one end of the sampling resistor is grounded, and the other end of the sampling resistor is connected with an active element.
9. The current control circuit of claim 7,
the sampling resistor is arranged outside the IC chip, the IC chip further comprises an enabling pin, one end of the sampling resistor is grounded, and the other end of the sampling resistor is connected with the enabling pin.
10. The current control circuit of claim 7, wherein the active element comprises a triode or a field effect transistor;
if the active element adopts a field effect transistor, the grid electrode of the field effect transistor is connected with the constant current driving module, the source electrode of the field effect transistor is connected with the output current sampling module, and the drain electrode of the field effect transistor is connected with the output voltage sampling module.
11. The current control circuit of claim 5, further comprising:
and the internal power circuit is respectively connected with the control module, the constant current driving module, the active element and the output voltage sampling module and supplies power to the modules and the elements connected with the internal power circuit.
12. The current control circuit of claim 9, further comprising:
the internal power circuit is connected with the rectifying module, the control module and the constant current driving module respectively, and supplies power to the modules connected with the internal power circuit by using direct current rectified by the rectifying module;
the IC chip further comprises a power supply pin, and the power supply pin is connected with the internal power supply circuit and the rectification module respectively.
13. The current control circuit of claim 11,
the IC chip and the sampling resistor respectively comprise at least two, and an enabling pin of each IC chip is correspondingly connected with one sampling resistor;
the power pins of at least two IC chips are respectively connected with the rectifying module, the output pins are respectively connected with the LED load, and the grounding pins are respectively connected with a ground end.
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| CN201822175352.7U CN209824078U (en) | 2018-12-24 | 2018-12-24 | Current control circuit |
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| CN201822175352.7U CN209824078U (en) | 2018-12-24 | 2018-12-24 | Current control circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109743811A (en) * | 2018-12-24 | 2019-05-10 | 欧普照明股份有限公司 | A kind of current control circuit |
| CN112105123A (en) * | 2020-10-19 | 2020-12-18 | 美芯晟科技（北京）有限公司 | Low-power-consumption constant-current control circuit and method |
-
2018
- 2018-12-24 CN CN201822175352.7U patent/CN209824078U/en active Active
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109743811A (en) * | 2018-12-24 | 2019-05-10 | 欧普照明股份有限公司 | A kind of current control circuit |
| CN112105123A (en) * | 2020-10-19 | 2020-12-18 | 美芯晟科技（北京）有限公司 | Low-power-consumption constant-current control circuit and method |
| CN112105123B (en) * | 2020-10-19 | 2024-01-23 | 美芯晟科技(北京)股份有限公司 | Low-power-consumption constant-current control circuit and method |
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