CN107787093B - Multi-path LED constant current control module, driving circuit and control method - Google Patents
Multi-path LED constant current control module, driving circuit and control method Download PDFInfo
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- CN107787093B CN107787093B CN201711224002.9A CN201711224002A CN107787093B CN 107787093 B CN107787093 B CN 107787093B CN 201711224002 A CN201711224002 A CN 201711224002A CN 107787093 B CN107787093 B CN 107787093B
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- H—ELECTRICITY
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- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
Abstract
The invention provides a multipath LED constant current control module, a driving circuit and a control method, comprising the following steps: a voltage input module; an inductance for outputting stable electric energy; a plurality of LED light strings; the output current sampling modules are in one-to-one correspondence with the LED lamp strings and generate output current sampling signals; an output voltage feedback module that generates an output voltage feedback signal; the multi-channel LED constant current control module is used for generating compensation current and performing constant current and constant voltage control; and a loop compensation module for generating a compensation voltage. And obtaining an output voltage feedback signal and each output current sampling signal, comparing the larger output voltage feedback signal and each output current sampling signal under the same working voltage with a reference voltage, and obtaining a common compensation voltage, so as to adjust the pulse width of a switch control signal and control the output to be constant. The invention processes each current loop signal and each voltage loop signal, shares one compensation network, realizes the buck conversion with constant output characteristic, reduces the number of components of the peripheral compensation network and saves the cost.
Description
Technical Field
The invention relates to a switching type step-down integrated circuit driving and converting technology, in particular to a multipath LED constant current control module, a driving circuit and a control method.
Background
Over the years, control ICs (integrated circuits) for various buck power supplies have been developed and used to achieve control of constant current or constant voltage output, with applications including backup power supplies for LED drivers, chargers, and mobile devices.
In the prior art, voltage information of an output end is obtained by carrying out partial pressure sampling on the output end, a current sampling resistor is connected in series to each output end, information of output end current is obtained according to pressure difference of two ends of the current sampling resistor, error amplification is carried out on each path of signal and a calibration point through an operational amplifier, then the duty ratio of a switch is controlled, and the control of constant current output is realized by utilizing the follow current characteristic of an inductor. In loop control formed by each path of signal, in order to stabilize the loops, each loop is subjected to loop compensation, so that more network components are used for compensation, the whole circuit is large in size, and the integration is not facilitated.
In summary, the current loop signal and the voltage loop signal respectively adopt one compensation network, so that the problems of more components, complicated circuit structure, large volume and the like of the compensation network are one of the problems to be solved urgently by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention aims to provide a multi-channel LED constant current control module, a driving circuit and a control method for sharing compensation, which are used for solving the problems of many components, complicated circuit structure, large volume and the like of the compensation network in the prior art.
To achieve the above and other related objects, the present invention provides a multi-path LED constant current control module, which at least includes:
the device comprises a signal processing unit, a voltage-to-current amplifying unit, a pulse width modulation unit, a first switch and a second switch;
the signal processing unit receives multiple paths of output current sampling signals and output voltage feedback signals of the multiple paths of LED constant current driving circuits, and selects the larger one of the output current sampling signals and the output voltage feedback signals which are positioned under the same working voltage as an output signal;
the input end of the voltage-to-current amplifying unit is respectively connected with the signal processing unit and a reference signal, the output signal of the signal processing unit is compared with the reference signal, the comparison result is converted into a current signal, and then compensation current is output, and the compensation current is connected with the external loop compensation module and is converted into compensation voltage;
the pulse width modulation unit is connected to the output end of the voltage-to-current amplification unit, and adjusts the duty ratio of the control signal of the first switch or the second switch according to the compensation voltage;
the first switch is connected between the input voltage of the multi-path LED constant current driving circuit and the inductor of the multi-path LED constant current driving circuit and is used for controlling the inductor to store and release electric energy so as to control the output current and the output voltage of the multi-path LED constant current driving circuit to be constant;
one end of the second switch is connected with a connecting node of the first switch and the inductor, and the other end of the second switch is grounded and used for controlling a follow current channel from ground to the inductor so as to reduce voltage drop and loss.
Preferably, the signal processing unit comprises a multiplexing output current sampling signal selecting subunit, a voltage converting subunit and a signal selecting subunit;
the multipath output current sampling signal selection subunit receives each output current sampling signal and selects the largest one of the output current sampling signals;
the voltage conversion subunit is connected with the output end of the multipath output current sampling signal selection subunit, and amplifies or reduces the maximum output current sampling signal into an output current conversion signal, wherein the working voltage of the output current conversion signal is consistent with the working voltage of the output voltage feedback signal;
the signal selection subunit is connected with the voltage conversion subunit and the output voltage feedback signal, and selects the larger one of the output current conversion signal and the output voltage feedback signal as the output signal. .
More preferably, the multiple output current sampling signal selecting subunit includes a plurality of one-out-of-two selectors, each one-out-of-two selector is serially connected in turn, and each output current sampling signal sequentially selects the larger one to select the largest output current sampling signal.
More preferably, the multiple output current sampling signal selecting subunit includes multiple two-for-one selectors, each two-for-one selector is connected step by step, the first-stage selector compares each output current sampling signal in parallel two by two, and then each-stage selector sequentially compares the comparison result of the previous stage two by two so as to select the largest output current sampling signal.
More preferably, the voltage conversion subunit comprises an operational amplifier, an NMOS tube, a first resistor and a second resistor; the positive phase input end of the operational amplifier is connected with the output signal of the multi-output current sampling signal selection subunit, the output end of the operational amplifier is connected with the gate end of the NMOS tube, the drain end of the NMOS tube is connected with a power supply, the source end of the NMOS tube is connected with the first resistor and the second resistor in series in sequence and then grounded, and the source end of the NMOS tube outputs the output current conversion signal; and the connection nodes of the first resistor and the second resistor are connected with the inverting input end of the operational amplifier.
More preferably, the signal selecting subunit is a one-out-of-two selector.
More preferably, the signal processing unit further includes a filter connected between each output current sampling signal and the multiple output current sampling signal selector.
To achieve the above and other related objects, the present invention also provides a multi-path LED constant current driving circuit, including at least:
the LED lamp string comprises a voltage input module, the multipath LED constant current control module, a loop compensation module, an inductor, an output voltage feedback module, multipath LED lamp strings and an output current sampling module which corresponds to each LED lamp string one by one;
the voltage input module provides input voltage;
one end of the inductor is connected with the multipath LED constant current control module, and the other end of the inductor is used as a voltage output end and is used for outputting stable output voltage and output current;
one end of each LED lamp string is connected with output voltage, the other end of each LED lamp string is grounded after passing through the output current sampling modules corresponding to the LED lamp strings one by one, and each output current sampling module generates multiple paths of output current sampling signals;
the output voltage feedback module is connected between the output voltage and the ground and is used for generating an output voltage feedback signal;
the multi-path LED constant current control module is connected with the voltage input module, the output voltage feedback module and the output ends of the output current sampling modules, generates compensation current according to the output current sampling signals and the output voltage feedback signals, and performs constant control on the output voltage and the output current under the control of the loop compensation module;
the loop compensation module is connected with the multipath LED constant current control module and is used for generating corresponding compensation voltage according to the compensation current.
Preferably, the output voltage feedback module includes a first sampling resistor and a second sampling resistor connected in series, where the first sampling resistor and the second sampling resistor divide the output voltage to obtain the output voltage feedback signal.
Preferably, the loop compensation module comprises a compensation resistor and a first compensation capacitor, one end of the compensation resistor is connected with the multipath LED constant current control module, the other end of the compensation resistor is connected with the first compensation capacitor, and the other end of the first compensation capacitor is grounded.
Preferably, the loop compensation module further comprises a second compensation capacitor, and one end of the second compensation capacitor is connected with the multipath LED constant current control module, and the other end of the second compensation capacitor is grounded.
Preferably, the multi-path LED constant current driving circuit further includes an output capacitor, and one end of the output capacitor is connected to the voltage output end, and the other end of the output capacitor is grounded.
To achieve the above and other related objects, the present invention provides a multi-path LED constant current control method, which at least includes:
sampling the output voltage and each path of output current, obtaining an output voltage feedback signal and a multipath output current sampling signal, comparing the larger output voltage feedback signal and the multipath output current sampling signal under the same working voltage with a reference voltage, obtaining a corresponding common compensation voltage according to a comparison result, and carrying out pulse width modulation on a switch control signal by using the compensation voltage so as to control output of constant voltage and constant current.
Preferably, the maximum voltage in each path of output current sampling signal is converted to obtain an output current conversion signal, so that the output voltage feedback signal and the output current conversion signal are positioned at the same working voltage, and the following formula is satisfied: senbf=k·sen; wherein SENBF is an output current conversion signal; k is a fixed constant, andV FB is a feedback voltage calibration point in constant voltage output, V CS Sampling voltage calibration points when constant current is output; SEN is the output current sampling signal with the largest value among the output current sampling signals.
Preferably, the constant current of the output current is adjusted by controlling the compensation voltage, and the following relation is satisfied:wherein I is OUT(n) For the nth output current, V CS(n) Is constantThe nth path of sampling voltage during stream output, R CS(n) A sampling resistor for outputting current in the nth path.
Preferably, the constant current of the output voltage is adjusted by controlling the compensation voltage, so as to satisfy the following relation:wherein V is OUT To output voltage V FB For the feedback voltage calibration point at constant voltage output, < >>Is the voltage dividing resistance ratio of the output voltage.
Preferably, the constant current or constant voltage control further includes: when the larger one of the output voltage feedback signal and each output current sampling signal under the same working voltage is larger than the reference voltage, the compensation voltage is reduced; when the larger of the output voltage feedback signal and each output current sampling signal under the same working voltage is smaller than the reference voltage, the compensation voltage is increased.
As described above, the multi-channel LED constant current control module, the driving circuit and the control method have the following beneficial effects:
the multi-path LED constant current control module, the driving circuit and the control method realize the buck conversion with constant current and constant voltage output characteristics by processing the current loop signals and the voltage loop signals and sharing one path of compensation network, so that the number of components serving as peripheral compensation networks is small, and if the compensation networks are built in a chip, the chip area can be reduced more, thereby saving the application cost.
Drawings
Fig. 1 shows a schematic structure of a multi-channel LED constant current driving circuit according to the present invention.
Fig. 2 shows an embodiment of the signal processing unit of the present invention.
Fig. 3 shows a schematic structure of a filtering subunit of the present invention.
Fig. 4 shows another embodiment of the signal processing unit of the present invention.
Fig. 5 is a schematic diagram showing the structure of a voltage converting subunit of the present invention.
Fig. 6 is a schematic diagram of an alternative selector according to the present invention.
Description of element reference numerals
1. Multipath LED constant current driving circuit
11. Voltage input module
12. Multipath LED constant current control module
121. Signal processing unit
1211. Filter subunit
12111. Filtering resistor
12112. Filter capacitor
1212. Multi-output current sampling signal selection subunit
1213. Voltage conversion subunit
12131. Operational amplifier
12132 NMOS tube
12133. First resistor
12134. Second resistor
1214. Signal selection unit
12141. Comparator with a comparator circuit
12142. First transmission gate
12143. Second transmission gate
12144. Inverter with a high-speed circuit
122. Voltage-to-current amplifying unit
123. Pulse width modulation unit
124. First switch
125. Second switch
13. Inductance
14. Output voltage feedback module
141. First sampling resistor
142. Second sampling resistor
151-153 LED lamp string
161-163 output current sampling module
17. Output capacitor
18. Loop compensation module
181. Compensation resistor
182. First compensation capacitor
183. Second compensation capacitor
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
Please refer to fig. 1-6. It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present invention by way of illustration, and only the components related to the present invention are shown in the drawings and are not drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of the components in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.
As shown in fig. 1, the present invention provides a multi-path LED constant current driving circuit 1, the multi-path LED constant current driving circuit 1 includes:
the LED lamp string circuit comprises a voltage input module 11, a plurality of LED constant current control modules 12, an inductor 13, an output voltage feedback module 14, a plurality of LED lamp strings, an output current sampling module, an output capacitor 17 and a loop compensation module 18, wherein the output current sampling module corresponds to each LED lamp string one by one.
As shown in fig. 1, the voltage input module 11 is connected to the input ends of the multiple LED constant current control modules 12, and is configured to provide an input voltage VIN.
Specifically, in this embodiment, the voltage input module 11 is a voltage source. The voltage input module 11 may also convert an ac power to the input voltage VIN by using a rectifying circuit, which is not limited to the embodiment.
As shown in fig. 1, one end of the inductor 13 is connected to the multi-path LED constant current control module 12, and the other end outputs a stable output voltage VOUT and an output current IOUT.
As shown in fig. 1, the output voltage feedback module 14 is connected between the output voltage VOUT and ground for generating an output voltage feedback signal VFB.
Specifically, the output voltage feedback module 14 includes a first sampling resistor 141 and a second sampling resistor 142, and the first sampling resistor 141 and the second sampling resistor 142 divide the output voltage VOUT to obtain the output voltage feedback signal VFB.
As shown in fig. 1, one end of each LED string is connected to the output voltage VOUT, and the other end is grounded after passing through an output current sampling module corresponding to each LED string one by one. In this embodiment, the three LED strings are respectively a first LED string 151, a second LED string 152 and a third LED string 153; the three output current sampling modules, namely the first output current sampling module 161, the second output current sampling module 162 and the third output current sampling module 163, are included, and in practical application, the number of the LED light strings and the corresponding output current sampling modules can be set according to the needs, which is not limited by the embodiment.
Specifically, each output current sampling module is respectively connected in series with each LED string light, and converts the current flowing through each LED string light into output current sampling signals VCS1 to VCSN, wherein each output current sampling signal is a voltage signal. In this embodiment, each output current sampling module is a sampling resistor.
As shown in fig. 1, one end of the output capacitor 17 is connected to the output voltage VOUT, and the other end is grounded.
As shown in fig. 1, the multi-path LED constant current control module 12 is connected to the voltage input module 11, the output voltage feedback module 14, and the output ends of the output current sampling modules, generates a compensation current according to the output voltage feedback signal VFB and the output current sampling signals, and performs constant control on the output voltage VOUT or the output current IOUT under the control of the loop compensation module 18.
Specifically, the multi-path LED constant current control module 12 includes a signal processing unit 121, a voltage-to-current amplifying unit 122, a pulse width modulation unit 123, a first switch 124, and a second switch 125.
More specifically, as shown in fig. 2, the signal processing unit 121 receives the multiple output current sampling signals and the output voltage feedback signal VFB of the multiple LED constant current driving circuit, and selects the larger one of the multiple output current sampling signals and the output voltage feedback signal VFB, which are at the same operating voltage, as the output signal. The signal processing unit 121 includes a filtering subunit 1211, a multiplexed current sample signal selecting subunit 1212, a voltage converting subunit 1213, and a signal selecting subunit 1214.
The filtering subunit 1211 receives each output current sampling signal, and filters each output current sampling signal. The filtering subunit 1211 includes a plurality of filters, each filter being connected between each output current sampling signal and the multi-output current sampling signal selecting subunit 1212, each filter being in one-to-one correspondence with each output current sampling signal. The filter includes, but is not limited to, an RC filter, as shown in fig. 3, in this embodiment, the filter includes a filter resistor 12111 and a filter capacitor 12112; one end of the filter resistor 12111 is connected with the output current sampling signal corresponding to the filter resistor, and the other end is used as the output end of the filter; one end of the filter capacitor 12112 is connected to the output end of the filter, and the other end is grounded.
The multiple output current sampling signal selecting subunit 1212 receives each output current sampling signal and selects the largest one of the output current sampling signals. As an embodiment of the present invention, the multiple output current sampling signal selecting subunit 1212 includes a plurality of one-of-two selectors, each of the one-of-two selectors is serially connected in turn, and each of the output current sampling signals sequentially selects the larger one to select the largest output current sampling signal. As shown in fig. 2, the first two-by-one selector receives the first output current sampling signal CS1 and the second output current sampling signal CS2, selects the larger of the two, then selects the larger of the output signal of the first two-by-one selector and the third output current sampling signal CS3 through the second two-by-one selector, and so on, and finally obtains the maximum output current sampling signal SEN. As another embodiment of the present invention, the multiple output current sampling signal selecting subunit 1212 includes a plurality of two-for-one selectors, each of which is connected in a step-by-step manner, the first-stage selector compares the output current sampling signals two by two, and then each-stage selector sequentially compares the comparison result of the previous stage two by two to select the largest output current sampling signal. As shown in fig. 4, the first alternative selector receives the first output current sampling signal CS1 and the second output current sampling signal CS2, and selects the larger one of the two signals; the second alternative selector receives the third output current sampling signal CS3 and the fourth output current sampling signal CS4, and selects the larger one of the third output current sampling signal CS3 and the fourth output current sampling signal CS 4; the third alternative selector receives the output ends of the first alternative selector and the second alternative selector and selects the larger one of the two; the first selector and the second selector are first-stage selectors, and the third selector is a second-stage selector, and the number of stages of the selectors is correspondingly increased along with the increase of the number of output current sampling signals. If the number of the output current sampling signals is even, carrying out pairwise parallel comparison to obtain the maximum output current sampling signal SEN; if the number of the output current sampling signals is odd, the output current sampling signals with even number are selected for parallel comparison, and finally the output current sampling signals are compared and selected with the output current sampling signals with single output current sampling signals to obtain the maximum output current sampling signal SEN.
The voltage conversion subunit 1213 is connected to the output end of the multiple output current sampling signal selection subunit 1212, and amplifies or reduces the maximum output current sampling signal SEN into an output current conversion signal SENFB, where the working voltage of the output current conversion signal SENFB and the working voltage of the output voltage feedback signal VFB are maintainedAnd consistent. In this embodiment, the voltage conversion subunit 1213 includes an operational amplifier 12131, an NMOS tube 12132, a first resistor 12133 and a second resistor 12134. The non-inverting input end of the operational amplifier 12131 is connected with the output voltage SEN of the multi-output current sampling signal selecting subunit 1212, and the output end is connected with the gate end of the NMOS 12132; the drain end of the NMOS 12132 is connected to a power supply, and the source end is connected to the first resistor 12134 and the second resistor 12134 in series in sequence and then grounded; the drain terminal of the NMOS 12132 outputs the output current conversion signal SENBF; the connection node of the first resistor 12133 and the second resistor 12134 is connected to the inverting input terminal of the operational amplifier 12131. The output current conversion signal SENBF satisfies the following relationship: senbf=k·sen; wherein K is a fixed constant, anVFB is a feedback voltage calibration point during constant voltage output, and VCS is a sampling voltage calibration point during constant current output; SEN is the maximum output current sampling signal. In this embodiment, according to the principle of virtual short and virtual break, the connection node of the first resistor 12133 and the second resistor 12134 is forced to be equal to the maximum output current sampling signal SEN, then ∈ ->By setting the first resistor 12133 and the second resistor 12134, let +.>The required output current conversion signal SENBF can be obtained.
The signal selecting subunit 1214 is connected to the voltage converting subunit 1213 and the output voltage feedback signal VFB, and selects the larger one of the output current converting signal SENBF and the output voltage feedback signal VFB as the output signal DS. The signal selecting subunit 1214 may be implemented by an optional circuit with any structure, and is not limited to the specific structure listed in this embodiment. As shown in fig. 6, in the present embodiment, the signal selecting subunit 1214 includes a comparator 12141, a first transmission gate 12142, a second transmission gate 12143, and an inverter 12144. The comparator 1241 has a non-inverting input connected to the output current conversion signal SENBF, an inverting input connected to the output voltage feedback signal VFB, and an output connected to the inverter 12144. An input end of the first transmission gate 12142 is connected to the output current conversion signal SENBF, an output end thereof is connected to an output end of the second transmission gate 12143 and serves as an output end of the signal selection subunit 1214, a positive control signal thereof is connected to an output signal of the comparator 12141, and a negative control signal thereof is connected to an output end of the inverter 12144; an input terminal of the second transmission gate 12143 is connected to the output voltage feedback signal VFB, an output terminal thereof is connected to an output terminal of the first transmission gate 12142, a normal phase control signal is connected to an output terminal of the inverter 12144, and an inversion control signal is connected to an output signal of the comparator 12141. The circuit structure of the alternative selector in the multiple output current sampling signal selecting subunit 1212 is identical to that of the signal selecting subunit 1214, and is not described herein in detail.
More specifically, the input end of the voltage-to-current amplifying unit 122 is respectively connected to the signal processing unit 121 and a reference signal VREF, compares the output signal DS of the signal processing unit 121 with the reference signal VREF, converts the comparison result into a current signal, and outputs a compensation current, which is connected to the external loop compensation module and converted into a compensation voltage VCOMP. In this embodiment, the inverting input terminal of the voltage-to-current amplifying unit 122 is connected to the output terminal of the signal processing unit 121, and the non-inverting input terminal is connected to the reference voltage VREF. In practical applications, the polarity of the input terminal of the voltage-to-current amplifying unit 122 can be changed by adding an inverter, which is not limited to the present embodiment.
More specifically, the pulse width modulation unit 123 is connected to the output end of the voltage-to-current amplifying unit 122, and adjusts the duty ratio of the control signal of the first switch 124 or the second switch 125 according to the compensation voltage VCOMP.
More specifically, the first switch 124 is connected between the input voltage VIN and the inductor 13, and is used for controlling the inductor 13 to store and release electric energy, so as to control the output current IOUT and the output voltage VOUT of the multi-path LED constant current driving circuit 1 to be constant. When the first switch 124 is turned on, the input voltage VIN charges the inductor 13; when the first switch 124 is turned off, the inductor 13 discharges. The first switch 124 may be implemented with MOS switches including, but not limited to, NMOS and PMOS.
More specifically, one end of the second switch 125 is connected to the connection node of the first switch 124 and the inductor 13, and the other end is grounded, so as to control a freewheeling path from ground to the inductor 13 to reduce voltage drop and loss. The second switch 125 may be implemented by a MOS switch, including but not limited to an NMOS and a PMOS, and in this embodiment, the second switch 125 is an NMOS transistor.
As shown in fig. 1, the loop compensation module 18 is connected to the multi-path LED constant current control module 12, and is configured to generate a corresponding compensation voltage VCOM according to the compensation current.
Specifically, the loop compensation module 18 includes a compensation resistor 181, a first compensation capacitor 182, and a second compensation capacitor 183, one end of the compensation resistor 181 is connected to the multi-path LED constant current control module 12, the other end is connected to the first compensation capacitor 182, and the other end of the first compensation capacitor 182 is grounded; one end of the second compensation capacitor 183 is connected to the multi-path LED constant current control module 12, and the other end is grounded. In some implementations, the second compensation capacitor 183 may be omitted.
The invention also provides a multi-path LED constant current control method, which comprises the following steps:
sampling the output voltage and each path of output current, obtaining an output voltage feedback signal and a multipath output current sampling signal, comparing the larger output voltage feedback signal and the multipath output current sampling signal under the same working voltage with a reference voltage, obtaining a corresponding common compensation voltage according to a comparison result, and carrying out pulse width modulation on a switch control signal by using the compensation voltage so as to control output of constant voltage and constant current.
In this embodiment, a constant current control method is implemented based on the multi-path LED constant current driving circuit 1.
Specifically, the output voltage feedback signal VFB and each output current sampling signal are obtained based on the output voltage feedback module 14 and each output current sampling module, respectively.
Specifically, each output current sampling signal is filtered based on the filtering subunit 1211.
Specifically, the maximum output current sampling signal SEN among the output current sampling signals is selected based on the multi-path output current sampling signal selection subunit 1212; the maximum output current sampling signal SEN is amplified or reduced to an output current conversion signal SENFB based on the voltage conversion subunit 1213, and the operating voltage of the output current conversion signal SENFB is consistent with the operating voltage of the output voltage feedback signal VFB, so as to facilitate comparison of subsequent circuits. In this embodiment, according to the principle of virtual short and virtual break, the connection node of the first resistor 12133 and the second resistor 12134 is forced to be equal to the maximum output current sampling signal SENBy setting the first resistor 12133 and the second resistor 12134, let +.>The required output current conversion signal SENBF is obtained, so that the two input signals of the signal selection subunit 1214 are located at the same level. The required output current conversion signal SENBF satisfies the following relation: senbf=k·sen; wherein K is a fixed constant and +.>V FB Is a feedback voltage calibration point in constant voltage output, V CS And (5) sampling a voltage calibration point for constant current output.
Specifically, the larger one of the output current conversion signal SENBF and the output voltage feedback signal VFB is selected as the output signal DS based on the signal selection subunit 1214.
Specifically, the voltage-to-current amplifying unit 122 compares the output signal DS of the signal selecting subunit 1214 with the reference signal VREF, converts the comparison result into a current signal, and outputs a compensation current.
Specifically, the compensation current is received based on the loop compensation module 18 and converted to a compensation voltage VCOMP. When the larger of the output voltage feedback signal VFB and the output current conversion signal SENBF is greater than the reference voltage VREF, the compensation voltage VCOMP decreases; when the larger of the output voltage feedback signal VFB and the output current conversion signal SENBF is smaller than the reference voltage VREF, the compensation voltage VCOMP increases.
Specifically, the pulse width modulation unit 123 adjusts the on-time of the first switch 124 and the second switch 125 under the control of the compensation voltage VCOMP, so as to achieve the constant output voltage VOUT of the multi-path LED constant current driving circuit 1 and the constant output current through each LED string. In this embodiment, the output voltage VOUT satisfies the following relationship:wherein V is OUT To output voltage V FB For the feedback voltage calibration point at constant voltage output, < >>A dividing resistance ratio for the output voltage; the output current satisfies the following relation: />Wherein I is OUT(n) For the nth output current, V CS(n) The n-th path of sampling voltage is the constant current output, R CS(n) A sampling resistor for outputting current in the nth path.
More specifically, the first switch control signal HS of the pulse width modulation unit 123 controls the first switch 124, and in each period, the first switch control signal HS adjusts the on time of the first switch 124 according to the difference of the compensation voltage VCOMP values, which are in positive relationship. The second switch control signal LS of the pulse width modulation unit 123 controls the second switch 125, and the second switch control signal LS is related to the operation states of the first switch 124 and the inductor 13. The first switch 124 and the second switch 125 form two current loops: a first loop, in which when the first switch control signal HS controls the first switch 124 to be turned on and the second switch control signal LS controls the second switch 125 to be turned off, the voltage input module 11 is pressurized to the inductor 13 through the first switch 124, the lx end is at a high level, the VOU passes through the first switch 124 and the inductor 13, and then passes through each LED string and the output current sampling module corresponding to each LED string, and returns to the ground end of the voltage input module 11; in the second loop, after the first switch control signal HS controls the first switch 124 to be turned off, because of the freewheeling characteristic of the inductor 13, the voltage at two ends of the inductor 13 is inverted, the VOUT end is at a high level, the LX end is at a low level, the current gradually decreases, the current passes from the ground to the LX end through the second switch 125 and flows into the inductor 13, and then returns to the ground through each LED string and the output current sampling module corresponding to each LED string, when the current decreases to zero, that is, the voltage at the LX end is the same as the ground, the second switch control signal LS controls the second switch 125 to be turned off. That is, the first switch control signal HS and the second switch control signal LS control the first switch 124 and the second switch 125, which are characterized in that: when the first switch 124 is turned on, the second switch 125 is turned off; the second switch 125 is turned on only when the first switch 124 is turned off and LX voltage is lower than ground.
The multi-path LED constant current control module, the driving circuit and the control method realize the buck conversion with constant current and constant voltage output characteristics by processing the voltage loop signals and the current loop signals and sharing one path of compensation network, so that the number of components using the peripheral compensation network is less, and the chip area can be reduced more when the compensation network is arranged in a chip.
In summary, the present invention provides a multi-path LED constant current control module, a driving circuit and a control method, including: a voltage input module for providing an input voltage; an inductance for outputting stable electric energy; a plurality of LED light strings; the output current sampling modules are in one-to-one correspondence with the LED lamp strings and generate output current sampling signals; an output voltage feedback module that generates an output voltage feedback signal; the multi-channel LED constant current control module generates compensation current according to each output current sampling signal and output voltage feedback signal and is controlled by the loop compensation module to perform constant current and constant voltage control; and the loop compensation module generates corresponding compensation voltage according to the compensation current. Sampling the output voltage and each path of output current, obtaining an output voltage feedback signal and a multipath output current sampling signal, comparing the larger output voltage feedback signal and the multipath output current sampling signal under the same working voltage with a reference voltage, obtaining a corresponding common compensation voltage according to a comparison result, and carrying out pulse width modulation on a switch control signal by using the compensation voltage so as to control output of constant voltage and constant current. The multipath LED constant current control module, the driving circuit and the control method realize the buck conversion with constant current and constant voltage output characteristics by processing the current loop signals and the voltage loop signals and sharing one path of compensation network, so that the quantity of components serving as a peripheral compensation network is less, and the chip area can be reduced more when the compensation network is arranged in a chip. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The above embodiments are merely illustrative of the principles of the present invention and its effectiveness, and are not intended to limit the invention. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications and variations of the invention be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.
Claims (14)
1. A multipath LED constant current control module is characterized in that: the multipath LED constant current control module at least comprises:
the device comprises a signal processing unit, a voltage-to-current amplifying unit, a pulse width modulation unit, a first switch and a second switch;
the signal processing unit receives multiple paths of output current sampling signals and output voltage feedback signals of the multiple paths of LED constant current driving circuits, and selects the larger one of the output current sampling signals and the output voltage feedback signals which are positioned under the same working voltage as an output signal;
the input end of the voltage-to-current amplifying unit is respectively connected with the signal processing unit and a reference signal, the output signal of the signal processing unit is compared with the reference signal, the comparison result is converted into a current signal, and then compensation current is output, and the compensation current is connected with the external loop compensation module and is converted into compensation voltage;
the pulse width modulation unit is connected to the output end of the voltage-to-current amplification unit, and adjusts the duty ratio of the control signal of the first switch or the second switch according to the compensation voltage;
the first switch is connected between the input voltage of the multi-path LED constant current driving circuit and the inductor of the multi-path LED constant current driving circuit and is used for controlling the inductor to store and release electric energy so as to control the output current and the output voltage of the multi-path LED constant current driving circuit to be constant;
one end of the second switch is connected with a connecting node of the first switch and the inductor, and the other end of the second switch is grounded and used for controlling a follow current channel from ground to the inductor so as to reduce voltage drop and loss.
2. The multi-channel LED constant current control module of claim 1, wherein: the signal processing unit comprises a multipath output current sampling signal selection subunit, a voltage conversion subunit and a signal selection subunit;
the multipath output current sampling signal selection subunit receives each output current sampling signal and selects the largest one of the output current sampling signals;
the voltage conversion subunit is connected with the output end of the multipath output current sampling signal selection subunit, and amplifies or reduces the maximum output current sampling signal into an output current conversion signal, wherein the working voltage of the output current conversion signal is consistent with the working voltage of the output voltage feedback signal;
the signal selection subunit is connected with the voltage conversion subunit and the output voltage feedback signal, and selects the larger one of the output current conversion signal and the output voltage feedback signal as the output signal.
3. The multi-channel LED constant current control module of claim 2, wherein: the multi-channel output current sampling signal selection subunit comprises a plurality of two-out-of-one selectors, each two-out-of-one selector is sequentially connected in series, and each output current sampling signal sequentially selects the larger one so as to select the largest output current sampling signal.
4. The multi-channel LED constant current control module of claim 2, wherein: the multi-channel output current sampling signal selection subunit comprises a plurality of two-in-one selectors, each two-in-one selector is connected step by step, the first-stage selector compares each output current sampling signal in parallel, and then each-stage selector sequentially compares the previous-stage comparison result in pairs so as to select the largest output current sampling signal.
5. The multi-channel LED constant current control module according to any one of claims 2 to 4, wherein: the voltage conversion subunit comprises an operational amplifier, an NMOS tube, a first resistor and a second resistor; the positive phase input end of the operational amplifier is connected with the output signal of the multi-output current sampling signal selection subunit, the output end of the operational amplifier is connected with the gate end of the NMOS tube, the drain end of the NMOS tube is connected with a power supply, the source end of the NMOS tube is connected with the first resistor and the second resistor in series in sequence and then grounded, and the source end of the NMOS tube outputs the output current conversion signal; and the connection nodes of the first resistor and the second resistor are connected with the inverting input end of the operational amplifier.
6. The multi-channel LED constant current control module according to any one of claims 2 to 4, wherein: the signal selecting subunit is a two-out selector.
7. The multi-channel LED constant current control module according to any one of claims 2 to 4, wherein: the signal processing unit further comprises a filter connected between each output current sampling signal and the multiple output current sampling signal selector.
8. The utility model provides a multichannel LED constant current drive circuit which characterized in that, multichannel LED constant current drive circuit includes at least:
the LED lamp comprises a voltage input module, a multi-channel LED constant current control module, a loop compensation module, an inductor, an output voltage feedback module, a multi-channel LED lamp string and an output current sampling module which is in one-to-one correspondence with each LED lamp string, wherein the multi-channel LED constant current control module is as defined in any one of claims 1-7;
the voltage input module provides input voltage;
one end of the inductor is connected with the multipath LED constant current control module, and the other end of the inductor is used as a voltage output end and is used for outputting stable output voltage and output current;
one end of each LED lamp string is connected with output voltage, the other end of each LED lamp string is grounded after passing through the output current sampling modules corresponding to the LED lamp strings one by one, and each output current sampling module generates multiple paths of output current sampling signals;
the output voltage feedback module is connected between the output voltage and the ground and is used for generating an output voltage feedback signal;
the multi-path LED constant current control module is connected with the voltage input module, the output voltage feedback module and the output ends of the output current sampling modules, generates compensation current according to the output current sampling signals and the output voltage feedback signals, and performs constant control on the output voltage and the output current under the control of the loop compensation module;
the loop compensation module is connected with the multipath LED constant current control module and is used for generating corresponding compensation voltage according to the compensation current.
9. The multi-channel LED constant current drive circuit of claim 8, wherein: the output voltage feedback module comprises a first sampling resistor and a second sampling resistor which are connected in series, and the first sampling resistor and the second sampling resistor divide the output voltage so as to obtain the output voltage feedback signal.
10. The multi-channel LED constant current drive circuit of claim 8, wherein: the loop compensation module comprises a compensation resistor and a first compensation capacitor, one end of the compensation resistor is connected with the multipath LED constant current control module, the other end of the compensation resistor is connected with the first compensation capacitor, and the other end of the first compensation capacitor is grounded.
11. The multi-channel LED constant current drive circuit of claim 10, wherein: the loop compensation module further comprises a second compensation capacitor, one end of the second compensation capacitor is connected with the multipath LED constant current control module, and the other end of the second compensation capacitor is grounded.
12. The multi-channel LED constant current drive circuit of claim 8, wherein: the multi-path LED constant current driving circuit further comprises an output capacitor, wherein one end of the output capacitor is connected with the voltage output end, and the other end of the output capacitor is grounded.
13. The multi-path LED constant current control method is characterized by at least comprising the following steps:
sampling the output voltage and each path of output current to obtain an output voltage feedback signal and a multipath output current sampling signal, and comparing the larger of the output voltage feedback signal and the multipath output current sampling signal under the same working voltage with a reference voltage; the maximum of the output current sampling signals is voltage-converted to obtain an output current conversion signal, so that the output voltage feedback signal and the output current conversion signalAt the same operating voltage, the following formula is satisfied: senbf=k·sen; wherein SENBF is an output current conversion signal; k is a fixed constant, andV FB is a feedback voltage calibration point in constant voltage output, V CS Sampling voltage calibration points when constant current is output; SEN is the output current sampling signal with the largest median value of the output current sampling signals;
obtaining corresponding common compensation voltage according to the comparison result, and performing pulse width modulation on a switch control signal by using the compensation voltage so as to control and output constant voltage and constant current; and regulating the constant current of the output current through the control of the compensation voltage, wherein the following relation is satisfied:wherein I is OUT(n) For the nth output current, V CS(n) The n-th path of sampling voltage is the constant current output, R CS(n) A sampling resistor for outputting current for the nth path; and regulating the constant current of the output voltage by controlling the compensation voltage, wherein the following relation is satisfied: />Wherein V is OUT To output voltage V FB For the feedback voltage calibration point at constant voltage output, < >>Is the voltage dividing resistance ratio of the output voltage.
14. The multi-channel LED constant current control method of claim 13, wherein: the constant current or constant voltage control further includes:
when the larger one of the output voltage feedback signal and each output current sampling signal under the same working voltage is larger than the reference voltage, the compensation voltage is reduced; when the larger of the output voltage feedback signal and each output current sampling signal under the same working voltage is smaller than the reference voltage, the compensation voltage is increased.
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| CN111669875A (en) * | 2019-02-20 | 2020-09-15 | 江苏师范大学 | Control method of LED emergency lamp |
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| CN114189962A (en) * | 2021-12-17 | 2022-03-15 | 深圳民爆光电股份有限公司 | High-precision LED constant-current driving circuit and driving power supply thereof |
| CN115835449B (en) * | 2023-02-16 | 2023-05-16 | 东莞锐视光电科技有限公司 | Current stability control method and system for LED light source |
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| CN106658868A (en) * | 2017-02-16 | 2017-05-10 | 深圳市晟碟半导体有限公司 | LED driving apparatus, and line voltage compensation circuit and compensation method thereof |
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