CN116742945A - High-precision constant-current control circuit, switching power supply and lighting equipment - Google Patents

High-precision constant-current control circuit, switching power supply and lighting equipment Download PDF

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Publication number
CN116742945A
CN116742945A CN202310646985.4A CN202310646985A CN116742945A CN 116742945 A CN116742945 A CN 116742945A CN 202310646985 A CN202310646985 A CN 202310646985A CN 116742945 A CN116742945 A CN 116742945A
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CN
China
Prior art keywords
current
circuit
power supply
input end
voltage
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Pending
Application number
CN202310646985.4A
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Chinese (zh)
Inventor
黄宇
朱小安
邵宇
梁育
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Shenzhen Core Semiconductor Co ltd
Guangzhou Institute of Technology of Xidian University
Original Assignee
Shenzhen Core Semiconductor Co ltd
Guangzhou Institute of Technology of Xidian University
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Application filed by Shenzhen Core Semiconductor Co ltd, Guangzhou Institute of Technology of Xidian University filed Critical Shenzhen Core Semiconductor Co ltd
Priority to CN202310646985.4A priority Critical patent/CN116742945A/en
Publication of CN116742945A publication Critical patent/CN116742945A/en
Pending legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/38—Means for preventing simultaneous conduction of switches
    • H02M1/385—Means for preventing simultaneous conduction of switches with means for correcting output voltage deviations introduced by the dead time
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • G05F1/561—Voltage to current converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • H02M3/1582—Buck-boost converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a high-precision constant current control circuit, a switching power supply and lighting equipment, wherein the high-precision constant current control circuit comprises: the first input end of the error sampling circuit is connected with the output end of the switching tube, the second input end of the error sampling circuit is used for being connected with a first reference power supply, and the error sampling circuit is used for collecting average current flowing through the inductor and outputting a corresponding error detection signal according to the deviation between the average current and the first reference power supply; the turn-off time length modulation circuit is used for adjusting the turn-off time length of the switching tube in each working period according to the error detection signal so as to adjust the average current value flowing through the inductor to a preset current value; the technical scheme of the invention aims to solve the problem that when the switching power supply is influenced by input and output voltages, the output current fluctuates, and the constant current precision of the switching power supply is poor.

Description

High-precision constant-current control circuit, switching power supply and lighting equipment
Technical Field
The invention relates to the technical field of constant current dimming, in particular to a high-precision constant current control circuit, a switching power supply and lighting equipment.
Background
At present, the input voltage of the switching power supply is usually supplied by an alternating current power grid, a storage battery and the like, and the power supplies are often impure, so that the voltage accessed by the switching power supply can be greatly changed due to fluctuation of the power supply, the output voltage of the switching power supply is influenced, in addition, when the load LED is changed or disturbance occurs in the system, the output voltage of the system is correspondingly changed, the output current is not always kept constant, fluctuation is generated, and the constant current precision of the switching power supply is poor.
Disclosure of Invention
The invention mainly aims to provide a high-precision constant-current control circuit, a switching power supply and lighting equipment, and aims to solve the problem that when the switching power supply is influenced by input and output voltages, output current fluctuates, and the constant-current precision of the switching power supply is poor.
In order to achieve the above object, the high-precision constant current control circuit provided by the invention is applied to a switching power supply, the switching power supply comprises an inductor, a switching tube and a driving module, the inductor and the switching tube are sequentially connected in series between a direct current power supply and the ground, the driving module is connected with a controlled end of the switching tube, and the high-precision constant current control circuit comprises:
the first input end of the error sampling circuit is connected with the output end of the switching tube, the second input end of the error sampling circuit is used for being connected with a first reference power supply, and the error sampling circuit is used for collecting average current flowing through the inductor and outputting a corresponding error detection signal according to the deviation between the average current and the first reference power supply;
the first input end of the turn-off duration modulation circuit is connected with the output end of the switching tube, the third input end of the turn-off duration modulation circuit is connected with the output end of the error sampling circuit, the output end of the turn-off duration modulation circuit is used for being connected with the driving module, and the turn-off duration of the switching tube in each working period is adjusted according to the error detection signal so as to adjust the average current value flowing through the inductor to a preset current value.
Optionally, the off-time length modulation circuit includes:
the input end of the voltage-current conversion circuit is connected with the output end of the error sampling circuit and is used for carrying out voltage-current processing on the accessed error detection signal and outputting corresponding error current;
the first input end of the regulating circuit is connected with the output end of the voltage-current conversion circuit, the second input end of the regulating circuit is used for being connected with a conduction control signal, and the regulating circuit is used for discharging stored electric energy when the conduction control signal is received and charging according to the error current when the conduction control signal is not received;
and the positive phase input end of the comparator is used for accessing a first reference voltage, the negative phase input end of the comparator is electrically connected with the regulating circuit, and the comparator is also used for outputting a conduction trigger signal to the driving module when detecting that the terminal voltage of the regulating circuit reaches a first reference voltage.
Optionally, the off-time length modulation circuit includes:
the current mirror is electrically connected with the output end of the voltage-current conversion circuit and is used for mirroring the error current and outputting corresponding mirror current;
the first capacitor is connected in series between the negative phase output end of the comparator and the ground and is used for storing electric energy when the error current is received and discharging the electric energy when the mirror current is not received;
the charge-discharge control circuit is respectively and electrically connected with the current mirror, the first capacitor and the comparator, the controlled end of the charge-discharge control circuit is used for being connected with a conduction control signal, the charge-discharge control circuit is also used for controlling the first capacitor to discharge when receiving the conduction control signal, grounding the negative-phase input end of the comparator, and controlling the first capacitor to charge when not receiving the conduction control signal.
Optionally, the adjusting circuit includes a first MOS transistor and a second MOS transistor;
the drain electrode of the first MOS tube is connected with the output end of the current mirror, the grid electrode of the first MOS tube is used for being connected with the conduction control signal and the grid electrode of the second MOS tube, and the source electrode of the first MOS tube is respectively connected with the source electrode of the second MOS tube, the first end of the first capacitor and the negative phase input end of the comparator; and the source electrode of the second MOS tube is grounded.
Optionally, the first reference power supply specifically includes a second reference voltage, and the error sampling circuit includes:
the current sampling resistor is connected in series between the output end of the switching tube and the ground and is used for outputting corresponding sampling voltage;
the first input end of the digital low-pass filter is electrically connected with the current sampling resistor, the second end of the digital low-pass filter is used for being connected with the second reference voltage, the output end of the digital low-pass filter is connected with the input end of the turn-off duration modulation circuit, and the low-pass filter is used for comparing the sampling voltage with the second reference voltage and outputting a corresponding error detection signal.
Optionally, the error detection signal is specifically an error voltage, and the digital low-pass filter includes:
the first input end of the modulator is electrically connected with the current sampling resistor, the second input end of the modulator is used for being connected with the second reference voltage, and the modulator is also used for performing signal processing on the second reference voltage and the sampling voltage and outputting a corresponding error digital signal;
the input end of the counter is connected with the output end of the modulator, and the counter is used for counting the received error digital signals and outputting corresponding counting error digital signals;
the input end of the digital-to-analog conversion module is connected with the output end of the counter, the output end of the digital-to-analog conversion module is connected with the input end of the turn-off duration modulation circuit, and the digital-to-analog conversion module is used for carrying out digital-to-analog conversion processing on the accessed counting error digital signal and outputting an error detection signal of a corresponding analog voltage value.
Optionally, the high-precision constant current control circuit further includes:
the input end of the reference voltage modulation circuit is used for being connected with a constant voltage source, the controlled end of the reference voltage modulation circuit is used for being connected with a voltage regulation control signal, the output end of the reference voltage modulation circuit is connected with the second input end of the error sampling circuit, and the reference voltage modulation circuit is used for carrying out signal processing on the first reference power supply according to the received voltage regulation control signal so as to output the first reference power supply with a corresponding voltage value.
Optionally, the high-precision constant current control circuit further includes:
the first input end of the current peak value control circuit is connected with the output end of the switching tube, the second input end of the current peak value control circuit is used for being connected with a second reference power supply, the output end of the current peak value control circuit is electrically connected with the driving module, the current peak value control circuit is also used for collecting current flowing through the inductor, and when the current flowing through the inductor is larger than a current value represented by the second reference power supply, a turn-off control signal is output.
The invention also provides a switching power supply which comprises a BUCK circuit and the high-precision constant current control circuit;
the BUCK circuit is used for accessing alternating current and is electrically connected with the high-precision constant-current control circuit; and the constant current source is used for outputting stable constant current under the control of the high-precision constant current control circuit.
The invention also provides a lighting device comprising the LED and the switch power supply.
According to the technical scheme, when the output voltage of the switching power supply changes, a corresponding switching-off time length adjusting signal is output according to the received error detection signal, the switching-off time length of the switching tube in the working period and the working period after the working period is controlled by the driving module, the product of the output voltage and the dead time length is kept unchanged all the time by adjusting the dead time length, so that the peak-valley difference of the inductance current is kept constant, the average current flowing through the inductance is kept unchanged, namely the output current of the switching power supply is kept constant, and the problem that the constant current precision of the switching power supply is poor due to the fact that the output current fluctuates due to the fluctuation of the output voltage of the switching power supply is avoided.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a high precision constant current control circuit according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of another embodiment of a high precision constant current control circuit according to the present invention;
FIG. 3 is a schematic diagram of a high-precision constant current control circuit according to another embodiment of the present invention;
FIG. 4 is a schematic diagram of a high-precision constant current control circuit according to another embodiment of the present invention;
FIG. 5 is a schematic diagram of a high-precision constant current control circuit according to another embodiment of the present invention;
FIG. 6 is a schematic diagram of a high-precision constant current control circuit according to another embodiment of the present invention;
fig. 7 is a current waveform diagram of the high-precision constant current control circuit of the present invention.
Reference numerals illustrate:
the achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Furthermore, descriptions such as those referred to as "first," "second," and the like, are provided for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implying an order of magnitude of the indicated technical features in the present disclosure. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
The invention provides a high-precision constant-current control circuit which is applied to a switching power supply.
Referring to fig. 1, in an embodiment, the switching power supply includes an inductor, a switching tube, and a driving module, where the inductor and the switching tube are sequentially connected in series between the dc power supply and the ground, and the driving module is connected with a controlled end of the switching tube M, and the high-precision constant current control circuit includes:
the first input end of the error sampling circuit 100 is connected with the output end of the switching tube M, and the second input end of the error sampling circuit is used for being connected with a first reference power supply and outputting a corresponding error detection signal according to the deviation between the average current and the first reference power supply;
the first input end of the turn-off duration modulating circuit 200 is connected with the output end of the switching tube M, the third input end of the turn-off duration modulating circuit 200 is connected with the output end of the error sampling circuit 100, the output end of the turn-off duration modulating circuit is connected with the driving module, and the turn-off duration modulating circuit 200 is further used for adjusting the turn-off duration of the switching tube M in each working period according to the error detection signal so as to adjust the average current value flowing through the inductor to a preset current value.
It can be understood that the existing switching power supply can carry out PWM chopping on the accessed direct current according to the requirements of electric equipment when in normal operation, and the output current is regulated by regulating the duty ratio of PWM signals. The output current of the switching power supply can be according to the formula(I average For the average current flowing through the inductance, i.e. the actual output current of the switching power supply, I pk For peak current through inductance ΔI L Peak-to-valley difference of inductor current) is found at the current peak I pk When the peak-valley difference delta I of the inductive current is fixed L To keep stable, thereby enabling the output current I of the switching power supply average Constant. The switching power supply is internally provided with a peak current control circuit, when the switching power supply works normally, once the current flowing through the inductor is detected to reach a preset peak value, the switching tube M is controlled to be turned off, and the current flowing through the inductor is controlled to stop rising, so that the peak value of the current flowing through the inductor is always a constant value, namely I pk As a result, the average current flowing through the inductor is equal to the peak-to-valley difference ΔI of the inductor L Related to the following.
Wherein, the peak-valley difference delta I of the inductance current L Can be according to the formula(V IN Input power for switching power supplyPressure V OUT L is the inductance value of the inductor, T is the output voltage of the switching power supply ON For on time, T OFF For turn-off time), the turn-on time or turn-off time is fixed when the input voltage and the output voltage are stable, so that the peak-valley difference delta I of the inductance current can be well caused L Constant, thereby maintaining the output current I of the switching power supply average Constant.
In this embodiment, the error sampling circuit 100 includes two parts, namely sampling and error detection, wherein the sampling may adopt a current sampling resistor, the error detection may adopt a transconductance amplifier 120, a comparator 230 or other operational amplifier devices, the error sampling circuit 100 acquires and integrates the current of the on period of the switching tube M to obtain the average current of the on period of the working period, as shown in fig. 7, when the switching power supply is in the working and CCM modes, the average current of the on period is the same as the average current of the off period, so that the average current of the working period can be obtained by obtaining the average current of the on period of the working period, thereby obtaining a corresponding error value according to the first reference power supply and outputting an error detection signal representing the error value; the turn-off duration modulation circuit 200 may be a composite circuit composed of a plurality of MOS transistors, capacitors, and the like.
It should be noted that, the input voltage of the switching power supply is usually supplied by an ac power grid, a storage battery, etc., these power supplies are often impure, which makes the voltage of the switching power supply connected to the switching power supply change greatly due to the fluctuation of the power supply, so that the output voltage of the switching power supply is affected, in addition, when the load LED changes or the disturbance occurs in the system, the output voltage of the system also changes correspondingly, according to the following conditionsWhen the output voltage of the switching power supply changes, if the switching tube M is turned off for a time T OFF Kept constant, the peak-valley difference delta I of the inductance current is caused L Changes in the influence received, at I pk On the premise of being constant, due to +.>So that the output current I of the switching power supply average Is affected.
In order to prevent the output current of the switching power supply from being caused by the output voltage V of the switching power supply OUT Is varied and fluctuates, and is required to output voltage V OUT When changing, turn-off time T of switch tube M OFF Based on the adaptive adjustment, the invention sets the turn-off time length modulation circuit 200 to output voltage V of the switching power supply OUT When the switching tube M changes, a corresponding switching-off duration adjusting signal is output according to the received error detection signal, and the switching-off duration of the switching tube M in the working period and the following working periods is controlled through the driving module. Thereby maintaining V by adjusting the off-time period OUT And T is OFF The product of (2) is always kept unchanged, so that the peak-valley difference delta I of the inductive current L To maintain constant and thus the average current I flowing through the inductor average The constant output current of the switching power supply is realized. Therefore, the switching-off duration modulation circuit 200 adjusts the switching-off duration of the switching tube M, so that the problem that the constant current precision of the switching power supply is poor due to fluctuation of the output voltage of the switching power supply and fluctuation of the output current can be avoided.
When the constant current circuit works normally, the error sampling circuit 100 collects the average current flowing in the on period, if the power supply fluctuates or the internal resistance of the load device changes suddenly, the error sampling circuit 100 detects that the average current in the on period also changes, and outputs a corresponding error detection signal to the turn-off time control circuit 200. The turn-off duration modulating circuit 200 determines an error between the average current in the on time and the first reference power according to the error detection signal, so as to output a corresponding turn-off duration adjusting signal according to the error, so as to maintain V by adjusting the turn-off duration of the switching transistor M OUT And T is OFF Is constant.
For example, the off-time length modulation circuit 200, when determining that the average current is large based on the error detection signal, saysAt the moment of brightness output voltage V OUT The off-time modulating circuit 200 outputs an off-time adjusting signal representing the extension of the off-time to the driving circuit to increase the off-time T of the switching tube M in each working period OFF To maintain the output voltage V OUT And the turn-off time length T OFF The product of (2) is constant and the output current is reduced. Similarly, when it is determined that the average current flowing through the inductor is smaller according to the error detection signal, the turn-off duration modulation circuit 200 outputs a turn-off duration adjustment signal indicating that the turn-off duration is shortened to the driving circuit, so that the driving circuit reduces the turn-off duration T of the switching tube M in each working period OFF To maintain the output voltage V OUT And the turn-off time length T OFF The product of (2) is constant and the output current is increased. By fixing V OUT And T is OFF To fix DeltaI L The current accuracy is improved.
The invention sets the switch-off time length modulation circuit 200 to output voltage V of the switch power supply OUT When the change occurs, a corresponding turn-off time length adjusting signal is output according to the received error detection signal, the turn-off time length of the switching tube M in the working period and the following working periods is controlled by the driving module, and the dead time length is adjusted to keep V OUT And T is OFF The product of (a) is kept constant all the time, thereby the peak-valley difference delta I of the inductive current is obtained L Keep constant, keep the average current I flowing through the inductor averape The constant output current of the switching power supply is kept unchanged, so that the problem that the constant current precision of the switching power supply is poor due to fluctuation of the output voltage of the switching power supply and fluctuation of the output current is avoided.
Referring to fig. 1 to 2, in an embodiment, the off-time period modulation circuit 200 includes:
the input end of the voltage-current conversion circuit 210 is connected with the output end of the error sampling circuit 100, and is used for performing voltage-current processing on the accessed error detection signal and outputting a corresponding error current;
a first input end of the regulating circuit 220 is connected to an output end of the voltage-current converting circuit 210, a second input end of the regulating circuit 220 is used for accessing a conduction control signal, the regulating circuit 220 is used for discharging stored electric energy when the conduction control signal is received, and charging according to the error current when the conduction control signal is not received;
the positive phase input end of the comparator 230 is used for accessing a first reference voltage, the negative phase input end of the comparator 230 is electrically connected with the first capacitor, and the comparator 230 is further used for outputting a conduction trigger signal to the driving module when detecting that the terminal voltage of the regulating circuit 220 reaches the first reference voltage.
In this embodiment, when the switching power supply works normally, the error detection signal output by the error sampling circuit 100 is input to the voltage-current conversion circuit 210, and since the error detection signal is a voltage signal, after the voltage-current conversion by the voltage-current conversion circuit 210, a corresponding error current can be output as the charging current of the adjusting circuit 220, the current value of the error current is positively correlated with the error represented by the error detection signal, and the magnitude of the error represented by the error detection signal can automatically adjust the magnitude of the error current.
When the adjusting circuit 220 receives the on control signal, it indicates that the switching tube M is in the on period, and at this time, the adjusting circuit 220 discharges the stored electric energy and controls the negative phase input terminal of the comparator 230 to be grounded, so that the terminal voltage of the negative phase input terminal of the comparator 230 is always lower than the terminal voltage of the positive phase input terminal of the comparator 230, and output 1, it should be noted that the comparator 230 is only valid when output is 0, that is, when output of the comparator 230 is 1, no influence is caused to the current working state of the switching tube M.
When the adjusting circuit 220 stops receiving the on control signal, it is indicated that the switching tube M starts to enter the off period and starts to store the received error current, and in this process, the terminal voltage of the negative phase input terminal of the comparator 230 is lower than the terminal voltage of the positive phase input terminal of the comparator 230, and is still output as 1, so that the switching tube M remains in the off state until the voltage value output by the adjusting circuit 220 reaches the first reference voltage again, the terminal voltage of the negative phase input terminal of the comparator 230 reaches the terminal voltage of the positive phase input terminal of the comparator 230, and a signal 0 representing the on trigger signal is output, so as to trigger the power tube to be turned on again, and complete the control of the power tube in one period.
Referring to fig. 1 to 6, in an embodiment, the adjusting circuit 220 includes:
a current mirror electrically connected to the output end of the voltage-current conversion circuit 210, for mirroring the error current and outputting a corresponding mirrored current;
a first capacitor connected in series between the negative phase output terminal of the comparator 230 and ground for storing electric energy when the mirror current is received and discharging electric energy when the mirror current is not received;
the charge-discharge control circuit is electrically connected with the current mirror, the first capacitor and the comparator 230, the controlled end of the charge-discharge control circuit is used for accessing a conduction control signal, the charge-discharge control circuit is further used for controlling the first capacitor to discharge when receiving the conduction control signal, grounding the negative phase input end of the comparator 230, and controlling the first capacitor to charge when not receiving the conduction control signal.
In this embodiment, when the switching power supply works normally, the error current output by the voltage-current conversion circuit 210 is received by the current mirror, and mirrored by the current mirror, so that the error current 1 is set according to the design requirement of the developer: n equal-proportion replication, where N is a positive number other than 0. The current mirror outputs the mirrored error current as a charging current.
When the switching tube M is in the on period, the charge-discharge control circuit receives the on control signal, at the moment, the charge-discharge control circuit disconnects the connection between the output end of the current mirror and the first capacitor, and connects the negative phase input end of the comparator 230 to the ground, the terminal voltage of the negative phase input end of the comparator 230 is always lower than the terminal voltage of the positive phase input end of the comparator 230, 1 is output, when the switching tube M starts to enter the off period, the charge-discharge control circuit stops receiving the on control signal, the output end of the current mirror is connected with the first capacitor, so that the first capacitor starts to store the received mirror current until the voltage value of the first capacitor reaches the first reference voltage again, the terminal voltage of the negative phase input end of the comparator 230 reaches the terminal voltage of the positive phase input end of the comparator 230, 0 signal representing the on trigger signal is output, the power tube is triggered to be turned on again, and the control of the power tube is completed.
Referring to fig. 1 to 6, in an embodiment, the adjusting circuit 220 includes a first MOS transistor Q1 and a second MOS transistor Q2;
the drain electrode of the first MOS transistor Q1 is connected to the output end of the current mirror, the gate electrode of the first MOS transistor Q1 is used for accessing the on control signal and is connected to the gate electrode of the second MOS transistor Q2, and the source electrode of the first MOS transistor Q1 is connected to the source electrode of the second MOS transistor Q2, the first end of the first capacitor C1, and the negative phase input end of the comparator 230, respectively; the source electrode of the second MOS tube Q2 is grounded.
In this embodiment, the first MOS transistor Q1 is a PMOS transistor, and the second MOS transistor Q2 is an NMOS transistor.
When the switch tube M is in the on period, the gate of the first MOS tube Q1 and the gate of the second MOS tube Q2 receive the high-level on control signal, at this time, the first MOS tube Q1 is turned off, the second MOS tube Q2 is turned on, so that the output end of the current mirror is disconnected from the first capacitor, and the negative phase input end of the comparator 230 is grounded. When the switching tube M starts to enter the off period, the gate of the first MOS transistor Q1 and the gate of the second MOS transistor Q2 receive the low level, at this time, the first MOS transistor Q1 is turned on, the second MOS transistor is turned off, the output end of the current mirror is turned on with the first capacitor C1, and the negative phase input end of the comparator 230 is turned off from the ground.
When the switching power supply is applied to constant current dimming, the LED may flash obviously if the output voltage fluctuates, and this phenomenon is called stroboscopic. The prior art scheme generally adopts an RC filter circuit to filter voltage fluctuation, but because the ripple interference frequency generated by an alternating current power grid is generally very low when the switching power supply is connected to the alternating current power supply, the interference signal cannot be well filtered by a common filter from a few Hz to a dozen Hz, and the current output by the circuit still has a stroboscopic problem.
Referring to fig. 1 to 3, in an embodiment, the first reference power supply specifically includes a second reference voltage, and the error sampling circuit 100 includes:
the current sampling resistor is connected in series between the output end of the switching tube M and the ground and is used for outputting corresponding sampling voltage;
the first input end of the digital low-pass filter 110 is electrically connected with the current sampling resistor, the second end of the digital low-pass filter 110 is used for accessing the second reference voltage, the output end of the digital low-pass filter 110 is connected with the input end of the turn-off duration modulation circuit 200, and the low-pass filter is used for comparing the sampling voltage with the second reference voltage and outputting a corresponding error detection signal.
In this embodiment, the filtering frequency band of the digital low-pass filter 110 is below 50hz, so that the low-frequency interference carried by the ac power grid can be well filtered.
Specifically, when the switching tube M is turned on, the current flowing through the inductor is output to the current sampling resistor through the switching tube M, and the current sampling resistor converts the received current into a sampling voltage for output. The digital low-pass filter 110 integrates the received sampling voltage after low-pass filtering to obtain a voltage signal corresponding to the average current, compares the voltage signal with a second reference voltage to obtain an error voltage of the two voltages, and outputs the error voltage as a corresponding error detection signal to the off-duration modulation circuit 200.
Referring to fig. 1 to 4, in an embodiment, the error detection signal is specifically an error voltage, and the digital low-pass filter 110 includes:
the first input end of the modulator 111 is electrically connected with the current sampling resistor, the second input end of the modulator 111 is used for accessing the second reference voltage, and the modulator 111 is also used for performing signal processing on the second reference voltage and the sampling voltage and outputting a corresponding error digital signal;
the input end of the counter 112 is connected with the output end of the modulator 111, and the counter 112 is used for counting the received error digital signals and outputting corresponding counting error digital signals;
the input end of the digital-to-analog conversion module 113 is connected with the output end of the counter 112, and the output end of the digital-to-analog conversion module is connected with the input end of the turn-off duration modulation circuit 200, and is used for performing digital-to-analog conversion processing on the accessed count error digital signal and outputting an error detection signal of a corresponding analog voltage value.
In this embodiment, the modulator 111 performs signal processing on the sampling signal Vcs and the second reference voltage to obtain a PDM code (pulse density modulation), the counter counts the PDM code sampled multiple times, averages the value to be the current effective value, and finally performs digital-to-analog conversion processing on the value of the counter 112 through the digital-to-analog conversion module 113 to convert the value to an error detection signal represented by an analog error voltage, and the digital low-pass filter 110 can effectively overcome fluctuation interference caused by accidental factors by averaging multiple samples during operation, and realize a filtering function on measured parameters with slow changes of temperature, liquid level and the like, so that the output current is not influenced by input power frequency ripple and PWM signal ripple, the strobe problem is solved, and the constant current precision is improved.
Referring to fig. 1 to 4, in an embodiment, the high-precision constant current control circuit further includes:
the input end of the reference voltage modulation circuit 300 is used for being connected with a constant voltage source, the controlled end of the reference voltage modulation circuit 300 is used for being connected with a voltage regulation control signal, the output end of the reference voltage modulation circuit 300 is connected with the second input end of the error sampling circuit 100, and the reference voltage modulation circuit 300 is used for performing signal processing on the constant voltage source according to the received voltage regulation control signal so as to output a first reference power source with a corresponding voltage value.
In this embodiment, the reference voltage modulation circuit 300 may include switching devices such as a switching transistor and a power transistor.
When the output voltage of the switching power supply is controlled through the interactive components such as the keys, the reference voltage modulation circuit 300 receives the corresponding voltage regulation signal, and the constant voltage source is processed into the first reference voltage output with different voltage values according to different duty ratios represented by the voltage regulation signal by performing PWM chopping processing on the constant voltage source.
Referring to fig. 1 to 5, in an embodiment, the high-precision constant current control circuit further includes:
the first input end of the current peak control circuit 400 is connected with the output end of the switching tube M, the second input end of the current peak control circuit 400 is used for accessing a second reference power supply, the output end of the current peak control circuit 400 is electrically connected with the driving module, the current peak control circuit 400 is also used for collecting the current flowing through the inductor, and outputting a turn-off control signal when the current flowing through the inductor is larger than the current value represented by the second reference power supply.
In this embodiment, the current peak control circuit 400 may be the comparator 230, or may be a circuit having a comparison function such as a differential circuit.
When the switching power supply works normally, if the switching tube M is in the on period, the inductor current rises linearly, the current peak control circuit 400 starts to collect the current flowing through the inductor, and once the current flowing through the inductor is detected to reach the preset peak value, the switching tube M is controlled to be turned off, and the current flowing through the inductor is controlled to stop rising, so that the peak value of the current flowing through the inductor is always constant, namely I pk Is a fixed value.
The invention also provides a switching power supply which comprises a BUCK circuit and the high-precision constant-current control circuit; the BUCK circuit is used for accessing alternating current and is electrically connected with the high-precision constant-current control circuit; and the constant current source is used for outputting stable constant current under the control of the high-precision constant current control circuit. The specific structure of the high-precision constant-current control circuit refers to the above embodiments, and because the switching power supply adopts all the technical schemes of all the embodiments, the switching power supply has at least all the beneficial effects brought by the technical schemes of the embodiments, and the details are not repeated here.
The invention also provides a lighting device comprising the LED and the switch power supply. The specific structure of the switch power supply refers to the above embodiments, and because the lighting device adopts all the technical solutions of all the embodiments, the switch power supply at least has all the beneficial effects brought by the technical solutions of the embodiments, and the details are not repeated here.
The foregoing description is only of the optional embodiments of the present invention, and is not intended to limit the scope of the invention, and all the equivalent structural changes made by the description of the present invention and the accompanying drawings or the direct/indirect application in other related technical fields are included in the scope of the invention.

Claims (10)

1. The utility model provides a high accuracy constant current control circuit, is applied to switching power supply, its characterized in that, switching power supply includes inductance, switching tube and drive module, inductance, switching tube establish ties in proper order and set up between DC power supply and ground, drive module with the controlled end of switching tube is connected, high accuracy constant current control circuit includes:
the first input end of the error sampling circuit is connected with the output end of the switching tube, the second input end of the error sampling circuit is used for being connected with a first reference power supply, and the error sampling circuit is used for collecting average current flowing through the inductor and outputting a corresponding error detection signal according to the deviation between the average current and the first reference power supply;
the first input end of the turn-off duration modulation circuit is connected with the output end of the switching tube, the third input end of the turn-off duration modulation circuit is connected with the output end of the error sampling circuit, the output end of the turn-off duration modulation circuit is used for being connected with the driving module, and the turn-off duration of the switching tube in each working period is adjusted according to the error detection signal so as to adjust the average current value flowing through the inductor to a preset current value.
2. The high-precision constant current control circuit according to claim 1, wherein the off-time length modulation circuit includes:
the input end of the voltage-current conversion circuit is connected with the output end of the error sampling circuit and is used for carrying out voltage-current processing on the accessed error detection signal and outputting corresponding error current;
the first input end of the regulating circuit is connected with the output end of the voltage-current conversion circuit, the second input end of the regulating circuit is used for being connected with a conduction control signal, and the regulating circuit is used for discharging stored electric energy when the conduction control signal is received and charging according to the error current when the conduction control signal is not received;
and the positive phase input end of the comparator is used for accessing a first reference voltage, the negative phase input end of the comparator is electrically connected with the regulating circuit, and the comparator is also used for outputting a conduction trigger signal to the driving module when detecting that the terminal voltage of the regulating circuit reaches a first reference voltage.
3. The high-precision constant current control circuit according to claim 2, wherein the adjusting circuit comprises:
the current mirror is electrically connected with the output end of the voltage-current conversion circuit and is used for mirroring the error current and outputting corresponding mirror current;
the first capacitor is connected in series between the negative phase output end of the comparator and the ground and is used for storing electric energy when the error current is received and discharging the electric energy when the mirror current is not received;
the charge-discharge control circuit is respectively and electrically connected with the current mirror, the first capacitor and the comparator, the controlled end of the charge-discharge control circuit is used for being connected with a conduction control signal, the charge-discharge control circuit is also used for controlling the first capacitor to discharge when receiving the conduction control signal, grounding the negative-phase input end of the comparator, and controlling the first capacitor to charge when not receiving the conduction control signal.
4. The high-precision constant current control circuit according to claim 3, wherein the charge-discharge control circuit comprises a first MOS tube and a second MOS tube;
the drain electrode of the first MOS tube is connected with the output end of the current mirror, the grid electrode of the first MOS tube is used for being connected with the conduction control signal and the grid electrode of the second MOS tube, and the source electrode of the first MOS tube is respectively connected with the source electrode of the second MOS tube, the first end of the first capacitor and the negative phase input end of the comparator; and the source electrode of the second MOS tube is grounded.
5. The high precision constant current control circuit according to claim 1, wherein the first reference power supply specifically includes a second reference voltage, and the error sampling circuit includes:
the current sampling resistor is connected in series between the output end of the switching tube and the ground and is used for outputting corresponding sampling voltage;
the first input end of the digital low-pass filter is electrically connected with the current sampling resistor, the second end of the digital low-pass filter is used for being connected with the second reference voltage, the output end of the digital low-pass filter is connected with the input end of the turn-off duration modulation circuit, and the low-pass filter is used for comparing the sampling voltage with the second reference voltage and outputting a corresponding error detection signal.
6. The high precision constant current control circuit according to claim 5, wherein the error detection signal is embodied as an error voltage, and the digital low pass filter comprises:
the first input end of the modulator is electrically connected with the current sampling resistor, the second input end of the modulator is used for being connected with the second reference voltage, and the modulator is also used for performing signal processing on the second reference voltage and the sampling voltage and outputting a corresponding error digital signal;
the input end of the counter is connected with the output end of the modulator, and the counter is used for counting the received error digital signals and outputting corresponding counting error digital signals;
the input end of the digital-to-analog conversion module is connected with the output end of the counter, the output end of the digital-to-analog conversion module is connected with the input end of the turn-off duration modulation circuit, and the digital-to-analog conversion module is used for carrying out digital-to-analog conversion processing on the accessed counting error digital signal and outputting an error detection signal of a corresponding analog voltage value.
7. The high-precision constant current control circuit according to claim 1, wherein the high-precision constant current control circuit further comprises:
the input end of the reference voltage modulation circuit is used for being connected with a constant voltage source, the controlled end of the reference voltage modulation circuit is used for being connected with a voltage regulation control signal, the output end of the reference voltage modulation circuit is connected with the second input end of the error sampling circuit, and the reference voltage modulation circuit is used for carrying out signal processing on the first reference power supply according to the received voltage regulation control signal so as to output the first reference power supply with a corresponding voltage value.
8. The high-precision constant current control circuit according to claim 1, wherein the high-precision constant current control circuit further comprises:
the first input end of the current peak value control circuit is connected with the output end of the switching tube, the second input end of the current peak value control circuit is used for being connected with a second reference power supply, the output end of the current peak value control circuit is electrically connected with the driving module, the current peak value control circuit is also used for collecting current flowing through the inductor, and when the current flowing through the inductor is larger than a current value represented by the second reference power supply, a turn-off control signal is output.
9. A switching power supply, characterized in that the switching power supply comprises a BUCK circuit and the high-precision constant current control circuit according to claims 1-8;
the BUCK circuit is used for accessing alternating current and is electrically connected with the high-precision constant-current control circuit; and the constant current source is used for outputting stable constant current under the control of the high-precision constant current control circuit.
10. A lighting device comprising an LED and the switching power supply of claim 9.
CN202310646985.4A 2023-06-01 2023-06-01 High-precision constant-current control circuit, switching power supply and lighting equipment Pending CN116742945A (en)

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CN202310646985.4A CN116742945A (en) 2023-06-01 2023-06-01 High-precision constant-current control circuit, switching power supply and lighting equipment

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CN202310646985.4A CN116742945A (en) 2023-06-01 2023-06-01 High-precision constant-current control circuit, switching power supply and lighting equipment

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117729666A (en) * 2023-12-08 2024-03-19 深圳市谐振电子有限公司 Power supply control circuit for deep dimming and novel switching power supply device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117729666A (en) * 2023-12-08 2024-03-19 深圳市谐振电子有限公司 Power supply control circuit for deep dimming and novel switching power supply device

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