CN112271924A - Constant-current output circuit and method based on voltage feedback of buck converter - Google Patents
Constant-current output circuit and method based on voltage feedback of buck converter Download PDFInfo
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- CN112271924A CN112271924A CN202011255048.9A CN202011255048A CN112271924A CN 112271924 A CN112271924 A CN 112271924A CN 202011255048 A CN202011255048 A CN 202011255048A CN 112271924 A CN112271924 A CN 112271924A
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- buck converter
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- 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
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/345—Current stabilisation; Maintaining constant current
Abstract
The invention provides a constant current output circuit and a method based on voltage feedback of a buck converter, wherein the constant current output circuit comprises a resistance network, an integrated operational amplifier, the buck converter, a filter network and a controller; constant current output is realized through voltage feedback of the buck converter, driving current is greatly increased, and the function of driving the laser diode with large current and constant current is realized. The precision enable input of the invention simplifies the control of the voltage stabilizer and the sequencing of the system power supply, and also has various protection characteristics such as periodic current limit protection, thermal sensing and thermal shutoff protection for coping with overlarge power consumption, output overvoltage protection and the like. The invention can be applied to all product devices which need constant current to drive the laser diode, such as semiconductor laser ranging, LED lighting and other devices, and the application range is expanded. The invention has the advantages of low cost, simple and reliable realization and wider applicability.
Description
Technical Field
The invention belongs to the technical field of constant current driving, and particularly relates to a constant current output circuit and method based on voltage feedback of a buck converter.
Background
With the technological progress of industries such as LED packaging integration, luminescent materials and the like, the manufacturing and application technology of semiconductor laser diodes is rapidly developed in the field of distance measurement, and the semiconductor laser diodes penetrate into laser distance measurement products in the military field in the greatest extent and depth, so that the semiconductor laser diodes become the core for realizing high-tech and informatization of military reconnaissance.
In the currently developed photoelectric ranging products, no matter the products are handheld or servo photoelectric platforms, the ranging module is required to be small in size, light in weight, resistant to impact and long in ranging distance; the traditional solid laser has the advantages of large volume, more peripheral devices, complex control, difficulty in integration and difficulty in realizing repetition frequency ranging, and the semiconductor microchip laser has the advantages of small volume, light weight, small divergence angle of laser beams and simple realization of repetition frequency control.
The driving of the semiconductor laser diode requires a large current and the current is constant, otherwise the device is vulnerable. In the market, a plurality of constant voltage driving chips are provided, a plurality of special constant current driving chips are provided, and the driving power is limited. Therefore, the technology of constant current driving laser diode with large current is researched, and the miniaturization of photoelectric distance measurement is imperative.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: a constant current output circuit and method based on voltage feedback of a buck converter are provided, which are used for driving a laser diode with a large current and a constant current.
The technical scheme adopted by the invention for solving the technical problems is as follows: a constant current output circuit based on voltage feedback of a buck converter comprises a sampling network, an amplifier N2 and a buck converter N1; the sampling network is connected in series in the load loop and used for accurately sampling the load current; the signal input end + IN of the amplifier N2 is connected with the current sampling network and used for amplifying and driving the sampling voltage; the feedback terminal FB of the buck converter N1 is connected to the signal output terminal OUT of the amplifier N2, the energy input terminal SW of the buck converter N1 is connected to an external power source, and the energy output terminal SW of the buck converter N1 is connected to the energy input terminal of the load, and is used for performing voltage conversion according to the sampling signal and providing drive for the load.
According to the scheme, the device further comprises a controller, wherein a signal output end of the controller is connected with a controlled end of the buck converter N1 and is used for controlling the current output by the buck converter N1 to be continuously adjustable.
Furthermore, the controller comprises a periodic current limiting protection module, a thermal sensing and thermal shutoff protection module and an output overvoltage protection module; the periodic current limiting protection module is used for limiting the peak value of the periodic current of the load so as to protect the load from being burnt by large current; the thermal sensing and thermal shutdown protection module is used for shutting down or reducing the current source when the power consumption of the load exceeds a preset value so as to protect the load from being damaged by high temperature; the output overvoltage protection module is used for limiting the maximum value of the output voltage of the buck converter so as to protect the load from breakdown.
The filter network is connected between the energy output end SW of the buck converter N1 and the energy input end of the load in series and is used for afterflow and current filtering and providing a clean constant current source for the load; the filter network comprises a voltage stabilizing diode V1, a filter capacitor C3 and an inductor L1.
Further, the sampling network comprises a sampling resistor Rf.
Further, amplifier N2 employs a high performance, low noise rail-to-rail amplifier.
Further, the buck converter N1 adopts an integrated high-side buck regulator, and the output power is greater than 20W during stable operation.
A constant current output method based on voltage feedback of a buck converter comprises the following steps:
s1: the constant current output circuit based on voltage feedback of the buck converter is built and comprises a sampling resistor Rf, an amplifier N2, a buck converter N1, a filter network and a controller; the sampling resistor Rf is connected with the load D1 in series; a signal input end + IN of the amplifier N2 is connected with a sampling end of the load D1, and a signal output end of the amplifier N2 is connected with a feedback end FB of the buck converter N1; an energy input end VIN of the buck converter N1 is connected with an external power supply, and an energy output end SW of the buck converter N1 is sequentially connected with a filter network and an energy input end of a load D1 in series; the signal output end of the controller is connected with the controlled end of the buck converter N1;
s2: the circuit is powered on, and the output voltage V of the buck converter N1OUTGenerating a proportional drive current to load D1; if the driving current is increased, the feedback voltage at the two ends of the sampling resistor Rf is increased, and if the driving current is reduced, the feedback voltage is reduced;
s3: the feedback voltage is amplified by an amplifier N2 and is input to the FB terminal of the buck converter N1;
s4: when the feedback voltage rises, the oscillation output of the SW pin of the buck converter N1 weakens, and the output voltage VOUTDecrease; if the feedback voltage is reduced, the oscillation output is increased, and the output voltage V isOUTRising until the voltage across the sampling resistor Rf stabilizes at the design value, thereby keeping the current flowing through the sampling resistor Rf and the load D1 constant;
s5: the output current is continuously adjustable by the controller sending a control signal to the controlled end of the buck converter N1 to change the set value of the output current.
The invention has the beneficial effects that:
1. the constant current output circuit and the method based on the voltage feedback of the buck converter realize constant current output by utilizing the voltage feedback of the buck converter, greatly increase the driving current and realize the function of driving the laser diode with large current and constant current.
2. The step-down converter adopted by the invention is an integrated high-side step-down voltage stabilizer, has a wider input voltage range, and is suitable for various applications from industry to automobiles; the sampling feedback operational amplifier is a high-performance, low-noise and rail-to-rail amplifier, the adjustable switching frequency range is wide, the efficiency and the external element size are optimized, and the number of external elements is reduced to the maximum extent through internal loop compensation.
3. The precision enable input of the present invention simplifies voltage regulator control and system power sequencing.
4. The circuit of the invention also has various protection characteristics such as periodic current limit protection, thermal sensing and thermal shutoff protection for coping with overlarge power consumption, output overvoltage protection and the like.
5. The invention can be applied to all product devices which need constant current to drive the laser diode, such as semiconductor laser ranging, LED lighting and other devices, and the application range is expanded.
6. The invention has the advantages of low cost, simple and reliable realization and wider applicability.
Drawings
FIG. 1 is a functional block diagram of an embodiment of the present invention.
Fig. 2 is a typical circuit diagram of a buck converter according to an embodiment of the invention.
Fig. 3 is a circuit diagram of an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1, an embodiment of the present invention includes a sampling resistor network, an integrated operational amplifier, a buck converter, a filter network, and a controller.
The current sampling network comprises a sampling resistor connected in series in the load loop and used for accurately sampling the load current.
The signal input end of the integrated operational amplifier is connected with a current sampling network and used for amplifying and driving sampling voltage; the integrated operational amplifier adopts a high-performance, low-noise and rail-to-rail amplifier, the adjustable switching frequency range is wider, the efficiency and the external element size are optimized, and the number of external elements is reduced to the maximum extent through internal loop compensation.
The feedback end of the buck converter is connected with the signal output end of the integrated operational amplifier, and the energy output end of the buck converter is connected with the energy input end of the load through a filter network and used for completing voltage conversion according to the sampling signal and providing drive for the load; the step-down converter adopts an integrated high-side step-down voltage stabilizer, has a wider input voltage range, has output power more than 20W during stable work, and is suitable for various applications from industry to automobiles.
The filter network comprises a voltage stabilizing diode, a filter capacitor and an inductor and is used for afterflow and current filtering and providing a clean constant current source for the load.
The signal output end of the controller is connected with the controlled end of the buck converter and is used for controlling the current output by the buck converter to be continuously adjustable;
the controller comprises a periodic current limit protection module, a thermal sensing and thermal shutoff protection module and an output overvoltage protection module; the periodic current limiting protection module is used for limiting the peak value of the periodic current of the load so as to protect the load from being burnt by large current; the thermal sensing and thermal shutdown protection module is used for shutting down or reducing the current source when the power consumption of the load exceeds a preset value so as to protect the load from being damaged by high temperature; the output overvoltage protection module is used for limiting the maximum value of the output voltage of the buck converter so as to protect the load from breakdown.
Referring to fig. 3, the present invention improves upon the typical constant voltage output circuit of the buck converter of fig. 2.
In FIG. 2, the feedback voltage is taken from resistor RFBBAnd a voltage VOUTIs in direct proportion; if VOUTThe feedback voltage rises, the converter oscillation decreases, and V isOUTReduced feedback voltage, increased converter oscillation, VOUT(ii) is increased; thus V is made by negative feedbackOUTThe voltage remains stable.
In fig. 3, a laser diode D1 as a load and a sampling resistor Rf are connected in series in the output loop of a buck converter N1, and a precision low-noise rail-to-rail amplifier N2 is connected in series between the sampling point and the feedback point of the buck converter N1; when the driving current of the load D1 changes, the voltage across the resistor Rf changes, and is amplified by the amplifier N2 and input to the FB terminal of the buck converter N1, and the oscillating output of the SW pin of the buck converter N1 changes inversely until the voltage across the sampling resistor Rf stabilizes at the designed value, so that the current flowing through the sampling resistor Rf and the load D1 is kept constant. The output current is continuously adjustable by the controller sending a control signal to the controlled end of the buck converter N1 to change the set value of the output current.
The above embodiments are only used for illustrating the design idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention accordingly, and the protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes and modifications made in accordance with the principles and concepts disclosed herein are intended to be included within the scope of the present invention.
Claims (8)
1. A constant current output circuit based on buck converter voltage feedback is characterized in that: comprises a sampling network, an amplifier N2 and a buck converter N1;
the sampling network is connected in series in the load loop and used for accurately sampling the load current;
the signal input end + IN of the amplifier N2 is connected with the current sampling network and used for amplifying and driving the sampling voltage;
the feedback terminal FB of the buck converter N1 is connected to the signal output terminal OUT of the amplifier N2, the energy input terminal SW of the buck converter N1 is connected to an external power source, and the energy output terminal SW of the buck converter N1 is connected to the energy input terminal of the load, and is used for performing voltage conversion according to the sampling signal and providing drive for the load.
2. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 1, wherein: the voltage regulator further comprises a controller, wherein a signal output end of the controller is connected with a controlled end of the buck converter N1 and is used for controlling the current output by the buck converter N1 to be continuously adjustable.
3. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 2, wherein: the controller comprises a periodic current limit protection module, a thermal sensing and thermal shutoff protection module and an output overvoltage protection module; the periodic current limiting protection module is used for limiting the peak value of the periodic current of the load so as to protect the load from being burnt by large current; the thermal sensing and thermal shutdown protection module is used for shutting down or reducing the current source when the power consumption of the load exceeds a preset value so as to protect the load from being damaged by high temperature; the output overvoltage protection module is used for limiting the maximum value of the output voltage of the buck converter so as to protect the load from breakdown.
4. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 1, wherein: the filter network is connected between the energy output end SW of the buck converter N1 and the energy input end of the load in series and is used for afterflow and current filtering and providing a clean constant current source for the load; the filter network comprises a voltage stabilizing diode V1, a filter capacitor C3 and an inductor L1.
5. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 1, wherein: the sampling network comprises a sampling resistor Rf.
6. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 1, wherein: amplifier N2 employs a high performance, low noise rail-to-rail amplifier.
7. The constant-current output circuit based on voltage feedback of the buck converter, according to claim 1, wherein: the buck converter N1 adopts an integrated high-side buck regulator, and the output power is more than 20W during stable operation.
8. The constant-current output method of the constant-current output circuit based on the voltage feedback of the buck converter is characterized in that: the method comprises the following steps:
s1: the constant current output circuit based on voltage feedback of the buck converter is built and comprises a sampling resistor Rf, an amplifier N2, a buck converter N1, a filter network and a controller;
the sampling resistor Rf is connected with the load D1 in series;
a signal input end + IN of the amplifier N2 is connected with a sampling end of the load D1, and a signal output end of the amplifier N2 is connected with a feedback end FB of the buck converter N1;
an energy input end VIN of the buck converter N1 is connected with an external power supply, and an energy output end SW of the buck converter N1 is sequentially connected with a filter network and an energy input end of a load D1 in series;
the signal output end of the controller is connected with the controlled end of the buck converter N1;
s2: the circuit is powered on, and the output voltage V of the buck converter N1OUTGenerating a proportional drive current to load D1; if the driving current is increased, the feedback voltage at the two ends of the sampling resistor Rf is increased, and if the driving current is reduced, the feedback voltage is reduced;
s3: the feedback voltage is amplified by an amplifier N2 and is input to the FB terminal of the buck converter N1;
s4: when the feedback voltage rises, the oscillation output of the SW pin of the buck converter N1 weakens, and the output voltage VOUTDecrease; if the feedback voltage is reduced, the oscillation output is increased, and the output voltage V isOUTRising until the voltage across the sampling resistor Rf stabilizes at the design value, thereby keeping the current flowing through the sampling resistor Rf and the load D1 constant;
s5: the output current is continuously adjustable by the controller sending a control signal to the controlled end of the buck converter N1 to change the set value of the output current.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011255048.9A CN112271924A (en) | 2020-11-11 | 2020-11-11 | Constant-current output circuit and method based on voltage feedback of buck converter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011255048.9A CN112271924A (en) | 2020-11-11 | 2020-11-11 | Constant-current output circuit and method based on voltage feedback of buck converter |
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| CN112271924A true CN112271924A (en) | 2021-01-26 |
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Application publication date: 20210126 |