CN210157439U - LED current sampling circuit and LED driving power supply - Google Patents
LED current sampling circuit and LED driving power supply Download PDFInfo
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- CN210157439U CN210157439U CN201920547471.2U CN201920547471U CN210157439U CN 210157439 U CN210157439 U CN 210157439U CN 201920547471 U CN201920547471 U CN 201920547471U CN 210157439 U CN210157439 U CN 210157439U
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Abstract
The utility model discloses a LED current sampling circuit and a LED driving power supply, wherein the current sampling circuit comprises a sampling resistor which is used for converting a current signal flowing through an LED into a voltage signal; the amplifying circuit is used for amplifying the terminal voltage of the sampling resistor; an integration circuit for integrating the output voltage of the amplification circuit; the sampling resistor is connected with the input end of the amplifying circuit, and the output end of the amplifying circuit is connected with the input end of the integrating circuit. The utility model discloses a LED current sampling circuit realizes the sampling function of LED electric current through sampling resistor, and amplifier circuit amplifies the terminal voltage of sampling resistor, guarantees under the same circumstances of voltage signal that feeds back in the current sampling process, can reduce the resistance of sampling resistor to play the loss that reduces sampling resistor; meanwhile, the output voltage of the amplifying circuit is subjected to integral operation through the integral circuit, so that the filtering effect on fluctuation and high-frequency interference is achieved.
Description
Technical Field
The utility model relates to an electronic circuit technical field, more specifically say and relate to a LED current sampling circuit and LED drive power supply who uses thereof.
Background
Because of the volt-ampere characteristic (the current flowing through an LED changes exponentially with the voltage at its end) and the temperature characteristic of an LED (light emitting diode), a constant current driving power supply is generally used as an LED driving power supply in the prior art.
It is clear to a person skilled in the art that deviations or fluctuations in the current through an LED affect not only the operational lifetime of the LED, its luminous flux or brightness, but also the spectral distribution of its emitted light. In some occasions with higher requirements on brightness and spectrum, such as an LED light source used for calibration of a photoelectric system or an LED solar simulator, the LED constant current precision control has stricter requirements.
At present, most common LED constant current driving chips adopt a peak current control mode, a resistor is connected in series with an LED current loop to sample LED current, then sampling voltage is sent to a switching power supply chip to be processed, the duty ratio of on-off of a switching device is controlled, and the current is controlled. Such a current sampling circuit has the following drawbacks: 1. although the current sampling circuit is simple in structure and only needs one sampling resistor, the loss is high, and the larger the resistance value of the sampling resistor is, the higher the loss is; 2. the low sampling accuracy of the current results in low current control accuracy of the driving power supply.
SUMMERY OF THE UTILITY MODEL
The to-be-solved technical problem of the utility model is: how to improve the current control precision of the LED driving power supply and reduce the loss of a sampling circuit in the driving power supply.
The utility model provides a solution of its technical problem is:
an LED current sampling circuit comprising:
the sampling resistor is used for converting a current signal flowing through the LED into a voltage signal;
the amplifying circuit is used for amplifying the terminal voltage of the sampling resistor;
an integration circuit for integrating the output voltage of the amplification circuit;
the sampling resistor is connected with the input end of the amplifying circuit, and the output end of the amplifying circuit is connected with the input end of the integrating circuit.
As a further improvement of the above technical solution, the integrating circuit is a dual integrating circuit, the integrating circuit includes two integrating units, which are a first integrating unit and a second integrating unit, respectively, an output end of the first integrating unit is connected to an input end of the second integrating unit, and an output end of the amplifying circuit is connected to an input end of the first integrating unit.
As a further improvement of the above technical solution, the first integrating unit includes an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3, and a capacitor C1, one end of the resistor R1 is connected to an inverting input terminal of the operational amplifier U1, the other end of the resistor R1 is used as an input terminal of the first integrating unit, a non-inverting input terminal of the operational amplifier U1 is grounded through a resistor R3, two ends of the resistor R2 are respectively connected to the inverting input terminal and an output terminal of the operational amplifier U1, two ends of the capacitor C1 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier U1, and an output terminal of the operational amplifier U1 is used as an output terminal of the first integrating unit.
As a further improvement of the above technical solution, the second integrating unit includes an operational amplifier U2, a resistor R4, a resistor R5, a resistor R6, and a capacitor C2, one end of the resistor R4 is connected to an inverting input terminal of the operational amplifier U2, the other end of the resistor R4 is used as an input terminal of the second integrating unit, a non-inverting input terminal of the operational amplifier U2 is grounded through a resistor R6, two ends of the resistor R5 are respectively connected to the inverting input terminal and an output terminal of the operational amplifier U2, two ends of the capacitor C2 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier U2, and an output terminal of the operational amplifier U2 is used as an output terminal of the second integrating unit.
As a further improvement of the above technical solution, the amplifying circuit is a differential amplifying circuit, the amplifying circuit includes an operational amplifier U3, a resistor R7, a resistor R8, a resistor R9, and a resistor R10, one end of the resistor R7 is connected to an inverting input terminal of the operational amplifier U3, one end of the resistor R9 is connected to a non-inverting input terminal of the operational amplifier U3, the other end of the resistor R7 and the other end of the resistor R9 are used as two input terminals of the amplifying circuit, the non-inverting input terminal of the operational amplifier U3 is grounded through the resistor R10, two ends of the resistor R8 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 is used as an output terminal of the amplifying circuit.
The application also discloses LED drive power supply, including DC-DC circuit, DC-DC circuit includes switching power supply chip and above-mentioned any one LED current sampling circuit, the switching power supply chip is equipped with the current sampling end, integrator circuit's output is connected with the current sampling end of switching power supply chip.
The utility model has the advantages that: the utility model discloses a LED current sampling circuit realizes the sampling function of LED electric current through sampling resistor, and amplifier circuit amplifies the terminal voltage of sampling resistor, guarantees under the same circumstances of voltage signal that feeds back in the current sampling process, can reduce the resistance of sampling resistor to play the loss that reduces sampling resistor; meanwhile, the output voltage of the amplifying circuit is subjected to integral operation through an integral circuit, so that the effect of filtering interference following the fluctuation of inductive current and high-frequency burr interference existing in a sampling voltage signal is achieved;
among the LED drive power supply, integrator circuit feeds back the fluctuating and high frequency interference's of filtering voltage signal to switching power supply chip's current sampling end, effectively improves drive power supply's current control precision.
Drawings
In order to more clearly illustrate the technical solution in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below. It is clear that the described figures represent only some embodiments of the invention, not all embodiments, and that a person skilled in the art can also derive other designs and figures from these figures without inventive effort.
Fig. 1 is a frame diagram of the sampling circuit of the present invention;
fig. 2 is a schematic diagram of an embodiment of a sampling circuit of the present invention;
fig. 3 is a power circuit diagram of the sampling circuit of the present invention combined with a switching power chip with model number PT 4115;
fig. 4 is a power circuit diagram of the utility model combining the sampling circuit with the switching power supply chip with the model of UC 3842.
Detailed Description
The conception, specific structure, and technical effects of the present application will be described clearly and completely with reference to the accompanying drawings and embodiments, so that the purpose, features, and effects of the present application can be fully understood. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application. In addition, all the connection relations mentioned herein do not mean that the components are directly connected, but mean that a better connection structure can be formed by adding or reducing connection accessories according to the specific implementation situation. All technical characteristics in the invention can be interactively combined on the premise of not conflicting with each other. Finally, it should be noted that the terms "center, upper, lower, left, right, vertical, horizontal, inner, outer" and the like as used herein refer to an orientation or positional relationship based on the drawings, which is only for convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present application.
Referring to fig. 1 to 2, in order to improve the current control accuracy of the LED driving power supply and reduce the loss of the sampling circuit in the driving power supply, the present application provides a current sampling circuit applied in the LED driving power supply, where a first embodiment of the current sampling circuit includes:
the sampling resistor RS is used for converting a current signal flowing through the LED into a voltage signal;
the amplifying circuit is used for amplifying the terminal voltage of the sampling resistor RS;
an integration circuit for integrating the output voltage of the amplification circuit;
the sampling resistor RS is connected with the input end of the amplifying circuit, and the output end of the amplifying circuit is connected with the input end of the integrating circuit.
Specifically, the LED current sampling circuit realizes the sampling function of the LED current through the sampling resistor RS, the amplifying circuit amplifies the terminal voltage of the sampling resistor RS, and the resistance value of the sampling resistor RS can be reduced under the condition that the voltage signals fed back in the current sampling process are the same, so that the loss of the sampling resistor RS is reduced; meanwhile, the output voltage of the amplifying circuit is subjected to integral operation through the integral circuit, so that the filtering effect on fluctuation and high-frequency interference is achieved.
Further, in a preferred implementation manner, in this embodiment, the integration circuit is a dual integration circuit, the integration circuit includes two integration units, which are a first integration unit and a second integration unit, respectively, an output end of the first integration unit is connected to an input end of the second integration unit, and an output end of the amplification circuit is connected to an input end of the first integration unit.
More specifically, the first integrating unit includes an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3, and a capacitor C1, one end of the resistor R1 is connected to an inverting input terminal of the operational amplifier U1, the other end of the resistor R1 is used as an input terminal of the first integrating unit, a non-inverting input terminal of the operational amplifier U1 is grounded through a resistor R3, two ends of the resistor R2 are respectively connected to the inverting input terminal and an output terminal of the operational amplifier U1, two ends of the capacitor C1 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier U1, and an output terminal of the operational amplifier U1 is used as an output terminal of the first integrating unit. The second integration unit comprises an operational amplifier U2, a resistor R4, a resistor R5, a resistor R6 and a capacitor C2, one end of the resistor R4 is connected with the inverting input end of the operational amplifier U2, the other end of the resistor R4 is used as the input end of the second integration unit, the non-inverting input end of the operational amplifier U2 is grounded through a resistor R6, two ends of the resistor R5 are respectively connected with the inverting input end and the output end of the operational amplifier U2, two ends of the capacitor C2 are respectively connected with the inverting input end and the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is used as the output end of the second integration unit.
In the embodiment, the dual-integration circuit is formed by the operational amplifier U1, the operational amplifier U2 and the peripheral circuit thereof, so that the triangular fluctuation of the current signal collected by the sampling resistor RS can be smoothed, and meanwhile, the fluctuation and high-frequency interference are filtered, so that the original sampling signal with the triangular fluctuation is changed into ripple output with small fluctuation and approximate sine wave shape, the sampling signal precision is higher, and the current control precision of the applied driving power supply is improved. In addition, the dual integration circuit is used in the embodiment, mainly to obtain a better filtering effect on fluctuation and high frequency interference, and simultaneously, because the input signals in the first integration unit and the second integration unit are directly input to the inverting input end of the operational amplifier, the polarity of the current sampling signal is kept unchanged, and inconvenience brought to driving due to polarity inversion caused by one-time integration is avoided. The current sampling signal collected by the sampling resistor RS is regarded as a combination of a constant direct current signal and a fluctuation signal, the frequency of the fluctuation signal is high, the capacitive reactance of the capacitor C1 and the capacitor C2 is low, the resistor R2 and the resistor R6 are negligible, the integrating circuit plays a two-stage reverse integration effect on the fluctuation signal, the capacitor C1 and the capacitor C2 are equivalent to open circuits on the direct current signal, and the integrating circuit is equivalent to a two-stage reverse proportional operational amplifier on the direct current signal.
Further, in a preferred embodiment, the amplifying circuit is a differential amplifying circuit, the amplifying circuit includes an operational amplifier U3, a resistor R7, a resistor R8, a resistor R9, and a resistor R10, one end of the resistor R7 is connected to an inverting input terminal of the operational amplifier U3, one end of the resistor R9 is connected to a non-inverting input terminal of the operational amplifier U3, the other end of the resistor R7 and the other end of the resistor R9 serve as two input terminals of the amplifying circuit, the non-inverting input terminal of the operational amplifier U3 is grounded via the resistor R10, two ends of the resistor R8 are respectively connected to the inverting input terminal and the output terminal of the operational amplifier U3, and the output terminal of the operational amplifier U3 serves as an output terminal of the amplifying circuit. Specifically, for the case that the sampling resistor RS is arranged on the LED driving power supply by using a high-end current detection structure (as shown in fig. 3), the amplifying circuit in this embodiment specifically uses a differential amplifying circuit structure, when the high-end current detection structure is used to sample the LED current, the differential mode signal in the collected current signal is smaller, and the common mode signal is larger, so that the differential amplifying circuit is used to suppress the common mode signal, and because the common mode suppression ratio of the integrated operational amplifier is higher, the differential amplifying circuit is formed by the operational amplifier U3 and its peripheral circuit in this embodiment to achieve the amplification function of the voltage at the sampling resistor RS. Of course, the amplifying circuit described in this embodiment is also applicable to the case where the sampling resistor RS is disposed on the LED driving power supply by using a low-side current detection structure.
The application also discloses an LED driving power supply structure applying the current sampling circuit. The first embodiment of the LED driving power supply comprises a DC-DC circuit, wherein the DC-DC circuit comprises a switching power supply chip and any one of the LED current sampling circuits, the switching power supply chip is provided with a current sampling end, and the output end of the integrating circuit is connected with the current sampling end of the switching power supply chip. In the LED driving power supply described in this embodiment, the integrating circuit feeds back the voltage signal after filtering fluctuation and high-frequency interference to the current sampling end of the switching power supply chip, so as to effectively improve the current control accuracy of the driving power supply.
To better illustrate the applicability of the present embodiment, the present application provides two complete circuit diagrams of LED driving power source combined with the above current sampling circuit through fig. 3 and 4. Fig. 3 is a power supply circuit diagram of the combination of the current sampling circuit and a switching power supply chip with model number PT4115, and fig. 4 is a power supply circuit diagram of the combination of the current sampling circuit and a switching power supply chip with model number UC 3842. Of course, this application LED current sampling circuit's application scope is not limited to in fig. 3 and fig. 4 the switching power supply chip of model, this application LED current sampling circuit is applicable in the switching power supply chip of various models, and any LED drive power supply as long as use this application LED current sampling circuit all belong to this application's protection scope.
The application also discloses a current control method of the LED driving power supply, and the first embodiment of the current control method of the LED driving power supply comprises the following steps:
step 100, collecting a current signal of an LED, and converting the current signal into a voltage signal;
step 200, amplifying the voltage signal;
step 300, performing double integration operation on the voltage signal;
and step 400, controlling the duty ratio of a switching tube of the LED driving power supply by taking the voltage signal as a feedback signal.
Specifically, the current control method for the LED driving power supply according to this embodiment converts the current signal output to the LED into a voltage signal, and uses the amplified and integrated voltage signal as a feedback signal to control the duty ratio of the switching tube in the driving power supply, so as to effectively reduce the loss of the current sampling resistor, filter the fluctuation and the high-frequency interference, and improve the current control accuracy of the driving power supply.
While the preferred embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that the invention is not limited to the details of the embodiments, but is capable of various modifications and substitutions without departing from the spirit of the invention.
Claims (6)
1. An LED current sampling circuit, comprising:
the sampling resistor is used for converting a current signal flowing through the LED into a voltage signal;
the amplifying circuit is used for amplifying the terminal voltage of the sampling resistor;
an integration circuit for integrating the output voltage of the amplification circuit;
the sampling resistor is connected with the input end of the amplifying circuit, and the output end of the amplifying circuit is connected with the input end of the integrating circuit.
2. The LED current sampling circuit of claim 1, wherein: the integrating circuit is a double integrating circuit and comprises two integrating units, namely a first integrating unit and a second integrating unit, wherein the output end of the first integrating unit is connected with the input end of the second integrating unit, and the output end of the amplifying circuit is connected with the input end of the first integrating unit.
3. The LED current sampling circuit of claim 2, wherein: the first integrating unit comprises an operational amplifier U1, a resistor R1, a resistor R2, a resistor R3 and a capacitor C1, one end of the resistor R1 is connected with the inverting input end of the operational amplifier U1, the other end of the resistor R1 is used as the input end of the first integrating unit, the non-inverting input end of the operational amplifier U1 is grounded through a resistor R3, two ends of the resistor R2 are respectively connected with the inverting input end and the output end of the operational amplifier U1, two ends of the capacitor C1 are respectively connected with the inverting input end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is used as the output end of the first integrating unit.
4. The LED current sampling circuit of claim 3, wherein: the second integration unit comprises an operational amplifier U2, a resistor R4, a resistor R5, a resistor R6 and a capacitor C2, one end of the resistor R4 is connected with the inverting input end of the operational amplifier U2, the other end of the resistor R4 is used as the input end of the second integration unit, the non-inverting input end of the operational amplifier U2 is grounded through a resistor R6, two ends of the resistor R5 are respectively connected with the inverting input end and the output end of the operational amplifier U2, two ends of the capacitor C2 are respectively connected with the inverting input end and the output end of the operational amplifier U2, and the output end of the operational amplifier U2 is used as the output end of the second integration unit.
5. The LED current sampling circuit of claim 1, wherein: the amplifying circuit is a differential amplifying circuit, the amplifying circuit comprises an operational amplifier U3, a resistor R7, a resistor R8, a resistor R9 and a resistor R10, one end of the resistor R7 is connected with the inverting input end of the operational amplifier U3, one end of the resistor R9 is connected with the non-inverting input end of the operational amplifier U3, the other end of the resistor R7 and the other end of the resistor R9 are used as two input ends of the amplifying circuit, the non-inverting input end of the operational amplifier U3 is grounded through the resistor R10, two ends of the resistor R8 are respectively connected with the inverting input end and the output end of the operational amplifier U3, and the output end of the operational amplifier U3 is used as the output end of the amplifying circuit.
6. An LED drive power supply characterized in that: the LED current sampling circuit comprises a DC-DC circuit and the LED current sampling circuit comprises a switching power supply chip and the LED current sampling circuit of any one of claims 1 to 5, wherein the switching power supply chip is provided with a current sampling end, and the output end of the integrating circuit is connected with the current sampling end of the switching power supply chip.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201920547471.2U CN210157439U (en) | 2019-04-19 | 2019-04-19 | LED current sampling circuit and LED driving power supply |
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| CN201920547471.2U CN210157439U (en) | 2019-04-19 | 2019-04-19 | LED current sampling circuit and LED driving power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110062501A (en) * | 2019-04-19 | 2019-07-26 | 佛山职业技术学院 | A kind of LED current sample circuit and LED drive power and current control method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110062501A (en) * | 2019-04-19 | 2019-07-26 | 佛山职业技术学院 | A kind of LED current sample circuit and LED drive power and current control method |
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