CN203840596U - Ripple current suppression circuit and LED circuit - Google Patents
Ripple current suppression circuit and LED circuit Download PDFInfo
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- CN203840596U CN203840596U CN201420143422.XU CN201420143422U CN203840596U CN 203840596 U CN203840596 U CN 203840596U CN 201420143422 U CN201420143422 U CN 201420143422U CN 203840596 U CN203840596 U CN 203840596U
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Abstract
The utility model discloses a ripple current suppression circuit and an LED circuit. The ripple current suppression circuit comprises a variable impedance device, a current detection device, a reference signal generation circuit, and a first comparator. The LED circuit comprises a former LED driving circuit, an LED lamp, and the above mentioned ripple current suppression circuit. The ripple current suppression circuit is serially connected with the LED lamp, and is parallely connected with a capacitor, and then is connected to the output end of the former LED driving circuit. By adopting the ripple current suppression circuit, the current across the load, which is serially connected with the circuit, is basically constant, and therefore the current ripple of the load can be reduced.
Description
Technical Field
The utility model relates to a LED technical field especially relates to a ripple current suppression circuit and LED circuit.
Background
In an existing LED circuit, an LED (Light-Emitting Diode) driving circuit is usually implemented by a single-stage PFC (Power Factor Correction) circuit in order to meet the requirements of Power Factor and cost. However, the current ripple output by the single-stage PFC circuit is very large, so that the light emitted by the LED has twice the flicker frequency of the mains supply, which causes discomfort to human eyes and brings trouble to the monitoring equipment.
In order to solve the problem of the existing LED circuit, a large capacitor is often connected in parallel to two ends of the LED driving circuit to smooth the current, so that the cost and the area are both increased.
SUMMERY OF THE UTILITY MODEL
On the one hand, the embodiment of the utility model provides a ripple current suppression circuit is provided, this circuit includes: an impedance variable device, a current detection device, a reference signal generation circuit and a first comparator; wherein,
an impedance variable device provided with a first end, a second end and a third end; the first end receives a control signal, and the impedance variable device adjusts the impedance value of the impedance variable device according to the control signal; the impedance variable device is connected to the external current circuit through the second end and the third end;
a current detection device connected to the impedance variable device for detecting a current value of the impedance variable device;
a reference signal generation circuit for generating a reference signal;
a first comparator including first and second input terminals for receiving a reference signal and a detected current value of the impedance variable device, respectively; the comparison result is used as a control signal of the impedance variable device.
On the other hand, the embodiment of the utility model provides a LED circuit, this circuit include preceding stage LED drive circuit and LED lamp, still include above-mentioned ripple current suppression circuit, above-mentioned ripple current suppression circuit establishes ties with the LED lamp after, and the output that connects in parallel to preceding stage LED drive circuit with electric capacity again.
The embodiment of the utility model provides a ripple current suppression circuit can make the electric current that flows through the series connection load with it invariable basically to reduce the electric current ripple on the load.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly described below, and it is obvious that the drawings in the description below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic view of an application scenario of a ripple current suppression circuit provided in an embodiment of the present invention;
fig. 2A is a block diagram of a ripple current suppression circuit according to an embodiment of the present invention;
fig. 2B is a block diagram of another ripple current suppression circuit according to an embodiment of the present invention;
fig. 3A is a circuit diagram of a ripple current suppression circuit according to an embodiment of the present invention;
fig. 3B is a circuit diagram of another ripple current suppression circuit according to an embodiment of the present invention;
FIG. 4 is a block diagram of one implementation of the reference signal generating circuit of FIG. 2;
FIG. 5 is a block diagram of another implementation of the reference signal generating circuit of FIG. 2;
FIG. 6 is a block diagram of yet another implementation of the reference signal generating circuit of FIG. 2;
FIG. 7 is a block diagram of an embodiment of the maximum selector shown in FIGS. 5 and 6;
fig. 8 is a schematic diagram of an output voltage waveform.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
The preceding LED driving circuit in the existing LED circuit can be regarded as a current source, which provides a constant average current to its Load (LED), but this current may fluctuate up and down with the mains frequency. If the ripple current flowing through the LED is reduced simply by connecting a capacitor in parallel with the Load (LED), the LED circuit needs a large capacitor to achieve a good effect because the internal resistance of the LED itself is small.
In order to reduce the current ripple that flows on the LED to and reduce LED circuit cost and area, the embodiment of the utility model provides a ripple current suppression circuit.
Fig. 1 is a scene schematic diagram of an application of a ripple current suppression circuit provided by an embodiment of the present invention. As shown in fig. 1, the ripple current suppression circuit 120 is connected in series with the LED130 and then connected in parallel with the capacitor 140 at the output end of the previous stage LED driving circuit 110. During one mains cycle, the current of the ripple current suppression circuit 120 is substantially constant, so that the current flowing through the LED is also substantially constant, thereby reducing the current ripple on the LED. Since the series ripple current suppression circuit 120 increases the internal resistance of the branch, the required capacitance can be greatly reduced. In addition, in order to adapt to different front-stage LED driving circuits 110 and reduce the power consumption of the ripple current suppression circuit 120, the steady-state current of the LED130 is set in an adaptive manner, that is, after the LED circuit operates stably, the average value of the direct current on the LED30 is equal to the average value of the output current of the front-stage LED driving circuit 110, so as to ensure that the voltage across the ripple current suppression circuit 120 is low enough and the ripple is small enough.
Fig. 2A is a block diagram of a ripple current suppression circuit according to an embodiment of the present invention. As shown in fig. 2A, the ripple current suppression circuit 120 includes an impedance variable device 21, a current detection device 22, a first comparator 23, and a reference signal generation circuit 24.
The impedance variable device 21 is provided with a first terminal, a second terminal and a third terminal, wherein the first terminal is connected with the output terminal of the first comparator 23, and is used for receiving a control signal and adjusting the impedance value thereof according to the control signal; the third terminal is connected to the external LED130 and outputs a constant current thereto. The first terminal of the impedance variable device 21 is a control terminal, and the voltage or the current of the control terminal determines the impedance and the current of the impedance variable device 21. In an actual circuit, the magnitude of the impedance-variable device 21 and the magnitude of the signal at the control terminal have a monotonic correlation, for example, the control terminal voltage rises and the impedance falls.
One end of the current detection device 22 is connected to the second end of the impedance variable device 21, and a connection point a thereof is connected to an input end of the first comparator 23. The current detection device 22 is used to detect the current value of the impedance variable device 21, thereby obtaining the value of the current flowing through the LED. The first comparator 23 compares the current value with a reference value, and controls the impedance variable device 21 by negative feedback, so that the output current is substantially constant in a period.
The first comparator 23 is configured to compare the current value of the impedance variable device 21 detected by the current detection device 22 with the reference signal VREF generated by the reference signal generation circuit 24, and the comparison result is used as a control signal of the impedance variable device 21.
Preferably, the impedance variable device 21 in the embodiment of the present invention may select an NMOS transistor, where the gate of the NMOS transistor is a first terminal, the source is a second terminal, and the drain is a third terminal, and the gate voltage determines the impedance of the NMOS transistor. It should be noted that the impedance variable device 21 may have other implementations besides the NMOS transistor, for example, a PMOS transistor is used.
The current sensing device 22 may be implemented as a resistor whose voltage is proportional to the current. One end of the resistor is grounded, and the other end of the resistor is directly connected in series with the impedance variable device 21, or directly connected in parallel with the impedance variable device 21 (as shown in fig. 2B), and implemented by mirroring the current of the impedance variable device 21.
An output terminal of the reference signal generating circuit 24 is connected to the other input terminal of the first comparator 23 for generating the reference signal VREF. Preferably, the reference signal generating circuit 24 generates the reference signal VREF according to the three-terminal signal value of the impedance variable device 21 and the current value detected by the current detecting device 22. Fig. 4 to fig. 6 are three block diagrams of the reference signal generating circuit 24 according to the embodiment of the present invention.
First implementation block diagram as shown in fig. 4, the reference signal generating circuit 24 includes a second comparator 41, an amplifier 42, a first comparison voltage 43, and a second comparison voltage 44.
An input end of the second comparator 41 is connected to a voltage difference between two ends of the impedance variable device 21, that is, a voltage difference between the second end and the third end of the impedance variable device 21; the other input terminal is connected to the first comparison voltage 43, and the output terminal is connected to one input terminal of the amplifier 42, for comparing the voltage across the impedance variable device 21 with the first comparison voltage 43, and outputting the comparison result to the amplifier 42. The first comparison voltage 43 is generally determined according to the characteristics of the resistance variable device 21, and is generally a voltage drop of the resistance variable device 21 plus a value between 0 and vdd at the maximum current.
An input end of the amplifier 42 is connected to the output end of the second comparator 41, and another input end thereof is connected to the second comparison voltage 44, for amplifying the comparison result of the second comparator 41 and then comparing with the second comparison voltage 44, and the difference value is used as the output reference signal VREF. Second comparison voltage 44 is a value between 0 and vdd and is used to control the ratio of 0 and vdd output from second comparator 41 during steady state conditions.
Preferably, the amplifier 42 is a low bandwidth amplifier, which typically has a bandwidth less than the fundamental frequency of the input current ripple.
Preferably, the first comparison voltage 43 and the second comparison voltage 44 vary according to a temperature change of the LED circuit. When the temperature of the LED circuit rises, the first comparison voltage 43 and the second comparison voltage 44 change accordingly, the current ripple on the LED gradually increases, and the power consumption of the LED circuit also decreases accordingly, so that negative feedback is formed, thereby preventing the temperature of the LED circuit from rising too high.
The first comparison voltage 43 and the second comparison voltage 44 may also be dynamically varied according to changes in time. For example, when the power supply is just turned on, the comparison voltage gradually reaches the final value, so that the ripple is large at the beginning and then gradually reaches the stable state, and the power consumption of the circuit is gradually increased from small to large.
Second implementation block diagram as shown in fig. 5, the reference signal generating circuit 24 includes a maximum selector 51, an amplifier 42, a first comparison voltage 43, and a second comparison voltage 44.
An input end of the maximum selector 51 is connected to a voltage difference between two ends of the impedance variable device, that is, a voltage difference between the second end and the third end of the impedance variable device; the other input terminal is connected to a first comparison voltage 43, and the output terminal is connected to one input terminal of the amplifier 42, for outputting the maximum value or the minimum value of the voltage across the impedance variable device and the first comparison voltage.
One input end of the amplifier 42 is connected to the output end of the maximum comparator 51, and the other input end thereof is connected to the second comparison voltage 44, for amplifying the comparison result of the maximum comparator 41 and then comparing with the second comparison voltage 44, and the difference value is used as the output reference signal VREF.
Third implementation block diagram as shown in fig. 6, the reference signal generating circuit 24 includes a maximum selector 51, an amplifier 42, a first comparison voltage 43, and a second comparison voltage 44.
One input end of the maximum selector 51 is connected to the control end voltage of the impedance variable device 51, i.e. the first end voltage of the impedance variable device, which is generally between 0 and vdd; the other input terminal is connected to a first comparison voltage 43, and the output terminal is connected to one input terminal of the amplifier 42, for outputting the maximum value or the minimum value of the voltage across the impedance variable device and the first comparison voltage. The first comparison voltage 43 selects a voltage value between 0 and vdd according to the characteristics of the impedance variable device.
One input end of the amplifier 42 is connected to the output end of the maximum comparator 51, and the other input end thereof is connected to the second comparison voltage 44, for amplifying the comparison result of the maximum comparator 41 and then comparing with the second comparison voltage 44, and the difference value is used as the output reference signal VREF. The second comparison voltage 44 is typically a voltage between the first comparison voltage 43 and vdd and is also used to control the current ripple.
Fig. 3A is a circuit diagram of a ripple current suppression circuit provided by an embodiment of the present invention. As shown in fig. 3A, the ripple current suppression circuit 120 includes an NMOS transistor 21, a current detection device 22, a first comparator 23, and a reference signal generation circuit 24.
The gate of the NMOS transistor 21 is connected to the output of the first comparator 23 for receiving the control signal, and the NMOS transistor 21 is connected to the external current circuit through the source and the drain.
One end of the current detection device 22 is connected with the source of the NMOS transistor 21 and is used for detecting the current value of the NMOS transistor 21;
a reference signal generation circuit 24 for generating a reference signal;
a first comparator 23 comprising first and second input terminals for receiving the reference signal and the current value of the NMOS transistor 21, respectively; the comparison result is used as a control signal for the NMOS transistor 21.
Fig. 3B is a circuit diagram of another ripple current suppression circuit according to an embodiment of the present invention. As shown in fig. 3B, the ripple current suppression circuit 120 includes a first MOS transistor 21a, a second MOS transistor 21B, a resistor 22, a first comparator 23, and a reference signal generation circuit 24, where the first NMOS transistor 21a is an impedance variable device, and the resistor 22 and the NMOS transistor 21B constitute a current detection device.
The gates of the first NMOS transistor 21a and the second NMOS transistor 21b are connected to the output terminal of the first comparator 23, and are configured to receive the control signal, and the impedance values of the first NMOS transistor 21a and the second NMOS transistor 21b are adjusted according to the control signal. The drain of the first NMOS transistor 21a and the drain of the second NMOS transistor 21b are connected in series. One end of the resistor 22 is connected to the source of the first NMOS transistor 21a, and the connection point is connected to an input terminal of the first comparator 23.
An output of the reference signal generating circuit 24 is connected to another input of the first comparator 23 for generating a reference signal.
The first comparator 23 compares the reference signal with the current at the source connection point of the resistor 22 and the first NMOS transistor 21a, and the comparison result is used as the control signal for the first NMOS transistor 21a and the second NMOS transistor 21 b.
Fig. 7 is a schematic diagram of a circuit structure of a maximum selector according to an embodiment of the present invention. As shown in fig. 7, the maximum selector 51 includes a PMOS transistor V1 and a PMOS transistor V2, and the output signal Vo is the lowest value of V1 and V2 plus a preset threshold voltage Vth.
Fig. 8 is a schematic diagram showing waveforms of output voltages of the impedance variable device, the comparator and the maximum selector when the ripple current suppression circuit according to the embodiment of the present invention is in operation.
The embodiment of the utility model provides a ripple current suppression circuit can establish ties with LED after again with electric capacity and hookup at preceding stage LED driven output. In a commercial power cycle, the embodiment of the utility model provides a ripple current suppression circuit's electric current remains unchanged basically to make LED's electric current also basically invariable, thereby reduced the electric current ripple on the LED. Because the embodiment of the utility model provides a ripple current suppression circuit and LED series connection have increased the internal resistance of this branch road, consequently can reduce required electric capacity.
While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the exemplary embodiments of the present invention and its broader aspects. It is therefore intended that the appended claims encompass within their scope all such changes and modifications as do not depart from the true spirit and scope of the exemplary embodiments of this invention.
Claims (9)
1. A ripple current suppression circuit, comprising: an impedance variable device, a current detection device, a reference signal generation circuit and a first comparator; wherein,
an impedance variable device provided with a first end, a second end and a third end; the first end receives a control signal, and the impedance variable device adjusts the impedance value of the impedance variable device according to the control signal; the impedance variable device is connected to the external current circuit through the second end and the third end;
a current detection device connected to the impedance variable device for detecting a current value of the impedance variable device;
a reference signal generation circuit for generating a reference signal;
a first comparator including first and second input terminals for receiving a reference signal and a detected current value of the impedance variable device, respectively; the comparison result is used as a control signal of the impedance variable device.
2. The circuit of claim 1, wherein the reference signal generation circuit comprises:
the input end of the second comparator is connected with the voltage difference at the two ends of the impedance variable device, the other input end of the second comparator is connected with the first comparison voltage, and the output end of the second comparator is connected with the input end of the amplifier and is used for comparing the voltage difference at the two ends of the impedance variable device with the first comparison voltage;
and one input end of the amplifier receives the comparison result of the second comparator, the other input end of the amplifier is connected with a second comparison voltage, the amplifier is used for amplifying the comparison result of the second comparator and then comparing the amplified comparison result with the second comparison voltage, and the difference value is used as an output reference signal.
3. The circuit of claim 1, wherein the reference signal generation circuit comprises:
a maximum selector, one input end of which is connected to the voltage difference between the two ends of the impedance variable device, the other input end of which is connected to a first comparison voltage, and the output end of which is connected to one input end of the amplifier and is used for outputting the maximum value or the minimum value of the voltage difference between the two ends of the impedance variable device and the first comparison voltage;
and one input end of the amplifier is connected with the output end of the maximum selector, the other input end of the amplifier is connected with a second comparison voltage, the amplifier is used for amplifying the output result of the maximum selector and then comparing the output result with the second comparison voltage, and the difference value is used as an output reference signal.
4. The circuit of claim 1, wherein the reference signal generation circuit comprises:
a maximum selector, one input end of which is connected with the first terminal voltage of the impedance variable device, the other input end of which is connected with the first comparison voltage, and the output end of which is connected with one input end of the amplifier and is used for outputting the maximum value or the minimum value of the control terminal voltage of the impedance variable device and the first comparison voltage;
and one input end of the amplifier is connected with the output end of the maximum selector, the other input end of the amplifier is connected with a second comparison voltage, the amplifier is used for amplifying the output result of the maximum selector and then comparing the output result with the second comparison voltage, and the difference value is used as an output reference signal.
5. The circuit of claim 1, wherein the current detection device is a resistor, the impedance variable device is a MOS transistor, the MOS transistor has a gate terminal as a first terminal, a drain terminal as a second terminal, and a source terminal as a third terminal; or the gate electrode of the MOS transistor is a first end, the source electrode is a second end, and the drain electrode is a third end.
6. The circuit of claim 1, wherein the impedance variable device is a first MOS transistor, the current detection device comprises a resistor and a second MOS transistor, the second MOS transistor is connected in series with the resistor, and a connection point of the second MOS transistor is connected to the second input terminal of the first comparator; the current detection device and the impedance variable device are connected in parallel.
7. The circuit of any of claims 2 to 4, wherein the first comparison voltage and/or the second comparison voltage is adjusted in response to a change in circuit temperature.
8. The circuit of any one of claims 2 to 4, wherein the first comparison voltage and/or the second comparison voltage are dynamically adjusted in response to changes in time.
9. An LED circuit comprising a preceding LED driving circuit and an LED lamp, further comprising the ripple current suppression circuit according to claim 1, wherein the ripple current suppression circuit is connected in series with the LED lamp and then connected in parallel with a capacitor to an output terminal of the preceding LED driving circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420143422.XU CN203840596U (en) | 2014-03-27 | 2014-03-27 | Ripple current suppression circuit and LED circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420143422.XU CN203840596U (en) | 2014-03-27 | 2014-03-27 | Ripple current suppression circuit and LED circuit |
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| CN203840596U true CN203840596U (en) | 2014-09-17 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN201420143422.XU Expired - Lifetime CN203840596U (en) | 2014-03-27 | 2014-03-27 | Ripple current suppression circuit and LED circuit |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103889121A (en) * | 2014-03-27 | 2014-06-25 | 美芯晟科技（北京）有限公司 | Ripple current suppression circuit |
| WO2016054739A1 (en) * | 2014-10-08 | 2016-04-14 | Queen's University At Kingston | Average current modulator for an led driver |
| CN110838789A (en) * | 2018-08-17 | 2020-02-25 | 美芯晟科技（北京）有限公司 | Ripple suppression circuit, system and method |
-
2014
- 2014-03-27 CN CN201420143422.XU patent/CN203840596U/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103889121A (en) * | 2014-03-27 | 2014-06-25 | 美芯晟科技（北京）有限公司 | Ripple current suppression circuit |
| CN103889121B (en) * | 2014-03-27 | 2016-04-06 | 美芯晟科技（北京）有限公司 | A kind of ripple current suppresses circuit |
| WO2016054739A1 (en) * | 2014-10-08 | 2016-04-14 | Queen's University At Kingston | Average current modulator for an led driver |
| CN110838789A (en) * | 2018-08-17 | 2020-02-25 | 美芯晟科技（北京）有限公司 | Ripple suppression circuit, system and method |
| CN110838789B (en) * | 2018-08-17 | 2021-06-04 | 美芯晟科技（北京）有限公司 | Ripple suppression circuit, system and method |
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Address after: Room 01, 10 / F, block a, Tiangong building, Keda, 30 Xueyuan Road, Haidian District, Beijing 100089 Patentee after: Meixinsheng Technology (Beijing) Co.,Ltd. Address before: 1006, office building, Crowne Plaza, No. 106, Zhichun Road, Haidian District, Beijing 100086 Patentee before: MAXIC TECHNOLOGY (BEIJING) Co.,Ltd. |
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Granted publication date: 20140917 |
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