CN210781469U - Circuit for inhibiting low-frequency ripple current of light-emitting diode - Google Patents
Circuit for inhibiting low-frequency ripple current of light-emitting diode Download PDFInfo
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- CN210781469U CN210781469U CN201920180913.4U CN201920180913U CN210781469U CN 210781469 U CN210781469 U CN 210781469U CN 201920180913 U CN201920180913 U CN 201920180913U CN 210781469 U CN210781469 U CN 210781469U
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Abstract
The application discloses a circuit for suppressing emitting diode low frequency ripple current includes: the circuit comprises a rectifying circuit, a linear constant current circuit and a low-frequency ripple suppression circuit. The rectification circuit is configured to rectify an alternating current power supply input to provide a rectified direct current output to the linear constant current circuit and the low frequency ripple suppression circuit. The linear constant current circuit is configured to be connected with the low frequency ripple suppression circuit to provide a constant current to the LED load. The low-frequency ripple suppression circuit comprises an LED load, a control chip comprising a metal-oxide semiconductor field effect transistor (MOSFET), an output capacitor, a diode and a plurality of resistors. The control chip is configured to detect an output characterization voltage characterizing an output voltage across the LED load or the output capacitance, and to control the MOSFET to turn on and off based on the output characterization voltage, the first reference voltage, and the second reference voltage.
Description
Technical Field
The present application relates to the field of circuits, and more particularly, to a circuit for suppressing a low-frequency ripple current of a light emitting diode.
Background
The output power of a Light Emitting Diode (LED) driver with a high Power Factor (PF) varies with the input power frequency voltage, resulting in voltage fluctuation (i.e., ripple) of the power frequency on its output filter output capacitor, and due to the characteristics of LEDs, the smaller voltage fluctuation results in larger current fluctuation, i.e., stroboscopic of LEDs, on the current. The strobe is not visible to the naked eye, but noticeable streaking is visible when photographed by a device such as a cell phone.
With the continuous maturity of LED technology and the increasing demand for LEDs, low frequency flash has gradually become the basic demand for LEDs. The traditional LED low flash solution cannot meet the current market requirements due to the low PF. In order to reduce the low-frequency ripple current of the LED, the high-PF scheme needs to use an output capacitor with large volume and large capacity, so that the cost of the whole system is greatly increased; on the other hand, the circuit is large in size and cannot be applied to small-size bulbs, filament lamps and the like.
SUMMERY OF THE UTILITY MODEL
In view of one or more of the above-mentioned problems, the present application provides a circuit for suppressing a low-frequency ripple current of an LED.
A circuit for suppressing a low-frequency ripple current of a Light Emitting Diode (LED) according to an embodiment of the application comprises: a rectifier circuit, a linear constant current circuit, and a low frequency ripple rejection circuit, wherein the rectifier circuit is configured to rectify an ac power supply input to provide rectified dc output to the linear constant current circuit and the low frequency ripple rejection circuit; the linear constant current circuit is configured to be connected with the low-frequency ripple suppression circuit to provide a constant current to an LED load; the low-frequency ripple suppression circuit comprises the LED load, a control chip comprising a metal-oxide semiconductor field effect transistor (MOSFET), an output capacitor, a diode and a plurality of resistors, wherein one end of the output capacitor is connected with a positive voltage end of the LED load, the other end of the output capacitor is used as a reference ground of the control chip and is connected to one end of a voltage division network, the other end of the voltage division network is connected to a system ground, a source electrode of the MOSFET is connected to the reference ground of the control chip, and a drain electrode of the MOSFET and a cathode electrode of the LED load are connected to the linear constant current circuit together; wherein the control chip is configured to detect an output characterization voltage characterizing an output voltage across the LED load or the output capacitance, and to control the turning on and off of the MOSFET based on the output characterization voltage, a first reference voltage, and a second reference voltage.
In one embodiment, the output characterization voltage is obtained by dividing the voltage between the reference ground of the control chip and the system ground through the voltage dividing network.
In one embodiment, the control chip further comprises: a first comparator for comparing the output characterization voltage with the first reference voltage to obtain a first comparison result; the second comparator is used for comparing the output characterization voltage with the second reference voltage to obtain a second comparison result; and the logic control component is used for controlling the on and off of the internal MOSFET based on the first comparison result and the second comparison result.
In one embodiment, the control chip further comprises an oscillator, and the control chip is configured to control the on and off of the MOSFET based on a frequency and a duty cycle of an output of the oscillator.
In one embodiment, the first reference voltage is greater than the second reference voltage, the logic control component configured to: when the output characterization voltage is increased to be equal to the second reference voltage, the MOSFET of the control chip is cut off, so that a discharge path of the output capacitor to the LED load is cut off; when the output characterization voltage is increased to be equal to a first reference voltage, the MOSFET of the control chip is turned on, so that a discharge path of the output capacitor to the LED load is turned on; when the output characterization voltage increases again to equal the second reference voltage, the MOSFET is turned off again.
In one embodiment, the first reference voltage is greater than the second reference voltage, the logic control component configured to: when the output characterization voltage is increased to be equal to the second reference voltage, the MOSFET of the control chip is cut off, so that a discharge path of the output capacitor to the LED load is cut off; when the output representative voltage increases to equal the first reference voltage, configuring the MOSFET at the provided discharge frequency and duty cycle to cause the output capacitor to PWM pulse discharge the LED load; and stopping the PWM pulse discharge when the output characterization voltage is lower than a second reference voltage, and conducting the internal MOSFET until the output characterization voltage is increased to be equal to the second reference voltage again.
In one embodiment, the linear constant current circuit is a non-dimming linear constant current circuit.
In one embodiment, the linear constant current circuit is a TRIAC dimming linear constant current circuit.
In one embodiment, the rectifier circuit is a bridge rectifier circuit.
The circuit for restraining the low-frequency ripple current of the light-emitting diode provided by the embodiment of the application provides an effective LED high-PF low-frequency flash solution, so that the system cost can be reduced, and the circuit can be flexibly applied to various small volumes.
Drawings
The present application may be better understood from the following description of specific embodiments thereof taken in conjunction with the accompanying drawings, in which:
fig. 1 is a circuit diagram of a circuit for suppressing LED low frequency ripple current according to one embodiment of the present disclosure;
fig. 2 is an example of a circuit for suppressing LED low frequency ripple current using a thyristor-dimmed linear constant current circuit;
fig. 3 shows an example of a control chip in the low frequency ripple rejection module shown in fig. 1;
FIG. 4 shows a timing diagram of a control chip controlling the output capacitance to discharge an LED according to one embodiment of the present disclosure; and
fig. 5 shows a timing diagram of a control chip controlling an output capacitor to discharge an LED according to another embodiment of the present disclosure.
Detailed Description
Features and exemplary embodiments of various aspects of the present application will be described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present application by illustrating examples thereof. The present application is in no way limited to any specific configuration presented below, but rather covers any modification, substitution, and improvement of elements, components, and algorithms without departing from the spirit of the present application. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present application.
In order to solve the problem that the existing high PF low-frequency flash scheme for the LED is high in cost and large in size, the application provides a novel circuit for inhibiting LED low-frequency ripple current.
Fig. 1 is a circuit diagram of a circuit 100 for suppressing LED low frequency ripple current according to one embodiment of the present disclosure. The circuit 100 includes a rectifying circuit 102, a linear constant current circuit 104, and a low frequency ripple rejection circuit 106. Specifically, the input terminal of the ac rectification circuit 102 receives an ac input voltage VAC(e.g. ac mains) to supply an ac input voltage VACConverted to a rectified dc output Vin, and the output terminal of the rectifying circuit 102 is connected to the input terminals of the linear constant current circuit 104 and the low-frequency ripple suppression circuit 106 to provide dc input to the linear constant current circuit 104 and the low-frequency ripple suppression circuit 106. In one embodiment, the rectifying circuit 102 includes a bridge rectifying circuit formed by four diodes D1, D2, D3 and D4 butted two by two for converting an ac input voltage to a full wave dc output voltage.
The linear constant current circuit 104 includes a first terminal 104-1 and a second terminal 104-2, wherein the first terminal 104-1 is connected to an output of the rectifier circuit to be powered by the dc output of the rectifier circuit 102. The second terminal 104-2 of the linear constant current circuit 104 is connected to a low frequency ripple rejection circuit. In one embodiment, the linear constant current circuit 104 may be any non-dimming, TRIAC-dimming linear constant current circuit. In one embodiment, the linear constant current circuit 104 may be a triac dimming linear constant current circuit, for example, fig. 2 illustrates the application of the triac dimming linear constant current circuit in the present application. A typical triac dimming linear constant current circuit utilizes a blanking control component and a constant current control component to provide a constant current to the load.
Referring back to fig. 1, the low-frequency ripple suppression circuit 106 includes a control chip U1, a diode D5, an LED load, an output capacitor C1, and a plurality of resistors R2, R3, R4, R5. In one embodiment, the LED load may include one or more LEDs, with the cathode of the LED load connected to the second terminal 104-2 of the linear constant current circuit 104 along with the Drain pin of the control chip U1, e.g., as shown in fig. 2, in the case of a linear triac dimming linear constant current circuit, the cathode of the LED load connected to the Drain terminal (i.e., terminal 104-2) of the constant current control component in the linear constant current circuit 104 along with the Drain pin of the control chip U1. The dc output of the rectifier circuit 102 is input to the LED load, the control chip U1 and the output capacitor C1 through the diode D5, and the diode D5 is turned off when the output voltage is higher than the input voltage to prevent the output capacitor C1 from flowing backward into the linear constant current circuit 104. One end of the output capacitor C1 is connected with the positive voltage end of the LED load, the other end of the output capacitor C1 is used as the reference ground of the control chip U1 and is connected to one end of a voltage division network composed of resistors R2 and R3, and the other end of the voltage division network is connected to the system ground.
In one embodiment, a voltage dividing network formed by resistors R2 and R3 divides the voltage between the reference ground of the control chip and the system ground to generate an output characterization voltage VFB characterizing the output voltage of the LED load or the output capacitor; the control chip U1 controls the turn-on and turn-off of the MOSFET based on the output characterization voltage VFB, the first reference voltage Vref1, and the second reference voltage Vref2 to reduce the magnitude of ripple of the output current of the LED load when the input voltage Vin fluctuates at a low frequency.
The control chip U1 of the low frequency ripple control circuit 106 includes the following pins: an HV pin, namely a high-voltage power supply input pin, for connecting with a direct-current full-wave output voltage Vin of the rectifying circuit 102, so as to supply power to the chip U1; a GND pin, i.e., a chip reference ground; drain pin, i.eA MOSFET drain pin inside the chip U1 that is connected to the second terminal 104-2 of the linear constant current circuit 104 along with the cathode of the LED load; pin F, a frequency setting pin, which needs to be externally connected with a resistor (as shown in fig. 1-2, resistor R5) to the chip reference ground for outputting the discharging frequency of capacitor C1; a D pin, i.e., a duty cycle pin, which needs to be externally connected with a resistor (as shown in fig. 1-2, resistor R4) to a chip reference ground for outputting a duty cycle when the capacitor C1 discharges; the FB pin, i.e. the voltage detection pin, for detecting an output representative voltage V representing the output voltage of the LED load or the output capacitorFB。
Fig. 3 shows an example of a control chip in the low frequency ripple rejection circuit shown in fig. 1-2. Such as
As shown in fig. 3, the control chip U1 includes: a first voltage comparator 301 for characterizing the voltage V to the outputFBAnd a first reference voltage VREF1Comparing to obtain a first comparison result, and inputting the first comparison result into the logic control assembly; a second voltage comparator 302 for characterizing the voltage V to the outputFBAnd a second reference voltage VREF2Comparing to obtain a second comparison result, and inputting the second comparison result into the logic control component 305; an oscillator 303 connected to an F pin and a D pin of the control chip U1, and generating a discharge frequency and a duty ratio for the output capacitor C1 based on a frequency output from the F pin and a duty ratio output from the D pin; a metal-oxide semiconductor field effect transistor (MOSFET)304, a Drain of the MOSFET 304 being connected to a Drain pin of the control chip U1, a source of the MOSFET being connected to a GND pin of the control chip U1; a logic control component for controlling the turning on and off of the MOSFET 304 based on the first and second comparison results and/or based on a discharge frequency and duty cycle provided by the oscillator. In one embodiment, the frequency and duty cycle may be set according to the CEC2.0 power frequency ripple requirement, for example, frequency 25KHz, duty cycle 50%.
Fig. 4 shows a timing diagram of a control chip controlling an output capacitor to discharge an LED load according to one embodiment of the present disclosure. Wherein Vc1 represents the voltage of the output capacitor C1; vin represents a dc output voltage output by a rectifier circuit (e.g., rectifier circuit 102 shown in fig. 1); ILED represents the current of the LED load; REF1 and REF2 represent a first reference voltage and a second reference voltage, respectively, wherein the first reference voltage REF1 is greater than the second reference voltage REF 2; FB denotes the output characterization voltage detected by the FB pin of the chip.
As shown in fig. 4, as Vin decreases, when the FB voltage increases to be equal to the second reference voltage REF2, the MOSFET inside the control chip U1 is turned off, so as to cut off the discharge path of the output capacitor C1 to the LED load, at which time the dc full-wave output voltage Vin output by the rectifying circuit supplies power to the LED load and the FB voltage continues to increase; when Vin continues to drop to a value that the LED load cannot be supplied with current, the FB voltage increases to be equal to the first reference voltage REF1, the MOSFET inside the control chip U1 is turned on, and the discharge path of the output capacitor C1 to the LED load is turned on, and the FB voltage drops; when the FB voltage again increases with the drop in Vin to equal the second reference voltage REF2, the MOSFET is turned off again, and the action repeats. The logic control component of the control chip is configured to control the turning on and off of the MOSFET based on the logic.
Fig. 5 shows a timing diagram of a control chip controlling an output capacitor to discharge an LED according to another embodiment of the present disclosure. As shown in fig. 5, as Vin decreases, when the FB voltage increases to be equal to the second reference voltage REF2, the MOSFET inside the control chip U1 is turned off, so as to cut off the discharge path of the output capacitor C1 to the LED load, at which time the dc full-wave output voltage Vin output by the rectifying circuit supplies power to the LED load and the FB voltage continues to increase; when Vin continues to drop to a point where it is unable to supply current to the LED load, at which point the FB voltage increases to equal the first reference voltage REF1, the internal MOSFETs are configured with a frequency set at the chip F pin and a duty cycle set at the chip D pin such that the output capacitor C1 discharges the LED load in PWM pulses; the PWM pulse discharge is stopped when the FB voltage decreases to equal said second reference voltage REF2 as Vin increases, the internal MOSFET turns on until the FB voltage again increases to equal the second reference voltage REF2 as Vin decreases, turning off the MOSFET again, and so on. The logic control component of the control chip is configured to control the turning on and off of the MOSFET based on the logic.
The circuit for restraining the low-frequency ripple current of the light-emitting diode provided by the embodiment of the application provides an effective LED high-PF low-frequency flash solution, so that the system cost can be reduced, and the circuit can be flexibly applied to various small volumes.
In the above, reference is made to "one embodiment", "another embodiment", "yet another embodiment", however, it is to be understood that the features mentioned in the respective embodiments are not necessarily applicable only to this embodiment, but may be applicable to other embodiments. Features from one embodiment may be applied to another embodiment or may be included in another embodiment.
It should be understood that the numerical subscripts to the devices and circuits referred to above are also for ease of description and reference and do not have an ordinal relationship.
The present invention has been described with reference to particular embodiments thereof, but it will be understood by those skilled in the art that the above embodiments are illustrative and not restrictive. Different features which are present in different embodiments may be combined to advantage. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art upon studying the drawings, the specification, and the claims. Any reference signs in the claims shall not be construed as limiting the scope. The functions of the various parts appearing in the claims may be implemented by a single hardware or software module. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Claims (9)
1. A circuit for suppressing light emitting diode low frequency ripple current, comprising: a rectifying circuit, a linear constant current circuit, and a low-frequency ripple suppression circuit, wherein,
the rectification circuit is configured to rectify an alternating current power input to provide rectified direct current output to the linear constant current circuit and the low frequency ripple rejection circuit;
the linear constant current circuit is configured to be connected with the low-frequency ripple suppression circuit to provide a constant current to an LED load;
the low-frequency ripple suppression circuit comprises the LED load, a control chip comprising a metal-oxide semiconductor field effect transistor (MOSFET), an output capacitor, a diode and a plurality of resistors, wherein one end of the output capacitor is connected with a positive voltage end of the LED load, the other end of the output capacitor is used as a reference ground of the control chip and is connected to one end of a voltage division network, the other end of the voltage division network is connected to a system ground, a source electrode of the MOSFET is connected to the reference ground of the control chip, and a drain electrode of the MOSFET and a cathode electrode of the LED load are connected to the linear constant current circuit together;
wherein the control chip is configured to detect an output characterization voltage characterizing an output voltage across the LED load or the output capacitance, and to control the turning on and off of the MOSFET based on the output characterization voltage, a first reference voltage, and a second reference voltage.
2. The circuit of claim 1, wherein the output characterization voltage is obtained by dividing a voltage between a reference ground of the control chip and a system ground by the voltage dividing network.
3. The circuit of claim 1, wherein the control chip further comprises:
a first comparator for comparing the output characterization voltage with the first reference voltage to obtain a first comparison result;
the second comparator is used for comparing the output characterization voltage with the second reference voltage to obtain a second comparison result;
and the logic control component is used for controlling the on and off of the MOSFET based on the first comparison result and the second comparison result.
4. The circuit of any of claims 1-3, wherein the control chip further comprises an oscillator, the control chip configured to control the turning on and off of the MOSFETs based on a frequency and duty cycle of the oscillator output.
5. The circuit of claim 3, wherein the first reference voltage is greater than the second reference voltage, the logic control component configured to:
when the output characterization voltage is increased to be equal to the second reference voltage, the MOSFET of the control chip is cut off, so that a discharge path of the output capacitor to the LED load is cut off; when the output characterization voltage is increased to be equal to a first reference voltage, the MOSFET of the control chip is turned on, so that a discharge path of the output capacitor to the LED load is turned on; when the output characterization voltage increases again to equal the second reference voltage, the MOSFET is turned off again.
6. The circuit of claim 4, wherein the first reference voltage is greater than the second reference voltage, the logic control component configured to:
when the output characterization voltage is increased to be equal to the second reference voltage, the MOSFET of the control chip is cut off, so that a discharge path of the output capacitor to the LED load is cut off; when the output representative voltage increases to equal the first reference voltage, configuring the MOSFET at the provided discharge frequency and duty cycle to cause the output capacitor to PWM pulse discharge the LED load; and stopping the PWM pulse discharge when the output characterization voltage is lower than a second reference voltage, and conducting the internal MOSFET until the output characterization voltage is increased to be equal to the second reference voltage again.
7. The circuit of claim 1, wherein the linear constant current circuit is a non-dimming linear constant current circuit.
8. The circuit of claim 1, wherein the linear constant current circuit is a TRIAC dimmed linear constant current circuit.
9. The circuit of claim 1, wherein the rectifying circuit is a bridge rectifying circuit.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920180913.4U CN210781469U (en) | 2019-02-01 | 2019-02-01 | Circuit for inhibiting low-frequency ripple current of light-emitting diode |
| TW108203255U TWM582726U (en) | 2019-02-01 | 2019-03-18 | Circuit for suppressing low-frequency ripple current of light-emitting diode |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201920180913.4U CN210781469U (en) | 2019-02-01 | 2019-02-01 | Circuit for inhibiting low-frequency ripple current of light-emitting diode |
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| Publication Number | Publication Date |
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| CN210781469U true CN210781469U (en) | 2020-06-16 |
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| CN201920180913.4U Active CN210781469U (en) | 2019-02-01 | 2019-02-01 | Circuit for inhibiting low-frequency ripple current of light-emitting diode |
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| Country | Link |
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| TW (1) | TWM582726U (en) |
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| TWI718925B (en) * | 2020-04-08 | 2021-02-11 | 大陸商北京集創北方科技股份有限公司 | Short-time pulse elimination circuit, voltage detection circuit and display driver chip |
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