CN112020176B - Driving circuit of light emitting diode - Google Patents
Driving circuit of light emitting diode Download PDFInfo
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- CN112020176B CN112020176B CN201910458074.2A CN201910458074A CN112020176B CN 112020176 B CN112020176 B CN 112020176B CN 201910458074 A CN201910458074 A CN 201910458074A CN 112020176 B CN112020176 B CN 112020176B
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Abstract
The invention provides a driving circuit of a light emitting diode, which comprises a chip, a bridge rectifier, a first diode, a second diode and a first capacitor. The light emitting diode comprises an anode and a cathode, and the cathode of the light emitting diode is grounded. The chip is provided with a first input pin, a second input pin and an output pin, wherein the output pin is coupled with the anode of the light emitting diode through a resistor. The bridge rectifier is bridged to an alternating voltage source and is provided with a grounding end and a current output end, and the current output end is connected to a first input pin of the chip. The cathode of the first diode is connected to the second input pin of the chip. The cathode of the second diode is connected to the anode of the first diode, and the anode of the second transistor is grounded. The cathode end of the first capacitor is connected with the anode of the first diode, and the anode end of the first capacitor is connected with the current output end of the bridge rectifier.
Description
Technical Field
The present invention relates to a driving circuit for a light emitting diode, and more particularly, to a driving circuit for a light emitting diode capable of reducing the occurrence of a Flicker (Flicker).
Background
In general, in order to reduce the energy consumption, the commercial power is transmitted from the power plant to the user terminal in an ac mode, the commercial power in taiwan area of china is 60Hz ac, and when the backlight source of the LED screen uses the commercial power as the power source, the human eyes receive the flickering vision due to the sudden brightness of the backlight source, which causes the phenomenon of Flicker (Flicker).
Disclosure of Invention
In order to reduce the phenomenon of screen-flash easily perceived by human eyes generated by the LED light source, it is necessary to invent a light-emitting diode driving circuit capable of reducing screen-flash.
In an embodiment of the driving circuit of the light emitting diode of the present invention, the driving circuit includes a chip, a bridge rectifier, a first diode, a second diode, and a first capacitor. The light emitting diode comprises an anode and a cathode, and the cathode of the light emitting diode is grounded. The chip is provided with a first input pin, a second input pin and an output pin, wherein the output pin is coupled with the anode of the light emitting diode through a resistor. The bridge rectifier is bridged to an alternating voltage source and is provided with a grounding end and a current output end, and the current output end is connected to a first input pin of the chip. The cathode of the first diode is connected to the second input pin of the chip. The cathode of the second diode is connected to the anode of the first diode, and the anode of the second diode is grounded. The cathode end of the first capacitor is connected with the anode of the first diode, and the anode end of the first capacitor is connected with the current output end of the bridge rectifier.
In one embodiment, when the driving circuit operates in the first mode, the driving current of the driving circuit flows from the current output terminal of the bridge rectifier to the first input pin of the chip, and then flows from the output pin of the chip to the light emitting diode.
In one embodiment, the driving circuit operates in the first mode when the input voltage generated by the ac voltage source is higher than the forward bias voltage of the light emitting diode but lower than the sum of the forward bias voltage of the light emitting diode and the voltage across the first capacitor.
In one embodiment, when the driving circuit operates in the second mode, the driving current of the driving circuit flows from the current output terminal of the bridge rectifier to the second input pin of the chip, and then flows from the output pin of the chip to the light emitting diode.
In one embodiment, the driving circuit operates in the second mode when the input voltage generated by the ac voltage source is higher than the sum of the forward bias voltage of the light emitting diode and the voltage across the first capacitor.
In an embodiment, when the driving circuit operates in the third mode, the driving current of the driving circuit flows from the first capacitor to the first input pin of the chip, and then flows from the output pin of the chip to the light emitting diode.
In an embodiment, when the voltage across the first capacitor is higher than the input voltage generated by the ac voltage source and higher than the forward bias voltage of the light emitting diode, the driving circuit operates in the third mode.
In one embodiment, the chip includes a first operational amplifier, a first transistor, a second operational amplifier, and a second transistor. The non-inverting input terminal of the first operational amplifier is connected to a reference voltage. The drain electrode of the first transistor is connected to the first input pin of the chip, the grid electrode of the first transistor is connected to the output end of the first operational amplifier, and the source electrode of the first transistor is connected to the output pin of the chip and the negative phase input end of the first operational amplifier. The non-inverting input terminal of the second operational amplifier is also connected to the reference voltage. The drain electrode of the second transistor is connected with the second input pin of the chip, the grid electrode of the second transistor is connected with the output end of the second operational amplifier, and the source electrode of the second transistor is connected with the output pin of the chip and the negative phase input end of the second operational amplifier.
In an embodiment, the chip further has a third input pin, and the driving circuit further includes a second capacitor coupled between the anode of the light emitting diode and the third input pin of the chip.
In one embodiment, the third input pin of the chip is connected to the first operational amplifier and the second operational amplifier to provide the operating voltage to the first operational amplifier and the second operational amplifier.
When the driving circuit is switched among the first mode, the second mode and the third mode, the light-emitting diode is driven by the continuous current, so that the light-emitting diode can always maintain a light-emitting state, and the phenomenon of screen flashing does not occur.
Drawings
FIG. 1 depicts a circuit diagram of an embodiment of a driving circuit for a light emitting diode of the present invention;
FIG. 2 depicts a circuit diagram of an embodiment of the chip IC of FIG. 1;
FIG. 3 is a schematic diagram of a driving circuit of the LED of the present invention operating in a first mode;
FIG. 4 is a schematic diagram of the driving circuit of the LED of the present invention operating in a second mode;
fig. 5 depicts a schematic diagram of the driving circuit of the light emitting diode of the present invention when operating in the third mode.
[ list of reference numerals ]
1. Driving circuit
2. Light emitting diode
A1 and A2 operational amplifier
AC voltage source
C1 First capacitor
C2 Second capacitor
D1, D2 diode
DS1, DS2, LV, RS pins
I drive current
IC chip
M1, M2 transistors
RE bridge rectifier
R resistor
Vref1, vref2 reference voltage
Detailed Description
The driving circuit of the light emitting diode can continuously provide driving current for the light emitting diode, so that the light emitting diode is always in a conducting and luminous state, and therefore, the phenomenon of screen flashing does not occur.
For a full understanding of the objects, features and advantages of the present invention, reference should be made to the following detailed description of the invention, taken in conjunction with the accompanying drawings, in which:
referring to fig. 1, fig. 1 is a circuit diagram of an embodiment of a driving circuit of a light emitting diode according to the present invention. The driving circuit 1 is used for providing a driving current I for the light emitting diode 2, so that the light emitting diode 2 can conduct and emit light. As shown in fig. 1, the driving circuit 1 includes a chip IC, a bridge rectifier RE, a first diode D1, a second diode D2, a coupling second capacitor C2, and a first capacitor C1. In a preferred embodiment, the first capacitor C1 may be an electrolytic capacitor. The chip IC has a first pin DS1, a second pin DS2, a third pin LV and a fourth pin RS. The anode of the light emitting diode 2 is coupled to the fourth pin RS of the chip IC through the resistor R, and the cathode of the light emitting diode 2 is connected to the ground.
The bridge rectifier bridge RE has a current output terminal, a ground terminal and two voltage input terminals. The AC voltage source AC is bridged between the two voltage input terminals of the bridge rectifier RE, so that the AC voltage source AC can generate an output with the same polarity at the current output terminal of the bridge rectifier RE after full-wave rectification of the bridge rectifier RE. The current output end of the bridge rectifier RE is connected to the first pin DS1 of the chip IC, so that the driving current I output by the bridge rectifier RE can flow into the chip IC through the first pin DS1, and the ground end of the bridge rectifier RE is connected to the ground.
The cathode of the first diode D1 is connected to the second pin DS2 of the chip IC, and the anode of the first diode D1 is connected to one end of the first capacitor C1. The other end of the first capacitor C1 is connected to the first pin DS1 of the chip 1. The cathode of the second diode D2 is connected to the anode of the first diode D1, and the anode of the second transistor D2 is connected to ground. The third pin LV of the chip IC is connected to one end of the second capacitor C2, and the other end of the second capacitor C2 is connected to the anode of the light emitting diode 2.
Referring to fig. 2, fig. 2 is a circuit diagram of an embodiment of the chip IC in fig. 1. As can be seen from fig. 2, the chip IC includes a first operational amplifier A1, a first transistor M1, a second operational amplifier A2 and a second transistor M2. In this embodiment, the non-inverting input terminal of the first operational amplifier A1 is connected to the reference voltage Vref1, and the non-inverting input terminal of the second operational amplifier A2 is connected to the reference voltage Vref2. The first transistor M1 is configured to guide the driving current I from the first pin DS1 of the chip IC to the fourth pin RS of the chip IC, so that the drain of the first transistor M1 is connected to the first pin DS1 of the chip IC, the source of the first transistor M1 is connected to the fourth pin RS of the chip IC, the gate of the first transistor M1 is connected to the output terminal of the first operational amplifier A1, and when the voltage at the output terminal of the first operational amplifier A1 is higher than the threshold voltage of the first transistor M1, the first transistor M1 is turned on to guide the driving current I from the first pin DS1 of the chip IC to the fourth pin RS of the chip IC. In addition, the source of the first transistor M1 is also negatively feedback connected to the negative input terminal of the first operational amplifier A1.
Similarly, the second transistor M2 is configured to guide the driving current I from the second pin DS2 of the chip IC to the fourth pin RS of the chip IC, so that the drain of the second transistor M2 is connected to the second pin DS2 of the chip IC, the source of the second transistor M2 is connected to the fourth pin RS of the chip IC, the gate of the second transistor M2 is connected to the output terminal of the second operational amplifier A2, and when the voltage of the output terminal of the second operational amplifier A2 is higher than the threshold voltage of the second transistor M2, the second transistor M2 is turned on to guide the driving current I from the second pin DS2 of the chip IC to the fourth pin RS of the chip IC. In addition, the source of the second transistor M2 is also negatively feedback connected to the negative input terminal of the second operational amplifier A2.
The first operational amplifier A1 and the second operational amplifier A2 are further connected to the third pin LV of the chip IC, and the voltage across the second capacitor C2 provides the operating voltage to the first operational amplifier A1 and the second operational amplifier A2.
Referring to fig. 3, fig. 3 is a schematic diagram illustrating a driving circuit of the led according to the present invention operating in a first mode. As shown in fig. 3, when the input voltage (i.e., the voltage at the current output end of the bridge rectifier RE) generated by the AC voltage source AC after full-wave rectification of the bridge rectifier bridge RE gradually increases to be larger than the forward bias voltage of the light emitting diode 2 and the voltage across the first capacitor C1, the driving circuit 1 operates in the first mode, and the light emitting diode 2 is turned on to emit light due to the input voltage being larger than the forward bias voltage of the light emitting diode 2, so that the driving current I flows into the first pin DS1 of the chip IC. When the driving circuit 1 operates in the first mode, the path of the driving current I is shown by the arrow in fig. 3.
Referring to fig. 4, fig. 4 is a schematic diagram illustrating the driving circuit of the led according to the present invention operating in the second mode. When the input voltage is continuously increased, the driving circuit 1 is changed from the first mode operation to the second mode operation when the sum of the voltages across the light emitting diode 2 and the first capacitor C1 is larger, and the voltage across the first capacitor C1 is continuously increased, but the voltage across the first capacitor C1 is maintained as the first diode C1 is turned on, so that the input voltage is larger than the sum of the forward bias voltage of the light emitting diode 2 and the voltage across the first capacitor C1. When the driving circuit 1 is switched to operate in the second mode, the first diode C1 is turned on, so that the driving current I flows into the second pin DS2 of the chip IC. At this time, the input voltage is higher than the sum of the forward bias voltage of the light emitting diode 2 and the voltage across the first capacitor C1, and the input voltage is still higher than the forward bias voltage of the light emitting diode 2 after the voltage drop across the first capacitor C1, so that the light emitting diode 2 is turned on to emit light. When the driving circuit 1 operates in the second mode, the path of the driving current I is shown by the arrow in fig. 4.
Referring to fig. 5, fig. 5 is a schematic diagram illustrating the driving circuit of the led according to the present invention operating in the third mode. As can be seen from fig. 5, when the input voltage starts to decrease, the driving circuit 1 is switched from the second mode to the third mode. When the input voltage gradually decreases and becomes smaller than the voltage across the first capacitor C1, the driving circuit 1 will switch to operate in the third mode, at this time, the first capacitor C1 will start to discharge, the driving current I flows from the first capacitor C1 to the first pin DS1 of the chip IC, at this time, as long as the voltage across the first capacitor C1 is still higher than the forward bias voltage of the light emitting diode 2, the light emitting diode 2 can be turned on to emit light until the input voltage gradually increases and until the input voltage is higher than the forward bias voltage of the light emitting diode 2, at this time, the driving circuit 1 will switch to operate in the first mode. When the drive circuit 1 operates in the third mode, the path of the drive current I is shown by the arrow in fig. 5.
In summary, the driving circuit of the light emitting diode of the present invention can keep the diode conducting and emitting light in the first mode, the second mode and the third mode respectively, so that no flash phenomenon occurs.
The invention has been described hereinabove in terms of preferred embodiments, but it will be understood by those skilled in the art that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of the invention. It should be noted that all changes and substitutions equivalent to the embodiment are intended to be included in the scope of the present invention. Accordingly, the scope of the invention is defined by the appended claims.
Claims (9)
1. A driving circuit for driving a light emitting diode, the light emitting diode comprising an anode and a cathode, the cathode of the light emitting diode being grounded, the driving circuit comprising:
the chip is provided with a first input pin, a second input pin and an output pin, wherein the output pin is coupled with the anode of the light-emitting diode through a resistor;
the bridge rectifier is bridged to an alternating voltage source and is provided with a grounding end and a current output end, and the current output end is connected to a first input pin of the chip;
a first diode having a first cathode and a first anode, the first cathode being connected to the second input pin;
the second diode is provided with a second cathode and a second anode, the second cathode is connected with the first anode of the first diode, and the second anode is grounded; and
a first capacitor having a third cathode terminal and a third anode terminal, the third cathode terminal being connected to the first anode of the first diode and the third anode terminal being connected to the current output terminal of the bridge rectifier,
wherein the chip comprises:
the first operational amplifier is provided with a first positive-phase input end, a first negative-phase input end and a first output end, wherein the first positive-phase input end is connected with a reference voltage;
the first transistor is provided with a first source electrode, a first drain electrode and a first grid electrode, wherein the first drain electrode is connected with a first input pin of the chip, the first grid electrode is connected with a first output end of the first operational amplifier, and the first source electrode is connected with the output pin of the chip and a negative phase input end of the first operational amplifier;
the second operational amplifier is provided with a second positive-phase input end, a second negative-phase input end and a second output end, and the second positive-phase input end is connected with the reference voltage; and
the second transistor is provided with a second source electrode, a second drain electrode and a second grid electrode, wherein the second drain electrode is connected with a second input pin of the chip, the second grid electrode is connected with a second output end of the second operational amplifier, and the second source electrode is connected with the output pin of the chip and a negative phase input end of the second operational amplifier.
2. The driving circuit of claim 1, wherein when the driving circuit operates in the first mode, a driving current of the driving circuit flows from a current output terminal of the bridge rectifier to a first input pin of the chip, and then flows from an output pin of the chip to the light emitting diode through a resistor.
3. The driving circuit of claim 2, wherein the driving circuit operates in the first mode when an input voltage generated by the ac voltage source is higher than a forward bias voltage of the light emitting diode but lower than a sum of the forward bias voltage and a voltage across the first capacitor.
4. The drive circuit of claim 1, wherein when the drive circuit is operated in the second mode, a drive current of the drive circuit flows from the current output of the bridge rectifier to the second input pin of the chip and then from the output pin of the chip to the light emitting diode.
5. The driving circuit of claim 4, wherein the driving circuit operates in the second mode when the input voltage generated by the ac voltage source is higher than a sum of the forward bias of the light emitting diode and the voltage across the first capacitor.
6. The drive circuit of claim 1, wherein when the drive circuit is operated in a third mode, a drive current of the drive circuit flows from the first capacitor to a first input pin of the chip and then from an output pin of the chip to the light emitting diode.
7. The driving circuit of claim 6, wherein the driving circuit operates in the third mode when a voltage across the first capacitor is higher than an input voltage generated by the ac voltage source and higher than a forward bias voltage of the light emitting diode.
8. The driving circuit of claim 1, wherein the chip further comprises a third input pin, and the driving circuit further comprises a second capacitor coupled between the anode of the light emitting diode and the third input pin.
9. The driving circuit of claim 8, wherein a third input pin of the chip is connected to the first operational amplifier and the second operational amplifier to provide an operating voltage to the first operational amplifier and the second operational amplifier.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910458074.2A CN112020176B (en) | 2019-05-29 | 2019-05-29 | Driving circuit of light emitting diode |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201910458074.2A CN112020176B (en) | 2019-05-29 | 2019-05-29 | Driving circuit of light emitting diode |
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| CN112020176B true CN112020176B (en) | 2023-05-12 |
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