CN113068287B - Dimming circuit with stable output voltage - Google Patents
Dimming circuit with stable output voltage Download PDFInfo
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- CN113068287B CN113068287B CN201911286113.1A CN201911286113A CN113068287B CN 113068287 B CN113068287 B CN 113068287B CN 201911286113 A CN201911286113 A CN 201911286113A CN 113068287 B CN113068287 B CN 113068287B
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Abstract
The invention mainly discloses a light modulation circuit with stable output voltage, which is applied to an LED power supply circuit and comprises: a dimming signal processing unit, a stabilizing unit, a dimming turn-off unit, and an isolating unit. In the present invention, the dimming signal processing unit receives a dimming control signal, and the dimming processing unit generates a dimming turn-off signal to the dimming turn-off unit when the dimming control signal is smaller than a threshold value. Then, the dimming turn-off unit starts the stabilizing unit to stabilize an output power supply of a switching power converter, so as to improve the defect that the output voltage of the conventional power supply jumps to cause the light-emitting unit to flicker when the conventional power supply is turned on after being turned off.
Description
Technical Field
The present invention relates to the field of LED driving control, and more particularly, to a dimming circuit with stable output voltage.
Background
Light-Emitting diodes (LEDs) have been widely used in daily lighting due to their advantages of small size, energy saving and long service life. Furthermore, a dimming circuit of the light emitting diode is developed, so that a user can adjust the brightness of the LED according to the actual use environment and situation.
In order to conveniently control the dimming and extinguishing of the LED lighting, a conventional LED dimming circuit usually uses a Metal-Oxide-Semiconductor Field-effect transistor (MOSFET) as its switching unit. Referring to fig. 1, a block diagram of a conventional dimming circuit is shown. As shown in fig. 1, a conventional dimming circuit 1' includes: a current source 11 ', a driving unit 12', a light emitting unit 13 ', a signal processing unit 14', a feedback unit 15 ', and a switching unit 16'. The driving unit 12 ' is coupled between the current source 11 ' and the light emitting unit 13 '. Then, the signal processing unit 14 ' receives a dimming signal of a dimming unit 2 ' and outputs a current reference signal to the feedback unit 15 ', so that the feedback unit 15 ' correspondingly transmits a current adjusting signal to the driving unit 12 '. Thus, the feedback unit 15 ' is coupled to the primary side of the driving unit 12 ' to change the output current of the driving unit 12 ' by adjusting the duty ratio or frequency, thereby achieving the purpose of dimming. However, when the dimming signal of the dimming unit 2 'is an off signal, the signal processing unit 14' correspondingly turns off the switch unit 16 ', and further turns off the power output line of the dimming circuit 1'; thus, the dimming circuit 1' achieves the effect of complete dimming. Although the above-mentioned dimming circuit 1 'has the effect of dimming and extinguishing, the dimming circuit 1' still has the following disadvantages:
(1) as is well known to engineers familiar with circuit system design, the use of MOSFETs as switching cells will increase overall cost. Meanwhile, in order to take into account that the MOSFET may be suddenly short-circuited in normal operation when used as a switching unit, the conventional dimming circuit 1' usually selects a MOSFET with a high pulse current specification, which results in a higher manufacturing cost of the stripe circuit. On the other hand, when the MOSFET is turned off and turned on, the output voltage of the conventional dimming circuit 1 'is unstable, which causes the light emitting unit 13' to flicker, and further causes the user to feel discomfort such as eye fatigue or headache. Therefore, it is an urgent trend in the related art to reduce the component cost of the dimming circuit and improve the flicker phenomenon of the light emitting unit.
As can be seen from the above, the conventional light adjusting circuit 1' still has many defects, which causes its disadvantages. Accordingly, the present invention provides a light adjusting circuit with stable output voltage, which is capable of providing stable output voltage.
Disclosure of Invention
The present invention provides a dimming circuit with stable output voltage, which is applied in an LED power supply circuit and includes: a dimming signal processing unit, a stabilizing unit, a dimming turn-off unit, and an isolating unit. Particularly, the dimming signal processing unit of the present invention receives a dimming control signal, and generates a dimming turn-off signal to the dimming turn-off unit when the dimming control signal is smaller than a threshold value. Then, the dimming turn-off unit enables the stabilizing unit to stabilize an output power of the switching power converter. Therefore, the dimming circuit with stable output voltage not only improves the defect that the output voltage of the existing power supply has jump and instability when being turned off to be turned on, which causes the light-emitting unit to generate flicker. Meanwhile, the problems that the existing circuit uses the MOSFET as the switch unit, so that the cost of the component is high and the component is easy to damage are solved.
To achieve the above objective of the present invention, the inventor provides an embodiment of the dimming circuit with stable output voltage, which is applied in an LED power supply circuit including a switching power converter, a voltage feedback unit, a current feedback unit, and an optocoupler; the dimming circuit includes:
a dimming signal processing unit having a first signal receiving terminal, a second signal receiving terminal and a signal output terminal, wherein the first signal receiving terminal is coupled to a dimming signal input terminal of the current feedback unit, and the second signal receiving terminal is coupled to a dimming control signal;
a stabilizing unit having a first electrical terminal and a second electrical terminal, wherein the first electrical terminal is coupled to an output terminal of the switching power converter;
a light-adjusting turn-off unit having a first receiving end, a second receiving end and an output end, wherein the first receiving end is coupled to the signal output end of the light-adjusting signal processing unit, and the second receiving end is coupled to the second electrical end of the stabilizing unit; and
an isolation unit having a first electrical connection end, a second electrical connection end, a third electrical connection end, and a fourth electrical connection end, wherein the first electrical connection end is coupled to the output end of the dimming turn-off unit, the second electrical connection end is coupled to a current error signal output end of the current feedback unit, the third electrical connection end is coupled to a voltage error signal output end of the voltage feedback unit, and the fourth electrical connection end is coupled to a signal input end of the optical coupler;
when the dimming control signal is smaller than a critical value, the dimming signal processing unit generates a dimming turn-off signal to the dimming turn-off unit, the dimming turn-off unit couples the signal input end of the optical coupler to a ground end, and the dimming turn-off unit enables the stabilizing unit to stabilize an output power of the switching power converter.
Drawings
FIG. 1 is a block diagram of a conventional dimming circuit;
FIG. 2 is a first block diagram of a dimming circuit with a stable output voltage according to the present invention;
FIG. 3 is a circuit diagram of a dimming circuit with a stable output voltage according to the present invention;
FIG. 4 is a graph showing the relationship between the current and the voltage of a light emitting unit using the dimming circuit with a stable output voltage according to the present invention; and
FIG. 5 is a graph showing the relationship between the dimming control signal and the brightness of the light emitting unit.
The main symbols in the figures illustrate:
1' light modulation circuit
11' current source
12' drive unit
13' light emitting unit
14' signal processing unit
15' feedback unit
16' switch unit
2' light modulation unit
1 light modulation circuit with stable output voltage
11 dimming signal processing unit
111 first signal receiving terminal
112 second signal receiving terminal
113 signal output terminal
12 stabilizing unit
121 first electrical terminal
122 second electrical terminal
13 dimming turn-off unit
131 first receiving end
132 second receiving terminal
133 output terminal
14 isolation unit
141 first electrical connection terminal
142 second electrical connection terminal
143 third electrical connection terminal
144 fourth electrical connection terminal
145 first diode
146 second diode
147 third diode
2 LED power supply circuit
21 switching power converter
211 input terminal
22 voltage feedback unit
221 voltage error signal output terminal
23 current feedback unit
231 dimming signal input terminal
232 current error signal output terminal
24 optical coupler
DCS dimming control signal
G ground terminal
R resistance
Vcc power supply
ACs power supply
3 light emitting unit
Detailed Description
In order to more clearly describe the dimming circuit with stable output voltage proposed by the present invention, the following description will be made in detail with reference to the accompanying drawings.
Referring to fig. 2, a first block diagram of a dimming circuit with a stable output voltage according to the present invention is shown. Fig. 3 is a circuit diagram of the dimming circuit with stable output voltage according to the present invention. As shown in fig. 2 and fig. 3, the Light adjusting circuit 1 with stable output voltage of the present invention is applied in a Light-emitting diode (LED) power supply circuit 2, and the LED power supply circuit 2 mainly includes: a switching power converter 21, a voltage feedback unit 22, and a current feedback unit 23. The dimming circuit 1 with a stable output voltage of the present invention includes: a dimming signal processing unit 11, a stabilizing unit 12, a dimming turn-off unit 13, and an isolating unit 14. More specifically, an input 211 of the switching power converter 21 is coupled to a power source ACs. The voltage feedback unit 22 is connected in parallel to an output end of the switching power converter 21, and the current feedback unit 23 is coupled between the output end of the switching power converter 21 and a light emitting unit. In addition, the LED power supply circuit 2 may further include an optical coupler 24; the optocoupler 24 is coupled between the isolation unit 14 and an input end 211 of the switching power converter 21. In addition, the optical coupler 24 is further coupled to a resistor R and a power supply Vcc. As shown in fig. 2, the dimming signal processing unit 11 has a first signal receiving terminal 111, a second signal receiving terminal 112 and a signal output terminal 113, and the first signal receiving terminal 111 is coupled to a dimming signal input terminal 231 of the current feedback unit 23; the second signal receiving terminal 112 of the dimming signal processing unit 11 is coupled to an external dimming control signal DCS. Then, the stabilizing unit 12 has a first electrical terminal 121 and a second electrical terminal 122, wherein the first electrical terminal 121 is coupled to the output terminal of the switching power converter 21.
With continued reference to fig. 2 and 3, the isolation unit 14 has a first electrical connection 141, a second electrical connection 142, a third electrical connection 143, and a fourth electrical connection 144. As shown in fig. 3, the first electrical connection 141 is coupled to the dimming shutdown unit 13, and the second electrical connection 142 is coupled to a current error signal output end 232 of the current feedback unit 23. Moreover, the third electrical connection terminal 143 of the isolation unit 14 is coupled to a voltage error signal output terminal 221 of the voltage feedback unit 22, and the fourth electrical connection terminal 144 is coupled to a signal input terminal of the optical coupler 24. Thus, when the dimming signal processing unit 11 receives the dimming control signal DCS from the outside and the dimming control signal DCS is smaller than a threshold value, the dimming signal processing unit 11 generates a dimming off signal (Dim off signal) to the dimming off unit 13. Then, the dimming shutdown unit 13 couples the signal input terminal of the optical coupler 24 to a ground terminal G, and the dimming shutdown unit 13 activates the stabilizing unit 12 to stabilize an output power of the switching power converter 21. Therefore, the dimming circuit 1 with stable output voltage of the present invention enables the switching power converter 21 of the LED power supply circuit 2 to continuously output a stable voltage to the stabilizing unit 12, so as to improve the problem that the output voltage of the conventional power supply has a jump and instability when being turned off to be turned on, which causes the light emitting unit to generate flicker. Meanwhile, the disadvantage that the existing dimming circuit 1' uses the MOSFET as the switch unit thereof to increase the overall cost is improved.
On the other hand, when the dimming control signal DCS is greater than the threshold value, the dimming signal processing unit 11 generates a dimming signal to the current feedback unit 23. The current feedback unit 23 obtains a reference signal according to the output power of the switching power converter 21. Then, the current feedback unit 23 correspondingly outputs a current error signal to an input end 211 of the switching power converter 21 via the isolation unit 14 and the optical coupler 24 according to the dimming signal and the reference signal, so as to adjust the output power of the switching power converter 21 to adjust the brightness of the light emitting unit 3. It should be noted that the stabilizing unit 12 is a resistor, and the dimming signal processing unit 11 can be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET); moreover, the first signal receiving terminal 111, the second signal receiving terminal 112 and the signal output terminal 113 of the dimming signal processing unit 11 are a drain terminal, a gate terminal and a source terminal of the mosfet, respectively. On the other hand, the dimming signal processing unit 11 may also be a silicon-controlled rectifier (SCR); the first signal receiving terminal 111, the second signal receiving terminal 112 and the signal output terminal 113 of the dimming signal processing unit 11 are an emitter terminal, a base terminal and a collector terminal of a silicon controlled diode, respectively.
Referring again to fig. 3, as shown in fig. 3, the isolation unit 14 includes a first diode 145, a second diode 146, and a third diode 147. One cathode terminal of the first diode 145 is used as the third electrical connection terminal 143. The second diode 146 has a cathode terminal as the second electrical connection terminal 142, an anode terminal coupled to an anode terminal of the first diode 145, a cathode terminal of the third diode 147 as the third electrical connection terminal 143, and an anode terminal coupled to the anode terminal of the second diode 146 and the signal input terminal of the optical coupler 24 as the fourth electrical connection terminal 144. Thus, the isolation unit 14 can achieve the isolation function between the voltage feedback unit 22, the current feedback unit 23 and the dimming shutdown unit 13. To explain in more detail, the dimming turn-off unit 13 of the present invention includes: a switching transistor and a resistor. A collector terminal of the switching transistor serves as the second receiving terminal 132 and the output terminal 133, an emitter terminal thereof serves as a ground terminal G, and a base terminal thereof serves as the first receiving terminal 131. The resistor of the dimming turn-off unit 13 has one electrical end coupled to the base terminal of the switching transistor, and the other electrical end coupled to the emitter terminal of the switching transistor.
With continuing reference to fig. 2 and 3 and with simultaneous reference to fig. 4 and 5, graphs of current and voltage of the light emitting unit and graphs of the dimming control signal and the brightness of the light emitting unit using the dimming circuit with stable output voltage according to the present invention are shown. Fig. 4 is a graph showing a relationship between a voltage and a current of the light emitting unit 3 of the dimming circuit 1 with a stable output voltage according to the present invention, and it can be known from fig. 4 that when the voltage of the light emitting unit 3 reaches a minimum value (Vmin), the current flowing through the light emitting unit is 0 ampere; that is, the light adjusting circuit 1 with stable output voltage of the present invention achieves the effect of adjusting light and turning off (Dim off), and has the function of setting the minimum value of the voltage across the light emitting unit 3 to a constant value (Vmin) to solve the problem of flicker caused by unstable voltage. Next, as can be seen from fig. 5, when the dimming control signal is lower than a certain level, the brightness of the light emitting unit 3 is 0.
Thus, the technical features and the perspective view of the dimming circuit with stable output voltage of the present invention are fully and clearly illustrated, and the following advantages can be obtained from the above description:
(1) the conventional dimming circuit 1 'is different from the conventional dimming circuit 1' in that the MOSFET is used as a switching unit to increase the component cost, and the light emitting unit 13 'is easy to flicker due to the jump and instability of the output voltage of the conventional dimming circuit 1'. The main objective of the present invention is to provide a dimming circuit 1 with stable output voltage, which is applied in an LED power supply circuit 2 including a switching power converter 21, a voltage feedback unit 22, a current feedback unit 23, and an optocoupler 24. It should be noted that the dimming signal processing unit 11 of the present invention receives a dimming control signal DCS, and the dimming signal processing unit 11 generates a dimming off signal (Dim off signal) to the dimming off unit 13 when the dimming control signal DCS is smaller than a threshold. Then, the dimming turn-off unit 13 activates the stabilizing unit 12 to stabilize an output power of the switching power converter 21. As can be seen from the above, the dimming circuit 1 with stable output voltage of the present invention enables a switching power supply 21 to stably output power. Therefore, the dimming circuit 1 with stable output voltage of the present invention not only improves the disadvantage of the flicker of the light emitting unit caused by the jump and instability of the output voltage of the conventional power supply when the power supply is turned on after being turned off. Meanwhile, the problems that the existing circuit uses the MOSFET as the switch unit, so that the cost of the component is high and the component is easy to damage are solved.
It should be emphasized that the above detailed description is specific to possible embodiments of the invention, but this is not to be taken as limiting the scope of the invention, and all equivalent implementations or modifications that do not depart from the technical spirit of the invention are intended to be included within the scope of the invention.
Claims (8)
1. A light modulation circuit with stable output voltage is applied to an LED power supply circuit comprising a switching power converter, a voltage feedback unit, a current feedback unit and an optical coupler; characterized in that, this dimmer circuit includes:
a dimming signal processing unit having a first signal receiving terminal, a second signal receiving terminal and a signal output terminal, wherein the first signal receiving terminal is coupled to a dimming signal input terminal of the current feedback unit, and the second signal receiving terminal is coupled to a dimming control signal;
a stabilizing unit having a first electrical terminal and a second electrical terminal, wherein the first electrical terminal is coupled to an output terminal of the switching power converter;
a light-adjusting turn-off unit having a first receiving end, a second receiving end and an output end, wherein the first receiving end is coupled to the signal output end of the light-adjusting signal processing unit, and the second receiving end is coupled to the second electrical end of the stabilizing unit; and
an isolation unit having a first electrical connection end, a second electrical connection end, a third electrical connection end, and a fourth electrical connection end, wherein the first electrical connection end is coupled to the output end of the dimming turn-off unit, the second electrical connection end is coupled to a current error signal output end of the current feedback unit, the third electrical connection end is coupled to a voltage error signal output end of the voltage feedback unit, and the fourth electrical connection end is coupled to a signal input end of the optical coupler;
when the dimming control signal is smaller than a critical value, the dimming signal processing unit generates a dimming turn-off signal to the dimming turn-off unit, the dimming turn-off unit couples the signal input end of the optical coupler to a ground end, and the dimming turn-off unit enables the stabilizing unit to stabilize an output power of the switching power converter.
2. The dimming circuit of claim 1, wherein the output power source is any one of the following: an output voltage, an output current, or a combination of the two.
3. The dimming circuit of claim 1, wherein the dimming signal processing unit generates a dimming signal to the current feedback unit when the dimming control signal is greater than the threshold, and the current feedback unit outputs a current error signal to an input terminal of the switching power converter according to the dimming signal and a reference signal to adjust the output power of the switching power converter.
4. The dimming circuit of claim 1, wherein the stabilizing unit is a resistor.
5. The dimming circuit of claim 1, wherein the dimming signal processing unit is a mosfet, and the first signal receiving terminal, the second signal receiving terminal and the signal output terminal are a drain terminal, a gate terminal and a source terminal of the mosfet, respectively.
6. The dimming circuit of claim 1, wherein the dimming signal processing unit is a silicon controlled diode, and the first signal receiving terminal, the second signal receiving terminal and the signal output terminal are an emitter terminal, a base terminal and a collector terminal of the silicon controlled diode, respectively.
7. The dimming circuit of claim 1, wherein the isolation unit comprises:
a first diode, wherein a cathode end of the first diode is used as the third electrical connection end;
a second diode, wherein a cathode terminal of the second diode is used as the second electrical connection terminal, and an anode terminal of the second diode is coupled to an anode terminal of the first diode; and
and a third diode, having a cathode terminal as the third electrical connection terminal and an anode terminal as the fourth electrical connection terminal, and coupled to the anode terminal of the second diode and the signal input terminal of the optical coupler.
8. The dimming circuit according to claim 1, wherein the dimming turn-off unit comprises:
a switching triode, having a collector terminal as the second receiving terminal and the output terminal, an emitter terminal as a ground terminal, and a base terminal as the first receiving terminal; and
and a resistor, having a cathode terminal coupled to the base terminal of the switching transistor and an anode terminal coupled to the emitter terminal of the switching transistor.
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| CN201911286113.1A CN113068287B (en) | 2019-12-13 | 2019-12-13 | Dimming circuit with stable output voltage |
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| CN201911286113.1A CN113068287B (en) | 2019-12-13 | 2019-12-13 | Dimming circuit with stable output voltage |
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| CN113068287B true CN113068287B (en) | 2022-04-12 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW201008389A (en) * | 2008-08-05 | 2010-02-16 | Chi Mei Optoelectronics Corp | Light-source driving circuit, back-light module and liquid crystal display |
| CN105792415A (en) * | 2016-03-18 | 2016-07-20 | 明纬(广州)电子有限公司 | Dimming control apparatus |
| CN109413791A (en) * | 2017-08-18 | 2019-03-01 | 明纬(广州)电子有限公司 | Feedback circuit |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TWI423732B (en) * | 2009-11-03 | 2014-01-11 | Cal Comp Electronics & Comm Co | Lighting apparatus, driving circuit of light emitting diode and driving method using the same |
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- 2019-12-13 CN CN201911286113.1A patent/CN113068287B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW201008389A (en) * | 2008-08-05 | 2010-02-16 | Chi Mei Optoelectronics Corp | Light-source driving circuit, back-light module and liquid crystal display |
| CN105792415A (en) * | 2016-03-18 | 2016-07-20 | 明纬(广州)电子有限公司 | Dimming control apparatus |
| CN109413791A (en) * | 2017-08-18 | 2019-03-01 | 明纬(广州)电子有限公司 | Feedback circuit |
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