CN109640448B - Constant current feedback control circuit - Google Patents
Constant current feedback control circuit Download PDFInfo
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- CN109640448B CN109640448B CN201811593582.3A CN201811593582A CN109640448B CN 109640448 B CN109640448 B CN 109640448B CN 201811593582 A CN201811593582 A CN 201811593582A CN 109640448 B CN109640448 B CN 109640448B
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- 230000000087 stabilizing effect Effects 0.000 claims 5
- 230000006872 improvement Effects 0.000 description 7
- 238000000034 method Methods 0.000 description 3
- 230000009471 action Effects 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
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- 238000004134 energy conservation Methods 0.000 description 1
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- 230000008569 process Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
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Abstract
The invention discloses a constant current feedback control circuit which comprises a constant current control module, a closed loop feedback circuit and a gear shifting control module, wherein a first output end of the constant current control module is connected with an input end of the closed loop feedback circuit, an output end of the closed loop feedback circuit is connected with a first input end of the gear shifting control module, and a second output end of the constant current control module is connected with a second input end of the gear shifting control module. According to the constant current feedback control circuit, the constant current control module and the closed loop feedback circuit are used for feeding back PWM signals, so that dynamic constant current control is realized, noise can be effectively reduced, and constant current output is realized. The invention can be widely applied to the field of electronic circuits.
Description
Technical Field
The invention relates to the technical field of electronic circuits, in particular to a constant current feedback control circuit.
Background
The LED is called a fourth-generation illumination light source or a green light source, has the characteristics of energy conservation, environmental protection, long service life, small volume and the like, and can be widely applied to various fields of indication, display, decoration, backlight source, common illumination, urban night scenes and the like. Since LEDs are semiconductor devices that are sensitive in characteristics and have negative temperature characteristics, they need to be stably operated and protected during application, thereby creating a driving concept. The LED device has almost strict requirements on a driving power supply, and the LED is not like a common incandescent bulb and can be directly connected with 220V alternating current mains supply. Since the light characteristics of LEDs are generally described as a function of current rather than voltage, the luminous flux (phiv) versus IF, luminance can be better controlled using constant current source driving. The constant current driving of LEDs on the market at present mostly produces professional driving ICs, which increases driving costs.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a constant current feedback control circuit.
The technical scheme adopted by the invention is as follows:
the constant current feedback control circuit comprises a constant current control module, a closed loop feedback circuit and a gear shifting control module, wherein a first output end of the constant current control module is connected with an input end of the closed loop feedback circuit, an output end of the closed loop feedback circuit is connected with a first input end of the gear shifting control module, and a second output end of the constant current control module is connected with a second input end of the gear shifting control module.
As a further improvement of the invention, the constant current control module comprises a first resistor, a second resistor, a first MOS tube and a constant current logic unit, wherein a first output end of the constant current logic unit is connected with a grid electrode of the first MOS tube, a drain electrode of the first MOS tube is connected with a source electrode of the first MOS tube through the first resistor, the source electrode of the first MOS tube is connected with a second output end of the constant current logic unit, the source electrode of the first MOS tube is connected with the ground through the second resistor, a third output end of the constant current logic unit is connected with a second input end of the shift control module, and the drain electrode of the first MOS tube is connected with an input end of the closed loop feedback circuit.
As a further improvement of the present invention, the closed loop feedback circuit includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor, a second capacitor, a first comparator, a first transistor and a first diode, wherein the first output end of the constant current control module is further connected with the non-inverting input end of the first comparator through the third resistor, the non-inverting input end of the first comparator is further connected with the ground through the first capacitor, the inverting input end of the first comparator is further connected with the power supply end through the fourth resistor, the inverting input end of the first comparator is further connected with the ground through the second resistor, the inverting input end of the first comparator is further connected with the ground through the fifth resistor, the inverting input end of the first comparator is further connected with the positive electrode end of the first diode through the sixth resistor, the negative electrode end of the first diode is further connected with the first input end of the shift control module, the output end of the first comparator is further connected with the power supply end through the eighth resistor, and the output end of the first comparator is further connected with the first emitter through the first transistor.
As a further improvement of the present invention, the shift control module includes a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor, a second diode, a second transistor, a first voltage regulator and a bistable logic unit, wherein an output end of the closed loop feedback circuit is connected with a first input end of the bistable logic unit, a second output end of the constant current control module is connected with a second input end of the bistable logic unit, the bistable logic unit is further connected with a collector of the second transistor through the third capacitor, a collector of the second transistor is connected with a power supply end through the ninth resistor, an emitter of the second transistor is connected with ground, a base of the second transistor is connected with an anode of the first voltage regulator through the tenth resistor, a cathode of the first voltage regulator is further connected with an anode of the first voltage regulator through the fourth capacitor, an anode of the first voltage regulator is connected with a cathode of the second diode, and an anode of the second diode is connected with ground.
As a further improvement of the invention, the first MOS tube is a depletion type NMOS tube.
As a further improvement of the present invention, the first transistor is an NPN transistor.
As a further improvement of the present invention, the second transistor is an NPN transistor.
As a further improvement of the present invention, the fourth capacitor is an electrolytic capacitor.
The beneficial effects of the invention are as follows:
according to the constant current feedback control circuit, the constant current control module and the closed loop feedback circuit are used for feeding back PWM signals, so that dynamic constant current control is realized, noise can be effectively reduced, and constant current output is realized.
Drawings
Fig. 1 is a schematic circuit diagram of a constant current feedback control circuit of the present invention.
Detailed Description
The following is a further description of embodiments of the invention, taken in conjunction with the accompanying drawings:
referring to fig. 1, the constant current feedback control circuit comprises a constant current control module, a closed loop feedback circuit and a gear shifting control module, wherein a first output end of the constant current control module is connected with an input end of the closed loop feedback circuit, an output end of the closed loop feedback circuit is connected with a first input end of the gear shifting control module, and a second output end of the constant current control module is connected with a second input end of the gear shifting control module.
Further as the preferred implementation manner, the constant current control module comprises a first resistor R1, a second resistor R2, a first MOS tube T1 and a constant current logic unit, wherein a first output end of the constant current logic unit is connected with a grid electrode of the first MOS tube T1, a drain electrode of the first MOS tube T1 is connected with a source electrode of the first MOS tube T1 through the first resistor R1, the source electrode of the first MOS tube T1 is connected with a second output end of the constant current logic unit, the source electrode of the first MOS tube T1 is connected with the ground through the second resistor R2, a third output end of the constant current logic unit is connected with a second input end of the gear shifting control module, and a drain electrode of the first MOS tube T1 is connected with an input end of the closed loop feedback circuit.
Further as a preferred embodiment, the closed loop feedback circuit includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a first capacitor C1, a second capacitor C2, a first comparator U1, a first transistor Q1 and a first diode D1, the first output end of the constant current control module is further connected with the non-inverting input end of the first comparator U1 through the third resistor R3, the non-inverting input end of the first comparator U1 is further connected with the ground through the first capacitor C1, the inverting input end of the first comparator U1 is further connected with the power supply end through the fourth resistor R4, the inverting input end of the first comparator U1 is further connected with the ground through the second capacitor C2, the inverting input end of the first comparator U1 is further connected with the ground through the fifth resistor R5, the inverting input end of the first comparator U1 is further connected with the non-inverting input end of the first diode D1 through the sixth resistor R6, the inverting input end of the first comparator U1 is further connected with the first diode D1, the inverting input end of the first comparator U1 is further connected with the first diode Q1 through the first resistor R7, and the inverting input end of the first comparator U1 is further connected with the ground.
Further as a preferred embodiment, the shift control module includes a ninth resistor R9, a tenth resistor R10, a third capacitor C3, a fourth capacitor C4, a second diode D2, a second transistor Q2, a first voltage regulator DZ1, and a bistable logic unit, an output end of the closed loop feedback circuit is connected to a first input end of the bistable logic unit, a second output end of the constant current control module is connected to a second input end of the bistable logic unit, the bistable logic unit is further connected to a collector of the second transistor Q2 through a third capacitor C3, a collector of the second transistor Q2 is connected to a power supply end through a ninth resistor R9, an emitter of the second transistor Q2 is connected to ground, a base of the second transistor Q2 is connected to an anode of the first voltage regulator DZ1 through a tenth resistor R10, a cathode of the first voltage regulator DZ1 is further connected to an anode of the first voltage regulator DZ1 through a fourth capacitor C4, and a cathode of the first voltage regulator DZ1 is further connected to an anode of the first voltage regulator DZ1, and a cathode of the second transistor D2 is connected to a cathode of the second diode D2.
In this embodiment, the constant current feedback control circuit is applied to an LED tube, the first MOS transistor T1 is a depletion NMOS transistor, the second transistor Q2 is an NPN transistor, the fourth capacitor C4 is an electrolytic capacitor, the on/off of the first MOS transistor T1 is controlled by a constant current logic unit, and the current cannot be completely turned off by a first resistor R1, because the constant current logic unit automatically turns on/off the first MOS transistor T1 according to a reference value set by comparing current feedback information, the constant current logic unit has a characteristic of self-oscillation, the first MOS transistor T1 can be regarded as an automatically-adjusted adjustable resistor, because i=u/R, when U has a certain ripple, the most effective method is to ensure that the value of I is unchanged, namely, the value of R is changed along with the change of V, so that the quotient of the two is a constant, that is the LED lamp is always turned on.
The voltage values at two ends of the first MOS tube T1 are tracked by the closed loop feedback circuit through the first comparator U1, and since the first MOS tube T1 can be regarded as a continuously adjustable "resistor", the voltage signal at two ends of the "resistor" just reflects the ripple signal on the tenth capacitor, it must be ensured that the voltage on the LED cannot exceed the safety range or be too low, i.e. be within a reasonable range. After the voltage information on the LED is obtained, the voltage information is compared with a reference value, and the on-off state of the second capacitor C2 is determined by controlling the on-off state of the first transistor Q1, so that the duty ratio on the switching power supply control module is controlled to form a closed loop of the control system, namely, when the capacitor voltage is found to be too high, the duty ratio on the switching power supply control module is reduced, and otherwise, the duty ratio is increased. The closed loop feedback circuit is mainly used for intercepting the signal at the first MOS transistor T1, because the signal is simple and has less noise, it should be noted that the withstand voltage value of the first transistor Q1 should be greater than 400V.
The gear shifting control module adopts a bistable logic unit to realize the gear shifting of two gears, and can also be realized by a singlechip programming method. It is critical that both the signal source and the power supply must be at a voltage from the tenth capacitor which is either higher than 38V (for example, a 7-and-15-string LED array) or lower, i.e. the LED is on only when this voltage is reached. Because the action of lamp tube shifting is implemented by switching on and off a power supply, in the embodiment, the voltage of the lamp tube shifting is measured at two ends of the tenth capacitor, and the voltage can quickly rise to 38V and then slowly rise to 45V when the lamp tube shifting is electrified; the voltage drops rapidly from 45V to less than 38V at the time of lamp failure, and then drops slowly. In this embodiment, a 39V second voltage regulator is used to collect the signal source. When powered down, the voltage of the LED drops very slowly after as low as 38V, and redundant charge is absorbed cleanly for more than 5 seconds. Therefore, the power supply of the constant current feedback module is taken from the tenth capacitor, and the power supply is maintained for a long time after the lamp is turned off, so that the power supply has great advantages for maintaining the gear shifting information, and even if a person with relatively slow actions is personally required to use the gear shifting function, the person cannot keep pace with the on-off switch in the process.
While the preferred embodiment of the present invention has been described in detail, the invention is not limited to the embodiment, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the invention, and these modifications and substitutions are intended to be included in the scope of the present invention as defined in the appended claims.
Claims (5)
1. A constant current feedback control circuit is characterized in that: the automatic control device comprises a constant current control module, a closed loop feedback circuit and a gear shifting control module, wherein a first output end of the constant current control module is connected with an input end of the closed loop feedback circuit, an output end of the closed loop feedback circuit is connected with a first input end of the gear shifting control module, and a second output end of the constant current control module is connected with a second input end of the gear shifting control module; the constant current control module comprises a first resistor, a second resistor, a first MOS tube and a constant current logic unit, wherein a first output end of the constant current logic unit is connected with a grid electrode of the first MOS tube, a drain electrode of the first MOS tube is connected with a source electrode of the first MOS tube through the first resistor, the source electrode of the first MOS tube is connected with a second output end of the constant current logic unit, the source electrode of the first MOS tube is connected with the ground through the second resistor, a third output end of the constant current logic unit is connected with a second input end of the gear shifting control module, and a drain electrode of the first MOS tube is connected with an input end of the closed loop feedback circuit;
the closed loop feedback circuit comprises a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first capacitor, a second capacitor, a first comparator, a first transistor and a first diode, wherein the first output end of the constant current control module is connected with the non-inverting input end of the first comparator through the third resistor, the non-inverting input end of the first comparator is connected with the ground through the first capacitor, the inverting input end of the first comparator is connected with the power supply end through the fourth resistor, the inverting input end of the first comparator is connected with the ground through the second resistor, the inverting input end of the first comparator is connected with the ground through the fifth resistor, the inverting input end of the first comparator is connected with the positive electrode end of the first diode through the sixth resistor, the negative electrode end of the first diode is connected with the first input end of the shift control module, the output end of the first comparator is connected with the power supply end through the eighth resistor, the output end of the first comparator is connected with the first emitter through the first transistor;
the gear shifting control module comprises a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor, a second diode, a second transistor, a first voltage stabilizing tube and a bistable logic unit, wherein the output end of the closed loop feedback circuit is connected with the first input end of the bistable logic unit, the second output end of the constant current control module is connected with the second input end of the bistable logic unit, the bistable logic unit is connected with the collector electrode of the second transistor through the third capacitor, the collector electrode of the second transistor is connected with the power supply end through the ninth resistor, the emitter electrode of the second transistor is connected with the ground, the base electrode of the second transistor is connected with the anode of the first voltage stabilizing tube through the tenth resistor, the cathode of the first voltage stabilizing tube is connected with the anode of the first voltage stabilizing tube through the fourth capacitor, the anode of the first voltage stabilizing tube is connected with the cathode end of the second diode, and the anode end of the second diode is connected with the ground.
2. The constant current feedback control circuit according to claim 1, wherein: the first MOS tube is a depletion type NMOS tube.
3. The constant current feedback control circuit according to claim 1, wherein: the first transistor is an NPN transistor.
4. The constant current feedback control circuit according to claim 1, wherein: the second transistor is an NPN transistor.
5. The constant current feedback control circuit according to claim 1, wherein: the fourth capacitor is an electrolytic capacitor.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811593582.3A CN109640448B (en) | 2018-12-25 | 2018-12-25 | Constant current feedback control circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201811593582.3A CN109640448B (en) | 2018-12-25 | 2018-12-25 | Constant current feedback control circuit |
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| CN109640448A CN109640448A (en) | 2019-04-16 |
| CN109640448B true CN109640448B (en) | 2024-02-13 |
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| CN112462835B (en) * | 2020-11-04 | 2022-10-11 | 昂维格(厦门)科技有限公司 | Low-voltage linear voltage stabilizer |
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