CN112020180B - PWM dimming circuit with current limiting and short-circuit protection functions and application circuit thereof - Google Patents
PWM dimming circuit with current limiting and short-circuit protection functions and application circuit thereof Download PDFInfo
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- CN112020180B CN112020180B CN202011127861.8A CN202011127861A CN112020180B CN 112020180 B CN112020180 B CN 112020180B CN 202011127861 A CN202011127861 A CN 202011127861A CN 112020180 B CN112020180 B CN 112020180B
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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]
- H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
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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
- H05B45/32—Pulse-control circuits
- H05B45/325—Pulse-width modulation [PWM]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
- Y02B20/30—Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
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- Circuit Arrangement For Electric Light Sources In General (AREA)
Abstract
The invention discloses a PWM dimming circuit with current limiting and short circuit protection functions and an application circuit thereof; one end of the resistor R1 is connected with the first power supply, and the other end is connected with the resistor R2, the light-emitting diode D3 and the base electrode of the triode Q2; the resistor R2 is connected with the collector of the triode Q1; the light emitting diode D3 is connected with the third power supply; one end of the resistor R3 is connected with the second power supply, and the other end is connected with the base of the triode Q1 and the resistor R4; the resistor R4 is connected with the collector of the triode Q2, and the joint of the resistor R4 and the collector of the triode Q2 is connected with an LED light source; the emitter of the triode Q1 is used for receiving a level signal; the third power supply is also connected with the resistor R5, and the resistor R5 is connected with the emitter of the triode Q2; the LED D3 is used for limiting the voltage of the resistor R5. The invention has simple circuit and low cost, and can protect equipment from being damaged under the conditions of short circuit and overload.
Description
Technical Field
The invention belongs to the field of circuit protection, and particularly relates to a PWM dimming circuit with current limiting and short-circuit protection functions and an application circuit thereof.
Background
The LED light source is a constant voltage load, the loaded voltage fluctuates slightly, the fluctuation of the current flowing through the LED light source is very large, and the current can easily exceed the limiting current of the LED light source, so that the LED light source is damaged. Therefore, the current flowing through the LED light source is limited, and the current flowing through the LED light source must be limited to be equal to or lower than a set value. Most PWM dimming output circuits in the current market use a single transistor, and if a low-power transistor is used, the transistor is damaged due to short circuit, so that the circuit fails; if a high power transistor is used, although short circuit is not damaged, the cost is increased, and at the same time, when short circuit or overload occurs, the output current is large, so that the transistor is very hot, which is very unfavorable for stable operation of the circuit, and equipment may be damaged due to large current. Therefore, a PWM dimming output circuit with low cost, which can solve the problems of short circuit damage and serious heating of heavy load, is needed to adjust the brightness of the LED light source and also protect the device from damage.
Disclosure of Invention
The present invention provides a PWM dimming circuit with current limiting and short circuit protection functions and an application circuit thereof, aiming to make the circuit output current constantly and protect the equipment from damage under short circuit and overload conditions.
The technical scheme for solving the technical problems comprises the following steps:
the PWM dimming circuit with the current-limiting and short-circuit protection functions and the application circuit thereof comprise a first power supply, a second power supply, a third power supply, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2 and a light-emitting diode D3;
one end of the resistor R1 is connected with the first power supply, and the other end is connected with the resistor R2, the light-emitting diode D3 and the base electrode of the triode Q2; the resistor R2 is connected with the collector of the triode Q1; the light emitting diode D3 is connected with the third power supply;
one end of the resistor R3 is connected with the second power supply, and the other end is connected with the base of the triode Q1 and the resistor R4; the resistor R4 is connected with the collector of the triode Q2, and the joint of the resistor R4 and the collector of the triode Q2 is connected with an LED light source; the emitter of the triode Q1 is used for receiving a PWM dimming level signal "red";
the third power supply is also connected with the resistor R5, and the resistor R5 is connected with the emitter of the triode Q2; the LED D3 is used for limiting the voltage of the resistor R5.
Preferably, the first power supply voltage 56V, the second power supply voltage 3.3V, and the third power supply voltage 7V.
Preferably, the resistance value of the resistor R1 is 18k Ω, the resistance value of the resistor R2 is 1.6k Ω, the resistance value of the resistor R3 is 10k Ω, the resistance value of the resistor R4 is 150k Ω, and the resistance value of the resistor R5 is 8.2 Ω.
Preferably, the anode of the light emitting diode D3 is connected to the resistor R1, and the cathode is connected to the third power source.
The application circuit of the PWM dimming circuit with the current-limiting and short-circuit protection functions is characterized by comprising a DCDC switching power supply dimming circuit, a 3.3V linear voltage stabilizing circuit, a control module and the PWM dimming circuit with the current-limiting and short-circuit protection functions; the PWM dimming circuit with the current limiting and short-circuit protection function is connected with the DCDC switching power supply dimming circuit in parallel; the 3.3V linear voltage stabilizing circuit is connected with the control module in series; the control module is respectively connected with the DCDC switching power supply dimming circuit and the PWM dimming circuit with current limiting and short-circuit protection functions in series.
Preferably, the output of the PWM dimming circuit with the current limiting and short-circuit protection functions is connected with a red light source, a blue light source and a green light source; and the output of the DCDC switching power supply dimming circuit is connected with a cold light source and a warm light source.
The invention has the following beneficial effects: compared with the conventional circuit, the LED power supply has the advantages that the output current is limited or reduced under the condition of an overweight load or an output short circuit, the protection circuit cannot be damaged due to overcurrent or overheat, the quality of the LED power supply is improved, the current-limiting and short-circuit protection effects are achieved, the circuit is simple, the cost is low, and the protection device is not damaged under the conditions of short circuit and heavy load.
Drawings
Fig. 1 is a schematic structural diagram of a PWM dimming circuit with current limiting and short circuit protection functions;
fig. 2 is a schematic structural diagram of an application circuit of a PWM dimming circuit with current limiting and short circuit protection functions;
wherein, the reference numbers:
a first power supply 1, a second power supply 2, and a third power supply 3.
Detailed Description
The PWM dimming circuit with current limiting and short circuit protection functions and the application circuit thereof shown in fig. 1 are described as follows:
the PWM dimming circuit with current-limiting and short-circuit protection functions and an application circuit thereof comprise a first power supply 1, a second power supply 2, a third power supply 3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2 and a light-emitting diode D3;
one end of the resistor R1 is connected with the first power supply 1, and the other end is connected with the resistor R2, the light emitting diode D3 and the base electrode of the triode Q2; the resistor R2 is connected with the collector of the triode Q1; the light emitting diode D3 is connected with the third power supply 3;
one end of the resistor R3 is connected with the second power supply 2, and the other end is connected with the base of the triode Q1 and the resistor R4; the resistor R4 is connected with the collector of the triode Q2 and the connection part is connected with a load; the emitter of the triode Q1 is used for receiving a level signal;
the third power supply 3 is also connected with the resistor R5, and the resistor R5 is connected with the emitter of the triode Q2; the LED D3 is used for limiting the voltage of the resistor R5.
The emitter of the transistor Q1 receives one of the PWM signals "red" or "green" or "blue" and performs a switching control function on the transistor Q1. The maximum output current calculation formula of the circuit is the maximum output current value set for the circuit, namely the limit current value, wherein the maximum output current value is the difference between the limit voltage of the light emitting diode D3 and the conducting voltage of the transistor Q2 of 0.7V, and the resistance value of the resistor R5 is removed. When the circuit outputs heavy load, the circuit current is limited below a limited current value, and the circuit is in a current-limiting protection state.
In addition, the circuit is in a closed no-output state, a PWM signal "red" is input to a low level, that is, the emitter voltage of the transistor Q1 is 0V, the current of the second power supply 2 is limited by the resistor R3, then flows to the base of the transistor Q1, and then flows out to 0V from the emitter of the transistor Q1, so that the transistor Q1 is in a conducting state. The resistor R2 is connected in series with the collector of the transistor Q1, and since the resistor R2 is large, the transistor Q1 is in a saturated conducting state. On the other hand, the resistor R2 and the base of the transistor Q2 are both connected with the resistor R1, and the resistor R2 and the base of the transistor Q2 are connected in parallel. After the current of the first power supply 1 is limited by the resistor R1, the current respectively flows into the resistor R2 and the triode Q2, the resistor R2 shunts the base of the triode Q2, and the resistor R2 has a large shunt ratio, so that the base and the emitter of the triode Q2 do not reach a conduction voltage difference and are in a cut-off state, no current passes through a load connected with the triode Q2, and no output is generated by the circuit. The lowest voltage of the emitter of the transistor Q2 corresponds to the voltage of the third power supply 3.
Additionally, when the circuit is in a normal output state, when a PWM signal "red" is inputted to the emitter of the transistor Q1, the transistor Q1 does not reach the emitter turn-on voltage, the transistor Q1 is not turned on, the resistor R2 has no current flowing through it, and does not shunt the base of the transistor Q2, and all the current flows into the base of the transistor Q2, so that the transistor Q2 is in saturated conduction. At this time, the current flowing through the LED light source does not reach the limited current value, the base voltage of the transistor Q2 does not reach the limited voltage of the light emitting diode D3, and the base of the transistor Q2 is not shunted, so the transistor Q2 operates in a saturated conducting state. Since the transistor Q2 operates in a saturated conducting state, the loss is minimal and the efficiency is highest.
Additionally, when the circuit is in a current-limiting protection output state, the current reaches a limited current value, the voltage of the base of the transistor Q2 is increased and reaches the conducting voltage of the light-emitting diode D3, the base of the transistor Q2 is shunted, and partial current flows into the light-emitting diode D3, so that the transistor Q2 is in an amplification working state, and the light-emitting diode D3 limits the highest voltage of the resistor R5 to limit the maximum output current value of the circuit, so as to protect the circuit and the LED light source from being damaged.
In addition, the circuit is in a short-circuit trickle protection state, when the circuit outputs a short circuit or an overweight load, the collector voltage of the triode Q2 is increased, the base voltage of the triode Q1 is increased to reach an emitter junction conducting voltage, the triode Q1 is conducted in a saturated mode, the resistor R2 has current passing through, the base of the triode Q2 is shunted, and the collector current of the triode Q2 is reduced. The transistor Q2 works in an amplifying state, but the circuit outputs a tiny trickle current to achieve the functions of a protection circuit and an LED light source.
In one embodiment, the first power supply 1 voltage is 56V, the second power supply 2 voltage is 3.3V, and the third power supply 3 voltage is 7V.
In one embodiment, the resistor R1 has a resistance of 18k Ω, the resistor R2 has a resistance of 1.6k Ω, the resistor R3 has a resistance of 10k Ω, the resistor R4 has a resistance of 150k Ω, and the resistor R5 has a resistance of 8.2 Ω.
Additionally, the first power supply 1 voltage is 56V, the second power supply 2 voltage is 3.3V, the third power supply 3 voltage is 7V, the resistor R1 is 18k Ω, the resistor R2 is 1.6k Ω, the resistor R3 is 10k Ω, the resistor R4 is 150k Ω, the resistor R5 is 8.2 Ω, the led D3 limits the voltage to 1.8V, and the PWM input level is 3.3V.
If the circuit is in the off state, the voltage of the emitter of the transistor Q1 is 0V, and the transistor is in the saturation conducting state, so the voltage of the collector is 0.3V, and at this time, the voltage of the base of the transistor Q2 is:
. The voltage at the base of the transistor Q2 is 4.8V lower than the voltage of the third power supply 3 by 7V, and the emitter junction of the transistor Q2 is reverse biased, so that the transistor Q2 operates in the off state.
If the circuit is in a normal output state, the rated current value set by us is 100mA, i.e. the current passing through the resistor R5 is about 100mA, the voltage of R5 is 0.8V, the collector voltage of the transistor Q2 is 7V +0.8V +0.3V — 8.1V, and the base voltage of the transistor Q1 is:
If the circuit is in the current-limiting protection output state, the led D3 is turned on, the Q1 transistor is turned off, the transistor Q2 is in the amplification operating state, and the base voltage of the transistor Q1 is required to be less than 3.3V +0.7V =4V, so the voltage at the collector of the transistor Q2 is less than:
if the circuit is in the short-circuit trickle protection state, the collector voltage of the transistor Q2 is higher than 14.5V, at this time, the transistor Q1 is in saturated conduction, the resistor R2 has current passing through, which shunts the base of the transistor Q2, so that the collector current of the transistor Q2 is reduced, the transistor Q2 is in the amplification state, but the output current is about 10% trickle output, the voltage of the C pole of the transistor Q1 is 3.3V + 0.3V-3.6V, and the voltage of the B pole of the transistor Q2 is:
In one embodiment, the anode of the led D3 is connected to the resistor R1, and the cathode is connected to the third power source 3.
The application circuit of the PWM dimming circuit with the current-limiting and short-circuit protection functions comprises a DCDC switching power supply dimming circuit, a 3.3V linear voltage stabilizing circuit, a control module and the PWM dimming circuit with the current-limiting and short-circuit protection functions, wherein the PWM dimming circuit with the current-limiting and short-circuit protection functions is connected with the DCDC switching power supply dimming circuit in parallel; the 3.3V linear voltage stabilizing circuit is connected with the control module in series; the control module is respectively connected with the DCDC switching power supply dimming circuit and the PWM dimming circuit with the current-limiting and short-circuit protection functions in series, and the control module respectively controls the DCDC switching power supply dimming circuit and the PWM dimming circuit with the current-limiting and short-circuit protection functions.
In one embodiment, the output of the PWM dimming circuit with the current limiting and short-circuit protection functions is connected with a red light source, a blue light source and a green light source; and the output of the DCDC switching power supply dimming circuit is connected with a cold light source and a warm light source.
The PWM dimming circuit with the current limiting and short-circuit protection functions is applied to a multi-path dimming output circuit, and meets the requirements of using different LED light sources; the PWM dimming circuit with the current-limiting and short-circuit protection functions is respectively connected with the corresponding red light source, the green light source and the blue light source, and the PWM dimming circuit which is built by discrete elements, is simple, has low cost and has the current-limiting and short-circuit protection functions is very suitable for use because the red light source, the green light source and the blue light source need lower power in application and the output quality requirement is lower. The output of the DCDC switching power supply dimming circuit is connected with the warm light source and the cold light source, and the warm light source and the cold light source have relatively large power and relatively high requirements on output ripples and the like in application, so that the DCDC switching power supply dimming circuit only can be used at relatively high cost. The 3.3V linear voltage stabilizing circuit supplies power to the control module and the PWM dimming circuit with the current limiting and short-circuit protection functions. The control module controls the output power of the PWM dimming circuit with the current limiting and short-circuit protection function and the output power of the DCDC switching power supply dimming circuit.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.
Claims (6)
1. The PWM dimming circuit with the current-limiting and short-circuit protection functions is characterized by comprising a first power supply, a second power supply, a third power supply, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a triode Q1, a triode Q2 and a light-emitting diode D3;
one end of the resistor R1 is connected with the first power supply, and the other end is connected with the resistor R2, the light-emitting diode D3 and the base electrode of the triode Q2; the resistor R2 is connected with the collector of the triode Q1; the light emitting diode D3 is connected with the third power supply;
one end of the resistor R3 is connected with the second power supply, and the other end is connected with the base of the triode Q1 and the resistor R4; the resistor R4 is connected with the collector of the triode Q2, and the joint of the resistor R4 and the collector of the triode Q2 is connected with an LED light source; the emitter of the triode Q1 is used for receiving a level signal;
the third power supply is also connected with the resistor R5, and the resistor R5 is connected with the emitter of the triode Q2; the LED D3 is used for limiting the voltage of the resistor R5.
2. The PWM dimming circuit with current limiting and short-circuit protection according to claim 1, wherein the first power voltage is 56V, the second power voltage is 3.3V, and the third power voltage is 7V.
3. The PWM dimming circuit with current limiting and short circuit protection functions according to claim 1, wherein the resistor R1 has a resistance value of 18k Ω, the resistor R2 has a resistance value of 1.6k Ω, the resistor R3 has a resistance value of 10k Ω, the resistor R4 has a resistance value of 150k Ω, and the resistor R5 has a resistance value of 8.2 Ω.
4. The PWM dimming circuit with current limiting and short-circuit protection functions according to claim 1, wherein the anode of the LED D3 is connected to the resistor R1, and the cathode is connected to the third power supply.
5. The application circuit of the PWM dimming circuit with the current limiting and short-circuit protection function comprises the PWM dimming circuit with the current limiting and short-circuit protection function as claimed in any one of claims 1 to 4, and is characterized by further comprising a DCDC switching power supply dimming circuit, a 3.3V linear voltage stabilizing circuit and a control module; the PWM dimming circuit with the current limiting and short-circuit protection function is connected with the DCDC switching power supply dimming circuit in parallel; the 3.3V linear voltage stabilizing circuit is connected with the control module in series; the control module is respectively connected with the DCDC switching power supply dimming circuit and the PWM dimming circuit with current limiting and short-circuit protection functions in series.
6. The application circuit of the PWM dimming circuit with the current limiting and short-circuit protection function according to claim 5, wherein the output of the PWM dimming circuit with the current limiting and short-circuit protection function is connected with a red light source, a blue light source and a green light source; and the output of the DCDC switching power supply dimming circuit is connected with a cold light source and a warm light source.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011127861.8A CN112020180B (en) | 2020-10-21 | 2020-10-21 | PWM dimming circuit with current limiting and short-circuit protection functions and application circuit thereof |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011127861.8A CN112020180B (en) | 2020-10-21 | 2020-10-21 | PWM dimming circuit with current limiting and short-circuit protection functions and application circuit thereof |
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| CN112020180B true CN112020180B (en) | 2021-02-05 |
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| CN211720776U (en) * | 2020-02-21 | 2020-10-20 | 深圳亚锐光电科技有限公司 | Dimming circuit, dual-output dimming circuit and dimmer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8072160B2 (en) * | 2008-12-22 | 2011-12-06 | Bcd Semiconductor Manufacturing Limited | Low power non-isolated driver |
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| CN104811173A (en) * | 2015-02-25 | 2015-07-29 | 雅安小航电器有限责任公司 | Simple driving circuit with load short circuit protection and self recovery functions |
| CN209250213U (en) * | 2018-09-10 | 2019-08-13 | 广州视源电子科技股份有限公司 | Short-circuit protection circuit |
| CN210328087U (en) * | 2019-08-09 | 2020-04-14 | 佛山市迅盈电源科技有限公司 | Short-circuit protection circuit that constant voltage was adjusted luminance |
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