Dimming circuit of dimmer
Technical Field
The utility model belongs to the technical field of the LED lamp adjusts luminance, specifically be a dimming circuit who relates to a light modulator.
Background
The existing LED lamp is usually dimmed by a TRIAC dimmer, and the TRIAC dimmer changes the input voltage in a phase-cut mode, so that the voltage input to the LED lamp is changed, and the current on the LED lamp is changed to dim the LED lamp. In the phase-cut process, when the voltage value of the input voltage reaches the lighting voltage of the LED lamp, the LED lamp lights up for illumination, and when the voltage value of the input voltage is smaller than the lighting voltage of the LED lamp, the LED lamp is turned off, and the fluctuation of the input voltage can cause the LED lamp to flicker. Therefore, a current maintaining circuit needs to be arranged on a driving circuit of the LED lamp to ensure that the LED lamp does not flicker during dimming. At present, the TRIAC dimmer can only be used for an LED lamp with a current maintaining circuit, and when a common LED lamp without the current maintaining circuit is dimmed, a flicker phenomenon occurs, which affects the dimming effect and results in a small application range.
Disclosure of Invention
The utility model discloses solve the technical problem that above-mentioned prior art exists, provide a dimmer circuit of light modulator.
The above technical problem of the present invention can be solved by the following technical solutions: the utility model provides a dimming circuit of light modulator, includes rectifier circuit, supply circuit, has the dimming control circuit of variable resistance, rectifier circuit's input links to each other with the commercial power, one way of rectifier circuit output links to each other with supply circuit's input, another way of rectifier circuit output is connected with the LED lamp, supply circuit's output links to each other with dimming control circuit's input, dimming control circuit's output links to each other with the LED lamp, changes the duty cycle of dimming control circuit output through the resistance of adjusting variable resistance, makes the voltage conduction angle of inputing to the LED lamp change, changes the electric current that flows through the LED lamp to make the luminance of LED lamp change along with the regulation of variable resistance.
Preferably, the power supply circuit comprises a resistance step-down circuit and an LDO step-down circuit, and the resistance step-down circuit divides the direct current rectified by the rectifying circuit, outputs the direct current to the LDO step-down circuit, and outputs the direct current to the dimming control circuit after being stepped down by the LDO step-down circuit.
Preferably, the resistance step-down circuit comprises a diode D1, a resistor Ra, a resistor Rb, and a zener diode ZD1, wherein the anode of the diode D1 is connected to the positive output end of the rectifying circuit, the cathode of the diode D1 is connected to one end of the resistor Ra, the other end of the resistor Ra is connected to one end of the resistor Rb, the other end of the resistor Rb is connected to the cathode of the zener diode ZD1 and the input end of the LDO step-down circuit, the anode of the zener diode ZD1 is connected to the negative output end of the rectifying circuit, and the common connection end of the zener diode ZD1 is connected to ground.
Preferably, the LDO buck circuit includes chip U1, electric capacity C1 and electric capacity C2, chip U1 has 3 feet, chip U1's first foot connects resistance buck circuit's output, electric capacity C1's one end and dimming control circuit respectively, electric capacity C1's the other end ground connection, chip U1's second foot ground connection, chip U1's third foot connects electric capacity C2's one end and dimming control circuit's input, electric capacity C2's the other end ground connection.
Preferably, the dimming control circuit comprises a variable resistor RT, a resistor R1, a resistor R2, a chip U2, a transistor Q1 and a MOS transistor Q2, the chip U2 has 4 pins, a first pin of the chip U2 is connected with an output end of the power supply circuit and one end of the variable resistor RT, a second pin of the chip U2 is connected with the other end of the variable resistor RT and one end of the resistor R1, the other end of the resistor R1 is grounded, a third pin of the chip U2 is connected with a gate of the transistor Q1, a collector of the transistor Q1 is connected with one end of a resistor R2 and a gate of the MOS transistor Q2, the other end of the resistor R2 is connected with the power supply circuit, an emitter of the transistor Q1 is connected with a fourth pin of the chip U2 and a source of the MOS transistor Q2, a common connection end of the transistor Q2 is connected with the drain of the LED lamp.
The utility model discloses beneficial effect who has: the utility model discloses an adoption has the dimming control circuit of variable resistance to adjust luminance, utilizes the resistance of adjusting variable resistance, makes chip U2 output different PWM duty cycle, changes triode Q1's break-make time, and then changes MOS pipe Q2's break-make time, makes the voltage conduction angle of inputing to the LED lamp change, changes the electric current that flows through the LED lamp to the luminance that makes the LED lamp changes along with variable resistance's regulation. The utility model discloses not only can use on having the LED lamp of electric current holding current, also can use on ordinary LED lamp, the range of application grow.
Drawings
Fig. 1 is a block circuit diagram of the present invention;
fig. 2 is a circuit diagram of the present invention.
In the figure: 1. a rectifying circuit; 2. a power supply circuit; 3. a dimming control circuit; 4. a resistance step-down circuit; 5. LDO step-down circuit.
Detailed Description
The technical solution of the present invention is further specifically described below by way of examples and with reference to the accompanying drawings.
Example (b): a dimming circuit of a dimmer, as shown in figures 1-2, for dimming an LED lamp, comprises a rectifying circuit 1, a power supply circuit 2, a dimming control circuit 3 with a variable resistor, the input end of the rectification circuit 1 is connected with the commercial power, the rectification circuit 1 rectifies the commercial power, the output end of the rectification circuit 1 is provided with two paths, one path of the output end of the rectification circuit 1 is connected with the input end of the power supply circuit 2, the other path of the output end of the rectification circuit 1 is connected with an LED lamp, the output end of the power supply circuit 2 is connected with the input end of the dimming control circuit 3, the output end of the dimming control circuit 3 is connected with the LED lamp, the duty ratio output by the dimming control circuit 3 is changed by adjusting the resistance value of the variable resistor, so that the voltage conduction angle input to the LED lamp is changed, the current flowing through the LED lamp is changed, and the brightness of the LED lamp is changed along with the adjustment of the variable resistor.
The power supply circuit 2 comprises a resistance voltage reduction circuit 4 and an LDO voltage reduction circuit 5, the input end of the resistance voltage reduction circuit 4 is connected with the output end of the rectification circuit 1, the output end of the resistance voltage reduction circuit 4 is connected with the input end of the LDO voltage reduction circuit 5, the output end of the LDO voltage reduction circuit 5 is connected with the input end of the dimming control circuit 3, the direct current rectified by the rectification circuit 1 is divided by the resistance voltage reduction circuit 4 and is output to the LDO voltage reduction circuit 5, and the LDO voltage reduction circuit 5 outputs to the dimming control circuit 3 after further reducing the voltage.
Resistance step-down circuit 4 includes diode D1, resistance Ra, resistance Rb and zener diode ZD1, diode D1's positive pole connects rectifier circuit 1's positive output end, diode D1's negative pole connects resistance Ra's one end, resistance Ra's the other end termination resistance Rb's one end, another termination zener diode ZD 1's of resistance Rb negative pole, and its common connecting end is as resistance step-down circuit 4's output, connects LDO buck circuit 5's input, zener diode ZD 1's positive pole connects rectifier circuit 1's negative output end, and its common connecting end ground connection.
LDO step-down circuit 5 includes chip U1, electric capacity C1 and electric capacity C2, chip U1 has 3 feet, chip U1's first foot connects electric capacity C1's one end and the other end of R2 among the dimming control circuit 3, and its common connecting end is as LDO step-down circuit 5's input, connects resistance step-down circuit 4's output, and is the common connecting end of resistance Rb and zener diode ZD1, electric capacity C1's other end ground connection, chip U1's second foot ground connection, chip U1's third foot connects electric capacity C2's one end, and its common connecting end is as LDO step-down circuit 5's output, connects dimming control circuit 3's input, electric capacity C2's the other end ground connection.
The dimming control circuit 3 comprises a variable resistor RT, a resistor R1, a resistor R2, a chip U2, a transistor Q1 and a MOS transistor Q2, the chip U2 has 4 pins, a first pin of the chip U2 is connected with one end of the variable resistor RT, a common connection end of the chip U2 is used as an input end of the dimming control circuit 3 and is connected with an output end of the LDO step-down circuit 5, namely a common connection end of a third pin of the chip U1 and a capacitor C2, a second pin of the chip U2 is connected with the other end of the variable resistor RT and one end of a resistor R1, the other end of the resistor R1 is connected with ground, a third pin of the chip U2 is connected with a gate of the transistor Q1, a collector of the transistor Q1 is connected with one end of a resistor R2 and a gate of the MOS transistor Q2, the other end of the resistor R2 is connected with an input end of the LDO step-down circuit 5, namely a common connection end of the first pin of the chip U1 and the common connection end of the capacitor C1, an emitter of the transistor Q1 is connected with a fourth pin 2 and a source of the MOS transistor Q2, and the common connection end is grounded, and the drain electrode of the MOS tube Q2 is connected with the LED lamp.
The variable resistor RT is connected with a dimmer, the resistance value of the variable resistor RT can be adjusted through the dimmer, the voltage output to the second pin of the chip U2 is changed, the third pin of the chip U2 outputs different PWM duty ratios to the triode Q1, and therefore on-off of the triode Q1 is achieved, namely when the triode Q1 is conducted, the grid electrode of the MOS tube Q2 is grounded, and the MOS tube Q2 is disconnected; when the triode Q1 is turned off, the gate of the MOS transistor Q2 inputs a high level to turn on the MOS transistor Q2, and the turning on and off of the MOS transistor Q2 changes the voltage conduction angle input to the LED lamp, and changes the current flowing through the LED lamp, so that the brightness of the LED lamp changes along with the adjustment of the variable resistor RT.
To sum up, the utility model discloses an adopt the dimming control circuit who has variable resistance to adjust luminance, utilize the resistance of adjusting variable resistance, make chip U2 output different PWM duty cycle, change triode Q1's break-make time, and then change MOS pipe Q2's break-make time, make the voltage conduction angle of inputing to the LED lamp change, change the electric current that flows through the LED lamp to the luminance that makes the LED lamp changes along with variable resistance's regulation. The utility model discloses not only can use on having the LED lamp of electric current holding current, also can use on ordinary LED lamp, the range of application grow.
Finally, it should be noted that the above embodiments are merely representative examples of the present invention. Obviously, the present invention is not limited to the above-described embodiments, and many modifications are possible. Any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention should be considered as belonging to the protection scope of the present invention.