A dimming circuit capable of stably outputting voltage

Abstract

The present invention discloses a dimming circuit capable of stably outputting voltage, which includes a rectification and filtering module, a boost dimming constant current module, a voltage output module, and an LED load. It is characterized in that it further includes a voltage stabilization control module; the input end of the rectification and filtering module is connected to the mains power supply, the output end of the rectification and filtering module is connected to the input end of the voltage output module, the boost dimming constant current module is connected to the voltage output module, the output end of the voltage output module is connected to the voltage stabilization control module, the voltage stabilization output module controls the boost dimming constant current module through a PWM signal, and the voltage stabilization control module is connected to the LED load. The present invention provides a MOS transistor connected to the LED load, and compensates for the voltage drop of the load LED load by controlling the voltage drop change of the MOS transistor, so as to achieve the purpose of stably outputting voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of LED lighting, and in particular to a dimming circuit capable of stably outputting voltage. Background Art

[0002] Illumination plays an indispensable role in people's daily life, enabling the human eye to see things clearly, thus bringing convenience to people's life and work. In recent years, with the emphasis on energy and environmental protection issues and the improvement of living quality, lighting is no longer limited to single-brightness illumination. Under the trend of various brightness illumination requirements, dimming lighting devices have emerged.

[0003] A "switch dimming circuit" disclosed in a Chinese patent document, with the publication number CN106714411A and the publication date May 24, 2017, includes a power switch and a drive circuit. The drive circuit includes a power supply module, an energy storage module, and a control module. The power supply module is used to convert the AC voltage output by the AC power supply into a DC voltage. The control module includes a first switching tube and a control device. The control device is used to control the conduction or cutoff of the first switching tube to control the charging of the energy storage module by the power supply module or the discharging of the energy storage module. The control device is used to detect the discharge end pulse of the energy storage module and control the conduction or cutoff of the first switching tube according to the line current flowing through the first switching tube and the discharge end pulse. The control device is used to determine that the power switch is disconnected and turn off the control device when the discharge end pulse is not detected within a predetermined time. The switch dimming circuit of the embodiment of the invention can accurately adjust the brightness of the light source. However, after dimming, due to the decrease in the output current, the voltage of the LED lamp string also decreases, and when the voltage drops to a certain extent, the circuit cannot work stably. Summary of the Invention

[0004] The present invention is to overcome the problem that when the dimming circuit dims in the prior art, the output voltage will decrease due to the decrease in the output current, resulting in the unstable operation of the circuit. A dimming circuit capable of stably outputting voltage is provided, which uses the voltage drop of the MOS tube in the voltage stabilization output module to compensate for the decrease in the voltage of the LED lamp string and ensure the stability of the output voltage.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A dimming circuit capable of stably outputting voltage, including a rectifying and filtering module, a boost dimming constant current module, and a voltage output module, characterized in that it further includes a voltage stabilization control module; the input end of the rectifying and filtering module is connected to the mains supply, the output end of the rectifying and filtering module is connected to the input end of the voltage output module, the boost dimming constant current module is connected to the voltage output module, the output end of the voltage output module is connected to the voltage stabilization control module, the voltage stabilization output module controls the boost dimming constant current module through a PWM signal, and the voltage stabilization control module is connected to the load.

[0007] The rectifying and filtering module converts the input mains power from AC power into DC power after filtering and rectifying. The boost dimming constant current module boosts the voltage of the circuit and realizes the control of constant current and dimming of the circuit. The voltage output module is responsible for supplying power to the load lamp string with a stable voltage output. The voltage stabilization control module is the key point of the present invention. By setting a MOS transistor connected to the LED lamp string and adjusting it, the function of stabilizing the output voltage is achieved.

[0008] Preferably, the voltage stabilization control module includes a chip U2. The power supply pin of the chip U2 is connected to the module supply voltage. The voltage detection terminal of the chip U2 is connected to one end of a resistor R4 and one end of a resistor R5. The other end of the resistor R4 is connected to the output terminal of the voltage output module and the input terminal of the load. The other end of the resistor R5 is connected to the source electrode of a MOS transistor Q2 and grounded. The drain electrode of the MOS transistor Q2 is connected to the output terminal of the load. The gate electrode of the MOS transistor Q2 is connected to one end of a resistor R6 and one end of a capacitor C4. The other end of the capacitor C4 is grounded. The MOS transistor Q2 stabilizes the output voltage by adjusting the voltage drop between the drain and source electrodes. The other end of the resistor R6 is connected to the first signal output terminal of the chip U2. The second signal output terminal of the chip U2 outputs a PWM signal to the chip U1.

[0009] In the voltage stabilization control module, the chip U2 controls the dimming of the boost dimming constant current module by outputting a PWM dimming signal. Its voltage detection terminal can convert the sampled voltage in the circuit from an analog signal into a digital signal and input it into the chip. The first signal output terminal of the chip U2 can output a control signal to control the gate voltage of the MOS transistor Q2 to control the voltage drop between its drain and source electrodes, thereby compensating for the voltage drop of the LED lamp string during dimming, so as to ensure the stability of the output voltage.

[0010] Preferably, the chip U2 is a radio frequency control chip, which can realize the control function using a remote control or an APP. The transceiver function of the wireless communication protocol and the MCU function are integrated on the chip U2 of the wireless control module, so as to realize non-contact intelligent control. Its wireless communication mode can be selected from WIFI, BLE or ZIGBEE.

[0011] Preferably, the voltage output module includes an electrolytic capacitor C3. The positive electrode of the electrolytic capacitor C3 is connected to the cathode of a diode D1 and is also connected to the other end of the resistor R4. The negative electrode of the electrolytic capacitor C3 is connected to the other end of the resistor R5 and grounded. The anode of the diode D1 is connected to one end of an inductor L2A and is also connected to the drain electrode of a MOS transistor Q1. The other end of the inductor L2A is connected to the output terminal of the rectifying and filtering circuit.

[0012] Inductor L2A is an energy storage inductor that can store electrical energy and forms a step-down transformer with the secondary inductor L2B. Diode D1 is an output diode that controls the output direction of the voltage. The two ends of the electrolytic capacitor C3 are the output voltage of the circuit. The purpose of the present invention is to ensure the voltage stability across the two ends of the electrolytic capacitor C3.

[0013] Preferably, the boost dimming constant current module includes a chip U1, the driving end of the chip U1 is connected to the gate of the MOS tube Q1, the drain of the MOS tube Q1 is connected to the anode of the diode D1, the source of the MOS tube Q1 is connected to the current detection end of the chip U1 and is grounded through the resistor R3, the other end of the secondary inductor L2B is connected to the anode of the diode D2 and is grounded, one end of the secondary inductor L2B is connected to the cathode of the diode D2, the anode of the diode D3 and one end of the resistor R1, the cathode of the diode D3 is connected to one end of the capacitor C5 and connected to the voltage input end of the chip U1, the other end of the resistor R1 is connected to one end of the resistor R2 and connected to the feedback end of the chip U1, the compensation end of the chip U1 is grounded through the capacitor C6, and the ground end of the chip U1 is connected to the other end of the capacitor C5 and the other end of the resistor R2 and is grounded.

[0014] In the boost dimming constant current module, the secondary inductor L2B supplies power to the chip U1 and provides feedback of the output voltage. The chip U1 receives the PWM dimming signal from the chip U2 and performs dimming operation. The driver end of the chip U1 controls the on and off of the MOS tube Q1 to achieve constant current control, and its current detection end is responsible for detecting the current passing through the resistor R3.

[0015] Preferably, the rectifier filter module includes a filter unit and a rectifier unit, the filter unit input end is connected to the mains, the filter unit output end is connected to the rectifier unit input end, the rectifier unit output end is connected to one end of capacitor C7 and connected to the input end of the voltage output module, and the other end of capacitor C7 is grounded. The filter unit is a π-type filter, and the rectifier unit is a rectifier bridge, which converts AC power into DC power input circuit after filtering, rectification and filtering operations.

[0016] Preferably, the load is an LED light string, the input end of the LED light string is connected to the other end of the resistor R4, and the output end of the LED light string is connected to the drain of the MOS tube Q2.

[0017] Preferably, the dimming circuit further comprises a circuit protection unit, which is connected between the input end of the rectifier and filter circuit and the mains input. The circuit protection unit is a fuse, which is connected to the live wire of the input end of the rectifier and filter circuit. When the mains input exceeds the fuse's bearing capacity, the fuse is disconnected to stop the circuit from working, thereby protecting the circuit.

[0018] The beneficial effects of the present invention are as follows: A voltage stabilization control module is provided. By controlling the gate voltage of the MOS transistor, the voltage drop between the drain and source of the MOS transistor is regulated, thereby compensating for the voltage drop during the dimming of the LED lamp string, so that the output voltage of the circuit always remains stable. The voltage stabilization control module selects a wireless control module as the control chip, which can be controlled by a remote control or a mobile phone APP, making it more convenient for people to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the circuit block diagram of the present invention;

[0020] Figure 2 is the circuit schematic diagram of the present invention;

[0021] Figure 3 is the voltage change curve diagram of the LED lamp string during dimming in the embodiment of the present invention;

[0022] Figure 4 is the output voltage control change curve diagram during dimming in the embodiment of the present invention;

[0023] In the figure: 1. Voltage across both ends of electrolytic capacitor C3 (output voltage); 2. Voltage of the LED lamp string; 3. Voltage between the drain and source of MOS transistor Q2 (VDS); 4. Voltage between the gate and source of MOS transistor Q2 (VGS). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0025] As Figure 1 shown, a dimming circuit capable of stably outputting voltage includes a rectification and filtering module, a boost dimming constant current module, a voltage output module, a voltage stabilization control module, and an LED load. The input end of the rectification and filtering module is connected to the mains power supply, the output end of the rectification and filtering module is connected to the input end of the voltage output module, the boost dimming constant current module is connected to the voltage output module, the output end of the voltage output module is connected to the voltage stabilization control module, the voltage stabilization output module controls the boost dimming constant current module through a PWM signal, and the voltage stabilization control module is connected to the LED load.

[0026] As Figure 2As shown, the voltage stabilization control module A4 includes a chip U2. In this embodiment, the chip U2 uses a low-power zigbee3.0 module of the BWMZB02 model, which consists of a highly integrated radio frequency chip EFR32MG13F732 and a small amount of peripheral circuits. The 3.3V power supply pin of the chip U2 is connected to the 3.3V module power supply voltage. The ADC pin of the chip U2 is connected to one end of the resistor R4 and one end of the resistor R5. The other end of the resistor R4 is connected to the output end of the voltage output module and is connected to the input end of the load. The other end of the resistor R5 is connected to the source electrode of the MOS transistor Q2 and is grounded. The drain electrode of the MOS transistor Q2 is connected to the output end of the load. The gate electrode of the MOS transistor Q2 is connected to one end of the resistor R6 and one end of the capacitor C4. The other end of the capacitor C4 is grounded. The MOS transistor Q2 stabilizes the output voltage by adjusting the voltage drop VDS between the drain electrode and the source electrode. The other end of the resistor R6 is connected to the PWM_W pin of the chip U2. The PWM_C pin of the chip U2 outputs a PWM signal to the chip U1.

[0027] The voltage output module A2 includes an electrolytic capacitor C3. The positive electrode of the electrolytic capacitor C3 is connected to the cathode of the diode D1 and is connected to the other end of the resistor R4. The negative electrode of the electrolytic capacitor C3 is connected to the other end of the resistor R5 and is grounded. The anode of the diode D1 is connected to the 2nd port of the inductor L2A and is connected to the drain electrode of the MOS transistor Q1. The 1st port of the inductor L2A is connected to the output end of the rectifying and filtering circuit.

[0028] The boost dimming constant current module A3 includes a chip U1. In this embodiment, the chip U1 uses an integrated circuit chip of the JW1606 model. The GATE pin of the chip U1 is connected to the gate electrode of the MOS transistor Q1. The drain electrode of the MOS transistor Q1 is connected to the anode of the diode D1. The source electrode of the MOS transistor Q1 is connected to the SNP pin of the chip U1 and is grounded through the resistor R3. The 3rd port of the secondary side inductor L2B is connected to the anode of the diode D2 and is grounded. The 3rd port of the secondary side inductor L2B and the 1st port of the inductor L2A are the same name terminals. The 4th port of the secondary side inductor L2B is connected to the cathode of the diode D2, the anode of the diode D3, and one end of the resistor R1. The cathode of the diode D3 is connected to one end of the capacitor C5 and is connected to the VCC pin of the chip U1. The other end of the resistor R1 is connected to one end of the resistor R2 and is connected to the FB pin of the chip U1. The COMP pin of the chip U1 is grounded through the capacitor C6. The grounding end of the chip U1 is connected to the other end of the capacitor C5 and the other end of the resistor R2 and is grounded.

[0029] The rectifier and filter module A1 includes a filter unit and a rectifier unit. The filter unit is a π-type filter. One end of the inductor L1 is connected to one end of the capacitor C1 on the live wire. The other end of the inductor L1 is connected to one end of the capacitor C2. The other end of the capacitor C1 is connected to the other end of the capacitor C2 and is connected to the neutral wire. The rectifier unit is a rectifier bridge. The 1st terminal of the rectifier bridge BS1 is connected to one end of the capacitor C2, and its 3rd terminal is connected to the other end of the capacitor C2. The 2nd terminal of the rectifier bridge BS1 is connected to one end of the capacitor C7 and is connected to the 1st port of the inductor L2A. The 4th terminal of the rectifier bridge BS1 and the other end of the capacitor C7 are both grounded.

[0030] One end of the fuse F1 is connected to the mains power supply, and the other end is connected to one end of the inductor L1

[0031] The LED load A5 is an LED light string. The input end of the LED light string is connected to the other end of the resistor R4, and the output end of the LED light string is connected to the drain of the MOS transistor Q2.

[0032] The rectifier and filter module converts the input mains power from AC power into DC power after filtering and rectifying. The boost dimming constant current module boosts the voltage of the circuit and realizes the control of constant current and dimming of the circuit. The voltage output module is responsible for providing a stable voltage output to supply power to the load light string. The voltage stabilization control module is the key point of the present invention. By setting the MOS transistor connected to the LED light string and adjusting it, the function of stabilizing the output voltage is achieved.

[0033] In the voltage stabilization control module, the chip U2 controls the dimming of the boost dimming constant current module by outputting a PWM dimming signal. Its ADC pin can convert the sampled voltage in the circuit from an analog signal into a digital signal and input it into the chip. The resistors R4 and R5 are voltage dividing resistors and can be used for voltage sampling. The PWM_W pin of the chip U2 can output a control signal to control the gate voltage VGS of the MOS transistor Q2 to control the voltage drop VGS between its drain and source, thereby compensating for the voltage drop of the LED light string during dimming, so as to ensure the stability of the output voltage. Using the wireless control module as the chip U2, it integrates the transceiver function of the wireless communication protocol and the MCU function, thus realizing contactless intelligent control. Its wireless communication mode can not only select ZIGBEE, but also select WIFI or BLE, enabling users to achieve remote intelligent control through a remote control or a mobile phone APP, etc., making the operation more convenient.

[0034] In the voltage output module, the inductor L2A is a storage inductor that can store electrical energy and forms a step-down transformer with the secondary inductor L2B. The diode D1 is an output diode that can control the output direction of the voltage. The voltage across the electrolytic capacitor C3 is the output voltage of the circuit. The purpose of the present invention is to ensure the stability of the voltage across the electrolytic capacitor C3.

[0035] In the boost dimming constant current module, the secondary inductor L2B supplies power to the chip U1 and provides feedback of the output voltage. The diode D2 is a rectifier diode, and the capacitor C5 filters the power supply of the chip U1. The chip U1 receives the PWM dimming signal from the chip U2 and performs the dimming operation. The GATE pin of the chip U1 controls the on and off of the MOS tube Q1 to achieve constant current control, and its SNP pin is responsible for detecting the current passing through the resistor R3.

[0036] The circuit protection unit is connected between the input end of the rectifier and filter circuit and the mains input. The circuit protection unit is a fuse, which is connected to the live wire at the input end of the rectifier and filter circuit. When the mains input exceeds the fuse's bearing capacity, the fuse is disconnected to stop the circuit from working, thereby protecting the circuit.

[0037] In the embodiment of the present invention, the AC input voltage of the mains is converted into a DC input voltage output module after passing through a rectifier and filter circuit. At the same time, due to the inductor L2A and the secondary inductor L2B, the output voltage is also input into the chip U1. The output voltage in the secondary inductor L2B can be input into the VCC port as the power supply voltage of the chip U1 after rectification and filtering by the diode D2 and the capacitor C5. At the same time, the voltage can also be detected by the voltage-dividing resistors R1 and R2 and input into the FB pin of the chip U1, thereby controlling the voltage output.

[0038] The voltage output module receives the input voltage after rectification and filtering, and passes through the output diode D1. The voltage across the filter output capacitor C3 is the output voltage in the circuit, which supplies power to the LED load. In this process, since the anode of the diode D1 is connected to the drain of the MOS tube Q1, the MOS tube Q1 acts as a switch-converted power device in the circuit, and combined with the current detection resistor R3, constant current control can be achieved. The principle is: the GATE pin is the drive pin of the MOS tube Q1, and the output is a square wave; the SNP pin is the peak current detection pin of the MOS tube, and a comparator is provided inside. When the voltage on the resistor R3 reaches the comparator threshold, the chip U1 turns off the MOS tube Q1 to achieve constant current control, and forms a linear regulation rate compensation with the internal circuit to improve the linear regulation rate of the circuit.

[0039] The voltage output module outputs the voltage to the voltage stabilizing control module, and the LED load is connected through the voltage stabilizing control module to make the circuit work. The voltage stabilizing control module is to stabilize the output voltage.

[0040] like Figure 3 As shown, when the dimming circuit is not provided with a voltage stabilizing control module, the LED load is directly connected to the voltage output module. At this time, after the dimming operation is performed in the circuit, the voltage across the LED load will drop from the normal working 400V to below 350V. At this time, the output voltage is also below 350V, making the circuit unable to work stably.

[0041] Therefore, a voltage stabilization control module is provided in the present invention. As Figure 4 shown, after adding the voltage stabilization control module and then performing the dimming operation of the circuit, the voltage across the LED load will still drop from the normal operating voltage of 400V to below 350V. However, a voltage drop VDS will occur between the drain and source of the MOS transistor Q2 connected to the LED load, which rises from 0.3V to 50V. After combining the two, the output voltage always remains around 400V, enabling the circuit to operate stably.

[0042] The working principle of the voltage stabilization control module is as follows. First, the output voltage is sampled by voltage dividing resistors R4 and R5, and the sampled voltage is input to the ADC pin of chip U2. It converts the analog signal into a digital signal and inputs it. Chip U2 determines the signal output of the PWM_W pin according to the detected voltage. The output PWM signal is converted into a DC voltage through the integrating capacitor C4 to control the gate voltage VGS of the MOS transistor Q2. By changing the gate voltage VGS, the MOS transistor Q2 is controlled to be in the conduction state or the variable resistance region to change the voltage drop VDS between its drain and source. When the voltage of the LED load is 400V, as Figure 4 shown in the time period from t0 to t1 in, the circuit is not dimmed, and at this time the output voltage is also 400V. Therefore, the gate voltage VGS is 3.3V, making the MOS transistor Q2 in a fully conducting state, and its voltage drop VDS is 0.3V, which can be ignored compared to 400V. When the circuit starts to be dimmed, as Figure 4 shown in the time period from t1 to t2 in, the voltage of the LED load drops from 400V to 350V. To keep the output voltage stable at 400V, chip U2 controls the gate voltage VGS to gradually decrease to 1.2V, making the MOS transistor Q2 in the variable resistance region. During the process of the decrease of VGS, the voltage drop VDS of the MOS transistor Q2 gradually increases from 0.3V to 50V, so that the output voltage still remains at 400V for operation.

[0043] The above embodiments are only for the description and explanation of the present invention for easy understanding, and are not any limitation to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dimming circuit capable of stably outputting voltage, comprising a rectification and filtering module, a boost dimming constant current module, a voltage output module, and a circuit protection unit, characterized in that, it further comprises a voltage stabilization control module; the input end of the rectification and filtering module is connected to the mains supply, and a circuit protection unit is connected between the input end of the rectification and filtering module and the mains supply input; the output end of the rectification and filtering module is connected to the input end of the voltage output module, the boost dimming constant current module is connected to the voltage output module, the output end of the voltage output module is connected to the voltage stabilization control module, the voltage stabilization control module controls the boost dimming constant current module through a PWM signal, and the voltage stabilization control module is connected to the load; The voltage stabilization control module includes a chip U2, a resistor R4, a resistor R5, a resistor R6, a MOS transistor Q2, and a capacitor C4. The voltage detection end of U2 is connected to one end of the resistor R4 and one end of the resistor R5. The other end of R4 is connected to the output end of the voltage output module and is connected to the load input end. The other end of R5 is connected to the source electrode of the MOS transistor Q2 and is grounded. The drain electrode of Q2 is connected to the load output end. The gate electrode of Q2 is connected to one end of the resistor R6 and one end of the capacitor C4. The other end of C4 is grounded. Q2 adjusts the voltage drop between the drain electrode and the source electrode to stably output voltage. The other end of R6 is connected to the first signal output end of U2, and the second signal output end of U2 outputs a PWM signal.

2. A dimming circuit capable of stably outputting voltage according to claim 1, characterized in that, the power supply pin of the chip U2 is connected to the module supply voltage; the second signal output end of the chip U2 outputs a PWM signal to the chip U1 in the boost dimming constant current module.

3. A dimming circuit capable of stably outputting voltage according to claim 2, characterized in that, the chip U2 is a radio frequency control module.

4. A dimming circuit capable of stably outputting voltage according to claim 1, characterized in that, the voltage output module includes an electrolytic capacitor C3. The positive electrode of the electrolytic capacitor C3 is connected to the cathode of the diode D1 and is connected to the other end of the resistor R4. The negative electrode of the electrolytic capacitor C3 is connected to the other end of the resistor R5 and is grounded. The anode of the diode D1 is connected to one end of the inductor L2A and is connected to the drain electrode of the MOS transistor Q1. The other end of the inductor L2A is connected to the output end of the rectification and filtering circuit.

5. A dimming circuit capable of stably outputting voltage according to claim 1, characterized in that, The boost dimming constant current module includes a chip U1. The driving end of the chip U1 is connected to the gate of a MOS transistor Q1. The drain of the MOS transistor Q1 is connected to the anode of a diode D1. The source of the MOS transistor Q1 is connected to the current detection end of the chip U1 and grounded through a resistor R3. The other end of a secondary side inductor L2B is connected to the anode of a diode D2 and grounded. One end of the secondary side inductor L2B is connected to the cathode of the diode D2, the anode of a diode D3, and one end of a resistor R1. The cathode of the diode D3 is connected to one end of a capacitor C5 and to the voltage input end of the chip U1. The other end of the resistor R1 is connected to one end of a resistor R2 and to the feedback end of the chip U1. The compensation end of the chip U1 is grounded through a capacitor C6. The grounding end of the chip U1 is connected to the other end of the capacitor C5 and the other end of the resistor R2 and grounded.

6. A dimming circuit capable of stably outputting voltage according to claim 1, characterized in that the rectifying and filtering module includes a filtering unit and a rectifying unit. The input end of the filtering unit is connected to the mains power supply. The output end of the filtering unit is connected to the input end of the rectifying unit. The output end of the rectifying unit is connected to one end of a capacitor C7 and to the input end of the voltage output module. The other end of the capacitor C7 is grounded.

7. A dimming circuit capable of stably outputting voltage according to claim 1, characterized in that the load is an LED lamp string. The input end of the LED lamp string is connected to the other end of a resistor R4. The output end of the LED lamp string is connected to the drain of a MOS transistor Q2.

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