Alternating current square wave dimming circuit

Abstract

The invention provides an alternating current square wave dimming circuit which comprises a central processing unit, an SPI-to-DAC circuit, a triode control switch circuit, an operation in-phase and out-phase circuit, a switch chip circuit, a power supply circuit and a power operational amplifier. The central processing unit is connected with the SPI-to-DAC circuit through an SPI port of the central processing unit, the triode control switch circuit is connected with the central processing unit through a PWM interface of the central processing unit, the operation in-phase and out-phase circuit is connected with the SPI-to-DAC circuit and the switch chip circuit, the switch chip circuit is connected with the power operational amplifier, and the power operational amplifier is connected with the triode control switch circuit. The triode control switch circuit, the switch chip circuit and the power operational amplifier are all connected with the power supply circuit; the central processing unit is used for changing the duty ratio of the power supply, and the SPI-to-DAC circuit is used for providing four paths of dimming output for the central processing unit. Through the alternating-current square-wave dimming circuit, the purpose of regulating and controlling the transmittance of the industrial dimming glass is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of dimming circuits, and in particular to an alternating current square wave dimming circuit. Background Art

[0002] As the demand for energy-saving and intelligent lighting solutions continues to grow, AC square wave dimming technology is expected to continue to expand its market share, especially in industrial dimming glass projects. AC square wave dimming technology will become more advanced, providing more features such as dynamic dimming and integration with other systems. The hardware technology cost of AC square wave dimming technology in this solution is reduced, the integration is smaller, and the performance is stable, making this technology more popular and affordable.

[0003] However, the existing AC square wave dimming is not suitable for industrial dimming glass projects. Summary of the invention

[0004] In view of this, the embodiments of this specification provide an AC square wave dimming circuit to achieve the purpose of adjusting the transmittance of industrial dimming glass.

[0005] The embodiments of this specification provide the following technical solutions:

[0006] An AC square wave dimming circuit, comprising:

[0007] Central processing unit, SPI to DAC circuit, transistor control switch circuit, operational inverse phase circuit, switch chip circuit, power supply circuit, power operational amplifier;

[0008] The central processing unit is connected to the SPI to DAC circuit via the SPI port of the central processing unit, the transistor control switch circuit is connected to the central processing unit via the PWM interface of the central processing unit, the operational inverse phase circuit is respectively connected to the SPI to DAC circuit and the switch chip circuit, the switch chip circuit is connected to the power operational amplifier, and the transistor control switch circuit, the switch chip circuit and the power operational amplifier are all connected to the power supply circuit;

[0009] The central processing unit is used to change the duty cycle of the power supply, the SPI to DAC circuit is used to provide 4-way dimming output for the central processing unit, the transistor control switch circuit is used to increase the voltage range to 0-5V, the switch chip circuit is used to output a square wave signal to the power operational amplifier, the power operational amplifier is used to adjust the output voltage and output current and output them through an external interface, and the power supply circuit is used to provide power for the transistor control switch circuit, the switch chip circuit and the power operational amplifier.

[0010] Further, the SPI to DAC circuit includes a digital to analog converter;

[0011] The digital-to-analog converter includes VDD pin, VREFL pin, VREFH pin, VSS pin, CS pin, CLK pin, SDI pin, register reset pin RESETSEL, chip reset pin RESET, and chip latch status pin LOADDACS;

[0012] The VDD pin is connected to the 5V reference voltage, the VSS pin is connected to the -5V reference voltage, the CS pin, CLK pin, and SDI pin are respectively connected in series with the first resistor R577, the second resistor R578, and the third resistor R579 and then connected to the SPI1_CS pin, SPI1_CLK pin, and SPI1_DSI pin of the central processing unit, the VREFL pin is connected to the 2.5V reference voltage, the VREFH pin is connected to the -2.5V reference voltage, the register reset pin RESETSEL, the chip reset pin RESET, and the chip latch status pin LOADDACS are respectively connected to the GPIO pins of the central processing unit.

[0013] Further, the operational in-phase reverse phase circuit includes:

[0014] DAC chip reference voltage circuit, a first operational amplifier and a second operational amplifier;

[0015] The output voltage of the DAC chip reference voltage circuit is connected to the +IN pin of the first operational amplifier through the fourth resistor R504 in series, the -IN pin of the first operational amplifier is connected to the fifth resistor R500 and then grounded, and is connected to the OUT pin of the first operational amplifier after connecting the sixth resistor R501 and the first capacitor C501, the OUT pin of the first operational amplifier is connected to the seventh resistor R503 and then connected to the output control switch SA1, the voltage of the output control switch SA1 is connected to the -IN pin of the second operational amplifier after connecting the eighth resistor R516 in series, and is connected to the OUT pin of the second operational amplifier after connecting the ninth resistor R512 and the second capacitor C505, the +IN pin of the second operational amplifier is connected to the tenth resistor R514 and grounded, the OUT pin of the second operational amplifier is connected to the eleventh resistor R513 and the third capacitor C519, the V-0 pin, V-1 pin, and V-2 pin of the first operational amplifier and the second operational amplifier are all connected to the -24V voltage, the V+ pin of the first operational amplifier and the second operational amplifier is connected to the +24V voltage, and the FLAG pins of the first operational amplifier and the second operational amplifier are grounded.

[0016] Furthermore, the switch chip circuit includes:

[0017] S1A pin, S1B pin, D1 pin, D2 pin, VDD pin, VSS pin, PAD pin;

[0018] The VDD pin is connected to +15V, and the VSS pin and PAD pin are connected to -15V.

[0019] The S1A pin, S1B pin and D1 pin form a 1-way switch;

[0020] The voltage output by the D1 and D2 pins is a square wave signal with a voltage of ±10V, a frequency of 60HZ, and a duty cycle of 50%.

[0021] Further, the power operational amplifier comprises:

[0022] Output connector J5_A2, VIN- pin, VO pin and +IN pin;

[0023] The switch chip is connected to the VIN- pin through the twelfth resistor R634, and is connected to the VO pin through the thirteenth resistor R635 and the fourth capacitor C667, the +IN pin is grounded through the fourteenth resistor R706, the VO pin is connected to the 1PIN pin of the output connector J5_A2 through the fifteenth resistor R640, and the VO pin is grounded through the fifth capacitor C600.

[0024] Furthermore, the power supply circuit comprises:

[0025] a first voltage conversion circuit, a second voltage conversion circuit, and a third voltage conversion circuit;

[0026] The first voltage conversion circuit is used to convert 12V into 5V;

[0027] The second voltage conversion circuit is used to convert 5V into ±15V;

[0028] The third voltage conversion circuit is used for converting 12V into ±24V.

[0029] Furthermore, the transistor control switch circuit includes:

[0030] triode;

[0031] The base of the transistor is connected to the PWM port of the central processing unit through the sixteenth resistor R627;

[0032] The collector of the transistor is connected to the IN1 port of the switch chip circuit;

[0033] The emitter of the transistor is grounded after passing through the seventeenth resistor R626 and the eighteenth resistor R649.

[0034] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects:

[0035] The purpose of regulating the transmittance of industrial dimming glass is achieved through the AC square wave dimming circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 is an overall structural diagram of an AC square wave dimming circuit according to an embodiment of the present invention;

[0038] Figure 2 is a structural diagram of an SPI to DAC circuit according to an embodiment of the present invention;

[0039] Figure 3 is a structural diagram of a DAC chip reference voltage circuit according to an embodiment of the present invention;

[0040] Figure 4 is a structural diagram of an operational in-phase and in-phase circuit according to an embodiment of the present invention;

[0041] Figure 5 is a structural diagram of a triode control switch circuit according to an embodiment of the present invention;

[0042] Figure 6 is a structural diagram of a switch chip circuit according to an embodiment of the present invention;

[0043] Figure 7 is a structural diagram of an operational amplifier according to an embodiment of the present invention;

[0044] Figure 8 is a structural diagram of a first voltage conversion circuit in a power supply circuit according to an embodiment of the present invention;

[0045] Fig. 9 is a structural diagram of a second voltage conversion circuit in a power supply circuit according to an embodiment of the present invention;

[0046] Fig.10 is a structural diagram of a third voltage conversion circuit in the power supply circuit of an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0048] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0049] like Figure 1As shown, the AC square wave dimming circuit includes: a central processing unit, an SPI to DAC circuit, a transistor control switch circuit, an operational inverse phase circuit, a switch chip circuit, a power supply circuit, and a power operational amplifier.

[0050] The central processing unit is connected to the SPI to DAC circuit via the SPI port of the central processing unit, the transistor control switch circuit is connected to the central processing unit via the PWM interface of the central processing unit, the operational inverse phase circuits are respectively connected to the SPI to DAC circuit and the switch chip circuit, the switch chip circuit is connected to the power operational amplifier, and the transistor control switch circuit, the switch chip circuit and the power operational amplifier are all connected to the power supply circuit.

[0051] The central processing unit is used to change the duty cycle of the power supply, the SPI to DAC circuit is used to provide 4-way dimming output for the central processing unit, the transistor control switch circuit is used to increase the voltage range to 0-5V, the switch chip circuit is used to output a square wave signal to the power operational amplifier, the operational amplifier is used to adjust the output voltage and output current and output them through an external interface, and the power supply circuit is used to provide power for the transistor control switch circuit, the switch chip circuit and the power operational amplifier.

[0052] In one embodiment of the present invention, the dimming control board can use the RK339K platform. RK3399K is a 64-bit six-core processor, ARM Cortex-A72 dual-core 1.8GHz + Cortex-A53 quad-core 1.4GHz; standard 4GB memory; standard 8GB EMMC storage space; 3-way RS485 adopts isolation solution chip; 2-way RS232 also adopts isolation solution; 2-way USB power supply adopts isolated power supply; 1-way 100M network port; 5-way GPIO detection; 2-way output 12V; using analog circuit solution to output 4-way voltage of ±24V, power of 10W, frequency of 60HZ, and duty cycle of 50% dimming interface.

[0053] The hardware dimming hardware part is digital-to-analog conversion (SPI interface to DAC), operational amplifier in-phase and inverting amplification, switch rectification, power operational amplifier inverting amplification and power supply. The working principle of the hardware part is that the PC end realizes the communication of the dimming board through the USB to RS485 interface, and the RK3399K receives the instruction through the SPI interface by outputting the instruction on the serial port interface of the PC end to realize the digital-to-analog conversion. The analog voltage is amplified in-phase and inverted by the first-stage operational amplifier to realize the AC square wave to the switch chip, and then the second-stage power operational amplifier inverts the amplification to realize the output of ±24V power, 10W frequency, 60HZ duty cycle and 50%.

[0054] Because the RK3399K of the dimming board lacks analog DAC pin output, it is necessary to connect the chip DAC7614U_1K through the SPI interface of RK3399K to realize the SPI interface to DAC. The DAC pin outputs an analog voltage of 0-2.5V; the analog voltage 0-2.5V is amplified in the same phase and inverting phase through the operational amplifier; the positive and negative voltages are given to a switch chip respectively, and the PWM pin of RK3399K outputs a square wave with a frequency of 60HZ, a duty cycle of 50%, and a voltage of 0-1.8V. After the transistor, 0-1.8V is changed to 0-5V range, and the switch chip is controlled to realize a frequency of 60HZ, a duty cycle of 50%, and a voltage of ±10V; the frequency of 60HZ, the duty cycle of 50%, and the voltage of ±10V are output through the power operational amplifier with a frequency of 60HZ, a duty cycle of 50%, and a voltage of ±24V.

[0055] Because the dimming board of the central processor needs 4 dimming outputs, the SPI to DAC circuit (such as DAC7614U_1K chip) is used to realize 4 DAC outputs. The 4 DAC can realize two outputs, one is -2.5V to 2.5V output, and the other is 0V to 2.5V output. The 4 DAC outputs -2.5V to 2.5V, the VDD pin of the SPI to DAC circuit needs to be connected to 5V, the VSS pin is connected to -5V, the VREFH pin is connected to a 2.5V reference voltage, and the VREFH pin is connected to a -2.5V reference voltage; the 4 DAC outputs 0-2.5V, the VDD pin needs to be connected to 5V, VSS is grounded, the VREFH pin is connected to a 2.5V reference voltage, and the VREFH pin is connected to ground. Among them, CS, CLK, and SDI of DAC7614U_1K are respectively connected to the SPI1_CS, SPI1_CLK, and SPI1_DSI pins of the central processor to realize the communication between the SPI interface of the central processor and DAC7614U_1K, and a 22Ω resistor is connected in series in the middle for SPI impedance matching; the register reset pin RESETSEL, chip reset pin RESET, and chip latch state pin LOADDACS of the SPI to DAC circuit are respectively connected to the GPIO port pins of the CPU. After power-on, wait for RK3399K to start up and pull up the RESETSEL pin, RESET pin, and LOADDACS pin; this solution uses 0-2.5V output, so the voltage reference chip REF3025AIDBZR is required to realize 3.3V to 2.5V conversion and connect it to the VREFH pin and add 2 capacitors for filtering. The VREFHL pin is connected to the ground, VDD needs to be connected to 5V and add 2 capacitors for filtering, and VSS is grounded. The central processor controls the output 0-2.5V through the DAC of the SPI to DAC circuit.

[0056] like Figure 2As shown, the SPI to DAC circuit includes a digital to analog converter.

[0057] The digital-to-analog converter includes a VDD pin, a VDD pin, a VREFL pin, a VREFH pin, a VSS pin, a CS pin, a CLK pin, an SDI pin, a register reset pin RESETSEL, a chip reset pin RESET, and a chip latch status pin LOADDACS. The VDD pin is connected to a 5V reference voltage, the VSS pin is connected to a -5V reference voltage, the CS pin, the CLK pin, and the SDI pin are connected to the SPI1_CS pin, the SPI1_CLK pin, and the SPI1_DSI pin of the central processing unit after being connected in series with a first resistor R577, a second resistor R578, and a third resistor R579, respectively, the VREFL pin is connected to a 2.5V reference voltage, the VREFH pin is connected to a -2.5V reference voltage, the register reset pin RESETSEL, the chip reset pin RESET, and the chip latch status pin LOADDACS are connected to the GPIO pins of the central processing unit, respectively.

[0058] The embodiment of the present invention uses an operational amplifier for in-phase amplification and inverting amplification. The 0-2.5V output by the reference voltage circuit of the DAC chip needs to be amplified 4 times in-phase and 1 times inverting, and the output voltage supports -10V to 10V.

[0059] like Figure 3 and Figure 4 As shown, the operational in-phase and out-of-phase circuit includes: a DAC chip reference voltage circuit, a first operational amplifier and a second operational amplifier. The output voltage of the DAC chip reference voltage circuit is connected to the +IN pin of the first operational amplifier through the fourth resistor R504 in series, the -IN pin of the first operational amplifier is connected to the fifth resistor R500 and then grounded, and is connected to the OUT pin of the first operational amplifier after connecting the sixth resistor R501 and the first capacitor C501, the OUT pin of the first operational amplifier is connected to the seventh resistor R503 and then connected to the output control switch SA1, the voltage of the output control switch SA1 is connected to the -IN pin of the second operational amplifier after connecting the eighth resistor R516 in series, and is connected to the OUT pin of the second operational amplifier after connecting the ninth resistor R512 and the second capacitor C505, the +IN pin of the second operational amplifier is connected to the tenth resistor R514 and grounded, the OUT pin of the second operational amplifier is connected to the eleventh resistor R513 and the third capacitor C519, the V-0 pin, V-1 pin, and V-2 pin of the first operational amplifier and the second operational amplifier are all connected to the -24V voltage, the V+ pin of the first operational amplifier and the second operational amplifier is connected to the +24V voltage, and the FLAG pins of the first operational amplifier and the second operational amplifier are grounded.

[0060] The embodiment of the present invention uses a switch chip to output a square wave signal with a voltage of ±10V, a frequency of 60HZ, and a duty cycle of 50%.

[0061] like Figure 5 As shown, the transistor control switch circuit includes: a transistor. In order to increase the driving capability and avoid the critical point of the control voltage, the voltage range is increased to 0-5V through the transistor.

[0062] The base of the transistor is connected to the PWM port of the CPU through the sixteenth resistor R627. The collector of the transistor is connected to the IN1 port of the switch chip circuit. The emitter of the transistor is grounded after passing through the seventeenth resistor R626 and the eighteenth resistor R649.

[0063] like Figure 6 As shown, the switch chip circuit includes: S1A pin, S1B pin, D1 pin, D2 pin, VDD pin, VSS pin, and PAD pin.

[0064] The VDD pin is connected to +15V, and the VSS pin and PAD pin are connected to -15V. The S1A pin, S1B pin and D1 pin form a 1-way switch. The D1 pin and D2 pin output a square wave signal with a voltage of ±10V, a frequency of 60HZ and a duty cycle of 50%.

[0065] The embodiment of the present invention uses a power operational amplifier to convert ±10V to ±24V voltage output, and a square wave signal with a frequency of 60HZ and a duty cycle of 50%. In one embodiment of the present invention, the power operational amplifier uses OPA544FKTTT.

[0066] like Figure 7 As shown, the power operational amplifier includes: an output connector J5_A2, a VIN- pin, a VO pin, and a VIN+ pin. The switch chip is connected to the VIN- pin through a twelfth resistor R634, and is connected to the VO pin through a thirteenth resistor R635 and a fourth capacitor C667, the VIN+ pin is grounded through a fourteenth resistor R706, the VO pin is connected to the 1PIN pin of the output connector J5_A2 through a fifteenth resistor R640, and the VO pin is grounded through a fifth capacitor C600.

[0067] The D pin of the switch chip outputs a voltage of ±10V, a frequency of 60HZ, and a square wave signal with a duty cycle of 50%. However, the switch chip does not support high power and cannot meet the four-way dimming output requirement of 10W. The output voltage is ±24V, so a power operational amplifier chip is required with an output voltage range of ±35V and an output current of 2A. The D pin of the switch chip connects resistor R634 to the power operational amplifier VIN- and connects resistors R635 and C667 to the VO pin of the operational amplifier. VIN+ connects resistor R706 to ground. The inverting amplification factor is through resistor -(R635 / 634) = -2.4. The VO pin of the operational amplifier is connected to the 1PIN pin of the resistor R640 output connector J5_A2 and stabilized by capacitor C600. The output voltage is -2.4X±10V = ±24V. The 2PIN pin of J5_A2 connects R708 to ground.

[0068] In order to improve the integration and miniaturization, this power module is designed on the dimming board. The relevant circuits in the AC 24V square wave solution need 12V, 5V, ±15V, and ±24V for power supply. In one embodiment, the power circuit uses the chip TPS54A24RTW (5V input 10A output), ADP1613ARMZ-R7 (±15V input 2A output) and ADP5070AREZ (±24V input 2A output), and the input voltage of the power circuit is 12V. Among them, 5V is used for the chip ADP1613ARMZ-R7 to perform boost and negative voltage conversion and PWM power supply for the switching switch; 12V is used for the chip ADP5070ARE to perform boost and negative voltage conversion.

[0069] like Figures 8 to 10 As shown, the power supply circuit includes: a first voltage conversion circuit, a second voltage conversion circuit and a third voltage conversion circuit.

[0070] like Figure 8 As shown, the first voltage conversion circuit is used to convert 12V into 5V.

[0071] like Fig. 9 As shown, the second voltage conversion circuit is used to convert 5V into ±15V.

[0072] like Fig.10 As shown, the third voltage conversion circuit is used to convert 12V into ±24V.

[0073] Beneficial effects of the embodiments of the present invention:

[0074] The AC square wave dimming control circuit of the embodiment of the present invention is mainly used to provide an AC square wave signal for adjusting the transmittance of dimming glass, and is powered by DC12V. It has 2 RS232, 3 RS485, 2 5V controllable outputs, 1 Ethernet communication interface, 2 USB, 5 IO ports, 2 12V controllable outputs, and 4 dimming interfaces with voltage of ±24V, power of 10W, frequency of 60HZ, and duty cycle of 50%. The dimming board can communicate with the capacitive touch key board through the RS485 interface to collect the dimming control signal provided by the key board, and can also receive the dimming control touch signal of the capacitive touch screen through the USB, and then generate the corresponding AC square wave signal for adjusting the transmittance of dimming glass to control the change of the transmittance of dimming glass. The board reserves the onboard CPU debugging interface and the burning interface of the external capacitive touch key board to facilitate the maintenance of the board; the transmittance of industrial dimming glass is adjusted by adjusting the transmittance of industrial dimming glass according to the embodiment of the present invention.

[0075] The above is only a specific embodiment of the present invention, and cannot be used to limit the scope of the invention. Therefore, the replacement of equivalent components, or equivalent changes and modifications made according to the scope of protection of the patent of the present invention, should still fall within the scope of this patent. In addition, the technical features of the present invention can be freely combined with each other, with each other, and with each other.

Claims

1. An AC square wave dimming circuit, characterized in that: include: Central processing unit, SPI to DAC circuit, transistor control switch circuit, operational inverse phase circuit, switch chip circuit, power supply circuit, power operational amplifier; The central processing unit is connected to the SPI to DAC circuit via the SPI port of the central processing unit, the transistor control switch circuit is connected to the central processing unit via the PWM interface of the central processing unit, the operational inverse phase circuit is respectively connected to the SPI to DAC circuit and the switch chip circuit, the switch chip circuit is connected to the power operational amplifier, and the transistor control switch circuit, the switch chip circuit and the power operational amplifier are all connected to the power supply circuit; The central processing unit is used to change the duty cycle of the power supply, the SPI to DAC circuit is used to provide 4 dimming outputs for the central processing unit, the transistor control switch circuit is used to increase the voltage range to 0-5V, the switch chip circuit is used to output a square wave signal to the power operational amplifier, the power operational amplifier is used to adjust the output voltage and output current and output through an external interface, and the power supply circuit is used to provide power for the transistor control switch circuit, the switch chip circuit and the power operational amplifier.

2. The AC square wave dimming circuit according to claim 1, characterized in that: The SPI to DAC circuit includes a digital to analog converter; The digital-to-analog converter includes a VDD pin, a VREFL pin, a VREFH pin, a VSS pin, a CS pin, a CLK pin, an SDI pin, a register reset pin RESETSEL, a chip reset pin RESET, and a chip latch state pin LOADDACS; The VDD pin is connected to a 5V reference voltage, the VSS pin is connected to a -5V reference voltage, the CS pin, the CLK pin, and the SDI pin are respectively connected in series with a first resistor R577, a second resistor R578, and a third resistor R579 and then connected to the SPI1_CS pin, SPI1_CLK pin, and SPI1_DSI pin of the central processing unit, the VREFL pin is connected to a 2.5V reference voltage, the VREFH pin is connected to a -2.5V reference voltage, the register reset pin RESETSEL, the chip reset pin RESET, and the chip latch status pin LOADDACS are respectively connected to the GPIO pins of the central processing unit.

3. The AC square wave dimming circuit according to claim 1, characterized in that: The operational in-phase and out-phase circuit comprises: DAC chip reference voltage circuit, a first operational amplifier and a second operational amplifier; The output voltage of the DAC chip reference voltage circuit is connected to the +IN pin of the first operational amplifier through the fourth resistor R504 in series, the -IN pin of the first operational amplifier is connected to the fifth resistor R500 and then grounded, and is connected to the OUT pin of the first operational amplifier after connecting the sixth resistor R501 and the first capacitor C501, the OUT pin of the first operational amplifier is connected to the seventh resistor R503 and then connected to the output control switch SA1, the voltage of the output control switch SA1 is connected to the -IN pin of the second operational amplifier after being connected in series with the eighth resistor R516 and connected to the ninth resistor R512 and the second capacitor C505 are connected to the OUT pin of the second operational amplifier, the +IN pin of the second operational amplifier is connected to the tenth resistor R514 and grounded, the OUT pin of the second operational amplifier is connected to the eleventh resistor R513 and the third capacitor C519, the V-0 pin, V-1 pin, and V-2 pin of the first operational amplifier and the second operational amplifier are all connected to a -24V voltage, the V+ pin of the first operational amplifier and the second operational amplifier is connected to a +24V voltage, and the FLAG pins of the first operational amplifier and the second operational amplifier are grounded.

4. The AC square wave dimming circuit according to claim 1, characterized in that: The switch chip circuit comprises: S1A pin, S1B pin, D1 pin, D2 pin, VDD pin, VSS pin, PAD pin; The VDD pin is connected to a +15V voltage, and the VSS pin and the PAD pin are connected to a -15V voltage; The S1A pin, the S1B pin and the D1 pin constitute a 1-way switch; The voltage outputted by the D1 pin and the D2 pin is a square wave signal with a voltage of ±10V, a frequency of 60HZ and a duty cycle of 50%.

5. The AC square wave dimming circuit according to claim 1, characterized in that: Power operational amplifiers include: Output connector J5_A2, VIN- pin, VO pin and +IN pin; The switch chip is connected to the VIN- pin through the twelfth resistor R634, and is connected to the VO pin through the thirteenth resistor R635 and the fourth capacitor C667, the +IN pin is grounded through the fourteenth resistor R706, the VO pin is connected to the 1PIN pin of the output connector J5_A2 through the fifteenth resistor R640, and the VO pin is grounded through the fifth capacitor C600.

6. The AC square wave dimming circuit according to any one of claims 1 to 5, characterized in that: The power supply circuit comprises: a first voltage conversion circuit, a second voltage conversion circuit, and a third voltage conversion circuit; The first voltage conversion circuit is used to convert 12V into 5V; The second voltage conversion circuit is used to convert 5V into ±15V; The third voltage conversion circuit is used to convert 12V into ±24V.

7. The AC square wave dimming circuit according to any one of claims 1 to 5, characterized in that: The transistor control switch circuit comprises: triode; The base of the transistor is connected to the PWM port of the central processing unit through a sixteenth resistor R627; The collector of the transistor is connected to the IN1 port of the switch chip circuit; The emitter of the transistor is grounded after passing through the seventeenth resistor R626 and the eighteenth resistor R649.

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