Control protection circuit for photochromic glass

Abstract

The invention provides a control protection circuit for photochromic glass, which is characterized by comprising a power supply, an anti-reverse and overvoltage protection circuit, an input current-limiting protection circuit, an H-bridge voltage control circuit and an overvoltage and short-circuit protection circuit, the anti-reverse and overvoltage protection circuit is connected with the power supply, is arranged at the input end of the power supply, and is used for electrostatic discharge and plugging pulse overvoltage protection; the H-bridge voltage control circuit is used for controlling the input voltage of the photochromic glass, and the H-bridge voltage control circuit is connected with the resistor R0 to be measured in series and is grounded; the input current-limiting protection circuit comprises a differential amplifier and is used for collecting current I0 output to the photochromic glass, and when the current I0 exceeds a first current threshold value, the input current-limiting protection circuit is used for turning off input voltage of the photochromic glass; the overvoltage and short circuit protection circuit is used for collecting the current of the output end of the H-bridge voltage control circuit, and when the current of the output end exceeds a second current threshold value, the overvoltage and short circuit protection circuit is used for turning off the circuit. After the technical scheme is adopted, the control protection of circuit safety can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of electricity, and particularly to a control and protection circuit for electrochromic glass. Background Art

[0002] The essence of electrochromic glass is to regulate the transparency of the glass by adjusting the applied voltage, enabling the driver to adjust the window transparency as needed. It is increasingly being used in vehicles, and correspondingly, a variety of electrochromic glass control circuits have emerged. Most of the core parts use an H-bridge circuit composed of 4 MOS transistors to adjust the output positive and negative voltages through a certain switching timing. However, the short-circuit protection and over-current protection parts in these control circuits are often overlooked or inadequately protected. Summary of the Invention

[0003] In order to overcome the above technical defects, the purpose of the present invention is to provide a control and protection circuit that can effectively provide reverse protection, over-voltage protection, over-current protection, and short-circuit protection, improving the safety of the circuit.

[0004] Specifically, the present invention discloses a control and protection circuit for electrochromic glass, including: a power supply, an anti-reverse and over-voltage protection circuit, an input current-limiting protection circuit, an H-bridge voltage control circuit, and an over-voltage and short-circuit protection circuit;

[0005] The anti-reverse and over-voltage protection circuit is connected to the power supply and is provided at the input end of the power supply for electrostatic discharge and over-voltage protection against plugging and unplugging pulses;

[0006] The H-bridge voltage control circuit is used to control the input voltage VOUT2 of the electrochromic glass, and the H-bridge voltage control circuit is grounded in series with a resistance R0 to be measured;

[0007] The input current-limiting protection circuit includes a differential amplifier for collecting the current I0 output to the electrochromic glass. When the current I0 exceeds the first current threshold, the input current-limiting protection circuit is used to turn off the input voltage of the electrochromic glass. The output line refers to the line output to the electrochromic glass;

[0008] The over-voltage and short-circuit protection circuit is used to collect the output current of the H-bridge voltage control circuit. When the output current exceeds the second current threshold, the over-voltage and short-circuit protection circuit is used to turn off the circuit.

[0009] Preferably, the anti-reverse and over-voltage protection circuit includes a capacitor C2, a first TVS diode D1, and a second TVS diode D3. The capacitor C2 and the first TVS diode are connected in parallel and are successively connected to the power supply;

[0010] The first end of the capacitor C2 is grounded, and the second end of the first capacitor C2 is connected to the power supply; the first TVS diode D1 is a bidirectional TVS diode, the first end of the first TVS diode D1 is grounded, and the second end of the first TVS diode D1 is connected to the power supply;

[0011] The second TVS diode D3 is a unidirectional TVS diode, the positive electrode of the second TVS diode D3 is connected to the second end of the first TVS diode D1, and the negative electrode of the second TVS diode D3 outputs current.

[0012] Preferably, the input current limiting protection circuit includes a differential amplifier for collecting the current I0 passing through the resistor under test R0; the first end of the resistor under test R0 is connected to the non-inverting input end of the differential amplifier, and the second end of the resistor under test R0 is connected to the output end of the H-bridge voltage control circuit;

[0013] The output voltage of the differential amplifier is U0, and both ends of the first resistor R 47 are respectively connected to the output end and the inverting end of the differential amplifier, the first end of the second resistor R 48 is connected to the inverting end of the differential amplifier, the second end of the second resistor R 48 is connected between the second end of the resistor under test R0 and the output end of the H-bridge voltage control circuit, and the amplification factor β of the differential amplifier is R 47 / R 48 ;

[0014] The input current limiting protection circuit is used to determine the current I0 of the resistor under test R0 according to formula (1),

[0015] I0 = R 48 *U0 / (R 47 + R0) Formula (1);

[0016] When the current I0 is greater than the first current threshold, the input current limiting protection circuit is used to turn off the input voltage of the electrochromic glass.

[0017] Preferably, the output end of the differential amplifier is connected to the MCU via the third resistor R211;

[0018] The first end of the first capacitor C50 is grounded, and the second end of the first capacitor C50 is connected between the third resistor R211 and the MCU;

[0019] The second capacitor C147 is in parallel with the first resistor R 47 and both ends of the second capacitor C147 are connected between the output end and the inverting end of the differential amplifier;

[0020] The first end of the resistor R0 to be measured is connected to the non-inverting terminal of the differential amplifier via the fourth resistor R46. The first end of the fifth resistor R147 is grounded, and the second end of the fifth resistor R147 is connected between the fourth resistor R46 and the non-inverting terminal of the differential amplifier.

[0021] The first end of the third capacitor C10 is grounded, and the second end of the third capacitor C10 is connected to the first end of the resistor R0 to be measured.

[0022] The first end of the fourth capacitor C11 is grounded, and the second end of the fourth capacitor C11 is connected between the second end of the second resistor R 48 and the output terminal of the H-bridge voltage control circuit.

[0023] The first end of the fifth capacitor C76 is grounded, and the second end of the fifth capacitor C76 is connected between the second end of the fourth capacitor C11 and the output terminal of the H-bridge voltage control circuit.

[0024] Preferably, the H-bridge voltage control circuit includes four bridge circuits forming an H-shaped circuit in a clockwise direction, namely the first bridge circuit, the second bridge circuit, the third bridge circuit, and the fourth bridge circuit. The first bridge circuit and the second bridge circuit are located on the upper side of the H shape, and the third bridge circuit and the fourth bridge circuit are located on the lower side of the H shape.

[0025] The first bridge circuit, the second bridge circuit, the third bridge circuit, and the fourth bridge circuit each include four parallel MOS transistors, namely the first MOS transistor Q1, the second MOS transistor Q2, the third MOS transistor Q3, and the fourth MOS transistor Q4 in sequence.

[0026] The bridge circuit includes a parallel combination of a sixth resistor R137 and a third triode T28, and a first triode T13 and a second triode T13 connected in series in sequence. Among them, the first triode T13 is a PNP-type triode, and the second triode T13 is an NPN-type triode.

[0027] The first end of the resistor R137 is grounded, the second end of the sixth resistor R137 is connected to the gate of the MOS transistor, the collector of the first triode T13 is connected to the second end of the second resistor R137, the base of the first triode T13 is connected to the collector of the second triode T13, and the emitter of the first triode T13 is connected to a 9V power supply.

[0028] The emitter of the second triode T13 is grounded, the base of the second triode T13 is connected to the first MCU, and the first MCU is used to control the working state of the bridge circuit.

[0029] The emitter of the third triode T28 is grounded, and the collector of the triode T28 is connected between the sixth resistor R137 and the first triode T13;

[0030] The first end of the capacitor C57 is connected between the source of the second MOS transistor and the drain of the third MOS transistor, and the second end of the capacitor C57 is connected between the source of the first MOS transistor Q1 and the drain of the fourth MOS transistor;

[0031] When the first MOS transistor Q1 and the third MOS transistor Q3 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTB at the first end of the capacitor C57; when the second MOS transistor Q2 and the fourth MOS transistor Q4 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTA at the second end of the capacitor C57.

[0032] Preferably, the overvoltage and short-circuit protection circuit includes an overvoltage protection H-bridge circuit and a pre-stage power supply line protection circuit;

[0033] The first end of the overvoltage protection H-bridge circuit is connected to the base of the third triode T28 and grounded through the seventh resistor R213 and the eighth resistor R214 connected in series in sequence. The first end of the ninth resistor R215 is connected between the seventh resistor R213 and the eighth resistor R214, and the second end of the ninth resistor R215;

[0034] The first end of the tenth resistor R141 is connected to the positive electrode of the zener diode D21, and the second end of the tenth resistor R141 is grounded; the negative electrode of the zener diode D21 is connected to the VOUT2.

[0035] The first end of the pre-stage power supply line protection circuit is connected to the first end of the resistor R0 to be measured, grounded through the sixth capacitor C41. The drain of the fifth MOS transistor is connected between the first end of the protection pre-stage circuit and the sixth capacitor C41. The gate of the fifth MOS transistor is grounded through the eleventh resistor R204. The first end of the seventh capacitor C73 is grounded, and the second end is connected to the source of the fifth MOS transistor.

[0036] After adopting the above technical solutions, compared with the prior art, the control and protection circuit in the present invention can effectively play the roles of reverse connection prevention, overvoltage protection, overcurrent protection and short-circuit protection, and effectively improve the circuit safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of a control and protection circuit for a color-changing glass in an embodiment of the present invention;

[0038] Figure 2 is Figure 1 a schematic diagram of the anti-reverse and overvoltage protection circuit in the shown embodiment;

[0039] Figure 3 For Figure 1 the schematic diagram of the input current limiting protection circuit in the illustrated embodiment;

[0040] Figure 4 For Figure 1 the schematic diagram of the H-bridge voltage control circuit in the illustrated embodiment;

[0041] Figure 5 (1) For Figure 1 the schematic diagram of the overvoltage protection H-bridge circuit in the illustrated embodiment;

[0042] Figure 5 (2) For Figure 1 the schematic diagram of the front-stage power supply line protection circuit in the illustrated embodiment. Detailed implementation manners

[0043] The advantages of the present invention will be further elaborated below in conjunction with the accompanying drawings and specific embodiments.

[0044] Here, the exemplary embodiments will be described in detail, and the examples are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present disclosure. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present disclosure as detailed in the appended claims.

[0045] The terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The singular forms "a", "the", and "said" used in the present disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0046] It should be understood that although the terms first, second, third, etc. may be used in the present disclosure to describe various information, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present disclosure, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "when" or "while" or "in response to determining".

[0047] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0048] In the following description, the use of suffixes such as "module", "component", or "unit" for representing components is only for the convenience of the description of the present invention, and it has no specific meaning by itself. Therefore, "module" and "component" can be used interchangeably.

[0049] Figure 1 It is a schematic diagram of a control and protection circuit for a color-changing glass in an embodiment of the present invention. The control and protection circuit in this embodiment includes: a power supply ( Figure 1 not shown in the figure), an anti-reverse and overvoltage protection circuit, an input current-limiting protection circuit, an H-bridge voltage control circuit, and an overvoltage and short-circuit protection circuit.

[0050] The anti-reverse and overvoltage protection circuit is connected to the power supply and is provided at the input end of the power supply for electrostatic discharge and plug-and-play pulse overvoltage protection; the H-bridge voltage control circuit is used to control the input voltage VOUT2 of the color-changing glass, and the H-bridge voltage control circuit is grounded in series with the resistance R0 to be measured; the input current-limiting protection circuit includes a differential amplifier for collecting the current I0 output to the color-changing glass. When the current I0 exceeds the first current threshold, the input current-limiting protection circuit is used to turn off the input voltage of the color-changing glass. The output line refers to the line output to the color-changing glass; the overvoltage and short-circuit protection circuit is used to collect the output current of the output end of the H-bridge voltage control circuit. When the output current exceeds the second current threshold, the overvoltage and short-circuit protection circuit is used to turn off the circuit.

[0051] Specifically, Figure 2 It is a schematic diagram of the anti-reverse and overvoltage protection circuit in this embodiment. The anti-reverse and overvoltage protection circuit in this embodiment includes a capacitor C2, a first TVS tube D1, and a second TVS tube D3. The capacitor C2 and the first TVS tube are connected in parallel and are successively connected to the power supply;

[0052] The first end of the capacitor C2 is grounded, and the second end of the first capacitor C2 is connected to the power supply; the first TVS tube D1 is a bidirectional TVS tube. The first end of the first TVS tube D1 is grounded, and the second end of the first TVS tube D1 is connected to the power supply;

[0053] The second TVS tube D3 is a unidirectional TVS tube. The positive electrode of the second TVS tube D3 is connected to the second end of the first TVS tube D1, and the negative electrode of the second TVS tube D3 outputs current.

[0054] Among them, the first TVS tube D1 can play a role in electrostatic discharge and overvoltage protection against plugging and unplugging pulses. When the circuit is working normally, the first TVS tube D1 is in a cut-off state (high impedance state) and does not affect the normal operation of the circuit. Under the specified reverse application conditions, when it withstands a high-energy instantaneous overvoltage pulse, its working impedance can immediately drop to a very low conduction value, allowing a large current to pass through, and clamping the voltage to a predetermined level, thereby effectively protecting the precision components in the electronic circuit from damage.

[0055] Figure 3 It is a schematic diagram of the input current limiting protection circuit in this embodiment, including a differential amplifier for collecting the current I0 passing through the measured resistor R0. The first end of the measured resistor R0 is connected to the non-inverting input end of the differential amplifier, and the second end of the measured resistor R0 is connected to the output end of the H-bridge voltage control circuit. The voltage at the second end is the input voltage VOUT2 of the electrochromic glass; the output voltage of the differential amplifier is U0, and both ends of the first resistor R 47 are respectively connected to the output end and the inverting input end of the differential amplifier. The first end of the second resistor R 48 is connected to the inverting input end of the differential amplifier, and the second end of the second resistor R 48 is connected between the second end of the measured resistor R0 and the output end of the H-bridge voltage control circuit. The amplification factor β of the differential amplifier is R 47 / R 48 ;

[0056] The input current limiting protection circuit is used to determine the current I0 of the measured resistor R0 according to formula (1),

[0057] I0 = R 48 *U0 / (R 47 + R0) Formula (1);

[0058] When the current I0 is greater than the first current threshold, the input current limiting protection circuit is used to turn off the input voltage of the electrochromic glass.

[0059] Moreover, the output end of the differential amplifier is connected to the MCU via the third resistor R211; the first end of the first capacitor C50 is grounded, and the second end of the first capacitor C50 is connected between the third resistor R211 and the MCU; the second capacitor C147 and the first resistor R 47In parallel, both ends of the second capacitor C147 are connected to the output terminal and the inverting terminal of the differential amplifier; the first end of the resistor under test R0 is connected to the non-inverting terminal of the differential amplifier via the fourth resistor R46, the first end of the fifth resistor R147 is grounded, and the second end of the fifth resistor R147 is connected between the fourth resistor R46 and the non-inverting terminal of the differential amplifier; the first end of the third capacitor C10 is grounded, the second end of the third capacitor C10 is connected to the first end of the resistor under test R0, the first end of the fourth capacitor C11 is grounded, and the second end of the fourth capacitor C11 is connected between the second end of the second resistor R 48 and the output terminal of the H-bridge voltage control circuit; the first end of the fifth capacitor C76 is grounded, and the second end of the fifth capacitor C76 is connected between the second end of the fourth capacitor C11 and the output terminal of the H-bridge voltage control circuit.

[0060] Assume that the threshold current flowing through the resistor under test R0 is 500 mA. When the current I flowing through R43 is greater than 500 mA, the current line outputs an abnormality, the H-bridge control signal is pulled low, and the voltage input of the electrochromic glass is turned off, so as to play a role in overloading and short-circuit protection.

[0061] Figure 4 It is a schematic diagram of the H-bridge voltage control circuit in this embodiment. The H-bridge voltage control circuit in this embodiment sequentially includes four bridge circuits forming an H-shaped circuit in a clockwise direction, namely a first bridge circuit, a second bridge circuit, a third bridge circuit, and a fourth bridge circuit. The first bridge circuit and the second bridge circuit are located on the upper side of the H shape, and the third bridge circuit and the fourth bridge circuit are located on the lower side of the H shape.

[0062] The first bridge circuit, the second bridge circuit, the third bridge circuit, and the fourth bridge circuit sequentially include four parallel MOS transistors, namely a first MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3, and a fourth MOS transistor Q4.

[0063] The bridge circuit includes a sixth resistor R137 and a third triode T28 connected in parallel, and a first triode T13 and a second triode T13 connected in series in sequence. Among them, the first triode T13 is a PNP-type triode, and the second triode T13 is an NPN-type triode.

[0064] The first end of the resistor R137 is grounded, the second end of the sixth resistor R137 is connected to the gate of the MOS transistor, the collector of the first triode T13 is connected to the second end of the second resistor R137, the base of the first triode T13 is connected to the collector of the second triode T13, and the emitter of the first triode T13 is connected to the 9V power supply.

[0065] The emitter of the second triode T13 is grounded, the base of the second triode T13 is connected to the first MCU, and the first MCU is used to control the working state of the bridge circuit; the emitter of the third triode T28 is grounded, and the collector of the triode T28 is connected between the sixth resistor R137 and the first triode T13;

[0066] Moreover, the first end of the capacitor C57 is connected between the source of the second MOS transistor and the drain of the third MOS transistor, and the second end of the capacitor C57 is connected between the source of the first MOS transistor Q1 and the drain of the fourth MOS transistor; when the first MOS transistor Q1 and the third MOS transistor Q3 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTB at the first end of the capacitor C57; when the second MOS transistor Q2 and the fourth MOS transistor Q4 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTA at the second end of the capacitor C57.

[0067] In this embodiment, the H-bridge voltage control circuit composed of MOS transistors and triodes, during normal operation, Q1 and Q3 are turned on and off synchronously, and Q2 and Q4 are turned on and off synchronously to achieve the output of positive and negative voltages. When an abnormal situation occurs in the control circuit, the control of each circuit can be controlled separately, or the Boolean logic operation mode of "OR" can be adopted to achieve the simultaneous shutdown of multiple circuits when one or more of them are abnormal.

[0068] Figure 5 It is a schematic diagram of the overvoltage and short-circuit protection circuit in this embodiment. The overvoltage and short-circuit protection circuit includes an overvoltage protection H-bridge circuit and a pre-stage power supply line protection circuit.

[0069] Among them, Figure 5 (1) It is a schematic diagram of the overvoltage protection H-bridge circuit in this embodiment. The first end of the overvoltage protection H-bridge circuit is connected to the base of the third triode T28 and is grounded through the seventh resistor R213 and the eighth resistor R214 connected in series in sequence. The first end of the ninth resistor R215 is connected between the seventh resistor R213 and the eighth resistor R214, and the second end of the ninth resistor R215; the first end of the tenth resistor R141 is connected to the positive electrode of the zener diode D21, and the second end of the tenth resistor R141 is grounded; the negative electrode of the zener diode D21 is connected to the VOUT2. As shown in the figure, when the voltage of VOUT2 is abnormal, the OVP_OUT2FB terminal receives a signal to turn off the H-bridge.

[0070] When VOUT2 is less than the breakdown voltage of the Zener diode D21, OVP_VOUT2 is a low-level signal. At this time, the output is less than the Vth of the transistors T18, T19, T28, and T29 in the H-bridge circuit. The control of the MOS tubes Q1-Q4 is controlled by the input signals of T13, T14, T15, and T16. When VOUT2 is abnormal, the Zener diode D21 is broken down, OVP_VOUT2 is a high-level signal, OVP_VOUT2>Vth, and the transistors T18, T19, T28, and T29 are turned on to pull down the control signals of the MOS tubes Q1-Q4, and the corresponding MOS tubes are turned off.

[0071] Figure 5 (2) is a schematic diagram of the front-stage power supply line protection circuit in this embodiment. The first end of the front-stage power supply line protection circuit is connected to the first end of the resistor to be measured R0, and is grounded through the sixth capacitor C41. The drain of the fifth MOS tube is connected between the first end of the protection front-stage circuit and the sixth capacitor C41. The gate of the fifth MOS tube is grounded through the eleventh resistor R204. The first end of the seventh capacitor C73 is grounded, and the second end is connected to the source of the fifth MOS tube.

[0072] The front-stage power supply line protection circuit uses the body diode of the MOS tube to protect the front-stage power supply line. When a high voltage appears on VOUT2, the body diode of D5 is used to isolate and block the high voltage of VOUT2 from damaging the high voltage of the front-stage circuit.

[0073] It should be noted that the embodiments of the present invention have better practicability and do not impose any form of limitation on the present invention. Any technician familiar with the field may use the technical content disclosed above to change or modify it into an equivalent effective embodiment. However, any modification or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A control and protection circuit for a color-changing glass, It is characterized in that Including: power supply, anti-reverse and overvoltage protection circuit, input current limiting protection circuit, H-bridge voltage control circuit and overvoltage and short circuit protection circuit; The anti-reverse and overvoltage protection circuit is connected to the power supply, and is arranged at the input end of the power supply, and is used for electrostatic discharge and plug-in pulse overvoltage protection; The H-bridge voltage control circuit is used to control the input voltage VOUT2 of the color-changing glass, and the H-bridge voltage control circuit is connected to ground in series with the resistor to be measured R0; The input current limiting protection circuit includes a differential amplifier, which is used to collect the current I0 output to the photochromic glass. When the current I0 exceeds a first current threshold, the input current limiting protection circuit is used to shut off the input voltage of the photochromic glass. The output line refers to the route output to the photochromic glass. The overvoltage and short-circuit protection circuit is used to collect the output current of the H-bridge voltage control circuit. When the output current exceeds a second current threshold, the overvoltage and short-circuit protection circuit is used to shut down the circuit.

2. The control protection circuit for color-changing glass according to claim 1, characterized in that: The anti-reverse and overvoltage protection circuit includes a capacitor C2, a first TVS tube D1 and a second TVS tube D3, the capacitor C2 and the first TVS tube are connected in parallel and are connected to the power supply in sequence; The first end of the capacitor C2 is grounded, and the second end of the first capacitor C2 is connected to the power supply; the first TVS tube D1 is a bidirectional TVS tube, the first end of the first TVS tube D1 is grounded, and the second end of the first TVS tube D1 is connected to the power supply; The second TVS tube D3 is a unidirectional TVS tube, the positive electrode of the second TVS tube D3 is connected to the second end of the first TVS tube D1, and the negative electrode of the second TVS tube D3 outputs current.

3. The control protection circuit for color-changing glass according to claim 2, characterized in that: The input current limiting protection circuit includes a differential amplifier, which is used to collect the current I0 passing through the resistor R0 to be measured; The first end of the resistor to be measured R0 is connected to the in-phase end of the differential amplifier, and the second end of the resistor to be measured R0 is connected to the output end of the H-bridge voltage control circuit; The output voltage of the differential amplifier is U0, and both ends of the first resistor R 47 are respectively connected to the output terminal and the inverting terminal of the differential amplifier. The first end of the second resistor R 48 is connected to the inverting terminal of the differential amplifier. The second end of the second resistor R 48 is connected between the second end of the resistor under test R0 and the output terminal of the H-bridge voltage control circuit. The amplification factor β of the differential amplifier is R 47 / R 48 ; The input current limiting protection circuit is used to determine the current I0 of the resistor R0 to be measured according to formula (1), I0 = R 48 *U0 / (R 47 + R0) Equation (1); The current I0 is greater than or exceeds a first current threshold, and the input current limiting protection circuit is used to shut down the input voltage of the photochromic glass.

4. The control protection circuit for color-changing glass according to claim 3, characterized in that: The output end of the differential amplifier is connected to the MCU via a third resistor R211; A first end of the first capacitor C50 is grounded, and a second end of the first capacitor C50 is connected between the third resistor R211 and the MCU; The second capacitor C147 is in parallel with the first resistor R 47 Both ends of the second capacitor C147 are connected to the output terminal and the inverting terminal of the differential amplifier; The first end of the resistor to be measured R0 is connected to the non-inverting end of the differential amplifier via the fourth resistor R46, the first end of the fifth resistor R147 is grounded, and the second end of the fifth resistor R147 is connected between the fourth resistor R46 and the non-inverting end of the differential amplifier; The first terminal of the third capacitor C10 is grounded, and the second terminal of the third capacitor C10 is connected to the first terminal of the resistor R0 to be measured; The first terminal of the fourth capacitor C11 is grounded, and the second terminal of the fourth capacitor C11 is connected between the second terminal of the second resistor R 48 and the output terminal of the H-bridge voltage control circuit; The first terminal of the fifth capacitor C76 is grounded, and the second terminal of the fifth capacitor C76 is connected between the second terminal of the fourth capacitor C11 and the output terminal of the H-bridge voltage control circuit.

5. The control and protection circuit for a color-changing glass according to claim 4, wherein The H-bridge voltage control circuit sequentially includes four bridge circuits forming an H-shaped circuit in a clockwise direction, namely a first bridge circuit, a second bridge circuit, a third bridge circuit, and a fourth bridge circuit. The first bridge circuit and the second bridge circuit are located on the upper side of the H shape, and the third bridge circuit and the fourth bridge circuit are located on the lower side of the H shape; The first bridge circuit, the second bridge circuit, the third bridge circuit, and the fourth bridge circuit sequentially include four parallel MOS transistors, namely a first MOS transistor Q1, a second MOS transistor Q2, a third MOS transistor Q3, and a fourth MOS transistor Q4; The bridge circuit includes a sixth resistor R137 and a third triode T28 connected in parallel, and a first triode T13 and a second triode T13 connected in series in sequence. Among them, the first triode T13 is a PNP-type triode, and the second triode T13 is an NPN-type triode; The first terminal of the resistor R137 is grounded, the second terminal of the sixth resistor R137 is connected to the gate of the MOS transistor, the collector of the first triode T13 is connected to the second terminal of the second resistor R137, the base of the first triode T13 is connected to the collector of the second triode T13, and the emitter of the first triode T13 is connected to a 9V power supply; The emitter of the second triode T13 is grounded, the base of the second triode T13 is connected to the first MCU, and the first MCU is used to control the working state of the bridge circuit; The emitter of the third triode T28 is grounded, and the collector of the triode T28 is connected between the sixth resistor R137 and the first triode T13; The first terminal of the capacitor C57 is connected between the source of the second MOS transistor and the drain of the third MOS transistor, and the second terminal of the capacitor C57 is connected between the source of the first MOS transistor Q1 and the drain of the fourth MOS transistor; When the first MOS transistor Q1 and the third MOS transistor Q3 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTB at the first terminal of the capacitor C57; when the second MOS transistor Q2 and the fourth MOS transistor Q4 are turned on, the H-bridge voltage control circuit outputs the voltage VOUTA at the second terminal of the capacitor C57.

6. The control and protection circuit for a color-changing glass according to claim 5, wherein The overvoltage and short-circuit protection circuit includes an overvoltage protection H-bridge circuit and a front-stage power supply line protection circuit; The first end of the overvoltage protection H-bridge circuit is connected to the base of the third triode T28 and grounded through the serially connected seventh resistor R213 and eighth resistor R214 in sequence. The first end of the ninth resistor R215 is connected between the seventh resistor R213 and the eighth resistor R214, and the second end of the ninth resistor R215; The first end of the tenth resistor R141 is connected to the positive electrode of the voltage stabilizing diode D21, and the second end of the tenth resistor R141 is grounded; the negative electrode of the voltage stabilizing diode D21 is connected to the VOUT2; The first end of the pre-stage power supply line protection circuit is connected to the first end of the measured resistor R0, grounded through the sixth capacitor C41. The drain of the fifth MOS transistor is connected between the first end of the pre-protection circuit and the sixth capacitor C41. The gate of the fifth MOS transistor is grounded through the eleventh resistor R204. The first end of the seventh capacitor C73 is grounded, and the second end is connected to the source of the fifth MOS transistor.

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