Solar audio and video monitoring system

Abstract

The invention relates to a solar audio and video monitoring system, which is applied to the field of audio and video monitoring, and comprises a solar battery pack, camera equipment, a sound post and a power supply adapter plate, the solar battery pack is electrically connected with the camera equipment and the power supply adapter plate respectively and is used for supplying power to the camera equipment and the power supply adapter plate; the power supply adapter plate is electrically connected with the sound post and is used for supplying power to the sound post under a power-on condition; an isolation transformation circuit is arranged in the power supply adapter plate, and the isolation transformation circuit is used for isolating a power supply loop from the solar battery pack to the power supply adapter plate and a power supply loop from the power supply adapter plate to the sound post. The camera equipment and the sound post are prevented from being connected with the ground wire of the same loop, audio noise caused by ground wire crosstalk can be reduced, and the sound post noise elimination effect is improved.

Description

Technical Field

[0001] The present application relates to the field of audio and video processing, and in particular to a solar audio and video monitoring system. Background Art

[0002] Solar video surveillance system with sound column is also called solar audio and video surveillance system. In the existing solar audio and video surveillance system and voice broadcasting system, the camera is directly plugged into the external sound column through the RCA terminal, and the solar lithium battery panel outputs 12V to power the camera and the sound column respectively through the wire splitting method. Since the power of the sound column is relatively large, and the audio signal output by the camera is a small analog signal, the camera is easily interfered by the peripheral digital circuit and power devices, resulting in audio noise.

[0003] At present, facing the problem of audio noise, usually RCL filter circuit is added to the power input and audio signal output of the camera mainboard. However, the cost of modifying the mainboard schematic and PCB wiring is high, the PCB design is difficult, and the space size of the camera mainboard is very limited, resulting in a low success rate of adding RCL filter circuit to eliminate audio noise. At the same time, there are consistency issues between individual components in the camera mainboard, and audio noise cannot be completely eliminated by modifying the hardware of the camera mainboard; therefore, the effect of eliminating audio noise in the solar audio and video monitoring system in the prior art needs to be improved.

[0004] With regard to the problem that the audio noise elimination effect in the solar audio and video monitoring system is poor in the related art, no effective solution has been proposed yet. Summary of the invention

[0005] In this embodiment, a solar audio and video monitoring system is provided to solve the problem of poor audio noise elimination effect in the solar audio and video monitoring system in the related art.

[0006] In a first aspect, a solar audio and video monitoring system is provided in this embodiment, the system comprising: a solar cell group, a camera device, a sound column and a power adapter board; The solar cell group is electrically connected to the camera device and the power adapter board respectively, and is used to supply power to the camera device and the power adapter board; The power adapter board is electrically connected to the sound column and is used to supply power to the sound column when powered on; The power adapter board is provided with an isolation transformer circuit, and the isolation transformer circuit is used to isolate the power supply circuit from the solar cell group to the power adapter board and the power supply circuit from the power adapter board to the sound column.

[0007] In some of the embodiments, the isolation transformer circuit includes a transformer; The input end of the transformer is connected to the solar cell group, and the output end of the transformer is connected to the sound column; the isolation transformer circuit provides a working voltage to the sound column when the power adapter board is powered on.

[0008] In some of the embodiments, the isolation transformer circuit further includes a primary transformer unit and a secondary transformer unit; The output end of the primary transformer unit and the input end of the secondary transformer unit are magnetically coupled through the transformer.

[0009] In some of the embodiments, the primary voltage transformation unit includes a power supply controller and a power switch tube; The power supply controller comprises a switch output end; the power switch tube is connected to the switch output end of the power supply controller; The power supply controller is used to detect the output voltage of the sound column and output a switch signal to the power switch tube through the switch output terminal; The power switch tube is used to receive the switch signal output by the switch output end, and open or close according to the switch signal.

[0010] In some of the embodiments, the secondary voltage transformation unit includes: a power feedback component and a stabilizing capacitor; The two ends of the stabilizing capacitor are respectively connected to the input end and the output end of the power feedback component, so as to adjust the frequency response of the power feedback component; the output end of the power feedback component is also connected to the sound column; the power feedback component is used to output a stable power supply to the sound column.

[0011] In some of the embodiments, the input end of the power feedback component is also connected to the power controller.

[0012] In some embodiments, the power adapter board further includes an overcurrent detection circuit; the overcurrent detection circuit is connected to the isolation transformer circuit to control the on or off of the output power of the isolation transformer circuit; The overcurrent detection circuit includes a differential amplifier and a single chip microcomputer; The differential amplifier is connected to the single-chip microcomputer, and is used to detect the current of the sound column, convert the current into an amplified voltage, and send the converted amplified voltage to the single-chip microcomputer; The single chip microcomputer is used to detect the converted amplified voltage and control the opening or closing of the power supply for the sound column according to the detection result.

[0013] In some of the embodiments, the overcurrent detection circuit further includes a field effect transistor; The input end of the differential amplifier includes a first input end and a second input end; the source and the drain of the field effect tube are connected to the first input end and the second input end respectively.

[0014] In some of the embodiments, the primary voltage transformation unit further includes a current detection resistor; The current detection resistor is connected to the power switch tube, and the current detection resistor is used to adjust the peak current of the transformer.

[0015] In a second aspect, a power supply control method for a solar audio and video monitoring system is provided in this embodiment. The method is applied to the solar audio and video monitoring system in the first aspect, and the method includes: The differential amplifier converts the sound column current to obtain a converted amplified voltage, and sends the converted amplified voltage to the single chip microcomputer; The single chip computer determines whether the current value of the sound column exceeds a preset current threshold value according to the received amplified voltage; If it exceeds, the output port of the single-chip microcomputer is controlled to output a low level to the power supply of the sound column to stop supplying power to the sound column; the output port is connected to the sound column.

[0016] Compared with the related art, a solar audio and video monitoring system provided in this embodiment sets an isolation transformer circuit in the power adapter board, so that the isolation transformer circuit separates the power supply circuit connecting the camera device and the sound column to avoid the camera device and the sound column being connected to the ground wire of the same circuit, which is beneficial to reducing audio noise caused by ground wire crosstalk and improving the effect of eliminating sound column noise.

[0017] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 It is a schematic diagram of a power supply device for a sound column in the prior art; Figure 2 It is a schematic diagram of a power supply device for a sound column provided in an embodiment of the present application; Figure 3 is a flow chart of a power supply control method provided in an embodiment of the present application; Figure 4 is a schematic diagram of a solar audio and video monitoring system provided in this specific embodiment; Figure 5is a schematic diagram of the structure of the isolation transformer circuit provided in this specific embodiment; Figure 6 is a structural schematic diagram of another isolation transformer circuit provided in this specific embodiment; Figure 7 It is a structural schematic diagram of the sound column overcurrent detection provided in this specific embodiment; Figure 8 is a circuit diagram of an overcurrent detection circuit provided in this specific embodiment. DETAILED DESCRIPTION

[0019] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0020] Unless otherwise defined, the technical terms or scientific terms involved in this application shall have the general meaning understood by people with general skills in the technical field to which this application belongs. The words "one", "a", "the", "these" and the like in this application do not indicate a quantitative limitation, and they may be singular or plural. The terms "include", "comprise", "have" and any variants thereof involved in this application are intended to cover non-exclusive inclusions; for example, a process, method and system, product or device comprising a series of steps or modules (units) is not limited to the listed steps or modules (units), but may include unlisted steps or modules (units), or may include other steps or modules (units) inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" may mean: A exists alone, A and B exist at the same time, and B exists alone. Generally, the character " / " indicates that the objects associated with each other are in an "or" relationship. The terms "first", "second", "third", etc. in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0021] The existing solar video surveillance and voice broadcasting system with sound column does not have a separate power adapter board, and each module of the system shares a ground network. Figure 1 This is a schematic diagram of a power supply device for a sound column in the prior art. Figure 1, where the solar cell group provides 9V-12.6V power supply voltage for the sound column and camera respectively, and at the same time, the solar cell group, camera and sound column share a common ground. The RCA port connected to the camera is directly plugged into the external sound column, and the lithium battery panel in the solar cell group outputs 12V to power the camera and the sound column respectively through the wire splitting method. However, this way of powering the sound column causes ground bounce when the power of the sound column is large, and the audio signal output by the camera is a small analog signal, which is easily interfered by the peripheral digital circuit, power device, and especially the power ground. Therefore, when the sound column is working, the speaker will produce a buzzing sound of current, but when the sound column is unplugged and the camera's built-in speaker is normal; in addition, the power input of the sound column is directly derived from the solar lithium battery panel. The voltage corresponding to different amounts of electricity is different, and the voltage range is 9V~12.6V, while the loudness of the speaker of the sound column is proportional to the voltage value of the solar lithium battery. The sound difference between the lowest and highest voltages is large, resulting in a poor user experience.

[0022] At present, when encountering audio noise problems, generally an RCL filter circuit is added to the power input and audio signal output of the camera mainboard. However, the cost of modifying the mainboard schematic and PCB wiring is high, the PCB design is difficult, and the success rate is low. Because the camera mainboard has limited space and contains a large number of high-speed signals such as: mipi, sdio, wifi / 4g radio frequency signals, and there are consistency problems between individual components, modifying the hardware may not completely solve the ground crosstalk problem, and it is impossible to completely cut off the sound column noise. This application provides a solar audio and video monitoring system, which effectively solves the common ground problem of the power module (sound column) and the camera by setting a power adapter board, that is, starting from the interference path, cutting off the interference path. Figure 2 Schematic diagram of a power supply device for a sound column provided in an embodiment of the present application. Figure 2 , based on the existing power supply device of the sound column, a power adapter board is added; the solar cell group directly supplies power to the camera and the power adapter board, the power adapter board sends a constant voltage to the sound column, the power adapter board is connected between the solar cell group and the sound column, and the power adapter board adopts transformer isolation technology, so that the input and output of the power adapter board have their own circuits, that is, the solar cell group, the camera and the power adapter board share the same ground, and the power adapter board separately provides a constant 12V voltage to the sound column, avoiding the volume difference between the lowest and highest voltages of the sound column. At the same time, the circuit of the power adapter board connecting the sound column and the circuit of the power adapter board connecting the solar cell group are isolated by the power adapter board. In terms of design, the ground wire provided by the power adapter board to the camera is isolated from the ground wire of the sound column by a transformer, which completely cuts off the ground noise of the sound column at the source, so that the ground bounce will not interfere with the camera, and the sizzling sound of the audio current output from the mainboard to the sound column disappears.

[0023] Based on this, the embodiment of the present application provides a solar audio and video monitoring system, the system comprising: a solar cell group, a camera device, a sound column and a power adapter board; A solar cell group is electrically connected to the camera device and the power adapter board respectively, and is used to supply power to the camera device and the power adapter board; A power adapter board, electrically connected to the sound column, is used to supply power to the sound column when powered on; An isolation transformer circuit is provided in the power adapter board, and the isolation transformer circuit is used to isolate the power supply circuit from the solar cell group to the power adapter board and the power supply circuit from the power adapter board to the sound column from each other.

[0024] In this embodiment, the solar cell group directly supplies power to the connected camera device and the power adapter board respectively, and then supplies power to the sound column through the powered power adapter board, avoiding the situation in the prior art where the solar cell group directly supplies power to the sound column; at the same time, by providing an isolation transformer circuit in the power adapter board, the power supply circuit from the power adapter board to the sound column is isolated from other power supply circuits in the solar audio and video monitoring system, that is, the power supply circuit from the solar adapter board to the camera device and the power supply circuit from the power adapter board to the sound column are isolated to avoid the situation where the camera device and the sound column share a common ground; by providing an isolation transformer circuit in the power adapter board, the isolation transformer circuit separates the power supply circuit connecting the camera device and the sound column to avoid the camera device and the sound column being connected to the ground wire of the same circuit, which is beneficial to reducing audio noise caused by ground wire crosstalk.

[0025] In some of the embodiments, the isolation transformer circuit includes a transformer; the input end of the transformer is connected to the solar cell group, and the output end of the transformer is connected to the sound column; the isolation transformer circuit provides a working voltage to the sound column when the power adapter board is powered on.

[0026] In this embodiment, the isolation transformer circuit includes a transformer; the input and output ends of the transformer are connected to the solar cell group and the sound column respectively, so that the solar cell group does not directly power the sound column, but receives the power supply voltage of the solar cell group through the power adapter board, and then the power adapter board sends a constant power supply voltage to the sound column. Since the power supply voltage provided by the solar cell group has a fluctuation range, the fluctuation of the power supply voltage will affect the volume of the sound played by the sound column. Through the setting of the above transformer, when the lithium battery voltage in the solar cell group fluctuates, the power supply adapter board is used to supply power to the sound column, so that the sound column can still receive a power supply voltage constant at 12V, thereby improving the consistency of the sound played by the sound column.

[0027] In some of the embodiments, the isolation transformer circuit further includes a primary transformer unit and a secondary transformer unit; the output end of the primary transformer unit and the input end of the secondary transformer unit are magnetically coupled via a transformer.

[0028] Furthermore, the primary transformer unit includes a power controller and a power switch tube; the power controller includes a switch output end; the power switch tube is connected to the switch output end of the power controller; the power controller is used to detect the output voltage of the sound column and output a switch signal to the power switch tube through the switch output end; the power switch tube is used to receive the switch signal output from the switch output end and open or close according to the switch signal. The primary transformer unit also includes a current detection resistor; the current detection resistor is connected to the power switch tube, and the current detection resistor is used to adjust the peak current of the transformer.

[0029] In this embodiment, it can be known that the primary transformer unit and the secondary transformer unit in the isolation transformer circuit are connected through a transformer, the primary transformer unit is connected to the solar cell group, and receives the power supply voltage output by the solar cell group; the primary transformer unit includes a power controller and a power switch tube, the power controller detects the voltage of the load sound column, and outputs a switching signal with a duty cycle, and controls the on and off of the power switch tube according to the switching signal to adjust the stability of the voltage output to the load sound column, that is, dynamically adjusts the duty cycle of the transformer through the output voltage change of the sound column; at the same time, the transformer peak current, i.e., ip current, is designed through the external circuit of the power controller to realize the first-level detection of the sound column current, so as to avoid the problem of high-temperature spontaneous combustion of the lithium battery in the solar cell group due to continuous large current, so as to realize the first-level overcurrent protection.

[0030] Furthermore, in some of the embodiments, the secondary transformer unit includes: a power feedback component and a stabilizing capacitor; the two ends of the stabilizing capacitor are respectively connected to the input end and the output end of the power feedback component, for adjusting the frequency response of the power feedback component; the output end of the power feedback component is also connected to the sound column; the power feedback component is used to output a stable power supply to the sound column. The input end of the power feedback component is also connected to the power controller.

[0031] In this embodiment, a secondary transformer unit is also provided in the isolation transformer circuit, and the secondary transformer unit includes a power feedback component, and the power feedback component is connected to the power controller, so that the power controller detects the output voltage of the load sound column, and dynamically adjusts the duty cycle of the transformer according to the output voltage change of the load sound column to achieve a stable voltage output to the sound column; illustratively, a 12V stable voltage is output to the load sound column.

[0032] The power feedback component includes a reference voltage chip, which is used to output a stable power supply voltage to the sound column to prevent the fluctuation of the power supply voltage from affecting the volume of the sound column and causing a poor user experience. At the same time, the power feedback component is also connected to a stabilizing capacitor to adjust the frequency response of the power feedback component and further improve the stability of the power supply voltage output by the power feedback component.

[0033] In some of the embodiments, the power adapter board also includes an overcurrent detection circuit; the overcurrent detection circuit is connected to the isolation transformer circuit, and is used to control the on or off of the output power of the isolation transformer circuit; the overcurrent detection circuit includes a differential amplifier and a single-chip microcomputer; the differential amplifier and the single-chip microcomputer are connected, the differential amplifier is used to detect the current of the sound column, and convert the current into an amplified voltage, and send the converted amplified voltage to the single-chip microcomputer; the single-chip microcomputer is used to detect the converted amplified voltage, and control the on or off of the power supply for the sound column according to the detection result.

[0034] Furthermore, the overcurrent detection circuit also includes a field effect tube; the input end of the differential amplifier includes a first input end and a second input end; the source and drain of the field effect tube are respectively connected to the first input end and the second input end. It can be understood that the on-state internal resistance of the field effect tube is fixed, and the voltage value is obtained by multiplying the input current by the internal resistance. The field effect tube is provided to help improve the accuracy of subsequent detection results.

[0035] In this embodiment, an overcurrent detection circuit is also provided in the power adapter board, and the overcurrent detection circuit is connected to the primary transformer unit in the aforementioned isolation transformer circuit. At the same time, the differential amplifier in the overcurrent detection circuit obtains the input current of the load sound column and converts the current. Specifically, the current is converted into a voltage, and the voltage is amplified to obtain the amplified voltage. Thereafter, the amplified voltage is sent to the digital-to-analog converter ADC of the single-chip microcomputer for reading. The single-chip microcomputer connected to the differential amplifier detects the converted amplified voltage and obtains a detection result. According to the detection result, combined with the current threshold value pre-set by the single-chip microcomputer, it is determined whether to power the sound column. Exemplarily, when the current in the power supply signal is determined to be abnormal in the detection result, a low level is output to control the shutdown of the sound column power supply to achieve secondary overcurrent protection of the sound column.

[0036] In this embodiment, a power supply control method for a solar audio and video monitoring system is provided. Figure 3 is a flow chart of a power supply control method provided in an embodiment of the present application, specifically including a method for overcurrent protection of a secondary sound column, such as Figure 3 As shown, the process includes the following steps: In step S310, the differential amplifier converts the current of the sound column to obtain a converted amplified voltage, and sends the converted amplified voltage to the single chip microcomputer.

[0037] In step S320, the single chip microcomputer determines whether the current value of the sound column exceeds a preset current threshold value according to the received amplified voltage.

[0038] Step S330, if exceeded, the output port of the single-chip microcomputer is controlled to output a low level to the power supply of the sound column to stop supplying power to the sound column; the output port is connected to the sound column.

[0039] The present embodiment is described and illustrated by means of specific examples below.

[0040] This specific embodiment provides a solar audio and video monitoring system. Figure 4 is a schematic diagram of the solar audio and video monitoring system provided in this specific embodiment, referring to Figure 4 , including a connection diagram of a camera and a sound column combination, wherein the solar cell group includes a solar panel bracket, and an interface connected to the solar charging interface on the power adapter board is provided on the back of the solar panel, and the interface is used to output the electric energy converted by solar energy in the solar cell group to the power adapter board in the system. The power adapter board is provided with a power display interface, a boat-shaped key switch, a power charging DC port (DC power interface), a sound column power supply interface connected to the sound column, and a camera power supply interface connected to the camera; in addition, a camera sound column interface is provided on the camera, so that the camera and the sound column are connected, the camera sends audio broadcast information to the sound column, and obtains the playback status of the sound column in real time.

[0041] Specifically, an isolation transformer circuit and an overcurrent detection circuit are provided in the power adapter board. Figure 5 Schematic diagram of the structure of the isolation transformer circuit provided in this specific embodiment. Figure 5 The isolation transformer circuit in the figure mainly includes the power controller U4, the power switch tube Q3 and the transformer T15 in the primary transformer unit. The primary transformer unit receives the input power voltage sent by the solar cell group, namely VCC12V_IN, and receives the audio enable signal at the same time. When the voltage is below 1.2V, the audio enable signal is pulled into the low current standby mode. When the voltage is below 0.4V, the audio enable signal is pulled into the shutdown mode. When the input DC power supply voltage is 9V, the enable voltage of the enable signal of the control working mode is 1.4V. The audio enable signal terminal is connected to the pin 3 of the power controller U4 through the diode D20.

[0042] Exemplarily, the power controller U4 here is an isolated transformer control chip. Pin 1 of the isolated transformer controller is the RT pin, which is used for resistor timing. The external resistor from this pin to the GND pin programs the switching frequency between 100kHz and 1.2MHz. Pin 2 is the SS pin, which is the soft start programming pin. The capacitor between the SS pin and the GND pin sets the soft start time. Pin 3 is the EN pin, which is the enable pin. Floating this pin will enable the chip. Drop the voltage below 1.2V to enter the low current standby mode, and pull it below 0.4V to enter the shutdown mode; the EN pin can be used to implement an adjustable undervoltage lockout using two resistors. Pin 4 is the COMP pin, which is the output of the internal transconductance error amplifier. The feedback loop compensation network is connected from this pin to GND; Pin 5 is the FB pin, which is the error amplifier input and feedback pin for voltage regulation. Connect this pin to a resistor divider to set the output voltage. Pin 6 is the GND pin, which is used for grounding. Pin 7 is the CS pin, the current sensing pin. Connect an external current sensing resistor between this pin and GND. The voltage on this pin is used for the current control loop and overcurrent detection. The overcurrent protection threshold is typically 80mV. Pin 8 is the DRV pin, the low-side gate driver output. Connect this pin to the gate of the low-side N-channel MOSFET. When the VIN bias is removed, the internal 200kΩ resistor pulls LDRV to PGND, where the LDRV (Low-Side Driver) pin is typically used to control the low-side switch (usually a MOSFET). Pin 9 is the VCC pin, which serves as the output of the internal LDO and the power supply for the internal control circuit and gate driver. VCC is typically 10V. Connect a low-ESR ceramic capacitor from this pin to PGND. The capacitance range is recommended to be from 0.47µF to 10µF. Pin 10 is the VIN pin, which is the input power pin of the chip. Connect VIN to a power supply voltage between 3.5V and 60V; it is acceptable for the voltage on the VIN pin to be different from the boost power stage input. In addition, Pin 11 is the PAD pin, which is connected to EGND. Where possible, use thermal vias to connect to internal ground planes for improved power dissipation.

[0043] refer to Figure 5, the audio enable signal is connected to the power controller U4 through pin 3, and the power supply voltage of the solar cell group is input to the power controller U4 through pin 10, and the capacitor C55 is connected to pin 2 for setting the soft start time; pin 11 is connected to EGND, and pin 7 is connected to ground EGND through parallel resistors R53 and R60; at this time, according to the resistance values ​​of resistors R53 and R60, the current peak is set to realize overcurrent detection, and pin 7 is also connected to the source of the power switch tube Q3 through resistor R52; exemplarily, when the reference voltage value is 0.08V, and the resistance values ​​of resistors R53 and R60 are both 0.015Ω, the peak protection current is calculated to be 0.08V / 0.015Ω=5.3A. Pin 8 is connected to the gate of the power switch tube Q3 through resistor R54 as a control switch to control the conduction and closing of the power switch tube. Pin 9 is connected to EGND through capacitor C56.

[0044] The drain of the power switch tube Q3 is connected to the port 1 and port 2 of the transformer, and a resistor R8 and a capacitor C14 are also provided to remove the peak to protect the power switch tube Q3. Furthermore, the port receiving the input power supply voltage sent by the solar cell group is connected to the port 4 and port 5 of the transformer T15 through the inductor L2, wherein the inductor L2 is used to filter to obtain a 12V power supply, and the filtered power supply is input to the transformer through the port 4 and port 5.

[0045] Furthermore, pin 4 of the power controller is connected to the power feedback component to detect the output voltage of the load sound column, and dynamically adjust the duty cycle of the transformer through the output voltage change to achieve a 12V stable voltage output to the sound column; pin 7 of the power controller is a primary overcurrent detection circuit, which reads the voltage of the current detection resistor including resistor R53 and resistor R60. At this time, the peak current of the load sound column is set by resistor R53 and resistor R60, thereby realizing primary overcurrent detection. The switch signal with duty cycle output by pin 8 of the power controller controls the on and off of the power switch tube Q3 to adjust the output voltage stability. Through the power feedback component and the current detection resistor, two-level detection of the load sound column is realized, which is conducive to improving the stability and accuracy of the voltage output to the load sound column.

[0046] Depend on Figure 5 It can be seen that the grounding in the primary transformer unit is connected to the ground wire EGND. Figure 6 is a schematic diagram of the structure of another isolation transformer circuit provided in this specific embodiment. Figure 6, the isolation transformer circuit includes a power feedback component and a voltage stabilizing capacitor in the secondary transformer unit, and the voltage stabilizing capacitor includes capacitor C51 and capacitor C52; wherein, the ground in the secondary transformer unit is connected to the ground wire GND1. It can be understood that the primary transformer unit and the secondary transformer unit magnetically coupled by the transformer T15 in the isolation transformer circuit in this embodiment are not the same circuit, so the power supply circuits of the solar cell group, the camera device and the power adapter board connected to the primary transformer unit, and the power supply circuit connecting the power adapter board of the secondary transformer unit to the sound column are isolated by the transformer, avoiding the connection of the camera device and the sound column to the ground wire of the same circuit, which is conducive to reducing the audio noise caused by ground wire crosstalk and improving the effect of eliminating the noise of the sound column.

[0047] refer to Figure 6 , the power feedback component includes a photocoupler U3, an adjustable precision shunt regulator D7, a resistor R45 and a resistor R59, wherein in the photocoupler U3, pin A1 represents the anode of the light-emitting diode, pin C represents the cathode of the light-emitting diode, pin COL represents the collector of the phototransistor, and pin EMIT represents the emitter of the phototransistor. It can be understood that although the secondary transformer unit includes the photocoupler U3, in actual applications, the phototransistor in the photocoupler U3 belongs to the primary transformer unit, wherein the emitter of the phototransistor is connected to EGND. The cathode of the light-emitting diode-pin C is connected to pin 3 of the adjustable precision shunt regulator D7, where D7 is a reference voltage chip. Resistors R45 and R59 are sampling resistors, and capacitors C51 and C52 are used to adjust the zero and pole points. By adjusting their capacitance values, the positions of the zero and pole points in the transfer function are changed, thereby affecting the dynamic performance, stability and frequency response of the system, and are used to adjust the loop stability.

[0048] Furthermore, the power adapter board is also provided with an overcurrent detection circuit. Figure 7 Schematic diagram of the structure of the sound column overcurrent detection provided in this specific embodiment. Figure 7 The positive pole of the lithium battery voltage output by the solar cell group is connected to the positive access terminal VIN+ of the differential operational amplifier OP, and is connected to the reverse input terminal VIN- of the differential operational amplifier through the field effect transistor PMOS. Here, the PMOS is turned on. When the Vgs voltage of the field effect tube is constant, the on-resistance is a fixed value. By using this feature, the input voltage difference of the differential amplifier is obtained by multiplying the current flowing through the field effect tube by the on-resistance. The negative pole of the lithium battery voltage output by the solar cell group is grounded. In one of the specific embodiments, an actual circuit diagram of an overcurrent detection circuit is also provided. Figure 8 is a circuit diagram of an overcurrent detection circuit provided in this specific embodiment. Figure 8The lithium battery input voltage output by the solar cell group is connected to the positive access terminal VIN+ of the differential operational amplifier U7B through the field effect tube PMOS-Q9. At the same time, the opening and closing of Q10 is controlled by controlling the power switch of the audio amplifier. When it is at a high level, Q10 is turned on.

[0049] refer to Figure 7 and Figure 8 The differential operational amplifier converts and amplifies the input current into a voltage signal and sends it to the microcontroller; the microcontroller completes the analog-to-digital conversion and determines whether the current at the input end of the load sound column exceeds the preset threshold, and decides whether to turn on or off the sound column power supply based on the judgment result, that is, the current supplied to the sound column by the lithium battery is detected in real time through the differential operational amplifier. The MCU determines whether the current exceeds the standard through the ADC principle. The normal working current is within 2A (the maximum peak current of the sound column). Considering the device error, when the detected current value exceeds the set 2.5A, the microcontroller immediately cuts off the load.

[0050] refer to Figure 7 and Figure 8 , resistor R1 is connected to the positive access terminal of the differential operational amplifier, resistor R2 is connected to the reverse access terminal of the differential operational amplifier, and resistor R3 is connected to the positive input terminal and output terminal of the differential operational amplifier to provide bias voltage, change the frequency response characteristics of the operational amplifier, and thus improve the stability of the circuit. One end of resistor R4 is connected to the reverse access terminal of the differential operational amplifier, and the other end is grounded.

[0051] For example, when the on-resistance of the field effect tube PMOS is 50mΩ and the current of the sound column is 2A, the voltage difference across the two ends of the field effect tube PMOS is: ΔV=2(A)×50(mΩ)=100mV Therefore, the voltage difference between the positive input terminal VIN+ and the reverse input terminal VIN- is also equal to 100mV. When R1=10K, R2=10K, R3=100K, R4=100K, calculate the voltage after the differential amplifier amplifies: At this time, when the MCU samples the Vout voltage of 1V through the AD pin, it means that the current of the sound column has reached 2A; and so on, when the current of the sound column is 2.5A: Vout=2.5(A)×50(mΩ)×10=1.25V At this time, the MCU determines that the sound column current exceeds the preset threshold, that is, it is abnormal. The MCU firmware outputs a low level through the general input / output interface GPIO to turn off the sound column power supply, which plays a role in overcurrent protection of the lithium battery.

[0052] In one of the specific embodiments, the primary of the transformer in the solar audio and video monitoring system is connected to the output of the solar cell group, and the secondary output is used to power the sound column. The input and output have their own return. The isolation function of the transformer prevents the noise of the sound column load from leaking to the input end and causing audio noise. The output voltage is kept constant by adaptively setting the parameters such as the magnetic core, copper wire, and turns ratio of the transformer T15.

[0053] Specifically, in this solar audio and video monitoring system, the input voltage of the power conversion board is 9V~12.6V, the rated output power is 12V×2A=24W, the target efficiency is 90%, and the switching frequency is 250KHz. The transformer design includes: (1) Select the main control chip. The power conversion board in this application uses a 3.5V to 60V input boost / SEPIC / flyback DC-DC controller, which has low power consumption, high precision, switching frequency (SWf) can be set between 100KHz-1.2MHz, and duty cycle (D) can be adjusted between 0-90%. In order to reduce the impact of the "right half plane zero" on the flyback topology, it is expected that its maximum duty cycle is limited to 45%, and the switching frequency is set to 250HKz. When the circuit is fully loaded, it is in BCM critical conduction mode (Boundary Conduction Mode, BCM, also known as critical conduction mode), and when not fully loaded, it works in DCM discontinuous conduction mode (Discontinuous Conduction Mode, DCM), so as to improve the efficiency of the circuit operation.

[0054] (2) Select the core specifications: Determine the core specifications based on the rated output power of 24W, the current density of the coil wire of 200A / cm², the target conversion efficiency of the transformer of not less than 80%, and the relationship between the core cross-sectional area and power: P = Ae × Aw × η × δ.

[0055] Where: P is the output power of the transformer; Ae is the effective cross-sectional area of ​​the magnetic core (unit: cm²). Aw is the window area of ​​the magnetic core (unit: cm²). η is the conversion efficiency of the transformer. δ is the current density of the coil wire (unit: A / cm²).

[0056] Based on the above conditions, Ae×Aw=0.15 can be obtained. Combined with the switching frequency of 250KHz, the RM6 core and its frame can be selected.

[0057] (3) Calculate the number of primary turns of the transformer: According to the formula of Faraday's law of electromagnetic induction: We can get: E=N(△B×S) / (△T) Where E is the induced electromotive force (V), N is the number of coil turns (TS), B is the magnetic flux density (T), S is the cross-sectional area of ​​the core (m2), and t is the time (S). The number of turns can be calculated: N=E×(△T) / (△B×S) Formula (1) Where: E is the minimum input voltage (unit: V). S is the effective cross-sectional area of ​​the core (unit: m²). B is the magnetic flux density of the core (unit: T). T is the conduction time of the transformer primary in one cycle.

[0058] In a specific embodiment, the effective magnetic flux density of the magnetic core is 0.3T. However, due to the low input voltage and high switching frequency of this circuit, in order to reduce the hysteresis loss, the magnetic flux density △B of the magnetic core is set to 0.1. Substituting the above parameters into formula (1), the number of turns N = 9.5×(0.45×1 / 250000) / (0.1×37 / 1000000)=4.62, which is rounded to approximately 5 (TS).

[0059] (4) Calculate the number of secondary turns of the transformer: According to the transformer principle: Np / Ns=Vp / Vs Where Np is the number of turns of the primary winding (input side), and Ns is the number of turns of the secondary winding (output side). Vp is the voltage on the primary winding. Vs is the voltage on the secondary winding. We can get: Ns=Np×Vs / Vp×(1-D) That is, Ns = 5 × 12.3 / 9 × (1-0.45) = 12.42, which is rounded to approximately 12 (TS). Therefore, the turns ratio of Ns / Np is 1 to 2.4.

[0060] (5) Calculate the actual maximum duty cycle and minimum duty cycle of the circuit: According to the relationship between the input Vi and the output voltage Vo of the flyback topology: Vo=Vi×Ns / Np×(D / 1-D) Among them, Ns is the number of turns of the secondary winding (output side), Np is the number of turns of the primary winding (input side), and D represents the duty cycle. It can be calculated that when the input voltage is 9V, the maximum duty cycle of this circuit will be about 35%, and when the maximum input is 12.6V, the minimum duty cycle is about 28%. Its maximum and minimum duty cycles are between 5% and 45%, indicating that the turns ratio is appropriately selected and within the expected design range; (6) Calculate the primary inductance: Inductance calculation formula: V=L×di / dt L=V×dt / di Formula (2) Where: V represents the minimum input voltage (unit: V). dt represents the maximum conduction time of the transformer primary (unit: S). di represents the transformer primary inductor ripple current (unit: A).

[0061] Since the circuit is designed to work in DCM mode, the transformer primary inductor ripple current is: di=(Po / η / Vimin / Dmax)×2 Among them, Po is the output power, η is the minimum efficiency of the entire circuit design, Vimin is the minimum input voltage, and Dmax is the maximum duty cycle during actual operation.

[0062] That is: di = (24 / 0.9 / 9 / 0.35) × 2 = 17 (A). Substituting the actual value into formula (2), we get the primary inductance L: L=V×dt / di=(9×1.8 / 1000000) / 17=0.95(uH) That is, the value of the primary inductance L is 0.95uH.

[0063] (7) Calculate the primary and secondary currents of the transformer and select the appropriate wire diameter: The above method has estimated that the primary current of Ip is about 17A. According to the transformer principle: Np / Ns=Ip / Is It can be obtained that Is=17×2.4=41(A). That is, the 2UEW enameled wire with a cross-sectional area of ​​0.2mm² can effectively pass 1A current, so the primary uses the 2UEW enameled wire with an effective cross-sectional area of ​​3.4mm², and the secondary uses the TEX-E enameled wire with an effective cross-sectional area of ​​8.2mm².

[0064] (8) Calculation of core air gap: The transformer air gap can be calculated according to the following formula: Air gap length (mm) = 0.4π × Ae × N² / L × 10 4 Substituting the actual value into the above formula, we can get the air gap length (mm) to be approximately 0.12 (mm).

[0065] (9) Transformer winding process: RM6 vertical 3+3 row spacing 14.4×18.0 high 8.95 frame is used. In order to reduce the impact of leakage inductance on the circuit, the "sandwich winding method" is used to control the leakage inductance within 1%; in order to reduce the skin effect, the primary and secondary are both wound in 7P parallel; in order to increase the primary and secondary withstand voltage effect, the secondary winding uses triple insulation wire, and a grounding winding is added between the primary and secondary windings to improve EMI performance.

[0066] The secondary of the transformer uses TEX-E Ф1.25×7P (densely wound) from the 4th foot of the frame and the 5th foot, and is wound 6 turns clockwise, and a layer of insulation tape is added. Use 2UEW Ф0.2×2P (densely wound), from the 1st foot of the frame, one layer is wound clockwise as the grounding shielding layer, and a layer of insulation tape is added.

[0067] The transformer primary uses 2UEW Ф0.8×7P (closely wound) from the 2nd foot of the frame, and the 3rd foot is wound clockwise for 5 seconds, and a layer of insulating tape is added. When using 2UEW Ф0.2×2P (closely wound), when starting from the 1st foot of the frame, a layer of close winding is done clockwise as the grounding shielding layer, and a layer of insulating tape is added.

[0068] The secondary of the transformer uses TEX-EФ1.25×7P (densely wound), entering from pin 5 of the frame and exiting from pin 6, winding 6 turns clockwise, and adding a layer of insulating tape.

[0069] Use 2UEWФ0.2×2P (densely wound), start from the first foot of the skeleton and tightly wind one layer clockwise as the grounding shielding layer, and add a layer of insulating tape.

[0070] Finally, insert the magnetic core into the transformer frame and tie it with insulating tape, and measure whether the primary inductance and leakage inductance are within the design range. If not, the magnetic core air gap and winding process need to be re-fine-tuned until it meets the design parameters. Then, soak the transformer in insulating paint and dry it.

[0071] Through the above transformer parameter design, the transformer is applied to the solar audio and video monitoring system in this embodiment to achieve a constant output power supply voltage.

[0072] It can be understood that the structure for isolating the ground wires of the camera equipment and the sound column in the above-mentioned solar audio and video monitoring system, as well as the power supply control method can also be applied to various products with audio monitoring in the security industry, products with many vehicle-mounted peripherals and audio and video functions, and products encountering problems of audio noise and video image interference. The specific application is set according to the adaptability of the usage scenario and is not specifically limited here.

[0073] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of this application.

[0074] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

[0075] The term "embodiment" in this application refers to a specific feature, structure or characteristic described in conjunction with the embodiment that can be included in at least one embodiment of the present application. The appearance of this phrase in various locations in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. It is clearly or implicitly understood by those of ordinary skill in the art that the embodiments described in this application can be combined with other embodiments without conflict.

[0076] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A solar audio and video monitoring system, characterized in that: The system comprises: a solar cell group, a camera device, a sound column and a power adapter board; the solar cell group is electrically connected to the camera device and the power adapter board respectively, and is used to supply power to the camera device and the power adapter board; The power adapter board is electrically connected to the sound column and is used to supply power to the sound column when powered on; The power adapter board is provided with an isolation transformer circuit, and the isolation transformer circuit is used to isolate the power supply circuit from the solar cell group to the power adapter board and the power supply circuit from the power adapter board to the sound column.

2. The solar audio and video monitoring system according to claim 1, characterized in that: The isolation transformer circuit comprises a transformer; The input end of the transformer is connected to the solar cell group, and the output end of the transformer is connected to the sound column; the isolation transformer circuit provides a working voltage to the sound column when the power adapter board is powered on.

3. The solar audio and video monitoring system according to claim 2, characterized in that: The isolation transformer circuit also includes a primary transformer unit and a secondary transformer unit; The output end of the primary transformer unit and the input end of the secondary transformer unit are magnetically coupled through the transformer.

4. The solar audio and video monitoring system according to claim 3, characterized in that: The primary transformer unit includes a power supply controller and a power switch tube; The power supply controller comprises a switch output end; the power switch tube is connected to the switch output end of the power supply controller; The power supply controller is used to detect the output voltage of the sound column and output a switch signal to the power switch tube through the switch output terminal; The power switch tube is used to receive the switch signal output by the switch output end, and open or close according to the switch signal.

5. The solar audio and video monitoring system according to claim 4, characterized in that: The secondary transformer unit includes: a power feedback component and a stabilizing capacitor; The two ends of the stabilizing capacitor are respectively connected to the input end and the output end of the power feedback component, so as to adjust the frequency response of the power feedback component; the output end of the power feedback component is also connected to the sound column; the power feedback component is used to output a stable power supply to the sound column.

6. The solar audio and video monitoring system according to claim 5, characterized in that: The input end of the power feedback component is also connected to the power controller.

7. The solar audio and video monitoring system according to claim 1, characterized in that: The power adapter board also includes an overcurrent detection circuit; The overcurrent detection circuit is connected to the isolation transformer circuit and is used to control the on or off of the output power of the isolation transformer circuit; The overcurrent detection circuit includes a differential amplifier and a single chip microcomputer; The differential amplifier is connected to the single-chip microcomputer, and is used to detect the current of the sound column, convert the current into an amplified voltage, and send the converted amplified voltage to the single-chip microcomputer; The single chip microcomputer is used to detect the converted amplified voltage and control the opening or closing of the power supply for the sound column according to the detection result.

8. The solar audio and video monitoring system according to claim 7, characterized in that: The overcurrent detection circuit also includes a field effect transistor; The input end of the differential amplifier includes a first input end and a second input end; the source and the drain of the field effect tube are connected to the first input end and the second input end respectively.

9. The solar audio and video monitoring system according to claim 4, characterized in that: The primary voltage transformation unit also includes a current detection resistor; The current detection resistor is connected to the power switch tube, and the current detection resistor is used to adjust the peak current of the transformer.

10. A power supply control method for a solar audio and video monitoring system, the method being applied to the solar audio and video monitoring system according to any one of claims 7 or 8, characterized in that: The method comprises: The differential amplifier converts the current of the sound column to obtain a converted amplified voltage, and sends the converted amplified voltage to the single chip microcomputer; The single chip computer determines whether the current value of the sound column exceeds a preset current threshold value according to the received amplified voltage; If it exceeds, the output port of the single-chip microcomputer is controlled to output a low level to the power supply of the sound column to stop supplying power to the sound column; the output port is connected to the sound column.

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