Switching power supply circuit and air conditioner

Abstract

The embodiment of the invention provides a switching power supply circuit and an air conditioner, and relates to the technical field of air conditioner main control boards. The circuit comprises a rectification module, a transformer, a primary side control power switch module, an isolation voltage output module, a non-isolation voltage output module and a non-isolation voltage feedback module. The output end of the isolation voltage output module is used for supplying power to the low-voltage module (display panel); the output end of the non-isolated voltage output module is used for supplying power to a master control MCU chip, and the ground of the master control MCU chip and the ground of circuits except the low-voltage module are the ground of the auxiliary winding. The ground of the auxiliary winding is the hot ground, so that the main control MCU chip can directly control the circuits connected with the hot ground without an optical coupling isolation device or a second main control MCU chip, and the problems of production cost and communication cost caused by two MCU chips of the cold ground and the hot ground are avoided.

Description

Technical Field

[0001] The present application relates to the technical field of air conditioner main control boards, and in particular to a switching power supply circuit and an air conditioner. Background Art

[0002] At present, the main control boards of cabinet air conditioners are generally divided into two types: one is the main control board with integrated fan drive circuit (used with DC fans with external drive circuits), and the other is the main control board without integrated fan drive circuit (used with DC fans with built-in drive circuits). At present, the main control boards of most cabinet air conditioners on the market are integrated with fan drive circuits because the cost of this integrated solution is relatively low. There are generally two MCU chips on this main control board: one MCU is specifically used to drive the fan driver chip, and the ground supply of this chip is a non-isolated (isolation means sharing a ground with high voltage electricity) hot ground (hot ground is a high voltage ground, which is dangerous and cannot be touched by people); the other MCU is used to drive the wind sweeping motor, temperature sensing package circuit, display board communication, etc. The ground supply of this chip is an isolated cold ground (cold ground is a low voltage ground that can be touched by people).

[0003] The switching power supply of the main control board with integrated fan drive circuit outputs non-isolated 15V, 5V and isolated 12V, 5V, among which: the non-isolated 15V supplies power to loads such as IPM (Intelligent Power Module), the non-isolated 5V supplies power to the driver chip specifically driving the fan, the isolated 12V supplies power to the stepper motor, display panel, sterilization, etc., and the isolated 5V supplies power to the chip driving the stepper motor, display panel, sterilization, temperature sensing package and other loads.

[0004] Because the ground of the driver chip that drives the fan is the "hot ground", and the chip that drives the stepper motor, display panel, sterilization, and temperature sensing package is the "cold ground", so Communication between two chips requires optocoupler isolation .

[0005] After research by the applicant, the following shortcomings of the prior art are summarized: Due to the insufficient design of the heat-proof ground in the air conditioner structure, many circuits need to be cold grounded and isolated from the hot ground, which requires an MCU chip connected to the cold ground to control these circuits, and the main control board needs There are two chips, cold ground and hot ground Driving different loads separately results in high cost and low production efficiency. Summary of the invention

[0006] In response to the shortcomings of the existing technology, the applicant proposed that the future trend is: to design a new switching power supply circuit, and to perform heat-proof treatment on the structure, so that only one chip is needed on the main control board to drive all loads, reducing costs and improving production efficiency; the communication between the display and the main control is achieved through a newly designed display communication circuit, which is simple, highly reliable, and has strong anti-static capabilities.

[0007] In the first aspect, the embodiment of the present application provides a switching power supply circuit of an air conditioner main control board, the switching power supply circuit comprising: a rectifier module, a transformer, a primary side control power switch module, an isolated voltage output module, a non-isolated voltage output module and a non-isolated voltage feedback module. It has the following connection relationship:

[0008] The output end of the rectifier module is connected to the first end of the primary winding of the transformer, the second end of the primary winding is connected to the first end of the primary control power switch module, and the second end of the primary control power switch module is connected to the ground of the auxiliary winding of the transformer;

[0009] One end of the secondary winding of the transformer is connected to the input end of the isolated voltage output module, and the other end of the secondary winding is used as a cold ground; the output end of the isolated voltage output module is used to power the low voltage module;

[0010] The power supply end of the auxiliary winding is connected to the input end of the non-isolated voltage output module, and the output end of the non-isolated voltage output module is used to power a main control MCU chip, and the main control MCU chip Except for low voltage modules The ground of the circuit is the ground of the auxiliary winding;

[0011] The non-isolated voltage feedback module is connected between the non-isolated voltage output module and the primary-side controlled power switch module, and is used to feed back the output voltage of the non-isolated voltage output module to the primary-side controlled power switch module.

[0012] Optionally, the isolated voltage output module includes a diode, a buffer protection circuit and a dummy load. The buffer protection circuit and the diode are connected in parallel and then in series with the dummy load. After the series connection, they are connected between the power supply end of the auxiliary winding and the ground of the auxiliary winding; the two ends of the dummy load are used to output the isolation voltage.

[0013] Optionally, the non-isolated voltage output module includes a diode, a buffer protection circuit and a dummy load. The buffer protection circuit and the diode are connected in parallel and then in series with the dummy load. After the series connection, they are connected between the power supply end of the auxiliary winding and the ground of the auxiliary winding; the two ends of the dummy load are used to output a non-isolated voltage.

[0014] Optionally, the buffer protection circuit includes a capacitor and a resistor; the capacitor and the resistor are connected in series and then connected in parallel with the diode.

[0015] Optionally, the non-isolated voltage output module includes an NPN transistor, a first voltage stabilizing diode, a first resistor and a first capacitor. The connection relationship is as follows:

[0016] The collector of the NPN transistor is connected to the power supply end of the auxiliary winding, the first resistor is connected between the collector and the base of the NPN transistor, the base of the NPN transistor is connected to the cathode of the first voltage regulator diode, the anode of the first voltage regulator diode is connected to the negative electrode of the first capacitor and to the ground of the auxiliary winding, and the positive electrode of the first capacitor is connected to the emitter of the NPN transistor; the positive electrode of the first capacitor is used to output a non-isolated voltage.

[0017] Optionally, the non-isolated voltage feedback module includes a second voltage stabilizing diode, a voltage dividing component, and an amplifier tube. The connection relationship is as follows:

[0018] The cathode of the second voltage-regulating diode is connected to the output end of the non-isolated voltage output module, the anode of the second voltage-regulating diode is connected to the first end of the voltage-dividing component, the second end of the voltage-dividing component is connected to the ground of the auxiliary winding, the control end of the amplifier tube is connected to the third end of the voltage-dividing component, the first end of the amplifier tube is connected to the feedback end of the primary-side controlled power switch module, and the second end of the amplifier tube is connected to the ground of the auxiliary winding.

[0019] Optionally, the switching power supply circuit further includes an over-voltage and under-voltage protection module; the over-voltage and under-voltage protection module includes a first resistor module, a second resistor module, and a third switch module. The connection relationship is as follows:

[0020] One end of the second resistor module and the third switch module connected in parallel is grounded, and the other end is connected to the first end of the first resistor module and to the over-voltage and under-voltage protection end of the primary-side control power switch module; the second end of the first resistor module is connected to the output end of the rectifier module;

[0021] The third switch module is used to be turned on when there is an overvoltage.

[0022] Optionally, the third switch module includes a diode unit and a resistor unit, and the diode unit and the resistor unit are connected in series.

[0023] Optionally, the low-voltage module is a cabinet air-conditioning display module, and the cabinet air-conditioning display module is communicatively connected to the main control MCU chip via an optical coupler.

[0024] In a second aspect, an embodiment of the present application provides an air conditioner, which includes a low-voltage module, a main control MCU chip, a motor group, a temperature sensing package and the switching power supply circuit described in the first aspect.

[0025] The output end of the isolated voltage output module of the switching power supply circuit is used to power the low voltage module, and the output end of the non-isolated voltage output module of the switching power supply circuit is used to power the main control MCU chip, the motor group and the temperature sensing package, and the main control MCU chip is used to communicate with the motor group and the temperature sensing package.

[0026] Compared with the prior art, this application has the following beneficial effects:

[0027] The switching power supply circuit provided in the embodiment of the present application only needs to connect the secondary winding to a module that must use a low voltage, such as the circuit at the display panel position of the indoor unit of a cabinet air conditioner. Other circuits all use power from the auxiliary winding. The primary side controls the power switch module to connect the grounds of the primary winding and the auxiliary winding. It can be inferred that the ground of the auxiliary winding is the hot ground, that is, these circuits are all connected to the hot ground. Then, only one main control MCU chip that is also connected to the hot ground is needed to control these circuits. No second main control MCU chip is needed, thus avoiding the production cost and communication cost problems caused by two MCU chips with cold ground and hot ground. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of a switching power supply circuit provided in an embodiment of the present application;

[0030] Figure 2 A schematic diagram of a switching power supply circuit with an over-voltage and under-voltage protection module provided in an embodiment of the present application;

[0031] Figure 3 A schematic diagram of a switching power supply circuit showing the configuration of resistors and capacitors provided in an embodiment of the present application;

[0032] Figure 4 A schematic diagram of a large current thermal ground and a small current thermal ground connected by a small resistor provided in an embodiment of the present application;

[0033] Figure 5 A schematic diagram of a display communication circuit provided in an embodiment of the present application.

[0034] Description of reference numerals:

[0035] 100-Switching Power Supply Circuit

[0036] 101-Rectifier module

[0037] 102-Transformer

[0038] 1021- Transformer primary winding

[0039] 1022-Transformer secondary winding

[0040] 1023-Transformer auxiliary winding

[0041] 103-Primary side control power switch module

[0042] 104-Isolated Voltage Output Module

[0043] 105-Non-isolated voltage output module

[0044] 106-Non-isolated voltage feedback module

[0045] 107-Overvoltage and undervoltage protection module

[0046] 201-Low voltage module

[0047] 202- a main control MCU chip DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described in the drawings here can be arranged and designed in various different configurations.

[0049] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for which protection is sought, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0050] In the description of this application, it should be noted that relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium.

[0051] The existing main control board needs to be equipped with a power supply because of the different design of the switch power supply and the lack of heat protection treatment on the structure. There are two chips Drive different loads respectively.

[0052] To overcome the above problems, please refer to Figure 1 The embodiment of the present application provides a switching power supply circuit 100, which is applied to an indoor unit of an air conditioner. The switching power supply circuit 100 includes: a rectifier module 101, a transformer 102, a primary side control power switch module 103, an isolated voltage output module 104, a non-isolated voltage output module 105 and a non-isolated voltage feedback module 106. It has the following connection relationship:

[0053] The output end of the rectifier module 101 is connected to the first end of the primary winding 1021 of the transformer;

[0054] The second end of the primary winding 1021 is connected to the first end of the primary control power switch module 103, and the second end of the primary control power switch module 103 is connected to the ground GND-DC of the auxiliary winding 1023 of the transformer (the ground of the auxiliary winding is a hot ground, because the primary control power switch module 103 is connected to the ground of the primary winding and the auxiliary winding, and the primary winding is high voltage);

[0055] One end of the secondary winding 1022 of the transformer is connected to the input end of the isolated voltage output module 104, and the other end of the secondary winding 1022 is used as a cold ground; the output end of the isolated voltage output module 104 is used to supply power to the low voltage module 201;

[0056] The power supply end of the auxiliary winding 1023 is connected to the input end of the non-isolated voltage output module 105, and the output end of the non-isolated voltage output module 105 is used to power a main control MCU chip 202, and The main control MCU chip 202 and the low voltage module 201 The ground of the circuits other than the auxiliary winding 1023 is GND-DC;

[0057] The non-isolated voltage feedback module 106 is connected between the non-isolated voltage output module 105 and the primary-side controlled power switch module 103 , and is used to feed back the output voltage of the non-isolated voltage output module 105 to the primary-side controlled power switch module 103 .

[0058] According to the above connection relationship, the ground of the main control MCU chip 202 and the circuits except the low voltage module 201 are all the ground of the auxiliary winding 1023, that is, except for the low voltage module, the main control MCU chip and other circuits that need to be controlled share the same ground, and are connected to the hot ground. It breaks the traditional design of using cold ground for many circuits, so that the main control MCU chip can directly control these interfaces. Hot ground circuit, without the need for optocoupler isolation devices, nor the need for a second main control MCU chip. This is in sharp contrast to the existing "one main control MCU chip needs to be connected to the cold ground to control the circuit connected to the cold ground, and the other main control MCU chip needs to be connected to the hot ground to control the circuit connected to the hot ground." This avoids the production cost and communication cost problems caused by two MCU chips with cold and hot grounds, which is a core beneficial effect of this application.

[0059] For the indoor unit of cabinet air conditioner, the above Low voltage module 201 is a cabinet air conditioner display module Since the display panel is on the outside and easily touched by people, and the display panel may also have buttons, the circuit of the display panel is connected to a cold ground to prevent the risk of electric shock.

[0060] For circuits other than the display panel, such as the air conditioner's fan, stepper motor, sweeping motor and other motor groups, sterilization facilities, IPM (Intelligent Power Module), etc., these are all located inside the air conditioner and need to be disassembled to be touched. For the air conditioner that has been assembled normally, there will be no disassembly incident when the air conditioner is running. Therefore, these circuits can use the hot ground as the ground, and there is no need to set a cold ground like the display module.

[0061] It is particularly important to note that the grounding end of the temperature sensor package can also be connected to the hot ground, but because the temperature sensor package is located on the outside of the back of the cabinet air conditioner, a more robust mechanical structure can be designed to prevent children from disassembling it and getting an electric shock.

[0062] The primary-side control power switch module is a module with a switch function. According to the feedback of the non-isolated voltage feedback module 106, it controls the conduction and disconnection of the primary winding of the transformer to the GND-DC loop, thereby stabilizing the output voltage. The primary-side control power switch module can be implemented by an existing primary-side control power switch chip (also known as a flyback power supply chip, such as U6513X). Some primary-side control power switch chips also have overvoltage and undervoltage protection functions. Figure 2 , an over-voltage and under-voltage protection module 107 may be provided to be connected to the input voltage (e.g., the output end of the rectifier module 101) and the primary control power switch module 103. In this way, when over-voltage and under-voltage occur, the primary control power switch module 103 will sense the abnormality and disconnect.

[0063] Figure 3 The figure shows an implementation method of using the Xinpengwei PN8733 as the primary side control power switch module 103. The voltage is input from the AC-L and AC-N terminals on the left side of the figure, and then passes through the rectifier module 101 to the transformer ( Figure 3TR1 in the figure), the primary winding is between pin 1 and pin 2 of the transformer, and the RCD circuit (composed of R4, R5, R6, R7, D1, and CRV11) is connected in parallel to both ends of the primary winding. According to the number of resistors and the setting of the resistance value in the figure, the RCD circuit is used to absorb the peak inductive voltage, and the absorption effect is good. It can effectively reduce the VDS voltage of the PN8733 chip, protect the chip and improve EMC.

[0064] Pin 2 of the transformer is connected to the drain D of the PN8733 chip, and the source S (pin 1 of the PN8733 chip) is connected to the negative pole of the rectifier module through two 2Ω resistors (R20, R21) in parallel.

[0065] The BR pin (pin 2) of the PN8733 chip is connected to the over-voltage and under-voltage protection module 107. The principle of the over-voltage and under-voltage protection module 107 is described below.

[0066] (1) The PN8733 chip can only work when the BR pin is ≥0.7V. If the BR pin is 0.7V, the voltage drop of the diodes D2 and D3 in series is 0.7*2V>0.7V, which is not enough to conduct. The R18, R19, D2, and D3 loops are cut off, and only the R13~R17 series loops are turned on. One end of the R13~R17 series loop is connected to DC-310V, which is the output end of the rectifier module, and the other end is connected to the hot ground GND-DC. The BR pin voltage is the voltage divided by the two ends of R17, and is 0.7V. Then the current of the R13~R17 series loop can be calculated as: 0.7 / R17, and the output end voltage of the rectifier module is recorded as Udc. At this time, the voltage across R13+R14+R15+R16 is 0.7 / R17*(R13+R14+R15+R16), so:

[0067] Udc=0.7 / R17*(R13+R14+R15+R16)+0.7

[0068] Substitute the resistance value in the figure, that is, Udc=0.7 / 15KΩ*1590KΩ+0.7=74.9V, converted to AC power, Uac==74.9 / 1.414=52.9V, that is, when the input AC power is less than 52.9V, under-voltage protection occurs.

[0069] (2) When the BR pin is ≤ 2.8V, the PN8733 chip triggers the overvoltage protection. If the BR pin is 2.8V, the voltage drop of the series diodes D2 and D3 is 0.7*2V, which is sufficient to conduct. The R18, R19, D2, and D3 loop is turned on. After the current flows through R13, R14, R15, and R16, it flows through R17 and then through R18, R19, D2, and D3.

[0070] The total current is:

[0071] I=UR13+R14+R15+R16 / (R13+R14+R15+R16)=2.8 / R17+(2.8-1.4) / (R18

[0072] Parallel R19)

[0073] Then the voltage across R13+R14+R15+R16 can be calculated as 2.8 / R17+(2.8-1.4) / (R18 in parallel with R19)*(R13+R14+R15+R16), and the output voltage of the rectifier module Udc=(2.8 / R17+(2.8-1.4) / (R18 in parallel with R19)

[0074] R19))*(R13+R14+R15+R16)+2.8.

[0075] Substituting the resistance value in the figure, we get Udc=485.1V, which is converted to AC power, Uac==485.1 / 1.414=343V, that is, when the input AC power is greater than 343V, undervoltage protection occurs.

[0076] According to the above (1) and (2), it can be known that one implementation of the over-voltage and under-voltage protection module 107 is composed of a first resistor module (R13+R14+R15+R16), a second resistor module (R17), and a third switch module (R18, R19, D2, D3). The third switch module may also be implemented by a transistor or MOS tube with a certain conduction voltage.

[0077] In the figure, C18 is the filter capacitor of the BR pin, which plays a filtering role; the two series-connected diodes D2 and D3 are used as diode units, and other numbers of diodes can also be selected as needed. The two parallel-connected R18 and R19 in the figure are used as resistor units, and other numbers of resistors in series and parallel can also be selected. Assume that the conduction voltage of the diode unit is U D , the resistance value of the resistor unit is R X The resistance value of the first resistance module is R1, the resistance value of the second resistance module is R2, and the DC voltage output by the rectifier module is U DCH When overvoltage protection is applied, the overvoltage protection terminal of the primary side control power switch module is U BR , then the following relationship is satisfied:

[0078] U BR / R2+(U BR -U D ) / R X =(U DCH -U BR ) / R1.

[0079] That is, the smaller the resistance value of the resistance unit is, the more obvious the improvement of the overvoltage protection value is. The resistance value of the resistance unit is selected to meet:

[0080] R X =(U BR -U D ) / ((U DCH -U BR ) / R1-U BR / R2)

[0081] Ordinary overvoltage and undervoltage protection generally only has the first resistor module and the second resistor module to divide the voltage to obtain a voltage, and then judge the overvoltage and undervoltage according to the size of this voltage. The embodiment of the present application increases the upper limit of the overvoltage protection by setting the third switch module compared to the overvoltage protection circuit without the third switch module. Or after determining the overvoltage protection value, the undervoltage protection value can be reduced by using the setting of the third switch module. In short, the third switch module can broaden the range of the setting of the normal working voltage.

[0082] Continue to refer Figure 3 The FB pin of the PN8733 chip is connected to the non-isolated voltage feedback module 106, and the non-isolated voltage feedback module 106 includes a second voltage regulator diode ZD2, a voltage divider component (composed of R23 and R24 in the figure), and an amplifier tube Q2.

[0083] The FB pin of the PN8733 chip is connected to a voltage through a pull-up resistor, and the amplifier Q2 can adjust the current of the pull-up resistor, so that the PN8733 chip can get feedback. The control terminal voltage of the amplifier Q2 is taken from the voltage divider component. When the voltage connected to the cathode of the second voltage zener diode ZD2 is too large, the current passes through the second voltage zener diode ZD2 and the voltage divider component to the hot ground GND-DC. At this time, the greater the voltage connected to the cathode of the second voltage zener diode ZD2, the greater the control terminal voltage of the amplifier Q2, and the greater the current of the pull-up resistor.

[0084] In addition, C19 is the filter capacitor of the feedback FB pin (generally 102~103 can be selected). The capacitance selection of C19 also affects the loop stability of the switching power supply. In this embodiment, 102 is selected, the phase margin is better and the loop stability is good. If 103 is selected, the phase margin will be small or unstable; ZD3 protects the FB pin to avoid overvoltage damage. R23 and R24 are selected to be 200Ω to ensure sensitive feedback regulation. ZD2 selects an 11V voltage regulator to ensure that the voltage can effectively output non-isolated 12V.

[0085] The +12V-1 terminal connected to the cathode of ZD2 is also the +12V voltage output terminal of the non-isolated voltage output module 105 in the figure. The feedback voltage of the switching power supply circuit is taken from the non-isolated 12V at both ends of the capacitor E4, and this non-isolated 12V is rectified from the auxiliary winding (i.e., the 4th foot of the transformer), so in the load loop, two 510Ω resistors R11 and R12 are designed and the package is selected as 2010 package, connected to this non-isolated 12V and GND, that is, a "dummy load" is designed to make the feedback signal stable.

[0086] Two rectifier diodes D5 and D6 are also designed in the non-isolated voltage output module 105. When used in a model with a small load, only D5 is installed, and when used in a model with a large load, both D5 and D6 are installed; capacitors CRV13 and R10 form a buffer protection circuit. Since the transformer has a self-inductance electromotive force, the reverse recovery current requires a reverse recovery event. CRV13 and R10 can protect diodes D5 and D6 from breakdown.

[0087] After the +12V-1 terminal, non-isolated 5V can be obtained through the 7805 chip to power the main control MCU chip. Non-isolated 5V can also be obtained directly through auxiliary winding rectification, or through voltage regulators, triodes, etc.

[0088] The isolated voltage output module 104 can be designed to output isolated 12V and isolated 5V. The structure is similar to the non-isolated voltage output module 105 described above. It also has a dummy load. Both ends of the dummy load can be connected to a filter capacitor. Regardless of the load on the isolated 12V or the load on the non-isolated 12V, whether it is a light load state or a rated load state, it can ensure that the isolated 12V voltage and the non-isolated 12V voltage output are very stable with small fluctuations. The isolated 12V can be used to power the display light and the buzzer, and the isolated 5V can be used to power the display panel of the display module.

[0089] In order to meet various requirements, the non-isolated voltage output module 105 may also include non-isolated 15V voltage output and other voltage outputs, which may be obtained from the auxiliary winding. Figure 3The paper shows an implementation method of non-isolated +15V output. By connecting the resistor R25, transistor Q1 and the first voltage stabilizing diode ZD1 in an ingenious way and selecting appropriate devices, the three devices can stably output "about 15V". The actual output is about 14.3V, which can power the IPM. The capacitor E6 is an electrolytic capacitor for voltage stabilization and filtering at the input end, and the capacitor E7 is an electrolytic capacitor for voltage stabilization and filtering at the output end. The voltage stabilizing diode ZD1 is connected to the base of the transistor Q1. When the voltage across the capacitor E7 is lower than 14.3V, the transistor Q1 is turned on to charge the capacitor E7. When the voltage of the capacitor E7 increases and the voltage of the transistor Ube is less than 0.7V, the transistor is turned off and E7 stops charging. This circuit has stable output voltage, small ripple, high reliability and high cost performance.

[0090] In general, Figure 3 In the example, the auxiliary winding's 3 (connected to GND-DC), 4, and 5 pins can output non-isolated 15V, 12V, and 5V voltages, and the secondary winding's 8 and 10 pins can output isolated 12V and 5V. In order to achieve a very good EMC effect, Figure 3 Three X capacitors CRV3, CRV4, and CRV5 are reserved, and the appropriate value can be selected according to the EMC effect. IND2 selects a 12mH common mode inductor, and designs a polyester capacitor C1 (103 capacitor) at the position where the rear end of the rectifier bridge is connected to the hot ground. This capacitor can effectively improve EMC, and with the design of CRV7, CRV8, CRV9, and CRV10 (lower left in the figure), the EMC effect is very good. The chip capacitors C2, C3, C4, C5, C10, C11, C12, C13, C20, C21, C22, and C23 behind the non-isolated 15V, 12V, and isolated 12V can effectively filter out the interference signal on the power supply, improve EMC, and make the EMC effect of the entire switching power supply and the entire machine particularly good.

[0091] In addition, the thermal ground GND-DC positions on different circuit boards can also be connected through resistors with smaller resistance values, such as Figure 4 For example, two 1.6Ω resistors can be connected in parallel to form a 0.8Ω resistor, which is connected between different GND-DC terminals. This allows a large current to flow through the large current GND-DC, and a small current to flow through the small current GND-DC, without causing local overheating of the circuit board.

[0092] For display modules that cannot be connected to the hot ground, a new display communication circuit is designed such as Figure 5 , so that the communication signal between the display board and the main control MCU chip is stable and reliable, and is not affected by hot or cold ground. The principle is:

[0093] (1) The process of the main control MCU transmitting signals to the display board: the display TX port outputs a high level +5V, the transistor Q3 is turned on, the optocoupler IC5 is turned on, and the pin 4 of the terminal CN1 receives a high level +5V, thus transmitting the signal to the display board;

[0094] (2) The process of the main control MCU receiving the display panel signal: The display panel sends a high-level +5V signal through pin 3 of terminal CN1. At this time, Q4 and IC4 are turned on, and the display RX port receives a high-level +5V signal. In this way, the display panel signal is transmitted to the main control board.

[0095] Among them, optocouplers IC4 and IC5 play an isolation role. Because the main control is a non-isolated hot ground and the display is an isolated cold ground, the two grounds cannot be connected directly, so the signal transmission is isolated by optocouplers, which can also play a role. Anti-static effect ; R28, R29, R31, R32, R33, and R34 are current limiting resistors, which play a current limiting role. R30 and R35 play a current limiting and voltage dividing role. C24 plays a filtering role to ensure that the received signal is free of interference.

[0096] The above embodiments and the selection of each device in the figure have been tested, and the output voltage is stable, the reliability is high, the filtering effect is good, the EMC effect is good, and it has dual 12V output. The transmission signal of the display communication circuit is stable and the anti-static ability is strong.

[0097] Based on the above embodiments, the embodiments of the present application further provide an air conditioner, which includes a low-voltage module 201, a main control MCU chip 202, a motor group, a temperature sensing package and the above-mentioned switching power supply circuit 100.

[0098] The output end of the isolated voltage output module 104 of the switching power supply circuit 100 is used to power the low voltage module 201, and the output end of the non-isolated voltage output module 105 of the switching power supply circuit 100 is used to power the main control MCU chip 202, the motor group and the temperature sensing package. The main control MCU chip 202 is used to communicate with the motor group and the temperature sensing package.

[0099] The above-described device and system embodiments are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. A person skilled in the art may understand and implement the present embodiment without creative effort.

[0100] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A switching power supply circuit (100), characterized in that: Applied to an indoor unit of an air conditioner, the switching power supply circuit (100) comprises: a rectifier module (101), a transformer (102), a primary side control power switch module (103), an isolated voltage output module (104), a non-isolated voltage output module (105) and a non-isolated voltage feedback module (106); The output end of the rectifier module (101) is connected to the first end of the primary winding (1021) of the transformer, the second end of the primary winding (1021) is connected to the first end of the primary control power switch module (103), and the second end of the primary control power switch module (103) is connected to the ground of the auxiliary winding (1023) of the transformer; One end of the secondary winding (1022) of the transformer is connected to the input end of the isolated voltage output module (104), and the other end of the secondary winding (1022) serves as a cold ground; the output end of the isolated voltage output module (104) is used to supply power to the low voltage module (201); The power supply end of the auxiliary winding (1023) is connected to the input end of the non-isolated voltage output module (105), and the output end of the non-isolated voltage output module (105) is used to supply power to a main control MCU chip (202), and the main control MCU chip (202) The ground of the auxiliary winding (1023) is the same as the ground of the circuits other than the low voltage module (201); The non-isolated voltage feedback module (106) is connected between the non-isolated voltage output module (105) and the primary-side controlled power switch module (103), and the non-isolated voltage feedback module (106) is used to feed back the output voltage of the non-isolated voltage output module (105) to the primary-side controlled power switch module (103).

2. The switching power supply circuit (100) according to claim 1, characterized in that: The isolated voltage output module (104) comprises a diode, a buffer protection circuit and a dummy load. The buffer protection circuit and the diode are connected in parallel and then in series with the dummy load. After the series connection, the dummy load is connected between the power supply end of the auxiliary winding (1023) and the ground of the auxiliary winding (1023); the two ends of the dummy load are used to output the isolated voltage.

3. The switching power supply circuit (100) according to claim 1, characterized in that: The non-isolated voltage output module (105) comprises a diode, a buffer protection circuit and a dummy load. The buffer protection circuit and the diode are connected in parallel and then in series with the dummy load. After the series connection, the dummy load is connected between the power supply end of the auxiliary winding (1023) and the ground of the auxiliary winding (1023); the two ends of the dummy load are used to output a non-isolated voltage.

4. The switching power supply circuit (100) according to claim 2 or 3, characterized in that: The buffer protection circuit includes a capacitor and a resistor; the capacitor and the resistor are connected in series and then connected in parallel with the diode.

5. The switching power supply circuit (100) according to claim 1, characterized in that: The non-isolated voltage output module (105) comprises an NPN transistor (Q1), a first voltage stabilizing diode (ZD1), a first resistor (R25) and a first capacitor (E7); The collector of the NPN transistor (Q1) is connected to the power supply end of the auxiliary winding (1023); the first resistor (R25) is connected between the collector and the base of the NPN transistor (Q1); the base of the NPN transistor (Q1) is connected to the cathode of the first voltage-stabilizing diode (ZD1); the anode of the first voltage-stabilizing diode (ZD1) is connected to the negative electrode of the first capacitor (E7) and to the ground of the auxiliary winding (1023); the positive electrode of the first capacitor (E7) is connected to the emitter of the NPN transistor (Q1); and the positive electrode of the first capacitor (E7) is used to output a non-isolated voltage.

6. The switching power supply circuit (100) according to claim 1, characterized in that: The non-isolated voltage feedback module (106) comprises a second voltage stabilizing diode (ZD2), a voltage dividing component, and an amplifier tube (Q2); The cathode of the second voltage stabilizing diode (ZD2) is connected to the output end of the non-isolated voltage output module (105), the anode of the second voltage stabilizing diode (ZD2) is connected to the first end of the voltage divider component, the second end of the voltage divider component is connected to the ground of the auxiliary winding (1023), the control end of the amplifier tube (Q2) is connected to the third end of the voltage divider component, the first end of the amplifier tube (Q2) is connected to the feedback end of the primary side control power switch module (103), and the second end of the amplifier tube (Q2) is connected to the ground of the auxiliary winding (1023).

7. The switching power supply circuit (100) according to claim 1, characterized in that: The switching power supply circuit (100) further comprises an over-voltage and under-voltage protection module (107); the over-voltage and under-voltage protection module (107) comprises a first resistance module, a second resistance module, and a third switch module; One end of the second resistor module and the third switch module after being connected in parallel is grounded, and the other end is connected to the first end of the first resistor module and to the over-voltage and under-voltage protection end of the primary-side control power switch module (103); the second end of the first resistor module is connected to the output end of the rectifier module (101); The third switch module is used to be turned on when there is an overvoltage.

8. The switching power supply circuit (100) according to claim 7, characterized in that: The third switch module includes a diode unit and a resistor unit, and the diode unit and the resistor unit are connected in series.

9. The switching power supply circuit (100) according to claim 1, characterized in that: The low-voltage module (201) is a cabinet air Adjust the display module The cabinet air conditioner display module is connected to the main control MCU chip through an optical coupler.

10. An air conditioner, characterized in that: The air conditioner comprises a low-voltage module (201), a main control MCU chip (202), a motor group, a temperature sensing package and a switching power supply circuit (100) according to any one of claims 1 to 9; The output end of the isolated voltage output module (104) of the switching power supply circuit (100) is used to supply power to the low voltage module (201), and the output end of the non-isolated voltage output module (105) of the switching power supply circuit (100) is used to supply power to the main control MCU chip (202), the motor group and the temperature sensing package; the main control MCU chip (202) is used to communicate with the motor group and the temperature sensing package.

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