Air conditioner charging circuit, charging control method and air conditioner having the circuit

Abstract

The present invention provides an air conditioner charging circuit, including an AC power supply, a filter component, an electrolytic capacitor group, a rectifier, a first switch, a second switch and a switch control unit, wherein the AC power supply is connected to the filter component and the rectifier in sequence, and the rectifier is connected to the electrolytic capacitor group. A first switch and a second switch are arranged on the line connecting the AC power supply to the rectifier, and the second switch is connected in parallel with the first switch. The first switch and the second switch are connected to the switch control unit, and the switch control unit is used to control the closing and opening of the first switch and the second switch. Compared with the prior art, the air conditioner charging circuit described in the present invention has the following advantages: (1) The air conditioner charging circuit described in the present invention has a simple charging circuit structure, flexible operation, high reliability, and solves many hidden dangers of charging circuits with PTC. (2) The air conditioner charging circuit described in the present invention inputs voltage through a resistor voltage divider network, which plays a protective role in the switch control microcontroller.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioners, and in particular to an air conditioner charging circuit, a charging control method and an air conditioner having the circuit. Background Art

[0002] The inverter circuit is equipped with a large electrolytic capacitor for energy storage. There is a large current spike at the moment of power-on, which can easily burn out the components in the circuit. Therefore, a charging circuit needs to be added to the circuit to limit the current spike. The common practice of existing inverter outdoor units is to use a PTC resistor plus a relay for charging.

[0003] The existing solution must use PTC resistors, which has the following problems:

[0004] 1) There are many models, and different models use different types of PTC resistors, which results in high material management costs;

[0005] 2) Large units require multiple PTC resistors in parallel, which is costly and bulky;

[0006] 3) In a high temperature environment, the PTC resistor becomes high resistance due to overheating, resulting in charging failure;

[0007] 4) Multiple frequent charging processes cause the PTC resistor to enter high resistance and the charging process fails. Summary of the invention

[0008] In view of this, the present invention aims to propose an air conditioner charging circuit, so that without using a PTC resistor, the charging current can still be more stable and reliable, there is no problem of charging failure due to multiple charging, and there is no problem of charging failure due to using a PTC resistor in a high temperature environment. The circuit structure is simple and cost-effective.

[0009] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0010] An air conditioner charging circuit includes an AC power supply, a filter component, an electrolytic capacitor group, a rectifier, a first switch, a second switch and a switch control unit, wherein the AC power supply is connected to the filter component and the rectifier in sequence, the rectifier is connected to the electrolytic capacitor group, a first switch and a second switch are arranged on a line connecting the AC power supply to the rectifier, and the second switch is connected in parallel with the first switch, the first switch and the second switch are connected to the switch control unit, and the switch control unit is used to control the closing and opening of the first switch and the second switch.

[0011] Furthermore, the filter component includes a filter inductor and a first electrolytic capacitor, the electrolytic capacitor group includes a second electrolytic capacitor, a third electrolytic capacitor, and a fourth electrolytic capacitor; the rectifier includes a second rectifier bridge, the AC power supply is connected to the filter inductor, the first electrolytic capacitor, and the second rectifier bridge in sequence, the second rectifier bridge is connected in parallel with the second electrolytic capacitor, the third electrolytic capacitor, and the fourth electrolytic capacitor, respectively, and a first switch and a second switch are set on the line connecting the AC power supply to the second rectifier bridge, and a first voltage divider resistor and a second voltage divider resistor are connected in series at the positive ends of the second electrolytic capacitor, the third electrolytic capacitor, and the fourth electrolytic capacitor, and the voltage detection pin of the switch control unit is connected to the connection point of the first voltage divider resistor and the second voltage divider resistor.

[0012] Furthermore, the switch control part includes a power conversion unit and a switch control microcontroller. The power conversion unit is connected to the AC power supply and is used to convert the AC power supply into DC power to supply power to the switch control microcontroller. A group of ports of the switch control microcontroller are connected to the power conversion unit, and another group of ports are respectively connected to the first switch and the second switch for controlling the closing and opening of the first switch and the second switch. The voltage detection pin of the switch control microcontroller is connected to the connection point of the first voltage divider resistor and the second voltage divider resistor.

[0013] Furthermore, the power conversion unit includes a first rectifier bridge, a small electrolytic capacitor, a switching power supply, and a diode. The AC power supply is connected to the first rectifier bridge, and a small electrolytic capacitor and a switching power supply are connected in parallel on the first rectifier bridge. The switching power supply is connected to a switch control microcontroller for supplying power to the switch control microcontroller. A diode is arranged on the line connecting the first rectifier bridge and the small electrolytic capacitor.

[0014] Compared with the prior art, the air conditioner charging circuit of the present invention has the following advantages:

[0015] (1) The air conditioner charging circuit described in the present invention has a simple charging circuit structure, flexible operation, and high reliability, and solves many hidden dangers existing in the PTC charging circuit.

[0016] (2) The air conditioner charging circuit described in the present invention inputs a voltage through a resistor voltage divider network, thereby protecting the switch control microcontroller.

[0017] Another object of the present invention is to provide an air conditioner charging circuit control method to solve the many hidden dangers of the PTC charging circuit, so that the charging process is smooth and stable, and the impact on the circuit is smaller.

[0018] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0019] A method for controlling an air conditioner charging circuit, using the aforementioned air conditioner charging circuit, wherein the first switch and the second switch are both normally open switches, and the method comprises:

[0020] The switch control unit controls the second switch to close for a time period of t1, and then disconnects the second switch. After an interval of t2, the second switch is controlled to close for a time period of t1 again, and the second switch is closed and disconnected in sequence. At the same time, the switch control unit monitors the voltage on the electrolytic capacitor group through a resistor divider network to determine whether the voltage of the electrolytic capacitor group reaches the charging completion standard. If so, the first switch is closed and the second switch is disconnected to complete the charging process.

[0021] Furthermore, the charging completion standard includes:

[0022] The voltage value of the electrolytic capacitor bank reaches its maximum capacity, or

[0023] The difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was last closed is less than the first threshold value.

[0024] Further, according to the formula D = K * △ V o Determine the duty cycle D, where ∆V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, K is a preset proportional coefficient, the duty cycle D is the ratio of t1 to (t1+t2), where (t1+t2) is a preset period value, and the t1 value and t2 value are determined according to the duty cycle D and the value of (t1+t2).

[0025] Furthermore, the method comprises:

[0026] Step 1: Power on the switch control unit;

[0027] Step 2: The switch control unit controls the second switch to close for a period of time t1, and then opens the second switch;

[0028] Step 3: The switch control unit detects whether the voltage on the electrolytic capacitor group reaches its maximum capacity. If so, the second switch is opened and the first switch is closed. If not, the switch waits for a t2 period of time and then returns to step 2.

[0029] Furthermore, the switch control unit has an AD sampling port, and the method for determining the t1 time period and the t2 time period includes:

[0030] Step 1': Power on the switch control unit;

[0031] Step 2': The AD sampling port of the switch control unit collects the voltage divided by the resistor divider network, and converts the divided voltage into a digital signal;

[0032] Step 3': the switch control unit performs software filtering on the digital signal;

[0033] Step 4': the switch control unit samples and calculates the digital signal at intervals of △t to obtain a voltage value V1 corresponding to the current moment;

[0034] Step 5': The switch control unit calculates the difference (V1-V0) between the current voltage value V1 and the voltage value V0 obtained by sampling the digital signal △t time ago, and determines it as the △V o ;

[0035] Step 6': According to the formula D = K * △ V o Determine the duty cycle D, where ∆V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, and K is the preset proportionality coefficient;

[0036] Step 7': Determine the t1 value and the t2 value according to the formula D=t1 / (t1+t2), where (t1+t2) is a preset period value.

[0037] Compared with the prior art, the air conditioner charging circuit control method of the present invention has the following advantages:

[0038] (1) The air conditioner charging circuit control method of the present invention charges the electrolytic capacitor group by intermittently adjusting the second switch to be turned on and off, and the charging time width is adjustable; thus, PTC components are saved and costs are reduced.

[0039] (2) The air conditioner charging circuit control method described in the present invention adopts a PI adjustment method to determine the charging time width, taking into account the balance between charging efficiency and charging voltage.

[0040] Another object of the present invention is to provide an air conditioner, which uses the aforementioned air conditioner charging circuit.

[0041] The advantages of the air conditioner and the above-mentioned air conditioner charging circuit over the prior art are the same, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 This is a first structural schematic diagram of an air conditioner charging circuit according to an embodiment of the present invention;

[0044] Figure 2 This is a second structural schematic diagram of an air conditioner charging circuit according to an embodiment of the present invention;

[0045] Figure 3This is a third structural schematic diagram of an air conditioner charging circuit according to an embodiment of the present invention;

[0046] Figure 4 This is a fourth structural schematic diagram of an air conditioner charging circuit according to an embodiment of the present invention;

[0047] Figure 5 A schematic diagram of determining a duty cycle according to an embodiment of the present invention;

[0048] Figure 6 This is a schematic flow chart of an air conditioner charging method according to an embodiment of the present invention;

[0049] Figure 7 Schematic diagram of a method for determining t1 and t2 values ​​according to an embodiment of the present invention.

[0050] Description of reference numerals:

[0051] 1-AC power supply, 20-filter component, 2-filter inductor, 3-first electrolytic capacitor, 40-electrolytic capacitor group, 4-second electrolytic capacitor, 5-third electrolytic capacitor, 6-fourth electrolytic capacitor, 70-rectifier, 7-second rectifier bridge, 8-first switch, 9-second switch, 10-switch control unit, 11-first voltage-dividing resistor, 12-second voltage-dividing resistor, 101-power conversion unit, 1011-first rectifier bridge, 1012-small electrolytic capacitor, 1013-switching power supply, 1014-diode, 102-switch control microcontroller. DETAILED DESCRIPTION

[0052] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0053] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0054] An air conditioner charging circuit, such as Figure 1As shown, it includes an AC power supply 1, a filter component 20, an electrolytic capacitor group 40, a rectifier 70, a first switch 8, a second switch 9 and a switch control unit 10. The AC power supply 1 is connected to the filter component 20 and the rectifier 70 in sequence. The rectifier 70 is connected to the electrolytic capacitor group 40. On the line connecting the AC power supply 1 to the rectifier 70, a first switch 8 and a second switch 9 are arranged, and the second switch 9 is connected in parallel with the first switch 8. The first switch 8 and the second switch 9 are connected to the switch control unit 10, and the switch control unit 10 is used to control the closing and opening of the first switch 8 and the second switch 9. With such a circuit structure, the switch control unit 10 can be used to control the closing and opening of the first switch 8 and the second switch 9 in a programming manner according to the preset switch logic, and the switch control unit 10 can be used to control the closing time and the opening time of the second switch 9, thereby achieving the purpose of intermittently charging the electrolytic capacitor group, so that the charging of the electrolytic capacitor group is stable, and the charging time width is adjustable; PTC components are saved and costs are reduced.

[0055] Further, such as Figure 2 As shown, the filter component 20 includes a filter inductor 2 and a first electrolytic capacitor 3, and the electrolytic capacitor group 40 includes a second electrolytic capacitor 4, a third electrolytic capacitor 5, and a fourth electrolytic capacitor 6; the rectifier 70 includes a second rectifier bridge 7, and the AC power supply 1 is connected to the filter inductor 2, the first electrolytic capacitor 3, and the second rectifier bridge 7 in sequence, and the second rectifier bridge 7 is connected in parallel with the second electrolytic capacitor 4, the third electrolytic capacitor 5, and the fourth electrolytic capacitor 6, respectively. On the line connecting the AC power supply 1 to the second rectifier bridge 7, a first switch 8 and a second switch 9 are set, and a first voltage-dividing resistor 11 and a second voltage-dividing resistor 12 are connected in series at the positive ends of the second electrolytic capacitor 4, the third electrolytic capacitor 5, and the fourth electrolytic capacitor 6, and the voltage detection pin of the switch control unit 10 is connected to the connection point of the first voltage-dividing resistor 11 and the second voltage-dividing resistor 12.

[0056] Further, such as Figure 3 As shown, the switch control unit 10 includes a power conversion unit 101 and a switch control microcontroller 102. The power conversion unit 101 is connected to the AC power supply 1, and is used to convert the AC power supply into DC power to supply power to the switch control microcontroller 102. A group of ports of the switch control microcontroller 102 is connected to the power conversion unit 101, and another group of ports are respectively connected to the first switch 8 and the second switch 9, and are used to control the closing and opening of the first switch 8 and the second switch 9. The voltage detection pin of the switch control microcontroller 102 is connected to the connection point of the first voltage divider resistor 11 and the second voltage divider resistor 12.

[0057] Further, such as Figure 4As shown, the power conversion unit 101 includes a first rectifier bridge 1011, a small electrolytic capacitor 1012, a switching power supply 1013, and a diode 1014. The AC power supply 1 is connected to the first rectifier bridge 1011, and a small electrolytic capacitor 1012 and a switching power supply 1013 are connected in parallel to the first rectifier bridge 1011. The switching power supply 1013 is connected to the switch control microcontroller 102 for supplying power to the switch control microcontroller 102; a diode 1014 is arranged on the line connecting the first rectifier bridge 1011 and the small electrolytic capacitor 1012.

[0058] In the present invention, the parallel body of the second electrolytic capacitor 4, the third electrolytic capacitor 5, and the fourth electrolytic capacitor 6 is referred to as an electrolytic capacitor group. It can be understood that any capacitive element composed of one or more capacitors in a charging circuit that is used in the same manner as the electrolytic capacitor group described in the present invention can be considered to be equivalent to the electrolytic capacitor group described in the present invention.

[0059] The present invention also provides an air conditioner charging circuit control method, using the aforementioned air conditioner charging circuit, the first switch and the second switch are both normally open switches, and the method includes:

[0060] The switch control unit controls the second switch to close for a time period of t1, and then disconnects the second switch. After an interval of t2, the second switch is controlled to close again for a time period of t1, and the second switch is closed and disconnected in sequence. At the same time, the switch control unit monitors the voltage on the electrolytic capacitor group through a resistor voltage-dividing network composed of a first voltage-dividing resistor 15 and a second voltage-dividing resistor 16, and determines whether the voltage of the electrolytic capacitor group reaches the charging completion standard. If so, the first switch is closed and the second switch is disconnected to complete the charging process. By adopting such a charging method, intermittent power supply to the electrolytic capacitor group can be achieved, the charging current can be made more stable, and the voltage on the electrolytic capacitor group can be slowly increased, which can protect the electrolytic capacitor group, and there is no need to use a PTC resistor, thus avoiding many problems that may arise when using a PTC resistor.

[0061] Further, the charging completion standard includes: the voltage value of the electrolytic capacitor group reaches the maximum value of its own capacity. Or, it may also include: the difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time is less than the first threshold value. When the voltage value of the electrolytic capacitor group reaches the maximum value of its own capacity, it means that the charging of the electrolytic capacitor group is completed and no further charging is required; when the difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time is less than the first threshold value, it means that the voltage increase on the electrolytic capacitor group during the two charging processes is limited or too small, which also confirms that the electrolytic capacitor group tends to be saturated with electricity and no further charging is required. The method of judging the voltage difference of the electrolytic capacitor group charged twice can be used without using a fixed electricity threshold as the standard, and judging whether the electricity is saturated according to the current actual situation of the electrolytic capacitor group, so that the judgment result is more true and reliable.

[0062] Further, according to the difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time, the duty cycle D is determined by PI operation, and the duty cycle D is the ratio of t1 to (t1+t2), where (t1+t2) is a preset period value, and the t1 value and t2 value are determined according to the duty cycle D and the value of (t1+t2). Figure 5 As shown, the control of the closing and opening of the second switch can be regarded as the control of the square wave with a certain duty cycle output. When the square wave value is 1, it is regarded as the closing of the second switch, and when the square wave value is 0, it is regarded as the opening of the second switch. In this way, the control of the closing and opening time of the second switch can be analogous to the control of the square wave duty cycle D. The difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time is used to determine the duty cycle D through PI calculation, that is, when the difference between the two voltages is large, the duty cycle is large, that is, the charging time in one cycle is correspondingly long, and when the difference between the two voltages is small, the duty cycle is small, that is, the charging time in one cycle is correspondingly short, thereby realizing fast and stable charging.

[0063] Further, according to the formula D = K * △ V o Determine the duty cycle D, where ∆V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, and K is a preset proportional coefficient.

[0064] Furthermore, the value range of (t1+t2) is 10μs to 100μs. The upper limit of the duty cycle (the value of t1) is also limited by the DC bias value of the filter inductor 2. The filter inductor specification should be consulted to ensure that the filter inductor 2 does not enter saturation.

[0065] Further, such as Figure 6 As shown, the air conditioner charging circuit control method may include:

[0066] S1: Switch control unit is powered on;

[0067] S2: the switch control unit controls the second switch to close for a period of time t1, and then opens the second switch;

[0068] S3: The switch control unit detects whether the voltage on the electrolytic capacitor group reaches its maximum capacity. If so, the second switch is opened and the first switch is closed. If not, the switch waits for a t2 period of time and then returns to execute S2.

[0069] Furthermore, the switch control unit has an AD sampling port, such as Figure 7 As shown, the method for determining the t1 time period and the t2 time period includes:

[0070] S1': switch control unit is powered on;

[0071] S2': the AD sampling port of the switch control unit collects the voltage divided by the resistor divider network and converts the divided voltage into a digital signal;

[0072] S3': the switch control unit performs software filtering on the digital signal;

[0073] S4': the switch control unit samples and calculates the digital signal at intervals of △t to obtain a voltage value V1 corresponding to the current moment;

[0074] S5': The switch control unit calculates the difference (V1-V0) between the current voltage value V1 and the voltage value V0 obtained by sampling the digital signal △t time ago, and determines it as the △V o ;

[0075] S6': According to the formula D = K*△V o Determine the duty cycle D, where ∆V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, and K is the preset proportionality coefficient;

[0076] S7': Determine the t1 value and the t2 value according to the formula D=t1 / (t1+t2), wherein (t1+t2) is a preset period value.

[0077] In this way, when the t1 value and the t2 value are determined, the duration of closing the second switch and the duration of opening the second switch can be determined, so as to achieve a smooth and stable charging effect.

[0078] Furthermore, the present invention also provides an air conditioner, which uses the aforementioned air conditioner charging circuit.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An air conditioner charging circuit, characterized in that: The invention comprises an AC power source (1), a filter component (20), an electrolytic capacitor group (40), a rectifier (70), a first switch (8), a second switch (9) and a switch control unit (10), wherein the AC power source (1) is connected to the filter component (20) and the rectifier (70) in sequence, the rectifier (70) is connected to the electrolytic capacitor group (40), a first switch (8) and a second switch (9) are arranged on a line connecting the filter component (20) and the rectifier (70), and the second switch (9) is connected in parallel with the first switch (8), the first switch (8) and the second switch (9) are connected to the switch control unit (10), and the switch control unit (10) is used to control the closing and opening of the first switch (8) and the second switch (9), The switch control unit controls the second switch to close for a time period of t1, and then disconnects the second switch. After an interval of t2, the second switch is controlled to close for a time period of t1 again, and the second switch is closed and disconnected in sequence. At the same time, the switch control unit monitors the voltage on the electrolytic capacitor group through a resistor voltage divider network to check whether the voltage of the electrolytic capacitor group reaches the charging completion standard. If so, the first switch is closed and the second switch is disconnected to complete the charging process; The charging completion standard includes: The voltage value of the electrolytic capacitor bank reaches its maximum capacity, or The difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time is less than the first threshold value. According to the difference between the current voltage value of the electrolytic capacitor group and the voltage value before the second switch was closed last time, According to the formula D = K * △ V o The duty cycle D is determined by PI operation. The duty cycle D is the ratio of t1 to (t1+t2), where (t1+t2) is a preset period value. The t1 value and t2 value are determined according to the duty cycle D and the value of (t1+t2). △V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, and K is a preset proportional coefficient.

2. The air conditioner charging circuit according to claim 1, characterized in that: The filter assembly (20) comprises a filter inductor (2) and a first electrolytic capacitor (3); the electrolytic capacitor group (40) comprises a second electrolytic capacitor (4), a third electrolytic capacitor (5), and a fourth electrolytic capacitor (6); the rectifier (70) comprises a second rectifier bridge (7); the AC power supply (1) is connected to the filter inductor (2), the first electrolytic capacitor (3), and the second rectifier bridge (7) in sequence; the second rectifier bridge (7) is connected in parallel with the second electrolytic capacitor (4), the third electrolytic capacitor (5), and the fourth electrolytic capacitor (6); a first switch (8) and a second switch (9) are provided on the line connecting the filter inductor (2) and the second rectifier bridge (7); a first voltage divider resistor (11) and a second voltage divider resistor (12) are connected in series at the positive terminals of the second electrolytic capacitor (4), the third electrolytic capacitor (5), and the fourth electrolytic capacitor (6); and a voltage detection pin of the switch control unit (10) is connected to a connection point between the first voltage divider resistor (11) and the second voltage divider resistor (12).

3. The air conditioner charging circuit according to claim 2, characterized in that: The switch control unit (10) comprises a power conversion unit (101) and a switch control single chip microcomputer (102); the power conversion unit (101) is connected to the AC power source (1) and is used to convert the AC power source into DC power to supply power to the switch control single chip microcomputer (102); a group of ports of the switch control single chip microcomputer (102) are connected to the power conversion unit (101), and another group of ports are respectively connected to the first switch (8) and the second switch (9) and are used to control the closing and opening of the first switch (8) and the second switch (9); a voltage detection pin of the switch control single chip microcomputer (102) is connected to a connection point of a first voltage divider resistor (11) and a second voltage divider resistor (12).

4. The air conditioner charging circuit according to claim 3, characterized in that: The power conversion unit (101) comprises a first rectifier bridge (1011), a small electrolytic capacitor (1012), a switching power supply (1013), and a diode (1014); the AC power supply (1) is connected to the first rectifier bridge (1011); the small electrolytic capacitor (1012) and the switching power supply (1013) are connected in parallel to the first rectifier bridge (1011); the switching power supply (1013) is connected to a switch control single chip microcomputer (102) for supplying power to the switch control single chip microcomputer (102); and a diode (1014) is arranged on a line connecting the first rectifier bridge (1011) and the small electrolytic capacitor (1012).

5. The air conditioner charging circuit according to claim 1, characterized in that: The first switch and the second switch are both normally open switches.

6. The air conditioner charging circuit according to claim 1, characterized in that: Also includes: Step 1: Power on the switch control unit; Step 2: The switch control unit controls the second switch to close for a period of time t1, and then opens the second switch; Step 3: The switch control unit detects whether the voltage on the electrolytic capacitor group reaches its maximum capacity. If so, the second switch is opened and the first switch is closed. If not, the switch waits for a t2 period of time and then returns to step 2.

7. The air conditioner charging circuit according to claim 1, characterized in that: The switch control unit has an AD sampling port, and the method for determining the t1 time period and the t2 time period includes: Step 1': Power on the switch control unit; Step 2': The AD sampling port of the switch control unit collects the voltage divided by the resistor divider network, and converts the divided voltage into a digital signal; Step 3': the switch control unit performs software filtering on the digital signal; Step 4': the switch control unit samples and calculates the digital signal at intervals of △t to obtain a voltage value V1 corresponding to the current moment; Step 5': The switch control unit calculates the difference (V1-V0) between the current voltage value V1 and the voltage value V0 obtained by sampling the digital signal △t time ago, and determines it as the △V o ; Step 6': According to the formula D = K * △ V o Determine the duty cycle D, where ∆V o is the difference between the current voltage value and the voltage value before the second switch was closed last time, and K is the preset proportionality coefficient; Step 7': Determine the t1 value and the t2 value according to the formula D=t1 / (t1+t2), where (t1+t2) is a preset period value.

8. An air conditioner, characterized in that: The air conditioner uses an air conditioner charging circuit as described in any one of claims 1 to 4.

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