Harmonic correction circuit and power adapter

Abstract

The utility model is suitable for the technical field of harmonic distortion compensation, and provides a harmonic correction circuit and a power adapter, and the harmonic correction circuit comprises a first electromagnetic interference protection unit, a second electromagnetic interference protection unit, a rectification unit and a resistor unit. The first electromagnetic interference protection unit is electrically connected with the resistor unit and the second electromagnetic interference protection unit, the second electromagnetic interference protection unit is electrically connected with the resistor unit and the rectification unit, and the first electromagnetic interference protection unit is used for being electrically connected with an interface. The impedance of the resistor unit is a fixed value, that is, the impedance of the resistor unit does not change along with the change of the loop temperature in the harmonic correction circuit, so that harmonic waves generated in the harmonic correction circuit are suppressed, and the problem that the harmonic waves are increased due to the fact that an existing harmonic correction circuit adopts a thermistor is effectively solved.

Description

Technical Field

[0001] This application belongs to the field of harmonic distortion compensation technology, and in particular relates to a harmonic correction circuit and a power adapter. Background Technology

[0002] A power adapter, also known as an external power supply, has the basic function of converting alternating current (AC) to direct current (DC) to power small portable electronic devices and appliances. Existing power adapters typically use a thermistor connected in series between the first and second electromagnetic interference (EMI) protection units in their harmonic correction circuits. However, the impedance of the thermistor changes with the temperature of the circuit loop in the harmonic correction circuit, leading to an increase in harmonics within the circuit. Utility Model Content

[0003] This application provides a harmonic correction circuit and a power adapter, which can solve the problem of increased harmonics caused by the use of thermistors in existing harmonic correction circuits.

[0004] In a first aspect, embodiments of this application provide a harmonic correction circuit, including a first electromagnetic interference protection unit, a second electromagnetic interference protection unit, a rectifier unit, and a resistor unit. The first electromagnetic interference protection unit is electrically connected to the resistor unit and the second electromagnetic interference protection unit, respectively. The second electromagnetic interference protection unit is electrically connected to the resistor unit and the rectifier unit, respectively. The first electromagnetic interference protection unit is used to be electrically connected to an interface, wherein the impedance of the resistor unit is a fixed value.

[0005] The first electromagnetic interference protection unit is used to filter out electromagnetic interference signals in the AC voltage signal output by the interface and output a first AC voltage signal; the resistor unit is used to output a current signal according to the first AC voltage signal; the second electromagnetic interference protection unit is used to output a second AC voltage signal according to the first AC voltage signal and the current signal; the rectifier unit is used to convert the second AC voltage signal into a target DC voltage signal.

[0006] In one possible implementation of the first aspect, the fixed value is greater than or equal to 0.5 ohms and less than or equal to 2 ohms.

[0007] In one possible implementation of the first aspect, the resistor unit includes a first resistor, a first end of which is electrically connected to the first electromagnetic interference protection unit, a second end of which is electrically connected to the second electromagnetic interference protection unit, and the impedance of the first resistor is the fixed value.

[0008] In one possible implementation of the first aspect, the first electromagnetic interference protection unit includes a varistor and a first common-mode inductor, a first terminal of the first common-mode inductor being electrically connected to a first terminal of the varistor and a first terminal of the interface, a second terminal of the first common-mode inductor being electrically connected to a second terminal of the varistor and a second terminal of the interface, a third terminal of the first common-mode inductor being electrically connected to the second electromagnetic interference protection unit, and a fourth terminal of the first common-mode inductor being electrically connected to the resistor unit.

[0009] In one possible implementation of the first aspect, the first electromagnetic interference protection unit further includes a first capacitor, the first terminal of which is electrically connected to the third terminal of the first common-mode inductor and the second electromagnetic interference protection unit, and the second terminal of which is electrically connected to the fourth terminal of the first common-mode inductor and the resistor unit.

[0010] In one possible implementation of the first aspect, the second electromagnetic interference protection unit includes a second common-mode inductor, a first end of the second common-mode inductor being electrically connected to the first electromagnetic interference protection unit, a second end of the second common-mode inductor being electrically connected to the resistor unit, and a third end of the second common-mode inductor and a fourth end of the second common-mode inductor being electrically connected to the rectifier unit.

[0011] In one possible implementation of the first aspect, the rectifier unit includes a first diode, a second diode, a third diode, and a fourth diode. The anodes of the first diode and the third diode are both grounded. The cathode of the first diode is electrically connected to the anode of the second diode and the second electromagnetic interference protection unit, respectively. The anode of the fourth diode is electrically connected to the cathode of the third diode and the second electromagnetic interference protection unit, respectively. The cathodes of the fourth diode and the second diode are both used for electrical connection to the load.

[0012] In one possible implementation of the first aspect, the harmonic correction circuit further includes a discharge unit, which is electrically connected to the second electromagnetic interference protection unit and the rectifier unit respectively, and the discharge unit is used to be electrically connected to the energy storage unit.

[0013] The discharge unit is used to output a discharge voltage to the energy storage unit according to the second AC voltage signal when the first electromagnetic interference protection unit does not receive the AC voltage signal.

[0014] In one possible implementation of the first aspect, the discharge unit includes a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The first end of the second resistor is electrically connected to the first end of the third resistor, the second electromagnetic interference protection unit, and the rectifier unit, respectively. The second end of the second resistor is electrically connected to the second end of the third resistor, the first end of the fourth resistor, the first end of the fifth resistor, and the energy storage unit, respectively. The second end of the fourth resistor is electrically connected to the second end of the fifth resistor, the second electromagnetic interference protection unit, and the rectifier unit, respectively.

[0015] Secondly, embodiments of this application provide a power adapter that includes the harmonic correction circuit described in any one of the first aspects.

[0016] The beneficial effects of the embodiments in this application compared with the prior art are:

[0017] The harmonic correction circuit provided in this application includes a first electromagnetic interference (EMI) protection unit, a second EMI protection unit, a rectifier unit, and a resistor unit. The first EMI protection unit filters out EMI signals from the AC voltage signal output from the interface and outputs a first AC voltage signal. The resistor unit outputs a current signal based on the first AC voltage signal. The second EMI protection unit outputs a second AC voltage signal based on the first AC voltage signal and the current signal; that is, the second EMI protection unit filters out EMI signals from the first AC voltage signal. The rectifier unit converts the second AC voltage signal into a target DC voltage signal, thereby supplying power to the load. Notably, the impedance of the resistor unit in this application is a fixed value, meaning that the impedance of the resistor unit does not change with the temperature of the circuit loop in the harmonic correction circuit, thereby suppressing harmonics generated in the harmonic correction circuit and effectively solving the problem of increased harmonics caused by the use of thermistors in existing harmonic correction circuits. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic block diagram of a harmonic correction circuit provided in one embodiment of this application;

[0020] Figure 2 The impedance of the resistor unit provided in one embodiment of this application is 0.5 ohms, which is the test result.

[0021] Figure 3The impedance of the resistor unit provided in one embodiment of this application is 1 ohm, which is the test result.

[0022] Figure 4 The impedance of the resistor unit provided in one embodiment of this application is 1.5 ohms, which is the test result.

[0023] Figure 5 The impedance of the resistor unit provided in one embodiment of this application is 2 ohms, which is the test result.

[0024] Figure 6 This is a circuit connection diagram of a harmonic correction circuit provided in an embodiment of this application;

[0025] Figure 7 This is a schematic block diagram of a harmonic correction circuit provided in another embodiment of this application.

[0026] In the diagram: 10, Harmonic correction circuit; 101, First electromagnetic interference protection unit; 102, Second electromagnetic interference protection unit; 103, Rectifier unit; 104, Resistor unit; 105, Discharge unit; 20, Interface; 30, Load; 40, Energy storage unit. Detailed Implementation

[0027] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0028] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0029] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0030] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [the described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [the described condition or event] is detected," or "in response to detection of [the described condition or event]."

[0031] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0033] In existing power adapters, harmonic correction circuits typically connect a thermistor in series between the first and second electromagnetic interference protection units. However, the impedance of the thermistor changes with the temperature of the circuit loop in the harmonic correction circuit, which causes an increase in harmonics in the harmonic correction circuit.

[0034] To address the aforementioned problems, the harmonic correction circuit provided in this application includes a first electromagnetic interference (EMI) protection unit, a second EMI protection unit, a rectifier unit, and a resistor unit. The first EMI protection unit filters out EMI signals from the AC voltage signal output from the interface and outputs a first AC voltage signal. The resistor unit outputs a current signal based on the first AC voltage signal. The second EMI protection unit outputs a second AC voltage signal based on the first AC voltage signal and the current signal; that is, the second EMI protection unit filters out EMI signals from the first AC voltage signal. The rectifier unit converts the second AC voltage signal into a target DC voltage signal, thereby supplying power to the load. Notably, the impedance of the resistor unit in this application is a fixed value, meaning that the impedance of the resistor unit does not change with the temperature of the circuit in the harmonic correction circuit, thereby suppressing harmonics generated in the harmonic correction circuit and effectively solving the problem of increased harmonics caused by the use of thermistors in existing harmonic correction circuits.

[0035] To illustrate the technical solution described in this application, specific embodiments are provided below.

[0036] Figure 1 A schematic block diagram of a harmonic correction circuit 10 according to an embodiment of this application is shown. See also Figure 1 As shown, the harmonic correction circuit 10 includes a first electromagnetic interference protection unit 101, a second electromagnetic interference protection unit 102, a rectifier unit 103, and a resistor unit 104. The first electromagnetic interference protection unit 101 is electrically connected to the resistor unit 104 and the second electromagnetic interference protection unit 102, respectively. The second electromagnetic interference protection unit 102 is electrically connected to the resistor unit 104 and the rectifier unit 103, respectively. The first electromagnetic interference protection unit 101 is used to electrically connect to the interface 20. The impedance of the resistor unit 104 is a fixed value.

[0037] Specifically, the first electromagnetic interference protection unit 101 can filter out electromagnetic interference signals in the AC voltage signal output from the interface 20 and output a first AC voltage signal. The resistor unit 104 outputs a current signal based on the first AC voltage signal. The second electromagnetic interference protection unit 102 is used to output a second AC voltage signal based on the first AC voltage signal and the current signal, that is, the second electromagnetic interference protection unit 102 can filter out electromagnetic interference signals in the first AC voltage signal. The rectifier unit 103 converts the second AC voltage signal into a target DC voltage signal, thereby supplying power to the load 30. The impedance of the resistor unit 104 in this application is a fixed value, that is, the impedance of the resistor unit 104 will not change with the temperature of the circuit in the harmonic correction circuit 10, thereby suppressing the harmonics generated in the harmonic correction circuit 10 and effectively solving the problem of increased harmonics caused by the use of thermistors in existing harmonic correction circuits 10.

[0038] In some embodiments, using a resistor unit 104 with a fixed impedance connected between the first electromagnetic interference protection unit and the second electromagnetic interference protection unit may cause the loop temperature in the harmonic correction circuit to rise, resulting in a relatively high temperature rise of the power adapter. Therefore, when selecting the fixed value, it is necessary to ensure that the temperature rise of the power adapter meets the standard, the harmonics meet the standard, and the cost is reduced.

[0039] Based on the above issues, the impedance of resistor unit 104 is set between 0.5 ohms and 2 ohms. This impedance range allows the power adapter to pass the harmonic testing in safety regulations, ensuring that the harmonics meet the requirements for Class A products in the Chinese national standard GB17625.1-2022 for safety certification, while also reducing costs. Furthermore, because the impedance of resistor unit 104 is fixed and relatively low, its temperature will not exceed its maximum operating temperature during long-term operation of the power adapter.

[0040] It should be noted that the test results for the impedance of resistor unit 104 being 0.5 ohms are as follows: Figure 2 As shown, the test results for the impedance of resistor unit 104 being 1 ohm are as follows: Figure 3 As shown, the test results for the impedance of resistor unit 104 of 1.5 ohms are as follows. Figure 4 As shown, the test results for the impedance of resistor unit 104 being 2 ohms are as follows: Figure 5 As shown. Where Hn is the harmonic frequency, i.e., the frequency at which harmonics occur, Ueff[V] is the actual voltage value obtained through measurement, Ueff[%] is the percentage value converted from the actual voltage value, Limit[%] is the harmonic limit value specified in the safety regulations, and Result is the test result. If the percentage value converted from the actual voltage value is less than the harmonic limit value specified in the safety regulations, the test result is qualified. According to... Figures 2 to 5 The data shows that the test results are qualified when the impedance of resistor unit 104 is 0.5 ohms, 1 ohm, 1.5 ohms and 2 ohms. This indicates that the impedance of resistor unit 104 is between 0.5 ohms and 2 ohms, which allows the power adapter to pass the harmonic test in the safety regulations.

[0041] For example, the designer can select the impedance of the resistor unit 104 according to the actual situation. For example, the impedance of the resistor unit 104 can be selected as 1.5 ohms.

[0042] In one embodiment of this application, such as Figure 6 As shown, the resistor unit 104 includes a first resistor, the first end of which is electrically connected to the first electromagnetic interference protection unit, and the second end of which is electrically connected to the second electromagnetic interference protection unit. The impedance of the first resistor is a fixed value.

[0043] Specifically, the impedance of the first resistor is a fixed value, meaning it does not change with the temperature of the circuit in the harmonic correction circuit 10. This suppresses the harmonics generated in the harmonic correction circuit 10, effectively solving the problem of increased harmonics caused by the use of thermistors in existing harmonic correction circuits 10. This also helps the power adapter pass the harmonic test in the safety regulations while reducing costs.

[0044] For example, the impedance of the first resistor can be set between 0.5 ohms and 2 ohms. For instance, the impedance of the first resistor can be set to 1.5 ohms.

[0045] For example, the first resistor can be a cement resistor with a fixed impedance. A cement resistor, also known as a carbon film resistor or ceramic film resistor, is a resistor encapsulated in a highly heat-resistant, moisture-resistant, and corrosion-resistant ceramic or plastic matrix. Its main components are carbon film or other types of resistive materials, which are pressed or coated onto a ceramic core during manufacturing and then encapsulated. Because the carbon film or other resistive materials used inside a cement resistor have good temperature and chemical stability, the impedance of the cement resistor will not drift significantly due to changes in ambient temperature or long-term use.

[0046] It should be noted that the resistor unit 104 may also include multiple resistors connected in series and parallel, wherein the total impedance of the series and parallel resistors is the same as the impedance of the first resistor, both being fixed values.

[0047] In one embodiment of this application, such as Figure 6 As shown, the first electromagnetic interference protection unit 101 includes a varistor VR1 and a first common-mode inductor LF1. The first end of the first common-mode inductor LF1 is electrically connected to the first end of the varistor VR1 and the first end of the interface 20, respectively. The second end of the first common-mode inductor LF1 is electrically connected to the second end of the varistor VR1 and the second end of the interface 20, respectively. The third end of the first common-mode inductor LF1 is electrically connected to the second electromagnetic interference protection unit 102, and the fourth end of the first common-mode inductor LF1 is electrically connected to the first end of the first resistor THR1.

[0048] Specifically, the varistor VR1 is used for overvoltage protection. Since the impedance of the varistor VR1 changes with voltage, when the AC voltage signal input to the harmonic correction circuit 10 exceeds the rated voltage of the varistor VR1, the varistor VR1 will exhibit a low resistance state, thereby absorbing and dissipating the overvoltage, thus protecting other components in the harmonic correction circuit 10 from damage caused by overvoltage. Simultaneously, the varistor VR1 can also be used for voltage stabilization to a certain extent. When the AC voltage signal input to the harmonic correction circuit 10 changes significantly, the varistor VR1 can automatically adjust its own impedance to limit the peak value of the AC voltage signal, thereby ensuring the operational stability of other components in the harmonic correction circuit 10. The first common-mode inductor LF1, through its special structural design, can exhibit high impedance in the circuit, thus producing a strong damping effect on common-mode electromagnetic interference signals, thereby suppressing the propagation of electromagnetic interference signals in the AC voltage signal.

[0049] It should be noted that common-mode interference refers to interference signals that act simultaneously on two signal lines of a circuit, usually caused by the potential difference between the power line and ground or the neutral line and ground. Common-mode inductors are commonly used at the input and output terminals of circuits to protect the circuit from external electromagnetic interference.

[0050] For example, the designer can select the model of the varistor VR1 according to the actual situation. For instance, the model of the varistor VR1 can be selected as 10N681. The designer can also select the inductance of the first common-mode inductor LF1 according to the actual situation. For instance, the inductance of the first common-mode inductor LF1 can be selected as 0.5mH.

[0051] In one embodiment of this application, such as Figure 6 As shown, the first electromagnetic interference protection unit 101 also includes a first capacitor C1. The first end of the first capacitor C1 is electrically connected to the third end of the first common mode inductor LF1 and the second electromagnetic interference protection unit 102, respectively. The second end of the first capacitor C1 is electrically connected to the fourth end of the first common mode inductor LF1 and the first end of the first resistor THR1, respectively.

[0052] Specifically, the function of the first capacitor C1 is to suppress differential-mode radiated interference at the input terminal, thereby improving the EMC (Electromagnetic Compatibility) of the power adapter itself.

[0053] For example, the designer can select the capacitance value of the first capacitor C1 according to the actual situation. For example, the capacitance value of the first capacitor C1 can be selected as 0.47uF.

[0054] In one embodiment of this application, such as Figure 6 As shown, the second electromagnetic interference protection unit 102 includes a second common mode inductor LF2. The first end of the second common mode inductor LF2 is electrically connected to the first electromagnetic interference protection unit 101. The second end of the second common mode inductor LF2 is electrically connected to the second end of the first resistor THR1. The third end and the fourth end of the second common mode inductor LF2 are both electrically connected to the rectifier unit 103.

[0055] Specifically, the second common-mode inductor LF2 has the same function as the first common-mode inductor LF1, which can present a high impedance in the circuit, thereby producing a strong damping effect on the common-mode electromagnetic interference signal, and thus suppressing the propagation of electromagnetic interference signal in the first AC voltage signal.

[0056] For example, the designer can select the inductance of the first common-mode inductor LF1 according to the actual situation. For example, the inductance of the first common-mode inductor LF1 can be selected as 10mH.

[0057] In one embodiment of this application, such as Figure 6As shown, the rectifier unit 103 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anodes of the first diode D1 and the third diode D3 are both grounded. The cathodes of the first diode D1 are electrically connected to the anodes of the second diode D2 and the second electromagnetic interference protection unit 102, respectively. The anodes of the fourth diode D4 are electrically connected to the cathodes of the third diode D3 and the second electromagnetic interference protection unit 102, respectively. The cathodes of the fourth diode D4 and the second diode D2 are both used for electrical connection to the load 30.

[0058] Specifically, four diodes form a rectifier bridge, primarily used to convert alternating current (AC) to direct current (DC). When the positive half-cycle of the second AC voltage signal is applied to the rectifier bridge, diodes D2 and D3 conduct, resulting in a positive-on-top, negative-on-bottom voltage across load 30, i.e., the positive half-cycle DC voltage. When the negative half-cycle of the second AC voltage signal is applied to the rectifier bridge, diodes D1 and D4 conduct, resulting in a positive-on-top, negative-on-bottom voltage across load 30, i.e., the negative half-cycle DC voltage. Through this rectification process of positive and negative half-cycles, regardless of the polarity of the second AC voltage signal, load 30 receives two half-cycle voltages, one positive and one negative. Thus, load 30 receives a continuous DC voltage, achieving the conversion from the second AC voltage signal to the target DC voltage signal.

[0059] It should be noted that, compared to a half-wave rectifier circuit, the bridge rectifier circuit described above utilizes the energy of the AC power supply more efficiently. This is because the bridge rectifier circuit can rectify the AC power in every half-cycle, while the half-wave rectifier circuit can only rectify it in the positive half-cycle. Therefore, the DC output voltage of the bridge rectifier circuit is more stable, and the output current ripple is smaller.

[0060] For example, designers can select the maximum forward current and maximum reverse withstand voltage that the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4 can withstand according to the actual situation. For example, the maximum forward current that all four diodes can withstand can be 4A, and the maximum reverse withstand voltage can be 1KV.

[0061] In one embodiment of this application, such as Figure 7 As shown, the harmonic correction circuit 10 also includes a discharge unit 105, which is electrically connected to the second electromagnetic interference protection unit 102 and the rectifier unit 103 respectively, and is used to be electrically connected to the energy storage unit 40.

[0062] Specifically, the discharge unit 105 is used to output a discharge voltage to the energy storage unit 40 according to the second AC voltage signal when the first electromagnetic interference protection unit 101 does not receive an AC voltage signal, that is, when the AC power is cut off, thereby quickly reducing the electrical energy stored in the harmonic correction circuit 10 to below the safe contact voltage of the human body, such as below 36V.

[0063] In one embodiment of this application, such as Figure 6 As shown, the discharge unit 105 includes a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. The first end of the second resistor R2 is electrically connected to the first end of the third resistor R3, the second electromagnetic interference protection unit 102, and the rectifier unit 103, respectively. The second end of the second resistor R2 is electrically connected to the second end of the third resistor R3, the first end of the fourth resistor R4, the first end of the fifth resistor R5, and the energy storage unit 40, respectively. The second end of the fourth resistor R4 is electrically connected to the second end of the fifth resistor R5, the second electromagnetic interference protection unit 102, and the rectifier unit 103, respectively.

[0064] Specifically, the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5 are all current-limiting resistors with large impedances, which can reduce the electrical energy stored in the harmonic correction circuit 10 when the AC power is cut off.

[0065] For example, designers can select the impedance and type of the second resistor R2, the third resistor R3, the fourth resistor R4, and the fifth resistor R5. For instance, the impedance of all four resistors can be selected as 1M ohms, and the type of all four resistors can be selected as 1206.

[0066] In one embodiment of this application, such as Figure 6 As shown, the harmonic correction circuit 10 also includes a second capacitor C2. The first end of the second capacitor C2 is electrically connected to the rectifier unit 103 and the load 30, respectively, and the second end of the second capacitor C2 is grounded.

[0067] Specifically, the second capacitor C2 is connected between the load 30 and the rectifier unit 103 to smooth the target DC voltage signal, filter out ripple, and provide a stable DC voltage for the load 30.

[0068] For example, designers can select the capacitance value and the maximum voltage value that the second capacitor C2 can withstand according to the actual situation. For example, the capacitance value of the second capacitor C2 can be selected as 68uF, and the maximum voltage that it can withstand can be 450V.

[0069] In one embodiment of this application, such as Figure 6 As shown, the harmonic correction circuit 10 also includes a first fuse F1, which is connected in series between the interface 20 and the first electromagnetic interference protection unit 101 for overcurrent protection.

[0070] For example, the designer can select the rated current and rated voltage of the first fuse F1 according to the actual situation. For instance, the rated current of the first fuse F1 can be selected as 3.15A, and the rated voltage can be selected as 250V. If the current in the harmonic correction circuit 10 is greater than 3.15A or the voltage in the harmonic correction circuit 10 is greater than 250V, the first fuse F1 will blow, thereby cutting off the power supply to protect the circuit.

[0071] This application also discloses a power adapter including the aforementioned harmonic correction circuit. The power adapter using this circuit can pass the harmonic testing requirements under safety regulations, while simultaneously reducing costs. Furthermore, since the impedance of the resistor unit in the voltage converter is fixed and small, the temperature of the resistor unit itself in the harmonic correction circuit will not exceed its maximum operating temperature during long-term operation of the power adapter, thus improving the reliability of the power adapter.

[0072] It should be noted that when designing the power adapter, a drive circuit, a transformer, and a feedback circuit also need to be set between the rectifier unit in the aforementioned harmonic correction circuit 10 and the load to realize the function of the power adapter. Since the drive circuit, transformer, and feedback circuit are all existing technologies, they will not be described in detail here.

[0073] Since the processing and functions implemented by the power adapter in this embodiment are basically the same as the embodiments, principles and examples of the aforementioned harmonic correction circuit, any details not covered in this embodiment can be found in the relevant descriptions in the aforementioned embodiments, and will not be repeated here.

[0074] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A harmonic correction circuit, characterized in that, It includes a first electromagnetic interference protection unit, a second electromagnetic interference protection unit, a rectifier unit, and a resistor unit. The first electromagnetic interference protection unit is electrically connected to the resistor unit and the second electromagnetic interference protection unit, respectively. The second electromagnetic interference protection unit is electrically connected to the resistor unit and the rectifier unit, respectively. The first electromagnetic interference protection unit is used to electrically connect to an interface. The impedance of the resistor unit is a fixed value. The first electromagnetic interference protection unit is used to filter out electromagnetic interference signals in the AC voltage signal output by the interface and output a first AC voltage signal; the resistor unit is used to output a current signal according to the first AC voltage signal; the second electromagnetic interference protection unit is used to output a second AC voltage signal according to the first AC voltage signal and the current signal; the rectifier unit is used to convert the second AC voltage signal into a target DC voltage signal.

2. The harmonic correction circuit according to claim 1, characterized in that, The fixed value is greater than or equal to 0.5 ohms and less than or equal to 2 ohms.

3. The harmonic correction circuit according to claim 1, characterized in that, The resistor unit includes a first resistor, a first end of which is electrically connected to the first electromagnetic interference protection unit, and a second end of which is electrically connected to the second electromagnetic interference protection unit. The impedance of the first resistor is the fixed value.

4. The harmonic correction circuit according to claim 1, characterized in that, The first electromagnetic interference protection unit includes a varistor and a first common-mode inductor. The first end of the first common-mode inductor is electrically connected to the first end of the varistor and the first end of the interface, respectively. The second end of the first common-mode inductor is electrically connected to the second end of the varistor and the second end of the interface, respectively. The third end of the first common-mode inductor is electrically connected to the second electromagnetic interference protection unit, and the fourth end of the first common-mode inductor is electrically connected to the resistor unit.

5. The harmonic correction circuit according to claim 4, characterized in that, The first electromagnetic interference protection unit further includes a first capacitor, the first end of which is electrically connected to the third end of the first common mode inductor and the second electromagnetic interference protection unit, and the second end of which is electrically connected to the fourth end of the first common mode inductor and the resistor unit.

6. The harmonic correction circuit according to claim 1, characterized in that, The second electromagnetic interference protection unit includes a second common-mode inductor. The first end of the second common-mode inductor is electrically connected to the first electromagnetic interference protection unit, the second end of the second common-mode inductor is electrically connected to the resistor unit, and the third end and the fourth end of the second common-mode inductor are both electrically connected to the rectifier unit.

7. The harmonic correction circuit according to claim 1, characterized in that, The rectifier unit includes a first diode, a second diode, a third diode, and a fourth diode. The anodes of the first diode and the third diode are both grounded. The cathode of the first diode is electrically connected to the anode of the second diode and the second electromagnetic interference protection unit, respectively. The anode of the fourth diode is electrically connected to the cathode of the third diode and the second electromagnetic interference protection unit, respectively. The cathodes of the fourth diode and the second diode are both used for electrical connection to the load.

8. The harmonic correction circuit according to any one of claims 1-7, characterized in that, The harmonic correction circuit further includes a discharge unit, which is electrically connected to the second electromagnetic interference protection unit and the rectifier unit respectively, and is used to be electrically connected to the energy storage unit. The discharge unit is used to output a discharge voltage to the energy storage unit according to the second AC voltage signal when the first electromagnetic interference protection unit does not receive the AC voltage signal.

9. The harmonic correction circuit according to claim 8, characterized in that, The discharge unit includes a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The first end of the second resistor is electrically connected to the first end of the third resistor, the second electromagnetic interference protection unit, and the rectifier unit, respectively. The second end of the second resistor is electrically connected to the second end of the third resistor, the first end of the fourth resistor, the first end of the fifth resistor, and the energy storage unit, respectively. The second end of the fourth resistor is electrically connected to the second end of the fifth resistor, the second electromagnetic interference protection unit, and the rectifier unit, respectively.

10. A power adapter, characterized in that, Includes the harmonic correction circuit according to any one of claims 1-9.

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