A power adapter and a working method thereof

Abstract

The present invention relates to a novel power adapter and a working method thereof, comprising a rectifier filter circuit, a flyback circuit, a compensation circuit and a control circuit, wherein the rectifier filter circuit is connected to the flyback circuit, and the flyback circuit and the compensation circuit are both electrically connected to the control circuit; the flyback circuit is connected to the compensation circuit; the compensation circuit comprises a secondary compensation winding W2, a first diode D1, and a compensation capacitor C a and a DC-DC circuit; one end of the secondary compensation winding W2 is connected to the anode of the first diode D1, and the other end of the secondary compensation winding W2 is connected to the compensation capacitor C a The cathode of the first diode D1 is connected to the compensation capacitor C a The other end is connected to the DC-DC circuit; the DC-DC circuit is connected to the flyback circuit and the control circuit respectively. The semiconductor device in the compensation circuit of the present invention starts to work only when the input voltage is too low to meet the output power, which effectively reduces the switching loss and is conducive to improving the efficiency of the whole machine.

Description

Technical Field

[0001] The invention relates to the field of power adapters, in particular to a power adapter and a working method thereof. Background Art

[0002] With the advancement of science and technology, the explosive growth of various electronic products has led to the vigorous development of various affiliated industries. As the basis of these electronic products, the power adapter is irreplaceable. High power density is an important development trend of power adapters. However, the volume of magnetic components has always been the main factor restricting the high power density of power adapters. Increasing the switching frequency of the switch tube can effectively reduce the volume and weight of the magnetic components in the power converter. At this time, the volume of the input electrolytic capacitor is comparable to that of the magnetic component, so people began to focus on the electrolytic capacitor.

[0003] In current power adapters, flyback topology is mostly used. Input electrolytic capacitors are an important component of AC-DC converters and play the role of energy storage and filtering in power adapters. Input electrolytic capacitors with suitable capacitance can effectively reduce the pulsation of input voltage after rectification, and release the stored energy when the input energy is insufficient, thereby stabilizing the circuit. Due to the requirement of wide range AC input (90~264V) of power adapters, the maximum peak value of the input voltage can reach 373.4V after full-bridge rectification. Under the premise of suitable capacitance, the input capacitor can only choose high-voltage electrolytic capacitors. However, high-voltage electrolytic capacitors are large in size, which greatly limits the size of the power adapter. Therefore, if the power adapter wants to achieve high power density, eliminating the input electrolytic capacitor is an indispensable link.

[0004] Eliminating the input electrolytic capacitor will cause the input voltage after full-bridge rectification to drop to close to 0, making the input energy insufficient to provide output energy for a period of time during the double power frequency cycle, causing the output voltage to drop and the voltage ripple to increase sharply.

[0005] At present, most power adapters on the market contain input electrolytic capacitors. Electrolytic capacitor-free technology is rarely used in power adapters, and is mostly used in the field of LED driver power supplies. Similar circuit topologies make electrolytic capacitor-free technology in the field of LED driver power supplies also have certain reference value in the field of power adapters. The electrolytic capacitor-free LED driver power supply topology can be divided into three categories: parallel auxiliary network topology, multi-port output topology, and integrated auxiliary network topology.

[0006] Parallel auxiliary network topology such as Figure 1 As shown, at the output of the DC-DC converter and the resistor R 0 A bidirectional converter is connected in parallel between the two circuits to make its input current equal to the double power frequency AC component in the pulsating current, so that the resistor R0 The driving current is a constant current. This method is to store energy in a capacitor through a bidirectional DC / DC converter, and when the main power output needs energy compensation, the energy in the capacitor is output through the resistor R of the bidirectional DC / DC converter. 0 To achieve energy compensation, thus reducing the resistance R 0 The output current ripple of this topology is generally around 7%. The bidirectional DC / DC converter in this structure always works in a high-frequency switching state, and energy flows in both directions on the converter, so there will be a certain efficiency loss.

[0007] Multi-port output topology such as Figure 2 As shown in the figure, the low-frequency output voltage ripple of the PFC converter is compensated in reverse by controlling the output voltage of the DC-DC converter. This solution eliminates the output ripple by optimizing the combination of two DC-DC converters and using the method of output voltage ripple reverse compensation, thereby eliminating the electrolytic capacitor. The output current ripple of this topology is generally around 5%. The DC / DC converter of this structure always works in a high-frequency switching state, so it will have a certain efficiency loss.

[0008] Integrate auxiliary network topology such as Figure 3 As shown in the figure, an auxiliary circuit is added to the main circuit, and the input power flows between the output side and the auxiliary side by controlling the switch tube. Among them, the energy storage capacitor is designed to have a large voltage ripple. When the input power is higher than the output power, the excess energy will be stored in the energy storage capacitor; and when the input power is lower than the output power, the insufficient energy will be provided by the energy storage capacitor. The output current ripple of this topology is generally around 5%, and three switch tubes are required to control the flow of energy. The switch tube loss is large, and there will be a certain efficiency loss.

[0009] The above-mentioned prior arts are all applied to the field of LED driver power supply, and the output ripple requirement of LED driver power supply is much lower than that of power adapter (generally the output current ripple is less than 5%), so it cannot meet the demand of the power adapter field (output voltage ripple is less than 0.75%). At the same time, the semiconductor devices in the compensation circuit of the above-mentioned technology are always working in a high-frequency switching state, so there is a problem of efficiency loss. Summary of the invention

[0010] In view of this, the purpose of the present invention is to provide a power adapter and a working method thereof, which adds a compensation circuit on the basis of a traditional power adapter, eliminates the input electrolytic capacitor while maintaining a small output ripple, thereby improving the power density of the power adapter.

[0011] The present invention is implemented by the following scheme: a power adapter, including a rectifier filter circuit, a flyback circuit, a compensation circuit and a control circuit, wherein the rectifier filter circuit is connected to the flyback circuit, and the flyback circuit and the compensation circuit are both electrically connected to the control circuit; the flyback circuit is connected to the compensation circuit; the compensation circuit includes a secondary compensation winding W 2 , the first diode D 1 , compensation capacitor C a and DC-DC circuit; the secondary compensation winding W 2 One end of the first diode D 1 The anode connection of the secondary compensation winding W 2 The other end of the compensation capacitor C a and the DC-DC circuit, the first diode D 1 The cathode of the compensation capacitor C a The other end is connected to the DC-DC circuit; the DC-DC circuit is connected to the flyback circuit and the control circuit respectively; the first input capacitor C in1 and the second input capacitor C in2 Ceramic capacitors are used.

[0012] Furthermore, the rectification and filtering circuit includes: a third diode D 3 , the fourth diode D 4 , the fifth diode D 5 , the sixth diode D 6 , the first inductor L 1 , the first resistor R 1 , the first input capacitor C in1 , the second input capacitor C in2 The flyback circuit includes a primary winding W 0 , switch tube S 0 , Secondary first winding W 1 、Diode D 0 , capacitor C 0 and resistor R 0 One end of the external AC power supply is respectively connected to the third diode D 3 The anode of the fifth diode D 5 The cathode of the external AC power supply is connected to the cathode of the sixth diode D 6 The cathode of the fourth diode D 4 The anode of the third diode D 3 The cathode of the fourth diode D 4 The cathode of the first inductor L 1 one end and the first resistor R 1 One end of the first input capacitor Cin1 One end of the first resistor R 1 One end of the first inductor L 1 The other end of the first resistor R 1 The other end and the second input capacitor C in2 One end of each primary winding W 0 The fifth diode D 5 The anode of the sixth diode D 6 The anode of the first input capacitor C in1 The other end of the second input capacitor C in2 The other end and the switch tube S 0 The source electrodes of the primary winding W are grounded; 0 The other end of the switch tube S 0 The drain of the switch tube S 0 The gate of the secondary side is electrically connected to the control circuit; the secondary side first winding W 1 One end of the diode D 0 The anode connection of the secondary first winding W 1 The other end of the capacitor C 0 One end of the resistor R 0 One end of the diode D is connected to the ground; 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other ends are connected to the DC-DC circuit.

[0013] Furthermore, the DC-DC circuit adopts a buck circuit, and the buck circuit includes a first switch tube S 1 , the second diode D 2 , inductor La; the first switch tube S 1 The drain of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the second diode D2 is connected to the cathode of the second diode D2 and one end of the inductor La; the other end of the inductor La is connected to the cathode of the second diode D2 and one end of the inductor La; 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the second diode D 2 The anode of the secondary compensation winding W 2 The other end of the compensation capacitor C a and grounded.

[0014] Furthermore, the DC-DC circuit adopts a boost circuit, and the boost circuit includes a first switch tube S 1 , the second diode D 2 、Inductance L a One end of the inductor La is connected to the switch tube S 1 The drain of the diode D 2 The anode of the switch tube S 1 The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the switch tube S is connected and grounded; 1 The gate of the inductor L is connected to the control circuit; a The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the second diode D 2 The cathode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0015] Furthermore, the DC-DC circuit adopts a buck-boost circuit; the buck-boost circuit includes a first switch tube S 1 , the second diode D 2 、Inductance L a The first diode D 1 The cathode and the compensation capacitor C a The other end is connected to the first switch tube S 1 The drain of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the inductor L a One end of the second diode D 2 The cathode connection of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of each of the second diodes D is connected to the other end of the inductor La and is grounded; 2 The anode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0016] Furthermore, the DC-DC circuit adopts a Cuk circuit; the Cuk circuit includes a first switch tube S1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first compensation inductor L a1 One end of the first switch tube S 1 Drain, the first capacitor C 1 One end of the first capacitor C 1 The other end of the second diode D 2 The anode of the second compensation inductor L a2 The first compensation inductor L a1 The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the second diode D 2 The cathode of the second compensation inductor L is connected to the ground; a2 The other end of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0017] Furthermore, the DC-DC circuit adopts a Sepic circuit; the Sepic circuit includes a first switch tube S 1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first compensation inductor L a1 One end of the first switch tube S 1 The drain of the first capacitor C 1 One end of the first capacitor C 1 The other end of the second compensation inductor L a2 One end and the second diode D 2 The anode connection of the first compensation inductor L a1 The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the second compensation inductor L a2 The other end of the first switch tube S is connected to the ground; 1 The gate of the second diode D is connected to the control circuit; 2 The cathode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0018] Furthermore, the DC-DC circuit adopts a Zeta circuit; the Zeta circuit includes a first switch tube S 1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first switch tube S 1 The source is respectively connected to the first compensation inductor L a1 one end of the first capacitor C 1 One end of the first capacitor C 1 The other end of the second diode D 2 The cathode and the second compensation inductor L a2 The first switch tube S 1 The drain of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate is connected to the control circuit; the second diode D 2 The anode of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end and the first compensation inductor L a1 and grounded; the second compensation inductor L a2 The other end of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0019] Preferably, the present invention also provides a working method of a power adapter, connecting the first input capacitor C in1 and the second input capacitor C in2After that, the rectified input voltage becomes a 100Hz steamed bun wave, the minimum value is close to 0, and the voltage pulsation is large; let the output power remain unchanged, at [t 1 -t 2 ] If the input energy is sufficient during the time period, the compensation winding W 2 For compensation capacitor C a Charging; at [t 3 -t 4 ] time period, the input energy is insufficient, the control circuit controls the first switch tube S in the DC-DC circuit 1 , to the resistor R 0 Supplement the required energy to keep the power adapter having a stable output voltage; where t 1 <t 2 <t 3 <t 4 ;

[0020] When the switch S 0 When the duty cycle does not reach the maximum value and the input power can meet the output power requirement, the DC-DC circuit does not work and the first switch tube S 1 Keep off, i La Always 0; in [t 0 -t 1 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy, namely the primary winding W 0 The current on the compensation capacitor C a Through the secondary compensation winding W 2 Start energy storage; S 0 After shutdown, the flyback circuit passes through the secondary first winding W 1 To resistor R 0 Transfer energy;

[0021] When the input voltage is relatively small, due to the switch tube S 0 When the duty cycle reaches the set maximum value and cannot continue to increase, so that it does not meet the output power requirement, the control circuit controls the DC-DC circuit according to the currently sampled output voltage; at this time, the secondary compensation winding W 2 The voltage on the compensation capacitor C a Voltage across the first diode D 1 Reverse cutoff, i w2 Keep it at 0; 0 -t 2 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy. w0 is increasing; in addition, 0 -t 1 ] The first switch tube S 1On, inductance L a Start storing energy, La Also increasing; [t 2 -t 4 ] period, the flyback transformer passes through the secondary first winding W 1 To resistor R 0 Provide energy; 1 -t 3 ] time period, if the DC-DC circuit adopts a buck circuit or a boost circuit or a buck-boost circuit, the compensation inductor L a Also to the resistor R 0 Provide energy to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter; if the DC-DC circuit adopts Cuk circuit, Sepic circuit or Zeta circuit, the first compensation inductor L a1 and the second compensation inductor L a2 To resistor R 0 Provide energy to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter.

[0022] Furthermore, the control circuit adopts a single-chip microcomputer minimum system circuit, and the single-chip microcomputer in the single-chip microcomputer minimum system circuit can be selected to include STM8 series or TI's C2000 series single-chip microcomputer.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention adds a compensation circuit on the basis of the flyback main circuit, thereby eliminating the input electrolytic capacitor, reducing the volume of the power adapter while maintaining low output ripple and increasing the power density of the power adapter.

[0025] (2) The present invention not only eliminates the input electrolytic capacitor that occupies a large volume in the traditional power adapter, promotes the development of high power density of the power adapter, but also ensures that the output voltage ripple can be maintained at a small level. At the same time, the semiconductor device in the compensation circuit only starts to work when the input voltage is too low to meet the output power, effectively reducing the switching loss and facilitating the improvement of the overall efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 4 is a topological diagram of a parallel auxiliary network in the prior art of an embodiment of the present invention.

[0027] Figure 2 FIG. 4 is a diagram of a multi-port output topology structure in the prior art of an embodiment of the present invention.

[0028] Figure 3This is a diagram of an integrated auxiliary network topology in the prior art of an embodiment of the present invention.

[0029] Figure 4 This is a topological diagram of a power adapter without input electrolytic capacitors and an additional compensation circuit according to an embodiment of the present invention.

[0030] Figure 5 It is a main working waveform diagram under the power frequency cycle of an embodiment of the present invention.

[0031] Figure 6 This is a main working wave diagram of the embodiment of the present invention in a switching cycle when the input power is sufficient.

[0032] Figure 7 It is a main working waveform diagram of the embodiment of the present invention in the switching cycle when the input power is insufficient.

[0033] Figure 8 FIG. 1 is a waveform diagram of input voltage of a conventional power adapter according to an embodiment of the present invention.

[0034] Fig. 9 FIG. 4 is a waveform diagram of an output voltage of a conventional power adapter according to an embodiment of the present invention.

[0035] Fig.10 This is an input voltage waveform diagram of a power adapter without input electrolytic capacitor and with an additional compensation circuit according to an embodiment of the present invention.

[0036] Fig.11 This is an output voltage waveform diagram of a power adapter without input electrolytic capacitors and with a compensation circuit added according to an embodiment of the present invention.

[0037] Fig.12 1 is a boost circuit diagram of an embodiment of the present invention.

[0038] Fig.13 FIG. 4 is a buck-boost circuit diagram of an embodiment of the present invention.

[0039] Fig.14 4 is a Cuk circuit diagram of an embodiment of the present invention.

[0040] Fig.15 4 is a Sepic circuit diagram of an embodiment of the present invention.

[0041] Fig.16 4 is a Zeta circuit diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0043] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0044] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0045] like Figure 4 As shown, this embodiment provides a power adapter, including a rectifier filter circuit, a flyback circuit, a compensation circuit and a control circuit; the rectifier filter circuit is connected to the flyback circuit, and the flyback circuit and the compensation circuit are both electrically connected to the control circuit; the flyback circuit is connected to the compensation circuit; the compensation circuit includes a secondary compensation winding W 2 , the first diode D 1 , compensation capacitor C a and DC-DC circuit; the secondary compensation winding W 2 One end of the first diode D 1 The anode connection of the secondary compensation winding W 2 The other end of the compensation capacitor C a and the DC-DC circuit, the first diode D 1 The cathode of the compensation capacitor C a The other end is connected to the DC-DC circuit; the DC-DC circuit is connected to the flyback circuit and the control circuit respectively; the first input capacitor C in1 and the second input capacitor C in2 Ceramic capacitors are used.

[0046] In this embodiment, the rectification and filtering circuit includes: a third diode D 3 , the fourth diode D 4 , the fifth diode D 5 , the sixth diode D 6 , the first inductor L 1 , the first resistor R 1 , the first input capacitor C in1 , the second input capacitor C in2 The flyback circuit includes a primary winding W 0 , switch tube S 0 , Secondary first winding W1 、Diode D 0 , capacitor C 0 and resistor R 0 One end of the external AC power supply is respectively connected to the third diode D 3 The anode of the fifth diode D 5 The cathode of the external AC power supply is connected to the cathode of the sixth diode D 6 The cathode of the fourth diode D 4 The anode of the third diode D 3 The cathode of the fourth diode D 4 The cathode of the first inductor L 1 one end and the first resistor R 1 One end of the first input capacitor C in1 One end of the first resistor R 1 One end of the first inductor L 1 The other end of the first resistor R 1 The other end and the second input capacitor C in2 One end of each primary winding W 0 The fifth diode D 5 The anode of the sixth diode D 6 The anode of the first input capacitor C in1 The other end of the second input capacitor C in2 The other end and the switch tube S 0 The source electrodes of the primary winding W are grounded; 0 The other end of the switch tube S 0 The drain of the switch tube S 0 The gate of the secondary side is electrically connected to the control circuit; the secondary side first winding W 1 One end of the diode D 0 The anode connection of the secondary first winding W 1 The other end of the capacitor C 0 One end of the resistor R 0 One end of the diode D is connected to the ground; 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other ends are connected to the DC-DC circuit.

[0047] like Figure 4 As shown, in this embodiment, the DC-DC circuit adopts a buck circuit, and the buck circuit includes a first switch tube S 1 , the second diode D 2 、Inductance La The first switch tube S 1 The drain of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the second diode D 2 The cathode and the inductor L a One end of the inductor L a The other end of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the second diode D 2 The anode of the secondary compensation winding W 2 The other end of the compensation capacitor C a and grounded.

[0048] like Fig.12 As shown, in this embodiment, the DC-DC circuit adopts a boost circuit, and the boost circuit includes a first switch tube S 1 , the second diode D 2 、Inductance L a The inductor L a One end of the switch tube S 1 The drain of the diode D 2 The anode of the switch tube S 1 The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the switch tube S is connected and grounded; 1 The gate of the inductor L is connected to the control circuit; a The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the second diode D 2 The cathode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0049] like Fig.13 As shown, in this embodiment, the DC-DC circuit adopts a buck-boost circuit; the buck-boost circuit includes a first switch tube S 1 , the second diode D 2 、Inductance La The first diode D 1 The cathode and the compensation capacitor C a The other end is connected to the first switch tube S 1 The drain of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the inductor L a One end of the second diode D 2 The cathode connection of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the inductor L a The other end of the second diode D is connected to the ground; 2 The anode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0050] like Fig.14 As shown, in this embodiment, the DC-DC circuit adopts a Cuk circuit; the Cuk circuit includes a first switch tube S 1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first compensation inductor L a1 One end of the first switch tube S 1 Drain, the first capacitor C 1 One end of the first capacitor C 1 The other end of the second diode D 2 The anode of the second compensation inductor L a2 The first compensation inductor L a1 The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate of the first switch tube S is connected to the control circuit; 1 The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the second diode D 2 The cathode of the second compensation inductor L is connected to the ground; a2 The other end of the diode D 0 The cathode of the capacitor C 0The other end of the resistor R 0 The other end of the connection.

[0051] like Fig.15 As shown, in this embodiment, the DC-DC circuit adopts a Sepic circuit; the Sepic circuit includes a first switch tube S 1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first compensation inductor L a1 One end of the first switch tube S 1 The drain of the first capacitor C 1 One end of the first capacitor C 1 The other end of the second compensation inductor L a2 One end and the second diode D 2 The anode connection of the first compensation inductor L a1 The other end of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The source of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end of the second compensation inductor L a2 The other end of the first switch tube S is connected to the ground; 1 The gate of the second diode D is connected to the control circuit; 2 The cathode of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0052] like Fig.16 As shown, in this embodiment, the Zeta circuit includes a first switch tube S 1 , the second diode D 2 , the first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C 1 The first switch tube S 1 The source is respectively connected to the first compensation inductor L a1 one end of the first capacitor C 1 One end of the first capacitor C 1 The other end of the second diode D 2 The cathode and the second compensation inductor L a2The first switch tube S 1 The drain of the first diode D 1 The cathode and the compensation capacitor C a The other end of the first switch tube S 1 The gate is connected to the control circuit; the second diode D 2 The anode of the secondary compensation winding W 2 The other end of the compensation capacitor C a One end and the first compensation inductor L a1 and grounded; the second compensation inductor L a2 The other end of the diode D 0 The cathode of the capacitor C 0 The other end of the resistor R 0 The other end of the connection.

[0053] Preferably, this embodiment provides a working method based on a power adapter, comprising: connecting the first input capacitor C in1 and the second input capacitor C in2 After that, the rectified input voltage becomes a 100Hz steamed bun wave, the minimum value is close to 0, and the voltage pulsation is large; let the output power remain unchanged, at [t 1 -t 2 ] time, the input current cannot reach infinity, so there is a problem of mismatch between input and output power in this time period. The compensation circuit added in this embodiment solves this problem well, such as Figure 5 As shown, in [t 1 -t 2 ] If the input energy is sufficient during the time period, the compensation winding W 2 For compensation capacitor C a Charging; at [t 3 -t 4 ] time period, the input energy is insufficient, the control circuit controls the switch tube S in the DC-DC circuit 1 , to the resistor R 0 Supplement the required energy to keep the power adapter having a stable output voltage; where t 1 <t 2 <t 3 <t 4 ;

[0054] When the switch S 0 When the duty cycle does not reach the maximum value and the input power can meet the output power requirement, the DC-DC circuit does not work and the first switch tube S 1 Keep off, i La Always 0; Figure 6As shown, in [t 0 -t 1 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy, namely the primary winding W 0 The current on the compensation capacitor C a Through the secondary compensation winding W 2 Start energy storage; S 0 After shutdown, the flyback circuit passes through the secondary first winding W 1 To resistor R 0 Transfer energy; the flyback transformer consists of a primary winding W 0 , Secondary first winding W 1 , secondary compensation winding W 2 And magnetic core.

[0055] When the input voltage is relatively small, due to the switch tube S 0 When the duty cycle reaches the set maximum value and cannot continue to increase, so that it does not meet the output power requirement, the control circuit controls the DC-DC circuit according to the currently sampled output voltage; at this time, the secondary compensation winding W 2 The voltage on the compensation capacitor C a Voltage across the first diode D 1 Reverse cutoff, i w2 Keep it at 0; Figure 7 As shown, in [t 0 -t 2 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy. w0 is increasing; in addition, 0 -t 1 ] The first switch tube S 1 On, inductance L a Start storing energy, La It is also increasing; 2 -t 4 ] period, the flyback transformer passes through the secondary first winding W 1 To resistor R 0 Provide energy; 1 -t 3 ] time period, if the DC-DC circuit adopts a buck circuit or a boost circuit or a buck-boost circuit, the compensation inductor L a Also to the resistor R 0 Provide energy to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter; if the DC-DC circuit adopts Cuk circuit, Sepic circuit or Zeta circuit, the first compensation inductor L a1 and the second compensation inductor L a2 To resistor R0 Provide energy to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter.

[0056] Preferably, in this embodiment, the flyback transformer is composed of a primary winding W 0 , secondary compensation winding W 2 and the secondary first winding W 1 composition.

[0057] In this embodiment, the control circuit adopts a single-chip microcomputer minimum system circuit, and the single-chip microcomputer in the single-chip microcomputer minimum system circuit can be selected to include STM8 series or TI's C2000 series single-chip microcomputer.

[0058] Preferably, the specific working principle of the power adapter of this embodiment is as follows:

[0059] The main circuit uses the flyback circuit commonly used in power adapters, and adds a compensation circuit to the flyback circuit, such as Figure 4 As shown. The compensation circuit consists of a compensation winding W 2 、Diode D 1 , compensation capacitor C a and a buck circuit, wherein the buck circuit can be replaced by other DC-DC circuits. Different from conventional power adapters, the input capacitor C in this embodiment in1 With C in2 Larger electrolytic capacitors can be replaced with ceramic capacitors, which greatly improves the overall power density of the power adapter. Figure 5 As shown in the figure, after the input capacitor is replaced by a ceramic capacitor with a smaller capacitance, the rectified input voltage becomes a 100Hz steamed bun wave, with the minimum value close to 0 and a large voltage ripple. Assuming that the output power is constant, at [t 1 -t 2 ], the input current cannot reach infinity, so there is a problem of mismatch between input and output power during this period. The compensation circuit added in the present invention solves this problem well. 1 -t 2 ] If the input energy is sufficient during the time period, the compensation winding W 2 For compensation capacitor C a Charging; at [t 3 -t 4 ] period, the input energy is insufficient, the control circuit controls the switch tube S in the buck circuit 1 , to the resistor R 0 Accurately replenish the required energy to maintain a stable output voltage of the power adapter. Since only a small amount of power flows through the compensation circuit, the inductor L can be guaranteed. a , switch tube S1 、Diode D 1 With D 2 It only occupies a small volume, thus achieving high power density of the power adapter.

[0060] When the input voltage is large enough to meet the output power requirement, the buck circuit does not work, S 1 Keep off, i La Always 0. Figure 6 As shown, in [t 0 -t 1 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy, and the winding W 0 The current on the compensation capacitor C a Through the winding W 2 Start storing energy. 0 After shutdown, the flyback converter passes winding W 1 To resistor R 0 Transfer energy.

[0061] When the input voltage is relatively small and does not meet the output power requirement due to the limitation of duty cycle, the control circuit controls the buck circuit according to the currently sampled output voltage. 2 The voltage on the diode D is small. 1 Reverse cutoff, i w2 Keep it at 0. Figure 7 As shown, in [t 0 -t 2 ] During the time period, the switch tube S 0 The flyback transformer starts to store energy. w0 In addition, in [t 0 -t 1 Internal switch tube S 1 On, inductance L a Start storing energy, La It is also increasing. 2 -t 4 ] period, the flyback transformer passes winding W 1 To resistor R 0 Provide energy. 1 -t 3 ] period, the compensation inductor also flows to the resistor R 0 Provide energy to make up for the insufficient input power at this time, thereby ensuring the stability of the output voltage of the power adapter.

[0062] Preferably, in this embodiment, the specific examples are as follows:

[0063] Example 1: The input voltage of the flyback power adapter is 90VAC, the output power is 60W (20V / 3A), and the switching frequency is 50kHz. The input capacitor is replaced by a 27uF+18uF+27uF, 400V withstand voltage electrolytic capacitor with a 2×2.2uF, 400V withstand voltage ceramic capacitor. The output capacitor is 2×680uF, 25V withstand voltage unchanged.

[0064] The input capacitor is 27uF+18uF+27uF, 400V withstand voltage electrolytic capacitor, and without compensation circuit, the input voltage waveform obtained by Simulink simulation is as follows Figure 8 As shown, the output voltage is Fig. 9 shown.

[0065] The input capacitor is a 2×2.2uF, 400V withstand voltage ceramic capacitor. When a compensation circuit is added, the input voltage waveform obtained by Simulink simulation is as follows: Fig.10 As shown, the output voltage is Fig.11 As shown in the waveform diagram, after eliminating the input electrolytic capacitor, the input voltage fluctuation range after rectification is larger, while the output voltage ripple is only 136.3mV, which meets the output ripple requirement.

[0066] Preferably, in this embodiment, the buck circuit in the gray box of the compensation circuit can be replaced by a boost, buck-boost, Cuk, Sepic, or Zeta circuit to achieve the same effect.

[0067] The power adapter circuit structure of this embodiment not only eliminates the input electrolytic capacitor that occupies a large volume in the traditional power adapter, promotes the high power density development of the power adapter, but also ensures that the output voltage ripple can be maintained at a small level. At the same time, the semiconductor devices in the compensation circuit of this method only start to work when the input voltage is too low to meet the output power, effectively reducing the switching loss and facilitating the improvement of the overall efficiency. The power adapter circuit structure has great practical engineering significance.

[0068] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A power adapter, characterized in that: The invention comprises a rectifier filter circuit, a flyback circuit, a compensation circuit and a control circuit; the rectifier filter circuit is connected to the flyback circuit, and the flyback circuit and the compensation circuit are both electrically connected to the control circuit; the flyback circuit is connected to the compensation circuit; the compensation circuit comprises a secondary compensation winding W2, a first diode D1, a compensation capacitor C a and a DC-DC circuit; one end of the secondary compensation winding W2 is connected to the anode of the first diode D1, and the other end of the secondary compensation winding W2 is connected to the compensation capacitor C a and the DC-DC circuit, the cathode of the first diode D1 is respectively connected to the compensation capacitor C a The other end is connected to the DC-DC circuit; The DC-DC circuit is connected to the flyback circuit and the control circuit respectively; The rectifying and filtering circuit includes: a third diode D3, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first inductor L1, a first resistor R1, a first input capacitor C in1 , the second input capacitor C in2 The flyback circuit includes a primary winding W0, a switch tube S0, a secondary first winding W1, a diode D0, a capacitor C0 and a resistor R0; one end of the external AC power supply is respectively connected to the anode of the third diode D3 and the cathode of the fifth diode D5, and the other end of the external AC power supply is respectively connected to the cathode of the sixth diode D6 and the anode of the fourth diode D4; the cathode of the third diode D3 and the cathode of the fourth diode D4 are both connected to one end of the first inductor L1 and one end of the first resistor R1; the first input capacitor C in1 One end of the first inductor L1 is connected to one end of the first resistor R1; the other end of the first inductor L1, the other end of the first resistor R1 and the second input capacitor C in2 One end of each of the first input capacitor C is connected to one end of the primary winding W0; the anode of the fifth diode D5, the anode of the sixth diode D6, and the first input capacitor C in1 The other end of the second input capacitor C in2 The other end of the primary winding W0 and the source of the switch tube S0 are both grounded; the other end of the primary winding W0 is connected to the drain of the switch tube S0; the gate of the switch tube S0 is electrically connected to the control circuit; one end of the secondary first winding W1 is connected to the anode of the diode D0; the other end of the secondary first winding W1 is connected to one end of the capacitor C0 and one end of the resistor R0, and is grounded; the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0 are all connected to the DC-DC circuit; the first input capacitor C in1 and the second input capacitor C in2 Ceramic capacitors are used; The DC-DC circuit adopts a buck circuit, which includes a first switch tube S1, a second diode D2, an inductor L a The drain of the first switch tube S1, the cathode of the first diode D1 and the compensation capacitor C a The gate of the first switch tube S1 is connected to the control circuit; the source of the first switch tube S1 is connected to the cathode of the second diode D2 and one end of the inductor La; the inductor L a The other end of the second diode D2 is connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0; the anode of the second diode D2 is connected to the other end of the secondary compensation winding W2 and the compensation capacitor C a and grounded.

2. A power adapter according to claim 1, characterized in that: The DC-DC circuit adopts a boost circuit, which includes a first switch tube S1, a second diode D2, and an inductor L a The inductor L a One end of the switch tube S1 is connected to the drain of the switch tube S1 and the anode of the diode D2; the source of the switch tube S1 is connected to the other end of the secondary compensation winding W2 and the compensation capacitor C a and grounded; the gate of the switch tube S1 is connected to the control circuit; the inductor L a The other end is connected to the cathode of the first diode D1 and the compensation capacitor C a the cathode of the second diode D2 is connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0.

3. A power adapter according to claim 1, characterized in that: The DC-DC circuit adopts a buck-boost circuit; the buck-boost circuit includes a first switch tube S1, a second diode D2, an inductor L a The cathode of the first diode D1 and the compensation capacitor C a The other end of each of the first switch tube S1 is connected to the drain of the first switch tube S1; the gate of the first switch tube S1 is connected to the control circuit; the source of the first switch tube S1 is connected to the inductor L a The other end of the secondary compensation winding W2 is connected to the cathode of the second diode D2; the other end of the secondary compensation winding W2 is connected to the compensation capacitor C a One end of the inductor L a the other end of the capacitor C0 and the other end of the resistor R0 are connected; the anode of the second diode D2 is connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0.

4. A power adapter according to claim 1, characterized in that: The DC-DC circuit adopts a Cuk circuit; the Cuk circuit includes a first switch tube S1, a second diode D2, a first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C1; the first compensation inductor L a1 One end of the first switch tube S1 is connected to the drain and one end of the first capacitor C1; the other end of the first capacitor C1 is connected to the anode of the second diode D2 and the second compensation inductor L a2 The first compensation inductor L a1 The other end is connected to the cathode of the first diode D1 and the compensation capacitor C a The gate of the first switch tube S1 is connected to the control circuit; the source of the first switch tube S1 is respectively connected to the other end of the secondary compensation winding W2 and the compensation capacitor C a The cathode of the second diode D2 is connected to the ground; the second compensation inductor L a2 The other end of is respectively connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0.

5. The power adapter according to claim 1, characterized in that: The DC-DC circuit adopts a Sepic circuit; the Sepic circuit includes a first switch tube S1, a second diode D2, a first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C1; the first compensation inductor L a1 One end of the first switch tube S1 is connected to the drain of the first switch tube S1 and one end of the first capacitor C1; the other end of the first capacitor C1 is connected to the second compensation inductor L a2 One end of the first compensation inductor L is connected to the anode of the second diode D2; a1 The other end is connected to the cathode of the first diode D1 and the compensation capacitor C a The source of the first switch tube S1 is respectively connected to the other end of the secondary compensation winding W2 and the compensation capacitor C a One end of the second compensation inductor L a2 The other end of the first switch tube S1 is connected to the control circuit; the cathode of the second diode D2 is connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0.

6. A power adapter according to claim 1, characterized in that: The DC-DC circuit adopts a Zeta circuit; the Zeta a The circuit includes a first switch tube S1, a second diode D2, a first compensation inductor L a1 , the second compensation inductor L a2 and the first capacitor C1; the source of the first switch tube S1 is respectively connected to the first compensation inductor L a1 and one end of the first capacitor C1; the other end of the first capacitor C1 is connected to the cathode of the second diode D2 and the second compensation inductor L a2 The drain of the first switch tube S1 is connected to the cathode of the first diode D1 and the compensation capacitor C a The gate of the first switch tube S1 is connected to the control circuit; the anode of the second diode D2 is respectively connected to the other end of the secondary compensation winding W2 and the compensation capacitor C a One end and the first compensation inductor L a1 and grounded; the second compensation inductor L a2 The other end of is respectively connected to the cathode of the diode D0, the other end of the capacitor C0, and the other end of the resistor R0.

7. A working method of the power adapter according to any one of claims 1 to 6, characterized in that: Connect the first input capacitor C in1 and the second input capacitor C in2 After that, the rectified input voltage becomes a 100Hz steamed bun wave, with the minimum value close to 0 and large voltage pulsation; let the output power remain unchanged, and the input energy is sufficient during the time period [t1-t2], then the compensation capacitor C is compensated through the secondary compensation winding W2. a charging; if the input energy is insufficient during the time period [t3-t4], the control circuit controls the first switch tube S1 in the DC-DC circuit to supplement the required energy to the resistor R0 to maintain the power adapter to have a stable output voltage; wherein, t1 <t2<t3<t4; When the duty cycle of the switch tube S0 does not reach the maximum value and the input power can meet the output power requirement, the DC-DC circuit does not work, and the first switch tube S1 remains off. La Always 0; in the [t0-t1] time period, the switch tube S0 is turned on, the flyback transformer starts to store energy, that is, the current on the primary winding W0 continues to increase, and the compensation capacitor C a Energy storage starts through the secondary compensation winding W2; after S0 is turned off, the flyback circuit transfers energy to the resistor R0 through the secondary first winding W1; When the input voltage is relatively small, that is, because the duty cycle of the switch tube S0 reaches the set maximum value and cannot continue to increase, so that it does not meet the output power requirement, the control circuit controls the DC-DC circuit according to the currently sampled output voltage; at this time, the voltage on the secondary compensation winding W2 is less than the compensation capacitor C a The voltage across both ends, the first diode D1 is reverse cutoff, i w2 Keep at 0; in the period [t0-t2], the switch tube S0 is turned on, and the flyback transformer starts to store energy, i w0 In addition, during [t0-t1], the first switch S1 is turned on, and the inductor L a Start storing energy, La Also increases continuously; During the time period [t2-t4], the flyback transformer provides energy to the resistor R0 through the secondary first winding W1; During the time period [t1-t3], if the DC-DC circuit adopts a buck circuit or a boost circuit or a buck-boost circuit, the compensation inductor L a It also provides energy to the resistor R0 to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter; if the DC-DC circuit adopts the Cuk circuit, Sepic circuit or Zeta circuit, the first compensation inductor L a1 and the second compensation inductor L a2 Provide energy to the resistor R0 to supplement the insufficient input power at this time to ensure the stability of the output voltage of the power adapter.

8. The working method of a power adapter according to claim 7, characterized in that: The control circuit adopts a single-chip microcomputer minimum system circuit, and the single-chip microcomputer in the single-chip microcomputer minimum system circuit can be selected to include STM8 series or TI's C2000 series single-chip microcomputer.

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