An adapter circuit

Abstract

The utility model discloses an adapter circuit, comprising an input rectifying and filtering circuit, a first absorption circuit, a high-frequency transformer, a PWM control circuit and an output rectifying and filtering circuit. The high-frequency transformer comprises a primary winding, an auxiliary winding, a shielding layer and a secondary winding which are wound in sequence from bottom to top. The primary winding starts from the second pin of the high-frequency transformer and is wound at the first pin of the high-frequency transformer. The auxiliary winding starts from the fifth pin of the high-frequency transformer and is wound at the fourth pin of the high-frequency transformer. The shielding layer starts from the fourth pin of the high-frequency transformer and is wound in a suspended manner. The secondary winding starts from the ninth pin of the high-frequency transformer and is wound at the sixth pin of the high-frequency transformer. The input end of the input rectifying and filtering circuit is connected to the AC input end of the mains power. The output end of the input rectifying and filtering circuit is connected to the primary winding after passing through the first absorption circuit. The auxiliary winding is connected to the PWM control circuit. The secondary winding is connected to the DC output end after passing through the output rectifying and filtering circuit.

Description

Technical Field

[0001] The utility model relates to the technical field of power adapters, in particular to an adapter circuit. Background Art

[0002] Traditional power adapters all use Y capacitors connected between the primary and secondary grounds to filter out EMI (Electromagnetic Interference). However, the leakage current of the adapter including the Y capacitor is relatively large and cannot meet the needs of products requiring a smaller leakage current. Therefore, the adapter including the Y capacitor is not suitable for products requiring a smaller leakage current. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide an adapter circuit which can filter out EMI without arranging a Y capacitor connected between the primary and secondary grounds in the adapter.

[0004] In order to solve the above technical problems, the purpose of the utility model is achieved through the following technical solutions: an adapter circuit is provided, including an input rectifier filter circuit, a first absorption circuit, a high-frequency transformer, a PWM control circuit and an output rectifier filter circuit, the high-frequency transformer includes a primary winding, an auxiliary winding, a shielding layer and a secondary winding wound in sequence from bottom to top, the primary winding of the high-frequency transformer starts from the second pin of the high-frequency transformer and winds up at the first pin of the high-frequency transformer, the auxiliary winding of the high-frequency transformer starts from the fifth pin of the high-frequency transformer and winds up at the fifth pin of the high-frequency transformer Four pins, the shielding layer of the high-frequency transformer starts from the fourth pin of the high-frequency transformer and is wound up and suspended, the secondary winding of the high-frequency transformer starts from the ninth pin of the high-frequency transformer and is wound up at the sixth pin of the high-frequency transformer; the input end of the input rectifier and filter circuit is connected to the AC input end of the mains, the output end of the input rectifier and filter circuit is connected to the primary winding of the high-frequency transformer after passing through the first absorption circuit, the auxiliary winding of the high-frequency transformer is connected to the PWM control circuit, and the secondary winding of the high-frequency transformer is connected to the DC output end after passing through the output rectifier and filter circuit.

[0005] The beneficial technical effect of the utility model is that: the adapter circuit of the utility model is provided with a high-frequency transformer including a primary winding, an auxiliary winding, a shielding layer and a secondary winding which are wound sequentially from bottom to top, and the primary winding starts from the second pin of the high-frequency transformer and is wound at the first pin of the high-frequency transformer, the auxiliary winding starts from the fifth pin of the high-frequency transformer and is wound at the fourth pin of the high-frequency transformer, the shielding layer starts from the fourth pin of the high-frequency transformer and is wound in the air, and the secondary winding starts from the ninth pin of the high-frequency transformer and is wound at the sixth pin of the high-frequency transformer, so that distributed capacitance is generated between the primary winding, the auxiliary winding and the secondary winding, thereby achieving The function of the Y capacitor is to significantly reduce the common mode current, thereby suppressing EMI interference, so that the power adapter can pass the EMI test without using the Y capacitor, reducing the generation of leakage current, and is suitable for products that require a smaller leakage current. In addition, by setting a first absorption circuit in the adapter circuit, and the first absorption circuit is electrically connected between the input rectification and filtering circuit and the primary winding of the high-frequency transformer, the leakage inductance energy of the high-frequency transformer can be absorbed, and the influence of the leakage inductance energy on the PWM control circuit connected to the auxiliary winding of the high-frequency transformer can be reduced. The PWM control circuit can be used to control the accuracy of the output voltage, and in conjunction with the output rectification and filtering circuit, the interference of the output voltage can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0007] Figure 1 A schematic diagram of a framework of an adapter circuit provided by an embodiment of the utility model;

[0008] Figure 2 A circuit schematic diagram of an adapter circuit provided by an embodiment of the utility model;

[0009] Figure 3 A schematic diagram of a high-frequency transformer of an adapter circuit provided by an embodiment of the utility model;

[0010] Figure 4 This is a structural diagram of a high-frequency transformer of an adapter circuit provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0012] See also Figures 1 to 4 , Figure 1 The schematic diagram of the framework of the adapter circuit provided by the embodiment of the utility model, the adapter circuit 10 includes an input rectifier filter circuit 11, a first absorption circuit 12, a high-frequency transformer T1, a PWM control circuit 13 and an output rectifier filter circuit 14, the high-frequency transformer T1 includes a primary part and a secondary part, the primary part includes a first pin 1, a second pin 2, a fourth pin 4 and a fifth pin 5 of the high-frequency transformer T1, the secondary part includes a ninth pin 9 and a sixth pin 6 of the high-frequency transformer T1, the high-frequency transformer T1 includes a primary winding N1, an auxiliary winding N2, a shielding layer N3 and a secondary winding N4 wound sequentially from bottom to top, the primary winding N1 of the high-frequency transformer T1 starts from the second pin 2 of the high-frequency transformer T1 and winds up at the first pin 1 of the high-frequency transformer T1, the auxiliary winding N2 of the high-frequency transformer T1 starts from the first pin 1 of the high-frequency transformer T1, and the shielding layer N3 and the secondary winding N4 of the high-frequency transformer T1 are wound sequentially from bottom to top. The fifth pin 5 is wound around the fourth pin 4 of the high-frequency transformer T1, the shielding layer N3 of the high-frequency transformer T1 starts from the fourth pin 4 of the high-frequency transformer T1 and is wound around and suspended, then the second end of the shielding layer N3 of the high-frequency transformer T1 is suspended, the secondary winding N4 of the high-frequency transformer T1 starts from the ninth pin 9 of the high-frequency transformer T1 and is wound around the sixth pin 6 of the high-frequency transformer T1; the input end of the input rectifying and filtering circuit 11 is connected to the AC input end AC_INPUT of the mains, the output end of the input rectifying and filtering circuit 11 is connected to the primary winding N1 of the high-frequency transformer T1 after passing through the first absorption circuit 12, the auxiliary winding N2 of the high-frequency transformer T1 is connected to the PWM control circuit 13, and the secondary winding N4 of the high-frequency transformer T1 is connected to the DC output end DC_Output after passing through the output rectifying and filtering circuit 14.

[0013] The winding methods of the primary winding N1, the auxiliary winding N2, the shielding layer N3 and the secondary winding N4 are all forward dense winding. The second pin 2, the fifth pin 5 and the ninth pin 9 of the high-frequency transformer T1 are the same-name terminals. The adapter circuit 10 is provided with a high-frequency transformer T1 including a primary winding N1, an auxiliary winding N2, a shielding layer N3 and a secondary winding N4 wound in sequence from bottom to top, and the primary winding N1 starts from the second pin 2 of the high-frequency transformer T1 and winds up at the first pin 1 of the high-frequency transformer T1, the auxiliary winding N2 starts from the fifth pin 5 of the high-frequency transformer T1 and winds up at the fourth pin 4 of the high-frequency transformer T1, the shielding layer N3 starts from the fourth pin 4 of the high-frequency transformer T1 and winds up in the air, and the secondary winding N4 starts from the ninth pin 9 of the high-frequency transformer T1 and winds up at the sixth pin 6 of the high-frequency transformer T1, so that distributed capacitance is generated between the primary winding N1, the auxiliary winding N2 and the secondary winding N4. The function of the Y capacitor is realized, and the common mode current is significantly reduced, thereby suppressing EMI interference, so that the power adapter can pass the EMI test without using the Y capacitor, reducing the generation of leakage current, and is suitable for products that require a smaller leakage current. In addition, by setting the first absorption circuit 12 in the adapter circuit 10, and the first absorption circuit 12 is electrically connected between the input rectification and filtering circuit 11 and the primary winding N1 of the high-frequency transformer T1, the leakage inductance energy of the high-frequency transformer T1 can be absorbed, and the influence of the leakage inductance energy on the PWM control circuit 13 connected to the auxiliary winding N2 of the high-frequency transformer T1 can be reduced. The PWM control circuit 13 can be used to control the accuracy of the output voltage, and in conjunction with the output rectification and filtering circuit 14, the interference of the output voltage can be reduced.

[0014] Specifically, in this embodiment, two insulating layers are provided between the primary winding N1 of the high-frequency transformer T1 and the auxiliary winding N2 of the high-frequency transformer T1, between the auxiliary winding N2 of the high-frequency transformer T1 and the shielding layer N3 of the high-frequency transformer T1, between the shielding layer N3 of the high-frequency transformer T1 and the secondary winding N4 of the high-frequency transformer T1, and outside the secondary winding N4 of the high-frequency transformer T1.

[0015] Specifically, in this embodiment, the insulating layer is a Mylar tape. The second insulating layer can be two Mylar tapes stacked together.

[0016] Specifically, in this embodiment, Figure 4As shown, the primary winding N1 of the high-frequency transformer T1 is densely wound in two layers on the frame of the high-frequency transformer T1, the auxiliary winding N2 of the high-frequency transformer T1 is densely wound in one layer on the frame of the high-frequency transformer T1, the shielding layer N3 of the high-frequency transformer T1 is densely wound at the upper end of the frame of the high-frequency transformer T1, and the secondary winding N4 of the high-frequency transformer T1 is densely wound in one layer on the frame of the high-frequency transformer T1. After the shielding layer N3 is wound, the tail wire NC wire is hung at the top bump position and cut off. Figure 4 The middle black dot indicates the starting position of the winding.

[0017] Specifically, in the present embodiment, the first absorption circuit 12 includes a first resistor R1, a first capacitor C1, a first connecting capacitor C1A, a second resistor R2 and a first diode D1, the first capacitor C1, the first connecting capacitor C1A, the second resistor R2 and the first diode D1 are connected in series in sequence, one end of the first resistor R1 and the first end of the first capacitor C1 are both connected to the output end of the input rectifier and filter circuit 11 and the first pin 1 of the high-frequency transformer T1, the second end of the first capacitor C1 is connected to the first end of the first connecting capacitor C1A, the second end of the first connecting capacitor C1A and the other end of the first resistor R1 are both connected to one end of the second resistor R2, the other end of the second resistor R2 is connected to the cathode of the first diode D1, and the anode of the first diode D1 is connected to the PWM control circuit 13 and the second pin 2 of the high-frequency transformer T1.

[0018] Specifically, in this embodiment, the PWM control circuit 13 includes a PWM chip U1, a drain pin DRAIN of the PWM chip U1 is connected to the anode of the first diode D1 and the second pin 2 of the high-frequency transformer T1, a fifth pin 5 of the high-frequency transformer T1 is connected to a fourth resistor R4 and a fifth resistor R5 connected in series in sequence, and an input pin INV of the PWM chip U1 is electrically connected between the fourth resistor R4 and the fifth resistor R5, and is used to detect a voltage change of an auxiliary winding N2 of the high-frequency transformer T1, so as to adjust the conduction of the high-voltage MOS tube built into the PWM chip U1. The output voltage is kept stable for a certain period of time. One end of the fifth resistor R5 is connected to the fourth resistor R4. The other end of the fifth resistor R5 is connected to one end of the seventh resistor R7, one end of the eighth resistor R8 and the ground. The other end of the seventh resistor R7 and the other end of the eighth resistor R8 are both connected to the current detection pin CS of the PWM chip U1. One end of the seventh resistor R7 and one end of the eighth resistor R8 are both grounded. The seventh resistor R7 and the eighth resistor R8 are connected in parallel. The voltage changes on the seventh resistor R7 and the eighth resistor R8 can be detected through the current detection pin CS to limit the maximum output current. Among them, the PWM chip U1 is built with a high-voltage MOS tube, which can control the high-frequency transformer T1 to switch between energy storage and energy transfer in the high-frequency on and off state. The first absorption circuit 12 absorbs the leakage inductance energy of the high-frequency transformer T1, which can reduce the voltage stress of the voltage difference VDS between the drain and the gate of the high-voltage MOS tube built in the PWM chip U1, and avoid the overvoltage breakdown of the high-voltage MOS tube built in the PWM chip U1.

[0019] Specifically, in this embodiment, the fifth pin 5 of the high-frequency transformer T1 is connected to the digital power pin VDD of the PWM chip U1 through the second diode D2 and the third resistor R3, and a third polarity capacitor EC3 with a negative electrode grounded is electrically connected between the third resistor R3 and the digital power pin VDD of the PWM chip U1. The fifth pin 5 of the high-frequency transformer T1 is connected to one end of the fourth resistor R4 and the anode of the second diode D2, the cathode of the second diode D2 is connected to the positive electrode of the third polarity capacitor EC3 and the digital power pin VDD of the PWM chip U1 through the third resistor R3, and the other end of the fourth resistor R4 is connected to one end of the fifth resistor R5, the sixth grounding resistor R6, the second grounding capacitor C2 and the input pin INV of the PWM chip U1.

[0020] Specifically, in this embodiment, the fifth pin 5 of the high-frequency transformer T1 is connected to the sixth capacitor C6, the seventh capacitor C7 and the eleventh resistor R11 which are connected in series in sequence, and one end of the eleventh resistor R11 and the fourth pin 4 of the high-frequency transformer T1 are both grounded, so as to form an RC absorption circuit of the auxiliary winding N2 through the sixth capacitor C6, the seventh capacitor C7 and the eleventh resistor R11.

[0021] Specifically, in this embodiment, the output rectifier and filter circuit 14 includes a fourth diode D4, a third capacitor C3, a third connection capacitor C3A, a tenth resistor R10 and a fourth polarity capacitor EC4, the third capacitor C3, the third connection capacitor C3A and the tenth resistor R10 are connected in series in sequence, the third capacitor C3, the third connection capacitor C3A and the tenth resistor R10 constitute an RC absorption circuit of the fourth diode D4, the ninth pin 9 of the high-frequency transformer T1 is connected to the anode of the fourth diode D4 and the first end of the third capacitor C3, the second end of the third capacitor C3 is connected to the first end of the third connection capacitor C3A, the second end of the third connection capacitor C3A is connected to one end of the tenth resistor R10, the other end of the tenth resistor R10 and the cathode of the fourth diode D4 are connected to the positive electrode V+ of the DC output terminal DC_Output, and the negative electrode V- of the DC output terminal DC_Output and the sixth pin 6 of the high-frequency transformer T1 are grounded.

[0022] Specifically, in this embodiment, the magnetic core of the high-frequency transformer T1 is connected to the fourth pin 4 of the high-frequency transformer T1. The magnetic core of the high-frequency transformer T1 is grounded, and double-conducting self-adhesive copper foil needs to be attached to the corner of the magnetic core.

[0023] In summary, the adapter circuit of the utility model is provided with a high-frequency transformer including a primary winding, an auxiliary winding, a shielding layer and a secondary winding which are wound sequentially from bottom to top, and the primary winding starts from the second pin of the high-frequency transformer and is wound at the first pin of the high-frequency transformer, the auxiliary winding starts from the fifth pin of the high-frequency transformer and is wound at the fourth pin of the high-frequency transformer, the shielding layer starts from the fourth pin of the high-frequency transformer and is wound in the air, and the secondary winding starts from the ninth pin of the high-frequency transformer and is wound at the sixth pin of the high-frequency transformer, so that distributed capacitance is generated between the primary winding, the auxiliary winding and the secondary winding, and the function of the Y capacitor is realized. The common mode current is significantly reduced, thereby suppressing EMI interference, so that the power adapter can pass the EMI test without using a Y capacitor, reducing the generation of leakage current, and is suitable for products that require a smaller leakage current. In addition, by setting a first absorption circuit in the adapter circuit, and the first absorption circuit is electrically connected between the input rectification and filtering circuit and the primary winding of the high-frequency transformer, the leakage inductance energy of the high-frequency transformer can be absorbed, and the influence of the leakage inductance energy on the PWM control circuit connected to the auxiliary winding of the high-frequency transformer can be reduced. The PWM control circuit can be used to control the accuracy of the output voltage, and the output voltage interference can be reduced in conjunction with the output rectification and filtering circuit.

[0024] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. An adapter circuit, characterized in that: The invention comprises an input rectifying and filtering circuit, a first absorption circuit, a high-frequency transformer, a PWM control circuit and an output rectifying and filtering circuit. The high-frequency transformer comprises a primary winding, an auxiliary winding, a shielding layer and a secondary winding which are wound in sequence from bottom to top. The primary winding of the high-frequency transformer starts from the second pin of the high-frequency transformer and winds up at the first pin of the high-frequency transformer. The auxiliary winding of the high-frequency transformer starts from the fifth pin of the high-frequency transformer and winds up at the fourth pin of the high-frequency transformer. The shielding layer of the high-frequency transformer starts from the fourth pin of the high-frequency transformer and winds up in the air. The secondary winding of the high-frequency transformer starts from the ninth pin of the high-frequency transformer and winds up at the sixth pin of the high-frequency transformer. The input end of the input rectifying and filtering circuit is connected to the AC input end of the mains power. The output end of the input rectifying and filtering circuit is connected to the primary winding of the high-frequency transformer after passing through the first absorption circuit. The auxiliary winding of the high-frequency transformer is connected to the PWM control circuit. The secondary winding of the high-frequency transformer is connected to the DC output end after passing through the output rectifying and filtering circuit.

2. The adapter circuit according to claim 1, characterized in that: Two insulating layers are provided between the primary winding of the high-frequency transformer and the auxiliary winding of the high-frequency transformer, between the auxiliary winding of the high-frequency transformer and the shielding layer of the high-frequency transformer, between the shielding layer of the high-frequency transformer and the secondary winding of the high-frequency transformer, and outside the secondary winding of the high-frequency transformer.

3. The adapter circuit according to claim 2, characterized in that: The insulating layer is a Mylar tape.

4. The adapter circuit according to claim 1, characterized in that: The primary winding of the high-frequency transformer is densely wound in two layers on the skeleton of the high-frequency transformer, the auxiliary winding of the high-frequency transformer is densely wound in one layer on the skeleton of the high-frequency transformer, and the secondary winding of the high-frequency transformer is densely wound in one layer on the skeleton of the high-frequency transformer.

5. The adapter circuit according to claim 1, characterized in that: The first absorption circuit includes a first resistor, a first capacitor, a first connecting capacitor, a second resistor and a first diode. The first capacitor, the first connecting capacitor, the second resistor and the first diode are connected in series in sequence. One end of the first resistor and the first end of the first capacitor are both connected to the output end of the input rectifier and filter circuit and the first pin of the high-frequency transformer. The second end of the first capacitor is connected to the first end of the first connecting capacitor. The second end of the first connecting capacitor and the other end of the first resistor are both connected to one end of the second resistor. The other end of the second resistor is connected to the cathode of the first diode. The anode of the first diode is connected to the PWM control circuit and the second pin of the high-frequency transformer.

6. The adapter circuit according to claim 5, characterized in that: The PWM control circuit includes a PWM chip, a drain pin of the PWM chip is connected to the anode of the first diode and the second pin of the high-frequency transformer, a fifth pin of the high-frequency transformer is connected to a fourth resistor and a fifth resistor connected in series in sequence, an input pin of the PWM chip is electrically connected between the fourth resistor and the fifth resistor, one end of the fifth resistor is connected to the fourth resistor, the other end of the fifth resistor is connected to one end of the seventh resistor, one end of the eighth resistor and ground, the other end of the seventh resistor and the other end of the eighth resistor are both connected to the current detection pin of the PWM chip, and one end of the seventh resistor and one end of the eighth resistor are both grounded.

7. The adapter circuit according to claim 6, characterized in that: The fifth pin of the high-frequency transformer is connected to the digital power pin of the PWM chip via the second diode and the third resistor, and a third polarity capacitor with a negative electrode grounded is electrically connected between the third resistor and the digital power pin of the PWM chip.

8. The adapter circuit according to claim 1, characterized in that: The fifth pin of the high-frequency transformer is connected to a sixth capacitor, a seventh capacitor and an eleventh resistor which are connected in series in sequence, and one end of the eleventh resistor and the fourth pin of the high-frequency transformer are both grounded.

9. The adapter circuit according to claim 1, characterized in that: The output rectification and filtering circuit includes a fourth diode, a third capacitor, a third connection capacitor, a tenth resistor and a fourth polarity capacitor. The third capacitor, the third connection capacitor and the tenth resistor are connected in series in sequence. The ninth pin of the high-frequency transformer is connected to the anode of the fourth diode and the first end of the third capacitor. The second end of the third capacitor is connected to the first end of the third connection capacitor. The second end of the third connection capacitor is connected to one end of the tenth resistor. The other end of the tenth resistor and the cathode of the fourth diode are connected to the positive electrode of the DC output end. The negative electrode of the DC output end and the sixth pin of the high-frequency transformer are grounded.

10. The adapter circuit according to claim 1, characterized in that The magnetic core of the high-frequency transformer is connected to the fourth pin of the high-frequency transformer.

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