CN107147093A - Anti-lightning circuit applied in high-power power adapter and the power adapter - Google Patents

Abstract

An anti-lightning circuit which can resist lightning surge and has no current leakage and is composed of lower-cost separating elements and applied to a high-power adapter and the power adapter. The circuit module is composed of low-cost separation elements arranged between the power input end and the rectification circuit and can replace a lightning surge resistant circuit module with a Y capacitor function, and the circuit module is composed of a lightning protection fuse, a piezoresistor, a thermistor, an X capacitor, a plurality of resistors and a common mode inductor. The anti-lightning circuit can not only resist the interference of 4kV lightning surge to a power adapter provided with the circuit and avoid other elements in the adapter from being punctured and damaged, but also can replace a Y capacitor to prevent current leakage and ensure the normal work of the power adapter. The power adapter adopting the circuit module can pass the energy efficiency certification of the California energy efficiency level six and the European Union energy efficiency level six, the energy conversion efficiency can reach 87%, and accordingly, the allowance of the power module of the adapter is correspondingly expanded.

Description

Anti-lightning circuit applied in high-power power adapter and the power adapter

technical field

The invention relates to a control circuit in a high-power power adapter, in particular to an anti-lightning circuit capable of resisting 4kV lightning surge and EMI interference and a power adapter using the anti-lightning circuit.

Background technique

Power adapters are widely used in people's lives, from mobile devices, small household appliances to communication equipment, which can convert AC power into DC power and provide safe and stable DC output to power supply equipment (such as mobile terminals, portable speakers, etc.).

When the user goes out with the power adapter and enters a harsh environment, a high-altitude lightning-prone area, or an area without lightning protection devices to charge the electrical device, the sudden lightning will generate an instantaneous voltage on the mains transmission line Or current spikes (that is, surge currents), the voltage or current spikes will generate strong common-mode noise in the power adapter, thus, it is very likely to cause damage to the power adapter.

As people have higher and higher requirements on the power supply of electrical equipment, in order to ensure normal and stable power supply, Y capacitors are set between the primary and ground terminals of the transformer of the power adapter in the prior art, but this setting has the following disadvantages:

1) The Y capacitor will interfere with the related communication equipment connected to the power adapter. The principle is: the Y capacitor will couple part of the common-mode noise interference generated by the primary winding of the transformer to the secondary winding, and connect to the secondary winding The data transmission channel is coupled to the relevant terminal equipment, resulting in data transmission distortion.

2) The Y capacitor will cause current leakage, causing potential safety hazards.

In addition, the existing 18W power adapter (such as 12V1.5A or 12V2A) needs to add gas discharge tubes, TVS tubes and other devices to pass the lightning strike 4KV test, and the gas discharge tubes and TVS tubes are high in cost and bulky, and they are not suitable for power adapters or charging. When the internal space of the device is limited, the defects of using gas discharge tubes and TVS tubes are particularly obvious.

Contents of the invention

The technical problem to be solved by the present invention is to provide an anti-lightning circuit for a high-power power adapter and the power adapter, which can resist lightning surge and have no current leakage, and is composed of relatively low-cost separate components.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

The anti-lightning circuit applied in the high-power power adapter of the present invention includes a power input terminal and a rectification circuit, and an anti-lightning circuit composed of low-cost separate components and which can replace the Y capacitor function is arranged between the power input terminal and the rectification circuit. A lightning surge circuit module, the circuit module is composed of a lightning protection fuse, a varistor, a thermistor, an X capacitor, multiple resistors and a common mode inductor, wherein,

One end of the varistor is connected to the L terminal of the power input through the lightning protection fuse, and the other end is connected to one end of the thermistor and connected to the N terminal of the power input;

One end of the X capacitor is connected to the power input L terminal through the lightning protection fuse, and the other end is connected to the other end of the thermistor;

The resistor R1 and the resistor R2 are connected in series and connected to both ends of the X capacitor;

The resistor R1A and the resistor R2A are connected in series and connected to both ends of the X capacitor;

The common mode inductor is connected in the round-trip loop between the rectifier circuit and the X capacitor.

The lightning surge voltage that the circuit module can resist is not less than 4kV.

In the high-power power adapter of the present invention, the anti-lightning circuit applied in the high-power power adapter of the present invention is provided between the power input terminal and the rectification circuit.

The transformer in the power adapter adopts EE22 framework, and each winding is composed of inner primary winding, feedback layer winding, secondary winding, shielding layer winding and outer primary winding sequentially from inside to outside.

The inner primary winding, the feedback layer winding, the shielding layer winding and the outer primary winding are wound in the same direction, and the secondary winding is wound in the opposite direction to the other groups of windings.

The power adapter output power is 18W.

The invention adopts relatively low-cost separate components, such as ordinary fuses, piezoresistors, thermistors, X capacitors and common-mode inductors, to form an anti-lightning circuit. The anti-lightning circuit can not only resist the interference of 4kV lightning surge to the power adapter configured with the circuit, and prevent other components in the adapter from being broken down and damaged, but also can replace the Y capacitor to prevent current leakage and ensure the normal operation of the power adapter. Work.

In the present invention, X capacitors and common mode inductors are used in combination, so that the ability to resist EMI interference is improved without Y capacitors. The power adapter adopting this structure can pass the California Energy Efficiency Level VI and EU Level VI energy efficiency certifications, and the energy conversion efficiency It can reach 87%, thus, correspondingly, the margin of the adapter power module is expanded.

Description of drawings

FIG. 1 is a schematic diagram of a power module of the present invention.

Figure 2 is a schematic diagram of the lightning strike circuit.

Fig. 3 is a schematic circuit diagram of the charger of the present invention.

Figure 4 is the EMI test chart.

FIG. 5 is a schematic diagram of a transformer circuit used in the power adapter of the present invention.

FIG. 6 is a schematic diagram showing the structure of each winding corresponding to the transformer in FIG. 5 .

The reference signs are as follows:

detailed description

As shown in Figures 1, 2 and 3, the anti-lightning circuit applied to high-power power adapters of the present invention is mainly used in power adapters or chargers with output power≧18W.

It is mainly to set a lightning surge resistant circuit module composed of low-cost discrete components between the power input terminal and the rectifier circuit in the power adapter or charger. This circuit module can not only improve the resistance of the power adapter or charger to 4kV lightning surge voltage, and it can also replace the role of Y capacitors in suppressing common-mode noise interference.

The circuit module is composed of lightning protection fuse F1, piezoresistor VR1, thermistor RT1, X capacitor CX1, multiple resistors and common mode inductor L1, wherein one end of piezoresistor VR1 is connected to the power input through lightning protection fuse F1 L terminal, the other end is connected to one end of the thermistor RT1 and is connected to the power input N terminal; one end of the X capacitor CX1 is connected to the power input L terminal through the lightning protection fuse F1, and the other end is connected to the thermistor. The other end; the resistor R1 and the resistor R2 are connected in series and connected to both ends of the X capacitor; the resistor R1A and the resistor R2A are connected in series and connected to both ends of the X capacitor CX1; the common mode inductor L1 is connected to the rectifier circuit In the round-trip loop with the X capacitor CX1.

The above circuit modules are not equipped with Y capacitors, and do not use more expensive lightning protection TVS tubes and gas discharge tubes. They only need simple varistors, fuses, inductors and other components to form a reasonable combination with high resistance to 4KV lightning surges. circuit.

In the above-mentioned circuit module, the fuse F1 adopts a slow-blow fuse to prevent the fuse from blowing out quickly when a lightning surge strikes. The varistor VR1 is used for voltage clamping when a lightning strike occurs and overvoltage, and absorbs excess current to protect sensitive devices. Use thermistor RT1 to increase the impedance of the input circuit. The selection of RT1 is based on the balance between efficiency and absorbing surge resistance. A large resistance value will lead to a decrease in efficiency, and a small drop value cannot play the role of absorbing surge current.

In the above circuit module, the function of reducing residual voltage and filtering noise is realized by safety X capacitor CX and common mode inductor L1, CX1 is connected before common mode inductor L1; There is a certain dead voltage peak. Using the principle that the current of the common mode inductor L1 cannot change suddenly, this circuit is used to filter out the peak after the first circuit. Resistors R1, R1A, R2, and R2A are used to discharge the X capacitor CX1, and the safety standards all have the same discharge requirements for the X capacitor. The specific requirement is to discharge all X-caps to less than 37% of the original within 1 second after power off, so the discharge resistance must be increased. The X capacitor is used to connect between the L and N lines, and after passing through the discharge resistor, the two ends of the X capacitor are connected between the two ends of the common mode inductor. The combination of common-mode inductance and X-capacitor can not only filter out the residual voltage of the front-end circuit, but also reduce the differential-mode interference caused by the primary input and filter out the common-mode interference generated by the back-end circuit.

Installing the anti-lightning strike circuit of the present invention in the power adapter or the charger can greatly improve the anti-lightning strike capability of the power adapter and the charger.

In order to improve the anti-EMI interference of the power adapter or charger, the transformer selected by the present invention adopts EE22 skeleton, and each winding on it is sequentially arranged according to the inner layer primary winding, feedback layer winding, secondary winding, shielding layer winding and outer winding from inside to outside. Layer primary winding structure (hereinafter referred to as the sandwich winding method, see Figure 5, 6).

The inner primary winding, the feedback layer winding, the shielding layer winding and the outer primary winding are wound in the same direction, and the secondary winding is wound in the opposite direction to the other groups of windings.

The inner primary winding uses Ф0.3*1 enameled wire to be wound forward and tightly for 48 turns.

The feedback layer winding is made of Ф0.17*3 enameled wire and is tightly wound forward for 11 turns.

The secondary winding is made of Ф0.6*1 triple insulated wire, and it is reversely and densely wound for 9 turns.

The winding of the shielding layer is made of Ф0.17*2 enameled wire and is tightly wound forward for 9 turns.

The primary winding of the outer layer is made of enameled wire with Ф0.3*1 and 22 turns in the forward direction.

This structure does not require the copper skin as the shielding layer, nor does it need the magnetic core to be connected to the primary ground terminal through the lead wire. While saving costs, it also reduces the manual welding process required for using the copper skin as the shielding layer. When making each winding of the transformer, it only needs to use the winding machine once to complete the winding of all windings, so that the automatic production of transformers can be realized.

The inner primary winding, the feedback winding and the outer primary winding use enameled wires of the same specification, and the specification is determined according to the output power and the input current (the prior art also determines the specification in this way). The specifications of the enameled wire used in the secondary winding are also determined according to the size of the output current. Adjust the anti-electromagnetic interference ability by adjusting the coil wire of the shielding layer winding.

The sandwich winding method also has the following advantages:

1) The sandwich winding method can reduce the leakage inductance of the transformer, thereby reducing the voltage peak, reducing the voltage stress of the switch tube, and the reduction of the leakage inductance can also effectively absorb the loss in the loop and reduce the AC loss between the primary winding and the secondary winding .

2) Improve EMI: The common mode interference current generated between the switch tube and the ground can also be reduced, thereby improving EMI; since a secondary winding is added between the inner primary winding and the outer primary winding, the transformer is reduced The primary interlayer distributed capacitance, and the reduction of interlayer capacitance will reduce the parasitic oscillation in the circuit, which can also reduce the voltage and current stress of the switch tube and the secondary rectifier tube, and improve EMI (the test data curve is shown in Figure 4 shown).

3) By adjusting the number of turns of the shielding layer winding, the distributed capacitance between the primary winding and the secondary winding can be effectively reduced, thereby achieving the effect of reducing common-mode noise interference without setting the Y capacitor.

4) By reducing one shielding layer (note: the above-mentioned sandwich winding method has one less shielding layer than in the prior art), the efficiency can be effectively improved while meeting the EMI test.

The sandwich winding method of the present invention can achieve the effect of the Y capacitor without setting the Y capacitor by adjusting the shielding winding and adding a common mode inductor L2 at the output end, and its energy efficiency conversion efficiency is higher than that of the European Union and the United States. Level 6 energy efficiency requirements.

The lightning strike circuit has simple elements, can reduce the cost, and only needs to occupy less space of the product.

Claims (6)

1. a kind of anti thunder strike circuit being applied in large power supply adapter, including power input and rectification circuit, it is special Levy and be：Resolution element composition and alternative Y capacitance work(provided with low cost between the power input and rectification circuit Can anti-lightning surge circuit module, the circuit module is by lightning protection fuse, piezo-resistance, thermistor, X electric capacity, multiple Resistance and common mode inductance are constituted, wherein,

One end of piezo-resistance is connected to power input L ends by lightning protection fuse, and its other end connects with one end of thermistor And power input N-terminal is connected to altogether；

One end of X electric capacity is connected to power input L ends by lightning protection fuse, its another other end for being terminated at thermistor；

The two ends of the X electric capacity are connected to after resistance R1, resistance R2 concatenation；

The two ends of the X electric capacity are connected to after resistance R1A, resistance R2A concatenation；

Common mode inductance is connected between rectification circuit and X electric capacity and come and gone in loop.

2. the anti thunder strike circuit according to claim 1 being applied in large power supply adapter, it is characterised in that：It is described The lightning surge voltage that circuit module can resist is not less than 4kV.

3. a kind of large power supply adapter, it is characterised in that：Set and have the right between its power input and rectification circuit It is required that the anti thunder strike circuit being applied in large power supply adapter described in 1 or 2.

4. large power supply adapter according to claim 3, it is characterised in that：Transformer in the power supply adaptor Using EE22 skeletons, each winding presses inner primary winding, feedback layer winding, secondary windings, screen layer winding successively from inside to outside Constituted with outer primary winding.

5. large power supply adapter according to claim 4, it is characterised in that：The inner primary winding, feedback layer Winding, screen layer winding and the coiling in the same direction of outer primary winding, the coiling direction phase of the secondary windings and other each group windings Instead.

6. large power supply adapter according to claim 5, it is characterised in that：The power supply adaptor power output is 18W。