KR20050117091A - Emi shielding apparatus for charger and adaptor of mobile phone - Google Patents

Abstract

The present invention relates to a technique for shielding electromagnetic waves without generating leakage current by installing a shield on a transformer in a portable charger and an adapter of an SMPS type mobile phone. The present invention includes a primary snubber circuit 203 for attenuating electromagnetic waves of a voltage which is converted from alternating current into direct current and supplied to the primary winding of the transformer 207; A PWM circuit unit 204 for controlling driving of the transformer 207 by using a pulse width modulation signal; A feedback signal processor 205 for controlling the pulse width modulation signal based on a voltage / current control signal fed back from an output terminal to output a target constant voltage and a constant current; Driven by the control of the PWM circuit unit 204, the output voltage of the primary snubber circuit 203 is converted into an alternating voltage of a predetermined level and output, and a wire shield or a copper shield is provided on each winding side to provide electromagnetic waves. Is achieved by a transformer 207 shielding it.

Description

Electromagnetic shielding device of mobile phone charger and adapter {EMI SHIELDING APPARATUS FOR CHARGER AND ADAPTOR OF MOBILE PHONE}

The present invention relates to a technology for blocking electromagnetic waves in an SMPS type portable charger and adapter of a mobile phone, and more particularly, to an electromagnetic wave shielding device for a mobile phone charger and an adapter, in which a shield is installed on a transformer to block electromagnetic waves without generating a leakage current. It is about.

1 is a block diagram of an electromagnetic wave shielding device of a mobile phone charger and an adapter according to the prior art, and as shown therein, an AC / DC converter 101 for converting a commercial AC voltage into a DC voltage; A noise filter (102) for removing noise components contained in the output power of the AC / DC converter (101); A primary snubber circuit (103) provided between the noise filter (102) and the primary winding (L11) of the transformer (106) for attenuating electromagnetic waves; A PWM circuit unit 104 for controlling the driving of the transformer 106 by using a pulse width modulation (PWM) signal; A feedback signal processor 105 for controlling the PWM signal based on a voltage / current control signal fed back from an output terminal to output a target constant voltage and a constant current; A transformer (106) driven by the control of the PWM circuit unit (104) for converting the output voltage of the primary snubber circuit (103) to an alternating voltage of a predetermined level; A voltage / current controller 107 for controlling the AC voltage output from the transformer 106 to output a DC constant voltage / constant current to the constant voltage output unit 110; A voltage control signal feedback unit 108 and a current control signal feedback unit 109 for controlling the voltage / current control unit 107 to return the voltage / current control signal to the feedback signal processing unit 105 respectively; Consists of a capacitor (C1) connected between the bias winding (L12) and the secondary winding (L21) of the transformer 106 in order to block the electromagnetic waves. same.

A commercial AC voltage is input to an AC / DC converter 101 of a charger and a portable adapter (hereinafter referred to as an "adapter") and converted into a DC voltage. Then, the converted DC voltage is removed by the noise filter 102, and the primary winding of the transformer 106 after the electromagnetic wave (EMI: Electromagnetic Interference) is attenuated by the primary snubber circuit 103. It is supplied to (L11).

In such a state, the PWM circuit unit 104 controls the switching drive of the transformer 106 by using a pulse width modulation (PWM) signal, thereby switching to the secondary winding L21 of the transformer 106. The AC voltage corresponding to the frequency is excited. At this time, a predetermined bias voltage is maintained in the bias winding L12 of the transformer 106.

The voltage / current controller 107 controls the AC voltage and the current output from the transformer 106 to output the DC constant voltage / constant current to the constant voltage output unit 110, and outputs the constant voltage and the constant current regardless of the load variation. The voltage / current control signal is outputted through the photocoupler of the voltage control signal feedback unit 108 and the current control signal feedback unit 109 in order to ensure that the signal is controlled.

Accordingly, the feedback signal processing unit 105 performs a PWM of the PWM circuit unit 104 on the basis of the voltage / current control signal returned from the output terminal through the voltage control signal feedback unit 108 and the current control signal feedback unit 109. By controlling the signal, the target constant voltage and constant current are output regardless of the load variation.

On the other hand, when a user connects to a portable charger and an adapter to charge a mobile phone and then makes a call or receives a call from the other party, the user often uses the portable charger and the adapter connected. In this case, the electromagnetic wave is projected more than the prescribed value from the charger and adapter to the head, which is reported to adversely affect the user's health, in order to block the bias winding (L12) and secondary winding (L21) of the transformer 106 The capacitor C1 was installed in between.

However, in the conventional portable charger and adapter of the mobile phone there is a problem that a leakage current flows through a capacitor installed to block electromagnetic waves, causing an electric shock.

Cell phone chargers and adapters are two types of insulators that regulate the leakage current below a predetermined value (eg 250μA) .However, due to the importance of design, metals (eg chromium plating) are used a lot, so it is less than 100μA. In addition, cases of complaining of electric shock have occurred, and according to race, severe cases have been reported to feel electric shock even at 50 μA.

Accordingly, an object of the present invention is to design a mobile phone charger and adapter, so that the electromagnetic wave can be blocked without providing a leakage current by installing a shield in the transformer without using a capacitor to block the electromagnetic wave.

Figure 2 is a block diagram showing an embodiment of the electromagnetic wave shielding device of the mobile phone charger and adapter according to the present invention, as shown therein, the AC / DC converter 201 for converting a commercial AC voltage to a DC voltage; A noise filter (202) for removing noise components contained in the output power of the AC / DC converter (201); A primary snubber circuit 203 provided between the noise filter 202 and the primary winding 207B of the transformer 207 for attenuating electromagnetic waves; A PWM circuit unit 204 for controlling the driving of the transformer 207 using a pulse width modulation (PWM) signal; A feedback signal processor 205 for controlling the PWM signal based on a voltage / current control signal fed back from an output terminal to output a target constant voltage and a constant current; A bias snubber circuit (206) for attenuating electromagnetic waves (EMI) on the bias winding (207C) side of the transformer (207); Driven under the control of the PWM circuit unit 204, the output voltage of the primary snubber circuit 203 is converted into an AC voltage of a predetermined level and outputted, and a wire shield or a copper shield is provided on each winding side to generate electromagnetic waves. A shield 207 for shielding; A voltage / current controller 208 for controlling the AC voltage output from the transformer 207 to output a DC constant voltage / constant current to the constant voltage output unit 211; Under the control of the voltage / current control unit 208 is composed of a voltage control signal feedback unit 209 and a current control signal feedback unit 210 for respectively returning the voltage / current control signal to the feedback signal processing unit 205, Referring to Figure 3 attached to the operation of the present invention configured as described above in detail as follows.

Commercial AC voltage is input to the AC / DC converter 201 of the charger and the adapter and converted into DC voltage. After the converted DC voltage is removed by the noise filter 202, the noise component is removed, and the electromagnetic wave EMI is attenuated by the primary snubber circuit 203, and then the primary winding 207B of the transformer 207 is used. Supplied to.

In such a state, the PWM circuit unit 204 controls the switching drive of the transformer 207 by using a pulse width modulation (PWM) signal, thereby switching to the secondary winding 207F of the transformer 207. The AC voltage corresponding to the frequency is excited. At this time, a predetermined bias voltage is maintained in the bias winding 207C of the transformer 207.

The voltage / current controller 208 controls the AC voltage and the current output from the transformer 207 to output the DC constant voltage / constant current to the constant voltage output unit 211, and outputs the constant voltage and the constant current regardless of the load variation. The voltage / current control signal is output through the photocoupler of the voltage control signal feedback unit 209 and the current control signal feedback unit 210 in order to ensure that the voltage / current control signal is returned.

Accordingly, the feedback signal processing unit 205 performs the PWM of the PWM circuit unit 204 based on the voltage / current control signal returned from the output terminal through the voltage control signal feedback unit 209 and the current control signal feedback unit 210. By controlling the signal, the target constant voltage and the constant current are output from the constant voltage output unit 211 regardless of the load variation.

Meanwhile, in the present invention, the shield 207 is shielded to remove electromagnetic waves. That is, the first wire shield 207A on the primary winding 207B side of the transformer 207, the second wire shield 207D on the bias winding 207C side, the secondary winding 207F, the primary winding The first and second copper plate shields 207E and 207G were respectively provided at 207B to remove electromagnetic waves.

3 is a longitudinal cross-sectional view of the transformer 207 shielded as described above, with reference to this the shield processing according to the present invention will be described.

The first wire shield 207A is installed on the bobbin 207H, the primary winding 207B is wound, and the first wire shield 207A is connected to the high voltage tap HVT of the primary winding 207B.

Subsequently, after winding the bias winding 207C and installing the second wire shield 207D, the second wire shield 207D is connected to the ground terminal GND1 on the bias winding 207C side, and then the first copper plate After the shield 207E is provided and the secondary winding 207F is wound, the first copper shield 207E is connected to the ground terminal GND2 on the secondary winding 207F side.

Finally, the shielding process is completed by installing a second copper plate shield 207G and connecting it to the ground terminal GND1.

Therefore, electromagnetic waves (including noise) due to the high speed switching of the primary winding 207B are attenuated by the first and second wire shields 207A and 207D.

In addition, the noise between the primary winding 207B and the secondary winding 207F is shielded by the first copper plate shield 207E, and the parasitic capacitor components induced between the windings are also reduced, resulting in effective EMI suppression.

Finally, noise components conducted and radiated by the second copper plate shield 207G are shielded.

Separately, a bias snubber circuit 206 is provided between the feedback signal processing unit 205 and the bias winding 207C so that pulsed noise is reduced and radiation noise in a specific frequency band (for example, 30 to 40 MHz) is suppressed. It was.

As described in detail above, the present invention provides a shield in the transformer to block electromagnetic waves, thereby effectively preventing leakage current due to the electromagnetic wave blocking element while blocking the electromagnetic waves, and blocking electromagnetic waves. Since no separate device is used, cost is reduced.

1 is a block diagram of an electromagnetic wave blocking device of a mobile phone charger and adapter according to the prior art.

Figure 2 is a block diagram of the electromagnetic wave shielding device of the mobile phone charger and adapter according to the present invention.

3 is a longitudinal sectional view of a transformer according to the present invention;

*** Description of the symbols for the main parts of the drawings ***

201: AC / DC converter 202: noise filter

203: primary snubber circuit 204: PWM circuit portion

205: feedback signal processing unit 206: bias snubber circuit

207: transformer 207A: first wire shield

207B: Primary winding 207C: Bias winding

207D: 2nd Wire Shield 207E: 1st Copper Shield

207F: 2nd winding 207G: 2nd copper shield

207H: Bobbin 208: Voltage / Current Control

209: voltage control signal feedback section 210: current control signal feedback section

211: constant voltage output unit

Claims (6)

A primary snubber circuit for attenuating electromagnetic waves of a voltage converted from alternating current to direct current and supplied to the primary winding of the transformer; A PWM circuit unit for controlling the driving of the transformer using a pulse width modulated signal; A feedback signal processor for controlling the pulse width modulation signal based on a voltage / current control signal fed back from an output terminal to output a target constant voltage and a constant current; A transformer which is driven by the control of the PWM circuit unit and converts the output voltage of the primary snubber circuit into an alternating voltage of a predetermined level, and installs a wire shield or a copper shield on each winding side to shield electromagnetic waves. Electromagnetic wave blocking device of a mobile phone charger and adapter, characterized in that configured by. The transformer according to claim 1, wherein the transformer is provided with a first wire shield on the primary winding side, a second wire shield on the bias winding side, and a secondary winding and first and second copper plate shields on the primary winding, respectively. Electromagnetic wave shielding device for mobile phone chargers and adapters. 3. The electromagnetic shielding device of claim 2, wherein the first wire shield is connected to a high voltage tap of the primary winding. 3. The electromagnetic shielding device for a cellular phone charger and adapter according to claim 2, wherein the second wire shield is connected to a ground terminal on the bias winding side. 3. The electromagnetic shielding device for a cellular phone charger and adapter according to claim 2, wherein the first copper shield is connected to a ground terminal on the secondary winding side, and the second copper shield is connected to a ground terminal on the bias winding side. The electromagnetic wave shielding device of a mobile phone charger and an adapter according to claim 1, wherein a bias snubber circuit for attenuating electromagnetic waves is further provided on the bias winding side of the transformer.