NOISE SUPPRESSION CIRCUIT FOR POWER ADAPTER

• US 20130099854A1
• Filed: 10/25/2011
• Published: 04/25/2013
• Est. Priority Date: 10/25/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Peter W. Richards
• Inventors: Hotelling, Steven Porter, RICHARDS, Peter W.
• Granted Patent: US 9,042,132 B2
• Time in Patent Office: Days
• US Class Current: 327/551
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters

Abstract

A noise suppression circuit for a power adapter is disclosed. The noise suppression circuit can reduce or eliminate adapter-induced noise that could interfere with an electronic device powered by the adapter. In one example, the noise suppression circuit can include an active circuit to detect and attenuate or cancel the induced noise. In another example, the noise suppression circuit can include an RLC circuit in parallel with the adapter choke to suppress the induced noise at the operating frequencies of the powered electronic device. In still another example, the noise suppression circuit can include a modified adapter Y capacitor connection so as to bypass the adapter choke, thereby reducing or eliminating the choke'"'"'s induced noise.

Claims

1. A noise suppression circuit for a power adapter comprising:

an active circuit coupled between a first side and a second side of the adapter, the active circuit configured to cause current to flow from the second side to the first side, or from the first side to the second side, so as to attenuate noise between the first side and the second side, the noise being induced into an adapter voltage.

2. The circuit of claim 1, wherein the active circuit is configured to cause the current to flow by detecting the noise between the first side and the second side and using the detected noise to control the current flow from the second side to the first side or from the first side to the second side.

3. The circuit of claim 2, wherein the active circuit comprises:

a capacitance multiplier configured to detect the noise; and

a feedback capacitor configured to control the current flow so as to attenuate the noise between the first side and the second side.

4. The circuit of claim 3, wherein the capacitance multiplier comprises:

a sense capacitor configured to simulate a larger capacitance so as to detect the noise; and

an operational amplifier coupled to the sense capacitor to help simulate the larger capacitance in the sense capacitor.

5. The circuit of claim 1, wherein the active circuit is coupled to an AC neutral line on the first side and to a transformer output on the second side.

6. The circuit of claim 1, wherein the active circuit is coupled to the first side at a first point where the adapter voltage is substantially free of the induced noise and to the second side at a second point where the adapter voltage has the induced noise.

7. A noise suppression circuit for a power adapter comprising:

an RLC circuit in parallel with a component of the adapter, the RLC circuit configured to suppress noise induced in the component at select frequencies of an adapter voltage.

8. The circuit of claim 7, wherein the component of the adapter is a choke, the choke inducing the noise.

9. The circuit of claim 8, wherein the RLC circuit is configured to lower choke impedance at the select frequencies so as to suppress the induced noise at the select frequencies.

10. The circuit of claim 7, wherein the component of the adapter is a Y capacitor, the Y capacitor inducing the noise.

11. The circuit of claim 7, wherein the select frequencies coincide with operating frequencies of an electronic device powered by the adapter.

12. A noise suppression circuit for a power adapter comprising:

a Y capacitor coupled between an AC neutral line and a ground of the adapter, the coupling to the AC neutral line being upstream of a component of the adapter, the Y capacitor configured to bypass the component of the adapter so as to suppress noise induced in the component of the adapter.

13. The circuit of claim 12, wherein the component of the adapter is a choke, the choke inducing the noise.

14. The circuit of claim 12, wherein a voltage at the coupling to the AC neutral line is substantially free of the induced noise.

15. A power adapter for noise suppression comprising:

a plug configured to connect to a power source;

a connector configured to connect to a device;

a power circuit configured to receive a first voltage from the power source, to transform the first voltage into a second voltage compatible with the device, and to send the second voltage to the device to power the device; and

a noise suppression circuit configured to suppress noise induced in the power circuit.

16. The adapter of claim 15, wherein the noise suppression circuit comprises a feedback circuit configured to sense and cancel out the induced noise.

17. The adapter of claim 15, wherein the noise suppression circuit comprises an RLC circuit configured to suppress the induced noise at select frequencies, the select frequencies coinciding with operating frequencies of the device.

18. The adapter of claim 15, wherein the noise suppression circuit comprises a modified Y capacitor connection to bypass an adapter component that induces the noise.

19. The adapter of claim 15, wherein the device comprises a touch sensitive device configured to sense a proximity of an object to the device and to perform an action based on a sense signal indicative of the sensed proximity.

20. The adapter of claim 19, wherein the noise suppression circuit is configured to suppress the induced noise so as to avoid adversely affecting the sense signal.

21. A system for noise suppression comprising:

an electronic device configured to generate signals; and

a power adapter configured to power the electronic device, the adapter lacking a plug ground prong and including a noise suppression circuit configured to suppress noise induced in the adapter from interfering with the generated signals of the device.

22. The system of claim 21, wherein the electronic device is a touch sensitive device configured to generate sense signals indicative of a proximity of an object to the touch sensitive device, and

wherein the noise suppression circuit is configured to suppress the induced noise and prevent the induced noise from interfering with the sense signals.

23. The system of claim 21, wherein the electronic device is an audio device configured to generate audio signals for listening by a user, and

wherein the noise suppression circuit is configured to suppress the induced noise and prevent the induced noise from interfering with the audio signals.

24. The system of claim 21, wherein the electronic device is a video device configured to generate video signals for viewing by a user, and

wherein the noise suppression circuit is configured to suppress the induced noise and prevent the induced noise from interfering with the video signals.