METHOD AND APPARATUS FOR DC RESTORATION USING FEEDBACK

• US 20110069236A1
• Filed: 08/23/2010
• Published: 03/24/2011
• Est. Priority Date: 08/22/2006
• Status: Active Grant

• Current Assignee: Donald E. Parreco, Raymond William Hall
• Original Assignee: Donald E. Parreco, Raymond William Hall
• Inventors: Hall, Raymond William, Parreco, Donald E.
• Granted Patent: US 8,154,664 B2
• Time in Patent Office: Days
• US Class Current: 348/691
• CPC Class Codes: H04N 9/72 for reinsertion of DC and slowly varying components of colour signals camera processing pipelines for reinsertion of DC or slowly varying components of colour signals H04N23/87

Abstract

A feedback circuit for restoration of DC in video signals is presented. A sample pulse representing the back porch of an incoming video signal is generated from the horizontal sync signal. The sample pulse triggers a sample and hold circuit to acquire the correct offset voltage in the output signal during this back porch period. The offset voltage feeds back through a summing node upstream of either the circuit causing the offset or an input amplifier thereby restoring the video signal to the desired DC voltage level with respect to ground.

Claims

1. A feedback circuit for compensating for DC offset in an output signal comprising:

a sampling circuit configured to sample said output signal at a time during which a DC amplitude of an input signal has a known value to obtain a DC offset value;

a compensation circuit for applying an inverse of said DC offset value to said input signal.

2. The feedback circuit of claim 1 wherein said input signal comprises a video signal.

3. The feedback circuit of claim 1 wherein said sampling circuit comprises a sample-and-hold circuit.

4. A method for compensating for DC offset in an output signal comprising:

sampling the output signal at a time during with the DC amplitude of an input signal has a known value to obtain a DC offset value;

subtracting said DC offset value from the input signal.

5. The method of claim 4 wherein said input signal comprises a video signal.

6. The method of claim 5 wherein said time is during a back porch of said video signal.