Wobble signal detection circuit and optical disk device

• US 6,859,425 B2
• Filed: 12/06/2002
• Issued: 02/22/2005
• Est. Priority Date: 12/07/2001
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Maegawa, Hiroshi, Shigemori, Toshihiro
• Primary Examiner(s): Young, W. R.
• Assistant Examiner(s): ORTIZ CRIADO, JORGE L
• Application Number:
  US10/313,036
• Publication Number:
  US 20030128641A1
• Time in Patent Office: 809 Days
• Field of Search: 369/47.15, 369/47.3, 369/47.34, 369/47.35, 369/47.23, 369/47.25, 369/47.48, 369/59.11, 369/59.14, 369/59.15, 369/53.34, 369/124.12
• US Class Current: 369/47.3
• CPC Class Codes: G11B 2220/257 DVDs belonging to the plus family, i.e. +R, +RW, +VR
• CPC Class Codes: G11B 27/24 by sensing features on the record carrier other than the transducing track ; sensing signals or marks recorded by another method than the main recording
• CPC Class Codes: G11B 7/0045 Recording G11B7/006, G11B7/0065 take precedence
• CPC Class Codes: G11B 7/0053 Reproducing non-user data, e.g. wobbled address, prepits, BCA
• CPC Class Codes: G11B 7/24082 Meandering

Abstract

An wobble signal detection circuit that is provided on an optical disk device and can detect a wobble signal having high accuracy and stability at least when recording information on an optical disk. This wobble signal detection circuit can be applied to plural types of optical recording media. With the wobble signal detection circuit, during a period for forming a space region, a first voltage signal provided from a first light receiving element is sampled and amplified to be a target voltage, a second voltage signal provided from a second light receiving element is sampled and amplified to be the target voltage. The difference between the two amplified signals are output as the wobble signal. The first and second light receiving elements are divided from each other in the direction tangential to a recording region on the optical recording medium.

Claims

1. A wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection circuit comprising:

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first voltage adjustment circuit for adjusting a signal level of the sampled first voltage signal so that an average voltage of the adjusted first voltage signal output from the first sample circuit can be equal to a first target voltage;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second voltage adjustment circuit for adjusting a signal level of the sampled second voltage signal so that an average voltage of the adjusted second voltage signal output from the second sample circuit can be equal to the first target voltage; and

a subtracting circuit for outputting a wobble signal that is a difference in level between the first voltage signal adjusted and output by the first voltage adjustment circuit and the second voltage signal adjusted and output by the second voltage adjustment circuit.

2. The wobble signal detection circuit according to claim 1, further comprising:

a first signal adjustment circuit provided at an upstream side of the first voltage adjustment circuit for adjusting an amplitude of the sampled first voltage signal, wherein a gain used in the amplitude adjustment during a recording operation is different from a gain used in the amplitude adjustment during a reproducing operation; and

a second signal adjustment circuit provided at an upstream side of the second voltage adjustment circuit for adjusting an amplitude of the sampled second voltage signal, wherein the gain used in the amplitude adjustment during the recording operation is different from the gain used in the amplitude adjustment during the reproducing operation.

3. The wobble signal detection circuit according to claim 1, further comprising:

a target voltage setting circuit for setting the first target voltage and a second target voltage achieved by the first voltage adjustment circuit so that the first target voltage set for during the recording operation can be different from the second target voltage set for during a reproducing operation, and setting the first and second target voltages achieved by the second voltage adjustment circuit so that the first target voltage set for during the recording operation can be different from the second target voltage set for during the reproducing operation.

4. The wobble signal detection circuit according to claim 1, further comprising:

a speed setting circuit for setting first and second response speeds of the first voltage adjustment circuit to the sampled first voltage signal input thereto so that the first response speed immediately after switching between a recording operation and a reproducing operation is performed is larger than the second response speed during the recording operation; and

setting the first and second response speed of the second voltage adjustment circuit to the sampled second voltage signal input thereto so that the first response speed set for immediately after switching between the recording operation and the reproducing operation is performed is larger than the second response speed set for during the recording operation.

5. A wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection circuit comprising:

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first amplifying circuit for amplifying an amplitude of the sampled first voltage signal output from the first sample circuit, and outputting the amplified first voltage signal;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second amplifying circuit for amplifying the sampled second voltage signal output from the second sample circuit, and outputting the amplified second voltage signal; and

an arithmetic processing circuit for receiving the amplified first voltage signal output by the first amplifying circuit, the amplified second voltage signal output by the second amplifying circuit, the first voltage signal output by the first light receiving element, and the second voltage signal output by the second light receiving circuit, and for performing an arithmetic process on the received signals so as to output the wobble signal.

6. The wobble signal detection circuit according to claim 5, wherein the arithmetic processing circuit comprises:

a first adding circuit for adding the amplified first voltage signal output by the first amplifying circuit and the first voltage signal provided from the first light receiving element, and outputting the added signal;

a second adding circuit for adding the amplified second voltage signal output by the second amplifying circuit and the second voltage signal provided from the second light receiving element, and outputting the added signal; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the added signal output by the first adding circuit and the added signal output by the second adding circuit.

7. The wobble signal detection circuit according to claim 5, wherein the arithmetic processing circuit comprises:

a first subtracting circuit for outputting a subtracted signal that is a difference in level between the amplified first voltage signal output by the first amplifying circuit and the amplified second voltage signal output by the second amplifying circuit;

a second subtracting circuit for outputting a subtracted signal that is a difference in level between the first voltage signal provided from the first light receiving element and the second voltage signal provided from the second light receiving element; and

an adding circuit for adding the subtracted signal output by the first subtracting circuit and the subtracted signal output by the second subtracting circuit so as to output the added signal as the wobble signal.

8. The wobble signal detection circuit according to claim 5, wherein the arithmetic processing circuit comprises:

a first subtracting circuit for outputting a subtracted signal that is a difference in level between the amplified first voltage signal output by the first amplifying circuit and the amplified second voltage signal output by the second amplifying circuit;

a second subtracting circuit for outputting a subtracted signal that is a difference in level between the first voltage signal provided from the first light receiving element and the second voltage signal provided from the second light receiving element;

a signal switching circuit for, in sync with the specific control signal, selecting the subtracted signal output by the first subtracting circuit during a period for forming the space region, and selecting the subtracted signal output by the second subtracting circuit during a period for forming a mark region so as to output the selected signal as the wobble signal.

9. The wobble signal detection circuit according to claim 5, further comprising a first DC component removing circuit provided at an upstream side of the arithmetic processing circuit for removing a DC component from the amplified first voltage signal to be received by the arithmetic processing circuit, a second DC component removing circuit provided at an upstream side of the arithmetic processing circuit for removing a DC component from the amplified second voltage signal to be received by the arithmetic processing circuit, a third DC component removing circuit provided at an upstream side of the arithmetic processing circuit for removing a DC component from the first voltage signal that is provided from the first light receiving element and is to be received by the arithmetic processing circuit, and a fourth DC component removing circuit provided at an upstream side of the arithmetic processing circuit for removing a DC component from the second voltage signal that is provided from the second light receiving element and is to be received by the arithmetic processing circuit.

10. A wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection circuit comprising:

a first amplitude adjustment circuit for adjusting an amplitude of a first voltage signal so that the amplitude of the first voltage signal can be equal to a target amplitude, wherein the first voltage signal corresponds to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, and outputting the adjusted first voltage signal;

a second amplitude adjustment circuit for adjusting an amplitude of a second voltage signal so that the amplitude of the second voltage signal can be equal to the target amplitude, wherein the second voltage signal corresponds to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element, and outputting the adjusted second voltage signal;

a target amplitude setting circuit for setting the target amplitude achieved by the first amplitude adjustment circuit, and the target amplitude achieved by the second amplitude adjustment circuit; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the adjusted first voltage signal output by the first amplitude adjustment circuit and the adjusted second voltage signal output by the second amplitude adjustment circuit.

11. A wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection circuit comprising:

a first amplitude adjustment circuit for adjusting an amplitude of a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, and outputting the adjusted first voltage signal;

a second amplitude adjustment circuit for adjusting an amplitude of a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element, and outputting the adjusted second voltage signal; and

a speed setting circuit for setting first and second response speeds of the first amplitude adjustment circuit to the first voltage signal input thereto, and the first and second response speeds of the second amplitude adjustment circuit to the second voltage signal input thereto so that the first response speed set for immediately after switching between a recording operation and a reproducing operation is performed is larger than the second response speed set for during the recording operation.

12. The wobble signal detection circuit according to claim 11, further comprising a subtracting circuit for outputting the wobble signal that is a difference in level between the adjusted first voltage signal output by the first amplitude adjustment circuit and the adjusted second voltage signal output by the second amplitude adjustment circuit.

13. The wobble signal detection circuit according to claim 11, wherein the first amplitude adjustment circuit adjusts the amplitude of the first voltage signal so that the adjusted amplitude of the first voltage signal can become a target amplitude, and the second amplitude adjustment circuit adjusts the amplitude of the second voltage signal so that the amplitude of the second voltage signal can become the target amplitude.

14. A wobble signal detection unit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection unit comprising a first wobble signal detection circuit and a second wobble signal detection circuit,

wherein the first wobble signal detection circuit includes:

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first voltage adjustment circuit for adjusting a signal level of the sampled first voltage signal so that an average voltage of the adjusted first voltage signal output from the first sample circuit can be equal to a first target voltage;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second voltage adjustment circuit for adjusting a signal level of the sampled second voltage signal so that an average voltage of the adjusted second voltage signal output from the second sample circuit can be equal to the first target voltage; and

a subtracting circuit for outputting a wobble signal that is a difference in level between the first voltage signal adjusted and output by the first voltage adjustment circuit and the second voltage signal adjusted and output by the second voltage adjustment circuit,

wherein the second wobble signal detection circuit includes;

a first sample circuit for, in sync with a specific control signal, sampling the first voltage signal corresponding to the electric signal converted from the light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to the period for forming a space region when recording information on the optical recording medium;

a first amplifying circuit for amplifying an amplitude of the sampled first voltage signal output from the first sample circuit, and outputting the amplified first voltage signal;

a second sample circuit for, in sync with the specific control signal, sampling the second voltage signal corresponding to the electric signal converted from the light signal being based on the reflected light received by the second light receiving element;

a second amplifying circuit for amplifying the sampled second voltage signal output from the second sample circuit, and outputting the amplified second voltage signal; and

an arithmetic processing circuit for receiving the amplified first voltage signal output by the first amplifying circuit, the amplified second voltage signal output by the second amplifying circuit, the first voltage signal output by the first light receiving element, and the second voltage signal output by the second light receiving circuit, and for performing an arithmetic process on the received signals so as to output the wobble signal,

and wherein the wobble signal detection unit further comprises a selecting circuit for selecting either the first wobble signal detection circuit or the second wobble signal detection circuit, based on a signal indicating a type of the optical recording medium.

15. The wobble signal detection unit according to claim 14, wherein the first wobble signal detection circuit further includes:

a first signal adjustment circuit provided at an upstream side of the first voltage adjustment circuit for adjusting an amplitude of the sampled first voltage signal, wherein a gain used in the amplitude adjustment during a recording operation is different from a gain used in the amplitude adjustment during a reproducing operation; and

a second signal adjustment circuit provided at an upstream side of the second voltage adjustment circuit for adjusting an amplitude of the sampled second voltage signal, wherein the gain used in the amplitude adjustment during the recording operation is different from the gain used in the amplitude adjustment during the reproducing operation.

16. The wobble signal detection unit according to claim 14, wherein the first wobble signal detection circuit further includes:

a target voltage setting circuit for setting the first target voltage and a second target voltage achieved by the first voltage adjustment circuit so that the first target voltage set for during the recording operation can be different from the second target voltage set for during a reproducing operation, and setting the first and second target voltages achieved by the second voltage adjustment circuit so that the first target voltage set for during the recording operation can be different from the second target voltage set for during the reproducing operation.

17. The wobble signal detection unit according to claim 14, wherein the arithmetic processing circuit of the second wobble signal detection circuit includes:

a first adding circuit for adding the amplified first voltage signal output by the first amplifying circuit and the first voltage signal provided from the first light receiving element, and outputting the added signal;

a second adding circuit for adding the amplified second voltage signal output by the second amplifying circuit and the second voltage signal provided from the second light receiving element, and outputting the added signal; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the added signal output by the first adding circuit and the added signal output by the second adding circuit.

18. The wobble signal detection unit according to claim 14, wherein the arithmetic processing circuit of the second wobble signal detection circuit includes:

a first subtracting circuit for outputting a subtracted signal that is a difference in level between the amplified first voltage signal output by the first amplifying circuit and the amplified second voltage signal output by the second amplifying circuit;

a second subtracting circuit for outputting a subtracted signal that is a difference in level between the first voltage signal provided from the first light receiving element and the second voltage signal provided from the second light receiving element; and

an adding circuit for adding the subtracted signal output by the first subtracting circuit and the subtracted signal output by the second subtracting circuit so as to output the added signal as the wobble signal.

19. The wobble signal detection unit according to claim 14, wherein the arithmetic processing circuit of the second wobble signal detection circuit includes:

a first subtracting circuit for outputting a subtracted signal that is a difference in level between the amplified first voltage signal output by the first amplifying circuit and the amplified second voltage signal output by the second amplifying circuit;

a second subtracting circuit for outputting a subtracted signal that is a difference in level between the first voltage signal provided from the first light receiving element and the second voltage signal provided from the second light receiving element;

a signal switching circuit for, in sync with the specific control signal, selecting the subtracted signal output by the first subtracting circuit during a period for forming the space region, and selecting the subtracted signal output by the second subtracting circuit during a period for forming a mark region so as to output the selected signal as the wobble signal.

20. A wobble signal detection unit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium, the wobble signal detection unit comprising a first wobble signal detection circuit and a second wobble signal detection circuit,

wherein the first wobble signal detection circuit includes:

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first voltage adjustment circuit for adjusting a signal level of the sampled first voltage signal so that an average voltage of the adjusted first voltage signal output from the first sample circuit can be equal to a first target voltage;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second voltage adjustment circuit for adjusting a signal level of the sampled second voltage signal so that an average voltage of the adjusted second voltage signal output from the second sample circuit can be equal to the first target voltage; and

a subtracting circuit for outputting a wobble signal that is a difference in level between the first voltage signal adjusted and output by the first voltage adjustment circuit and the second voltage signal adjusted and output by the second voltage adjustment circuit,

wherein the second wobble signal detection circuit includes;

a first amplitude adjustment circuit for adjusting an amplitude of the first voltage signal so that the amplitude of the first voltage signal can be equal to a target amplitude, wherein the first voltage signal corresponds to the electric signal converted from the light signal being based on the reflected light received by the first light receiving element, and outputting the adjusted first voltage signal;

a second amplitude adjustment circuit for adjusting an amplitude of the second voltage signal so that the amplitude of the second voltage signal can be equal to the target amplitude, wherein the second voltage signal corresponds to the electric signal converted from the light signal being based on the reflected light received by the second light receiving element, and outputting the adjusted second voltage signal;

a target amplitude setting circuit for setting the target amplitude achieved by the first amplitude adjustment circuit, and the target amplitude achieved by the second amplitude adjustment circuit; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the adjusted first voltage signal output by the first amplitude adjustment circuit and the adjusted second voltage signal output by the second amplitude adjustment circuit,

and wherein the wobble signal detection unit further comprises a selecting circuit for selecting either the first wobble signal detection circuit or the second wobble signal detection circuit, based on a signal indicating a type of the optical recording medium.

21. An optical disk device that records information on the optical recording medium, comprising:

a wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium; and

a processing unit for performing a recording operation by using the wobble signal detected by the wobble signal detection circuit,

wherein the wobble signal detection circuit comprising;

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first voltage adjustment circuit for adjusting a signal level of the sampled first voltage signal so that an average voltage of the adjusted first voltage signal output from the first sample circuit can be equal to a first target voltage;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second voltage adjustment circuit for adjusting a signal level of the sampled second voltage signal so that an average voltage of the adjusted second voltage signal output from the second sample circuit can be equal to the first target voltage; and

a subtracting circuit for outputting a wobble signal that is a difference in level between the first voltage signal adjusted and output by the first voltage adjustment circuit and the second voltage signal adjusted and output by the second voltage adjustment circuit.

22. An optical disk device that records information on the optical recording medium, comprising:

a wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium; and

a processing unit for performing a recording operation by using the wobble signal detected by the wobble signal detection circuit,

wherein the wobble signal detection circuit comprises;

a first sample circuit for, in sync with a specific control signal, sampling a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, wherein the specific control signal is specific to a period for forming a space region when recording information on the optical recording medium;

a first amplifying circuit for amplifying an amplitude of the sampled first voltage signal output from the first sample circuit, and outputting the amplified first voltage signal;

a second sample circuit for, in sync with the specific control signal, sampling a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a second amplifying circuit for amplifying the sampled second voltage signal output from the second sample circuit, and outputting the amplified second voltage signal; and

an arithmetic processing circuit for receiving the amplified first voltage signal output by the first amplifying circuit, the amplified second voltage signal output by the second amplifying circuit, the first voltage signal output by the first light receiving element, and the second voltage signal output by the second light receiving circuit, and for performing an arithmetic process on the received signals so as to output the wobble signal.

23. An optical disk device that records information on the optical recording medium, comprising:

a wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium; and

a processing unit for performing a recording operation by using the wobble signal detected by the wobble signal detection circuit,

wherein the wobble signal detection circuit comprises;

a first amplitude adjustment circuit for adjusting an amplitude of a first voltage signal so that the amplitude of the first voltage signal can be equal to a target amplitude, wherein the first voltage signal corresponds to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, and outputting the adjusted first voltage signal;

a second amplitude adjustment circuit for adjusting an amplitude of a second voltage signal so that the amplitude of the second voltage signal can be equal to the target amplitude, wherein the second voltage signal corresponds to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element, and outputting the adjusted second voltage signal;

a target amplitude setting circuit for setting the target amplitude achieved by the first amplitude adjustment circuit, and the target amplitude achieved by the second amplitude adjustment circuit; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the adjusted first voltage signal output by the first amplitude adjustment circuit and the adjusted second voltage signal output by the second amplitude adjustment circuit.

24. An optical disk device that records information on the optical recording medium, comprising:

a wobble signal detection circuit for detecting a wobble signal based on signals provided from first and second light receiving elements that are divided from each other in a direction tangential to a spiral or concentric recording region of an optical recording medium in which the first and second light receiving elements receive light that is reflected from a surface of the optical recording medium; and

a processing unit for performing a recording operation by using the wobble signal detected by the wobble signal detection circuit,

wherein the wobble signal detection circuit comprises;

a first amplitude adjustment circuit for adjusting an amplitude of a first voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the first light receiving element, and outputting the adjusted first voltage signal;

a second amplitude adjustment circuit for adjusting an amplitude of a second voltage signal corresponding to an electric signal converted from a light signal being based on the reflected light received by the second light receiving element;

a speed setting circuit for setting first and second response speeds of the first amplitude adjustment circuit to the first voltage signal input thereto, and the first and second response speeds of the second amplitude adjustment circuit to the second voltage signal input thereto so that the first response speed set for immediately after switching between a recording operation and a reproducing operation is performed is larger than the second response speed set for during the recording operation; and

a subtracting circuit for outputting the wobble signal that is a difference in level between the adjusted first voltage signal output by the first amplitude adjustment circuit and the adjusted second voltage signal output by the second amplitude adjustment circuit.