Tuning system with DC-DC converter

• US 5,742,898 A
• Filed: 11/14/1995
• Issued: 04/21/1998
• Est. Priority Date: 11/15/1994
• Status: Expired due to Term

• Current Assignee: Callahan Cellular LLC (Intellectual Ventures LLC)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Brekelmans, Johannes H. A.
• Primary Examiner(s): VO, NGUYEN THANH
• Application Number:
  US08/557,446
• Time in Patent Office: 889 Days
• Field of Search: 455/193.1, 455/193.2, 455/193.3, 455/195.1, 455/343, 455/121, 455/120, 455/122, 455/123, 455/289, 455/290, 455/196.1-197.3, 455/255-257, 348/730, 348/731, 348/733
• US Class Current: 455/193.1
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
• CPC Class Codes: H04N 5/50 Tuning indicators; Automatic tuning control

Abstract

In a tuning system, a DC-DC converter DDC provides a tuning control voltage Vt for a tuner TUN. The DC-DC converter DDC is in the form of a series arrangement of an AC source CAC, an inductive element IND and a rectifier circuit REC. The AC signal provided by the AC source Vac1 is controlled by a tuning error signal Se from a tuning detector circuit TED. The inductive element IND transforms this AC signal Vac1 into an AC signal of higher amplitude Vac2. The latter AC signal Vac2 is rectified to provide the tuning control voltage Vt. In effect, the DC-DC converter DDC is part of a tuning control loop. This tuning control loop TUN, TED, DDC determines the output voltage of the DC-DC converter Vt.

Claims

1. A tuning system comprising:

a tuner;

a tuning detector for providing a tuning-error signal which depends on the tuning state of said tuner;

a controllable DC-DC converter whose output voltage depends on the tuning-error signal;

a feedback circuit for deriving a feedback signal from the output voltage of the controllable DC-DC converter;

a difference detector for controlling the controllable DC-DC converter in response to the difference between said feedback signal and said tuning error signal; and

tuning means for varying the tuning state of said tuner in response to the output voltage of the controllable DC-DC converter.

2. A tuning system comprising:

a tuner;

a tuning detector for providing a tuning-error signal which depends on the tuning state of said tuner;

a controllable DC-DC converter whose output voltage depends on the tuning-error signal;

an output section for drawing a current from the controllable DC-DC converter in response to the tuning-error signal;

a difference detector for controlling the controllable DC-DC converter in response to the difference between said current and a target value; and

tuning means for varying the tuning state of said tuner in response to the output voltage of the controllable DC-DC converter.

3. A receiver comprising:

a combination of a mixer and a local oscillator for converting an input signal in frequency;

a reference-frequency oscillator;

a phase-frequency detector having a first input for receiving an output signal from the local oscillator, and a second input for receiving an output signal from the reference-frequency oscillator, the phase-frequency detector being arranged for providing a tuning-error signal in response to the signals received at its first and second inputs;

a controllable DC-DC converter whose output voltage depends on the tuning-error signal; and

tuning means for varying the frequency of the local oscillator in response to the output voltage of the controllable DC-DC converter.

4. A multimedia apparatus having a reception board comprising:

a combination of a mixer and a local oscillator for converting an input signal in frequency;

a reference-frequency oscillator;

a phase-frequency detector having a first input for receiving an output signal from the local oscillator, and a second input for receiving an output signal from the reference-frequency oscillator, the phase-frequency detector being arranged for providing a tuning-error signal in response to the signals received at its first and second inputs;

a controllable DC-DC converter whose output voltage depends on the tuning-error signal; and

tuning means for varying the frequency of the local oscillator in response to the output voltage of the controllable DC-DC converter.

5. A circuit arrangement, comprising an integrated frequency-control circuit, for controlling the frequency of an external oscillator, the integrated frequency-control circuit comprising:

a first input for receiving an output signal from the external oscillator;

a second input for receiving an output signal from a reference-frequency oscillator;

a phase-frequency detector being arranged for providing a tuning-error signal in response to the signals received at the first and second inputs;

an AC source for providing an AC signal at an output; and

control means for varying at least one property of the AC signal in response to the tuning-error signal, said circuit arrangement further comprising means for rectifying said AC signal, an output from said rectifying means being used to control the frequency of said external oscillator, wherein said AC source and said rectifying means form a DC-DC converter.