CN2532644Y

CN2532644Y - Electronic tuner with built in pulse width modulation control tuning voltage circuit

Info

Publication number: CN2532644Y
Application number: CN01271632U
Authority: CN
Inventors: 孙燕
Original assignee: Chengdu Xuguang Technology Co ltd
Current assignee: Chengdu Xuguang Technology Co ltd
Priority date: 2001-11-05
Filing date: 2001-11-05
Publication date: 2003-01-22
Anticipated expiration: 2011-11-05

Abstract

The utility model discloses an electronic tuner with internal pulse width modulating, and controlling and tuning voltage circuit; and comprises a high pass filtering loop 1, a medium frequency wave trap loop 2, an input loop 3, a high level radioactive loop 4, an interstage double tuning and frequency selecting loop 5, a frequency mixer 6, an oscillating loop 7, a medium frequency selecting loop 9, a medium frequency amplifying loop 10, and a PWM mode controlling circuit 8 arranged in the same metal chamber of the electronic tuner. The micro controller inside a TV receiver directly performs tuning by altering the duty ratio of pulse signals. Compared with prior public known electronic tuners, the utility model has a certain effect to simplifying the integrate circuit of TV receivers and reducing the cost of TV receivers.

Description

The electronic tuning unit of built-in pulse width modulation control tuning voltage circuit

The utility model belongs to frequently looks receiving equipment, relates to a kind of electronic tuning unit with additional control function specifically.

At present, band IC interior bus (I ²C) each big TV factory produces Kong Zhi digital to television machine in a large number in the whole nation, cooperates the tuner of the international standard type that the IC interior bus uses to be gradually adopted.This tuner generally is to put back to road, inter-stage frequency selection by dual-tune loop, frequency mixer, oscillation circuit, frequency-selecting of intermediate frequency loop, intermediate frequency amplifying return circuit etc. by high-pass filtering loop, intermediate frequency trap-wave loop, input circuit, height to constitute, wherein the high-pass filtering loop links to each other with the aerial signal input, and the intermediate frequency amplifying return circuit links to each other with medium frequency output end.Wherein, input circuit, inter-stage frequency selection by dual-tune loop, oscillation circuit are controlled by tuning voltage BT, make the signal of output be fixing intermediate-freuqncy signal, and BT change in voltage scope is generally between 0～30V.This tuner has and uses simple, performance index advantage preferably, but concerning television set, control BT change in voltage just needs to increase a part of circuit, this not only increased television set cost, make the components and parts crypto set more on the TV SKD, television set originally the circuit of more complicated become more complicated, and present television set is developed to ultra-thin direction add to the difficulties.

The purpose of this utility model is the electronic tuning unit of a kind of PWM of having mode controlled function of design, makes it to have the good result that reduces the television set cost, simplifies TV set circuit.

For achieving the above object, developed the tuner with PWM mode controlled function, this electronic tuning unit comprises that high-pass filtering loop 1, intermediate frequency trap-wave loop 2, input circuit 3, height put back to road 4, inter-stage frequency selection by dual-tune loop 5, frequency mixer 6, oscillation circuit 7, frequency-selecting of intermediate frequency loop 9, loop 10.Added PWM mode control circuit 8 for reaching the purpose of this utility model.

Like this, the BT voltage that need add variation is originally become only need add the variable pulse signal of a fixed voltage and duty ratio (ratio of shared time of shared time of high level and low level in the pulse signal) and just can carry out tuning.The variable pulse signal of duty ratio is directly produced by the microcontroller (MCU) of television set inside, does not need to increase extra circuit.

Described PWM (pulse width modulation) mode control circuit 8 mainly is made of triode V1 and peripheral circuit thereof, one of two input links to each other with the fixed voltage BTL that television set provides, one provides pwm signal to link to each other with television set, output is connected to each needs tuning place, also links to each other with the AFC terminal by big resistance.

Compare with existing known electronic tuning unit, use this product to have certain effect for the cost of simplifying television receiver circuitry, reduction television receiver.

Fig. 1 is the circuit block diagram of this product.

Fig. 2 is the schematic diagram of this product P WM control circuit part.

Below in conjunction with accompanying drawing the utility model is described in further detail:

Fig. 1 has provided total circuit block diagram of this product, and it is identical with the circuit of the electronic tuning unit of at present general international standard type that the high-pass filtering loop 1 among the figure, intermediate frequency trap-wave loop 2, input circuit 3, height are put back to road 4, inter-stage frequency selection by dual-tune loop 5, frequency mixer 6, oscillation circuit 7, frequency-selecting of intermediate frequency loop 9, intermediate frequency amplifying return circuit 10.For the cost, the simplification TV set circuit that reduce television set, this product has added to have PWM mode controlled function circuit 8 in tuner inside.

The operation principle of PWM mode controlled function circuit is as shown in Figure 2:

PWM (pulse width modulation) mode control circuit 8.Mainly be made of triode V1 and peripheral circuit thereof, the peripheral circuit of triode V1 comprises resistance R 50, R51, R52, R53, R54, R55 and capacitor C 57, C58, C59, C60, and the big resistance that links to each other with AFC comprises R43, R44, R45.

When on the BTL terminal, adding fixed voltage (requiring fixed voltage) greater than high tuning voltage 30V, on the PWM terminal, add pulse signal again, when pulse is high level, the base stage of triode V1 is a high level, the current collection that triode V1 conducting, BTL voltage make triode V1 by pull down resistor R51 is low level very; When pulse was low level, the base stage of triode V1 was a low level, and triode V1 ends, and the current collection that BTL voltage makes triode V1 by pull down resistor R51 is high level very.Therefore, when on the PWM terminal, adding pulse signal, collector electrode at triode V1 can produce the much higher pulse signal of amplitude, this pulse signal forms a fixing tuning voltage through R52 and C58, R53 and the three rank integrating circuit that C59, R54 and C60 form at output tuning voltage BT place.When the duty ratio of input pulse signal is different, the duty ratio of the pulse signal that produces on triode V1 collector electrode is also different, by the three rank integrating circuit that R52 and C58, R53 and C59, R54 and C60 form, also different in the tuning voltage of output BT place generation.Therefore, the duty ratio ratio of the pulse signal on being added in the PWM terminal is very little when changing between very big, can produce the arbitrary tuning voltage between 0～BTL terminal voltage at output BT place.Television receiver is in search during program, only needs to change the duty ratio of the pulse signal of the PWM terminal that outputs to the tuner that has PWM mode controlled function, just can by low channel to high channel or by high channel to the low channel searching TV program.After receiving TV signal, television receiver only needs the duty ratio that produces the pulse signal of the required tuning voltage of this channel is noted, and just this channel memory can be got up.Tuning voltage BT also links to each other with the AFC terminal by big resistance R 43, R44, R45, can finely tune tuning voltage BT and make the intermediate-freuqncy signal of electronic tuning unit output be always a fixed value when the change in voltage on the AFC terminal.

Though this product is described, this product can be made amendment by many modes, and all such modifications are easy to do for the professional and technical personnel, so some modifications can not be regarded as a departure from spirit and scope described herein like this.

Claims

1, a kind of electronic tuning unit of built-in pulse width modulation control tuning voltage circuit, comprise high-pass filtering loop 1, intermediate frequency trap-wave loop 2, input circuit 3, height and put back to road 4, inter-stage frequency selection by dual-tune loop 5, frequency mixer 6, oscillation circuit 7, frequency-selecting of intermediate frequency loop 9, intermediate frequency amplifying return circuit 10, it is characterized in that, in the same metallic cavity of electronic tuning unit, be provided with PWM mode control circuit 8.

2, put the electronic tuning unit of pulse width modulation control tuning voltage circuit within described according to claim 1, it is characterized in that, described PWM mode control circuit 8 mainly is made of triode V1 and peripheral circuit thereof, one of two input links to each other with the fixed voltage BTL that television set provides, one provides pwm signal to link to each other with television set, output is connected to each needs tuning place, also links to each other with the AFC terminal by big resistance.