JPS6117413B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a volume control device for a television receiver or the like. In recent years, television receivers have been using audio circuit ICs that are capable of controlling the gain of an audio amplifier circuit using a DC voltage to change the volume. Therefore, recently, we have targeted ICs for audio circuits using direct current control, and are controlling the volume control voltage applied to these ICs using pushbutton key operations or microprocessors that use remote control signals as control inputs. A volume control circuit has been proposed in which the volume is adjusted digitally. One method of volume control using such digital processing is to create a pulse train signal whose duty cycle changes depending on the length of time the push button key is pressed, and convert this pulse train signal into a DC voltage. There is a device that converts the DC voltage and uses this DC voltage as the control voltage. This method is effective because processing by a microprocessor or the like is relatively simple, but conventionally, the pulse train signal, that is, the pulse train signal, is Since the magnitude of the control voltage was changed at a constant ratio, the following drawbacks occurred. That is, while the relationship between the control voltage applied to the audio circuit IC and the audio output voltage from this IC is approximately linear as shown by the solid line in Figure 1, the relationship between the audio output voltage and the actual human ear The relationship between the perceived volume and the volume is greatly curved as shown in the broken line in the figure, so we created a voltage that increases at a constant rate in proportion to the number of volume control steps, as shown in the solid line in Figure 2, and this voltage If it is applied as is as the control voltage of the audio circuit IC, the volume will be a slightly gentler curve with respect to the change in the number of steps than the broken line in Figure 1, but it will still curve as shown in Figure 2. It will change non-linearly as shown by the broken line. For this reason, the degree of change in volume is large when the volume is low, and becomes small when the volume is high, which is extremely inconvenient. Therefore, the present invention takes these points into consideration and proposes a volume control device in which the volume can be changed substantially linearly with respect to the number of volume control steps in the digital volume control circuit as described above. and
The details will be explained below. FIG. 3 shows a schematic configuration of the volume control device of the present invention, in which 1 is a push button circuit comprising a volume up key 1a and a volume down key 1b, and 2 is an arithmetic process using signals from the keys as control inputs. A circuit section, 3 is a control pulse generation circuit section that creates a pulse train signal for volume control according to a control code signal derived therefrom, and 4 is a low-pass filter circuit that converts the pulse train signal output from there into a DC voltage. It is. The arithmetic processing circuit section 2 includes a timer circuit 5 that derives one pulse every 0.5 seconds, for example, and the determination circuit 6 detects the presence or absence of a signal from the push button circuit 1 at the timing of the pulse. Then, when the up key 1a is pressed and a signal from that key is being input, the determination circuit 6 gives an instruction to the arithmetic circuit 7 to perform addition, and the arithmetic circuit 7 reads the previous step number (before pressing the key 1a) stored in the memory circuit 8 consisting of a RAM (random access memory), etc., performs an operation to add 1 to the step number, and calculates the result of the operation. is newly stored in the storage circuit 8. At that time, this memory circuit 8 stores the above step number as a 6-bit code with two "0"s added to the upper digit (left) side of the 4-bit binary number shown in Table 1.The reason is It will become clear later. Further, in this embodiment, the number of steps for volume control is 16 from 0 to 15. Therefore, for example, if the number of steps = 3, that is, the code 000011 is stored in the memory circuit 8, if the up key 1a is pressed, the first code from the timer circuit 5 will be When the pulse reaches the determination circuit 6, the arithmetic circuit 7 performs the calculation 3+1=4, and similarly, the next pulse
The calculation +1=5 is performed, and here the above key 1a
When released, the calculation result 5, 000101, is stored in the memory circuit 8.
will be memorized. Further, when the down key 1b is pressed, the operation is the same as described above except that the arithmetic circuit 7 subtracts 1. The binary code signal representing the step number derived from the storage circuit 8 is introduced into the code conversion circuit 9, from which it is derived as a parallel 6-bit control code signal shown in Table 2. This code conversion circuit 9 may use, for example, a ROM (read only memory) or the like in which the control codes in Table 2 are stored in advance using the binary code derived from the storage circuit 8 as an address. When the processing circuit section 2 and the pulse generation circuit section 3 are configured by a microprocessor (so-called microcomputer), the code conversion function can be achieved through software processing as shown in FIG. Can be done. The reason why the aforementioned binary code (step number) is stored in the storage circuit 8 as a 6-bit signal is because it is convenient to perform such processing. Of course, it is also possible to store the bit binary code as is in the storage circuit 8, and when reading it out, convert it into a 6-bit binary code and then perform such processing. Each bit output of the control code signal derived from the code conversion circuit 9 is sent to six pulse generation circuits 10 in order from the upper digit (left side) of Table 2.
A to 10d and 10e and 10f are applied respectively. Each of the pulse generating circuits generates a pulse train signal having the following pulse width at the timing shown in FIG. 5 when the corresponding bit of the control code signal is "1". That is, the pulse generation circuit 10a generates a reference pulse _P1 having a pulse width sufficiently shorter than the repetition period (0.5 seconds) of the timer circuit 5 described above, and the pulse generation circuit 1
0b generates a pulse P ₂ with a pulse width twice that of its reference pulse, and similarly 10c, 1
0d are 2 ² = 4 times and 2 ^{3 times} the reference pulse above, respectively.
Pulses P ₄ and P ₈ with a pulse width of =8 times are generated, and 10e and 10f are pulses P with a pulse width of 1/2 and 1/2 ² = 1/4 of the reference pulse P ₁ , respectively. _h and P _g are generated. Note that in FIG. 5, t ₀ represents the time point at which the control code signal arrives from the code conversion circuit 9. Therefore, the pulse generation circuits 10a to 10f
The output of the OR gate 11 which receives each output as input is as shown in FIG. 6 for the control code in Table 2.
Moreover, each of the above-mentioned pulse generation circuits is designed to repeatedly generate each pulse every 0.5 seconds unless the corresponding bit of the control code signal applied to them becomes "0". As long as the contents do not change, that is, keys 1a, 1
When none of the buttons b are pressed, the OR gate 11 repeatedly generates one of the pulses 0 to 15 in FIG. 6 every 0.5 seconds. Furthermore, when either key 1a or 1b is kept pressed, the content of the control code changes every 0.5 seconds depending on the content of the calculation in the calculation circuit 7. pulses are derived one after another. The pulse train signal derived from the OR gate 11 is converted into a DC voltage by passing through a filter circuit 4 consisting of an integrating circuit or the like. The magnitude of this DC voltage is determined by the duty cycle of the pulse train signal shown in FIG. That is, in FIG. 6, the longer the total time length of the "high" periods, the greater the DC voltage from the filter circuit 4.
At that time, each pulse train signal in Figure 6 is created based on a reference pulse and pulses with pulse widths 2, 4, 8 times, 1/4, and 1/2 of the reference pulse according to Table 2. Therefore, the DC voltage from the filter circuit 4 does not increase or decrease monotonically (at a constant ratio) in proportion to the change in the number of steps, but instead changes in a curve like the solid line in FIG. Therefore, if this DC voltage is applied as the gain control voltage of the audio circuit IC explained at the beginning, the characteristics indicated by the broken line in Figure 1 will be corrected, and the listener will notice a change in the number of steps. The volume can be heard as it changes approximately linearly, and the intended purpose can be achieved. Furthermore, this point will be explained regarding the prior art. That is, in the prior art, a 4-bit binary code signal corresponding to the step number derived from the memory circuit 8 (in this case, the 4-bit binary number may be stored as is in the memory circuit 8). ] are directly transmitted to the pulse generation circuits 10a to 10d.
[In this case, pulse generation circuits 10e, 1
If pulses P ₁ to _{P 6} are generated at the timing shown in FIG. 8 by not providing 0f], the pulse train signal derived from the OR gate 11 will follow the above-mentioned standard according to the number of steps as shown in FIG. The "high" period increases or decreases by the pulse width. For this reason,
The DC voltage obtained by passing this pulse train signal through the filter circuit 4 has a linear characteristic as shown by the broken line in FIG. 7, and therefore causes the problem described at the beginning. Note that until now, the arithmetic processing circuit section 2 in FIG.
Although the explanation has been made based on the case where the pulse generating circuit section 3 is constructed of discrete circuits, as described above, all of these can be achieved by software processing using a microcomputer or the like. It is also provided with a so-called initializer function for setting the memory circuit 8 to a predetermined number of steps when the power is turned on so that the television receiver or the like operates at a predetermined volume when the power is turned on. However, since such a point is outside the gist of the present invention, further explanation will be omitted. Further, in the embodiment shown in FIG. 3, although no particular explanation was given when introducing the signal from the push button circuit 1 to the arithmetic processing circuit section 2 , the signal from the push button circuit is directly introduced into the circuit section 2 as an electric signal. Of course, it may also be introduced as a remote control signal using light, ultrasonic waves, or the like as a medium. As detailed above, according to the volume control device of the present invention, in the volume control circuit that digitally controls the volume according to the operation time of a push button key for volume control, etc. Generate a pulse train signal whose duty cycle changes non-linearly in accordance with changes in the number of steps of the corresponding volume control, and apply the DC voltage obtained by converting the pulse train signal as the gain control voltage of the audio amplification circuit. This makes it possible to correct the non-linear characteristics of the volume with respect to the audio output voltage and change the volume approximately linearly in accordance with the change in the number of steps, making it suitable for use in television receivers, etc. Bass has a great effect.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the DC control voltage vs. audio output voltage characteristics and the relationship between audio output voltage and volume of the audio circuit IC targeted by the present invention, and FIG. 2 is a diagram showing the characteristics of a conventional volume control circuit. FIG. 3 is a diagram showing a schematic configuration of the volume control device of the present invention, FIG. 4 is a diagram for explaining the code conversion operation when the main part of the circuit in FIG. 3 is configured with a microcomputer, and FIG. FIG. 6 is a diagram showing the output signal waveform of the pulse generation circuit in FIG. 3, FIG. 6 is a diagram showing the output signal waveform of the OR gate in FIG.
The figure shows a comparison of the characteristics of the circuit in Figure 3 and the prior art, and Figures 8 and 9 show the characteristics of the prior art circuit.
FIG. 6 is a diagram similar to FIG. DESCRIPTION OF SYMBOLS 1... Volume control push button circuit, 2 ... Arithmetic circuit section, 3 ... Pulse generation circuit section, 4... Low pass filter circuit, 5... Timer circuit, 6... Judgment circuit, 7... Arithmetic circuit, 8 ... Memory circuit, 9 ... Code conversion circuit, 10a to 10f ... Pulse generation circuit, 11 ... OR gate.

【table】

【table】

【table】

Claims (1)

[Claims] 1. A pulse calculation unit that counts timing pulses generated at fixed time intervals during the operation of a push button key and outputs the binary count value as a binary code signal indicating the number of steps of volume change. By reading predetermined binary data for each code of the binary code signal in accordance with the binary code signal, the numerical value changes exponentially with respect to the numerical change of the code signal. a code converter that outputs a control code signal; a ^minimum pulse width that is sufficiently shorter than the pulse interval of the timing pulse when triggered by the control code signal;
0, 1, 2,... Those generating pulses with smaller pulse widths are arranged so as to correspond to lower digits of the control code signal, and each of them is triggered by the output of logic 1 of the corresponding digit of the control code signal,
a pulse generator configured to derive a logical sum output of the output pulses of each of the pulse generators; and a pulse train signal outputted from the pulse generator in response to the control code signal. A volume control device comprising a control voltage generation unit that generates a DC voltage that changes approximately exponentially with respect to the number of steps, and the DC voltage from the control voltage generation unit is applied as a gain control voltage to an audio amplification circuit. Device.