JPS60117451A - Digital audio device - Google Patents

Abstract

PURPOSE:To cancell glitch by providing an analog switch similar to an analog switch which connects or cuts off analog signals and applying outputs of them to an operational amplifier with phases opposite to each other. CONSTITUTION:Since analog switches 15 and 21 are driven by control signal pulses having the same polarity from a control terminal 16, glitch of the amplitude determined by a parasitic capacity of the analog switch 15 and a capacity 20 is outputted to an output terminal 17, and glitch of the amplitude determined by a parasitic capacity of the analog switch 21 and a capacity 24 is outputted to the upper end of a resistance 22. Glitch which is outputted to the output terminal 17 through the inverted input of the operational amplifier is inverted and outputted. As the result, glitch outputted to the output terminal 17 and glitch outputted to the upper end of the resistance 22 have phases opposite to each other, and therefore, a waveform of the upper end of the resistance 22 is divided to proper amplitudes by resistances 22 and 23 and is applied to the non-inverted input of an operational amplifier 14 to cancell unnecessary waveforms accompanied with glitch.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a digital audio recording/playback device, and is particularly suitable for accurately resampling the output of a digital/analog converter. -Relating to sample and hold circuit for digital converter [Background of the invention] A conventional digital audio device is shown in FIG. 1
is an analog signal input terminal, 2 is a sample/hold circuit, 3 is an analog-to-digital conversion circuit (hereinafter abbreviated as ADC), 4 is a recording digital signal processing circuit that performs processing such as interleaving, and 5 is a recording amplifier circuit. , 6 is a recording medium, 7 is a demodulation circuit that equalizes the waveform of the electric signal obtained from the recording medium 6, 8 is a digital signal processing circuit for reproduction, 9 is a digital-to-analog conversion circuit (hereinafter abbreviated as DAC), 10 is a resampling circuit, and 11 is an analog signal output terminal.

A recording system extends from the input terminal 1 to the recording medium 6, and a reproduction system extends from the recording medium 6 to the output terminal 11. Compact disc players and playback-only devices such as broadcasters are recording media 6.
It consists of only output terminals 11.

Next, the resample circuit 10 will be explained.

FIG. 2 shows a sample and hold circuit as an example of a sample circuit. 12 is the input terminal of the sample and hold circuit which is the output of the DAC, 15.14 is the operational amplifier, 15
is an analog switch that conducts or cuts off a signal,
16 is a control terminal of the switch, 17 is an output terminal 18 and 19 of a sample-and-hold circuit is a resistor, and 20 is a capacitor.

The resampling circuit has a time required for the DAC to change from a change in the input digital value to the corresponding analog value (generally called settling time), so the DAC
After the C output reaches an accurate value, the switch 15 is made conductive to the capacitor 20 and the inverting input side of the operational amplifier 14 for a certain period of time to obtain a voltage corresponding to the DAC output at the output terminal 17 and charge the capacitor 20. At other times, the switch 15 is cut off and the voltage 5. charged in the capacitor 20 is held at the output terminal 17. Operational amplifier 13
This is to reduce the influence of the output impedance of the DAC connected to the input terminal 12 on the resistor 18.

However, in this conventional circuit, the control signal pulse from the control terminal 16 leaks due to the parasitic capacitance of the analog switch 15 and is output, resulting in whisker-like noise (generally called a glitch), and unnecessary noise that occurs as the noise is charged and discharged. Since a waveform or the like appears at the output terminal 17, the accurate analog value of the DAC output cannot be conducted and maintained, resulting in a disadvantage that faithful reproduction cannot be performed.

Next, the sample and hold circuit 2 shown in FIG. 1 will be explained. This circuit has a circuit configuration and operation sample circuit 10.
It is exactly the same as , but the purpose of use is different, and it is used to hold the sampled value of the analog signal for the time required for the ADC to convert.

In this case, the above unwanted voltage while sampling is
Although it does not affect the conversion, glitches that occur when moving from sample to hold may affect the hold value, causing the conversion output by the ADC to have a different value.

[Purpose of the invention]

The purpose of the present invention is to reduce the effects of the above-mentioned glitches, conduct and hold more accurate analog values, and provide a digital circuit that is equipped with a sample circuit and an ADC sample-and-hold circuit that enables high-fidelity waveform reproduction. Our purpose is to provide audio equipment.

[Summary of the invention]

The present invention provides that the glitch is connected to the conduction of the analog switch.
Taking advantage of the phenomenon that occurs with cut-off, we set up an analog switch similar to the analog switch that conducts and cuts off analog signals, and added it to the operational amplifier so that they have an opposite phase relationship, thereby canceling out the glitch. be.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to FIG. 21
22 and 23 are analog switches, and resistor 24 is a capacitor. Components with the same symbols as in FIG. 2 indicate the same functions. An analog switch 21 equivalent to 15 analog switches is provided, a capacitor 24 with approximately the same capacitance value as the capacitor 20 is connected to the analog switch 21, and its waveform is connected to the resistors 22 and 23.
The signal is divided appropriately and applied to the non-inverting input of the operational amplifier 14. Since the analog switches 15 and 21 are driven by control signal pulses of the same polarity from the control terminal 16, a glitch with an amplitude determined by the parasitic capacitance of the analog switch 15 and the capacitance 20 is generated at the output terminal 17, and the glitch of the analog switch 21 is A glitch with an amplitude determined by the capacitance and the capacitance 24 is output to the upper end of the resistor 22 . Of the glitches at this time, the one appearing at the output terminal 17 via the inverting input of the operational amplifier is inverted and output. As a result, the output terminal 17 and the glitch output to the upper end of the resistor 22 have an opposite phase relationship, so
By dividing the waveform at the upper end of the resistor 22 into appropriate amplitudes by the resistors 22 and 23 and applying it to the non-inverting input of the operational amplifier 14, unnecessary waveforms due to glitches are canceled out.

〔Effect of the invention〕

According to the present invention, it is possible to reduce glitches that occur when changing from a conductive state to a held state or from a held state to a conductive state.

The experimental results of this situation are shown in FIG. Capacity at this time 2
0, 24 is a 7 DI) F,, resistance 18.19,2
2.23 is 3.9Ω. FIG. 6(a) shows a signal applied to the control terminal 16 to control the analog switches 15 and 21 of FIGS. Suppose that it is cut off in the potential state. In FIG. 6(b), the input terminal 12 in FIG. 2 has no signal, and the control terminal 16 in FIG.
) shows the voltage waveform at the output terminal 17 when a signal of

A particularly large glitch occurs at the rise of the control signal, and the electric charge in the capacitor 20 charged by the glitch is discharged by the time constant of the resistors 18 and 19 when the analog fist switch 15 conducts, so that it gradually decreases to a constant value during the conduction period. become.

FIG. 6(C) shows the circuit of FIG. 3 according to an embodiment of the present invention, 7
.

The voltage waveform of the output terminal 17 is shown when using.

Similar to the case of Fig. 2, the glitch waveform caused by the conduction of the analog switch 15 is similar to the waveform of the opposite phase.
When the switch 21 becomes conductive, it is output and the operational amplifier 14
In order to add to this, unnecessary waveforms during the conduction period are reduced at the output terminal 17.

As explained with the above waveforms, if the present invention is used, DA
The accurate analog value of the C output can be conducted and maintained. Alternatively, if applied to a sample-and-hold circuit, more accurate analog-to-digital conversion is possible, and high-fidelity reproduction, which is a characteristic of digital audio equipment, can be further promoted.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional digital audio device.
Figure 2 shows the sample circuit 10 or sample circuit shown in Figure 1.
FIG. 3 is a circuit diagram of the hold circuit 2, FIG. 3 is a diagram showing a sample and hold sample according to an embodiment of the present invention, and FIG. 4 is a diagram illustrating the present invention in detail.・ 8 ・ 1...Analog signal input terminal, 2...Sample/hold circuit, 10...Resample circuit, 15.21...Analog switch. Figure 1 $z Figure 3 Figure 1 4th diagram 1-1
0246n TIME Cps) 20c

Claims (1)

[Claims] 1. Converting an analog information signal to a digital signal,
Digitally recording or transmitting signals by extracting the entire signal by optical or magnetic means from a recording medium such as a disk or tape recorded by optical or magnetic means, or by receiving transmission signals such as radio waves. a digital signal processing circuit that detects and corrects errors in the digital signal obtained by the demodulation circuit; a digital-analog conversion circuit that converts the digital signal output from the digital signal processing circuit into an analog signal; In a digital audio device consisting of an analog switch and an operational amplifier, or a sampling circuit, the output of a conversion circuit is turned on and off at the same timing as the analog switch, and the signal is turned on and off at a fixed potential. What is claimed is: 1. A digital audio device comprising: an analog switch that connects an output to an input of the operational amplifier, which has an input side in a reverse phase relationship with the input side of the analog switch. 2. When converting an analog information signal into a digital signal, it is composed of an analog switch and an operational amplifier that conducts and cuts the signal at appropriate timing in order to sample the analog signal, and converts the sampled analog value into an analog signal.・Equipped with a sample and hold circuit that holds the digital converter until it completes the conversion operation, conducts and cuts at the same timing as the analog switch, receives a fixed potential as input, and has a reverse phase relationship with the input side of the analog switch. 2. The digital audio device according to claim 1, further comprising an analog switch connecting an output to an input of said operational amplifier serving as an input side of said operational amplifier.