KR100431002B1 - Signal conversion device for resolution improvement and method of the same - Google Patents

Abstract

A signal conversion device for improving the resolution of an input signal is disclosed. The pulse generator selectively outputs a pulse for a modulated signal by selectively performing a pulse width modulation method and a pulse frequency modulation method on an input signal. The comparison unit compares the difference between the magnitude of the input signal and the feedback signal output from the pulse generator. The controller controls the pulse generator to selectively perform the pulse width modulation method and the pulse frequency modulation method according to the difference between the magnitudes of the comparison results. As a result, by using either the pulse width modulation method or the pulse frequency modulation method, it is possible to prevent the phenomenon that the pulse width is subdivided or the frequency becomes too low to obtain high resolution. That is, by using a matrix structure in which both a pulse width modulation method and a pulse frequency modulation method are applicable, resolution of all regions of the input signal can be improved.

Description

Signal conversion device for resolution improvement and method of the same}

The present invention relates to a signal converter, and more particularly, to a signal converter for improving the resolution of an input signal input from the outside.

Pulse Width Modulation (PWM) refers to a modulation method that varies a pulse width generated at a fixed period unit. In general, the PWM method is used in the control of voltage or current and phase control in electronic components or electronic products. Pulse Frequency Modulation (PFM) refers to a modulation method that varies the frequency of a pulse in accordance with the magnitude of a signal wave.

Conventional signal conversion apparatus for improving the resolution by selecting any one of the PWM method or PFM method to improve the resolution of the input signal. In the case of the PWM method, the frequency is fixed and in the case of the PFM method, the pulse width is fixed. If high resolution is required, the frequency should be lowered in the PWM method.

1 is a diagram illustrating a general PWM scheme, and FIG. 2 is a diagram illustrating a PFM scheme.

Referring to FIG. 1, a PWM method of modulating a pulse width at a predetermined frequency is a waveform when a pulse width is changed from 1 mm to 2 mm at a frequency of 1 Hz. Duty is a pulse width for a frequency of one cycle. When the pulse width is 1 mm at a frequency of 1 Hz, the duty is 1 mm / sec, and when the pulse width is 2 mm, the duty is 2 mm / sec.

In addition, as shown in FIG. 1, when the fixed frequency is 1 Hz and the pulse width is 1 mm, the resolution of the duty that can be obtained at 1 Hz is 1,000 pieces. Here, the resolution indicates how many pulses can be generated by dividing one section into equal parts for pulse width modulation.

On the contrary, FIG. 2 shows a PFM method of modulating a frequency at a predetermined pulse width with a waveform when a pulse width is fixed at 1 mm and a frequency is changed from 1 Hz to 2 Hz. The duty at the frequency of 1 Hz and 2 Hz is 1 mm / sec and 1 mm / 0.5 sec, respectively.

As shown in FIG. 2, the PFM method fixes the pulse width and changes the frequency. The PFM method has a resolution of 1,000 when the frequency is 1 Hz and the pulse width is fixed to 1 mm, as in the PWM method. But when the frequency changes from 1Hz to 2Hz, the resolution is 500.

For example, in order to obtain 10,000 resolutions using the PFM method, the resolution must be 10,000 when the frequency is set from 1 Hz to 0.1 Hz. However, if the frequency is too low, it will exceed the operating frequency range of the switching IC. This is possible if low frequency sampling is required, but the frequency of 0.1 Hz is in the range of the unusable range. In addition, when applying the PFM method, a lot of frequency modulation is required to obtain high resolution. When the PFM method is applied, the signal can be finely adjusted than when the PWM method is applied. However, the response speed of the signal is slow.

As such, when the PWM method and the PFM method are applied alone, the configuration itself is difficult because high frequency or a smaller duty width of the pulse is required for high resolution.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a signal conversion device and method capable of improving the resolution of an input signal by adaptively performing a PWM method and a PFM method.

1 is a view showing a general PWM method,

2 is a diagram illustrating a general PFM scheme;

3 is a block diagram of an embodiment of a signal conversion device of a class D amplifier for improving resolution according to the present invention;

4 is a diagram illustrating a circuit configuration of a switching unit and a low pass filter according to the present invention;

5 is a flowchart of an embodiment of a signal conversion apparatus for improving resolution according to the present invention.

Explanation of symbols on the main parts of the drawings

300: A / D conversion unit 310: the first calculation unit

320: second output unit 330: comparison unit

340: control unit 350: storage unit

360: pulse generator 370: switching unit

380 low pass filter

Signal conversion device for improving the resolution according to the present invention for achieving the above technical problem, the pulse generation to selectively output the pulse width modulation method and the pulse frequency modulation method for the input signal to generate a pulse for the modulated signal A comparison unit for comparing the difference between the magnitude of the input signal and the feedback signal output from the pulse generator, and selectively selecting the pulse width modulation method and the pulse frequency modulation method according to the difference value of the magnitude as a result of the comparison. It has a control unit to control to perform.

Preferably, a first calculation unit for calculating respective slopes of the previous value and the current value of the input signal sampled with the digital signal, and each of the previous value and the current value of the feedback signal sampled with the digital signal A second calculation unit for calculating a slope is further provided, wherein the comparison unit compares the difference between each of the slopes calculated from the first calculation unit and each of the slopes calculated from the second calculation unit.

The apparatus may further include a storage configured to store a lookup table relating to a duty ratio for at least one frequency and at least one pulse width, wherein the controller is configured to select one of the duty ratios among the plurality of duty ratios stored in the storage. When the input signal is selected, the pulse width modulation method and the pulse frequency modulation method are selectively performed to correspond to the selected duty ratio.

When the difference value of the slope is greater than a reference value as a result of the comparison of the comparator, the controller controls to modulate the feedback signal by performing the pulse width modulation method based on the selected duty ratio. On the contrary, when the comparison result of the comparison unit is smaller than the difference value of the reference value, the control unit performs the pulse frequency modulation method based on the selected duty ratio to control to modulate the feedback signal.

According to another aspect of the present invention, there is provided a signal conversion method for improving resolution according to the present invention, by selectively performing a pulse width modulation method and a pulse frequency modulation method on an input signal to output pulses for a modulated signal. Comparing the difference between the magnitude of the input signal and the feedback signal output from the pulse generator, and selectively selecting the pulse width modulation method and the pulse frequency modulation method according to the difference value of the magnitude as a result of the comparison step. It has a step of controlling to perform.

Preferably, the method further includes calculating respective inclinations for the previous value and the current value of the input signal and the feedback signal sampled with the digital signal before the comparing step, wherein the comparing step includes calculating each of the calculated values. Compare the difference in slopes.

The control step may be configured to selectively perform the pulse width modulation method and the pulse frequency modulation method so that the input signal corresponds to the selected duty ratio when any one of a plurality of previously stored duty ratios is selected. do.

As a result of the comparison in the comparison step, if the difference value of the slope is larger than a predetermined reference value, the control step controls to modulate the feedback signal by performing the pulse width modulation method based on the selected duty ratio. In contrast, when the difference value of the slope is smaller than a predetermined reference value as a result of the comparison in the comparison step, the control step controls to modulate the feedback signal by performing the pulse width modulation method based on the selected duty ratio.

Therefore, by using either the PWM method or the PFM method, it is possible to prevent a phenomenon in which the pulse width is subdivided or the frequency is too low to obtain high resolution. That is, by using a matrix structure that can be applied to both the PWM method and the PFM method, the resolution of all areas of the input signal can be improved.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

3 is a block diagram of an embodiment of a signal conversion device of a class D amplifier for improving resolution according to the present invention.

Referring to FIG. 3, the signal conversion apparatus includes an A / D converter 300, a first calculator 310, a second calculator 320, a comparator 330, a controller 340, and a storage 350. ), A pulse generator 360, a switching unit 370, and a low pass filter 380.

The A / D converter 300 receives an input signal input from the outside and a feedback signal output from the pulse generator 360 to convert the input signal into a digital signal. When the input signal is converted into a digital signal through the A / D converter 300, the comparator 330 compares the difference between the input signal and the feedback signal output from the pulse generator 360. The controller 340 controls the pulse generator 360 to selectively perform the PWM method and the PFM method according to the difference between the input signal and the feedback signal.

Preferably, the first calculation unit 310 and the second calculation unit 320 for calculating the slope of the input signal and the feedback signal sampled as a digital signal, respectively. The first calculator 310 calculates respective inclinations of the previous value and the current value of the input signal sampled as the digital signal. The second calculation unit 320 calculates respective inclinations of the previous value and the current value of the feedback signal converted into the digital signal.

The comparator 330 compares the difference between each slope calculated from the first calculator 310 and the slope calculated from the second calculator 320. The controller 340 controls to selectively perform a PWM method for modulating a pulse width at a predetermined frequency and a PFM method for modulating a frequency at a predetermined pulse width according to a difference value of the slope generated as a result of the comparison of the comparator 330. do.

The pulse generator 360 selectively outputs a pulse in response to the signal modulated by the switching unit 370 by selectively performing the PWM method and the PFM method according to the control signal of the controller 340. The switching unit 370 performs a switching operation according to the high or low signal of the pulse generator 370. As a signal according to the switching operation of the switching unit 370, unnecessary high frequency components are removed by the low pass filter 380.

4 is a diagram illustrating a circuit configuration of a switching unit and a low pass filter according to the present invention.

Referring to the drawing, the pulse output from the pulse generator 360 is applied to the gates of the switching elements Q1 and Q2 composed of MOSFETs. At this time, when the output pulse from the pulse generator 360 is high, the first switching device Q1 is turned on to obtain an output signal from the output terminal of the first switching device Q1. In contrast, when the output pulse of the pulse generator 360 is low, the output is obtained from the output terminal of the second switching element Q2.

The signal generated by the switching elements Q1 and Q2 is provided to the low pass filter 380. The signals generated by the switching operations of the switching elements Q1 and Q2 include not only input signal components but also high frequency components that are not necessary. This high frequency component is removed by a low pass filter 380 composed of an inductor L1 and a capacitor C1.

Accordingly, the final output signal is a signal from which unnecessary high frequency components are removed by the low pass filter 380. The signal output through the low pass filter 380 is fed back to another input of the A / D converter 300 through a feedback loop.

Preferably, the storage unit 350 stores a look-up table composed of duty ratios for at least one frequency and at least one pulse width.

Table 1 shows an example of a lookup table stored in the storage 350.

PWM method PWMpulse Width = 0.1mm PWMpulse Width = 0.2mm PWMpulse Width = 0.3mm PWMpulse Width = 0.4mm PFMpulse Frequency = 1 Hz duty = 0.1 / 1 duty = 0.2 / 1 duty = 0.3 / 1 duty = 0.4 / 1 PFMpulse Frequency = 2 Hz duty = 0.1 / 2 duty = 0.2 / 2 duty = 0.3 / 2 duty = 0.4 / 2 PFMpulse Frequency = 3 Hz duty = 0.1 / 3 duty = 0.2 / 3 duty = 0.3 / 3 duty = 0.4 / 3 PFMpulse Frequency = 4 Hz duty = 0.1 / 4 duty = 0.2 / 4 duty = 0.3 / 4 duty = 0.4 / 4

The vertical cell of Table 1 shows a PFM method for modulating a frequency at a fixed pulse width to a predetermined value, and the horizontal cell shows a PWM method for modulating a pulse width at a fixed frequency.

Meanwhile, the data corresponding to the frequency and the pulse width shown in [Table 1] are not fixed values, and may be referred to as setting data that can be changed according to characteristics of the input signal. In addition, the frequency and the pulse width are not necessarily arranged sequentially, and as shown in Table 1, not only the 4 × 4 shape but also a matrix structure capable of improving resolution can be used.

When an input signal is input from the outside, the controller 340 selects one duty ratio among a plurality of duty ratios stored in the storage 350 to selectively perform the PWM method and the PFM method. That is, the pulse generator 360 generates a pulse for a signal modulated by a preset duty ratio, a PWM method, and a PFM method, the first time in the initialization state.

For example, when the initial setting value is a PWM method and is set to a duty ratio having a pulse width of 0.4 mm at a frequency of 1 Hz, the pulse generator 360 performs a PWM method on the input signal to set a duty ratio (duty = 0.4 / 1). Generates a pulse with

The switching unit 370 performs a switching operation according to the high or low signal of the pulse generator 370. The high frequency component included in the signal output from the switching unit 370 is removed by the low pass filter 380. The signal from which the high frequency component is removed by the low pass filter 380 is fed back to the A / D converter 300 through a feedback loop. The first and second calculators 310 and 320 calculate tilt values for the input signal and the feedback signal, respectively, which are converted into digital signals.

The comparator 330 compares the inclination value of the input signal and the inclination value of the feedback signal calculated by the first and second calculation units 310 and 320, respectively. As a result of the comparison by the comparator 330, when the difference between the two inclination values is greater than the predetermined reference value, the controller 340 controls to perform the PWM method. That is, the frequency corresponding to the difference value of the slope value is selected while the pulse width is fixed at 0.4 mm.

For example, when the difference between the slopes of the input signal and the feedback signal is 0.1, the controller 340 of the plurality of duty ratios stored in the storage 350 has a duty ratio of 0.4 mm and a frequency of 1 Hz. Select 0.4 / 1) to control the PWM method.

On the contrary, when the difference between the two inclination values is smaller than the predetermined reference value, the control unit 340 controls to perform the PFM method. That is, the frequency is fixed at 1 Hz and the pulse width corresponding to the difference value of the slope value is selected. For example, when the difference between the two slope values is 0.1, the pulse width is selected as 0.1, and when the difference between the two slope values is 0.2, the pulse width is selected as 0.2.

Therefore, the controller 340 performs the PFM method when the difference between the slope of the feedback signal and the slope of the input signal is smaller than the predetermined reference value, and performs the PWM method when the difference between the slope is greater than the predetermined reference value. . The pulse generator 360 selectively outputs a pulse width modulated signal and a pulse frequency modulated signal by selectively performing the PWM method and the PFM method according to the control signal of the controller 340.

That is, by adaptively performing the PWM method and the PFM method according to the comparison result of the difference between the slope of the input signal and the feedback signal with a predetermined reference value, the PWM method or the PFM method is more than the case of performing either the PWM method or the PFM method Many resolutions can be obtained.

On the other hand, by improving the resolution as described above, it is possible to control the current and the voltage applied to the load stage. That is, since the supply of current is different according to the adjustment of the pulse width and the frequency, the voltage of the output terminal can be adjusted.

For example, when the pulse width is 1 mm while the frequency is fixed at 1 Hz, the duty is 1. This means the supply of current while the duty is 1, after which the current naturally curves down. Also, if the pulse width is 2mm at the frequency of 1Hz, the duty becomes 2, the current is supplied for 2 days, and then the curve decreases for the remaining time. Therefore, the supply amount of current applied to the load stage varies depending on the width of the pulse. In addition, since the number of supply of the current is different when the pulse width is fixed at 1 mm and the frequency is 1 Hz and the frequency is 2 Hz, the amount of current actually applied to the load also varies. In this case, the frequency is 1 Hz, but the current is supplied once, but in the case of 2 Hz, the current is supplied twice.

Accordingly, the PWM method and the PFM method can be adaptively performed to improve the resolution according to the pulse width and frequency modulation. This indicates that by improving the resolution, it is possible to control the current and voltage applied to the load stage.

5 is a flowchart of an embodiment of a signal conversion method for improving resolution according to the present invention.

Before an input signal is applied from the outside, one of at least one frequency and a duty ratio for at least one pulse width stored in the lookup table of the storage 350 is selected and set as an initial value. When the input signal is received (S500), the controller 340 controls the pulse generator 360 to generate a pulse based on the preset frequency and the pulse width. The pulse generator 360 selectively performs the PWM method and the PFM method according to the control signal of the controller 340, and outputs a pulse according to the performed result.

The switching unit 370 performs a switching operation according to the high or low signal of the pulse generator 360. The signal output through the switching unit 370 is a signal from which an undesired high frequency component is removed by the low pass filter 380. The output signal output through the low pass filter 380 is fed back to the A / D converter 300 through a feedback loop.

When an input signal and a feedback signal are input, the A / D converter 300 converts the input signal and the feedback signal into a digital signal. The first and second calculators 310 and 320 calculate slopes of the input signal and the feedback signal sampled with the digital signal, respectively (S510). The comparator 330 compares a difference between respective inclinations of the input signals calculated by the first and second calculation units 310 and 320, respectively, and the inclinations of the feedback signals (S520).

When the difference between the slope of the input signal and the slope of the feedback signal is greater than a predetermined reference value in operation S520 (S530), the controller 340 controls the pulse generator 360 to perform a PWM method (S540). . When the PWM method is selected by comparing the difference value of the slope with a predetermined reference value, the controller 340 fixes the pulse width to an initial setting state based on the preset initial value, and applies the difference value of the slope among the plurality of frequencies. A duty ratio having a corresponding frequency is selected (S550).

On the contrary, when the difference value of the slope between the input signal and the feedback signal is smaller than the predetermined reference value in operation S520, the controller 340 controls the pulse generator 360 to perform the PFM method (S560). When the PFM method is selected according to the difference between the slopes of the input signal and the feedback signal, the controller 340 fixes the frequency to the initial setting state based on the preset initial value and corresponds to the difference value of the slope among the plurality of pulse widths. A duty ratio having a pulse width to be selected is selected (S570).

The pulse generator 360 selectively outputs a pulse corresponding to the modulated signal to the switching unit 370 by selectively performing a PWM method of modulating a frequency and a PFM method of modulating a pulse width according to a control signal of the controller (S580). ). The signal output through the switching unit 370 is a signal from which a high frequency component is removed by the low pass filter 380. The signal output through the low pass filter 380 is fed back to the A / D converter 300 through a feedback loop.

When the feedback signal is fed back to the A / D converter 300, the process is repeated in step S510 to compensate for the feedback signal. Resolution can be improved by adaptively performing PWM and pulse frequency modulation to adjust the frequency and pulse width according to the difference between the slopes of the input signal and the feedback signal.

Although the present embodiment has been described with respect to the signal conversion device of the class D amplifier for improving the resolution, it is not necessarily limited to this, it is possible to apply to both the device for improving the resolution by applying the conventional PWM method and PFM method.

According to the signal conversion apparatus and method for improving the resolution according to the present invention, by using any one of the PWM method or PFM method to prevent the phenomenon that the pulse width is too subdivided or the frequency is too low to obtain a high resolution Can be. That is, by using a matrix structure that can apply both PWM and PFM methods, the burden on hardware and software can be reduced, and by performing both methods selectively, resolution can be improved for all areas of the input signal.

Although the present invention has been described in detail through the representative embodiments, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention with respect to the embodiments described above. Will understand. Therefore, the scope of the present invention should not be limited to the embodiments described, but should be defined by the claims below and equivalents thereof.

Claims (10)

A pulse generator for selectively outputting a pulse for a modulated signal by selectively performing any one of a pulse width modulation method and a pulse frequency modulation method on an input signal; A storage unit for storing a lookup table including a duty ratio for each of at least one pulse width and at least one pulse frequency; A calculator which calculates a first slope value for the input signal and a second slope value for the feedback signal fed back from the pulse generator; A comparison unit comparing the calculated first slope value and the second slope value; And The pulse width generator is controlled to output the input signal as a pulse having a selected duty ratio among a plurality of duty ratios stored in the lookup table, based on the selected duty ratio based on a difference between the first and second slope values. And a controller for adaptively varying any one of a set pulse width and a pulse frequency. delete delete The method of claim 1, When the difference between the first and second slope values is equal to or greater than a preset reference value, the controller is configured to fix the pulse width of the feedback signal to a pulse width corresponding to the selected duty ratio and vary the pulse frequency of the feedback signal. And a control unit for controlling the pulse generator to perform a width modulation method. The method of claim 1, When the difference between the first and second slope values is less than or equal to a preset reference value, the controller is configured to fix the pulse frequency of the feedback signal to a pulse frequency corresponding to the selected duty ratio and vary the pulse width of the feedback signal. And a control unit for controlling the pulse generator to perform a pulse frequency modulation method. A first step of modulating an input signal in a set modulation scheme and outputting a pulse having a predetermined pulse width and a predetermined pulse frequency; Calculating a first slope value for the input signal and a second slope value for the feedback signal fed back from the first step; A third step of comparing the calculated first slope value and the second slope value; And Compensating the output signal of the first step by adaptively performing a pulse width modulation method for varying the pulse width and a pulse frequency modulation method for varying the pulse frequency in accordance with the difference between the first and second slope values. 4; signal conversion method comprising a. delete delete The method of claim 6, As a result of the comparison in the third step, when the difference between the first and second slope values is equal to or greater than a preset reference value, in the fourth step, the feedback signal is fixed while the pulse width of the feedback signal is fixed to the predetermined pulse width. Compensating the output signal of the first step by varying the pulse frequency of the signal conversion method. The method of claim 6, When the difference between the first and second slope values is less than or equal to a preset reference value, the fourth step compares the feedback signal with the pulse frequency of the feedback signal fixed at the predetermined pulse frequency. Compensating the output signal of the first step by varying the pulse width of the signal conversion method.