JP3486914B2 - Pulse width modulator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for comparing a triangular carrier signal with a control signal and performing pulse width modulation. FIG. 3 is a block diagram of a conventional pulse width modulation device. In the figure, 1 is a control signal generator, 2 is a carrier generator, and 3 is a digital comparator. FIG. 4 shows signal waveforms at various parts of the conventional pulse width modulator shown in FIG. FIG. 4A shows data b of a triangular wave carrier signal input to the digital comparator 3.
FIG. 4B shows a pulse width modulation signal c output from the digital comparator 3 as a result of comparing the magnitudes of the two input signals. As shown in FIG. 4, control signal data a
Changes the pulse width of the pulse width modulation signal c. In the conventional pulse width modulation device, if the amount of change in the data a of the control signal is large, a phenomenon occurs in which an extra narrow pulse is generated. FIG. 5 is a signal waveform of each part showing a state in which an extra pulse is generated by a step change of the data a of the control signal of the conventional pulse width modulator shown in FIG. FIG.
5A shows the data b of the triangular wave carrier signal and the data a of the control signal input to the digital comparator 3 in FIG.
(B) is a pulse width modulation signal c output from the digital comparator 3 as a result of comparing the two input signals. As shown in FIG. 5, the data a of the control signal coincides with the data b of the triangular carrier signal at time T
Since the value changes in a step-like manner, it again matches the triangular carrier signal b, and as a result, an extra narrow pulse is generated. Due to this extra pulse, there is a problem that the PWM signal is distorted. The present invention has been made in consideration of the above problems, and has as its object to prevent a pulse width modulation device from generating an extra pulse even when a control signal changes stepwise. In order to solve the above problems, a pulse width modulation circuit according to the present invention is controlled by a carrier signal.
In a pulse width modulation device for pulse width modulation of a control signal,
A carrier signal generator for outputting a triangular carrier signal;
A control signal generator for outputting a step-like control signal,
Up signal when the carrier signal is increasing, down when the carrier signal is decreasing
An up / down signal generator for outputting a signal;
The transmission signal and control signal are input and compared to detect a match.
And a matching device for outputting a matching pulse signal.
Output pulse signal and up / down signal generator output
Input a power signal and generate a pulse width modulation signal
A coincidence pulse signal is output,
After the width modulation signal changes to H level or L level,
H level or L level immediately before the first pulse
The pulse width is determined while maintaining the pulse width . According to the present invention, when the data of the carrier signal coincides with the data of the control signal while the data of the carrier is increasing,
The output pulse is set to the H level, and when the data of the carrier signal is coincident with the data of the control signal while the data of the carrier is decreasing, the output pulse is set to the L level to prevent generation of an extra pulse. Things. An embodiment of the pulse width modulation apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a pulse width modulation apparatus according to one embodiment of the present invention, and FIG. 2 is a signal waveform of each part in FIG. In the drawing, the same components and signal waveforms as those of the conventional example are denoted by the same reference numerals as those of the conventional example, and the description of the same components will be omitted. 4 is a coincidence device that outputs a coincidence pulse signal d when the coincidence between the carrier signal data b and the control signal data a is detected. 5 is an up signal while the carrier data is increasing.
No., reduction in the up-down signal generator for outputting a down signal, 6 is a pulse generator for generating a pulse width modulated signal from the coincidence pulse signal and the output signal of the up-down signal device. The operation of the pulse width modulation device configured as described above will be described below with reference to FIGS. FIG. 2 shows signal waveforms at various points in FIG. FIG. 2A shows data b of a triangular wave carrier signal input to the matching device 4 and data a of a step-like control signal. When the two data match, the matching device 4 starts
The coincidence pulse signal d is output as shown in (b). Further, up-down signal generator 5, the up signal is in increasing the data b of the carrier signal as shown in FIG. 2 (c)
Signal , a down signal is output during the decrease. The pulse width of the pulse width modulation signal output from the pulse generator 6 is shown in FIG.
As shown in (d), it is determined by the level of the coincidence pulse signal d output from the coincidence device 4 and the level of the up / down signal e output from the up / down signal generator 5.
You . That is, the output signal of the pulse generator 6 is
Pulse width by up-down signal e changes to match the pulse <br/> the signal d is inputted H-level, L-level when the coincidence pulse signal d is input at the down signal when the up signal A modulated signal is generated. This pulse width
Is up-down when the coincidence pulse signal d is output.
After the change of the up or down signal of the
Determined by maintaining the level immediately before the first pulse
Is done . As described above, the pulse width modulation device of the present invention
Is up / down when the coincidence pulse signal is output
First after the signal up or down signal changes
By maintaining the previous level until the first pulse of
The width is determined , and extra matching pulses are used when performing pulse width modulation.
Even if a signal is generated, the generation of an extra pulse width modulation signal can be prevented without changing the level of the pulse width modulation signal in the middle . As described above, according to the present invention, when the triangular carrier data coincides with the control signal data, the triangular carrier data is increasing or decreasing. Depending on
By determining the level of the pulse width modulation pulse, generation of an extra modulation pulse can be prevented, and distortion of the modulation pulse signal can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a signal waveform diagram of each part in FIG. 1. FIG. 3 is a block diagram of a conventional pulse width modulation device. FIG. 5 is a signal waveform diagram of each unit in FIG. 3. FIG. 5 is a waveform diagram of each unit showing a state in which an extra pulse is generated due to a step change in data of a control signal in the block diagram in FIG. 2 Carrier generator 3 Digital comparator 4 Matching device 5 Up / down signal generator 6 Pulse generator

Claims (1)

(57) [Claim 1] A control signal is changed in pulse width by a carrier signal.
Triangular carrier signal in a pulse width modulator
A carrier signal generator that outputs
And a control signal generator for outputting the carrier signal.
An up signal is output during addition and a down signal is output during reduction.
And a carrier signal and a control signal.
And compare them, and when a match is detected, a match pulse signal
And a matching pulse signal of the matching device.
And the output signal of the up / down signal generator
And a pulse generator for generating a pulse width modulation signal.
The coincidence pulse signal is output and the pulse width modulation signal is
After changing to the bell or L level, the first pulse
To maintain the previous H level or L level to increase the pulse width.
Pulse width modulator to determine .