JPS62130016A - Pulse width modulation control circuit - Google Patents

Abstract

PURPOSE:To generate an accurate waveform by a simple circuit by applying synchronization to triangle wave generators so as to generate triangle waves or sawtooth waves respectively whose phase differs by 180 deg.. CONSTITUTION:The 3rd oscillator 11 generates waveforms (g), (h), that is, two rectangulat wave signals whose time ratio is 50% and whose phase differs by 180 deg., the rectangular wave signal (g) is fed to the 1st oscillator 5a and the signal (h) is fed to the 2nd oscillator 5b respectively. The 1st and 2nd oscillators 5a, 5b generate sawtooth waves (j), (k) synchronized with the rectangular wave signals (g), (h) and are inputted to a non-inverting input terminal (+) of the 1st and 2nd comparators 6, 7. On the other hand, an error amplifier 4 compares a detection signal with a reference signal, amplifies the difference and inputs the result to an inverting input terminal (-) of the 1st and 2nd comparators 6, 7. The comparators 6, 7 compare the sawtooth waves (j), (k) with an output (i) of the error amplifier 4 and a signal having a pulse width in response to the output level of the error amplifier 4 is outputted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pulse width modulation control circuit, and more specifically, a pulse width modulation control circuit, such as a push-pull buck-boost converter, whose phase differs by 180 degrees with respect to input/output fluctuations. The present invention relates to a pulse width modulation (hereinafter referred to as PWM) control circuit that can change the on-time ratio of two switching elements from 0 to 100%.

[Conventional technology]

Generally, control circuits such as converters and switching regulators include error amplifiers and oscillators.

It consists of a modulation section, a logic gate circuit, and, if the switching is a push-pull configuration, a two-phase split circuit.

FIGS. 3 and 4 are a configuration diagram and an operating waveform diagram of a conventional PWM control circuit such as a push-pull buck-boost converter. In FIG. 3, 1 is an input terminal for the detection signal;
2 and 3 are output terminals for pulse width controlled signals, and 4 is the detection signal and reference! ! an error amplifier that compares and amplifies the voltage IO;
5 is a triangular wave generator, 6.7 is a comparator for comparing the error signal and the triangular waveform, 8 is an inverting amplifier, and 9 is a level shift circuit. In FIG. 4, a is the output signal of the error amplifier 4, b is the output signal of the triangular wave generator 5, C is the output signal of the inverting amplifier 8), d is the output signal of the level shift circuit 9, and e is the output terminal. 2, and f is the waveform of output terminal 3.

In Figure 3, the detection output is taken out from the output circuit of the converter or switching regulator and the input terminal l
and is compared with a reference pressure 10 in an error amplifier 4. On the other hand, the generator 5 generates a reference square wave, inputs its output as it is to one input terminal of the comparison tG 6, inputs the other output to the inverting amplifier 8 to take out the inverted output, and further This inverted output is input to the level shift circuit 9 to create a triangular wave whose phase is 180 degrees different from the triangular wave generated by the generator 5, and input to one input terminal of the comparator 7. Further, the output of the error amplifier 4 is inputted to the other input terminals of both comparators 6 and 7, respectively.

Figure 4 (A) shows the operating waveform of the comparator 6, and the ratio unit 6 compares the triangular wave with each error signal, subtracts the error signal a from the triangular wave, and only the positive polarity portion is constant. When the level is output, the PWM output e shown in FIG. 4(d) is obtained. Further, as shown in FIG. 4(b), since the output signal C of the inverting amplifier 8 has negative polarity, it is converted to positive polarity d by the level shift circuit 9 and output to the comparator 7. Figure 4 (
The operation is as shown in c). In Figure 4 (c),
By subtracting the error signal a from the triangular wave d and outputting the positive polarity portion at the same level, the PWM output f shown in FIG. 4(e) is obtained. The switching elements are controlled by the PWM outputs e and f.

[Problem that the invention seeks to solve]

In this way, in the conventional circuit shown in FIG. 3, the oscillator 5 generates a triangular wave, and the inverting amplifier 8 and level shift circuit 9 generate a pulse width side fi whose phase differs by 180 degrees from the triangular wave.
'111 is being generated. However, with such a configuration, if the rising and falling slopes of the triangular wave output signal of the oscillator 5 are not the same, it becomes impossible to accurately shift the phases of the pulse width control signals of the output terminals 2 and 3 by 180 degrees. . Further, since the inverting amplifier 8 and the level shift circuit 9 are required, there is a problem that the circuit configuration becomes complicated and the number of parts increases.

It is an object of the present invention to overcome these conventional problems, and to obtain two control signals whose phases are 180 degrees apart and whose hour ratio changes from 0 to 100% with a simple configuration, and which requires only one circuit. An object of the present invention is to provide a pulse width modulation control circuit that can reduce the number of parts.

c. Means for Solving Problems] In order to achieve the above object, the pulse width modulation control circuit of the present invention includes an error amplifier that compares and amplifies a detection voltage and a reference voltage, and an output of the error amplifier and a sawtooth wave or a double wave. A sawtooth wave or a square wave is generated in a pulse width modulation control circuit equipped with two or more comparators that compare the outputs of oscillators that generate square waves and output signals with pulse widths according to the detected voltage. a third oscillator for synchronizing the output signals of the first and second oscillators by shifting their phases by 180 degrees;
The feature is that one comparator compares the first oscillator output and the error signal, and the other comparator compares the second oscillator output and the error signal.

[For production]

In the circuit shown in Figure 3, the output of one triangular wave generation circuit is inverted and level shifted to convert it into a triangular wave with a different phase, so errors may occur in the output due to different slopes of rise and fall. Become. Therefore, in the present invention, by synchronizing the two triangular wave generators,
By generating triangular waves or sawtooth waves whose phases differ by 180 degrees, accurate waveforms can be generated and realized with a clean circuit with a small number of components.

[Example] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a PWM control circuit showing an embodiment of the present invention, and FIG. 2 is an operation waveform diagram of each part of FIG. 1. In Fig. 1, ■ is the input terminal of the detection signal, 2
, 3 is the pulse width controlled (output terminal of No. 3, 4 is an error amplifier that compares and amplifies the detection signal and the reference voltage, 5a, 5b
are first and second oscillators that generate sawtooth waves or triangular waves, 6 and 7 are first and second comparators, 10 is a reference voltage, and 11 is a third oscillator that synchronizes the first and second oscillators.
It is an oscillator. In FIG. 2, g+h is the output of the third oscillator 11 with a 180 degree phase difference, i is the output of the error amplifier 4, j is the output of the first oscillator 5a, and k is the output of the second oscillator 5a.
Q is the output waveform of the output terminal 2, and m is the output waveform of the output terminal 3.

First, the third oscillator 11 generates waveforms g+h shown in FIGS. 2(a) and 2(b), that is, two rectangular wave signals with a duty ratio of 50% and a phase difference of 180 degrees from each other. These rectangular wave signals g are supplied to the first oscillator 5a, and h is supplied to the second oscillator 5b. The first and second oscillators 5a, 5b.

A sawtooth wave or a triangular wave (a sawtooth wave is generated in Fig. 2 (c) and (d)) synchronized with the respective rectangular wave signals g and h is generated, and the non-conductive signals of the first and second comparators 6 and 7 are generated. Input to the inverting input terminal (+).

On the other hand, the error amplifier 4 compares the detection signal and the reference signal,
The difference between them is amplified and input to the inverting input terminals 7-(-) of the first and second comparators 6 and 7.

Each comparator 6, 7 connects the fJA toothed wave J+ to the error amplifier 4.
, and outputs a signal with a pulse width corresponding to the output level of the error amplifier 4. That is, the first comparator 6
As shown in FIG. 2(c), the sawtooth wave j is at a high level only during JtIJ, which is larger than the error signal i, and is at a low level during the period when j is smaller than i, that is, a rectangular wave signal P
A WM control signal Q (see FIG. 2 (E)) is output. In addition, in the second comparator 7, as shown in FIG. 2(d), the sawtooth wave k is at a high level only during the period when it is larger than the error signal i, and the rectangular wave 4 is at a low level during the period when k is smaller than i.
No. 8, that is, the PWM system 919 signal m (see Figure 2) is output. In this embodiment, as the detection signal level increases, the pulse width decreases, and the detection (output according to the No. 8 level) is performed. The pulse widths of terminals 2 and 3 have a phase difference of 180 degrees.
Changes from 0 to 180% in the idle state.

Furthermore, in this embodiment, since the configuration is as described above, the error amplifier 4, the first oscillator 5a, and the first comparator 6 are
One PWM control circuit IC can be used, and the second
The oscillator 5b and the second comparator 7 also have one PWM control I
C can be used. Further, the third oscillator 11 is
The oscillator of the auxiliary power supply circuit that converters that use the PWM control circuit of this embodiment generally have can be used. That is, in this example, the phase is 180
It is possible to reduce the number of components of a PWM control circuit that obtains two control signals whose duty ratios vary from 0 to 100%.

〔Effect of the invention〕

As explained above, according to the present invention, the circuit configuration is such that a general PWM control IC can be easily applied, so that two control signals with a 180 degree phase difference and a 1 o'clock ratio changing from 0 to 100% can be easily controlled. It is possible to output with a simple configuration and a small number of parts.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a PWM control circuit showing an embodiment of the present invention, FIG. 2 is an operational waveform diagram of each part in FIG. 1, and FIG. 3 is a configuration diagram of a conventional PWM control circuit. FIG. 4 is an operational waveform diagram of each part in FIG. 3. 1: Detection signal input terminal, 2, 3: Pulse width control signal output terminal, 4: Error amplifier, 5+ 5a, 5b: Sawtooth wave or triangular wave oscillator, 6, 7: Comparator, 8: Inverting amplifier, 9 two-level shift 1 ~ circuit, 10: u (v4 voltage, ll
:Third oscillator. Patent applicant Nippon Telegraph and Telephone Corporation, -7 ■ 1 Figure Cow Figure 2 Figure 5 Cow Figure 4

Claims (1)

[Claims] (1) An error amplifier that compares and amplifies the detected voltage and a reference voltage, and compares the output of the error amplifier with the output of an oscillator that generates a sawtooth wave or triangular wave, and outputs a signal with a pulse width corresponding to the detected voltage. In a pulse width modulation control circuit equipped with two or more comparators, first and second oscillators that generate sawtooth waves or triangular waves are synchronized by shifting the phases of the output signals of the first and second oscillators by 180 degrees. 3rd to multiply
1. A pulse width modulation circuit comprising an oscillator, wherein one comparator compares a first oscillator output and an error signal, and the other comparator compares a second oscillator output and an error signal.