CN108494387B

CN108494387B - Operational PWM generating circuit

Info

Publication number: CN108494387B
Application number: CN201810251369.8A
Authority: CN
Inventors: 陈建锋; 刘建朋
Original assignee: Cixi Zhongfa Lamps Co ltd
Current assignee: Cixi Zhongfa Lamps Co ltd
Priority date: 2018-03-26
Filing date: 2018-03-26
Publication date: 2022-04-19
Anticipated expiration: 2038-03-26
Also published as: CN108494387A

Abstract

The invention discloses an operational PWM generating circuit, which comprises an analog signal input end, an analog signal operation module, a frequency-adjustable waveform generator, a comparator, a logic output control circuit and a PWM signal output end, wherein the analog signal input end provides an input analog voltage signal for the analog signal operation module, the analog signal operation module performs operation to send the operated input analog voltage signal to the comparator, the comparator compares the operated input analog voltage signal with a waveform signal output by the frequency-adjustable waveform generator and outputs a digital pulse signal, and finally, the digital pulse signal is output to the corresponding PWM signal output end through the logic control output circuit. The invention has the capability of realizing corresponding PWM signal output on the premise that the input analog signal is not subjected to AD conversion and is calculated by software, thereby being widely applied to a circuit for converting the analog signal input into the PWM output.

Description

Operational PWM generating circuit

Technical Field

The invention relates to an operational PWM generating circuit.

Background

Pulse Width Modulation (PWM) is a very efficient technique for controlling analog circuits using the digital output of a microprocessor, and is widely used in many fields ranging from measurement, communications to power control and conversion, and LED lighting. By controlling the analog circuitry in a digital manner, the cost and power consumption of the system can be greatly reduced. In addition, many microcontrollers and DSPs already contain PWM controllers on chip, which makes the implementation of digital control easier. The existing PWM has no operation performance, so that the light source jitter is unstable, the multi-light-source adjusting capability is limited, and the application range is limited.

Disclosure of Invention

Technical problem to be solved

The present invention is directed to overcome the above-mentioned disadvantages, and aims to provide an operational PWM generating circuit.

(II) technical scheme

In order to achieve the above object, the operational PWM generating circuit of the present invention includes an analog signal input terminal, an analog signal operational module, a frequency-adjustable waveform generator, a comparator, a logic output control circuit, and a PWM signal output terminal; the analog signal input end provides an input analog voltage signal for the analog signal operation module, the analog signal operation module performs operation, the operated input analog voltage signal is sent to the comparator, the comparator compares the operated input analog voltage signal with a waveform signal output by the frequency-adjustable waveform generator and outputs a digital pulse signal, and finally, the digital pulse signal is output to a corresponding PWM signal output end through the logic control output circuit.

Further, the analog signal input includes V1in, V2in, and OPA1 followers; the analog signal operation module comprises an OPA2 subtraction circuit; the frequency-adjustable waveform generator comprises a Rosc generator, a Cosc generator and a sawtooth generator, wherein the sawtooth generator is used for outputting a specific waveform, and the Rosc generator and the Cosc generator are used for adjusting the frequency and the amplitude of the specific waveform; the comparators comprise a COMP1 comparator, a COMP2 comparator and a COMP3 comparator; the PWM signal output terminals comprise PWM1, PWM2 and PWM 3.

Further, the V1in is divided into two paths of signals through an OPA1 follower, wherein one path of signals is compared with output signals of a sawtooth wave generator through a COMP1 comparator to obtain a pulse signal 1; the other path of signal is calculated by an OPA2 subtraction circuit and V2in to output the difference (V1in-V2in) between the two signals, the output signal of the OPA2 subtraction circuit is compared with the output signal of a sawtooth generator by a COMP2 comparator to obtain a pulse signal 2; the V2in is also compared with the output signals of a COMP3 comparator and a sawtooth wave generator to obtain a pulse signal 3.

Further, the pulse signal 1, the pulse signal 2 and the pulse signal 3 are output to the corresponding output terminals PWM1, PWM2 and PWM3 through the logic control output circuit.

Further, the specific waveform includes a periodic sawtooth wave, a triangular wave, a sine wave, and a cosine wave whose amplitudes are positive values.

Further, the logic control output circuit includes a circuit having de-jitter and having a push-pull configuration.

Further, the de-jittering and push-pull structure circuit is composed of an RS trigger and a push-pull output.

(III) advantageous effects

Compared with the prior art, the technical scheme of the invention has the following advantages: the invention has very high input impedance, and does not influence the input characteristic of the circuit; the frequency adjustable waveform generator has the characteristic that the output waveform has the frequency continuously adjusted by adjusting the value of the resistor capacitor; the output logic control circuit has the driving capability of debouncing and strong output; the input analog signal can realize the corresponding PWM signal output capacity without AD conversion and software calculation, so the method is widely applied to a circuit for converting the analog signal input into the PWM output.

Drawings

FIG. 1 is a block diagram of an operational PWM generating circuit according to the present invention;

FIG. 2 is a circuit diagram of an operational PWM generating circuit according to the present invention;

fig. 3 is a schematic circuit diagram of an operational PWM generating circuit according to an embodiment of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

As shown in fig. 1 and fig. 2, the operational PWM generating circuit of the present invention includes an analog signal input terminal, an analog signal operation module, a frequency-adjustable waveform generator, a comparator, a logic output control circuit, and a PWM signal output terminal; the analog signal input end provides an input analog voltage signal for the analog signal operation module, the analog signal operation module performs operation, the operated input analog voltage signal is sent to the comparator, the comparator compares the operated input analog voltage signal with a waveform signal output by the frequency-adjustable waveform generator and outputs a digital pulse signal, and finally, the digital pulse signal is output to a corresponding PWM signal output end through the logic control output circuit.

The analog signal input comprises a V1in, a V2in and an OPA1 follower; the analog signal operation module comprises an OPA2 subtraction circuit; the frequency-adjustable waveform generator comprises a Rosc generator, a Cosc generator and a sawtooth generator, wherein the sawtooth generator is used for outputting a specific waveform, and the Rosc generator and the Cosc generator are used for adjusting the frequency and the amplitude of the specific waveform; the comparators comprise a COMP1 comparator, a COMP2 comparator and a COMP3 comparator; the PWM signal output terminals comprise PWM1, PWM2 and PWM 3.

The V1in is divided into two paths of signals through an OPA1 follower, wherein one path of signals is compared with output signals of a sawtooth generator through a COMP1 comparator to obtain a pulse signal 1; the other path of signal is calculated by an OPA2 subtraction circuit and V2in to output the difference (V1in-V2in) between the two signals, the output signal of the OPA2 subtraction circuit is compared with the output signal of a sawtooth generator by a COMP2 comparator to obtain a pulse signal 2; the V2in is also compared with the output signals of a COMP3 comparator and a sawtooth wave generator to obtain a pulse signal 3.

The pulse signal 1, the pulse signal 2 and the pulse signal 3 are output to corresponding output ends PWM1, PWM2 and PWM3 through a logic control output circuit.

The specific waveform includes a periodic sawtooth wave, a triangular wave, a sine wave and a cosine wave with positive amplitude.

The logic control output circuit includes a circuit having de-jitter and having a push-pull configuration.

The de-jittering and push-pull structure circuit is composed of an RS trigger and a push-pull output.

The practical application circuit is shown in fig. 3, two sliding varistors of R1 and R2, a fixed resistor R3 and a capacitor C1 are added in the circuit, wherein V1out is directly connected to one end of the sliding varistor R2. The analog voltage of V1in is taken from the voltage of the sliding varistor R1, and the voltage of V2in is taken from the voltage division of V1out on the sliding varistor R2, so that V2in is V1in Rx/R2, where Rx is the resistance of the V2in pin with respect to ground in the sliding varistor R2. Therefore, according to the analysis of the previous circuit, it can be found that the analog voltage corresponding to the PWM2 is V1in (1-Rx/R2), while the analog signal corresponding to the PWM3 is V1in Rx/R2, and the analog voltage corresponding to the PWM1 is Vin, and the magnitude of the voltage is adjusted by the sliding resistor R1. Therefore, the output signals corresponding to the PWM1 and the PWM2 can drive two LED arrays with different color temperatures, so that the sum of the output power of the two LEDs is always kept constant, and the size of the two LEDs is adjusted by the R1 sliding rheostat. When the brightness is fixed, the duty ratios of the PWM2 and the PWM3 can be complementarily changed by adjusting the slide rheostat R2, and therefore the combination that the two paths of LEDs with different color temperatures have different brightness and generate different color temperatures is achieved.

The invention has very high input impedance, and does not influence the input characteristic of the circuit; the frequency adjustable waveform generator has the characteristic that the output waveform has the frequency continuously adjusted by adjusting the value of the resistor capacitor; the output logic control circuit has the driving capability of debouncing and strong output; the input analog signal can realize the corresponding PWM signal output capacity without AD conversion and software calculation, so the method is widely applied to a circuit for converting the analog signal input into the PWM output.

In summary, the above embodiments are not intended to be limiting embodiments of the present invention, and modifications and equivalent variations made by those skilled in the art based on the spirit of the present invention are within the technical scope of the present invention.

Claims

1. An operational PWM generating circuit, comprising: the device comprises an analog signal input end, an analog signal operation module, a frequency-adjustable waveform generator, a comparator, a logic output control circuit and a PWM signal output end; the analog signal input end provides an input analog voltage signal for the analog signal operation module, the analog signal operation module performs operation, the operated input analog voltage signal is sent to the comparator, the comparator compares the operated input analog voltage signal with a waveform signal output by the frequency-adjustable waveform generator and outputs a digital pulse signal, and finally, the digital pulse signal is output to a corresponding PWM signal output end through the logic control output circuit;

the analog signal input comprises a V1in, a V2in and an OPA1 follower; the analog signal operation module comprises an OPA2 subtraction circuit; the frequency-adjustable waveform generator comprises a Rosc generator, a Cosc generator and a sawtooth generator, wherein the sawtooth generator is used for outputting a specific waveform, and the Rosc generator and the Cosc generator are used for adjusting the frequency and the amplitude of the specific waveform; the comparators comprise a COMP1 comparator, a COMP2 comparator and a COMP3 comparator; the PWM signal output end comprises PWM1, PWM2 and PWM 3;

2. The operable PWM generation circuit according to claim 1, wherein: the pulse signal 1, the pulse signal 2 and the pulse signal 3 are output to corresponding output ends PWM1, PWM2 and PWM3 through a logic control output circuit.

3. The operable PWM generation circuit according to claim 2, wherein: the specific waveform includes a periodic sawtooth wave, a triangular wave, a sine wave and a cosine wave with positive amplitude.

4. The operable PWM generation circuit according to claim 3, wherein: the logic control output circuit includes a circuit having de-jitter and having a push-pull configuration.

5. The operable PWM generation circuit according to claim 4, wherein: the de-jittering and push-pull structure circuit is composed of an RS trigger and a push-pull output.