PWM modulator

Abstract

The PWM modulator comprises a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3, a chip U1A, a chip U1B and a triode Q1, one end of the capacitor C1 is connected with the resistor R1, the resistor R3, the resistor R4, the resistor R5, a potentiometer VR1 and a power supply VCC, the other end of the resistor R1 is connected with the resistor R2, the resistor R6 and a pin 5 of the chip U1B, the other end of the resistor R6 is connected with the other end of the capacitor C1, a capacitor C3 and a grounding end, and the triode Q1 is connected with the capacitor C1. According to the utility model, chip control is not needed, the hysteresis function of the comparator is ingeniously utilized to set the frequency of the sawtooth wave, and the amplification functions of the adjustable potentiometer and the triode are utilized to set a comparison threshold value for the comparator and compare the sawtooth wave to output PWM, so that not only can the frequency be modulated, but also the duty ratio of the PWM can be modulated. The method can be widely applied to electronic control products needing PWM adjustment.

Description

Technical Field

[0001] The utility model relates to the technical field of PWM, in particular to a PWM modulator. Background Art

[0002] A PWM (Pulse Width Modulation) modulator is an electronic component or system that is used to control the output of an analog circuit by adjusting the width of a pulse signal (i.e., the duty cycle). PWM modulators are widely used in motor control, power management, LED lighting regulation, and other fields.

[0003] The existing PWM modulators have poor versatility, low sensitivity and high cost. Utility Model Content

[0004] In order to make up for the deficiencies of the prior art, the embodiments of the present application propose a PWM modulator to solve the problems mentioned in the prior art.

[0005] In order to solve the above technical problems, the utility model provides the following technical solutions:

[0006] A PWM modulator comprises a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3, a chip U1A, a chip U1B and a transistor Q1, wherein one end of the capacitor C1 is connected to the resistor R1, the resistor R3, the resistor R4, the resistor R5, a potentiometer VR1 and a power supply VCC, the other end of the resistor R1 is connected to the resistor R2, the resistor R6 and the pin 5 of the chip U1B, the other end of the resistor R6 is connected to the other end of the capacitor C1, the capacitor C3 and a ground terminal, the other end of the capacitor C3 is connected to the resistor R7, the pin 6 of the chip U1B and the pin 3 of the chip U1A, the other end of the resistor R2 is connected to the resistor R3, the resistor R7 and the pin 7 of the chip U1B, the other end of the potentiometer VR1 is connected to the resistor R8 and the base of the transistor Q1, the emitter of the transistor Q1 is connected to the resistor R4, the capacitor C2 and the pin 2 of the chip U1A, the other end of the resistor R8 is connected to the other end of the capacitor C2 and the collector of the transistor Q1, and the pin 1 of the chip U1A is connected to the other end of the resistor R5 and PWM.

[0007] As a further technical solution of the utility model: the transistor Q1 is a PNP transistor.

[0008] As a further technical solution of the present invention: the chip U1A is a comparator chip.

[0009] As a further technical solution of the present invention: the chip U1 B is a comparator chip.

[0010] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: the utility model does not require chip control, and cleverly uses the hysteresis function of the comparator to set the frequency of the sawtooth wave, and uses the adjustable potentiometer and the amplification function of the transistor to set the comparison threshold of the comparator, and compares the sawtooth wave to output PWM, which can not only modulate the frequency, but also modulate the duty cycle of PWM. It can be widely used in electronic control products that require PWM adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 The utility model provides a PWM modulator principle diagram according to an embodiment of the present invention. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the utility model are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0013] Reference Figure 1 A PWM modulator includes a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3, a chip U1A, a chip U1B and a transistor Q1, one end of the capacitor C1 is connected to the resistor R1, the resistor R3, the resistor R4, the resistor R5, the potentiometer VR1 and the power supply VCC, the other end of the resistor R1 is connected to the resistor R2, the resistor R6 and the pin 5 of the chip U1B, the other end of the resistor R6 is connected to the other end of the capacitor C1, the capacitor C3 and the ground terminal, the other end of the capacitor C3 is connected to the resistor R7, the pin 6 of the chip U1B and the pin 3 of the chip U1A, the other end of the resistor R2 is connected to the resistor R3, the resistor R7 and the chip U1 B's pin 7, the other end of the potentiometer VR1 is connected to the resistor R8 and the base of the transistor Q1, the emitter of the transistor Q1 is connected to the resistor R4, the capacitor C2 and the pin 2 of the chip U1A, the other end of the resistor R8 is connected to the other end of the capacitor C2 and the collector of the transistor Q1, and the pin 1 of the chip U1A is connected to the other end of the resistor R5 and PWM.

[0014] Here’s how it works:

[0015] Sawtooth wave generation circuit: cleverly using the hysteresis comparator principle, the DC voltage VCC will generate two thresholds V1 = VCC * [R1 * (R2 + R6) / (R2 * R6)], V2 = VCC * [(R1 * R2 * R6) / (R1 + R2)] at the same direction end of the 5th pin of the comparator U1 B through the voltage division of the resistor R1 and the resistor R6, and the feedback effect of R2. When powered on, the voltage of the same direction end of the 5th pin of the comparator U1B is higher than that of the reverse end 6th pin, and the output end 7th pin of the comparator U1B outputs a high level. At the same time, VCC charges the capacitor C3 through R7. Because the voltage of the capacitor C3 cannot change suddenly, it can only rise at a certain slope. When the voltage of the capacitor C3 at the reverse end 6th pin of the comparator U1B rises to the high threshold voltage V2, the output end 7th pin of the comparator U1B is pulled down to the reference ground. Due to the effect of the hysteresis comparator, the charge of the capacitor C3 will be released to the low threshold V1 at this time. At this time, the voltage at the same direction end of pin 5 of the comparator U1B is higher than the voltage at the reverse direction end pin 6, and the pin 7 of the comparator U1B charges the capacitor C3 again, and the cycle repeats over and over again. By changing the capacitance of capacitor C3, the charging time of the capacitor can be changed, thereby changing the frequency.

[0016] PWM generation circuit: The sawtooth wave generated above is compared with the inverse end 2 pin of comparator U1A through the same direction end 3 pin of comparator U1A. The threshold voltage of the inverse end 2 pin of comparator U1A is obtained by the voltage division of adjustable resistor VR1 and resistor R8 by using the amplification effect of PNP transistor. By adjusting the resistance value of resistor VR1 and the voltage division of R8, the threshold voltage of the same direction end 3 pin of comparator U1A can be adjusted, and the duty cycle can be changed.

[0017] From the above principle, it can be seen that once this circuit is built, adjusting the capacity of capacitor C3 can change the frequency of PWM, and adjusting the adjustable resistor VR1 can adjust the duty cycle of PWM.

[0018] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

[0019] In addition, it should be understood that although this specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment have also been appropriately combined to form other implementation modes that are easy for those skilled in the art to understand.

Claims

1. A PWM modulator, comprising a capacitor C1, a capacitor C2, a resistor R1, a resistor R2, a resistor R3, a chip U1A, a chip U1B and a transistor Q1, characterized in that: One end of the capacitor C1 is connected to resistor R1, resistor R3, resistor R4, resistor R5, potentiometer VR1 and power supply VCC, the other end of resistor R1 is connected to resistor R2, resistor R6 and pin 5 of chip U1 B, the other end of resistor R6 is connected to the other end of capacitor C1, capacitor C3 and ground, the other end of capacitor C3 is connected to resistor R7, pin 6 of chip U1 B and pin 3 of chip U1A, the other end of resistor R2 is connected to resistor R3, resistor R7 and pin 7 of chip U1 B, the other end of potentiometer VR1 is connected to resistor R8 and the base of transistor Q1, the emitter of transistor Q1 is connected to resistor R4, capacitor C2 and pin 2 of chip U1A, the other end of resistor R8 is connected to the other end of capacitor C2 and the collector of transistor Q1, and pin 1 of chip U1A is connected to the other end of resistor R5 and PWM.

2. A PWM modulator according to claim 1, characterized in that: The transistor Q1 is a PNP transistor.

3. A PWM modulator according to claim 1, characterized in that: The chip U1A is a comparator chip.

4. A PWM modulator according to claim 1, characterized in that: The chip U1 B is a comparator chip.

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