Circuit for controlling the frequency of PWM IC

Abstract

The present invention comprises a frequency control circuit of a PWM IC (integrated circuit) connected to a frequency control pin of the PWM IC to control the PWM (Pulse Width Modulation) frequency in an analog circuit, the circuit comprising: a first resistor (R1); a second resistor (R2); a third resistor (R3) connected to the frequency control pin of the PWM IC; an optocoupler (100) including a phototransistor with a collector connected to one end of the first resistor and an emitter connected to one end of the second resistor, and an LED with a cathode connected to the third resistor; and an operational amplifier (300) having an output terminal connected to one end of the third resistor and an input signal applied to an inverting input terminal.

Description

Technology Field

[0001] The present invention relates to a frequency control circuit for a Pulse Width Modulation (PWM) IC (integrated circuit), and more particularly to a frequency control circuit for a PWM IC that can control the frequency of the PWM IC by changing a resistor connected to a frequency control pin of the PWM IC. Background Technology

[0002] Generally, in digital circuits, the PWM frequency is controlled via a microcontroller. On the other hand, in analog circuits, to adjust the PWM frequency, it was necessary to add a frequency regulator IC to the PWM IC or to use a PWM IC with a frequency regulation function.

[0003] However, while PWM ICs with frequency control functions exist commercially, they do not exist as space components, and there was a problem in that adding a frequency control IC would complicate the circuit design. Prior art literature

[0004] Republic of Korea Registered Patent No. 10-1179413 {Title of Invention: Digital PWM Generator and Light Emitting Element Driving Device} The problem to be solved

[0005] The present invention has been made in consideration of the above situation, and the objective of the present invention is to provide a frequency control circuit for a PWM IC that can control the frequency of the PWM IC in an analog circuit with a simple circuit configuration. means of solving the problem

[0006] To achieve the above objective, the frequency control circuit of a PWM IC according to an embodiment of the present invention is a frequency control circuit of a PWM IC connected to a frequency control pin of a PWM IC (integrated circuit) to control the PWM (Pulse Width Modulation) frequency in an analog circuit, and is characterized by comprising: a first resistor (R1); a second resistor (R2); a third resistor (R3) connected to the frequency control pin of the PWM IC; an optocoupler including a phototransistor with a collector connected to one end of the first resistor and an emitter connected to one end of the second resistor, and an LED with a cathode connected to the third resistor; and an operational amplifier having an output terminal connected to one end of the third resistor and an input signal applied to an inverting input terminal.

[0007] The frequency control circuit of the PWM IC according to the above embodiment may further include a blocking diode configured to block the current flow between the optocoupler and the operational amplifier.

[0008] In the frequency control circuit of the PWM IC according to the above embodiment, the resistance value applied to the frequency control pin of the PWM IC can be reduced as the amount of opening and closing of the phototransistor of the optocoupler increases.

[0009] In the frequency control circuit of the PWM IC according to the above embodiment, the operational amplifier can be configured as a PID controller in which the output voltage and current are fed back.

[0010] In the frequency control circuit of the PWM IC according to the above embodiment, the current of the LED of the optocoupler can be controlled by the output of the operational amplifier and the resistance value of the third resistor (R3). Effects of the invention

[0011] According to the frequency control circuit of a PWM IC according to an embodiment of the present invention, the circuit is configured to include: a first resistor (R1) connected to the frequency control pin of the PWM IC; a second resistor (R2); a third resistor (R3); an optocoupler comprising a phototransistor with a collector connected to one end of the first resistor and an emitter connected to one end of the second resistor, and an LED with a cathode connected to the third resistor; and an operational amplifier with an output terminal connected to one end of the third resistor and an input signal applied to an inverting input terminal; thereby providing an excellent effect of being able to control the frequency of the PWM IC in an analog circuit with a simple circuit configuration. Brief explanation of the drawing

[0012] Figure 1 is a detailed circuit diagram of a frequency control circuit of a PWM IC according to an embodiment of the present invention. Specific details for implementing the invention

[0013] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or practices of the user or operator. Therefore, such definitions should be based on the content throughout this specification. Terms used in the detailed description are intended merely to describe the embodiments of the present invention and should not be interpreted restrictively. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form. In this description, expressions such as "include" or "comprise" are intended to refer to certain characteristics, numbers, steps, actions, elements, parts thereof, or combinations thereof, and should not be interpreted as excluding the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts thereof, or combinations thereof other than those described.

[0014] In each system illustrated in the drawings, elements in some cases may have the same or different reference numbers, suggesting that the represented elements may be different or similar. However, elements may have different implementations and may operate with some or all of the systems shown or described herein. The various elements illustrated in the drawings may be the same or different. It is optional which is referred to as the first element and which is referred to as the second element.

[0015] In this specification, the phrase “transmits,” “delives,” or “provides” data or signals from one component to another component includes not only the direct transmission of data or signals from one component to another component, but also the transmission of data or signals to another component through at least one other component.

[0017] Hereinafter, a frequency control circuit of a PWM IC according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0018] Figure 1 is a detailed circuit diagram of a frequency control circuit of a PWM IC according to an embodiment of the present invention.

[0019] The frequency control circuit of a PWM IC according to an embodiment of the present invention is connected to the frequency control pin (RT) of a PWM IC (integrated circuit) (10) as shown in FIG. 1. The frequency control circuit of a PWM IC according to an embodiment of the present invention includes a first resistor (R1), a second resistor (R2), a third resistor (R3), an optocoupler (100), a blocking diode (200), and an operational amplifier (300).

[0020] The first resistor (R1) is connected to the frequency control pin (RT) of the PWM IC (10) and serves to determine the reference frequency of the PWM IC (10) (the smaller the resistance value, the higher the frequency).

[0021] The second resistor (R2) is connected to the phototransistor emitter of the optocoupler (100) and forms a parallel equivalent resistor with the first resistor (R1), determining the resistance applied to the frequency control pin (RT) of the PWM IC (10). This determined resistance is a factor that determines the frequency of the PWM IC (10). The greater the amount of switching of the phototransistor of the optocoupler (100), the smaller the resistance value (parallel equivalent resistor value) applied to the frequency control pin (RT) of the PWM IC (10).

[0022] The third resistor (R3) is connected to the LED cathode of the optocoupler (100). The resistance value of the third resistor (R3) and the output of the operational amplifier (300) are factors that regulate the current applied to the LED of the optocoupler (100).

[0023] The optocoupler (100) includes a phototransistor with a collector connected to one end of a first resistor (R1) and an emitter connected to one end of a second resistor (R2), and an LED with a cathode connected to a third resistor (R3). Depending on the switching operation (switching operation) of the optocoupler (100), the parallel combined resistance value of the first resistor (R1) and the second resistor (R2) can be determined.

[0025] The blocking diode (200) serves to block the current flow between the optocoupler (100) and the operational amplifier (300).

[0026] The operational amplifier (300) has its output terminal connected to one end of the third resistor (R3) through the blocking diode (200), and an input signal is applied to the inverting input terminal (-). The operational amplifier (300) can be configured as a PID controller in which the output voltage and current are fed back. When the output of the operational amplifier (300) is HIGH, the corresponding output is above the potential of the optocoupler (100) side, so current flows only through the third resistor (R3), whereas when the output of the operational amplifier (300) is LOW, the corresponding output is lower than the potential of the optocoupler (100) side, so current flows to the operational amplifier (300) side.

[0028] The operation of the frequency control circuit of the PWM IC according to an embodiment of the present invention is explained.

[0029] First, the output value of the operational amplifier (300) is determined according to the input signal, and the current applied to the LED of the optocoupler (100) is controlled by the output of the operational amplifier (300) and the resistance value of the third resistor (R3).

[0030] Next, the optocoupler (100) switches according to the current value applied to the LED, and the parallel combined resistance value of the first resistor (R1) and the second resistor (R2) is determined, and the frequency of the PWM IC (10) can be adjusted by this determined parallel combined resistance value.

[0031] According to the frequency control circuit of a PWM IC according to an embodiment of the present invention, the circuit is configured to include: a first resistor (R1) connected to the frequency control pin of the PWM IC; a second resistor (R2); a third resistor (R3); an optocoupler comprising a phototransistor with a collector connected to one end of the first resistor and an emitter connected to one end of the second resistor, and an LED with a cathode connected to the third resistor; and an operational amplifier with an output terminal connected to one end of the third resistor and an input signal applied to an inverting input terminal; thereby allowing the frequency of the PWM IC in an analog circuit to be controlled with a simple circuit configuration.

[0032] Optimal embodiments have been disclosed in the drawings and specification, and specific terms have been used, but these are used only for the purpose of describing embodiments of the invention and are not intended to limit the meaning or the scope of the invention as described in the claims. Therefore, those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0033] R1: First resistor R2: Second resistor R3: Third resistor RT: Frequency control pin of the PWM IC 10: PWM IC 100: Optocoupler 200: Blocking diode 300: Operational amplifier

Claims

Claim 1 A frequency control circuit of a PWM IC (integrated circuit) (10) connected to a frequency control pin of the PWM IC to control the PWM (Pulse Width Modulation) frequency in an analog circuit, comprising: a first resistor (R1); a second resistor (R2); a third resistor (R3) connected to the frequency control pin of the PWM IC; an optocoupler (100) including a phototransistor with a collector connected to one end of the first resistor and an emitter connected to one end of the second resistor, and an LED with a cathode connected to the third resistor; and an operational amplifier (300) having an output terminal connected to one end of the third resistor and an input signal applied to an inverting input terminal. Claim 2 A frequency control circuit of a PWM IC according to claim 1, further comprising a blocking diode (200) configured to block current flow between the optocoupler (100) and the operational amplifier (300). Claim 3 A frequency control circuit of a PWM IC according to claim 1, wherein the resistance value applied to the frequency control pin of the PWM IC (10) becomes smaller as the amount of phototransistor switching of the optocoupler (100) increases. Claim 4 In claim 1, the operational amplifier (300) is a frequency control circuit of a PWM IC that forms a PID controller in which output voltage and current are fed back. Claim 5 In claim 1, the LED of the optocoupler (100) is a frequency control circuit of a PWM IC in which the current is controlled by the output of the operational amplifier (300) and the resistance value of the third resistor (R3).

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