A suppression and filtering circuit

Abstract

The present invention belongs to the technical field of electronic circuits, and relates to a suppression and filtering circuit. It is used in products where a large impact current in the back-end circuit may cause damage to the front-end power supply equipment or switch, and the impact current can be effectively suppressed, while taking into account the filtering and isolation effects. Compared with traditional current suppression circuits, this circuit can effectively solve the problem that the input and output at the moment of power-on may bypass the device through the shell to make it lose its suppression ability. The filtering and current suppression are designed as an integrated circuit, and an optocoupler is used as the core switching device. The isolation effect can be effectively exerted after the product is working normally. It has the characteristics of simple circuit structure, integrated current suppression and filtering, low power consumption, and strong anti-interference ability.

Description

Technical Field

[0001] The invention belongs to the technical field of electronic circuits and relates to a suppression and filtering circuit. Background Art

[0002] In circuit design, there is often a large capacitance to ground in the back-end circuit, which will generate a large impact current when the product is powered on. Long-term use may cause damage to the front-end power supply equipment or switching. This impact current is often suppressed, but at the same time, the filtering effect in the circuit has to be taken into account. This circuit designs filtering and current suppression as an integrated circuit, and uses optocouplers as core switching devices. After the product works normally, it can effectively play an isolation role. It has the characteristics of simple circuit structure, integrated current suppression and filtering, low power consumption, and strong anti-interference ability. Summary of the invention

[0003] The purpose of the present invention is to utilize a suppression and filtering circuit to solve the problem of surge current suppression in a circuit while taking into account isolation and filtering functions.

[0004] The technical solution of the present invention is:

[0005] A suppression and filtering circuit, in which the power supply DC input terminal Vin is connected in series with a resistor R1 and a photosensitive diode at the input terminal of an optocoupler to a DC input ground GNDin of the power supply, and a capacitor C1 is connected in parallel at both ends of the photosensitive diode. The power supply DC input Vin and GNDin are filtered by a common-mode inductor L1, and GNDin has a capacitor C3 to the shell ground before L1, and Vin has a capacitor C4 to the shell ground before L1, and GNDin has a capacitor C6 to the shell ground after L1, and Vin has a capacitor C5 to the shell ground after L1, as a filtering circuit. GNDin is connected to the negative output terminal of the optocoupler after filtering by L1, and a resistor R3 is connected in parallel to the output terminal of the optocoupler. The positive output terminal of the optocoupler and Vin filtered by the common-mode inductor L1 are used as the output voltage of the circuit module to supply power to the load-end capacitor C2 and the resistor R4, and C3 and R4 are connected in parallel.

[0006] The impact current is limited by the current limiting resistor R3. After being suppressed, the current meets the requirement of i≤Vin / R3, which can be selected according to needs.

[0007] In the RC delay circuit composed of R1 and C1, a resistor with a larger resistance should be selected, and the corresponding resistance value should be selected according to the DC output voltage.

[0008] The resistor is preferably above 10K level.

[0009] The optical coupler is a photoelectric coupler GH302-1.

[0010] The filter circuit is a common mode inductor L1 connected in series after the power supply DC input Vin and GNDin terminals, and there are shell ground capacitors C3, C4, C5, C6 before and after L1. The inductance value of L1 needs to be selected according to the electromagnetic sensitive frequency band of the circuit.

[0011] The C3 and C4 are preferably equipped with 1uf low-frequency filter capacitors, and the C5 and C6 are preferably equipped with 0.1uf low-frequency filter capacitors.

[0012] The load-end capacitor C2 and resistor R4 are the reasons for the surge current generated at the moment of power-on in the actual back-end circuit, which is often caused by the large capacitance of C2. Here, they should be the equivalent circuit of the actual back-end load circuit and should be selected according to the actual circuit during debugging or simulation.

[0013] The GNDin is used as an external ground in the circuit, and the GNDout is used as an internal ground in the circuit. In actual use, it is not allowed to short-circuit the two through an external cross-linking relationship.

[0014] The advantages and beneficial effects of the present invention are as follows: the advantage of this circuit is that the filtering and current suppression are designed as an integrated circuit, and the optocoupler is used as the core switch device, and the product can effectively play an isolation role after normal operation. It has the characteristics of simple circuit structure, integrated current suppression and filtering, low power consumption, strong anti-interference ability, etc. It greatly simplifies the suppression, filtering, and isolation design requirements in the product circuit, which is of great significance to reducing product power consumption and circuit optimization design. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The circuit schematic diagram of the present invention is DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with embodiments. The following are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Suppression and filtering circuit, in the current suppression circuit, the power supply DC input terminal Vin and the resistor R1, the photosensitive diode at the optocoupler input terminal are connected in series to the power supply DC input ground GNDin, and a capacitor C1 is connected in parallel at both ends of the photosensitive diode. The power supply DC input Vin and GNDin are filtered by the common mode inductor L1, GNDin has a capacitor C3 to the shell ground before LI, Vin has a capacitor C4 to the shell ground before LI, GNDin has a capacitor C6 to the shell ground after LI, and Vin has a capacitor C5 to the shell ground after LI, as a filtering circuit. GNDin is connected to the negative end of the optocoupler output after filtering by L1, and the optocoupler output terminal is connected in parallel with the resistor R3. The positive end of the optocoupler output and the Vin filtered by the common mode inductor L1 are used as the output voltage of the circuit module to supply power to the load end capacitor C2 and the resistor R4, and C3 and R4 are connected in parallel.

[0018] Since the load end is a capacitor C2 with a relatively large capacitance, the potential difference between the two ends of the capacitor is small at the moment of power-on, resulting in a surge current. By connecting a current-limiting resistor R3 in series with C2, the surge current can be limited at the moment of power-on, and the current will be limited to i≤Vin / R3. Then, the input end of the optocoupler GH302-1 is controlled by using the RC delay circuit composed of R1 and C1. C1 starts to charge after power-on. When the voltage across C1 meets the current loop composed of R2 and the photodiode at the input end of the optocoupler, the current does not reach the minimum trigger current of the optocoupler GH302-1. The output end of the optocoupler is in the amplification area at this time. As the voltage across C1 increases, the optocoupler As the input current increases, the resistance of the optocoupler output terminal decreases, and the potential difference between GNDout and GNDin decreases. When the voltage across C1 meets the current loop formed by R2 and the photodiode at the optocoupler input terminal, the current reaches the minimum trigger current of the optocoupler GH302-1, and the optocoupler output terminal reaches saturation, R3 is short-circuited, GNDout and GNDin are turned on, and the product is powered on. The optocoupler output terminal is gradually turned on through RC charging control, and the potential difference between GNDout and GNDin gradually decreases, achieving the function of delayed power-on.

[0019] The impact current is limited by the current limiting resistor R3. After being suppressed, the current meets the requirement of i≤Vin / R3, which can be selected according to needs.

[0020] In the RC delay circuit composed of R1 and C1, in order to prevent the generation of impact current due to the charging of C1 when power is turned on, R1 has a current limiting function, and a resistor with a larger resistance should be selected. The corresponding resistance value is selected according to the DC output voltage, preferably above 10K.

[0021] The core device is the photocoupler GH302-1, so the power-on delay of the product is required to be as short as possible. If the power-on delay is long, and the power is turned on multiple times in a short period of time, the capacitor will have a secondary discharge, which will cause a new impact current. Therefore, an optocoupler is selected, which has the advantages of isolation, strong anti-interference, and short response time.

[0022] The filtering circuit is a common-mode inductor L1 connected in series after the power supply DC input Vin and GNDin terminals, and there are shell ground capacitors C3, C4, C5, C6 before and after L1. The inductance value of L1 needs to be selected according to the electromagnetic sensitive frequency band of the circuit. C3 and C4 are preferably 1uf low-frequency filter capacitors, and C5 and C6 are preferably 0.1uf low-frequency filter capacitors.

[0023] The load-end capacitor C2 and resistor R4 are the reasons for the surge current generated at the moment of power-on in the actual back-end circuit, which is often caused by the large capacitance of C2. Here, they should be the equivalent circuit of the actual back-end load circuit and should be selected according to the actual circuit during debugging or simulation.

[0024] The GNDin is used as the external ground in the circuit, and the GNDout is used as the internal ground in the circuit. In actual use, it is not allowed to short-circuit the two through an external cross-linking relationship, otherwise the suppression circuit will be short-circuited, and the expected effect of surge current suppression cannot be achieved at the moment of power-on.

[0025] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those skilled in the art in the field to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here. The specific implementation methods described above further explain the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A suppression and filtering circuit, characterized in that: The power supply DC input terminal Vin is connected in series with the resistor R1 and the photosensitive diode at the input terminal of the optocoupler to the power supply DC input ground GNDin, and a capacitor C1 is connected in parallel at both ends of the photosensitive diode; the power supply DC input Vin and GNDin are filtered by the common mode inductor L1, GNDin has a capacitor C3 to the shell ground before LI, Vin has a capacitor C4 to the shell ground before LI, GNDin has a capacitor C6 to the shell ground after LI, and Vin has a capacitor C5 to the shell ground after LI, as a filtering circuit; GNDin is connected to the negative end of the optocoupler output after being filtered by L1, and the optocoupler output end is connected in parallel with resistor R3. The positive end of the optocoupler output and Vin filtered by the common-mode inductor L1 are used as the output voltage of the circuit to supply power to the load end capacitor C2 and resistor R4, and C3 is connected in parallel with R4.

2. A suppression and filtering circuit according to claim 1, characterized in that: The limit of the inrush current is determined by the current limiting resistor R3. After suppression, the current meets the requirement of i≤Vin / R3, which can be selected according to needs.

3. A suppression and filtering circuit according to claim 1, characterized in that: In the RC delay circuit composed of R1 and C1, resistors with a resistance value of 10K or above should be selected, and the corresponding resistance value should be selected according to the DC output voltage.

4. A suppression and filtering circuit according to claim 1, characterized in that: The optical coupler is a photoelectric coupler GH302-1.

5. A suppression and filtering circuit according to claim 1, characterized in that: The filter circuit is a common mode inductor L1 connected in series after the power supply DC input Vin and GNDin terminals, and there are shell ground capacitors C3, C4, C5, C6 before and after L1. The inductance value of L1 needs to be selected according to the electromagnetic sensitive frequency band of the circuit.

6. A suppression and filtering circuit according to claim 1, characterized in that: The C3 and C4 are selected as 1uf low-frequency filter capacitors, and the C5 and C6 are selected as 0.1uf low-frequency filter capacitors.

7. A suppression and filtering circuit according to claim 1, characterized in that: The load-end capacitor C2 and resistor R4 are the reasons for the surge current generated at the moment of power-on in the actual back-end circuit, which is often caused by the large capacitance of C2. Here, they should be the equivalent circuit of the actual back-end load circuit and should be selected according to the actual circuit during debugging or simulation.

8. A suppression and filtering circuit according to claim 1, characterized in that: The GNDin is used as an external ground in the circuit, and the GNDout is used as an internal ground in the circuit. In actual use, it is not allowed to short-circuit the two through an external cross-linking relationship.

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