Disclosure of Invention
The purpose of the invention is: a suppression and filtering circuit is provided to solve the problem of suppression of inrush current in the circuit and to achieve both isolation and filtering functions.
The technical scheme of the invention is as follows:
in the current suppression circuit, a power supply direct current input end Vin, a resistor R1 and a photosensitive diode at an optical coupling input end are connected in series to a power supply direct current input ground GNDin, and two ends of the photosensitive diode are connected with a capacitor C1 in parallel. The DC inputs Vin and GNDin of the power supply are filtered by a common mode inductor L1, the GNDin has a capacitor C3 to the shell ground before LI, the Vin has a capacitor C4 to the shell ground before LI, the GNDin has a capacitor C6 to the shell ground after LI, and the Vin has a capacitor C5 to the shell ground after LI as a filter circuit. GNDin is filtered by L1 and then connected to the negative end of an optical coupler output, the output end of the optical coupler is connected in parallel with a resistor R3, Vin filtered by a common-mode inductor L1 and the positive end of the optical coupler output are used as output voltage of the circuit module to supply power to a load end capacitor C2 and a resistor R4, and C3 is connected in parallel with R4.
The limit of the impact current is determined by a current limiting resistor R3, the current after being restrained meets the requirement that i is less than or equal to Vin/R3, and the current can be selected and matched according to the requirement.
In the RC delay circuit consisting of R1 and C1, a resistor with a larger resistance value is selected, a corresponding resistance value is selected according to the DC output voltage,
the resistor is preferably above the 10K level.
The optical coupler is a photoelectric coupler GH 302-1.
The filter circuit is characterized in that a common mode inductor L1 is connected in series behind a direct current input Vin and a GNDin end of a power supply, and the front and the rear of LI are provided with inductance values of shell ground capacitors C3, C4, C5, C6, L1 and L1 which need to be selected and matched according to an electromagnetic sensitive frequency band of the circuit.
And the C3 and the C4 are preferably matched with 1uf low-frequency filter capacitors, and the C5 and the C6 are preferably matched with 0.1uf low-frequency filter capacitors.
The load end capacitor C2 and the resistor R4 are the reasons for the surge current generated at the power-on moment in the actual back end circuit, and are often caused by the large capacitance value of C2, and should be an equivalent circuit of the actual back end load circuit, and should be selected and matched according to the actual circuit during debugging or simulation.
The GNDin is used as an external ground in the circuit, and the GNDout is used as an internal ground in the circuit, so that the GNDin and the GNDout are not allowed to be shorted through an external cross-linking relation in practical use.
The invention has the advantages and beneficial effects that: the circuit has the advantages that the filtering and current suppression are designed into an integrated circuit, the optocoupler is used as a core switch device, and the product can effectively play an isolation role after normal work. The circuit has the characteristics of simple structure, integration of current collection suppression and filtering, low power consumption, strong anti-interference capability and the like. The design requirements of suppression, filtering and isolation in a product circuit are greatly simplified, and the method has great significance for reducing the power consumption of the product and optimizing the design of the circuit.
Detailed Description
The present invention will be further described with reference to the following examples. The following description is only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the current suppression circuit, a power supply direct current input end Vin, a resistor R1 and a photosensitive diode at an optical coupler input end are connected in series to a power supply direct current input ground GNDin, and two ends of the photosensitive diode are connected in parallel with a capacitor C1. The DC inputs Vin and GNDin of the power supply are filtered by a common mode inductor L1, the GNDin has a capacitor C3 to the shell ground before LI, the Vin has a capacitor C4 to the shell ground before LI, the GNDin has a capacitor C6 to the shell ground after LI, and the Vin has a capacitor C5 to the shell ground after LI as a filter circuit. GNDin is filtered by L1 and then connected to the negative end of an optical coupler output, the output end of the optical coupler is connected in parallel with a resistor R3, Vin filtered by a common-mode inductor L1 and the positive end of the optical coupler output are used as output voltage of the circuit module to supply power to a load end capacitor C2 and a resistor R4, and C3 is connected in parallel with R4.
Because the load end is the capacitor C2 with a large capacitance value, the potential difference between the two ends of the capacitor is small at the power-on moment, and the generation of impact current is caused. By connecting a current-limiting resistor R3 in series with C2, the effect of limiting impact current can be achieved at the moment of power-on, the current is limited to be i less than or equal to Vin/R3, then the input end of an optocoupler GH302-1 is controlled by using a RC delay circuit formed by R1 and C1, C1 starts to be charged after power-on, when the voltage at two ends of C1 meets the condition that the current in a current loop formed by the R2 and a photodiode at the input end of the optocoupler does not reach the minimum trigger current of the optocoupler GH302-1, the output end of the optocoupler is positioned in an amplification area, the current at the input end of the optocoupler is increased along with the increase of the voltage at two ends of C1, the resistance at the output end of the optocoupler is reduced, the potential difference between GNDout and GNDin is reduced, when the voltage at two ends of C1 meets the condition that the current in the current loop formed by the R2 and the photodiode at the input end of the optocoupler reaches the minimum trigger current of the optocoupler GH302-1, the output end reaches the saturation, the optocoupler, the output end reaches the saturation, R3 is shorted, and the GNDin is conducted, after the product is electrified, the output end of the optocoupler is controlled to be gradually conducted through RC charging, and the potential difference between GNDout and GNDin is gradually reduced, so that the function of delaying electrification is achieved.
The limit of the impact current is determined by a current limiting resistor R3, the current after being restrained meets the requirement that i is less than or equal to Vin/R3, and the current can be selected and matched according to the requirement.
In the RC delay circuit consisting of the R1 and the C1, in order to prevent the generation of impact current caused by C1 charging during power-on, a resistor with a larger resistance value is selected for the current-limiting function of the R1, and the corresponding resistance value is selected according to the direct current output voltage, preferably more than 10K grade.
The core device is a photoelectric coupler GH302-1, so that the power-on delay of a product is required to be as short as possible, if the power-on delay is long, and multiple power-on is carried out in a short time, secondary discharge exists in a capacitor, and new impact current can be caused, so that the selected photoelectric coupler has the advantages of being high in isolation and anti-interference performance, short in response time and the like.
The filter circuit is characterized in that a common mode inductor L1 is connected in series behind the direct current input Vin and GNDin ends of a power supply, the front and the rear of LI are provided with shell ground capacitors C3, C4, C5, C6, L1 and L1 inductance values which need to be selected and matched according to the electromagnetic sensitive frequency band of the circuit, and C3 and C4 are preferably selected and matched with a 1uf low-frequency filter capacitor, and C5 and C6 are preferably selected and matched with a 0.1uf low-frequency filter capacitor.
The load end capacitor C2 and the resistor R4 are the reasons for the surge current generated at the power-on moment in the actual back end circuit, and are often caused by the large capacitance value of C2, and should be an equivalent circuit of the actual back end load circuit, and should be selected and matched according to the actual circuit during debugging or simulation.
The GNDin is used as an external ground in the circuit, and the GNDout is used as an internal ground in the circuit, so that the GNDin and the GNDout are not allowed to be short-circuited through an external cross-linking relation in practical use, otherwise, the suppression circuit is short-circuited, and the expected effect of surge current suppression cannot be achieved at the moment of power-on.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.