Optimized energizing current suppression circuit

Abstract

The utility model relates to the technical field of circuit design, in particular to an optimized power-on current suppression circuit, a voltage dependent resistor RV1, a safety capacitor CX1 and a discharge resistor are connected in parallel between a live wire L and a zero line N. The voltage dependent resistor RV1 is located at the rear end of a fuse F1, the safety capacitor CX1 is located at the rear end of the voltage dependent resistor RV1, the discharge resistor is located at the rear end of the safety capacitor CX1, and the discharge resistor is located at the rear end of the safety capacitor CX1. The rear end of the discharge resistor is connected with a common mode inductor L1, the rear end of the common mode inductor L1 is connected with a rectifier bridge DB1, the rear end of the rectifier bridge DB1 is connected with a rectification filter electrolytic capacitor EC1, a first capacitor C1 and a second capacitor C2 are connected in parallel between the live wire L and the null line N, and the live wire L is connected in series with an NTC thermistor RT1. Compared with the prior art, the optimized energizing current suppression circuit not only can suppress energizing impact current, but also can improve EMC / EMI effects of the circuit.

Description

[Technical field]

[0001] The utility model relates to the technical field of circuit design, in particular to an optimized power-on current suppression circuit. [Background technology]

[0002] Electrical equipment usually has a power conversion circuit inside, which converts the external power supply into an internal power supply that can meet the voltage and current requirements of the internal circuit. In order to ensure the stability of the internal power output, this part of the power conversion circuit often uses a large-capacitance filter capacitor. In this way, the filter capacitor is charged when the power is turned on. Because the circuit input internal resistance is small, a large impact current will be formed during the charging stage. This impact current will have a strong impact on the input fuse. When the filter capacitor has a large capacitance and the input voltage is high, if the rated current of the selected fuse is not large enough, it may cause the fuse to blow. If the rated current of the fuse is increased, the fuse will react insensitively, and the fuse will react slowly when it should be protected from blowing, and it will not play a good protective role. [Contents of the utility model]

[0003] In order to overcome the above problems, the utility model proposes an optimized on-current suppression circuit which can effectively solve the above problems.

[0004] The utility model provides a technical solution to solve the above technical problems: an optimized power-on current suppression circuit is provided, comprising a live wire L and a neutral wire N, the input end of the live wire L is connected with a fuse F1, a varistor RV1, a safety capacitor CX1 and a discharge resistor are connected in parallel between the live wire L and the neutral wire N, the varistor RV1 is located at the rear end of the fuse F1, the safety capacitor CX1 is located at the rear end of the varistor RV1, the discharge resistor is located at the rear end of the safety capacitor CX1, the rear end of the discharge resistor is connected with a common-mode inductor L1, the rear end of the common-mode inductor L1 is connected with a rectifier bridge DB1, and the rear end of the rectifier bridge DB1 is connected with a rectifier and filter electrolytic capacitor EC1; a first capacitor C1 and a second capacitor C2 are also connected in parallel between the live wire L and the neutral wire N, and an NTC thermistor RT1 is connected in series on the live wire L.

[0005] Preferably, the first capacitor C1, the second capacitor C2, the NTC thermistor RT1 and the common mode inductor L1 form a π-type filter circuit.

[0006] Preferably, the first capacitor C1 is located between the safety capacitor CX1 and the discharge resistor, the second capacitor C2 is located between the common-mode inductor L1 and the rectifier bridge DB1, and the NTC thermistor RT1 is located between the discharge resistor and the common-mode inductor L1.

[0007] Preferably, the first capacitor C1 and the second capacitor C2 are located between the rectifier bridge DB1 and the rectifier filter electrolytic capacitor EC1, and the NTC thermistor RT1 is located between the first capacitor C1 and the second capacitor C2.

[0008] Preferably, the first capacitor C1 is located between the varistor RV1 and the safety capacitor CX1, the NTC thermistor RT1 is located between the first capacitor C1 and the safety capacitor CX1, and the second capacitor C2 is located between the common mode inductor L1 and the rectifier bridge DB1.

[0009] Preferably, the numbers of turns of the windings on both sides of the common-mode inductor L1 are different.

[0010] Preferably, the discharge resistor includes a first resistor R1 and a second resistor R2, and the first resistor R1 and the second resistor R2 are connected in series.

[0011] Compared with the prior art, the optimized power-on current suppression circuit of the utility model can not only suppress the power-on impact current, but also improve the EMC / EMI effect of the circuit. Only three components are added, which has low cost and small volume. The NTC thermistor itself forms negative feedback, which is simple, practical and highly reliable.

Brief Description of the Drawings

[0012] Figure 1 A structural diagram of the first embodiment of the power-on current suppression circuit optimized for the utility model;

[0013] Figure 2 This is a structural diagram of the second embodiment of the power-on current suppression circuit optimized for the utility model;

[0014] Figure 3 This is a structural diagram of the third embodiment of the power-on current suppression circuit optimized for the utility model. [Specific implementation method]

[0015] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below with reference to the accompanying drawings and implementation examples. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0016] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are limited to relative positions on the specified view rather than absolute positions.

[0017] In addition, in the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0018] See also Figures 1 to 3 The optimized power-on current suppression circuit of the utility model includes a live wire L and a neutral wire N, the input end of the live wire L is connected with a fuse F1, a varistor RV1, a safety capacitor CX1 and a discharge resistor are connected in parallel between the live wire L and the neutral wire N, the varistor RV1 is located at the rear end of the fuse F1, the safety capacitor CX1 is located at the rear end of the varistor RV1, the discharge resistor is located at the rear end of the safety capacitor CX1, the rear end of the discharge resistor is connected with a common-mode inductor L1, the rear end of the common-mode inductor L1 is connected with a rectifier bridge DB1, and the rear end of the rectifier bridge DB1 is connected with a rectifier filter electrolytic capacitor EC1.

[0019] A first capacitor C1 and a second capacitor C2 are connected in parallel between the live wire L and the neutral wire N, and an NTC thermistor RT1 is connected in series to the live wire L.

[0020] The first capacitor C1, the second capacitor C2, the NTC thermistor RT1 and the common mode inductor L1 form a π-type filter circuit. By adjusting parameters and changing the frequency point of the π-type filter circuit, the EMC / EMI effect of the circuit can be effectively improved.

[0021] In the first embodiment of the optimized power-on current suppression circuit of the utility model, the first capacitor C1 is located between the safety capacitor CX1 and the discharge resistor, the second capacitor C2 is located between the common-mode inductor L1 and the rectifier bridge DB1, and the NTC thermistor RT1 is located between the discharge resistor and the common-mode inductor L1.

[0022] In the second embodiment of the optimized power-on current suppression circuit of the present invention, the first capacitor C1 and the second capacitor C2 are located between the rectifier bridge DB1 and the rectifier filter electrolytic capacitor EC1, and the NTC thermistor RT1 is located between the first capacitor C1 and the second capacitor C2.

[0023] In the third embodiment of the optimized power-on current suppression circuit of the utility model, the first capacitor C1 is located between the varistor RV1 and the safety capacitor CX1, the NTC thermistor RT1 is located between the first capacitor C1 and the safety capacitor CX1, and the second capacitor C2 is located between the common-mode inductor L1 and the rectifier bridge DB1.

[0024] The discharge resistor includes a first resistor R1 and a second resistor R2, and the first resistor R1 and the second resistor R2 are connected in series.

[0025] The optimized power-on current suppression circuit design of the utility model adds three components, a first capacitor C1, a second capacitor C2 and an NTC thermistor RT1. The position of the NTC thermistor RT1 is very important and can be placed between the common-mode inductor L1 and the rectifier bridge DB1, but not in front of the varistor RV1.

[0026] The safety capacitor CX1 is an X2 safety capacitor, and its capacitance and volume are subject to certain restrictions. The first capacitor C1 connected in parallel with it cannot be cancelled, and the first capacitor C1 can flexibly adjust parameters to adjust the effect of the π-type filter circuit.

[0027] Although fuse F1 also has a certain resistance, it must be placed first because of safety regulations. Do not place fuse F1 behind safety capacitor CX1.

[0028] The number of turns of the windings on both sides of the common mode inductor L1 is different, which can also improve the EMC / EMI effect of the circuit.

[0029] NTC thermistor RT1 can improve the power factor PF value of the circuit. Since the capacitance of the rectifier filter electrolytic capacitor EC1 is usually relatively large, the improvement effect will be relatively limited, but it will significantly improve the harmonic performance of the circuit.

[0030] Compared with the design of the first embodiment, the design of the second embodiment moves C1, RT1, and C2 backward, and changes them from the input end of the rectifier bridge DB1 to the output end of the rectifier bridge DB1. If the capacity of C1 and C2 is large, the cost of using non-polar capacitors for C1 and C2 in the design of the first embodiment will be relatively high. By changing to the design of the second embodiment, lower-cost electrolytic capacitors can be used.

[0031] When the capacity of CX1 is too large, the design of embodiment 1 will also generate a certain impact current when CX1 is powered on. At this time, C1 and RT1 can be moved forward and placed in front of CX1 to obtain the design of embodiment 3. In this way, RT1 can also suppress the impact current generated by CX1 when it is powered on.

[0032] Although the design circuits of the first, second and third embodiments are different, their basic principles are the same. The optimized current suppression circuits are based on the following basic design ideas:

[0033] 1. Use the resistance of the NTC thermistor to suppress the inrush current when power is turned on. In addition to the NTC thermistor, other resistive components such as power resistors can also be used to suppress the current.

[0034] 2. The added resistive components and the existing safety capacitors, common-mode inductors, and electrolytic capacitors in the circuit form a π-type filter circuit to improve the circuit's filtering capability.

[0035] 3. Add C1 and C2 to further improve the high frequency characteristics of the π-type filter circuit.

[0036] 4. The placement of the added resistive device is very important, try to form a π-type filter circuit topology.

[0037] 5. If an NTC thermistor is used, the current value of the NTC thermistor needs to be selected according to the actual working current of the overall circuit. The working temperature of the NTC thermistor should be 70-80℃.

[0038] 6. The maximum value of the power-on surge current must meet the requirements of fuse F1.

[0039] The core design idea of ​​this circuit is that resistive components suppress current, and resistive components and other components form a filter circuit to improve the EMC / EMI effect of the circuit. This circuit design principle is also applicable to circuits with DC input.

[0040] This circuit design uses resistive components and other components to form a π-type filter circuit. The π-type filter circuit construction method can be adjusted based on the circuit shown in the figure. It does not have to be completely consistent with the circuit shown in the figure. The π-type filter circuit can also be simplified to form an RC filter circuit, which can also improve the EMC / EMI effect of the circuit to a certain extent.

[0041] In addition to being used in AC input filter circuits, this circuit design principle is also applicable to DC input circuits.

[0042] Compared with the prior art, the optimized power-on current suppression circuit of the utility model can not only suppress the power-on impact current, but also improve the EMC / EMI effect of the circuit. Only three components are added, which has low cost and small volume. The NTC thermistor itself forms negative feedback, which is simple, practical and highly reliable.

[0043] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any modifications, equivalent substitutions and improvements made within the concept of the present invention should be included in the patent protection scope of the present invention.

Claims

1. An optimized on-current suppression circuit, characterized in that: It includes a live wire L and a neutral wire N, the input end of the live wire L is connected to a fuse F1, a varistor RV1, a safety capacitor CX1 and a discharge resistor are connected in parallel between the live wire L and the neutral wire N, the varistor RV1 is located at the rear end of the fuse F1, the safety capacitor CX1 is located at the rear end of the varistor RV1, the discharge resistor is located at the rear end of the safety capacitor CX1, the rear end of the discharge resistor is connected to a common-mode inductor L1, the rear end of the common-mode inductor L1 is connected to a rectifier bridge DB1, and the rear end of the rectifier bridge DB1 is connected to a rectifier filter electrolytic capacitor EC1; A first capacitor C1 and a second capacitor C2 are connected in parallel between the live wire L and the neutral wire N, and an NTC thermistor RT1 is connected in series to the live wire L.

2. The optimized on-current suppression circuit according to claim 1, characterized in that: The first capacitor C1, the second capacitor C2, the NTC thermistor RT1 and the common mode inductor L1 form a π-type filter circuit.

3. The optimized on-current suppression circuit according to claim 1, characterized in that: The first capacitor C1 is located between the safety capacitor CX1 and the discharge resistor, the second capacitor C2 is located between the common mode inductor L1 and the rectifier bridge DB1, and the NTC thermistor RT1 is located between the discharge resistor and the common mode inductor L1.

4. The optimized on-current suppression circuit according to claim 1, characterized in that: The first capacitor C1 and the second capacitor C2 are located between the rectifier bridge DB1 and the rectifier filter electrolytic capacitor EC1, and the NTC thermistor RT1 is located between the first capacitor C1 and the second capacitor C2.

5. The optimized on-current suppression circuit according to claim 1, characterized in that: The first capacitor C1 is located between the varistor RV1 and the safety capacitor CX1, the NTC thermistor RT1 is located between the first capacitor C1 and the safety capacitor CX1, and the second capacitor C2 is located between the common mode inductor L1 and the rectifier bridge DB1.

6. The optimized on-current suppression circuit according to claim 1, characterized in that: The numbers of turns of the windings on both sides of the common mode inductor L1 are different.

7. The optimized on-current suppression circuit according to claim 1, characterized in that: The discharge resistor includes a first resistor R1 and a second resistor R2, and the first resistor R1 and the second resistor R2 are connected in series.

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