CN219394427U

CN219394427U - Improved active structure surge protection circuit for direct-current power supply

Info

Publication number: CN219394427U
Application number: CN202320444966.9U
Authority: CN
Inventors: 蔡云枝
Original assignee: Taicang Haiyun Testing Co ltd; Taicang T&W Electronics Co Ltd
Current assignee: Taicang Haiyun Testing Co ltd; Taicang T&W Electronics Co Ltd
Priority date: 2023-03-10
Filing date: 2023-03-10
Publication date: 2023-07-21
Anticipated expiration: 2033-03-10

Abstract

The utility model relates to the field of surge protection circuits, in particular to an improved active structure surge protection circuit for a direct current power supply, which comprises a circuit power supply and a post-stage circuit, wherein a capacitor C1 is connected in parallel between the positive electrode and the negative electrode of the circuit power supply, the post-stage circuit is connected with the capacitor C1 in parallel, the negative electrode of the circuit power supply is grounded, an MOS (metal oxide semiconductor) tube Q1, an absorption capacitor C2 and a discharge resistor R1 are connected in parallel between the capacitor C1 and the post-stage circuit, the absorption capacitor C2 is connected with the MOS tube Q1 in series, the discharge resistor R1 is connected with the absorption capacitor C2 in parallel, and the grid electrode of the MOS tube Q1 is connected with a voltage detection and driving circuit.

Description

Improved active structure surge protection circuit for direct-current power supply

Technical Field

The utility model relates to the field of surge protection circuits, in particular to an improved active structure surge protection circuit for a direct current power supply.

Background

In circuit design, surge refers to strong pulse generated in the power supply at the moment when the power supply is just turned on, and external pulse received by other parts in the power supply and the circuit, including surge voltage and surge current, the circuit is likely to be damaged at the moment when the surge arrives, such as PN junction, capacitor breakdown, resistor burnout and the like, so that a surge protection structure is needed to be added in the circuit, and the surge energy is released, absorbed or consumed by utilizing components in the structure, so that the whole circuit is protected from being damaged.

At present, the surge protection structure in a circuit is mainly divided into a passive type and an active type, wherein the passive type usually adopts a TVS transient voltage suppression diode to release surge energy, and the TVS diode has small volume and quick response, but has high requirement on hardware performance of the circuit and is not fine in protection; the active type MOS transistor is used for absorbing surge energy, and the MOS transistor has a simple structure and high safety level, but has high requirements on the power level of components.

Moreover, only positive surges (i.e., overvoltage surges in the same direction as the supply voltage) are considered in the active configuration, and negative surges (i.e., overvoltage surges in the opposite direction to the supply voltage) are not considered.

Disclosure of Invention

Aiming at the technical problems in the prior art, the utility model provides an improved active structure surge protection circuit for a direct current power supply.

The technical scheme for solving the technical problems is as follows:

the utility model provides an improved generation initiative structure surge protection circuit for DC power supply, including circuit power supply and post-stage circuit, parallelly connected absorption capacitor C1 between the positive negative pole of circuit power supply, post-stage circuit and absorption capacitor C1 are parallelly connected, circuit power supply negative pole ground connection, parallelly connected MOS pipe Q1, absorption capacitor C2 and discharge resistance R1 between absorption capacitor C1 and the post-stage circuit, and absorption capacitor C2 and MOS pipe Q1 establish ties, discharge resistance R1 and absorption capacitor C2 are parallelly connected, MOS pipe Q1's grid has connect voltage detection and drive circuit.

Further, the voltage detection and driving circuit comprises an operational amplifier and four resistors with the resistance value of 100K, wherein the four resistors are divided into two groups, and the two resistors in each group are connected in series;

one end of one group is connected with the reference voltage Vref, and the other end is connected with the grid voltage Vg1 of the output end of the operational amplifier;

one end of the other group is connected with the signal voltage Vin, and the other end is grounded;

the inverting input end of the operational amplifier is connected between two resistors of one group, and the homodromous input end of the operational amplifier is connected between two resistors of the other group.

Further, a reverse diode D2 is connected in parallel between the snubber capacitor C1 and the circuit power supply.

Further, the capacitance value of the absorption capacitor C1 is 1uF, the capacitance value of the absorption capacitor C2 is 20uF, and the resistance value of the discharge resistor R1 is 5 ohms.

The beneficial effects of the utility model are as follows:

1. the utility model provides a surge protection circuit with an absorption capacitor on the basis of an active mode, which keeps the advantage of finer protection of an active structure compared with a passive structure, connects an inexpensive capacitor and a resistor in parallel to form the absorption circuit, avoids the condition that an MOS tube is instantaneously burnt by surge energy, uses a low-cost low-power MOS tube to replace a high-cost high-power MOS tube, and reduces the circuit cost. If the power MOS tubes with the same power level are adopted, the designed circuit can greatly improve the surge voltage level and the stability of the whole circuit.

2. Meanwhile, the reverse diode D2 is used for compensating the negative surge solution missing in the active structure, and the diode also has the protection of reverse polarity connection of the power supply.

Drawings

FIG. 1 is a block diagram of a passive surge protection circuit of a conventional DC power supply;

FIG. 2 is a forward surge discharging path diagram of a passive surge protection circuit of a conventional DC power supply;

FIG. 3 is a negative surge discharging path diagram of a passive surge protection circuit of a conventional DC power supply;

FIG. 4 is a block diagram of a surge protection circuit of an active structure;

FIG. 5 is a circuit block diagram of a voltage detection and drive circuit in a surge protection circuit of an active structure;

FIG. 6 is a block diagram of an active surge protection circuit of the present utility model;

fig. 7 is a block diagram of an improved active surge protection circuit of the present utility model.

Detailed Description

The principles and features of the present utility model are described below with reference to the drawings, the examples are illustrated for the purpose of illustrating the utility model and are not to be construed as limiting the scope of the utility model.

Before enumerating the embodiments, a conventional surge protection structure is first described:

passive surge protection structures typically employ Transient Voltage Suppression (TVS) diodes to bleed off the surge energy, with a specific circuit configuration as shown in fig. 1. In fig. 1, D1 is a TVS diode, and C1 is an absorption capacitor.

The passive surge protection and forward surge discharging path is shown in fig. 2, and mainly utilizes the reverse breakdown clamping effect of the TVS, and the absorption capacitor C1 is transversely combined into a circuit to guide the high-frequency transient component into the ground.

The passive surge protection and negative surge discharging path is shown in fig. 3, and the negative surge is returned to the source by mainly utilizing the positive conduction effect of the TVS, so that the later-stage circuit is protected.

The TVS diode protection is adopted, so that the protection is simpler, but the protection is not fine enough for a later-stage circuit, such as a TVS commonly used in a POE54V circuit: the reverse breakdown voltage of the SMCJ58A is 64V, the stable clamping voltage is 85V-90V, and the post-stage circuit must withstand voltage is higher than 90V to have a safe working space.

In actual operation, the maximum safety allowable voltage Vh of the protected circuit should be made higher than the maximum clamp voltage Vref. If TVS diode is used for surge protection, vref is at least greater than the breakdown voltage Vb of the TVS diode, and Vh of the subsequent stage circuit is at least 1.5 times greater than Vref. Theoretically, vb is at least 1.2 times the highest voltage Vs of the load in the post-stage circuit, and vh=1.5vb=45v can be obtained by calculation assuming that Vs is 25V and Vb is minimum 30V, and the voltage withstand of the post-stage circuit can be greatly improved by the Vh value, and the improvement of the voltage withstand inevitably increases the hardware cost of the whole circuit.

Based on the above description, in order to reduce the hardware cost of the post-stage circuit, the problem that Vh is higher than Vs has to be solved, the present utility model provides the following preferred embodiments:

embodiment one:

referring to fig. 4 and 5, an improved active structure surge protection circuit for a dc power supply includes an active surge protection circuit structure composed of a voltage detection and driving circuit and a power MOS transistor, wherein the voltage detection and driving circuit is a subtraction circuit composed of an operational amplifier;

the voltage detection and driving circuit comprises an operational amplifier and four resistors with the resistance value of 100K, wherein the four resistors are divided into two groups, and the two resistors in each group are connected in series;

Obtaining the conduction voltage of the MOS tube according to circuit analysis:

Vg1＝Vin-Vref(1)

under the normal working condition, when a surge is not generated, the signal voltage Vin is smaller than the reference voltage Vref=30V, vg1=0V, and the power MOS tube Q1 is closed; when a surge occurs, vin will rise, but Vg1 is still smaller than Vth (Vth is the on threshold of the power MOS transistor Q1), so Q1 is still not turned on; if Vg1 is larger than Vth due to continuous rising of Vin, so that Q1 is conducted, surge energy is discharged through Q1, and the surge protection effect can be achieved.

The technical solution in the first embodiment can greatly reduce Vh and thus reduce hardware cost, but this surge protection structure has an economic problem, because the Q1 has to be high enough to bleed off the instantaneous energy, and the MOS transistor has to be high in size and high in manufacturing cost, so we propose a second embodiment:

embodiment two:

aiming at the defects of the traditional structure, the utility model provides a surge protection circuit structure capable of achieving the same surge protection effect, in the structure, the Vh is obviously reduced, and the cost of the whole circuit is also greatly reduced.

Referring to fig. 6, an improved active structure surge protection circuit for a direct current power supply comprises a circuit power supply and a post-stage circuit, wherein an absorption capacitor C1 is connected in parallel between the positive electrode and the negative electrode of the circuit power supply, the post-stage circuit is connected with the absorption capacitor C1 in parallel, the negative electrode of the circuit power supply is grounded, a MOS tube Q1, an absorption capacitor C2 and a discharge resistor R1 are connected in parallel between the absorption capacitor C1 and the post-stage circuit, the absorption capacitor C2 and the MOS tube Q1 are connected in series, the discharge resistor R1 and the absorption capacitor C2 are connected in parallel, and the grid electrode of the MOS tube Q1 is connected with a voltage detection and driving circuit.

In fig. 6, the circuit structure is composed of an active module and a buffer circuit, the buffer circuit is composed of an absorption capacitor C2 and a discharge resistor R1 in parallel, the function of the low-cost capacitor C2 is mainly to absorb part of surge energy, the discharge resistor R1 slowly releases the energy on the absorption capacitor C2 after the surge, and the structure adopts a low-cost low-power MOS transistor Q1 to absorb the rest of surge energy on the basis of greatly reducing Vh, so that the cost of the whole circuit is reduced.

Similar to the embodiment, the on voltage of the MOS tube is obtained according to the circuit state analysis:

Vg1＝Vin+Vc-Vref(2)

from equation (2), vg1 is also related to the voltage of the absorption capacitance in the circuit.

Experimental results show that after C2 is added, the novel circuit can obviously absorb surge energy at the surge moment, and the surge voltage level is greatly improved; the absorption loop composed of the low-cost capacitor and the low-cost resistor can greatly reduce the requirement of the circuit structure on the Q1 performance, so that the cost of the whole surge protection circuit is obviously reduced.

To solve the defect that the active structure only considers forward surge, we continue to improve the circuit, so we propose the third embodiment:

embodiment III:

inspired from an example of a discharge path of a negative surge when a TVS is adopted in FIG. 3, we can simply connect an inverse diode D2 in parallel to a circuit to solve the problem of the negative surge;

further, a reverse diode D2 is connected in parallel between the snubber capacitor C1 and the circuit power supply, and the final solution circuit is shown in fig. 7, and it is obvious that the reverse diode can also prevent the power supply with wrong polarity from being connected into the system.

The foregoing description of the preferred embodiments of the utility model is not intended to limit the utility model, but rather to enable any modification, equivalent replacement, improvement or the like to be made within the spirit and principles of the utility model.

Claims

1. The utility model provides an improved generation initiative structure surge protection circuit for DC power supply, includes circuit power supply and post-stage circuit, its characterized in that, parallelly connected absorption electric capacity C1 between the positive negative pole of circuit power supply, post-stage circuit and absorption electric capacity C1 are parallelly connected, circuit power supply negative pole ground connection, parallelly connected MOS pipe Q1, absorption electric capacity C2 and discharge resistance R1 between absorption electric capacity C1 and the post-stage circuit, and absorption electric capacity C2 and MOS pipe Q1 establish ties, discharge resistance R1 and absorption electric capacity C2 are parallelly connected, MOS pipe Q1's grid has connect voltage detection and drive circuit.

2. The improved active structure surge protection circuit for a direct current power supply according to claim 1, wherein the voltage detection and driving circuit comprises an operational amplifier and four resistors with the resistance value of 100K, the four resistors are divided into two groups, and two resistors in each group are connected in series;

3. An improved active structure surge protection circuit for a dc power supply according to claim 1, wherein a reverse diode D2 is connected in parallel between the snubber capacitor C1 and the circuit power supply.

4. An improved active structure surge protection circuit for a dc power supply according to claim 2 or 3, wherein the capacitance of the absorption capacitor C1 is 1uF, the capacitance of the absorption capacitor C2 is 20uF, and the resistance of the discharge resistor R1 is 5 ohms.