CN212660107U

CN212660107U - Secondary side lossless active clamp circuit

Info

Publication number: CN212660107U
Application number: CN202021191059.0U
Authority: CN
Inventors: 俞昌林; 杜颖辉
Original assignee: YANGZHOU COMMUNICATION EQUIPMENT CO Ltd
Current assignee: YANGZHOU COMMUNICATION EQUIPMENT CO Ltd
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2021-03-05
Anticipated expiration: 2030-06-24

Abstract

The utility model relates to an active clamp circuit technical field, specifically speaking relates to a harmless active clamp circuit of secondary side. It includes transformer T1, active clamp circuit and voltage ware leakage inductance L1, its characterized in that: the transformer T1 and the voltage transformer leakage inductance L1 are connected through an active clamp circuit, the voltage transformer leakage inductance L1 is grounded through a capacitor C2, the active clamp circuit comprises a resistor R1, an inverter D1, a capacitor C4 and a capacitor C1, one end of the resistor R1 is connected with the transformer T1, the other end of the resistor R1 is connected with the capacitor C4 through an inverter D1, and the capacitor C4 is connected with the voltage transformer leakage inductance L1 through a capacitor C1. The utility model provides a with PWM modulation mode output power rectification part switch peak problem, reduced the withstand voltage of output rectifier device, can select the rectifier device that switches on the internal resistance littleer to improved power efficiency, simultaneously, the utility model discloses need not special control chip, use reliable and stable, can adapt to the rectifier tube absorption loop of all PWM adjustments.

Description

Secondary side lossless active clamp circuit

Technical Field

The utility model relates to the technical field, specifically speaking relates to a harmless active pincers circuit of secondary side.

Background

With the rapid development of electronic technology, the application field of electronic products has penetrated into various industries, the variety of electronic equipment is more and more, and the requirements on power supplies are more flexible and changeable. Miniaturization and cost reduction of electronic devices have prompted tremendous changes in power supplies. The clamp circuit clamps peak voltage generated when the switching power supply works within a certain range, so that a power switching tube is protected.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a harmless active pincers circuit of secondary side to solve the problem that proposes among the above-mentioned background art.

In order to achieve the above object, the utility model provides a secondary side lossless active clamp circuit, including transformer T1, active clamp circuit and voltage transformer leakage inductance L1, pass through active clamp circuit connection between transformer T1 and the voltage transformer leakage inductance L1, voltage transformer leakage inductance L1 passes through electric capacity C2 ground connection, transformer T1 utilizes the electromagnetic induction principle for change the alternating voltage of a certain grade into the alternating voltage of another grade that the frequency is the same, in order to satisfy the demand of different loads; the active clamp circuit is used for clamping the peak voltage generated when the switching power supply works within a certain range, so that the power switching tube is protected; the transformer leakage inductance L1 is used for detecting the deformation condition of the coil of the transformer T1; the transformer leakage inductance L1, which corresponds to the reactive component of the short-circuit impedance, is determined by the geometry of the transformer T1 coil and is measured by the equation:

Lx＝ω²Λ；

wherein ω is the number of turns of the primary coil, Λ is the permeance of the leakage flux path, Lx is the leakage inductance value of the transformer, the magnetic path through which the leakage flux passes forms a cylindrical shape in space, the average diameter of the cylinder is equal to the average diameter D of the primary and secondary coils, and the thickness is equal to the thickness of the two coils (D₁+d₂) In addition, the coil gap d, the height of the cylinder is equal to the axial height h of the coil, the permeance Λ of the leakage magnetic path is in direct proportion to the product of the circumference and the equivalent thickness of the cylinder and in inverse proportion to the equivalent height of the cylinder, and considering that the part of the magnetic flux passing through the cross section of the coil is not linked with the influence of the turns of the whole coil, the total permeance of the leakage magnetic path is as follows:

Λ＝μ0πD[d+1/3(d₁+d₂)]/h′；

in the formula, μ 0 is the magnetic permeability of air, and h' is the equivalent height of the coil.

The active clamp circuit comprises a resistor R1, an inverter D1, a capacitor C4 and a capacitor C1, wherein one end of the resistor R1 is connected with a transformer T1, the other end of the resistor R1 is connected with the capacitor C4 through the inverter D1, and the capacitor C4 is connected with a voltage leakage inductor L1 through the capacitor C1.

As a further improvement of the technical scheme, the other end of the resistor R1 is grounded through a voltage stabilizing diode V2.

As a further improvement of the technical scheme, a capacitor C3 and a resistor R2 are connected in series between the resistor R1 and the inverter D1.

As a further improvement of the present technical solution, the resistor R2 is grounded.

As a further improvement of the technical scheme, a resistor R3 is connected in series between the capacitor C4 and the capacitor C1.

As a further improvement of the present technical solution, the resistor R3 is grounded.

Compared with the prior art, the beneficial effects of the utility model are that: among this harmless active pincers circuit of secondary side, solve with PWM modulation mode output power rectification partial switch peak problem, reduceed output rectifier device's withstand voltage, can select to switch on the rectifier device that the internal resistance is littleer to improved power efficiency, simultaneously, the utility model discloses need not special control chip, it is reliable and stable to use, can adapt to all PWM adjustment's rectifier tube absorption loop.

Drawings

FIG. 1 is a schematic diagram of a lossless active clamp circuit according to embodiment 1;

FIG. 2 is a timing diagram of the lossless active clamp of example 1;

fig. 3 is a graph showing the effect of active clamping in example 1.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Example 1

Referring to fig. 1-3, the present embodiment provides a secondary lossless active clamp circuit, including a transformer T1, an active clamp circuit transformer leakage inductance L1, the transformer T1 and the transformer leakage inductance L1 are connected through an active clamp circuit, the transformer leakage inductance L1 is grounded through a capacitor C2, and the transformer T1 uses the principle of electromagnetic induction to convert an ac voltage of a certain level into an ac voltage of another level with the same frequency, so as to meet the requirements of different loads; the active clamp circuit is used for clamping the peak voltage generated when the switching power supply works within a certain range, so that the power switching tube is protected; the transformer leakage inductance L1 is used for detecting the deformation condition of the coil of the transformer T1; transformer leakage inductance L1, which corresponds to the reactive component of the short-circuit impedance, is determined by the geometry of the transformer T1 coil and is measured by the equation:

Lx＝ω²Λ；

Λ＝μ0πD[d+1/3(d₁+d₂)]/h′；

The inverter D1 is a CMOS inverter, when the input voltage is at high level, the load tube is cut off, the input tube is connected, and the load current is injected into the input tube, when the input voltage is at low level, the load tube is connected, the input tube is cut off, and the load current is source current.

In this embodiment, the other end of the resistor R1 is grounded through the zener diode V2, the zener diode V2 is a semiconductor device having a high resistance up to a critical reverse breakdown voltage at which the reverse resistance decreases to a small value, the current increases in the low resistance region while the voltage is kept constant, and the zener diode V2 is stepped according to the breakdown voltage because of its characteristic that the zener diode V2 is mainly used as a regulator or a voltage reference element, the zener diode V2 may be connected in series so as to be used at a higher voltage, and more stable voltage may be obtained by connecting in series.

Further, a capacitor C3 and a resistor R2 are connected in series between the resistor R1 and the inverter D1, and the capacitor C3 is a neutralization capacitor and is used for forming a negative feedback network so as to inhibit self-oscillation caused by capacitance between the voltage stabilizing diode V2.

Specifically, the resistor R2 is grounded to discharge static electricity in the circuit, thereby preventing the risk of discharge after static electricity is accumulated, and simultaneously, the ground resistor R2 is controlled to reduce the ground current.

In addition, a resistor R3 is connected in series between the capacitor C4 and the capacitor C1 and is used for matching the output impedance of the source ends of the capacitor C4 and the capacitor C1 with the characteristic impedance of the transmission line and inhibiting the signal reflected from the load end from being reflected again.

In addition, the resistor R3 is grounded for discharging static electricity in the circuit to prevent discharging danger after static electricity is accumulated, and simultaneously, the grounding resistor R2 is controlled to reduce grounding current.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the description in the above embodiments and the description is only preferred examples of the present invention, and is not intended to limit the present invention, and that the present invention can have various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications all fall into the scope of the claimed invention. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A secondary side lossless active clamp circuit comprises a transformer T1, an active clamp circuit and a voltage transformer leakage inductance L1, and is characterized in that: the transformer T1 and the voltage transformer leakage inductance L1 are connected through an active clamp circuit, the voltage transformer leakage inductance L1 is grounded through a capacitor C2, and the transformer T1 is used for converting alternating voltage of a certain grade into alternating voltage of another grade with the same frequency;

2. The secondary-side lossless active clamp circuit of claim 1, wherein: the other end of the resistor R1 is grounded through a zener diode V2.

3. The secondary-side lossless active clamp circuit of claim 1, wherein: and a capacitor C3 and a resistor R2 are connected in series between the resistor R1 and the inverter D1.

4. The secondary side lossless active clamp circuit according to claim 3, wherein: the resistor R2 is connected to ground.

5. The secondary-side lossless active clamp circuit of claim 1, wherein: a resistor R3 is connected in series between the capacitor C4 and the capacitor C1.

6. The secondary-side lossless active clamp circuit according to claim 5, wherein: the resistor R3 is connected to ground.