CN218570084U - Secondary active clamping forward circuit - Google Patents

Abstract

The utility model discloses an active clamp of secondary limit is just swashing circuit, including high frequency transformer, afterflow MOS pipe, rectification MOS pipe, clamp MOS pipe, high frequency switch pipe, high frequency transformer connects in power input end, and it includes primary winding, auxiliary winding and secondary winding, and primary winding switches on through high frequency switch pipe. The utility model discloses only use several devices, provide the voltage signal who resets through the transformer sampling, use clamp MOS pipe and absorption capacitance to accomplish high frequency transformer's the reseing for can obtain the square wave and be used for driving the rectification MOS pipe at the in-process that resets.

Description

Secondary active clamping forward circuit

Technical Field

The utility model relates to the technical field of power, especially, relate to an active clamper of vice limit is just swashing circuit.

Background

Under the trend that the power density of the current module power supply is continuously improved, and the cost is continuously reduced under the unit power density, for a power supply module with 48V input, 3.3V/12.5A low-voltage and high-current, a forward-excitation synchronous rectification circuit is a very high-efficiency selection.

However, if the resonant reset forward circuit is selected, the reset voltage is a sine half-wave, and the synchronous rectification driving circuit on the secondary side needs to modify the sine half-wave into a square wave to drive the MOSFET, so that the complexity of the circuit is remarkably increased and the reliability is reduced, and if the MOSFET is directly driven by the sine half-wave, the working efficiency is greatly reduced; if the primary side active clamping forward circuit is selected, the price of a special control chip is very high, and the shelf life is very long, which is a very contradictory place.

SUMMERY OF THE UTILITY MODEL

In view of above technical problem, the utility model provides a vice limit active clamp is just swashing circuit only uses several devices, uses clamp MOS pipe and absorption capacitance to accomplish high frequency transformer's restoration for can obtain the square wave and be used for driving the rectification MOS pipe in the reset process.

Other features and advantages of the invention will be apparent from the following detailed description, or may be learned by practice of the invention in part.

The utility model aims at providing a vice limit active clamp is just swashing circuit, including high frequency transformer, afterflow MOS pipe, rectification MOS pipe, clamp MOS pipe, high frequency switch pipe, high frequency transformer connects in power input end, and it includes primary winding, auxiliary winding and vice limit winding, primary winding passes through high frequency switch pipe switches on, the drain electrode of afterflow MOS pipe connect in the upper end of vice limit winding with rectification MOS pipe source electrode, its grid with the drain electrode of rectification MOS pipe connect jointly in the lower extreme of vice limit winding with the lower extreme of auxiliary winding, the source electrode of afterflow MOS pipe connect in the source electrode of rectification MOS pipe, parallelly connected have first absorption electric capacity between the drain electrode of afterflow MOS pipe and the source electrode, parallelly connected second absorption electric capacity between the drain electrode of rectification MOS pipe and the source electrode, the source electrode of clamp MOS pipe connect in the lower extreme of vice limit winding with the lower extreme of auxiliary winding, and be connected to through resistance the source electrode of afterflow MOS pipe with the common end of the source electrode of rectification MOS pipe, the drain electrode of clamp MOS pipe connects third absorption electric capacity, the grid is connected to the upper end of auxiliary winding.

Furthermore, the input end of the primary winding of the high-frequency transformer is provided with a plurality of groups of input filter capacitors connected in parallel, and the output end of the secondary winding of the high-frequency transformer is provided with a plurality of groups of output filter capacitors connected in parallel.

The high-frequency switch tube is characterized by further comprising a power supply inductor, wherein the power supply inductor is connected with the secondary winding and supplies power to a PWM signal chip for driving the high-frequency switch tube through a self-power supply unit.

Furthermore, a resistor is arranged between the grid of the clamping MOS tube and the upper end of the auxiliary winding, and a diode is connected in parallel to the resistor.

The technical scheme of the utility model following beneficial effect has:

the utility model discloses only use several devices, provide the voltage signal who resets through the transformer sampling, use clamp MOS pipe and absorption capacitance to accomplish high frequency transformer's the reseing for can obtain the square wave and be used for driving the rectification MOS pipe at the in-process that resets.

Drawings

Fig. 1 is a schematic circuit diagram of a secondary active clamp forward circuit according to an embodiment of the present disclosure.

Detailed Description

Exemplary embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It is to be understood that the invention is capable of other and different embodiments and its several details are capable of modification without departing from the scope of the invention, and that the description and drawings are to be regarded as illustrative in nature and not as restrictive. In the description of the present invention, it is to be noted that, unless otherwise specified or limited, the term "connected" means that the elements related to the present invention are electrically connected according to their inherent characteristics and their logical relationship of schemes for realizing the technical purpose of the present invention, and may be either directly connected to each other to form an electrical connection relationship or indirectly connected to each other through an intermediate medium. The specific meaning of each term in the present application document in the present invention can be understood according to specific situations by those skilled in the art.

As shown in fig. 1, the embodiment of the utility model provides a secondary active clamping normal shock circuit, including high-frequency transformer, follow current MOS transistor Q3, rectification MOS transistor Q2, clamping MOS transistor Q4, high-frequency switch tube Q1, high-frequency transformer connects in power input end vin, it includes primary winding T1, auxiliary winding T2 and secondary winding T3, primary winding T1 switches on through high-frequency switch tube Q1, follow current MOS transistor Q3's drain electrode is connected in secondary winding T3's upper end and rectification MOS transistor Q2 source electrode, its grid and rectification MOS transistor Q2's drain electrode are connected in secondary winding T3's lower extreme and auxiliary winding T2's lower extreme jointly, follow current MOS transistor Q3's source electrode is connected in rectification MOS transistor Q2's source electrode, parallel connection has first absorption electric capacity C4 between follow current MOS transistor Q3's drain electrode and the source electrode, parallel connection has second absorption electric capacity C5 between rectification MOS transistor Q2's drain electrode and the source electrode, follow current MOS transistor Q4's source electrode is connected in the lower extreme and auxiliary winding T3's drain electrode through resistance R7, and the common connection of follow current MOS transistor Q2's drain electrode is connected to the third absorption electric capacity C3, the supplementary gate of MOS transistor Q2, the drain electrode is connected to the supplementary transistor Q3, the third side of follow current transistor Q3, the drain electrode is connected to the supplementary transistor Q3, the drain electrode of follow current transistor Q3, the drain electrode is connected to the supplementary gate of follow current transistor Q3, the drain electrode.

The DC/DC converter topology is a single-ended forward converter, the DC/DC converter topology works in a Continuous Conduction Mode (CCM), a synchronous rectification mode is adopted on the secondary side because the circuit is a low-voltage heavy-current circuit, and an active clamping circuit is used on the auxiliary winding T3 of the transformer, so that the magnetic reset of the transformer and the dead time of a synchronous rectifier tube can be controlled.

Specifically, when the high-frequency switching tube Q1 is switched on during operation, the rectifying MOS tube Q2 of the secondary winding T2 is switched on, and the primary winding T1 transfers energy to the secondary winding T2, which is a circuit when a conventional forward circuit is switched on. In the turn-off time of the high-frequency switch tube Q1, the first absorption capacitor C4 of the follow current MOS tube Q3 discharges, the second absorption capacitor C5 of the rectification MOS tube Q2 charges, and the third absorption capacitor C29 is also charged through the body diode of the clamping MOS tube Q4, when the discharge of the first absorption capacitor C4 of the follow current MOS tube Q3 is finished, and after the charge of the second absorption capacitor C5 of the rectification MOS tube Q2 is finished, the high-frequency switch tube Q1 and the follow current MOS tube Q3 are turned off, at this time, the secondary winding T2 of the high-frequency transformer bears a negative voltage, the gate of the follow current MOS tube Q2 has a positive voltage, the follow current MOS tube Q2 is turned on, and meanwhile, the auxiliary winding T3 of the high-frequency transformer drives the clamping MOS tube Q4 to turn on, and continues to charge the third absorption capacitor C29, and the third absorption capacitor C29 plays a role in quickly resetting the high-frequency transformer, so as to prevent the follow current MOS tube Q2 from rising. Until the next switching cycle comes, the secondary winding T2 of the high-frequency transformer bears a positive-negative voltage, at which time the rectifying MOS transistor Q2 is turned off and the freewheeling MOS transistor Q3 is turned on.

In one embodiment, the input end of the primary winding T1 of the high-frequency transformer is provided with a plurality of sets of input filter capacitors C1, C2, and C3 connected in parallel, and the output end of the secondary winding T2 of the high-frequency transformer is provided with a plurality of sets of output filter capacitors C12, C9, C10, C7, C8, C11, and C31 connected in parallel. Wherein, when this practicality is used on the on-vehicle circuit, because the unstable line of engine electricity generation sets up input filter capacitor and output filter capacitor can steady voltage.

In an embodiment, the high-frequency switch tube Q1 further includes a power supply inductor L1, the power supply inductor L1 is connected to the secondary winding T2, and the power supply inductor L1 supplies power to the PWM signal chip driving the high-frequency switch tube Q1 through a self-power supply unit. The auxiliary coil of the power supply inductor L1 is used for supplying power, so that power loss can be reduced.

In one embodiment, a resistor R20 is disposed between the gate of the clamp MOS transistor Q4 and the upper end of the auxiliary winding T3, and a diode D8 is connected in parallel to the resistor R20. The diode D8 in the auxiliary winding T3 can shorten the discharge time of the junction capacitor between the grid and the source of the clamping MOS tube Q4 when the clamping MOS tube is turned off, and the turn-off speed is improved.

The utility model discloses only use several devices, provide the voltage signal who resets through the transformer sampling, use clamp MOS pipe and absorption capacitance to accomplish high frequency transformer's the reseing for can obtain the square wave and be used for driving the rectification MOS pipe at the in-process that resets.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention. Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.

Claims (4)

1. A secondary active clamping forward circuit is characterized by comprising a high-frequency transformer, a follow current MOS tube, a rectification MOS tube, a clamping MOS tube and a high-frequency switch tube, wherein the high-frequency transformer is connected to a power input end and comprises a primary winding, an auxiliary winding and a secondary winding, the primary winding is conducted through the high-frequency switch tube, a drain electrode of the follow current MOS tube is connected to the upper end of the secondary winding and a source electrode of the rectification MOS tube, a grid electrode of the follow current MOS tube and a drain electrode of the rectification MOS tube are connected to the lower end of the secondary winding and the lower end of the auxiliary winding together, a source electrode of the follow current MOS tube is connected to the source electrode of the rectification MOS tube, a first absorption capacitor is connected between the drain electrode and the source electrode of the follow current MOS tube in parallel, a second absorption capacitor is connected between the drain electrode and the source electrode of the rectification MOS tube in parallel, a source electrode of the clamping MOS tube is connected to the lower end of the secondary winding and the lower end of the auxiliary winding, and the source electrode of the rectification MOS tube together through a resistor, a drain electrode of the clamping MOS tube is connected to a third absorption capacitor, and a grid electrode of the auxiliary winding is connected to the upper end of the rectification MOS tube.

2. The secondary active-clamping forward circuit of claim 1, wherein the input end of the primary winding of the high-frequency transformer is provided with a plurality of sets of input filter capacitors connected in parallel, and the output end of the secondary winding of the high-frequency transformer is provided with a plurality of sets of output filter capacitors connected in parallel.

3. The secondary active clamp forward circuit of claim 1, further comprising a power supply inductor, wherein the power supply inductor is connected to the secondary winding, and the power supply inductor supplies power to a PWM signal chip for driving the high-frequency switching tube through a self-power supply unit.

4. The secondary active clamp forward circuit of claim 1, wherein a resistor is arranged between the gate of the clamp MOS transistor and the upper end of the auxiliary winding, and a diode is connected in parallel to the resistor.

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