CN213243819U

CN213243819U - High-voltage input flyback converter

Info

Publication number: CN213243819U
Application number: CN202021901199.2U
Authority: CN
Inventors: 关文龙; 王小亮; 蔡旭佳
Original assignee: Mornsun Guangzhou Science and Technology Ltd
Current assignee: Mornsun Guangzhou Science and Technology Ltd
Priority date: 2020-09-03
Filing date: 2020-09-03
Publication date: 2021-05-18
Anticipated expiration: 2030-09-03

Abstract

The utility model provides a flyback converter is imported to high pressure, including input circuit, input circuit includes voltage-sharing unit, clamping circuit unit and the elementary switch unit of at least two-stage. In the clamping circuit units, at least one stage is an active clamping circuit, the rest stages are passive clamping circuits, the active clamping circuit comprises a first switch tube, a first resistor and a first capacitor, one end of the first resistor and one end of the first capacitor are connected with the synonym end of the primary winding of the corresponding stage, the other end of the first resistor and the other end of the first capacitor are connected with the drain electrode of the first switch tube, and the source electrode of the first switch tube is connected with the synonym end of the primary winding of the corresponding stage. The utility model discloses ingenious active clamp circuit through setting up at least one-level retrieves the leakage inductance energy that corresponds the primary winding of level, makes electric capacity among the active clamp circuit and the primary winding that corresponds the level produce the resonance for the main power switch tube realizes the ZVS state, improves product efficiency, reliability and product power density.

Description

High-voltage input flyback converter

Technical Field

The utility model relates to a flyback converter field, in particular to flyback converter circuit is inputed to high pressure.

Background

With the global energy crisis becoming more serious, the development and utilization of clean energy are imperative. Therefore, solar power generation is rapidly developed. In photovoltaic power generation and power transmission, the input voltage of a control system is very high and reaches several kilovolts, and the conventional single-stage power supply topology cannot meet the design requirement due to the voltage stress of a switching tube and cannot be suitable. Therefore, a cascade technique is often used for input voltage expansion.

Fig. 1 is a circuit structure of a known high-voltage input flyback converter, which has an automatic voltage-equalizing function and is disclosed in "design of high-voltage tolerant overlap flyback DC-DC converter" of journal of electrical engineering "2001, 5, the known high-voltage input flyback converter includes an input circuit, the input circuit includes a voltage-equalizing unit, a clamp circuit unit and a primary switch unit, the number of the units is equal and is at least two, the primary switch unit includes a primary winding and a switch tube, the clamp circuit unit of each stage is connected in parallel with the primary winding of the corresponding stage, the primary switch unit of each stage is connected in parallel with the voltage-equalizing unit of the corresponding stage, the primary switch units of each stage are connected in series, and a winding connection point is formed between every two adjacent primary switch units; the pressure equalizing units of each level are connected in series, and a pressure equalizing series point is formed between every two adjacent pressure equalizing units; the input end of the first-stage primary switch unit is connected with a positive voltage end of the direct-current voltage, the output end of the last-stage primary switch unit is connected with a reference ground of the direct-current voltage, and the input ends of the primary switch units except the first stage are connected with the output end of the first-stage primary switch unit; the voltage-sharing unit comprises a capacitor, the different-name end of the primary winding is used as the input end of the primary switch unit, the same-name end of the primary winding is connected with the drain electrode of the switch tube, the source electrode of the switch tube is used as the output end of the primary switch unit, the grid electrode of the switch tube applies a synchronous driving signal, and the primary windings of all levels are controlled in phase and share a magnetic core. The scheme belongs to the known technology, and the specific implementation working principle is not described in detail. Because the main power switch tube of the circuit scheme is in a hard switching state, the switching loss of the switch tube is very large under the condition of ultrahigh input voltage, particularly the output equivalent capacitance of the high-voltage switch tube device is relatively large, and the switching loss of the switch tube is further increased. Resulting in low converter efficiency, low product reliability, and increased overall cost of product design.

SUMMERY OF THE UTILITY MODEL

In view of this, the technical problem to be solved by the present invention is to overcome the shortcomings of the existing circuit hard switch, and to provide a high-Voltage input flyback converter, so that the switch tube of the main power is in a soft Switching state (soft Switching: by introducing resonance before and after the Switching process, the Voltage between the drain and source electrodes of the main power switch tube is reduced to Zero before Switching on, the drain and source current is reduced to Zero before Switching off, and the loss of the switch tube caused by Voltage and current overlapping in the Switching process is eliminated.

In order to solve the technical problem, the utility model discloses a following technical measure realizes:

the input circuit comprises a voltage-sharing unit, a clamping circuit unit and a primary switch unit, the number of stages of each unit is equal and is at least two, the primary switch unit comprises a primary winding and a switch tube, the clamping circuit unit of each stage is connected with the primary winding of the corresponding stage in parallel, the primary switch unit of each stage is connected with the voltage-sharing unit of the corresponding stage in parallel, the primary switch units of each stage are connected with each other in series, the voltage-sharing units of each stage are connected with each other in series, the input end of the primary switch unit of the first stage is connected with the positive voltage end of direct current voltage, and the output end of the primary switch unit of the last stage is connected with the reference ground of the direct.

The voltage-sharing unit comprises a capacitor; at least one stage of the clamping circuit unit is an active clamping circuit, and the rest stages can be passive clamping circuits; the primary switch units respectively comprise primary windings and switch tubes, the different-name ends of the primary windings are used as the input ends of the primary switch units, the same-name ends of the primary windings are connected with the drain electrodes of the switch tubes, the source electrodes of the switch tubes are used as the output ends of the primary switch units, synchronous driving signals are applied to the grid electrodes of the switch tubes, and the primary windings of all levels are controlled in phase and share a magnetic core.

As a specific embodiment of the active clamping circuit, the active clamping circuit includes a first switch tube, a first resistor, and a first capacitor, one end of the first resistor and one end of the first capacitor are connected to the synonym end of the primary winding of the corresponding stage, the other end of the first resistor and the other end of the first capacitor are connected to the drain of the first switch tube, and the source of the first switch tube is connected to the synonym end of the primary winding of the corresponding stage.

As a specific embodiment of the passive clamp circuit, the passive clamp circuit includes a diode, a second resistor, and a second capacitor, one end of the second resistor and one end of the second capacitor are connected to the synonym terminal of the primary winding of the corresponding stage, the other end of the second resistor and the other end of the second capacitor are connected to the cathode of the diode, and the anode of the diode is connected to the synonym terminal of the primary winding of the corresponding stage.

Preferably, the capacitor is formed by connecting low-voltage capacitors in series.

Preferably, the first switch tube is an MOS tube.

The utility model discloses ingenious through changing the clamp circuit mode, with the leakage inductance energy recuperation of primary winding, produce the resonance through clamp capacitance (be the first electric capacity in the clamp circuit unit promptly) and the primary winding of corresponding level and make the main power switch tube realize the ZVS state, improve product efficiency and reliability for this circuit topology can design into the power product of higher power output.

Compared with the prior art, the utility model relates to a flyback converter is imported to high pressure has following beneficial effect:

1. according to the scheme, the leakage inductance energy of the primary winding is recovered by applying the at least one stage of active clamping circuit, and the first capacitor and the primary winding generate resonance, so that the main power switch tube realizes a ZVS state, and the product efficiency, reliability and product power density are improved;

2. the circuit of the scheme has the advantages of simple structure, easy design and high product cost performance.

Drawings

Fig. 1 is a circuit schematic diagram of a prior art high voltage input flyback converter;

fig. 2 is a circuit diagram of a flyback converter with high voltage input according to a first embodiment of the present invention;

fig. 3 is a circuit diagram of a flyback converter with high voltage input according to a second embodiment of the present invention.

Detailed Description

In order to make the present invention more clearly understood, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

First embodiment

Referring to fig. 2, a schematic circuit diagram of a high voltage input flyback converter according to a first embodiment of the present invention is shown, where the high voltage input flyback converter includes an input circuit, an output circuit and a transformer, the input circuit includes a two-stage voltage equalizing unit, a two-stage clamping circuit unit and a two-stage primary switch unit, the first stage voltage equalizing unit includes a capacitor C1, the second stage voltage equalizing unit includes a capacitor C2, a capacitor C1 is connected in parallel with the first stage primary switch unit and is connected in series with the capacitor C2, a capacitor C2 is connected in parallel with the second stage primary switch unit, the first stage primary switch unit includes a primary winding N1 and a switch Q1, a diode Qd1 is a parasitic diode of the switch Q1, the second stage primary switch unit includes a primary winding N2 and a switch Q2, a diode Qd2 is a parasitic diode of the switch Q2, the two-stage primary windings are controlled in-phase and are connected together, a different-name terminal of the primary winding N1 is connected to, the dotted terminal of the primary winding N1 is connected to the drain of the switch tube Q1, the source of the switch tube Q1 is connected to the dotted terminal of the primary winding N2, the dotted terminal of the primary winding N2 is connected to the drain of the switch tube Q2, and the source of the switch tube Q2 is connected to the reference ground of the DC voltage.

The first-stage clamping circuit unit is composed of a resistor R1, a capacitor C3 and a switch tube Q3, a diode Qd3 is a parasitic diode of the switch tube Q3, the first-stage clamping circuit unit is an active clamping circuit, the switch tube Q3 is an MOS tube, a source electrode of the switch tube Q3 is used as an input end of the first-stage clamping circuit unit and is connected with a homonymy end of a primary winding N1, one end of the resistor R1 and one end of the capacitor C3 are connected with a drain electrode of the switch tube Q3, the other end of the resistor R1 and the other end of the capacitor C3 are used as output ends of the first-stage clamping circuit unit and are connected with a heteronymy end of the primary winding N1.

The second-stage clamping circuit unit is composed of a diode D2, a resistor R2 and a capacitor C4 and is a passive clamping circuit, the anode of the diode D2 is used as the input end of the second-stage clamping circuit unit and is connected with the dotted end of the primary winding N2, one end of a resistor R2 and one end of a capacitor C4 are connected with the cathode of the diode D2, and the other end of the resistor R2 and the other end of the capacitor C4 are used as the output end of the second-stage clamping circuit unit and are connected with the unlike end of the primary winding N2.

The control terminals of the switching tube Q1 and the switching tube Q2 apply synchronous driving signals.

The working principle of the embodiment is as follows:

the switching tube Q1 and the switching tube Q2 use synchronous driving signals, when the switching tube Q1 and the switching tube Q2 are switched on, the primary winding N1 and the primary winding N2 store energy, and simultaneously the leakage inductance Lk1 and the leakage inductance Lk2 (wherein the leakage inductance Lk1 is the leakage inductance of the primary winding N1 to the secondary winding, and the leakage inductance Lk2 is the leakage inductance of the primary winding N2 to the secondary winding) also store energy. When the switching tube Q1 and the switching tube Q2 are turned off, the energy stored in the primary winding N1 and the primary winding N2 is output to the output end through the secondary winding of the transformer to be used by a load. However, the energy stored in the leakage inductance Lk1 and the leakage inductance Lk2 cannot be transferred to the secondary side. When a double-wire winding process is adopted between the primary winding N1 and the primary winding N2, the coupling coefficient between the primary winding N1 and the primary winding N2 is approximately 1. At this time, the energy stored in the leakage inductance Lk1 is transferred and wound into the capacitor C3 through the parasitic diode Qd3 of the switching tube Q3, most of the energy stored in the leakage inductance Lk2 is also transferred into the capacitor C3 through the parasitic diode Qd3 of the switching tube Q3 and a very small part of the energy is transferred into the capacitor C4 through the diode D2 by the coupling factor between the primary winding N2 and the primary winding N1. After the process of transferring the leakage inductance energy to the clamping capacitor (capacitor C3) is finished, the switching tube Q3 is turned on before the switching tube Q1 and the switching tube Q2 are turned on next time, the energy stored in the capacitor C3 is transferred to the primary winding N1, the primary winding N2, the leakage inductance Lk1 and the leakage inductance Lk2, the switching tube Q3 is turned off before the energy transfer process is finished completely, the current on the primary winding N1 flows, the current direction of the current flows from the same name end to the different name end, the parasitic diode Qd1 of the switching tube Q1 and the parasitic diode Qd2 of the switching tube Q2 are turned on during the current flowing process, the drain-source voltages of the switching tube Q1 and the switching tube Q2 are negative, the drain-source voltages are the voltage drops of the respective parasitic diode Qd1 and the parasitic diode Qd2, and the switching tube Q1 and the switching tube Q2 are turned on at this time. Under the condition, ZVS states are realized on the switching tube Q1, the switching tube Q2 and the switching tube Q3, the switching loss of a product is reduced, and the efficiency and the reliability of the product are improved.

Second embodiment

Fig. 3 shows a schematic diagram of a flyback converter with high voltage input according to a second embodiment of the present invention, which is different from the first embodiment in that: the voltage equalizing unit, the clamping circuit unit and the primary switch unit are all N (N is more than 2), and M (M is more than or equal to 1 and less than or equal to N) stages in the clamping circuit unit are active clamping circuits. The voltage equalizing unit, the active clamp circuit, and the primary switching unit are all configured as in the first embodiment. When M is more than or equal to 1 and less than N, the rest clamping circuit units are composed of passive clamping circuits, the structure of the clamp circuit without the original clamping circuit is the same as that in the first embodiment, and the positions of the active clamping circuit and the passive clamping circuit in the whole circuit topology can be changed according to actual conditions.

The working principle of this embodiment is the same as that of the first embodiment, and the same effects can be achieved, which is not described herein.

According to the above-mentioned contents of the present invention, by using the common technical knowledge and conventional means in the field, the present invention can make other modifications, replacements or changes in various forms without departing from the basic technical idea of the present invention, all falling within the protection scope of the present invention.

Claims

1. The utility model provides a high pressure input flyback converter, includes the clamp circuit unit, and the clamp circuit unit is two-stage at least, and the clamp circuit unit is parallelly connected with the primary winding of corresponding level in the high pressure input flyback converter, its characterized in that: at least one stage of the clamping circuit unit is an active clamping circuit, and the rest stages are passive clamping circuits.

2. A high voltage input flyback converter as claimed in claim 1, wherein: the active clamping circuit comprises a first switch tube, a first resistor and a first capacitor, wherein one end of the first resistor and one end of the first capacitor are connected with the synonym end of the primary winding of the corresponding stage, the other end of the first resistor and the other end of the first capacitor are connected with the drain electrode of the first switch tube, and the source electrode of the first switch tube is connected with the homonymy end of the primary winding of the corresponding stage;

the passive clamping circuit comprises a diode, a second resistor and a second capacitor, one end of the second resistor and one end of the second capacitor are connected with the synonym ends of the primary windings of the corresponding stages, the other end of the second resistor and the other end of the second capacitor are connected with the cathode of the diode, and the anode of the diode is connected with the synonym ends of the primary windings of the corresponding stages.

3. A high voltage input flyback converter as claimed in claim 2, characterized in that: the capacitor is formed by serially connecting low-voltage capacitors.

4. A high voltage input flyback converter as claimed in claim 2, characterized in that: the first switch tube is an MOS tube.