CN212305149U - High-voltage input switching power supply circuit - Google Patents

Abstract

The utility model provides a high pressure input switching power supply circuit, including input circuit, input circuit includes the voltage-sharing unit of the primary winding unit of energy storage unit, electric current sampling unit, at least two-stage and at least two-stage. The utility model discloses the circuit structure of adjustment voltage-sharing unit and current sampling unit, with the inside current sampling unit of voltage-sharing unit of former being revised as the circuit structure who connects in parallel with the energy storage unit after establishing ties with voltage-sharing unit again, turn-off inconsistent non-voltage-sharing and the current sampling abnormal problem that produces with the switch tube in the primary winding unit thoroughly solve, reduce the impedance in the circuit simultaneously, improve product efficiency.

Description

High-voltage input switching power supply circuit

Technical Field

The utility model relates to a switching power supply circuit, in particular to switching power supply circuit of high-voltage input.

Background

With the increasing global energy crisis, 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-withstanding overlapped flyback DC-DC converter with an automatic voltage-equalizing function, which is disclosed in the design of a high-voltage-withstanding overlapped flyback DC-DC converter in the 5 th phase of 2001 in the journal of electrical engineering.

A circuit schematic diagram of a known high-voltage-resistant overlapped flyback converter (also referred to as a high-voltage-resistant flyback converter for short) is shown in fig. 1, and the high-voltage-resistant flyback converter comprises an input circuit and an output circuit, wherein the input circuit comprises two stages of same primary winding units and voltage-sharing units which are connected in series, the primary winding unit of each stage is connected with the voltage-sharing unit in parallel, the primary winding units of each stage are connected in series, and the voltage-sharing units of each stage are connected in series. The first-stage voltage-sharing unit consists of a capacitor C1; the voltage equalizing unit of the final stage consists of a capacitor C2; the primary winding unit of the primary level comprises a primary winding N1 and a switching tube Q1, one end of the primary winding N1 serves as the input end of the primary winding unit of the primary level, the other end of the primary winding N1 is connected with the conduction current inflow end of the switching tube Q1, and the conduction current outflow end of the switching tube Q1 serves as the output end of the primary winding unit of the primary level. The primary winding unit of the final stage comprises a primary winding N2 and a switching tube Q2, one end of the primary winding N2 serves as the input end of the primary winding unit of the final stage, the other end of the primary winding N2 is connected with the conduction current inflow end of the switching tube Q2, and the conduction current outflow end of the switching tube Q2 serves as the output end of the primary winding unit of the final stage. The input circuit is a two-stage series connection structure, the input circuits at all stages have the same structure and comprise primary winding units and voltage-sharing units, the primary winding units at all stages comprise primary windings and switching tubes, the primary windings and the switching tubes are connected in series to form a series branch, and voltage-sharing capacitors are connected in parallel with the series branch. The input end of the first-stage primary winding unit is connected with a positive voltage end of direct-current voltage, the output end of the last-stage primary winding unit is grounded, the control end of each switching tube applies synchronous driving signals, and the primary windings of all stages are controlled in phase and share a magnetic core.

The known circuit structure is different from a common single-ended flyback converter in that a primary winding of the high-voltage tolerant overlap flyback converter circuit is divided into two identical parts, namely a primary winding N1 and a primary winding N2, the on-off of the primary windings N1 and N2 is controlled by switching tubes Q1 and Q2 respectively, and synchronous driving signals are applied to gates of the switching tubes Q1 and Q2. Thus, under ideal working conditions, the switching tubes Q1 and Q2 are simultaneously turned on and off, and the potential at the point A is equalized due to the consistency of the primary windings N1 and N2. Although the circuit can solve the problem of overhigh voltage stress of the switching tube, when the circuit is actually applied to a product, a plurality of reliability problems exist. Because the turn-on voltages of the two switching tubes and the driving signals of the two switching tubes cannot be perfectly consistent, there are many uncontrollable differences, which will inevitably cause the turn-on and turn-off of the power switching tubes Q1 and Q2 in the circuit structure to be asynchronous, and once the switching-on and turn-off are asynchronous, there will be the following problems:

1. as shown in fig. 2, when the switching tubes are not turned on consistently, assuming that the switching tube Q1 is turned on first, at this time, the terminal voltage Vc1 of the capacitor C1 is still greater than the terminal voltage Vc2 of the capacitor C2, because the switching tube Q2 is not turned on yet, at this time, the polarity of the primary winding N2 is positive and negative, the forward voltage V2 induced by the primary winding N2 is greater than the terminal voltage Vc2, and the forward voltage V2 charges the capacitor C2 through the body diode of the switching tube Q2, and this forward current is very large, which may generate a very large negative voltage on the current sampling resistor, which may affect the normal sampling of the control IC, resulting in poor consistency of the overcurrent point during the product batch.

2. As shown in fig. 3, when the switching transistors are turned off inconsistently, the two primary windings N1 and N2 of the transformer store energy before the switching transistors Q1 and Q2 are turned off, and the total energy stored is

Assuming that the switch Q1 is turned off first, the switch Q2 is turned on, so the secondary diode D1 is still turned off, the energy stored in the transformer is not changed according to the law of conservation of energy, and the primary winding N1 is turned off because the switch Q1 has no current, i.e. no energy, so all the stored energy of the transformer is applied to the primary winding N2, i.e. the switch Q2 is turned on

Is composed of J₂J gives I₂2I, that is to say, when the switch tube Q1 is turned off first, the switch tube Q2 will bear twice of the inductive current, after the actual product is made, the turn-off sequence is fixed, and the problem of uneven heating of the switch tube and the reliability of the explosion machine will occur after long-time operation. Wherein A is_LThe inductance of the transformer is N is the number of turns of the primary winding N1 or N2, I is the current flowing through the primary side of the transformer when the switching tubes Q1 and Q2 are simultaneously conducted, I is₂After the switching tube Q1 is turned off, the current flows through the loop of the switching tube Q2.

In the prior art, as shown in fig. 4, a resistor R1 is connected in series in a wire between a voltage-sharing point a and a midpoint of a transformer T1, when switching tubes are not turned on consistently, as shown in fig. 5, a forward voltage induced by a later-turned-on winding charges a capacitor through an added series resistor R1, the resistor R1 plays a role in limiting current, so that the forward current is not very large, and thus current sampling of a control chip is not affected, and the added resistor R1 has a larger resistance value and is better.

However, as shown in fig. 6, when the switching transistors are not turned off uniformly, the current of the inductor cannot change abruptly, so that the resistor R1 does not function as a current limiter, and a large power consumption P ═ I is generated in the resistor R1₂ ²*R₁After the product is finished, the turn-off sequence is fixed, the resistor R1 is damaged due to serious heating after long-time work, and finally the product is failed, and the more the series stages of the windings in the circuit structure are, the more the switching tubes are connected in series, the more the problem is, and the lower the reliability of the product is.

An optimized circuit scheme is proposed in application No. 201810767207.X, as shown in fig. 7. An R11 resistor is added to a loop formed by the capacitor C1, the primary winding N1 and the switching tube Q1 and is used for compensating a current sampling resistor R12 in the loop formed by the capacitor C2, the primary winding N2 and the switching tube Q2. Although the circuit scheme can solve the problems of current sampling error and inconsistent product overcurrent points caused by inconsistent equivalent impedances in two switch loops, the power loss in the loops is increased due to the introduction of a new resistor R11, and the product efficiency is seriously influenced in high-power output products.

In order to improve the efficiency of high power products, another optimized circuit scheme is proposed under application No. 201810767186.1, as shown in fig. 8. A capacitor C11 and a resistor R1 are newly added to a loop consisting of the capacitor C1, the primary winding N1 and the switching tube Q1, and a capacitor C12 and a resistor R1 are newly added to a loop consisting of the capacitor C2, the primary winding N2 and the switching tube Q2. The capacitors C11 and C12 are high-frequency capacitors, the capacitors C11 and C12 are very small in capacity, only high-frequency current in corresponding loops can be absorbed, power loss on the current-sharing resistor R1 is relieved, power loss of the resistor R1 cannot be completely eliminated, and the resistor R1 still has a large failure risk after a product works for a long time, so that the voltage sharing of the main power MOS transistor of the product cannot be realized. And the sampling resistor Rcs in the circuit is still in a power loop formed by the capacitor C2, the primary winding N2 and the switching tube Q2, and when the switching tubes are inconsistent in switching, if the primary side coupling current of the transformer is in the loop of the capacitor C2, the primary winding N2 and the switching tube Q2, negative voltage still exists on the resistor Rcs, so that current sampling errors are caused.

SUMMERY OF THE UTILITY MODEL

In view of this, the technical problem to be solved by the present invention is to provide a more reliable high-voltage input switching power supply circuit.

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

a high-voltage input switching power supply circuit comprises an input circuit, wherein the input circuit comprises an input energy storage unit, a current sampling unit, at least two primary winding units and at least two voltage-sharing units, the primary winding units are connected with the voltage-sharing units in parallel, the primary winding units are mutually connected in series, and a winding connection point is formed between every two adjacent primary winding units; the pressure equalizing units 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 winding unit is connected with the positive electrode of the energy storage unit and the positive voltage end of the direct-current voltage, and the output end of the last-stage primary winding unit is connected with the input end of the current sampling unit; the output end of the current sampling unit is connected with the negative electrode of the energy storage unit and the reference ground of the direct-current voltage; each stage of primary winding unit comprises a primary winding and a switch tube, one end of the primary winding is used as the input end of the primary winding unit, the other end of the primary winding is connected with the conduction current inflow end of the switch tube, the conduction current outflow end of the switch tube is used as the output end of the primary winding unit, the control end of each switch tube applies synchronous driving signals, and the primary windings of each stage are controlled in phase and share a magnetic core.

Preferably, the energy storage unit is composed of a first capacitor or a low-voltage capacitor connected in series.

Preferably, the voltage equalizing unit is composed of a second capacitor, or a first resistor connected in parallel with the second capacitor.

Preferably, the current sampling unit is composed of a resistor or an inductor.

Preferably, the switching tube is an MOS tube, the conduction current inflow end of the switching tube is a drain of the MOS tube, and the conduction current outflow end of the switching tube is a source of the MOS tube.

Preferably, the switch tube is a triode, the conduction current inflow end of the switch tube is a collector of the triode, and the conduction current outflow end of the switch tube is an emitter of the triode.

Interpretation of related terms:

the conduction current inflow end of the switching tube is as follows: after the switch is turned on, a port into which current flows, for example, for an MOS (metal oxide semiconductor) tube, refers to a drain electrode of the MOS tube, and no matter an N-channel, a P-channel, an enhancement type or a depletion type MOS tube, when the MOS tube is turned on, the current flows from the drain electrode with high voltage to the source electrode with low voltage; in the case of a transistor, the collector of the transistor is referred to, and when conducting, current flows from the collector with a high voltage to the emitter with a low voltage.

Conduction current outflow end of the switching tube: after the switch is switched on, the port where the current flows out, such as for an MOS tube, refers to the source electrode of the MOS tube; for a triode, the emitter of the triode is referred to.

Compared with the prior art, the utility model relates to a high voltage input switch power supply circuit has following beneficial effect:

1. the utility model discloses a circuit structure of voltage-sharing unit and current sampling unit is adjusted, the current sampling unit that originally is located inside the voltage-sharing unit is revised to be the circuit structure that is parallelly connected with the energy storage unit after establishing ties with the voltage-sharing unit, will be because of the switch of switch tube inconsistent, the inductive current that produces absorbs in the twinkling of an eye, improve the voltage-sharing effect in every return circuit, increase product reliability;

2. the position of the sampling circuit in the whole circuit is adjusted, so that the accuracy of sampling current is guaranteed, meanwhile, the impedance in a loop is reduced, the product efficiency is improved, and the circuit topology can be designed into a power supply product with higher power output;

3. the voltage-sharing effect in each loop can be improved by arranging the voltage-sharing capacitor, and the reliability of the product is improved;

4. the number of added devices is small, the cost is low, the design is easy, and the reliability is high.

Drawings

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

fig. 2 is a current loop diagram of a prior art high voltage flyback converter circuit when switching transistors are not turned on uniformly;

fig. 3 is a current loop diagram of a prior art high voltage flyback converter circuit when the switching transistors are turned off inconsistently;

fig. 4 is a schematic diagram of a prior art improved high withstand voltage flyback converter circuit;

fig. 5 is a current loop diagram of a prior art improved high voltage flyback converter circuit when switching tubes are not turned on uniformly;

fig. 6 is a current loop diagram of a prior art improved high voltage flyback converter circuit when the switching transistors are turned off inconsistently;

FIG. 7 is a high withstand voltage flyback converter circuit with resistance optimization;

FIG. 8 is a high withstand voltage flyback converter circuit optimized with capacitors;

fig. 9 is a circuit diagram of a first embodiment of a high-voltage input switching power supply circuit according to the present invention;

fig. 10 is a circuit diagram of a second embodiment of the high-voltage input switching power supply circuit according to 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

As shown in fig. 9, the first embodiment of the present invention is a schematic diagram of a high-voltage input switching power supply circuit, and the high-voltage input switching power supply circuit includes: the input circuit comprises an energy storage capacitor, a sampling resistor, two stages of primary winding units and two stages of voltage-sharing units, wherein the primary winding units are connected in parallel with the voltage-sharing units, the primary winding units are connected in series, and the voltage-sharing units are connected in series; the input end of the first-stage primary winding unit is connected with the positive electrode of the energy storage capacitor and the positive voltage end of the direct-current voltage, the output end of the last-stage primary winding unit is connected with one end of the sampling resistor, and the other end of the sampling resistor is connected with the negative electrode of the energy storage capacitor and the reference ground. In this embodiment, the two-stage voltage equalizing units are respectively a capacitor C1 and a capacitor C2.

The primary winding unit comprises a primary winding N1 and a switching tube Q1, the switching tube Q1 is an MOS tube, wherein one end of the primary winding N1 is used as the input end of the primary winding unit, the other end of the primary winding N1 is connected with the drain electrode of the MOS tube Q1, and the source electrode of the MOS tube Q1 is used as the output end of the primary winding unit. One end of the capacitor C1 is connected with the input end of the primary winding unit, and the other end of the capacitor C1 is connected with the output end of the primary winding unit.

The final stage primary winding unit comprises a primary winding N2 and a switching tube Q2, wherein the switching tube Q2 is a MOS tube, one end of the primary winding N2 is used as the input end of the final stage primary winding unit, the other end of the primary winding N2 is connected with the drain electrode of the MOS tube Q2, and the source electrode of the MOS tube Q2 is used as the output end of the final stage primary winding unit. One end of the capacitor C2 is connected to the input terminal of the final primary winding unit, and the other end of the capacitor C2 is connected to the output terminal of the final primary winding unit.

The control end of the switch tube applies synchronous drive signals, and primary windings of all levels are controlled in phase and share a magnetic core.

The primary windings N1 and N2 control the on-off of the switching tubes Q1 and Q2 of the corresponding primary winding units. The capacitor C1 is connected with the first-stage winding unit in parallel to form a first-stage input circuit, and the capacitor C2 is connected with the last-stage winding unit in parallel to form a last-stage input circuit. Each stage of circuit independently sees that after current flows out from a positive voltage end Vg of direct-current voltage, a loop of a first-stage capacitor C1 is formed by a primary winding N1, a switch tube Q1 and a capacitor C1; and a loop of a final-stage capacitor C2 is formed by the primary winding N2, the switching tube Q2 and the capacitor C2. If the current flows from the positive voltage end Vg of the dc voltage, then passes through the primary winding N1 and the switching tube Q1 of the first stage, then passes through the primary winding N2 and the switching tube Q2 of the last stage, and then returns to the negative voltage end of the dc voltage through the sampling resistor Rcs, as seen from the whole input circuit.

The utility model discloses high withstand voltage flyback converter's theory of operation as follows:

as shown in fig. 9, when the driving timings of the switching tubes are inconsistent due to circuit parasitic parameters, the energy stored in the voltage-sharing capacitors C1 and C2 provides buffer time for the corresponding switching loops, so as to ensure the voltage balance among the primary winding N1, the switching tube Q1, the primary winding N2 and the switching tube Q2, the primary windings N1 and N2 with the common magnetic core form automatic coupling adjustment, and the voltages of the capacitors C1 and C2 are further stabilized by the mutual inductance current balance principle among the primary windings N1 and N2. In order to avoid the influence of the current mutual inductance phenomenon between the primary windings N1 and N2 on the sampling current in the dynamic process, the sampling resistor originally in the voltage equalizing unit in fig. 1 is modified into a circuit structure which is connected in series with the voltage equalizing unit and then connected in parallel with the energy storage unit, as shown in fig. 9. The biggest difference between the two circuit structures is that the sampling resistor in fig. 1 samples mutual inductance current between N1 and N2 during the dynamic process of the circuit, so that negative voltage occurs on the Rcs, and a control chip current sampling module can be broken down seriously, but the circuit structure in fig. 9 does not have the situation, and the current flowing on the Rcs under the steady state or dynamic condition is the peak current of the main power part, and no negative voltage occurs.

Second embodiment

Fig. 10 is a schematic diagram of a high-voltage input switching power supply according to a second embodiment of the present invention, which is different from fig. 9 in that: the primary winding unit is N (N >2) level, and the voltage-sharing capacitor is N (N >2) level.

The working principle of the circuit after the series superposition is the same as that of the first embodiment, and the same effect can be achieved, and the details are not repeated herein.

The embodiment of the present invention is not limited to this, and in other embodiments, the voltage equalizing unit may also be formed by connecting a capacitor in parallel with a resistor; the switching tube Q1 may also be a triode to achieve the same or similar function; 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 (9)

1. A high-voltage input switching power supply circuit comprises an input circuit, wherein the input circuit comprises an energy storage unit, a current sampling unit, at least two primary winding units and at least two voltage-sharing units, the primary winding units are connected in parallel with the voltage-sharing units, the primary winding units are mutually connected in series, and a winding connection point is formed between every two adjacent primary winding units; the pressure equalizing units are connected in series, and a pressure equalizing series point is formed between every two adjacent pressure equalizing units; the input end of the primary winding unit is connected with a positive voltage end of direct-current voltage, and the primary winding unit is characterized in that:

one end of the current sampling unit is connected with a connection point of the output end of the final-stage primary winding unit and the final-stage voltage-sharing unit, the other end of the current sampling unit is connected with one end of the energy storage unit, one end of the energy storage unit is also connected with a reference ground, and the other end of the energy storage unit is connected with the input end of the first-stage primary winding unit.

2. A high voltage input switching power supply circuit according to claim 1, wherein: the primary winding units comprise primary windings and switching tubes, one ends of the primary windings are used as input ends of the primary winding units, the other ends of the primary windings are connected with conduction current inflow ends of the switching tubes, and conduction current outflow ends of the switching tubes are used as output ends of the primary winding units; the control end of each switching tube applies synchronous drive signals, and the primary windings of all stages are controlled in phase and share a magnetic core.

3. A high voltage input switching power supply circuit according to claim 1, wherein: the energy storage unit is composed of a first capacitor or a low-voltage capacitor connected in series.

4. A high voltage input switching power supply circuit according to claim 1, wherein: the voltage-sharing unit is composed of a second capacitor or a first resistor connected with the second capacitor in parallel.

5. A high voltage input switching power supply circuit according to claim 1, wherein: the current sampling unit consists of a resistor or an inductor.

6. A high voltage input switching power supply circuit according to claim 2, wherein: the switch tube is an MOS tube.

7. A high voltage input switching power supply circuit according to claim 2, wherein: the switch tube is a triode.

8. The utility model provides a high-voltage input switching power supply circuit, includes input circuit, and input circuit includes input energy storage unit, current sampling unit, the primary winding unit of at least two-stage and the voltage-sharing unit of at least two-stage, its characterized in that:

the primary winding units are connected with the voltage equalizing unit in parallel, the primary winding units are connected in series, and a winding connection point is formed between every two adjacent primary winding units; the pressure equalizing units 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 winding unit is connected with the positive electrode of the energy storage unit and the positive voltage end of the direct-current voltage, and the output end of the last-stage primary winding unit is connected with the input end of the current sampling unit; the output end of the current sampling unit is connected with the negative electrode of the energy storage unit and the reference ground of the direct-current voltage;

the primary winding unit comprises a primary winding and a switching tube, one end of the primary winding is used as the input end of the primary winding unit, the other end of the primary winding is connected with the conduction current inflow end of the switching tube, and the conduction current outflow end of the switching tube is used as the output end of the primary winding unit; synchronous driving signals are applied to the control end of the switching tube, and primary windings of all levels are controlled in phase and share a magnetic core;

the energy storage unit comprises a first capacitor, the voltage-sharing unit comprises a second capacitor, the current sampling unit comprises a resistor, and the switch tube is an MOS tube.

9. The high voltage input switching power supply circuit according to claim 8, wherein: the switch tube is a triode.

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