CN117937934A - Back-end energy-storage isolation flyback conversion device - Google Patents

Abstract

The back-end energy storage isolation flyback conversion device comprises a reflux switch, a driving switch, an energy storage capacitor, a transformer, a resonant inductor, a first rectifier, an output end capacitor and a controller, wherein the transformer comprises a primary side winding and a secondary side first winding; the return switch is conducted by the controller, so that the energy storage capacitor is charged by primary side current flowing through the resonant inductor and the primary side winding through the return switch, and the secondary side first winding is powered by the primary side current; then, when the primary side current turns negative, the energy storage capacitor discharges to continuously transmit power to the secondary side first winding through the return switch and the primary side winding.

Description

Back-end energy-storage isolation flyback conversion device

Technical Field

The present invention relates to a flyback converter, and more particularly to a rear-end energy-storage isolated flyback converter.

Background

In modern life, power is supplied to a user terminal from an ac power source (e.g., a wall outlet) after rectification, power factor correction, and application matching. At present, switching power converters are numerous; for DC to DC, there are Forward, fly-back, buck, boost, buck-boost, resonance, etc., and for AC to DC there are boost fly-back PFC, totem pole PFC, synchronized rectifier, etc.

Although the current switching power converters are numerous, each switching power converter can only boost or only buck, which is a disadvantage.

Disclosure of Invention

In order to solve the above problems, an objective of the present invention is to provide a back-end energy-storage isolated flyback converter.

In order to achieve the above object of the present invention, a back-end energy storage isolated flyback converter of the present invention comprises: a reflux switch; the driving switch is electrically connected to the reflux switch; the energy storage capacitor is electrically connected to the reflux switch; the transformer is electrically connected to the reflux switch and the driving switch and comprises a primary side winding and a secondary side first winding; a resonant inductor electrically connected to the primary side winding; a first rectifier electrically connected to the secondary side first winding; an output end capacitor electrically connected to the first rectifier; the controller is electrically connected to the reflux switch and the driving switch, wherein the reflux switch is conducted by the controller, so that the energy storage capacitor is charged by primary side current flowing through the resonant inductor and the primary side winding through the reflux switch, and the secondary side first winding is powered by the primary side current; then, when the primary side current turns negative, the energy storage capacitor discharges to continuously transmit power to the secondary side first winding through the return switch and the primary side winding.

The invention has the effect of boosting and reducing pressure in a large range.

For a further understanding of the technology, means, and efficacy of the present invention, reference should be made to the following detailed description of the invention and to the accompanying drawings, which are included to provide a further understanding of the invention, and to the specific features and aspects of the invention, however, are given by way of illustration and not limitation.

The foregoing summary is for the purpose of the specification only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features of the present application will become apparent by reference to the drawings and the following detailed description.

Drawings

In the drawings, the same reference numerals refer to the same or similar parts or elements throughout the several views unless otherwise specified. The figures are not necessarily drawn to scale. It is appreciated that these drawings depict only some embodiments according to the disclosure and are not therefore to be considered limiting of its scope.

Fig. 1 is a circuit block diagram of a back-end energy-storage isolated flyback conversion device according to a first embodiment of the present invention.

Fig. 2 is a timing waveform diagram of a first embodiment of the back-end energy-storage isolated flyback conversion device of the present invention.

Fig. 3 is a circuit block diagram of a second embodiment of the back-end energy-storage isolated flyback conversion device of the present invention.

Fig. 4 is a circuit block diagram of a third embodiment of a back-end energy-storage isolated flyback converter according to the present invention.

Fig. 5 is a circuit block diagram of a back-end energy-storage isolated flyback conversion device according to a fourth embodiment of the present invention.

Fig. 6 is a timing waveform diagram of a buck mode of a fourth embodiment of the back-end energy-storage isolated flyback converter of the present invention.

Fig. 7 is a timing waveform diagram of a boost mode of a fourth embodiment of the back-end energy-storage isolated flyback converter of the present invention.

Fig. 8 is a circuit block diagram of a fifth embodiment of a back-end energy-storage isolated flyback converter according to the present invention.

Fig. 9 is a circuit block diagram of a back-end energy-storage isolated flyback conversion device according to a sixth embodiment of the present invention.

Fig. 10 is a circuit block diagram of a seventh embodiment of a back-end energy-storage isolated flyback conversion device according to the present invention.

FIG. 11 is a block diagram of an eighth embodiment of a back-end energy-storage isolated flyback converter according to the present invention.

Fig. 12 is a circuit block diagram of a back-end energy-storage isolated flyback conversion device according to a ninth embodiment of the present invention.

Fig. 13 is a circuit block diagram of a back-end energy-storage isolated flyback conversion device according to a tenth embodiment of the present invention.

Reference numerals illustrate:

10: the back end energy storage isolation flyback conversion device;

20: a power supply device;

102: a secondary side first winding;

104: a first rectifier;

106: a second rectifier;

108: a secondary side second winding;

110: a primary side capacitance;

112: a third rectifier;

114: a secondary side inductance;

116: a controller;

118: a power supply output terminal;

120: a secondary side switch;

cout: an output capacitance;

Cs: an energy storage capacitor;

i1: primary side current;

I2: a secondary side current;

Lm: a primary side winding;

l: a firing line;

Lr: a resonant inductance;

n: a zero line;

Q1: a reflux switch;

Q2: a drive switch;

q3: a first auxiliary switch;

Q4: a second auxiliary switch;

t01: a first time interval;

t02: a second time interval;

t03: a third time interval;

t04: a fourth time interval;

t05: a fifth time interval;

T1: a transformer;

VB: a first voltage;

Vout: outputting a voltage;

VS: a second voltage.

Detailed Description

In the present disclosure, numerous specific details are provided to provide a thorough understanding of embodiments of the invention; however, it will be apparent to one skilled in the art that the present invention may be practiced without one or more of these specific details; in other instances, well-known details are not shown or described in order to avoid obscuring the invention. The technical content and detailed description of the present invention are described below with reference to the drawings:

First, the basic architecture of the present invention may be referred to as Storage-Boosted Isolated Fly-back (SBIF) DC-DC converter, and the main concept of the present invention is "back-end energy Storage". Because of the low voltage operation requirements, the present invention basically adopts a "boost+store" architecture. The inductance on the circuit can be compared to the (inertial) mass of the mechanical system, while the capacitance can be compared to the spring; therefore, the design concept of the back-end energy storage is to make the input end power supply push the current of the inductance (mass), and the current can be received by the capacitor (spring) at the other end to be converted into potential energy, and the potential energy can be higher than the voltage of the power supply; when the energy of the energy storage capacitor discharges through the reflux switch, the secondary side output can be driven, and the energy is not limited by the power supply voltage directly. The high-voltage end of a general booster circuit is an output end, a rear-end energy storage capacitor is arranged at the rear end of the booster circuit, and the output is rectified and output by the secondary side of an inductor. This application uses fly-back mode to store part of the energy in the inductor core and then transfer it from the flyback phase to the (isolated) secondary side. The primary and secondary sides of a transformer often employ different numbers of windings, the voltage on one side of the transformer being reflected on the other side (REFLECTED VOLTAGE) in the ratio of the number of windings; in describing the high-low comparison of the input voltage with the output voltage, it has been implicitly assumed that the effect of the turns ratio is accounted for. In addition, the actual transformer has magnetizing inductance (magnetization inductance) and leakage inductance (leakage inductance), and the series resonant inductance Lr described below can sometimes be directly used to achieve the effect of resonant inductance without providing a separate inductance element.

The switch described in the following embodiments adopts NMOS, where MOS is the switch, and when MOS is not on, since there is a body diode (or called parasitic diode), it is also turned on unidirectionally (for example, NMOS is turned on in the direction of source to drain), and the switching element of Insulated Gate Bipolar Transistor (IGBT), gaN or SiC of the power system is already quite common at present, so that it can be used as the switch instead of MOS. In the following timing waveforms, the control timings of the switches are slightly different from each other for convenience of distinction, but this is independent of the control logic. The following timing diagram is for explaining the basic operation principle of the circuit with a specific case, so the selection of the specific case is mainly for convenience of explanation, and it does not indicate that the circuit architecture can only be used as such.

The horizontal axis of the timing waveform diagram below is time in seconds, u represents microseconds, and time is from simulation, so absolute values are not particularly significant; the vertical axis is in volts for voltage signals and amperes for current signals.

The diodes in the present drawings are for rectifying (unidirectional conduction), and the diodes are shown for simplicity and understanding only; the diodes in the scheme are rectifiers in the scheme, and all the rectifying diodes can be replaced by rectifying switches, and the control time sequence of the rectifying diodes is synchronous with the direction of current, namely synchronous rectification; the current synchronous rectification technology is mature, and the rectifier can be a diode or can be realized by a synchronous switch.

The controller in the following embodiments controls the operation of the whole circuit by controlling the time sequence (gate voltage time sequence) of the switches, and then adjusts (i.e., feedback control) the time sequence of the switches at any time by detecting the voltage and current at the key position on the circuit, so as to achieve the effect of closed-loop dynamic control; the controller is typically integrated into a single chip IC to generate switch control signals to control the operation of the switches; however, the control function is not necessarily concentrated in the same block, that is, the control function (for example, the function of detecting and judging the generation of the control signal) may be achieved by a plurality of control blocks, respectively (referred to as distributed control).

The power supply device in the figure can provide direct current power (or voltage) or alternating current power (or voltage); the dc power supply (or voltage) refers to a "power supply (or voltage) with unchanged polarity", and the dc power supply (or voltage) is not limited to the power supply (or voltage) and may be a rectified power supply (or voltage), for example, a mains supply with waveform of sine wave is rectified, and the power supply (or voltage) still changes with time, but the polarity is not changed because the mains frequency (for example, 60 Hz) is far lower than the switching frequency (for example, 60 kHz), so the dc power supply can be regarded as dc instantaneously.

Referring to fig. 1, a circuit block diagram of a first embodiment of a back-end energy-storage isolated flyback converter 10 according to the present invention is shown. The back-end energy-storage isolated flyback conversion device 10 of the present invention is applied to a power supply device 20, and the back-end energy-storage isolated flyback conversion device 10 includes a reflux switch Q1, a driving switch Q2, a controller 116, an energy-storage capacitor Cs, a transformer T1, a resonant inductor Lr, a first rectifier 104, an output end capacitor Cout and a power output end 118, wherein the transformer T1 includes a primary winding Lm and a secondary side first winding 102. The return switch Q1, the driving switch Q2, the controller 116, the energy storage capacitor Cs, the primary winding Lm, the resonant inductor Lr and the power supply device 20 are electrically connected to each other and are generally referred to as a primary side, and the secondary side first winding 102, the first rectifier 104, the output capacitor Cout and the power output 118 are electrically connected to each other and are generally referred to as a secondary side.

In one embodiment of the invention, but not limiting the invention: one end of the driving switch Q2 is directly connected to one end of the return switch Q1; one end of the energy storage capacitor Cs is directly connected to the other end of the reflux switch Q1, and the other end of the energy storage capacitor Cs is directly connected to the other end of the driving switch Q2; one end of the primary side winding Lm is directly connected to the one end of the return switch Q1 and the one end of the drive switch Q2; the resonant inductance Lr is directly connected in series with the primary side winding Lm, or the resonant inductance Lr is a leakage inductance of the primary side winding Lm; one end of the first rectifier 104 is directly connected to one end of the secondary side first winding 102; one end of the output terminal capacitor Cout is directly connected to the other end of the first rectifier 104, and the other end of the output terminal capacitor Cout is directly connected to the other end of the secondary side first winding 102. Furthermore, the resonant inductor Lr may be replaced by the leakage inductance of the primary winding Lm of the transformer T1, because the leakage inductance of the transformer adds an additional series inductance to the equivalent circuit, and the leakage inductance is utilized to participate in the circuit resonant behavior, which is very common in resonant converters, such as the so-called LLC architecture.

The power output 118 is connected to a load (not shown in fig. 1), and the back-end energy-storage isolated flyback conversion device 10 converts a dc voltage (not shown in fig. 1) provided by the power supply 20 into an output voltage Vout to transmit the output voltage Vout to the load. A first voltage VB is present between the return switch Q1 and the driving switch Q2, which is the voltage driven by the half-bridge switch. A second voltage VS exists between the return switch Q1 and the storage capacitor Cs.

Referring to fig. 2, a timing waveform diagram of a first embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; please refer to fig. 1 at the same time. In fig. 2: the uppermost timing diagram is a voltage timing diagram, wherein the solid line is the first voltage VB, the single dot dashed line is the dc voltage provided by the power supply device 20, and the double dot dashed line is the output voltage Vout (i.e., the voltage isolating the low voltage output); the middle timing diagram is the current timing diagram, where the solid line is the primary side current I1 (this is the current on the bridge (through the inductance) because the current is continuous) and the dashed line is the secondary side current I2; the bottom timing diagram is the control timing diagram, wherein the solid line is the control signal of the driving switch Q2, and the dotted line is the control signal of the return switch Q1.

Please refer to fig. 1 and fig. 2 simultaneously; the steady state operation of the first embodiment of the back-end energy storage isolated flyback converter 10 of the present invention comprises the following 10 steps in sequence:

1. The primary side current I1 of the previous time (in this step, the primary side current I1 is a negative current) drives the internal diode of the driving switch Q2 to conduct, and the first voltage VB is about-1 volt (about the forward conduction voltage of the internal diode). The primary current I1 flowing from the power supply device 20 to the resonant inductor Lr is referred to as positive current (from left to right in fig. 1), and the primary current I1 flowing from the resonant inductor Lr to the power supply device 20 is referred to as negative current (from right to left in fig. 1).

2. The driving switch Q2 is turned on by the controller 116, and the dc voltage provided by the power supply device 20 drives the primary current I1 gradually from negative current to gradually positive current.

3. The primary winding Lm is at a positive voltage in the dotted position of fig. 1, and the secondary side is blocked by the first rectifier 104. Energy is stored in the primary winding Lm and the resonant inductance Lr.

4. When a predetermined condition (e.g., depending on time or the primary side current I1) is reached, the controller 116 turns off the driving switch Q2.

5. The electromotive force of the freewheeling of the primary winding Lm is reversed, the secondary side is turned on, and energy is transmitted to the secondary side output.

6. The primary side current I1 forces the first voltage VB slightly higher than the second voltage VS (i.e., a diode forward voltage across about 1V), and the primary side current I1 charges the storage capacitor Cs, stores energy and keeps the bridge at a sufficiently high voltage across the output voltage of the secondary side.

7. The return switch Q1 is turned on by the controller 116, and the primary side current I1 rapidly drops because the boost charges the storage capacitor Cs and feeds the secondary side. In more detail, the return switch Q1 is turned on, so that the storage capacitor Cs is charged by the primary side current I1 flowing through the resonant inductor Lr and the primary side winding Lm through the return switch Q1, and the secondary side first winding 102 is fed by the primary side current I1.

8. The primary side current I1 goes negative, at which time the storage capacitor Cs discharges, thereby continuing to deliver energy to the secondary side. In more detail, when the primary side current I1 turns negative, the storage capacitor Cs discharges to continuously transmit power to the secondary side first winding 102 through the return switch Q1 and the primary side winding Lm.

9. When the primary side current I1 is fast to wake (depending on time, e.g., half-cycles of the resonant inductor Lr and the storage capacitor Cs, or depending on the primary side current I1, etc.), the controller 116 turns off the return switch Q1.

10. The residual primary side current I1 (in this step, the primary side current I1 is a negative current) freewheels the first voltage VB to-1 volt, returning to step 1 above.

Furthermore, regarding the above-mentioned 7 th and 8 th steps, the control device is used to turn on the MOS switch by means of, for example, PWM signals, which is a conventional technology, and although the present disclosure discloses that the controller 116 is used to turn on the reflux switch Q1, the present invention is not limited thereto, that is, the present invention may also be used to turn on the reflux switch Q1 without the controller 116, for example, in a manner that the gate to source of the NMOS is turned on by a high voltage, and the gate to source of the NMOS is turned on by applying a proper voltage, which is a conventional technology; after the return switch Q1 is turned on, the remaining content of step 7 and step 8 can be performed by the circuit layout and device arrangement of fig. 1 of the present invention.

Please refer to fig. 2 again; the first time interval t01 belongs to a driving phase, when the driving switch Q2 is turned on by the controller 116, the power supply device 20 supplies power, and the primary winding Lm and the resonant inductor Lr store energy; a second time interval t02 belongs to the transfer phase, when the return switch Q1 is turned on by the controller 116, and energy is transferred to the secondary side; the second time interval t02 can be subdivided into a third time interval t03 and a fourth time interval t04; in a third time interval t03, the primary side current I1 freewheels and drives the secondary side current I2 while storing energy in the energy storage capacitor Cs; in a fourth time interval t04, the energy storage capacitor Cs continuously transfers energy to the secondary side; in a fifth time interval T05, the energy of the transformer T1 is released, the secondary side is not energized, and the primary side current I1 freewheels.

The invention has the following effects, characteristics and advantages:

1. the novel boost-type back-end energy storage structure can adjust the driving voltage of the secondary side by the energy storage capacitor Cs so as to achieve the function that the (power supply) can be driven even at very low voltage.

2. The large capacitance (i.e., the output end capacitance Cout) is disposed on the secondary side without the problem of surge current (inrush current).

3. The present invention can achieve zero voltage switching (zero voltage switching) with certainty, as shown by the dashed circle in the top timing diagram in fig. 2.

4. A low voltage output may be provided.

5. The voltage can be increased and decreased in a large range so as to be more suitable for power factor correction; because the invention is of buck-boost type (conventional converters are either buck-boost type only), the output of the PFC can be tied to a voltage that is convenient to use.

6. Totem pole PFC (which is not achievable with conventional converters) is achieved by directly using an inductor to face the input power; that is, by controlling the timing (e.g., duty cycle) of the switches, energy can be efficiently and controllably transferred from the primary side (power input) to the secondary side (output) regardless of whether the input voltage is higher or lower than the output voltage.

Referring to fig. 3, a circuit block diagram of a second embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 3 are identical to those shown in fig. 1, and thus, a description thereof will not be repeated here for the sake of brevity. The embodiment of fig. 1 described above may be referred to as a basic version, and fig. 3 is a symmetrical version of the basic version, which is the same principle, except that the secondary winding is reversed, where the roles of Q1 and Q2 switches are reversed, i.e., in fig. 3, Q2 is the return switch and Q1 is the drive switch.

Referring to fig. 4, a circuit block diagram of a third embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 4 are identical to those shown in fig. 1, and thus, a description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a second rectifier 106, and the second rectifier 106 is electrically connected to the output capacitor Cout and the first rectifier 104; the transformer T1 further includes a secondary side second winding 108, the secondary side second winding 108 being electrically connected to the second rectifier 106. Wherein the secondary side second winding 108 is provided for full-wave rectification at the secondary side of the transformer T1; therefore, another alternative of the present invention is to perform full-wave rectification of the diode bridge directly after the secondary side first winding 102, which is equivalent to half-wave rectification performed by each of the two windings (i.e., the secondary side first winding 102 and the secondary side second winding 108) of fig. 4, and the designer can choose the arrangement.

Fig. 4 is a full-wave version of the basic type (fig. 1), which is the same principle, but belongs to full-wave output, which is isolated output and zero-voltage switching, and the characteristic of energy storage boost (storage boost) is added, so that the control is more flexible, and the control can be directly used for power factor correction. The advantage of the full-wave version of fig. 4 is that both the forward drive and the return process transfer energy to the secondary side when the supply voltage is high (i.e., when the supply voltage is higher than the output voltage reflected on the primary side by the turns ratio); however, when the supply voltage is insufficient to drive the secondary current in the forward direction, the primary side will store energy in the inductance of the transformer, and in the phase of the freewheeling of the inductance, energy will be transferred to the secondary side on the one hand, and energy will be transferred to the storage capacitor Cs on the other hand; during the return flow, the energy of the storage capacitor Cs is transferred again to the secondary side.

The two symmetrical full-wave plates are overlapped to obtain the power factor correction with the isolated back-end energy storage, as shown in fig. 5. Referring to fig. 5, a circuit block diagram of a back-end energy-storage isolated flyback converter 10 according to a fourth embodiment of the present invention is shown; the elements shown in fig. 5 are identical to those shown in fig. 4, and thus, the description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a first auxiliary switch Q3 and a second auxiliary switch Q4, wherein the first auxiliary switch Q3 is electrically connected to the reflux switch Q1 and the energy-storage capacitor Cs, and the second auxiliary switch Q4 is electrically connected to the first auxiliary switch Q3; the power supply device 20 has a live line L and a neutral line N, and supplies an ac voltage. The basic structure and the concept of alternating positive and negative half cycles of the PFC of the push-pull output circuit (totem pole) are combined, and the invention can finish an isolated PFC by using the back-end energy storage.

The steady-state operation of the circuit of the fourth embodiment sequentially comprises the following 10 steps (the following steps assume that the ac voltage provided by the power supply device 20 is positive for half a cycle, the live line L is positive, the neutral line N is negative, the second auxiliary switch Q4 is turned on, and the first auxiliary switch Q3 is turned off):

1. The primary side current I1 of the previous time (in this step, the primary side current I1 is a negative current) drives the inscribed diode of the driving switch Q2 to conduct, and the first voltage VB is about-1 volt.

2. And (3) performing a driving stage: the driving switch Q2 is turned on by the controller 116, the positive ac voltage provided by the power supply device 20 drives the primary side current I1 to linearly increase (from negative to positive) from the negative current, and the primary side current I1 continuously increases.

3. The position where the primary side winding Lm is dotted in fig. 5 is a positive voltage; if the ac voltage provided by the power supply 20 is greater than the secondary side voltage, the second rectifier 106 is turned on, energy is transferred to the secondary side and stored in the primary winding Lm and the resonant inductor Lr.

4. The controller 116 turns off the driving switch Q2 when a predetermined condition (e.g., depending on time, the primary side current I1, or the second voltage VS) is reached.

5. The primary winding Lm reverses the electromotive force, belonging to the freewheel phase, and the first rectifier 104 is turned on, and energy continues to be transferred to the secondary output.

6. The primary side current I1 forces the first voltage VB slightly higher than the second voltage VS (i.e., a diode forward voltage across about 1V), and the primary side current I1 charges the storage capacitor Cs, stores energy and keeps the bridge at a sufficiently high voltage across the output voltage of the secondary side.

7. The return switch Q1 is turned on by the controller 116, and the primary side current I1 rapidly drops because the boost charges the storage capacitor Cs and feeds the secondary side.

8. The primary current I1 turns negative, belonging to the return phase, and the storage capacitor Cs discharges, thereby continuing to send energy to the secondary side, and part of the energy is restored to the input terminal. Here, a part of energy is restored to the input terminal (and a current flowing back to the power terminal, which will be described later herein) to be energy to be returned to the input terminal (power terminal); in general, an ac power source is connected between the wall outlet and the PFC, and an anti-interference high-frequency filter is usually provided, which is composed of, for example, an inductance and a capacitance, so that this energy (current) is mainly charged back to the capacitance of the high-frequency filter.

9. When the primary side current I1 is fast to a preset condition (e.g., depending on time, the primary side current I1, or the second voltage VS), the controller 116 turns off the return switch Q1.

10. The residual primary side current I1 (in this step, the primary side current I1 is a negative current) freewheels the first voltage VB to-1 volt, returning to step 1 above.

Furthermore, when the ac voltage provided by the power supply device 20 is negative half cycle: the zero line N is positive, the live line L is negative, the first auxiliary switch Q3 is turned on, the second auxiliary switch Q4 is turned off, and the left side of the resonant inductor Lr is a negative voltage power supply relative to the second voltage VS; q1 becomes the drive switch and Q2 becomes the return switch (i.e., both roles intermodulation).

Referring to fig. 6, a timing waveform diagram of a buck mode of a fourth embodiment of the back-end energy-storage isolated flyback converter 10 of the present invention is shown; please refer to fig. 5 at the same time. In fig. 6: the first time interval t01 belongs to the driving phase, the driving switch Q2 is turned on, the power supply device 20 supplies power, the primary winding Lm and the resonant inductor Lr store energy, and the energy is transferred from the primary side to the secondary side (i.e. the secondary side has received energy); the second time interval t02 belongs to a follow current stage, the reflux switch Q1 is conducted, and the current transmits energy and pushes up the voltage of the energy storage capacitor Cs; the third time interval t03 belongs to the return phase, the return switch Q1 is turned on, and the current returns toward the power source terminal and transfers energy to the secondary side.

Please refer to fig. 5 and fig. 6 simultaneously; in fig. 6: the uppermost timing diagram is a voltage timing diagram, wherein the solid line is the first voltage VB, which is the voltage driven by the half-bridge switch, the dotted line is the voltage of the storage capacitor Cs, and the single-dot dotted line is the output voltage Vout (i.e., the voltage isolating the low-voltage output); the middle timing diagram is the current timing diagram, where the solid line is the primary side current I1 of the transformer T1 (this is the current on the bridge because the current is continuous) and the dashed line is the secondary side current I2; the bottom timing diagram is the control timing diagram, wherein the solid line is the control signal of the driving switch Q2, and the dotted line is the control signal of the return switch Q1.

Referring to fig. 7, a timing waveform diagram of a boost mode of a back-end energy-storage isolated flyback converter 10 according to a fourth embodiment of the present invention is shown. Fig. 7 is the same as fig. 6, in which the uppermost timing diagram is a voltage timing diagram, the solid line is the first voltage VB, the broken line is the voltage of the storage capacitor Cs, and the single-dot broken line is the output voltage Vout; the middle timing diagram is the current timing diagram, wherein the solid line is the primary side current I1, and the dotted line is the secondary side current I2; the bottom timing diagram is the control timing diagram, wherein the solid line is the control signal of the driving switch Q2, and the dotted line is the control signal of the return switch Q1. Fig. 7 is the same as fig. 5, but in order to illustrate the boosting application of the circuit of fig. 5, in the case of fig. 7, the output voltage Vout is raised, the input voltage provided by the power supply device 20 is lowered, and it is illustrated that in the on-phase of the driving switch, the secondary side has no current because the input voltage is low, but energy is stored in the inductor, and in the freewheeling phase part of the energy is stored in the storage capacitor Cs, and part of the energy is transferred to the secondary side.

Please refer to fig. 5 and fig. 7 simultaneously; in fig. 7: the first time interval t01 belongs to the driving phase, the driving switch Q2 is turned on, the power supply device 20 supplies power, the primary winding Lm and the resonant inductor Lr store energy, and energy is not transferred from the primary side to the secondary side (i.e., no energy is received by the secondary side); the second time interval t02 belongs to the upper end freewheeling stage, the reflux switch Q1 is turned on, and the current transmits energy and pushes up the voltage of the energy storage capacitor Cs; the third time interval t03 is a reflux phase (when the primary side current I1 changes from positive to negative, i.e. when the upper end freewheel phase changes to the reflux phase), the reflux switch Q1 is turned on, and the current is refluxed toward the power source end and energy is transmitted to the secondary side; the fourth time interval t04 belongs to the lower freewheel phase.

The boost mode of the fourth embodiment of the back-end energy-storage isolated flyback converter 10 of the present invention sequentially comprises the following steps:

1. and a driving stage: the driving switch Q2 is turned on, the input voltage is across the primary winding Lm of the transformer T1, and since the input voltage is smaller than the output voltage, only the inductance is charged, and the secondary side has no current.

2. The controller 116 turns off the driving switch Q2 according to the primary side current I1 reaching a preset value or a switch having reached a preset time.

3. Upper freewheel phase: the boost energy of the flywheel turns on the internal diode of the return switch Q1 (zero voltage switching element), and the flyback electromotive force charges the storage capacitor Cs and also transfers energy to the secondary side.

4. And (3) a reflux stage: if the return switch Q1 is turned on, when the inductive energy is exhausted by the freewheeling current, the direction of the primary current I1 is reversed, the voltage of the storage capacitor Cs drives the reverse current, the secondary side is charged, and the current flows back toward the power supply terminal.

5. The system turns off the return switch Q1 according to a preset condition (e.g., current or time).

6. The lower end freewheel stage: the freewheeling of the inductor turns on the inscribed diode of the drive switch Q2 (zero voltage switching element), and the freewheeling current drops rapidly.

7. Returning to the drive phase.

The circuit of the fourth embodiment of the invention has the following effects, characteristics and advantages:

1. the novel boost-type back-end energy storage structure can adjust the driving voltage of the secondary side by the energy storage capacitor Cs so as to achieve the function that the (power supply) can be driven even at very low voltage.

2. The large capacitance (i.e., the output end capacitance Cout) is disposed on the secondary side without the problem of surge current (inrush current).

3. Zero voltage switching zero voltage switching is reliably achieved, as indicated by the dashed circles in the uppermost timing waveforms in fig. 6 and 7.

4. A low voltage output may be provided.

5. Both forward and flyback transfer energy to the secondary side, and time and element usage efficiency are high.

6. The voltage can be increased and decreased in a large range so as to be more suitable for power factor correction; because the invention is of buck-boost type (conventional converters are either buck-boost type only), the output of the PFC can be tied to a voltage that is convenient to use.

7. This architecture achieves a totem pole PFC (which is not possible with conventional converters) low voltage isolated output; that is, by controlling the timing (e.g., duty cycle) of the switches, energy can be efficiently and controllably transferred from the primary side (power input) to the secondary side (output) regardless of whether the input voltage is higher or lower than the output voltage.

Referring to fig. 8, a circuit block diagram of a fifth embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 8 are identical to those shown in fig. 1, and thus, a description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a first auxiliary switch Q3 and a second auxiliary switch Q4, wherein the first auxiliary switch Q3 is electrically connected to the resonant inductor Lr, and the second auxiliary switch Q4 is electrically connected to the first auxiliary switch Q3 and the resonant inductor Lr.

The circuit of fig. 8 is a Double-Tower bridge type (Double-Tower Fly-Back (DTFB) which is a buck-like structure arranged in front of the basic type (boost-like structure) of the present invention to form an isolated buck-boost DC-DC converter; the half-bridge of the power supply end and the half-bridge of the rear end energy storage end are separated (therefore called a double tower), which is different from a common bridge (no boost effect is generated without separation); the biggest benefit of the double tower is that the energy storage capacitor Cs can be utilized to perform the most elastic application of the driving voltage (primary side to inductive energy storage) and the discharging voltage (energy transfer to secondary side).

Referring to fig. 9, a circuit block diagram of a sixth embodiment of a back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 9 are identical to those shown in fig. 8, and thus, a description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a second rectifier 106, the second rectifier 106 is electrically connected to the output capacitor Cout and the first rectifier 104, the transformer T1 further includes a secondary-side second winding 108, and the secondary-side second winding 108 is electrically connected to the second rectifier 106. The circuit of fig. 9 may be referred to as a full-wave version of a double-tower flyback, i.e., a double-tower resonant switching converter, which adds the advantage of full-wave output.

Referring to fig. 10, a circuit block diagram of a seventh embodiment of a back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 10 are identical to those shown in fig. 9, and thus, the description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a primary side capacitor 110, and the primary side capacitor 110 is electrically connected to the return switch Q1, the driving switch Q2 and the primary side winding Lm. FIG. 10 is a resonant version of a Double-tower flyback type switching converter (Double-Tower Resonant DC-DC converter), which takes advantage of the advantages of high resonant efficiency and low noise, and the characteristics of storage-boost, so that the control is more flexible and the power factor correction can be directly performed.

Referring to fig. 11, a circuit block diagram of an eighth embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 11 are identical to those shown in fig. 5, and thus, the description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a secondary side switch 120, wherein the secondary side switch 120 is electrically connected to the output capacitor Cout, the secondary side first winding 102 and the secondary side second winding 108. Fig. 11 adds this secondary side switch 120 on the secondary side, blocking current during the primary side drive phase, forcing the primary side to store energy in the core. Since the secondary side has a rectifier already provided, the secondary side switch 120 only needs to be provided in the direction opposite to the rectifying direction. The rectifier diode may be replaced with a transistor switch (e.g., MOSFET, gaN, siC, etc.).

Referring to fig. 12, a circuit block diagram of a ninth embodiment of a back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 12 are identical to those shown in fig. 11, and thus, the description thereof will not be repeated here for the sake of brevity. Furthermore, the back-end energy-storage isolated flyback converter 10 further includes a secondary inductor 114, and the secondary inductor 114 is electrically connected to the first rectifier 104, the second rectifier 106 and the output capacitor Cout. In fig. 12, the secondary inductor 114 is disposed on the secondary side to receive the driving voltage of the primary side (e.g. to control the rate of change of the secondary current I2), and the secondary inductor 114 and the resonant inductor Lr have a relatively similar effect, so that a designer can flexibly set them. In addition, the secondary side switch 120 shown in fig. 11 may be disposed in addition to the secondary side inductor 114, and if the secondary side inductor 114 and the secondary side switch 120 are disposed at the same time, a third rectifier 112 may be disposed to provide a freewheeling path of the secondary side inductor 114, that is, the back-end energy-storage isolated flyback converter 10 may further include the third rectifier 112, and the third rectifier 112 is electrically connected to the first rectifier 104, the second rectifier 106 and the secondary side inductor 114.

Referring to fig. 13, a circuit block diagram of a tenth embodiment of the back-end energy-storage isolated flyback converter 10 according to the present invention is shown; the elements shown in fig. 13 are identical to those shown in fig. 4, and thus, a description thereof will not be repeated here for the sake of brevity. In fig. 13, only the storage capacitor Cs at the back end is disposed above the power supply, and this architecture has the advantage that the voltage across the capacitor itself will be lower than that of fig. 4, but because the storage capacitor Cs is disposed at the power supply end, this architecture is not suitable for totem pole PFC applications.

In summary, the present invention is an innovative boost-type back-end energy storage architecture, and the energy storage capacitor Cs can regulate the driving voltage to the secondary side, so as to achieve the function of driving (power supply) with very low voltage. The invention can boost and buck in a large range so as to be more suitable for power factor correction; because the invention is of buck-boost type (conventional converters are either buck-boost type only), the output of the PFC can be tied to a voltage that is convenient to use. The invention directly faces the input power source by the inductor, so totem pole PFC (which is not achieved by the prior converter) can be achieved; that is, by controlling the timing (e.g., duty cycle) of the switches, energy can be efficiently and controllably transferred from the primary side (power input) to the secondary side (output) regardless of whether the input voltage is higher or lower than the output voltage.

However, the foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, i.e. the invention is not limited to the specific embodiments described herein, but is intended to cover modifications and variations within the scope of the invention. The present invention is capable of other and further embodiments and its several details are capable of modification and variation in light of the present invention, as will be apparent to those skilled in the art, without departing from the spirit and scope of the invention. In summary, the present invention has industrial applicability, novelty and creativity, and the structure of the present invention is not found in the similar products and is disclosed, which completely accords with the requirements of the patent application, and the patent application is filed according to the patent laws.

Claims (9)

1. A back-end energy storage isolated flyback converter, comprising:

A reflux switch;

the driving switch is electrically connected to the reflux switch;

the energy storage capacitor is electrically connected to the reflux switch;

the transformer is electrically connected to the reflux switch and the driving switch and comprises a primary side winding and a secondary side first winding;

a resonant inductor electrically connected to the primary side winding;

a first rectifier electrically connected to the secondary side first winding;

an output end capacitor electrically connected to the first rectifier; and

A controller electrically connected to the return switch and the driving switch,

The controller is connected with the return switch, so that the energy storage capacitor is charged by primary side current flowing through the resonant inductor and the primary side winding through the return switch, and the secondary side first winding is powered by the primary side current; then, when the primary side current turns negative, the energy storage capacitor discharges to continuously transmit power to the secondary side first winding through the return switch and the primary side winding.

2. The back-end energy-storage isolated flyback conversion device of claim 1, further comprising:

a second rectifier electrically connected to the output capacitor and the first rectifier,

Wherein, this transformer still includes:

the secondary side second winding is electrically connected to the second rectifier.

3. The back-end energy-storage isolated flyback conversion device of claim 2, further comprising:

the first auxiliary switch is electrically connected to the reflux switch and the energy storage capacitor; and

The second auxiliary switch is electrically connected to the first auxiliary switch.

4. The back-end energy-storage isolated flyback conversion device of claim 1, further comprising:

the first auxiliary switch is electrically connected to the resonant inductor; and

The second auxiliary switch is electrically connected to the first auxiliary switch and the resonant inductor.

5. The back-end energy-storage isolated flyback conversion device of claim 4, further comprising:

a second rectifier electrically connected to the output capacitor and the first rectifier,

Wherein, this transformer still includes:

the secondary side second winding is electrically connected to the second rectifier.

6. The back-end energy-storage isolated flyback conversion device of claim 5, further comprising:

And the primary side capacitor is electrically connected to the reflux switch, the driving switch and the primary side winding.

7. The back-end energy-storage isolated flyback conversion device of claim 3, further comprising:

and the secondary side switch is electrically connected to the output end capacitor, the secondary side first winding and the secondary side second winding.

8. The back-end energy-storage isolated flyback conversion device of claim 7, further comprising:

The third rectifier is electrically connected to the first rectifier and the second rectifier; and

The secondary side inductor is electrically connected to the first rectifier, the second rectifier, the third rectifier and the output end capacitor.

9. The back-end energy-storage isolated flyback conversion device of claim 1, further comprising:

the power output end is electrically connected to the first rectifier and the output end capacitor.