WO2007068186A1

WO2007068186A1 - A resonant soft-switched converter

Info

Publication number: WO2007068186A1
Application number: PCT/CN2006/003302
Authority: WO
Inventors: Yiping Zhang
Original assignee: Shenzhen Clou Power Technology Co., Ltd
Priority date: 2005-12-15
Filing date: 2006-12-06
Publication date: 2007-06-21
Also published as: CN1794548A; CN100361379C

Abstract

A resonant soft-switched converter includes a half-bridge composed of two power switches (Q1, Q2), the center point of the half-bridge is connected in series to one AC input of the rectifier bridge (QL), the other AC input of the rectifier bridge (QL), a resonant inductor (Lr), a resonant capacitor (Cr) and the negative terminal of the input power supply in turns, the positive and negative terminals of the rectifier bridge are connected in parallel to an output filter capacitor (Cf), and the output voltage derives from two terminals of the output filter capacitor (Cf). The converter further includes an additional inductor (L2), a third diode (D3) and a fourth diode (D4), the additional inductor (L2) is connected in parallel between the center point of the half-bridge and the anode of the third diode (D3), the cathode of the third diode (D3) and the anode of the fourth diode (D4) are connected to the positive and negative terminals of the input power supply, respectively, the node between the anode of the third diode (D3) and the cathode of the fourth diode (D4) is connected with the node between the resonant capacitor (Cr) and the resonant inductor (Lr).

Description

Resonant soft switching converter

Technical field

The invention relates to a switching converter which can be used in a switching power supply, in particular to a soft switching converter, and more particularly to an inductor and a capacitor series resonant circuit, which realizes zero current shutdown of a power tube, an output rectifying device and a zero voltage of a power tube. A resonant type soft switching converter is turned on. Background technique

In the field of power electronics, a device that converts one type of electrical energy into another type of electrical energy (such as a DC 5 volts converted DC 3 volts) for power conversion is called a converter, and the components that make adjustments in the power conversion alternately operate in the open ( The converter that is turned on and off (ie, turned off) is called a switching converter.

In the switching converter, try to change the voltage across the power tube or the current passing through the sinusoidal law. When the voltage is zero, the power transistor is turned "on" (from off to on). It is called zero voltage switch. , or "off" (from on to off) when the current is zero is called a zero current switch, collectively referred to as a soft switch. Further, a converter that uses a series connection of an inductor or a capacitor or a parallel resonant circuit to create a soft switching condition for a power tube is called a resonant type soft switching converter. In a conventional switching converter, when the power transistor is turned on when the voltage is non-zero or turned off when the current is non-zero, it is called a hard switch.

Compared with traditional hard-switching converters, converters using soft-switching technology have outstanding advantages such as high conversion efficiency and small electromagnetic interference. Therefore, they have been widely used, and the proportion is also increasing. Research and application of new soft switches Technology has become the focus and mainstream in the field of switching converters.

Further, introduce the professional work of the soft-switching converter "Soft-switching technology of DC switching power supply" (Edited by Xin Xinbo, Yan Yangguang, Beijing. · Science Press, January 2000, first edition, ISBN7 3- 007766-0, Chinese version library CIP Data Verification (1999) No. 32120), in Figure 2.12 series load series resonant converter (a) on page 66, describes the line connection form of a half-bridge resonant soft-switching converter, for convenience of description , the order of the series components is adjusted and redrawn into Figure 1 in the drawing of the specification; on page 69 of the book, the main waveform of the current interrupted operation mode (fs<0.55fr) is given to The waveform of the terminal voltage and the passing current of the main components in the above converter are changed in a working cycle, and the pattern related to the present invention is selected and redrawn into the drawing in the drawing.

1

Confirmation 2. Where fs is the operating frequency of the power transistors Q1 and Q2, and fr is the free resonant frequency of the resonant inductor Lr and the capacitor Cr, the value of which is the square root of Lr*Cr and the reciprocal of 2 π (π is the pi, 3. 1416) times 3⁄43⁄4, The details are as follows - as shown in Figure 1, the resistor RL represents the load, the capacitor C3 is the output capacitor between the collector and the emitter of the power transistor Q1, and the capacitor C4 is the output capacitor between the collector and the emitter of the power transistor Q2. Clearly drawn. In FIG. 2, the waveforms DQ1 and DQ2 respectively indicate the driving waveforms of the power transistors Q1 and Q2, and the power tube is turned on when the high level is driven, and the power tube is turned off when the low level is driven.

As shown in Fig. 2, the output current io has a large current amplitude during the period t0-tl, and the current amplitude is small during the period of t1 to t2, and the total average value (i.e., the current supplied to the load) is affected by the latter in one cycle. Will be significantly less than the average of the tO-tl time period. Therefore, the half-bridge resonant soft-switching converter shown in FIG. 1 does not fully utilize the capability of the resonant tank to transfer energy, and the current supplied to the load is small; it can also be said that if the required load current is constant, the power transistor Q1 flows. And the current of Q2, resonant inductor Lr, resonant capacitor Cr, rectifier bridge QL, etc., the average value at time tO-tl will be significantly larger than the total average value in one cycle, resulting in a significant increase in the effective value of the current flowing through the above components. Need to choose higher specification components, resulting in increased costs. 2 At the time t3 when the power tube Q2 is turned on, the voltage of VAB is Vin/2, the voltage of point B is Vin/2, and the voltage across the power tube Q2 is Vin/2+VAB=Vin, and the voltage of the terminal of the power tube Q2 is seen to be higher. High, the stored energy of the output capacitor C4 will be lost during the turn-on process, causing the power tube Q2 to heat up, which has a negative impact on the efficiency of the converter. The power tube Q1 has the same problem at the time of t6. This problem leads to a large power-tube turn-on loss in the prior art half-bridge resonant type soft-switching converter. SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is how to provide a resonant type soft-switching converter, which can fully utilize the resonant circuit to transfer energy, and supplies the load to the existing resonant-type soft-switching converter under the same resonant inductor and resonant capacitor specifications. The current is large; further, the power tube zero voltage can be turned on.

In the prior art, the macroscopic effect of the capacitor C1, the capacitor C2, and the resonant capacitor Cr in the resonant type soft-switching converter shown in FIG. 1 is equivalent to a capacitor, so in the present invention, a resonant capacitor Cr is uniformly used to be equivalent, and the resonance of the present invention is equivalent. The capacitance Cr can be a combination of 'three or other number of capacitances. The present invention solves the above technical problem, and provides a first power tube Q1 and a first diode D1. The collector and the emitter of the first power tube Q1 are respectively connected to the cathode and the anode of the first diode D1; The power tube Q2 and the second diode D2, the collector and the emitter of the second power tube Q2 are respectively connected to the cathode and the anode of the second diode D2; the cathode of the first diode D1, the second two The anode of the pole tube D2 is respectively connected to the positive and negative ends of the input power source Vin, the anode of the first diode D1, the cathode of the second diode D2 are connected, and then connected to the rectifier bridge QL-AC terminal, the rectifier bridge QL another The alternating-side series resonant inductor LIT is connected to one end of the resonant capacitor Cr; the other end of the resonant capacitor Cr is connected to the negative terminal of the input power; the positive and negative ends of the rectifier bridge QL are connected in parallel with an output filter capacitor Cf, The output voltage Vo is taken from both ends of the output filter capacitor Cf. The method further includes a third diode D3, a fourth diode D4, a cathode of the third diode D3, and a fourth diode D4. The anode is connected to the positive and negative ends of the input power supply, respectively. The anode of diode D3, the cathode of the diode D4 and the fourth connection connected to the resonant capacitor Cr, a connection point between the resonant inductor Lr.

The resonant type soft switching converter according to the present invention further includes an auxiliary inductor L2 connected in parallel between the third diode 'anode D3 and the first diode anode D1, or in parallel in the rectification Between the two AC ends of the bridge QL.

According to the resonant type soft switching converter provided by the present invention, the diodes D1, D2, D3, and D4 are all fast recovery or ultrafast recovery diodes.

According to the resonant type soft switching converter provided by the present invention, the power transistors Q1, Q2 may be power field effect transistors M0SFET or insulated gate bipolar transistor IGBTs. Diodes D1 and D2 are omitted when using the M0SFET.

The above technical problem of the present invention can also be solved by providing a resonant-type soft-switching converter with transformer isolation, comprising a first power tube Q1 and a first diode D1, respectively, a collector and an emitter of the first power tube Q1 Connected to the cathode and anode of the first diode D1; the second power tube Q2 and the second diode D2, the collector and the emitter of the second power tube Q2 are respectively connected to the cathode and the anode of the second diode D2 The anode of the first diode D1 and the anode of the second diode D2 are respectively connected to the positive and negative ends of the input power source Vin, and the anode of the first diode D1 and the cathode of the second diode D2 are connected. Connected to one end of the primary transformer NP of the isolation transformer T, the other end of the primary transformer NP of the isolation transformer T is connected to one end of the resonant capacitor Cr; the other end of the resonant capacitor Cr is connected to the negative terminal of the input power supply; The two ends of the secondary NS of the isolation transformer T are respectively connected to two alternating current ends of the rectifier bridge QL; the positive and negative ends of the rectifier bridge QL are correspondingly connected with an output filter capacitor Cf, and the output voltage Vo is taken from both ends of the output filter capacitor Cf. The third diode D3 and the fourth diode D4 are further included, and the cathode of the third diode D3 and the anode of the fourth diode D4 are respectively connected to the positive and negative ends of the input power source. After the anode of the third diode D3 and the cathode of the fourth diode D4 are connected, they are connected to a connection point between the resonant capacitor Cr and the resonant inductor Lr.

Further provided in accordance with the invention includes an auxiliary inductor L2 connected in parallel between the third diode anode D3 and the anode of the first diode D1, or in parallel between the ends of the primary NP of the isolation transformer T. Resonant soft switching converter.

According to the resonant type soft-switching converter provided by the present invention, the diodes D1, D2, D3, and D4 are all fast recovery or ultra-fast recovery diodes.

The resonant soft-switching converter provided by the invention not only can fully utilize the capability of the resonant circuit to transfer energy, but can provide greater load to the load than the prior art resonant-type soft-switching converter under the same resonant inductor and resonant capacitor specifications. Current, output more power; and in the further improved circuit, the power tube realizes zero voltage turn-on, the efficiency is improved, the operating frequency of the converter is increased without increasing the loss, and the isolation transformer can be reduced by increasing the operating frequency of the converter The volume of the resonant inductor, which in turn reduces the volume of the entire converter, achieves miniaturization and low cost; at the same time, zero voltage turn-on can effectively reduce the voltage time change rate and reduce electromagnetic radiation. Therefore, the resonant type soft switching converter provided by the invention has the outstanding advantages of small electromagnetic interference, high efficiency, low cost and the like. DRAWINGS

The invention will be further described in detail below with reference to the drawings and specific embodiments.

1 is a schematic diagram of a prior art series load series resonant converter;

2 is a waveform diagram of a partial electric quantity in the series-connected series resonant converter shown in FIG. 1; FIG. 3 is a schematic diagram of a first resonant type soft switching converter according to an embodiment of the present invention; Figure 4 is a waveform diagram of main electric quantities in one of the embodiments shown in Figure 3;

5 is a schematic diagram of a modified version of a second type of resonant soft-switching converter according to the second embodiment of the present invention; FIG. 6 is a waveform diagram of main power in the second embodiment of FIG.

Figure 7 is a schematic diagram of a third resonant type soft-switching isolating converter according to the third embodiment of the present invention; and Figure 8 is a schematic diagram showing a modified version of a fourth resonant-type soft-switching isolating converter according to the fourth embodiment of the present invention. detailed description

(A) A first resonant type soft switching converter according to one embodiment of the present invention:

1 basic circuit, the structure shown in Figure 3, comprising: a first power tube Q1 and a first diode D1, the collector and the emitter of the first power tube Q1 are respectively connected to the cathode and anode of the first diode D1 a second power tube Q2 and a second diode D2, the collector and the emitter of the second power tube Q2 are respectively connected to the cathode and the anode of the second diode D2; the cathode of the first diode D1, The anode of the second diode D2 is respectively connected to the positive and negative ends of the input power source Vin, the anode of the first diode D1, the cathode of the second diode D2 are connected and connected to the rectifier bridge QL-AC terminal), The other end of the rectifier bridge QL is connected to one end of the resonant capacitor Cr; the other end of the resonant capacitor Cr is connected to the negative terminal of the input power supply Vin; the positive of the rectifier bridge QL (+ The negative (-) terminal corresponds to the parallel output filter capacitor Cf, and the output voltage Vo is taken from both ends of the output filter capacitor Cf;

The third diode D3 and the fourth diode D4 are further included. The cathode of the third diode D3 and the anode of the fourth diode D4 are respectively connected to the positive and negative ends of the input power source Vin, and the third diode. After the cathode of the tube D3 and the cathode of the fourth diode M are connected, they are connected to a connection point between the resonant capacitor Cr and the resonant inductor Lr.

In FIG. 3, the capacitor C3 is the sum of the output capacitance and the external parallel capacitance between the collector and the emitter of the first power transistor Q1, and the capacitor C4 is the output capacitance between the collector and the emitter of the second power transistor Q2. The sum of the external and parallel capacitors, the resistance RL represents the load.

The first type of resonant soft-switching converter according to one embodiment of the present invention, by adding the third two 4 and the tube D3, the fourth diode M, when the power tube Q1 (or Q2) is turned on, passing through the resonant capacitor When the Cr and the resonant inductor Lr transfer current to the load, the resonant capacitor Cr can be connected to the resonant inductor Lr. The voltage of the point does not exceed the positive (or negative) end of the input power source, thereby preventing the resonant capacitor Gr and the resonant inductor Lr from continuing to resonate in the negative (or positive) direction, which can save the reverse resonance in the prior art, that is, the small current is transmitted in FIG. In the period of tl-t2 (or t4-t5), the ratio of the large current transmission time is increased to increase the average value of the output current.

2 working principle, the working process of this embodiment will be described in detail with reference to FIG.

First, in order to facilitate the analysis of the working principle of the converter, the following four assumptions are made -

1. All components are ideal, that is, the conduction voltage drop of the power tube is ignored, the leakage current of the diode and the power tube is ignored, and the series resistance of the capacitor is ignored.

2. Output Filter Capacitor Cf is large enough to be equivalent to a constant voltage source Vo during one switching cycle.

3. When there is current flowing through the two AC terminals of the rectifier bridge QL, the voltage of the two AC terminals is clamped on Vo+2Vd, where Vo is the output voltage and 2Vd is the forward voltage drop of the two diodes inside the rectifier bridge QL. (about 1V each).

4. The voltage of the unspecified reference point is relative to the negative terminal of the input power supply.

Then, a complete working period t0--t6 of the embodiment can be divided into six time segments to describe, and the main power waveform is as shown in FIG. 4, and the basic description is as follows: In FIG. 4, each from top to bottom The meaning of the waveform is: (1) DQ1 and DQ2 are the driving waveforms of the power transistors Q1 and Q2 respectively. When the high level is driven, the power tube is turned on, and when the low level is driven, the power tube is turned off; (2) VC is the anode of the diode D3. That is, the voltage at point C relative to the negative terminal of the input power supply, iLr is the current through the resonant inductor Lr, io is the current flowing out of the positive terminal of the rectifier bridge QL, and the current flowing to the load RL is the average value of io; (3) due to the change of the rectifier bridge QL For the action, the current io is always kept positive, which is the absolute value of the current iLr.

Finally, the six time periods in a complete working cycle of the present embodiment are specifically described in conjunction with FIG. 4 (before the tO time, the initial state of the circuit is: the power pipes Q1 and Q2 are all in the off state):

1. to- tl time period

As shown in FIG. 4, at time t0, the power tube Q1 is turned on by the driving pulse DQ1, and the input power source Vin forms a current through the power tube Q1, the two alternating current ends of the rectifier bridge QL, the resonant inductor Lr, and the resonant capacitor Cr. path.

In the above path, the power tube Q1 is equivalent to a short circuit, and the two AC terminals of the rectifier bridge QL are equivalent to a voltage source of Vo+2Vd, so a voltage is applied to the resonant inductor Lr and the resonant capacitor Cr series circuit. Source, the voltage value of about Vin- (Vo + 2Vd) ₀ resonant inductor Lr, resonant capacitor Cr series resonance starts, through the resonant inductor Lr of the current iLr from 0 resonant rise, increased to a peak and then gradually decreases to form a sinusoidal Shaped waveform.

The resonant capacitor Cr, under the action of the current iLr, and the voltage VC at the junction C of the resonant inductor Lr continue to rise from zero. Until the time t1, when the voltage of the point reaches Vin+Vd (Vd is the conduction voltage of the diode D3), the diode D3 is turned on, the VC is clamped and no longer rises, and the resonant capacitor Cr exits the resonance. After tl, the current iLr forms a path through the power tube Q1, the two AC terminals of the rectifier bridge QL, and the diode D3, indicating that the free resonance ends.

2. tl-12 time period

As shown in Fig. 4, during the period t1 to t2, the current iLr forms a path through the power tube Q1, the two AC terminals of the rectifier bridge QL, and the diode D3. The power tube Q1 is equivalent to a short circuit, and the two AC terminals of the rectifier bridge QL are equivalent to a voltage source of Vo+2Vd, and the current iLr linearly decreases under the action of the voltage source Vo+2Vd + Vd (Vd is the conduction voltage of the diode D3). Until time t2, the current iLr drops to zero. During this time, VC—mainly remains Vin+Vd.

3. t2-13 time period

As shown in Figure 4, during the period t2-13, the current iLr remains at 0. During this period, the power transistor Q1 is turned off to zero current, and the two diodes in the rectifier bridge QL are also turned off.

In particular, the present invention prevents the current iLr from changing in the opposite direction during the conduction of the power transistor Q1 by clamping the voltage at point C. Compared with the prior art, the time in the reverse direction of the prior art, that is, the time for transmitting a small current in FIG. 2, can be saved, and the proportion of time occupied by the large current transfer is increased, thereby increasing the average value of the current to the load.

4-6. t3— 14. t4—5, t5— 1:6 time period:

As shown in FIG. 4, at time tS, the power transistor Q2 is turned on by the driving pulse DQ2. The following three time periods are consistent with the above three previous time periods in this embodiment, and must be mapped according to the following five mapping relationships, including: (1) The turned-on power tube is mapped from Q1 to Q2; The diode of the C-point voltage is clamped from D3 to D4; (3) The voltage at point C rises from 0 to Vin+Vd and maps from Vin+Vd to -Vd; (4) The current iLr is mapped from forward to Reverse, (5) time period t0 - 1:1, tl - t2, t2 - T3 is mapped in order to t3 - 4, t4 - t5, t5 - 6. T6 is the beginning of the next duty cycle, equivalent to the to of the current cycle.

From the above circuit analysis, the following conclusions can be drawn: The diodes in the power tube Q1, the power tube Q2, and the rectifier bridge QL are both zero current-off during operation, and thus, the embodiment increases the time occupied by the large current transfer. The ratio, which increases the average of the current delivered to the load, can output more power than the prior art.

(2) The second type of resonant soft-switching converter of the second embodiment of the present invention is improved:

1 basic circuit, the structure shown in Figure 5, based on the first resonant type soft switching converter, further includes an auxiliary inductor L2, the auxiliary inductor L2 is connected in parallel to the anode of the first diode D1, the third Between the anodes of diode D3 or between the two AC terminals of rectifier bridge QL.

By adding the auxiliary inductor L2, the energy is stored when the power tube is turned on, and the output capacitor of the power tube is resonated during the time when both power tubes are turned off, and the energy storage output of the power tube output capacitor to be turned on is released. When it is turned off, it creates conditions for its zero voltage turn-on, realizes the zero voltage turn-on of the power transistors Q1 and Q2, further improves the efficiency of the converter, and reduces the voltage change rate, realizing low electromagnetic radiation.

First, also for the convenience of analyzing the operation principle of the converter, a four-point assumption is made which is identical to the assumption made by the first resonance type soft-switching converter of one of the above embodiments.

Then, a complete switching period tO--tl0 of the present embodiment can be divided into 10 time segments to describe, and the main power waveform is as shown in FIG. 6, and the basic description is as follows: In FIG. 6, each waveform from top to bottom The meanings are as follows: (1) DQ1 and DQ2 are the driving waveforms of the medium power tubes Q1 and Q2 respectively. When the high level is driven, the power tube is turned on, and when the low level is driven, the power tube is turned off; (2) VA is the anode of the diode D1. That is, the voltage at point A; iL2 is the current through the auxiliary inductor L2; VC is the voltage at the anode of diode D3, point C; iLr is the current through the resonant inductor Lr, io is the current flowing out of the positive terminal of rectifier bridge QL, the current flowing to the load It is the average value of io; (3) Due to the commutation of the rectifier bridge QL, the current io is always kept positive, which is the absolute value of the current iLr.

Finally, with reference to FIG. 6, respectively, 10 time periods in a complete working cycle of the present embodiment are specifically described (before the time t0, the initial state of the circuit is: the power pipes Q1 and Q2 are all in the off state): l. tO- tl period As shown in FIG. 6, at time t0, the power tube Q1 is turned on by the driving pulse DQ1, and the input power source Vin passes through the power tube Q1, the two alternating current ends of the rectifier bridge QL, the resonant inductor Lr, and the resonant capacitor Cr. A current path. At the same time, the input power source Vin passes through the power tube Q1, the auxiliary inductor L2, and the resonant capacitor Cr to form a second current path.

In practical applications, the inductance of the auxiliary inductor L2 is much larger than the resonant inductor Lr. The magnitude of the current iL2 through the auxiliary inductor L2 is small, and is much smaller than the amplitude of the current iLr through the resonant inductor Lr, and the first current path is resonated. The impact of the process is negligible and can be ignored. The latter description ignores the effect of current iL2.

In the first current path, the power tube Q1 is equivalent to a short circuit, and the two AC terminals of the rectifier bridge QL are equivalent to a voltage source of Vo+2Vd, so a voltage source is applied to the resonant inductor Lr and the resonant capacitor Cr series circuit. , its voltage value is about Vin- (Vo + 2Vd). The resonant inductor Lr and the resonant capacitor Cr start to resonate freely. The current iLr through the resonant inductor Lr rises resonantly from 0, increases to a peak value, and then gradually decreases to form a sinusoidal waveform.

The resonant capacitor Cr, under the action of the current iLr, and the voltage VC at the junction C of the resonant inductor Lr continue to rise from zero. Until time t1, when the voltage reaches Vin+Vd (Vd is the conduction voltage of diode D3), diode D3 is turned on, VC is clamped and no longer rises, and resonant capacitor Cr exits series resonance. After tl, the current iLr forms a path through the power tube Q1, the two AC terminals of the rectifier bridge QL, and the diode D3, indicating that the series resonance ends.

In the second current path, the current iL2 through the auxiliary inductor L2 also rises resonantly, forming a sinusoidal waveform that continuously rises from the negative direction to the positive maximum value at time t1.

2. tl--t2 time period

As shown in Fig. 6, during the period of tl-t2, the current iLr forms a path through the power tube Q1, the two AC terminals of the rectifier bridge QL, and the diode D3. The power tube Q1 is equivalent to a short circuit, and the two AC terminals of the rectifier bridge QL are connected. The voltage is Vo+2Vd, and the current iLr decreases linearly under the action of the voltage source Vo+2Vd+Vd (Vd is the turn-on voltage of the diode D3). Until time t2, the current iLr drops to zero. During this time, VC—mainly remains Vin+Vd. As shown in Fig. 6, during the period of tl-t2, the auxiliary inductor L2, the power transistor Q1, and the diode D3 form a path, and the voltage applied to the auxiliary inductor L2 is Vd, which is close to 0, so the current iL2 is maintained at the positive maximum value. Almost unchanged.

3. t2-13 time period

As shown in Figure 6, during the period t2-3, the current iLr remains at 0, and the two diodes in the rectifier bridge QL are turned off with zero current. During this period, diode D3, power transistor Q1, and auxiliary inductor L2 form a current path, and the current iL2 passed remains at the maximum value.

4. t3-4 time period

As shown in Fig. 6, at 1:3, the voltage across the power transistor Q1 is 0. Due to the buffering effect of the capacitor C3, the shutdown is zero voltage shutdown; at time t3, the current flowing through the power transistor Q1 is iL2 positive. To the maximum value, the value is also small as described above, and the turn-off can be approximated as zero current turn-off.

From the graph depicted in Figure 6, the current iL2 is not small, mainly to clearly describe the details of the current change, intentionally amplified, and the current iLr uses different ratios. In practical applications, the ratio of the current iL2 to the current iLr For 1:10 to 1:30, the difference is even bigger.

After the power transistor Q1 is turned off, the diode D3, the auxiliary inductor L2, the capacitors C3 and C4, and the input power source Vin form a path. Under the action of the current iL2, the capacitor C3 continues to be charged, the capacitor C4 continues to discharge, and the power tube Q2 collector and emitter The voltage VA continues to drop from Vin. Until time M, diode D2 turns on and voltage VA clamps on - Vd (diode D2 forward voltage drop).

5. t4 - t5 time period

As shown in Fig. 6, during the t4-t5 period, the diode D3, the auxiliary inductor L2, the diode D2, and the input power source Vin form a path, and the current iL2 linearly decreases by the action of the reverse Vin, and the voltage VA continues to remain at -Vd.

6. 1:5-1:6, t6-17, t7-18, t8-9, t9-tlO time period As shown in Fig. 6, at time t5, the voltage of the collector and emitter of the power transistor Q2 is the voltage VA, which is maintained at -Vd (about IV, which is approximately 0 compared to the input power source Vin), and the power transistor Q2 is now The driving pulse DQ2 is turned on, and the zero voltage is turned on.

The following five time periods after the power tube Q2 is turned on are consistent with the above five previous time periods in this embodiment, and are corresponding to the following seven mapping relationships, including: ω-conducting power tube is mapped from Q1 to Q2, (The diode of clamp C point voltage is mapped from D3 to D4, (the voltage at point C rises from 0 to Vin+Vd and maps from Vin+Vd to -Vd, (4) current iLr maps from forward to reverse (5) The current iL2 rises from the negative direction to the positive direction, and the current iL2 decreases from the positive direction to the negative direction. (6) The voltage at point A decreases from Vin to -Vd and maps from -Vd to Vin, ( 7) Time periods t0-tl, tl-t2, t2-t3, t3-14, t4-t5 are mapped in order to time segments t5-6, t6-17, t7-8, t8-t9, t9-tlO0

As shown in Fig. 6, the time t10 is the start of the next duty cycle, and the power transistor Q2 is turned on at the moment, and is zero voltage turned on. The time tlO is equivalent to the to of the current cycle.

From the above introduction, the following conclusions can be drawn: The diodes in the power tube Q1, the power tube Q2, and the rectifier bridge QL are zero current-off during the working process, and the power tube Q1 and the power tube Q2 are zero-voltage-on, so the efficiency Compared with the prior art, it is suitable for reducing the volume of the resonant inductor Lr and the auxiliary inductor L2 by the high frequency of the operating frequency, thereby realizing miniaturization of the converter; meanwhile, the present embodiment improves the occupation of large current. The proportion of time, thereby increasing the average of the current delivered to the load, can output more power than in the prior art.

(C) A third resonant type soft-switching isolating converter of the third embodiment of the present invention:

1 basic circuit, the structure shown in Figure 7, comprising: a first power tube Q1 and a first diode D1, the collector and the emitter of the first power tube Q1 are respectively connected to the cathode and anode of the first diode D1 a second power tube Q2 and a second diode D2, the collector and the emitter of the second power tube Q2 are respectively connected to the cathode and the anode of the second diode D2; the cathode of the first diode D1, The anodes of the second diode D2 are respectively connected to the positive and negative ends of the input power source Vin, the anode of the first diode D1, the cathode of the second diode D2 are connected and connected to one end of the primary NP of the isolation transformer T; The other end of the isolation transformer T primary NP is connected to one end of the resonant capacitor Cr, and the other end of the resonant capacitor Cr is connected to the negative terminal of the input power supply; the two ends of the secondary transformer NS of the isolation transformer T are respectively connected to the rectification The two AC terminals O of the bridge QL; the positive (+) and negative (-) terminals of the rectifier bridge QL are correspondingly connected with an output filter capacitor Cf, and the output voltage Vo is taken from both ends of the output filter capacitor Cf;

The third diode D3 and the fourth diode M are further included. The cathode of the third diode D3 and the anode of the fourth diode D4 are respectively connected to the positive and negative ends of the input power source, and the third diode. After the D3 anode and the cathode of the fourth diode D4 are connected in parallel, they are connected to the connection point of the resonant capacitor Cr and the resonant inductor.

In FIG. 7, the capacitor C3 is the sum of the output capacitance and the external parallel capacitance between the collector and the emitter of the first power transistor Q1, and the capacitor C4 is the output capacitance between the collector and the emitter of the second power transistor Q2. The sum of the external and parallel capacitors, the resistance RL represents the load.

2 working principle, the difference between the working process of the first resonant type soft switching converter shown in FIG. 3 is as follows: 1) When the current iLr of the resonant inductor Lr passes through the isolation transformer T primary NP, the clamp at both ends of the primary NP The bit voltage is (Vo+2*Vd) *NP/NS, where Vo is the output voltage, 2 is the number of diodes that are simultaneously turned on in the rectifier bridge, Vd is the diode forward voltage, and NP is the number of turns of the isolation transformer T primary NS is the number of turns of the secondary of the isolation transformer T; 2) The output current io is the absolute value of the current iLr*NP/NS with a coefficient NP/NS in the middle.

Other aspects of the working process of this embodiment are identical to those of the first resonant type soft switching converter. The third resonant type soft-switching isolating converter of the third embodiment of the present invention increases the third diode D3 and the fourth diode D4 in the process of transmitting current to the load through the resonant capacitor Cr and the resonant inductor Lr. The voltage at the connection point between the resonant capacitor Cr and the resonant inductor Lr can be limited not to exceed the positive and negative ends of the input power source, thereby preventing the resonant capacitor Cr and the resonant inductor Lr from continuing to resonate in the opposite direction, thereby saving the reverse resonance in the prior art. 2 The time for transmitting a small current increases the proportion of time taken by the large current transfer, thereby increasing the average value of the current delivered to the load.

(4) A fourth modified type of soft-switching isolating converter of the fourth embodiment of the present invention:

1 basic circuit, the structure shown in Figure 8, on the basis of the third resonant type soft-switching isolating converter, further includes an auxiliary inductor L2, the auxiliary inductor L2 is connected in parallel with the emitter of the first power tube Q1, Between the anodes of the three diodes D3, or between the two ends of the primary NP of the isolation transformer T.

In FIG. 8, the capacitor C3 is the sum of the output capacitance and the external parallel capacitance between the collector and the emitter of the first power transistor Q1, and the capacitor C4 is the output capacitance between the collector and the emitter of the second power transistor Q2. The sum of the external parallel capacitors, the resistance RL represents the load. 2 working principle, the difference between the working process of the second resonant type soft switching converter shown in FIG. 5 is as follows: 1) When the current iLr of the resonant inductor Lr passes through the isolation transformer T primary NP, the clamp at both ends of the primary NP The bit voltage is (Vo+2*Vd) *NP/NS, where Vo is the output voltage, 2 is the number of diodes that are simultaneously turned on in the rectifier bridge, Vd is the diode forward voltage, and NP is the number of turns of the isolation transformer T primary NS is the number of turns of the secondary of the isolation transformer T; 2) The output current io is the absolute value of the current iLr*NP/NS with a coefficient NP/NS in the middle. ,

Other aspects of the operation of this embodiment are identical to those of the second resonant type soft switching converter shown in Fig. 5.

In this embodiment, by adding the auxiliary inductor L2, energy is stored when the power tube is turned on, and when the two power tubes are turned off, the output capacitor of the power tube is resonated, and the energy storage of the power tube output capacitor to be turned on is stored. Released, creating conditions for its zero voltage turn-on, realizing zero voltage turn-on of power transistors Ql, Q2, further improving the efficiency of the converter, and reducing the voltage change rate, achieving low electromagnetic radiation.

In particular, the first to fourth diodes D1, D2, D3, and D4 in this embodiment are both fast recovery or ultrafast recovery diodes, and have low loss during high frequency operation.

The power transistor in the above embodiment may be a power field effect transistor MOSFET, an insulated gate bipolar transistor IGBT, or a bipolar transistor BJT. When using the MOSFET, diodes D1 and D2 can be omitted because parasitic diodes are parasitic in the process.

Claims

Rights request

A resonant type soft switching converter comprising a first power tube (Q1) and a first diode (D1), wherein a collector and an emitter of the first power tube (Q1) are respectively connected to the first diode (D1) cathode, anode; second power tube (Q2) and second diode (D2), the collector and the emitter of the second power tube (Q2) are respectively connected to the second diode (D2) a cathode, an anode; a cathode of the first diode (D1) and an anode of the second diode (D2) are respectively connected to the positive and negative ends of the input power source Vin, and the first diode

The anode of the (D1) and the cathode of the second diode (D2) are connected in parallel to the rectifier bridge (QL) - an alternating current terminal, and the other alternating current terminal of the rectifier bridge (QL) is connected to the resonant capacitor by a series resonant inductor (Lr). One end of (Cr); the other end of the resonant capacitor (Cr) is connected to the negative terminal of the input power; the positive and negative ends of the rectifier bridge (QL) are correspondingly connected with an output filter capacitor. (Cf), output voltage (Vo) taken from both ends of the output filter capacitor (Cf.); characterized in that it further includes a third diode (D3), a fourth diode (D4), and the third diode (D3) The anodes of the cathode and the fourth diode (D4) are respectively connected to the positive and negative ends of the input power source, and the cathodes of the third diode (D3) and the cathode of the fourth diode (D4) are connected, and the resonant capacitor

(Cr), the connection point between the resonant inductors (Lr) is connected.

2. The resonant type soft switching converter according to claim 1, further comprising an auxiliary inductor (L2) connected in parallel to the anode of the first diode (D1), the third two Between the anodes of the pole tube (D3).

The resonant type soft switching converter according to claim 1, further comprising an auxiliary inductor (L2) connected in parallel between the two AC terminals of the rectifier bridge (QL).

The resonant type soft switching converter according to claim 1, 2 or 3, wherein said first diode (D1), second diode (D2), and third diode ( D3), the fourth diode (D4) is a fast recovery or ultra fast recovery diode.

The resonant type soft switching converter according to claim 1, 2 or 3, wherein the first power tube (Q1) and the second power tube (Q2) are power field effect transistors or insulated gates. Bipolar transistor.

6. A resonant soft-switching isolating converter comprising a first power tube (Q1) and a first diode (D1), wherein a collector and an emitter of the first power tube (Q1) are respectively connected to the first diode Tube (D1) a cathode, an anode; a second power tube (Q2) and a second diode (D2), wherein the collector and the emitter of the second power tube (Q2) are respectively connected to the cathode and the anode of the second diode (D2); The cathode of the first diode (D1) and the anode of the second diode (D2) are respectively connected to the positive and negative ends of the input power source Vin, the anode of the first diode (D1), and the second diode. (D2) the cathode is connected in parallel to one end of the isolation transformer (T) primary NP, and the other end of the isolation transformer (T) primary NP is connected in series with a resonant inductor (Lr) and connected to one end of the resonant capacitor (Cr); The other end of the resonant capacitor (Cr) is connected to the negative terminal of the input power supply; the two ends of the secondary NS of the isolation transformer (T) are respectively connected to two alternating current ends of the rectifier bridge (QL); the rectifier bridge (QL) The positive and negative terminals are connected in parallel with an output filter capacitor (Cf), and the output voltage Vo is taken from both ends of the output filter capacitor (Cf); and is characterized in that it further includes a third diode (D3) and a fourth diode (D4) The anode of the third diode (D3) and the anode of the fourth diode (D4) are respectively connected to an input power source Positive and negative terminals, the third diode (D3) anode, the fourth diode (D4) cathode, and into contact with the resonant capacitor (Cr), is connected to the connection point between the resonance inductor (Lr).

7. The resonant type soft switching converter according to claim 6, further comprising an auxiliary inductor (L2) connected in parallel to the anode of the first diode (D1), the third Between the anodes of the diode (D3).

The resonant type soft switching converter according to claim 6, further comprising an auxiliary inductor (L2) connected in parallel between the two ends of the isolation transformer (T) primary NP.

The resonant type soft switching converter according to claim 6, 7 or 8, wherein said first diode (D1), second diode (D2), and third diode ( Both D3) and fourth diode (D4) are fast recovery or ultrafast recovery diodes.

The resonant type soft switching converter according to claim 6, 7 or 8, wherein the first power tube (Q1) and the second power tube (Q2) are power field effect transistors or insulated gates. Bipolar transistor.