CN101902129B - Current-type multi-resonance direct current (DC) converter - Google Patents

Abstract

The present invention relates to DC step-up power conversion technology, and discloses a current-type multi-resonance DC converter, which includes a square wave current source generator, a multi-resonance network, and a rectification and filtering output unit connected in series in sequence, and is characterized in that the multi-resonance The network includes a transformer, a parallel resonant inductance, a parallel resonant capacitor and a series resonant inductance, the series resonant inductor is connected to the primary side of the transformer; the rectification and filtering output unit includes a diode rectification circuit and a filter capacitor connected in parallel at the output end of the diode rectification circuit.

Description

A Current Mode Multi-Resonant DC Converter

technical field

The invention relates to a DC step-up power conversion technology, in particular to a current-mode multi-resonance DC converter.

Background technique

With the increasingly serious environmental problems brought by fossil fuels and the depletion of traditional energy sources, the new energy industry has developed rapidly. However, many emerging energy sources, including solar energy and fuel cells, have low-voltage, high-current DC output characteristics, and high-efficiency boost power conversion technology has become the key to effectively utilizing these emerging energy sources.

The voltage-type boost converter has the advantages of simple structure and easy control. However, its boost function completely depends on the high transformation ratio of the transformer. Transformers with a high step-up ratio often have poor primary-secondary coupling, large leakage inductance, and large inter-turn capacitance, which will generate voltage and current spikes in the circuit, which not only reduces the operating frequency of the transformer, but also limits the efficiency of the converter. work efficiency. In addition, emerging energy sources such as solar energy and fuel cells are greatly affected by current ripple. The input current of the voltage-type boost converter is pulsating, and a large input filter must be introduced to eliminate the current ripple, which greatly increases the conversion device size and cost.

Compared with the voltage source converter, the current source converter has outstanding advantages such as high step-up capability and small current ripple, while the current source converter using parallel resonance technology can further increase the voltage gain, thereby further reducing the transformer transformation ratio and Corresponding parasitic parameters such as leakage inductance and inter-turn capacitance.

Most of the primary switching tubes of traditional current-mode parallel resonant DC converters work in the zero-voltage turn-on (ZVS: Zero Voltage Switching) state. However, in the application of low-voltage and high-current input, ZVS is not very important to achieve zero-current turn-off (ZCS: Zero Current Switching) is crucial to the reduction of switching loss. For the current-mode parallel resonant DC converter, the leakage inductance of the transformer still exists, which will also cause the overvoltage of the switching tube. Some current-mode multi-resonant DC converters realize the ZCS of the primary switching tube by introducing the resonance of the transformer leakage inductance and the parallel resonant capacitor, but in order to realize the ZCS in the full load range, the primary leakage inductance must be controlled according to the full load condition. It will cause a large circulating current of the converter to flow through the anti-parallel diode of the primary switching tube under light load, thereby seriously affecting the working efficiency under light load.

Excessive circulating energy in the resonant network will also increase the on-state loss of the converter and reduce the working efficiency of the converter. Some people introduce transformers to feed back additional resonance energy to reduce circulation losses, but the introduced transformers will increase the volume of the converter and affect the quality factor, so this method is not suitable for occasions that require high power density and voltage regulation .

In addition, the rectifier diode of the current-mode parallel resonant DC converter still has the problem of reverse recovery, and the voltage stress of the rectifier diode is still high. It is difficult to select an ultra-fast recovery diode with a lower withstand voltage and a lower on-state voltage drop as the rectifier diode.

Contents of the invention

The present invention aims to provide a new type of current-mode multi-resonant DC converter aiming at the shortcomings of the above existing current-mode resonant DC converter. This kind of converter can provide higher voltage gain, has smaller circulating current in the whole load range, both the switch tube and the rectifier diode work in the ZCS state, and it also has higher efficiency when working under light load.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve.

A current-type multi-resonance DC converter, comprising a square wave current source generator, a multi-resonance network, and a rectification and filtering output unit connected in series in sequence, wherein the multi-resonance network includes a transformer, a parallel resonant inductor, a parallel resonant capacitor and A series resonant inductance, the series resonant inductance is connected to the primary side of the transformer; the rectification and filtering output unit includes a diode rectification circuit and a filter capacitor connected in parallel at the output end of the diode rectification circuit.

Features and effects of the present invention are described as follows:

(1) The square wave current source generator adopts a current-mode half-bridge structure, a current-mode full-bridge structure or a current-mode push-pull structure. The square wave current source generator can generate a square wave current, has a small input current ripple, and the ripple frequency is twice the switching frequency, and the ripple can be filtered by a low-cost, small-volume non-polar capacitor.

(2) The multi-resonant network includes a transformer, a parallel resonant inductor, a parallel resonant capacitor and a series resonant inductor, and the series resonant inductor is connected to the primary side of the transformer. When the switching tubes of the square wave current source generator are turned on at the same time, the series resonant inductance and the parallel resonant capacitor resonate, so that the current flowing into the multi-resonant network undergoes soft commutation, realizing the ZCS of the switching tube and reducing the series resonant inductance The switch tube voltage spike caused by it. The multi-resonant network provides high voltage gain to the converter through the resonance of parallel inductors and parallel capacitors. In a multi-resonant network, the high voltage gain provided by parallel inductors and parallel capacitors through resonance can further reduce the transformer ratio and related parasitic parameters such as leakage inductance and inter-turn capacitance. At this time, the inter-turn capacitance of the transformer and the rectifier The diode junction capacitances of the filter output unit are used as parallel resonant capacitors, and the current spikes caused by them are well suppressed.

(3) the turn-on duty cycle of the switch tube of the square wave current source generator is greater than 0.5, forming a duty cycle overlap time (the turn-on duty cycle of the switch tube is less than half of the resonance cycle of the series resonant inductor and the parallel resonant capacitor) The empty ratio is greater than 0.5 and less than 0.7). During the time when the duty cycle overlaps, the input terminal of the multi-resonant network is short-circuited, and the series resonant inductor and parallel resonant capacitor realize the soft commutation of the input current of the multi-resonant network through resonance, and the input current of the multi-resonant network after commutation is in the switch After the tube is turned off, it flows through its anti-parallel diode, and the switching tube of the square wave current source generator can realize zero current shutdown, and at the same time reduce the voltage peak of the switching tube caused by the series resonant inductance.

(4) The rectification and filtering output unit includes a diode rectification circuit and a filter capacitor connected in parallel at the output end of the diode rectification circuit. The diode rectification circuit adopts a full-bridge rectification circuit, a full-wave rectification circuit or a voltage doubler rectification circuit. The use of a voltage doubler rectifier circuit can further increase the voltage gain, thereby reducing the transformation ratio of the transformer and related parasitic parameters such as leakage inductance and inter-turn capacitance, and improving efficiency.

Since the rectification and filtering output unit adopts a rectification circuit with a filter capacitor, the maximum voltage of the parallel resonant capacitor can be clamped to the output voltage by the filter capacitor, thereby reducing the circulating current energy in the parallel resonant inductor and the parallel resonant capacitor and the result of the circulating current. resulting in on-state losses. The current flowing through the rectifying diode of the rectifying and filtering output unit is the difference between the input current of the multi-resonant network and the current of the parallel resonant inductor. During the conduction period of the rectifying diode, the input current of the multi-resonant network is approximately constant, and the current of the parallel resonant inductor increases linearly until It is equal to the input current of the multi-resonant network, so the rectifier diode can realize zero-current shutdown, which solves the reverse recovery problem of the rectifier diode.

At light load, due to the shortened conduction time of the rectifier diode, the clamping time of the parallel resonant capacitor is also relatively reduced, and the resonant time of the parallel resonant inductor and the parallel resonant capacitor will be longer, so that the initial storage of the parallel resonant capacitor and the series resonant inductor resonate Can be reduced, thereby limiting the overshoot of the multi-resonant network input current when the converter is operating at light load.

The "current-type multi-resonance DC converter" of the present invention improves the efficiency of the boost power converter on the basis of the prior art (the measured converter can obtain a peak efficiency of about 95% under the condition of 15 times boost), greatly reducing the Input current ripple, so that many new energy sources with low voltage and high current DC output characteristics, including solar energy and fuel cells, can be used more effectively.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the circuit schematic diagram of current mode multi-resonance DC converter of the present invention;

Figure 2 (a) to (d) are the multi-resonant network topology diagrams including transformers with no center tap on the primary and secondary sides;

Figure 3(a) to (d) are topology diagrams of a multi-resonant network including a transformer with a center tap on the secondary side;

Figure 4(a) to (d) are topology diagrams of multi-resonant networks including transformers with center taps on the primary side;

Fig. 5(a) is a topology diagram of a rectification and filtering output unit adopting a full-bridge rectification circuit structure;

Figure 5(b) is a topology diagram of a rectification and filtering output unit using a full-wave rectification circuit structure;

Figure 5(c) is a topology diagram of a rectification and filtering output unit using a voltage doubler rectification circuit structure;

Fig. 6 is a simplified circuit schematic diagram of a current-mode multi-resonance DC converter;

Fig. 7 is a working mode diagram of a simplified circuit of a current-mode multi-resonance DC converter;

Fig. 8 is a simplified model diagram of an AC equivalent circuit of a current-mode multi-resonant DC converter;

Fig. 9 is a simplified circuit diagram of the resonant network during the overlapping time of the duty cycle of the primary switching tube;

Figure 10 (a) to (f) are six working mode diagrams of the current-mode multi-resonant DC converter;

Fig. 11 is a working waveform diagram of a current-mode multi-resonance DC converter;

Fig. 12 is a waveform diagram of the driving v _g1 and v _g2 of the two switching tubes on the primary side, the voltage v _AB between points A and B, and the input current i _pri of the multi-resonant network under full-load working conditions;

Fig. 13 is a waveform diagram of the driving v _g1 and v _g2 of the two switching tubes on the primary side, the voltage v _AB between points A and B, and the input current v _pri of the multi-resonant network under the working condition of 20% load;

Fig. 14 is a waveform diagram of the voltage v _Cp across the parallel resonant capacitor _Cp , the voltage _vD2 across the rectifier diode _D2 , and the current i _rec flowing into the rectifying and filtering output unit under full-load operating conditions;

Fig. 15 is a waveform diagram of the voltage v _Cp across the parallel resonant capacitor _Cp , the voltage v _D2 across the rectifier diode _D2 , and the current i _rec flowing into the rectifier and filter output unit under the working condition of 20% load;

Fig. 16 is a waveform diagram of the current i _Lin1 flowing through the input inductor L _in1 , the input current i _in of the converter, and the output voltage v _o under full load conditions;

Fig. 17 is an efficiency curve diagram of a current-source multi-resonance DC converter, wherein the abscissa indicates the load rate, and the ordinate indicates the operating efficiency of the converter.

Detailed ways

(1) Further illustrate the circuit topology of the present invention.

Referring to Fig. 1, it is a typical current-mode multi-resonant DC converter of the present invention, which is a three-level series connection, wherein the first level is a square wave current source generator, the second level is a multi-resonant network, and the third level is a rectification and filtering output unit.

(1) Square wave current source generator

The low-voltage DC power supply V _in is connected between the positive and negative input terminals of the square-wave current source generator, and the low-voltage filter capacitor C _in , the first switch branch, and the the second switch branch. The first switch branch is formed by connecting the first inductor L _in1 in series with the first switch tube, wherein the diode D _Q1 and the capacitor C _Q1 are the anti-parallel diode and output capacitor of the switch tube _Q1 itself. The second switch branch is formed by connecting the second inductance L _in2 and the second switching tube _Q2 in series, wherein the diode D _Q2 and the capacitor C _Q2 are the anti-parallel diode and output capacitor of the switching tube _Q2 itself. The series connection point of the first inductor L _in1 and the first switch tube _Q1 , and the series connection point of the second inductor L _in2 and the second switch tube _Q2 lead to positive and negative output ends of the square wave current source generator respectively. A square wave current is formed by controlling the on-off of the first switch tube and the second switch tube.

The square-wave current source generator can adopt a current-mode half-bridge structure, a current-mode full-bridge structure or a current-mode push-pull structure. The square-wave current source generator can generate square-wave current with small input current ripple and ripple The frequency is twice the switching frequency, and this ripple can be filtered out by low-cost, small-volume, non-polarized capacitors.

(2) Multi-resonant network

The multi-resonance network includes transformer T, parallel resonant inductor L _p , parallel resonant capacitor C _p and series resonant inductor L _r . The series resonant inductor L _r is connected to the primary side of the transformer, and the parallel resonant inductor L _p and parallel resonant capacitor C _p are connected to the transformer Secondary side, as shown in Figure 2(a). Combined with Figure 2(b) the parallel resonant inductance L _p and parallel resonant capacitor C _p can also be connected to the primary side of the transformer; combined with Figure 2(c) and 2(d) the parallel resonant inductance L _p and parallel resonant capacitor C _p can also be connected respectively Connected to the primary and secondary sides of the transformer.

As shown in Figure 3, the transformer T can also be a structure with a center tap on the secondary side. The parallel resonant inductor L _p and the parallel resonant capacitor C _p can be connected to the primary side of the transformer as shown in Figure 3(a), or they can be connected as shown in Figure 3 All shown in (b) are connected to the secondary side of the transformer, or are connected to the primary side and secondary side of the transformer respectively referring to Figure 3(c) and 3(d).

The transformer T can also adopt a structure with a center tap on the primary side as shown in Figure 4, at this time, the series resonant inductance L _r is connected to the center tap of the primary side of the transformer. The parallel resonant inductance L _p and the parallel resonant capacitor C _p can all be connected to the secondary side of the transformer as shown in Figure 4(a). As shown in Figure 4(b), the parallel resonant inductors L _p1 and L _p2 , and the parallel resonant capacitor C _p can all be connected to the primary side of the transformer. The parallel resonant inductance L _p and the parallel resonant capacitor C _p can also be connected to the primary side and the secondary side of the transformer respectively with reference to FIGS. 4( c ) and 4 ( d ).

The series resonant inductance L _r can be an external independent inductance or the leakage inductance of the transformer T; the parallel resonant inductance L _p can be an external independent inductance or the excitation inductance of the transformer; the parallel resonant capacitor C _p can be the transformer T The inter-turn capacitance can also be an external independent capacitance. When one or both of the parallel resonant inductance L _p and the parallel resonant capacitor C _p are placed on the primary side of the transformer, the two ends of the parallel resonant element are directly connected in parallel with the two ports of the primary side of the transformer, and one end of the series resonant inductor L _r is connected to the primary side of the transformer. One port on one side is connected, and the other end is connected to a port of the square wave current source generator.

(3) Rectification filter output unit

The rectification and filtering output unit includes a diode rectification circuit and a filter capacitor connected in parallel at the output end of the diode rectification circuit. The diode full-wave rectification circuit may adopt the full-bridge rectification circuit shown in FIG. 5( a ), or the full-wave rectification circuit shown in FIG. 5( b ). As shown in Figure 5(c), the diode full-wave rectifier circuit can also use a voltage doubler rectifier circuit to further increase the voltage gain, thereby reducing the transformation ratio of the transformer and related parasitic parameters such as leakage inductance and inter-turn capacitance, and improving efficiency. D ₁ -D ₄ in Fig. 5 (a) is a rectifier diode, C ₀ is a filter capacitor, _RL is a load resistance of the converter. In Figure 5(b), D ₁ -D ₂ are rectifier diodes, C ₀ is the filter capacitor, and _RL is the load resistance of the converter. In Figure 5(c), D ₁ -D ₂ are rectifier diodes, C ₁ and C ₂ are voltage doubler filter capacitors, and R _L is the load resistance of the converter.

(2) Further explain the parameter design method of the typical current-mode multi-resonant DC converter shown in Fig. 1 .

(a) Design of resonant network:

When deriving the gain G of the converter, because the switching tube duty cycle overlap time of the square wave current source generator is small, it is assumed that the current flowing into the parallel resonant network is a square wave current, and the simplified circuit diagram and waveform diagram of the converter are shown in Figure 6 As shown in Figure 7, where v _g1 and v _g2 are the driving signals of the first and second switching tubes, V _o is the output voltage of the converter, v _Lp is the current flowing into L _p , i _CS is the square wave current, v _rec is the output voltage of the multi-resonant network, i _rec is the current flowing into the rectifier filter output unit, v _{rec_1} , i _{rec_1} and i _{CS_1} are the fundamental components of v _rec , i _rec and i _CS after Fourier expansion respectively, θ is the conduction phase angle of the rectifier diode, φ, Ψ and α are the phase angles of v _{rec_1} , i _{rec_1} and i _{CS_1} respectively, δ is the phase difference between v _{rec_1} and i _{rec_1} , and λ is the phase difference between v _{rec_1} and i _{CS_1} .

Because v _{rec_1} lags i _{rec_1} , the lag angle is δ, and the output of the multi-resonant network is a capacitive load, so the simplified model of the AC equivalent circuit can be obtained, as shown in Figure 8, where i _{CS_1} is the square wave current i _CS The fundamental wave after Fourier expansion, Re _{and Ce} are the equivalent output capacitive loads of the multi-resonant network, Z _in is the input impedance of the AC equivalent circuit, V _{rec1_pk} is the output voltage of the multi-resonant network after Fourier The expanded fundamental peak value, I _{CS1_pk,} is the fundamental peak value after Fourier expansion of the square wave current flowing into the parallel resonant network. The expressions of R _e , C _e , Z _in and I _{CS1_pk} are shown in (2), (3), (4), and (5).

where F is the normalized value of the angular frequency ω of the switching frequency relative to the angular frequency ω _p of the parallel resonant network resonant frequency, Z _p is the impedance of the parallel resonant network, Q _p is the quality factor of the converter output load, and Q _e is the AC The load quality factor of the equivalent circuit is expressed by formulas (6), (7), (8), and (9) respectively. Equation (10) is the expression of the efficiency η of the converter. Among them, N is the transformation ratio of the transformer, V _in and I _in are the input voltage and input current of the converter, V _o is the output voltage of the converter, and _RL is the load resistance of the converter.

$\frac{{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">V</figure-callout></span><figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">V</figure-callout></span><figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

tan(|δ|)＝ωC _e R _e (3)

$<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">V</figure-callout></span><figure-callout\; id="1"\; label="V\; rec"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="e\; Z\; p"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">e</figure-callout></span><figure-callout\; id="1"\; label="e\; Z\; p"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{}{\mathrm{<span\; class="notranslate">\; p</span>}}_{}}{\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; tan</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="I\; CS"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">I</figure-callout></span><figure-callout\; id="1"\; label="I\; CS"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{\mathrm{<span\; class="notranslate">\; \&pi;N</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&eta;</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&eta;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

From (5), (1), (4), (9) and (10) the gain G of the converter can be obtained, as shown in formula (11). The input phase angle λ of the resonant network of the AC equivalent circuit is shown in formula (12).

时刻C_p存储的能量

要大于谐振电感L_r的电流换向所需的能量，如式(14)所示。When designing a resonant network, firstly, according to formulas (1), (2), (3) to determine the range of operating frequency, resonant angular frequency ω _p and load quality factor Q _L , in order to meet the voltage regulation requirements while achieving The ZCS of the switching tube of the square wave current source generator realizes the soft commutation of the input current i _pri of the multi-resonance network. The condition for realizing the soft commutation of the input current i _pri of the multi-resonant network is that i _pri is ahead of the voltage v _rec at both ends of the multi-resonant network, that is, λ is less than zero, and

Energy stored at time C _p

The energy required for the current commutation to be greater than the resonant inductance L _r is shown in formula (14).

$\mathrm{<span\; class="notranslate">\; G</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&eta;</span>}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; o</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;\&eta;N</span>}\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="I\; CS"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">I</figure-callout></span><figure-callout\; id="1"\; label="I\; CS"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;\&eta;N</span>}\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L\; R\; e"\; filenames="HSA00000192755900052.png,HSA00000192755900081.png"\; state="\{\{state\}\}">L</figure-callout></span><figure-callout\; id="2"\; label="L\; R\; e"\; filenames="HSA00000192755900052.png,HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{}{\mathrm{<span\; class="notranslate">\; e</span>}}_{}}{\mathrm{<span\; class="notranslate">\; 2</span>}}}\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; |</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&pi;\&eta;N</span>}\sqrt{\frac{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Q\; e"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">Q</figure-callout></span><figure-callout\; id="1"\; label="Q\; e"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>{<span\; class="notranslate">\; [</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; tan</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; e</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; the\; tan</span>}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; |</span>\mathrm{<span\; class="notranslate">\; \&delta;</span>}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

λ<0 (13)

$\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; Cp</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Greater\; Equal;</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Second, calculate the minimum voltage gain G _min and select the transformer ratio N. According to the fixed ω _p and Q _L , the values of L _p and C _P are calculated by formula (7). Then calculate the value of L _r according to formula (14). The resonant network is used to absorb the parasitic parameters of the transformer.

(b) Calculation of duty cycle:

According to the value of L _r , C _P and N, by Fig. 9 and formula (15), (16), (17), (18), (19), (20), (21), (22), (23 ) can get the duty cycle constraints. Among them, D _min and D _max are the maximum duty cycle and the minimum duty cycle, ΔT _1,2 and ΔT _1,4 are the time period from t ₁ to t ₂ and the time period from t ₁ to t ₄ in Figure 11, respectively, C' _p is the equivalent capacitance of C _p to the primary side of the transformer, ω _r is the series resonant angular frequency of L _r and C' _p , and Z _r is the impedance of the series resonant network composed of L _r and C' _p .

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Delta;<figure-callout\; id="1"\; label="T"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1,2</span>}}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 15</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; D.</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Delta;<figure-callout\; id="1"\; label="T"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">T</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 4</span>}}}{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 16</span>}<span\; class="notranslate">\; )</span>$

ΔT _1,2 =t ₂ -t ₁ (17)

ΔT _1,4 =t ₄ -t ₁ (18)

C' _p = N ² C _p (19)

${\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 20</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; one</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;<figure-callout\; id="1"\; label="T"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}"><figure-callout\; id="2"\; label="T"\; filenames="HSA00000192755900052.png,HSA00000192755900081.png"\; state="\{\{state\}\}">T</figure-callout></figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1,2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}{\mathrm{<span\; class="notranslate">\; New\; Zealand</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; Cp</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; N</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; Cp</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; two</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&Delta;<figure-callout\; id="1"\; label="T"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}"><figure-callout\; id="4"\; label="T"\; filenames="HSA00000192755900081.png"\; state="\{\{state\}\}">T</figure-callout></figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1,4</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; three</span>}<span\; class="notranslate">\; )</span>$

(c) Calculation of input inductance:

When the switches are turned on at the same time, the input current i _in increases linearly, and i _in decreases linearly in the rest of the time. Therefore, the frequency of the input current ripple is twice the switching frequency, and the amplitude of the input current ripple can be calculated by formula (24), where Δi _in is the peak-to-peak value of the input current ripple, and ΔT _ov is the simultaneous turn-on time.

${\mathrm{<span\; class="notranslate">\; \&Delta;i</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}\frac{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; in</span>}}}{\mathrm{<span\; class="notranslate">\; L</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}_{\mathrm{<span\; class="notranslate">\; ov</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; twenty\; four</span>}<span\; class="notranslate">\; )</span>$

According to the selected input current ripple value, the value L of the input inductance L _in1 and L _in2 can be calculated by formula (24).

(3) Further combining with FIG. 10 and FIG. 11 , the working principle of the typical current-mode multi-resonant DC converter shown in FIG. 1 is described.

Among them, Figure 10(a) to (f) are the six working mode diagrams of the current-source multi-resonant DC converter in the first half cycle, the six working mode diagrams of the converter in the second half cycle and the first half cycle Symmetry, Figure 11 is the corresponding circuit working waveform diagram.

Before time _t0 , _Q1 turns on and _Q2 turns off. The input power supply V _in charges the input inductor L _in1 , and the energy stored in the input inductor L _in2 is delivered to the load through the rectifier diodes D ₂ and D ₃ . The voltage v _Cp of the parallel resonant capacitor C _p is clamped at the negative output voltage V _o , and the current of the parallel resonant inductor L _p increases linearly in reverse. The current flowing through the rectifier diodes D ₂ and D ₃ is equal to the transformer secondary current i _sec minus the current i _Lp flowing through L _p .

Mode 1 (t ₀ -t ₁ ): At time t ₀ , i _Lp is equal to i _sec , and the current flowing through D ₂ and D ₃ drops to zero. After that, _Q1 continues to conduct, _Q2 remains off, all rectifier diodes are turned off, V _in continues to charge L _in1 , the series resonant inductance L _r is absorbed by the input inductance L _in2 , the current flowing through L _in2 flows into L _{in and} The resonant network composed of C _p , during mode 1, C _p discharges, its energy storage decreases. At time _t1 , _Q2 turns on and mode 1 ends.

Mode 2 (t ₁ -t ₂ ): From time t ₁ , Q ₁ and Q ₂ are turned on at the same time, A and B are short-circuited, all rectifier diodes remain off, and the series resonant inductor L _r participates in L _p and C The resonance of _p , the energy stored in the capacitor C _p makes the primary current i _pri begin to commutate, at this time the current i _Q2 flowing through _Q2 increases, and the current t _Q1 flowing through _Q1 decreases. At time _t2 , i _Q1 decreases to zero and mode 2 ends. It is very important to design a suitable L _r value, which can ensure that i _Q1 decreases to zero and has only a small overshoot during the overlap time when the primary switch is turned on, so that Q ₁ can achieve the minimum circulating current. Zero current shutdown. During mode 2, V _in charges L _in1 and L _in2 at the same time, and the voltage of C _p continues to decrease.

Mode 3 (t ₂ -t ₃ ): Mode 3 is similar to Mode 2, except that the direction of i _Q1 is opposite, L _r continues to participate in the resonance of L _p and C _p , when i _pri resonates to the peak value, the voltage of C _p is zero, The current flowing through _Lp also peaks. At time _t3 , _Q1 turns off and mode 3 ends. During mode 3, the voltage v _Cp of C _p starts to increase after crossing zero, but the value of v _Cp is still smaller than v _o .

Mode 4 (t ₃ -t ₄ ): Mode 4 is similar to Mode 3, except that after Q ₁ is turned off at time t ₃ , i _Q1 flows through the anti-parallel diode of Q ₁ . At _t4 moment, _tQ1 goes through reverse peak resonance to zero, _Q1 's anti-parallel diode _DQ1 turns off, and mode 4 ends. By properly controlling the turn-off time of _Q1 , the conduction time of the anti-parallel diode can be reduced, thereby reducing the on-state loss of the anti-parallel diode.

Mode 5 (t ₄ -t ₅ ): From time t ₄ , D _Q1 turns off, Q ₂ continues to turn on, L _r is absorbed by the large inductance L _in1 , and the current flowing through L _in1 is composed of L _p and C _p The resonant network of V _in charges L _in2 . During this period, the C _p voltage continues to increase until t ₅ when v _Cp is equal to v _o , and mode 5 ends.

Mode 6 (t ₅ -t ₆ ): At time t ₅ , v _Cp is equal to v _o , the rectifier diodes D ₁ and D ₄ are turned on, the energy stored in L _in1 is delivered to the load through diodes D ₁ and D ₄ , and V _in is given to L _in2 Charging, V _o charges L _p . The current flowing through D ₁ and D ₄ is equal to the difference between the current i _sec flowing out of the secondary side of the transformer and the current i _Lp flowing through L _p . At time t ₆ , i _Lp is equal to i _sec , and the current flowing through D ₁ and D ₄ The current drops to zero and mode 6 ends.

As shown in Figure 12, the switch tube works in the ZCS state, and the switch tube has small voltage spikes and current overshoots. The voltage spike of v _AB is mainly caused by the reverse recovery of the antiparallel diodes D _Q1 and D _Q2 of the switching tubes Q ₁ and Q ₂ .

As shown in Figure 13, under light load conditions, the conduction time of the rectifier diode is shortened, and the time for the parallel resonant capacitor to be clamped is relatively reduced, and the time for the parallel resonant inductor and parallel resonant capacitor to resonate will be longer, making the parallel resonant capacitor and parallel resonant capacitor The initial energy storage of series resonant inductor resonance can be reduced, so that i _pri has a small overshoot when working at light load, and the light-load efficiency of the converter will not be greatly affected.

As shown in Figures 14 and 15, the rectifier diodes work under ZCS conditions under both full load and light load conditions. Under light load conditions, the conduction time of the rectifier diode and the clamping time of v _Cp will be significantly reduced, so that the initial energy storage of the parallel resonant capacitor and the series resonant inductance can be reduced, which can limit the converter to work under light load When i _pri overshoot.

Figure 16 shows the waveform when there is no input filter capacitor. It can be seen from the figure that i _in has a small ripple whose frequency is twice the switching frequency.

It can be seen from Figure 17 that the light-load efficiency of the converter is not seriously reduced.

To sum up, the converter of the present invention can provide a higher voltage gain, and has a smaller circulating current in the full load range, and both the switch tube and the rectifier diode work in the ZCS state, and also have a higher s efficiency.

Claims (3)

1. current-type multi-resonance direct current (DC) converter; The square wave current source generator, multi resonant vibrating network, the rectifying and wave-filtering output unit that comprise series connection successively; Said multi resonant vibrating network comprises transformer, parallel resonant inductor, parallel resonance electric capacity and series resonance inductance; Parallel resonant inductor, parallel resonance electric capacity are all parallelly connected with the transformer secondary, and said series resonance inductance is connected the former limit of transformer; Said rectifying and wave-filtering output unit comprises diode rectifier circuit and the filter capacitor that is connected in parallel on the diode rectifier circuit output; It is characterized in that: the square wave current source generator comprises DC power supply, low-voltage filter electric capacity, first switching branches and second switch branch road; Low-voltage filter electric capacity, first switching branches and second switch branch road all are connected in parallel on the DC power supply two ends; First switching branches is formed by first inductance and the series connection of first switching tube; Second switch props up route second inductance and second switching tube series connection forms; The series connection contact of first inductance and first switching tube, the series connection contact of second inductance and second switch pipe is drawn the positive-negative output end as the square wave current source generator respectively; Break-make through controlling first switching tube and second switch pipe forms square wave current.

2. current-type multi-resonance direct current (DC) converter according to claim 1 is characterized in that, the switching tube of said square wave current source generator open duty ratio greater than 0.5, less than 0.7.

3. current-type multi-resonance direct current (DC) converter according to claim 1 and 2 is characterized in that, said diode rectifier circuit adopts full bridge rectifier, full-wave rectifying circuit or voltage doubling rectifing circuit.

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