CN110611444B - Bridgeless integrated AC-DC (alternating current-direct current) rectifying circuit and rectifying method - Google Patents

Abstract

The invention proposes a bridgeless integrated AC-DC rectification circuit and a rectification method, including: a single-phase AC power supply, a first inductor, and the like. Wherein, the post-stage DC-DC circuit includes, but is not limited to, a half-bridge LLC resonant circuit, a full-bridge LLC resonant circuit, a dual-active full-bridge conversion circuit, a dual-active half-bridge conversion circuit, and the like. The present invention has two control degrees of freedom, including: pre-stage control: the control object is the first bridge arm (low frequency), and the duty cycle of the bridge arm switch tube is adjusted in real time through the sine pulse width modulation method to realize power factor correction function and the adjustment of the PFC output DC side voltage; post-stage control: the control object is the second bridge arm (high frequency), and the output voltage of the post-stage DC-DC circuit is adjusted in real time through frequency conversion control or phase-shift control; the control method makes The front and rear stages can be controlled separately. At the same time, the bridge arm can be shared with the post-stage DC-DC conversion circuit, so as to improve the efficiency.

Description

A bridgeless integrated AC-DC rectifier circuit and rectification method

technical field

The invention relates to the technical field of power electronic conversion, in particular to a bridgeless integrated AC-DC rectifier circuit and method.

Background technique

At present, the large-scale use of bridge uncontrolled rectification not only causes serious harmonic pollution to the power grid, but also causes waste of electric energy due to the low power factor of the AC side. The power factor correction technology can realize the AC side current tracking the AC side voltage, which can improve the power factor of the AC side.

Power factor correction technology must be able to achieve high power factor and low input current harmonics to meet the IEC61000-3-2 harmonic standard. Therefore, the traditional power supply generally includes a two-stage power conversion structure, a Boost boost circuit and a DC-DC conversion circuit, where the Boost boost circuit is used as a power factor correction (PFC) to achieve high power factor and low input current harmonics, DC -DC conversion circuit for outputting the required DC voltage. The two-stage circuit topology allows the circuit to achieve the best performance, such as high power factor, stable PFC output DC side voltage, and stable DC-DC output voltage. However, the two-stage structure has more power consumption due to too many components, the efficiency is relatively low, the circuit control is more complicated, and most of the system losses are consumed in the rectifier diodes.

There are two main solutions to the problem of reducing the efficiency caused by too many components. One is to improve the topology of the first-stage power factor correction circuit to form a bridgeless PFC structure to minimize the number of diodes and switches. number. At present, there are many bridgeless PFC circuits, such as dual Boost PFC circuits, dual inductor PFC circuits, totem pole PFC circuits, etc.; the other is to share a first-level PFC circuit and a second-level DC-DC circuit through a The bridge arm is integrated.

Some scholars have combined these two solutions and proposed a topology that integrates the totem-pole PFC and the post-stage DC-DC conversion circuit by sharing a bridge arm. Although the number of switching devices can be further reduced, this will make the circuit. The topology has only one control degree of freedom, which will cause the PFC output DC side voltage to be uncontrollable. When the input voltage increases to a certain extent, the PFC output DC side voltage and the voltage stress of the switching device are too high, which may easily lead to device damage. Moreover, due to the PFC output The DC side voltage is uncontrollable, and the voltage change is too large, which will lead to poor design of the parameters of the subsequent DC-DC circuit.

Aiming at the problem of uncontrollable output DC side voltage of PFC, some scholars proposed a solution to control the output DC side voltage of PFC by combining pulse frequency modulation and pulse width. When the PFC output DC side voltage does not exceed the specified limit, the pulse frequency modulation is used; when the PFC output DC side voltage is close to or exceeds the specified limit, the combination of pulse frequency modulation and pulse width modulation is used to change the duty cycle. To achieve the purpose of reducing the output DC side voltage of the PFC, however, this will increase the input harmonic current, reduce the power factor, and the duty cycle is restricted by the change of the input voltage, which will deteriorate the working conditions of the subsequent DC-DC circuit. Optimizing the design, the overall circuit efficiency will also be affected to some extent.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the above-mentioned problems, and proposes 1. a bridgeless integrated AC-DC rectifier circuit and method, characterized in that it includes: a single-phase AC power supply, a first inductor, a first switch tube, a second switch tube, the third switch tube, the fourth switch tube, the post-stage DC-DC circuit;

The post-stage DC-DC circuit adopts a half-bridge LLC resonant circuit, including: a single-phase AC power supply, a first inductor, a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a dc capacitor, and a first capacitor , the second capacitor, the first transformer, the first diode, the second diode, the third capacitor and the first load resistor;

One end of the single-phase AC power supply is connected to one end of the first inductor; the other end of the single-phase AC power supply is connected to the drain of the fourth switch tube; the other end of the first inductor is connected to the first inductor _The source of the switch tube S1 is connected; the drain of the first switch tube, the drain of the third switch tube, and the dc capacitor are connected to the positive pole of the first capacitor; The source is connected to the drain of the second switch; the source of the third switch and the drain of the second switch are connected to one end of the primary side of the first transformer; the first capacitor The negative electrode of the second capacitor and the positive electrode of the second capacitor are connected to the other end of the primary side of the first transformer; the source electrode of the second switch tube, the source electrode of the fourth switch tube, the dc capacitor and the The negative electrode of the second capacitor is connected; one end of the secondary side of the first transformer is connected to the anode of the first diode; the middle end of the first transformer is connected to the negative electrode of the third capacitor and one end of the first resistor; The third end of the secondary side of the first transformer is connected to the anode of the second diode; the anode of the first diode, the second diode and the third capacitor is connected to the anode of the first resistor. Connect the other end.

2. a kind of bridgeless integrated AC-DC rectifier circuit according to claim 1 is characterized in that, the latter stage DC-DC circuit adopts half-bridge LLC resonant circuit, or full-bridge LLC resonant circuit, or dual active full-bridge conversion circuit, or dual active half-bridge conversion circuit.

Wherein, the single-phase AC power supply is used to provide input AC power; the first inductor is used to store and release energy; the first switch tube is used to control the output of DC voltage; the second switch tube , used to control the output of the DC voltage; the third switch tube is used to control the output of the DC voltage; the fourth switch tube is used to control the output of the DC voltage; the dc capacitor is used to filter the output DC voltage ripple; the first and second capacitors are used to resonate with the inductor; the first load resistor is used to provide DC voltage output; the first transformer is used to transfer energy to the output side; the The first diode is used for providing a current flow path; the second diode is used for providing a current flow path; the third capacitor is used for filtering the DC voltage ripple on the output side.

A method for rectifying using a bridgeless integrated AC-DC rectifier circuit, characterized in that, comprising:

Front-end control: The control object is the first bridge arm, and the first bridge arm is low frequency. Through the sinusoidal pulse width modulation method, the duty cycle of the switch tube of the bridge arm is adjusted in real time to realize the function of power factor correction and PFC output DC side voltage regulation;

Post-stage control: The control object is the second bridge arm, and the second bridge arm is high frequency. Through frequency conversion control or phase shift control, the output voltage of the post-stage DC-DC circuit is adjusted in real time;

The control method enables the front and rear stages to be controlled separately; at the same time, the bridge arm can be shared with the rear-stage DC-DC conversion circuit, so as to achieve the purpose of improving efficiency;

The expression of the PFC output DC side voltage is:

Among them, V _dc represents the output voltage of the DC side of the PFC; V _i represents the input voltage of the AC side; D ₁ represents the duty cycle of the low frequency bridge arm switch S2 _{; D 2 represents the} duty cycle of the high frequency bridge arm switch S3.

Compared with the prior art, the present invention has the following advantages:

The present invention possesses two degrees of freedom of control. The first bridge arm is a low-frequency bridge arm. Through the sinusoidal pulse width modulation method, the duty cycle of the switch tube of this bridge arm is adjusted in real time to realize the function of power factor correction and the adjustment of the output DC side voltage of the PFC; the second bridge arm is The high-frequency bridge arm, with a fixed duty cycle, can share the bridge arm with the half-bridge LLC resonant DC-DC circuit to achieve integration and bring a soft switching effect, thereby achieving the purpose of improving efficiency.

Description of drawings

Fig. 1 is the circuit diagram of the system of the present invention.

FIG. 2 is a typical circuit diagram of a half-bridge LLC resonant DC-DC circuit connected to the rear stage of the system of the present invention.

Figure 3 shows the waveforms of the switching tubes S3 and S4 driving signals, input inductor current, resonant current, excitation inductor current, current flowing through the first diode and the second diode under the steady working state of the typical circuit of the system of the present invention.

FIG. 4 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 1 of operation.

FIG. 5 is an equivalent circuit diagram of a typical circuit of the system of the present invention during operating mode 2. FIG.

FIG. 6 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 3 of operation.

FIG. 7 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 4 of operation.

FIG. 8 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 5 of operation.

FIG. 9 is an equivalent circuit diagram of a typical circuit of the system of the present invention during mode 6 of operation.

Detailed ways

In order to facilitate the understanding and implementation of the present invention by those of ordinary skill in the art, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, but not to limit it. this invention.

The circuit of this embodiment is shown in Figure 1,

Single-phase AC power supply v _in , first inductor L ₁ , first switch S ₁ , second switch S ₂ , third switch S ₃ , fourth switch S ₄ , dc capacitor C _dc , first capacitor C ₁ , a first capacitor C ₂ , a first transformer T ₁ , a first diode D ₁ , a second diode D ₂ , a third capacitor C ₃ and a first load resistor R ₁ ;

One end of the single-phase AC power source _vin is connected to _one end of the first inductor L1; the other end of the single-phase AC power source _vin is connected to the drain of the _fourth switch tube S4; the first inductor _The other end of L1 is connected to the source of the _first switch S1 _; the drain of the first switch S1, the drain of the _third switch S3, and the anode of the dc capacitor are connected to the The anode of the first capacitor _C1 is connected; the source of the _first switch S1 is connected to the drain of the _second switch S2; the source of the _third switch S3, the The drain of the _fourth switch S4 is connected to one end of the primary side of the _first transformer T1; the negative electrode of the first capacitor _C1 and the positive electrode of the _second capacitor C2 are connected to the _first transformer T1 The other end of the primary side is connected; the source of the _second switch tube S2, the source of the _fourth switch tube S4, and the negative pole of the dc capacitor are connected to the negative pole of the _second capacitor C2; One end of the secondary side of the _first transformer T1 is connected to the anode of the _first diode D1; the middle end of the _first transformer T1 is connected to the negative electrode of the _third capacitor C3 and _one end of the first resistor R1 ; The third end of the secondary side of the first transformer T ₁ is connected to the anode of the second diode D ₂ ; the first diode D ₁ , the second diode D ₂ , the third _The anode of the capacitor C3 is connected to the other end of the _first resistor R1.

Below in conjunction with Fig. 2 to Fig. 9, the specific embodiment of the present invention is introduced as follows:

Let the current of the first inductor L ₁ be i _in , the voltage be v _L , the voltage of the first capacitor C ₁ to be v _C1 , the voltage of the second capacitor C ₂ to be v _C2 , and the voltage of the third capacitor C ₃ to be v _C3 , The output voltage of the DC side of the PFC is v _dc , v _dc =v _C1 +v _C2 , the current flowing through the first diode D ₁ is i _D1 , the current flowing through the first diode D ₂ is i _D2 , and the current flowing through the first diode D 2 is i D2 . The current of the leakage inductance of the _first transformer T1 is _{i Lr} , the current flowing through the excitation inductance of the _first transformer T1 is im , and the voltage of the _first load resistor R1 is _vo .

Since the working process of the upper and lower tubes of S ₁ and S ₂ is symmetrical, only the 6 working stages when the upper tube of S ₁ is opened are analyzed. 4 to 9 are schematic diagrams of the equivalent circuit of the working mode of the circuit diagram shown in FIG. ₁ when the upper transistor _{S 1} is turned on, wherein, FIG. S ₂ , the fourth switch S ₄ is turned off, the first diode D ₁ is turned on in the forward direction, and the second diode D ₂ is turned off in the reverse direction; Fig. 5 is the first switch S ₁ The equivalent circuit when the _third switch S3 is turned on, the _second switch S2 and the _fourth switch S4 are turned off, and the _first diode D1 and the _second diode D2 are turned off in reverse Schematic diagram; FIG. 6 is that the first switch S ₁ is turned on, the second switch S ₂ , the third switch S ₃ are turned off, the fourth switch S ₄ is turned off, the first diode D ₁ , the second two _The schematic diagram _of the equivalent circuit when the pole tube _D2 is _turned off in reverse _; A schematic diagram of an equivalent circuit when the first diode D ₁ is turned off in reverse and the second diode D ₂ is turned on in a forward direction; FIG. 8 shows the first switch tube S ₁ , the second switch tube S ₂ , and the third switch tube The schematic diagram _of the equivalent circuit when S3 is turned off, the _fourth switch S4 is turned on, and the _first diode D1 and the _second diode D2 are turned off in reverse; FIG. 9 is the _first switch S1, A schematic diagram of an equivalent circuit when the second switch S ₂ , the third switch S ₃ , and the fourth switch S ₄ are turned off, and the first diode D ₁ and the second diode D ₂ are turned off in reverse.

The working conditions of each mode will be analyzed in detail below. Since the DC side output voltage can be adjusted by adjusting the duty cycle of the low-frequency bridge arm, the average current i _Lave in a single switching cycle of the first inductor L ₁ is constant. , the rate-of-change expressions of i _in and v _C1 , v _C2 , and v _C3 will not be listed in each modal analysis, and i _Lave will be used to replace the current value i _in of the first inductor L ₁ in the steady-state analysis. It should be pointed out that, if there are any processes or parameters that are not described in detail below, those skilled in the art can understand or implement them with reference to the prior art.

As shown in Figure 4, it is Mode 1, which corresponds to the time period t ₀ to t ₁ in Figure 3:

At t=t ₀ , the first switch S ₁ and the third switch S ₃ are turned on at zero voltage, the second switch S ₂ and the fourth switch S ₄ are turned off, and the input current i _in passes through the first inductor L once _1. The first switch tube S ₁ , the third switch tube S ₃ , and then back to the single-phase AC power supply v _in . At this time, the inductor energy increases, the inductor current i _in increases linearly, and the inductor current i _in can be expressed as:

At the same time, the first capacitor C ₁ , the third switch tube S ₃ , the first transformer leakage inductance L _r , the first transformer resonant inductance L _m , and the second capacitor C ₂ form a resonant circuit, and the resonant current _{i Lr} is higher than the excitation inductor current im Therefore, the current flowing through the primary side of the transformer is positive on the upper side and negative on the lower side, and the amplitude is the difference between the resonant current and the excitation current. Therefore, the _first diode D1 on the secondary side of the transformer is turned on. The primary voltage of the transformer is clamped at nV _o , the magnetizing inductor current increases linearly, and the magnetizing inductor current i _Lr can be expressed as:

在t₁时刻，谐振电感电流等于励磁电感电流时，模态1工作模式结束。At this stage, the resonant frequency is:

At time _t1 , when the resonant inductor current is equal to the excitation inductor current, the mode 1 working mode ends.

As shown in Figure 5, it is Mode 2, which corresponds to the time period from t ₁ to t ₂ in Figure 3:

在这一模态下，因为谐振电流等于励磁电感电流，因此变压器二次侧第一二极管、第二二极管都反向关断，所以没有能量传递至副边。在t＝t₂时，第三开关管S₃关断，模态2结束。At t=t ₁ , the first switch S ₁ and the third switch S ₃ are continuously turned on, and the input inductor current i _in continues to increase linearly until reaching the maximum value at t=t ₂ . In addition, at time _t1 , when the resonant inductor current _{i Lr} is equal to the excitation inductor current im, the first diode is turned off at zero current. In this mode, the first capacitor C ₁ , the third switch tube S ₃ , the first transformer leakage inductance L _r , the first transformer resonant inductance L _m , and the second capacitor C ₂ form a resonant circuit, and the resonant frequency is:

In this mode, because the resonant current is equal to the magnetizing inductor current, the first diode and the second diode on the secondary side of the transformer are both turned off in reverse, so no energy is transferred to the secondary side. At t= _t2 , the _third switch S3 is turned off, and the mode 2 ends.

As shown in Figure 6, it is Mode 3, which corresponds to the time period t ₂ to t ₃ in Figure 3:

In this mode, corresponding to the dead time of the switching signal, the third switch S ₃ and the fourth switch S ₄ are turned off, and the input inductor current i _in decreases linearly. The parameter relationship is:

Due to the existence of parasitic capacitances of the third switch tube S ₃ and the fourth switch tube S ₄ , the excitation current discharges to these parasitic capacitances, thereby realizing zero-voltage turn-on of the fourth switch tube S ₄ . When t= _t3 , the _fourth switch S4 is turned on.

As shown in Figure 7, it is Mode 4, which corresponds to the time period from t ₃ to t ₄ in Figure 3:

At t=t ₃ , the drain-source voltage of the _fourth switch S4 will be zero, therefore, the _fourth switch S4 is turned on at zero voltage. In this mode, the input inductor current i _in continues to decrease linearly; because the _fourth switch S4 is turned on, the input voltage of the resonant tank is zero. In this mode, the resonant current is greater than the excitation inductor current. According to the polarity relationship of the transformer, the _second diode D2 on the secondary side of the transformer conducts forward, the voltage on the primary side of the transformer is clamped at -nV _o , and the excitation inductor current i _m decreases linearly, and the excitation inductor current can be expressed as:

At t=t ₄ , the resonant current is equal to the excitation inductor current, and Mode 4 ends.

As shown in Figure 8, it is Mode 5, which corresponds to the time period from t ₄ to t ₅ in Figure 3:

The _fourth switch S4 remains _on , at t=t4, the resonant current is equal to the excitation inductor current, the _second diode D2 is turned off at zero current, and at t= _t5 , the _fourth switch S4 is turned off off, mode 5 ends,

As shown in Figure 9, it is Mode 6, which corresponds to the time period from t ₅ to t ₆ in Figure 3:

In this mode, all primary side switches and secondary side diodes are all turned off. This stage is the same as mode 3. Due to the existence of parasitic capacitances of the third switch S ₃ and the fourth switch S ₄ , so the excitation current discharges these parasitic capacitances, thereby realizing the zero-voltage turn-on of the third switch tube. When t=t6, the _third switch S3 is turned _on .

The 6 working stages when the second switch tube is turned on are similar to this, and will not be repeated here.

According to the analysis of the above modes, the relationship between the parameters of the system in steady state is analyzed using the principle of volt-second balance for the first inductor L ₁ . The variables represented by the following capital letters are the steady-state values of the corresponding variables. Assume that the turn-on time of the first switch S1 is ( ₁ -D ₁ )T _s1 , the turn-on time of the _second switch S2 is D ₁ T _s1 , and the turn-on time of the third switch S ₃ is D ₂ T _s2 . The turn-on time of the fourth switch S ₄ is (1-D ₂ )T _s2 , wherein D ₁ is the duty ratio of the first switch S ₁ , and (1-D ₁ ) is the duty of the second switch S ₂ ratio, D ₂ is the duty ratio of the third switch tube S ₃ , and (1-D ₄ ) is the duty ratio of the fourth switch tube S ₄ . T _s1 , T _s2 are switching periods, and T _s1 is greater than T _s2 . Using the volt-second balance principle for the first inductance L ₁ , we get:

After finishing formula (5), we can get:

The above-mentioned embodiment is a typical circuit of the system of the present invention, but the implementation of the present invention is not limited by the above-mentioned embodiment. Typical circuits formed by LLC resonant circuit, dual active full-bridge conversion circuit, dual active half-bridge conversion circuit, etc.) are all included in the protection scope of the present invention.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the described embodiments, and any other changes, modifications, substitutions, Combinations and simplifications should all be equivalent replacement modes, which are all included in the protection scope of the present invention.

It should be understood that the above description of the preferred embodiments is relatively detailed, and therefore should not be considered as a limitation on the protection scope of the patent of the present invention. In the case of the protection scope, substitutions or deformations can also be made, which all fall within the protection scope of the present invention, and the claimed protection scope of the present invention shall be subject to the appended claims.

Claims (1)

1. A bridgeless integrated AC-DC rectifier circuit, characterized in that it comprises: a single-phase AC power supply, a first inductor, a first switch tube, a second switch tube, and a rear-stage DC-DC circuit; The post-stage DC-DC circuit adopts a half-bridge LLC resonant circuit, including: a dc capacitor, a first capacitor, a second capacitor, a first transformer, a first diode, a second diode, a third capacitor and a first load resistor , the third switch tube, the fourth switch tube; One end of the single-phase AC power supply is connected to one end of the first inductor; the other end of the single-phase AC power supply is connected to the drain of the fourth switch tube; the other end of the first inductor is connected to the first inductor the source of the switch tube is connected; the drain of the first switch tube and one end of the dc capacitor are connected to the positive pole of the first capacitor; the source of the first switch tube is connected to the drain of the second switch tube The source of the third switch tube is connected to the drain of the fourth switch tube, and the drain of the fourth switch tube is connected to one end of the primary side of the first transformer; the negative pole of the first capacitor , the anode of the second capacitor is connected to the other end of the primary side of the first transformer; the source of the second switch tube, the source of the fourth switch tube, and the other end of the dc capacitor are connected to the The negative electrode of the second capacitor is connected; one end of the secondary side of the first transformer is connected to the anode of the first diode; the middle end of the secondary side of the first transformer is connected to the negative electrode of the third capacitor and one end of the first resistor ; The third end of the secondary side of the first transformer is connected to the anode of the second diode; the cathode of the first diode, the cathode of the second diode, and the anode of the third capacitor are connected to the other end of the first resistor is connected; The post-stage DC-DC circuit adopts a half-bridge LLC resonant circuit, or a full-bridge LLC resonant circuit, or a dual-active full-bridge conversion circuit, or a dual-active half-bridge conversion circuit; A method for rectifying by using a bridgeless integrated AC-DC rectifier circuit, including: Front-end control: The control object is the first bridge arm, and the first bridge arm is low frequency. Through the sinusoidal pulse width modulation method, the duty cycle of the switch tube of the bridge arm is adjusted in real time to realize the function of power factor correction and PFC output DC side voltage regulation; Post-stage control: The control object is the second bridge arm, and the second bridge arm is high frequency. Through frequency conversion control or phase shift control, the output voltage of the post-stage DC-DC circuit is adjusted in real time; The control method enables the front and rear stages to be controlled separately; at the same time, the bridge arm can be shared with the rear-stage DC-DC conversion circuit, so as to achieve the purpose of improving efficiency; The expression of the PFC output DC side voltage is:

Among them, V _dc represents the output voltage of the DC side of the PFC; V _i represents the input voltage of the AC side; D ₁ represents the duty cycle of the _{second switch S2; D 2 represents} the duty cycle of the _third switch S3, the first one The bridge arm includes a first switch tube and a second switch tube; the second bridge arm includes a third switch tube and a fourth switch tube.

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