CN104201894B - Voltage-multiplying high frequency rectification isolated transformer based on switched capacitors - Google Patents

Abstract

The invention discloses a multi-voltage high-frequency rectification and isolation converter based on switched capacitors, which belongs to the technical field of power electronic converters. The multi-voltage high-frequency rectification isolation converter based on switched capacitors is composed of a primary circuit, a transformer, and a rectifier circuit, wherein the rectifier circuit consists of two diodes, two switch tubes, two auxiliary capacitors, and two output filter capacitors , a high-frequency inductance and a load, the present invention utilizes a high-frequency inductance and a switch tube to enable the rectifier circuit to have a controllable boost rectification capability, and uses an auxiliary capacitor to form a switched capacitor circuit to enhance the boost capability of the rectifier circuit. The present invention not only enables The rectifier circuit has a high boost capability, and realizes soft switching of all switching tubes, which can effectively reduce switching loss and improve efficiency, and is especially suitable for high-efficiency, high-gain isolated boost DC power conversion applications.

Description

A Multi-Voltage High-Frequency Rectification Isolation Converter Based on Switched Capacitors

technical field

The invention relates to a multi-voltage high-gain high-frequency rectification isolation converter, which belongs to the technical field of power electronic converters, in particular to the technical field of isolated DC-DC power conversion.

Background technique

In applications in technical fields such as renewable energy power generation, aviation, aerospace, automobiles, and medical care, isolated boost DC converters are usually required for safety reasons and to meet voltage requirements. How to increase the voltage gain of the isolated converter, reduce the voltage stress of the devices used in the converter, and realize high-efficiency power conversion has always been a key issue in this technical field.

The traditional isolated DC converter realizes various boosting functions by adjusting the transformation ratio of the transformer. However, the following problems exist in simply relying on adjusting the transformation ratio of the transformer to realize the voltage boost: the voltage stress of the switching device is high, especially the converter secondary The voltage stress of the side rectifier diode is much higher than the output voltage; the leakage inductance of the transformer increases, causing voltage spikes and oscillations of the switching device, which further aggravates the stress of the switching device and reduces reliability and efficiency. In addition, traditional isolated DC converters usually cannot realize the soft switching of all switching devices, especially the secondary side devices of the transformer, which greatly affects the efficiency of the converter.

The galvanic isolation converter is one of the typical solutions of the isolated boost converter, as shown in Figure 1, in this solution, the boost circuit is placed in the primary side circuit of the isolated converter, and the isolation can be realized by adjusting the duty cycle of the switch tube Boost function, this solution can effectively reduce the number of turns of the transformer winding, the rectifier diode is directly clamped by the output voltage, and the voltage stress is low. However, the main problem is that the voltage stress of the primary switching tube is too high, especially when the switching tube is turned off, the leakage inductance of the transformer will cause a huge voltage spike, which seriously affects the normal operation of the converter. Therefore, it is necessary to add a suitable active Or passive absorption circuit, resulting in complex circuit. In addition, although this circuit scheme can realize boosting, the boosting capability is limited, and the switching tube cannot realize soft switching, and the conversion efficiency is also affected.

Literature "Chuan Yao, Xinbo Ruan, Xuehua Wang, Chi K. Tse. Isolated Buck-BoostDC/DC Converters Suitable for Wide Input-Voltage Range[J]. IEEE Transactions on Power Electronics, 2011, 26(9): 2599-2613. "The non-isolated boost circuit is placed on the secondary side of the isolated buck converter and connected after the output of the rectifier circuit to realize the isolated boost function. The main problem of this solution is that the rectifier circuit and non-isolated boost circuit on the secondary side of the transformer are all hard switches, and two-stage power conversion is required from input to output, which will greatly reduce the overall efficiency of the converter.

Contents of the invention

The object of the present invention is to address the deficiencies of the prior art, and provide a multi-voltage high-frequency rectification isolation converter based on switched capacitors for the occasion of isolated boost power conversion.

The purpose of the present invention is achieved through the following technical solutions:

The multi-voltage high-frequency rectification and isolation converter based on switched capacitors is composed of a primary circuit (10), a transformer (T) and a rectification circuit (20), wherein the transformer (T) includes a secondary winding ( _NS ) and A primary winding (N _P ), the rectifier circuit (20) consists of a high-frequency inductor (L _H ), a first switching tube (S ₁ ), a second switching tube (S ₂ ), a first auxiliary capacitor (C _a1 ), The second auxiliary capacitor (C _a2 ), the first diode (D ₁ ), the second diode (D ₂ ), the first output filter capacitor (C _o1 ), the second output filter capacitor (C _o2 ) and the load (R _o ); one end of the secondary winding ( _NS ) of the transformer (T) is connected to one end of the high-frequency inductor (L _H ), and the other end of the high-frequency inductor (L _H ) is connected to the first auxiliary capacitor ( One end of C _a1 ), the other end of the first auxiliary capacitor (C _a1 ) is connected to the drain of the first switch (S ₁ ), the source of the second switch (S ₂ ) and the second auxiliary capacitor (C _a2 ), the source of the first switching tube (S ₁ ) is connected to one end of the first output filter capacitor (C _o1 ), one end of the load (R _o ) and the other end of the transformer (T) secondary winding ( _NS ) One end, the drain of the second switch tube (S ₂ ) is connected to the other end of the first output filter capacitor (C _o1 ), one end of the second output filter capacitor (C _o2 ) and the first diode (D ₁ ) Anode, the other end of the second auxiliary capacitor (C _a2 ) is connected to the cathode of the first diode (D ₁ ) and the anode of the second diode (D ₂ ), the cathode of the second diode (D ₂ ) Connect to the other end of the second output filter capacitor (C _o2 ) and the other end of the load (R _o ).

The primary side circuit (10) is connected to both ends of the primary side winding ( _NP ) of the transformer (T), and the function of the primary side circuit (10) is to generate an AC rectangular wave voltage with a positive and negative pulse width of 50% respectively, and apply it across the primary winding (N _P ) of the transformer (T). In order to achieve this purpose, the primary side circuit (10) can be a circuit topology such as a full bridge or a half bridge.

The essential difference between the technical solution of the present invention and the existing technical solution is that the boost circuit is integrated into the high-frequency rectification circuit of the isolation converter, and a high boost ratio is realized through the switched capacitor circuit, which can not only effectively reduce the device stress, The boost ratio is improved, and the soft switching of all switching tubes can be realized to improve the conversion efficiency.

The present invention has following beneficial effects:

(1) The rectifier circuit itself can realize the boost function, which effectively reduces the number of turns of the transformer winding used, thereby greatly reducing the leakage inductance of the transformer and improving efficiency;

(2) The voltage gain can be greatly increased through the switched capacitor circuit, which can further reduce the number of turns of the required transformer winding;

(3) All switching tubes can realize soft switching, and the conversion efficiency is high;

(4) All switching tubes and diode power devices can naturally realize voltage clamping, and the device voltage stress is low.

Description of drawings

Accompanying drawing 1 is a schematic diagram of a traditional current-mode isolated boost converter;

Accompanying drawing 2 is the schematic diagram of the multi-voltage high-frequency rectifier converter based on switched capacitors of the present invention;

Accompanying drawing 3 is the schematic diagram of the multi-voltage high-frequency rectifier converter based on switched capacitors with a full-bridge circuit topology as the primary side of the present invention;

Accompanying drawing 4 is the schematic diagram of the multi-voltage high-frequency rectifier converter based on switched capacitors using the half-bridge circuit topology on the primary side of the present invention;

Accompanying drawing 5 is the main working waveform diagram of the multi-voltage high-frequency rectifier converter based on switched capacitors using the full-bridge circuit topology on the primary side;

Accompanying drawings 6 to 9 are the equivalent circuit diagrams in each switching mode of the multi-voltage high-frequency rectifier converter based on switched capacitors using the full-bridge circuit topology on the primary side;

The symbol names in the above drawings: 10 is the primary circuit; 20 is the rectifier circuit; T is the transformer; N _P and N _S are the primary winding and secondary winding of the transformer (T) respectively; L _H is the high frequency inductance; S ₁ and S ₂ are the first and second switch tubes respectively; D ₁ and D ₂ are the first and second diodes respectively; C _a1 and C _a2 are the first and second auxiliary capacitors respectively; C _o1 and C _o2 are the first and second output filter capacitors respectively; R _o is the load; U _o is the output voltage; U _in is the input source; L ₁ and L ₂ are inductors, D ₃ and D ₄ are diodes; C _o is the output filter Capacitance; S _P1 , S _P2 , S _P3 and S _P4 are switching tubes; C _in1 and C _in2 are capacitors; u _NP is the voltage across the primary winding of the transformer (T); i _LH is the current of the high-frequency inductor; u _GSP1 , u _GSP2 , u _GSP3 and u _GSP4 are the drive voltages of the switch tubes S _P1 , _{SP2 , S P2 and S P4 respectively ;} u _GS1 and u _GS2 are the voltages of the first and second switch tubes (S ₁ and S ₂ ) Driving voltage; u _DSP4 and u _DS2 are respectively the voltage between the drain and source of the switch tube _SP4 and the second switch tube (S ₂ ); i _SP1 , i _SP2 , i _SP3 and i _SP4 are the voltages flowing into the switch tube S _P1 , S _P2 , S _P3 and S _P4 drain currents; t ₀ , t ₁ , t ₂ , t ₃ , t ₄ and t ₅ are times.

detailed description

The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 2, the multi-voltage high-frequency rectification and isolation converter based on switched capacitors is composed of a primary circuit (10), a transformer (T) and a rectification circuit (20), wherein the transformer (T) includes a secondary side winding ( _NS ) and a primary winding ( _NP ), the rectifier circuit (20) consists of a high-frequency inductor (L _H ), a first switching tube (S ₁ ), a second switching tube (S ₂ ), a first Auxiliary capacitor (C _a1 ), second auxiliary capacitor (C _a2 ), first diode (D ₁ ), second diode (D ₂ ), first output filter capacitor (C _o1 ), second output filter Capacitor (C _o2 ) and load (R _o ); one end of the secondary winding ( _NS ) of the transformer (T) is connected to one end of the high-frequency inductor (L _H ), and the other end of the high-frequency inductor (L _H ) Connected to one end of the first auxiliary capacitor (C _a1 ), the other end of the first auxiliary capacitor (C _a1 ) is connected to the drain of the first switch (S ₁ ), the source of the second switch (S ₂ ) and One end of the second auxiliary capacitor (C _a2 ), the source of the first switch tube (S ₁ ) is connected to one end of the first output filter capacitor (C _o1 ), one end of the load (R _o ) and the secondary side of the transformer (T) The other end of the winding (NS ), the drain of the second switching tube ( _{S 2} ) is connected to the other end of the first output filter capacitor (C _o1 ), one end of the second output filter capacitor (C _o2 ) and the first two The anode of the diode (D ₁ ), the other end of the second auxiliary capacitor (C _a2 ) is connected to the cathode of the first diode (D ₁ ) and the anode of the second diode (D ₂ ), the second diode The cathode of the tube (D ₂ ) is connected to the other end of the second output filter capacitor (C _o2 ) and the other end of the load (R _o ).

In the present invention, the primary side circuit (10) is connected to both ends of the primary side winding ( _NP ) of the transformer (T), and the function of the primary side circuit (10) is to generate positive and negative pulse widths of 50% respectively. AC rectangular wave voltage and apply it across the primary winding ( _NP ) of the transformer (T). In order to achieve this purpose, the primary side circuit (10) has various circuit topologies to choose from, for example, it can be full bridge, half bridge and other circuit topologies. Accompanying drawing 3 has provided the schematic diagram of the multi-voltage high-gain high-frequency rectification isolation converter based on switched capacitors when the primary side circuit (10) adopts a full-bridge circuit topology, and the primary side circuit includes an input source (U _in ) and Four switching tubes ( _SP1 , _SP2 , _SP3 and _SP4 ), the four switching tubes form a full bridge circuit structure, the midpoint of the two switching bridge arms is connected to the two primary windings ( _NP ) of the transformer (T) end connected. Accompanying drawing 4 shows the schematic diagram of the multi-voltage high-gain high-frequency rectification isolation converter based on switched capacitors when the primary circuit adopts a half-bridge circuit topology. The primary circuit in the figure includes an input source (U _in ), two switches tubes (S _P1 , S _P2 ) and two capacitors (C _in1 and C _in2 ).

The purpose of the present invention is to achieve high-efficiency isolated boost conversion. In order to achieve this purpose, the present invention creatively places the boost circuit in the rectifier circuit of the isolated converter, and through the high-frequency inductor and switch tube in the rectifier circuit Together to achieve boosting, and with the help of switched capacitor circuits to improve the boosting capability, this can greatly reduce the number of turns of the transformer winding, reduce device stress, and improve efficiency.

The working principle of the present invention will be described below by taking the multi-voltage, high-gain, high-frequency rectification and isolation converter based on switched capacitors with a full-bridge circuit topology on the primary side shown in FIG. 3 as an example. Figure 5 shows the main working waveforms of the switched capacitor-based multi-voltage, high-gain, high-frequency rectification-isolation converter using a full-bridge circuit topology on the primary side.

Before time t ₀ , the primary switches S _P2 and S _P3 are turned on, and the full-bridge circuit applies a negative voltage to the primary winding (NP) of the transformer ( _T ), and the current in the high-frequency inductor (L _H ) is negative , the first switch tube (S ₁ ) and the first diode (D ₁ ) are turned on, and the input source (U _in ) is transferred to the first auxiliary capacitor (C _a1 ) through the transformer (T) and the high frequency inductor (L _H ). Charging, the first output filter capacitor (C _o1 ) charges the second auxiliary capacitor (C _a2 ); at time t ₀ , the primary switch tubes _SP2 and _SP3 are turned off, because the current of the high-frequency inductor (L _H ) cannot change abruptly, The current reflected to the primary winding (N _P ) of the transformer (T) flows through the body diodes of the primary switches S _P1 and S _P4 , providing conditions for the zero-voltage turn-on of S _P1 and S _P4 , and at the same time applied to the transformer (T) The voltage of the primary winding ( _NP ) becomes positive, and the current value of the high-frequency inductor (L _H ) begins to decrease linearly. The modal equivalent circuit is shown in Figure 6.

At time _t1 , the switches S _P1 and S _P4 are turned on with zero voltage, and the modal equivalent circuit is shown in Fig. 7 .

At time _t2 , the current of the high-frequency inductor L _H commutates naturally.

At time _t3 , the first switching tube (S ₁ ) is turned off, and the high-frequency inductor (L _H ) current flows through the body diode of the second switching tube (S ₂ ), which provides conditions for the zero-voltage turn-on of S ₂ , and the input source ( U _in ) charges the first output filter capacitor (C _o1 ) through the transformer (T), the high-frequency inductor (L _H ), the body diode of the second switch tube (S ₂ ) and the first auxiliary capacitor (C _a1 ), and at the same time The second diode (D ₂ ) conducts, and the second auxiliary capacitor (C _a2 ) charges the second output filter capacitor (C _o2 ). The modal equivalent circuit is shown in FIG. 8 .

_At time t4, the second switching tube (S ₂ ) is turned on with zero voltage, and the modal equivalent circuit is shown in FIG. 9 .

_At time t5, the second half of the switching cycle begins, and the working process is similar, so the description will not be repeated.

According to the description of the above working process, it can be seen that the present invention can realize soft switching of all switching tubes, and can effectively improve conversion efficiency.

Claims (3)

1. the many multiplication of voltages high-frequency rectification isolated converter based on switching capacity it is characterised in that:

Described many multiplication of voltages high-frequency rectification isolated converter based on switching capacity is by primary circuit (10), transformer (t) and rectification Circuit (20) is constituted, and wherein transformer (t) comprises a vice-side winding (n_s) and a primary side winding (n_p), rectification circuit (20) By high-frequency inductor (l_h), first switch pipe (s₁), second switch pipe (s₂), the first auxiliary capacitor (c_a1), the second auxiliary capacitor (c_a2), the first diode (d₁), the second diode (d₂), the first output filter capacitor (c_o1), the second output filter capacitor (c_o2) With load (r_o) composition；

Described transformer (t) vice-side winding (n_s) one end be connected in high-frequency inductor (l_h) one end, high-frequency inductor (l_h) the other end It is connected in the first auxiliary capacitor (c_a1) one end, the first auxiliary capacitor (c_a1) the other end be connected in first switch pipe (s₁) drain electrode, Second switch pipe (s₂) source electrode and the second auxiliary capacitor (c_a2) one end, first switch pipe (s₁) source electrode be connected in the first output Filter capacitor (c_o1) one end, load (r_o) one end and transformer (t) vice-side winding (n_s) the other end, second switch pipe (s₂) drain electrode be connected in the first output filter capacitor (c_o1) the other end, the second output filter capacitor (c_o2) one end and the one or two Pole pipe (d₁) anode, the second auxiliary capacitor (c_a2) the other end be connected in the first diode (d₁) negative electrode and the second diode (d₂) anode, the second diode (d₂) negative electrode be connected in the second output filter capacitor (c_o2) the other end and load (r_o) another One end.

2. the many multiplication of voltages high-frequency rectification isolated converter based on switching capacity according to claim 1 it is characterised in that: institute State the primary side winding (n of primary circuit (10) and transformer (t)_p) two ends be connected, described primary circuit (10) produces positive and negative arteries and veins Rush the ac square wave voltage that width is respectively 50% and put on transformer (t) primary side winding (n_p) two ends.

3. the many multiplication of voltages high-frequency rectification isolated converter based on switching capacity according to claim 1 it is characterised in that: institute Stating primary circuit (10) is full-bridge type or half bridge circuit topology.