CN106787757A - A kind of CLTCL resonance DCs converter - Google Patents

Abstract

The invention discloses a CLTCL resonant DC converter, which is composed of a half-bridge inverter circuit, a CLTCL resonant circuit and a diode rectifier circuit connected in sequence. Output from a diode rectifier circuit; the half-bridge inverter circuit is composed of a first switching tube and a second switching tube; the CLTCL resonant circuit is composed of a first capacitor, a second capacitor, a first inductor, a second inductor, and a first transformer and the second transformer; the diode rectifier circuit includes a first diode, a second diode, a third diode, a fourth diode and a third capacitor; the converter is a new type of DC conversion The circuit topology of the switch can realize zero voltage switching (Zero voltage switching, ZVS), quasi-zero current switching (Quasi-Zero current switching, Q-ZCS) of the switch tube, and zero-current switching (ZCS) of the rectifier circuit diode ), which improves the efficiency and capacity of the converter, and has the characteristics of wide-range adjustable input and output voltages.

Description

A CLTCL resonant DC converter

technical field

The invention belongs to a resonant soft-switching DC converter, in particular to a CLTCL resonant DC converter with high efficiency, wide frequency and wide voltage range.

Background technique

The vigorous development of new energy and the vigorous development of distributed energy have a significant role in alleviating the energy crisis, environmental pollution and other problems brought about by traditional fossil energy, and will play a more important role in the future. In the future household distributed energy system, various new energy sources such as small wind power generation, photovoltaic power generation, and fuel cells will be integrated in the same energy system and connected to the AC and DC voltage busbar of the household system to flexibly realize energy transmission and application. Among them, as an important part of the DC bus, the DC-DC converter plays an important role, with multiple functions such as controlling the bus voltage, interconnecting different levels of DC buses, and connecting the DC bus and DC loads.

At present, DC-DC converters in household distributed energy systems mostly use traditional Boost circuits, Buck circuits, and improved circuits based on these two basic circuits, although these circuits have the advantages of mature technology, simple control, and high reliability. , but there are also problems such as low efficiency and low power density, so related technologies need to be further improved.

In order to solve the above problems, relevant scholars have proposed a soft-switching resonant circuit based on a resonant element, which effectively improves the conversion efficiency of the converter. The most basic soft-switching resonant circuit can be divided into two types: series LC resonant circuit and parallel LC resonant circuit. The former connects resonant inductors and capacitors in series, which has many advantages such as high efficiency, zero-voltage turn-on soft switching, isolation of DC voltage at the input side of the circuit, and input current following load changes. However, it is difficult to adjust the output voltage when the circuit is light-loaded. and other issues; the parallel LC circuit is to connect the resonant inductor and capacitor elements in parallel, which has the advantages of high efficiency, zero-voltage turn-on soft switch, and adjustable output voltage at no-load, but at the same time, it has low efficiency at light load, etc. question. Further, some literatures have proposed LLC resonant circuit, which has all the advantages of series and parallel LC circuits at the same time, while avoiding the shortcomings of the two traditional circuits and has good operating characteristics, but there are still some problems in this circuit: the switch tube is only It can realize zero-voltage turn-on soft switching, but cannot realize soft switching off of the switching tube at the same time, so that the efficiency of the converter cannot be further improved; the input and output voltage ranges are narrow, and the application range is limited; only a single power converter, considering the saturation of magnetic components Problems, limited transmission power of the converter, etc. In recent years, various new resonant soft-switching DC converters proposed by experts and scholars at home and abroad also have similar problems, and further research is still needed.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, in order to improve the conversion efficiency of the DC converter, realize the ZVS and Q-ZCS soft switching of the power switching device, broaden the input/output voltage range, and widen the power range, provide a kind of Resonance-based high-efficiency, high-power, wide-voltage range isolated CLTCL DC converter, this converter is a new type of DC converter circuit topology, which can realize zero-voltage switching (ZVS) of switching tubes, quasi- Zero-current switching (Quasi-Zero current switching, Q-ZCS), and the zero-current switching (ZCS) of the rectifier circuit diode in the subsequent stage, improve the efficiency and capacity of the converter, and have the characteristics of wide-range adjustable input and output voltages .

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

A CLTCL resonant DC converter is composed of a half-bridge inverter circuit, a CLTCL resonant circuit and a diode rectifier circuit connected in sequence, the converter is input by the half-bridge inverter circuit, and the diode rectifier circuit output; the half-bridge inverter circuit is composed of a first switching tube and a second switching tube; the CLTCL resonant circuit is composed of a first capacitor, a second capacitor, a first inductor, a second inductor, a first transformer and a second transformer Composition; the diode rectifier circuit includes a first diode, a second diode, a third diode, a fourth diode and a third capacitor; in the CLTCL resonant circuit, one end of the first capacitor is connected to the The midpoint of the half-bridge inverter circuit is connected, and the other end is sequentially connected to the first inductor and the primary side of the first transformer; one end of the primary side of the first transformer is connected to the first inductor, and the other end is respectively connected to the first transformer. Two capacitors are connected to the second inductance; one end of the secondary side of the first transformer is respectively connected to a midpoint of the diode rectifier circuit, and the other end is connected to one end of the secondary side of the second transformer; one end of the second capacitor is respectively connected to the first The primary side of the transformer is connected to the second inductor, and the other end is respectively connected to the source of the second switching tube and the primary side of the second transformer; one end of the second inductor is connected to the primary side of the first transformer and the second capacitor respectively, The other end is connected to the primary side of the second transformer; one end of the primary side of the second transformer is connected to the second inductance, and the other end is respectively connected to the source of the second capacitor and the second switching tube; the secondary side of the first transformer and the second transformer The sides are connected in series, which changes the resonant network and resonant frequency of the circuit, and widens the input voltage range and output voltage range of the circuit.

The input voltage range is 350V-600V; the output voltage range is 0V-52V.

Compared with the prior art, the beneficial effects brought by the technical solution of the present invention are:

1. The converter of the present invention can realize the zero-voltage turn-on of the switching tube, the quasi-zero-current turn-off soft switch, and the zero-current turn-off soft switch of the diode, which improves the working efficiency of the converter;

2. The converter of the present invention can have a wide voltage adjustment range in the low-frequency working section, and can realize the output voltage adjustable from zero to the rated value;

3. The converter of the present invention has a flat voltage gain in the high frequency band, and the change of the voltage gain with the change of frequency is relatively slow, which is very suitable for the application occasion of constant voltage output.

4. The converter of the present invention has two transformers, which can widen the power application range;

5. The converter of the present invention can increase the operating frequency and improve the power density of the converter through reasonable parameter design.

Description of drawings

Fig. 1 is the topology schematic diagram of the converter of the present invention;

Fig. 2 is the voltage gain curve of converter of the present invention;

Figure 3-1 to Figure 3-6 are equivalent circuit diagrams of the working process of the converter of the present invention respectively;

Fig. 4 is the main working wave diagram of converter of the present invention;

Fig. 5 is a simulation waveform of the converter of the present invention.

detailed description

Below in conjunction with accompanying drawing, the present invention will be further described:

A CLTCL resonant DC converter is composed of a half-bridge inverter circuit, a CLTCL ("capacitance-inductance-transformer-capacitance-inductance" type) resonant circuit and a diode rectifier circuit connected in sequence, and the converter consists of the half-bridge inverter The circuit input is output from the diode rectifier circuit after the action of the CLTCL resonant circuit; in this embodiment, the half-bridge inverter circuit is composed of the _first switching tube S1 and the _second switching tube S2, and the CLTCL resonant circuit is composed of the first capacitor C ₁ , the second capacitor C ₂ , the first inductance L ₁ , the second inductance L ₂ , the first transformer T ₁ and the second transformer T ₂ , the diode rectifier circuit consists of the first diode D ₁ , the second diode Tube D ₂ , the third diode D ₃ , the fourth diode D ₄ and the third capacitor C _o , where R _o is the load resistance.

As shown in Figure 1, in the CLTCL resonant circuit, one end of the first capacitor _C1 is connected to the midpoint of the half-bridge inverter circuit, and the other end is connected to the first inductor L1; the _first inductor L1 is connected to the _first capacitor _C1 , the other end is connected to the primary side of the first transformer T1 _{; one} end of the primary side of the first transformer T1 is connected to the _first inductor L1, the other end of the primary side is connected to the _second capacitor C2 and the _second inductor L2, and the secondary One end of one side is connected to a midpoint of the diode rectifier bridge, and the other end is connected to one end of the secondary side of the _second transformer T2; one end of the _second capacitor C2 is connected to the primary side of the _first transformer T1 and the _second inductor L2, and the other end It is connected to the source of the _second switching tube S2 and the primary side of the second transformer T2 _; one end of the _second inductance L2 is connected to the primary side of the _first transformer T1 and the _second capacitor C2, and the other end is connected to the _second transformer T2 The primary side is connected; one end of the primary side of the second transformer T ₂ is connected to the second inductor L ₂ , and the other end is connected to the second capacitor C ₂ and the source of the second switching tube S ₂ . The secondary sides of the two transformers are connected in series, which changes the resonant network of the circuit and at the same time changes the resonant frequency of the circuit, so that the circuit has a wider input and output voltage range. Wherein V _in represents the DC input voltage of the circuit, L _m1 and L _m2 represent the equivalent excitation inductance of the first transformer T ₁ and the second transformer T ₂ respectively.

The CLTCL resonant soft-switching DC converter has two resonant frequencies, which can be divided into the first resonant frequency fr ₁ and the second resonant frequency fr ₂ according to the relationship between frequencies, where fr ₁ is smaller than fr ₂ . The voltage gain curve of the CLTCL converter in this embodiment is shown in Figure 2. After the circuit parameter design, the circuit obtains the maximum value of the voltage gain M _v near the first resonance point fr ₁ , and with the control switching frequency f _s of the circuit The increase of the increase quickly drops to zero, so the output voltage has an adjustable range from zero to the rated voltage; further as the switching frequency continues to rise, the converter reaches the maximum value of the voltage gain near the second resonance point fr ₂ , and the voltage gain increases with As the frequency continues to increase, it will slowly decrease. At this time, the converter can be applied in scenarios that require constant voltage output. The CLTCL converter can realize ZVS turn-on soft switching in the full power range after the AB section and C section in Figure 2, and the diode in the rectifier circuit can realize ZCS turn-off soft switching; _1. Realize Q-ZCS soft switching near fr ₂ .

The working equivalent circuit and main waveforms of the CLTCL resonant soft-switching DC converter are shown in Figure 3-1 to Figure 3-6 and Figure 4, t ₀ to t ₆ are the waveform diagrams of the converter in half the working cycle, and other The working conditions of the half cycle are completely symmetrical and will not be described in detail; where t ₀ , t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , and t ₆ represent the moments between modes respectively, and PWM1 and PWM2 are the first PWM driving signals of the switching tube S ₁ and the second switching tube S ₂ .

Mode 1[t ₀ , t ₁ ]: The equivalent circuit of this mode is shown in Figure 3-1. This mode is the dead section of the control signal. At time _t0 , the _second switching tube S2 is turned off, and the _first switching tube S1 remains off. The current flowing through the first capacitor C ₁ is denoted as i ₁ , and at this time, i ₁ reversely flows through the parasitic diode and parasitic inductance of the first switching tube S ₁ , and the voltage across the first switching tube S ₁ remains zero. The excitation current i _Lm1 of the _first transformer T1 flows in reverse. The exciting current i _Lm2 of the _second transformer T2 flows in the forward direction. The current i _C2 of the _second capacitor C2 flows in reverse. The current i _L2 flowing through the second inductor L ₂ flows forward. The secondary currents of transformers T ₁ and T ₂ are equal, denoted as i _S , and flow in the forward direction. The diodes D ₁ and D ₄ are turned on, and the circuit supplies power to the load R _o . At time t ₁ , the first switching tube S ₁ is turned on. At this time, since the voltage across S ₁ remains zero, the zero-voltage turn-on soft switch is realized; at the same time, i ₁ and _iLm2 are both zero.

Mode 2[t ₁ , t ₂ ]: The equivalent circuit of this mode is shown in Figure 3-2. In this mode, i ₁ starts to rise from zero, i _Lm2 starts to fall from zero, and the other variables keep the original direction and continue to participate in the circuit resonance. At time t ₂ , the current i _C2 of the second capacitor C ₂ rises to zero, and this mode ends.

Mode 3[t ₂ , t ₃ ]: The equivalent circuit of this mode is shown in Figure 3-3. In this mode, i _C2 starts to rise from zero, and the other variables keep the original direction and continue to participate in the circuit resonance. At time _t3 , the excitation current i _Lm1 of the _first transformer T1 rises to zero, and this mode ends.

Mode 4[t ₃ , t ₄ ]: The equivalent circuit of this mode is shown in Figure 3-4. In this mode, i _Lm1 starts to rise from zero, and the other variables keep the original direction unchanged, and continue to participate in the circuit resonance. _At time t4, the current _i2 of the _second inductor L2 drops to zero, and this mode ends.

Mode 5[t ₄ , t ₅ ]: The equivalent circuit of this mode is shown in Figure 3-5. In this mode, i ₂ starts to drop from zero, and the other variables keep the original direction and continue to participate in the circuit resonance. At time t ₅ , the secondary current i _S of transformers T ₁ and T ₂ drops to zero, diodes D ₁ and D ₄ are naturally turned off, realizing ZCS turn-off soft switching, and this mode ends.

Mode 6[t ₅ , t ₆ ]: The equivalent circuit of this mode is shown in Figure 3-6. In this mode, diodes D ₂ and D ₃ are turned on, i _S flows in the negative direction, and other variables remain in the original direction and continue to participate in circuit resonance. _At time t6, the _first switching tube S1 is turned off. At this time, the direction and magnitude of the current flowing through the switching tube are the same as i1, and i1 is very close to ₀ , so the _first switching tube S1 can realize quasi _- zero current off Break soft switch. So far, the operation of the CLTCL converter circuit in the half cycle ends, and it starts to work in the other half cycle.

Fig. 5 is the simulation waveform of the CLTCL converter, as can be seen from the figure, the _first switching tube S1 can realize zero-voltage turn-on soft switching and quasi-zero current turn-off soft switching, the diode current naturally drops to zero, and the diode realizes Zero current turn-off soft switch. Therefore, the CLTCL resonant soft switching converter has higher conversion efficiency.

The present invention is not limited to the embodiments described above. The above description of the specific embodiments is intended to describe and illustrate the technical solution of the present invention, and the above specific embodiments are only illustrative and not restrictive. Without departing from the gist of the present invention and the scope of protection of the claims, those skilled in the art can also make many specific changes under the inspiration of the present invention, and these all belong to the protection scope of the present invention.

Claims (2)

1. a kind of CLTCL resonance DCs converter, it is characterised in that by the half-bridge inversion circuit, the CLTCL resonance electricity that are sequentially connected Road constitutes with diode rectifier circuit, converter by half-bridge inversion circuit be input into, through the CLTCL resonance circuits act on after from Diode rectifier circuit is exported；The half-bridge inversion circuit is by first switch pipe (S₁) and second switch pipe (S₂) composition；It is described CLTCL resonance circuits are by the first electric capacity (C₁), the second electric capacity (C₂), the first inductance (L₁), the second inductance (L₂), the first transformer (T₁) and the second transformer (T₂) composition；The diode rectifier circuit includes the first diode (D₁), the second diode (D₂)、 3rd diode (D₃), the 4th diode (D₄) and the 3rd electric capacity (C_o)；In CLTCL resonance circuits, the first electric capacity (C₁) one End be connected with the midpoint of the half-bridge inversion circuit, the other end successively with the first inductance (L₁) and the first transformer (T₁) Primary side is connected；First transformer (the T₁) primary side one end and the first inductance (L₁) connect, the other end is electric with described second respectively Hold (C₂) and the second inductance (L₂) connection；First transformer (T₁) secondary one end respectively with the diode rectifier circuit The connection of a midpoint, the other end and the second transformer (T₂) secondary one end connection；Second electric capacity (C₂) one end is respectively with first Transformer (T₁) primary side and the second inductance (L₂) connection, the other end respectively with the second switch pipe (S₂) source electrode, second become Depressor (T₂) primary side connection；Second inductance (L₂) one end respectively with the first transformer (T₁) primary side and the second electric capacity (C₂) even Connect, the other end and the second transformer (T₂) primary side connection；Second transformer (T₂) primary side one end and the second inductance (L₂) even Connect, the other end respectively with the second electric capacity (C₂) and second switch pipe (S₂) source electrode connection；First transformer (T₁) and the second transformation Device (T₂) secondary be coupled in series, change the resonant network and resonant frequency of circuit, and widened the input of circuit Voltage range and output voltage range.

2. a kind of CLTCL resonance DCs converter according to claim 1, it is characterised in that the input voltage range is 350V~600V；Output voltage range is 0V~52V.