CN102710126A - High-gain type step-up direct current converter - Google Patents

Abstract

The invention relates to a high-gain step-up DC converter, which includes an input power supply, a main switch, a freewheeling diode and a filter capacitor. The negative pole of the input power supply, one end of the main switch and one end of the filter capacitor are connected to each other. The other end of the filter capacitor is connected to the cathode of the freewheeling diode, and the converter also includes a clamping capacitor and a boost unit, and the two ends of the clamping capacitor are respectively connected to the main switch and the anode of the freewheeling diode. The two output terminals of the boost unit are respectively connected to the two ends of the clamp capacitor, and the input terminal of the boost unit is connected to the positive pole of the input power supply. Compared with the prior art, the invention has the advantages of high gain, low noise, low cost and the like.

Description

A High-Gain Step-Up DC Converter

technical field

The invention relates to a step-up direct-current converter for converting low voltage into high voltage, in particular to a high-gain step-up direct-current converter.

Background technique

In distributed power generation systems that use solar energy, wind energy, fuel cells, and storage batteries as input sources, because these input sources have low input power characteristics, it is indispensable to have a boost DC converter that converts low voltage into high voltage. The key components. The conventional step-up DC converter is shown in Figure 1. In order to obtain a higher voltage conversion gain, the usual method is to use a larger duty cycle in the traditional boost DC converter, but it is impossible to achieve a high input-output voltage ratio due to the influence of parasitic parameters; other The best way is to use transformers, coupled inductors, and multi-stage connections. However, these methods have certain disadvantages:

1) In order to achieve high gain in traditional boost DC converters, the main switch usually adopts a large duty cycle. This directly leads to an increase in the conduction time of the main switch and an increase in the peak value of the input current, resulting in a large switch conduction loss and directly reducing the overall conversion efficiency.

2) In order to achieve high gain, transformers and coupled inductors with high turns ratio are used, resulting in increased overall volume and difficulty in core design.

3) The leakage inductance and parasitic capacitance of transformers and coupled inductors can easily lead to high-frequency oscillations, resulting in switching voltage spikes and EMI (Electromagnetic Interference, electromagnetic interference).

4) In order to suppress the peak signal and EMI generated by various parasitic parameters, additional buffer circuits must be designed, resulting in an increase in the number of devices and a decrease in conversion efficiency, and complicating the design process.

5) The multi-stage connection directly leads to the complexity of the main circuit and the control circuit, reduces the power density, and increases the design and manufacturing costs.

6) The voltage stress of the main switch is clamped by the output voltage, and power devices with higher withstand voltage levels must be selected, which increases hardware costs, increases the on-resistance of the main switch, and reduces conversion efficiency.

In view of the above reasons, it is difficult for traditional boost DC converters to achieve the goals of high efficiency, small size, low noise, and low cost.

Contents of the invention

The object of the present invention is to provide a high-gain step-up DC converter capable of obtaining relatively high voltage conversion gain, low noise, and low cost in order to overcome the above-mentioned defects in the prior art.

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

A high-gain step-up DC converter, including an input power supply, a main switch, a freewheeling diode and a filter capacitor, the negative pole of the input power supply, one end of the main switch and one end of the filter capacitor are connected to each other, and the filter capacitor The other end of the freewheeling diode is connected to the cathode of the freewheeling diode. The converter also includes a clamping capacitor and a boost unit. The two ends of the clamping capacitor are respectively connected to the main switch and the anode of the freewheeling diode. The booster The two output ends of the unit are respectively connected to the two ends of the clamp capacitor, and the input end of the boost unit is connected to the positive pole of the input power supply.

The step-up unit includes a first inductor, a second inductor, a first capacitor, a second capacitor, a first diode and a second diode, and one end of the first inductor is respectively connected to the positive pole of the input power supply and the second capacitor. A capacitor, the other end of which is respectively connected to the clamping capacitor and the second capacitor, one end of the second inductance is respectively connected to the cathode of the first diode and the second capacitor, and the other end is respectively connected to the anode of the second diode and the first Capacitor, the anode of the first diode is connected to the positive pole of the input power supply, and the cathode of the second diode is connected to the clamp capacitor.

The converter also includes an auxiliary switch and a third inductance, one end of the third inductance is connected to the clamp capacitor, the other end is connected to the anode of the freewheeling diode, one end of the auxiliary switch is connected to the main switch, and the other end is connected to the third inductance.

Compared with the prior art, the present invention implements a new circuit topology by adopting a simple series-parallel connection of inductance and capacitance on the basis of the topology of the traditional boost DC converter. The present invention has the following advantages:

1) Higher voltage conversion gain can be obtained;

2) The conduction time of the main switch is shortened, the peak value of the input current is effectively reduced, and the conduction loss is reduced;

3) Reduce the ripple of the output voltage;

4) The voltage stress applied to both ends of the main switch is reduced, and switching devices with lower withstand voltage levels can be selected to reduce hardware manufacturing costs;

5) There is no need to use transformers, coupled inductors and multi-stage connection methods, and the circuit topology is simple;

6) Compared with traditional step-up DC converters, high-gain step-up DC converters can achieve the goals of high efficiency, small size, low noise and low cost.

Description of drawings

Fig. 1 is a schematic structural diagram of a conventional step-up DC converter;

Fig. 2 is the structural representation of converter of the present invention;

Fig. 3 is the relationship curve of duty cycle and output voltage in embodiment 1;

Fig. 4 is each voltage schematic diagram in embodiment 1;

Fig. 5 is the relationship curve of input current and switching time in embodiment 1;

Fig. 6 is the relational curve of output voltage ripple and switching time;

Fig. 7 is another structural schematic view of the converter of the present invention;

Fig. 8 is the relationship curve of duty cycle and output voltage in embodiment 2;

FIG. 9 is a schematic diagram of various voltages in Embodiment 2.

Detailed ways

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

Example 1

As shown in Figure 2, a high-gain step-up DC converter includes an input power supply, a main switch S, a freewheeling diode D _o , a filter capacitor C _o , a clamp capacitor C _c and a boost unit. The input The negative pole of the power supply, one end of the main switch S and one end of the filter capacitor C _o are connected to each other, the other end of the filter capacitor C _o is connected to the cathode of the freewheeling diode D _o , and the converter also includes a clamping capacitor C _c and a boost unit, the two ends of the clamping capacitor C _c are respectively connected to the anode of the main switch S and the freewheeling diode D _o , and the two output ends of the boost unit are respectively connected to the two ends of the clamping capacitor C _c The input terminal of the step-up unit is connected to the positive pole of the input power supply.

The boost unit includes a first inductor L ₁ , a second inductor L ₂ , a first capacitor C ₁ , a second capacitor C ₂ , a first diode D ₁ and a second diode D ₂ , and the One end of the first inductance L ₁ is respectively connected to the positive pole of the input power supply and the first capacitor C ₁ , the other end is respectively connected to the clamping capacitor C _c and the second capacitor C ₂ , and one end of the second inductance L ₂ is respectively connected to the first diode The cathode of the tube D ₁ and the second capacitor C ₂ , the other end is respectively connected to the anode of the second diode D ₂ and the first capacitor C ₁ , and the anode of the first diode D ₁ is connected to the positive pole of the input power supply , the cathode of the second diode _D2 is connected to the clamp capacitor _Cc .

The working state of the above-mentioned high-gain step-up DC converter in one switching cycle can be divided into two stages;

Stage 1: When the main switch S is turned on, the first inductor _L1 enters the energy storage stage and is charged by the input power supply; at the same time, the second inductor L2 enters the energy discharge stage, and the potential difference between the clamping capacitor C _c and the input power supply ( V _cc -V _in ) to discharge.

Stage 2: When the main switch S is turned off, the inductor L ₁ enters the energy discharge stage, and D _o is forward-conducting, which is carried out by the potential difference (V _o -V _cc -V _in ) of the output voltage, the clamping capacitor C _c and the input power supply. Discharging; at the same time, the inductor L ₂ enters the energy storage stage, and is charged by the potential difference (V _o -V _cc -V _in ) of the output voltage, the clamping capacitor C _c and the input power supply.

钳位电容电压V_cc＝V_in×2；开关的电压应力：V_ds＝V_o-V_cc＝V_o-2V_in，其中d为主开关S的占空比。According to the principle of magnetic balance, under the same duty cycle condition, the gain of the high-gain step-up DC converter in this embodiment can be calculated as

The clamping capacitor voltage V _cc =V _in ×2; the voltage stress of the switch: V _ds =V _o -V _cc =V _o -2V _in , where d is the duty cycle of the main switch S.

两者之间的占空比和输出电压的关系曲线如图3所示。图4为输入电源Vin＝50V，输出电压V_o＝200V，输出电流I_o＝5A的仿真波形，可以看出此时的占空比d＝0.5，主开关的电压应力V_ds＝V_o-2V_in＝200-100＝100V(V_ds为主开关S的学习漏极-源极电压)，符合以上的理论分析。图4中，V_gs为主开关S的栅极-源极电压。图5和图6分别为输入电流、输出电压纹波和开关时间的关系，也可以看出通过减小开关导通时间，可有效降低输入电流幅值和输出电压纹波。The gain of the converter in this embodiment is greater than that of the traditional type

The relationship between the duty cycle and the output voltage is shown in Figure 3. Figure 4 is the simulation waveform of input power Vin=50V, output voltage V _o =200V, and output current I _o =5A. It can be seen that the duty cycle d=0.5 at this time, and the voltage stress of the main switch V _ds =V _o - 2V _in =200-100=100V (V _ds is the learned drain-source voltage of the main switch S), which conforms to the above theoretical analysis. In Figure 4, V _gs is the gate-source voltage of the main switch S. Figure 5 and Figure 6 respectively show the relationship between input current, output voltage ripple and switching time. It can also be seen that by reducing the switch on time, the input current amplitude and output voltage ripple can be effectively reduced.

Example 2

As shown in Figure 7, a high-gain step-up DC converter is similar to the structure in Embodiment 1, the difference is that the converter in this embodiment also includes an auxiliary switch _S2 and a third inductor _L3 , one end of the third inductance L ₃ is connected to the clamping capacitor C _c , and the other end is connected to the anode of the freewheeling diode D _o , one end of the auxiliary switch S ₂ is connected to the main switch S, and the other end is connected to the third inductance L ₃ .

The working state of the high-gain step-up DC converter in this embodiment can be divided into two stages within one switching cycle;

Stage 1: The main switches S ₁ and S ₂ are turned on together, and the inductor L ₁ enters the energy storage stage and is charged by the input power. Inductor L ₂ enters the energy discharge stage, and discharges through the potential difference (V _cc -V _in ) between the clamp capacitor C _c and the input power supply. At the same time, the inductor L ₃ also enters the energy storage stage, and the voltage V of the clamp capacitor C _{c cc} for charging.

Stage 2: The main switches S ₁ and S ₂ are cut off together, the inductor L ₁ enters the energy discharge stage, D _o conducts forwardly, _and the potential difference (V _{1 -V cc} -V _in ) to discharge. The inductor L ₂ enters the energy storage stage, and is charged by the potential difference (V ₁ -V _cc -V _in ) of the potential of V ₁ , the clamping capacitor C _c and the input power supply. At the same time, the inductor L ₃ also enters the energy discharge stage, and is discharged by the potential difference (V _o -V ₁ ) between the output voltage V _o and V ₁ .

V1点电位

钳位电容电压V_cc＝V_in×2；主开关的电压应力

辅开关的电压应力 According to the principle of magnetic balance, under the same duty cycle condition, the gain of the high-gain step-up DC converter in this embodiment can be calculated as

V1 point potential

Clamp capacitor voltage V _cc =V _in ×2; voltage stress of the main switch

Voltage Stress of Auxiliary Switches

两者之间的占空比和输出电压的关系曲线如图8所示。图9为输入电源V_in＝50V，输出电压V_o＝300V，输出电流Io＝5A的仿真波形，可以看出此时的占空比d＝0.5，主开关的电压应力V_ds＝V_o-2V_in＝200-100＝100V，符合以上的理论分析。The gain of the converter in this embodiment is greater than that of the traditional type

The relationship between the duty cycle and the output voltage is shown in Figure 8. Figure 9 is the simulation waveform of input power supply V _in =50V, output voltage V _o =300V, output current Io =5A, it can be seen that the duty cycle d=0.5 at this time, the voltage stress of the main switch V _ds =V _o - 2V _in =200-100=100V, which conforms to the above theoretical analysis.

Claims (3)

1. high-gain type voltage boosting dc transducer; Comprise input power supply, main switch, fly-wheel diode and filter capacitor; The negative pole of described input power supply is connected with an end of main switch, an end of filter capacitor respectively, and the other end of described filter capacitor connects the negative electrode of fly-wheel diode, it is characterized in that; Described transducer also comprises clamp capacitor and boosting unit; The two ends of described clamp capacitor connect the other end of main switch and the anode of fly-wheel diode respectively, and two outputs of described boosting unit are connected with the two ends of clamp capacitor respectively, and the input of described boosting unit is connected with the positive pole of input power supply.

2. a kind of high-gain type voltage boosting dc transducer according to claim 1; It is characterized in that; Described boosting unit comprises first inductance, second inductance, first electric capacity, second electric capacity, first diode and second diode, and described first inductance, one end connects the positive pole and first electric capacity of importing power supply respectively, and the other end connects the clamp capacitor and second electric capacity respectively; Described second inductance, one end connects the negative electrode and second electric capacity of first diode respectively; The other end connects the anode and first electric capacity of second diode respectively, and the anode of described first diode is connected with the positive pole of input power supply, and the negative electrode of described second diode is connected with clamp capacitor.

3. a kind of high-gain type voltage boosting dc transducer according to claim 2; It is characterized in that; Described transducer also comprises auxiliary switch and the 3rd inductance, and described the 3rd inductance one end connects clamp capacitor, and the other end connects the anode of fly-wheel diode; Described auxiliary switch one end connects main switch, and the other end connects the 3rd inductance.

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