TWI452811B - Single - stage single - switch power conversion device - Google Patents

Description

Single-stage single-switch power conversion device

The invention relates to a single-stage single-switching power conversion device, in particular to a single-stage buck converter using a small-capacitance DC-coil capacitor, in particular to convert a high-voltage power supply into a low-voltage power supply. A converter that uses electrical energy for low voltage loads.

According to the general non-isolated buck converter, as shown in Figure 12, the ideal buck converter (Buck Converter), which is a basic buck converter, mainly by the control IC, active semiconductor power switch SW , Diode D , energy storage inductor L and capacitor C. The action is originally when the active semiconductor power switch SW is turned on, at which time the voltage source charges the storage inductor L , and simultaneously charges the capacitor C and supplies energy to the output load. When the active semiconductor power switch SW is turned off, The energy storage inductor L charges its capacitor C via the flywheel diode D while providing energy to the output load.

When the active semiconductor power switch SW is turned on, the inductor current increment Δ i _{L ( on )} can be approximated by the following equation (31):

Wherein T _s is a switching period of the switch; and the D _on is a duty cycle of the power crystal conduction. When the active semiconductor power switch SW is turned off, the inductor current increment Δ i _{L ( off )} can be approximated by the following equation (32):

According to the volt-second equilibrium theorem, the following equation (33) can be obtained:

Further, the relationship between the input voltage and the output voltage can be obtained as the following equation (34):

It can be seen from the above equation that the duty cycle D _{on of the} active switching element determines the step-down ratio of the buck converter.

From the foregoing results, it is known that D _{on is} relatively small in order to obtain a higher pressure reduction ratio. Taking 311 volts (V) down to 12V as an example, Equation (4) shows that D _on is about 0.038. However, due to the limitations of physical and control circuits, this duty cycle is difficult to achieve, and the step-down ratio is also physically limited. It is difficult to achieve the desired value, and a very small duty cycle will cause large high-frequency noise interference and reduce efficiency.

Due to the limitation of the duty cycle, in today's non-isolated high step-down ratio applications, a multi-stage circuit architecture is often used, and multiple buck circuits are connected in series to obtain a higher high drop ratio, as shown in FIG. However, due to the non-ideal characteristics of the components, the conversion efficiency of each converter is less than 100%. When the converters are connected in series, the efficiency is the product of the efficiency of each converter, so the efficiency is not good; and so needs to be used. Quite a lot of components and control circuits, the cost is relatively increased.

The commonly used isolated buck circuit is a flyback converter. As shown in Figure 14, it is mainly applied to loads below 100 watts (W). Due to the simplicity of the circuit and the low cost, the flyback transformer in the circuit can It is also used as a storage inductor, and only one diode and one capacitor are needed on the secondary side. From the perspective of cost, the flyback converter circuit is very competitive in the market. The flyback converter circuit is mainly composed of a control IC, an active semiconductor power switch SW , a flyback transformer T , a diode D, and a capacitor C , and the control IC controls the conduction and the cutoff of the active semiconductor power switch SW . After the magnetizing inductance of the flyback transformer T is used for energy storage and energy release, and the secondary side diode D and the capacitor C are used for rectifying and filtering the output voltage, the DC voltage output can be obtained. The basic operating principle is that the flyback transformer T has the triple function of electrical isolation and voltage transformation as the energy storage inductance. In the rigorous reason, the flyback transformer T is not a true transformer, but is coupled. Inductor. By turning on and off the active semiconductor power switch SW , the energy stored in the flyback transformer T is transmitted to the secondary side, and the capacitor C is charged via the diode D , and the DC voltage is maintained at a set value. Wherein, when the active semiconductor power switch SW is turned on, at this time, the voltage source v _in charges the flyback transformer T , and the diode D is reverse biased, and the capacitor C supplies energy to the output terminal; When the active semiconductor power switch SW is turned off, the flyback transformer T supplies energy to the capacitor C via the diode D to supply energy to the output terminal.

The relationship between the output voltage and the input voltage is as follows (35):

According to the working principle of the buck converter and the flyback converter, the duty cycle of the active switching element D _on determines the step-down ratio of the converter, wherein the step-down ratio of the step-down converter and the flyback transformer Therefore, the flyback converter can obtain a larger step-down ratio, but the flyback transformer in the circuit will make the converter circuit larger in size, cost increase, and difficult to IC, such as a higher step-down ratio. Due to the limitation of the minimum duty cycle, the flyback transformer requires a larger turns ratio, and after the secondary energy conversion, the conversion efficiency is lower than that of the non-isolated buck converter. Therefore, the general practitioners cannot meet the needs of the user in actual use.

The main object of the present invention is to overcome the above problems encountered in the prior art and to provide a single stage with a power factor correction and a high step-down ratio characteristic, which can reduce the higher DC voltage on the input side to the lower DC voltage on the output side. Single-switch power conversion device.

A secondary object of the present invention is to provide a single stage buck converter that avoids the use of electrolytic capacitors and uses small capacitance values of DC link capacitors.

Another object of the present invention is to provide a conversion circuit that can be used with multiple DC pairs, and can effectively reduce the amount of components used by using only one active switch, thereby reducing the cost and achieving the advantages of single stage high efficiency.

To achieve the above purpose, the present invention is a single-stage single-switch power conversion device that converts a high-voltage power supply into a low-voltage power supply and supplies power to a low-voltage load. The circuit structure is composed of three inductors ( L ₁ , L ₂ , L ₃ ), three capacitors ( C ₁ , C ₂ , C ₃ ), two diodes ( D ₁ , D ₂ ) and an active semiconductor power switch SW , wherein the two ends are connected from the input side a series circuit comprising a first inductor L ₁ , a first capacitor C ₁ and a second inductor L ₂ , wherein the positive voltage terminal and the negative voltage terminal of the first capacitor C ₁ are sequentially connected to an active semiconductor power switch SW And one end of the first diode D ₁ to the third inductor L ₃ , and the second capacitor C ₂ and the second diode D _{2 are} connected to the common negative terminal of the input side and the output side by the end point, and the third The capacitor C ₃ is connected to the other end of the third inductor L ₃ and the negative voltage terminal of the output side, and finally the other end of the third inductor L ₃ is connected to the positive voltage terminal of the output side. The first capacitor C ₁ is a small capacitance value capacitor.

In a preferred embodiment, the inductance value of the input inductor L ₁ is changed, thereby changing the voltage of the DC link capacitor C ₁ terminal of the small capacitance value and changing the input power level.

In a preferred embodiment, by changing the capacitance value of the capacitance of the DC link small capacitance value C _1, thereby changing the small capacitance value of the DC link capacitor C _a voltage magnitude, and to change the input power level.

In a preferred embodiment, by changing the inductance of the input inductor L _1, thereby changing the size of the input current, and changing the time constant of the circuit operation.

In a preferred embodiment, by changing the capacitance value of the capacitance of the DC link small capacitance value C _1, thereby changing the size of the input current, and changing the time constant of the circuit operation.

In a preferred embodiment, the active semiconductor changing the duty cycle of the power switch SW, the frequency, thereby changing the small capacitance value capacitor C ₁ DC link voltage magnitude.

In a preferred embodiment, the absolute value of the input chord is used to achieve the same function.

In a preferred embodiment, the inductance value of the second inductor L ₂ is changed, thereby changing the magnitude of the input current and changing the voltage of the DC link capacitor C ₁ of the small capacitance value.

In a preferred embodiment, by changing the inductance of the third inductor L _3, thereby changing the output current ripple and output ripple voltage of magnitude.

In a preferred embodiment, by changing the output voltage regulation of the capacitance value of capacitor C _3, thereby changing the output current ripple and the size of the output voltage ripple.

Please refer to FIG. 1 to FIG. 4 , which are schematic diagrams of a single-stage single-switch power conversion circuit structure according to the present invention, a circuit architecture diagram of a first embodiment of the present invention, and a circuit according to a second embodiment of the present invention. Schematic diagram of the architecture and schematic diagram of the circuit architecture of the third embodiment of the present invention. As shown in the figure: The present invention is a single-stage single-switching power conversion device that converts a high-voltage power supply into a low-voltage power supply and supplies power to a low-voltage load 10, the circuit structure of which is composed of three inductors ( L ₁ , L ₂ , L ₃ ) 11, 12, 13, three capacitors ( C ₁ , C ₂ , C ₃ ) 14, 15, 16, two diodes ( D ₁ , D ₂ ) 17, 18 and an active semiconductor The power switch ( SW ) 19 is composed of a series circuit composed of a first inductor 11, a first capacitor 14 and a second inductor 12, and a positive voltage terminal and a negative voltage of the first capacitor 14 The voltage terminals are sequentially connected to one of the active semiconductor power switch 19 and one of the first diode 17 to the third inductor 13 , and the second capacitor 15 and the second diode 18 are connected to the input side and the output side by the end point. The common negative terminal, the third capacitor 16 is connected to the other end of the third inductor 13 and the negative voltage terminal of the output side, and finally the other end of the third inductor 13 is connected to the positive voltage terminal of the output side, thereby forming a Single-stage single-switch power conversion device with better efficiency and step-down ratio.

When applied to an AC power source, the voltage waveform must be a sine wave absolute value via a bridge rectifier (Rode Bridge Rectifier) 20. The output current must be constant and the first inductor L ₁ operates in the input current discontinuous conduction mode. In order to achieve the power factor correction function, as shown in Figure 2. When applied to a DC power supply, the output current of the power supply must also be a positive value. The circuit wiring is as shown in Figure 3. In addition, the wiring method of the present invention can also be designed through the circuit component parameters, so that the input inductor operates continuously in the current. Mode, thereby reducing the current ripple at the input, as shown in Figure 4. The operation principle of the present invention is as follows: when the active semiconductor power switch SW is turned off, the first diode D ₁ is turned on, the current of the first inductor L ₁ of the first _charging capacitor C, this time the output energy from the first The second inductor L ₂ and the third inductor L _{3 are} provided. Since the first capacitor C ₁ is the capacitance of the capacitor small, its terminal voltage increases quickly, limiting the current flowing through the first inductor L ₁ and the size is reduced to zero, the ability to achieve high step-down ratio and correcting the power factor; this When the active semiconductor power switch SW is turned on, the first diode D _{1 is} turned off, the first capacitor C ₁ starts to charge the second inductor L ₂ , and the first inductor L ₁ also begins to store energy; When the energy of the first capacitor C _{1 is} released, the second diode D ₂ is turned off. At this time, the second inductor L ₂ transfers energy to the second capacitor C ₂ and the third inductor L ₃ to be the active semiconductor power. When the switch SW is turned on again, the operation of one switching cycle is completed.

To clearly illustrate single-stage single working principle of switching power conversion circuit proposed by the present invention, the following is assumed that all of the circuit elements are over, the voltage source is a DC power supply, constant output power is positive, while the load is assumed to Load Pure resistance R _L . The working principle of the single-stage single-switching power conversion circuit is described as follows:

[Work Mode 1]

Please refer to FIG. 5, which is a schematic diagram of an equivalent circuit of the single-stage single-switch power conversion device of the present invention in the working mode. As shown in the figure: at this time, the active semiconductor power switch SW is turned on, the first diode D _{1 is} turned off, and the first capacitor C ₁ transfers the stored energy to the second inductor L ₂ via the second diode D ₂ while The first inductor L ₁ is pressurized and stored by the power supply terminal v _dc , and the third inductor L ₃ is supplied with energy to the load R _{L of the} output terminal via the second diode D ₂ . According to Fig. 5, the following state equations (1) to (6) can be listed, where v _dc is the input voltage; v _o is the output voltage; i _L1 is the current on the first inductor L ₁ ; i _L2 is the second inductor The current on L ₂ ; i _L3 is the current on the third inductor L ₃ ; i _SW is the current on the active semiconductor power switch SW ; v _C1 is the voltage on the first capacitor C ₁ ; v _C2 is the second capacitor C ₂ The voltage on the voltage; v _C3 is the voltage on the third capacitor C ₃ ; v _SW is the voltage on the active semiconductor power switch SW ; and v _D1 is the voltage on the first diode D ₁ . When the energy of the capacitor C ₁ is released, the operation mode 2 is entered.

[Working mode 2]

Please refer to FIG. 6 , which is an equivalent circuit diagram of the single-stage single-switch power conversion device of the present invention in the working mode 2. As shown in the figure: at this time, the first diode D _{1 is} turned on, the second diode D _{2 is} turned off, and the first inductor L ₁ and the second inductor L ₂ together transfer their energy storage to the second capacitor C ₂ and the load. R _L . According to Fig. 6, the following equations of state (7) ~ (12) can be listed. When the active semiconductor power switch SW is turned off, it enters the operational mode three.

[Work Mode 3]

Please refer to FIG. 7 , which is an equivalent circuit diagram of the single-stage single-switch power conversion device of the present invention in the working mode 3. As shown in the figure: after the active semiconductor power switch SW is turned off, the first inductor L ₁ starts to store energy to the first capacitor C ₁ , and the second inductor L ₂ continuously transmits energy to the third inductor L ₃ , and The two capacitors C ₂ generate resonance. According to Fig. 7, the following equations of state (13) ~ (18) can be listed. When the voltage of the second capacitor C ₂ resonates to zero, it enters the operating mode four.

[Work Mode 4]

Please refer to FIG. 8 , which is a schematic diagram of an equivalent circuit of the single-stage single-switch power conversion device of the present invention in the working mode 4. As shown in the figure: at this time, the second diode D _{2 is} turned on, the first inductor L ₁ continues to charge the first capacitor C ₁ , and the second inductor L ₂ passes through the first diode D ₁ and the second diode Body D _{2 is} reflowed and output inductor L ₃ outputs energy to load R _L . According to Fig. 8, the following equations of state (19) to (24) can be listed. When the energy of the first inductor L _{1 is} released, the operation mode 5 is entered. When the input of this circuit a first inductor L ₁ into the operating state to the continuous conduction mode, the switch to complete a cycle of switching operation at the end of this mode.

[Work mode five]

Please refer to FIG. 9 , which is a schematic diagram of an equivalent circuit of the single-stage single-switch power conversion device of the present invention in operation mode 5. As shown in the figure: when the energy of the first inductor L _{1 is} released, its current is zero, and the second inductor L _{2 is} still recirculated through the first diode D ₁ and the second diode D ₂ , and the output inductor L ₃ continues. Energy is released to the load R _L via the second diode D ₂ . According to Fig. 9, the following equations of state (25) ~ (30) can be listed. When the active semiconductor power switch SW is turned on again, the action of one switching cycle is completed.

Please refer to FIG. 10 and FIG. 11 for a schematic diagram of each of the key analog waveforms of the circuit of the present invention and a schematic diagram of each of the key analog waveforms of the circuit of the present invention. As shown in the figure, in a preferred embodiment, the present invention uses a DC power source v _dc that inputs an absolute value of a sine wave with a voltage peak of 312V, an output DC voltage of 12V, and an output power of 120W. The wiring method is as described above. Figure 2 shows. The parameters of the components of the circuit of the present invention are: the inductance of the input inductor L ₁ is 650 μH, the capacitance of the intermediate storage capacitor C ₁ is 0.01 μF, the inductance of the intermediate storage inductor L ₂ is 100 μH, and the capacitance of the capacitor C ₂ The value is 0.047μF, the inductance of the output inductor L ₃ is 100μH, the capacitance of the output capacitor C ₃ is 1000μF, the active semiconductor power switch SW is SPP20N60S5 (MOSFET), the bridge rectifier is KBU2506, and the diode D ₁ is DSEP15- 06A, the diode D ₂ uses SRF20H40CT, the active semiconductor power switch driver IC uses HCPL3120, and the control IC uses TL494. According to the simulation, it can be observed from Fig. 10 that the power factor of the power supply v _ac terminal is as high as 0.999, and the capability of high power factor and high step-down ratio is high; and the key waveform of each component in the switching cycle in FIG. 11 is It can be observed that the duty cycle of the switch is 0.22, which proves that the present invention can achieve a high step-down ratio without requiring a minimum switching duty cycle.

Accordingly, the present invention is a conversion device for reducing a higher DC voltage on the input side to a lower DC voltage on the output side, and is a single-stage buck converter using a DC capacitor of a small capacitance value, having power factor correction and high drop. The pressure ratio characteristic can not only avoid the use of electrolytic capacitors, but also can be used with multiple DC pairs, and only one active switch can effectively reduce the component usage, thereby reducing the cost and achieving the advantages of single-stage high efficiency.

In summary, the present invention is a single-stage single-switch power conversion device, which can effectively improve various disadvantages of the conventional use, has power factor correction and high step-down ratio characteristics, can not only avoid the use of electrolytic capacitors, but also can be used with multiple DC pairs. And only one active switch can effectively reduce the component usage, thereby reducing the cost and achieving the advantages of single-stage high efficiency, thereby making the invention more progressive, more practical, and more suitable for the user. Has met the requirements of the invention patent application, and filed a patent application according to law.

However, the above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto; therefore, the simple equivalent changes and modifications made in accordance with the scope of the present invention and the contents of the invention are modified. All should remain within the scope of the invention patent.

10‧‧‧ load

11, 12, 13‧‧‧Inductance ( L ₁ , L ₂ , L ₃ )

14, 15, 16‧‧‧ Capacitors ( C ₁ , C ₂ , C ₃ )

17, 18‧‧‧ diodes ( D ₁ , D ₂ )

19‧‧‧Active semiconductor power switch ( SW )

20‧‧‧Bridge rectifier

Fig. 1 is a schematic diagram showing the structure of a single-stage single-switch power conversion circuit of the present invention.

Fig. 2 is a schematic diagram showing the circuit architecture of the first embodiment of the present invention.

Figure 3 is a schematic diagram of the circuit architecture of the second embodiment of the present invention.

Figure 4 is a schematic diagram of the circuit architecture of the third embodiment of the present invention.

Fig. 5 is a schematic diagram showing an equivalent circuit of the single-stage single-switch power conversion device of the present invention in the operating mode.

Fig. 6 is a schematic diagram showing the equivalent circuit of the single-stage single-switch power conversion device of the present invention in the operation mode 2.

Figure 7 is a schematic diagram showing the equivalent circuit of the single-stage single-switch power conversion device of the present invention in the operation mode 3.

Figure 8 is a schematic diagram of an equivalent circuit of the single-stage single-switch power conversion device of the present invention in the operating mode 4.

Figure 9 is a schematic diagram of an equivalent circuit of the single-stage single-switch power conversion device of the present invention in operation mode 5.

Figure 10 is a schematic diagram of each of the key analog waveforms of the circuit of the present invention.

Figure 11 is a schematic diagram of two key analog waveforms of the circuit of the present invention.

Figure 12 is a schematic diagram of the circuit architecture of a conventional buck converter.

Figure 13 is a schematic diagram of a multi-stage non-isolated buck circuit architecture.

Figure 14 is a schematic diagram of the circuit architecture of a flyback converter used in a conventional isolated buck circuit.

10‧‧‧ load

11, 12, 13‧‧‧Inductance ( L ₁ , L ₂ , L ₃ )

14, 15, 16‧‧‧ Capacitors ( C ₁ , C ₂ , C ₃ )

17, 18‧‧‧ diodes ( D ₁ , D ₂ )

19‧‧‧Active semiconductor power switch ( SW )

Claims (5)

A single-stage single-switch power conversion device converts a high-voltage power supply into a low-voltage power supply and supplies power to a low-voltage load. The circuit structure is composed of three inductors, three capacitors, two diodes, and one active The semiconductor power switch is composed of a series circuit composed of a first inductor, a first capacitor and a second inductor, and a positive voltage terminal and a negative voltage terminal of the first capacitor are sequentially connected to each other. An active semiconductor power switch and one of the first diode to the third inductor, and one end of the third inductor is connected to the second capacitor and the second diode to a common negative terminal of the input side and the output side, the third capacitor Then connected to the other end of the third inductor and the negative voltage terminal of the output side, and finally the other end of the third inductor is connected to the positive voltage terminal of the output side, wherein: when the active semiconductor power switch is turned off, the first two The pole body is turned on, the current of the first inductor charges the first capacitor, and the output energy is provided by the second inductor and the third inductor, and the voltage of the first capacitor terminal increases rapidly. The current flowing through the first inductor is reduced to zero to achieve a high step-down ratio and power factor correction; and when the active semiconductor power switch is turned on, the first diode is turned off, and the first capacitor begins to The second inductor is charged, the first inductor also begins to store energy; when the first capacitor energy is released, the second diode is turned off, and the second inductor transmits energy to the second capacitor and the third The inductor completes a switching cycle period when the active semiconductor power switch is turned on again. The single-stage single-switch power conversion device according to claim 1, wherein the first capacitor is a small capacitance capacitor. According to the single-stage single-switch power conversion device described in claim 1 of the patent application scope, When applied to an AC power source, the voltage waveform is a sine wave absolute value through a bridge rectifier (Rode Bridge Rectifier), the output current is always positive, and the first inductor is operated in the input current discontinuous conduction mode. . According to the single-stage single-switch power conversion device described in the first paragraph of the patent application, when applied to a DC power supply, the power supply output current is always positive, and the first inductance is operated in the input current discontinuous conduction mode. . According to the single-stage single-switch power conversion device described in the first paragraph of the patent application, when applied to a DC power supply, the power supply output current is always a positive value, and the first inductance is operated in the input current continuous conduction mode.