TW201501458A - AC-DC power conversion device and control method thereof - Google Patents

Abstract

An AC-DC power conversion device includes a rectifier, a boost DC-DC power converter, an energy buffer, an isolated DC-DC power converter and a controller. An AC-DC power conversion control method includes: detecting an input voltage of an AC voltage source; judging the input voltage higher or lower than a predetermined value; when the input voltage is higher than the predetermined value, two capacitors of the energy buffer is operated with a serial connection and the boost DC-DC power converter is operated to boost the input voltage to a first voltage of the energy buffer; when the input voltage is lower than the predetermined value, the two capacitors of the energy buffer is operated with a parallel connection and the boost DC-DC power converter is operated to boost the input voltage to a second voltage of the energy buffer; wherein the energy buffer is operated to provide with two voltage levels so as to reduce a duty cycle of a switch of the boost DC-DC power converter when the input voltage of the AC voltage source is relatively low.

Description

AC-DC power conversion device and control method thereof

The present invention relates to an AC-DC power conversion device and a control method thereof; and more particularly to an AC-DC power conversion device and a control method for improving electrical energy conversion efficiency and having electrical isolation.

The conventional AC-DC power conversion technology, such as the 〝 exchange power supply device of the Republic of China Patent No. I347735, is an invention patent, which discloses an exchange power supply device 1. Referring to FIG. 1 , the switching power supply device 1 includes an AC input voltage source 11 , a bridge rectifier 12 , a boost DC-DC power converter 13 , an electrical energy buffer 14 , and an electrical isolation. A DC-DC power converter 15, a load detection circuit 16 and a load 17. The bridge rectifier 12 and the step-up DC-DC power converter 13 have a function of power factor correction. When the galvanically isolated DC-DC power converter 15 determines to detect that the load 17 is a light load, the function of the step-up DC-DC power converter 13 is immediately stopped, thereby improving the conversion efficiency in the light load mode.

However, in the above-mentioned publication No. I347735, since the switching power supply device 1 employs the conventional step-up type DC-DC power converter 13, when the duty cycle of the power switch is high, the conversion efficiency of the overall power converter is lowered.

Another conventional AC-DC power conversion technology, such as the high-efficiency charging circuit and power supply system of the Republic of China Patent No. I373900, discloses a high-efficiency charging circuit 2. Referring to FIG. 2, the high efficiency charging circuit 2 includes an AC input voltage source 21, A bridge rectifier 22, a boost DC-DC power converter 23, a filter capacitor 24, a buck-boost DC-DC power converter 25, a detection circuit 26, a PWM controller 27, and a battery pack 28.

However, the above-mentioned publication No. I373900 does not have the function of power factor correction because the boost type DC-DC power converter 23 does not have the function of increasing the circuit line loss and the distortion of the power supply voltage waveform generated by the harmonic current. In addition, since the high-efficiency charging circuit 2 also uses the conventional step-up DC-DC power converter 23, when the duty cycle of the power switch is high, the conversion efficiency of the overall power converter is lowered. The above-mentioned patents and patent applications are merely for the purpose of the technical background of the present invention and are not intended to limit the scope of the present invention.

In view of the above, in order to meet the above technical problems and needs, the present invention provides an AC-DC power conversion device and a control method thereof, which utilize an energy buffer when an input voltage of an AC input voltage source is greater than a set value, The capacitor of the electric energy buffer is operated in series; when the input voltage of the AC input voltage source is less than the set value, the two capacitors of the electric energy buffer are operated in parallel, so that the output voltage is divided into two different voltage levels, The problem that the duty cycle of the power switch is too high when the voltage of the AC input voltage source is low is solved, and therefore the advantage of improving the conversion efficiency is compared with the conventional AC-DC power conversion device.

The main object of the preferred embodiment of the present invention is to provide an AC-DC power conversion device and a control method thereof, which utilize an energy buffer to generate an input voltage of an AC input voltage source greater than a set value. The capacitor is operated in series; when the input voltage of the AC input voltage source is less than the set value, the two capacitors of the power buffer are operated in parallel, and the output voltage is divided into two different voltage levels to solve the AC input voltage. When the source voltage is low, the duty cycle of the power switch is too high, so as to achieve the purpose of improving the conversion efficiency of the AC-DC power.

In order to achieve the above object, an AC-DC power conversion apparatus according to a preferred embodiment of the present invention includes: a rectifier connected to an AC input voltage source, the AC input voltage source supplying an input voltage; and a step-up DC-DC conversion Connected to the rectifier, the step-up DC-DC converter comprises a power switch; an energy buffer connected to the boost DC-DC converter, the power buffer comprising two filter capacitors; An electrically isolated DC-DC converter coupled to the power buffer; and a controller coupled to control the boost DC-DC converter, the power buffer, and the electrically isolated DC-DC converter Wherein the power buffer uses the input voltage of the AC input voltage source to be greater than a set value, the two filter capacitors of the power buffer are operated in a series connection manner, and at this time, the step-up DC-DC converter will The input voltage is boosted to a first voltage of the power buffer; when the input voltage of the AC input voltage source is lower than the set value, the electrical energy The two filter capacitors of the punch are operated in a parallel connection manner. At this time, the step-up DC-DC converter boosts the input voltage to a second voltage of the power buffer to make the output voltage of the power buffer Divided into two different voltage levels, so that the duty cycle of the power switch of the step-up DC-DC converter can be reduced when the voltage of the AC input voltage source is low.

The controller of the preferred embodiment of the present invention comprises a voltage external loop processing unit, a current inner loop processing unit and a pulse width modulation circuit for controlling the boost DC-DC converter; The outer loop processing unit comprises a voltage detector, a waveform generating circuit, an absolute value circuit, a voltage detector, a subtractor, a proportional integral controller and a multiplier, and the current inner loop processing unit comprises a current detecting , a subtractor and a proportional integral controller.

The controller of the preferred embodiment of the present invention includes a load voltage processing unit and a pulse width modulation circuit for controlling the DC-DC converter with an electrically isolated connection to the DC load; the load voltage processing The unit includes a voltage detector, a subtractor, and a proportional integral controller.

The controller of the preferred embodiment of the present invention comprises a battery current processing unit, a battery voltage processing unit, a selection switch and a pulse width modulation circuit for electrically isolating the DC-DC converter. The battery pack current processing unit includes a current detector, a subtractor and a proportional integral controller. The battery pack voltage processing unit includes a voltage detector, a subtractor and a proportional integral control. Device.

In the preferred embodiment of the invention, the controller includes a voltage detector, an absolute value circuit, a comparator and a switching signal generator for controlling the power buffer.

In order to achieve the above object, an AC-DC power conversion control method according to a preferred embodiment of the present invention includes: detecting an input voltage of an AC input voltage source; determining that an input voltage of the AC input voltage source is higher or lower than a set value; When the input voltage of the AC input voltage source is higher than the set value, the two filter capacitors of an electric energy buffer are operated in series connection, and the input voltage is boosted by a boost type DC-DC converter to a first voltage of the power buffer; and when the input voltage of the AC input voltage source is lower than the set value, the two filter capacitors of the power buffer are operated in a parallel connection manner, and the boost type DC is utilized The DC converter boosts the input voltage to a second voltage of the power buffer; wherein the output voltage of the power buffer is divided into two different The voltage level is such that when the voltage of the AC input voltage source is low, the duty cycle of one of the boost DC-DC converters is reduced.

A preferred embodiment of the present invention employs a controller including a voltage external loop processing unit, a current inner loop processing unit, and a pulse width modulation circuit for performing the boost DC-DC converter The voltage outer loop processing unit comprises a voltage detector, a waveform generating circuit, an absolute value circuit, a voltage detector, a subtractor, a proportional integral controller and a multiplier, and the current inner loop processing unit A current detector, a subtractor and a proportional integral controller are included.

A preferred embodiment of the present invention employs a controller including a load voltage processing unit and a pulse width modulation circuit for controlling when an electrically isolated DC-DC converter is connected to a DC load; The load voltage processing unit includes a voltage detector, a subtractor and a proportional integral controller.

A preferred embodiment of the present invention employs a controller including a battery pack current processing unit, a battery pack voltage processing unit, a selection switch, and a pulse width modulation circuit for directing an electrically isolated DC - the DC converter is controlled when connected to a battery pack; the battery pack current processing unit comprises a current detector, a subtractor and a proportional integral controller, the battery pack voltage processing unit comprises a voltage detector, a subtractor and A proportional integral controller.

A preferred embodiment of the invention employs a controller that includes a voltage detector, an absolute value circuit, a comparator, and a switching signal generator for steering the power buffer.

1‧‧‧Switching power supply unit

11‧‧‧AC input voltage source

12‧‧‧Bridge rectifier

13‧‧‧Boost DC-DC Energy Converter

14‧‧‧Electric energy buffer

15‧‧‧DC-DC power converter with electrical isolation

16‧‧‧Load detection circuit

17‧‧‧ load

2‧‧‧High efficiency charging circuit

21‧‧‧AC input voltage source

22‧‧‧Bridge rectifier

23‧‧‧Boost DC-DC Energy Converter

24‧‧‧Filter capacitor

25‧‧‧Buck-boost DC-DC energy converter

26‧‧‧Detection circuit

27‧‧‧PWM controller

28‧‧‧Battery Pack

3‧‧‧AC-DC power conversion device

31‧‧‧AC input voltage source

32‧‧‧Rectifier

33‧‧‧Boost DC-DC Converter

331‧‧‧Inductors

332‧‧‧Power switch

333‧‧‧ diode

34‧‧‧Electric energy buffer

341‧‧‧Power switch

342‧‧‧Power switch

343‧‧‧Filter capacitor

344‧‧‧Filter capacitor

345‧‧‧ diode

35‧‧‧DC-DC converter with electrical isolation

351‧‧‧Power switch

352‧‧‧Transformer

353‧‧‧ diode

354‧‧‧ diode

355‧‧‧Inductors

356‧‧‧Filter capacitor

36‧‧‧load

4‧‧‧ Controller

41‧‧‧First control block architecture

411‧‧‧Voltage outer loop processing unit

4111‧‧‧Voltage detector

4112‧‧‧ Waveform generating circuit

4113‧‧‧Absolute value circuit

4114‧‧‧Voltage detector

4115‧‧‧Subtractor

4116‧‧‧Proportional Integral Controller

4117‧‧‧Multiplier

412‧‧‧current inner loop processing unit

4121‧‧‧ Current Detector

4122‧‧‧Subtractor

4123‧‧‧Proportional integral controller

413‧‧‧ Pulse width modulation circuit

42‧‧‧Second control block architecture

421‧‧‧Load voltage processing unit

4211‧‧‧Voltage detector

4212‧‧‧Subtractor

4213‧‧‧Proportional integral controller

422‧‧‧ Pulse width modulation circuit

43‧‧‧ Third Control Block Architecture

431‧‧‧Battery pack current processing unit

4311‧‧‧ Current Detector

4312‧‧‧Subtractor

4313‧‧‧Proportional Integral Controller

432‧‧‧Battery pack voltage processing unit

4321‧‧‧Voltage detector

4322‧‧‧Subtractor

4323‧‧‧Proportional Integral Controller

433‧‧‧Selection switch

434‧‧‧ Pulse width modulation circuit

44‧‧‧fourth control block architecture

441‧‧‧Voltage detector

442‧‧‧Absolute value circuit

443‧‧‧ comparator

444‧‧‧Switch signal generator

Fig. 1 is a schematic view showing the structure of an exchange type power supply device of the Republic of China Patent Publication No. I347735.

Figure 2: The high efficiency of the Republic of China Patent Announcement No. I373900 Schematic diagram of the structure of the charging circuit.

Fig. 3 is a block diagram showing the structure of an AC-DC power conversion apparatus according to a preferred embodiment of the present invention.

4A is a block diagram showing a controller of a boost type DC-DC converter according to a preferred embodiment of the present invention.

Figure 4B is a block diagram of a DC-DC converter with electrical isolation in accordance with a preferred embodiment of the present invention employing a controller when the load is a general DC load.

Figure 4C is a block diagram of a controller having an electrically isolated DC-to-DC converter in accordance with a preferred embodiment of the present invention when the load is a battery pack.

Figure 4D: The serial/parallel power buffer of the preferred embodiment of the present invention is used A block diagram of the controller.

In order to fully understand the present invention, the preferred embodiments of the present invention are described in detail below, and are not intended to limit the invention.

The AC-DC power conversion apparatus and the control method thereof according to the preferred embodiment of the present invention are applicable to various AC-DC power conversion systems, but are not intended to limit the scope of the present invention. Fig. 3 is a block diagram showing the structure of an AC-DC power conversion apparatus according to a preferred embodiment of the present invention. Referring to FIG. 3, the AC-DC power conversion device 3 of the preferred embodiment of the present invention includes an AC input voltage source 31, a rectifier 32, a step-up DC-DC converter 33, and an electric energy buffer. A serial/parallel power buffer 34, an electrically isolated DC-DC converter 35, a load 36 and a controller 4. The AC input voltage source 31 is connected to the rectifier 32. The rectifier 32 is further connected to the step-up DC-DC converter 33. The boost DC-DC converter 33 is connected to the power buffer 34. The buffer 34 is in turn coupled to the electrically isolated DC-to-DC converter 35, which is in turn coupled to the load 36. In addition, the controller 4 is connected to control the boost type DC-DC converter 33 and the power buffer. 34 and DC-DC converter 35 with electrical isolation.

For example, the rectifier 32 is selected from a combination of four diodes, and the rectifier 32 has a first end (ie, an input end) and a second end (ie, an output end). The two ends of the first end of the rectifier 32 are connected to the AC input voltage source 31, and the second end of the rectifier 32 outputs a DC voltage and a DC current.

Referring to FIG. 3 again, the step-up DC-DC converter 33 includes an inductor 331, a power switch 332, and a diode 333. The power switch 332 is selected from a semiconductor switching device. The step-up DC-DC converter 33 has a first end and a second end. For example, the two ends of the first end [input terminal] of the step-up DC-DC converter 33 are connected to the second end [output end] of the rectifier 32.

Referring to FIG. 3 again, the power buffer 34 includes two power switches (including bypass diodes) 341, 342, two filter capacitors 343, 344, and a diode 345, and the two power switches 341 342 is an upper power switch and a lower power switch. The two filter capacitors 343 and 344 are an upper capacitor and a lower capacitor. The power switch 341 or 342 is selected from a semiconductor switching element. Each of the power switches 341, 342 has a first end and a second end. Each of the filter capacitors 343, 344 also has a first end and a second end. The diode 345 also has a first end and a second end.

In addition, the power buffer 34 has a first end and a second end. The two ends of the second end [output terminal] of the step-up DC-DC converter 33 and the first end (positive end) of the filter capacitor 343 of the power buffer 34 and the second end of the filter capacitor 344 Negative end] connection.

For example, the power buffer 34 includes four end points, which are a first end (positive end) of the filter capacitor 343, a second end (negative end) of the filter capacitor 344, and a diode 345. The first end [anode end] and the second end [cathode end] of the diode 345. The filter capacitor The first end (positive end) of the 343 is connected to the first end of the power switch 342, and the second end (negative end) of the filter capacitor 344 is connected to the second end of the power switch 341. The first end (anode end) is connected to the first end of the power switch 341, and the second end (cathode end) of the diode 345 is connected to the second end of the power switch 342.

Referring to FIG. 3 again, the galvanically isolated DC-DC converter 35 includes a power switch 351, a transformer 352, two diodes 353, 354, an inductor 355, and a filter capacitor 356. The power switch 351 is selected from a semiconductor switching element. The electrically isolated DC-DC converter 35 has a first end and a second end.

For example, the first end [input terminal] of the galvanically isolated DC-DC converter 35 and the first end (positive end) of the filter capacitor 343 of the power buffer 34 and the second end of the filter capacitor 344 The [negative terminal] is connected, and the second end [output terminal] of the electrically isolated DC-DC converter 35 is connected to the load 36.

Referring to FIG. 3 again, the operation mode of the power buffer 34 is determined by a set value, and the output voltage of the step-up DC-DC converter 33 is divided into two different voltage levels to reduce the rise. The duty cycle of the power switch 332 of the compact DC-DC converter 33 is achieved to achieve the overall conversion efficiency of the AC-DC power conversion device 3. The step-up DC-DC converter 33 regulates the filter capacitors 343 and 344 of the power buffer 34, and is regulated to one half of the highest voltage of the power buffer 34, and performs power factor correction. The function of the factor correction (PFC) is such that the input current of the AC-DC power conversion device 3 tends to be a sine wave and is in phase with the AC input voltage source 31 to improve the power factor of the AC-DC power conversion device 3. To reduce the circuit line loss and suppress the distortion of the power supply waveform caused by harmonic current.

Please refer to FIG. 3 again to control the power buffer 34. The method uses the voltage of the AC input voltage source 31 to compare with the set value to determine that the power buffer 34 operates in a series or parallel mode. When the voltage of the power buffer 34 at the AC input voltage source 31 is greater than the set value, the two filter capacitors 343 and 344 of the power buffer 34 are connected in series. At this time, the step-up DC-DC converter 33 boosts the input voltage to a first voltage of the power buffer 34, which is higher than a voltage peak of the AC input voltage source 31.

Referring to FIG. 3 again, when the voltage of the power buffer 34 at the AC input voltage source 31 is less than the set value, the two filter capacitors 343 and 344 of the power buffer 34 are connected in parallel. . At this time, the step-up DC-DC converter 33 boosts the input voltage to a second voltage of the power buffer 34, and the second voltage tends to be one half of the first voltage, so that the power buffer 34 The output voltage is divided into two different voltage levels, so that when the voltage of the AC input voltage source 31 is low, the duty cycle of the power switch 332 of the step-up DC-DC converter 33 is lowered to improve the overall Conversion efficiency of the AC-DC power conversion device 3. The galvanically isolated DC-DC converter 35 regulates the filter capacitor 356, and the output of the galvanically isolated DC-DC converter 35 is a stable voltage source to provide a stable voltage source to the load. 36.

Referring again to FIG. 3, the load 36 can be a DC load (ie, a general DC load) or a battery pack. If the load 36 is a battery pack, the battery pack is charged using a mixed constant current-constant voltage charging method. The mixed constant current-constant voltage charging method can effectively reduce the charging time when charging in the constant current mode, and does not cause overcharging of the battery pack when charging in the constant voltage mode.

Referring to FIG. 3 again, the controller 4 is configured to respectively control the power switch 332 of the step-up DC-DC converter 33, the power switches 341 and 342 of the power buffer 34, and the DC with the electrical isolation. -DC The power switch 351 of the converter 35 is switched so that the AC-DC power conversion device 3 can achieve the above functions.

FIG. 4A is a block diagram showing the controller 4 in which the step-up DC-DC converter 33 of the preferred embodiment of the present invention is used. Referring to FIG. 4A, the step-up DC-DC converter 33 employs a first control block architecture 41. The first control block architecture 41 includes a voltage outer loop processing unit 411, a current inner loop processing unit 412, and a pulse width modulation circuit 413. The voltage outer loop processing unit 411 includes a voltage detector 4111, a waveform generating circuit 4112, an absolute value circuit 4113, a voltage detector 4114, a subtractor 4115, a set voltage of a filter capacitor 344, and a proportional integral controller. 4116 and a multiplier 4117. The current inner loop processing unit 412 includes a current detector 4121, a subtractor 4122, and a proportional integral controller 4123.

Referring to FIGS. 3 and 4A again, the voltage outer loop processing unit 411 and the current inner loop processing unit 412 detect the voltage of the filter capacitor 344 and the current of the inductor 331 to generate a control signal. The voltage detector 4114 is configured to detect the voltage of the filter capacitor 344. The set voltage of the filter capacitor 344 is subtracted from the output of the voltage detector 4114 to the subtractor 4115 to obtain a voltage error signal of the filter capacitor 344. The output of the subtractor 4115 is sent to the proportional integral controller 4116 to obtain a DC voltage control signal. The AC input voltage source 31 is detected by the voltage detector 4111, and then the voltage of the AC input voltage source 31 is sent to the waveform generating circuit 4112 to generate a unit sine wave signal in phase with the AC input voltage source 31. The output of the waveform generating circuit 4112 is sent to the absolute value circuit 4113, and the output signal of the absolute value circuit 4113 and the output signal of the proportional integral controller 4116 are sent to the multiplier 4117 for multiplication to generate the inductance. Current reference signal of the device 331. After the current of the inductor 331 is detected by the current detector 4121, the current of the inductor 331 and the current reference signal output by the multiplier 4117 The number is sent to the subtractor 4122 for subtraction. The output of the subtractor 4122 is sent to the proportional integral controller 4123, and the output of the proportional integral controller 4123 is sent to the pulse width modulation circuit 413 to generate a pulse width modulation signal. To control the power switch 332 of the step-up DC-DC converter 33.

FIG. 4B is a block diagram showing the electrically isolated DC-DC converter 35 of the preferred embodiment of the present invention when the load 36 is a general DC load. Referring to FIG. 4B, the electrically isolated DC-DC converter 35 employs a second control block architecture 42. The second control block architecture 42 includes a load voltage processing unit 421 and a pulse width modulation circuit 422. The load voltage processing unit 421 includes a voltage detector 4211, a set voltage of a load 36, a subtractor 4212, and a proportional integral controller 4213.

Referring to FIGS. 3 and 4B again, the voltage detector 4211 is configured to detect the voltage of the load 36, and send the set voltage of the load 36 to the output of the voltage detector 4211 to the subtractor 4212 to subtract A voltage error signal is obtained. The output of the subtractor 4212 is sent to the proportional integral controller 4213, and the output of the proportional integral controller 4213 is sent to the pulse width modulation circuit 422 to generate a pulse width modulation signal. To control the power switch 351 of the galvanically isolated DC-DC converter 35.

FIG. 4C is a block diagram showing the electrically isolated DC-DC converter 35 of the preferred embodiment of the present invention when the load 36 is a battery pack. Referring to FIG. 4C, the electrically isolated DC-DC converter 35 employs a third control block architecture 43. The third control block architecture 43 includes a battery current processing unit 431, a battery voltage processing unit 432, a selection switch 433, and a pulse width modulation circuit 434. The battery current processing unit 431 includes a current detector 4311, a subtractor 4312, and a proportional integral controller 4313. The battery voltage processing unit 432 includes a voltage detector 4321, a subtractor 4322, and a proportional integral controller 4323.

Referring to FIGS. 3 and 4C again, the current detector 4311 is configured to detect the battery pack input current, and send the set current of the battery pack to the output of the current detector 4311 to the subtractor 4312. The output of the subtractor 4312 is sent to the proportional integral controller 4313. The voltage detector 4321 is configured to detect an input voltage of the battery pack, and send the battery set voltage to the output of the voltage detector 4321 to be subtracted from the subtractor 4322. The output of the subtractor 4322 is sent to the proportional integral controller 4323. The output of the proportional-integral controller 4313 and the output of the proportional-integral controller 4323 are sent to the selection opening 433, and the selection switch 433 is executed according to the current control mode, and the charging of the battery pack can be selectively performed or Constant voltage charging. When the selection switch 433 selects the output of the proportional-integral controller 4313, constant current charging can be performed; when the selection switch 433 selects the output of the proportional-integral controller 4323, constant-voltage charging can be performed. The output of the selection switch 433 is sent to the pulse width modulation circuit 434 to generate a pulse width modulation signal for controlling the power switch 351 of the electrically isolated DC-DC converter 35.

FIG. 4D is a block diagram showing the power buffer 34 of the preferred embodiment of the present invention. Referring to FIG. 4D, the power buffer 34 employs a fourth control block architecture 44. The fourth control block architecture 44 includes a voltage detector 441, an absolute value circuit 442, a comparator 443, and a switching signal generator 444.

Referring to FIGS. 3 and 4D again, after the AC input voltage source 31 is detected by the voltage detector 441, the voltage of the AC input voltage source 31 is sent to the absolute value circuit 442, and the absolute value circuit 442 is used. The output and a set value are sent to the comparator 443, and the output of the comparator 443 is sent to the switch signal generator 444, and the switch signal generator 444 is used to control the power switch 341 of the power buffer 34 and Power switch 342.

The foregoing preferred embodiments are merely illustrative of the invention and the technical features thereof, and the techniques of the embodiments can be carried out with various substantial equivalent modifications and/or alternatives; therefore, the scope of the invention is subject to the appended claims. The scope defined by the scope shall prevail. The copyright limitation of this case is used for the purpose of patent application in the Republic of China.

3‧‧‧AC-DC power conversion device

31‧‧‧AC input voltage source

32‧‧‧Rectifier

33‧‧‧Boost DC-DC Converter

331‧‧‧Inductors

332‧‧‧Power switch

333‧‧‧ diode

34‧‧‧Electric energy buffer

341‧‧‧Power switch

342‧‧‧Power switch

343‧‧‧Filter capacitor

344‧‧‧Filter capacitor

345‧‧‧ diode

35‧‧‧DC-DC converter with electrical isolation

351‧‧‧Power switch

352‧‧‧Transformer

353‧‧‧ diode

354‧‧‧ diode

355‧‧‧Inductors

356‧‧‧Filter capacitor

36‧‧‧load

4‧‧‧ Controller

Claims (10)

An AC-DC power conversion device includes: a rectifier connected to an AC input voltage source, the AC input voltage source supplies an input voltage; and a step-up DC-DC converter connected to the rectifier The step-up DC-DC converter comprises a power switch; an energy buffer connected to the step-up DC-DC converter, the power buffer comprising two filter capacitors; and an electrically isolated DC-DC converter And a controller coupled to control the step-up DC-DC converter, the power buffer, and the DC-DC converter with electrical isolation; wherein the power buffer utilizes the AC When the input voltage of the input voltage source is greater than a set value, the two filter capacitors of the power buffer are operated in series connection, and at this time, the step-up DC-DC converter boosts the input voltage to the power buffer. a first voltage; when the input voltage of the AC input voltage source is lower than the set value, the two filter capacitors of the power buffer are The connection mode is operated. At this time, the step-up DC-DC converter boosts the input voltage to a second voltage of the power buffer, so that the output voltage of the power buffer is divided into two different voltage levels. In order to reduce the duty cycle of the power switch of the step-up DC-DC converter when the voltage of the AC input voltage source is low. The AC-DC power conversion device according to claim 1, wherein the controller comprises a voltage outer loop processing unit, a current inner loop processing unit and a pulse width modulation circuit for boosting The DC-DC converter is operated; the voltage external loop processing unit comprises a voltage detector, a waveform generating circuit, an absolute value circuit, a voltage detector, a filter capacitor setting voltage, a subtractor, and a proportional integral control. And a multiplier, and the current inner loop processing unit comprises a current detector, a subtractor and a proportional integral controller. The AC-DC power conversion device according to claim 1, wherein the controller comprises a load voltage processing unit and a pulse width modulation circuit for connecting the electrically isolated DC-DC converter The control is performed during a DC load; the load voltage processing unit includes a voltage detector, a load setting voltage, a subtractor, and a proportional integral controller. The AC-DC power conversion device according to claim 1, wherein the controller comprises a battery current processing unit, a battery voltage processing unit, a selection switch and a pulse width modulation circuit, so that The galvanically isolated DC-DC converter is controlled when a battery pack is connected; the battery current processing unit includes a current detector, a subtractor and a proportional integral controller, and the battery voltage processing unit includes a voltage A detector, a subtractor and a proportional integral controller. The AC-DC power conversion device according to claim 1, wherein the controller comprises a voltage detector, an absolute value circuit, a comparator and a switch signal generator for controlling the power buffer . An AC-DC power conversion control method includes: detecting an input voltage of an AC input voltage source; determining that an input voltage of the AC input voltage source is higher or lower than a set value; and inputting an input voltage of the AC input voltage source Above the set value, two filter capacitors of an electric energy buffer are operated in series connection, and the input voltage is boosted to a first voltage of the electric energy buffer by using a step-up DC-DC converter. And when the input voltage of the AC input voltage source is lower than the set value, the two filter capacitors of the power buffer are operated in parallel connection, and the input voltage is boosted by the step-up DC-DC converter a second voltage to the one of the power buffers; wherein the output voltage of the power buffer is divided into two different voltage levels to reduce the boost when the voltage of the AC input voltage source is low The duty cycle of one of the DC-DC converters. According to the AC-DC power conversion control method described in claim 6, wherein a controller includes a voltage outer loop processing unit, a current inner loop processing unit, and a pulse width modulation circuit, so that The step-up DC-DC converter is controlled; the voltage external loop processing unit comprises a voltage detector, a waveform generating circuit, an absolute value circuit, a voltage detector, a filter capacitor setting voltage, a subtractor, A proportional integral controller and a multiplier, and the current inner loop processing unit includes a current detector, a subtractor and a proportional integral controller. According to the AC-DC power conversion control method described in claim 6, wherein a controller is provided, which comprises a load voltage processing unit and a pulse width modulation circuit for DC isolation of an electrical isolation- The DC converter is controlled when the load is always flowing; the load voltage processing unit includes a voltage detector, a load setting voltage, a subtractor, and a proportional integral controller. According to the AC-DC power conversion control method described in claim 6, wherein a controller includes a battery current processing unit, a battery voltage processing unit, a selection switch, and a pulse width modulation a circuit for controlling when an electrically isolated DC-DC converter is coupled to a battery pack; the battery current processing unit includes a current detector, a subtractor, and a proportional integral controller, the battery pack voltage processing The unit includes a voltage detector, a subtractor, and a proportional integral controller. According to the AC-DC power conversion control method described in claim 6, wherein a controller includes a voltage detector, an absolute value circuit, a comparator and a switching signal generator for the electric energy The buffer is manipulated.