TW201909530A - Isolated high step-down buck converter - Google Patents

Abstract

An isolated high step-down buck converter is used to solve the problem of conventional buck converters that cannot achieve both high step-down and high overall conversion rate. The isolated high step-down buck converter includes a buck conversion module and an isolated transformer module. The buck conversion module includes an energy storage inductor accepting an input voltage and charging a first energy storage capacitor. The first energy storage capacitor charges a second energy storage capacitor. A first coupling coil is charged by the first energy storage capacitor and the second energy storage capacitor by turns and generates an induced magnetic field. The isolated transformer module includes a second coupling coil and a third coupling coil. Each of the second and third coupling coils has mutual induction with the first coupling coil. The second and third coupling coils generate an induced current and are electrically connected to an output inductor to convert the induced current into an output voltage. The buck conversion module and the isolated transformer module are separated by electrical isolation.

Description

 Isolated high buck converter  

The present invention relates to an isolated high buck converter, and more particularly to an isolated high buck converter with high buck and high conversion efficiency.

The conventional transformer is used for the voltage rise and fall of the alternating current, which is composed of an iron core wound around the primary coil and the secondary coil respectively, and the principle is that a varying voltage is generated in the primary coil by a varying voltage, and is transmitted to the secondary coil via the iron core. A correspondingly varying electromotive force is generated, and the ratio of the input voltage to the output voltage is equal to the ratio of the number of primary coil turns to the number of turns of the secondary coil. However, conventional transformers used for DC voltage transformation require DC to AC processing, which increases the component cost of the circuit and the energy consumption of the conversion process. In addition, in order to achieve the high voltage drop requirement, it is necessary to increase the coil turns ratio and reduce The coupling coefficient of the coil causes energy loss of the leakage inductance and reduces the overall conversion rate.

Another conventional buck converter is a switch that controls the current through an inductor. When the switch is turned on, the current of the inductor increases and generates an electromotive force that resists the input voltage, causing the output voltage to decrease; when the switch is open, the inductor is turned on. The current drops and is equivalent to the power supply providing the output voltage. However, the conventional buck converter has a limited step-down rate. To achieve high buck demand, more than two buck converters need to be used in series, and the energy loss in the process is accumulated to reduce the overall conversion rate.

In view of this, the conventional buck converter does have the need to improve.

In order to solve the above problems, the present invention provides an isolated high buck converter suitable for DC power conversion, and adopts a low turns ratio, which can effectively achieve high buck and high overall conversion rate.

The isolated high-voltage step-down converter of the present invention comprises: a step-down conversion module, wherein the step-down conversion module has a first power switch electrically connected to a storage inductor end and a flywheel diode negative pole, The anode of the flywheel diode is electrically connected to a second power switch and a cathode of the first switching energy storage capacitor, and the other end of the energy storage inductor is electrically connected to the anode of the first switching energy storage capacitor and a third power switch. a non-circular end of the first coupling coil is electrically connected to a positive pole of a second switching energy storage capacitor, the second power switch, the third power switch, and the second switching port The negative pole of the capacitor is electrically connected to a first ground end, and the first coupling coil is wound around an iron core; an isolated transformer module, the isolated transformer module has a second coupling coil and a first a three-coupling coil, the non-circular end of the second coupling coil and the dot end of the third coupling coil are electrically connected, and the dot end of the second coupling coil is electrically connected to the positive end of the first rectifying diode The non-dot end of the third coupling coil is electrically connected a positive end of the second rectifying diode, a negative end of the first rectifying diode and a negative end of the second rectifying diode are electrically connected to one end of the output inductor, and the other end of the output inductor is electrically connected One end of the output capacitor and one end of the output resistor, the other end of the output resistor, the negative pole of the output capacitor, the non-circular end of the second coupling coil, and the dot end of the third coupling coil are electrically connected to a second a grounding end, the second coupling coil and the third coupling coil are wound around the core; and a control unit electrically connecting the first power switch, the second power switch and the third power switch The step-down conversion module is electrically isolated from the isolated transformer module, and the first ground terminal and the second ground terminal do not share a ground conductor.

Accordingly, the isolated high-voltage buck converter of the present invention can effectively reduce the voltage on the primary side of the transformer, and the low-turn ratio coupling coil can achieve the purpose of high voltage reduction, and the primary side coil and the secondary side are improved. The coupling coefficient of the coil reduces leakage inductance, so that the invention can achieve high voltage reduction, high conversion efficiency, and component parameter selection flexibility.

The control unit generates a first pulse width modulation signal and a second pulse width modulation signal. In this way, it has the function of controlling the charge and discharge of each energy storage inductor and capacitor.

The first pulse width modulation signal and the second pulse width modulation signal have the same cycle period. In this way, the parameter values of the components vary according to a fixed cycle, and have the effect of stabilizing the output voltage.

The phase difference between the first pulse width modulation signal and the second pulse width modulation signal is half of the cycle period. In this way, each of the energy storage inductors and capacitors is charged and discharged for the same time in each half cycle, and has the effect of stabilizing the output voltage.

The first power switch, the second power switch, and the third power switch are metal oxide semiconductor field effect transistors. In this way, each power switch can receive a pulse width modulation signal, and has the function of controlling charging and discharging of each energy storage inductor and capacitor.

The withstand voltage of the second power switch and the third power switch is lower than the input voltage. In this way, the second power switch and the third power switch are subjected to low voltage stress, which has the effect of saving component cost.

The number of turns of the first coupling coil is a multiple of the number of turns of the second coupling coil and the third coupling coil, and the number of turns of the second coupling coil and the third coupling coil is the same. In this way, the induced voltage of the first coupling coil is several times higher than the induced voltage of the second coupling coil and the third coupling coil, and the induced voltages of the second coupling coil and the third coupling coil are equal. The effect of stabilizing the output voltage.

Among them, the hysteresis curve of the iron core works through the first and third quadrants. In this way, the utilization rate of the iron core can be improved, which has the effect of reducing the core volume and saving component costs.

1‧‧‧Buck conversion module

11‧‧‧First power switch

12‧‧‧ Storage inductance

13‧‧‧Flywheel diode

14‧‧‧second power switch

15‧‧‧First switching storage capacitor

16‧‧‧ Third power switch

17‧‧‧First coupled coil

18‧‧‧Second switched storage capacitor

2‧‧‧Isolated transformer module

21‧‧‧Second coupling coil

22‧‧‧ Third Coupling Coil

23‧‧‧First rectifying diode

24‧‧‧Secondary rectifier diode

25‧‧‧Output inductance

26‧‧‧Output capacitor

27‧‧‧Output resistance

3‧‧‧Control unit

Vi‧‧‧ input voltage

Vo‧‧‧ output voltage

G1‧‧‧first ground

G2‧‧‧second ground

P1‧‧‧First pulse width modulation signal

P2‧‧‧second pulse width modulation signal

Ia‧‧‧ Energy storage inductor current

Ib‧‧‧first induced current

Ic‧‧‧second induced current

Id‧‧‧ third induced current

Io‧‧‧ output current

Figure 1 is a circuit diagram of an embodiment of the present invention.

Fig. 2 is a timing chart showing changes in parameters of circuit elements according to an embodiment of the present invention.

Fig. 3 is a view showing the operation state of the circuit of the embodiment of the present invention at the stage t0~t1.

Fig. 4 is a view showing the operation state of the circuit of the embodiment of the present invention at the stage t1 to t2.

Fig. 5 is a view showing the operation state of the circuit of the embodiment of the present invention at the stage t2 to t3.

Figure 6 is a diagram showing the operation state of the circuit of the embodiment of the present invention at the stage t3~t4.

Figure 7 is a diagram showing the operation state of the circuit of the embodiment of the present invention at the stage t4~t5.

Figure 8 is a diagram showing the operation state of the circuit of the embodiment of the present invention at the stage of t5~t6.

Figure 9 is a diagram showing the operation state of the circuit of the embodiment of the present invention at the stage t6~t7.

Fig. 10 is a view showing the operation state of the circuit of the embodiment of the present invention at the stage t7~t8.

The above and other objects, features, and advantages of the present invention will become more apparent from the aspects of the appended claims. The first embodiment of the isolated high-voltage buck converter of the present invention comprises a step-down conversion module 1, an isolated transformer module 2 and a control unit 3, and the step-down conversion module 1 is integrated. And the isolated voltage transformer module 2, the input voltage Vi is electrically connected to the buck conversion module 1, and the output voltage Vo is obtained by the isolated transformer module 2, and the control unit 3 is electrically connected to the buck conversion mode Group 1.

The step-down conversion module 1 has a first power switch 11 , an energy storage inductor 12 , a flywheel diode 13 , a second power switch 14 , a first switching energy storage capacitor 15 , and a third power switch 16 . a first coupling coil 17 and a second switching energy storage capacitor 18, the first power switch 11 is electrically connected to the anode of the input voltage Vi, and the source is electrically connected to one end of the energy storage inductor 12 and The anode of the flywheel diode 13 is electrically connected to the anode of the second power switch 14 and the cathode of the first switching storage capacitor 15, and the other end of the energy storage inductor 12 is electrically Connected to the anode of the first switching storage capacitor 15 , the drain of the third power switch 16 and the dot end of the first coupling coil 17 , the non-dot end of the first coupling coil 17 is electrically connected to the first Switching the anode of the storage capacitor 18, the drain of the second power switch 14, the source of the third power switch 16, the cathode of the second switched storage capacitor 18, and the cathode of the input voltage Vi are electrically connected to a first grounding terminal G1, the first power switch 11, the second power switch 14, and the third power The off 16 can be a metal oxide semiconductor field effect transistor.

The isolated transformer module 2 has a second coupling coil 21, a third coupling coil 22, a first rectifying diode 23, a second rectifying diode 24, an output inductor 25, and an output capacitor 26. And an output resistor 27, the non-circular end of the second coupling coil 21 and the dot end of the third coupling coil 22 are electrically connected, and the dot end of the second coupling coil 21 is electrically connected to the first rectifying The non-circular end of the third coupling coil 22 is electrically connected to the positive terminal of the second rectifying diode 24, the negative terminal of the first rectifying diode 23 and the second rectifying diode The negative terminal of the body 24 is electrically connected to one end of the output inductor 25. The other end of the output inductor 25 is electrically connected to the anode of the output capacitor 26 and one end of the output resistor 27. The other end of the output resistor 27, the output The anode of the capacitor 26, the non-circular end of the second coupling coil 21, and the dot end of the third coupling coil 22 are electrically connected to the second ground terminal G2.

The control unit 3 generates a Pulse Width Modulation (PWM) signal and outputs the signal to the buck conversion module 1. A first pulse width modulation signal P1 is output to the gate of the first power switch 11 and the gate A gate of the second power switch 14 and a second pulse width modulation signal P2 are output to the gate of the third power switch 16.

The first coupling coil 17 is a primary side of the transformer, and the secondary side of the second coupling coil 21 and the third coupling coil 22 are wound around an iron core, and the number of turns of the first coupling coil 17 is The number of turns of the second coupling coil 21 and the third coupling coil 22 is the same, the number of turns of the second coupling coil 21 and the third coupling coil 22 is the same, and the primary side and the secondary side are electrically insulated. The step-down conversion module 1 and the isolated transformer module 2 are electrically isolated. The first ground terminal G1 and the second ground terminal G2 do not share a ground conductor and have different potentials.

The withstand voltage of the second power switch and the third power switch is lower than the input voltage, and the second power switch and the third power switch are subjected to low voltage stress, thereby saving component cost.

Referring to the first and second figures, the control unit 3 provides the first pulse width modulation signal and the second pulse width modulation signal according to the same cycle period, the first pulse width modulation signal and the second pulse. The phase difference of the width modulation signal is half of the cycle period, so that the step-down conversion module 1 and the isolated transformer module 2 operate, and the parameter values of each component are divided into eight stages of t0~t8 for one cycle. .

Referring to FIG. 2 to FIG. 4, the first pulse width modulation signal P1 is output to turn on the first power switch 11 and the second power switch 14 in the t0~t2 phase, and the second pulse width modulation signal P2 The zero output turns off the third power switch 16; the input voltage Vi turns on the energy storage inductor 12, causes the stored inductor current Ia to increase and generates the input voltage Vi of the induced voltage offset portion, and the energy storage inductor 12 is stored in a magnetic field; the flywheel diode 13 is reverse biased non-conducting; the first switching storage capacitor 15 is discharged to transfer energy to the first coupling coil 17 and the second switching storage capacitor 18 The first coupling coil 17 has a first induced current Ib to generate a varying magnetic field, and the second coupling coil 21 generates a second induced current Ic through the core transfer, and the third coupled coil 22 generates a third induced current. Id.

In the t0~t1 phase, the first induced current Ib is increased, and at the same time, the second induced current Ic is increased, the third induced current Id is decreased, and when the third induced current Id is decreased to zero current, the second rectified second The pole body 24 prevents a negative current from being generated, causes the third coupling coil 22 to stop operating, and enters a stage t1~t2. Due to the lack of the induced magnetic field of the third coupling coil 22, the first induced current Ib and the second induced current Ic rise. The high trend is slowing down.

Referring to FIG. 2, FIG. 5 and FIG. 6 , the first pulse width modulation signal P1 zero output causes the first power switch 11 and the second power switch 14 to be disconnected, and the second pulse width is adjusted. The zero output of the variable signal P2 turns off the third power switch 16; the energy storage inductor 12 stops accepting the input voltage Vi, causes the stored inductor current Ia to drop and generates a reverse induced voltage, and the energy storage inductor 12 releases energy. The first switching energy storage capacitor 15 stores energy in an electric field manner; the flywheel diode 13 is turned on in a forward bias.

In the t2~t3 phase, the first induced current Ib decreases, the second switched storage capacitor 18 stores energy in an electric field manner, and at the same time, the second induced current Ic decreases, and the third induced current Id rises when the first The induced current Ib drops to zero current, and the reverse bias of the second switching storage capacitor 18 stops the third power switch 16 from grounding, causing the first coupling coil 17 to stop operating, and enters the stage t3~t4, due to the lack of the first An induced magnetic field of the coupling coil 17, the second induced current Ic and the third induced current Id are decreased.

Referring to FIG. 2, FIG. 7 and FIG. 8 , in the stage of t4 to t6, the first pulse width modulation signal P1 zero output causes the first power switch 11 and the second power switch 14 to be disconnected, and the second pulse width is adjusted. The output signal P2 output turns on the third power switch 16; the stored energy inductor current Ia decreases, the energy storage inductor 12 releases energy, and the first switched energy storage capacitor 15 stores energy in an electric field manner; the flywheel diode 13 The second switching storage capacitor 18 is discharged to transfer energy to the first coupling coil 17; the first coupling coil 17 generates the first induced current Ib, which is transmitted through the core to make the first The second coupling coil 21 generates the second induced current Ic, and the third coupling coil 22 generates the third induced current Id.

During the period from t4 to t5, the first induced current Ib rises in the opposite direction, and at the same time, the second induced current Ic decreases, the third induced current Id rises, and when the second induced current Ic falls to zero current, the first A rectifying diode 23 prevents a negative current from being generated, causing the second coupling coil 21 to stop operating, and enters a stage t5~t6. Due to the lack of the induced magnetic field of the second coupling coil 21, the first induced current Ib and the third sensing The tendency for the current Ic to rise is slowed down.

Referring to the second, ninth, and tenth diagrams, the first pulse width modulation signal P1 zero output causes the first power switch 11 and the second power switch 14 to be disconnected, and the second pulse width is adjusted. The zero output of the variable signal P2 turns off the third power switch 16; the stored inductor current Ia decreases, the energy storage inductor 12 releases energy, and the first switched storage capacitor 15 stores energy by an electric field; the flywheel diode 13 is forward biased to conduct.

In the t6~t7 phase, the first induced current Ib decreases, the first switched storage capacitor 15 stores energy in an electric field manner, and at the same time, the second induced current Ic rises, and the third induced current Id decreases when the first The induced current Ib drops to zero current, and the reverse bias of the first switching storage capacitor 15 stops the second power switch 14 from grounding, causing the first coupling coil 17 to stop operating, and enters the stage of t7~t8, due to the lack of the first An induced magnetic field of the coupling coil 17, the second induced current Ic and the third induced current Id are decreased.

Referring to FIGS. 1 and 2, the output inductor 25 has an output current Io, which is a combination of the second induced current Ic and the third induced current Id. The duty cycle of the output current Io is the cycle of the control unit 3 Half of the output current Io is shunted to the output capacitor 26 and the output resistor 27, and an output voltage Vo is formed at the output resistor 27.

The energy storage inductor 12, the first switching energy storage capacitor 15 and the second switching energy storage capacitor 18 alternately release and store energy at different stages, halving the voltage applied to the first coupling coil 17, and passing The first induced current Ib is inverted twice in the cycle period.

The reversal of the first induced current Ib causes the direction of the induced magnetic field generated by the first coupling coil 17 to be alternately reversed, so that the hysteresis curve of the wound core is passed through the first and third quadrants, thereby improving the utilization of the core.

In summary, the isolated high-voltage buck converter of the present invention can effectively reduce the voltage on the primary side of the transformer, and the low-turn ratio coupling coil can achieve the purpose of high voltage reduction, and improve the primary side coil and the secondary. The coupling coefficient of the side coil reduces the leakage inductance, and the utilization of the core can reduce the core volume, and the same output frequency can be achieved in half the number of cycles, so that the invention can achieve high step-down and high conversion efficiency. Reduce the cost of components and the flexibility of component parameter selection.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

Claims (8)

 An isolated high-voltage step-down converter includes: a step-down conversion module having a first power switch electrically connected to a storage inductor end and a flywheel diode negative pole, the flywheel 2 The anode of the pole body is electrically connected to a second power switch and a cathode of the first switching energy storage capacitor, and the other end of the energy storage inductor is electrically connected to the anode of the first switching energy storage capacitor, a third power switch and a first a non-circular end of the first coupling coil is electrically connected to a positive pole of a second switching energy storage capacitor, the second power switch, the third power switch and the second switching energy storage capacitor The negative pole is electrically connected to a first grounding end, and the first coupling coil is wound around an iron core; an isolated transformer module having a second coupling coil and a third coupling a coil, the non-circular end of the second coupling coil and the dot end of the third coupling coil are electrically connected, and the dot end of the second coupling coil is electrically connected to the positive terminal of the first rectifying diode, The non-dot end of the third coupling coil is electrically connected a positive terminal of the rectifying diode, a negative terminal of the first rectifying diode and a negative terminal of the second rectifying diode are electrically connected to one end of the output inductor, and the other end of the output inductor is electrically connected to an output capacitor One end of the positive electrode and one output resistor, the other end of the output resistor, the negative pole of the output capacitor, the non-circular end of the second coupling coil, and the dot end of the third coupling coil are electrically connected to a second ground end The second coupling coil and the third coupling coil are wound around the core; and a control unit electrically connecting the first power switch, the second power switch and the third power switch, The step-down conversion module is electrically isolated from the isolated transformer module, and the first ground terminal and the second ground terminal do not share a ground conductor.    The isolated high buck converter of claim 1, wherein the control unit generates a first pulse width modulation signal and a second pulse width modulation signal.    The isolated high buck converter of claim 2, wherein the first pulse width modulation signal and the second pulse width modulation signal have the same cycle period.    The isolated high buck converter of claim 3, wherein the phase difference between the first pulse width modulation signal and the second pulse width modulation signal is half of a cycle period.    The isolated high buck converter of claim 1, wherein the first power switch, the second power switch, and the third power switch are metal oxide semiconductor field effect transistors.    The isolated high buck converter of claim 1, wherein the second power switch and the third power switch have a withstand voltage lower than the input voltage.    The isolated high buck converter according to claim 1, wherein the number of turns of the first coupling coil is several times the number of turns of the second coupling coil and the third coupling coil, and the second The coupling coil and the third coupling coil have the same number of turns.    The isolated high buck converter according to claim 1, wherein the magnetic hysteresis curve of the iron core passes through the first and third quadrants.