TWM449407U - Power converting device - Google Patents

Abstract

A power converting device includes a switching unit, a resonant unit, a converting unit, a rectifying and filtering unit, an inductance sensing unit and a driver. The resonant unit is electrically connected to the switching unit and includes a resonant capacitor, a resonant inductor and a variable magnetizing-inductor. The converting unit is electrically connected to the resonant unit, and the rectifying and the filtering unit is electrically connected to the converting unit. The inductance sensing unit is electrically connected to the rectifying the filtering unit for sensing the inductance of the variable magnetizing-inductor. The driver is electrically connected to the inductance sensing unit and the switching unit for controlling the switching frequency of the switching unit according to the inductance sensed by the inductance sensing unit.

Description

Power conversion device

This creation is about a power conversion device, especially a DC-DC power converter that can improve light load efficiency.

The DC-DC converter, as its name suggests, regulates the input DC power supply by adjusting the voltage level, including boosting and stepping down, and stabilizing the adjusted voltage to the set voltage value. The DC-DC converter is mainly used in a distributed power system, so that the power supply of the previous stage can be fixed to a voltage level, and the second stage can be connected to the corresponding DC-to-DC converter according to the individual power requirements of the system.
Among them, the DC-DC converter can be further divided into a Pulse Width Modulation (PWM) power converter and a resonant power converter. Since the switching of the pulse width modulation power converter is a hard switching, resulting in severe switching loss, the power conversion efficiency cannot be improved, so a resonant power converter is developed, and the resonant circuit itself has soft switching. Features, reduce switching loss and improve overall converter efficiency.
Among them, LLC resonant converter (LLC Resonant Converter) has zero-voltage switching (ZVS) and zero-current switching (ZCS) switching characteristics, so it will be considered in high-efficiency, high-power power supply circuits. Adopt LLC resonant circuit architecture.
Referring to the first figure, it is a circuit diagram of a conventional power supply device. The power supply device includes two switching elements Q1, Q2, a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2, a first diode D1, and a second two The body D2, a transformer T1 and a controller 50. The switching elements Q1, Q2 and the controller 50 cooperate to form a switching circuit for switching the DC voltage source VIN into a DC ripple signal. The DC ripple signal passes through the first capacitor C1, the first inductor L1 and the second inductor L2 to form a resonant network to generate resonance, and is transmitted to the secondary side of the voltage device T1 via the first diode The body D1, the second diode D2, and the second capacitor C2 are converted into a DC voltage supply load.
Referring to the second figure, it is an inductance value-current graph corresponding to the second inductor shown in the first figure. As can be seen from the second figure, in the non-magnetic saturation state, the inductance value of the second inductor L2 is substantially fixed, so when the power conversion device is under light load operation, the switching elements Q1, Q2 are switched. The frequency is to increase the switching frequency in order to stabilize the output voltage. However, the increase of the switching frequency will cause the power conversion device to be inferior in light load operation, as shown in the third figure, wherein the third figure shows the power supply. The frequency response curve of the conversion device under heavy load operation, and the solid line is the frequency response curve of the power conversion device under light load operation.

In view of the prior art, it is an object of the present invention to provide a power supply device that can improve light load efficiency.
To achieve the above objective, the present invention provides a power conversion device including a switching unit, a resonating unit, a converting unit, a rectifying and filtering unit, an inductance estimating unit and a driver; the resonating unit is electrically connected to the switching unit The resonant unit includes a resonant capacitor, a resonant inductor, and a variable excitation inductor; the conversion unit is electrically connected to the resonant unit, the rectifying and filtering unit is electrically connected to the conversion unit; and the inductance estimating unit is electrically connected The rectifying and filtering unit is configured to estimate an inductance value of the variable excitation inductor; the driver is electrically connected to the inductance estimation unit and the switching unit, and is controlled according to the inductance value estimated by the inductance estimation unit. The switching frequency of the switching unit.
The variable magnetizing inductance of the power conversion device of the present invention has at least two different inductance values, and the inductance estimating unit instantaneously estimates the inductance value of the variable excitation inductor, and transmits the inductance value To the driver, the driver controls the switching frequency of the switching unit according to the cut-off frequency value of the corresponding inductance value, so that the switching loss of the switching unit can be reduced, thereby improving the light load efficiency of the power conversion device.

Referring to the fourth figure, the circuit diagram of the power conversion device of the present invention. The power conversion device 10 is configured to adjust the voltage of one of the input DC power sources VIN, and the adjustment mode includes boosting or stepping down, and the adjusted voltage is stabilized at the set voltage value, and then output to a voltage. Load R. The power conversion device includes a switching unit 110, a resonating unit 120, a converting unit 130, a rectifying and filtering unit 140, an inductance estimating unit 150, a controller 160, and a driver 170.
The switching unit 110 is electrically connected to the DC power supply VIN and the driver 170. The switching unit 110 includes a plurality of switching elements 112 and a plurality of diodes D. The number of the diodes D is the same as that of the switching elements 112. The number is used and the diodes D are respectively connected in parallel to the switching elements 112. In this embodiment, the switching unit 110 is a half bridge switching circuit including two switching elements 112, and the switching elements 112 are electrically connected in series. In this embodiment, each of the switching elements 112 may be a metal-oxide-semiconductor field-effect transistor (MOSFET), and the diode is connected between the drain and the source of the MOSFET. Body D, or the diode D may be a parasitic diode of the MOSFET. In actual implementation, the switching unit 110 can also be a full-bridge switching circuit, and can be used in conjunction with other power switches having a switching function, such as an insulated gate bipolar transistor (IGBT). Each of the switching elements 112 is electrically coupled to the driver 170, and a signal is provided by the driver 170 to switch to an on state or an off state to generate a pulsating DC signal.
The resonant unit 120 is electrically connected to the switching unit 110 and located between the two switching elements 112 to receive a pulsating DC signal when the two switching elements 112 are alternately turned on and off. The resonant unit 120 includes a resonant capacitor Cr, a resonant inductor Lr, and a variable excitation inductor Lm. The resonant capacitor Cr is electrically connected in series to the resonant inductor Lr, which is connected in parallel to one of the primary windings Np of the converting unit 130. The resonant capacitor Cr forms a resonant circuit with the resonant inductor Lr and the variable excitation inductor Lm in addition to blocking a DC component passing through the pulsating DC signal. The variable excitation inductor Lm can be implemented as an external inductor as shown in the fourth figure, or the variable excitation inductor Lm can be the magnetization inductance of the conversion unit 130.
The variable excitation inductor Lm has at least two inductance values as shown in the sixth figure. The variable excitation inductor Lm has a relatively high inductance value and a relatively low inductance value, wherein the variable excitation inductor Lm has a light load operation (light current operation) when the power conversion device 10 is operated A relatively high inductance value, the variable magnetizing inductance Lm has a relatively low inductance value when the power conversion device is in a heavy load operation (high current operation).
Referring to the fourth figure, the conversion unit 130 is electrically connected to the resonating unit 120. The conversion unit 130 includes the primary side coil Np and a secondary side coil Ns for converting electrical energy into magnetic energy. The converted magnetic energy is transmitted to the secondary side coil Ns, which converts magnetic energy into electrical energy to achieve a task of boosting or stepping down. In this embodiment, the conversion unit 130 is a center tapped transformer.
The rectifying and filtering unit 140 is electrically connected to the converting unit 130. The rectifying and filtering unit 140 includes a rectifying circuit 142 and a filtering circuit 144. The rectifying circuit 142 includes two rectifying diodes Dr, and the rectifying diodes Dr are electrically connected to the secondary side coils Ns to form a center-tap full-wave rectifying circuit for converting alternating current into direct current having a high frequency pulsating component. . The filter circuit 144 includes a filter capacitor Cf for filtering out the high frequency ripple component and outputting a smooth direct current. The filter capacitor Cf is electrically connected to the rectifier diodes Dr and spans the output load.
The inductance estimation unit 150 is electrically connected to the rectification and filtering unit 140. The inductance estimation unit 150 is configured to estimate the inductance value of the variable excitation inductor Lm.
The controller 160 is electrically connected to the inductance estimating unit 150. The controller 160 uses the inductance value output by the inductance estimating unit 150 to calculate a switching frequency value corresponding to the switching frequency value, and transmits the switching frequency value to the electrical connection. The driver 170 of the controller 160 causes the driver 170 to switch the switching elements 112 of the switching unit 110 corresponding to the switching frequency value. The inductor estimation unit 150, the controller 160, and the driver 170 can be implemented as different units as shown in the fourth figure, or the inductor estimation unit 150, the controller 160, and the driver 170 can be integrated into one. Integrated circuit.
Referring to the fifth figure, it is an AC equivalent circuit diagram of the power conversion device corresponding to the fourth figure. In the fifth figure, the AC load impedance Rac is a group side load equivalent to the primary side of the conversion unit 130, and the output current Io is a current flowing through the AC impedance Rac.
The relationship between the output voltage Vo and the input voltage Vi can be derived by the equivalent circuit diagram of the power conversion device:

In the above formula, F is the ratio of the switching frequency fs to the resonance frequency fr, that is,

K is the ratio of the excitation inductor Lm to the resonant inductor Lr, ie

Also, switching the frequency variation And the amount of change in the magnetizing inductance Defined as:

Therefore, the switching frequency change rate And magnetizing inductance Relationship is


Referring to the seventh figure, the frequency response diagram of the power supply device of the present invention. The dotted line shows the frequency response curve of the power conversion device 10 under heavy load operation, and the solid line is the frequency response curve of the power conversion device 10 under light load operation. Since the variable excitation inductor Lm has at least two different inductance values and is respectively suitable for light load operation and heavy load operation, the switching of the switching elements 112 under light load operation can be reduced. The power loss further increases the light load efficiency of the power conversion device 10.
In summary, the variable magnetizing inductance Lm of the power conversion device 10 of the present invention has at least two different inductance values, and the inductance estimating unit 150 is used to estimate the variable excitation inductor Lm in real time. Inductance value, and the inductance value is transmitted to the controller 160, the controller 160 calculates a switching frequency value corresponding to the inductance value to cause the driver 170 to control the switching frequency of the switching unit 110 according to the switching frequency value, As a result, the switching loss of the switching unit 110 can be reduced, thereby improving the light load efficiency of the power conversion device.
However, the above is only a preferred embodiment of the present invention, and the scope of the present invention cannot be limited, that is, the equal changes and modifications made by the scope of the patent application of the present invention should still be covered by the patent of the present invention. The scope of the scope is intended to protect.

10‧‧‧Power conversion device
110‧‧‧Switch unit
112, Q1, Q2‧‧‧ switching components
120‧‧‧Resonance unit
130‧‧‧Transfer unit
140‧‧‧Rectifier and Filter Unit
142‧‧‧Rectifier circuit
144‧‧‧Filter circuit
150‧‧‧Inductance Estimation Unit
160, 50‧‧‧ controller
170‧‧‧ drive
Cr‧‧‧Resonance Capacitor
Cf‧‧‧Filter Capacitor
C1‧‧‧First Capacitor
C2‧‧‧second capacitor
Dr‧‧‧Rected Diode
D‧‧‧ diode
D1‧‧‧First Diode
D2‧‧‧ second diode
Io‧‧‧ output current
Lm‧‧‧Magnetic Inductors
Lr‧‧‧Resonant Inductors
L1‧‧‧First Inductor
L2‧‧‧second inductor
Np‧‧‧ primary side coil
Ns‧‧‧ secondary coil
R‧‧‧ load
Rac‧‧‧AC load impedance
T1‧‧‧ transformer

The first figure is a circuit diagram of a conventional power supply device.
The second figure is an inductance-current graph corresponding to the second inductor shown in the first figure.
The third figure is a frequency response diagram of a conventional power supply device.
The fourth figure is a circuit diagram of the power supply device of the present invention.
The fifth figure is an AC equivalent circuit diagram of the power conversion device corresponding to the fourth figure.
The sixth figure is a graph of the reactance-current curve corresponding to the variable excitation inductor shown in the third figure.
The seventh figure is a frequency response diagram of the power supply device of the present invention.

10‧‧‧Power conversion device

110‧‧‧Switch unit

112‧‧‧Switching components

120‧‧‧Resonance unit

130‧‧‧Transfer unit

140‧‧‧Rectifier and Filter Unit

142‧‧‧Rectifier circuit

144‧‧‧Filter circuit

150‧‧‧Inductance Estimation Unit

160‧‧‧ Controller

170‧‧‧ drive

Cr‧‧‧Resonance Capacitor

Cf‧‧‧Filter Capacitor

D‧‧‧ diode

Dr‧‧‧Rected Diode

Io‧‧‧ output current

Lm‧‧‧Magnetic Inductors

Lr‧‧‧Resonant Inductors

Np‧‧‧ primary side coil

Ns‧‧‧ secondary coil

R‧‧‧ load

Claims (8)

A power conversion device comprising:
a switching unit;
a resonant unit electrically connected to the switching unit, the resonant unit comprising a resonant capacitor, a resonant inductor and a variable excitation inductor;
a conversion unit electrically connected to the resonance unit;
a rectifying and filtering unit electrically connected to the converting unit;
An inductance estimating unit electrically connected to the rectifying and filtering unit for estimating an inductance value of the variable excitation inductor;
A driver is electrically connected to the inductance estimating unit and the switching unit, and estimates an inductance value according to the inductance estimating unit to control a switching frequency of the switching unit. The power conversion device of claim 1, wherein the variable excitation inductor has a large inductance value during light load operation, and the variable excitation inductor has a small inductance value during heavy load operation. The power conversion device of claim 1, wherein the rectifying and filtering unit comprises a rectifying circuit and a filtering circuit, the rectifying circuit is electrically connected to one of the secondary side coils of the converting unit, and the filtering circuit is electrically connected In the rectifier circuit. The power conversion device of claim 1, wherein the switching unit comprises at least two switching elements electrically connected to the respective switching elements. The power conversion device of claim 4, further comprising a dipole, each of the diodes being connected in parallel to each of the switching elements. The power conversion device of claim 1, wherein the resonant capacitor, the resonant inductor, and one of the primary side coils of the conversion unit are connected in series, and the variable excitation inductor and the primary side coil are connected in parallel. . The power conversion device of claim 1, wherein the conversion unit is a center tapped transformer. The power conversion device of claim 1, further comprising a controller electrically connected to the inductance estimating unit and the driver, wherein the controller uses an inductance estimation unit to output an inductance value to calculate a corresponding One switches the frequency value and the switching frequency value is passed to the drive.