CN-122026726-A - Isolation DC-DC circuit capable of eliminating ripple current and control method thereof

CN122026726ACN 122026726 ACN122026726 ACN 122026726ACN-122026726-A

Abstract

The invention relates to an isolation DC-DC circuit capable of eliminating ripple current and a control method thereof, comprising an isolation transformer, a high-voltage DC circuit and a low-voltage DC circuit, wherein the low-voltage DC circuit comprises a first low-voltage DC circuit or a second low-voltage DC circuit; when the impedance of the first low-voltage loop and the impedance of the second low-voltage loop in the low-voltage direct-current circuit are equal or the difference is smaller, the seventh switching tube and the eighth switching tube are always conducted, and the second low-voltage direct-current circuit is equivalent to the first low-voltage direct-current circuit. When the impedance is unequal or the difference is larger, the current of the first inductor and the current of the second inductor are regulated by controlling the PWM duty ratio of the seventh switching tube and the eighth switching tube until the regulated current of the first inductor is equal to the regulated current of the second inductor, the output current is almost free from ripple after superposition, the output ripple current and systematic loss are effectively reduced, and the voltage peak is reduced by arranging an active clamping branch in a low-voltage direct-current circuit, so that the stability is effectively improved.

Inventors

LIU BO
FAN ZHIMING
CHEN RIZHI

Assignees

深圳深川电源技术有限公司

Dates

Publication Date: 20260512
Application Date: 20260109

Claims (10)

1. An isolated DC-DC circuit capable of eliminating ripple current is characterized by comprising an isolated transformer, wherein the isolated transformer comprises a plurality of windings, the windings are respectively connected with a high-voltage direct current circuit or a low-voltage direct current circuit, and the low-voltage direct current circuit comprises a first low-voltage direct current circuit or at least a second low-voltage direct current circuit; the first low-voltage direct current circuit comprises a ninth switching tube, a tenth switching tube, a fifth capacitor, a first inductor and a second inductor; the second low-voltage direct current circuit comprises a seventh switching tube, an eighth switching tube, a ninth switching tube, a tenth switching tube, a fifth capacitor, a first inductor and a second inductor; the seventh switching tube, the ninth switching tube, the first inductor and the fifth capacitor form a first low-voltage branch, and the eighth switching tube, the tenth switching tube, the second inductor and the fifth capacitor form a second low-voltage branch, wherein the first low-voltage branch and the second low-voltage branch share the fifth capacitor; The seventh switching tube, the first inductor, the fifth capacitor, the tenth switching tube, and the eighth switching Guan Xingcheng first low-voltage loop, the eighth switching tube, the second inductor, the fifth capacitor, the ninth switching tube, and the seventh switching Guan Xingcheng second low-voltage loop; When the impedance in the first low-voltage loop and the impedance in the second low-voltage loop are not equal or the difference is larger, the current of the first inductor and the current of the second inductor are regulated by controlling the PWM duty ratio of the seventh switching tube and the eighth switching tube, so that an active ripple current eliminating mode is formed, and when the impedance in the first low-voltage loop and the impedance in the second low-voltage loop are equal or the difference is smaller, the seventh switching tube and the eighth switching tube are all in an on state all the time, and the second low-voltage direct current circuit is equivalent to the first low-voltage direct current circuit, so that a passive ripple current eliminating mode is formed.
2. An isolated DC-DC circuit as claimed in claim 1, wherein when the isolation transformer comprises two windings, the windings comprise a first winding and a second winding, the first winding being connected to the high voltage DC circuit, and the second winding being connected to the first low voltage DC circuit or the second low voltage DC circuit.
3. An isolated DC-DC circuit capable of removing ripple current according to claim 1, wherein when the isolating transformer comprises more than two windings, there is one of the windings connected to the high voltage DC circuit, and a plurality of the windings are correspondingly connected to a plurality of the second low voltage DC circuits.
4. The isolated DC-DC circuit capable of eliminating ripple current according to claim 2, wherein the first low-voltage branch circuit and the second low-voltage branch circuit are connected in parallel in a staggered manner and are connected to two ends of the second winding, the second winding is an input end of the first low-voltage DC circuit or the second low-voltage DC circuit, and two ends of the fifth capacitor are output ends of the first low-voltage DC circuit or the second low-voltage DC circuit and form a low-voltage DC port.
5. The isolated DC-DC circuit of claim 4, wherein the first low voltage DC circuit and the second low voltage DC circuit each comprise a fifth switching tube, a third capacitor, a sixth switching tube, and a fourth capacitor, the fifth switching tube and the third capacitor forming a first active clamp branch, the sixth switching tube and the fourth capacitor forming a second active clamp branch, the first active clamp branch and the second active clamp branch being located at opposite ends of the second winding, respectively, and configured to suppress voltage spikes.
6. The isolated DC-DC circuit capable of eliminating ripple current according to claim 5, wherein the high-voltage DC circuit comprises a first bridge arm, a second bridge arm, a first capacitor and a second capacitor, the first bridge arm comprises a first switch tube and a second switch tube, the second bridge arm comprises a third switch tube and a fourth switch tube, the second capacitor is connected with the first winding, the second capacitor and the first winding are both located between the first bridge arm and the second bridge arm, the first capacitor is connected with the first bridge arm and the second bridge arm in parallel, two ends of the first capacitor are input ends of the high-voltage DC circuit and form a high-voltage DC port, and the first winding is an output end of the high-voltage DC circuit.
7. The isolated DC-DC circuit of claim 6, wherein the PWM control logic of the first and second switching transistors are opposite and dead time is set, the PWM control logic of the third and fourth switching transistors are opposite and dead time is set, and the PWM control logic of the first and third switching transistors have a phase difference of 0 to 180 degrees to control the current direction of the second winding.
8. The isolated DC-DC circuit of claim 7, wherein PWM control logic of the ninth switching tube and the tenth switching tube are opposite and dead time is set, wherein the fifth switching tube is turned on during a period in which the first switching tube and the fourth switching tube are simultaneously turned on and is turned off before the first switching tube and the fourth switching tube are turned off, and wherein the sixth switching tube is turned on during a period in which the second switching tube and the third switching tube are simultaneously turned on and is turned off before the second switching tube and the third switching tube.
9. The control method of the isolated DC-DC circuit capable of eliminating ripple current is characterized by comprising the following steps: s1, determining the number of windings in a preset isolation transformer; S2, determining the type and the number of preset low-voltage direct current circuits, wherein the low-voltage direct current circuits comprise a first low-voltage direct current circuit or a second low-voltage direct current circuit; S3, electrically connecting the isolation transformer, the low-voltage direct current circuit and a preset high-voltage direct current circuit; S4, respectively connecting a preset current sampling circuit with a preset first inductor and a preset second inductor in the low-voltage direct current circuit, wherein the current sampling circuit is used for respectively collecting currents of the first inductor and the second inductor and obtaining a first sampling current and a second sampling current; s5, inputting high-voltage direct current to a high-voltage direct current port preset in the high-voltage direct current circuit; s6, performing preset PWM logic control on preset switching tubes in the low-voltage direct current circuit and the high-voltage direct current circuit through a preset controller; s7, outputting low-voltage direct current through a low-voltage direct current port preset in the low-voltage direct current circuit.
10. The method for controlling an isolated DC-DC circuit capable of eliminating ripple current according to claim 9, wherein the step of performing a preset PWM logic control on preset switching tubes in the low voltage DC circuit and the high voltage DC circuit by a preset controller further comprises: Judging whether the low-voltage direct current circuit is the second low-voltage direct current circuit or not through the controller; If so, the controller controls PWM duty ratios of a seventh switching tube and an eighth switching tube preset in the second low-voltage direct-current circuit according to the first sampling current and the second sampling current so that the first sampling current and the second sampling current are equal, and the output current is almost free from ripple after superposition.

Description

Isolation DC-DC circuit capable of eliminating ripple current and control method thereof Technical Field The invention relates to the technical field of power electronics, in particular to an isolated DC-DC circuit capable of eliminating ripple current and a control method thereof. Background With the continuous increase of global power demand, the rapid development of industries such as AIDC (automatic identification and data acquisition), energy storage, new energy automobiles and the like, the indexes such as energy efficiency, power density, reliability and the like of power switching power supply products are highly focused by industry experts. In the new energy automobile industry, the industry puts forward higher and higher requirements on the input and output range, reliability, conversion efficiency, power density, EMC (electromagnetic compatibility) and other characteristics of the vehicle-mounted power supply, and the high standard of the system level also promotes the industry engineers to continuously optimize the top-layer topology structure of the power supply module and the control mode thereof to meet the current market demands. In the existing isolated DC-DC (direct current-direct current) power supply converter technology, two most commonly used isolated DC-DC conversion circuit topologies are LLC resonant topology and phase-shifting full-bridge topology, LLC topology conversion efficiency is highest, but LLC topology cannot meet the wide-range input condition of a vehicle-mounted power battery, so that an isolated DC-DC conversion topology of a new energy automobile generally adopts a phase-shifting full-bridge architecture, an internal high-frequency transformer of the new energy automobile generally adopts a central spindle nose type, but peak current is larger in the working process of the phase-shifting full-bridge topology, magnetic core loss, switching loss and conduction loss of a switching tube become larger along with the peak current, conversion efficiency is lower than that of the LLC topology, and the cruising mileage of the new energy automobile is influenced to a certain extent; in addition, as the switching-off instant current of the phase-shifting full bridge is larger than that of the LLC topology and the soft switching state cannot be entered in the full load range, dv/dt (voltage change rate) and di/dt (current change rate) are larger in the high-frequency switching process, and EMC characteristics are relatively poorer, a better filter circuit is required to meet the EMC characteristic requirements, meanwhile, the voltage stress of the low-voltage port synchronous rectification switch tube is increased due to the larger dv/dt, di/dt and leakage inductance of the transformer, the reliability of the phase-shifting full bridge topology power converter is further influenced, and the systematic technical problems are determined by the topology structure of the phase-shifting full bridge and the control mode of the phase-shifting full bridge, so that how to improve the conversion efficiency of the phase-shifting full bridge topology, ensure the reliability, improve the power density and improve the EMC characteristics are the problems which are needed to be solved by the industry. Disclosure of Invention The invention aims to solve the technical problems of large loss and poor reliability, and provides an isolated DC-DC circuit capable of eliminating ripple current and a control method thereof aiming at the defects of the existing phase-shifting full-bridge topology circuit technology. The technical scheme adopted for solving the technical problems is as follows: An isolation DC-DC circuit capable of eliminating ripple current is constructed, wherein the isolation DC-DC circuit comprises an isolation transformer, the isolation transformer comprises a plurality of windings, the windings are respectively connected with a high-voltage direct current circuit or a low-voltage direct current circuit, and the low-voltage direct current circuit comprises a first low-voltage direct current circuit or at least a second low-voltage direct current circuit; the first low-voltage direct current circuit comprises a ninth switching tube, a tenth switching tube, a fifth capacitor, a first inductor and a second inductor; the second low-voltage direct current circuit comprises a seventh switching tube, an eighth switching tube, a ninth switching tube, a tenth switching tube, a fifth capacitor, a first inductor and a second inductor; the seventh switching tube, the ninth switching tube, the first inductor and the fifth capacitor form a first low-voltage branch, and the eighth switching tube, the tenth switching tube, the second inductor and the fifth capacitor form a second low-voltage branch, wherein the first low-voltage branch and the second low-voltage branch share the fifth capacitor; The seventh switching tube, the first inductor, the fifth capacitor, the tenth switching tube, and the ei