DE-102024137972-A1 - POWER CONVERTER FOR AN ON-BOARD CHARGER FOR ELECTRIC VEHICLES

Abstract

An AC-DC converter for an onboard electric vehicle charger is described. The converter comprises a first circuit (102) with rectifier elements for rectifying input AC power into unregulated DC power, and the second circuit (104) comprises a common switching branch with at least one first switching element (S1) and one second switching element (S2), wherein the second circuit (104) is configured to convert the unregulated DC power into high-frequency AC power. The converter includes a third circuit (106) comprising an isolated DC-DC converter. Furthermore, the common switching branch forms a primary bridge of the isolated DC-DC converter. The third circuit (106) is configured to convert the high-frequency AC power into a target output DC voltage. The AC-DC converter utilizes the switch-sharing concept and operates in resonant mode to reduce switching losses and thereby achieve higher efficiency.

Inventors

• Surender Elumalai
• Arun Chandrasekharan Nair
• Jay PANDYA

Assignees

• Mercedes-Benz Group AG

Dates

Publication Date

20260513

Application Date

20241216

Priority Date

20241108

Claims (10)

1. Power converter for an on-board charger for electric vehicles, comprising: a first circuit (102) containing a plurality of rectifier elements for rectifying an input alternating current (AC) into an unregulated direct current (DC); a second circuit (104) electrically coupled to the first circuit (102), wherein the second circuit (104) comprises a common switching branch, the common switching branch comprising at least a first switching element (S1) and a second switching element (S2), wherein the second circuit (104) is configured to convert the unregulated DC power into high-frequency AC power; and a third circuit (106) electrically coupled to the second circuit (104), the third circuit (106) comprising: an isolated DC-DC converter, the common switching branch being formed on a primary bridge side of the isolated DC-DC converter, the third circuit (106) being configured to convert the high-frequency AC power into a target DC output voltage.
2. Power converters according to Claim 1 , wherein the common switching branch is operated alternately to transfer the high-frequency AC power between the second circuit (104) and the third circuit (106) on the basis of positive half-cycles and negative half-cycles of the input AC power.
3. Power converters according to Claim 1 , wherein the second circuit (106, 204) further comprises: a series choke (L3) connected to the common switching branch, the common switching branch comprising an upper sub-circuit and a lower sub-circuit, the upper sub-circuit being electrically connected to the lower sub-circuit to form a first junction (J1), the upper sub-circuit comprising the first switching element (S1) and a first capacitor (C P1 ), and the lower sub-circuit comprising the second switching element (S2) and a second capacitor (C P2 ), a first end of the series inductor (L3) being electrically connected to an output of the first circuit (104, 202) and a second end of the series inductor (L3) being electrically connected to the first junction (J1).
4. Power converters according to Claim 1 , wherein the isolated DC-DC converter comprises: a transformer having: a primary winding (L1) electrically connected to the common switching branch, and a secondary winding (L2) electromagnetically coupled to the primary winding (L1); and a secondary bridge configured as a voltage doubler, wherein the voltage doubler comprises: a first diode (D5), a second diode (D6), a third capacitor (C _S1 ) and a fourth capacitor (C _S2 ), and wherein: the secondary winding (L2) is electrically connected at one end to an anode of the first diode (D5) and a cathode of the second diode (D6); the secondary winding (L2) is electrically connected at another end to a first terminal of the third capacitor (C _S1 ) and a first terminal of the fourth capacitor (C _S2 ); a cathode of the first diode (D5) is electrically connected to a second terminal of the third capacitor (C _S1 ); and an anode of the second diode (D6) and a second terminal of the fourth capacitor (C S2 ) are electrically connected to a ground.
5. Power converters according to Claim 3 , wherein: during a first positive half-cycle and a first negative half-cycle of the AC input power: the first switching element (S1) is off and the second switching element (S2) is on, and when the second switching element (S2) is turned on, the target output DC voltage is generated based on a resonance produced by the lower sub-circuit and a secondary side of the isolated DC-DC converter, and during a second positive half-cycle and a second negative half-cycle of the AC input power: the first switching element (S1) is on and the second switching element (S2) is off, and when the first switching element (S1) is turned on, the target output voltage is generated based on a resonance produced by the upper sub-circuit, the lower sub-circuit and a secondary side of the isolated DC-DC converter.
6. Power converters according to Claim 1 , wherein the isolated DC-DC converter is configured to turn on the first switching element (S1) and the second switching element (S2) at zero voltage and to turn off the first switching element (S1) and the second switching element at zero current.
7. Power converters according to Claim 1 , wherein the first circuit (102) is a rectifier circuit, the second circuit (104) is a step-up circuit and the isolated DC-DC The converter is an integrated upward resonant converter.
8. A method for operating an AC-DC power converter, the method comprising: rectifying an AC input power into unregulated DC power; converting the unregulated DC power into high-frequency AC power based on alternating switching cycles connected to a common switching branch; and converting the high-frequency AC voltage into a target DC voltage, the common switching branch comprising a first switching element (S1) and a second switching element (S2).
9. Procedure according to Claim 8 , wherein the common switching branch is operated alternately to transfer the high-frequency AC power between a second circuit (104) and a third circuit (106) on the basis of positive half-cycles and negative half-cycles of the input AC power.
10. Procedure according to Claim 8 , wherein: during a first positive half-cycle and a first negative half-cycle of the AC input power: switching off the first switching element (S1) and switching on the second switching element (S2), and upon switching on the second switching element (S2), generating the target DC output voltage based on the creation of resonance by a lower sub-circuit and a secondary side of an isolated DC-DC converter, and during a second positive half-cycle and a second negative half-cycle of the AC input power: switching on the first switching element (S1) and switching off the second switching element (S2), and upon switching on the first switching element (S1), generating the target output voltage based on the creation of resonance by a lower sub-circuit and a secondary side of an isolated DC-DC converter.

Description

TECHNICAL AREA The present subject matter relates generally to the field of onboard charging topology and in particular, but not exclusively, to an alternating current (AC)/direct current (DC) energy converter for an onboard charger for electric vehicles. BACKGROUND The production and use of battery-powered electric vehicles, such as electric cars, including battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs), has increased recently with technological advancements. To use an AC charging station, these vehicles require onboard systems that convert the station's AC power to direct current (DC) to charge the batteries. These systems are often referred to as onboard chargers. Onboard chargers typically consist of three stages. The first stage may contain a diode bridge rectifier. The diode bridge rectifier converts an input alternating current into an unregulated direct current. The second stage may contain a booster cell. The booster cell is used to correct the power factor and shapes the waveform of the input current to meet mains standards. The third stage may contain an isolated DC-DC converter. The isolated DC-DC converter boosts the DC voltage to the requirements of the target vehicle's battery while ensuring galvanic isolation as required by safety standards such as those of the International Electrotechnical Commission (IEC). IEC) 61851-23 This is required. The boost cell, a crucial component in this architecture, typically consists of several components that contribute to the complexity and cost of the overall system. Consequently, existing battery charging technologies attempt to simplify the onboard charger by reducing or eliminating the components of the boost cell, using active components such as an active rectifier instead of the diode bridge rectifier. However, the use of active components increases the overall cost. One of the existing techniques described in the patent publication with the number US20210399643 The disclosed design provides for a single-stage power converter comprising an up-shift segment and a blocking segment, which share common switching devices to reduce the need for an additional switching stage. Another existing technique, described in patent publication no. CN201766508 The disclosed information concerns a single-phase full-bridge inverter in isolated form for power factor correction with soft-start charging circuit. Another existing technique, which is described in the patent publication JP2017163657 What is disclosed is a three-phase power converter for improving the power factor in order to balance the current of a single phase. Another existing technique, which is described in the patent publication CN203233307 What is revealed is a bridgeless forward correction of the power factor by controlling various switching tubes. Another existing technique, described in patent publication no. KR101776617 disclosed is a power factor corrector for converting electrical power from an alternating current source into direct current and for supplying a load with direct current. Another existing technique, which is described in the patent publication USRE44136 The disclosed document discloses methods and devices for the adaptive configuration of an array of voltage converter modules. However, there is still a need for an improved AC-DC converter for an onboard charger that reduces active switching components, cost, weight, space requirements and switching losses. The information disclosed in this section concerning the background of the disclosure is provided solely for a better understanding of the general background of the disclosure and is not to be understood as an acknowledgment or an indication that this information is part of the prior art already known to the person skilled in the art. SUMMARY OF THE DISCLOSURE The present disclosure overcomes one or more shortcomings of the prior art and offers additional advantages, which are explained herein. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered part of the claimed disclosure. The main purpose of this disclosure is to provide an AC-DC converter for an on-board electric vehicle charger that is capable of achieving soft switching with the fewest possible active switches. Another purpose of the revelation is to reduce the number of components, weight and space requirements by reducing the switching losses of the charger. Another task of the revelation is to utilize the switch-sharing concept to minimize the active switching components. Another objective of the disclosure is to provide a converter topology for AC-DC conversion with power factor correction and galvanic isolation. Another task of the revelation is to provide a converter topology that operates in resonance mode in order to reduce switching losses and thereby achieve higher efficiencies. Another task