FR2997579A1 - System i.e. single phase charger for charging car's battery, has secondary rectifier stage connected to secondary of transformer, and control unit to control inverter so as to generate rectified voltage at terminals of resonant circuit - Google Patents

Abstract

The system (SYS) has an input interface (1) to receive alternating current inlet voltage, and an inverter (2) connected to a primary insulation transformer (5) through a resonant circuit (4). A secondary rectifier stage (6) is connected to a secondary insulation transformer. A control unit (8) is configured to control the inverter in order to generate rectified voltage at terminals of the resonant circuit irrespective of sign of input voltage. A current sensor (CPT) measures a sign of the current circulating in the resonant circuit.

Description

The invention relates to battery chargers for a motor vehicle, and more particularly to single-phase battery chargers for a motor vehicle. In the development of low-cost electric vehicles, the charging system, like the electric powertrain (GMPe) or the battery, has a significant cost item that needs to be reduced to meet the overall target cost. . Currently, there are two major technological families for single-phase load. The first family includes insulated chargers, which contain an element (usually a transformer) isolating the high voltage network of the vehicle from the power grid from which it is recharged. The main advantage is to greatly limit the common mode disturbances conducted in the network. The disadvantages are the generally higher cost because of the greater complexity of the electronic circuit topology and the lower efficiency due to the need to add a conversion stage to ensure isolation. The second family includes uninsulated chargers, whose main advantages are cost and energy efficiency.

From the state of the art, the following documents are known: Document US 2010-0244773 discloses a charger which provides control of the power factor and the form factor of the current absorbed on the network at the cost of a yield and efficiency. an unsatisfactory cost because of the topology used.

WO95 / 34932 discloses a resonant charger comprising three series conversion stages (including a sinusoidal current absorption rectifier and power factor control (typically a Power Factor Corrector (PFC)) connected to the transformer primary) which limit the overall performance of the function. JP 2010-263683 discloses a dual resonance DC / DC function. However, to be applied to a charger, it must again add a rectifier sinusoidal current absorption and power factor control that degrades the overall efficiency of the conversion by inserting in series in the conversion chain. Associated with the electric powertrain, it is appropriate to associate a system of "slow recharge" that is to say that takes its energy on the single-phase network with a power less than or equal to 7kW (typically that absorbs 10A, 16A or 32A on the single-phase network and compatible with a domestic socket). According to one embodiment of the invention, there is provided a so-called resonance structure, capable of performing this function of "slow charging" while ensuring a galvanic isolation between the sector and the battery of the vehicle. The invention also proposes in particular to overcome a rectifier diode bridge connected to the primary of the transformer.

According to one aspect of the invention, it is thus proposed a charging system of a motor vehicle battery, comprising an input interface for receiving an AC input voltage, an inverter connected to the primary of a transformer of a motor vehicle. isolation via a resonant circuit, rectifying means and control means of the inverter. According to a general characteristic of this aspect, the rectifying means are only connected to the secondary of the isolation transformer and the control means are configured to control the inverter so as to generate across the resonant circuit a rectified voltage whatever the sign of the input voltage. Thus, the control mode of the inverter eliminates a rectifier diode bridge connected to the primary of the transformer. In other words, here any primary rectification stage is suppressed by the use of a specific control law of the inverter. According to one embodiment, the system further comprises means for measuring the sign of the current flowing in the resonant circuit and the inverter comprises four modules each comprising a controllable switch and an antiparallel diode. A first module is connected between a first input of the input interface and a first input of the resonant circuit with the cathode of the diode facing the input interface.

A second module is connected between a second input of the input interface and a second input of the resonant circuit with the cathode of the diode facing the input interface. The cathode of the diode of the third module is connected to the anode of the diode of the first module and to said first input of the resonant circuit. The cathode of the diode of the fourth module is connected to the anode of the diode of the second module and to said second input of the resonant circuit. The anodes and diodes of the third and fourth modules are connected together. The control means are configured to successively and cyclically close the first switch when the current flowing in the resonant circuit is positive and open the other switches, close one of the second and fourth switches and open the others, close the third switch when the current is negative and open the others, and close the other of the fourth and second switches and open the others. Furthermore, the duration of closure of the second or fourth switch depends on the desired gain for the resonant circuit given the value of the input voltage and the desired value of the battery voltage. The closing order of the second and fourth switches depends on the desired phase for the current of the resonant circuit with respect to the voltage of the resonant circuit. Thus, if it is desired that the mode of operation is a resonance in hyporesonance, that is to say that the resonant circuit is used so that the current of the resonant circuit is always in advance of phase on the voltage of the resonant circuit, the control means are then configured to close the second switch between the closures of the first and third switch and to close the fourth switch between the closures of the third and the first switch. The resonant circuit may be a parallel circuit or parallel series. The use of a parallel series circuit provides a gain / frequency curve having a wider peak around the resonant frequency, which gives greater flexibility in gain control.

Other advantages and characteristics of the invention will appear on examining the detailed description of embodiments, in no way limiting, and the accompanying drawings, in which: FIG. 1 diagrammatically illustrates an embodiment of a charging system according to the invention, and Figures 2 and 3 illustrate examples of control laws of the inverter. In FIG. 1, the reference SYS designates a charging system connected at the input E1, E2 to a power supply network RES and at the output to a battery 7 to be charged. The charging system here is a "slow charging" system compatible with a domestic power supply. The charging system is powered by the single-phase power supply network, typically with a power of less than or equal to 7kW which typically absorbs 10A, 16A or 32A of the single-phase network. The charging system comprises an input interface 1 whose two inputs E1 and E2 are connected to the network RES. The input interface preferably comprises a differential filter formed for example of a resistive capacitive inductive network. The two outputs S1 and S2 of the input interface 1 are connected to an inverter 2. The two outputs ER1 and ER2 of the inverter 2 are connected to a resonant circuit 4 associated with an isolation transformer 5. The secondary transformer 5 is connected to a secondary rectifier stage 6 conventionally comprising a rectifier diode bridge. The output of the secondary rectifier stage 6 forms the output of the charging system and is connected to the battery 7. It can thus be seen here that the charging system does not have a primary rectifying stage, such as a diode bridge. , located at the primary of the isolation transformer 5. The inverter 2 comprises four modules M1-M4.

Each Mi module comprises a controllable switch for example a MOS transistor, and an antiparallel di di connected to the terminals of the switch. The first module M1 is connected between the first output Si, and consequently the first input E1 of the input interface 1 and the first input ER1 of the resonant circuit 4. The diode D1 of the module M1 has its cathode turned towards the input interface that is to say that its cathode is connected to the input El of the input interface while its anode is connected to the input ER1 of the resonant circuit.

The second module M2 is connected between the second output S2, and therefore the second input E2 of the input interface 1 and the second input ER2 of the resonant circuit 4.

Here again, the cathode of the diode D2 is turned towards the input interface E1 while its anode is connected to the input ER2 of the resonant circuit. The cathode of the diode D3 of the third module M3 is connected to the anode of the diode D1 of the module M1 and to the input ER1 of the resonant circuit. The anode of the diode D3 is connected to the anode of the diode D4 of the fourth module M4. The cathode of the diode D4 is connected to the anode of the diode D2 of the module M2 as well as to the other input ER2 of the resonant circuit. The SYS system also comprises control means 8 for supplying four control signals SC1-SC4 for respectively controlling the four switches I1-14. These control means are for example configured to deliver pulse signals SCi modulated according to a pulse width modulation (PWM modulation). In general, the control means 8 are configured to control the inverter so as to generate across the resonant circuit 4 a rectified voltage V res regardless of the sign of the input voltage of the network. This is illustrated more particularly in FIGS. 2 and 3. FIG. 2 illustrates an example of a control law of the switches II-I4 when the input voltage (mains voltage) is positive while FIG. 3 illustrates the control law. and the corresponding change in the current I res flowing in the resonant circuit and the voltage across the resonant circuit V res, when the input voltage (mains voltage) is negative. The control sequences comprise four phases PH1, PH2, PH3 and PH4 which are repeated successively and cyclically.

In the phase PH1, the signal SC4 is in the high state closing the switch 14. In the phase PH2, the signal SC1 is in the high state closing the switch H.

In the phase PH3, the signal SC2 is in the high state closing the switch 12. In the phase PH4, the signal SC3 is in the high state closing the switch 13.

In each of the phases, when one of the control signals is in the high state, the other three are in the low state, opening the corresponding switches. In FIGS. 2 and 3, the sequence of the successive phases is as follows: PH1, PH2, PH3, PH4, PH1, PH2. The same sequence of phases is found in FIG. 3. According to this control law , the control means 8 are configured to close the switch 11 when the current Ires is positive (phase PH2) and open the other switches and to close the switch 13 when the current Ires is negative (phase PH4) and open the others . In this respect, a current sensor of conventional structure referenced CPT, is disposed on one of the branches of the resonant circuit 4. In the example described here, between phases PH2 and PH4 is phase PH3 in which the means of control are configured to close the switch 12 and open the others. Likewise, between phase PH4 and phase PH2 is phase PH1 in which the control means are configured to close switch 14 and open the others. The duration T12 during which the switches 11 and 12 are successively closed and the duration T34 during which the switches 13 and 14 are successively closed depends on the desired gain for the resonant circuit given the value of the input voltage. In other words, the gain of the resonant circuit is adapted as a function of the voltage of the network and of the desired charging voltage at the terminals of the battery 7. The control means 8 therefore adjust the duration T12 and T34 as a function of the desired gain. And, as the duration T10 during which the switch It is closed, can be easily determined (because it starts when the switch 14 opens and ends when the current Ires becomes negative), the duration of closing of the switch 12 is then the difference between the durations T12 and T10. The same reasoning applies for the determination of the closing duration of the switch 14 which is equal to the difference between the duration T34 and the duration T30. It can therefore be seen that with this control law, when the voltage of the network is positive, the voltage at the terminals of the resonant circuit V res is a rectified voltage in positive or zero square, whereas when the voltage of the network is negative, the voltage V is res is a rectified voltage in negative or zero slot (Figure 3). The mode of operation which has just been described in FIGS. 2 and 3 is a hyporesonance resonance, that is to say that the resonant circuit is used so that the current of the resonant circuit Ires is always in phase advance on the resonant circuit voltage V res. It would also be possible to provide the following phase sequence: ... PH3, PH2, PH1, PH4, PH3, ... This would lead to a current of the resonant circuit always in phase lag on the resonant circuit voltage. Although it is possible to use a parallel circuit as a resonant circuit, it is advantageous to use, as illustrated in FIG. 1, a parallel series circuit at the level of the capacitors and inductance. This allows for greater flexibility in adjusting the gain of the resonant circuit.

Claims (4)

REVENDICATIONS1. Charging system of a motor vehicle battery, comprising an input interface (1) for receiving an AC input voltage, an inverter (2) connected to the primary of an isolation transformer (5) by the intermediate of a resonant circuit (4), rectifying means and control means (8) of the inverter, characterized in that the rectifying means (6) are only connected to the secondary of the isolation transformer (5). ), and the control means (8) are configured to control the inverter so as to generate at the terminals of the resonant circuit a rectified voltage regardless of the sign of the input voltage. 2. System according to claim 1, further comprising means for measuring (CPT) the sign of the current flowing in the resonant circuit and wherein the inverter (2) comprises four modules (Ml-M4) each having a controllable switch ( I1-I4) and an antiparallel diode (D1-D4), a first module (M1) being connected between a first input (El) of the input interface and a first input (ER1) of the resonant circuit (4) with the cathode of the diode (D1) facing the input interface, a second module (M2) being connected between a second input (E2) of the input interface and a second input (ER2) of the resonant circuit with the cathode of the diode (D2) facing the input interface, the cathode of the diode (D3) of the third module being connected to the anode of the diode (D1) of the first module and to said first input of the circuit resonant, the cathode of the diode (D4) of the fourth module being connected to the anode of the diode (D2) of the second module and said second input of the resonant circuit, the anodes of the diodes (D3, D4) of the third and fourth modules being connected, and said control means (8) are configured to successively and cyclically close the first switch (I1) when said current is positive (I res) and open the others, close one of the second (I2) and fourth (I4) switches and open the others, close the third switch (I3) when the current (I res) is negative and open the others, and close the other of the fourth (I4) and second (I2) switches and open the others, the duration of closure of the second or fourth switch depending on the desired gain for the resonant circuit given the value of the input voltage. 3. System according to claim 2, wherein the control means (8) are configured to close the second switch (I2) between the closures of the first (I1) and third (I3) switches, and to close the fourth switch ( I4) between the closures of the third (I3) and the first (I1) switches. 4. System according to one of the preceding claims, wherein the resonant circuit (4) is a series-parallel circuit.