Arrangement for measuring at least one voltage in an AC power transmission device whose output terminals are connected to a rectifier circuit

Abstract

Arrangement for measuring at least one voltage (U1; U2) in an inductive AC power transmission device (L1, L2) having a primary (L1) and a secondary coil (L2), the output terminals of which are connected to a rectifier circuit (3) having a first input terminal (10) and a second input terminal (11) and a first output terminal (12) for a high potential and a second output terminal (13) for a low potential, wherein a voltage measuring device (8) is connected at its first terminal to the first input terminal (10) of the rectifier circuit (3) and at its second terminal to the second input terminal (11) or the second output terminal (13) of the rectifier circuit (3), wherein the voltage measuring device (8) is an inductive transformer (L3, L4) in which the terminals of its primary coil (L3) form the first and second terminals of the voltage measuring device (8).wherein this second connection is connected to the second input connection (11) of the rectifier circuit (3), and from which a voltage (U3) corresponding to the voltage (U1) to be measured can be tapped at the connections of a secondary coil (L4).

Description

[0001] There are many applications in which energy is transmitted in the form of alternating voltage and alternating current, but should be available to a consumer as direct voltage and direct current, for example, for charging an energy storage device such as a battery. The alternating voltage energy transmission device used for this purpose can be inductive, such as a transformer, capacitive, such as opposing conductive plates or foils, or conductive, using cables.

[0002] DE 10 2014 207 854 A1, for example, discloses an inductive AC power transmission device with a primary coil and a secondary coil coupled via an air gap. The primary coil is intended to be installed in a parking space for a motor vehicle, for example, embedded in the parking space floor or placed on it. The secondary coil is typically arranged in the vehicle floor.

[0003] US 2009 / 0 015 197 A1 discloses a power transmission device comprising a resonant capacitor forming a series resonant circuit with a primary coil, a first current transmission driver and a second current transmission driver driving the primary coil, and a control IC outputting drive control signals to the first and second current transmission drivers.

[0004] WO 2014 / 125698 A1 discloses a power receiving device comprising: a non-contact power supply that transmits and receives high-frequency energy contactlessly through a spatial gap; a rectifier circuit that converts the high-frequency energy transmitted and received by the above non-contact power supply into direct current energy; and a load that consumes the above direct current energy converted by the above rectifier circuit, wherein the above non-contact power supply has a secondary winding that is electromagnetically inductively coupled to the primary winding and a secondary capacitor that resonates with the secondary winding.

[0005] WO 2014 / 125698 A1 discloses a power receiving device comprising: a non-contact power supply that transmits and receives high-frequency energy contactlessly through a spatial gap; a rectifier circuit that converts the high-frequency energy transmitted and received by the above non-contact power supply into direct current energy; and a load that consumes the above direct current energy converted by the above rectifier circuit, wherein the above non-contact power supply has a secondary winding in electromagnetic inductive coupling with the primary winding and a secondary capacitor resonant with the secondary winding.

[0006] US 2014 / 0 074 332 A1 discloses a contactless energy transfer system that supplies a vehicle with power without contact. The energy transfer device and the vehicle are configured to exchange information wirelessly. The vehicle is equipped with an RFID tag in which information about the vehicle is stored in advance.

[0007] US 2015 / 0 229 132 A1 discloses a method for compensating the electromagnetic-inductive pressure level of an electromagnetic pen.

[0008] DE 101 01 513 A1 discloses a method for determining the magnitude of a sinusoidal mains input voltage in a circuit arrangement in which it is converted into a direct voltage for feeding an electrical load using a power supply transformer and a Graetz bridge circuit with a smoothing capacitor arranged in parallel.

[0009] DE 10 2013 220 683 A1 discloses a device for detecting a phase sequence in a vehicle. The device includes a control module for operatively coupling to a power grid to receive an incoming power signal therefrom, wherein the incoming power signal provides a first voltage and a second voltage in a vehicle. The control module is configured to determine a phase difference between the first voltage and the second voltage and to determine a signal frequency of the incoming signal to determine the country type of the power grid.

[0010] Both the primary and secondary circuits are often operated in resonance to ensure better power transfer. Suitable circuits provide the AC voltage for the primary circuit and convert the AC voltage of the secondary circuit into a DC voltage suitable for the energy storage device used. For this purpose, at least rectifiers are used; half-wave rectifiers can also be used, but full-wave rectifiers are usually preferred.

[0011] In electric vehicles, the energy storage units usually have a high voltage of several hundred volts, thus forming a high-voltage network that often supplies not only the electric motors but also other high-voltage consumers. It can be useful if the energy storage units can be disconnected from the high-voltage network.

[0012] While there are contactors that can disconnect the energy storage device from the high-voltage network, there are usually no additional contactors that can disconnect the AC power transfer device from the vehicle's high-voltage network. Therefore, in most vehicle states, such as driving, stationary with the ignition on, charging, etc., the voltage from the energy storage device is present at the output of the AC power transfer device.

[0013] Only when sufficient power is coupled into the secondary coil of the AC energy transfer device does the AC voltage in front of the rectifier rise to such an extent that it reaches the voltage at the energy storage device, overcomes the forward voltage of the rectifier diodes and a charging current can flow.

[0014] The output voltage and current of the AC power transmission device must always match the current requirements of the energy storage management system, which regulates the charging process and the required charge of the energy storage device. To enable adjustment to specific target values, the voltage is tapped on the output side, measured using a measuring channel, and transmitted, for example, via CAN.

[0015] This measurement is taken near the output of the AC power transmission device, since its output voltage is the relevant value. If there are filters behind the rectifier, the voltage is already filtered at this point, which facilitates the measurement.

[0016] Depending on the requirements, the measurement channel used for the measurement can contain a voltage divider, but also other elements such as filters, limiters, converters, etc. Galvanic isolation can also be integrated if necessary to isolate a high-voltage and a low-voltage area. Active elements of the measurement channel must then be supplied by a galvanically isolated auxiliary voltage source.

[0017] In certain cases, it is desirable to measure the voltage generated by the secondary coil even if the input power is insufficient to overcome the forward voltage of the rectifier diodes. This may be necessary, for example, when approaching certain target values, which must be done from the bottom up for safety reasons, as the energy storage limits must not be exceeded. Another situation may arise when the primary and secondary coils are used in advance to transmit information through clocked switching on and off, or when positioning the vehicle to measure and optimize the distance between the primary and secondary coils and thus the efficiency of the energy transfer.

[0018] Since in these cases the secondary coil voltage does not reach the voltage at the energy storage device, it cannot be measured behind the rectifier.

[0019] It is therefore the object of the invention to provide an arrangement for measuring at least one voltage in an AC power transmission device whose output terminals are connected to a rectifier circuit, in which this is possible.

[0020] The object is achieved by an arrangement according to claim 1 or claim 2. Advantageous further developments are specified in the subclaims.

[0021] Accordingly, in an arrangement for measuring at least one voltage in an inductive AC energy transmission device having a primary and a secondary coil, the output terminals of which are connected to a rectifier circuit having a first input terminal and a second input terminal and a first output terminal for a high potential and a second output terminal for a low potential, a voltage measuring device is connected with its first terminal to the first input terminal of the rectifier circuit and with its second terminal to the second input terminal or the second output terminal of the rectifier circuit.

[0022] By connecting the voltage measuring device upstream of the rectifier circuit according to the invention, it is possible to measure the voltage at the secondary coil, even if it is lower than the voltage at the energy storage device.

[0023] The voltage measuring device is an inductive transformer in which the terminals of its primary coil form the first and second terminals of the voltage measuring device. This second terminal is connected to the second input terminal of the rectifier circuit. A voltage corresponding to the voltage to be measured can be tapped off at the terminals of a secondary coil. The ratio of the voltage to be measured to this corresponding voltage is determined primarily by the transformer's transformation ratio, but possibly also by downstream voltage dividers or other circuits.

[0024] This has the advantage of creating a galvanic separation between the high-voltage range and the measuring range, whose voltages are usually below 10 volts.

[0025] In an alternative embodiment, the arrangement for measuring at least one voltage comprises an inductive AC energy transmission device having a primary and a secondary coil, the output terminals of which are connected to a rectifier circuit having a first input terminal and a second input terminal, and a first output terminal for a high potential and a second output terminal for a low potential. A voltage measuring device is connected by its first terminal to the first input terminal of the rectifier circuit and by its second terminal to the second input terminal or the second output terminal of the rectifier circuit.The voltage measuring device is formed with a voltage divider which is connected between the terminals of the voltage measuring device, wherein the second terminal is connected to the second output terminal of the rectifier circuit, and in which a voltage corresponding to the voltage to be measured can be tapped off at a connection point of two resistors of the voltage divider.

[0026] Due to this connection, the base point of the voltage measuring device is connected to the ground of the high-voltage network, so that a ground reference is available.

[0027] The voltage divider is followed by a galvanic isolation circuit, at whose output the voltage to be measured can be tapped.

[0028] This not only provides a ground reference but also galvanic isolation.

[0029] In an advantageous embodiment of the arrangement according to the invention, the rectifier circuit is formed with a full-bridge rectifier.

[0030] In one embodiment of the arrangement according to the invention, a further voltage measuring device is connected between the output terminals of the rectifier circuit, so that not only the voltage before the rectifier circuit but also the voltage after the rectifier circuit can be measured.

[0031] The invention will be described in more detail below using exemplary embodiments with the aid of figures. Fig. 1 a first embodiment of an arrangement according to the invention, Fig. 2 a second embodiment of an arrangement according to the invention, Fig. 3 a third embodiment of an arrangement according to the invention, Fig. 4 a fourth embodiment of an arrangement according to the invention.

[0032] The Fig. 1 shows a first embodiment of an arrangement according to the invention for measuring at least one voltage U1 in an AC power transmission device, which is formed with a primary coil L1 and a secondary coil L2. The primary coil L1 is intended to be part of a primary circuit 1, which also includes, for example, a capacitor (not shown) and circuits (likewise not shown) for generating the high-frequency oscillation driving the resonant circuit thus formed. The secondary coil L2 is part of a secondary circuit 2, which is also formed with at least one rectifier circuit 3. The secondary circuit 2 can also contain a capacitor (not shown), for example, to form a resonant circuit.

[0033] The rectifier circuit 3 has two input terminals 10, 11 and two output terminals 12, 13 and, in the illustrated embodiment, is formed as a full-bridge rectifier with four conventionally connected rectifier diodes 3a, 3b, 3c, 3d.

[0034] The two input terminals 10, 11 of the rectifier circuit 3 are connected to the terminals of the secondary coil L2, the two output terminals 12, 13 of the rectifier circuit 3 are each connected via a contactor 5 and 6 to the terminals of an energy storage device, in the illustrated embodiment to the poles of a battery 4.

[0035] To charge the battery 4, an alternating voltage is applied to the primary coil L1, which is coupled to the secondary coil L2 via an air gap and induces a secondary voltage U1 there, which leads to a charging of the battery 4 via the rectifier circuit 3 if the voltage U2 at the output terminals 12, 13 of the rectifier circuit 3 is greater than the voltage of the battery 4.

[0036] In this case, the voltage at the input terminals 10, 11 of the rectifier circuit 3 could be deduced from the knowledge of the voltage drop across the rectifier diodes 3a, 3b, 3c, 3d, whereby the secondary voltage U1 at the terminals of the secondary coil L2 could be determined.

[0037] However, if the secondary voltage U1 is smaller than the voltage at the battery 4 plus the forward voltage of the rectifier diodes 3a, 3b, 3c, 3d, this relationship is no longer correct and therefore the secondary voltage U1 cannot be determined at the output of the rectifier circuit 3.

[0038] Therefore, according to the invention, a voltage measuring device 8 in the form of a transformer is connected between the input terminals 10, 11 of the rectifier circuit 3, with the terminals of the primary coil L3 of this transformer being connected to the input terminals 10, 11 of the rectifier circuit 3. A voltage U3 is present at the terminals of the secondary coil L4 of the transformer, which is proportional to the secondary voltage U1 to be measured and can be rectified, smoothed, filtered, or subjected to other processing if necessary.

[0039] This allows the secondary voltage U1 at the terminals of the secondary coil L2 of the AC power transmission device to be determined in an advantageous manner, even if it has small values.

[0040] This may be the case for the following reasons, for example: • Control-related reasons (approaching setpoints from below) • Use of the energy transmission path for message transmission • Air gap measurement for wireless energy transmission • Support of certain test pulses / test modes before the energy transfer is started • Diagnostic functions to find errors (almost) without energy transfer • Checking safety functions (pre-drive check of shutdown paths, etc.) • controlled preheating of components • controlled charging of capacities (to avoid excessive inrush currents) • targeted (low) loading of the source without transferring energy to the sink.

[0041] In the Fig. Figure 2 shows an alternative embodiment of a voltage measuring device 3 with an otherwise identical AC power transmission device and rectifier circuit 3. There, the voltage measuring device 8 is formed with a voltage divider comprising two series-connected resistors R1, R2, at whose junction a voltage U4 corresponding to the voltage U1 to be measured can be tapped. Further circuits for processing the measured voltage U4, such as filters, rectifiers, etc., can also be connected downstream of this junction.

[0042] The voltage measuring device 8 of the Fig. 2 is arranged between the first input terminal 10 and the second output terminal 13 of the rectifier circuit 3 and thus has a ground reference to the high-voltage network at the output of the rectifier circuit 3. However, it is not galvanically decoupled like the transformer of the Fig. 1. In addition, the determined voltage U4 at the connection point of the voltage divider R1, R2 only shows the positive half-waves of the secondary voltage U1.

[0043] The Fig. 3 shows a further development of the arrangement according to Fig. 2, in which the voltage divider R1, R2 is followed by a circuit for galvanic isolation 7, at the output of which a voltage U5 corresponding to the voltage U1 to be measured can be tapped. This variant of the arrangement according to the invention thus combines the advantages of the embodiments of Fig. 1 and Fig. 2.

[0044] In Fig. 4 shows a detail of a further development of the arrangement according to the invention with a further voltage measuring device with a voltage divider with two resistors R3 and R4, which is arranged between the output terminals 12, 13 of the rectifier circuit 3 and in addition to the Fig. 1 to 3 can be used to also detect the voltage U2 at the output terminals 12, 13 of the rectifier circuit 3.

Claims

[1] Arrangement for measuring at least one voltage (U1; U2) in an inductive AC energy transmission device (L1, L2) having a primary coil (L1) and a secondary coil (L2), the output terminals of which are connected to a rectifier circuit (3) having a first input terminal (10) and a second input terminal (11) and a first output terminal (12) for a high potential and a second output terminal (13) for a low potential, in which a voltage measuring device (8) is connected with its first terminal to the first input terminal (10) of the rectifier circuit (3) and with its second terminal to the second input terminal (11) or the second output terminal (13) of the rectifier circuit (3), wherein the voltage measuring device (8) is an inductive transformer (L3, L4), in which the terminals of its primary coil (L3) form the first and second terminals of the voltage measuring device (8),wherein this second terminal is connected to the second input terminal (11) of the rectifier circuit (3), and in which a voltage (U3) corresponding to the voltage (U1) to be measured can be tapped off at the terminals of a secondary coil (L4). [2] Arrangement for measuring at least one voltage (U1; U2) in an inductive AC energy transmission device (L1, L2) having a primary coil (L1) and a secondary coil (L2), the output terminals of which are connected to a rectifier circuit (3) having a first input terminal (10) and a second input terminal (11) and a first output terminal (12) for a high potential and a second output terminal (13) for a low potential, in which a voltage measuring device (8) is connected with its first terminal to the first input terminal (10) of the rectifier circuit (3) and with its second terminal to the second input terminal (11) or the second output terminal (13) of the rectifier circuit (3), wherein the voltage measuring device (8) is a voltage divider which is connected between the terminals of the voltage measuring device (8),wherein the second terminal thereof is connected to the second output terminal (13) of the rectifier circuit (3), and wherein a voltage (U4) corresponding to the voltage (U1) to be measured can be tapped off at a connection point of two resistors (R1, R2) of the voltage divider, wherein a circuit for galvanic isolation (7) is connected downstream of the voltage divider (R1, R2), at the output of which a voltage (U5) corresponding to the voltage (U1) to be measured can be tapped off. [3] Arrangement according to one of the preceding claims, in which the rectifier circuit (3) is a full-bridge rectifier (3a, 3b, 3c, 3d). [4] Arrangement according to one of the preceding claims, in which a further voltage measuring device (R3, R4) is connected between the output terminals (12, 13) of the rectifier circuit (3).

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