Device for the inductive transmission of electrical energy

Abstract

Device for the inductive transmission of electrical energy with a primary circuit (PK) and a secondary circuit (SK), which is connected via a rectifier (GR) to the positive and negative poles of an energy storage device (ESP) to be charged by the electrical energy, wherein the rectifier (GR) is a full-bridge rectifier formed with controllable switching means (SM1, SM2, SM3, SM4), wherein the controllable switching means (SM1, SM2, SM3, SM4) are transistors with substrate diodes (D1, D2, D3, D4) and wherein the control terminals of the controllable switching means (SM1, SM2, SM3, SM4) are connected to a control circuit (StS), characterized in that the control connections of the switching means (SM3, SM4) connected to the negative pole of the energy storage device (ESP) are connected to a passive blocking device (SV) which is connected to the positive pole of the energy storage device (ESP) and which is designed to put the switching means (SM3, SM4) connected to the negative pole of the energy storage device (ESP) into the conductive state in the event of a failure of the control circuit (StS) when energy is transferred via the primary circuit, so that a current flow begins in the secondary circuit and via the substrate diodes (D1, D2, D3, D4) of the rectifier (GR).

Description

[0001] The invention relates to a device for the inductive transmission of electrical energy with a primary circuit and a secondary circuit which is connected via a rectifier to the positive pole and the negative pole of an energy storage device to be charged by the electrical energy, wherein the rectifier is a full-bridge rectifier formed with controllable switching means, wherein the controllable switching means are transistors with substrate diodes and wherein the control terminals of the controllable switching means are connected to a control circuit.

[0002] A device for the inductive transmission of electrical energy, comprising a primary circuit and a secondary circuit connected via a rectifier to the positive and negative poles of an energy storage device to be charged with the electrical energy, is known from WO 2017 / 089014 A1. There, the primary and secondary circuits are designed as resonant circuits, each with a coil and capacitors connected in series, with ohmic losses indicated by a series resistance. In this known device, the secondary circuit upstream of the rectifier can be switched off by means of a switching device controlled by a control device in order to prevent a malfunction or avert a dangerous situation.

[0003] EP 3 163 737 A1 also discloses a device for the inductive transmission of electrical energy with a primary circuit and a secondary circuit which is connected via a rectifier to the positive pole and the negative pole of an energy storage device to be charged by the electrical energy, wherein the rectifier can be designed as a full-bridge rectifier and formed with switching means with diodes connected in parallel.

[0004] Due to the (substrate) diodes connected in parallel with the switching devices in these rectifiers, a rectified current can flow at any time as long as energy is supplied from the primary side and the energy transfer to the energy storage device is not actively prevented by the control circuit. Interrupting this energy transfer is usually achieved by additional or existing switches in the rectifier.

[0005] The rectifier circuits used have the problem that even without a supply voltage for the rectifier electronics, such as a drop in battery voltage during the charging process, power can continue to be drawn without the control of the control circuit. Active charging interruption is no longer possible due to the failure of the control circuit.

[0006] DE 10 2015 107 957 A1 discloses a rectification and control circuit for a wireless power receiver comprising a coil, a full-wave rectifier circuit, and a regulator. The full-wave rectifier has a first pair of controllable rectifiers comprising a first transistor connected to a first terminal of the coil and a second transistor connected to a second terminal of the coil. The regulator is configured to control the switching of the transistors of the full-wave rectifier such that the full-wave rectifier (a) generates a rectified output for charging a battery of the wireless power receiver by rectifying current through the coil or voltage across the coil and (b) controls the rectified output.

[0007] DE 10 2014 221 714 A1 discloses an active converter in which a number of AC voltage terminals are each connected to a first DC voltage terminal by means of first current valves controllable via control terminals and to a second DC voltage terminal by means of second current valves, wherein the control terminals of the first current valves are connected to at least one first control unit which is configured to control the first current valves with a first control signal when an output voltage between the second DC voltage terminal and the first DC voltage terminal exceeds an upper threshold value.

[0008] It is therefore the object of the invention to enable deactivation of the rectifier even in the event of a failure of the control circuit.

[0009] The object is achieved by a device according to claim 1. An advantageous further development is specified in the subclaim.

[0010] Accordingly, in a device for the inductive transmission of electrical energy having a primary circuit and a secondary circuit, which is connected via a rectifier to the positive pole and the negative pole of an energy storage device to be charged by the electrical energy, wherein the rectifier is a full-bridge rectifier formed with controllable switching means, wherein the controllable switching means are transistors with substrate diodes and wherein the control terminals of the controllable switching means are connected to a control circuit, the control terminals of the switching means connected to the negative pole of the energy storage device are connected to a passive blocking device, which is connected to the positive pole of the energy storage device and which is designed to put the switching means connected to the negative pole of the energy storage device into the conductive state in the event of a failure of the control circuit when energy is transmitted via the primary circuit,so that a current flows in the secondary circuit and through the substrate diodes of the rectifier.

[0011] This makes it possible to prevent a charging current via the rectifier even without the control circuit.

[0012] When energy is transferred via the primary circuit, a current flows in the secondary circuit and through the rectifier, which now operates passively and without control. This current flow causes a voltage to build up on the positive side of the rectifier, which is simultaneously used to control the switches via the passive blocking device. By controlling the switches with an auxiliary voltage generated by the passive blocking device, the rectifier is blocked, preventing energy transfer. The rectifier can only be activated with the supply voltage of the control circuit present and the auxiliary voltage actively switched off. A solution with a passive blocking device is therefore proposed, which is designed to block the rectifier without the need for a supply voltage from the control circuit. To ensure the charging process, the rectifier must be able to be actively kept open at all times.If the supply voltage drops or the rectifier cannot be kept open due to another fault, it blocks immediately.

[0013] In an advantageous embodiment of the device according to the invention, the passive blocking device is formed with the series circuit of a pull-up resistor and a Zener diode, which is connected between the positive and the negative pole of the energy storage device, wherein the control terminals of the switching means connected to the negative pole of the energy storage device are connected to the connection point of the pull-up resistor and the Zener diode.

[0014] As a result, the switching devices connected to the negative pole of the energy storage device are closed, so that the secondary circuit is virtually short-circuited via their forward resistances as soon as the voltage at the output of the rectifier, i.e. at the positive pole of the energy storage device, exceeds the switching voltage of the switching device.

[0015] The invention will be explained in more detail below using an exemplary embodiment with the aid of figures. Fig. 1 a schematic diagram of a device according to the invention and Fig. 2 a possible embodiment of a device with a locking device according to the invention.

[0016] In the embodiment of a device according to the invention for the inductive transmission of electrical energy to an energy storage device ESP, in particular of a motor vehicle according to Fig. 1 is a primary circuit PK with an alternating voltage source U P The primary circuit PK is designed as a resonant circuit and has the series connection of a primary circuit coil L P , a primary circuit capacitor C P and a primary circuit resistance R P In the primary circuit coil L Pan alternating magnetic field is generated which, when a secondary circuit SK is suitably positioned and arranged in a motor vehicle, induces an alternating voltage in the latter.

[0017] The secondary circuit SK is also designed as a resonant circuit and has a secondary circuit coil L S , a secondary circuit capacitor C S and a secondary circuit resistance S S Several secondary circuit coils and several secondary circuit capacitors can also be provided.

[0018] Ideally, both the primary circuit PK and the secondary circuit SK are located at the frequency of the alternating voltage of the alternating voltage source U P in resonance so that as much energy as possible can be transferred from the primary circuit PK to the secondary circuit SK.

[0019] To store the transferred energy in the energy storage device ESP, the alternating voltage present at the output of the secondary circuit SK must be rectified. This is accomplished by a rectifier GR, which is configured as a full-bridge rectifier. It comprises four switching devices SM1 to SM4, which in the illustrated embodiment are embodied as MOSFETs, each of which has a diode D1 to D4 connected in parallel. The diodes D1 to D4 are typically incorporated as substrate diodes in the switching devices SM1 to SM4. The output terminals HV_DC and HV_GND of the rectifier GR are connected to the energy storage device ESP, with a DC voltage present at these terminals.

[0020] It goes without saying that smoothing capacitors can be present and instead of the capacitors used in the embodiment of the Fig. In addition to the MOSFETs shown in Figure 1, other electronic switching elements can also be used as switching means SM1 to SM4. The switching means SM1 to SM4 have control terminals connected to a control circuit StS, allowing the rectifier GR to function as a switched rectifier.

[0021] However, due to the diodes D1 to D4 connected in parallel with the switching devices SM1 to SM4, the rectifier GR will also function as a rectifier when the switching devices SM1 to SM4 are open, so that in the event of a malfunction of the control circuit StS, the rectifier GR cannot be switched off and, when an alternating voltage is applied to the primary circuit PK, energy would always be transferred to the energy storage device ESP.

[0022] In order to counteract this problem, a passive blocking device SV is provided according to the invention, which is connected to the control terminals of the switching means SM3, SM4 of the rectifier GR connected to the negative pole HV_GND of the energy storage device ESP and controls them in such a way that the two switching means SM3, SM4 are closed and thus virtually short-circuit the secondary circuit SK, since this is then only loaded with the forward resistance of these two switching means SM3, SM4.

[0023] In Fig. Figure 2 shows a possible design of the blocking device SV, where, for clarity, only the secondary circuit SK is shown. The control terminals of the switching elements SM1 and SM2 of the rectifier GR, which are connected to the positive pole HV_DC of the energy storage device ESP, are each connected to a terminal of the secondary circuit SK.

[0024] The blocking device SV is formed by a series circuit of three resistors R1 to R3 and a diode D5, which are connected between the two output terminals HV_DC and HV_GND of the rectifier GR. The junction point between the resistors R1 to R3 and the diode D5 is connected to the control terminals of the switching devices SM3 and SM4, which are connected to the negative pole HV_GND of the energy storage device ESP. This simple blocking circuit SV, when a sufficiently high voltage is present at the output of the rectifier GR, pulls the control terminals of the switching devices SM3 and SM4 to a positive potential via the pull-up resistors R1 to R3, so that the switching devices SM3 and SM4 are both switched on, thus deactivating the rectifier GR.

Claims

[1] Device for the inductive transmission of electrical energy with a primary circuit (PK) and a secondary circuit (SK), which is connected via a rectifier (GR) to the positive and negative poles of an energy storage device (ESP) to be charged by the electrical energy, wherein the rectifier (GR) is a full-bridge rectifier formed with controllable switching means (SM1, SM2, SM3, SM4), wherein the controllable switching means (SM1, SM2, SM3, SM4) are transistors with substrate diodes (D1, D2, D3, D4) and wherein the control terminals of the controllable switching means (SM1, SM2, SM3, SM4) are connected to a control circuit (StS), characterized by , that the control connections of the switching means (SM3, SM4) connected to the negative pole of the energy storage device (ESP) are connected to a passive blocking device (SV) which is connected to the positive pole of the energy storage device (ESP) and which is designed to put the switching means (SM3, SM4) connected to the negative pole of the energy storage device (ESP) into the conductive state in the event of a failure of the control circuit (StS) when energy is transferred via the primary circuit, so that a current flow begins in the secondary circuit and via the substrate diodes (D1, D2, D3, D4) of the rectifier (GR). [2] Device according to claim 1, characterized bythat the passive blocking device (SV) is formed with the series circuit of a pull-up resistor (R1, R2, R3, R4) and a Zener diode (D5) which is connected between the positive and the negative pole of the energy store (ESP), wherein the control terminals of the switching means (SM3, SM3) connected to the negative pole of the energy store (ESP) are connected to the connection point of the pull-up resistor (R1, R2, R3, R4) and the Zener diode (D5).

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