DC VEHICLE CHARGING CIRCUIT COMPRISING A TRANSISTOR AND AN INVERSE DIODE FOR BLOCKING FAULT CURRENT CAUSED BY CHARGING-STATION VARISTORS
A DC vehicle charging circuit is equipped with an input, a converter circuit designed as a boost converter, and an output. A first input potential of the input is connected to a first output potential of the output via the converter circuit. The converter circuit is connected to a second output potential of the output via a connection point. A second input potential of the input is connected to the connection point without semiconductor switches, except for one transistor. The transistor has an inverse diode, the forward direction of which corresponds to the direction of a charging current that flows when energy is transferred from the input to the output.
1 . A DC vehicle charging circuit having an input converter circuit in the form of a boost converter, and an output, wherein a first input potential of the input is connected to a first output potential of the output via the converter circuit, and the converter circuit is connected to a second output potential of the output via a connection point, wherein a second input potential of the input is connected to the connection point without any semiconductor switches, apart from a transistor, and wherein the transistor has an inverse diode, the forward direction of which points in the direction of the charging current that flows in the HV-minus path when energy is transferred from the input to the output.
2 . The DC vehicle charging circuit as claimed in claim 1 , further comprising a control device which is configured to determine whether the condition is met that at the input a voltage limiting element is connected between one of the input potentials and a ground potential, the threshold voltage of which is below a nominal voltage of the output, and wherein the control device is connected so as to drive the transistor and is configured to hold the transistor in the open state if it is determined that the condition is met.
3 . The DC vehicle charging circuit as claimed in claim 2 , wherein the control device is configured in a charging state to keep the transistor in the open state if it is determined that the condition is met, and is configured in the charging state to control the transistor in the closed state if it is determined that the condition is not met.
4 . The DC vehicle charging circuit as claimed in claim 2 , wherein the control device has a communication input, which is configured to receive a signal that reproduces a charging station standard, and the control device is configured to determine whether the charging station standard provides voltage limiting elements, the threshold voltage of which is above the nominal voltage of the output or does not exceed this nominal voltage, wherein in the latter case the control device provides the condition as being met.
5 . The DC vehicle charging circuit as claimed in claim 1 , wherein the converter circuit is designed bidirectionally.
6 . The DC vehicle charging circuit as claimed in claim 1 , wherein the converter circuit has a series circuit of two working transistors, the connecting node of which is connected to the first input potential via a working inductance of the converter circuit, either directly or via a fusible link or pyrofuse.
7 . The DC vehicle charging circuit as claimed in claim 1 , wherein the transistor is connected to the second input potential directly or via a fusible link or pyrofuse.
8 . The DC vehicle charging circuit as claimed in claim 1 , wherein the converter circuit is accommodated in a first housing, and the transistor is accommodated in a second housing which is interposed between the input and the first housing.
9 . The DC vehicle charging circuit as claimed in claim 6 , wherein the working inductance, via which the converter circuit is connected to the input, is provided by a serial inductance of an inductive input filter which is connected downstream of the input.