Apparatus and method for recognizing an error in a power bridge circuit

An apparatus for recognizing an error in a power bridge circuit having a load with a high-side connection and a low-side connection, a high-side branch having a high-side power switch connected between the high-side connection of the load and a supply connection for a high-potential of a supply voltage, and a low-side branch having a low-side power switch connected between the low-side connection of the load and a supply connection for a low-potential of the supply voltage, the apparatus comprising:

• a first switched current source connected to the load and having a diagnosis connection for a high-potential of a diagnosis voltage;
• a second switched current source connected to the load and having a diagnosis connection for a low-potential of the diagnosis voltage;
• a control device for controlling said first switched current source and said second switched current source, said control device embodied such that when the high-side power switch is open and the low-side power switch is open, said control device switches on one of said first and second switched current sources, while the other of said first and second switched current sources is switched off, and then said control device switches off one of said first and second switched current sources and switches on the other of said first and second switched current sources;
• and
• a testing device for testing a voltage at the load when one of said first and second switched current sources is switched on and the other of said first switched current sources is switched off, and when said one of said first and second switched current sources is switched off and said other of said first and second switched current sources is switched on.

A method for recognizing an error in a power bridge circuit containing a load, a high-side branch having a high-side power switch disposed between a high-side connection of the load and a supply connection for a high- potential of a supply voltage, and a low-side branch having a low-side power switch disposed between a low-side connection of the load and a supply connection for a low-potential of the supply voltage, which comprises the steps of:

• connecting a first switched current source to the load and to a diagnosis connection for a high-potential of a diagnosis voltage;
• connecting a second switched current source to the load and to a diagnosis connection for a low-potential of the diagnosis voltage;
• controlling the first switched current source and the second switched current source by means of a control device in such a manner that when the high-side power switch is open and the low-side power switch is open, one of the first and second switched current sources is switched on, while another of the first and second switched current sources is switched off, and then one of the first and second switched current sources is switched off and the other of the switched current sources is switched on;
• and
• testing a voltage at the load by means of a testing device when one of the first and second switched current sources is switched on and the other of the first and second switched current sources is switched off, and when one of the first and second switched current sources is switched off and the other of the first and second switched current sources is switched on.