Circuit for blocking a semiconductor switching device on overcurrent

• US 6,351,359 B1
• Filed: 08/20/1999
• Issued: 02/26/2002
• Est. Priority Date: 03/13/1997
• Status: Expired due to Fees

• Current Assignee: Danfoss Drives A/S (Danfoss A/S)
• Original Assignee: Danfoss A/S
• Inventors: Jæger, Jens Ulrik
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/367,658
• Time in Patent Office: 921 Days
• Field of Search: 361/18, 361/23, 361/31, 361/57, 361/93.1, 361/93.9, 323/282, 323/284, 323/289, 323/276, 323/277, 363/50, 363/52, 363/53, 363/55, 363/56, 363/74, 363/75, 363/76, 363/78
• US Class Current: 361/93.9
• CPC Class Codes: H02H 7/1222 responsive to abnormalities in the input circuit, e.g. transients in the DC input
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current

Abstract

A conventional circuit for blocking a semiconductor switching device (7) on overcurrent, the semiconductor switching device (7) having at least one continuously driven semiconductor switch (9), comprises a diver circuit (11), which has a driver stage (12) for each semiconductor switch (9), a control pulse generator (10) for producing control pulses (P₁ to P₆), which are fed in operation to a control input of the semiconductor switching device (7) via the driver circuit (11), and a monitoring device (34), which measures the current (I) flowing through the semiconductor switching device (7) and, when an overcurrent occurs, generates a fault signal (E), which initiates blocking of the semiconductor switching device (7). When the semiconductor switching device is being blocked, a high overvoltage can occur therein, possibly leading to destruction of the semiconductor switching device. In order to reduce, with little outlay, the overvoltage in the semiconductor switching device during blocking thereof, provision is made such that the operating voltage (U) of the driver circuit (11) is arranged to be switched over briefly by the fault signal to a lower, interim value corresponding to a lower current (I) through the semiconductor switching device (7) and then, within the maximum permissible duration for loading the semiconductor switching device (7) with an overcurrent, to be switched off completely.

Claims

1. Circuit for blocking a semiconductor switching device on overcurrent, the semiconductor switching device having at least one continuously driven semiconductor switch, which circuit comprises a driver circuit having a driver stage for each semiconductor switch, a control pulse generator for producing control pulses, which are fed in operation to a control input of the semiconductor switching device via the driver circuit, and a monitoring device which measures current flowing through the semiconductor switching device and which, when an overcurrent occurs, generates a fault signal, which initiates blocking of the semiconductor switching device, the driver circuit having means to switch its operating voltage over briefly upon generation of the fault signal to a lower interim value corresponding to a lower current through the semiconductor switching device and then, within a maximum permissible duration for loading the semiconductor switching device with an overcurrent, to switch off the operating voltage completely.

2. Circuit according to claim 1, including, for several of said semiconductor switches jointly supplied from one operating voltage source, said monitoring device in a supply line common to all the semiconductor switches for measuring the current flowing through the semiconductor switches.

3. Circuit according to claim 1, in which driver stages for the semiconductor switches are all supplied from a common operating voltage source which is galvanically isolated from the driver stages and which, as a function of the fault signal, is arranged to be switched over to the interim value and then switched off.

4. Circuit according to claim 3, in which the operating voltage source of the driver circuit is a direct-current voltage source having a chopper controlled by a pulsed switching signal and a transformer having a secondary winding for each driver stage and a rectifying circuit connected to the secondary winding, each driver stage being connected to said at least one semiconductor switch, and the switching signal that controls the chopper being frequency- or pulse-length-modulated as a function of the fault signal.

5. Circuit according to claim 4, in which the control pulses of the control pulse generator are combined with the switching signal controlling the chopper by means of an AND gate.

6. Circuit according to claim 3, in which the control pulses and the operating voltage for each driver stage are transmitted by means of a high-frequency carrier signal of an oscillator that is common to all the driver stages, by a galvanic isolation stage.

7. Circuit according to claim 1, in which the control pulses of the control pulse generator are fed in operation to a control input of the driver circuit.

8. Circuit according to claim 1, in which the operating voltage source of the driver circuit has an output for a high, normal value and an output for the low, interim value, one of which outputs can be selected for the supply of the operating voltage as a function of the fault signal.

9. Circuit according to claim 8, in which one output is connected by a diode to one end of a switching path of a controllable switch, the other output is connected by a diode to another end of the switching path and to the driver circuit, and the switch is arranged to be switched as a function of the fault signal.