Bipolar transistor drivers

A switch mode power converter including a bipolar switching device and a voltage sensing system for sensing a voltage on a terminal of said switching device, wherein said voltage sensing system comprises:

• a driver configured to apply to a control terminal of said switching device a drive signal, said drive signal to drive said switching device to be on;
• a capacitor having one plate coupled to a terminal of said device and a second plate coupled to an output of said voltage sensing system;
• and a reset device having a first connection coupled to said second plate of said capacitor and a second connection coupled to a reference voltage to reset said voltage on said second plate of said capacitor when a said drive is applied to a control terminal of said switching device and to enable monitoring of variations of said voltage on said terminal of said switching device when said drive signal maintains said switching device on subsequent to said reset, whereby said driver may control said degree of saturation of said bipolar switching device.

A switch mode power converter including a bipolar switching device and a saturation control system for controlling a degree of saturation of said switching device when said device is switched on, said saturation control system having a control loop including a controller responsive to a peak value of a signal derived from a voltage on a terminal of said bipolar switching device,

• wherein the converter comprises a driver configured to apply to a control terminal of said switching device a drive signal, said drive signal to drive said switching device to be on, and
• wherein said converter has a voltage sensing system for sensing a voltage on a terminal of said switching device, the voltage sensing system comprising a first capacitor, one side of said first capacitor being coupled to said collector terminal of said switching device and a second side of said first capacitor being coupled to a reset device to reset a voltage on said first capacitor when said drive signal is applied to a control terminal of said switching device, whereby variations in said sensed voltage when said drive signal maintains said switching device on subsequent to said reset may be monitored by said converter to control said degree of saturation of said bipolar switching device.

A protection system for a power converter including a bipolar switching device and a switching control system to control switching on of said bipolar switching device for an on-period, the protection system comprising:

• a voltage sensing system to sense a voltage on a collector terminal of said device;
• a comparator coupled to said voltage sensing system to compare said sensed voltage to a threshold;
• and a protection mechanism coupled to said comparator and responsive to said sensed voltage exceeding said threshold to terminate said on-period early, wherein said voltage sensing system comprises a first capacitor, one side of said first capacitor being coupled to said collector terminal of said switching device and a second side of said first capacitor being coupled to a reset device to reset a voltage on said first capacitor when a drive signal drives said switching device to be on, whereby variations in said sensed voltage when said drive signal maintains said switching device on subsequent to said reset may be monitored by said protection system to control said degree of saturation of said bipolar switching device.