Arrangement including a delayed-action semiconductor switch
AssigneeLicentia Patent-Verwaltungs-G.m.b.H.
InventorJurgen Zeis
Life of this patent
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Abstract
In a circuit including a semiconductor switch for switching a load current, the so-called storage time of the semiconductor switch, i.e. the delay occurring during switching from the conductive state to the blocking state, is regulated so as to decrease undesired variation of same, i.e. the storage period is maintained substantially constant. This is achieved in the case, for example, of a transistor in that, dependent on the collector voltage, the control or base current for switching on the transistor, and possibly a reverse base voltage applied to block the transistor, are varied so as to maintain the storage period at a desired value.
Claims14
In a circuit arrangement including at least one delayed-action semiconductor switch having a load current path leading through the switching path of said semiconductor switch and a control electrode connected via a control signal path to an input terminal for an input signal for switching said semiconductor switch between its conductive (switch-on phase) and blocking (blocking phase) states, and auxiliary circuit means, having a first control path extending from a tap in said load current path to a circuit point in said control signal path, for obtaining an actual value at said tap and for utilizing same to vary a control value fed to said control electrode during said switch-on phase to shorten the storage period of said semiconductor switch, i.e., the delay occurring during switching of said semiconductor switch from the conductive (switch-on phase) to the blocking (blocking phase) state;
- the improvement wherein said auxiliary circuit means includes:
- comparator circuit means, connected in said first control path and having one input connected to said tap and a further input connected to said input terminal, for comparing the voltage at said tap with the voltage of the input signal at said input terminal to provide an output signal responsive to the voltage at said tap during said storage period of said semiconductor switch;
- a memory connected to said comparator circuit means for storing a voltage value corresponding to said output signal;
- and
- control circuit means, disposed in said control signal path and responsive to said input signal and to the voltage value stored in said memory, for regulating the control current supplied to said control electrode of said semiconductor switch during the next switch-on phase so as to maintain said storage period of said semiconductor switch substantially constant.
In a circuit arrangement including at least one delayed-action semiconductor switch having a load current path leading through the switching path of said semiconductor switch and a control electrode connected via a control signal path to an input terminal for an input signal for switching said semiconductor switch between its conductive (switch-on phase) and blocking (blocking phase) states, and auxiliary circuit means, having a first control path extending from a tap in said load current path to a control point in said control signal path, for obtaining an actual value at said tap and for utilizing same to vary a control value fed to said control electrode during said switch-on phase to shorten the storage period of said semiconductor switch, i.e., the delay occurring during switching of said semiconductor switch from the conductive (switch-on phase) to the blocking (blocking phase) state;
- the improvement wherein said auxiliary circuit means includes:
- a rectifying means connected in said first control path between said control point and said tap for providing a control current to said tap when the residual voltage present across said switching path in the conductive state drops to values which lead to an undesirably high storage period for said semiconductor switch;
- at least one component which is connected in said control signal path and which, when a control current is flowing in said control signal path, causes a voltage drop, which increases with increasing control current, between said control point and said control electrode, said component having a resistance value which is approximately equal to the product of the forward conducting current gain of said semiconductor switch in its desired operating range and the voltage between said tap and said control electrode, divided by the forward load current of said semiconductor switch;
- and
- a constant current source means connected in said control circuit path between said input terminal and said control point and responsive to the input signal at said input terminal for furnishing an essentially constant current in the forward conducting state, whereby said auxiliary circuit means regulates said storage period in the sense of an improved constancy.
Dependencies are inferred from the claim text.