Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
147 words
Overcurrent protection apparatus for protecting a power switching element, the switching of which power switching element, to interrupt an electric current delivering power, is controlled by switching control pulses, the apparatus comprising overcurrent detection means for issuing an overcurrent detection signal after detecting that an electric current flowing into the power switching element has exceeded a prescribed value, characterised in that the apparatus includes memory means set by the overcurrent detection signal, a gate circuit for turning off the power switching element by blocking the switching control pulses when said memory means has been set, and reset means for resetting said memory means in response to the trailing edge of a switching control pulse, wherein the power switching element is turned off when said memory means has been set, and subjected to switching control in accordance with the control pulses when said memory means has been reset.
Claim 2
Dependent Claim
147 words
Overcurrent protection apparatus for protecting a power switching element, the switching of which power switching element, to interrupt an electric current delivering power, is controlled by switching control pulses, the apparatus comprising overcurrent detection means for issuing an overcurrent detection signal after detecting that an electric current flowing into the power switching element has exceeded a prescribed value, characterised in that the apparatus includes memory means set by the overcurrent detection signal, a gate circuit for turning off the power switching element by blocking the switching control pulses when said memory means has been set, and reset means for resetting said memory means in response to the trailing edge of a switching control pulse, wherein the power switching element is turned off when said memory means has been set, and subjected to switching control in accordance with the control pulses when said memory means has been reset.
Claim 3
Dependent Claim
76 words
Apparatus as claimed in claim 1, wherein the power switching element is arranged for interrupting primary current of a transformer, and wherein the switching control pulses are generated by a control circuit operable to modulate the pulse width of those pulses in dependence upon variation in a rectified output voltage derived from the secondary side of the transformer, to control switching of the power switching element to maintain the rectified output voltage at a constant value.
Claim 4
Dependent Claim
19 words
Overcurrent protection apparatus according to claim 1 or 2, in which said reset means is composed of integrating circuitry.
Claim 5
Dependent Claim
19 words
Overcurrent protection apparatus according to claim 1 or 2, in which said reset means is composed of differentiating circuitry.
Claim 6
Dependent Claim
42 words
Overcurrent protection apparatus according to claim 1, 2, 3 or 4, in which the period of time for which the power switching element is normally off is longer than the period of time for which the power switching element is normally on.
Claim 7
Dependent Claim
23 words
Overcurrent protection apparatus according to claim 5, in which the power switching element is supplied with every other one of the control pulses.