CONTROL OF A CLAMP CIRCUIT DURING TRANSIENT CONDITIONS

摘要

According to example configurations herein, a clamp circuit includes: i) a power dissipation circuit disposed between a first node and a second node of the clamp circuit, and ii) a capacitive element disposed in a control path between the first node and a control input of the power dissipation circuit. During operation, when a voltage spike occurs at the first node, such as caused by opening of a respective switch, the capacitive element in the control path conveys a portion of energy from the first node to control activation of the power dissipation circuit. That is, during the voltage spike, based on conveyance of the energy over the control path, the power dissipation circuit turns ON to dissipate the transient voltage, protecting a main power switch.

主权项

1. An apparatus comprising:
a clamp circuit including a first clamp circuit node, a second clamp circuit node, a power dissipation circuit, a voltage-dependent circuit element, a capacitive element, and a discharge capacitor, wherein the power dissipation circuit includes a first resistor and a clamp switch, the clamp switch having a control input, the first resistor being serially connected to the clamp switch between the first clamp circuit node and the second clamp circuit node, wherein the voltage-dependent circuit element is connected to the first clamp circuit node, the voltage-dependent circuit element having an associated voltage threshold value, wherein the capacitive element is connected to the control input, the voltage-dependent circuit element being serially connected to the capacitive element in a control path between the first clamp circuit node and the control input, wherein the discharge resistor is connected between the control input and the second clamp circuit node, wherein the capacitive element is operative, in response to a transient voltage at the first clamp circuit node exceeding the voltage threshold value, to pass energy from the first clamp circuit node to the control input, thereby causing the clamp switch to operate in a saturation mode from a first time T1 to a second time T2, and wherein the discharge resistor is operative to discharge the capacitive element from about the second time T2 to a third time T3, thereby causing the clamp switch to operate in a linear mode from the second time T2 to the third time T3.