Cable network power unit for surge protector release
There is provided a cable network power unit ( 22 ) configured to generate a DC power signal periodically switching between a positive and negative voltage, the power unit ( 22 ) comprising a polarity switching module ( 66 ), current measuring device ( 60 ), and a controller ( 64 ), wherein the controller ( 64 ) is responsive to abrupt changes in current to trigger the polarity switching module ( 66 ) to switch polarity of the DC power signal, and thereby reset surge protectors in active devices such as nodes or amplifiers if they have triggered due to a power surge, for example from a lightning strike.
1 . A cable network power unit configured to generate a DC power signal periodically switching between a positive and negative voltage, the power unit comprising a polarity switching module, current measuring device, and a controller, wherein the controller is responsive to abrupt changes in current to trigger the polarity switching module to switch polarity of the DC power signal.
2 . A cable network power unit according to claim 1 , wherein the controller is connected between the current measuring device and the polarity switching module.
3 . A cable network power unit according to claim 1 , wherein a comparator element is disposed between the controller and the current measuring device to compare a measured value with a reference value.
4 . A cable network power unit according to claim 1 , wherein the current measurement device derives a value related to the current by measuring voltage across a resistive element.
5 . A cable network power unit according to claim 1 , wherein the controller is responsive to step changes in current.
6 . A cable network power unit according to claim 1 , wherein a switching frequency of the DC power signal is in the range 5 to 0.2 Hz.
7 . A cable network comprising at least one cable network unit in accordance with claim 1 .
8 . A cable network according to claim 7 , wherein the cable network is a hybrid fiber coaxial network.