Signal level crossing detector circuit

Abstract

A signal level crossing detector circuit includes a DC isolator and a detector circuit. The DC isolator has at least a first input, which is operable to receive a high voltage AC signal, and at least a first capacitor, a first plate of the first capacitor being electrically connected to the first input. The detector circuit is operable at a low voltage and has at least a first detector input, the first detector input being electrically connected to a second plate of the first capacitor, the low voltage detector circuit being operable to provide a change in output signal in dependence on a high voltage AC signal on the first input crossing a predetermined signal level. The signal level crossing detector may be single ended or differential.

1 . A Power Line Communication (PLC) device comprising:
 a Printed Circuit Board (PCB);   Power Line Communication (PLC) circuitry; and   a first capacitor and a second capacitor coupled between AC mains power and the PLC circuitry, a first plate of the first capacitor and a first plate of the second capacitor formed as conductive layers on opposite surfaces of the PCB, a second plate of the first capacitor formed as a conductive layer within the PCB and a second plate of the second capacitor formed as a differing conductive layer within the PCB.   
     
     
         2 . The PLC device of  claim 1 , wherein the second plate of the first capacitor is nearer the first plate of the first capacitor than the second plate of the second capacitor is to the first plate of the first capacitor. 
     
     
         3 . The PLC device of  claim 1 , wherein the second plate of the first capacitor and the second plate of the second capacitor form a third capacitor. 
     
     
         4 . The PLC device of  claim 3 , wherein the third capacitor has a larger capacitance than capacitance of each of the first capacitor and the second capacitor. 
     
     
         5 . The PLC device of  claim 1 , wherein the second plate of the first capacitor and the second plate of the second capacitor comprise first and second embedded conductive layers separated by at least one dielectric layer. 
     
     
         6 . The PLC device of  claim 5 , wherein:
 the first and second embedded layers are spaced apart by a first distance;   the first plate of the first capacitor and the first embedded layer are spaced apart by a second distance that is greater than the first distance; and   the first plate of the second capacitor and the second embedded layer are spaced apart by a third distance that is greater than the first distance.   
     
     
         7 . The PLC device of  claim 1 , wherein:
 the first plate of the first capacitor is configured to couple to a live conductor of the AC mains power; and   the first plate of the second capacitor is configured to couple to a neutral conductor of the AC mains power.   
     
     
         8 . The PLC device of  claim 7 , wherein the PLC circuitry comprises a detector circuit configured to provide an AC mains power zero crossing indication. 
     
     
         9 . The PLC device of  claim 8 , wherein the first capacitor and second capacitor couple between the AC mains power and the detector circuit. 
     
     
         10 . A Power Line Communication (PLC) device comprising:
 a Printed Circuit Board (PCB);   detector circuitry configured to produce an AC mains power zero crossing indication; and   DC isolation circuitry coupled between AC mains power and the detector circuitry, the DC isolation circuitry comprising a first capacitor and a second capacitor, a first plate of the first capacitor and a first plate of the second capacitor formed as conductive layers on opposite surfaces of the PCB, a second plate of the first capacitor formed as a conductive layer within the PCB and a second plate of the second capacitor formed as a differing conductive layer within the PCB.   
     
     
         11 . The PLC device of  claim 10 , wherein the second plate of the first capacitor is nearer the first plate of the first capacitor than the second plate of the second capacitor is to the first plate of the first capacitor. 
     
     
         12 . The PLC device of  claim 10 , wherein the second plate of the first capacitor and the second plate of the second capacitor form a third capacitor that has a larger capacitance than capacitance of each of the first capacitor and the second capacitor. 
     
     
         13 . The PLC device of  claim 10 , wherein the second plate of the first capacitor and the second plate of the second capacitor comprise first and second embedded conductive layers separated by at least one dielectric layer. 
     
     
         14 . The PLC device of  claim 13 , wherein:
 the first and second embedded layers are spaced apart by a first distance;   the first plate of the first capacitor and the first embedded layer are spaced apart by a second distance that is greater than the first distance; and   the first plate of the second capacitor and the second embedded layer are spaced apart by a third distance that is greater than the first distance.   
     
     
         15 . The PLC device of  claim 10 , wherein:
 the first plate of the first capacitor is configured to couple to a live conductor of AC mains power; and   the first plate of the second capacitor is configured to couple to a neutral conductor of the AC mains power.   
     
     
         16 . The PLC device of  claim 10 , wherein the detector circuitry comprises a comparator configured to compare voltages at the second plate of the first capacitor and the second plate of the second capacitor to provide the AC mains power zero crossing indication. 
     
     
         17 . A Power Line Communication (PLC) device comprising:
 a Printed Circuit Board (PCB);   DC isolation circuitry configured for coupling to AC mains power, the DC isolation circuitry comprising a first capacitor and a second capacitor, a first plate of the first capacitor and a first plate of the second capacitor formed as conductive layers on opposite surfaces of the PCB, a second plate of the first capacitor formed as a conductive layer within the PCB and a second plate of the second capacitor formed as a differing conductive layer within the PCB, a first comparator input; and   a comparator configured to produce an AC mains power zero crossing indication, having a first input coupled to the second plate of the first capacitor and a second input coupled to the second plate of the second capacitor.   
     
     
         18 . The PLC device of  claim 17 , wherein the second plate of the first capacitor and the second plate of the second capacitor form a third capacitor that has a larger capacitance than capacitance of each of the first capacitor and the second capacitor. 
     
     
         19 . The PLC device of  claim 17 , wherein the second plate of the first capacitor and the second plate of the second capacitor comprise first and second embedded conductive layers separated by at least one dielectric layer. 
     
     
         20 . The PLC device of  claim 17 , wherein:
 the first plate of the first capacitor is configured to couple to a live conductor of the AC mains power; and   the first plate of the second capacitor is configured to couple to a neutral conductor of the AC mains power.