Bias voltage circuit for biasing a transient suppression device and apparatus using same

Abstract

Embodiments provide a charge pump circuit which produces a bias voltage that is applied to a transient suppression device used to clamp both positive and negative transients on signal lines. The bias voltage can be set to a level that is above the sum of a DC voltage differential between positive and negative signal lines and the maximum signal voltage.

What is claimed is: 
     
         1 - 7 . (canceled) 
     
     
         8 . A transient suppression unit, comprising:
 a first connector and a second connector having a plurality of signal lines connecting the first and second connectors;   a plurality of positive polarity transient steering diodes each having an anode and a cathode, the anode connected to one of the plurality of signal lines where there is one positive polarity transient steering diode for each one of the plurality of signal lines;   a plurality of negative polarity transient steering diodes each having an anode and a cathode, the cathode connected to one of the plurality of signal lines, where there is one negative polarity transient steering diode for each one of the plurality of signal lines;   a transient suppression device having a positive side coupled to the cathode of each of the plurality of positive polarity transient steering diodes and a negative side coupled to each of the anodes of the plurality of negative polarity transient steering diodes, the transient suppression device having a clamp voltage at which the transient suppression device clamps the voltage on each of the plurality of signal lines; and   a bias circuit that provides a bias voltage across the transient suppression circuit that is generated from a power voltage differential between a first signal line and a second signal line of the plurality of signal lines, the bias voltage being generated at a level that is sufficiently high to reverse bias each of the plurality of positive polarity transient steering diodes and each of the plurality of negative polarity transient steering diodes to reduce the capacitance of each of the plurality of positive and negative polarity transient steering diodes such that the effects of the junction capacitance of the transient suppression device on signal transmission in each of the plurality of signal lines are substantially eliminated.   
     
     
         9 . The transient suppression unit of claim  1 , wherein the bias circuit is powered by a direct current (DC) voltage differential between the first signal line and the second signal line of the plurality of signal lines. 
     
     
         10 . The transient suppression unit of claim  2 , wherein the bias circuit comprises a charge pump circuit that generates the bias voltage from the DC differential voltage. 
     
     
         11 . The transient suppression unit of claim  3 , wherein the bias circuit comprises:
 an input network having a first input operable to be coupled to the first signal line and a second input operable to be coupled to the second signal line, the input network produces a direct current (DC) voltage between a positive input line and a negative input line from the power voltage differential between the first signal line and the second signal line; and   a bias voltage generator having a positive input connected to the positive input line of the input network and a negative input connected to the negative input line of the input network, the bias voltage generator circuit operable to produce a DC voltage output between a positive output and a negative output, the positive output coupled to a positive side of the transient suppression device, the negative output coupled to a negative side of the transient suppression device, the DC output voltage is at a level above the sum of a maximum amplitude of the power voltage differential between the first and second signal lines and a signal level between the first and second signal lines.   
     
     
         12 . The transient suppression unit of claim  4 , wherein the input network comprises a first input impedance between the first signal line and the positive input line of the input network, and a second input impedance between the second signal line and the negative input line of the input network, wherein the first and second impedances are substantially equal in magnitude. 
     
     
         13 . The transient suppression unit of claim  1 , further comprising a heating unit that is powered by the power voltage provided on the signal lines that provides heat to the transient suppression unit. 
     
     
         14 . The transient suppression unit of claim  1 , wherein the plurality of signal lines is an Ethernet bus. 
     
     
         15 . The transient suppression unit of claim  4 , wherein the bias voltage generator comprises a charge pump having a positive bridging diode connected to the positive input line and a negative bridging diode connected to negative input line. 
     
     
         16 . A transient protected electrical apparatus, comprising:
 a network connector configured to receive a powered network bus having a plurality of signal lines including a first signal line and a second signal line, wherein the first and second signal lines are operable to provide a power voltage differential between them;   a transient protection unit coupled to the plurality of signal lines and operable to be powered by the power voltage differential, and having a positive polarity transient steering diode and a negative polarity transient steering diode coupled to each signal line,   wherein the positive polarity transient steering diodes are coupled to the negative polarity transient steering diodes through a transient suppression device that is biased by a bias circuit of the transient protection unit with a direct current (DC) voltage that is at a bias voltage level that is higher than a sum of the voltage differential between the positive and negative signal lines and a maximum signal level, and wherein the bias voltage is generated at a level that is sufficiently high to reduce the capacitance of each of the positive and negative transient steering diodes such that the effects of the junction capacitance of the transient suppression device on signal transmission in each of the plurality of signal lines are substantially eliminated; and   a protected circuit coupled to the network bus.   
     
     
         17 . The transient protected electrical apparatus of  claim 9 , wherein the powered network bus is a powered Ethernet bus in conformance with an IEEE 802.3 specification. 
     
     
         18 . The transient protected electrical apparatus of  claim 9 , wherein the power voltage differential between the first and second signal lines is a DC power voltage differential. 
     
     
         19 . The transient protected electrical apparatus of  claim 11 , wherein the bias circuit comprises:
 an input network having a first input operable to be coupled to the first signal line and a second input operable to be coupled to the second signal line, the input network produces a direct current (DC) voltage between a positive input line and a negative input line from the power voltage differential regardless of a polarity of the power voltage differential between the first signal line and the second signal line; and   a bias voltage generator having a positive input connected to the positive input line of the input network and a negative input connected to the negative input line of the input network, the bias voltage generator circuit operable to produce a DC voltage output between a positive output and a negative output, the positive output coupled to a positive side of the transient suppression device, the negative output coupled to a negative side of the transient suppression device, the DC output voltage is at a level above the sum of a maximum amplitude of the power voltage differential between the first and second signal lines and a signal level between the first and second signal lines.   
     
     
         20 . The transient protected electrical apparatus of  claim 12 , wherein the bias voltage generator comprises a charge pump circuit. 
     
     
         21 . The transient protected electrical apparatus of  claim 9 , wherein the bias voltage is less than a clamp voltage of the transient suppression circuit. 
     
     
         22 . A method of suppressing transients on a plurality of signal lines, the method comprising:
 providing a plurality of positive polarity transient steering diodes each having an anode and a cathode;   connecting each of the plurality of signal lines to a respective anode of a respective positive polarity transient steering diode;   providing a plurality of negative polarity transient steering diodes each having an anode and a cathode;   connecting each of the plurality of signal lines to a respective cathode of a respective negative polarity transient steering diode;   providing a transient suppression device having a positive side and a negative side, the transient suppression device having a clamp voltage at which the transient suppression device transitions from a non-conducting state to a conducting state;   coupling the positive side of the transient suppression device to the respective cathode of each of the plurality of positive polarity transient steering diodes and coupling the negative side of the transient suppression device to the respective anode of each of the plurality of negative polarity transient steering diodes; and   reverse biasing each of the plurality of positive polarity transient steering diodes and each of the plurality of negative polarity transient steering diodes by applying a bias voltage across the transient suppression device that is sufficiently high to reduce the capacitance of each of the plurality of positive and negative polarity transient steering diodes such that the effects of the junction capacitance of the transient suppression device on signal transmission in each of the plurality of signal lines are substantially eliminated.   
     
     
         23 . The method of  claim 15 , comprising:
 generating said bias voltage from a power voltage differential between a first signal line and a second signal line of the plurality of signal lines.