Enabling Circuit for Avoiding Negative Voltage Transients

Abstract

An enabling circuit for enabling a DC-DC converter having a capacitor coupled to an output terminal of the DC-DC converter to be controlled by a control signal. The enabling circuit may include a comparison circuit configured to compare a feedback signal representative of a charge on the capacitor with a signal representative of a reference charge and to provide an output to in response to the comparison to enable the DC-DC converter to be controlled by the control signal if the charge on the capacitor is less than the reference charge. The enabling circuit may also include a discharge path configured to discharge the charge on the capacitor if the charge is greater than the reference charge. A related system and method are also provided.

1 . An enabling circuit for enabling a DC-DC converter having a capacitor coupled to an output terminal of said DC-DC converter to be controlled by a control signal, said enabling circuit comprising: 
 a comparison circuit configured to compare a feedback signal representative of a charge on said capacitor with a signal representative of a reference charge and to provide an output in response to said comparison to prevent said DC-DC converter from being controlled by said control signal if said charge on said capacitor is greater than said reference charge.    
   
   
       2 . The enabling circuit of  claim 1 , wherein said comparison circuit comprises a discharge path configured to discharge said charge on said capacitor if said charge is greater than said reference charge.  
   
   
       3 . The enabling circuit of  claim 2 , wherein said discharge path comprises at least one switch, said at least one switch configured to close to create said discharge path from said capacitor if said charge on said capacitor is greater than said reference charge.  
   
   
       4 . The enabling circuit of  claim 3 , further comprising an output decision circuit configured to receive at least said output from said comparison circuit and provide an enabling signal to enable said DC-DC converter to switch from a first state wherein said DC-DC converter is not controlled by said control signal to a second state wherein said DC-DC converter is controlled by said control signal if said charge on said capacitor is less than said reference charge.  
   
   
       5 . The enabling circuit of  claim 4 , wherein said output decision circuit is further configured to receive a condition signal, and wherein said output decision circuit provides said enabling signal in response to said condition signal.  
   
   
       6 . The enabling circuit of  claim 4 , wherein said comparison circuit comprises a comparator.  
   
   
       7 . The enabling circuit of  claim 1  wherein said comparison circuit is configured to enable said DC-DC converter to be controlled by said control signal if said charge on said capacitor is less than said reference charge.  
   
   
       8 . A system comprising: 
 a DC-DC converter configured to accept an input power level from a power source and provide a regulated output power level to a load, said DC-DC converter having a capacitor coupled to an output terminal of said DC-DC converter; and    an enabling circuit for enabling said DC-DC converter to be controlled by a control signal, said enabling circuit comprising: 
 a comparison circuit configured to compare a feedback signal representative of a charge on said capacitor with a signal representative of a reference charge and to provide an output in response to said comparison to prevent said DC-DC converter from being controlled by said control signal if said charge on said capacitor is greater than said reference charge.  
   
   
   
       9 . The system of  claim 8 , wherein said comparison circuit comprises a discharge path configured to discharge said charge on said capacitor if said charge is greater than said reference charge.  
   
   
       10 . The system of  claim 9 , wherein said discharge path comprises at least one switch, said at least one switch configured to close to create said discharge path from said capacitor if said charge on said capacitor is greater than said reference charge.  
   
   
       11 . The system of  claim 9 , further comprising an output decision circuit configured to receive at least said output from said comparison circuit and provide an enabling signal to enable said DC-DC converter to switch from a first state wherein said DC-DC converter is not controlled by said control signal to a second state wherein said DC-DC converter is controlled by said control signal if said charge on said capacitor is less than said reference charge.  
   
   
       12 . The enabling circuit of  claim 11 , wherein said output decision circuit is further configured to receive a condition signal, and wherein said output decision circuit provides said enabling signal in response to said condition signal.  
   
   
       13 . The system of  claim 8 , wherein said comparison circuit comprises a comparator.  
   
   
       14 . The system of  claim 8  wherein said comparison circuit is configured to enable said DC-DC converter to be controlled by said control signal if said charge on said capacitor is less than said reference charge.  
   
   
       15 . A method comprising: 
 monitoring a charge on a capacitor of a DC-DC converter coupled to an output terminal of said DC-DC converter;    preventing charging of said capacitor if said charge of said capacitor is greater than a reference charge; and    enabling said DC-DC converter to be controlled by a control signal if said charge of said capacitor is less than said reference charge.    
   
   
       16 . The method of  claim 15 , further comprising discharging said capacitor if said charge is greater than said reference charge.  
   
   
       17 . The method of  claim 16 , wherein said discharge operation further comprises closing a switch to create a discharge path from said capacitor to ground.  
   
   
       18 . The method of  claim 15  wherein said enabling step occurs if at least one non capacitor condition is satisfied.