Ringing Suppression Method and Apparatus for Power Converters

Abstract

A method of controlling a power converter for converting a DC input voltage to a DC output voltage is presented The power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, the method comprising: detecting an open loop condition of feedback control by the feedback circuit; and modifying at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control by the feedback circuit returns to the closed loop condition is reduced.

What is claimed is: 
     
         1 . A method of controlling a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, the method comprising:
 detecting an open loop condition of feedback control by the feedback circuit; and   modifying at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control returns to the closed loop condition is reduced, wherein detecting the open loop condition involves:   determining a gradient of the first feedback quantity; and   determining that the open loop condition is present if the determined gradient of the first feedback quantity is not within a predetermined range for the gradient of the first feedback quantity.   
     
     
         2 . The method according to  claim 1 , wherein
 modifying at least one of the one or more control parameters involves:   adjusting a serial impedance and/or a parallel impedance of the feedback circuit in a manner that a transfer function of the feedback circuit after the adjustment has at least one additional pole and at least one additional zero.   
     
     
         3 . The method according to  claim 1 , wherein
 modifying at least one of the one or more control parameters is performed after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         4 . A method of controlling a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, the method comprising:
 detecting an open loop condition of feedback control by the feedback circuit; and   modifying at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control returns to the closed loop condition is reduced,   wherein the feedback circuit generates the control signal further on the basis of a second feedback quantity indicative of an inductor current and a third feedback quantity indicative of a difference between the first feedback quantity and a reference voltage for the output voltage; and   detecting the open loop condition involves:   comparing the third feedback quantity to a voltage level corresponding to the second feedback quantity; and   determining that the open loop condition is present if a difference between the voltage level corresponding to the second feedback quantity and the third feedback quantity is different from zero for a full period of the switching operation of the switching elements.   
     
     
         5 . The method according to  claim 4 , wherein the feedback circuit comprises an operational amplifier element for generating the third feedback quantity by applying a gain factor to the difference between the first feedback quantity and the reference voltage for the output voltage; and
 modifying the at least one of the one or more circuit parameters involves:   reducing the gain factor that is applied by the operational amplifier element in generating the third feedback quantity.   
     
     
         6 . The method according to  claim 4 , wherein
 modifying at least one of the one or more control parameters involves:   adjusting a serial impedance and/or a parallel impedance of the feedback circuit in a manner that a transfer function of the feedback circuit after the adjustment has at least one additional pole and at least one additional zero.   
     
     
         7 . The method according to  claim 4 , wherein
 modifying at least one of the one or more control parameters is performed after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         8 . A method of controlling a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, the method comprising:
 detecting an open loop condition of feedback control by the feedback circuit; and   modifying at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control returns to the closed loop condition is reduced,   wherein the feedback circuit generates the control signal on the basis of the first feedback quantity and a fourth feedback quantity indicative of a sum of a fifth feedback quantity indicative of a result of a conversion of the second feedback quantity to a voltage value and a sixth feedback quantity indicative of a voltage output by a ramp generator; and   modifying at least one of the one or more control parameters involves:   decreasing a ramp slope of the ramp generator.   
     
     
         9 . The method according to  claim 8 , wherein
 modifying at least one of the one or more control parameters involves:   adjusting a serial impedance and/or a parallel impedance of the feedback circuit in a manner that a transfer function of the feedback circuit after the adjustment has at least one additional pole and at least one additional zero.   
     
     
         10 . The method according to  claim 8 , wherein
 modifying at least one of the one or more control parameters is performed after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         11 . A method of controlling a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, the method comprising:
 detecting an open loop condition of feedback control by the feedback circuit; and   modifying at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control returns to the closed loop condition is reduced,   wherein   modifying at least one of the one or more control parameters involves:   adjusting a serial impedance and/or a parallel impedance of the feedback circuit in a manner that a transfer function of the feedback circuit after the adjustment has at least one additional pole and at least one additional zero.   
     
     
         12 . The method according to  claim 11 , wherein
 modifying at least one of the one or more control parameters is performed after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         13 . A control apparatus within a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, wherein the control apparatus is configured to
 detect an open loop condition of feedback control by the feedback circuit; and wherein the control apparatus is configured to   modify at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control by the feedback circuit returns to the closed loop condition is reduced,   wherein the control apparatus is configured to detect the open loop condition   by determining a gradient of the first feedback quantity; and   by determining that the open loop condition is present if the determined gradient of the first feedback quantity is not within a predetermined range for the gradient of the first feedback quantity.   
     
     
         14 . The control apparatus according to  claim 13 , wherein the control apparatus is configured to
 modify at least one of the one or more circuit parameters after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         15 . A control apparatus within a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, wherein the control apparatus is configured to
 detect an open loop condition of feedback control by the feedback circuit; and wherein the control apparatus is configured to   modify at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control by the feedback circuit returns to the closed loop condition is reduced,   wherein the feedback circuit generates the control signal further on the basis of a second feedback quantity indicative of an inductor current and a third feedback quantity indicative of a difference between the first feedback quantity and a reference voltage for the output voltage; and wherein the control apparatus is configured to   detect the open loop condition   by comparing the third feedback quantity to a voltage level corresponding to the second feedback quantity; and   by determining that the open loop condition is present if a difference between the voltage level corresponding to the second feedback quantity and the third feedback quantity is different from zero for a full period of the switching operation of the switching elements.   
     
     
         16 . The control apparatus according to  claim 15 , wherein the control apparatus is configured to
 modify at least one of the one or more circuit parameters after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         17 . A control apparatus within a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, wherein the control apparatus is configured to
 detect an open loop condition of feedback control by the feedback circuit; and wherein the control apparatus is configured to 
 modify at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control by the feedback circuit returns to the closed loop condition is reduced, 
 wherein the feedback circuit generates the control signal on the basis of the first feedback quantity and a fourth feedback quantity indicative of a sum of a fifth feedback quantity indicative of a result of a conversion of the second feedback quantity to a voltage value and a sixth feedback quantity indicative of a voltage output by a ramp generator; and wherein the control apparatus is configured to 
 modify the at least one of the one or more circuit parameters 
 by decreasing a ramp slope of the ramp generator. 
 
     
     
         18 . The control apparatus according to  claim 17 , wherein the control apparatus is configured to
 modify at least one of the one or more circuit parameters after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.   
     
     
         19 . A control apparatus within a power converter for converting a DC input voltage to a DC output voltage, wherein the power converter comprises an inductor, one or more switching elements for energizing and de-energizing the inductor, a drive circuit for controlling switching operation of the one or more switching elements in accordance with a control signal, and a feedback circuit for generating the control signal on the basis of a first feedback quantity indicative of an actual output voltage of the power converter and in accordance with one or more circuit parameters of the feedback circuit, wherein the control apparatus is configured to
 detect an open loop condition of feedback control by the feedback circuit; and wherein the control apparatus is configured to   modify at least one of the circuit parameters of the feedback circuit in such a manner that a time until the feedback control by the feedback circuit returns to the closed loop condition is reduced,   wherein the control apparatus is configured to   modify at least one of the one or more circuit parameters   by adjusting a serial impedance and/or a parallel impedance of the feedback circuit in a manner that a transfer function of the feedback circuit after the adjustment has at least one additional pole and at least one additional zero.   
     
     
         20 . The control apparatus according to  claim 19 , wherein the control apparatus is configured to
 modify at least one of the one or more circuit parameters after the open loop condition of feedback control has been detected and the first feedback quantity has reached its peak value.