Patent Publication Number: US-2022224314-A1

Title: Adaptive capacitve filter circuit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Application No. 63/136,267, filed Jan. 12, 2021, which is hereby incorporated by reference. 
    
    
     BACKGROUND 
     As new electronic devices are developed and integrated circuit (IC) technology advances, new IC products are commercialized. One example IC product includes switches or switch control circuitry related to power management.  FIG. 1  is a diagram of a conventional power management system  100  having an alternating-current (AC) source  102 , a rectifier bridge  104 , and a capacitive filter  108 . As shown, the rectifier bridge  104  is coupled to the AC source  102  and includes a rectifier bridge output  106 . In operation, the rectifier bridge  104  is configured to rectify an input voltage (VIN) from the AC source  102 , resulting in an output voltage (VOUT) at the rectifier bridge output  106 . VOUT is provided to a load (not shown). In the example of  FIG. 1 , the capacitive filter  108  is configured to support two different VIN levels (e.g., 120V and 240V). As shown, the capacitive filter  108  includes a first capacitor (C 1 ) and a second capacitor (C 2 ). C 2  has a first electrode coupled to the rectifier bridge output  106  and a second electrode coupled to ground. C 1  has a first electrode coupled to the rectifier bridge output  106  and a second electrode coupled to ground via a switch (Q 1 ). Q 1  is controlled by the output of a comparator  110 , which is configured to compare VOUT (proportional to VIN) with a reference voltage (VREF) provided by a voltage source  112 . When VOUT is greater than VREF (e.g., above 190V), Q 1  is open, C 1  is disconnected, and C 2  (e.g., rated for 400V) is the only filter capacitor connected. When VOUT is not greater than VREF (e.g., not greater than 190V), Q 1  is closed, and C 1  (e.g., rated for 200V) is connected in parallel with C 2 . 
     With the capacitive filter  108 , the power management system  100  has various shortcomings. Firstly, a short to Q 1  results in a hazardous overvoltage condition on C 1 . Secondly, Q 1  needs to withstand the peak VIN. Also, the minimum value of C 2  may be limited by the root r mean square (RMS) current rating rather than the energy storage requirements. 
     SUMMARY 
     In one example embodiment, an adaptive capacitive filter circuit includes: a first adaptive capacitive filter circuit terminal adapted to be coupled to a rectifier bridge output; a second adaptive capacitive filter circuit terminal adapted to be coupled to ground; a first capacitor having a first electrode and a second electrode, the first electrode of the first capacitor coupled to the first adaptive capacitive filter circuit terminal; a second capacitor having a first electrode and a second electrode, the second electrode of the second capacitor coupled to the second adaptive capacitive filter circuit terminal; a first switch coupled between the second electrode of the first capacitor and the second adaptive capacitive filter circuit terminal; a second switch coupled between the first adaptive capacitive filter circuit terminal and the first electrode of the second capacitor; and a third switch coupled between the second electrode of the first capacitor and the first electrode of the second capacitor. 
     In another example embodiment, an integrated circuit includes control circuitry for an adaptive capacitive filter circuit. The control circuitry is configured to: detect whether an output voltage at a rectifier bridge output is greater than a threshold; responsive to detecting that the output voltage is greater than the threshold, provide a first set of switch drive signals for switches of the adaptive capacitive filter circuit to couple capacitors of the adaptive capacitive filter circuit in series; and responsive to detecting that the output voltage is not greater than the threshold, provide a second set of switch drive signals for switches of the adaptive capacitive filter circuit to couple the capacitors of the adaptive capacitive filter circuit in parallel. 
     In yet another example embodiment, a system includes an adaptive capacitive filter circuit having: a set of capacitors; a first adaptive capacitive filter circuit terminal adapted to be coupled to a rectifier bridge output; and a second adaptive capacitive filter circuit terminal adapted to be coupled to ground. The adaptive capacitive filter circuit is configured to connect capacitors of the set of capacitors in series or in parallel between the first adaptive capacitive filter circuit terminal and the second adaptive capacitive filter circuit terminal responsive to a control signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a conventional power management system having a capacitive filter. 
         FIG. 2  is a diagram of a power management system having an adaptive capacitive filter circuit in accordance with an example embodiment. 
         FIG. 3  is a diagram of another power management system having an adaptive capacitive filter circuit in accordance with an example embodiment. 
         FIG. 4  is a diagram of a system having an adaptive capacitive filter circuit in accordance with an example embodiment. 
         FIG. 5  is a flowchart of an adaptive capacitive filter circuit method in accordance with an example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The same reference numbers (or other reference designators) are used in the drawings to designate the same or similar (structurally and/or functionally) features.  FIG. 2  is a diagram of a power management system  200  having an adaptive capacitive filter circuit  210  in accordance with an example embodiment. As shown, the power management system  200  includes an alternating-current (AC) source  202  coupled to a rectifier bridge  204  having a rectifier bridge output  206 . In operation, the rectifier bridge  204  is configured to rectify an input voltage (VIN) from the AC source  202 , resulting in an output voltage (VOUT) at the rectifier bridge output  206 , where VOUT is smoothed by the adaptive capacitive filter circuit  210 . In the example of  FIG. 2 , the rectifier bridge output  206  is adapted to be coupled to a load, the adaptive capacitive filter circuit  210 , and a control circuit  250  for the adaptive capacitive filter circuit  210 . In operation, the adaptive capacitive filter circuit  210  and the control circuit  250  are configured to adjust a capacitive filter value at the rectifier bridge output  206  to account for two or more possible VIN levels (e.g., 120V and 240V) from the AC source  202  while protecting against possible fault conditions. In some example embodiments, the control circuit  250  is part of the adaptive capacitive filter circuit  210  rather than separate from and coupled to the adaptive capacitive filter circuit  210 . 
     In the example of  FIG. 2 , the adaptive capacitive filter circuit  210  includes a first adaptive capacitive filter circuit terminal  212 , a second adaptive capacitive filter circuit terminal  214 , and a third adaptive capacitive filter circuit terminal  216 . The first adaptive capacitive filter circuit terminal  212  is coupled to the rectifier bridge output  206  and is configured to receive VOUT. The second adaptive capacitive filter circuit terminal  214  is coupled to a control circuit output  254  of the control circuit  250  and is configured to receive a control signal (CS 1 ) that indicates whether VOUT is greater than a threshold. The third adaptive capacitive filter circuit terminal  216  is coupled to ground. As shown, the control circuit  250  includes a control circuit input  252 , the control circuit output  254 , and a control circuit terminal  256 . The control circuit input  252  is coupled to the rectifier bridge output  206  and is configured to receive VOUT. The control circuit terminal  256  is coupled to ground. In operation, the control circuit  250  is configured to provide CS 1  at the control circuit output  254  responsive to a comparison of VOUT with a threshold (e.g., the value of CS 1  varies depending on whether VOUT is greater than the threshold). 
     As shown, the adaptive capacitive filter circuit  210  includes a set of capacitors  218  having a first set of capacitors terminal  220  and a second set of capacitors terminal  222 . The first set of capacitors terminal  220  is coupled to the first adaptive capacitive filter circuit terminal  212 . The second set of capacitors terminal  222  is coupled to the switch arrangement  224 . The switch arrangement  224  includes a first switch arrangement terminal  226 , a second switch arrangement terminal  228 , a third switch arrangement terminal  230 , and a fourth switch arrangement terminal  232 . The first switch arrangement terminal  226  is coupled to the second set of capacitors terminal  222 . The second switch arrangement terminal  228  is coupled to the control circuit output  254 . The third switch arrangement terminal  230  is coupled to ground via the third adaptive capacitive filter circuit terminal  216 . The fourth switch arrangement terminal  232  is coupled to a fault sense circuit  240 . 
     In the example of  FIG. 2 , the fault sense circuit  240  includes a first fault sense circuit input  242 , a second fault sense circuit input  244 , and a fault sense circuit output  246 . The first fault sense circuit input  242  is coupled to the first set of capacitors terminal  220 . The second fault sense circuit input  244  is coupled to the second set of capacitors terminal  222 . The fault sense circuit output  246  is coupled to the fourth switch arrangement terminal  232 . In operation, the fault sense circuit  240  is configured to provide a control signal (CS 2 ) at the fault sense circuit output  246  responsive to sense signals received at the first fault sense circuit input  242  and the second fault sense circuit input  244 . In different example embodiments, the fault sense circuit  240  may include respective inputs to sense faults for any capacitor of the set of capacitors  218  and/or any switch of the switch arrangement  224 . 
     As described above, the control circuit  250  is configured to provide CS 1  at the control circuit output  254  based on a comparison of VOUT with a threshold. Responsive to CS 1 , the switch arrangement  224  is configured to provide a parallel connection option  234  for capacitors of the set of capacitors  218  or a series connection option  236  for capacitors of the set of capacitors  218 . In some example embodiments, if VOUT is above the threshold, CS 1  directs the switch arrangement  224  to use the series connection option  236  for capacitors of the set of capacitors  218 . If VOUT is not above the threshold, CS 1  directs the switch arrangement  224  to use the parallel connection option  234  for capacitors of the set of capacitors  218 . Without limitation, the set of capacitors  212  includes a first capacitor and a second capacitors that are coupled in series or in parallel based on the switch arrangement  214  and responsive to CS 1 . 
     With the fault sense circuit  240 , a fault condition (e.g., a capacitor fault and/or a switch fault) related to the adaptive capacitive filter circuit  210  may be detected. Responsive to a detected fault condition, the fault sense circuit  240  is configured to provide CS 2  to the fourth switch arrangement terminal  232  of the switch arrangement  224 . Responsive to CS 2 , the switch arrangement  224  is configured to use a fault option  238  for switches of the switch arrangement  224 . In some example embodiments, the fault option  238  assumes switches of the switch arrangement  224  will fault to a short circuit rather than an open circuit. In some example embodiments, the fault option  238  provides a path to ground (e.g., by connecting the first adaptive capacitive filter circuit terminal  212  to the third adaptive capacitive filter circuit  216  via switches of the switch arrangement  224 ) so that a fuse will trigger responsive to the detected fault condition. Without limitation, the fuse (not shown) may be between the AC source  202  and the rectifier bridge  204 . In some example embodiments, the switch arrangement  224  includes control logic (e.g., the control logic  320  in  FIGS. 3 and 4 ) configured to receive CS 1  and CS 2  and provide switch control signals responsive to CS 1  and CS 2 . When CS 2  indicates a fault condition, CS 2  has priority over CS 1 . 
     Together, the control circuit  250 , the fault sense circuit  240 , and such control logic form the control circuitry for the adaptive capacitive filter circuit  210 . In different example embodiments, the control circuitry for the adaptive capacitive filter circuit  210  may be part of one integrated circuit (IC) or multiple ICs. As another option, the switch arrangement  224  may be included with the same IC as the control circuitry. As another option, the set of capacitors  218  may be separate from the IC or ICs having the control circuitry and the switch arrangement  224 . 
     With the adaptive capacitive filter circuit  210  and the control circuit  250 , different VIN levels from the AC source  202  are supported while reducing the shortcomings of the conventional approach of  FIG. 1 . Some benefits of the adaptive capacitive filter circuit  210  relative to the conventional approach of  FIG. 1  include accounting for fault conditions and using capacitors with smaller ratings. Compared to Q 1  in  FIG. 1 , the switches of the switch arrangement  224  have smaller ratings and are physically smaller. 
       FIG. 3  is a diagram of another power management system  300  having an adaptive capacitive filter circuit  210 A (an example of the adaptive capacitive filter circuit  210  in  FIG. 2 ) in accordance with an example embodiment. As shown, the power management system  300  includes the AC source  202  coupled to the rectifier bridge  204 . The rectifier bridge output  206  of the rectifier bridge  204  is coupled to the adaptive capacitive filter circuit  210 A and a control circuit  250 A (an example of the control circuit  250  in  FIG. 1 ). In the example of  FIG. 3 , the rectifier bridge output  206  is adapted to be coupled to load (not shown). In operation, the rectifier bridge  204  is configured to rectify VIN from the AC source  202 , resulting in VOUT at the rectifier bridge output  206 , where VOUT is a smoothed by the adaptive capacitive filter circuit  210 A. In operation, the adaptive capacitive filter circuit  210 A and the control circuit  250 A are configured to adjust a capacitive filter value at the rectifier bridge output  206  to account for two VIN levels (e.g., 120V and 240V) while protecting against possible fault conditions. In some example embodiments, the control circuit  250 A is part of the adaptive capacitive filter circuit  210 A rather than coupled to the adaptive capacitive filter circuit  210 A. 
     In the example of  FIG. 3 , the adaptive capacitive filter circuit  210 A includes the first adaptive capacitive filter circuit terminal  212 , the second adaptive capacitive filter circuit terminal  214 , and the third adaptive capacitive filter circuit terminal  216 . Again, the first adaptive capacitive filter circuit terminal  212  is coupled to the rectifier bridge output  206  and is configured to receive VOUT. The second adaptive capacitive filter circuit terminal  214  is coupled to the control circuit output  254  of the control circuit  250 A and is configured to receive CS 1 . The third adaptive capacitive filter circuit terminal  216  is coupled to ground. 
     In the example of  FIG. 3 , the adaptive capacitive filter circuit  210 A includes capacitors C 3  and C 4  (an example of the set of capacitors  218  in  FIG. 2 ). The adaptive capacitive filter circuit  210 A also includes transistors Q 2 , Q 3 , and Q 4  (e.g., switches of the switch arrangement  224  in  FIG. 2 ). The adaptive capacitive filter circuit  210 A also includes a fault sense circuit  240 A (an example of the fault sense circuit  240  in  FIG. 2 ) and control logic  320 . 
     As shown, a first electrode of C 3  is coupled to the first adaptive capacitive filter circuit terminal  212 . A second electrode of C 3  is coupled to ground via Q 2 . Specifically, a first current terminal of Q 2  is coupled to the second electrode of C 3 , and a second current terminal of Q 2  is coupled to ground. Also, a first electrode of C 4  is coupled to the first adaptive capacitive filter circuit terminal  212  via Q 3 . Specifically, a first current terminal of Q 3  is coupled to the first adaptive capacitive filter circuit terminal  212 , and a second current terminal of Q 3  is coupled to the first electrode of C 4 . A second electrode of C 4  is coupled to ground. The first electrode of C 4  is also coupled to the second electrode of C 3  via Q 4 . Specifically, a first current terminal of Q 4  is coupled to the second electrode of C 3 , and the second current terminal of Q 4  is coupled to the first electrode of C 4 . With the switch arrangement of  FIGS. 3 , C 3  and C 4  can be connected in parallel, connected in series, or bypassed. 
     In the example of  FIG. 3 , the control of Q 2 , Q 3 , and Q 4  is based on the operations of the control circuit  250 A, the fault sense circuit  240 A, and the control logic  320 . As shown, the control circuit  250 A includes a comparator  302  having an inverting input, a non-inverting input, and a comparator output  304 . The inverting input of the comparator  302  is coupled to the control circuit input  252  and is configured to receive VOUT (proportional to VIN). The non-inverting input of the comparator  302  is coupled to a voltage source  308  and is configured to receive reference voltage (VREF) from the voltage source  308  (i.e., VREF is a threshold). Specifically, a first side of the voltage source  308  is coupled to the non-inverting input of the comparator  302 , and a second side of the voltage source  308  is coupled to ground via the control circuit terminal  256 . In operation, the comparator  302  is configured to adjust CS 1  at the comparator output  304  based on a comparison of VOUT with VREF. 
     In the example of  FIG. 3 , the fault sense circuit  240 A includes fault sense circuit inputs  310  configured to receive sense signals. The sense signals indicate, for example, the voltage across C 3 , the voltage across C 4 , the voltage across Q 3 , the voltage across Q 4 , the voltage across Q 5 , and/or other sense signals. As another option, current sense signals could indicate a fault condition. Responsive to the sense signals, particular thresholds, and comparison operations, the faults sense circuit  240 A is configured to adjust CS 2  at the fault sense circuit output  246  to indicate whether there are any faults. 
     As shown, CS 1  and CS 2  are provided to the control logic  320  as inputs. More specifically, the control logic  320  includes a first control logic input  322 , a second control logic input  324 , a first control logic output  326 , and a second control logic output  328 . The first control logic input  322  is configured to receive CS 1 . The second control logic input  324  is configured to receive CS 2 . The first control logic output  326  is coupled to the control terminals of Q 2  and Q 3 . The second control logic output  328  is coupled to the control terminal of Q 4 . In operation, the control logic  320  is configured to provide switch control signals for Q 2 , Q 3 , and Q 4  response to CS 1  and CS 2 . In some example embodiments, if CS 1  is a first value (indicating VOUT is greater than VREF), the control logic  320  is configured to provide switch control signals so that C 3  and C 4  are in series (i.e., Q 2  and Q 3  off, and Q 4  on) between the first adaptive capacitive filter circuit terminal  212  and ground. If CS 1  is a second value (indicating VOUT is not greater than VREF), the control logic  320  is configured to provide switch control signals so that C 3  and C 4  are in parallel (i.e., Q 2  and Q 3  on, and Q 4  off) between the first adaptive capacitive filter circuit terminal  212  and ground. If CS 2  indicates a fault condition, the control logic  320  is configured to provide switch control signals so that C 3  and C 4  are bypassed such that the first adaptive capacitive filter circuit terminal  212  is coupled to ground via Q 2 , Q 3 , and Q 4  (i.e., Q 2 , Q 3 , and Q 4  on or shorted). When CS 2  indicates a fault condition, CS 2  has priority over CS 1 . In some example embodiments, the number of voltage levels supported, the number of capacitors, and the number of switches may vary from the example of  FIG. 3   
     Together, the control circuit  250 A, the fault sense circuit  240 A, and the control logic  320  form the control circuitry for the adaptive capacitive filter circuit  210 A. In different example embodiments, the control circuitry for the adaptive capacitive filter circuit  210 A may be part of one IC or multiple ICs. As another option, Q 2 , Q 3 , and Q 4  may be included with the same IC as the control circuitry. As another option, C 3  and C 4  may be separate from the IC or ICs having the control circuitry and Q 2 , Q 3 , and Q 4 . 
     In the example of  FIG. 3 , the adaptive capacitive filter circuit  210 A includes a first terminal  330  and a second terminal  332 . The first terminal  330  is between the second current terminal of Q 3 , the second current terminal of Q 4 , and the first electrode of C 4 . The second terminal  332  is between the second electrode of C 3 , the first current terminal of Q 2  and the first current terminal of Q 4 . If C 3  and C 4  are external to the IC having the control circuitry and Q 2 , Q 3 , and Q 4 , the IC may include external terminals or pins related to the first terminal  330  and the second terminal  332  of the adaptive capacitive filter circuit  210 A to facilitate coupling C 3  and C 4  to the other components as shown in  FIG. 3 . The IC may also include external terminals or pins related to the first adaptive capacitive filter circuit terminal  212 , and the third adaptive capacitive filter circuit terminal  216 . In some example embodiments, the control circuit  250 A is internal to the IC having the control logic  320 . In such case, the second adaptive capacitive filter circuit terminal  214  is an internal terminal of the IC rather than an external terminal or pin. 
     In some example embodiments of the adaptive capacitive filter circuit  210 A, all switches (Q 2 , Q 3 , and Q 4 ) may be initially off (i.e., a cold start). After an input voltage (e.g., VIN from the AC source  202 ) is applied, C 3  and C 4  charge in series through the body diode of Q 4  to a voltage that is approximately equal to one half the peak input voltage. Consequently, all the switches are exposed to a voltage not higher than half the input voltage. Relative to transistor (e.g., Q 1 ) of the conventional approach of  FIG. 1 , the transistors of the adaptive capacitive filter circuit (e.g., Q 2 , Q 3 , and Q 4 ) will be rated to a voltage that is half that of Q 1 . The result is a substantial decrease in the specific on-resistance (Rsp) and relative size of Q 2 , Q 3 , and Q 4  relative to Q 1 . 
     In some example embodiments of the adaptive capacitive filter circuit, C 3  and C 4  are rated for half the peak input voltage. With a lower rating for C 3  and C 4 , a substantially higher root mean square (RMS) current capability exists relative to C 1  and C 2  in the conventional approach. Also, capacitance of the adaptive capacitive filter circuit is constrained by energy storage requirements rather than RMS current. 
     In some example embodiments, failure of either Q 2  or Q 3  results in overvoltage on capacitors C 3  or C 4 . Capacitor failure of C 3  or C 4  may result in a fault current that may not be high enough to clear the input fuse resulting in catastrophic venting/fire risk. To avoid this outcome, the voltage across C 1  and C 2  may be sensed. If the sense voltage exceeds a particular value, all switches (e.g., Q 2 , Q 3 , and Q 4  in  FIG. 3 ) are turned on simultaneously, thereby “crowbarring” the output of the bridge rectifier and creating a fault current sufficient to clear the input fuse. As another option, the voltage across Q 2 , Q 3 , or Q 4  may be sensed to detect a fault condition. 
     With the adaptive capacitive filter circuit  210 A and the control circuit  250 A, different VIN levels from the AC source  202  are supported while reducing the shortcomings of the conventional approach of  FIG. 1 . Some benefits of the adaptive capacitive filter circuit  210 A relative to the conventional approach of  FIG. 1  include accounting for fault conditions and using capacitors with smaller ratings. Compared to Q 1  in  FIG. 1 , Q 2 , Q 3 , and Q 4  in  FIG. 3  have smaller ratings and are physically smaller. 
       FIG. 4  is a diagram of a system  400  having an adaptive capacitive filter circuit  210 B in accordance with an example embodiment. The system  400  represents any electrical device having a load  430  and power management circuitry including: a power supply  401 ; the adaptive capacitive filter circuit  210 B; a power stage  410 ; and switching converter controller components for the power stage  410 . In the example of  FIG. 4 , the control circuitry (e.g., the control circuit  250 , the control logic  320 , and the fault sense circuit  240 A) and the switch arrangement  224  of the adaptive capacitive filter circuit  210 B are part of an IC  402 . Meanwhile, the set of capacitors  218  of the adaptive capacitive filter circuit  210 B are external to the IC  402 . In other example embodiments, control circuitry and the switch arrangement  224  of the adaptive capacitive filter circuit  2106  may be part of multiple ICs. 
     As shown, the power supply  401  includes the AC source  202  coupled to the rectifier bridge  204 . In the system  400 , the rectifier bridge output  206  of the rectifier bridge  204  is coupled to: an IC input  404  of the IC  402 ; and a power stage input  416  of a power stage  410 . In operation, the rectifier bridge  204  is configured to rectify VIN from the AC source  202 , resulting in an output voltage (VOUT 1 ) at the rectifier bridge output  206 , where VOUT 1  is a smoothed by the adaptive capacitive filter circuit  2106 . 
     In the example of  FIG. 4 , the IC  402  includes a switching converter controller components to control power switches  414  of the power stage  410 . Example switching converter controller components that may be included with the IC  402  include a control loop  406  and a driver circuit  408 . In operation, the control loop  406  and the driver circuit  408  are configured to power switch drive signals, such as a high-side control signal (HS_CS) and a low-side control signal (LS_CS), to the power stage  410 . As shown, the power stage  410  includes the power stage input  416 , a first drive signal input  418 , a second drive signal input  420 , a power stage output  422 , an inductor  412 , and the power switches  414 . Using the control loop  406  and the driver circuit  408 , the IC  402  is configured to provide power switch drive signals (e.g., HS_CS and LS_CS) to the power switches  414  via the first drive signal input  418  and the second drive signal input  420 . The power switch drive signals control the on/off state of the power switches  414  to regulate current in the inductor  412  and maintain a target output voltage (VOUT 2 ) while powering the load  430 . Over time, the demand of the load  430  may change. Example control options managed by the control loop  406  to adjust the power switch drive signals include determining feedback error between VOUT 2  and a reference voltage, performing pulse-width modulation (PWM) responsive to the feedback error, performing pulse-frequency modulation (PFM) responsive to the feedback error, performing zero crossing detection, performing multi-phase control, and/or other control options. 
     Using the control circuitry (e.g., the control circuit  250 , the control logic  320 , and the fault sense circuit  240 A) and the switch arrangement  224 , the IC  402  is configured to controls whether the capacitors of the set of capacitors  218  are coupled in series, in parallel, or bypassed as described herein. To enable the switch arrangement  224  to be coupled to the capacitors of the set of capacitors  218 , the IC  402  also include external terminals or pins  330  and  332  (corresponding to first and second terminals  330  and  332  in  FIG. 3 ). 
     In some example embodiments, the IC  402  is configured to: connect the capacitors of the set of capacitors  218  in series using the switch arrangement  224  (e.g., responsive to CS 1  indicating VOUT 1  is greater than the threshold); connect the capacitors of the set of capacitors  218  in parallel using the switch arrangement  224  (e.g., responsive to CS 1  indicating VOUT 1  is not greater than the threshold); or bypass the capacitors of the set of capacitors  218  using the switch arrangement  224  (e.g., connect the first adaptive capacitive filter circuit terminal  212  to ground responsive to CS 2  indicating a fault condition). 
     With the adaptive capacitive filter circuit  210 B and related components of the IC  402 , different VIN levels from the AC source  202  (e.g., 120V and 240V) are supported while reducing the shortcomings of the conventional approach of  FIG. 1 . Some benefits of the adaptive capacitive filter circuit  210 B relative to the conventional approach of  FIG. 1  include accounting for fault conditions and using capacitors having smaller ratings. Compared to Q 1  in  FIG. 1 , switches of the switch arrangement  224  in  FIG. 4  have smaller ratings and are physically smaller. By including at least some components of an adaptive capacitive filter circuit  210 B with an IC that also includes switching converter controller components as in the example embodiment of  FIG. 4 , the overall cost of a system that includes an adaptive capacitive filter circuit and a switching converter controller can be reduced relative to using multiple ICs for switching converter controller components and adaptive capacitive filter circuit components. 
       FIG. 5  is a flowchart of an adaptive capacitive filter circuit method  500  in accordance with an example embodiment. The method  500  is performed, for example, by the adaptive capacitive filter circuit  210  of  FIG. 2 , the adaptive capacitive filter circuit  210 A of  FIG. 3 , or the adaptive capacitive filter circuit  210 B of  FIG. 4 . As shown, the method  500  includes monitoring an output voltage (e.g., VOUT in  FIGS. 2 and 3 , or VOUT 1  in  FIG. 4 ) from a rectifier bridge and adaptive capacitive filter circuit faults at block  502 . If a fault is detected (determination block  504 ), a fault option for a switch arrangement (e.g., the switch arrangement  224  in  FIGS. 2 and 4 , or related switches in  FIG. 3 ) of the adaptive capacitive filter circuit is used at block  506 . If a fault is not detected (determination block  504 ), the method  500  determines if the output voltage is greater than a threshold (determination block  508 ). If the output voltage is greater than the threshold (determination block  508 ), a serial connection option for the switch arrangement is used at block  510 . If the output voltage is not greater than the threshold (determination block  508 ), a parallel connection option for the switch arrangement is used at block  512 . The method  500  may be repeated as needed. 
     In some example embodiments, an adaptive capacitive filter circuit (e.g., adaptive capacitive filter circuit  210  in  FIG. 2 , the adaptive capacitive filter circuit  210 A in  FIG. 3 , or the adaptive capacitive filter circuit  210 B in  FIG. 4 ) includes: a first adaptive capacitive filter circuit terminal (e.g., the first adaptive capacitive filter circuit terminals  212  in  FIGS. 2-4 ) adapted to be coupled to a rectifier bridge output (e.g., the rectifier bridge output  206  in  FIGS. 2-4 ); a second adaptive capacitive filter circuit terminal (e.g., the third rectifier bridge output terminal  216  in  FIGS. 2-4 ) adapted to be coupled to ground; a first capacitor (e.g., a first capacitor of set of capacitors  218  in  FIGS. 2 and 4 , or C 3  in  FIG. 3 ) having a first electrode and a second electrode, the first electrode of the first capacitor coupled to the first adaptive capacitive filter circuit terminal; a second capacitor (e.g., a second capacitor of set of capacitors  218  in  FIGS. 2 and 4 , or C 4  in  FIG. 3 ) having a first electrode and a second electrode, the second electrode of the second capacitor coupled to the second adaptive capacitive filter circuit terminal; a first switch (e.g., a first switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 2  in  FIG. 3 ) coupled between the second electrode of the first capacitor and the second adaptive capacitive filter circuit terminal; a second switch (e.g., a first second of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 3  in  FIG. 3 ) coupled between the first adaptive capacitive filter circuit terminal and the first electrode of the second capacitor; and a third switch (e.g., a first third of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 4  in  FIG. 3 ) coupled between the second electrode of the first capacitor and the first electrode of the second capacitor. 
     In some example embodiments, the adaptive capacitive filter circuit includes a control circuit (e.g., the control circuit  250  in  FIGS. 2 and 4 , or the control circuit  250 A in  FIG. 3 ) having a control circuit input (e.g., the control circuit input  252  in  FIGS. 2-4 ) and a control circuit output (e.g., the control circuit output  254  in  FIGS. 2-4 ), the control circuit input is adapted to be coupled to the first adaptive capacitive filter circuit terminal. The control circuit is configured to: receive an output voltage from the rectifier bridge output at the control circuit input; compare the output voltage with a threshold; and provide a control signal (e.g., CS 1  in  FIGS. 2-4 ) at the control circuit output responsive to the comparison. In some example embodiments, the control signal is a first control signal, and the adaptable capacitive filter circuit includes a fault sense circuit (e.g., the fault sense circuit  240  in  FIGS. 2 and 4 , or the fault sense circuit  240 A in  FIG. 3 ) having a fault sense circuit input (e.g., the fault sense circuit inputs  242  and  244  in  FIG. 2 , or the fault sense circuit inputs  310  in  FIG. 3 ) and a fault sense circuit output (e.g., the fault sense circuit output  246  in  FIG. 2 ). The fault sense circuit input is configured to receive a sense signal. The fault sense circuit is configured to provide a second control signal (e.g., CS 2  in  FIGS. 2-4 ) at the fault sense circuit output responsive to the sense signal. The second control signal indicates whether a fault condition exists for the adaptive capacitive filter circuit. In some example embodiments, the sense signal indicates a voltage across the first capacitor or the second capacitor, and the fault sense circuit is configured to: compare the voltage across the first capacitor or the second capacitor with a threshold; and provide the second control signal at the fault sense circuit output responsive to the comparison. 
     In some example embodiments, the adaptive capacitive filter circuit includes control logic (e.g., the control logic  320  in  FIGS. 3 and 4 ) having a first control logic input (e.g., the first control logic input  322  in  FIG. 3 ), a second control logic input (e.g., the second control logic input  324  in  FIG. 3 ), and control logic outputs (e.g., the first and second control logic outputs  326  and  328  in  FIG. 3 ). The first control logic input is coupled to the control circuit output. The second control logic input is coupled to the fault sense circuit output. The control logic outputs are coupled to control terminals of the first switch, the second switch, and the third switch. 
     In some example embodiments, the control logic of an adaptive capacitive filter circuit is configured to provide a set of switch drive signals at the control logic outputs responsive to the first control signal indicating the output voltage is greater than the threshold and the second control signal indicating absence of a fault condition. In such case, the set of switch drive signals includes a first switch drive signal to turn off the first switch, a second switch drive signal to turn off the second switch, and a third switch drive signal to turn on the third switch. In some example embodiments, the control logic is configured to provide a set of switch drive signals at the control logic outputs responsive to the first control signal indicating the output voltage is not greater than the threshold and the second control signal indicating absence of a fault condition. In such case, the set of switch drive signals includes a first switch drive signal to turn on the first switch, a second switch drive signal to turn on the second switch, and a third switch drive signal to turn off the third switch. In some example embodiments, the control logic is configured to provide a set of switch drive signals at the control logic outputs responsive to the second control signal indicating a fault condition exists. In such case, the set of switch drive signals including a first switch drive signal to turn on the first switch, a second switch drive signal to turn on the second switch, and a third switch drive signal to turn on the third switch. 
     In some example embodiments, the adaptive capacitive filter circuit includes control circuitry configured to: operate the first switch, the second switch, and the third switch to couple the first capacitor and the second capacitor in series between the first adaptive capacitive filter circuit terminal and the second adaptive capacitive filter circuit terminal responsive to an output voltage of the rectifier bridge output being greater than a threshold; and operate the first switch, the second switch, and the third switch to couple the first capacitor and the second capacitor in parallel between the first adaptive capacitive filter circuit terminal and the second adaptive capacitive filter circuit terminal responsive to the output voltage of the rectifier bridge output not being greater than the threshold. In some example embodiments, the control circuitry is configured to operate the first switch, the second switch, and the third switch to bypass the first capacitor and the second capacitor resulting in the first adaptive capacitive filter circuit terminal being coupled to ground responsive to a detected fault condition for the adaptive capacitive filter circuit. 
     In some example embodiments, an integrated circuit (e.g., the integrated circuit  402  in  FIG. 4 ) includes control circuitry (e.g., the control circuit  250  in  FIGS. 2 and 4 , the control circuit  250 A in  FIG. 3 , the fault sense circuit  240  in  FIGS. 2 and 4 , the fault sense circuit  240 A in  FIG. 3 , and the control logic  320  in  FIGS. 3 and 4 ) for an adaptive capacitive filter circuit. The control circuitry is configured to: detect whether an output voltage (e.g., VOUT in  FIGS. 2 and 3 , or VOUT 1  in  FIG. 4 ) at a rectifier bridge output is greater than a threshold (e.g., VREF in  FIG. 3 ); responsive to detecting that the output voltage is greater than the threshold, provide a first set of switch drive signals for switches (e.g., the switch arrangement  224  in  FIGS. 2 and 4 , or Q 2 , Q 3 , and Q 4  in  FIG. 3 ) of the adaptive capacitive filter circuit to couple capacitors of the adaptive capacitive filter circuit in series; and responsive to detecting that the output voltage is not greater than the threshold, provide a second set of switch drive signals for switches of the adaptive capacitive filter circuit to couple the capacitors of the adaptive capacitive filter circuit in parallel. 
     In some example embodiments, the control circuitry is further configured to: detect whether a fault condition exists for the adaptive capacitive filter circuit; and responsive to detecting a fault condition, provide a third set of switch drive signals for switches of the adaptive capacitive filter circuit to bypass the capacitors of the adaptive capacitive filter circuit. In some example embodiments, the switches of the adaptive capacitive filter circuit are part of the integrated circuit, and the capacitors of the adaptive capacitive filter circuit are external to the integrated circuit. 
     In some example embodiment, the switches include a first switch (e.g., a first switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 2  in  FIG. 3 ), a second switch (e.g., a second switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 3  in  FIG. 3 ) and a third switch (e.g., a third switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 4  in  FIG. 3 ), the capacitors include a first capacitor (e.g., a first capacitor of the set of capacitors  218  in  FIGS. 2 and 4 , or C 3  in  FIG. 3 ) and a second capacitor (e.g., a second capacitor of the set of capacitors  218  in  FIGS. 2 and 4 , or C 4  in  FIG. 3 ), and the integrated circuit includes: a first terminal (e.g., the first adaptive capacitive filter circuit terminal  212  in  FIGS. 2-4 ) adapted to be coupled to the rectifier bridge output; a second terminal (e.g., the third adaptive capacitive filter circuit terminal  216  in  FIGS. 2-4 ) adapted to be coupled to ground; a third terminal (e.g., the second terminal  332  in  FIGS. 3 and 4 ) coupled to a current terminal of the first switch and a first current terminal of the third switch, the third terminal adapted to be coupled to an electrode of the first capacitor; and a fourth terminal (e.g., the second terminal  330  in  FIGS. 3 and 4 ) coupled to a current terminal of the second switch and a second current terminal of the third switch, the fourth terminal adapted to be coupled to an electrode of the second capacitor. In some example embodiments, the integrated circuit includes switching converter controller components configured to control power switches (e.g., the power switch  414  in  FIG. 4 ) of a power stage (e.g., the power stage  410  in  FIG. 4 ) adapted to be coupled to the rectifier bridge output, the switching converter controller components including a control loop (e.g., the control loop  406  in  FIG. 4 ) and a driver circuit (e.g., the driver circuit  408  in  FIG. 4 ). 
     In some example embodiments, a system (e.g., the power management system  200  in  FIG. 2 , the power management system  300  in  FIG. 3 , or the system  400  in  FIG. 4 ) includes an adaptive capacitive filter circuit having: a set of capacitors (e.g., the set of capacitors  218   FIGS. 2 and 4 , or C 3  and C 4  in  FIG. 3 ); a first adaptive capacitive filter circuit terminal (e.g., the first adaptive capacitive filter circuit terminal  212  in  FIGS. 2-4 ) adapted to be coupled to a rectifier bridge output (e.g., the rectifier bridge output  206  in  FIGS. 2-4 ); and a second adaptive capacitive filter circuit terminal (e.g., the third adaptive capacitive filter circuit terminal  216  in  FIGS. 2-4 ) adapted to be coupled to ground. The adaptive capacitive filter circuit is configured to connect capacitors of the set of capacitors in series or in parallel between the first adaptive capacitive filter circuit terminal and the second adaptive capacitive filter circuit terminal responsive to a control signal (e.g., CS 1  in  FIGS. 2-4 ). 
     In some example embodiments, the adaptive capacitive filter circuit includes control circuitry (e.g., the control circuit  250  in  FIGS. 2 and 4 , the control circuit  250 A in  FIG. 3 , the fault sense circuit  240  in  FIGS. 2 and 4 , the fault sense circuit  240 A in  FIG. 3 , and the control logic  320  in  FIGS. 3 and 4 ) and a switch arrangement (e.g., the switch arrangement  224  in  FIGS. 2 and 4 , or Q 2 , Q 3 , and Q 4  in  FIG. 3 ) controlled by the control circuitry. The control circuitry is configured to: provide the control signal responsive to a comparison of an output voltage (e.g., VOUT in  FIGS. 2 and 3 , or VOUT 1  in  FIG. 4 ) at the rectifier bridge output with a threshold (e.g., VREF in  FIG. 3 ); responsive to the control signal indicating that the output voltage is greater than the threshold, provide a first set of switch drive signals to the switch arrangement to couple capacitors of the set of capacitors in series; and responsive to the control signal indicating that the output voltage is not greater than the threshold, provide a second set of switch drive signals to the switch arrangement to couple the capacitors of the set of capacitors in parallel. 
     In some example embodiments, the control signal is a first control signal, and the control circuitry is configured to: provide a second control signal (e.g., CS 2  in  FIGS. 2-4 ) responsive to a comparison of a sense signal related to a capacitor of the set of capacitors with a threshold; and responsive to the second control signal indicating a fault condition, provide a third set of switch drive signals for switches of the adaptive capacitive filter circuit to bypass the capacitors of the adaptive capacitive filter circuit. 
     In some example embodiments, the switch arrangement includes: a first switch (e.g., a first switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 2  in  FIG. 3 ) coupled between a first capacitor (e.g., C 3  in  FIG. 3 ) of the set of capacitors and ground; a second switch (e.g., a second switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 3  in  FIG. 3 ) coupled between the first adaptive capacitive filter circuit terminal and a second capacitor (e.g., C 4  in  FIG. 3 ) of the set of capacitors; and a third switch (e.g., a third switch of the switch arrangement  224  in  FIGS. 2 and 4 , or Q 4  in  FIG. 3 ) coupled between the first capacitor and the second capacitor. In some example embodiments, the system includes: a power stage (e.g., the power stage  410  in  FIG. 4 ) adapted to be coupled to the rectifier bridge output; and a switching converter controller (e.g., the control loop  406  and the driver circuit  408  in  FIG. 4 ) coupled to the power stage and configured to provide power switch drive signals (e.g., HS_CS and LS_CS in  FIG. 4 ) to the power stage, wherein the switching converter controller, the control circuitry, and the switch arrangement are part of an IC (e.g., the IC  402  in  FIG. 4 ). 
     In this description, the term “couple” may cover connections, communications, or signal paths that enable a functional relationship consistent with this description. For example, if device A generates a signal to control device B to perform an action: (a) in a first example, device A is coupled to device B by direct connection; or (b) in a second example, device A is coupled to device B through intervening component C if intervening component C does not alter the functional relationship between device A and device B, such that device B is controlled by device A via the control signal generated by device A. 
     As used herein, the terms “terminal,” “electrode,” “node,” “interconnection,” “pin,” “contact,” and “connection” are used interchangeably. Unless specifically stated to the contrary, these terms are generally used to mean an interconnection between or a terminus of a device element, a circuit element, an IC, a device or other electronics or semiconductor component. 
     The example embodiments above may use switches in the form of n-type metal-oxide semiconductor field-effect transistors (“NFETs”) or p-type metal-oxide semiconductor field-effect transistors (“PFETs”). Other example embodiments may utilize NPN bipolar junction transistors (BJTs), PNP BJTs, or any other type of transistor. Accordingly, when referring to a current electrode, such electrode may be an emitter, collector, source or drain. Also, the control electrode may be a base or a gate. 
     A device that is “configured to” perform a task or function may be configured (e.g., programmed and/or hardwired) at a time of manufacturing by a manufacturer to perform the function and/or may be configurable (or reconfigurable) by a user after manufacturing to perform the function and/or other additional or alternative functions. The configuring may be through firmware and/or software programming of the device, through a construction and/or layout of hardware components and interconnections of the device, or a combination thereof. 
     A circuit or device that is described herein as including certain components may instead be adapted to be coupled to those components to form the described circuitry or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and/or inductors), and/or one or more sources (such as voltage and/or current sources) may instead include only the semiconductor elements within a single physical device (e.g., a semiconductor die and/or IC package) and may be adapted to be coupled to at least some of the passive elements and/or the sources to form the described structure either at a time of manufacture or after a time of manufacture, for example, by an end-user and/or a third-party. 
     Circuits described herein are reconfigurable to include the replaced components to provide functionality at least partially similar to functionality available before the component replacement. Components shown as resistors, unless otherwise stated, are generally representative of any one or more elements coupled in series and/or parallel to provide an amount of impedance represented by the shown resistor. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in parallel between the same nodes. For example, a resistor or capacitor shown and described herein as a single component may instead be multiple resistors or capacitors, respectively, coupled in series between the same two nodes as the single resistor or capacitor. 
     Uses of the phrase “ground” in this description include a chassis ground, an Earth ground, a floating ground, a virtual ground, a digital ground, a common ground, and/or any other form of ground connection applicable to, or suitable for, the teachings of this description. Unless otherwise stated, “about,” “approximately,” or “substantially” preceding a value means+/−10 percent of the stated value. 
     Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.