[0001] This relates generally to electronic systems, and more specifically to an adaptive bus voltage auto- selection system.

BACKGROUND

[0002] Power supply circuits can be implemented in a variety of computer and/or wireless devices to provide power to circuit components therein. One example of a power supply system is a DC-DC power converter that is configured to convert a DC voltage to another DC voltage of a different amplitude. DC input voltages can typically be generated from an AC input voltage, such as based on universal plug-in adapters. The efficiency of power converters can be limited by large input voltage operating ranges. Thus, some power supply systems, such as designed for worldwide use, include input voltage selection capability that can generate a DC bus voltage from the AC input line voltage. Such selection capability can be implemented to generate the DC bus voltage from different amplitudes of AC input line voltage.

SUMMARY

[0003] In one example, an adaptive bus voltage auto- selection system includes an input bridge configured to rectify an AC input line voltage to generate a DC bus voltage. The system also includes a voltage monitor configured to monitor an amplitude of the AC input line voltage and to generate an activation signal based on the amplitude of the AC input line voltage relative to a predetermined reference voltage. The system further includes an anti-series transistor switch pair that is controlled via the activation signal to selectively couple and decouple the input bridge to an output stage to provide the DC bus voltage at a first amplitude based on a first state of the activation signal and at a second amplitude based on a second state of the activation signal, respectively.

[0004] In another example of a method for generating a DC bus voltage based on an input AC line voltage, the method includes providing the AC input line voltage to an input bridge and comparing the amplitude of the AC input line voltage to a predetermined reference voltage. The method further includes generating an activation signal at one of a first state in response to the amplitude of the AC input line voltage being less than the predetermined reference voltage and a second state in response to the amplitude of the AC input line voltage being greater than or equal to the predetermined reference voltage to selectively couple and decouple the input bridge to an output stage to provide the DC bus voltage at one of a first amplitude and a second amplitude, respectively.

[0005] In another example, an adaptive bus voltage auto- selection system includes an input bridge configured to rectify an AC input line voltage to generate a DC bus voltage. The system also includes a voltage monitor configured to monitor an amplitude of the AC input line voltage and to generate an activation signal based on the amplitude of the AC input line voltage relative to a predetermined reference voltage. The system also includes an anti-chatter circuit configured to activate an anti-chatter activation signal in response to the activation signal being generated in a first state for a comparison time duration. The system further includes an anti-series transistor switch pair that is controlled via the anti-chatter activation signal to selectively couple and decouple the input bridge to an output stage to provide the DC bus voltage at a first amplitude based on the first state of the activation signal and at a second amplitude based on a second state of the activation signal, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 illustrates an example of an adaptive bus voltage auto-selection system.

[0007] FIG. 2 illustrates another example of an adaptive bus voltage auto- selection system.

[0008] FIG. 3 illustrates yet another example of an adaptive bus voltage auto- selection system.

[0009] FIG. 4 illustrates an example of a method for generating a DC bus voltage based on an input AC line voltage.

DETAILED DESCRIPTION OF EXAMPLE EMB ODEVIENT S

[0010] This disclosure relates generally to electronic systems, and more specifically to an adaptive bus voltage auto- selection system. The adaptive bus voltage auto-selection system is configured to convert an AC input line voltage into a DC bus voltage based on an amplitude of the AC input line voltage. The adaptive bus voltage auto-selection system includes an input bridge that is configured to rectify the AC input line voltage and to provide the DC bus voltage based on the rectified AC input line voltage. The input bridge can be coupled to an output stage that includes a pair of capacitors that interconnect nodes associated with the DC bus voltage with a control node. Also, the adaptive bus voltage auto-selection system includes a voltage monitor configured to compare the AC input line voltage (e.g., an absolute value of the AC input line voltage) with a predetermined reference voltage.

[0011] The voltage monitor can thus generate an activation signal that is configured to control an anti-series transistor switch pair that is configured to selectively couple and decouple the input bridge to and from the output stage, respectively, based on the comparison of the AC input line voltage with the predetermined reference voltage. Therefore, the AC input line voltage can be provided to generate the DC bus voltage at separate amplitudes based on the separate respective amplitudes of the AC input line voltage. Additionally, because the switch that interconnects the input bridge and the output stage is implemented as an anti-series transistor pair, the switching of the adaptive bus voltage auto- selection system between modes (e.g., doubler mode and bridge mode) can be implemented in a much more rapid and power efficient manner.

[0012] FIG. 1 illustrates an example of an adaptive bus voltage auto-selection system 10. The adaptive bus voltage auto-selection system 10 can be implemented in a variety of circuit applications to generate a DC bus voltage VBUS based on an AC input line voltage VLINE. As an example, the AC input line voltage VLINE can be provided from a local power grid associated with public utility, and the DC bus voltage VBUS can be provided as a DC input voltage for a circuit system (e.g., a DC-DC power supply system).

[0013] The adaptive bus voltage auto-selection system 10 includes an input bridge 12 and an output stage 14. For example, the input bridge 12 can be configured as a diode-based input rectifier, and the output stage 14 can be configured as a capacitor pair that interconnects nodes on which the DC bus voltage VBUS is provided. The input bridge 12 can thus be configured to receive the AC input line voltage VLINE and to rectify the AC input line voltage VLINE. As an example, the input bridge 12 can be coupled to the output stage 14, such that the rectified AC input line voltage VLINE is provided to the output stage 14 to be filtered by the output stage 14, and thus provided as the DC bus voltage VBUS. As described in greater detail herein, the adaptive bus voltage auto- selection system 10 can operate in one of two modes. A first mode can correspond to a voltage doubler mode associated with a lesser amplitude of the AC input line voltage VLINE, and thus a lesser amplitude of the DC bus voltage VBUS. A second mode can correspond to a bridge mode associated with a greater amplitude of the AC input line voltage VLINE, and thus a greater amplitude of the DC bus voltage VBUS. [0014] The adaptive bus voltage auto-selection system 10 also includes a voltage monitor 16 that is configured to monitor the amplitude of the AC input line voltage VLINE. The voltage monitor 16 can compare the amplitude of the AC input line voltage VLINE with a predetermined reference voltage and generate an activation signal having a logic-state that corresponds to the comparison. As an example, the voltage monitor 16 can include an absolute value converter that is configured to generate an absolute value voltage corresponding to an absolute value amplitude of the AC input line voltage VLINE. Thus, the voltage monitor 16 can compare the amplitude of the absolute value voltage with the predetermined reference voltage to generate the activation signal. Thus, the activation signal can correspond to the state of the adaptive bus voltage auto- selection system.

[0015] The adaptive bus voltage auto-selection system 10 further includes an anti-series transistor pair 18. As described herein, the term "anti-series transistor pair" refers to a pair of transistors that are arranged in series but opposite orientation with respect to each other, and which are commonly controlled by a single signal. As an example, the anti-series transistor pair 18 can be arranged as a pair of N-channel field-effect transistors (FETs) (e.g., metal-oxide semiconductor (MOS)FETs) having a common source. However, the anti-series transistor pair 18 is not limited to N-channel FETs, but can instead be configured as any of a variety of other transistor pairs of various orientations, such as drain-connected N-FETs, NPN or PNP bipolar junction transistors (BJTs), P-channel FETs, J-FETs, LDMOSFETs, or other types of transistors.

[0016] The anti-series transistor pair 18 can be collectively controlled via the activation signal that is generated via the voltage monitor 16. The anti-series transistor pair 18 interconnects the input bridge 12 and the output stage 14. For example, the anti-series transistor pair 18 can interconnect the input bridge 12 and a control node that interconnects the two capacitors associated with the output stage 14. As a result, the anti-series transistor pair 18 can activate to couple the input bridge 12, and thus one leg of the AC input line voltage VLINE, to the control node to facilitate operation of the adaptive bus voltage auto-selection system 10 in the doubler mode, and can deactivate the decouple the input bridge 12, and thus the one leg of the AC input line voltage VLINE, from the control node to facilitate operation of the adaptive bus voltage auto-selection system 10 in the bridge mode. [0017] Therefore, the adaptive bus voltage auto-selection system 10 implements the anti-series transistor pair 18 to switch from the bridge mode to the doubler mode in a very rapid and power efficient manner. Thus, the anti-series transistor pair 18 provides a much more rapid switching solution than switching solutions provided by other typical adaptive bus voltage auto- selection systems, such as that implement a relay or a triac. As a result, the very rapid switching of the anti-series transistor pair 18 can substantially mitigate overvoltage conditions that result from a delay in switching in response to step-voltage changes. Furthermore, the anti-series transistor pair 18 can have a much lower voltage across it when activated than other switching solutions, and is therefore more power efficient. Therefore, the anti-series transistor pair 18 can provide a more efficient and effective switching solution.

[0018] FIG. 2 illustrates another example of an adaptive bus voltage auto-selection system 50. The adaptive bus voltage auto- selection system 50 can be implemented in a variety of circuit applications to generate a DC bus voltage VBUS based on an AC input line voltage VLINE that is demonstrated as being generated via an AC power source 52, which can correspond to a local power grid associated with public utility.

[0019] The adaptive bus voltage auto-selection system 50 includes an input bridge 54 and an output stage 56. The input bridge 54 is demonstrated in the example of FIG. 2 as a diode-based input rectifier that includes diodes DBl, DB2, DB3, and DB4, with the AC input line voltage VLINE being provided at the anode of the diode DBl and the cathode of the diode DB3 and at the anode of the diode DB2 and the cathode of the diode DB4. The input bridge 54 can thus be configured to receive the AC input line voltage VLINE and to rectify the AC input line voltage VLINE. The output stage 56 is demonstrated in the example of FIG. 2 as a capacitor pair CI and C2 that interconnects a first node 58 and a second node 60 on which the DC bus voltage VBUS is provided. Particularly, the first capacitor CI interconnects the first node 58 and a control node 62, and the second capacitor C2 interconnects the second node 60 and the control node 62. The first node 58 is also coupled to the cathodes of the diodes DB l and DB2, and the second node 60 is also coupled to the anodes of the diodes DB3 and DB4. Therefore, the rectified AC input line voltage VLINE is provided to the output stage 56 to be filtered by the output stage 56, and thus provided as the DC bus voltage VBUS. As described herein, the adaptive bus voltage auto-selection system 50 can operate in either a voltage doubler mode or a bridge mode. [0020] The adaptive bus voltage auto-selection system 50 also includes a voltage monitor 64 that is configured to monitor the amplitude of the AC input line voltage VLINE. In the example of FIG. 2, the voltage monitor 64 includes an absolute value converter 66 that is configured to generate an absolute value voltage VABS corresponding to an absolute value amplitude of the AC input line voltage VLINE. The voltage monitor 64 also includes a comparator 68 that is configured to receive the absolute value voltage VABS at an inverting input and a reference voltage VREF at a non-inverting input. The reference voltage VREF is demonstrated as being generated via a voltage supply 70, such as provided externally (e.g., provided to a pin on the IC chip in which the adaptive bus voltage auto- selection system 50 is arranged). The comparator 68 thus compares the absolute value voltage VABS with the reference voltage VREF to generate an activation signal ACT having a logic-state that is based on the amplitude of the absolute value voltage VABS relative to the reference voltage VREF.

[0021] The adaptive bus voltage auto-selection system 50 further includes an anti-series transistor pair 72. In the example of FIG. 2, the anti-series transistor pair 72 is demonstrated as a pair of N-FETs Nl and N2 having a common source connection. The anti-series transistor pair 72 interconnects the input bridge 52, at the anode of the diode DB2 and the cathode of the diode DB4, and the control node 62 of the output stage 56. The gate of each of the N-FETs Nl and N2 of the anti-series transistor pair 72 is controlled by the activation signal ACT, such that the activation signal ACT is provided to activate and deactivate the anti-series transistor pair 72.

[0022] In the example of FIG. 2, if the absolute value voltage VABS is greater than or equal to the reference voltage VREF, such as corresponding to a 230 VAC amplitude of the AC input line voltage VLINE, the activation signal ACT is provided at a logic-low state. Thus, the anti-series transistor pair 72 is deactivated to provide an open circuit between the input bridge 52 and the control node 62. Accordingly, the adaptive bus voltage auto-selection system 50 operates in the bridge mode to provide the DC bus voltage VBUS at a first amplitude. If the absolute value voltage VABS is less than the reference voltage VREF, such as corresponding to a 110 VAC amplitude of the AC input line voltage VLINE, the activation signal ACT is provided at a logic-high state. Thus, the anti-series transistor pair 72 is rapidly activated to couple the input bridge 52 to the control node 62. Accordingly, the adaptive bus voltage auto-selection system 50 operates in the doubler mode to provide the DC bus voltage VBUS at a second amplitude. [0023] FIG. 3 illustrates yet another example of an adaptive bus voltage auto- selection system 100. The adaptive bus voltage auto-selection system 100 can be implemented in a variety of circuit applications to generate a DC bus voltage VBUS based on an AC input line voltage VLINE that is demonstrated as being generated via an AC power source 102, which can correspond to a local power grid associated with public utility. The adaptive bus voltage auto- selection system 100 is demonstrated in the example of FIG. 3 as being substantially similar to the adaptive bus voltage auto-selection system 50 in the example of FIG. 2. However, as described in greater detail herein, the adaptive bus voltage auto-selection system 100 can be configured to substantially mitigate chatter associated with the change of state of the activation signal ACT.

[0024] The adaptive bus voltage auto-selection system 100 includes an input bridge 104 and an output stage 106. The input bridge 104 is demonstrated in the example of FIG. 3 as a diode-based input rectifier that includes diodes DBl, DB2, DB3, and DB4, with the AC input line voltage VLINE being provided at the anode of the diode DBl and the cathode of the diode DB3 and at the anode of the diode DB2 and the cathode of the diode DB4. The input bridge 104 can thus be configured to receive the AC input line voltage VLINE and to rectify the AC input line voltage VLINE. The output stage 106 is demonstrated in the example of FIG. 3 as a capacitor pair CI and C2 that interconnects a first node 108 and a second node 110 on which the DC bus voltage VBUS is provided. Particularly, the first capacitor CI interconnects the first node 108 and a control node 112, and the second capacitor C2 interconnects the second node 110 and the control node 112. The first node 108 is also coupled to the cathodes of the diodes DBl and DB2, and the second node 110 is also coupled to the anodes of the diodes DB3 and DB4. Therefore, the rectified AC input line voltage VLINE is provided to the output stage 106 to be filtered by the output stage 106, and thus provided as the DC bus voltage VBUS. As described herein, the adaptive bus voltage auto-selection system 100 can operate in either a voltage doubler mode or a bridge mode.

[0025] The adaptive bus voltage auto-selection system 100 also includes a voltage monitor 114 that is configured to monitor the amplitude of the AC input line voltage VLINE. In the example of FIG. 3, the voltage monitor 114 includes an absolute value converter 116 that is configured to generate an absolute value voltage VABS corresponding to an absolute value amplitude of the AC input line voltage VLINE. The voltage monitor 114 also includes a comparator 118 that is configured to receive the absolute value voltage VABS at an inverting input and a first reference voltage VREFl at a non-inverting input. The first reference voltage VREFl is demonstrated as being generated via a voltage supply 120, such as provided externally (e.g., provided to a pin on the IC chip in which the adaptive bus voltage auto-selection system 100 is arranged). The comparator 118 thus compares the absolute value voltage VABS with the first reference voltage VREFl to generate an activation signal ACT having a logic-state that is based on the amplitude of the absolute value voltage VABS relative to the first reference voltage VREFl . Further, as described in greater detail herein, the adaptive bus voltage auto- selection system 100 also includes an anti-series transistor pair 122 that operates similar to that described hereinabove based on the activation signal ACT.

[0026] Because the AC input line voltage VLINE can decrease less than the first reference voltage VREFl even at a higher amplitude (e.g., 230 VAC), the transition from the higher amplitude of the AC input line voltage VLINE to the lower amplitude of the AC input line voltage VLINE can result in chatter associated with the activation signal ACT, such that the activation signal ACT can change state twice in a given half-period of the AC input line voltage VLINE. Such chatter can provide conduction pulses associated with the anti-series transistor pair 122 that can, in turn, increase root-mean square (RMS) currents in the adaptive bus voltage auto-selection system 100, and thus further power dissipation of the adaptive bus voltage auto-selection system 100.

[0027] To substantially mitigate chatter, the adaptive bus voltage auto- selection system 100 includes an anti-chatter circuit 124 that receives the activation signal ACT and provides an anti-chatter activation signal ACT CH. The anti-chatter activation signal ACT CH thus changes state in response to a change of state of the activation signal ACT that is maintained for more than one-half the period of the AC input line voltage VLINE. The anti-chatter circuit 124 includes an RC filter that is arranged with a resistor Rl and a capacitor C3 that provides a filtered activation signal ACT F, and further includes a feedback diode Dl that provides feedback of the filtered activation signal ACT F to the activation signal ACT. The filtered activation signal ACT F is thus provided to an inverting input of a comparator 126 that is configured to compare the filtered activation signal ACT F with a second reference voltage VREF2. The second reference voltage VREF2 is demonstrated as being generated via a voltage supply 128, such as provided externally (e.g., provided to a pin on the IC chip in which the adaptive bus voltage auto-selection system 100 is arranged). The comparator 126 can thus generate the anti-chatter activation signal ACT CH based on the comparison of the filtered activation signal ACT F with the second reference voltage VREF2. Based on the RC filter arrangement of the resistor Rl and the capacitor C3, and the feedback diode Dl, the filtered activation signal ACT F is only de-asserted after the activation signal ACT is de-asserted for more than half of a period of the AC input line voltage VLINE, such that the comparator 126 likewise generates the anti-chatter activation signal ACT CH after more than half of a period of the AC input line voltage VLINE.

[0028] Similar to as demonstrated in the example of FIG. 2, the anti-series transistor pair 122 is demonstrated as a pair of N-FETs Nl and N2 having a common source connection in the example of FIG. 3. The anti-series transistor pair 122 interconnects the input bridge 102, at the anode of the diode DB2 and the cathode of the diode DB4, and the control node 112 of the output stage 106. The gate of each of the N-FETs Nl and N2 of the anti-series transistor pair 122 is controlled by the anti-chatter activation signal ACT CH, such that the anti-chatter activation signal ACT CH is provided to activate and deactivate the anti-series transistor pair 122.

[0029] Accordingly, if the absolute value voltage VABS is greater than or equal to the first reference voltage VREFl, such as corresponding to a 230 VAC amplitude of the AC input line voltage VLINE, the activation signal ACT is provided at a logic-low state. In response, the filtered activation signal ACT F can be driven to the logic-low state, and is compared with the second reference voltage VREF2. Based on the comparison of the filtered activation signal ACT F with the second reference voltage VREF2, the anti-chatter activation signal ACT CH is provided at a logic-low state. Therefore, the anti-series transistor pair 122 is deactivated to provide an open circuit between the input bridge 102 and the control node 112, such that the adaptive bus voltage auto- selection system 100 operates in the bridge mode to provide the DC bus voltage VBUS at a first amplitude.

[0030] Similarly, if the absolute value voltage VABS is less than the first reference voltage VREFl, such as corresponding to a 110 VAC amplitude of the AC input line voltage VLINE, the activation signal ACT is provided at a logic-high state. In response, the filtered activation signal ACT F can be driven to the logic-high state, and is compared with the second reference voltage VREF2. Based on the comparison of the filtered activation signal ACT F with the second reference voltage VREF2, the anti-chatter activation signal ACT CH is provided at a logic-high state. Therefore, the anti-series transistor pair 122 is rapidly activated to couple the input bridge 102 to the control node 112, such that the adaptive bus voltage auto- selection system 100 operates in the doubler mode to provide the DC bus voltage VBUS at a second amplitude.

[0031] In view of the structural and functional features described above, a method in accordance with various aspects of this disclosure is described with reference to FIG. 4. For simplicity of explanation, the method of FIG. 4 is shown and described as executing serially, but this disclosure is not limited by the illustrated order, because some aspects could (in accordance with this disclosure) occur in different orders and/or concurrently with other aspects. Moreover, some illustrated features are optional to implement a method in accordance with an aspect of this disclosure.

[0032] FIG. 4 illustrates a method 150 for generating a DC bus voltage (e.g., the DC bus voltage VBUS) based on an input AC line voltage (e.g., the AC line voltage VLINE). At 152, the AC input line voltage is provided to an input bridge (e.g., the input bridge 12). At 154, the amplitude of the AC input line voltage is compared to a predetermined reference voltage (e.g., the reference voltage VREF). At 156, an activation signal (e.g., the activation signal ACT) is provided at one of a first state in response to the amplitude of the AC input line voltage being less than the predetermined reference voltage and a second state in response to the amplitude of the AC input line voltage being greater than or equal to the predetermined reference voltage to selectively couple and decouple the input bridge to an output stage (e.g., the output stage 14) to provide the DC bus voltage at one of a first amplitude and a second amplitude, respectively.

[0033] Modifications are possible in the described embodiments, and other embodiments are possible, within the scope of the claims.