Patent Application
20140084895
1. Field of the Invention
The present invention relates to switching converters such as Buck (or step-down) converters, and more particularly, to a method for performing refreshing control of a DC-to-DC converter, and to an associated apparatus.
2. Description of the Prior Art
In a conventional switching converter such as a Buck (or step-down) converter, a Buck topology is typically utilized for converting an input voltage to a lower output voltage. For example, the conventional Buck converter may include a pair of switching transistors coupled in series, with a high side switch and a low side switch being coupled to the input voltage level and a ground voltage level, respectively, where the switches are controlled to alternatively conduct with complementary duty cycles to maintain a predetermined output voltage. An output filter is typically coupled to the interconnection between the pair of switching transistors to average the switched input voltage, in order to provide the output voltage.
According to the related art, the high side switch and the low side switch can be implemented with Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) such as N-channel MOSFETs (NMOSFETs). However, some problems may occur. More specifically, a gate to source voltage of approximately ten volts is required to fully enhance the NMOSFET switches, and therefore, implementing some special circuitry may become a must, in order to generate the required gate voltage for the high side NMOSFET switch. For example, the special circuitry is complicated, and additional costs are introduced due to the special circuitry. In another example, there is a tradeoff between the performance of the high side NMOSFET switch and the additional costs mentioned above. A proposal for providing the high side NMOSFET switch with the necessary gate drive voltage is charging a bootstrap capacitor with the input voltage or a regulated version thereof (e.g. a regulated voltage generated by regulating the input voltage, using a regulator), where some side effects and the associated tradeoff may be introduced. It seems unlikely that a sufficient gate voltage level can be continuously maintained. In a situation where the bootstrap capacitor is charged through the low side NMOSFET switch, its charge time and the bootstrap voltage thereof may decrease to an unacceptable level by the concomitantly reduced duty cycle of the low side NMOSFET switch. Thus, a novel method is required for refreshing the charge in a bootstrap capacitor within a DC-to-DC converter.
It is therefore an objective of the claimed invention to provide a method for performing refreshing control of a direct current (DC)-to-DC converter, and to provide an associated apparatus, in order to solve the above-mentioned problems.
It is another objective of the claimed invention to provide a method for performing refreshing control of a DC-to-DC converter, and to provide an associated apparatus, in order to properly refresh the charge in a bootstrap capacitor within the DC-to-DC converter.
An exemplary embodiment of a method for performing refreshing control of a DC-to-DC converter comprises the steps of: monitoring at least one duration of a control signal of a switching unit of the DC-to-DC converter to determine a statistics result, wherein the duration corresponds to a duty cycle of the control signal; and based upon the statistics result, performing refreshing control on a bootstrap capacitor within the DC-to-DC converter. In particular, the step of monitoring the duration of the control signal of the switching unit of the DC-to-DC converter to determine the statistics result further comprises monitoring whether a length of the duration falls within a predetermined range, wherein the statistics result represents a number of times that the length of the duration falls within the predetermined range. For example, the statistics result represents the number of times that the length of the duration successively falls within the predetermined range with respect to periods of the control signal.
An exemplary embodiment of an apparatus for performing refreshing control of a DC-to-DC converter is provided, wherein the apparatus comprises at least one portion of the DC-to-DC converter. The apparatus comprises a monitoring circuit and a control circuit. The monitoring circuit is arranged to monitor at least one duration of a control signal of a switching unit of the DC-to-DC converter to determine a statistics result, wherein the duration corresponds to a duty cycle of the control signal. In addition, based upon the statistics result, the control circuit performs refreshing control on a bootstrap capacitor within the DC-to-DC converter. In particular, the monitoring circuit monitors whether a length of the duration falls within a predetermined range, wherein the statistics result represents a number of times that the length of the duration falls within the predetermined range. For example, the statistics result represents the number of times that the length of the duration successively falls within the predetermined range with respect to periods of the control signal.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
Please refer to
As shown in
According to the first embodiment, the PWM controller 103 generates a plurality of control signals C1 and C2 (e.g. PWM control signals) for controlling the switching units 105-1 and 105-2, respectively. When the PWM controller 103 controls the control signal C1 to be at a high voltage level to turn on the switching unit 105-1, the PWM controller 103 controls the control signal C2 to be at a low voltage level. When the PWM controller 103 controls the control signal C2 to be at a high voltage level to turn on the switching unit 105-2, the PWM controller 103 controls the control signal C1 to be at a low voltage level. Thus, the switching units 105-1 and 105-2 are not turned on at the same time. In addition, the output filter 107 is coupled to a node between the pair of switching units 105-1 and 105-2 to average the switched input voltage, in order to provide the output voltage level VOUT.
In this embodiment, a bootstrap capacitor (not shown) of the DC-to-DC converter mentioned above can be utilized for providing the aforementioned high voltage level of the control signal C1. The monitoring circuit 110 is arranged to monitor at least one of the control signals C1 and C2 (e.g. the control signal C1 and/or the control signal C2) to generate at least one statistics result and provide the control circuit 120 with the aforementioned at least one statistics result. An exemplary coupling relationship between the monitoring circuit 110 and the aforementioned of the control signals C1 and C2 (e.g. the control signal C1 and/or the control signal C2) is illustrated in
In Step 210, the monitoring circuit 110 monitors at least one duration (e.g. one or more durations) of a control signal of a switching unit of the DC-to-DC converter, such as the control signal C1 of the switching unit 150-1 or the control signal C2 of the switching unit 150-2, to determine a statistics result, where the duration corresponds to a duty cycle of the control signal under consideration (e.g. the control signal C1 or the control signal C2). For example, in a situation where the control signal C1 is monitored by the monitoring circuit 110, the duration corresponds to a duty cycle of the control signal C1. In another example, in a situation where the control signal C2 is monitored by the monitoring circuit 110, the duration corresponds to a duty cycle of the control signal C2.
More particularly, the monitoring circuit 110 monitors whether a length of the duration under consideration, such as at least one ON duration or at least one OFF duration, falls within a predetermined range, where the statistics result represents the number of times that the length of the duration under consideration falls within the predetermined range. For example, the predetermined range may represent a range of an interval whose values are less than a first predetermined threshold. That is, the monitoring circuit 110 monitors whether the length of the duration under consideration is less than the first predetermined threshold. In another example, the predetermined range may represent a range of an interval whose values are greater than or equal to a predetermined threshold such as the first predetermined threshold. That is, the monitoring circuit 110 monitors whether the length of the duration under consideration is greater than or equal to the aforementioned predetermined threshold such as the first predetermined threshold. Please note that the ON duration mentioned above represents a duration in which the control signal under consideration, such as the control signal C1 or the control signal C2, turns on the associated switching unit such as the switching unit 105-1 or the switching unit 105-2, respectively. In addition, the OFF duration mentioned above represents a duration in which the control signal under consideration, such as the control signal C1 or the control signal C2, turns off the associated switching unit such as the switching unit 105-1 or the switching unit 105-2, respectively.
In Step 220, based upon the statistics result, the control circuit 120 performs refreshing control on the aforementioned bootstrap capacitor within the DC-to-DC converter. More particularly, in a situation where, in Step 210, the monitoring circuit 110 monitors whether the length of the duration under consideration, such as the aforementioned at least one ON duration or the aforementioned at least one OFF duration, falls within the predetermined range to generate the statistics result, the control circuit 120 can perform refreshing control on the aforementioned bootstrap capacitor within the DC-to-DC converter according to the statistics result regarding the number of times that the length of the duration under consideration falls within the predetermined range.
Based upon the method 200 shown in
Please note that, according to some embodiments, such as some variations of the embodiment shown in
In some embodiments, such as some variations of the embodiment shown in
According to these embodiments, as a result of triggering the operation of refreshing the bootstrap capacitor, the charge of the bootstrap capacitor is refreshed. According to some of these embodiments, as a result of triggering the operation of refreshing the bootstrap capacitor, the length of the corresponding duration in the next period (e.g. the next ON duration that comes immediately after the aforementioned at least one ON duration, or the next OFF duration that comes immediately after the aforementioned at least one OFF duration) can be corrected to fall outside the predetermined range, where re-triggering the operation of refreshing the bootstrap capacitor can be temporarily prevented for a while.
Please refer to
According to this embodiment, when the statistics result indicates that each of the lengths d11, d12, and d13 is less than the first predetermined threshold (and thus, the number of times that the length of the duration under consideration successively falls within the predetermined range reaches the second predetermined threshold), the control circuit 120 triggers the operation of refreshing the bootstrap capacitor within the DC-to-DC converter. As a result of triggering the operation of refreshing the bootstrap capacitor, the length of the corresponding OFF duration in the next period (i.e. the next OFF duration that comes immediately after the OFF duration having the length d13) can be corrected to be equivalent to the first predetermined threshold, where re-triggering the operation of refreshing the bootstrap capacitor can be temporarily prevented for a while. Similar descriptions are not repeated for this embodiment.
Please refer to
According to this embodiment, when the statistics result indicates that each of the lengths d21, d22, and d23 is less than the first predetermined threshold (and thus, the number of times that the length of the duration under consideration successively falls within the predetermined range reaches the second predetermined threshold), the control circuit 120 triggers the operation of refreshing the bootstrap capacitor within the DC-to-DC converter. As a result of triggering the operation of refreshing the bootstrap capacitor, the length of the corresponding ON duration in the next period (i.e. the next ON duration that comes immediately after the ON duration having the length d23) can be corrected to be equivalent to the first predetermined threshold, where re-triggering the operation of refreshing the bootstrap capacitor can be temporarily prevented for a while. Similar descriptions are not repeated for this embodiment.
It is an advantage of the present invention that the present invention method and apparatus can properly determine the output voltage level of the DC-to-DC converter according to the duty cycle of the control signal under consideration without introducing any of the side effects mentioned above. As a result, the goal of accurately generating the output voltage level of the DC-to-DC converter can be achieved, where the related art problems will no longer be an issue.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
