Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2001-08-13
2003-06-03
Berhane, Adolf Deneke (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C327S554000, C330S297000
Reexamination Certificate
active
06573695
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to power supplies in general, and, more particularly, to high-efficiency DC-to-DC converters, switching regulators, and tracking power-supplies.
BACKGROUND OF THE INVENTION
DC-to-DC converters are widely used today in many applications. Many of the efficient implementations are based on switching capacitors, and sometimes also inductors, and are referred to as switching regulators. Switching regulators that are based on capacitors only are becoming more popular since inductors are practically inconvenient for use especially where miniaturization and EMI is of concern.
Prior art switching regulators uses a two phase cycle. A charge-phase during which capacitors are charged while not being connected to the load, and a discharge-phase during which capacitors are discharged trough the load.
One problem associated with prior art switching regulators is that specific design parameters can only reach high efficiency within a relatively narrow range of output current and/or voltage requirements for applications where output current or voltage are changing significantly the efficiency of prior art switching regulators drops significantly.
Prior art methods to improve the ability to cope with a wide range of voltage/current requirements includes controlling the duty cycle between the charge and discharge phases, and/or controlling the resistance trough which the capacitors are charged during the charge-phase.
Another limiting factor of prior art implementations is that during the charge-phase there is power loss due the changing of the capacitor, that is proportions 1 to &Dgr;V*C.
In order to keep supplying power during the charge-phase, an output-capacitor is always connected at the output in parallel to the load. This output-capacitor needs to be charged to a voltage higher than the desired output voltage during the discharge-phase, so that it can keep supplying power during the charge-phase. This increases the ripple at the output of the power supply.
Another problem of current switching regulators is that the frequency content of the ripple (noise) at the output is dictated by the switching regulator circuit, and the power consumption, and can not be controlled to provide a noise frequency content that is more suitable for specific applications.
There is thus a widely recognized need for, and it would be highly advantageous to have, a high-efficiency power supply, that is capable of supporting a wide range of voltage/current requirements, while having low ripple with a controlled frequency content. These goals are met by the present invention.
REFERENCES
[1] EP0998795, WO9905806 “Method and apparatus for performance improvement by qualifying pulses in an oversampled, noise-shaping signal processor”
[2] EP0906659, WO9749175 “Oversampled, noise-shaping, mixed-signal processor”
[3] “Relationships between Noise Shaping and Nested Differentiating Feedback Loops”, by J. Vanderkooy, and M. O. J. Hawksford,
Journal of the Audio Engineering Society,
Vol. 47, No. 12, November 1999.
TERMS AND DEFINITIONS
Tracking Power Supply—A power supply capable of providing a variable output voltage. According to the present invention, an efficient tracking power-supply is implemented, having control logic controlling a network of switching capacitors. By controlling the switches, different network connections can be made, giving rise to different electrical circuits. This allows creating multiple supply voltages with high efficiency at the load terminals, and monitoring voltages through the sensor terminals.
Multi-Level Quantizer—The above tracking power-supply can be viewed as a quantizer (a “multi-level quantizer”) with multiple output levels possible during different time intervals, where the level changes during each time interval according to the voltages on the capacitors.
Network of Switched Capacitors—the network of switches and capacitors used in the tracking power-supply.
Network Connection—This is a specific set of connections, created by controlling the switches of the network of switched capacitors. This set of network connections creates an electrical circuit involving some or all of the capacitors, supplies, load terminals and sensor terminals.
Network State—The state of the network of switched capacitors at a certain time. The voltages across the capacitors define the network state.
1-Bit State—a specific case of a network state where a 1-bit state per capacitor indicates whether the voltage over it is higher or lower than some target voltage. This is useful when implementing the targeted capacitors selection algorithm.
Sensor—A sensor is any means of monitoring the network state while causing minimal affect. To monitor voltage over a certain capacitor, an appropriate network connection can be made by the control logic. A sensor for the 1-bit state can be the output of a comparator, comparing the voltage over the capacitor to the target voltage.
Estimated Network State—An estimated network state is a network state where some or all of the capacitor voltages are estimated rather than directly monitored.
Network Parameters—The network parameters include sufficient information about components involved in the network of switched capacitors. By way of example, this information may include electrical parameters of the load and main supplies, the capacitance of each capacitor, and the time intervals, whether absolute or relative. In certain embodiments of this invention, the control logic may need to know methods parameters in order to estimate, or predict, the estimated network state when direct monitoring is not feasible. The network parameters may be supplied to the control logic, or may be measured by the control logic through the sensor, whether during initialization time, during operation, or both.
Time Interval—A period of time during which the network connection is held fixed. The duration of such time intervals may be constant or variable, depending on the application.
Load Time Interval—A time interval during which the network connection involves the tracking power-supply output terminals.
Monitoring Time Interval—A time interval during which monitoring of the network state can be performed. A monitoring time interval can overlap a load time interval.
Control Logic—Logic controlling the network of switched capacitors via the switches, in order to create a desired network connection. The main task of the control logic is to determine the best network connection involving the load at any time interval. The control logic implements a selection algorithm, and attempts to minimize the value of the target function, while conforming to some other criteria. The control logic may be implemented fully in the digital domain, while monitoring the state of the network of switched capacitors through the sensor. Alternatively, the control logic can be implemented in the analog domain. The control logic unit has one or more inputs and one or more control outputs.
Target Function—At each load time interval, there is an ideal desired output from the tracking power-supply. Since in general the tracking power-supply cannot provide this output exactly, the target function is a ‘cost’ function that associates a cost with each possible output from the tracking power-supply during the current load time interval. The control logic uses this function as part of the selection algorithm to determine the best network connection for the current load time interval.
Selection Algorithm—The selection algorithm applied by the control logic tries to minimize the target function, while applying additional considerations as well. Such considerations can be of different natures, including, without limitation, minimizing the number of switching operations taking place, keeping voltages on capacitors within certain ranges, keeping voltages on capacitors close to a target voltage, maintaining certain characteristics of the power stage, and so forth.
Constrained Capacitors—A selection algorithm according to which each capacitor has a target v
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