WO2018106395A1 - Inverting switching regulator - Google Patents

Abstract

An inverting switching regulator develops an output voltage of one polarity from an input or supply voltage of an opposite polarity wherein the magnitude of the output voltage exceeds the magnitude of the supply voltage.

Description

INVERTING SWITCHING REGULATOR

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Serial No. 62/431887, filed December 9, 2016, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present principles relate generally to switching power supplies.

BACKGROUND

This section is intended to introduce the reader to various aspects of art, which may be related to various aspects of the present disclosure that are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

A sub-system included within most electronic devices is a power source or power supply. A power supply may be required to provide various output DC voltages, e.g., +5 VDC and +12 VDC, and may be required to provide both positive and negative polarities of output voltages, e.g., +/- 5VDC and +/-12 VDC. In addition, it is likely that each output voltage will have particular requirements as to power output and regulation of voltage and/or current. Switching power supplies are a well-known approach to providing such power sources. Implementations of switching supplies may involve an integrated circuit for controlling the switching supply operation. However, integrated circuits may be costly and controlling cost is a key criterion when developing electronic devices such as mass-produced consumer electronics devices. Integrated circuits may also limit options for parameters such as output voltage and regulation to values that are not compatible with requirements for a particular device. In addition, basing development of a device on a particular integrated circuit may limit availability of parts and/or limit alternative or "second" sources of parts. Ensuring an adequate supply of parts and multiple sources of parts is an important consideration for a device intended for large-scale production. SUMMARY

The present principles are generally directed to providing an inverting switching regulator.

In accordance with an aspect of the present principles, an embodiment generally involves a current-controlled, discrete-component inverting switching regulator to develop an output voltage of one polarity from an input or supply voltage of an opposite polarity.

In accordance with another aspect of the present principles, an embodiment generally involves a current-controlled, discrete-component inverting switching regulator to develop a negative output voltage from a positive input or supply voltage and the negative output voltage has a magnitude exceeding the magnitude of the positive input or supply voltage.

In accordance with another aspect of the present principles, another embodiment of an inverting regulator in accordance with the present principles may provide a positive output voltage from a negative supply voltage.

In accordance with another aspect of the present principles, an embodiment of an inverting switching regulator generally comprises discrete semiconductor components, thereby providing flexibility of circuit component selection for control of design criteria including cost and parts availability.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles includes: a switch coupled to a source of a first polarity of a DC supply voltage having a first magnitude; a storage capacitor coupled between an output and a source of a reference potential; an inductor coupled to the switch and conducting current from the source of the first polarity DC voltage to the source of the reference potential during a conductive mode of operation of the switch and coupled to the capacitor to provide a voltage at the output having a second polarity opposite to the first polarity during a nonconductive mode of operation of the switch, wherein the voltage on the capacitor provides a DC voltage at the output having the second polarity and having a second magnitude greater than the first magnitude of the first polarity DC supply voltage; and a control circuit responsive to a variation of the second polarity DC voltage at the output to produce a current signal controlling the operating mode of the switch between the conductive and non-conductive operating modes to regulate the second polarity DC voltage at the output.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles including a switch may further include the switch having a control input to receive a control signal to control the mode of operation of the switch; and the control circuit is coupled from the output to the control input of the switch to provide the control signal for the switch, wherein the control circuit comprises a switching circuit coupled to the control input and producing the control signal to control the switching device, and a feedback path coupled between the output and the switching circuit and responsive to a variation of the second polarity DC voltage at the output to produce a current signal causing the control signal to switch the operating mode of the switching device between the conductive and non-conductive operating modes for regulating the second polarity DC voltage at the output.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles includes: a switching device coupled to a source of a first polarity of a DC supply voltage having a first magnitude and having a control input coupled to receive a control signal for selecting a mode of operation of the switching device, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation; a storage capacitor coupled between an output and a source of a reference potential; an inductor coupled to the switching device and conducting current from the source of the first polarity DC voltage to the source of the reference potential during the conductive mode of operation of the switching device and coupled to the capacitor to provide a voltage at the output having a second polarity opposite to the first polarity during the nonconductive mode of operation of the switching device, wherein the voltage on the capacitor provides a DC voltage at the output having the second polarity and having a second magnitude greater than the first magnitude of the first polarity DC supply voltage; and a control circuit coupled from the output to the control input of the switching device to provide the control signal for the switching device, wherein the control circuit comprises a switching circuit coupled to the control input and producing the control signal to control the switching device, and a feedback path coupled between the output and the switching circuit and responsive to a variation of the second polarity DC voltage at the output to produce a current signal causing the control signal to switch the operating mode of the switching device between the conductive and non- conductive operating modes for regulating the second polarity DC voltage at the output.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles including a switching circuit may further include the switching circuit being responsive to the current signal and configured to cause a regenerative switching action of the switching circuit and a hysteresis characteristic in the control signal producing changes of the operating mode of the switching device between the conductive and non-conductive operating modes that occur abruptly and timed for limiting the variation of the second magnitude of the second polarity DC voltage at the output.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles may comprise a switching regulator including: a switching transistor coupled to a source of a positive DC supply voltage and having a control input coupled to receive a control signal for selecting a mode of operation of the switching transistor, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation; an inductor coupled to the switching transistor and conducting current from the source of the positive DC voltage to ground during the conductive mode of operation of the switching transistor and providing a negative voltage to a storage capacitor coupled to an output during the nonconductive mode of operation of the switching transistor to produce at the output a negative DC voltage having a magnitude greater than the magnitude of the positive DC supply voltage; and a control circuit coupled from the output to the control input of the switching transistor to provide the control signal for the switching transistor responsive to a variation of the negative DC voltage at the output and to produce a hysteresis characteristic in the control signal producing changes of the operating mode of the switching transistor between the conductive and non-conductive operating modes that occur abruptly and timed for limiting the variation of the negative DC voltage.

In accordance with another aspect, an embodiment of a switching regulator in accordance with the present principles including a control circuit may further comprise the control circuit including a feedback path coupled to the output and being responsive to a variation of the negative DC voltage at the output to produce a current signal; and a switching circuit coupled to the control input of the switching device and producing the control signal having the hysteresis characteristic to control the switching device and being responsive to the current signal from the feedback path to produce the control signal to switch the operating mode of the switching device between the conductive and non-conductive operating modes with a timing for regulating the negative DC voltage at the output.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles comprises an inverting switching regulator including: a switching transistor coupled to a source of a positive DC supply voltage and having a control input coupled to receive a control signal for selecting a mode of operation of the switching transistor, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation; an inductor coupled to the switching device and conducting current from the source of the positive DC supply voltage to ground during the conductive mode of operation of the switching transistor and providing a negative voltage to a storage capacitor coupled to an output during the nonconductive mode of operation of the switching transistor to produce at the output a negative DC voltage having a magnitude greater than the magnitude of the positive DC supply voltage; and a control circuit coupled from the output to the control input of the switching transistor to provide the control signal for the switching transistor, wherein the control circuit comprises a switching circuit coupled to the control input and producing the control signal to control the switching transistor, and a feedback path coupled between the output and the switching circuit and being responsive to a variation of the negative DC voltage at the output to produce a current signal coupled to the switching circuit; wherein the switching circuit is responsive to the current signal to produce a regenerative switching action and a hysteresis characteristic in the control signal causing the operating mode of the switching transistor to switch between the conductive and non- conductive operating modes abruptly and with a timing for limiting the variation of the negative DC voltage.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles including a switching circuit may further include the switching circuit comprising a transistor and a resistor and a capacitor configured to produce the hysteresis characteristic of the control signal.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles including a feedback path may further include the feedback path comprising a voltage divider coupled between the output and the source of reference potential to provide at a tap of the voltage divider a voltage between the output voltage and the reference potential; and a Zener diode having a first terminal coupled to the tap of the voltage divider and a second terminal coupled to the switching circuit, wherein a voltage at the tap exceeding a breakdown voltage of the Zener diode causes the switching circuit to control a duration of the conductive mode of operation of the switching device to decrease the output voltage.

In accordance with another aspect, an embodiment of apparatus in accordance with the present principles may further include a switch or switching device or switching transistor comprising a P-channel MOSFET transistor; the first polarity of a DC supply voltage corresponds to a positive DC supply voltage and the second polarity corresponds to a negative polarity; and the reference potential corresponds to a ground potential.

These and other aspects, features and advantages of the present principles will become apparent from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWNGS

These, and other aspects, features and advantages of the present disclosure will be described or become apparent from the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying exemplary figures in which:

FIG. 1 is a diagram showing, in circuit schematic form, an exemplary embodiment of an inverting switching regulator in accordance with the present principles; and

FIG. 2 through FIG. 6 are diagrams showing exemplary waveforms illustrating the operation of the embodiment shown in Figure 1 in accordance with aspects of the present principles.

DETAILED DESCRIPTION

The present principles are generally directed to inverting switching regulators. While one of ordinary skill in the art will readily contemplate various applications to which the present principles can be applied, the following description will focus on embodiments of the present principles applied to electronic devices such as digital televisions, gateways, set-top boxes, and mobile devices. However, one of ordinary skill in the art will readily contemplate other devices and applications to which the present principles can be applied, given the teachings of the present principles provided herein, while maintaining the spirit of the present principles. It is to be appreciated that the preceding listing of devices is merely illustrative and not exhaustive.

In addition, exemplary embodiments described herein may include or be utilized with other elements not shown or described, as readily contemplated by one of skill in the art, as well as omit certain elements. For example, various components and circuits such as input circuits supplying an input supply voltage and/or subsystems and components powered by a circuit in accordance with the present principles or other components can be included depending upon the particular implementation of the same, as readily understood by one of ordinary skill in the art. These and other variations are readily contemplated by one of ordinary skill in the art given the teachings of the present principles provided herein.

An exemplary embodiment of an inverting switching regulator in accordance with the present principles is shown in Figure 1 in circuit diagram or schematic diagram format. In addition to showing components in a circuit arrangement suitable for providing an exemplary embodiment of the present principles, the circuit shown in Figure 1 is also suitable for simulating circuit operation, e.g., using a program such as PSpice, and includes various components to facilitate such simulation as explained below. Simulation of the circuit of Figure 1 was used to generate the waveforms shown in Figures 2 through 6 for illustrating the operation of the embodiment shown in Figure 1. In Figures 2 through 6, current or voltage values are along the vertical or Y axis while time is along the horizontal or X axis. The time scale of the horizontal axis in Figures 2, 5 and 6 is relatively short, e.g., 20 μ8, to show switching or transient activity, especially during startup of the circuit of Figure 1. The time scale of the horizontal axis in Figures 3 and 4 is relatively long, e.g., 500 μ8, to show inverter operation after the initial startup interval, i.e., when the output voltage has reached and stabilized at the regulated output voltage value, e.g., -21 volts for the exemplary embodiment of Figure 1 as explained below.

The regulator of Figure 1 operates in a flyback mode of operation which involves storing energy in an inductor when a switching device is turned on, i.e., during a conductive mode of operation of the switching device. When the switching device is turned off or is in a non- conductive mode of operation, the inductor releases the energy to a storage capacitor at the output. The exemplary regulator functions in an inverting mode of operation which provides an output voltage of one polarity from an input or supply voltage of an opposite polarity. For example, the exemplary embodiment of Figure 1 provides a negative output voltage while using a positive input or supply voltage.

Switching of the switching device between conductive (switched "on") and non-conductive (switched "off) modes of operation is controlled by a control mechanism operating in a current- control mode. When the current through the switching device reaches a predetermined level, the switching device is turned off. Regulation of the output voltage is achieved by adjusting a current level at which the switching device is turned off. By adjusting the current level, the amount of energy that is stored in the inductor can be controlled, i.e., either increased or decreased. Controlling the energy stored in the inductor also controls the amount of energy that is released to the storage capacitor. That is, regulation of the output voltage occurs depending on the amount of power that is required to be delivered to the load. For example, an increased power or current demand by the load causes the control mechanism to increase the switched-on interval of the switching device, thereby storing an increased amount of energy in the inductor during the switched on-interval. This increased amount of energy is released or provided by the inductor to the output storage capacitor during the switched off interval. As a result, there is additional energy available in the storage capacitor to supply the increased power or current demand of the load without causing a decrease in the output voltage, i.e., the output voltage is maintained or regulated.

In more detail, the exemplary embodiment shown in Figure 1 includes a switching device M2, e.g., a P-channel MOSFET transistor such as type NDC7003P/FAI, coupled to a source of supply voltage and to an energy storage/release inductor L2 having an inductance, e.g., of 150 μΗ. In the exemplary embodiment of Figure 1, the input or supply voltage may be, for example, +12 volts DC and is illustratively shown in Figure 1 by a battery symbol VI providing 12-volts DC. As will be apparent to one skilled in the art, a supply voltage greater or less than that shown in Figure 1 may be used and/or may be appropriate depending on the design criteria for a particular application. Also, a DC voltage such as the +12 volt DC input shown in Figure 1 may be provided from various types of supplies such as a battery, or from AC mains via a power supply circuit such as a step-down transformer coupled to a rectifier and filter capacitor, or from a higher DC voltage via a voltage regulator such as an integrated circuit regulator. An output voltage of the exemplary embodiment of an inverting switching regulator shown in Figure 1 is produced across output storage capacitor C5, e.g., 220 nF. The exemplary embodiment shown produces an output voltage of -21 volts DC at 40 mA.

Also included in the exemplary embodiment shown in Figure 1 is a control circuit coupled to the control terminal of the switching device, e.g., gate of M2, that provides a control signal to control the switching operation. That is, the control circuit produces a control signal that selects or enables the conductive and non-conductive modes of operation of the switching device. In addition, the control circuit produces the control signal to control the duration of the conductive mode of operation ("on" or conducting period) and the duration of the non-conductive mode of operation ("off or non-conducting period). In the exemplary embodiment of Figure 1, the control circuit includes a switching circuit portion and a feedback path portion. In the exemplary embodiment of Figure 1, the switching circuit portion of the control circuit includes PNP transistor Q4, e.g., type Q2N2907, producing at the collector of transistor Q4 the control signal for switching device M2. The switching circuit further includes components including NPN transistor Q9, e.g., type MPAA20, resistors R14 (e.g., 3300 Ω), R25 (e.g., 1000 Ω), R28 (e.g., 6.8 kQ), and capacitor C 14 (e.g., 1 nF) . The feedback path portion of the control circuit comprises Zener diode D7, e.g., type BZX84C20/ZTX, resistor Rl l, e.g., 2200 Ω, and Cl l, e.g., 470 nF.

Operation of the exemplary embodiment shown in Figure 1 including the switching device, inductor and control circuit features described above will now be explained in more detail with reference to signal waveforms shown in Figures 2 through 6. Operation begins when the input or supply voltage is applied. That is, the first cycle of operation is initiated when the +12 V DC input voltage of supply VI is applied. Initially, transistor Q4 is non-conductive and resistor R12 (e.g., 1000 Ω) allows the voltage at a control terminal of the switching device, e.g., the gate voltage of switching device M2, to drop towards a reference potential, e.g., ground or zero volts in Figure 1. The change in gate voltage of switching device M2 is illustrated in the "M2 Gate Voltage" waveform shown in Figure 2. The gate voltage of switching device M2 dropping towards zero volts causes switching device M2 to enter a conductive mode of operation (turn on) and conduct. When switching device M2 conducts, current increases linearly through inductor L2 and generates a voltage across current sense resistor R27 (e.g., 10 Ω) that is proportional to the current flowing through inductor L2 as shown in Figure 2. The current change in switching device M2 is illustrated in the "M2 Drain Current" waveform shown in Figure 2. The voltage at the drain of switching device M2 is illustrated by the lower waveform in Figure 5 labeled "M2 Drain (L2 Top)". The label "M2 Drain (L2 Top)" indicates that the voltage at the drain of switching device M2 is substantially the same as the voltage at the top of inductor L2 because, as explained elsewhere in the present description, resistor R31 having a value of 1Ω is included merely for purposes of circuit simulation and has negligible impact on circuit operation. Current flowing through inductor L2 as a result of current conducted through switching device M2 produces voltage values on inductor L2 that are illustrated by the waveforms shown in Figure 6. The upper waveform of Figure 6 labeled "L2 Bottom" shows the voltage at the "bottom" of inductor L2, i.e., the node of inductor L2 coupled to resistor R27 in Figure 1. The lower waveform of Figure 6 labeled "L2 Top (M2 Drain)" is substantially the same as the lower waveform of Figure 5 (labeled "M2 Drain (L2 Top") and shows the voltage at the node in Figure 1 where the "top" of inductor L2 is coupled to resistor R31, capacitor C 13, and the cathode of diode Dl.

As the current increases through resistor R27, there is a corresponding increase in the base- to-emitter voltage on transistor Q9. The increasing base-emitter voltage causes transistor Q9 to begin to conduct. As a result, the collector voltage of transistor Q9 begins to decrease and the current through transistor Q9 increases. The operation of transistor Q9 is illustrated in the "Q9 Collector Voltage" and "Q9 Base-Emitter Voltage" waveforms shown in Figure 2 and the lower waveform in Figure 3 labeled "Q9 Emitter". Increasing current through transistor Q9 causes the voltage drop across resistor R25 to increase and produce a base-to-emitter voltage on transistor Q4 that causes transistor Q4 to conduct. Conduction of transistor Q4 causes the gate voltage of switching device M2 to begin to decrease and eventually switching device M2 ceases to conduct or enters a non-conductive or "off mode of operation. To ensure a solid, i.e., a sharp or abrupt, switching condition of the control of switching device M2, capacitor C14, e.g., 1 nF, and resistor R28, e.g., 6.8 kQ, provide a hysteresis characteristic in the control signal for switching device M2 that increases the base voltage of transistor Q9 as the gate voltage of switching device M2 increases toward the input supply voltage. The described hysteresis characteristic and the resulting abrupt or sharp change of the switching control signal at the gate of switching device M2 are illustrated by the "Q9 Base-Emitter Voltage" and "M2 Gate Voltage" waveforms shown in Figure 2.

When switching device M2 ceases to conduct or enters the non-conductive or "off operating mode, the energy stored in inductor L2 begins to be released and provided to output storage capacitor C5. Transient characteristics of inductor L2 cause the release of energy to produce a negative voltage that is provided to output capacitor C5 via diode Dl, e.g., type 1N4148, thereby producing a negative output voltage across capacitor C5. As energy is transferred from inductor L2 to output capacitor C5 to produce the output voltage, voltage across current sense resistor R27 drops causing transistor Q9 to turn off. Transistor Q9 turning off increases the voltage at the base of transistor Q4 causing transistor Q4 to turn off, thereby allowing the gate voltage of switching device M2 to decrease. Variations in the voltage at the base of transistor Q4 are illustrated in the upper waveform of Figure 5 labeled "Q4 Base". The next switching cycle is initiated when the gate voltage of switching device M2 drops sufficiently toward ground to turn switching device M2 on or enter the conductive or "on" mode of operation. Output voltage regulation to control the output voltage of the exemplary inverting regulator embodiment shown in Figure 1, e.g., to minimize variations of the output voltage, is provided by the feedback portion of the control circuit comprising Zener diode D7, resistor Rl 1, and capacitor Cl l. When the output of the regulator exceeds the breakdown voltage of the Zener diode, e.g., exceeds the 20 V breakdown voltage of the exemplary type BZX84C20/ZTX Zener diode shown in Figure 1, a negative voltage is produced at the emitter of transistor Q9. As the emitter voltage of transistor Q9 is reduced, a lower voltage level on the current sense resistor R27 will cause transistor Q9 to conduct. That is, the effect of the Zener diode breakdown of diode D7 in response to excessive output voltage is to effectively turn transistor Q9 on earlier causing, as explained above, switching device M2 to turn off earlier. The result is that the point at which switching device M2 switches from the conductive mode of operation to the non-conductive mode of operation occurs at a lower level of current through inductor L2 and current sense resistor R27. The lower current in the inductor stores less energy and the output voltage is reduced to the normal regulation point, i.e., the normal or design output voltage value. Resistor Rl 1 and capacitor Cl l provide a filter and time constant for the feedback loop. The voltage at the anode of Zener diode D7 is shown in Figure 4 over a long time scale beginning with startup of the inverter circuit of Figure 1. The upper waveform in Figure 3 illustrates that the output voltage decreases (becomes more negative) until reaching the intended regulated output value of -21 volts for the exemplary embodiment of Figure 1 at which point the operation of regulator including diode D7 maintains the output voltage at the intended value. The anode voltage of diode D7 is shown by the waveform in Figure 4 illustrating the described output voltage regulation feature.

Other components included in the exemplary embodiment shown in Figure 1 include capacitor C13 (e.g., 1 nF) and resistor R30 (e.g., 2200 Ω) to provide damping for the inductor to suppress or prevent ringing. Diode D13, e.g., type 1N4148, provides an initial current path to ground for transistor Q9 during startup of the switching regulator. Resistor R14, e.g., 3300 Ω, provides current limiting to protect transistor Q4 and modify the storage time of Q4, thereby impacting the switching speed. Resistor R20, e.g., 330 Ω, provides both current limiting in case of component failure and positive feedback that contributes to creating the above-described hysteresis characteristic in the control signal of the switching device M2. A resistor divider formed, e.g., by resistors R9 and R23 coupled in series, may be used to adjust the output voltage. In the exemplary embodiment of Figure 1, resistors R9 and R23 have exemplary values of 10 Ω and 27 ΚΩ, respectively, and the cathode of Zener diode D7 is coupled to the junction of these two resistors, i.e., a tap of the resistive divider. The exemplary arrangement of a resistive divider and Zener diode D7 enables the embodiment of Figure 1 to produce the above-mentioned -21 V DC output voltage. Varying the value of resistors R9 and R23 such that the junction or tap of the divider provides a different percentage of the output voltage to Zener diode D7 will change the output voltage value that activates the voltage regulation feedback circuit, thereby regulating the output voltage to a different value. As will be apparent to one skilled in the art, various combinations of resistor values and/or a variable resistor may be used to implement the described output voltage adjustment.

Also shown in Figure 1 are components such as resistor Rl, R31 and R24 that are included only for the purpose of enabling and/or facilitating simulation of the operation of the circuit, e.g., by circuit simulation software such as PSpice. That is, these components and their values are not important with respect to the operation of the exemplary embodiment shown in Figure 1. Resistors Rl and R31 shown as each having a value of 1 Ω are included merely to provide points at which circuit operation may be monitored during simulation of the operation of the circuit. Resistor R24 shown as having a value of 10 ΚΩ is included to provide a load on the output and enable simulation of the operation of the circuit under expected load conditions.

Another embodiment of an inverting regulator in accordance with the present principles may provide a positive output voltage from a negative supply voltage. Such an embodiment comprises, for example, in reference to Figure 1 using opposite polarity semiconductors including an NPN transistor instead of the PNP transistor used for Q4 in Figure 1 and an N-channel MOSFET for M2 instead of a P-channel MOSFET as in Figure 1. In addition, other components shown in Figure 1 including rectifier diode Dl, Zener diode D7 and signal diode D13 would be reversed in polarity as well.

The present description illustrates the present principles. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the present principles and are included within its spirit and scope. For example, the principles described herein could be combined with other power supply design features or approaches

All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the present principles and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions.

Moreover, all statements herein reciting principles, aspects, and embodiments of the present principles, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

Reference in the specification to "one embodiment" or "an embodiment" of the present principles, as well as other variations thereof, means that a particular feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present principles. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment", as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment.

It is to be appreciated that the use of any of the following "/", "and/or", and "at least one of, for example, in the cases of "A/B", "A and/or B" and "at least one of A and B", is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of both options (A and B). As a further example, in the cases of "A, B, and/or C" and "at least one of A, B, and C", such phrasing is intended to encompass the selection of the first listed option (A) only, or the selection of the second listed option (B) only, or the selection of the third listed option (C) only, or the selection of the first and the second listed options (A and B) only, or the selection of the first and third listed options (A and C) only, or the selection of the second and third listed options (B and C) only, or the selection of all three options (A and B and C). This may be extended, as readily apparent by one of ordinary skill in this and related arts, for as many items listed.

Other hardware, conventional and/or custom, may also be included. Similarly, any switches shown in the figures are conceptual only. Their function may be carried out through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, the particular technique being selectable by the implementer as more specifically understood from the context.

Herein, the phrase "coupled" is defined to mean directly connected to or indirectly connected with through one or more intermediate components. Although the illustrative embodiments have been described herein with reference to the accompanying drawings, it is to be understood that the present principles are not limited to those precise embodiments, and that various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the scope or spirit of the present principles. All such changes and modifications are intended to be included within the scope of the present principles.

Claims

1. Apparatus comprising:

a switch coupled to a source of a first polarity of a DC supply voltage having a first magnitude;

a storage capacitor coupled between an output and a source of a reference potential;

an inductor coupled to the switch and conducting current from the source of the first polarity DC voltage to the source of the reference potential during a conductive mode of operation of the switch and coupled to the capacitor to provide a voltage at the output having a second polarity opposite to the first polarity during a nonconductive mode of operation of the switch, wherein the voltage on the capacitor provides a DC voltage at the output having the second polarity and having a second magnitude greater than the first magnitude of the first polarity DC supply voltage; and

a control circuit responsive to a variation of the second polarity DC voltage at the output to produce a current signal controlling the operating mode of the switch between the conductive and non-conductive operating modes for regulating the second polarity DC voltage at the output.

2. The apparatus of claim 1 wherein:

the switch has a control input to receive a control signal to control the mode of operation of the switch; and

the control circuit is coupled from the output to the control input of the switch to provide the control signal for the switch, wherein the control circuit comprises:

a switching circuit coupled to the control input and producing the control signal to control the switching device, and

a feedback path coupled between the output and the switching circuit and being responsive to a variation of the second polarity DC voltage at the output to produce a current signal causing the control signal to switch the operating mode of the switching device between the conductive and non-conductive operating modes for regulating the second polarity DC voltage at the output.

3. Apparatus comprising:

a switching device coupled to a source of a first polarity of a DC supply voltage having a first magnitude and having a control input coupled to receive a control signal for selecting a mode of operation of the switching device, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation;

a storage capacitor coupled between an output and a source of a reference potential;

an inductor coupled to the switching device and conducting current from the source of the first polarity DC voltage to the source of the reference potential during the conductive mode of operation of the switching device and coupled to the capacitor to provide a voltage at the output having a second polarity opposite to the first polarity during the nonconductive mode of operation of the switching device, wherein the voltage on the capacitor provides a DC voltage at the output having the second polarity and having a second magnitude greater than the first magnitude of the first polarity DC supply voltage; and

a control circuit coupled from the output to the control input of the switching device to provide the control signal for the switching device, wherein the control circuit comprises:

a switching circuit coupled to the control input and producing the control signal to control the switching device, and

a feedback path coupled between the output and the switching circuit and being responsive to a variation of the second polarity DC voltage at the output to produce a current signal causing the control signal to switch the operating mode of the switching device between the conductive and non-conductive operating modes for regulating the second polarity DC voltage at the output.

4. The apparatus of claim 2 or 3 wherein the switching circuit being responsive to the current signal and configured to cause a regenerative switching action of the switching circuit and a hysteresis characteristic in the control signal producing changes of the operating mode of the switching device between the conductive and non-conductive operating modes that occur abruptly and timed for limiting the variation of the second magnitude of the second polarity DC voltage at the output.

5. A switching regulator comprising:

a switching transistor coupled to a source of a positive DC supply voltage and having a control input coupled to receive a control signal for selecting a mode of operation of the switching transistor, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation;

an inductor coupled to the switching transistor and conducting current from the source of the positive DC voltage to ground during the conductive mode of operation of the switching transistor and providing a negative voltage to a storage capacitor coupled to an output during the nonconductive mode of operation of the switching transistor to produce at the output a negative DC voltage having a magnitude greater than the magnitude of the positive DC supply voltage; and a control circuit coupled from the output to the control input of the switching transistor to provide the control signal for the switching transistor responsive to a variation of the negative DC voltage at the output and to produce a hysteresis characteristic in the control signal producing changes of the operating mode of the switching transistor between the conductive and non- conductive operating modes that occur abruptly and timed for limiting the variation of the negative DC voltage.

6. The apparatus of claim 5 wherein the control circuit comprises:

a feedback path coupled to the output and being responsive to a variation of the negative DC voltage at the output to produce a current signal; and

a switching circuit coupled to the control input of the switching device and producing the control signal having the hysteresis characteristic to control the switching device and being responsive to the current signal from the feedback path to produce the control signal to switch the operating mode of the switching device between the conductive and non-conductive operating modes with a timing for regulating the negative DC voltage at the output.

7. An inverting switching regulator comprising:

a switching transistor coupled to a source of a positive DC supply voltage and having a control input coupled to receive a control signal for selecting a mode of operation of the switching transistor, wherein the mode of operation comprises one of a conductive mode of operation and a nonconductive mode of operation; an inductor coupled to the switching device and conducting current from the source of the positive DC supply voltage to ground during the conductive mode of operation of the switching transistor and providing a negative voltage to a storage capacitor coupled to an output during the nonconductive mode of operation of the switching transistor to produce at the output a negative DC voltage having a magnitude greater than the magnitude of the positive DC supply voltage; and a control circuit coupled from the output to the control input of the switching transistor to provide the control signal for the switching transistor, wherein the control circuit comprises:

a switching circuit coupled to the control input and producing the control signal to control the switching transistor, and

a feedback path coupled between the output and the switching circuit and being responsive to a variation of the negative DC voltage at the output to produce a current signal coupled to the switching circuit; wherein

the switching circuit being responsive to the current signal to produce a regenerative switching action and a hysteresis characteristic in the control signal causing the operating mode of the switching transistor to switch between the conductive and non- conductive operating modes abruptly and with a timing for limiting the variation of the negative DC voltage.

8. The apparatus of any one of claims 4, 6, or 7 wherein the switching circuit comprises a transistor and a resistor and a capacitor configured to produce the hysteresis characteristic of the control signal.

9. The apparatus of any one of claims 2, 3, 4, 6, 7 or 8 wherein the feedback path comprises:

a voltage divider coupled between the output and the source of reference potential to provide at a tap of the voltage divider a voltage between the output voltage and the reference potential; and

a Zener diode having a first terminal coupled to the tap of the voltage divider and a second terminal coupled to the switching circuit, wherein a voltage at the tap exceeding a breakdown voltage of the Zener diode causes the switching circuit to control a duration of the conductive mode of operation of the switching device to decrease the output voltage.

10. The apparatus of any one of the preceding claims wherein:

the switch or switching device or switching transistor comprises a P-channel MOSFET transistor;

the first polarity of a DC supply voltage corresponds to a positive DC supply voltage and the second polarity corresponds to a negative polarity; and

the reference potential corresponds to a ground potential.