The present invention is directed in general to power electronics and, more particularly, to a power module operable to provide a high slew-rate, pulsed output current and/or voltage to power a load.
Power systems and modules sometimes operate in an environment that requires an output voltage and current provided by a power converter that can supply a rapidly changing output voltage and/or output current. Powering applications requiring pulsed currents with high slew rates are not well served with conventional off-line alternating current-direct current (“ac-dc”) power converters.
A typical approach for supporting these applications is to utilize a high bandwidth linear post-regulator coupled to an output of an off-line power converter. As introduced herein, a more efficient and reliable alternative to this approach utilizes high frequency switch-mode power conversion techniques.
These and other problems are generally solved or circumvented, and technical advantages are generally achieved, by advantageous embodiments of the present invention for constructing a post regulator for use with a power system. The post regulator is coupled to a power converter configured to produce a bus voltage on an output bus. In an embodiment, the post regulator includes a transistor circuit coupled to the output bus of the power converter, and further includes a controller configured to receive the bus voltage and control the transistor circuit to alter an output voltage of the post regulator for a period of time to enhance a slew rate of an output current and/or the output voltage of the post regulator from a first level to a second level.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows can be better understood. Additional features and advantages of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed can be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings, and which:
Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated, and cannot be redescribed in the interest of brevity after the first instance. The FIGUREs are drawn to illustrate the relevant aspects of exemplary embodiments.
The making and using of the present exemplary embodiments are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the systems, subsystems, and modules associated with a system and method for design of a power system and module operable in an environment that operates with a rapidly changing output current and/or a rapidly changing output voltage.
A system will be described herein with respect to exemplary embodiments in a specific context, namely, a broad class of power systems. The specific embodiments may include, but are not limited to, power systems and modules coupled to an ac or dc input voltage source and provide a dc output voltage with a rapidly changing output current and/or output voltage. The principles of the present invention are applicable to other power system designs operable from an ac or dc input voltage that may provide an ac or dc output voltage.
An objective of the disclosure is to provide a power system that converts locally available input electrical power (which is typically ac utility power) into a power type and magnitude more suitable for an end application, which may require pulsed electrical currents at high slew rates (i.e., for example, the amount of time required for the current to transition from a minimum value to a maximum value) and pulse repetition frequencies. Common application examples can provide power for semiconductor lasers with current transition times of the order of one microsecond (“μs”) for a 250 ampere (“A”) pulsed current, as illustrated in
As illustrated in
Turning now to
As illustrated in both of these applications, pulsed currents can require slew rates of 1,000 amperes per millisecond (“A/ms”), 5,000 A/ms or even higher, with currents in the hundreds of amperes. Delivered current in some applications can be unipolar, and sometimes can be bipolar. Common considerations in these types of applications include dealing with power levels of the order of 10's of kilowatts or more, powering processes that demand delivered current slew rates up to 1,000 A/ms or higher, providing a connection between the power converter and the load that can present significant inductance (which limits delivered rate of change of current (di/dt)), and working with off-line power supplies that generally have limited output slew rates.
Commercial ac-dc power supplies are generally designed for the primary task of providing a stable, constant dc output voltage for constant or varying input voltages or output currents. While these commercial ac-dc power supplies support, at some level, varying or pulsed output currents when operating with a constant output voltage, these supplies are typically not able to slew their output voltage quickly enough to force a controlled pulsing current at frequencies by many applications. A main reason for this is impedance limitations of dc output filter capacitors.
In the case of high-frequency switch-mode (“HFSM”) power supplies there are two criteria that set the value of these capacitors. A first criterion is providing a low impedance at the switching frequency to limit output voltage ripple. A second criterion is to provide adequate energy storage to limit output voltage excursions due to energy storage in the output filter inductor upon both application and removal of the load. Given these constraints, output capacitance is generally in the range of 30 to 50 microfarads (“μF”) per ampere of delivered output current. For example, a unit rated to 60 volts (“V”) at 100 amperes (“A”) (6 kW) will typically have around 4,000 μF of output capacitance.
Once an output capacitor is chosen, the unit's output voltage or output current control loops should be adjusted to provide stable operation. For HFSM regulators, the gain-crossover bandwidth (“GCB”) should be less than one half the unit's switching frequency. In practical terms, GCB is normally well below 10 kHz.
Output capacitors and the control loop's GCB, along with the converter's over-current protection (“OCP”) circuits limit the delivered slew rate. The OCP circuit limits the amount of charging current available to the capacitor in a program-up situation. For example, with reference to
Turning now to
Another method available to help improve slew rate is to temporarily increase output voltage during the current rise time. For example, with an output capacitance of 125 μF (1.3 μF per ampere), di/dt without any boost voltage is 409 A/ms. If a 20 volt boost is added during the ramp up time, di/dt can be improved by 34% to 549 A/ms as illustrated in
Turning now to
The input voltage to the post regulator 730 is usually maintained at a constant level above the required load current sustaining voltage to aid in overcoming any load connection inductance during a current pulse rise time. In the example illustrated in
Depending on design parameters, power in the pass transistor 770 in the post regulator 730 can cause issues with forward biased safe operating area of the pass transistor 770, as well as repetitive thermal cycling effects impacting long term reliability. It is tempting to allow transistor junction temperature to approach its rated value during these excursions, but reliability theory teaches this will have a detrimental effect on expected life of the pass transistor 770 due to the repeated mechanical stress imparted to the die and package due to thermal expansion and contraction. When these parameters are taken into consideration very often the linear pass regulator becomes economically and volume burdensome to the end design. This topology places a heavy burden on the pass transistor(s) 770 as it must block the difference between the ac-dc power converter output voltage (a bus voltage V_bus) and the load voltage V_load while also passing all the load current I_load.
In an example embodiment, the power system 700 is configurable for delivering current precision and accuracy approaching 100 parts per million (“ppm”). The power system 700 can be readily configured for operating voltages between zero and 1000 Vdc. The power system 700 can be configured to provide high current slew rates in the presence of output cable inductance in series with the load. The power system 700 is constructed employing a high frequency switch-mode post regulator 730 featuring hysteretic current control. The post regulator 730 can be realized in blocks that are parallel compatible. The power system 700 can be configured to utilize either air or liquid cooling for a particular application.
In an embodiment, the power system 700 can incorporate an onboard control interface. The onboard control interface can be configured to communicate and interact with a host system through either analog, discrete digital, or serial digital communication processes. The onboard control interface generates a control signal 740 that can store and implement operational routines as programmed by the host system. The onboard controller can provide near real-time system operational status information with very low latency. An approach to solving the problem of increasing slew rate includes adding a post regulator 730 between the output of the ac-dc power converter 720 and the load 750, and to temporarily and controllably increase the voltage produced by the power converter 720 in response to a signal generated by a host system on a host interface.
The following post regulator design requirements are preferable. One prerequisite is the ability to support high pulse currents, e.g., delivered peak power in the 10's of kilowatts. Another prerequisite is the ability to support input overhead voltage to aid in overcoming lead inductance during pulse rise time. A third is that the control bandwidth should be high enough to support required pulse repetition frequency. There should be sufficiently small output capacitance to support fast rise times (<5 μF/A). (“microfarads per ampere”). Careful management should be provided for repetitive peak semiconductor power and junction temperature to assure long-term reliability. Given these considerations, post regulator solutions have been developed as described herein based on a high frequency switch-mode technology.
Turning now to
An ac input voltage to the power converter 900 is coupled to input capacitors 910 to supply a dc voltage on a dc power bus 920 to power switches Sw1, Sw2, Sw3, Sw4. A switched voltage produced by the power switches Sw1, Sw2, Sw3, Sw4 is coupled to an output inductor 930 that are wired in series with current-sensing circuit element 940. The output of the current-sensing circuit element 940 is coupled to a control input of a local control and bias circuit 950 (a controller). The local control and bias circuit 950 produces duty-cycle signals D1, D2 that respond to a control input 960 from an external source (not shown) to control the power switches Sw1, Sw2, Sw3 and Sw4. Signals complementary to the duty cycle signals D1, D2 are symbolically shown in the drawing with a bar over each of the duty cycle signals D1, D2. An additional feature of the power converter 900 is the ability to reverse polarity of the delivered output voltage via power switches Sw3, Sw4. These are modulated to set the output polarity as signaled by a host system.
Turning now to
Hysteretic control forces the power switch Sw1 illustrated in
With an output capacitor (see output capacitors 970 in
Power conversion operating efficiency in the example design is greater than 97 percent (“%”), with power switch dissipation less than 6 W per part at full load. With conduction cooling employing a heat sink, this level of power dissipation in the power switch allows for modest switch temperature rise during pulsing operation, thereby limiting any impact on power switch life due to thermal cycling.
Turning now to a
The power system 1200 is formed with a front-end ac-dc power converter 1210 (“PC”) that is powered by 380-480 Vac, three-phase input power and occupies 2 U (referring to a modular height) of 19″ horizontal rack space and features liquid-cooling. The control interface can be realized through an eLink2 power system controller 1220 that communicates over a host interface 1230 through a discrete analog or high-speed serial digital bus, such as Ethernet.
The high frequency switch-mode power converter 1210 is configured to produce an output voltage (also referred to as a bus voltage Vbus) on an output bus 1215 controlled by a signal over the host interface 1230 that is generated by a host system (responsive to a control signal 1225 from the eLink2 power system controller 1220). The high frequency switch-mode power converter 1210 supplies dc power to a high pulse, post-regulator 1240 that produces a pulsed power output (including an output or load voltage V_load and an output or load current I_load) that is supplied to a load 1250. The post regulator 1240 has an input coupled to an output of the switch-mode power converter 1210 and is configured to produce the output voltage V_load controlled over the host interface 1230 (also responsive to a control signal 1225 from the eLink2 power system controller 1220). The host interface 1230 is employed to temporarily boost an output voltage V_bus, V_load of the switch-mode power converter 1210 and the post regulator 1240 for a period of time to enhance slewing of an output current I_load of the post regulator 1240 from a first level (e.g., a lower level) to a second level (e.g., a higher level) or vice versa.
The output voltage V_bus of the power converter 1210 is controlled by the e-Link2 power system controller 1220 that receives an input over the host interface 1230. The e-Link2 power system controller 1220, in addition to controlling the bus voltage V_bus of the power converter 1210, also controls the output voltage V_load of the high pulse post-regulator 1240. The e-Limk2 power system controller 1220 controls the power converter 1210 and high pulse post-regulator 1220 by controlling the respective switches thereof (see, e.g., power switches Sw1, Sw2, Sw3, Sw4 illustrated in
Thus, as introduced herein and with continuing reference to the FIGUREs herein, a post regulator (1240) for use with a power system (1200) includes a power converter (1210) configured to produce a bus voltage (V_bus) on an output bus (1215). The post regulator (1240) includes at least one switch (770) such as a transistor circuit (e.g., including a plurality of transistors) coupled to the output bus (1215) of the power converter (1210), and further includes a controller (1220) configured to receive the bus voltage (V_bus) and control the transistor circuit (770, see
In an embodiment, the controller (1220) is configured to control the transistor circuit (770) to boost the output voltage (V_load) of the post regulator (1240) for the period of time to enhance (e.g., increase) a slew rate of the output current (I_load) and/or the output voltage (V_load) of the post regulator (1240) from the first level to the second level. In an embodiment, the controller (1220) is configured to control the transistor circuit (770) to reduce the output voltage (V_load) of the post regulator (1240) for the period of time to enhance the slew rate of the output current (I_load) and/or the output voltage (V_load) of the post regulator (1240) from the second level to the first level.
In an embodiment, a level of the alteration of the output voltage (V_load) of the post regulator (1240) and the period of time are selected to accelerate transitioning the output current (I_load) and/or the output voltage (V_load) from the first level to the second level. In an embodiment, the controller (1220) is configured to control the transistor circuit (770) responsive to a control signal (1230) from a host system.
As introduced herein, a power system (1200) includes a power converter (1210) configured to produce a bus voltage (V_bus) on an output bus (1215) in response to a first control signal (1225) from a power system controller 1220 (responsive to a signal (1230) from a host system). The power system also includes a post regulator (1240) coupled to the power converter (1210). The post regulator (1240) includes a switches such as a transistor circuit (e.g., 770, including a plurality of transistors) coupled to the output bus (1215) of the power converter (1210), and a controller (1220) configured to receive the bus voltage (V_bus) and control the transistor circuit (770) to alter an output voltage (V_load) of the post regulator (1240) for a period of time to enhance a slew rate of an output current (I_load) and/or the output voltage (V_load) of the post regulator (1240) from a first level to a second level.
In an embodiment, the controller (1220) is configured to control the transistor circuit (770) to boost the output voltage (V_load) of the post regulator (1240) for the period of time to enhance (e.g., increase) the slew rate of the output current (I_load) and/or the output voltage (V_load) of the post regulator (1240) from the first level to the second level. In an embodiment, the controller (1220) is further configured to control the transistor circuit (770) to reduce the output voltage (V_load) of the post regulator (1240) for a period of time to enhance the slew rate of the output current (I_load) and/or the output voltage (V_load) of the post regulator (1240) from the second level to the first level.
In an embodiment, a level of the alteration of the output voltage (V_load) of the post regulator (1240) and the period of time are selected to accelerate transitioning the output current (I_load) and/or the output voltage (V_load) from the first level to the second level. In an embodiment, the controller (1240) is configured to control the transistor circuit (770) responsive to a second control signal (1230) from the host system. In an embodiment, the power converter (1210) is an alternating-current to direct-current power converter.
Various possibilities are contemplated herein for packaging of the power converters. For example,
Other examples of the scalable nature of this technology have been constructed including:
Thus, a high frequency switch mode technology has been introduced that provides an improved ac to pulsed dc output power system. The power system can provide output current slew rates greater than 5,000 A/ms while also managing component reliability considerations resulting from thermal fatigue and safe operating conditions.
Although the embodiments and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope thereof as defined by the appended claims. For example, many of the features and functions discussed above can be implemented in software, hardware, or firmware, or a combination thereof. Also, many of the features, functions, and steps of operating the same can be reordered, omitted, added, etc., and still fall within the broad scope of the various embodiments.
Moreover, the scope of the various embodiments is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized as well. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/303,567 filed Jan. 27, 2022, the disclosure of which is incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
63303567 | Jan 2022 | US |