DC POWER SUPPLY WITH REDUCED INPUT CURRENT RIPPLE
A power supply comprising a DC to DC converter coupled to a current limit controller and an accumulator. The accumulator discharges while the current limit controller limits the current draw of the DC to DC converter.
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This application is a continuation of U.S. patent application Ser. No. 15/872,890 filed Jan. 16, 2018 and titled “DC POWER SUPPLY WITH REDUCED RIPPLE” which claims the benefit of U.S. Provisional Application Ser. No. 62/573,990 filed Oct. 18, 2017 and titled “DC POWER SUPPLY WITH REDUCED RIPPLE,” which are hereby incorporated by reference in their entireties.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNone.
BACKGROUNDMany modern communications systems use waveforms that employ techniques such as frequency hopping, time division multiplexing, and vector modulation. These complex waveforms can cause noise and ripple effects on the input power supply lines, such as low frequency, high current pulse modulation. Additionally, harmonics and intermodulation distortion may also be created, which can extend the frequency impact to frequencies significantly higher than those directly associated with the waveform. It is advantageous to create a direct current (DC) power supply that provides more input line stability and can overcome the effects of using such modern waveforms, while minimizing its size and weight and maximizing its power efficiency.
SUMMARYA DC power supply comprising a switch-mode DC to DC converter. A current limit controller is used to limit the current draw of the switch-mode DC to DC converter. An energy storage device charges from the switch-mode DC to DC converter and discharges while the current limit controller is limiting the current draw of the switch-mode DC to DC converter.
For a detailed description of various embodiments, reference will now be made to the accompanying drawings in which:
The following discussion is directed to various embodiments. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.
The use of complex waveforms in modern communications systems may create noise and stability issues on the input power supply lines within modern electronics. These issues may include high frequency noise, as well as low frequency ripple. The high frequency components may be effectively filtered with the use of lumped elements, but the required capacitance and inductance values tend to be very large, with current handling capability below what would be necessary for the low frequency signals. The presence of high current, low frequency ripple may also create an alternating current (AC) voltage drop on the power supply lines. This voltage drop may interfere with other systems and cause systems to fail testing requirements. For example, the United States military requires certain equipment to pass electromagnetic interference (EMI) and Tempest tests (such as MIL-STD-461 CE 101). These kinds of tests seek to limit or prevent equipment from interfering with other devices or from leaking information susceptible to eavesdropping or intelligence gathering (such as through unintentional radio or electrical signals, sounds, and vibrations).
Systems and devices that may benefit from an improved DC power supply include, for example, aircraft and military mobile communication units. Aircraft often use 28 volt (V) DC power systems. In various embodiments, the aircraft may provide 28 V DC power to the communications system, though the use of other voltage levels is also contemplated in this description. A military mobile communications unit may utilize a modern communications system that would benefit from an improved DC power supply. In various embodiments, the military mobile communications unit may be powered by a 28V DC power supply, though use of other voltage levels is also contemplated in this disclosure. In addition to aircraft and military mobile communications units, other communications systems may also benefit from an improved DC power supply (e.g., cellular equipment, radio transceivers). Equipment other than communications equipment may benefit from an improved DC power supply as disclosed herein.
In various embodiments, the rise and fall of the current waveform may be periodic. The period may correspond to various states of the overall system. For example, a communication system may alternate between transmit and receive modes. Prior to the first point in time 190, the system may be operating in a receive mode that draws a low current value 120. During the receive mode, the system may be receiving signals on an antenna, but not need to provide much or any power to a power amplifier or transmission circuitry. The system may switch to a transmit mode at a first point in time 190 and remain in transmit mode until a second point in time 192. Between the first and second points in time 190, 192, the system may draw a high current value 130. This current may be required to provide power to a power amplifier or transmission circuitry. The system may return to a receive mode at a second point in time 192, to a transmit mode at a third point in time 194, and again to a receive mode at a fourth point in time 196.
As depicted in
The specific current waveform 100 depicted in
Voltage waveform 150 shows a possible voltage output value of a DC power supply.
Electronic devices may be built to tolerate a range of voltage values from a DC power supply. While the electronic devices may be built with a target voltage value 180 in mind, they may typically continue proper operations within a range of voltage values extending above and below the target voltage value 180. A potential minimum required voltage 170 is depicted on
In various embodiments, the switch-mode DC to DC converter 220 may output a DC voltage value by creating a square wave and filtering the square wave (such as with a low-pass filter) to create a DC voltage value. The low-pass filter may be a passive filter (such as one creating using inductive and capacitive elements) or an active filter. The switch-mode DC to DC converter 220 may adjust the DC voltage value by modifying the square wave's duty cycle. The duty cycle of the square wave is the proportion of time the square wave at its higher voltage. For example, using a square wave that alternates between 0 V and 10 V with a 50% duty cycle may result in a DC voltage value of approximately 5 V, while an 80% duty cycle may result in a DC voltage value of approximately 8 V and a 20% duty cycle may result in a DC voltage value of approximately 2 V.
In various embodiments, current limit control circuit 225 may control the switch-mode DC to DC converter 220 via one or more analog or digital signals. In various embodiments, the current limit control circuit 225 may specify a voltage to be generated by the switch mode DC to DC converter 220. In various embodiments, the current limit control circuit 225 may specify which duty cycle the switch-mode DC to DC converter uses in generating a voltage.
The switch-mode DC to DC converter 220 may be controlled at least in part by a current limit control circuit 225. The current limit control circuit 225 may control the switch-mode DC to DC converter 220 at least in part based on a voltage output of the switch-mode DC to DC converter 220 (such via a voltage feedback 228) and a voltage reference 227. The voltage reference 227 may be a programmable voltage reference and may remain constant or be changed during normal operation of the DC power supply. The voltage reference 227 may also be set during calibration, such as an external calibration or self-calibration. The self-calibration may be performed during startup of the DC power supply. A hold-up capacitor 230 may be coupled to the switch-mode DC to DC converter 220. While
In various embodiments, the primary voltage input 202 and the primary return 204 provide DC power to the DC power supply. The DC power may be provided by a battery, a motor, another DC power supply, an AC to DC converter, or some other source of DC power.
In various embodiments, the primary voltage input 202 and primary return 204 provide DC power as a constant voltage source, but only at a limited current. The switch-mode DC to DC converter 220 may include a control loop to regulate its output voltage. The current limit control circuit 225 may control the current consumption of the switch-mode DC to DC converter 220. This may cause the switch-mode DC to DC converter 220 to act as a near-constant voltage source. The current limit control circuit 225 may otherwise affect the operation of the control loop in the DC to DC converter 220, such as overriding or modifying input, output, or control signals. DC to Power Supply may be calibrated to affect the kind of operations or how much change the current limit control circuit 225 can introduce to the control loop and related circuitry of DC to DC converter 220. With renewed reference to
In accordance with various embodiments, the DC power supply may be used as a current source, rather than a voltage source. In various embodiments, the DC power supply may be powered by a current source. The DC power supply may be powered by AC power, and the DC power supply may convert the AC power to DC power, such as by an AC to DC converter (not depicted in
In various embodiments, systems may use components or sub-systems with large power requirements. For example, a system may use a power amplifier 250 that requires a large amount of power to operate. Such a power amplifier 250 may be used when transmitting a communications signal via an antenna 252. In various embodiments, such components or sub-systems with large power requirements may use a separate power supply from the rest of the system. Use of a separate power supply may prevent or reduce the large power components and sub-systems from introducing noise or ripple effects on the power lines used by other parts of the system. Such an approach may add considerable additional weight and cost to a project. In various embodiments, the large power components and sub-systems may use the same (or overlapping portions of the same) power supply.
In various embodiments, a DC power supply comprises an active filter using a switching power supply with programmable current source. The circuit implementation may have a boost converter, central processing unit (CPU), holdup capacitor(s), voltage loop, current loop, and a high frequency filter. During times of low current consumption, the programmable current source may charge a hold-up capacitor that may be discharged when high current consumption is required. In this way, ripple may be greatly reduced without requiring external equipment to protect the rest of the system. Using a combination of a voltage loop and a current loop may reduce the AC input ripple by charging and discharging the output capacitor as the input ripples. The output of the holdup capacitor may feed a fast response power supply that may deliver a constant voltage to the load. In testing such a solution, the current ripple rejection shows 30 db (decibel) improvement with an overall efficiency of 90%.
In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Actions shown or discussed as happening while other actions happen are meant to have some overlap in time, and the two actions do not need to always happen together. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and may be made without departing from the spirit and scope disclosed herein.
Claims
1. An apparatus comprising:
- a switch-mode DC to DC converter comprising an output terminal; and
- an accumulator coupled to the output terminal of the switch-mode DC to DC converter and configured to discharge to the output terminal of the switch-mode DC to DC converter while the switch-mode DC to DC converter is outputting an output DC voltage level to the output terminal and while a current draw of the switch-mode DC to DC converter is greater than zero.
2. The apparatus of claim 1, further comprising an isolating DC to DC converter coupled to the accumulator and the switch-mode DC to DC converter and configured to isolate the switch-mode DC to DC converter from a high-power component.
3. The apparatus of claim 2, further comprising a DC input filter, wherein the switch-mode DC to DC converter comprises two input terminals to receive input power, wherein the DC input filter is coupled to the two input terminals of the switch-mode DC to DC converter, and wherein the DC input filter rejects high-frequency noise.
4. The apparatus of claim 1, wherein the accumulator comprises one or more capacitors.
5. The apparatus of claim 1, further comprising a battery coupled to the switch-mode DC to DC converter and configured to provide DC power to the switch-mode DC to DC converter.
6. The apparatus of claim 1, wherein the switch-mode DC to DC converter converts an input DC voltage level to an output DC voltage level, and wherein the input DC voltage level is the same voltage level as the output DC voltage level.
7. The apparatus of claim 1, wherein the current limit controller limits the current draw of the switch-mode DC to DC converter based on the output DC voltage level and a reference voltage.
8. The apparatus of claim 1, wherein the current limit controller comprises a current limit output coupled to the switch-mode DC to DC converter in order to control a duty cycle of the switch-mode DC to DC converter.
9. An apparatus comprising:
- a DC to DC converter comprising an output terminal;
- an accumulator coupled to the DC to DC converter and configured to discharge to the output terminal of the DC to DC converter while DC to DC converter is outputting an output DC voltage level to the output terminal and while a current draw of the DC to DC converter is greater than zero.
10. The apparatus of claim 9, further comprising:
- an isolating DC to DC converter coupled to the accumulator and the DC to DC converter, wherein the isolating DC to DC converter is configured to isolate the DC to DC converter from a high-power component; and
- a DC input filter, wherein the DC to DC converter comprises two input terminals to receive input power, wherein the DC input filter is coupled to the two input terminals of the DC to DC converter, and wherein the DC input filter rejects high-frequency noise.
11. The apparatus of claim 10, wherein the DC to DC converter comprises two input terminals to receive a differential voltage input and two output terminals to provide a differential voltage output, wherein the accumulator is coupled across the two output terminals of the DC to DC converter, and wherein the DC to DC converter converts an input DC voltage level received on the two input terminals to an output DC voltage level provided on the two output terminals.
12. The apparatus of claim 11, wherein the input DC voltage level is the same voltage level as the output DC voltage level.
13. The apparatus of claim 12, wherein the isolating DC to DC converter provides DC power to a power amplifier.
14. (canceled)
15. A method comprising:
- receiving, by a pair of input DC power terminals, an input DC power signal;
- filtering, by an input filter, the input DC power signal;
- converting, by a DC to DC converter, the input DC power signal to a switched power signal;
- charging an accumulator, by the switched power signal;
- discharging the accumulator to an output terminal of the DC to DC converter;
- combining the switched power signal and the discharge of the accumulator at the output terminal; and
- limiting a current draw of the DC to DC converter while the accumulator is discharging, wherein the current draw of the DC to DC converter is greater than zero.
16. The method of claim 15, wherein the switched power signal is a DC power signal.
17. The method of claim 15, further comprising converting, by an isolated DC to DC converter, the switched power signal to an isolated DC power signal.
18. (canceled)
19. The method of claim 17, further comprising providing the isolated power signal to a power amplifier.
20. The method of claim 15, further comprising:
- receiving, by a current limit controller, a reference voltage value; and
- receiving, by the current limit controller, a voltage value of the switched power signal, wherein the current limit controller limits the current draw of the DC to DC converter based on the reference voltage value and the voltage value of the switched power signal.
21. The apparatus of claim 1, further comprising a current limit controller coupled to the switch-mode DC to DC converter and configured to limit the current draw of the switch-mode DC to DC converter, wherein the accumulator is configured to discharge to the output terminal of the switch-mode DC to DC converter while the current limit controller is limiting the current draw of the switch-mode DC to DC converter.
22. The apparatus of claim 9, further comprising a current limit controller coupled to the DC to DC converter and configured to limit the current draw of the DC to DC converter, wherein the accumulator is configured to discharge to the output terminal of the DC to DC converter while the current limit controller is limiting the current draw of the DC to DC converter.
Type: Application
Filed: Jul 22, 2019
Publication Date: Nov 14, 2019
Applicant: ELBIT SYSTEMS OF AMERICA LLC (FORT WORTH, TX)
Inventors: Eli ASHKENAZY (Fort Worth, TX), Jesse TERRELL (Fort Worth, TX)
Application Number: 16/518,920