Method and apparatus for integrated active-diode-ORing and soft power switching

This non-provisional application is related to co-pending non-provisional application titled “Method and Apparatus for Hot Swap of Line Replaceable Modules for AC and DC Electric Power Systems” filed concurrently herewith, the entire contents of which are hereby incorporated by reference.

1. Field of the Invention

The present invention relates to electric power systems, and more particularly to a method and apparatus for connection of multiple power supply inputs, and for soft-switching during hot swap of modules for AC and DC electric power systems.

2. Description of the Related Art

Electric systems used in complex environments such as aerospace systems, more electric aircraft systems, industrial environments, vehicles, etc., include a large number of electric modules. Various electric modules may need to be extracted and replaced with other modules, to change functionality or to replace modules that exhibit faults.

Hot swap, hot-plug, and hot-dock are terms used interchangeably to refer to the process of safely inserting or removing cards, PC boards, cables, and/or modules from a host system without removing power. The goal of hot swap is to insert or remove modules without disturbing, damaging, or degrading up/down-stream adjacent line replaceable modules/subsystems, to increase system availability, reduce down time, simplify system repair, and allow for system maintenance/upgrade without interrupting service to other loads.

Electric modules included in environments such as aerospace systems, more electric aircraft systems, industrial environments, vehicles, etc., may be connected to multiple power supply voltage inputs, and extract one voltage output to be used by the modules. During hot swap of electrical modules, the multiple power supply voltage inputs are also connected or disconnected from the host system, or from the removable electrical modules, without removing power.

If not designed for properly, hot swap can cause severe electrical, mechanical, thermal and operational problems in an electrical system. For example, pulling a board/module out while there is current passing through the module connectors, or inserting a board/module with all bulk/bypass capacitors at zero volts, can introduce severe electrical voltage/current transients which may adversely impact reliability and lead to safety consequences. Current chopping introduces Ldi/dt variations (where L is inductance of a load, for example) leading to very large voltage transients which are a major safety concern for maintenance people, as large voltage transients can cause high voltage electrical shock.

One problem with typical/conventional techniques for hot-swap is a lack of proper connection of multiple power supply voltage inputs for a voltage output for replaceable modules. Typical/conventional methods use passive diode-ORing systems to connect multiple power supply voltage inputs to a supply bus for replaceable modules. Such passive diode-ORing systems result in excessive power losses and voltage drops. Significant voltage drops, particularly when preferred paths of power consumption from AC and DC sources are required, are a major problem. Current chopping occurring during insertion or extraction of modules is a major contributor to excessive voltage/current transients that stress and damage individual components and reduce the Mean Time Between Failure (MTBF) for the host system and for the removable modules.

A number of publications have studied ORing systems for electrical modules. One such system is described in U.S. Pat. No. 6,891,425 B1 titled “Low Voltage OR'ing Circuits and Methods with Zero Recovery Time” by Thong Huynh. The system described in this patent includes a MOSFET coupled between a power supply and a load, a controller that senses the current through the MOSFET and turns the MOSFET off when the current falls below a predetermined threshold current, and a second MOSFET adding hot swap capability. This circuit, however, does not protect against transient voltages/currents when a board is taken-out from a motherboard/backplane. Moreover, the second MOSFET is designed to work both in the switch mode and in the linear mode. Because the second MOSFET has to operate both in the switch mode and in the linear mode, the linear range is narrow, which, together with typical variations in threshold voltage Vth, make the control of the second MOSFET in the linear mode hard to reproduce.

A disclosed embodiment of the application addresses these and other issues by utilizing a method and apparatus for integrated active-diode-ORing and soft power switching. The method and apparatus achieve proper connection of multiple power supply voltage inputs to realize a fault tolerant power supply bus for replaceable modules. The method and apparatus provide soft power-up/down capability during hot swap of modules for AC and DC electric power systems. The method and apparatus provide a single power bus from multiple power supply inputs, with minimum voltage drop, improved efficiency, and no looses in passive diodes. The method and apparatus provide integrated soft-switching that reduces turn-on in-rush current during board/module insertion and further eliminates current-chopping during interruption of current in inductive circuits. The method and apparatus can be used for both low and high power systems.

The present invention is directed to a method and an apparatus for power supply input connection. According to a first aspect of the present invention, an apparatus for power supply input connection comprises: a first switch module connected to a first power supply input; a first controller module connected to the first power supply input and to a secondary power connection, wherein said first controller module puts the first switch module in a first operating state when a parameter relating to the first power supply input is larger than a parameter relating to the secondary power connection, and puts the first switch module in a second operating state when the parameter relating to the first power supply input is smaller than the parameter relating to the secondary power connection; and a first driver module connected to the first controller module and to the first switch module, wherein the first driver module modifies a parameter relating to a drive characteristic of the first switch module.

According to a second aspect of the present invention, an apparatus for power supply input connection comprises: a first switch module connected to a first power supply input, the first switch module including a first field effect transistor; a first controller module connected to the first power supply input and to a secondary power connection, wherein the first controller module puts the first switch module in a first operating state when a parameter relating to the first power supply input is larger than a parameter relating to the secondary power system, and puts the first switch module in a second operating state when the parameter relating to the first power supply input is smaller than the parameter relating to the secondary power system; a first driver module connected to the first controller module and to the first switch module, wherein the first driver module modifies a parameter relating to a drive characteristic of the first switch module; and a first resistor connected to a body diode of the first field effect transistor, wherein the first resistor and the body diode of the first field effect transistor are connected in series between the first power supply input and the secondary power connection.

According to a third aspect of the present invention, a method for connection of power supply inputs comprises: providing a first power supply voltage input, a second power supply voltage input, and an output; isolating the first power supply voltage input from the output with a first switch module, the first switch module including a first gate; isolating the second power supply voltage input from the output with a second switch module, the second switch module including a second gate; and controlling the first switch module and the second switch module, the controlling step including turning the first switch module on when a voltage of the first power supply voltage input is larger than a voltage of the second power supply voltage input, turning the first switch module off when the voltage of the first power supply voltage input is smaller than the voltage of the second power supply voltage input, turning the second switch module on when a voltage of the second power supply voltage input is larger than a voltage of the first power supply voltage input, turning the second switch module off when the voltage of the second power supply voltage input is smaller than the voltage of the first power supply voltage input, modifying a parameter relating to a gate drive characteristic of the first switch module, and modifying a parameter relating to a gate drive characteristic of the second switch module.

Further aspects and advantages of the present invention will become apparent upon reading the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a general block diagram of an electrical system including a system for active-diode-ORing and soft power switching according to an embodiment of the present invention;

FIG. 2 is a block diagram of an electrical configuration containing a system for active-diode-ORing and soft power switching according to an embodiment of the present invention illustrated in FIG. 1 ;

FIG. 3A is a typical/conventional block diagram showing an electrical configuration containing a diode ORing system consisting of schottky diodes;

FIG. 3B is a typical/conventional block diagram showing an electrical configuration containing an active ORing circuit with one FET without driver;

FIG. 3C is a graph for load transfer between input sources for the electrical configuration containing an active ORing circuit with one FET without driver illustrated in FIG. 3B ;

FIG. 4A is a block diagram of an electrical configuration containing an active ORing circuit with one FET with a driver according to an embodiment of the present invention;

FIG. 4B is a graph for load transfer between input sources for the electrical configuration containing an active ORing circuit with one FET with a driver according to an embodiment of the present invention illustrated in FIG. 4A ;

FIG. 5A is a block diagram of an electrical configuration containing an active ORing circuit with two FETs with a driver according to a second embodiment of the present invention;

FIGS. 5B and 5C are graphs for signals and load transfers between input sources for the electrical configuration containing an active ORing circuit with two FETs with a driver according to a second embodiment of the present invention illustrated in FIG. 5A ;

FIG. 6A is a typical/conventional general block diagram illustrating a circuit for soft-start of a source and load;

FIG. 6B is a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention;

FIG. 7 illustrates an exemplary implementation for a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention illustrated in FIG. 6B ;

FIG. 8 illustrates another exemplary implementation for a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention illustrated in FIG. 6B ;

FIG. 9A is a graph of electrical parameters obtained when an LRM including the combined active ORing and soft-start circuit illustrated in FIG. 8 is plugged into a live PSM output;

FIG. 9B is a graph of electrical parameters obtained when an LRM without an active ORing and soft-start circuit is plugged into a live PSM output;

FIG. 9C is a graph of electrical parameters obtained when an LRM without an active ORing and soft-start circuit is unplugged from a live PSM; and

FIG. 9D is a graph of electrical parameters obtained when an LRM including the combined active ORing and soft-start circuit illustrated in FIG. 8 is unplugged from a live PSM output.

Aspects of the invention are more specifically set forth in the accompanying description with reference to the appended figures. FIG. 1 is a general block diagram of an electrical system including a system for active-diode-ORing and soft power switching according to an embodiment of the present invention. The electrical system 100 illustrated in FIG. 1 includes the following components: power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 ; a multiple power supply connecting system 89 ; and electrical systems 60 . Operation of the electrical system 100 in FIG. 1 will become apparent from the following discussion.

Electrical system 100 may be associated with an aircraft, a more electric aircraft, a ship, a laboratory facility, an industrial environment, etc. The power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 provide electrical energy in electrical system 100 . The power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 may include AC and DC power supplies, electrical components such as transformers, inductances, resistances, etc. The power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 may provide high DC or AC voltages or low DC or AC voltages to electrical systems 60 through multiple power supply connecting system 89 . Power inputs Vin 1 , Vin 2 , and Vin 3 from power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 are combined and integrated in multiple power supply connecting system 89 , which outputs one voltage output Vout to electrical systems 60 . Multiple power supply connecting system 89 includes three ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 . ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 are integrated active-diode-OR circuits and realize a fault tolerant power supply bus for the electrical systems 60 .

Electrical systems 60 may include various electrical systems, such as systems on an aircraft or ship, navigation systems, cabin systems, air conditioning systems, etc., systems in an industrial facility such as electrical equipment and tools, etc. Electrical systems 60 may include DC and AC loads, which are electric circuits using DC and AC power that enable functioning of various services onboard a vehicle or aircraft, in a complex environment such as a laboratory facility, etc. Services using AC and DC power may be an electric motor, an automatic braking system, a lighting system of a vehicle, a piece of industrial equipment, etc.

Electrical systems 60 may be replaceable modules that can be disconnected from electrical system 100 , or inserted into electrical system 100 . ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 provide soft power-up/down capability for electrical systems 60 during hot swap of electrical systems 60 .

ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 and electrical systems 60 may together be included in a replaceable module, so that ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 together with electrical systems 60 can be removed from or inserted into electrical system 100 . In this case, ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 provide soft power-up/down capability for a replaceable module that includes electrical systems 60 and ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 , during hot swap of the replaceable module from or into electrical system 100 .

Electrical systems 60 may be circuits/devices included in replaceable module such as an AC or DC Line Replaceable Module (LRM), a card, a PC board, etc. Electrical systems 60 may be part of a high voltage AC or DC LRM. Electrical systems 60 may be included in a replaceable module with on-board Solid State Switching Devices (SSSDs). Electrical systems 60 may be included in a high voltage Solid State AC or DC replaceable module switch, referred to in the industry as a Solid State Remote Power Controller (SSPC). Electrical systems 60 may be included in various types of LRMs such as: Power Supplies (PS-LRM), Digital Controllers (DC-LRM), AC Solid-State-Remote-Controller (AC-SSPC-LRM), DC Solid-State-Remote-Controller (DC-SSPC-LRM), LRMs used for aircraft platforms and More Electric platforms, PC boards or cards, etc. Solid State AC and DC switches can be used with a wide range of powers, from a few Watts to hundreds of KWatts. LRMs including AC and DC Solid State Switching Devices (SSSDs) may manage high voltage AC and DC powers and loads, and may control the flow of electrical power to internal and external circuitry/loads, to achieve proper protection based on i 2 ·t (instantaneous overcorrect protection for large currents and proportionally time-delayed overload protection for smaller currents) to protect the SSSDs or the wiring system.

Power source modules/backplane 50 _ 1 , 50 _ 2 , 50 _ 3 may provide various voltages to electrical systems 60 included in an LRM. Such voltages may be various AC voltages such as, for example, 115V or 230V or higher, with fixed frequencies (such as, for example, 50/60 Hz or 400 Hz), or variable frequencies (such as, for example 360-800 Hz for aerospace applications), or DC voltages such as, for example, 28V or 270V. The power of AC and DC LRMs may depend on the number of channels, as well as current rating and voltage of each channel. For example, an AC LRM for the Airbus A380 aircraft has 8 channels. Such AC and DC LRM boards are currently being deployed in aerospace and industry, and are poised to eventually replace traditional electromechanical AC/DC circuit breakers or relays, to reduce the overall system cost and weight, and improve reliability. Emerging Solid State AC and DC switches are poised to have widespread use in both commercial and military aerospace applications and general industry, for a few Watts to hundreds of KW power applications. Currently, due to excessive cost, weight and board space penalties, AC and DC SSPC LRM cards do not include integrated active diode ORing circuits for soft power-up/down capability, and circuit breakers or relays which could be turned-off before initiating a hot swap of a failed LRM with one or more SSPC devices failed short. Hence, conventional hot swap is not properly designed for such LRM/boards.

ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 provide soft power-up/down capability for electrical systems 60 during hot swap of electrical systems 60 , and protect components of electrical system 100 during hot swap insertion or removal of electrical systems 60 under normal or faulty modes of operation for high voltage DC and AC systems without the need to disconnect power. ORing systems 90 _ 1 , 90 _ 2 and 90 _ 3 are circuits with a combined function of active OR (low forward voltage drop and low reverse leakage) and soft-start/stop; provide integrated soft-switching to reduce turn-on in-rush current during board insertion; eliminate current-chopping during interruption of current in inductive circuits; contribute to safe and reliable insertion and removal of different types of LRMs during hot swap, without disturbing, damaging, or degrading up/down-stream adjacent LRMs and subsystems of electrical system 100 ; help high voltage AC and DC load management LRMs to control the flow of electrical power to internal and external circuitry/loads and achieve proper protection of SSSDs or the wiring system; provide a single power bus from multiple power supply input with minimized voltage drop and improved efficiency; help to safely insert a board/module when the board is not electrically initialized, and to safely pull a board-out while there is current passing through connectors; help provide hot swap protection beyond local boundaries of the replaceable modules; help mitigate hot swap effects, so that various bus activities and other operations taking place in electrical system 100 are not disturbed during hot swap of one or more replaceable modules; help in establishing autonomy of subsystems in electrical system 100 and automatic system reconfiguration based on the type of replaceable modules extracted or inserted; etc.

Although three power supply voltage inputs are shown in FIG. 1 , more than three or less than three power supply voltage inputs can be connected through multiple power supply connecting system 89 , with each power supply voltage inputs connecting to its own ORing system inside multiple power supply connecting system 89 .

Although the systems in electrical system 100 are shown as discrete units, it should be recognized that this illustration is for ease of explanation and that the associated functions of certain functional modules or systems can be performed by one or more physical elements.

FIG. 2 is a block diagram of an electrical configuration containing a system for active-diode-ORing and soft power switching according to an embodiment of the present invention illustrated in FIG. 1 . The electrical system illustrated in FIG. 2 includes two ORing systems 90 _ 1 and 90 _ 2 . ORing system 90 _ 1 includes a controller module 145 _ 1 , a switch module 143 _ 1 , and a driver module 160 _ 1 . ORing system 90 _ 2 includes a controller module 145 _ 2 , a switch module 143 _ 2 , and a driver module 160 _ 2 .

Controller module 145 _ 1 is connected to a first power supply input Vin 1 , and controller module 145 _ 2 is connected to a second power supply input Vin 2 . Controller module 145 _ 1 controls the switch module 143 _ 1 through the driver module 160 _ 1 , which modifies the drive capability of switch module 143 _ 1 . For example, driver module 160 _ 1 may provide current gain to reduce the driver impedance and speed the charging and discharging of a capacitance, when switch module 143 _ 1 includes a capacitor such as the capacitor of a MOSFET gate.

Controller module 145 _ 1 turns on the switch module 143 _ 1 when Vin 1 >Vc, and turns off the switch module 143 _ 1 when Vin 1 <Vc, or vice versa. Similarly, controller module 145 _ 2 turns on the switch module 143 _ 2 when Vin 2 >Vc, and turns off the switch module 143 _ 2 when Vin 2 <Vc, or vice versa. The output resistor and capacitor pick up electrical parameters, such as current or voltage, from switch modules 143 _ 1 and 143 _ 2 . Depending on the magnitudes of Vin 1 and Vin 2 , switch module 143 _ 1 or 143 _ 2 may be on or off, transmitting electrical parameters such as current or voltage to the output resistor and capacitor.

FIG. 3A is a typical/conventional block diagram showing an electrical configuration containing a diode ORing system consisting of schottky diodes. As shown in FIG. 3A , three schottky diodes 131 A, 131 B, and 131 C are used to obtain a voltage output Vout for an LRM, from three voltage inputs Vin 1 , Vin 2 , and Vin 3 . The three channels with inputs Vin 1 , Vin 2 , and Vin 3 are OR-ed with three 30BQ015 schottky diode rectifiers, to generate the power source Vout for an individual LRM. The 30BQ015 schottky diode rectifier is described in the Datasheet of 30BQ015 Schottky Rectifier from International Rectifier, which is herein incorporated by reference.

The circuit in FIG. 3A , however, presents a high forward voltage drop of Vf=0.25V at 1A and at Tj=25° C. (for 30BQ015), and a high reverse leakage current Ir=20 mA at Tj=100° C. (for 30BQ015). The circuit in FIG. 3A does not offer advantages such as inrush current control and negative clamping, for hot swap of LRMs.

A circuit such as the circuit shown in FIG. 3A is used in Gen2.0 of A380 SEPDS (Secondary Electrical Power Distribution System) design, AC and DC LRM, GW, and GFI cards, which are getting power from three different channels out of two Power Supply Modules (PSMs).

FIG. 3B is a typical/conventional block diagram showing an electrical configuration containing an active ORing circuit with one FET without driver. The electrical configuration 101 in FIG. 3B is a circuit for an active ORing configuration with one FET without a driver, with two channels of input Vin 1 and Vin 2 .

The ORing circuit in FIG. 3B uses an LTC4412HV controller in ThinSOT from Linear Technology (elements 145 A and 145 B) for each input channel. The LTC4412HV controller is described in the Datasheet of LTC4412HV, 36V, Low Loss PowerPath™ Controller in ThinSOT from Linear Technology, which is herein incorporated by reference. Each channel input also includes a P-channel HEXFET® Power MOSFET (elements 143 A and 143 B), which is described in the Datasheet of IRLML6401 from International Rectifier, which is herein incorporated by reference.

LTC4412HV provides the benefits of a wide operating temperature range of −40° C. to 125° C. and a small package of SOT23-6 (ThinSOT). Because LTC4412HV is a P-channel MOSFET controller, no charge pump is required, which is good when dealing with electromagnetic interference (EMI) effects. One drawback of the LTC4412HV controller is that the driving capability is low. Typically, the GATE pin can sink 50 uA and source only 2.5 uA.

FIG. 3C is a graph for load transfer between input sources for the electrical configuration containing an active ORing circuit with one FET without a driver illustrated in FIG. 3B .

The graph in FIG. 3C was obtain for exemplary values for load resistance 149 and capacitance 147 , chosen according to configurations associated with AC and DC LRM configurations receiving the output Vout. In particular, the load resistance 149 had a value of 6Ω, and the capacitance 147 had a value of 80 uF. The input voltage Vin 1 was 5.3V nominal, and the input voltage Vin 2 was 5.1V nominal. FIG. 3C illustrates the load transfer from 5.3V to 5.1V with one FET without a driver.

The waveforms in FIG. 3C show the transfer between the two input sources Vin 1 and Vin 2 . Initially, Vin 1 is 5.3V, and Vin 2 is 5.1V. When both Vin 1 and Vin 2 are on at 5.3V and 5.1V respectively, since Vin 1 is higher than Vin 2 , Vg 1 is low (switch 143 A is ON) and Vg 2 is high (switch 143 B is OFF). Ch 1 in FIG. 3C is the waveform of Vin 1 . Ch 4 is the waveform of Vg 1 , and Ch 2 is the waveform of Vg 2 . The output voltage Vout is shown in Ch 3 .

Vin 1 , which was initially 5.3V, is next turned off by, for example, a 1K resistor to ground. Vin 2 remains connected to a 5.1V supply. When Vin 1 is turned off, which happens at about after 2 divisions in the time scale in FIG. 3C , Vg 2 (Ch 2 ) quickly changes to low by dropping to zero, which turns switch 143 B ON. Vg 1 (Ch 4 ) also changes to high (switch 143 A is OFF).

However, due to the asymmetric driver capability of the controller in FIG. 3B , it takes a longer time for Vg 1 (Ch 4 ) to rise and turn switch 143 A OFF. As a result, both switches 143 A and 143 B are ON for some time. In FIG. 3C , it can be found the overlapped ON time for switches 143 A and 143 B is about 5 divisions, which corresponds to about 2 ms. Hence, Vin 1 (Ch 1 ) is backfed by Vin 2 . Such backfeed is not acceptable in some applications.

FIG. 4A is a block diagram of an electrical configuration containing an active ORing circuit with one FET with a driver according to an embodiment of the present invention. The electrical configuration 102 in FIG. 4A has improved gate drive. FIG. 4A is a design improvement to the circuit in FIG. 3B . The driver 160 A_ 1 shown in the block in dashed lines connects to FET 143 A. The driver 160 B_ 1 shown in the second block in dashed lines connects to FET 143 A. The drivers 160 A_ 1 and 160 B_ 1 in the dashed boxes show the design improvement over the typical/conventional design of FIG. 3B .

The active ORing circuit with one FET with driver in FIG. 4A has two input channels. Each input channel has a controller (elements 145 A and 145 B), a P-channel MOSFET (elements 143 A and 143 B), and drivers 160 A_ 1 and 160 B_ 1 .

The drivers 160 A_ 1 and 160 B_ 1 are totem-pole drivers composed of a pair of NPN and PNP transistors (totem-pole with 161 A and 163 A for one channel, and totem-pole with 161 B and 163 B for the second channel). The P-channel MOSFETS (elements 143 A and 143 B) are switch modules as illustrated in FIG. 2 .

The controllers (elements 145 A and 145 B) may be LTC4412HV controllers in ThinSOT from Linear Technology. Other controllers may also be used. Any ORing controller can be used for elements 145 A and 145 B. The P-channel MOSFET (elements 143 A and 143 B) may be an IRLML6401 P-channel HEXFET® Power MOSFET. Other P-channel MOSFETs may also be used; in fact any P-channel MOSFETs can be used.

The totem-pole driver composed of the pair of NPN ( 161 A) and PNP ( 163 A) transistors inserted between the controller 145 A and the MOSFET 143 A improves the gate drive capability. Similarly, the totem-pole driver composed of the pair of NPN ( 161 B) and PNP ( 163 B) transistors inserted between the controller 145 B and the MOSFET 143 B improves the gate drive capability.

The BC847 may be chosen for the NPN transistors 161 A and 161 B, with the BC847 described in the Datasheet of BC847 Small Signal NPN Transistors from ST Microelectronics, which is herein incorporated by reference. Other NPN transistors may also be used. The BC857 may be chosen for the PNP transistors 163 A and 163 B, with the BC857 described in the Datasheet of BC857 Small Signal PNP Transistors from ST Microelectronics, which is herein incorporated by reference. Other PNP transistors may also be used.

FIG. 4B is a graph for load transfer between input sources for the electrical configuration 102 containing the improved design of the active ORing circuit with one FET with a driver according to an embodiment of the present invention illustrated in FIG. 4A .

The graph in FIG. 4B was obtain for exemplary values for load resistance 149 and capacitance 147 , chosen according to configurations associated with AC and DC LRM configurations receiving the output Vout. In particular, the load resistance 149 had a value of 6Ω, and the capacitance 147 had a value of 80 uF. The input voltage Vin 1 was 5.3V nominal, and the input voltage Vin 2 was 5.1V nominal. The waveforms in FIG. 4B are obtained from same test performed for FIG. 3C , namely FIG. 4B illustrates the load transfer from 5.3V to 5.1V.

Initially, Vin 1 is 5.3V, and Vin 2 is 5.1V. Vin 1 is next turned off, while Vin 2 remains connected to the 5.1V supply. Vg 1 (Ch 2 ), Vg 2 (Ch 4 ), and Vout (Ch 3 ) are recorded. Significant improvement in gate rise time is achieved with the external driver circuits 160 A_ 1 and 160 B_ 1 . The rise time of the gate signal Vg 2 (Ch 4 ) in FIG. 4B is reduced to about 20 us, which is much smaller than the value of 2 ms for Vg 2 in FIG. 3C . The turn off of Vg 2 in FIG. 4B also happens at some time earlier than the turn on of Vg 1 in FIG. 4B . Hence, backfeeding is completely avoided with the circuit in FIG. 4A .

The circuit in FIG. 4A has improved gate drive compared to the circuit in FIG. 3B . One drawback of the circuit in FIG. 4A is that when the switch ( 143 A or 143 B) is turned off, the gate-to-source voltage is not completely 0. For the switch that is connected to Vin 1 for example,

Vgs=Vg 1− V out=( Vb 1 −Vbe )− V out=( V out− Vbe )− V out=− Vbe.

From the datasheet of IRLML6401, for example, the minimum gate-to-source voltage threshold can be −0.4V. From a P-Spice simulation at −40° C., the totem-pole drive output can be Vbe=0.37V. This will make the switch 143 A enter the linear region, which is not desirable.

FIG. 5A is a block diagram of an electrical configuration containing an active ORing circuit with two FETs with driver according to a second embodiment of the present invention. The electrical configuration in FIG. 5A is a complete active ORing circuit with two channels. The driver 160 A_ 1 shown in the block in dashed lines connects to FETs 143 A and 205 A. The driver 160 B_ 1 shown in the second block in dashed lines connects to FETs 143 B and 205 B.

The active ORing circuit in FIG. 5A has two input channels, but more input channels can be connected together. Each input channel has a controller (elements 145 A and 145 B), a switch (P-channel MOSFETs 143 A and 205 A, and P-channel MOSFETs 143 B and 205 B respectively), and a driver ( 160 A_ 1 and 160 B_ 1 ).

Drivers 160 A_ 1 and 160 B_ 1 are totem-pole drivers composed of a pair of NPN and PNP transistors (totem-pole with 161 A and 163 A for one channel, and totem-pole with 161 B and 163 B for the second channel).

The controller (elements 145 A and 145 B) may be a LTC4412HV controller in ThinSOT from Linear Technology. Other controllers may also be used. Any ORing controller can be used for elements 145 A and 145 B. The P-channel MOSFETs (elements 143 A, 143 B, 205 A, and 205 B) may be IRLML6401 P-channel HEXFET® Power MOSFETs. Other P-channel MOSFETs may also be used; in fact any P-channel MOSFETs can be used. The NPN transistors (elements 161 A and 161 B) may be BC847 transistors. Other NPN transistors may also be used. The PNP transistors (elements 163 A and 163 B) maybe BC857 transistors. Other PNP transistors may also be used.

The second FET 205 A prevents the switch of the first channel from entering linear region. The second FET 205 B prevents the switch of the second channel from entering linear region. The second FET 205 A (and similarly 205 B) is placed back-to-back in series with the original FET 143 A (similarly for 143 B). The body diode voltage drop cancels out the effect of Vbe in the drive circuit. For the switch that is connected to Vin 1 , for example:

Vgs=Vg 1− Vs 1=( Vb 1 −Vbe )−( V out− Vd )=( V out− Vbe )−( V out− Vd )= Vd−Vbe= 0.

FIGS. 5B and 5C are graphs for signals and load transfers between input sources for the electrical configuration 103 containing an active ORing circuit with two FETs with driver according to an embodiment of the present invention illustrated in FIG. 5A .

The graphs in FIGS. 5B and 5C were obtain for exemplary values for load resistance 149 and capacitance 147 , chosen according to configurations associated with AC and DC LRM configurations receiving the output Vout. In particular, the load resistance 149 had a value of 6Ω, and the capacitance 147 had a value of 80 uF. The input voltage Vin 1 was 5.3V nominal, and the input voltage Vin 2 was 5.1V nominal. FIG. 5B illustrates the load transfer from 5.3V to 5.1V for the active ORing circuit in FIG. 5A . In FIG. 5B , Ch 1 is Vin 1 , Ch 2 is Vg 1 , Ch 3 is Vout, and Ch 4 is Vg 2 .

FIG. 5C illustrates the load transfer from 5.1V to 5.3V for the active ORing circuit in FIG. 5A . In FIG. 5C , Ch 1 is Vin 1 , Ch 2 is Vg 1 , Ch 3 is the output, and Ch 4 is Vg 2 .

FIG. 6A is a typical/conventional general block diagram illustrating a circuit for soft-start of a load. The electrical system 104 in FIG. 6A includes a resistor R_ 1 in parallel with a switch 91 . By connecting resistor R_ 1 between source and load, soft-start is achieved. The switch block 91 will be turned on to short the resistor R_ 1 after an output capacitor connected at the output is charged.

FIG. 6B is a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention. FIG. 6B is an improvement on the typical/conventional circuit shown in FIG. 6A , obtained by incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit. The multiple power supply connecting system 311 shown in the dashed lines is the design improvement over the typical/conventional circuit shown in FIG. 6A .

In case of multi-channel input, along each channel a diode is connected in series with a resistor to isolate the inputs, as shown in FIG. 6B . The electrical system 105 in FIG. 6B includes an integrated active ORing circuit with soft-start/stop features for multi-channel inputs. The first channel uses an ORing system 90 _ 1 , a delay module 338 _ 1 , a diode D_ 1 , and resistor R_ 1 in series with the diode D_ 1 , with both R_ 1 and D_ 1 in parallel with ORing system 90 _ 1 . The second channel uses an ORing system 90 _ 2 , a delay module 338 _ 2 , a diode D_ 2 , and resistor R_ 2 in series with the diode D_ 2 , with both R_ 2 and D_ 2 in parallel with ORing system 90 _ 2 . The third channel uses an ORing system 90 _ 3 , a delay module 338 _ 3 , a diode D_ 3 , and resistor R_ 3 in series with the diode D_ 3 , with both R_ 3 and D_ 3 in parallel with ORing system 90 _ 3 .

Although three power supply voltage inputs are shown in FIG. 6B , more than three or less than three power supply voltage inputs can be connected through multiple power supply connecting system 311 , with each power supply voltage input connecting to its own ORing system with a diode and a resistor, inside multiple power supply connecting system 311 .

FIG. 7 illustrates an exemplary implementation for a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention illustrated in FIG. 6B . FIG. 7 shows an exemplary circuit that implements the block diagram of FIG. 6B . The three dashed boxes in FIG. 7 are a driver 160 A, a delay module 338 A, and soft start/stop block 340 including a diode and a resistor. The driver 160 A, the delay module 338 A, and the soft start/stop block 340 represent improvements over typical/conventional circuits.

As shown in FIG. 7 , the soft-start capability can be combined into the active oring circuit of FIG. 5A . The combined active ORing and soft-start circuit in FIG. 7 illustrates one input channel for a source. A plurality of input channels such as the one illustrated in FIG. 7 can be connected in parallel to create a multi-channel input. The input channel in FIG. 7 has a controller (element 145 ), a switch including a P-channel MOSFET (element 143 ) and a second P-channel MOSFET (element 205 ), a driver 160 A, a soft start/stop block 340 , and a delay module 338 A.

The driver 160 A includes a totem-pole driver composed of a pair of NPN and PNP transistors (totem-pole with 161 and 163 ). The delay module 338 A includes a capacitor Cx (element 355 ) and a resistor Rx (element 357 ) connected at the source side. The soft start/stop block 340 includes a resistor R 1 (element 351 ) and a diode D 1 (element 353 ) connected between source and load for soft-start capability. The value of Rx and Cx can be chosen such that the controller (element 145 ) is enabled after the output capacitor is charged.

The controller (element 145 ) may be a LTC4412HV controller in ThinSOT from Linear Technology. Other controllers may also be used. Any ORing controller can be used for element 145 . The P-channel MOSFETs (elements 143 and 205 ) may be IRLML6401 P-channel HEXFET® Power MOSFETs. Other P-channel MOSFETs may also be used; in fact any P-channel MOSFETs can be used. The NPN transistor (element 161 ) may be a BC847 transistor. Other NPN transistors may also be used. The PNP transistor (elements 163 ) may be a BC857 transistor. Other PNP transistors may also be used.

The MOSFETs 143 and 205 in FIG. 7 operate in switch mode, which leads to a higher efficiency, lower power dissipation, and optimized MOSFET selection. The hot swap is achieved by the parallel diode and resistor path through soft start/stop block 340 , together with the delay circuit 338 A for the gate signal. At initial power up, the delay module 338 A holds the MOSFETs off. The output voltage is charged up through the parallel diode and resistor path of soft start/stop block 340 . After a pre-defined delay, the MOSFETs are turned to bypass the diode and resistor D 1 and R 1 . The delay and the parallel resistor R 1 can be adjusted according to different applications. Hence, the design in FIG. 7 does not rely on MOSFET properties, and provides flexibility.

FIG. 8 illustrates another exemplary implementation for a block diagram of an electrical system incorporating soft start/stop into a multiple input/output power supply system using an active ORing circuit according to a third embodiment of the present invention illustrated in FIG. 6B . FIG. 8 shows further design improvement to the circuit of FIG. 7 . The circuit in FIG. 8 is more efficient, as it eliminates the discrete diode D 1 from the circuit in FIG. 7 , and uses the body diode of one of the MOSFETs (MOSFET 143 ) instead, to achieve soft-start. The three dashed boxes in FIG. 8 are a driver 160 A, a delay module 338 A, and a soft start/stop switch block 341 .

The circuit in FIG. 8 illustrates one input channel for a source. A plurality of input channels such as the one illustrated in FIG. 8 can be connected in parallel to create a multi-channel input. The input channel in FIG. 8 has a controller (element 145 ), a soft start/stop switch block 341 including a P-channel MOSFET (element 143 ), a second P-channel MOSFET (element 205 ), and a resistor R 1 (element 351 ), the driver 160 A, and the delay module 338 A.

The driver 160 A includes a totem-pole driver composed of a pair of NPN and PNP transistors (totem-pole with 161 and 163 ). The delay module 338 A includes a capacitor Cx (element 355 ) and a resistor Rx (element 357 ) connected at the source side. The value of Rx and Cx may be chosen such that the controller (element 145 ) is enabled after the output capacitor is charged.

The controller (element 145 ) may be a LTC4412HV controller in ThinSOT from Linear Technology. Other controllers may also be used. Any ORing controller can be used for element 145 . The P-channel MOSFETs (elements 143 and 205 ) may be IRLML6401 P-channel HEXFET® Power MOSFETs. Other P-channel MOSFETs may also be used; in fact any P-channel MOSFETs can be used. The NPN transistor (element 161 ) may be a BC847 transistor. Other NPN transistors may also be used. The PNP transistor (elements 163 ) may be a BC857 transistor. Other PNP transistors may also be used.

The MOSFETs 143 and 205 in FIG. 8 operate in switch mode, which leads to a higher efficiency, lower power dissipation, and optimized MOSFET selection. The hot swap is achieved by the parallel diode and resistor path through soft start/stop switch block 341 , together with the delay circuit 338 A for the gate signal. At initial power up, the delay module 338 A holds the MOSFETs off. The output voltage is charged up through the parallel diode and resistor path of soft start/stop switch block 341 . After a pre-defined delay, the MOSFETs are turned to bypass the resistor R 1 . The delay and the parallel resistor R 1 can be adjusted according to different applications. Hence, the design in FIG. 8 does not rely on MOSFET properties, and provides flexibility.

FIG. 9A is a graph of electrical parameters obtained when an LRM including the combined active ORing and soft-start circuit illustrated in FIG. 8 is plugged into a live PSM output. The modified LRM is obtained by replacing schottky diodes in DC LRM as illustrated in FIG. 3A , with the combined active ORing and soft-start circuit illustrated in FIG. 8 . Ch 1 in FIG. 9A shows the input current waveform (2 A/div). The peak inrush current is about 2.8 A. Ch 3 shows the output voltage, which rises gradually with overshoot. Ch 2 is the input voltage.

For comparison, FIG. 9B is a graph of electrical parameters obtained when an original LRM that does not include an active ORing and soft-start circuit (as illustrated in FIG. 3A ) is plugged into a live PSM output. In FIG. 9B , Ch 1 shows the input current waveform. The peak inrush current in this case is about 6 A (2 A/div). Ch 2 shows the output voltage, which overshoots and undershoots around the final value. Ch 3 is the input voltage, which is 28V, for a Line replaceable Module that includes the circuit in FIG. 3A , Ch 3 voltage is measured using a 50:1 differential probe.

FIG. 9C is a graph of electrical parameters obtained when an original LRM without an active ORing and soft-start circuit (as in FIG. 3A ) is unplugged from a live PSM. In FIG. 9C , Ch 1 shows the input current. Ch 2 shows the input voltage. Ch 3 shows the output voltage. Sharp voltage spikes can be seen on Ch 2 and Ch 3 .

For comparison, FIG. 9D is a graph of electrical parameters obtained when a modified LRM including the combined active ORing and soft-start circuit illustrated in FIG. 8 is unplugged from a live PSM output. In FIG. 9D , Ch 1 shows the input current. Ch 2 shows the input voltage. Ch 3 shows the output voltage. The sharp spikes that appeared in FIG. 9C are removed in the configuration of FIG. 9D , which shows that a successful soft stop has been achieved in FIG. 9D with the circuit from FIG. 8 .

The graphs in FIGS. 9A , 9 B, 9 C and 9 D were obtain for values for resistances, capacitance and the other electronic elements chosen according to configurations associated with AC and DC LRM configurations receiving the output Vout.

Although the active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D were discussed in the context of LRMs, the active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D are equally applicable to multi-channel input connection for other types of modules, circuits, and systems.

The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D properly connect multiple power supply voltage inputs to realize a fault tolerant power supply bus for LRMs; provide usage of an active ORing controller to achieve both active ORing and hot swap functions; avoid excessive power losses and voltage drops; control in-rush OR current chopping, and transient voltages/currents, during LRM hot swap insertion/extraction from a host system; avoid excessive voltage/current transients which stress/damage individual components and reduce MTBF; realize integrated active-diode-OR circuits that also provide soft power-up/down capability; provide a single power bus from multiple power supply input with minimum voltage drop and improved efficiency (no looses in the passive diodes); provide integrated soft-switching that reduces turn-on in-rush current during board insertion and further eliminates current-chopping during interruption of current in inductive circuits; provide methods to add/incorporate design improvement into active diode-OR circuits to achieve a better performance and at the same time provide a cost-effective soft-start and soft-stop method for hot-swap Line Replaceable Module applications; etc. The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D can be used with a variety of modules, including Line Replaceable Modules for AC and DC electric power systems which include AC/DC SSPC LRMs, Power Supply Modules, Digital Controller Boards/LRMs, etc.

The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D can be included in the hot swap systems presented in the co-pending non-provisional application titled “Method and Apparatus for Hot Swap of Line Replaceable Modules for AC and DC Electric Power Systems”, the entire contents of which are hereby incorporated by reference. The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D effectively reduce turn-on in-rush current transients (during board/module insertion) and eliminate current-chopping which would otherwise require complete shut-down of the larger electrical system before any hot swap of a board/module can be achieved. The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D, are particularly useful in hot swap of high voltage modules.

The active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D, can be implemented for hot swap at the level of basic hot swap, at the level of full hot swap, and at the level of highly available hot swap. The integration of the active diode ORing systems presented in FIGS. 1 , 2 , and all figures from 4 A to 9 D with the hot swap systems presented in the co-pending non-provisional application titled “Method and Apparatus for Hot Swap of Line Replaceable Modules for AC and DC Electric Power Systems”, for the three levels of hot swap, is described in the “Method and Apparatus for Hot Swap of Line Replaceable Modules for AC and DC Electric Power Systems” application, the entire contents of which are hereby incorporated by reference.

Although some aspects of the present invention have been described in the context of aerospace applications, it should be realized that the principles of the present invention are applicable to other environments.