United States Patent 19
`Pilukaitis et al.
`
`54
`
`INTEGRATED PROTECTION CIRCUIT FOR
`A POWER CONVERTER AND METHOD OF
`OPERATION THEREOF
`
`(75)
`
`73)
`
`Inventors: Raymond W. Pilukaitis, Garland; Ning
`Sun, Plano, both of Tex.
`Assignee: Lucent Technologies Inc., Murray Hill,
`N.J.
`
`Appl. No.: 09/045,425
`Filed:
`Mar 20, 1998
`Int. Cl." ............................ H02M 7/10; HO2H 7/00
`U.S. Cl. ................................................. 363/50, 361/18
`Field of Search .................................. 363/50, 52, 53,
`363/55, 56; 361/18, 79, 86, 87, 92
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`USOO5926383A
`Patent Number:
`11
`(45) Date of Patent:
`
`5,926,383
`Jul. 20, 1999
`
`
`
`... 363/41
`4,872,100 10/1989 Diaz ..............
`... 361/91
`5,424,897 6/1995 Mietus et al. ..
`5,757,635 5/1998 Seong........................................ 363/89
`Primary Examiner Matthew Nguyen
`57
`ABSTRACT
`For use with a controller, couplable to a network of first and
`Second comparators, that disables a power converter an
`actual output current thereof exceeds a threshold output
`current, an integrated protection circuit and method of
`operating the same. In one embodiment, the integrated
`protection circuit includes: (1) a Sensor that senses an actual
`input voltage of the power converter and (2) an isolation
`circuit, coupled to the first comparator, that Selectively
`decouples the first comparator from the controller, the
`Second comparator causing the controller to disable the
`power converter when the actual input Voltage falls below a
`threshold input voltage thereby allowing the protection
`circuit to provide both overcurrent and undervoltage pro
`tection.
`
`4,447.841
`
`5/1984 Kent .......................................... 361/18
`
`21 Claims, 4 Drawing Sheets
`
`
`
`Vint
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`U.S. Patent
`
`Jul. 20, 1999
`FIG. 1
`PRIOR ART
`
`Sheet 1 of 4
`
`5,926,383
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`? 100
`
`Vint
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`210
`
`
`
`
`
`
`
`FIG. 2
`PRIOR ART
`250
`
`
`
`UNIVERSAL
`
`MONITOR
`
`
`
`280
`
`POWER
`SUPPLY
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`U.S. Patent
`
`Jul. 20, 1999
`
`Sheet 2 of 4
`
`5,926,383
`
`396
`
`398
`
`N
`392
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`394
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`380
`
`PWM
`CONTROLLER
`
`PRIOR ART
`
`31 O
`
`315
`
`W
`REF1
`
`
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`U.S. Patent
`
`Jul. 20, 1999
`
`Sheet 3 of 4
`
`5,926,383
`
`sy
`
`FIG. 6
`
`VREF)
`
`(O 515
`
`538
`
`--- -
`
`ro
`524
`
`Vint
`
`VCC
`
`505
`
`|
`
`| I's
`
`522 |
`
`534
`
`530
`
`m u1526
`
`<
`
`IS
`
`F 520
`
`&
`
`-
`
`-
`
`-507
`
`-------- -
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`
`
`
`
`
`
`
`
`Jul. 20, 1999
`Jul. 20, 1999
`
`Sheet 4 of 4
`Sheet 4 of 4
`
`5,926,383
`
`U.S. Patent
`
`U.S. Patent
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`1
`INTEGRATED PROTECTION CIRCUIT FOR
`A POWER CONVERTER AND METHOD OF
`OPERATION THEREOF
`
`TECHNICAL FIELD OF THE INVENTION
`The present invention is directed, in general, to power
`conversion and, more Specifically, to an integrated protec
`tion circuit for a power converter and method of operation
`thereof.
`
`5
`
`BACKGROUND OF THE INVENTION
`Overcurrent, undervoltage and overVoltage protection cir
`cuits have been Separately used for power Supplies for more
`than a decade. Each protection circuit has its own merits and
`limitations, Such as function, cost and number of compo
`nents. The advantages of the Overcurrent protection circuits
`are that they are very simple, can completely shut-off the
`power Supply (e.g., a power converter) and will remain off
`until the overcurrent condition is removed and input power
`is recycled. The function is desirable to protect the power
`Supply from internal or external component failure and to
`prevent excessive heating in those failed components.
`The undervoltage lockout function is either provided by a
`dedicated undervoltage circuit or by a pulse width modula
`tion (PWM) integrated circuit (IC) controller. In either case,
`as the input voltage of the power converter increases from
`Zero, the undervoltage lockout function will keep the power
`converter off until the input Voltage rises to a predetermined
`level. Subsequently, as the input voltage drops from a
`normal operating input Voltage to Zero volts, the underVolt
`age lockout circuit will turn the power converter off when
`the input voltage falls below a predetermined threshold.
`The underVoltage lockout function is desirable Since the
`input current to the power converter tends to increase as the
`input Voltage decreases. This function can effectively limit
`that current. Further, the underVoltage lockout function can
`prevent Voltage drop and overcurrent shutdown in circuits
`with maximum duty cycle limiting. AS the input voltage is
`lowered, the duty cycle increases, eventually reaching its
`maximum, causing the output Voltage to fall out of regula
`tion.
`Unfortunately, Some types of overcurrent protection cir
`cuits interpret this as an overcurrent condition and will latch
`the power Supply off until the input power is recycled. AS a
`result, the power Supply could latch off or have low output
`Voltage during various input Voltage conditions, Such as
`Slowly rising input Voltage or momentary input Voltage loSS.
`An example of circuits that provide overVoltage protec
`tion is overVoltage clamping circuits. Overvoltage clamping
`circuits function in a number of different fashions. In one
`instance, a Sensor detects a higher than expected Voltage at
`the output of a power converter and a portion of the
`overVoltage clamp circuit clamps the output at a maximum
`Voltage. Once clamped, the Overvoltage clamp circuit con
`tinues to hold the output voltage at the clamped value, only
`allowing the Voltage to drop, not rise any higher.
`Additionally, Some circuits also have overVoltage shutdown
`abilities. If So, another portion of the overVoltage circuit
`eventually forces the power converter to shut down if the
`overVoltage condition persists thereby protecting the power
`converter and/or its load from damage due to high Voltage
`levels.
`An example of a power converter requiring the aforemen
`tioned protection functions is hereinafter described. For
`Some power Supply applications, a controller that limits a
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`duty cycle of the Switching devices of the power converter
`to fifty percent is desirable. The Switching devices Such as
`the metal-oxide Semiconductor field-effect transistors
`(MOSFETs) and Schottky diodes of a resonant reset forward
`converter, for instance, may Suffer very high Voltage Stresses
`during the Start-up proceSS and other transient conditions.
`The high Voltage Stresses are a result of the large duty cycle
`(e.g., eighty-five percent) imposed on the Switching devices
`of the power converter. Consequently, very little time in one
`cycle remains to reset the transformer and, therefore, the
`voltages of the transformer, MOSFET and diodes have to be
`extremely high to reset the transformer. The high Voltage
`stresses often contribute to the failure of the MOSFETs and
`diodes. To eliminate this problem, a controller (e.g., a PWM
`IC) that limits the duty cycle of the Switches to about fifty
`percent is employed for a forward converter with resonant
`reset. Further, when using peak current control converters, a
`lower maximum duty cycle is desired since these converters
`are known to have inherent instabilities where duty cycles of
`greater than fifty percent are employed.
`Accordingly, what is needed in the art is a recognition that
`merging protection functions for a power converter is advan
`tageous and, what is further needed in the art, is a circuit that
`combines at least overcurrent and undervoltage protections
`in an integrated fashion.
`
`SUMMARY OF THE INVENTION
`To address the above-discussed deficiencies of the prior
`art, the present invention provides for use with a controller,
`couplable to a network of first and Second comparators, that
`disables a power converter an actual output current thereof
`exceeds a threshold output current, an integrated protection
`circuit and method of operating the same. In one
`embodiment, the integrated protection circuit includes: (1) a
`Sensor that Senses an actual input Voltage of the power
`converter and (2) an isolation circuit, coupled to the first
`comparator, that Selectively decouples the first comparator
`from the Second comparator, the Second comparator causing
`the controller to disable the power converter when the actual
`input voltage falls below a threshold input Voltage thereby
`allowing the protection circuit to provide both overcurrent
`and underVoltage protection.
`The present invention, therefore, introduces the broad
`concept of combining the overcurrent and undervoltage
`protection functions in an integrated circuit. To accomplish
`the aforementioned functions, the first and Second compara
`tors cooperate to provide overcurrent protection and the
`Sensor and the Second comparator cooperate to provide
`undervoltage protection. The isolation circuit disengages the
`first comparator from the Second comparator when the actual
`input voltage falls below the threshold voltage.
`In one embodiment of the present invention, the protec
`tion circuit further includes a voltage clamp that temporarily
`clamps an output Voltage of the power converter at an upper
`limit, the overcurrent protection circuit Subsequently caus
`ing the controller to disable the power converter. In addition
`to overcurrent and underVoltage protection, the protection
`circuit is also capable of providing Overvoltage protection
`thereby providing three levels of protection for the power
`converter in a Single integrated circuit.
`In one embodiment of the present invention, the threshold
`input Voltage is partially derived from a reference Voltage
`coupled through a resistor to an input of the Second com
`parator. In this embodiment, the threshold input Voltage is
`derived from the reference Voltage and a Voltage Sensed by
`the Sensor.
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`5,926,383
`
`15
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`In one embodiment of the present invention, the Sensor
`includes a resistor divider network. Those skilled in the art
`are familiar with resistor divider networks and the advan
`tages associated therewith. The resistor values are user
`Selectable to partially define the threshold input voltage
`depending on the Specific application.
`In one embodiment of the present invention, the protec
`tion circuit further includes a clamp circuit that is capable of
`clamping a Voltage at an input of the Second comparator. In
`an embodiment to be illustrated and described, the clamp
`circuit is coupled to a node between first and Second resistors
`of the resistor divider network. The present scope of the
`present invention, however, is not limited to Sensors employ
`ing resistor divider networks.
`In one embodiment of the present invention, the isolation
`circuit includes a diode. In an embodiment to be illustrated
`and described, the diode isolates the overcurrent and und
`ervoltage protection functions under certain conditions. Of
`course, other isolation circuits are well within the broad
`Scope of the present invention.
`In one embodiment of the present invention, the network
`further includes a capacitor and a Switch. In an embodiment
`to be illustrated and described, the capacitor and Switch
`cooperate with the first and Second comparators to cause the
`controller to disable the converter during an overcurrent
`condition. Of course, circuit parameter variations that
`achieve analogous functionality are well within the broad
`Scope of the present invention.
`The foregoing has outlined, rather broadly, preferred and
`alternative features of the present invention So that those
`skilled in the art may better understand the detailed descrip
`tion of the invention that follows. Additional features of the
`invention will be described hereinafter that form the subject
`of the claims of the invention. Those skilled in the art should
`appreciate that they can readily use the disclosed conception
`and Specific embodiment as a basis for designing or modi
`fying other Structures for carrying out the same purposes of
`the present invention. Those skilled in the art should also
`realize that Such equivalent constructions do not depart from
`the Spirit and Scope of the invention in its broadest form.
`BRIEF DESCRIPTION OF THE DRAWINGS
`For a more complete understanding of the present
`invention, reference is now made to the following descrip
`tions taken in conjunction with the accompanying drawings,
`in which:
`FIG. 1 illustrates a Schematic diagram of a prior art
`overcurrent protection circuit;
`FIG. 2 illustrates a Schematic diagram of a prior art
`undervoltage lockout circuit;
`FIG. 3 illustrates a Schematic diagram of a prior art
`overVoltage clamp circuit;
`FIG. 4 illustrates a Schematic diagram of an embodiment
`of an integrated protection circuit constructed according to
`the principles of the present invention;
`FIG. 5 illustrates a Schematic diagram of a Second
`embodiment of an integrated protection circuit constructed
`according to the principles of the present invention; and
`FIG. 6 illustrates a Schematic of a power Supply employ
`ing an integrated protection circuit constructed according to
`the principles of the present invention.
`DETAILED DESCRIPTION
`Referring initially to FIG. 1, illustrated is a schematic
`diagram of a prior art overcurrent protection circuit 100. The
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`overcurrent protection circuit 100 consists of a first resistor
`110 coupled between a capacitor 120 and a transistor 140.
`The transistor 140 is further coupled across a noninverting
`input and an output of a first comparator 150 (an operational
`amplifier) thereby forming a positive feedback loop. First
`and second divider resistors 194, 196 are coupled to the
`inverting input of the first comparator 150 from a node 192.
`A secondary reference voltage V, is generated at the node
`192 located between the series-coupled first and second
`divider resistors 194, 196.
`A second resistor 160 is coupled between the output of a
`Second comparator 170 (an operational amplifier), which is
`only capable of Sinking current, and the noninverting input
`of the first comparator 150. The second resistor 160 is
`additionally coupled to the output of a controller operational
`amplifier 130 that is located in a PWM controller 133. A
`feedback resistor 180 is coupled between a noninverting
`input and an output of the Second comparator 170.
`A controller output voltage V, normally operates
`between 1 V to 4 V. A power supply coupled to the PWM
`controller 133 is operated in a peak current or duty cycle
`control mode of operation whereby the PWM controller 133
`regulates the output Voltage of the power Supply from light
`load to full load current by increasing or decreasing V.
`which correspondingly increases or decreases the duty cycle
`or peak current. If an overcurrent condition that exceeds a
`predetermined threshold exists, the output Voltage falls out
`of regulation and the output of the controller operational
`amplifier 130 will saturate high (approximately 5 V).
`The secondary reference voltage V, which is normally
`higher than the controller output voltage V, is measured
`from the first and second divider resistors 194, 196. During
`normal operation, the first comparator output voltage V is
`pulled down to near Zero as the controller output voltage
`V.
`is lower than the Secondary reference voltage V.
`During an overcurrent condition, the controller output Volt
`age V, exceeds the Secondary reference voltage V, and
`the first comparator output voltage V will rise to a bias
`supply voltage V of the control operational amplifier 130.
`Since the output of the first comparator 150 is an open
`collector output, the capacitor 120 will be charged to the
`supply voltage V through a first resistor 110. The transistor
`140 provides positive feedback to the first comparator 150
`input and causes the first comparator 150 to be latched high.
`With the first comparator 150 latched high, the PWM
`controller 133 will be disabled (thereby disabling the power
`Supply) until the overcurrent condition is removed and the
`input voltage is reapplied.
`Turning now to FIG. 2, illustrated is a Schematic diagram
`of a prior art undervoltage lockout circuit 200. The circuit
`200 consists of a first resistor 210 coupled to a second
`resistor 220 that is in turn coupled in parallel with a
`capacitor 230. The capacitor 230 is coupled to a first and
`second input of a universal voltage monitor (UVM) 240,
`which monitors undervoltage conditions. A third resistor 250
`is coupled between the first resistor 210 and the output of the
`UVM 240. A fourth resistor 260 is coupled to a third input
`of the UVM 240 and a fifth resistor 270 is coupled between
`the fourth resistor 260 and the output of the UVM 240.
`Finally, the output of the UVM 240 is coupled to a power
`supply 280.
`An input Voltage V is sensed and then compared to a
`reference voltage. The output of the UVM 240 will be zero
`when the input voltage V is lower than a reference Voltage.
`Once the output of the UVM 240 drops to zero, the power
`supply 280 will be disabled. Once the input voltage V rises
`above the reference voltage, the power supply 280 will be
`reactivated.
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`S
`Turning now to FIG. 3, illustrated is a Schematic diagram
`of a prior art overvoltage clamp circuit 300. The clamp
`circuit 300 consists of two stages, a control stage 310 and a
`clamping Stage 390. The control Stage consists of a first
`opto-transistor 315 coupled to a first resistor 320 which in
`turn is coupled to a noninverting input of an first operation
`amplifier 360. A second transistor 330 is coupled to the first
`opto-transistor 315 and is additionally coupled to the non
`inverting input of the first operational amplifier 360 and to
`a second resistor 370 which is further coupled to the output
`of the first operational amplifier 360. Further, a supply PWM
`controller 380 is coupled to the second resistor 370. A first
`diode 335 is coupled between the first operational amplifi
`er's 360 output and noninverting input, forming a positive
`feedback loop. Additionally, a capacitor 350 is series
`coupled to a third resistor 340 that is coupled to the
`noninverting input of the first operational amplifier 360. A
`first reference voltage V,
`is derived from a reference
`resistor 345 which is coupled to the third resistor 340. A
`second reference voltage V,
`is measured at the inverting
`input of the first operation amplifier 360. The output of a
`Second operational amplifier 362 is coupled to Second diode
`347 which is in turn coupled to the third resistor 340.
`The clamping stage 390 of the circuit 300 consists of a
`clamping resistor 392 Series-coupled to a clamping diode
`25
`394 which is further coupled to a Zener diode 398. A
`feedback resistor 396 is additionally coupled in parallel
`across a clamping resistor 392 and the clamping diode 394.
`The clamping Stage functions to clamp the output of a
`power Supply (not shown), coupled thereto, when an output
`Voltage V reaches a predesignated level. Once the output
`is clamped, the control Stage, Sensing the clamped output,
`signals the PWM controller 380 to shut down the power
`Supply and keep it latched-off until the fault condition is
`removed and the input Voltage is reapplied.
`When the output Voltage V is higher than the Zener
`diode 398 voltage, the Zener diode 398 starts to conduct and
`the clamping diode 394 also conducts. When conducting, the
`clamping diode 394 will transmit light to the first opto
`transistor 315 that will conduct a current. A voltage source
`(not shown) will charge the capacitor 350 and once the
`capacitor's 350 voltage charges up and the first operational
`amplifiers noninverting input voltage is higher than the
`second reference voltage V, the first operational ampli
`fier's output will by high. If the PWM controller 380 senses
`a voltage higher than 1 V, the controller 380 will shut off and
`latch-off the power Supply.
`Turning now to FIG. 4, illustrated is a Schematic diagram
`of an embodiment of an integrated protection circuit 400
`constructed according to the principles of the present inven
`tion. The protection circuit 400 consists of a first resistor 405
`coupled between a capacitor 407 and a transistor 415. A
`supply voltage V is measured at node 409, between the
`first resistor 405 and the transistor 415. The transistor 415 is
`further coupled between the noninverting input and the
`output of a first comparator 410 (e.g., an operational
`amplifier) forming a positive feedback loop. First and Sec
`ond divider resistors 424, 426 are coupled to the inverting
`input of the first comparator 410 from a node 422. A primary
`reference voltage V, measured at node 421, is reduced by
`the series-coupled first and second divider resistors 424, 426
`to generate a second reference voltage V, at node 422.
`A second resistor 435 is coupled between the output of a
`Second comparator 430 (e.g., an operational amplifier) and
`the noninverting input of the first comparator 410. The
`second resistor 435 is additionally coupled to the output of
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`a controller operational amplifier 470 that is located in a
`controller (e.g., a PWM controller IC) 475. A third resistor
`438 is coupled between the inverting input of the second
`comparator 430 and the primary reference voltage V. A
`fourth resistor 460 is coupled to the noninverting input of the
`second comparator 430 and the fifth resistor 465 is coupled
`between the second comparator's 430 noninverting input
`and the capacitor 407. Lastly, a feeback resistor 431 is
`coupled across the second comparator 430 between the
`output and the noninverting input.
`The protection circuit also includes an isolation circuit
`consisting of a first diode 440. The first diode 440 is coupled
`between the transistor 415 and the inverting input of the
`second comparator 430. The undervoltage lockout and over
`current protection functions are embodied, in part, in the
`isolation circuit (e.g., first diode 440), a sensor (e.g., a
`resistor divider network including third and fourth resistors
`460, 465) and a fifth resistor 438 in connection with the
`network of first and second comparators 410, 430. In addi
`tion to providing overcurrent protection, the integrated pro
`tection circuit Senses an input voltage of a power converter
`with the resistor divider network and compares the input
`voltage with a primary reference voltage V. The second
`comparator's 430 output will be nearly zero and the output
`voltage of the control operational amplifier 470 will be
`likewise reduced, causing the power converter to shut down
`when the Sensed input voltage V, is lower than the primary
`reference voltage V. Once the sensed input voltage V,
`rises above the primary reference voltage V, the output of
`the second comparator 430 will be high and the controller
`475 will be enabled. Further, those skilled in the art will
`recognize that the feedback resistor 431 can be used for
`hysteresis.
`The first diode 440 acts as an isolation circuit which
`allows the inverted input of the second comparator 430 to act
`as a reference Voltage for the undervoltage lockout function
`while the overcurrent protection is inactive (by Selectively
`decoupling the first comparator 410 from said controller
`475). The first diode 440 also allows for positive feedback
`required for overcurrent latching when the output of the first
`comparator 410 goes high.
`A controller output voltage V, which is proportional
`to the peak current, thereby controlling the power Supply
`output, normally operates between 1 V to 4 V. A power
`supply coupled to the PWM controller 475 is operated in a
`peak current control mode of operation whereby the PWM
`controller 475 regulates the output voltage of the power
`Supply from light load to full load current. If an overcurrent
`condition that exceeds a predetermined threshold exists, the
`output voltage falls out of regulation and the output of the
`controller operational amplifier 470 will saturate high
`(approximately 5 V) and shut off the unit. Additionally, those
`skilled in the art will understand that this embodiment works
`with other forms of circuit control (e.g. duty cycle control)
`where the controlled parameter is a function of the control
`signal, Vene.
`A second diode 450 is coupled between the noninverting
`input of the second comparator 430 and the first divider
`resistor 424 and acts as a Voltage clamp. When the Voltage
`at the first operational amplifier's 430 noninverting input
`increases to a value possibly higher than the Supply Voltage
`V, the second diode 450 clamps the voltage at the nonin
`Verting input. This may not be necessary if the Supply
`Voltage V is always adequately higher than the Voltage at
`the noninverting input.
`Turning now to FIG. 5, with continued reference to FIG.
`4, illustrated is a Schematic diagram of a Second embodiment
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`5,926,383
`
`8
`loop controller 650. This figure illustrates an embodiment of
`the present invention in working combination with other
`conventional circuits in the power supply 600. Those skilled
`in the art will recognize the operations of the conventional
`circuits and their interaction with each other and with the
`present invention.
`AS in most circuits and power Supplies, a calculatable
`output is desired. The minimum input voltage required to
`maintain the output Voltage within chosen parameters is
`calculated as follows:
`
`7
`of a protection circuit constructed according to the principles
`of the present invention that operates analogously to the
`embodiment shown in FIG. 4. The protection circuit 500
`consists of a first resistor 505 coupled between a capacitor
`507 and a transistor 515. The transistor 515 is further
`coupled between the noninverting input and the output of a
`first comparator 510 (e.g., an operational amplifier) forming
`a positive feedback loop. First and Second divider resistors
`524, 526 are coupled to the inverting input of the first
`comparator 510 from a node 522. A second reference voltage
`V,
`is sensed from the node 522 located between the
`series-coupled first and second divider resistors 524,526.
`A second resistor 535 is coupled between the output of a
`Second comparator 530 (e.g., an operational amplifier) and
`the noninverting input of the first comparator 510. The
`second resistor 535 is additionally coupled to the output of
`a controller operational amplifier 570 that is located in a
`controller (e.g., a PWM controller IC) 575. A third resistor
`538 is coupled between the inverting input of the second
`comparator and the first divider resistor 524. A fourth
`resistor 560 is coupled to the noninverting input of the
`second comparator 530 and the fifth resistor 565 is coupled
`between the second comparator's 530 noninverting input
`and the capacitor 507. Lastly, a feeback resistor 531 is
`coupled across the second comparator 530 between the
`output and the noninverting input.
`The integrated protection circuit also includes an isolation
`circuit consisting of first and second diodes 540, 550. The
`first diode 540 is coupled between the first comparator's 510
`output and the inverting input of the second comparator 530.
`The Zener diode 550 is coupled between the capacitor 507
`and the noninverting input of the second comparator 530.
`In addition to the advantages of the integrated protection
`circuit of FIG. 4, the integrated protection circuit 500 of
`FIG. 5 utilizes the Zener diode 550 that acts to clamp the
`sensed input voltage V. Also, the first diode 540 is con
`nected to the output of first comparator 510, functioning as
`an alternative means of coupling and decoupling the inter
`action of the first and second comparators 510, 530.
`The embodiments of the integrated protection circuits
`described with respect to FIGS. 4 and 5 may also employ a
`voltage clamp (e.g.,an output diode) which is placed across
`the output of the power converter to clamp the output
`Voltage, as part of an overVoltage clamp circuit function. The
`output diode will clamp the output Voltage and the unit will
`be in an overcurrent condition. Once the integrated protec
`tion circuit Senses the overcurrent condition, the circuit
`Signals the controller to disable the power converter until the
`overVoltage occurrence is remedied.
`Turning now to FIG. 6, illustrated is a schematic of a
`power Supply 600 employing an integrated protection circuit
`constructed according to the principles of the present inven
`tion. The power supply 600 employs an integrated
`overcurrent, underVoltage and overVoltage protection circuit
`610 constructed according to the principles of the present
`invention. This protection circuit 610 includes an output
`clamping diode 615. The output clamping diode 615 clamps
`the output voltage, not allowing the output to rise above a
`desired level and consequently, the unit operates in an
`overcurrent condition. The protection circuit 610 senses the
`overcurrent condition and Signals a peak current controller
`630 (e.g., manufacturer model number UC3845, by
`Motorola, Inc, of Phoenix, Ariz.) that then disables the
`power supply 600. Along with the protection circuit 610, the
`power supply 600 further consists of a start-up circuit 620,
`a forward converter 640 with resonant reset and a feedback
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`where: V, is the output Voltage, V is the output diode
`voltage drop, V, is the input voltage, n is the transformer
`turns-ratio and D,
`is the maximum duty cycle limit. The
`converter 640 start-up voltage depends on the controller 630
`Start-up threshold Voltage combined with the Start-up cir
`cuitry 620. The controller 630 has an internal lockout
`function to prevent turn-on until a certain threshold Voltage
`is reached. As the input voltage to the power supply 600
`rises, a fraction of the input Voltage is applied to the
`controller 630 by the start-up circuitry 620 and the converter
`640 will start when threshold voltage is reached. This input
`threshold Voltage is referred to as V.
`The undervoltage lockout Voltage V can be set higher
`than the minimum input Voltage V but lower than the
`input threshold Voltage V, which can be expressed as
`the following:
`
`iriirpora
`
`Epi
`
`irapair
`
`where: V, is the input Voltage corresponding to the
`controller turn-On threshold Voltage, V
`is the input
`Voltage corresponding to minimum Voltage which keeps the
`output voltage within the desired boundaries, and V is the
`input Voltage corresponding at which the undervoltage lock
`out circuit will turn the power supply 600 on or off.
`Utilizing the undervoltage lockout function, the power
`supply 600 stays in the off-state when the input voltage is
`below V, turns on at V, and turns off below V.
`Therefore, the power Supply 600 can turn-on and turn-off
`properly with the undervoltage lockout function in the
`circuit.
`Exemplary embodiments of the present invention have
`been illustrated above with reference to specific electronic
`components. Those skilled in the art are aware, however,
`that components may be Substituted (not necessarily with
`components of the same type) to create desired conditions or
`accomplish desired results. For instance, multiple compo
`nents may be Substituted for a single component and Vice
`Versa. Similarly, although the power transformers having a
`Single core and a Single primary winding has been
`illustrated, other power train topologies may be used to
`accomplish essentially the Same results disclosed by the
`present invention. Finally, those skilled in the art are aware
`that even though only one type of power converter was
`referenced above, other converter topologies including,
`without limitation, a push-push converter, a buck converter
`and a flyback converter, are also within the broad Scope of
`the present invention,
`For a better understanding of power electronics, power
`converter topologies, Such as forward power converters, and
`control circuits, see: Principles of Power Electronics, by J.
`Kassakian and M. Schlecht, Addison-Wesley Publishing
`Company (1991), which is incorporated herein by reference.
`Although the present invention has been described in
`detail, those skilled in the art should understand that they can
`
`Petitioner Intel Corp., Ex. 1014
`IPR2023-00783
`
`

`

`5,926,383
`
`make vari