U.S. patent application number 14/735843 was filed with the patent office on 2015-12-17 for method for improving safety of voltage regulator.
The applicant listed for this patent is LENOVO (SINGAPORE) PTE. LTD.. Invention is credited to JONATHAN RANDALL HINKLE, SHIGEFUMI ODAOHHARA.
Application Number | 20150364908 14/735843 |
Document ID | / |
Family ID | 54836976 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150364908 |
Kind Code |
A1 |
ODAOHHARA; SHIGEFUMI ; et
al. |
December 17, 2015 |
METHOD FOR IMPROVING SAFETY OF VOLTAGE REGULATOR
Abstract
A method for improving safety of voltage regulator is disclosed.
In order to improve safety of a voltage regulator, a MOS-FET is
disposed on a source power lane that receives power supplied from a
DC power supply. A set of voltage regulators is connected to a set
of fork power lanes, correspondingly, branching off from the source
power lane. PTC thermistors are disposed on a surface or in the
vicinity of semiconductor chips of the voltage regulators. When
temperature at any one of the PTC thermistors increases, a
protection controller turns off the MOS-FET. When temperature
detected by a temperature sensor incorporated within the
semiconductor chip has increased, each of the voltage regulators
turns off the MOS-FET via a base management controller.
Inventors: |
ODAOHHARA; SHIGEFUMI;
(Kanagawa-ken, JP) ; HINKLE; JONATHAN RANDALL;
(Raleigh, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LENOVO (SINGAPORE) PTE. LTD. |
Singapore |
|
SG |
|
|
Family ID: |
54836976 |
Appl. No.: |
14/735843 |
Filed: |
June 10, 2015 |
Current U.S.
Class: |
361/93.8 |
Current CPC
Class: |
H02H 9/001 20130101;
H02H 5/042 20130101; H02H 3/085 20130101; H02H 5/041 20130101 |
International
Class: |
H02H 3/08 20060101
H02H003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 2014 |
JP |
2014-122932 |
Claims
1. A power-supply system comprising: a protection switch disposed
on a power lane receiving power from a DC power supply; a plurality
of voltage regulators, wherein at least one of said voltage
regulators includes a switching element and branching off from said
power lane; a temperature sensor for detecting temperature of said
voltage regulators; and a controller for turning off said
protection switch when temperature at any one of said voltage
regulators has increased and for stopping power supplied to said
plurality of voltage regulators.
2. The power-supply system of claim 1, wherein said temperature
sensor detects temperature of a semiconductor chip when said
switching element is incorporated within said semiconductor
chip.
3. The power-supply system of claim 2, wherein said temperature
sensor detects temperatures inside of said semiconductor chip.
4. The power-supply system of claim 1, wherein said temperature
sensor includes a FTC thermistor.
5. The power-supply system of claim 1, wherein in response to an
abnormality for ON/OFF resistances of said switching elements, said
voltage regulators send a signal to turn off said protection switch
to said controller.
6. The power-supply system of claim 1, wherein said voltage
regulators include a first voltage regulator and a second voltage
regulator that output mutually different voltages, and loads of
said voltage regulators include a device that operates with output
voltage from said first voltage regulator and output voltage from
said second voltage regulator.
7. A sub-system for a computer comprising: a processor and a system
memory; a protection switch disposed on a power lane receiving
power from a DC power supply; a plurality of voltage regulators,
wherein at least one of said voltage regulators includes a
switching element to supply power to said processor and said system
memory; a first temperature sensor for detecting temperature of
said voltage regulators; and a first protection circuit for turning
off said protection switch in response to a temperature at any of
said voltage regulators has increased.
8. The sub-system of claim 7, wherein said switching element is
incorporated within a semiconductor chip, and said first protection
circuit turns off said protection switch in response to a
temperature of said semiconductor chip has increased.
9. The sub-system of claim 8, further comprising: a second
temperature sensor incorporated within said semiconductor chip; and
a second protection circuit for turning off said protection switch
in response to a temperature detected by said second temperature
sensor has increased.
10. A method for improving safety of a voltage regulator, said
method comprising: providing a voltage regulator with a switching
element at one of a plurality of fork power lanes branching off
from a source power lane; detecting temperature at said switching
element of one of said voltage regulators; and stopping power
supplied from said source power lane in response to a temperature
at any of said voltage regulators has increased.
11. The method of claim 10, wherein said detecting temperature
further includes detecting temperature of a semiconductor chip when
said switching element is incorporated within said semiconductor
chip.
12. The method of claim 10, further comprising: in response to an
abnormality occurs in ON resistance of said switching elements,
stopping power supplied from said source power lane.
13. The method of claim 10, further comprising: in response to an
abnormality occurs in OFF resistance of said switching elements,
stopping power supplied from said source power lane.
Description
PRIORITY CLAIM
[0001] The present application claims benefit of priority under 35
U.S.C. .sctn..sctn.120, 365 to the previously filed Japanese Patent
Application No. JP2014-122932 with a priority date of Jun. 14,
2014, which is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to voltage regulators in
general, and particularly to a method for improving the safety of a
voltage regulator having a switching element, and to a method for
preventing smoking and burning of a switching element.
[0004] 2. Description of Related Art
[0005] FIG. 7 describes the outline of a typical power-supply
system used for a server. A power-supply unit (PSU) 501 supplies
power to a group of sub-systems 503 to 507 making up a server with
DC voltage. Each sub-system 503 to 507 is mainly made up of voltage
regulators (VRs) 511a to 511c that convert the output voltage of
the PSU 501 to predetermined voltage and loads 513a to 513c
corresponding to the VRs, such as a central processing unit (CPU),
a memory, and a hard disk drive (HDD). The VRs 511a to 511c are
provided with fuses 509a to 509c, respectively, on the primary
side. The sub-system 503 is configured so that, even when power
supplied to any one of the loads 513a to 513c stops, the function
of the sub-system does not stop completely as long as power is
supplied to other loads.
[0006] A conventional DC power-supply apparatus including a
switching element is configured to protect the circuit by turning
the switching element OFF when the load generates a short-circuit
failure. The switching element can function as the protection
switch against a short-circuit failure only when such a switching
element normally operates. Since switching elements are
manufactured with a relatively high level of reliability, and so
cause less failure in general, such a protective idea may not have
a problem in that sense.
[0007] In the power-supply system of FIG. 7, if the switching
elements in the to close state of the VRs 511a to 511c fail and so
short-circuit current flow, the fuses 509a to 509c on the primary
side can be molten so as to interrupt the related system only.
Since the fuses 509a to 509c do not require a control circuit and
are inexpensive, such a protective idea is rational for the failure
of a switching element that hardly causes a failure.
[0008] In the power-supply system of FIG. 7; however, the VRs 511a
to 511c may cause smoking and burning. Investigations on such a
phenomenon show that a switching element burns severely. A direct
cause of the burning of a switching element results from the
element generating a large amount of heat due to large current. If
a switching element in the close state fails, short-circuit current
flowing will cause burnout of any one of the fuses 509a to 509c.
However, smoking or burning generated means that the fuses 509a to
509c do not melt, or the timing of the melting, if any, may not
work together with the circuit.
[0009] The fuses 509a to 509c have to have elements that is not
degraded due to repeated inrush current when energization starts at
the VRs 511a to 511c, and since they are disposed to protect the
circuit from short-circuit, its blowout current is quite larger
than the rated current of the VRs 511a to 511c, and its pre-arcing
time also has to be longer. In one example, the fuses 509a to 509c
have current-time characteristics such that it takes two minutes to
cause a blowout when current twice of the rated current of the VRs
511a to 511c flows. Such a current value and energizing time are
sufficient to cause smoking and burning at the switching
elements.
[0010] If a switching element whose resistance is close to zero
causes a short-circuit failure (this is called dead short-circuit),
the pre-arcing time is short in spite of a large current value, and
so the fuses 509a to 509c can be molten prior to smoking and
burning so as to interrupt the circuit. Recent studies show that,
however, if the switching element having some resistance causes a
short-circuit failure (this is called resistance short-circuit),
the switching element causes smoking and burning to interrupt the
circuit before burnout of the fuses 509a to 509c or without causing
a burnout of the fuses 509a to 509c.
[0011] Switching elements are degraded over time because they
frequently turn ON/OFF. If a switching element burns while
generating heat severely, all of the devices around it may be
damaged or a normal sub-system also has to be replaced in some
cases. Further, if a switching element generates heat, it causes
the risk of fire, and so it is not favorable to leave such a
situation unsolved even when the risk is small. The PSU 501 has to
supply power to each sub-system 503 to 507, and so has large rated
current compared with the VRs 511a to 511c, and so the protection
circuit thereof also cannot prevent smoking and burning when
resistance short-circuit occurs at the switching element.
[0012] Another problem occurs, which results from the loads 513a to
513c including a device that receives power from VRs 511a to 511c.
For instance, when the load 513b includes a device receiving power
from the VR 511a as well, and if the fuse 509a is molten, the
device receives power continuously from the VR 511b in spite of
stopping of the power-supply from the VR 511a. Then the device of
the load 513b generates latch up, which increases the risk leading
to secondarily generated smoking and burning.
[0013] Consequently, it would be desirable to provide a
power-supply system having improved safety against resistance
short-circuit of a switching element.
SUMMARY OF THE INVENTION
[0014] In accordance with a preferred embodiment of the present
invention, a power-supply system includes a protection switch
disposed on a power lane receiving power supply from a DC power
supply, a group of voltage regulators, each having a switching
element and branching off from the power lane, a temperature sensor
for detecting temperature of the voltage regulators, and a
controller for turning the protection switch OFF when temperature
at any one of the voltage regulators increases and stops power
supplied to the group of voltage regulators. With this
configuration, if the switching element fails due to resistance
short-circuit, the protection switch can be turned OFF in response
to the detection of temperature such that smoking and burning can
be prevented.
[0015] When the switching element is incorporated into a
semiconductor chip, the temperature sensor can detect temperature
at a surface or vicinity of the semiconductor chip. Temperature is
detected from the outside of the semiconductor chip, whereby the
temperature sensor is not affected from a sudden increase in
temperature, if any, and can turn the protection switch OFF
reliably. The temperature sensor may include a PTC thermistor. When
temperature detected by the temperature sensor incorporated in the
semiconductor chip increases, the controller can turn the
protection switch OFF.
[0016] A temperature sensor for detecting temperature outside of
the semiconductor chip, and a temperature sensor for detecting
temperature inside thereof are provided, whereby reliable
protection can be provided even when the switching element
generates heat suddenly. When ON resistance or OFF resistance of
the switching elements calculated from voltage and current
increases, the voltage regulators may send a signal to turn the
protection switch OFF to the controller. The present invention is
suitable for the case where the group of voltage regulators include
a first voltage regulator and a second voltage regulator that
output mutually different voltages, and loads of the voltage
regulators include a device that operates with output voltage from
the first voltage regulator and output voltage from the second
voltage regulator. With this configuration, if abnormality occurs
at any one of the voltage regulators, all of the voltage regulators
stop, and so latch up of the device as a load can be prevented.
[0017] All features and advantages of the present disclosure will
become apparent in the following detailed written description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The disclosure itself, as well as a preferred mode of use,
further objects, and advantages thereof, will best be understood by
reference to the following detailed description of an illustrative
embodiment when read in conjunction with the accompanying drawings,
wherein:
[0019] FIGS. 1A-1B are diagrams of a blade server;
[0020] FIG. 2 is a block diagram of the blade server from FIG.
1;
[0021] FIG. 3 is a block diagram of the sub-systems within a server
unit of the blade server from FIG. 1;
[0022] FIG. 4 is a schematic diagram of a main sub-system within
one of the sub-systems from FIG. 3;
[0023] FIG. 5 is a schematic diagram of a voltage regulator;
[0024] FIG. 6 is a flow diagram describing the operation of the
power-supply system; and
[0025] FIG. 7 is a block diagram of a typical power-supply system
used for a server.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0026] A power-supply system according to the present invention
preferably is applicable to a set-type computer system. A set-type
computer system includes a group of computer units, each having an
equivalent computer function. Each computer unit includes hardware
such as a processor, a system memory, an input/output (I/O)
controller, a memory and a peripheral device, and software such as
an operating system and an application program.
[0027] Each computer unit receives power from a power-supply unit
(PSU) that converts utility power to DC voltage. Only one PSU may
be provided for the computer system, or one PSU may be provided for
a group of a plurality of computer units. Each computer unit
includes a group of sub-systems. Each sub-system includes a group
of voltage regulators (VRs). The set-type computer system may be
implemented as a rack-mountable server, a blade server, a router or
the like.
[0028] FIGS. 1 to 3 describe the outline of a blade server 10. FIG.
1A illustrates the outside shape of the blade server 10, and FIG.
1B illustrates the internal configuration. FIG. 2 illustrates the
outline of a power-supply system including a PSU 21 and server
units 100a to 100h, and FIG. 3 is a block diagram of a group of
sub-systems making up the server unit 100a.
[0029] In FIG. 1A, a rack 11 includes a front panel 23 on the
surface, and internally accommodates the plurality of server units
100a to 100h, a midplane 13, a switch module 15, a chassis
management module (CMM) 17, a fan module 19 and the PSU 21. Each
server unit 100a to 100h includes a mother-board in an independent
enclosure, and internally includes hardware and software resources
to operate as an independent computer.
[0030] The midplane 13 is a circuit board including wiring for
signals and power and connectors on both faces for coupling with
the modules. The server unit 100a to 100h can connect to the
midplane 13 that is energized with the output voltage from the PSU
21 in a hot-swap manner. The switch module 15 includes a group of
switches for connection to a network or an external memory. The CMM
17 is to inform the operating state of the blade server 10 to a
distance or to display it on the front panel 23. The fan module 19
dissipates heat inside of the rack 11. The PSU 21 converts AC
voltage to DC voltage, and supplies power to the server units 100a
to 100h and other modules.
[0031] In FIG. 2, the server units 100a to 100h are connected to
the midplane 13 at their power terminals 105a to 105h and signal
terminals 107a to 107h. Then the PSU 21 and the CMM 17 are
connected to the midplane 13. The CMM 17 is connected to the front
panel 23. The PSU 21 supplies power to each server unit 100a to
100h via the midplane 13 and the power terminals 105a to 105h.
[0032] In FIG. 3, at the power terminal 105a of the server unit
100a, source power lanes 234a to 234c are connected to a route
power lane 106a. The source power lanes 234a and 234b are connected
to main sub-systems 151a and 151b, respectively, and the source
power lane 234c is connected to a common sub-system 151c. Herein
the route power lane 106a corresponds to a circuit that supplies
power from the PSU 21 to the three sub-systems 151a to 151c, and
the source power lanes 234a to 234c correspond to a circuit that
supplies power to the three sub-systems 151a to 151c.
[0033] The main sub-systems 151a and 151b each include a CPU and a
system memory, and operate mutually independently. The common
sub-system 151c includes an I/O controller and a HDD that both or
one of the main sub-systems 151a and 151b have to use to function
as a computer, and does not function independently. In the
application of the present invention, the number of the main
sub-systems 151a and 151b may be one or more. The function of the
common sub-system 151c may be incorporated into each main
sub-system 151a or 151b and be omitted. The sub-systems 151a to
151c include MOS-FETs 235a to 235c for protection, base management
controllers (BMC) 203a to 203c, VRs 205a to 209a, 205b to 209b, and
205c to 209c, respectively.
[0034] The VRs are switching regulators to convert output voltage
from the PSU 21 to predetermined stable voltage in accordance with
the load. The VRs 205a to 209a supply power to loads 211a to 215a,
such as a CPU and a system memory, the VRs 205b to 209b supply
power to loads 211b to 215b, such as a CPU and a system memory, and
the VRs 205c to 209c supply power to loads 211c to 215c, such as a
HDD and an I/O controller. The BMCs 203a to 203c inform the CMM 17
of the operating state of the sub-systems 151a to 151c via the
signal terminal 105b, and control the MOS-FETs 235a to 235c.
[0035] FIG. 4 is a schematic diagram describing the circuit
configuration of the main sub-system 151a. The PSU 21 supplies
power to an input terminal VIN on the source power lane 234a via
the route power lane 106a. The input terminal VIN is connected in
series with a current sense resistor 233a and an n-type MOS-FET
235a. The current sense resistor 233a has both ends connected to a
protection controller 201a. The MOS-FET 235a has a gate connected
to the protection controller 201a. Fork power lanes 204a to 204c
branch off from the MOS-FET 235a, to each of which the VR 205a to
209a is connected.
[0036] The fork power lanes 204a to 204c correspond to a circuit
that supplies power to their corresponding VRs 205a to 209a. The
VRs 205a to 209a output stable and predetermined voltage V21, V22
and V23, respectively, for use at their corresponding loads 211a to
215a. The VR 205a supplies power to the load 211a mainly including
a CPU, the VR 207a supplies power to the load 213a mainly including
a system memory, and the VR 209a supplies power to the load 215a
including another device.
[0037] Some devices included in the loads 211a to 215a operate with
voltage output from another VR and with a plurality of voltages.
The input terminal VIN is connected to the ground via a resistor
236a and Positive Temperature Coefficient (PTC) thermistors 351a to
355a connected in series. The PTC thermistors 351a to 355a are
elements having flat temperature-resistor characteristics at normal
temperatures, but suddenly increasing in resistance when the
temperature exceeds a certain level (Curie temperature).
[0038] The PTC thermistors 351a to 355a are disposed so as to
measure temperature at the surface or environmental temperature in
the vicinity of a semiconductor chip of a switching circuit 303
(FIG. 5) making up the VR 205a to 209a. A n-type MOS-FET 231a has a
gate connected to a connecting point of the resistor 236a and the
PTC thermistor 351a, a drain connected to a terminal 202a of the
protection controller 201a, and a source connected to the ground.
The drain of the MOS-FET 231a is connected to a connecting point
between voltage-dividing resistors 237a and 239a connected in
series between the input terminal VIN and the ground.
[0039] The drain of the MOS-FET 231a is connected to drains of
n-type MOS-FETs 251a and 253a that are connected in parallel. The
MOS-FETs 251a and 253a have sources connected to the ground. The
MOS-FET 251a has a gate connected to the BMC 203a. The MOS-FET 253a
has a gate connected to the BMC 203c included in the common
sub-system 151c.
[0040] A power-supply terminal VCC supplies power for driving of
the protection controller 201a, the VRs 205a to 209a and the BMC
203a. The main sub-system 151b also has a similar configuration,
and the common sub-system 151c is different in that it does not
include a MOS-FET corresponding to the MOS-FET 253a that operates
with a signal of the BMC 203a, 203b of another main sub-system
151a, 151b.
[0041] FIG. 5 is a schematic diagram describing the circuit
configuration of the VR 205a. Although the VR 205a actually
includes still more elements, FIG. 5 illustrates the elements in
the range required for understanding of the present invention. The
VR 205a mainly includes a PWM controller 301, a switching circuit
303 and a reactor 313. The switching circuit 303 is configured so
as to include a driver circuit 305, n-type MOS-FETs 309 and 311, a
temperature detection circuit 307 and the like incorporated into
one semiconductor chip.
[0042] The driver circuit 305 receives a PWM signal from the PWM
controller 301 and switching-controls the MOS-FETs 309 and 311
connected in series in the fork power lane 204a in a synchronous
rectification manner so as to convert input voltage V11 to stable
output voltage V21 and outputs it to an output terminal VOUTr via a
node 333 and the reactor 313. The driver circuit 305 includes an
operational amplifier, and so measures current I11 flowing through
the MOS-FET 311 that is calculated from the input voltage V11 at
the node 331, the output voltage V21 at the node 333, the ON
resistance of the MOS-FET 311 on the low side and the voltage at
the node 333, output current I21 calculated from the resistance of
the reactor 313 and the voltage at a capacitor 315, and the
like.
[0043] The driver circuit 305 feedbacks the output voltage V21 at
the node 333 to the PWM controller 301. Then the PWM controller 301
compares the fed-back voltage Vfb with set voltage to control the
duty ratio of the PWM signal. If abnormality occurs in the input
voltage V11, the output voltage V21, the current I21, I22 and the
like, and if ON resistance or OFF resistance of the MOS-FETs 309
and 311 calculated from voltage and current changes by a preset
value or more, the driver circuit 305 outputs an error signal to
the PWM controller 301.
[0044] The temperature detection circuit 307 includes a temperature
sensor incorporated into the semiconductor chip of the switching
circuit 303, and if the internal temperature T1 of the
semiconductor chip exceeds a predetermined value, then the
temperature detection circuit sends an error signal to the PWM
controller 301. Receiving an error signal from the driver circuit
305 or the temperature detection circuit 307, the PWM controller
301 outputs the error signal to the BMC 203a. The error signal may
be sent directly from the driver circuit 305 to the BMC 203a by
skipping the PWM controller 301.
[0045] The PTC thermistor 351a is attached to the surface of the
switching circuit 303 or the vicinity thereof, and is connected in
series with other PTC thermistors 353a and 355a between the input
terminal VIN (FIG. 4) of the source power lane 234a and the ground
in a circuit independent of the VR 205a. The VRs 207a and 209a also
may be configured similarly.
[0046] Note here that FIGS. 1 to 5 illustrate simplified
configuration and connection relationship of major hardware
relating to the present embodiment to describe the present
embodiment. In order to make up a power-supply system, many other
devices are used other than those described in the above. Since
they are well-known for those skilled in the art, detailed
descriptions thereon are omitted here. A group of blocks is
illustrated in the drawing may be one integrated circuit or device,
or conversely one block may be divided into a plurality of
integrated circuits or devices, which also are included in the
scope of the present invention as long as they are in the range
where those skilled in the art can select freely.
[0047] Referring now to the flow diagram of FIG. 6, the operation
of the power-supply system in FIGS. 4 and 5 is described below. The
following mainly describes the operation of the main sub-system
151a, and the operation of the main sub-system 151b and the common
sub-system 151c also can be understood similarly. At block 401, the
power terminal 105a and the signal terminal 1056 of the server unit
100a are connected to the midplane 13 in the energization state.
Then the protection controller 201a of the main sub-system 151a is
turned ON. At this time, the MOS-FETs 231a, 251a and 253a are
OFF.
[0048] When the protection controller 201a detects input voltage
VIN via the voltage-dividing resistors 237 and 239, the protection
controller controls the gate voltage of the MOS-FET 235a to
suppress inrush current. When the inrush current disappears, the
protection controller 201a turns the MOS-FET 235a ON completely.
Subsequently at block 403, the Vas 205a to 209a start operation to
supply power to the loads 211a to 215a.
[0049] At block 405, abnormality, such as increase in ON resistance
or OFF resistance of the MOS-FETs 309, 311, occurs at the VR 205a,
which may be a sign of or lead to resistor short-circuit of the
MOS-FET 309. At block 407, when the driver circuit 305 detects
abnormality at the VR 205a from the voltage V11, V21, the current
I11, I21 and the like, then the driver circuit outputs an error
signal, and the procedure proceeds to block 409. When the
temperature detection circuit 307 detects abnormality at the
internal temperature T1 as well, the temperature detection circuit
outputs an error signal, and the procedure proceeds to block
409.
[0050] At block 409, when the PWM controller 301 receives an error
signal from the driver circuit 305 or the temperature detection
circuit 307, then the PWM controller outputs the error signal to
the BMC 203a, in response to the error signal, the BMC 203a turns
the MOS-FET 251a ON. Then, the potential at the terminal 202a
drops, so that the protection controller 201a turns the MOS-FET
235a OFF, meaning that power-supply to all of the VRs 205a to 209a
stops. The circuit in which the driver circuit 305 or the
temperature detection circuit 307 outputs an error signal to turn
the MOS-FET 235a OFF is called a primary protection circuit.
[0051] When only the VR corresponding to the failure is stopped
through blowout of the fuse as in the power-supply system of FIG.
7, latch up may occur at the load of the VR keeping the operation
after the failure. On the other hand, in the present embodiment,
latch up does not occur because all of the VRs 205a to 209a stop.
Herein latch up is a phenomenon where parasitic transistor of a
bipolar type that is formed at a CMOS-type integrated circuit (IC)
turns a conductive state, and the IC causing latch up may be
broken. The VRs 207a, 209a, the main sub-system 151b and the common
sub-system 151c also operate similarly when abnormality occurs.
[0052] The primary protection circuit is effective for the case
where the PWM controller 301 and the driver circuit 305 or the
temperature detection circuit 307 can output an error signal.
However, they may fail due to heat prior to output of an error
signal. The primary protection circuit may be configured so as to
send a signal directly from the driver circuit 305 or the
temperature detection circuit 307 to the terminal 202a of the
protection controller 201a by skipping the BMC 203a.
[0053] At block 421, when the temperature at the PTC thermistor
351a to detect temperature increases along with the operation of
the primary protection circuit and exceeds the Curie temperature,
then the resistance value suddenly increases. As a result, the
MOS-FET 231a turns ON because the gate voltage increases, meaning
that the potential at the terminal 202a decreases, and so the
protection controller 201a turns the MOS-FET 235a OFF. At this
time, the protection controller 201a informs the BMC 203a of
stopping of power-supply to the source power lane 234a. The MOS-FET
235a turns OFF when the resistance of the PTC thermistors 353a and
355a corresponding to the VRs 207a and 209a increase as well.
[0054] The circuit where the PTC thermistors 351a to 355a turn the
MOS-FET 235a OFF is called a secondary protection circuit. The
secondary protection circuit is a system independent of the
switching circuit 303, the PWM controller 301 and the BMC 203a
making up the primary protection circuit, and so is not affected
from the heat generated at the switching circuit 303. In this way,
the secondary protection circuit can protect the circuit reliably
even when the primary protection circuit does not function. If both
of the primary protection circuit and the secondary protection
circuit do not function, then the MOS-FET 309 will burn in time.
Since the present embodiment has a double protection circuit, such
risk is low.
[0055] If the primary protection circuit or the secondary
protection circuit operates so as to stop the common sub-system
151c, then the main sub-systems 151a and 151h cannot fulfill the
function as the server unit 100. At block 411, when the common
sub-system 151c turns the MOS-FETs 235a to 235c for protection OFF,
then the procedure proceeds to block 413. When a failure occurs at
the VRs 205c to 209c, then the BMC 203c in the common sub-system
151c turns the MOS-FET 235c OFF and at the same time turns the
MOS-FETs 235a and 235b of the main sub-systems 151a and 151b
OFF.
[0056] The main sub-systems 151a and 151b are configured so that
only one of them can fulfill the function as the server unit 100
together with the common sub-system 151c. That is, even when one of
the main sub-systems 151a, and 151b turns the MOS-FETs 235a and
235b OFF, this does not stop the other main-sub system and the
common sub-system 151c.
[0057] At block 415, the BMC 203a to 203c that turns the MOS-FET
235a to 235c OFF informs the CMM 17 as such. Then the CMM 17
displays the error contents on the front panel 23. When the MOS-FET
235a is turned OFF through the operation of the MOS-FETs 231a, 251
a, and 253a, the protection controller 201a does not return the
state unless the user resets manually, so as to ensure the
security.
[0058] As has been described, the present disclosure provides a
method for improving the safety of a voltage regulator having a
switching element.
[0059] While the disclosure has been particularly shown and
described with reference to a preferred embodiment, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the disclosure.
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