U.S. patent application number 09/269679 was filed with the patent office on 2001-08-16 for electric heater for a motor vehicle.
Invention is credited to EISENHARDT, HARALD, FALLIANO, ROLF.
Application Number | 20010013512 09/269679 |
Document ID | / |
Family ID | 7837522 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013512 |
Kind Code |
A1 |
EISENHARDT, HARALD ; et
al. |
August 16, 2001 |
ELECTRIC HEATER FOR A MOTOR VEHICLE
Abstract
An electric heater for a motor vehicle uses heat generated by
power semiconductors as the heat source. The heat output by the
power semiconductors is used directly for heating. The power
semiconductors are regulated by circuit regulators to be able to
adjust the heating power continuously. In addition, switching
devices are provided which interrupt or shut down the respective
branch circuits individually in the event of short circuits in the
power semiconductors.
Inventors: |
EISENHARDT, HARALD;
(RUTESHEIM, DE) ; FALLIANO, ROLF; (STEINENBERG,
DE) |
Correspondence
Address: |
KENYON & KENYON
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
7837522 |
Appl. No.: |
09/269679 |
Filed: |
June 9, 1999 |
PCT Filed: |
July 13, 1998 |
PCT NO: |
PCT/DE98/01948 |
Current U.S.
Class: |
219/202 ;
219/209; 219/476; 257/E25.03 |
Current CPC
Class: |
H05B 1/0236 20130101;
H01L 2924/3011 20130101; H01L 2924/0002 20130101; B60H 1/2215
20130101; H05B 1/0205 20130101; H01L 25/162 20130101; H05B 3/14
20130101; H01L 2924/0002 20130101; H01L 2924/00 20130101; B60H
2001/2271 20130101 |
Class at
Publication: |
219/202 ;
219/209; 219/476 |
International
Class: |
H05B 003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 1997 |
DE |
197 33 04 |
Claims
1. An electric heater for a motor vehicle, using heat generated by
power semiconductors as the heat source, characterized in that
several branch circuits (Z1, Z2, Zn), each with one power
semiconductor (FET1, FET2, FETn) operated in high power loss
operation, are connected in parallel for generation of heat.
2. An electric heater for a motor vehicle, using heat generated by
power semiconductors as the heat source, characterized in that
several branch circuits (Z1, Z2, Zn), each with two
series-connected power semiconductors (FET11, FET12; FET21, FET22;
FETn1, FETn2) operated in high power loss operation, are connected
in parallel for generation of heat.
3. The electric heater according to claim 1 or 2, characterized in
that a switching device (FUSE1, FUSE2, FUSEn) which responds to
overload is connected in series to the power semiconductor (FET1,
FET2, FETn) in each branch circuit (Z1, Z2, Zn).
4. The electric heater according to claim 1 or 3, characterized in
that the power output by the power semiconductors (FET1, FET2,
FETn) can be regulated individually by a common predetermined
setpoint (Isoll) and by actual values (Ist1, Ist2, . . . , Istn)
derived from the power semiconductors (FET1, FET2, . . . ,
FETn).
5. The electric heater according to claim 2 or 3, characterized in
that the powers output by the respective first power semiconductors
(FET11, FET21, FETn1) of the branch circuits (Z1, Z2, Zn) can be
regulated individually by a common predetermined setpoint,(Isoll)
and by actual values (Ist11, Ist21, . . . , Istn1) derived at these
power semiconductors, and the powers output by the respective
second power semiconductors (FET12, FET22, . . . , FETn2) can be
regulated individually by a fixed predetermined control voltage
(ust) and by actual values (Ist12, Ist2, . . . , Istn2) derived at
these power semiconductors.
6. The electric heater according to one of claims 1 through 5,
characterized in that the power semiconductors (FET1, FET2, . . . ,
FETn; FET11, FET12, FET21, FET22, . . . FETn1, FETn2) are operated
in the short circuit.
7. The electric heater according to one of claims 1 through 6,
characterized in that the branch circuits (Z1, Z2, . . . , Zn)
supply power at the output to a low-resistance series resistor as a
load impedance.
8. The electric heater according to one of claims 1 through 7,
characterized in that the switching devices (FUSE1, FUSE2, . . . ,
FUSEn) are designed as a printed conductor part of the branch
circuits (Z1, Z2, . . . , Zn) which burn out in the event of a
fault at the elevated current occurring in the respective branch
circuit (Z1, Z2, . . . , Zn).
9. The electric heater according to one of claims 1 through 7,
characterized in that the switching devices (FUSE1, FUSE2, FUSEn)
are looped as shunts into branch circuits (Z1, Z2, Zn) which burn
out in the event of a fault at the elevated current occurring in
the respective branch circuit (Z1, Z2, . . . , Zn).
10. The electric heater according to one of claims 1 through 7,
characterized in that the connecting wires of the power
semiconductors (FET1, FET2, FETn; FET11, FET12, FET21, FET22,
FETn1, FETn2) are used as switching devices (FUSE1, FUSE2, FUSEn)
which burn out in the event of a fault at the elevated current
occurring in the respective branch circuit (Z1, Z2, Zn).
11. The electric heater according to one of claims 2, 3 and 5
through 7, characterized in that in the event of a short circuit in
one of the two power semiconductors (FET11 or FET12; FET21 or
FET22; FETn1 or FETn2) connected in series in a branch circuit (Z1,
Z2, Zn), an additional control signal can be derived from the
defective branch circuit (Z1, Z2, Zn) to reduce the power output by
the respective second power semiconductor (FET12 or FET11; FET22 or
FET21; FETn2 or FETn1) or switch it to a disconnect status.
12. The electric heater according to one of claims 1 through 11,
characterized in that it is designed as a heater module, with the
power semiconductors (FET1, FET2, . . . , FETn; FET11, FET12;
FET21, FET22; FETn1, FETn2) mounted in thermal contact on a cooling
body.
13. The electric heater according to claim 12, characterized in
that the power semiconductors (FET1, FET2, . . . , FETn; FET11,
FET12, FET21, FET22, . . . , FETn1, FETn2) and/or the cooling body
are monitored by temperature sensors to detect whether a
predetermined maximum temperature is exceeded, and in that the
output signals of the temperature sensor(s) reduce the power output
of the respective power semiconductors or all the power
semiconductors or switch them to a disconnect status.
14. The electric heater according to claim 13, characterized in
that the temperature sensors are integrated into the power
semiconductors (FET1, FET2, . . . , FETn; FET11, FET12, FET21,
FET22, . . . , FETn1, FETn2).
Description
BACKGROUND INFORMATION
[0001] The present invention relates to an electric heater for a
motor vehicle, using the heat generated by power semiconductors as
the heat source.
[0002] Such a heater is known from German Patent No. 34 42 350 C2.
With this known heater, the power semiconductor controls the
electric drive motor. The power semiconductor is connected to a
cooling body through which a liquid coolant flows, so the heat
generated is transferred to the liquid coolant by heat exchange.
The liquid coolant circulates in a closed line system having a pump
and the actual heater installation.
[0003] The efficiency of this known electric heater is not
especially great, because the heat generated by the power
semiconductor must be converted repeatedly. In addition, the heater
installation has a complicated design, depends on the engine
current present and thus cannot be regulated independently of the
latter.
SUMMARY OF THE INVENTION
[0004] The object of the present invention is to create an electric
heater of the type defined in the preamble where the efficiency is
greatly increased with a simple design and independent regulation
of heating power is possible.
[0005] This object is achieved according to a first embodiment of
the present invention by connecting several branch circuits, each
with one power semiconductor operated in high power loss operation,
in parallel for generation of heat, or according to a second
embodiment by connecting several branch circuits, each with two
series-connected power semiconductors operated in high power loss
operation, in parallel for generation of heat.
[0006] In these embodiments, the current is converted directly into
heat by the power semiconductors, which greatly increases
efficiency. Another advantage of the new heater is that no
additional control module is needed for the heater. Installation of
the heater in the motor vehicle is also greatly simplified. In
addition, the cabling complexity and manufacturing costs of the new
electric heater are also reduced.
[0007] No separate fuse protection for the heater in the vehicle
electrical system is necessary. When starting operation of the
heater, the high starting current surge can be prevented by a
regulated smooth current rise. The new heating module can be
cascaded in any desired fashion to increase the heating power and
can also be integrated easily into a fan regulator.
[0008] To protect the power semiconductors, one embodiment provides
for a switching device that responds to overload to be connected in
series with the power semiconductor in each branch circuit. In the
event of a fault, the branch circuit affected can be shut down with
this switching device without having to lose heater function as a
whole. Heating power is reduced only by the ratio of defective
branch circuits to total branch circuits.
[0009] According to one embodiment, regulation of the heating power
is easily made possible by the fact that the power output by the
power semiconductors can be regulated individually by a common
predetermined setpoint and by actual values derived from the power
semiconductors, or by the fact that the powers output by the
respective first power semiconductors of the branch circuits can be
regulated individually by a common predetermined setpoint and by
actual values derived at these power semiconductors, and the powers
output by the respective second power semiconductors can be
regulated individually by a fixed predetermined control voltage and
by actual values derived at these power semiconductors.
[0010] If the branch circuits are to supply power at the output to
a low-resistance series resistor as a load impedance, then the heat
generated by the series resistor can contribute to an increase in
heating power. Each power semiconductor can supply power to an
individual series resistor. All the power semiconductors may also
supply power to a common series resistor, or groups of power
semiconductors may each be connected to a group-individual series
resistor.
[0011] The switching devices for interrupting the branch circuits
can be implemented in various ways. Thus, according to one
embodiment, the switching devices may be designed as a printed
conductor part of the branch circuits which burn out in the event
of a fault at the elevated current occurring in the respective
branch circuit. The same effect can also be achieved by looping the
switching devices as shunts into the branch circuits, which burn
out in the event of a fault at the elevated current occurring in
the respective branch circuit, in which case the shunt can also be
used to derive another control signal. Finally, the branch circuit
can also be interrupted by using the connecting wires of the power
semiconductors which burn out in the event of a fault at the
elevated current occurring in the respective branch circuit.
[0012] A controlled reduction or interruption in the current in a
defective branch circuit occurs when measures are taken to ensure
that in the event of a short circuit in one of the two power
semiconductors connected in series in a branch circuit, an
additional control signal can be derived from the defective branch
circuit to reduce the power output by the respective second power
semiconductor or switching it to a disconnect status. The control
signal picked off at the shunt can be used as the control
signal.
[0013] The structural design of the new electric heater can be
simplified by designing it as a heater module, with the power
semiconductors mounted in thermal contact on a cooling body, with
the heat transfer via the cooling body being improved.
[0014] Simple temperature monitoring can be achieved with the
electric heater by the fact that the power semiconductors and/or
the cooling body are monitored by temperature sensors to detect
whether a predetermined maximum temperature is exceeded, and by the
fact that the output signals of the temperature sensor(s) reduce
the power output by the respective power semiconductors or all the
power semiconductors or switch them to a disconnect status. If the
power semiconductors are monitored by individual temperature
sensors, the expense of this is reduced by integrating the
temperature sensors into the power semiconductors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will now be explained in greater
detail on the basis of embodiments illustrated in the drawings,
which show:
[0016] FIG. 1: a circuit diagram of an electric heater with n
parallel branch circuits, each containing one power semiconductor,
and
[0017] FIG. 2: a circuit diagram of an electric heater with n
parallel branch circuits, each having two series-connected power
semiconductors.
DETAILED DESCRIPTION
[0018] As FIG. 1 shows, branch circuits Z1, Z2, . . . Zn are
connected in parallel to one another at power supply voltage Ubatt,
with each branch circuit Z1, Z2, . . . , Zn having a power
semiconductor FET1, FET2, . . . , FETn. The connection to power
supply voltage Ubatt is by way of switching devices FUSE1, FUSE2, .
. . , FUSEn, which perform an individual interruption of branch
circuit Z1, Z2, . . . , Zn in the event of a fault, e.g., a short
circuit of the power semiconductor at which the multiple current
occurs. A shunt which is not shown in detail may be added to the
connection of power semiconductors FET1, FET2, . . . , FETn at the
ground potential, where an individual actual value Ist1, Ist2, . .
. Istn can be derived for the branch circuit Z1, Z2, . . . , Zn. In
addition to the actual value picked off at the shunt, a setpoint
Isoll is supplied to the gate terminal of power semiconductors
FET1, FET2, FETn via a comparator or operational amplifier that
serves as a circuit regulator to permit continuous regulation of
the power in the respective power semiconductor. If the actual
value exceeds setpoint Isoll, then the circuit regulator switches
the power semiconductor into the disconnect status or reduces the
power output. In addition, switching device FUSE1, FUSE2, . . . ,
FUSEn can completely interrupt branch circuit Z1, Z2, . . . , Zn in
the event of a short circuit of respective power semiconductor
FET1, FET2, . . . , FETn.
[0019] Printed conductor segments of branch circuit Z1, Z2, . . . ,
Zn themselves can be used as switching devices FUSE1, FUSE2, FUSEn.
Depending on the design of branch circuits Z1, Z2, Zn and the
respective circuit regulator, the current may increase to a level
25 to 50 times higher in the event of a short circuit, so the
printed conductor part burns out. The shunt can also be used as a
switching device if it burns out with this current rise and
interrupts branch circuit Z1, Z2, . . . , Zn. Even the connecting
wires of power semiconductors FET1, FET2, . . . , FETn can be
dimensioned to assume the function of switching devices FUSE1,
FUSE2, . . . , FUSEn. The electric heater of this type may be
designed as a heater module, mounted on a cooling body and
integrated into a fan regulator; furthermore, the heater module
itself need no longer be fused with respect to the vehicle's
electrical system. However, it may be necessary to fuse the feeder
lines to the heater module.
[0020] In the embodiment according to FIG. 2, each branch circuit
Z1, Z2, . . . , Zn has two series-connected power semiconductors
FET11 and FET12, FET21 and FET22, . . . FETn1 and FETn2, each
controlled by its own circuit regulator. As in the embodiment
according to FIG. 1, a switching device FUSE1, FUSE2, FUSEn and a
shunt can be looped into branch circuits Z1, Z2, . . . , Zn.
Switching devices FUSE1, FUSE2, . . . , FUSEn in turn can be
designed in the variants described. Control signals characterizing
actual value Ist11, Ist21, . . . Istn1 of branch circuit Z1, Z2, .
. . , Zn can be picked off at the shunts of the branch circuits and
sent to the circuit regulators of the respective first power
semiconductors FET11, FET21, . . . , FETn1 to which can also be
sent a setpoint Isoll to regulate the power in branch circuit Z1,
Z2, . . . , Zn. The second power semiconductors FET12, FET22, . . .
, FETn2 are controlled by separate circuit regulators to which are
sent a fixed predetermined control voltage ust and an actual value
Ist12, Ist22, . . . , Istn2, which is derived from the voltage drop
at the first upstream power semiconductor FET11, FET21, FETn1. In
the event of a short circuit or defect in a power semiconductor
such as FET11 with this design of the circuit regulators, the
respective second power semiconductor, such as FET12, in branch
circuit Z1 can be shut down or the power output by it can be
reduced. However, the functioning of the remaining system is not
affected, and the heating power is merely reduced by the ratio of
defective branch circuits to total branch circuits.
[0021] If both power semiconductors, e.g., FET21 and FET22, are
short-circuited, then the switching device, e.g., FUSE2 as in the
embodiment according to FIG. 1, goes into operation and interrupts
the branch circuit, e.g., Z2, at the high current rise
occurring.
[0022] If only one common heat-dissipating, low-resistance series
resistor is used as the load impedance for all branch circuits Z1,
Z2, . . . , Zn to increase the heating power, then this resistor is
looped into the common line leading to battery voltage Ubatt. This
series resistor does not change the operation of the electric
heater, it merely limits the current rise to a lower level in the
event of a short circuit in a single power semiconductor (FIG. 1)
or both power semiconductors (FIG. 2), but this lower level is
still sufficient for a reliable response of switching device FUSE1,
FUSE2, . . . , FUSEn. The heat generated by the series resistor is
also used for heating, but it entails a power distribution which
can be utilized at a predetermined maximum heating power to expand
the temperature use range for the heater.
[0023] Each power semiconductor or each pair of power
semiconductors can also be connected to battery voltage Ubatt
across an individual series resistor. Groups of branch circuits may
also supply a series resistor. In any case, all the series
resistors are involved in the production of heat.
[0024] Temperature monitoring can easily be incorporated into the
new heater. Thus, a temperature sensor may be provided for each
power semiconductor and may also be integrated into the power
semiconductor. If a predetermined maximum temperature is exceeded
at the power semiconductor, the output signal of the temperature
sensor then controls the respective power semiconductor so that its
power output is reduced or it is completely shut down.
[0025] It is also possible to provide just one temperature sensor
for measuring the temperature of the cooling body, with all the
power semiconductors of the electric heater being in thermal
contact with it. If the temperature of the cooling body exceeds a
predetermined maximum temperature, then all the power
semiconductors are controlled with the output signal of the
temperature sensor in such a way that their power output is reduced
or they are completely shut down. Different values of the output
signal of the temperature sensor can be used for this purpose, with
the output signal initially triggering a power reduction at the
first lower value and a complete shutdown at the second higher
value of the output signal.
* * * * *