DE102012207654A1 - Motor vehicle-generator device has generator stabilizer, generator, rectifier and protection arrangement for noise suppression, where protection arrangement is formed such that suppresses short, low-power noise pulse - Google Patents

Abstract

The motor vehicle-generator device has a generator stabilizer (12), a generator, a rectifier (14) and a protection arrangement (15) for noise suppression, where the protection arrangement is formed such that suppresses short, low-power noise pulse. The rectifier has load dump protection elements (D1 to D6). The protection arrangement is formed such that it performs a limitation of noise voltage peaks at below the limit voltage of the load dump protection elements.

Description

The invention relates to a motor vehicle generator device with a protective device for noise suppression.

(State of the art)

Generator devices, which are provided for providing a voltage required in the electrical system of a motor vehicle DC voltage, are already known. Such generator devices have a generator controller, a generator and a rectifier, which converts the AC voltage generated by the generator usually using rectifier diodes into a DC voltage. For example, the alternating voltages of the three phases of an alternator are converted into DC voltage by means of six diodes, which are connected as a so-called B6 bridge. The output voltage UB + of a generator is usually controlled by means of a generator regulator. It is dependent on several influencing factors, which include the speed, the electrical load, the state of charge of the battery and the temperature. This regulation takes place via an adaptation of the exciter current flowing through the field winding of the generator, for example via a change of the pulse duty factor (pulse width modulation or PWM).

The rectifier diodes are designed for operation at high currents or at current densities of up to 500 A / cm ² and high temperatures, for example a junction temperature Tj <225 ° C. Typically, the voltage drop in the flow direction, the forward voltage UF, at the high currents used is about 1 volt. When operating in the reverse direction, however, generally only a very small reverse current IR flows up to a breakdown voltage UZ, which is about 20-40 volts depending on the vehicle electrical system voltage of the motor vehicle. From this voltage, the reverse current increases sharply. A further increase in voltage is therefore prevented. The diodes can be loaded in the breakthrough at least briefly with very high currents. They are therefore used to limit the excess generator voltage during load changes or load dump. In addition to these very rare load dump events occur at the output of a generator often transient, low-power voltage spikes or spikes, which can come for example from the electrical system connected to the generator system. These spikes often have a high repetition rate. These voltage peaks are also limited by the generator diodes.

In the 1 an example of such spikes is shown. In this case along the abscissa the time and along the ordinate the generator output voltage U is plotted, this diagram illustrates the time course of the generator output voltage of a three-phase generator very high speed and high charging current. The voltage spike indicated by an arrow corresponds to the diode breakdown voltage UZ. The duration of the voltage spike is about 100 ns. This spike occurs in the example shown about once per second. The horizontally extending flat line between 13.5 V and 14 V corresponds to the generator voltage UB +.

There must be a certain distance between the voltage UB + and the breakdown voltage UZ of the diodes, since during operation of a generator in certain operating states high energy-rich voltages occur over a longer period of time (waviness), which would lead to unacceptably high power losses in the diodes, if they are permanent would be operated in breakthrough. The relatively large voltage difference between the voltage UB + of a generator of for example 13.5 V and the breakdown voltage UZ of the diodes of, for example, 22 V represents a disadvantage. Voltage spikes can therefore occur up to a voltage of approximately UZ before being limited.

In the case of generators with pn diodes, the forward voltage drops at the diodes in the forward direction. Since the generator current must always pass through two diodes, there are therefore always two forward voltages. With the commonly used pn diodes, the average forward losses for a 100A generator are therefore about 200 W. The associated heating of diodes and rectifiers must be reduced by expensive cooling measures (heat sink, fan).

To reduce the forward losses, special Schottky diodes with a low forward voltage, referred to below as high-efficiency diodes or HEDs, can be used instead of the pn diodes. This reduces the diode losses by about 40%. The generator efficiency increases as a result. To reduce the reverse current, HEDs contain additional structures in addition to the actual Schottky contact. An arrangement which has proven to be particularly favorable is what is known as the trench MOS barrier Schottky diode (TMBS). A disadvantage of such diodes is that the reverse voltage increases during operation in the breakthrough and that this case of operation is only a limited time, based on the life of the device is allowed. The structure and operation of such diodes are for example in the DE 10 2010 028 203 described. Furthermore, special MOSFETs with very low threshold voltages, so-called pseudo-Schottky diodes (PSDs), can be used to reduce forward losses.

Disclosure of the invention

According to the present invention, a motor vehicle generator device is proposed which advantageously limits short, low-power spikes to voltages below the breakdown voltage of the load dump protection elements of the rectifier, which are preferably HEDs, such that the HEDs only in the case high, powerful - but less frequent - voltage increases (load dump) are burdened. This protects the system from very common voltage spikes without increasing the breakdown voltage of the diodes. Regardless of whether HEDs, PSDs or conventional pn-limiter diodes are used as rectifier diodes, low-power voltage peaks are also limited to values that are lower than the breakdown voltage UZ of the diodes.

The invention will be described below with reference to FIG 2 - 5 exemplified in more detail. It shows:

2 a circuit diagram of a motor vehicle generator apparatus according to the invention,

3 a diagram in which the breakdown current IZ is plotted against the generator output voltage UB +,

4 an embodiment of a realized as a semiconductor device protective resistor and

5 an embodiment of a realized as a semiconductor device protection arrangement.

An embodiment of a motor vehicle generator device according to the present invention is in the form of a simplified circuit diagram in the 2 shown. This generator device has an alternator 13 , which is designed here as a 3-phase alternator, a rectifier 14 with a total of six HEDs D1 to D6 designed as trench MOS barrier Schottky diodes (TMBS), an interference suppression capacitor C and a generator regulator 12 on, which contains a semiconductor device IC. For clarity, other elements of the regulator, such as EMC capacitors, interfaces, etc., in the 2 not shown. In the embodiment shown is the protective arrangement according to the invention 15 in the regulator 12 or integrated in the controller housing. In principle, however, the protective arrangement can also be integrated in the rectifier. Electrical represents the protection arrangement 15 a series connection of a protective diode 15a with a protective resistor 15b dar. The breakdown voltage of the protective diode 15a is UZS. Furthermore, in the 2 the motor vehicle electrical system shown, which has a battery B and a series circuit of a resistor R with an inductance L.

The protection arrangement 15 For example, as a series connection of a discrete protection diode 15a with a discrete protective resistor 15b or as an integrated element, in which the protective diode and the protective resistor are integrated in a semiconductor device, executed and in the controller housing 12 be mounted. Particularly advantageously, the protection arrangement can be integrated directly in the controller IC monolithic. Alternatively, the elements of the protection arrangement may also be mounted as discrete or integrated elements in press fit diode housings which are incorporated into the heat sink of the rectifier 14 are pressed.

The dimensioning of the voltage UZS at which the breakdown of the protective diode 15a starts, and the protective resistance 15b Depends on the breakthrough voltage range UZTOL2 - UZTOL1 caused by manufacturing tolerances of the breakdown voltage UZ of the diodes D1 to D6. UZ denotes the breakdown voltage of the diodes D1 to D6 at low breakdown currents IZ of, for example, 100 mA. This actually corresponds to the beginning of the voltage breakdown. UZTOL2 is the maximum production breakdown voltage UZ of the diodes D1 to D6, and UZTOL1 the lowest occurring voltage UZ. UZS and the resistance value RS of the protective resistor are designed so that the following relationships apply: UZS <UZTOL1 - UF (1) RS = (UZTOL2 - UF - UZS) / IZ (2)

In this case, it is considered that the following relationship applies between the generator voltage UB + and the breakdown voltage UZ of the diodes D1 to D6 because of the second Kirchoff law: UB + = UZ - UF (3)

The 3 shows a diagram in which along the abscissa the generator output voltage UB + and along the ordinate of the breakdown current IZ is plotted. In this diagram, an example is shown in which with respect to a breakdown current IZ = 100 mA, the breakdown voltage UZTOL2 26 V, the breakdown voltage UZTOL1 22 V and the forward voltage UF at high currents is 0.5 V each. The breakthrough of the protective diode 15a starts at UZS = 20 V. Taking into account the above relationship (2), this results in a resistance RS = 55 ohms.

Depending on the tolerance position of the breakdown voltage UZ, the diodes D1 to D6 start to break through between a breakdown current IZ of 27.3 mA and 100 mA. For glitches that result in smaller currents, the overvoltage from the protection arrangement 15 taken over without the diodes D1 to D6 being charged. This works especially as protection of TMBS diodes. In addition, the voltage at the vehicle electrical system is, at least insofar as the current is low, advantageously limited to values which are lower than the breakdown voltage UZ-UF. The electrical load on the protection arrangement 15 increases with increasing voltage UB +. If the voltage UB +, for example, in the case of a load dump through the diodes clamped to 34 V (worst case), then the short-term, ie for a period of less than 400 ms, lasting power to the protection arrangement would be 15 with UZS = 20 V after the relationship P = UB + · ((UB + - UZS) / RS) (4) about 8.7 W.

The protective diode 15a and the protective resistance 15b can be integrated into the controller IC in an advantageous manner with or alternatively be designed as a separate semiconductor device and soldered or glued into the controller housing. The protection arrangement 15 but can also be designed as a press-fit housing and pressed into a cooling plate of the rectifier. In this case, the thermal losses are very easy to dissipate.

As an alternative to the design of the protective diode as a pn-clamp diode (Zener diode), other voltage limiting elements such as a voltage limited MOSFET or PSDs may be used.

An exemplary embodiment of the protective arrangement is described below, in which the protective arrangement 15 is divided into two press-fit diode housing. Information about press-in diodes as such are for example in the DE 195 49 202 A1 disclosed.

The protective diode 15a is located in a first housing and the protective resistor 15b in a second housing. Both housings are pressed in the usual way in the cooling plates of the rectifier and welded or soldered together at the two leads. As a protective diode, a conventional press-in diode can be used for rectifiers, in which a pn diode between the two copper parts (head wire and socket) is soldered. It only has to have a slightly lower breakdown voltage UZS, where UZS is determined according to the above relationship (1).

As a protective resistor 15b For example, a semiconductor device according to the 4 used, which is provided on both sides with a solderable surface and can be soldered into a press-fit. On a, for example, 3 mm ² large, highly n + doped silicon substrate 1 There is an approximately 10 micron thick, n-doped silicon layer 2 with a doping concentration of about 4.8 × 10 ¹⁵ cm ^-3 . In the center of the semiconductor wafer is a flat, for example, circular, highly n + -doped layer 3 brought in. The diameter of the circular area is, for example, 36 μm. The surface concentration of the layer 3 is about 5 × 10 ¹⁹ cm ^-3 at a penetration depth of less than 0.5 microns.

At the edge of the chip is a circumferential area 4 same doping concentration and penetration depth. It usually becomes with the same doping step as the layer 3 generated. The area 4 extends from the edge of the chip, for example, 70 microns in the direction of the chip center. It is important that the distance of the area 3 from the area 4 is much larger than the thickness of the layer 2 , preferably at least 10 times larger. The surface of the n-doped silicon layer 2 is between the n + doped areas 3 and 4 with a dielectric layer 5 , For example, with a 1 micron thick oxide layer covered. This oxide layer is within the range 3 open. On the top and the bottom of the chip is in each case a metal or a metal system 6 . 7 applied. The metallizations 6 . 7 make ohmic contacts to the areas 3 and 1 and are designed to be solderable. Lies between the contacts 6 and 7 a voltage, then the current between the two contacts spreads from the area 3 about the areas 2 and 1 out. Because of the small area of the connection area 3 the resistance is relatively high despite the large chip area and here is for example 50-60 ohms.

In the 5 In a further embodiment, a protective arrangement is shown in cross-section, both the protective diode 15a as well as the protective resistance 15b contains and is also suitable for mounting in Einpressdiodengehäusen. The semiconductor chip is in this case provided on both sides with a solderable surface. In a about 250 microns thick, with 8.48 · 10 ¹⁵ cm ^-2 n-doped silicon wafer 1 become from the one side structures for the protection diode 15a and from the other side structures for the protective resistance 15b brought in. The chip area of the protective arrangement is, for example, 3 mm ² .

In the center of the semiconductor wafer is on the front side a flat, preferably circular, highly n + -doped layer 3 brought in. The diameter of the circular area is, for example, 36 μm. The surface concentration the layer 3 is about 5 × 10 ¹⁹ cm ^-3 , the penetration depth is less than 0.5 microns. At the edge of the chip is again a circumferential area 4 same doping concentration and penetration depth. It is usually in the same doping step as the layer 3 brought in. The area 4 extends from the edge of the chip, for example, 70 microns in the direction of the chip center. It is again important that the distance of the area 3 from the area 4 much larger than the width of the layer indicated by the letter W. 1 is.

The surface of the n-doped silicon layer 1 is between the n + doped areas 3 and 4 with a dielectric layer 5 , for example with a 1 Covered thick oxide layer. This oxide layer is within the range 3 open. On the top and the bottom of the chip is in each case a metal or a metal system 6 . 7 applied. The metallizations 6 . 7 make ohmic contacts to the areas 3 and 8th respectively. 8a and are designed to be solderable. From the back is an n-doped, Gaussian doped region 10 diffused. Its surface concentration is about 1 × 10 ¹⁹ cm ^-3 , its penetration depth xjP into the area 1 about 82 μm. The diffused area 10 However, does not extend over the entire surface of the back, but has circumferentially a distance E from the chip edge. The distance E is greater than the penetration depth xjP and is for example 140 microns.

Furthermore, a boron layer is from the back 8th with a surface concentration of about 4 × 10 ¹⁹ cm ^-3 diffused over the entire surface. In the middle, the diffusion is in the layer 10 up to a penetration depth of about 37 μm, at the edge in the layer 1 up to a penetration of about 68 microns. This has the diode at the edge, consisting of the p-layer 8a and the n-layer 1 , a much higher breakdown voltage than the internal diode resulting from the layers 8th and 10 composed. The values of the surface concentration and the penetration depths can be chosen somewhat differently, for example if the concentration profile does not have an exactly Gaussian distribution. It is only important that the profiles are designed so that the desired breakdown voltage UZS of, for example, 20 V is established. Alternatively, another, for example, flatter, doping profile for the protective diode 15a or another design for the protective resistor 15b to get voted. This protection arrangement, whose equivalent circuit diagram also in the 5 can in turn be soldered in a conventional manner in a press-fit diode housing and pressed into rectifier and mounted or it can be packed in another suitable housing and in the controller 12 to be assembled.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010028203 [0007]
• DE 19549202 A1 [0022]

Claims (11)

Motor vehicle generator device with a generator controller, a generator and a rectifier, characterized in that it has a protective arrangement ( 15 ) for interference suppression. Motor vehicle generator device according to claim 1, characterized in that the protective arrangement ( 15 ) is designed such that it suppresses short, low-power glitches. Motor vehicle generator device according to claim 1 or 2, characterized in that the rectifier ( 14 ) Loaddumpschutzelemente (D1 to D6) and that the protective arrangement ( 15 ) is designed such that it makes a limitation of interference voltage peaks already below the limiting voltage of the load dump protection elements. Motor vehicle generator device according to one of the preceding claims, characterized in that the protective arrangement ( 15 ) a series circuit of a breakdown voltage (UZS) having protective element ( 15a ) and a protective resistor ( 15b ) contains. Motor vehicle generator device according to claim 4, characterized in that the breakdown voltage of the protective element limits the vehicle electrical system voltage to values which is smaller than the limited by the load dump protection board voltage, as long as a predetermined current is not exceeded by the protective element. Motor vehicle generator device according to one of the preceding claims, characterized in that the protective element ( 15a ) is a breakthrough pn diode. Motor vehicle generator device according to one of Claims 3-6, characterized in that the load dump protection elements (D1 to D6) are pn diodes, trench MOS barrier Schottky diodes, actively clamped transistors, PSDs or pn diodes. Motor vehicle generator device according to one of the preceding claims, characterized in that the protective device ( 15 ) integrated component of the generator controller ( 12 ) or the rectifier ( 14 ). Motor vehicle generator device according to one of claims 4-8, characterized in that the protective resistor ( 15b ) is a discrete resistor. Motor vehicle generator device according to one of claims 4-8, characterized in that the protective element ( 15a ) and the protective resistor ( 15b ) are an integral part of a semiconductor. Motor vehicle generator device according to one of claims 8-10, characterized in that the protective element ( 15a ) and the protective resistor ( 15b ) are mounted in a press-fit diode housing.

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