DE102007050620A1 - Switching arrangement for operating electrical load, comprises controlled switching element for selective connection of operating potential with connection of load, where power supply system provides supply voltage - Google Patents

Abstract

The switching arrangement (10) comprises a controlled switching element (S1) for a selective connection of an operating potential with a connection of an electrical load (L1). A power supply system (24) provides a supply voltage (V1) for a control switch (12). The supply voltage is a potential (V-phase) attached to one of the inputs (K1,K2) of a measuring amplifier (16). The supply voltage is used for a supply voltage (V2) of the measuring amplifier.

Description

• – ein ansteuerbares Schaltelement zum wahlweisen Verbinden eines Betriebspotentials mit einem Anschluss der Last,
• – eine Ansteuerschaltung zum Ansteuern des Schaltelements,
• – einen in Reihenschaltung mit dem Schaltelement angeordneten Strommesswiderstand zur Messung eines Laststromes durch Erfassung einer am Strommesswiderstand abfallenden Messspannung mittels eines Messverstärkers, dessen Eingänge mit den beiden Anschlüssen des Strommesswiderstands verbunden sind.

The present invention relates to a circuit arrangement according to the preamble of claim 1, that is to operate an electrical load and comprising:

• A controllable switching element for selectively connecting an operating potential to a terminal of the load,
• A drive circuit for driving the switching element,
• - A arranged in series with the switching element current measuring resistor for measuring a load current by detecting a falling at the current measuring resistor measuring voltage by means of a measuring amplifier whose inputs are connected to the two terminals of the current sense resistor.

Such a circuit is z. B. from the DE 10 2005 029 813 A1 known and can be used for example for driving an electric drive.

A Particular feature of the known circuit arrangement is that a power supply of the measuring amplifier is designed so that this on one at one of the inputs of the amplifier applied potential is related. This "floating power supply" improves in particular for a strongly varying potential at Current measuring resistor the measurement accuracy significantly.

adversely is the circuitry in the known circuit arrangement Effort to realize this floating power supply for the measuring amplifier. In the known circuit arrangement will be provided one or two specially for this purpose Auxiliary voltage sources (essentially consisting of charge pumps) needed.

In front In this context, it is an object of the present invention to to simplify a circuit arrangement of the type mentioned, without In this case to affect the accuracy of the measurement of the load current.

According to the Invention, this object is achieved in that the circuit arrangement further comprises a power supply, one on one at a The potential applied to the inputs of the measuring amplifier referenced supply voltage for the drive circuit and that this supply voltage as well for the voltage supply of the measuring amplifier is being used.

at The invention thus advantageously a supply voltage for the drive circuit at the same time for the power supply of the measuring amplifier. This results in practice a considerable cost reduction due to a "double use" of power supply components.

The Invention is in particular z. B. for power amplifiers suitable, such as for an inverter for operating a electric drive. A particularly interesting in the context of the invention Field of application is the control of an electric drive in a vehicle (eg in an electric car or so-called Hybrid vehicle). Especially in these applications can the potential at the measuring resistor operational vary widely, suggesting the use of the proposed in the invention floating supply voltage for the measuring amplifier makes sense.

at the controllable switching element is preferably a Power semiconductors (eg transistor, in particular FET).

It It is conceivable that one on one of the inputs of the measuring amplifier applied potential related supply voltage for the drive circuit directly as a supply voltage for the To use measuring amplifier. In a preferred embodiment becomes the supply voltage for the drive circuit however indirectly for the voltage supply of the measuring amplifier used.

From in this case, the "indirect use" of the supply voltage In particular, the case may be included, in which the supply voltage (before the shared use of the measuring amplifier) of a filtering (eg by means of a capacitor, choke etc.) and / or a voltage conversion is subjected. For example, the said supply voltage as supply voltage for a voltage divider or Voltage regulator (eg integrated component) can be used, which in turn provides the supply voltage for the measuring amplifier.

In summary Advantageously, with the present invention, an "integrated Solution "for providing a floating Supply voltage for the measuring amplifier created. In this case, a supply generated for the drive circuit anyway Supply voltage for the voltage supply of the measuring amplifier shared. Despite a simplified supply, the measurement accuracy the load current measurement are maintained.

The Invention will be described below with reference to an embodiment further described with reference to the accompanying drawings. It shows:

1 a partially schematic circuit diagram of a circuit arrangement for operating an electric motor.

1 shows components of a power amplifier 10 for operating a three-phase AC electric motor EM, of which in the figure three star-connected excitation windings L1, L2 and L3 are shown.

The beyond in 1 Components shown are used for selectively applying a terminal of the winding L1 with a first phase potential Vphase (and the load current measurement).

to Actuation of the corresponding connections of the other Windings L2 and L3, corresponding components are provided, each identical to the circuit part shown in the figure are formed. It is therefore unnecessary a separate Description of these provided for the windings L2 and L3 Components.

to Energization of the motor windings L1 to L3 is a main source of voltage (Here, for example, a driving battery of a hybrid vehicle) provided which the main supply potentials Vbat + and Vbat- supplies. For a driving battery of an electric vehicle or hybrid vehicle is the difference between these potentials (= battery voltage) typically more than 100 V.

Between These potentials Vbat + and Vbat- are two switching transistors S1 and S1 'arranged in series (so-called half-bridge), the be switched on alternately during operation of the electric motor EM. Thus, the above-mentioned (phase) connection of the winding L1 alternately connected to the potentials Vbat + and Vbat- become. The phase connection is for this purpose over a Current measuring resistor ("shunt") Rs connected to an output node K0, via which the two switching transistors S1 and S1 'connected to each other are.

The switching transistor S1 is as shown by a first drive circuit 12 whereas the switching transistor S1 'is driven by a second drive circuit 14 is controlled. According to the number of 3 motor windings, the total system for driving the motor EM actually has a total of 3 × 2 = 6 switching transistors and 6 drive circuits.

The current measuring resistor Rs arranged in series with each of the switching transistors S1 and S1 'is used to measure a load current flowing from the output node K0 to the winding L1 (or vice versa) by detecting a measuring voltage Vin falling across the resistor Rs by means of a measuring amplifier 16 ,

The measuring amplifier 16 is designed as a fully differential differential amplifier (eg, operational amplifier with external circuitry (negative feedback)) and thus has a non-inverting amplifier input and an inverting amplifier input, between which the measurement voltage Vin is applied.

In the illustrated embodiment, the measuring amplifier 16 on the output side, a fully differential analog / digital converter 18 downstream of which an output signal Vout of the amplifier 16 is supplied and in turn an "isolation block" 20 which is the (digital) output signal Dout of the converter defined by a differential voltage 18 into a fixed reference potential (digital) signal Dout '.

in the Operation of the electric motor EM varies at the output node K0 of Half bridge prevailing potential Vphase very strong (between Vbat + and Vbat-). This potential Vphase is also on the two terminals of the current sense resistor Rs (Der Difference between the two potentials at the two connections of the resistance Rs (= measuring voltage) is in practice opposite the variation of the potential Vphase negligible).

In order that the measurement of the voltage drop Vin at the resistor Rs is not falsified by the large variation of the potential Vphase, there is a "floating voltage supply" of the amplifier 16 intended.

This is the amplifier 16 a supply voltage V2 supplied to the at the inverting input of the amplifier 16 or a circuit node K1 applied potential "0" is related.

The potential referred to here as "0" forms a sort of "floating reference point" for the supplies of the components intended for load current measurement 16 . 18 and 20 , In operation, this reference potential varies between the potentials Vbat + and Vbat-.

The advantages of the floating supply voltage are mentioned in the opening paragraph DE 10 2005 029 813 A1 therefore, no explanation is required at this point.

The essential feature of the power amplifier 10 consists in the way of providing the supply voltage V2. The voltage V2 is controlled by a voltage transformer 22 generated, like derum is supplied by a supply voltage V1, which also "floats" or is carried along with the output node potential Vphase. The supply voltage V1 is provided by a potential-free voltage source 24 whose reference-side output terminal is connected as shown via a Zener diode Z1 to the output node K0, so that the generated voltage V1 is related to the potential Vphase (or approximately related to the reference potential "0", since the latter only to the relative small measurement voltage Vin is different from the potential Vphase).

The main advantage of the illustrated power amplifier 10 is that the voltage source 24 for generating the supply voltage V1 for the first drive circuit 12 is required anyway, at the same time (indirectly) for the power supply of the measuring amplifier 16 is being used. Notwithstanding the illustrated embodiment, this could be the amplifier 16 directly the supply voltage V1 are supplied. However, the voltage V1 is preferably as shown as a supply voltage for a voltage converter 22 used, the output side, the supply voltage V2 for the amplifier 16 supplies. It is advantageous for the power supply of the amplifier 16 thus no dedicated auxiliary voltage source required. In the illustrated embodiment, the primary for the drive circuit 12 generated supply voltage V1 further a second voltage converter 26 supplied therefrom which generates a voltage V3, which at a reference potential input of the amplifier 16 is created.

In addition, the voltage V1 is a third voltage transformer 28 which generates a voltage V4 for supplying the analog-to-digital converter 18 is used.

The downstream isolation module 20 is supplied with the voltage V2.

In the illustrated embodiment, the voltages described have the following values: V1 = 20 V, V2 = 5 V, V3 = 2.5 V, V4 = 5 V. One for the supply of the second drive circuit 14 used voltage V1 'is as shown by a voltage source 30 whose reference-side output is connected via a further Zener diode Z1 'to the potential Vbat-. V1 'has a value of 20 V. The zener voltages are each about 5 V. Of course, the voltage values mentioned above are to be understood as exemplary only and may be provided otherwise according to the specific application.

Each of the voltage transformers 22 . 26 and 28 can z. B. be implemented by a conventional voltage converter module. Alternatively or additionally, at least one of the voltage transformers can also be realized as a simple voltage divider. The latter is in the illustrated embodiment z. B. in particular for the realization of the voltage converter 26 Interesting. In this case, the converter z. B. consist of a voltage applied to V1 series connection of two resistors, at the center tap, the voltage V3 is provided.

Deviating from the illustrated embodiment, the voltage converter could 26 be supplied with V2 instead of V1.

Since V2 = V4 in the present exemplary embodiment, the voltage transformers could 22 and 28 also be combined into a single entity.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• DE 102005029813 A1 [0002, 0028]

Claims (6)

Circuit arrangement for operating an electrical load (L1), comprising - a controllable switching element (S1) for selectively connecting an operating potential (Vbat +) to a terminal of the load (L1), - a drive circuit ( 12 ) for driving the switching element (S1), - a current measuring resistor (Rs) arranged in series with the switching element (S1) for measuring a load current by detecting a measuring voltage (Vin) dropping across the current measuring resistor (Rs) by means of a measuring amplifier ( 16 ) whose inputs (K1, K2) are connected to the two terminals of the current sense resistor (Rs), characterized in that the circuit arrangement ( 10 ) a power supply ( 24 ), one on one at one (K2) of the inputs (K1, K2) of the measuring amplifier ( 16 ) applied potential (Vphase) related supply voltage (V1) for the drive circuit ( 12 ), and that this supply voltage (V1) also for the power supply (V2) of the measuring amplifier ( 16 ) is being used. Circuit arrangement according to claim 1, wherein the supply voltage (V1) indirectly for the voltage supply (V2) of the measuring amplifier ( 16 ) is being used. Circuit arrangement according to claim 2, wherein the versor supply voltage (V1) is subjected to a filtering. Circuit arrangement according to Claim 2 or 3, the supply voltage (V1) being a voltage conversion (V1). 22 ). Circuit arrangement according to Claim 4, in which the supply voltage (V1) is used as the voltage supply for a voltage divider or a voltage regulator ( 22 ), in turn, the supply voltage (V2) for the measuring amplifier ( 16 ). Circuit arrangement according to one of the preceding claims, wherein the measuring amplifier ( 16 ) has a reference potential input and the supply voltage (V1) is also used for the provision of a reference potential input applied to the reference potential (V3).