DE102008056757A1 - Secondary electric heating device for vehicle i.e. car, has switching unit for switching battery voltage, and controller for controlling pulse width modulation duty of pulse width modulation signal according to calculated power consumption - Google Patents

Abstract

The device (200) has a switching unit for switching battery voltage. A current sensor (222) is connected to a heating apparatus, and senses current flowing through a positive temperature coefficient (PTC) heater part (214). A pulse width modulation (PWM) signal is authorized by the switching unit. A controller (224) is provided for calculating power consumption from perception current of the current sensor, and controls a PWM duty of the PWM signal according to the calculated power consumption. An independent claim is also included for a secondary electric heating method for a vehicle i.e. car.

Description

These The invention relates to an electric auxiliary heating system for a vehicle or its method. In general, the electric heating unit serves in vehicles for heating the interior and preheating the cooling water in one with a water cooler equipped engine or to heat the fuel.

The electric heating unit, which is a PTC (Positive Temperature Coefficient) heating is used either as auxiliaries for heaters in the Air conditioning or independent used as heating, composed of one or more heating means can be.

1 shows a drawing of the designed using conventional technology electrical Zusatzheizsystems.

According to 1 it leaves the microprocessor ( 16 ), in the auxiliary electrical heating system of the vehicles ( 10 ) to send a control signal.

According to the heating power value of the power transistors ( 11 ) preset PTC heating ( 17 ), the control signal from the power transistors ( 11 ) is activated.

As a result, the power transistors ( 11 ) by the control signal of the microprocessor ( 16 ) of the PTC heater ( 17 ) the required current by means of the PWM signal.

In this case, the temperature rises due to the heat output generated in the PTC heater ( 17 ) of which after the PWM signal (pulse width modulation signal) in the power transistors ( 11 ) had been preset.

The microprocessor ( 16 ), the PTC heater ( 17 ) with the help of the power transistors ( 11 ) of the power semiconductor element has a heating power of z. B. 1000 or 2000 W in the PTC heating ( 17 ) to create.

at the electric heating unit of conventional car technology can the electrical current setpoint with respect to the changing external conditions, eg. B. Operation the car radio, the rear window wiper and the interior lights and the headlight in PTC heaters are not generated. Furthermore can the electric auxiliary heating system or the PTC heating thereby except Function can be set, that their temperature due to excessive power consumption or otherwise increased Electricity is rising.

task

The The present invention has the object of loading the car battery by reducing the current setpoint in the PTC heater, when the battery voltage is higher Load of the battery is very weak, and that by means of the setpoint can be heated, provided that the output of the battery is sufficient is.

task solution

The task solution the present invention is that the actual power in accordance with the electric Current value of the PTC heater calculated by the PWM duty cycle of the PWM signal is modulated so that the required current in the setpoint the supply current of the battery is converted.

effect

The The present invention achieves the effect that the burden on the Car battery by lowering the current setpoint in the PTC heater is reduced when the battery voltage at higher load of the battery is very weak, and that are heated by means of the setpoint can, if the output power of the battery is sufficient.

Furthermore The system can use the current of the PTC heater, the actual power in the PTC heater calculate and the correct actual power of the PTC heater control so that the actual power approaches the setpoint.

The present invention includes switching, heating, current detection and control units. The switching unit has one or more switching means and switches depending on the PWM signal, the voltage of the battery. The heating part is in each case connected to the power source of the switching means and consists of one or more heating means. The current detection unit connected to this heating means detects the current in the heating unit. In the control unit, first data about the battery voltage are received and compared with the reference voltage. Subsequently, the heating current corresponding to the battery voltage is set as a set value if the voltage should be lower than the reference voltage. In the opposite case, the maximum heating current is set as the setpoint. As a result, the PWM signal from the PWM duty cycle is generated according to the above set value, and thus the switching means is activated. In the control unit, the PWM duty ratio of the PWM signal is modulated according to the actual actual power detected and calculated in the sensor device according to the above-mentioned target value. In the invention, one or more serve MOSFETs as switching means. The gate terminal of the first MOSFET to Nth MOSFET (N is a natural number) is connected to the control unit, and the drain terminal to the power source and the source terminal to the heating means.

There is also the switching means in this invention of one or more transistors, wherein each of their base terminal of the first to Nth transistor (N is a natural one Number) to the control unit, the collector connection to the power source the battery and the emitter connection are connected to the heating medium become.

The System also has a communication device on the the above data about the battery voltage is received and sent.

In this communication device of the invention is either RS-232 or RS-422, USB (Universal Serial Bus) or IEEE1394 or CAN (Controller Area Network) as a transmission path selected. The given abbreviations are synonymous as FireWire or as i. Link known and designate the expert known data transmission systems.

moreover The control unit also includes a transmission means that the above data about the voltage is received.

In addition, can the control unit of this invention, the PWM duty cycle of Reduce or increase the PWM signal, depending on whether the calculated Higher electricity or lower than the nominal value.

The Control unit can also one or more switching means of the PWM signal activate individually.

The one-piece constructed current detection unit is connected to one or more Heating medium connected.

The method according to the invention is subdivided into the following four steps:
In the first step, data about the battery voltage is received and compared with the reference voltage. In the second step, the heating current is set as the setpoint. If the received voltage is lower than the reference voltage, the heating current corresponding to this battery voltage is determined as the set value, otherwise the maximum heating current is set as rated current. In the third step, the PWM signal is generated by means of the setpoint value corresponding to the PWM duty cycle and the switching unit is thus activated. In the fourth step, the PWM duty cycle of the PWM signal is modulated according to the actual power calculated from the actual consumption and the above-mentioned desired value.

at the modulation of the PWM duty cycle of the PWM signal, this PWM duty cycle is reduced respectively elevated, if the previously calculated consumption flow rate is larger or less than the nominal amount of electricity.

at the transmission to the switching unit, the PWM signal of the PWM duty cycle for one or several switching means activated individually.

at the modulation of the PWM duty cycle the PWM signal becomes the current detected in the sensor device and actual power calculated with respect to the battery voltage actually consumed in one or more heating means of the heating unit becomes.

in the This invention will now be described by way of example with reference to the accompanying drawings in detail described. In the event that too detailed a description about the Structure and the functions of each element a clear understanding of this invention could complicate this is waived.

Brief explanation of the drawings

1 shows a block diagram of a conventional automotive electrical auxiliary heating system.

2 FIG. 12 is a block diagram of the auxiliary electric heating system of the present invention. FIG.

3 is a flowchart according to the invention for explaining the electrical Zusatzheizsystems.

4a is a diagram in which the course of the matching with the battery voltage setpoint of the PTC heater is shown according to the invention.

4b is a diagram in which the course of the matching with the battery voltage setpoint of the PTC heater is shown according to another example according to the invention.

5 is a block diagram of the switching unit, which consists of the 1st to 3rd power transistor according to the invention.

In 2 Fig. 12 is a block diagram of the electric heating unit of the vehicles designed according to this invention.

As 2 shows, the heating unit is the Vehicles ( 200 ) from the communication device ( 204 ), the switching unit ( 206 ), the PTC heater ( 214 ) and the current detection unit ( 222 ) and the control unit ( 224 ).

The communication unit ( 204 ) can in turn consist of an RS-232, an RS-422, a USB (Universal Serial Bus) as well as an IEEE 1394 or a CAN (Controller Area Network). In this part, data about the battery power source ( 300 ) received voltage and continue to the control unit ( 224 ) Posted.

In the switching unit ( 206 ) are the 1st MOSFET ( 208 ), the 2nd MOSFET ( 210 ) as well as the 3rd MOSFET ( 212 ) of the power semiconductor element; the drain terminals (D) of the first MOSFET ( 208 ) to 3. MOSFET ( 212 ) are connected to the power source of the battery ( 300 ), the gate connections (G) to the control unit ( 224 ) and the source connections (S) to one side of the PTC heater ( 214 ) connected.

On the other hand, the 1st MOSFET ( 208 ) until the 3rd MOSFET ( 212 ) by means of the drain connections (D) through the power source of the battery ( 300 ) the supply of battery voltage, at the same time the PWM signal of the control unit ( 224 ) is selectively activated by the gate terminals (G) and allows the PTC heating unit ( 214 ) by means of the source terminals (S), the switching of the voltage.

As is in 5 shows, the switching unit ( 206 ) from the 1st ( 208 ), the 2nd 210 ) and the third power transistor ( 212 ) of the power semiconductor element and the collector terminals (C) of the first 208 ) to 3. ( 212 ) Power transistor can be connected to the power source ( 300 ), the basic connections (B) to the control unit ( 224 ) and the emitter electrodes (E) to one side of the PTC heater ( 214 ) are connected.

5 shows a block diagram of the switching unit, which consists of the 1st to 3rd power transistor.

The 1. ( 208 ) to 3rd transistors ( 212 ) obtained by means of the collector terminals (C) from the power source of the battery ( 300 ) the battery voltage, at the same time through the base terminals (B) the PWM signal of the control means ( 224 ) is activated and allows the PTC heater ( 214 ) by means of the emitter terminals (E), the switching of the voltage.

On the other hand, the PTC heating unit ( 214 ) the 1st 216 ), the 2nd 128 ) as well as the 3rd PTC heating means ( 220 ) and a page of this 1. ( 216 ) to 3. PTC heating means ( 220 ) is respectively connected to the source terminals (S) (or to the emitter terminals (E)) of the first MOSFET ( 208 ) (or 1st power transistor) to 3rd MOSFET ( 212 ) (or 3rd power transistor) and the other side of the 1st ( 216 ) to 3. PTC heating means ( 220 ) at the current detection unit ( 222 ) appropriate.

Here, the actual power (P) in the 1st ( 216 ) to 3. PTC heating means ( 220 ) by the switching unit ( 206 ) optionally supplied voltage generated.

The current detection unit ( 222 ) is sent to one side of the 1st 216 ) to 3. heating means ( 220 ) of the PTC heater ( 214 ) and the other side to the control unit ( 224 ) connected. Thus, the current detected by at least one of the 1st 216 ) to 3. PTC heating means ( 220 ) flows. The current detection unit (shunt) equipped with a current detection unit (shunt) 222 ) can also be used to detect the current after the voltage dropped across the resistor.

Receives the control unit ( 224 ) on the other hand by the communication unit ( 204 ) Data about the voltage that is available from the power source of the battery ( 300 ), it decides whether the said voltage is higher than the reference voltage (Px) and the heating current (Py) is set according to the battery voltage as the set value (Py), the appropriate PWM duty cycle is calculated and the PWM signal with the calculated PWM duty cycle in the switching unit ( 206 ) is activated if said voltage is lower than the reference voltage (Px). In the opposite case, the maximum heating current (Pmax) is set according to the battery voltage as the setpoint (Pmax), the corresponding PWM duty cycle is calculated and the PWM signal is calculated with the calculated PWM duty cycle in the switching unit ( 206 ) is activated.

Here, the PWM signal of the control unit ( 224 ) in the gate terminal (G) (or base terminal (B)) in one or more than a first MOSFET ( 208 ) (or 1st transistor) to 3rd MOSFET ( 212 ) (or 3rd power transistor) optionally activated.

In addition, the control unit receives ( 224 ) from the current detection unit ( 222 ) the feedback current which is in one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) and calculates the actual power (P) of one or more 1. ( 216 ) to 3. heating means ( 220 ) according to the supply battery voltage or the detected current. Thereafter, it is first checked whether the matching with the supply battery voltage actual power (P) corresponds to the setpoint (heating current (Py) or the maximum heating current (Pmax)), and it is then checked whether the actual power (P) hö if the actual power (P) does not correspond to the setpoint (heating current (Py) or the maximum heating current (Pmax)). If the actual power (P) is lower than the setpoint (heating current (Py) or maximum heating current (Pmax)), the PWM signal with the increased PWM duty cycle in the switching unit ( 206 ) is optionally activated so that the actual power (P) is converted to the setpoint (heating current (Py) or maximum heating current (Pmax)). If the actual power (P) is higher than the setpoint (heating current (Py) or the maximum heating current (Pmax)), the PWM signal with the reduced PWM duty cycle in the switching unit ( 206 ) is selectively activated so that the actual power (P) is converted to the setpoint (heating current (Py) or maximum heating current (Pmax)).

It is - like 4a such as 4b - desired that the control device ( 224 ) contains a storage means in which the reference voltage and the heating current (Py = ax + b) (a and b are natural numbers, x is a variable) and the setpoint can be stored. Here, the heating current corresponding to the battery voltage is set, and this battery voltage should be lower than the reference voltage (Px) in this case. The setpoint includes the maximum heating current (Pmax), which is set in relation to the battery voltage; the battery voltage should be higher than the reference voltage (Px) in this case.

Ie. it is desirable that the setpoint be selected according to the battery power source of the vehicle ( 300 ) supplied battery voltage is already set in the storage means.

4a In this case, according to the invention, the diagram is shown as a diagram with regard to the nominal value of the PTC heater that corresponds to the battery voltage.

4b is a drawn according to this example diagram with respect to the battery voltage corresponding setpoint of the PTC heater.

3 Fig. 10 is a flowchart for explaining the electric replacement heating method in vehicles according to this invention.

As 3 shows the battery power source ( 300 ) in the electric replacement heating system for vehicles ( 200 ) with the switching on of the power source in the vehicle the drain terminal (D) (or collector terminals (C)) of the 1st MOSFET ( 208 ) (or 1st power transistor) to 3rd MOSFET ( 212 ) (3rd power transistor) in the switching unit ( 216 ) with battery voltage and sends the communication unit ( 204 ) according to the supplied battery voltage data about this value.

In this case, the switching unit ( 206 ) the first MOSFET ( 208 ), 2nd MOSFET ( 210 ) and 3rd MOSFET ( 212 ) (or the 1st, 2nd and 3rd power transistor); the drain electrodes (D) (or collector electrodes (C)) of the first MOSFET ( 208 ) (1st power transistor) to 3rd MOSFET ( 212 ) (3rd power transistor) are connected to the battery power source ( 300 ) and the gate terminals (G) (or base terminals (B)) to the control unit ( 224 ) and the source terminals (S) (or emitter terminals (E)) to one side of the PTC heater ( 214 ) connected.

The communication unit ( 204 ) Data from the battery power source ( 300 ) supplied voltage and sends it to the control unit ( 224 ) further.

This communication unit ( 204 ) consists of an RS-232, an RS-422, a USB (Universal Serial Bus) as well as an IEEE1394 or a CAN (Controller Area Network).

The control unit receives ( 224 ) from the communication unit ( 204 ) Data from the battery power source ( 300 ) and checks whether said voltage is higher than the reference voltage (Px) (S302).

Here it is - like the ones mentioned above 4a 4b - it is desirable that the control unit ( 224 ) contains a memory element in which the reference voltage and the heating current (Py = ax + b) (a and b are natural numbers, x is a variable) and the setpoint can be stored. Here, the heating current of the battery voltage is adjusted accordingly, wherein the battery voltage in this case should be lower than the reference voltage (Px). The setpoint represents the maximum heating current (Pmax), which is set in relation to the battery voltage; this battery voltage should be in this. all higher than the reference voltage (Px).

D. h., it is desirable that the reference voltage (Px) and that coincide with the battery voltage Setpoint already be set in the memory element.

If the voltage resulting from the examination of the above-mentioned step (S302) is lower than the reference voltage (Px), e.g. B. lower than the reference voltage (Px) of 27 [V] or 13.5 [V], the control unit ( 224 ) corresponding to the voltage data (eg 23.5 [V] or 11.75 [V]) heating current (Py) (eg 500 [W]) of the PTC heating device ( 214 ) as the set value (Py) (S303).

Then the control unit calculates ( 224 ) according to the setpoint (Py) and the versor supply voltage aligned PWM duty cycle of the PWM signal (S304) and selectively activates the PWM signal of the PWM duty cycle for the gate terminals (G) (or base terminals (B)) of one or more 1st MOSFET ( 208 ) (or 1. power transistors) to 3. MOSFET ( 212 ) (or 3rd power transistors) (S305).

Here, the 1st MOSFET ( 208 ) (or the 1st power transistor) to 3rd MOSFET ( 212 ) (or 3rd power transistor) of the switching unit ( 206 ) after the PWM signal with the calculated PWM duty cycle of the control unit ( 224 ) and supplies one or more of them by means of the source electrode (S) (or emitter electrode (E)). 216 ) to 3. PTC heating means ( 220 ) with tension. In this case, the actual power (P) by means of the switching unit ( 206 ) supplied voltage in one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) generated.

In this case, one side of the first ( 216 ) to 3. PTC heating means ( 220 ) to the source electrode (S) (or emitter electrode (E)) of the first MOSFET ( 208 ) (or 1st power transistor) to 3rd MOSFET ( 212 ) (or 3rd power transistor) and the other side of the 1st ( 216 ) to 3. PTC heating means ( 220 ) on the sensor device ( 222 ) appropriate.

In this case, the sensor device ( 222 ) the current which is present in one or more 1. PTC heating means ( 216 ) to 3. PTC heating means ( 220 ) flows.

Thereafter, the control unit ( 224 ) from the sensor device ( 222 ) the feedback current of one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) calculates (S307) and calculates the actual power (P) of one or more 1. ( 216 ) to 3. heating means ( 220 ) by means of the detected current and the supply battery voltage (S307).

Then the control unit checks ( 224 ), whether the calculated actual power (P) of the PTC heating device ( 214 ) the setpoint (Py) (eg 500 W) of the specified voltage of z. B. 23.5 [V] or 11.75 [V] corresponds to matching heating current (Py) (S308).

If the actual power (P) proves to be identical to the target value (eg 500 [W]) after the test result of the above-mentioned step (S308), the control unit performs ( 224 ) performs the above-mentioned step (S305).

If the actual power (P) is not identical to the target value (Py) according to the result of the above-mentioned step (S308), the control unit checks ( 224 ), whether the actual power (P) is higher than the target value (Py) (S309).

If the actual power (P) - as a result of the above-mentioned step (S309) - is higher than the target value (Py), the control unit reduces ( 224 ) the PWM duty cycle of the PWM signal such that the actual power (P) becomes the setpoint (Py) (eg, 500 [W]), which is one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) corresponds to (S310).

Then the control unit ( 224 ) performs the above-mentioned step (S305).

If the actual power (P) is lower than the target value (Py) after the result of the above-mentioned step (S309), the control unit increases ( 224 ) the PWM duty cycle of the PWM signal such that the actual power (P) becomes the setpoint (Py) (eg, 500 [W]), which is one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) corresponds to (S311).

Then the control unit ( 224 ) performs the above-mentioned step (S305).

Is the indicated voltage - as a result of the above-mentioned step (S302) - higher than the reference voltage (Py), z. 27 [V] or 13.5 [V], the control unit ( 224 ) the maximum heating current (Pmax) (eg 1000 [W]) of the PTC heating part ( 214 ) as the target current (Pmax) (S312). This maximum heating current then corresponds to the specified voltage (Py) (eg 29 [V] or 15 [V]), which is higher than the reference voltage (Py).

Then the control unit calculates ( 224 ) After the setpoint (Pmax) and the supply battery voltage, the PWM duty cycle of the PWM signal (S304) and optionally activated for the gate terminals (G) (or base terminals (B)) of one or more 1. MOSFET ( 208 ) (or 1st power transistor) to 3rd MOSFET ( 212 ) (or the third power transistor), the PWM signal of the PWM duty cycle (S305).

Here, the 1st MOSFET ( 208 ) (or the 1st power transistor) to 3rd MOSFET ( 212 ) (or the 3rd power transistor) of the switching means ( 206 ) after the PWM signal with the calculated PWM duty cycle of the control unit ( 224 ) and supplies one or more of them by means of the source terminal (S) (or emitter terminal (E)). 216 ) to 3. PTC heating means ( 220 ) with tension.

In this case, the actual power (P) by means of the switching unit ( 206 ) in one or more 1. (216) to 3. PTC heating means ( 220 ) generated. Subsequently, the control unit detects ( 222 ) the current in one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) flows.

Thereafter, the control unit receives ( 224 ) with the aid of the current detection unit ( 222 ) the rückgekop pelt electricity of one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) (S306) and calculates the actual power (P) of one or more 1. ( 216 ) to 3. heating means ( 220 ) by means of the detected current and the supply battery voltage (S307).

Then the control unit checks ( 224 ), whether the calculated actual power (P) of the PTC heater of z. B. 29 [V] or 15 [V] corresponds to the corresponding maximum heating current (Pmax) (S308).

If the actual power (P) proves to be identical to the target value (Pmax) (eg, 1000 [W]) according to the result of the above-mentioned step (S308), the control unit (FIG. 224 ) performs the above-mentioned step (S305).

If the actual power (P) does not prove to be identical to the target value (Pmax) according to the result of the above-mentioned step (S308), the control unit checks ( 224 ), whether the actual power (P) is greater than the target value (Pmax) (S309).

If the actual power (P) is greater than the target value (Pmax) according to the result of the above-mentioned step (S309), the control unit reduces ( 224 ) the PWM duty cycle of the PWM signal so that the actual power (P) becomes the setpoint (Pmax) (eg, 1000 [W]) corresponding to one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) corresponds to (S310).

Then the control unit ( 224 ) performs the above-mentioned step (S305).

If the actual power (P) is smaller than the target value (Pmax) according to the result of the above-mentioned step (S309), the control unit increases ( 224 ) the PWM duty cycle of the PWM signal so that the actual power (P) becomes the setpoint (Pmax) (eg, 1000 [W]) corresponding to one or more 1. ( 216 ) to 3. PTC heating means ( 220 ) corresponds to (S311).

Then the control unit ( 224 ) performs the above-mentioned step (S305).

As the previously described method for the electric auxiliary heater shows in vehicles, the load on the car battery by the Lowering the setpoint of the PTC heater lowered when the voltage due to excessive battery usage is low. Is the power of the battery sufficiently strong, can to heat with the rated current. As a result, a power efficiency is achieved, so that the car battery can work without load. The actual performance of PTC heating is calculated by means of the current of the PTC heater and in that the actual power and the rated current with each other in the same Can be controlled by a precise amount of consumed electricity PTC heating can be achieved.

The present description is only a brief explanation the technical idea of this invention by way of example and a professional can make changes and modifications within the scope of the essential feature of the invention make different way. Given the example above There is no intention to realize the technical idea of this To limit the invention, but only to explain them. The options The technical idea of this invention is not intended to be by the example given limited become. The protection of this invention is within the following Claims to interpret and all technical ideas within the same Range is to be understood as being within the rights of the presented invention.

200

electrical additional heating system

204

communication unit

206

switching unit

208

1. MOSFET

210

Second MOSFET

212

Third MOSFET

214

PTC heating unit

216

1. PTC heating

218

Second PTC heating

220

Third PTC heating

222

Current detection unit

224

control unit

300

Power supply unit

Claims (13)

Electric auxiliary heating system ( 200 ) for a vehicle, comprising: a switching unit ( 206 ) connected to at least one or more switching means ( 208 . 210 . 212 ), wherein the switching unit operates to switch a battery voltage in accordance with a PWM signal; a heating unit ( 214 ) containing at least one or more heating agents (216 . 218 . 220 ) each connected to each output of the switching means; a current detection unit ( 222 ), which is a current through the heating unit ( 214 ), wherein the current detection unit is connected to the heating means; and a control unit ( 224 ), in which a voltage value of the battery voltage is received and then compared with a reference voltage and, if this voltage value is smaller than the reference voltage, a target power is set to a heating power proportional to the battery voltage, and on the other hand, if the voltage value is greater than the reference voltage , the target power is set to a predetermined maximum heating power, and then the PWM signal is generated with a PWM duty cycle corresponding to the desired power and then transmitted to the switching means, and the PWM duty cycle of the PWM signal is adjusted in dependence on the target power and an actual power, wherein the actually consumed actual power is calculated from the current the current detection unit ( 222 ) detected. An auxiliary electrical heating system according to claim 1, wherein the switching means is composed of at least one or more MOSFETs, and gate terminals (G) of the first MOSFET to Nth MOSFET (N is a natural number) are connected to the control unit, and drain Connections (D) to a battery power source ( 300 ), and source terminals (S) are respectively connected to the heating means. An electric auxiliary heating system according to claim 1, wherein the switching means of at least one or more transistors exist, and basic connections (B) of the 1st transistor to Nth transistor (N is a natural number) connected to the control unit, and collector connections (C) connected to a battery power source, and emitter terminals (E) each connected to the heating means. An auxiliary electrical heating system according to claim 1, further comprising a communication unit ( 204 ) receiving and transmitting the voltage value of the battery voltage. An auxiliary electrical heating system according to claim 4, wherein the communication unit ( 204 ) is operated with any type of communication from RS-232, RS-422, USB (Universal Serial Bus), IEEE1394 and CAN (Controller Area Network). An auxiliary electrical heating system according to claim 1, wherein the control unit ( 224 ) comprises a communication means receiving the voltage value. An auxiliary electrical heating system according to claim 1, wherein the control unit ( 224 ), if the calculated actual power is larger or smaller than the target power, reduces or increases the PWM duty ratio of the PWM signal. An auxiliary electrical heating system according to claim 1, wherein the control unit ( 224 ) transmits the PWM signal individually to at least one or more switching means. An auxiliary electrical heating system according to claim 1, wherein the current detection unit ( 222 ) is formed as a housing, that it is connected to at least one or more heating means. Method of an electric auxiliary heating system for a vehicle, the following steps include: Compare a voltage value a battery voltage having a reference voltage upon receipt of the Voltage value of the battery voltage; Setting a nominal power on a heating power that is proportional to the battery voltage is smaller than the reference voltage if the voltage value is smaller than the reference voltage and, on the other hand, to a predetermined one maximum heat output, if the voltage value is greater than the reference voltage is; Transfer a PWM signal to a switching unit after generating the PWM signal with a PWM duty cycle corresponding to the target power; and To adjust of the PWM duty cycle the PWM signal depending from the target power and an actual power received one actually to calculate consumed power. Method of an electric Zusatzheizsystems after Claim 10, wherein in the step of adjusting the PWM duty cycle the adaptation of the PWM signal, if the calculated actual power is greater than or equal to less than the target power is done in such a way that the PWM duty cycle of the PWM signal is reduced or increased. Method of an electric Zusatzheizsystems after Claim 10, wherein in the step of transmitting the transmission is done in such a way that the PWM signal with the PWM duty cycle individually transmitted to at least one or more switching means of the switching unit becomes. The method of an auxiliary electric heating system according to claim 10, wherein in the step of adjusting the PWM duty of the PWM signal, the actual power actually consumed in heating means of at least one or more heating units is obtained from the battery voltage and one from a current detection unit. 222 ) detected current is calculated.