Method for operating a heating system and heating system

Abstract

The invention relates to a method for operating a heating system and to a heating system. Here, a battery direct voltage (HV) and a battery direct current (HC) are supplied to the heating system (1). A direct voltage converter (5) converts the battery direct voltage (HV) into a system voltage (SV) and the battery direct current (HC) into a system current (SC). The system voltage (SV) and the system current (SC) are then supplied to a PTC heater (4), and a control unit (3) controls the PTC heater (4) in order to achieve a heating power which is to be generated.

Description

Technical Field

[0001] This invention relates to a method for operating a heating system in a battery-powered vehicle, the heating system having an electric PTC heater and a control unit. The invention also relates to a heating system for implementing this method. Background Technology

[0002] In battery-powered vehicles, heating systems are used, for example, to heat the air flowing into the passenger compartment. These systems typically include a PTC heater (Positive Temperature Coefficient) and a control unit for controlling the PTC heater. The heating system is supplied with the battery voltage provided by the vehicle's battery. This battery voltage varies between 150 V and 1000 V, depending on the battery and its operating state or state of charge. However, the PTC heater exhibits optimal behavior over a narrow voltage range. This optimal behavior is particularly evident within a voltage range where the heating power of the PTC heater can be controlled or adjusted almost linearly. If the PTC heater operates outside this preset voltage range, control becomes difficult. For example, if the PTC heater is designed for higher battery voltages, maximum heating power cannot be achieved at lower battery voltages. If the PTC heater is designed for lower battery voltages, peak current will increase at higher battery voltages, and ripple current due to the switching process of the PTC heater will also increase. To address this issue, an additional filter is installed in the control unit, and an additional power switch is installed if necessary. However, this increases the cost of the heating system. Summary of the Invention

[0003] Therefore, the objective of this invention is to describe an improved or at least alternative embodiment of the method and heating system of the class, which overcomes the aforementioned disadvantages.

[0004] According to the invention, this task is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0005] The method according to the invention is configured or designed for operating a heating system in a battery-powered vehicle. This heating system includes an electric PTC heater, a control unit, and a DC-DC voltage converter. In this method, the battery DC voltage and battery DC current of the battery-powered vehicle are supplied to the heating system. The DC-DC voltage converter converts the battery DC voltage into a system voltage and the battery DC current into a system current. The system voltage and system current are then supplied to the PTC heater. Here, the system voltage and / or system current are pulse-width modulated by the control unit, thereby controlling the PTC heater to achieve the desired heating power.

[0006] In the method according to the invention, the PTC heater can be operated with a system voltage different from the battery DC voltage and a system current different from the battery DC current. Here, the system voltage and system current can be selected based on the thermal and electrical characteristics of the PTC heater, but not on the battery DC voltage and battery DC current. Therefore, the adverse effects of the battery DC voltage and battery DC current, which vary during PTC heater operation, on the control behavior of the PTC heater can be eliminated or at least reduced. Here, on the one hand, when the battery DC voltage and battery DC current are at their maximum, the peak current in the control unit and the ripple current generated during the switching process of the PTC heater can be reduced. On the other hand, when the battery DC voltage and battery DC current are at their minimum, the heating power of the PTC heater can be kept constant. In summary, compared with conventional solutions, the number of power switches used to control the PTC heater can be reduced. Furthermore, no additional filters and power switches are required, thereby reducing the cost of the heating system.

[0007] In this method, a battery DC voltage between 150 V and 1000 V can be provided to the heating system. A DC-DC voltage converter can convert this battery DC voltage between 150 V and 1000 V into a predetermined constant voltage value between 12 V and 1000 V, preferably between 300 V and 400 V, and particularly preferably equal to 350 V. The DC-DC voltage converter can be configured differently. For example, flyback converters and / or forward converters and / or buck converters and / or inverting converters and / or... UK converters and / or SEPIC converters and / or push-pull converters and / or half-bridge converters and / or full-bridge converters and / or resonant or quasi-resonant converters or other converters.

[0008] In this method, regardless of the heating power to be generated, the DC-DC converter can convert the battery DC voltage into a system voltage and / or the battery DC current into a system current. Then, regardless of the value of the heating power to be generated, the system voltage can be generated at a predetermined constant voltage value and / or the system current can be generated at a predetermined constant current value. The predetermined voltage value of the system voltage and / or the predetermined current value of the system current can be defined respectively based on the thermal and electrical characteristics of the PTC heater. In other words, the predetermined voltage value of the system voltage and / or the predetermined current value of the system current can be correspondingly defined or selected based on the optimal control behavior of the PTC heater. The optimal control behavior of the PTC heater is particularly found within a voltage range in which the heating power can be controlled or adjusted almost linearly. This voltage range is particularly dependent on the thermal and electrical characteristics of the PTC heater or the PTC ceramic installed in the PTC heater.

[0009] In this method, the power control unit of the control unit can pulse-width modulate the system voltage using a pulse-width modulated voltage control signal, and / or pulse-width modulate the system current using a pulse-width modulated current control signal. Here, for each heating power value to be generated, a pulse-width modulated system voltage can be generated using a voltage change curve related to the heating power to be generated, and / or a pulse-width modulated system current can be generated using a current change curve related to the heating power to be generated. The pulse-width modulated voltage control signal and / or the pulse-width modulated current control signal can be, for example, on / off signals for switching the system voltage applied to the PTC heater and / or the system current flowing in the PTC heater. In particular, the pulse-width modulated voltage control signal and / or the pulse-width modulated current control signal can have a duty cycle related to the heating power to be generated. The voltage variation curve of the system voltage and / or the current variation curve of the system current can be changed by using a pulse-width modulated voltage control signal and / or a pulse-width modulated current control signal, thereby adjusting the heating power to be generated based on the duty cycle of the pulse-width modulated voltage control signal and / or the pulse-width modulated current control signal.

[0010] In this method, a pulse-width modulated voltage control signal can be converted into a system voltage and / or a pulse-width modulated current control signal can be converted into a system current using at least one power switch in the power control unit. The at least one power switch can be, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). The at least one power switch and DC-DC voltage converter of the control unit can be, for example, mounted in a structural unit separate from other components of the control unit. Thus, the at least one power switch and DC-DC voltage converter can be arranged away from other components of the control unit, thereby reducing their impact on these components or improving their electromagnetic compatibility.

[0011] At least one power switch may be connected in series downstream of the PTC heater, for example. Therefore, at least one power switch may be a low-side switch. Alternatively, at least one power switch may be connected in series upstream of the PTC heater and downstream of the DC-DC converter.

[0012] In this method, the voltage sensor of the control unit can detect the current system voltage value on the PTC heater, and / or the current sensor of the control unit can detect the current system current value on the PTC heater. The control unit can then control the PTC heater based on the detected system voltage and / or system current values. This simplifies and optimizes the control of the PTC heater.

[0013] In this method, the current sensor of the control unit can detect the change of system current in the PTC heater over time. The control unit can then rely on the detected change of system current over time to determine the change of airflow through the PTC heater over time and / or the change of the amount of airflow through the PTC heater over time. This simplifies and optimizes the control of the PTC heater.

[0014] The present invention also relates to a heating system for a battery-powered vehicle. The heating system includes an electric PTC heater, a control unit, and a DC-DC voltage converter. This heating system is herein designed to implement the method described. It should be understood that the heating system may have all the hardware and software components required to perform the method. For the avoidance of repetition, see the foregoing description in this regard.

[0015] Other important features and advantages of the invention are apparent from the dependent claims, the drawings, and the description of the accompanying drawings based on the drawings.

[0016] It should be understood that the features described above and below can be used not only in combinations as described separately, but also in other combinations or individually, without departing from the scope of the invention. Attached Figure Description

[0017] Preferred embodiments of the present invention are shown in the accompanying drawings and explained in detail in the following description, wherein the same reference numerals denote the same or similar or functionally identical parts.

[0018] The following are illustrated in detail: Figure 1 A view is shown of a first embodiment of the heating system according to the invention when implementing the method according to the invention; Figure 2 A view is shown of a second embodiment of the heating system according to the invention when implementing the method according to the invention. Detailed Implementation

[0019] Figure 1 A view of a first embodiment of a heating system 1 according to the invention is shown when implementing method 2 according to the invention. The heating system 1 includes a control unit 3, a PTC heater 4, and a DC-DC voltage converter 5. The control unit 3 includes a microcontroller 6 and a power control unit 7, the power control unit having a driver 8 and a plurality of (two in this case) power switches 9. The power switches 9 are low-side switches in the form of IGBTs. Furthermore, the control unit 3 also includes a current sensor 10 and a voltage sensor 11.

[0020] In method 2 according to the invention, a battery DC voltage HV and a battery DC current HC are provided to the heating system 1. The battery DC voltage HV can be, for example, between 150 V and 1000 V. A DC voltage converter 5 converts the battery DC voltage HV into a system voltage SV and the battery DC current into a system current SC. Then, the system voltage SV and the system current SC are supplied to the PTC heater 4. The system voltage SV can be, for example, 350 V.

[0021] The system voltage SV is controlled using a pulse-width modulated (PWM) voltage control signal VST, depending on the desired heating power. To this end, the microcontroller 6 learns the system voltage SV required to adjust the desired heating power and controls the driver 8 using a voltage setpoint signal VSP. The driver 8 then provides a PWM voltage control signal VST based on the voltage setpoint signal VSP and switches the power switch 9 according to the PWM voltage control signal VST. This causes the system voltage SV applied to the PTC heater 4 to be pulse-width modulated according to the PWM voltage control signal VST, and adjusts the desired heating power on the PTC heater 4. The microcontroller 6 can detect the current system voltage SV, the current system current SC, and the adjusted heating power on the PTC heater 4 via the voltage sensor 11 and the current sensor 10.

[0022] In addition, the heating system 1 also includes an LV unit 12 for the drive control unit 3. The LV unit 12 includes an LV DC voltage converter 13, a transmitter-receiver unit 14, and a switching unit 15. In the heating system 1, the LV DC voltage converter 13, the transmitter-receiver unit 14, and the switching unit 15 are located on the so-called LV (LV: low voltage) side, while the other components of the heating system 1 are located on the so-called HV (HV: high voltage) side.

[0023] In method 2, the LV voltage LV and LV current are converted using an LV DC-Voltage Converter 13 and provided to the microcontroller 6 of the control unit 3. The transmitter-receiver unit 14 can receive external commands Lin via a LIN link, such as those concerning the heating power to be adjusted for the PTC heater 4, and forward them to the microcontroller 6 of the control unit 3. The switching unit 15 can be specifically designed for emergency shutdown of the control unit 3 and / or the PTC heater 4 and is supplied with a switching current In.

[0024] Figure 2 A view is shown of a second embodiment of the heating system 1 according to the invention, implemented in accordance with method 2. In the second embodiment, the power switch 9 of the power control unit 7 and the DC voltage converter 5 are both mounted in a common, separate structural unit 16.

[0025] In method 2 according to the invention, the battery DC voltage HV and battery DC current HC are provided to the heating system 1. A DC-DC converter 5 converts the battery DC voltage HV into a system voltage SV and the battery DC current into a system current SC. Depending on the heating power to be generated, a pulse-width modulated voltage control signal VST is used to control the system voltage SV and / or a pulse-width modulated voltage control signal is used to control the system current SC. For this purpose, a microcontroller 6 learns the system voltage SV and / or the system current SC required to adjust the heating power to be generated and transmits the corresponding voltage setpoint signal VSP and / or the corresponding current setpoint signal CSP to a power control unit 7. In the power control unit 7, the voltage setpoint signal VSP and / or the current setpoint signal CSP are converted using a driver 8 and a power switch 9 (not shown), and the system voltage SV and / or the system current SC are pulse-width modulated accordingly. In the embodiment shown here, the heating power to be generated is controlled by pulse-width modulating the system current SC.

[0026] List of reference numerals

[0027] 1 Heating System

[0028] 2 Methods

[0029] 3 Control Unit

[0030] 4 PTC heaters

[0031] 5 DC-DC voltage converter

[0032] 6 Microcontrollers

[0033] 7 Power Control Unit

[0034] 8 drives

[0035] 9 Power Switch

[0036] 10 Current Sensor

[0037] 11 Voltage Sensor

[0038] 12 LV units

[0039] 13 LV DC-DC converter

[0040] 14 Transmitter-Receiver Unit

[0041] 15 Switching Units

[0042] 16 structural units

[0043] HC battery DC current

[0044] HV Battery DC Voltage

[0045] LC current

[0046] LV voltage

[0047] Lin instructions

[0048] In switching current

[0049] SC system current

[0050] SV system voltage

[0051] VST voltage control signal

[0052] CST current setpoint signal

[0053] VSP voltage setpoint signal

Claims

1. A method (2) for operating a heating system (1) of a battery-powered vehicle, said heating system having an electric PTC heater (4), a control unit (3) and a DC voltage converter (5). - Wherein, the heating system (1) is provided with the battery DC voltage (HV) and battery DC current (HC) of the battery of the battery-powered vehicle. - in, The DC voltage converter (5) converts the battery DC voltage (HV) into system voltage (SV) and the battery DC current (HC) into system current (SC). - Wherein, the system voltage (SV) and the system current (SC) are supplied to the PTC heater (4). - Wherein, the control unit (3) pulse-width modulates the system voltage (SV) and / or the system current (SC), thereby controlling the PTC heater (4) to achieve the heating power to be generated.

2. The method (2) according to claim 1. Its features are, The DC voltage converter (5) converts the battery DC voltage (HV) into the system voltage (SV) and / or the battery DC current (HC) into the system current (SC) independently of the heating power to be generated. - The system voltage (SV) is generated at a predetermined constant voltage value and / or the system current (SC) is generated at a predetermined constant current value, independent of the value of the heating power to be generated.

3. The method (2) according to claim 2. Its features are, - The predetermined voltage value of the system voltage (SV) is determined based on the thermal and electrical characteristics of the PTC heater (4), and / or - The predetermined current value of the system current (SC) is determined based on the thermal and electrical characteristics of the PTC heater (4).

4. The method (2) according to any one of the preceding claims. Its features are, - The power control unit (7) of the control unit (3) pulse-width modulates the system voltage (SV) using a pulse-width modulated voltage control signal (VST), and / or pulse-width modulates the system current (SC) using a pulse-width modulated current control signal (CST), and - For each value of heating power to be generated, generate a pulse-width modulated system voltage (SV) using a voltage change curve related to the heating power to be generated, and / or for each value of heating power to be generated, generate a pulse-width modulated system current (SC) using a current change curve related to the heating power to be generated.

5. The method (2) according to claim 4. Its features are, The pulse-width modulated voltage control signal (VST) is converted into the system voltage (SV) and / or the pulse-width modulated current control signal (CST) is converted into the system current (SC) by means of at least one power switch (9) of the power control unit (7), preferably by means of at least one IGBT and / or at least one MOSFET.

6. The method (2) according to claim 5. Its features are, - The at least one power switch (9) is connected in series downstream of the PTC heater (4), or - The at least one power switch (9) is connected in series upstream of the PTC heater (4) and downstream of the DC voltage converter (5).

7. The method (2) according to any one of the preceding claims. Its features are, - The voltage sensor (11) of the control unit (3) detects the value of the current system voltage (SV) on the PTC heater (4), and / or the current sensor (10) of the control unit (3) detects the value of the current system current (SC) on the PTC heater, and - The control unit (3) controls the PTC heater (4) based on the value of the detected system voltage (SV) and / or the value of the detected system current (SC).

8. The method (2) according to any one of the preceding claims. Its features are, - The current sensor (10) of the control unit (3) detects the change in the system current (SC) on the PTC heater (4) over time, and - The control unit (3) determines the time-varying airflow through the PTC heater (4) and / or the time-varying amount of airflow through the PTC heater (4) based on the time-varying detected system current (SC).

9. The method (2) according to any one of the preceding claims. Its features are, - Provide the heating system (1) with a battery DC voltage (HV) between 150 V and 1000 V, and / or - The DC voltage converter (5) converts the battery DC voltage (HV) between 150 V and 1000 V into a system voltage (SV) having a predetermined constant voltage value between 12 V and 1000 V, preferably between 300 V and 400 V, and particularly preferably equal to 350 V.

10. A heating system for a battery-powered vehicle (1). - Wherein, the heating system (1) has an electric PTC heater (4), a control unit (3) and a DC voltage converter (5), and - in, The heating system (1) is designed to implement the method (2) of any one of the preceding claims.

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