Power supply unit for explosion-proof applications

Abstract

The invention relates to a power supply unit for operating an electronic device in an explosion-proof area, the power supply unit comprising: means (2) for providing a rectified input voltage (UE); a DC link capacitor (5) for buffering the DC link voltage; a phase section control section (4) that is controlled to apply the rectified input voltage to the DC link capacitance (5) during a period in which the rectified input voltage (UE) increases and is between a lower voltage threshold (Uu) and an upper voltage threshold (Uo), and to disconnect the rectified input voltage from the DC link capacitance (5) during a remaining period; a converter circuit (7) configured to convert the DC link voltage (UZ) into an output voltage.

Description

Technical Field

[0001] The invention relates to a power supply unit for supplying electrical applications in explosion-proof areas with electrical power. Furthermore, the invention relates to measures for simplifying the circuit design of a power supply unit for operating electrical devices in explosion-proof areas. Background Art

[0002] When developing electronic devices for use in Zone 2 explosion-proof areas, where input voltages greater than 80 V (according to IEC 60079-7) can be used for power supply (e.g. 230 V mains voltage), for example, requirements are specifically imposed on the circuit design and layout according to hazard protection regulations. Here, spacing and creepage distances need to be maintained between components and between the individual connections on the components, so that the power supply electronics usually have to be designed discretely. Therefore, modern, highly integrated power supply components, integrated power supply ICs (step-down ICs) and the like cannot be realized. However, discretely designed power supply electronics exhibit lower efficiency and require more space. In addition, the test for failure is more complicated because significantly more components and their distances must be tested.

[0003] Furthermore, production costs may increase, since the probability of component failure increases due to the greater number of different components and since restrictions with regard to the selection of components also apply when replacing the respective component.

[0004] If a power supply unit with a voltage supply of 230 V is provided for explosion proof areas, the DC link voltage in the power supply unit will typically be a voltage in excess of 80 V. This requires a discrete design of the power supply electronics which exhibits the above-mentioned disadvantages.

[0005] The object of the present invention is to provide an improved design of a power supply unit for supplying explosion-proof electronic equipment with power, which power supply unit can be constructed in a simplified manner and wherein in particular fewer restrictions on the construction of the electrical circuits need to be taken into account. Summary of the invention

[0006] This object is achieved by a power supply unit for supplying power to electronic devices in explosion-proof areas according to claim 1 .

[0007] Further embodiments are specified in the dependent claims.

[0008] According to one aspect, there is provided a power supply for operating electronic equipment in an explosion proof area, the power supply comprising:

[0009] - means for providing a rectified input voltage;

[0010] - a DC link capacitor, the DC link capacitor being used to buffer the DC link voltage;

[0011] a phase section control section controlled to apply the rectified input voltage to the DC link capacitor during a time period in which the rectified input voltage increases and is between a lower voltage threshold and an upper voltage threshold, and to disconnect the rectified input voltage from the DC link capacitor during a remaining time period;

[0012] - a converter circuit configured to convert the DC link voltage into an output voltage.

[0013] Furthermore, the means for providing a rectified input voltage may comprise a passive rectifier and in particular an EMC protection circuit.

[0014] Typically, power supply units for operating electronic equipment in explosion-proof areas are configured to generate a DC voltage between 5 V and 48 V from a mains voltage of 110 VAC or 230 VAC. This is typically done by providing a rectified DC link voltage whose voltage level is based on the applied supply voltage, i.e. the mains voltage, and therefore exceeds the voltage limits mentioned at the beginning.

[0015] According to the present invention, the input voltage of the power supply unit now needs to be reduced to a voltage below 80V immediately after rectification, for example by means of a phase segment control unit (i.e., a phase segment control unit), and the input voltage is provided as a DC link voltage. The reduced voltage can be buffered by means of a DC link capacitor.

[0016] By limiting the DC link voltage to a voltage below the voltage limit of the explosion-proof voltage of 80V, the need to provide insulation and creepage distances between components installed in explosion-proof areas is avoided for subsequent circuit components. As a result, efficient and compact integrated power supply solutions can be used, such as an integrated buck converter for converting the DC link voltage to the power supply output voltage, without having to use complex discrete solutions with lower efficiency and higher space requirements. In addition, the testing effort required to ensure compliance with the standards is enormous.

[0017] With the help of the phase section control part and the DC link capacitor, it is possible to reduce the rectified input voltage to a voltage lower than the explosion-proof voltage of 80V.

[0018] The phase section control unit can be configured with the aid of a control circuit and a low-resistance power semiconductor switch, such as a power MOSFET. The control circuit can be configured as a simple analog circuit, which generates a control signal to turn off the power semiconductor switch when the target voltage is reached, that is, when an upper voltage threshold selected as a voltage slightly lower than the explosion-proof voltage, such as between 80% and 95% of the explosion-proof voltage or between 70 volts and 75 volts, is reached, and the power semiconductor switch is turned on again at a lower voltage threshold selected to be lower than the upper voltage threshold. Alternatively, the upper voltage threshold can be set to be lower than the explosion-proof voltage according to a predetermined power requirement, in particular for electronic equipment. Here, the upper and lower voltage thresholds, the input voltage, the rectified input voltage, and the DC link voltage can be regarded as voltage specifications in terms of their magnitude.

[0019] The control circuit may comprise a microcontroller, wherein, in particular, the microcontroller is also configured to control an electronic device operated by the power supply unit. Thus, a microcontroller may also be used to switch the power semiconductor switch, which optimizes the operating state according to the input voltage of the power supply unit, the input frequency of the power supply unit and the output power, maintaining an upper voltage threshold and a lower voltage threshold. For example, the process of optimizing the operating state may be performed by omitting individual half-waves for charging the DC link capacitor or by selecting the voltage level of the DC link capacitor. The selected upper voltage threshold below the explosion-proof voltage may then be set according to the power requirements of subsequent devices. In particular, a microcontroller solution may be applied if a microcontroller is already present in the electronic device, which may also be used to operate the power supply unit.

[0020] It may be provided that the phase section control is controlled to permanently apply the rectified input voltage to the DC link capacitor at an input voltage below the explosion-proof voltage.

[0021] Furthermore, the control unit may be configured to deactivate the phase section control when the input voltage is below the explosion-proof voltage, since no voltage reduction needs to be provided for the DC link voltage.

[0022] According to a further aspect, a method for operating a power supply unit for operating electronic equipment in an explosion-proof area is provided, wherein the power supply unit has a device for providing a rectified input voltage, a DC link capacitor for buffering a DC link voltage, and a converter circuit configured to convert the DC link voltage into an output voltage, wherein the rectified input voltage is applied to the DC link capacitor during a time period when the rectified input voltage increases and is between a lower voltage threshold and an upper voltage threshold, and wherein the rectified input voltage is disconnected from the DC link capacitor during a remaining time period. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The embodiments are described in more detail below with reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic representation of a power supply unit for operating electronic equipment in an explosion-proof area according to a first embodiment;

[0025] Figure 2 is a graph for showing time characteristics of a rectified input voltage, a DC link voltage, and a capacitor current of a DC link capacitor; and

[0026] Figure 3 is a schematic representation of a power supply unit for operating electronic equipment in explosion-proof areas according to further embodiments. DETAILED DESCRIPTION

[0027] Figure 1 A schematic representation of a power supply unit 1 for an electronic device 10 to be operated in an explosion-proof area or a potentially explosive area is shown. According to the standard specification of IEC 60079-7, voltages above the explosion-proof voltage of 80 V are permitted in explosion-proof areas only if appropriate insulation and creepage distances between components (i.e. electronic components) are observed. The power supply unit has a rectifier 2 for applying an input voltage U E The input voltage U E The mains voltage is usually 120VAC or 230VAC.

[0028] Interference signals are removed from the rectified voltage by means of the subsequent EMC protection circuit 3. E’ Now it is applied to the output side of the EMC protection circuit 3. Due to the applied mains voltage, the rectified input voltage U E’ Usually higher than the explosion-proof voltage, especially the explosion-proof voltage of 80V.

[0029] Next, a voltage reduction circuit 4 which can be implemented by means of a phase section control unit is provided. The voltage reduction circuit 4 can be configured to reduce the DC link voltage U generated on the output side and stored in the DC link capacitor 5 according to the DC link voltage U Z The rectified input voltage U E’ Connect to the DC link capacitor 5 or rectify the input voltage U E’ The DC link capacitor 5 is disconnected.

[0030] The rectified input voltage U obtained after rectification E’ With a voltage gradient with a positive half-wave, such as Figure 2 The phase section control unit now operates in such a way that when the rectified input voltage U E’ Within the phase angle range of the increasing section, the rectified input voltage U E’Applied to the DC link capacitor 5, where the rectified input voltage U E’ The current voltage value is below the voltage threshold U u With the upper voltage threshold U o Between; and outside the voltage range or at the rectified input voltage U E’ In the case of the reduction section, the rectified input voltage U E’ The DC link capacitor 5 is disconnected.

[0031] Lower voltage threshold U u Lower than the DC link voltage U to be set Z , and is therefore below the explosion-proof voltage, which is usually 80 volts. For example, the lower voltage threshold U u can be between 60% and 70% of the explosion-proof voltage and corresponds to the DC link voltage U to be set Z The upper voltage threshold U o It can be between 75% and 90% of the explosion proof voltage.

[0032] When the rectified input voltage U E’ When the DC link capacitor 5 is charged, a significant charging current flows into the DC link capacitor 5, which can also be Figure 2 As shown in the figure.

[0033] Rectified input voltage U E’ The phase angle range applied to the DC link capacitor 5 is preferably set at a DC link voltage U Z Finish. Figure 2 shows the rectified input voltage U E’ The half-wave of the rectified input voltage U E’ The current flowing within the phase angle range applied to the DC link capacitor 5. The control can be realized accordingly by means of the control unit 6, once the rectified input voltage U E’ The upper voltage threshold U has been reached o The control unit 6 turns off the power semiconductor switch 41 of the phase segment control unit 4, and once the rectified input voltage U E’ In the next half wave, it increases again and exceeds the lower voltage threshold U u , the control unit 6 closes the power semiconductor switch 41. For example, the control unit 6 may include a Schmitt trigger.

[0034] The upper voltage threshold may correspond to the DC link voltage to be set and, as described above, may be between 75% and 90% of the explosion-proof voltage of 80 volts. The lower voltage threshold may be provided as a fixed value defined relative to the upper voltage threshold, for example between 10% and 20% below the upper voltage threshold, or may be set depending on the load or the output current obtained from the output side of the power supply unit. In this way, the DC link voltage U to be setZ It can also be set according to the power requirement of the connected electronic device 10.

[0035] A buck converter 7 may be connected to the DC link capacitor 5 , which buck converter 7 converts the DC link voltage U Z The desired power supply output voltage is reduced to the electronic device 10. The electronic device 10 may also be connected to the power supply unit 1 via a further DC / DC converter 8 to achieve galvanic isolation.

[0036] The step-down converter 7 is realized in particular in an integrated design, since at voltage levels below the explosion-proof voltage of 80 volts, the requirements for explosion protection with regard to insulation and creepage distances do not have to be met.

[0037] like Figure 1 In the embodiment shown in FIG. 1 , the phase segment control unit can be configured by means of a microcontroller as part of the control unit 6, which measures the DC link voltage U across the DC link capacitor 5. Z , and when the corresponding lower voltage threshold is reached, the power semiconductor switch 41 of the phase section control unit 4 is closed at an appropriate time point so that as the lower voltage threshold U u With the upper voltage threshold U o The increase curve of the half-wave of the rectified input voltage between the DC link voltage U Z When the voltage reaches the specified DC link voltage U Z When the upper voltage threshold of φ 2 is reached, the power semiconductor switch 41 controlled by the control unit 6 / microcontroller opens again and closes again in a corresponding manner only when the voltage of the next half-wave increases.

[0038] Depending on the power consumption of the subsequent technical device 10, if the DC link capacitor 5 can provide sufficient charge for the operation of the technical device, the closing of the power semiconductor switch can be interrupted for one or more charging cycles. In addition, the upper voltage threshold U o This is indicated, for example, by the degree of gradient of the DC link voltage after switching off the power semiconductor switch 41 , or may be signaled directly by the electronic device 10 .

[0039] In another embodiment, the phase section control unit 4 can be operated without the DC link voltage U Z This reduces the circuit complexity, but also reduces the upper voltage threshold U that can be achieved o The accuracy of the voltage threshold U cannot be reduced in this way by omitting individual charging cycles or by making the voltage threshold U o Adapt to different loads.

[0040] Microcontroller control has the following advantages: Figure 3 The implementation functions of the control unit 6 outlined in the illustrated embodiment can be implemented together with the functions of the microcontroller for the electronic device 10 operated by the power supply unit 1. Therefore, only one control unit 6 is required and the number of components can be significantly reduced. Such an implementation is possible in particular if the power supply unit and the electronic device 10 are implemented in a common module.

[0041] Furthermore, it can be provided that at an input voltage below the explosion-proof voltage, the voltage reduction circuit will be completely deactivated and the input voltage will be applied directly to the DC link capacitor. For this purpose, the power semiconductor switch 41 can be permanently closed. This means that the switching losses in the voltage reduction circuit can be reduced accordingly, since the voltage reduction circuit does not need to comply with explosion-proof requirements.

Claims

1. A power supply unit (1) for operating an electronic device (10) in an explosion-proof area, the power supply unit (1) comprising: Used to provide rectified input voltage (U E ) device (2); A DC link capacitor (5), the DC link capacitor (5) being used to buffer a DC link voltage; A phase section control unit (4) is controlled to E ) increases and is at the lower voltage threshold (U u ) and the upper voltage threshold (U o ), applying the rectified input voltage to the DC link capacitor (5) during a time period between the first and second periods, and disconnecting the rectified input voltage from the DC link capacitor (5) during a remaining time period; A converter circuit (7) configured to convert the DC link voltage (U Z ) is converted to output voltage.

2. The power supply unit (1) according to claim 1, wherein: The device for providing a rectified input voltage comprises a passive rectifier (2) and in particular an EMC protection circuit.

3. The power supply unit (1) according to claim 1 or 2, wherein: The upper voltage threshold (U o ) is lower than a predetermined explosion-proof voltage, in particular 80 volts, wherein the upper voltage threshold (U o ) is in particular between 80% and 95% of the explosion protection voltage, or wherein the upper voltage threshold (U o ) is set to be lower than the explosion-proof voltage according to a predetermined power requirement, in particular for the electronic device (10).

4. The power supply unit (1) according to one of claims 1 to 3, wherein: The control unit (6) is configured to: u ) in the event of interruption of the closing of the semiconductor switch (41) for one or more cycles.

5. The power supply unit (1) according to one of claims 1 to 4, wherein: The converter circuit (7) comprises a buck converter (7).

6. The power supply unit (1) according to one of claims 1 to 5, wherein: The control circuit (6) is configured to control the phase section control section including the power semiconductor switch (41).

7. The power supply unit (1) according to claim 6, wherein: The control circuit (6) comprises a microcontroller, wherein, in particular, the microcontroller is also configured to control an electronic device (10) operated by the power supply unit (1).

8. The power supply unit (1) according to claim 7, wherein: The control circuit (6) is configured to set the upper voltage threshold (U1) according to the input voltage of the power supply unit (1), the input frequency and the output power of the power supply unit (1). o ) and / or the lower voltage threshold (U u ), and / or the rectified input voltage is not applied to the DC link capacitor (5) during one or more half waves.

9. The power supply unit (1) according to one of claims 1 to 8, wherein: The phase section control unit (4) is controlled to operate at an input voltage (U E ) permanently applies the rectified input voltage to the DC link capacitor (5).

10. A method for operating a power supply unit (1) for operating an electronic device (10) in an explosion-proof area, wherein: The power supply unit has a function of providing a rectified input voltage (U E ) device (2), a DC link capacitor (5) for buffering a DC link voltage, and a device configured to convert the DC link voltage (U Z ) is converted into an output voltage by a converter circuit (7), wherein the rectified input voltage (U E ) increases and is at the lower voltage threshold (U u ) and the upper voltage threshold (U o ), the rectified input voltage is applied to the DC link capacitor (5) during the time period between the first and second periods, and the rectified input voltage is disconnected from the DC link capacitor (5) during the remaining time period.

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