Auxiliary Supply for a Switched-Mode Power Supply

Abstract

An auxiliary supply for a switched mode power supply, which includes at least a transformer with a primary side and a secondary side, wherein the auxiliary supply provides a power supply to units arranged on the secondary side of the switched mode power supply independently of an operating state of the switched mode power supply, where the auxiliary supply in this case, on the primary side, which corresponds to the primary side of the switched mode power supply, has a frequency generator for generating an ac voltage with a predetermined frequency, where on the secondary side, which corresponds to the secondary side of the switched mode power supply, the auxiliary supply has a rectifier unit for a secondary side supply current and/or a secondary side supply voltage, and where a galvanic separation unit, which is particularly formed by two capacitors, is provided between the primary side and the secondary side.

Claims

1. An auxiliary supply for a switched mode power supply including at least one transformer having a primary side and a secondary side, the auxiliary supply providing a power supply to units arranged on the secondary side of the switched mode power supply independently of an operating state of the switched mode power supply, the auxiliary supply comprising: a frequency generator arranged on the primary side of the at least one transformer for generating an AC voltage with a predetermined frequency; a rectifier unit arranged on the secondary side of the at least one transformer for generating at least one of (i) a secondary side supply current and (ii) a secondary side supply voltage; and a galvanic separation unit operatively coupled between the primary side and the secondary side of the at least one transformer.

2. The auxiliary supply as claimed in claim 1, further comprising: series resistors operatively connected, on the primary side of the at least one transformer, between the frequency generator and the galvanic separation unit.

3. The auxiliary supply as claimed in claim 1, further comprising: an evaluation unit arranged on the primary side of the at least one transformer for evaluating the secondary side supply voltage.

4. The auxiliary supply as claimed in claim 2, further comprising: an evaluation unit arranged on the primary side of the at least one transformer for evaluating the secondary side supply voltage.

5. The auxiliary supply as claimed in claim 1, wherein the frequency of the AC voltage generated by the frequency generator is settable such that the galvanic separation unit exhibits an impedance minimum.

6. The auxiliary supply as claimed in claim 2, wherein the frequency of the AC voltage generated by the frequency generator is settable such that the galvanic separation unit exhibits an impedance minimum.

7. The auxiliary supply as claimed in claim 3, wherein the frequency of the AC voltage generated by the frequency generator is settable such that the galvanic separation unit exhibits an impedance minimum.

8. The auxiliary supply as claimed in claim 1, wherein the galvanic separation unit is formed by two capacitors connected in series via the rectifier unit arranged on the secondary side of the at least one transformer.

9. The auxiliary supply as claimed in claim 2, wherein the galvanic separation unit is formed by two capacitors connected in series via the rectifier unit arranged on the secondary side of the at least one transformer.

10. The auxiliary supply as claimed in claim 3, wherein the galvanic separation unit is formed by two capacitors connected in series via the rectifier unit arranged on the secondary side of the at least one transformer.

11. The auxiliary supply as claimed in claim 5, wherein the galvanic separation unit is formed by two capacitors connected in series via the rectifier unit arranged on the secondary side of the at least one transformer.

12. The auxiliary supply as claimed in claim 8, wherein the capacitors of the galvanic separation unit comprise Y1 capacitors.

13. The auxiliary supply as claimed in claim 1, wherein the galvanic separation unit comprises a transformer.

14. The auxiliary supply as claimed in claim 1, wherein the frequency generator comprises a high frequency generator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention will be explained by way of examples below on the basis of the enclosed figures, in which:

[0017] FIG. 1 shows an exemplary schematic diagram of a simple configuration of the auxiliary supply for a secondary side of a switched-mode power supply in accordance with the invention; and

[0018] FIG. 2 shows an exemplary embodiment of the auxiliary supply of FIG. 1 with a capacitive, galvanic separation unit, which is also able to be used for evaluating a secondary-side supply voltage.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0019] FIG. 1 shows an exemplary schematic diagram of an embodiment of an auxiliary supply HV in its simplest form. The inventive auxiliary supply HV is used in a switched-mode power supply, where for reasons of improved clarity, the switched-mode power supply is not shown in FIG. 1. The switched-mode power supply comprises at least one transformer or a converter that includes a transformer, in order to establish a galvanic separation between a primary side P and a secondary side S. Here, a connection to a power source or a power network is usually located on the primary side P of the switched-mode power supply. An output voltage for connection of a load or a consumer will be delivered on the secondary side S of the switched-mode power supply.

[0020] For a supply of units EL arranged on the secondary side S of the switched-mode power supply independent of the operating state of the switched-mode power supply, such as secondary-side control electronics, a pilot light, or a display, an auxiliary supply HV is provided. A supply current and/or a supply voltage Uv are provided on the secondary side for these units EL by the auxiliary supply HV.

[0021] To this end, the inventive auxiliary supply HV, on a primary side P, which corresponds to the primary side P of the switched-mode power supply, i.e., this side of the auxiliary supply is connected to the respective power source or to the respective power network, has a frequency generator FG, which in particular can be formed as a high frequency generator, in order to generate an AC voltage in the high kHz or MHz range. An AC voltage with a predetermined frequency is generated by the frequency generator FG. The AC voltage in this case can be rectangular, triangular or sinusoidal. The frequency of the frequency generator FG is settable such that a galvanic separation unit TE, which is connected to the frequency generator FG, exhibits an impedance minimum.

[0022] The galvanic separation unit TE connected to the frequency generator FG separates the primary side P of the auxiliary supply HV from a secondary side S of the auxiliary supply HV, which corresponds to the secondary side or the output side of the switched-mode power supply. The galvanic separation unit TE can be realized (as explained later with reference to FIG. 2) by two capacitors TC1, TC2. As an alternative, the galvanic separation unit TE can be formed as a transformer.

[0023] On the secondary side, the galvanic separation unit TE is connected to a rectifier unit GL (consisting of four diodes, for example). With the aid of the rectifier unit GL, a supply current or a supply voltage Uv is made available on the secondary side for secondary-side devices EL of the switched-mode power supply. The supply voltage Uv can be tapped off, for example, on the secondary side S of the switched-mode power supply or of the auxiliary supply HV at the output of the rectifier unit GL, for example at terminals A1, A2. That is, a secondary-side device EL such as a control logic, or a pilot light is connectable at these terminals A1, A2. In this case, the terminals A1, A2 are at floating potential, i.e., they can be applied to any given potential or to ground potential. The supply voltage Uv able to be tapped off at the terminals A1, A2 is independent of the respective operating state of the switched-mode power supply.

[0024] An additional filtering, which consists of a capacitor C and a resistor R, can optionally be provided on the secondary side S of the auxiliary supply HV. Here, the filtering F is attached on the output side to the rectifier unit GL, in order to smooth the supply voltage Uv created by the rectifier unit GL, for example.

[0025] Shown in FIG. 2 is a specific, especially preferred embodiment of the inventive auxiliary supply HV for a switched-mode power supply. With the auxiliary supply HV shown in FIG. 2 by way of example and schematically, as well as a supply of secondary-side devices EL independently of the operating state of the switched-mode power supply, the secondary-side supply voltage Uv or a secondary-side load at output A1, A2 of the auxiliary supply HV can also be evaluated.

[0026] To this end, the auxiliary supply HV, on the primary side, has the frequency generator FG for generating an AC voltage with a predetermined frequency. On the secondary side, the rectifier unit GL, for example, consisting of four diodes, is again provided, from which a supply current or a supply voltage Uv for secondary-side devices EL of the switched-mode power supply is made available at output A1, A2. As an alternative, a contact K can be provided at output A1, A2, via which the output A1, A2 of the auxiliary supply HV or of the rectifier unit GL is able to be short-circuited. Furthermore, on the secondary side S at the output of the rectifier unit GL, the filtering F, consisting of the capacitor C and the resistor R, can optionally be attached.

[0027] For separation of the primary side P and secondary side S, the auxiliary supply HV in accordance with FIG. 2 likewise comprises the separation unit TE. This separation unit TE is realized, for example, by two capacitors TC1, TC2, where the two capacitors TC1, TC2 are connected in series via the secondary-side rectifier unit GL. For reasons of safety or so that, for example, the contact K can be safely opened or closed by a user, the capacitors TC1, TC2 of the separation unit TE are formed, for example, as Y1 capacitors. Y1 capacitors (for example, in accordance with the appropriate IEC Norm) thus have an increased insulation or a checkable increased electrical and mechanical safety and may therefore be used between the primary side P, which is connected to a power source or to the power network, and the secondary side S. As an alternative, the separation unit TE can be formed as a transformer.

[0028] For evaluation of the secondary-side supply voltage Uv or of the secondary-side load at output A1, A2 of the auxiliary supply, there are also at least two series resistors VR1, VR2 provided on the primary side P. The series resistors VR1, VR2 are attached between the frequency generator FG and the separation unit TE. If the separation unit TE (as shown FIG. 2) is realized by two capacitors TC1, TC2, then a first series resistor VR1 is arranged in a first connection V1 between the frequency generator FG and a first capacitor TC1 of the separation unit TE and a second series resistor VR2 in a second connection V2 between the frequency generator FG and a second capacitor TC2 of the separation unit TE. Furthermore the auxiliary supply HV, on the primary side P, includes an evaluation unit AW, which is linked to the connections V1, V2.

[0029] In order to generate a supply current or a supply voltage Uv on the secondary side S, an AC voltage with a predetermined frequency is generated by the frequency generator FG and this AC voltage is applied to the separation unit TE or to the two capacitors TC1, TC2. Here, the predetermined frequency of the AC voltage is selected so that the impedance of the separation unit TE or of the two capacitors TC1, TC2 is at a minimum. Usually an ac voltage with a high frequency (e.g., 100 kHz, or 1 MHz) is generated.

[0030] Through the primary-side application to the separation unit TE, an AC current or an AC voltage is transmitted by the separation unit TE to the secondary side S. In a separation unit TE, which consists of two capacitors TC1, TC2, there is an alternating current flow through the capacitors TC1, TC2, for example, which can be tapped off on the secondary side via the rectifier unit GL.

[0031] For evaluation of the supply voltage Uv or the load at output A1, A2 of the auxiliary supply HV, the separation unit TE or the two capacitors TC1, TC2 of the separation unit TE are activated accordingly via the series resistors VR1, VR2. If the output A1, A2 of the auxiliary supply HV or of the rectifier unit GL is now loaded with a device EL or is short-circuited via a contact K, then the AC voltage U also collapses accordingly on the primary side. This change of the AC voltage U can be detected and evaluated via the evaluation unit AW. The evaluation of the primary-side ac voltage U as well as a derivation of the load or of a resistor at output A1, A2 of the auxiliary supply HV can be achieved either by analog or by digital means. The results established with the evaluation unit AW can then be further processed accordingly. In this way a passive signal on the secondary side S, such as an opening and/or closing of the contact K at output A1, A2 of the auxiliary supply HV or a change of the resistor EL at output A1, A2 of the auxiliary supply HV, can be transmitted as information to the primary side P of the auxiliary supply.

[0032] When a contact K is used for a secondary-side signal at output A1, A2 of the auxiliary supply HV, this contact K is at floating potential and can, for example, be applied to the ground potential or to another potential. The information transmitted from the secondary side S to the primary side P (e.g., opening and/or closing of the contact K) can be used, for example, for switching-on and switching-off the switched-mode power supply.

[0033] If, as an alternative, for example, a change of the voltage Uv or of the load resistance EL at output A1, A2 of the auxiliary supply HV is evaluated, then the output A1, A2 of the auxiliary supply can be used, for example, for a realization of a display of a level.

[0034] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.