Safety switching device with a safe power supply unit

Patent metadata

Field	Value
Publication number	US-9923359-B2
Application number	US-201514813558-A
Country	US
Kind code	B2
Filing date	Jul 30, 2015
Priority date	Feb 1, 2013
Publication date	Mar 20, 2018
Grant date	Mar 20, 2018

Abstract

A safety switching device for an automated installation includes a power supply unit for providing at least one operating voltage for the device. The power supply unit receives an input voltage via a feed line and provides a defined output voltage on an output side. Electrical supply to the power supply unit is interrupted if an instantaneous output voltage is higher than the defined output voltage. The interruption is achieved by first and second switching elements arranged in series and connecting the input of the power supply unit to ground, and by an interrupter element in the feed line. The interrupter element triggers when both the first and the second switching elements are in a closed, low-impedance state. A reference point between the first and the second switching elements has a voltage value that corresponds to a first expectation value when the first switching element is in the closed, low-impedance state and the second switching element is in an open state, and corresponds to a second expectation value when the first switching element is in the open state and the second switching element is in the closed, low-impedance state.

First claim

What is claimed is:

1. A safety switching device for switching on or switching off a technical installation in a failsafe manner, comprising:
an input for receiving an input signal representing a safety condition,
a failsafe control/evaluation unit that processes the input signal in order to generate an output signal for switching on or switching off the technical installation in response thereto,
a power supply unit for providing at least one operating voltage for the control/evaluation unit, the power supply unit having an input side and an output side, said input side having a power input connected to a feed line and a ground connection for receiving an external input voltage provided between the feed line and the ground connection, and the power supply unit providing said at least one operating voltage at the output side,
a first and a second switching element arranged in series and bridging the power input to the ground connection, and
an interrupter element arranged between the power input and the feed line, which interrupter element triggers when both the first and the second switching elements are in a closed, low-impedance state,
wherein a reference point is defined between the first and the second switching elements, which reference point has a voltage value that corresponds to a first expectation value when the first switching element is in the closed, low-impedance state and the second switching element is in an open state, and said voltage value corresponds to a second expectation value when the first switching element is in an open state and the second switching element is in the closed, low-impedance state.

2. The safety switching device of claim 1 , further comprising a control element that selectively actuates the first or the second switching element and compares the voltage value at the reference point with the first and second expectation value.

3. The safety switching device of claim 1 , further comprising a third expectation value that occurs at the reference point if both the first switching element and the second switching element are in the open state.

4. The safety switching device of claim 1 , wherein the interrupter element does not trigger if only the first or the second switching element is in the closed, low-impedance state.

5. The safety switching device of claim 1 , further comprising a first monitoring unit and a second monitoring unit that are connected to the at least one operating voltage, wherein the first monitoring unit actuates the first switching element if the at least one operating voltage exceeds a first defined voltage value, and the second monitoring unit actuates the second switching element if the at least one operating voltage exceeds a second defined voltage value.

6. The safety switching device of claim 5 , wherein the first and second defined voltage values are adjustable.

7. The safety switching device of claim 5 , further comprising a control element that can adjust at least one of the first and second monitoring units independently of the at least one operating voltage.

8. The safety switching device of claim 1 , wherein the failsafe control/evaluation unit comprises at least two processing units that process the input signal in a redundant manner with respect to one another and perform logic signal operations in order to generate the output signal in response thereto.

9. The safety switching device of claim 8 , wherein the at least two processing units operate with different operating voltages.

10. The safety switching device of claim 1 , wherein the power supply unit is configured to generate at least one further operating voltage, wherein a third and a fourth monitoring unit are connected to the further operating voltage, the third monitoring unit actuating the first switching element if the further operating voltage exceeds a third defined voltage value and the fourth monitoring unit actuating the second switching element if the further operating voltage exceeds a fourth defined voltage value.

11. A method for monitoring a power supply unit of a safety switching device for switching on or switching off a technical installation in a failsafe manner, the method comprising the steps of:
providing a safety switching device having an input for receiving an input signal, a failsafe control/evaluation unit that processes the input signal in order to generate an output signal for switching on or switching off the technical installation in response thereto, and a power supply unit that has a power input and a ground connection, said power supply unit generating at least one operating voltage for the control/evaluation unit,
supplying electrical power to the power supply unit via a feed line and a ground connection,
arranging a first and a second switching element in series between the feed line and the ground connection,
arranging an interrupter element in the feed line,
actuating the first and second switching elements in an alternating manner, and
monitoring a voltage value at a reference point between the first and the second switching elements, wherein the voltage value is expected to correspond to a first expectation value in the case of a closed, low-impedance state of the first switching element and in the case of an open state of the second switching element, and wherein the voltage value is expected to correspond to a different second expectation value in the case of an open state of the first switching element and a closed, low-impedance state of the second switching element, and
triggering the interrupter element in order to disconnect the power supply unit from the electrical power if the voltage value at the reference point does not correspond to either the first or the second expectation value.

12. The method of claim 11 , wherein the interrupter element is triggered by bringing both the first and the second switching elements into the closed, low-impedance state.

Assignees

• Pilz Gmbh & Co Kg

Inventors

• Richter Sebastian
• Le Kim
• Roehmann Stefan

Classifications

• H02H9/041

  using a short-circuiting device · CPC title

• H02H9/042

  comprising means to limit the absorbed power or indicate damaged over-voltage protection device · CPC title

• H02H7/1213

  for DC-DC converters · CPC title

• H02H3/05 Primary

  with means for increasing reliability, e.g. redundancy arrangements {(for logic circuits H03K19/003)} · CPC title

• H02H3/20

  responsive to excess voltage · CPC title