US 2002/0118495 A1 · Circuit for operating voltage range extension for a relay

Abstract

A relay is designed to be used in a circuit where the voltage levels are high in comparison to the spacing between the contacts when open. Contact closure arcing is suppressed by actuating a MOSFET that shorts the contacts together while they open. The same MOSFET can momentarily short the contacts together just before they first begin to close, allowing a test current to be passed through the MOSFET and through the terminals connecting to both relay contacts, to insure that arc suppression will be successful; and if this test fails, then the relay can be disabled by a switch in series with the relay coil to prevent arcing and a possible fire hazard. Relay deactuation can be sensed to trigger arc suppression, and relay actuation can be sensed to initiate fail-safe testing by a circuit that responds no matter which way the relay coil is connected into the external circuit that drives it.

Claims39

Dependent claims

A method for safely suppressing the arcing of a relay's contacts when the contacts open using a solid state switch connected in parallel with the relay's contacts as an arc suppressing device, this method comprising the steps of:

sensing the relay coil energization signal before its contacts close;
in response, energizing the solid state switch to short the relay contacts together;
testing whether the potential across the relay's contacts drops to a very low potential in response to this energization of the solid state switch before the relay's contacts close;
if the potential across the relay's contacts is not very low:
preventing energization of the relay coil and subsequent contact closure at least until contact closure energization terminates;
and if the potential across the relay's contacts is very low:
permitting energization of the relay coil and subsequent contact closure;
sensing deenergization of the relay before its contacts open;
and in response, energizing the solid state switch again to short the relay contacts together long enough to suppress arcing that would otherwise occur when the relay's contacts open.

6 more elements

An arc suppression system for a relay having at least one pair of normally open contacts, having an energizing coil with at least two leads, and having at least two contact terminals and two coil terminals respectively electrically coupled to each of the contacts and to each of the coil leads, said system comprising:

a solid state contact shorting switch having two switch leads connected in parallel with the two contact terminals and having a control lead which, when energized with an input signal, causes said switch to effectively short circuit the two contacts of the relay;
a first timing pulse generator receiving an input signal from at least one of the two coil terminals and responding to a coil energizing signal by generating a first timing pulse which, when applied to the solid state switch's control lead, causes momentary conduction of the switch;
a circuit tester and coil switch having an input coupled to at least one of the two contact terminals independently of the switch leads of said solid state switch and arranged to signal, by its conductive or nonconductive state, whether the two relay contacts are or are not effectively short circuited by the solid state switch, this coil switch having two switch leads which form an electrically conductive part of one of the two electrical couplings between the coil leads and the coil terminals, such that the coil cannot be energized to close the relay contacts unless the coil switch first verifies the proper operation of the contact shorting switch and its connections to the contact terminals;
and
a second timing pulse generator receiving an input signal from at least one of the two coil terminals and responding to the termination of a coil energizing signal by generating a second timing pulse which, when applied to the solid state switch's control lead, causes conduction of the contact shorting switch of sufficient duration to suppress contact opening arcing.

2 more elements

A fail-safe arc suppression system for a relay whose contacts are subjected to voltages that are high relative to the relay's maximum open contact separation distance, thereby creating a risk of possible sustained arcing if contact opening arcing is not carefully and fully suppressed, said system comprising:

a relay having an energizing coil having first and second coil leads respectively electrically coupled to first and second relay coil terminals of the relay and having at least first and second normally open relay contacts respectively electrically coupled to first and second relay contact terminals of the relay, the relay contacts arranged to close upon energization of the energizing coil and arranged to open in response to deenergization of the energizing coil;
a first solid state switch having a first switch control lead and having first and second switch leads, the first and second switch leads being coupled electrically respectively to the first and second relay contact terminals such that energization of the control lead causes the switch to effectively short circuit the relay contacts;
a second solid state switch having a second switch control lead and having first and second switch leads that form part of the electrical coupling between at least one coil lead and its respective coil terminal such that a signal applied to the second switch control lead can permit or block the energization of the relay coil, said second switch control lead being electrically coupled to the one of said contact terminals that is intended to be connected to a load such that when the contact terminals are effectively short circuited, a signal is applied to the second switch control lead that permits the relay coil to be energized;
a circuit having at least one input electrically coupled to at least one of said first and second coil terminals and having an output electrically coupled to said first solid state switch's control lead;
said circuit responding to a signal change at the circuit's input in a direction signaling the removal of energy from said energizing coil by applying a first timing signal pulse having a first pulse duration to the first solid state switch control lead, the first pulse's duration being sufficiently long to cause the first solid state switch to effectively short circuit the relay contacts while they open to suppress contact closure arcing;
and
said circuit responding to a signal change at the circuit's input in a direction signaling the application of energy to said energizing coil by applying a pulse to the first solid state switch of sufficient duration to permit the second solid state switch to test for proper operation of said first solid state switch and its electrical coupling to the relay contact terminals before permitting the relay coil to be energized.

4 more elements

a solid state contact shorting switch having two switch leads connected in parallel to the two contact terminals and having a control lead which, when energized with an input signal, causes said switch to effectively short circuit the two contacts of the relay;
a timing pulse generator having two inputs receiving input signals respectively from both of the two coil terminals and responding to a signal fluctuation at either of the coil terminals in a direction indicating a cessation of an incoming relay energizing signal by causing conduction of the contact shorting switch of sufficient duration to suppress contact opening arcing.

A relay comprising:

a pair of normally-open relay contacts;
a pair of contact terminals electrically coupled to said respective relay contacts;
a relay coil magnetically coupled to at least one of said pair of relay contacts and arranged to close said pair of relay contacts when supplied with current, said coil having first and second leads;
a pair of coil terminals electrically coupled to said respective coil leads;
a solid state switch having a pair of switch leads electrically coupled to said respective contact terminals, said switch also having a control lead;
a timing circuit having first and second signal inputs and first and second power inputs and having a signal output electrically coupled to said switch control lead, said timing circuit providing a timed output signal pulse at its signal output in response to signal transitions at either of its signal inputs;
first and second electrical power couplings interconnecting said respective first and second power inputs to at least one of said coil or contact terminals, and at least one of said first and second electrical power couplings interconnecting the corresponding one of said first and second power supply inputs either to both of the coil terminals or to both of the contact terminals through diodes or their equivalents;
and
first and second signal supply couplings interconnecting said respective first and second signal inputs to said respective coil terminals to thereby permit said timing circuit to respond to signal fluctuations on either coil terminal.

6 more elements

A relay comprising:

a pair of normally-open relay contacts;
first and second contact terminals electrically coupled to said respective relay contacts in said pair of contacts:
a relay coil magnetically coupled to at least one of said pair of relay contacts and arranged to close said pair of relay contacts when supplied with current, said coil having first and second leads;
first and second coil terminals, said first coil terminal electrically coupled to said first coil lead;
a first solid state switch electrically coupling said second coil lead to said second coil terminal and having a first control lead;
a second solid state switch having first and second switch leads and having a second control lead;
first and second contact terminal electrical couplings respectively connecting said first and second switch leads to said first and second contact terminals;
a timing circuit having first and second signal inputs and first and second power inputs and having a signal output electrically coupled to said second control lead, said timing circuit providing a timed output signal pulse at its signal output in response to signal transitions of a first polarity received at its first signal input and in response to signal transitions of a second polarity received at its second signal input;
first and second electrical power couplings connecting said respective first and second power inputs to at least one of said coil or contact terminals;
first and second signal supply couplings connecting said respective first and second signal inputs to said second coil terminal;
and
a circuit test electrical coupling connecting said second contact terminal to said first control lead, this circuit test electrical coupling being electrically isolated from said second contact terminal electrical coupling such that a test signal flowing from said second switch lead of said second solid state switch to said first control lead of said first solid state switch must pass into and out of said second contact terminal.

9 more elements

Dependencies are inferred from the claim text.

Circuit for operating voltage range extension for a relay

Life of this patent

Circuit for operating voltage range extension for a relay

Life of this patent

Abstract

Claims39