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AC/DC two-wire control techniques

  • US 5,081,411 A
  • Filed: 12/20/1990
  • Issued: 01/14/1992
  • Est. Priority Date: 12/20/1990
  • Status: Expired due to Term
First Claim
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1. In an electrical system including a load capable of functioning for a predetermined purpose in response to transmission of at least a predetermined quantity of AC or DC electrical power through the load from an AC or DC source, an improved method for controlling transmission of the electrical power through the load in response to a predetermined condition comprising in combination the steps of:

  • conducting the predetermined quantity of electrical power through said load during a first operational state for causing the load to function for the predetermined purpose;

    preventing the conduction of said predetermined quantity of electrical power through said load during a second operating state for preventing the load from functioning for the predetermined purpose;

    storing electrical energy in response to said AC or DC source for enabling the monitoring of said predetermined condition;

    detecting the presence of said predetermined condition;

    cyclically during a time period when the presence of said predetermined condition is detected, switching to said first operating sate for causing the functioning of said load for the predetermined purpose, monitoring said predetermined condition by using the stored electrical energy, switching to the second operating state in response to the decrease of the stored electrical energy, switching to the second operating state in response to the decrease of the stored electrical energy below a predetermined value, replenishing the stored electrical energy during the second operating state for enabling the continued monitoring of said predetermined condition, and switching to said first operating state in response to the increase of the stored electrical energy for continuing the functioning of the load for the predetermined purpose, whereby the predetermined condition can be monitored in both the first and second operating states from an AC or DC source, wherein an electronic switch is connected in series with the load and the source, wherein said conducting step comprises the step of gating said electronic switch on in response to a first gating signal;

    generating pre-regulated DC power from said AC or DC source;

    generating regulated DC power in response to said pre-regulated DC power;

    charging said capacitor in response to said pre-regulated DC power;

    generating a reference signal in response to said sensing signal; and

    generating said first gating signal in response to a predetermined relationship between said reference signal and a signal proportional to the value of said stored electrical energy, wherein preventing step comprises a step of gating off said electronic switch in response to a second gating signal, wherein said detecting step comprises a step of generating a sensing signal for indicating the presence of said predetermined condition by use of said regulated DC power.

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