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Solenoid valve with supply voltage variation compensation

  • US 4,838,037 A
  • Filed: 08/24/1988
  • Issued: 06/13/1989
  • Est. Priority Date: 08/24/1988
  • Status: Expired due to Fees
First Claim
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1. A refrigeration system comprising:

  • a refrigeration compressor, a condenser, and an evaporator, all of which are connected in series to comprise a refrigeration circuit;

    a solenoid valve adapted to be coupled to a current supply and coupled to said refrigeration circuit by way of a pressure actuated valve connected between in series with said condenser and said evaporator, said solenoid valve being adapted to move between a fully open and a fully closed position upon receiving a DC electrical current supplied by said current supply, said pressure actuated valve having an opening that varies in response to the degree of opening of said solenoid valve, whereby said solenoid valve serves as a pilot valve for said pressure actuated valve, which in turn regulates a flow of refrigerant through said refrigeration circuit;

    a PWM circuit coupled in heat transfer relationship with said refrigeration circuit by way of a temperature sensor and electrically coupled to said solenoid valve and said current supply, said PWM circuit including a microcomputer for generating a PWM control signal having a pulse width that varies in response to a temperature signal provided by said temperature sensor, said PWM control signal being communicated to a transistor that repeatedly interrupts said electrical current at a frequency that is sufficiently high to generally balance said valve at an intermediate position between said fully open and said fully closed position, said PWM circuit including a comparator that compares the voltage level of said current supply to a reference voltage to facilitate further varying of said pulse width to compensate for some variation in the voltage level of said current supply, whereby said intermediate position is generally independent of variations in the voltage level of said current supply.

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