Electricity: motive power systems – Positional servo systems – Pulse-width modulated power input to motor
Reexamination Certificate
2001-06-20
2003-07-22
Leykin, Rita (Department: 2837)
Electricity: motive power systems
Positional servo systems
Pulse-width modulated power input to motor
C318S807000, C318S808000, C318S810000, C318S812000, C318S817000
Reexamination Certificate
active
06597144
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for detecting a power loss to an appliance and storage of current operation settings of the appliance when the power loss occurs.
Some appliances such as washing machines and dryers include a feature that allow the appliance to retain current operation settings in the event of a power outage. This is accomplished by monitoring the AC power input to the appliance, detecting when the AC power is lost and saving the current operation settings in a memory device such as a EEPROM so that when power is restored the washing machine cycle or dryer cycle will resume at the point in the cycle when power was lost. The period of time between loss of AC power and saving of the operation settings is critical since during this time a microprocessor or controller within the appliance is powered by a charged capacitor. Hence, the quicker that the current operation settings can be saved the more likely that the settings will actually be stored within the EEPROM.
In order to ensure that there is sufficient charge on the capacitor during power outage to store the current operation settings, an approach has been to increase the size of the capacitor so as to store more charge. However, larger capacitors are more expensive.
Additionally, appliances such as a washing machine or a dryer typically have a motor that turns a washing drum or a drying chamber, respectively. Other appliances, such as dishwashers, include motors which drive pumps. Microwave ovens often times include motors which drive rotating turntables. Most other domestic appliances also include motors and/or heating elements. During the power outage, the motor within the appliance continues to rotate for a short time, especially given a large washing or drying load, which increases the mass and, hence, the momentum of the washing drum or the drying chamber. This continued rotation of the motor after power outage causes transient voltages to be generated from the motor on the incoming line, that, in turn, cause noise to be present in the supply to a control microprocessor that is supplied with power by the incoming line through a power supply circuit. This noise creates a problem in that the microprocessor senses this noise and, thus, does not quickly recognize that power on the incoming AC line has been lost. Furthermore, by the time that the microprocessor recognizes power loss, the capacitor used to store the current operation settings of the appliance has been partially discharged due to continued operation of other loads such as a relay coil driving a contact to the motor or a heater element. The partial discharge of the capacitor during the time that the microprocessor does not recognize power loss leads to the inability of the microprocessor to save current operation settings since enough charge on the capacitor does not remain to effect this storage.
SUMMARY OF THE INVENTION
There is therefore a need for an apparatus and method for more quickly recognizing loss of input power to a device, such as an appliance, so that operation settings will not be lost in the event of transient noise generated from an electromechanical device within the device. Additionally, the need exists for faster recognition of AC power loss in order to reduce the discharge time of a capacitor and, hence, allowing the capacitor to have a smaller value.
These and other needs are met by the present invention including a method for monitoring power input to a device where at least a voltage signal on an incoming line to the device is monitored. Variations of a frequency of at least the monitored voltage signal from a prescribed frequency are sensed and a power loss signal is issued when a variation of the frequency from the prescribed frequency exceeds a first predetermined amount. The power loss signal indicates a detected loss of power input on the incoming line. By sensing variations of the frequency of the monitored voltage signal, the present method is able to take into account transient noise generated by a motor after power loss more quickly than the known art.
According to another aspect of the present invention, a method for monitoring power input to an appliance and storing current operation settings of the appliance when the power input is lost includes monitoring at least a voltage signal on an incoming line to the device and sensing variations of a frequency of at least the monitored voltage signal from a prescribed frequency. When a variation of the frequency from the prescribed frequency exceeds a first predetermined amount a power loss signal is issued. The power loss signal indicates that a loss of power input on the incoming line has been detected. Relay coils that control power input to at least one of an electromechanical device and heating device within the appliance are pulsed at a predetermined duty cycle in response to the power loss signal in order to increase a discharge time of an electric charge on a capacitor connected to the input line and also connected to the relay coil. Finally, current operation settings of the appliance are simultaneously stored in a memory using the charge of the capacitor. The pulsing of the relay coils allows the relay coils to still maintain closed contacts in order to avoid an unnecessary opening of the contacts in a situation such as a brown out, thereby mitigating deleterious effects to the relay coils in these situations. Additionally, since the relay coils are driven by capacitor power, the pulsing at a predetermined duty cycle conserves charge on the capacitor that is later or simultaneously used for storing the current operation settings. Hence, enough capacitor charge will be present to ensure proper storing of the current operation settings. A further advantage is that a smaller capacitor can be utilized since the pulsing of the relay coils affords conservation of capacitor charge, and, thereby, a minimization of capacitor cost.
According to yet another aspect of the present invention an apparatus is provided for monitoring power input to an appliance and saving current operation settings of the appliance in the event of a power input loss. The apparatus includes a power input line for supplying a power input to the appliance. In addition, a power supply circuit for converting a voltage of the power input into a plurality of supply voltages is included. A capacitor within the power supply circuit is connected between the first supply voltage and a ground. A voltage sensing circuit is connected to the second supply voltage and outputs a sensing signal having a frequency that corresponds to a power input frequency of the power input line. One or more relay coils that control power input from the power input line to at least one of an electromechanical device and a heating device within the appliance are included. Current operation settings of the appliance are stored by a provided memory device. A controller is included that is configured to detect the frequency of the sensing signal, control the relay coils and store current operation settings of the appliance in the memory device. The controller pulses the relay coils using an electric charge from the capacitor at a prescribed duty cycle and also stores current operation settings of the appliance in the memory device using the same electric charge from the same capacitor when the controller detects a change in the frequency of the sensing signal after a predetermined number of cycles of the sensing signal.
Additional advantages and novel features of the invention will be set forth, in part, in the description that follows and, in part, will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 3593103 (1971-07-01), Chandler et al.
patent: 3786219 (1974-01-01), Kornrumpf et al.
patent: 4074101 (1978-02-01), Kiuchi
Fox Marvin L.
Hansen Scott L.
Herman Mark L.
Pearson Steven L.
Krefman Stephen
Leykin Rita
Rice Robert O.
Roth Thomas J.
Whirlpool Corporation
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