VOLTAGE REGULATOR CIRCUIT
BACKGROUND OF THE INVENTION Ca, mpo of the Invention The present invention relates to an electrical signal regulator circuit such as, for example, a voltage regulator circuit, or a regulator circuit for a glass unit to protect from damage. to glass unit Related Technique Glass units can be heated to reduce fogging, condensation or other accumulation of moisture It can also be heated after the glass has been covered with mist in order to eliminate any accumulated condensation. Glasses such as those for refrigeration units in commercial establishments such as food stores and convenience markets, are often heated to minimize any mist formation or condensation of ambient humidity. Refrigerator doors, for example, are commonly coated with a resistant material to which a voltage for lime is applied The material to reduce or eliminate any condensate in the glass, or the potential for moisture to condense on the glass. These coatings are sometimes referred to as transparent conductors and are applied to a glass surface. The transparent conductor has a Inherent fixed resistivity and the strength of a given coating depends on the resistivity and bulky thickness of the coating and the size of the glass over which the coating is placed. The amount of heat produced in the coating for a given glass unit depends on the applied voltage which, according to conventional applications, is the most convenient and economical online voltage available from the electrical service. In the United States, the line voltage is 120 volts while the line voltage in Europe is 220/240 volts. Therefore, glass doors or other glass units used in the United States are coupled to control circuits designed to operate at 120 volts. The units used in Europe use the control circuits designed for 220/240 volts. Taking into account the glass units for the United States, then, the heating of said glass units depends on the size of the glass door and the resistivity of volume and thickness of the coating as to how much glass is going to be heated. Therefore, for a given environment, a larger door will have a different thickness to achieve the necessary heat production than a smaller door for the voltage in line with encional. For a given size door, a glass unit used in a wet area may require more heat to prevent fogging than would a glass unit used in an arid area. Therefore, a glass unit for a wet area could optionally be coated with less material than one for an arid area. However, in practice, a coating is normally applied to a glass unit so that the glass unit can be used in any area, regardless of humidity and ambient temperature. The relationship between door size, resistivity and voltage is derived from the resistivity of the material volume and the thickness of the material applied to the door, which translates to a resistance per square, where the area is a quantity without dimensions. The voltage that will be used is derived from the power equation P = l2 x R, where "P" is the power, "I" is the current and "R" the resistance, the last one being determined by the size of the door , assuming a predetermined resistance per frame. The voltage V will then be the square root of the product of "P" and "R". The glass units can now be produced uniformly with a uniform thickness of a given transparent conductor (i.e., a normal resistance per square), giving rise to the need for a means to apply the appropriate voltage to a glass unit for a size of given unit, and also preferably as a function of the surrounding environment. There is a need for a reliable, low cost and predictable method for applying voltage to the transparent conductive coating on said glass units in a known amount and characteristic. SUMMARY OF THE INVENTION The present invention provides a voltage regulator circuit for controlling the voltage or current applied to an element such as a transparent conductive coating. The circuit can be used to apply a voltage signal of a known value to the transparent conductor, regardless of the size of the unit, the number of trays in the glass unit, the environment in which the unit will be used and the like. is reliable, not expensive to incorporate into a refrigerator assembly and / or freezer doors, for example, and can be modified to provide additional protections. In accordance with one aspect of the present invention, the regulator circuit includes an inlet, an outlet for coupling to a load, such as a coating on a glass unit and a circuit control element for modifying the signal applied to the load A sensor circuit captures when a signal is applied to the load exceeds a defined limit, such as could occur to cause the glass to overheat In another form of the invention, a glass unit, such as for a refrigeration unit, includes a material with the glass unit to which a voltage or current is applied A regulator circuit is used with the glass unit and includes a circuit control element to modify the signal applied to the material A sensor circuit picks up when the voltage or current applied to the outlet exceeds a defined limit and operates the circuit control element when it exceeds the limit In the context of a glass unit, said regulator circuit minimizes the possibility that the glass unit will overheat will be broken or damaged. will damage in some way in the event that unwanted signals enter the input In one form of the invention, the circuit control is an interruption, such as a fuse that will serve to disconnect the line voltage of the load In another form of the invention, an actuator circuit is included, such as a silicon controlled rectifier (RCS) to cause a fuse there will be the circuit. Alternatively or otherwise, the RCS is designed to cause a main circuit breaker, such as in a utility panel, to move before any damage that could be caused to the glass unit even if the fuse is derived. In another form of the invention, a Voltage control is used to control the amount of voltage applied to the transparent conductive coating to be less than the line voltage at the input. For example, the voltage control device can be bidirectional tpstor (tpac) or other similar device to apply only a portion of an AC signal to the conductive coating on the glass A bidirectional tpac will reduce the average voltage applied to the glass unit The control circuit preferably also includes an element, such as a diac (electronic switch) to optimize the performance of the device voltage control In a further form of the present invention, a control circuit, such as a To apply voltage to conductive coatings on a glass unit includes a filter or an integration circuit to ignore or minimize the effects on the circuit of the time current such as current pulses and the like that may arise from the start or the detection of refrigeration units or other equipment for example The integration circuit determines the net power that could be applied to the coating during a given period to determine if the power exceeds a high level Therefore, it is an object of the present invention to provide a controlling circuit the signal applied to a load, such as a glass unit It is a further object of the present invention to provide a regulator circuit which minimizes the possibility of damage or other adverse effects on the glass units that may result from possible failure of circuit elements. It is a goal It is a further object of the present invention to provide such a circuit which is not costly and reliable for such applications as transparent conductive coatings on glass units. It is a further object of the present invention to provide said circuit which is taken into account for temporary currents, which minimizes the possibility of damage due to defective or inappropriate circuit repairs of vibrators and the like These and other objects of the present invention will become more apparent after considering the following brief description of the drawings and detailed description of the preferred embodiments BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1, is a front elevation view of a glass unit installed in a refrigeration unit according to an application of the present invention FIGURE 2 is a cross-sectional view of a glass unit having a transparent conductive coating, constituting a shape of an application for the present invention FIGURE 3, is a schematic block diagram, which represents a preferred form of the present invention FIGURE 4, is a circuit diagram, which represents a preferred form of an aspect of the present invention DESCRIPTION DETAILED OF PREFERRED MODALITIES In accordance with the present invention, a voltage regulator circuit is provided to control voltage or current applied to an element or charge such as a transparent conductive coating over part of a glass unit, so that it can be use in the glass door of commercial refrigerators The circuit can be a discrete unit separ or can be incorporated as an integral part of an assembly, such as part of a refrigeration unit. In the examples given herein the circuit will be described together with the controlled heating of a glass unit and the protection of the glass unit to prevent rupture or damage to the unit, although other applications are possible A refrigeration display cover 20 such as is normally found in liquor stores, convenience stores and the like, can be manufactured on a common or semi-common basis in which a cooling shroud 22 is incorporated into an opening 24 of a cabinet or the like. The refrigerated display shroud 20 is maintained at a lower temperature than the ambient temperature by conventional refrigeration equipment (not shown) in order to preserve the food products and the like The display cover 20 may include one or more hinged doors 26 for observing and permitting the acc that to the items within the cover, two doors that open to the right illustrated in Figure 1 Each door 26 includes areas of glass Vision 28 including one or more glass panels within the door frames 30 Numerous constructions of doors are well known in the refrigerator and freezer area. The doors are supported by and closed on surrounding frames 32 by defining an opening in the refrigerated cover. The doors 26 typically include handles 34, and, in the case of a vertical swing door, hinges 36 in the upper corner of the vertical or hinged side of the door for swinging outward from the display cover The lower portion of the hinged side of each door normally includes an automatic door closing mechanism 38 having a fixed portion to the frame surrounding 40 The set of hinges could include a mounting slide and an electrical connector 42 for mounting a pass connection hinge having an electrical mating contact to be mounted on the slider at the top of a respective door to the top of a surrounding frame. Said assembly is shown and described in U.S. Pat., 4,671,582, the description of which is incorporated herein by reference. Electrical connector 38 passes current at a predetermined voltage in the circuits in the door to heat the door frame as well as to heat one or more panels in the glass unit. provides an alternating current (AC) signal through the appropriate cable 44 from a connection 46 that receives power from an electrical service source through a circuit breaker 48 in a main junction box 50 Commercial refrigerator displays typically include a glass unit 52 (FIGURE 2) having one or more glass panels such as a forward glass panel 54 exposed to ambient air and a rear glass panel 56 exposed to the inside of the glass cover. refrigerator display A separator 58 separates the glass panels and a glass strip 60 that surrounds the perimeter of the glass unit In application is of low temperature and / or high humidity the outer glass panel 54 includes an inner surface 62 having a transparent conductive coating 64 for heating the glass pane forward 54 Current is supplied to the coating 64 at a defined voltage through a bus 66 through a circuit 70 for controlling the heating of the conductive coating 64 The circuit 70 can be placed separately in the surrounding frame construction, in a stabilizer of a surrounding frame or even in the door frame In the preferred embodiment , the circuit 70 takes an AC signal from an on-line power source, such as 120 volts at 60 Hz in the United States (FIGURE 3) The AC signal is then applied to a regulating element 72 which is then applied to the signal AC, modified or unmodified to a load 74 The signal applied to the load 74 is captured, displayed or tested by a sensor circuit 76 to determine whether or not A signal applied to the load exceeds a defined limit If the load signal exceeds the defined limit, the signal for the load is modified or interrupted to protect the load, or for any other purpose as desired. In the preferred embodiment, the circuit sensor 76 engages and controls a protection or control circuit 78 to protect the load and will interrupt the signal to the load or modify the signal applied to the load in a manner or time as determined by the sensor circuit 76 Alternatively, the timing or type of the modification or switch can be determined by the protection circuit In the preferred embodiment the protection circuit 78 is coupled through the input lines to the connection 46 or the other input The regulating element 72 controls preferably the voltage supplied to the load In the particular embodiment described herein, the regulator element 72 limits the voltage applied to the coating 64 The preferred or selected voltage will depend on the resistance of the coating, which in turn is determined by the volume resistivity, the thickness of the coating and the size of the door and the applied voltage is also selected based on the environmental conditions at which will use the door The characteristics of the regulating element 72 will also depend on the input line signal In the preferred embodiment, the regulating element 72 includes a tpac to apply a voltage to the load as a function of time, namely for only a certain part of the AC cycle The tpac are suitable to apply less than full voltage to the load, and are small enough to be placed in small areas. Transformers and potentiometers can serve to work the same but are relatively large and are not preferred for the application inside the cooling units A tpac provides a voltage controlled signal without creating a significant amount of heat in the circuit and is an economical substitute for a transformer, for example In alternative embodiments, the regulating element 72 may apply voltage to the load at reduced levels, or at different levels for different periods of time. The regulating element 72 also preferably includes an adjustment device, such as an enhancer for adjusting the regulating element. as a function of the particular door to which it will be connected, as well as to the characteristics of the environment The sensor element 76 to sense when a signal applied to the load exceeds a defined limit can pick up one or more of the current voltage levels of the signal applied to the load, the frequency with which the signals of a given voltage are applied to the load, or the length of time that is applied to a particular voltage to the load. It is also possible to pick up current through the sensor circuit. Particularly described herein, the sensor circuit includes one or more filter circuits to integrate or filter the signals applied to load and determine when these signals exceed a given voltage, for example the defined limit The defined limit could not normally be the preferred voltage applied to the glass unit since some signals slightly higher than the preferred voltage for the glass unit can be passed to the glass unit without any significant adverse effect For example, due to a significant concern with the door of a refrigerator having a conductive coating is to avoid overheating the conductive coating can easily adapt higher voltage signals, so that they can exceed the voltage in line (such as 200 volts), which can result in a temporary slight increase in the temperature of the door but a sustained signal of 200 to 400 volts having a pulse width over vain teachings of a second can damage the conductive coating or the door. Such a sustained signal may arise from a problem of being electrical vice or a problem of the line in another part of the building or the failure of regulator circuit For example a line of 220 to 400 volts can be inadvertently applied to the circuit to which the door is coupled or the voltage regulator circuit can start applying all the voltage of 110 RMS to the load continuously Therefore, in the preferred embodiment, the circuit is interrupted only after several excursions have been received, or after a sustained excursion has been received, to avoid interruption of the circuit. circuit after simply acceptable or permissible temporary currents are applied to the load. For example, in the embodiment herein described, the conductive coating is such that a number of temporary currents exceeding the maximum voltage can be applied to the coating driver without significant damage in other words, overheating can not occur However, if a number signifies Temporary streams are applied to the conductive coating, or if a continuous high-voltage level is applied to the conductive coating over a period of time the coating could be damaged or the glass could overheat, which would break the glass or otherwise damage the unit It should be noted that any electrical component is subject to failure and measures must be taken to minimize the possibility of failure. For example, the tpac may fail, and in the mode where the tpac is used to control the applied voltage a diverter may be used to load to protect the tpac from impulse or temporary current. The protection circuit 78 may be a control circuit that modifies the signal applied to the load but which preferably is an interruption that completely removes all the signals from the load. the load when the signal is applied to the load exceeds the defined limit In the preferred embodiment of the In this invention, the protection circuit is a current collector or drain that completely eliminates all signals from the load., the protection circuit includes a silicon controlled rectifier (RCS) and a fuse or circuit breaker or both, or some other means by which the signal can be completely removed from the load or reduced in a known manner to eliminate any damage possible to load, such as overheating of coating and the like Another heavy current carrying devices can be used such as relays and tpac Alternatively, the protection circuit can be such that it modifies the signal to a known constant value or has some different characteristics which preferably eliminate any possibility of an unwanted signal being applied to the load. A preferred circuit for applying and controlling the application of the signals to the load is shown in FIGURE 4 A suitable signal is applied from the circuit breaker 48 to a junction suitably 80 The positive output of the junction 80 is coupled to an internal fuse 82 which has a speed c As described more fully below, the fuse preferably has an amperage that is rated lower than that of the RCS so that the fuse will open when directed by the RCS. The other side of the fuse is coupled to the regulator circuit 72 that preferably includes a triac. 84 controlled by a diac 86, coupled between the control of the triac 84 and is neutral through a capacitor 88. The triac applies only a certain portion of the AC signal to the load so that the average voltage applied to the load during the Normal operation is preferably less than the line voltage. The regulator circuit 72 also includes a potentiometer 90, rated at 100 K Ohms, coupled to the triac input through the first resistor 92. The potentiometer is coupled to neutral through the capacitor 94. In the preferred embodiment, a second potentiometer 95 is coupled in series with the potentiometer 90 and is accessible to personnel, such as at the installation site, by adjusting the average voltage applied to the load to adapt various operating conditions, such as humidity. For example, potentiometer 95 can be a 20K Ohm potentiometer to provide an adjustment of + 20% for the voltage at the load. A resistor 96 has a side coupled between the potentiometer 90a and the capacitor 94 and the opposite side coupled between the diac 86 and the capacitor 88. In the preferred embodiment where the resistor 92 is a resistor of 47K Ohms, the potentiometer stabilizes the voltage threshold to which the triac leads. The potentiometer and capacitor 88 set the angle for the AC cycle during which the triac will conduct the triac. The capacitor 94 sets the phase angle for the regulator circuit 72. the diac 86 controls the triac 84 and improves the operation of the triac by angulating the offspring of the triac. thus modulating the transition from the state of Power Off to the Tpac The regulator circuit can alternatively use a transformer potentiometer, gate circuits, tpac connected in series and the like to apply the desired voltage to the load, but a tpac is preferred. output of the tpac is applied to one side of the load 74, the other side of which is connected to neutral The output of the tpac is also coupled to the input of the sensor circuit 76 through a diode 98, the opposite side of which is coupling through a resistor 100 to several RC filter networks. The first filter network includes the first resistor 102 connected in parallel and the first capacitor 104 The second side of the resistor 100 is also coupled to a Zener diode 104 to be fixed approximately where the sensor circuit determines that the signal applied to the load exceeds the defined limit The Zener diode, together with the filter circuits, establish a defined limit for the sensor circuit. The voltage is preferably somewhat above 90 volts. The opposite side of the Zener diode 106 is coupled to the second filter network, including a second resistor 108 and the second capacitor 110 The second load of the Zener diode is also coupled to the third filter network through a resistor 112 to the third resistor 114 and the third capacitor 116 The presently preferred values of these components are shown below. The resistor 112 is also coupled to the gate of an RCS 118 to drive the RCS when the signal applied to the load exceeds the defined limit In the preferred embodiment, the filter networks prevent the sensor circuit from interrupting the circuit to the load in cases where temporary currents occur for several seconds, but less frequently at 50 or 60 per second or, therefore, when a temporary current is held for a period of time. period such as for several tenths of a second As such, the sensor circuit 76 effectively integrates the voltage applied to the load over time and compares that integrated signal to the defined limit If the integrated signal exceeds the defined limit, the circuit breaker can be operated or some other function The sensing circuit can also be considered as a filter and therefore temporary impulse currents that can exceed the fixed voltage less frequently than, for example, 40 per second are ignored. Particular events that may cause signal interruption the load depends on the application Temporary or intermittent signals that exceed the desired parameters s for charging may arise from turning on or stopping refrigeration compressors, other large compressors or other electronic equipment that can extract large current. Normally, temporary currents arising from such conditions are relatively infrequent, relative to the line voltage that operates at 50 or 60 Hz Therefore, the values of the circuit elements in the sensor circuit will vary depending on the load, circumstances and individual preferences. It should be understood that other integration functions will also serve the same purpose of protecting the load while at the same time the interruption is not triggered on insignificant temporary currents For example, the sensing circuit can use a resistance heating element immediately adjacent to a thermistor as the integration / sensing element. The resistance is heated over time with the temporary streams but will exceed a limit only if the temporary current is a sustained impulse or occurs very frequently A heater / resistance thermistor is an alternative disintegration device Other elements can serve the same function and can also be applied to the present circuit The limit defined for the sensor circuit can be adjusted by any number For example, a potentiometer can be used instead of, or in addition to resistors at 108 or 112. Additionally, the movement point or threshold of the sensing circuit can be adjusted up or down in parallel with ascending or descending settings on the voltage level applied to the load Also, the sensing circuit may have circuit components or values that could allow it to have a filter arrangement in two stages instead of in three stages as shown in FIGURE 4 and the values of the components in the sensor circuit may vary depending on the application The protection circuit 7 8 preferably includes the RCS 118 The RCS 118 preferably is an RCS of 600 volts rated at 25 amps The RCS is preferably suitable for any voltage level predicable and has a rating that is higher than either the fuse 82 or the circuit breaker 48 so that the fuse can be opened and the circuit breaker can move under appropriate circumstances Under circumstances when the sensor circuit 76 indicates a signal or a set of signals that exceed the defined limit, the sensor circuit 76 will drive the RCS through the connection between the resistor 112 and the gate of the RCS 118 so that the RCS is conducted, thus drawing current through the fuse 83 to the ground connection. The maximum possible current will be extracted through the RCS Therefore, with a circuit breaker of 25 amps and a 15-amp fuse, fuse 82 should be before any undesirable additional signal is applied to the load 74 it is evident, the rating of the RCS preferably is greater than or at least equal to the rating of the circuit breaker 48 In the extraordinary situation where someone attempts to derive a fuse 82 by directly coupling the regulator circuit 72 of the link 80, such as by inserting a coin or some other substantial conductor, the RCS 118 will move the circuit breaker 48 as soon as the RCS begins to drive as a result of a signal that is being picked up by the sensor circuit 76 that exceeds the defined limit. to make refrigerator doors for low temperature applications by coating them with transparent conductive coatings that have a uniform resistivity and thickness thus providing uniform or normal strength per unit area. For normal doors that have normal dimensions and operate in most applications, which can be found at present, an RCS with a voltage lower than 110 volts is adequate to prevent the formation of glass unit fog. Sustained voltages of approximately 110 RCS will cause overheating of the glass unit damage. of regulator is then preferably designed so that I apply e the lower voltage, on average, the coating sufficient to inhibit the formation of haze but not so great that the glass unit overheats Under current circumstances the use of normal transparent conductive coatings of approximately twenty Ohms per square the average voltage that will be applied to the glass unit varies between 30 and 80 volts. In the unwanted presentation that the tpac or some other circuit element in the regulator circuit 72 does not operate well, or in some way becomes defective, two possibilities may arise. , the regulator circuit will vary from applying any signal to the load 74 In the context of the preferred embodiment of the present invention the failure of the regulator circuit 72 will simply result in failure to heat the glass unit thus resulting in the formation of mist from the door unit However no voltage is applied to the glass unit and no problem arises Electrical power The fog formation of the door will alert the staff of a problem resulting in an investigation to correct any defective circuit. In another <; '
In this case, the regulating element will vary to modify or reduce the AC signal applied to the load, in which case, the entire AC signal is applied to the load 74, thus finally resulting in overheating of the conductive coating 64 and thus Both of the glass panel 54 As a result, instead of being applied to the load approximately 30 to 80 volts on average, an RMS of 110 volts is applied to the load at 60 Hz, exceeding the requirements for the glass unit and also the defined limit for the sensor circuit The sensor circuit 76 will then detect the higher voltage
at the higher level than desired and will activate the RCS to lead it to the ground connection, thus opening the fuse 82 In both cases, the personnel and the doors are protected. The circuit components are selected in such a way that they produce signals that will be applied to the load that has a
minimum scale of 30 to 80 volts on average The Zener diode will largely determine the absolute value of the threshold voltage which, in part, will cause the sensor circuit 76 to drive the RCS 118. Preferably, the RCS will provide approximately 150% load of current to force the load of the fuse or the switch
circuit, under appropriate circumstances The load is then isolated from the power source The component values that are currently preferred are the following Component Value 25 Fuse 82 15 Amps Triac 84 600V, 15 amp Diac 86 Conventional Capacitor 88 0 082 microfarads Potentiometer 90 100K Ohms Resistor 92 47K Ohms Capacitor 94 0.1 microfarads Potentiometer 95 20K Ohms Resistor 96 47K Ohms Diode 98 600V, 100 mA Resistor 100 2.2K Ohms Resistor 102 10K Ohms Capacitor 104 1.0 microfarads Zener diode 106 48 volts Resistor 108 560 Ohms Capacitor 110 10 microfarads Resistor 114 10K Ohms Capacitor 116 2200 microfarads RCS 118 600 volts, 25 amps
Although the present invention has been described in detail with reference only to the currently preferred embodiments, it will be appreciated by those of ordinary skill in the art that modifications may be made in vain without departing from the spirit of the invention. Consequently, the invention is limited only by the following indications