FR2491692A1 - Auxiliary DC supply for electronic controller with volatile m - uses 9 volt battery with normally off voltage regulator to supply 5 volt to electronic circuit in the event of mains supply failure - Google Patents

Abstract

The system is used to maintain DC supply to non-permanent memory in electronic control circuits should the mains AC supply fail. The emergency power is provided by a disposable 9 Volt battery of the type widely available for domestic usage. A voltage regulator circuit reduces the voltage down to the five volt required by the volatile memory circuits incorporated in the electronic controller. The electronic regulator circuit has a series pass regulator connected to the standby battery. The base of the regulator transistor is driven by a transistor circuit which holds the regulator transistor off, preventing current drain from the battery, while the AC mains is available. When the mains fails the falling voltage is detected by the transistor circuits, allowing current to be drawn from the battery.

Description

 Many types of electronic control devices commonly used include non-permanent type electronic memories. The non-permanent memory in this type of device is typically protected by a backup type supply device. Normally, the auxiliary power device is a battery, and the battery has an output voltage which usually corresponds to the operating voltage of electronic circuits. Many known devices use this type of emergency or auxiliary power supply device and also include charging devices for recharging the battery. All these devices have the particular characteristic of having the output voltage of the auxiliary battery and the operating voltage of the electronic circuits roughly equal. Since the voltage of the auxiliary battery and the charge are comparable, the battery is normally not charged by electronic circuits when normal supply voltage for the device is available.

 The arrangements which have just been described typically require rather expensive batteries and battery charging devices. Most of the integrated type semiconductor electronic circuits that have become common in electronic control devices operate at about five volts. Because of this five-volt operating level, any auxiliary battery power source requires batteries that have an output voltage of approximately 5 volts. This type of battery is not readily available in an inexpensive form.

 With the appearance of solid-state electronic circuits, such as transistor radios, computers, toys, etc., the available nine-volt battery is widely used and is really inexpensive. Since most electronic devices using integrated circuits that include non-permanent memories operate at five volts, the connection of a nine-volt battery to this type of control device normally poses the problem of the battery which is constantly discharged in the device in operation even when there is a normal voltage source for the device.

 The present invention relates to a switching technique and step-down mechanism which is simple enough for an available nine-volt battery to supply the control device in the event of a failure of the normal AC source.

According to the present invention, an auxiliary battery supply device comprising a control device, a battery for supplying the control device in the event of failure of an alternating current source, an electronic load and a current supply source contained in the control device, the electronic load normally being supplied by the DC power source when the DC power source is powered by the AC power source, said auxiliary power device being characterized by this tool includes a available battery / dontrla ~ normal output ension is much higher than the
normal operating voltage of the power source
in direct current, a step-down means connected
between said battery and the power supply source
continuous to adjust the voltage supplied by the battery to a
value roughly equal to the value of the source voltage
DC power supply, and a switching means
transistors designed to connect the battery and the
medium step-down in response to loss of
normal operating voltage and thus supply the
battery control device available when
said voltage loss, the switching means
tors effectively disconnecting the battery from the device
when normal operating voltage is present for
prevent the battery from discharging into the power source
dation in direct current.

Other characteristics and advantages of the present invention will be highlighted in the following description, given by way of nonlimiting example, with reference to the appended drawings in which
- Figure 1 is a schematic representation of an auxiliary battery power device according to the present invention which includes a control device; and
- Figure 2 is a schematic representation of another embodiment of the present invention.

 In FIG. 1, an auxiliary battery supply device comprises a control device 10 which can be a temperature control device or thermostat. A conventional alternating current source is provided between conductors 11 and 12 to supply a step-down transformer 13. The step-down transformer has a secondary winding 14 which feeds the control device 10 and two loads such as a heating load 15 and a load cooling 16. The secondary winding 14 comprises a common conductor 20 which is connected to a terminal 21 constituting the mass for the control device 10. The conductor 2C is also connected directly to one side of the heating load 15 and to a side of the cooling load 16.The heating load 15 is connected to a terminal 22 while the cooling load 16 is connected to a terminal 23.

Another terminal 24 is connected to the other side of the secondary winding 14 so that the control device 10 is supplied by an alternating current source between conductors 25 and 26.

 The conductor 25 is connected to a common conductor 27 which constitutes a ground for the control device 10 and it is common with the conductor 20 of the transformer 13. The conductor 16 supplies an alternating current to two diodes 30 and 31 which are part of a DC power source generally indicated by the reference 29.

The diode 30 is connected to a capacitor 32 which is itself connected in parallel to a Zener diode 33. The capacitor 32 and the Zener diode 33 are connected by a conductor 32a to ground 27 to form a complete charging circuit for the capacitor 32 forming part of the DC power source 29. The DC power source 29 also includes the diode 31 and another capacitor 34 which is connected by a conductor 35 to ground. Capacitor 32 and Zener diode 33 produce a regulated voltage at junction point 36, while diode 31 and capacitor 34 produce another DC voltage at junction point 37.

 A diode 40 and an electronic charging means 41 are connected between the Junction point 36 and the ground 27.

The electronic charging means 41 is thus supplied by the regulated voltage available between earth 27 and the point of
Junction 36. The electronic charging means 41 can be of any type of condition control device, but in the present description the electronic charging means 41 will be described hereinafter as an integrated circuit which makes it possible to program and control a condition for an electronic type thermostat controlled by a clock.

The clock mechanism is an electronic clock which can be programmed for reset and set-up functions for the purpose of energy conservation during the operation of the heating 15 and cooling 16 loads. Programming of the electronic charging means 41 is normally carried out with an integrated logic circuit and a memory of the non-permanent type, and the power supply of the electronic charging means 41 must therefore be maintained all the time even if the alternating current supplied to the conductors 11 and 12 is lost for some reason. The electronic charging means 41 can be of any type with integrated circuit comprising a non-permanent memory. An example of such a device is a semiconductor thermostat sold by Honeywell and designated as the
Fuel Saving Thermostat type T800A. The mention of this particular type of thermostat is only made to complete the description, without however constituting a limitation in its application to the control device 10.

 The electronic charging means or thermostat 41 has two output conductors 42 and 43 which are connected to a load switching means indicated generally in FIG. 1 by the reference 44. The load switching means 44 is a group of transistors in integrated circuit which allow the operation of an output relay indicated by the reference 45. The output relay 45 is a latching relay of the polarized type which operates on pulses of electrical energy to open or close a contactor 46. An energy pulse supplied to the conductor 43 excites or allows the transistors 47, 48, 49 and 50 to become conductors so that a current flows through the relay 45 in a direction which allows the contactor 46 to operate step by step. If an energy pulse is supplied to the conductor 42, the transistors 51, 52, 53 and 59 can conduct the current flowing through the relay 45 in the opposite direction by reversing the operation of the contactor 46. This type of operation The pulsed relay is described in the U.S. Patent. n04 196 356.

 It is obvious that, whenever an energy pulse is supplied to the conductors 42 or 43, an appropriate switching action occurs at the contactor 46 by opening or closing the contact depending on whether the conductor 42 or the conductor 43 supplies the energy pulse.

 The contactor 46 closes an electrical circuit leading to the loads 15 and 16, according to what is determined by a mode selection switch indicated generally by the reference 54. The mode selection switch 54 makes it possible to select the heating condition, the condition cooling, or an intermediate "shutdown" condition. In the position shown, that is to say the control of the heating load, the operation of the contactor 46 closes a circuit connecting by the conductor 55 the terminal 24 to a conductor 56 which is itself connected by a conductor 57 to the mode selection switch 54.

The mode selection switch 54 is connected to terminal 22 via a conductor 58 to supply the heating load 15. It is obvious that by placing the mode selection switch in the cooling position, establishes a connection between a conductor 60 and the conductor 56 thereby closing a supply circuit leading to the cooling charge 16.

 The operation of the mode selection switch 54 also makes it possible to select the operating mode for the electronic charging means 41. The conductor or earth 27 is connected to the central terminal of a part of the mode selection switch -54 to close a circuit between the ground conductor 27 and a mode selection conductor 61. The mode selection conductor 61 indicates by electronic load 41 that the heating mode has been selected. If the mode selection switch 54 is set to the cooling position, a conductor 62 is connected by the mode selection switch 54 to the ground conductor 27, which indicates that the cooling mode has been selected.

 The device described Until now is basically a condition control device or thermostat of the complete electronic type which includes an electronic charging means 41. As long as current is continuously supplied to the transformer 13, the device is in operation and no loss no memory occurs inside the electronic charging means 41. The electronic charging means 41 is normally supplied by the DC power source 29 at a level of about 5 volts. This value represents a typical voltage for an integrated circuit device. If electrical power is lost Up to the transformer 13, it is quite obvious that, very soon after, the capacitors 32 and 34 are discharged and the control device 10 is de-energized with a loss of memory in the electronic charging means 41.The capacitor 32 in the DC power source 29 is large, which keeps the electronic charging means 41 energized for a period of time which is determined by the impedance of the charging means electronic 41. The capacitor 34 of the DC power source 29 has a lower capacity and it is in parallel with a resistor 63. This ensures that the capacitor 34 dissipates its charge before the capacitor 32, for reasons which will become evident in the following description. The Junction point 37 is further connected to the switching means 44 by a resistor 64 to complete the power source for the switching means ation 44. It follows from the above description that, if the capacitor 34 and its associated charge (in the form of the resistor 63 and the switching means 44) are suitably defined, the voltage at the junction point 37 will drop faster than the voltage at junction point 36. The present device is based on this type of design.

 The present control device 10 is completed by the connection of a battery 65 of the available type and of low cost between two terminals 66 and 67. The terminal 67 is connected directly by a conductor 70 to the ground 27 of the device. Terminal 66 is connected via a resistor 71 which is itself connected to a transistor 72 connected in turn to a transistor 73. The emitter of transistor 73 is connected to a conductor 74 which is itself connected to the Junction point 36. A resistor 75, connected to the base of the transistor 72, is also connected to the collector 76 of a transistor indicated overall by the reference 77 in FIG. 1. The emitter 78 of the transistor 77 is connected to a resistor 80 which is connected to the junction point 37 of the DC power source 29. The transistor 77 has its base 81 connected to the conductor 74 by a resistor 82 to complete the present circuit. The transistor 77 functions as a switch for controlling the transistors 72 and 73, the assembly forming a transistor switching means generally indicated by the reference 85 in FIG. 1. The transistor switching means 85 responds to the drop in voltage normal operation in the power source 29, and connects the control device 10 to the nine-volt battery and to the voltage drop resistor 71 to supply the control device 10 in the event of a voltage drop supplied to transformer 13.

We will now describe the way in which the circuit of FIG. 1 works. When the control device 10 operates normally, the voltages at the junction points 36 and 37 are approximately equal and the voltage between the base 81 and the transmitter 78 of transistor 77 is therefore not sufficient to force this Junction. As long as the device is suitably supplied by the transformer 13, the DC power source 29 provides all the current supply to the control device 10. In the event of an interruption of the electrical supply to the control device 10 , the transformer 13 loses its power and the DC power source 29 must rely on the load of the capacitors 32 and 34.The capacitor 32 and its associated load are selected so that the voltage at the Junction point 36 drops more slowly than the voltage at the Junction point 37 which is a function of the charge of the capacitor 34 and of its associated charge comprising the resistor 63 and the switching means 44. As soon as the voltage between the Junction points 36 and 37 is equal to the voltage of switching of transistor 77, this transistor becomes conductive. The transistors 72 and 73 thus become immediately conductive and the voltage of the available battery 65 is thus connected between the ground 27 and the point of Junction 36. The latter continues to apply a voltage to the point of Junction 36, this voltage being sufficient to maintain the electronic charging means 41 in a state where its memory is not lost. Since the transformer 13 has lost its supply power, nothing is done to supply the switching means 44, the supply of which is prevented by the diode 30. The available battery 65 maintains the electronic charging means 41 in a state of energizes the power supply for an extended period of time and overcomes most normal power failures. As soon as the power is restored for the transformer 13, the DC power source 29 again restores the voltages at the Junction points 36 and 37 at approximately the same level, which blocks the transistor 77 by completely removing a charge coming from the battery 65. It will also be noted that if the device is not supplied at all, the installation of a battery will not put the device under supply voltage. If a battery 65 is installed when the device 10 has been de-energized, the voltages at the points of
Junction 36 and 37 are the same and transistor 77 cannot connect battery 65 to the circuit. This protects a battery placed in the condition control device 10 when it is not in use and prevents it from discharging by the simple fact that it is installed in the device. The battery can only come into action after the power supply has been cut off, and the uneven voltage drop between the points of
Junction 36 and 37.

 FIG. 2 shows another embodiment of the transistor switching means 85 which is designated by the reference 85 '. This particular configuration uses an integrated circuit technology in which all the components shown in solid lines are integrated on the same substrate and include transistors of the same geometry and the same dimension. It is thus possible to manufacture a certain number of current circuits in geometric relationship or current mirrors which fulfill the function of the transistor switching means 85 of FIG. 1.

 A terminal 86 is connected to a transistor 87 which is connected like a diode. The transistor 87 is connected to a common conductor 88. A terminal 90 is connected to a transistor 91 which is also connected like a diode. The output of transistor 91 is connected to an input of a transistor 92. The transistor 92 is geometrically the same as the transistor 87 but does not include the diode interconnection. Transistors 87 and 92 operate as current mirrors. Any current flowing through transistor 87 also passes through transistor 92 from a separate source, which will be described later. Another connection 93 is provided where a conductor 94 is connected to two transistors 95 and 96. The transistor 95 is connected as a diode and forms an input for a transistor 97. The transistor 97 has a common connection with respect to the transistor 91 and all current flowing through transistor 97 must pass through transistor 92. Transistor 95, which was connected as a diode, is geometrically associated with transistor 96 and transistors 95 and 96 form another pair of current mirrors in which current passing through transistor 95 causes an identical amount of current to pass through transistor 96.

Two diodes 100 and 101 which complete the circuit are connected by the conductor 102 to terminal 90 and these diodes rectify any alternating current sent to terminal 90. The output of diodes 100 and 101 is connected to a terminal 103. A step-down transistor voltage 104 is connected between conductor 94 and terminal 103, and cooperates with a Zener diode 105 which is connected to the base of transistor 104 serving as a voltage lowering or adjustment means for controlling or adjusting the voltage applied by the conductor 94 at terminal 103. A capacitor 106, connected between terminal 103 and earth 88, is simply a representation of the capacitor of the power source. Capacitor 106 operates with diodes 100 and 101 as the power source for the device. A resistor 107 has been described as the load for the device on the
Figure 2, and the resistor 107 is a representation of the electronic charging means 41 of Figure 1. The circuit is completed by a resistor 108 which is external to the integrated circuit and forms an input voltage at terminal 86 coming from the means supply 106. Each time a supply current is supplied to the device shown in FIG. 2, and a voltage is present by means of supply or capacitor 106, this voltage is again applied to terminal 86 via resistor 108 so that a current flows through transistor 87 as will be described more fully below. Terminal 90 of the device in FIG. 2 is connected to the power supply line of the device and operates to supply power the supply means or capacitor 106 via diodes 100 and 101. Terminal 93 of the device in Figure 2 is the positive battery terminal equivalent to terminal 66 in Figure 1. The battery would be connected between terminal 93 and conductor 88.

 The operation of the device of Figure 2 must be considered taking into account that the transistors 87 and 92 are current mirrors, as well as the transistors 95 and 96. When a supply current is supplied to the capacitor 106, a voltage is applied to terminal 86 via resistor 108. Current flows through transistor 87 depending on the value of resistor 108 and the geometry of the integrated circuit.

The transistor 92 functions as a current mirror and is crossed by a current of identical level. Since a supply current is supplied to the terminal 90, the transistor 91 functions as a diode and supplies all the current to the transistor 92 by reflecting the current passing through the transistor 87. Under these conditions, no current passes through the transistor 97, and the transistor switching means of Figure 2 keeps the battery completely inactive when no current flows through transistors 95, 96, 97 and 104.

 When there is a drop in the alternating current voltage applied to the terminal 90, the diode 91 can no longer supply current to the transistor 92. At this moment, the transistor 97 begins to become conductive and it supplies current to the transistor 92 in an amount equal to the current passing through the transistor 87. The current passing through the transistor 97 is supplied by the transistor (diode) 95 and it is reflected as a current of the same value passing through the transistor 96. The transistor 104 thus becomes conductive and it is regulated by the Zener diode 105 to supply the necessary battery voltage lowered at terminal 103 to supply the supply means or capacitor 106 and the electronic charging means 107. It can therefore be seen that the set of transistors in the form of an integrated circuit which is shown in Figure 2 fulfills the same function as the transistor switching means 85 of Figure 1.

 The device according to the invention which has just been described is based on the application of a battery available as an auxiliary battery to a device which has a non-permanent memory. The available battery has a voltage higher than the voltage in the integrated circuit or.

the electronic charging means of the device, and the battery has its voltage lowered by a voltage drop means. This means is only active when the normal alternating current supplied to the power source is lost.

Claims (5)

 1. Auxiliary battery supply device comprising a control device (10), a battery for supplying the control device in the event of failure of an alternating current source, an electronic load (41) and a power source direct current (29) contained in the control device, the electronic load being supplied normally by the DC power source when this source is itself supplied by the AC power source, said auxiliary power device being characterized in that it comprises an available battery (65) having a normal output voltage which is much higher than the normal operating voltage of the DC power source, a voltage lowering means (71) connected between the battery and the DC power source to adjust the voltage supplied by the battery to a value roughly equal to the voltage of the neck power source continuous current, and a transistor switching means (85) adapted to connect the battery and the voltage lowering means in response to the loss of normal operating voltage and thereby supply the control device with the battery available when the voltage gate, the transistor switching means effectively disconnecting the battery from the device when the normal operating voltage is present to prevent the battery from discharging into the DC power source.  2. Auxiliary power supply device according to claim 1, characterized in that the DC power source (29) comprises two energy storage means (32 and 34) having different discharge speeds during a loss of voltage from the AC power source, the transistor switching means (85) being connected to the energy storage means being non-conductive when the two energy storage means are actually supplied, and by being switched to a conductive state when the two energy storage means are discharged to produce a voltage difference across the transistor switching means.  3. Auxiliary supply device according to any one of claims 1 and 2, characterized in that the transistor switching means (85 or 85 ') comprises a transistor (77) comprising a basic circuit, a circuit transmitter and a collector circuit, the base and transmitter circuits being connected to two capacitors (32 and 34), the voltages on the capacitors controlling the transistor switching means.  4. Auxiliary power supply device according to claim 3, characterized in that said transistor switching means (85 or 85 ') comprises other transistor switching means (72 and 73) controlled by the transistor (77) for connecting the battery and the voltage lowering means (71) at the DC power source and supplying the control device.  5. Auxiliary supply device according to any one of claims 1 to 4, characterized in that the control device being an electronically programmed thermostat, the electronic charging means (41) comprises a non-permanent electronic memory containing at least part of a thermostat operating program.