Power supply system

A power supply system includes a switching type regulated power supply operable to provide switched regulated D.C. output voltages. A first winding having a first terminal and a second terminal is provided. The first terminal is connected to be energized by the switched D.C. output voltage of the switching type regulated power supply such that a switched D.C. voltage is developed at the second terminal of the first winding. A second winding electromagnetically coupled to said first winding and having a first and a second terminal is also provided. A capacitor and a diode are coupled between the first and the second terminal of the first winding. Means connect the diode and the capacitor to the first terminal of the second winding. The power supply system may be part of a postage meter system. A postage meter includes accounting means operatively coupled to a postage printing means. The accounting means accounts for postage printed by the printing means. The accounting means include a nonvolatile memory for storing accounting and other data when no power is being supplied to the meter.

FIELD OF THE INVENTION 
The present invention relates to power supply systems and more particularly 
to power supply systems for electronic postage meters having nonvolatile 
memory. 
BACKGROUND OF THE INVENTION 
Electronic postage meter systems have been developed as for example the 
systems disclosed in U.S. Pat. No. 3,978,457 for Microcomputerized 
Electronic Postage Meter Systems, in U.S. Pat. No. 3,938,095 for Computer 
Responsive Postage Meter and in European Patent Application, Application 
Number 80400603.9, filed May 5, 1980 for Electronic Postage Meter Having 
Improved Security and Fault Tolerance Features. Electronic postage meters 
have also been developed employing plural computing systems. Such a system 
is shown in U.S. patent application Ser. No. 089,413, filed Oct. 30, 1979, 
now U.S. Pat. No. 4,301,507, for Electronic Postage Meter Having Plural 
Computing Systems and assigned to Pitney Bowes Inc. 
The accounting circuits of electronic postage meters include nonvolatile 
memory capability to store postage accounting information. This 
information includes, for example, the amount of postage remaining in the 
meter for subsequent printing or the total amount of postage printed by 
the meters. Other types of accounting or operating data may also be stored 
in the nonvolatile memory. The memory function in the electronic 
accounting circuits have replaced the function served in previous 
mechanical type postage meter by mechanical accounting registers. Postage 
meters with mechanical accounting registers are not subject to the many 
problems encountered by electronic postage meters. Conditions cannot 
normally occur in mechanical type postage meters that prevent the 
accounting for a printing cycle or which result in the loss of data stored 
in the registers. Moreover, in mechanical postage meters it is not 
necessary to electronically monitor the position of the mechanical 
components associated with printing postage. This, however, is not the 
case with electronic postage meters. 
Conditions can occur in electronic postage meters where information stored 
in electronic accounting circuits can be permanently lost. Conditions such 
as a total line power failure of fluctuation in voltage conditions can 
cause the microprocessor associated with the meter to operate erratically 
and either cause a loss of data or the storage of spurious data in the 
nonvolatile memory. Moreover, excessive heat within the confines of the 
meter housing can damage the nonvolatile memory, especially during a 
memory WRITE cycle for NMOS type nonvolatile memories. The loss of data or 
the storage of spurious data may result in a loss of information 
representing the postage funds stored in the meter. Since data of this 
type changes with the printing of postage and is not stored elsewhere 
outside of the meter, there is no way to recover or reconstruct the lost 
information. In such a situation, a user may suffer a loss of postage 
funds. 
To minimize the likehihood of a loss of information stored in the 
electronic accounting circuit, efforts have been expended to insure the 
high reliability of electronic postage meters. Some systems for protecting 
the critical information stored in the meter are disclosed in the 
abovenoted patents and applications. An additional arrangement to protect 
the postage meter accounting information is shown in U.S. Pat. No. 
4,285,050 for Electronic Postage Meter Operating Voltage Variation Sensing 
System. 
SUMMARY OF THE INVENTION 
It has been recognized that the power supplies for electronic postage 
meters must have a very high efficiency so that if a power failure occurs, 
sufficient operating voltage remains during the time required to transfer 
certain critical information resident in volatile memory to nonvolatile 
memory and to complete accounting transactions in progress. This must be 
achieved without the generation of noise which could result in spurious 
information being transferred to the nonvolatile memory. Even during 
normal, quiescent operation, the noise factor associated with the power 
supply must also be such that erroneous information is not written into 
the volatile memory of the meter. 
Since the electronic accounting circuits of the postage meter may be 
subject to the effects of electromagnetic radiation, they are desirably 
shielded by one or more enclosures. However, the power supply for the 
meter may also be housed within one of the enclosures shielding the 
accounting circuits and can even be located in close proximity to the 
accounting circuits. Thus, it is desirable that the power supply not 
generate excessive heat. Such heat may adversely affect the nonvolatile 
memory and other solid state devices. Moreover, it has been recognized 
that it is desirable to keep the power supply physically associated with 
and part of the meter. In the event of an external power failure, the 
power supply within the secure housing continues to generate a sufficient, 
regulated power, for at a sufficient time to orderly and accurately 
transfer critical information from volatile memory to nonvolatile memory. 
This problem is compounded because certain nonvolatile memories need 
several different voltages for proper operation. As an example, one type 
of solid state nonvolatile memory requires the presence of three different 
voltages for a WRITE operation. 
It has been discovered that a power supply system according to the present 
invention, involving only one switching regulator, can be employed to 
generate a plurality of voltages necessary to operate such memories. The 
supply can energize both the microprocessor and associated nonvolatile 
memory of a postage meter. 
A power supply system embodying the present invention includes a switching 
type regulated power supply operable to provide switched regulated D.C. 
output voltages. A first winding having a first terminal and a second 
terminal is provided. The first terminal is connected to be energized by 
the switched D.C. output voltage of the switching type regulated power 
supply such that a switched D.C. voltage is developed at the second 
terminal of the first winding. A second winding electromagnetically 
coupled to said first winding and having a first and a second terminal is 
also provided. A capacitor and a diode are coupled between the first and 
the second terminal of the first winding. Means connect the diode and the 
capacitor to the first terminal of the second winding. 
In accordance with a feature of the invention, a postage meter includes 
accounting means operatively coupled to a postage printing means. The 
accounting means account for postage printed by the printing means. The 
accounting means include a nonvolatile memory for storing accounting and 
other data when no power is being supplied to the meter. A first winding 
is provided with a first and second terminal. The first winding first 
terminal is energized from a source of alternating voltage. A second 
winding oppositely poled to the first winding is electromagnetically 
coupled to the first winding. A series connected capacitor and diode are 
connected between the first and the second terminal of the first winding. 
First circuit means are coupled between the second terminal of the first 
winding and the accounting means. Second circuit means are coupled between 
the second winding and the accounting means. 
In accordance with a further feature of the invention, the second winding 
may have a tap connection with third circuit means provided, coupling the 
tap connection to the accounting means.

DETAILED DESCRIPTION 
Reference is now made to FIG. 1. A postage meter 12 includes: an accounting 
module 14 having a microprocessor and nonvolatile memory such as a General 
Instrument Corporation ER3400 type electronically alterable read only 
memory (this device is described in a General Instrument Corporation 
manual data November 1977, entitled EAROM designated by number 
12-11775-1); a printing module 16 having microprocessor and motor control 
circuits; and a control module 18 having microprocessor and control 
circuits. The details of construction and operation of the system may be 
in accordance with the postage meter systems and the mechanical apparatus 
shown in the above-noted patent application for Electronic Postage Meter 
Having Plural Computing Systems and in U.S. Pat. No. 4,287,825 for 
Printing Control System. Postage meter 12 includes a series of 
opto-interrupters 20, 22, 24, 26, and 28. The opto-interrupters are used 
to sense the mechanical position of the parts of the meter. For example, 
the opto-interrupters can be employed to sense the position of the shutter 
bar which is used to inhibit operation of the meter under certain 
circumstances, the position of the digit wheels, the home position of the 
print drum, the position of the bank selector for the print wheels, the 
position of interposer, or any other movable mechanical component within 
the meter. These opto-interrupters are coupled to the printing module 16 
which monitors and controls the position of the mechanical components of 
the meter. 
The printing module 16 is connected to the accounting module 14 via a 
serial data bus 30 and communicates by means of an echoplex technique 
described in the above-noted U.S. Patent Application for Electronic 
Postage Meter Having Plural Computing Systems. Both ends of the bus are 
buffered by an optics buffer, not shown, which is energized by the power 
supply +5 volt line to be hereafter described. Similarly, the control 
module 18 is connected to the accounting module 14 via a serial data bus 
32 and also communicates by means of the echoplex technique. Optics 
buffers, not shown, are provided to buffer the bus. It should be 
recognized that the particular architecture of the postage meter system is 
not critical to the present invention. Plural or single microprocessor 
arrangements may each be employed with the present invention. 
A source of operating voltage, such as 110 volt 60 cycle supply, is applied 
across the meter input terminals 34. The voltage is applied to a linear 
10.8 volt power supply 36. The ouput from the 10.8 volt linear power 
supply 36 is supplied to a first 8 volt linear regulated power supply 38 
and to a second 5 volt linear regulated power supply 40. The 8 volt supply 
is used to power a display 42 which is operatively coupled via a bus 44 to 
the control module 18. The output from the power supply 40 is directly 
coupled to the control module 18 and is operated to energize the control 
module microprocessor. 
The AC operating voltage at terminals 34 are also applied to a silicone 
controlled rectifier type, 24 volt power supply 46. The regulated output 
from the power supply 46 is applied to the printwheel bank stepper motor 
48 and the printwheel stepper motor 50 associated with the printing module 
16. The 24 volt DC is coupled by an AC choke 52 to capacitor 54. The 
internal capacitance within the 24 volt power supply 46 provides 
sufficient energy storage to continue to properly energize a regulated 
switching regulator 56 should an AC power failure occur at terminals 34. 
In such event, the accounting module microprocessor 58 transfers 
information from the postage meter volatile memory (which may be internal 
or external to the microprocessor) via the data bus 67 to a nonvolatile 
memory 62. The switching power supply 56, in conjunction with a 
transformer with related circuitry, provide regulated output voltages used 
to energize the accounting module. 
A plus five volts is developed and is applied to the accounting module 
microprocessor 58, to NMOS nonvolatile memory 62, to the optic buffers 
(not shown) for the serial data bus 30 connected between the accounting 
and printing modules, to the printing module 16, and to the 
opto-interrupters 20-28. A minus 30 volts is also developed and is applied 
via an NPN transistor 64 to the nonvolatile memory 62. The operation of 
transistor 64 is controlled by the accounting module microprocessor 58. 
The minus 30 volts is required in conjunction with a minus 12 volts which 
is also developed and applied to the nonvolatile memory 62 and the plus 
five volts to enable the nonvolatile memory to have data written into the 
device. 
The switching regulator power supply 56 functions to selectively apply the 
24 volts developed across the capacitor 54 to the junction of a diode 66 
and poled transformer primary winding 68. The frequency at which the 
regulator 56 operates or switches is determined by a capacitor 70 which 
controls the operating frequency of the supply. Primary winding 68 is 
further coupled to ground by a capacitor 72. Diode 66 and capacitor 72 
form a complete circuit in series with the primary winding 68. The circuit 
path is through a point of fixed reference potential, here shown as 
ground. 
During quiescent operation, a +5 volts is developed across capacitor 72. 
This voltage is sensed and coupled via a series connected variable 
resistor 74 and a fixed resistor 76 to an input terminal on the regulator 
supply 56. The feed back path controls the supply to maintain a constant 
voltage across capacitor 72. For the component values shown, a voltage 
variation of approximately 10 millivolts can occur across the capacitor 
72. A step up secondary winding 78 oppositely poled to the primary winding 
and is electromagnetically coupled via a mollypermoly core 80 to the 
primary winding 68. The secondary winding 78 is connected to ground at one 
end and has its opposite end coupled via a diode 82 which operates in 
conjunction with a capacitor 84 and current limiting resistor 86 to 
develop a -30 volts across a zener diode 88. A center-tap 90 on the 
secondary winding 78 is connected to a diode 92 which operates in 
conjunction with a capacitor 94 and a current limiting resistor 96 to 
develop a -12 volts across a zener diode 98. 
Because of the filtering provided by capacitor 72 and the inductance of the 
primary winding 68, the noise introduced by the switching transients in 
the primary circuit is minimized. In a like manner, the capacitors 84 and 
94 and the inductance of the secondary winding 78, provide further 
filtering which also minimizes the noise introduced by the switching 
transients. 
In operation, when the switching regulator 56 is on (t.sub.ON), +24 volts 
is applied to terminal 1 of primary winding 68. The time constant created 
by the inductance of the primary winding 68 and the capacitance of the 
capacitor 72 allow capacitor 72 to charge a predetermined rate toward +5 
volts. When the proper voltage level is achieved, the feed-back circuit 
including resistors 74 and 76 and the control network within the supply, 
causes the switching regulator 56 to turn off the +24 volts applied to 
terminal 1 of primary winding 66. When the power is turned off, the energy 
stored in the inductance of primary winding 66 is passed to ground via the 
diode 66. At this time (t.sub.OFF), terminal 1 of primary winding 68 is 
classified at -0.7 volt. The voltage at terminal 2 of primary winding 68 
remains at a positive voltage, near +5 volts. 
It has been discovered that the energy being dumped through the diode 66 
during the off time of switching regulator 56 can be beneficially used to 
generate additional voltages for utilization within the postage meter. 
This is of particular value in reducing the number of power supplies and 
thereby the associated heat required to be dissipated within the walls of 
the postage meter housing. 
At the time when the switching regulator 56 is turned off, the polarity of 
the voltages across the primary winding 68 reverse and terminal 1 becomes 
negative with respect to terminal 2 of primary winding 68. The voltage at 
the junction of the capacitor 72 and the primary winding 68, however, is 
fixed at 30 5 volts and is blocked from discharging by the diode 66. The 
turn ratio between the primary and the secondary windings is selected to 
step up the voltages in the secondary winding to generate the required -12 
and -30 voltages. There is no current flow in the secondary winding 78 
when the switching regulator 56 is turned on because the windings are in a 
"bucking" mode. That is, the flux generated by the current flowing through 
the primary winding 68 is in a direction which is opposite to that of the 
flux generated by the current flowing in secondary winding 78. Thus, when 
the switching regulator 56 is turned on, the primary winding 68 drains 
energy from the secondary winding 78, and when the switching regulator 56 
is turned off, the secondary winding 78 drains energy from the primary 
winding 68. The transformer as shown in FIG. 1 may be in accordance with 
the following specifications: 
primary inductance--550.+-.10% uh 
permeability of core--125 nominal 
core inductance--68 MH per 1000 turns 
mean length of magnetic path--5.18 CM 
DC resistance of core per millihenries nominal--0.124 OHMS 
primary number of turns--90 
primary winding wire gauge--22 gauge (AWG 
secondary winding.andgate.260 turns--650 turns tapped 
secondary windings--190 34 AWG wire 
The various voltages wave forms developed at the terminals of transformer 
is shown in FIG. 2. The voltage wave forms at terminals 1 and 2 of the 
primary winding 68 and terminals 5 and 4 of secondary winding 78 are shown 
respectively in FIGS. 2A, 2B, 2C, and 2D. The voltage at terminal 3 is not 
shown but is held fixed at ground potential. The voltage developed at the 
anodes of diodes 92 and 82 are shown in FIGS. 2E and 2F, respectively. The 
three D.C. voltages for the postage meter system shown in FIG. 1 are 
developed at: terminal 2 of the primary winding and is shown in FIG. 2B 
(+5 volts); the anodes of diode 92 and is shown in FIG. 2E (-12 volts); 
and, the anode of diode 82 and is shown in FIG. 2F (-30 volts). 
Reference is now made to FIG. 3 which is a perspective view of an 
electronic postage meter suited to incorporate the present invention. The 
postage meter 12 is detachably secured to a base unit 100 so as to form a 
letter slot 102 therebetween at the front edge of the assembly. The base 
unit 100 may be mechanically of the type disclosed, for example, in U.S. 
Pat. No. 2,934,009 issued to Bach et al for Sheet Feeding and Treating. 
The base incorporates a mechanical drive, not shown, for providing 
mechanical drive energy for the printing drum of meter 12. The postage 
meter 12 is an electronic postage meter in the sense that the accounting 
system within the meter, including the registers, is electronic as opposed 
to mechanical. Power is supplied to the meter 12 via an AC power cord 104. 
The power cord 104 is connected to terminal 34 within the conductive 
shielding provided by the metal meter housing 106. A keyboard 108 and 
display 110 are provided and are connected to the control module 18 
microprocessor and control circuit.