Electronic energy converter having two resonant circuits

A power line-operated electronic converter is adapted to deliver a relatively constant magnitude high frequency signal to a load (113) and is operable to draw a substantially sinusoidal current from the AC voltage source (101). The converter has DC input terminals (V+, V-) having a capacitor (108) connected therebetween, rectifying bridge (103) and boosting rectifiers (D5,D6) coupled to the DC input terminals, a resonant oscillator circuit coupled to the DC input terminals and to the transistor inverter (106) employing two integrated and synchronized resonant circuits having two resonant capacitors (114,112) and one common resonant inductor (110) wherein one circuit is used to operate the load and the other to provide boosted pulsating DC voltage to be naturally added and integrated with the rectified voltage of the AC voltage source.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to single stage electronic energy converters 
operated from alternating power line and capable of supplying, at the 
output, a load such as gas discharge lamp. 
2. Description of Prior Art 
The electronic energy converters, or as sometimes called "switching power 
supplies" need to operate directly from the alternating power line. 
Electric utility companies are setting requirements for specific groups of 
electricity-powered appliances in regards to power quality drawn by these 
appliances. 
The electronic ballast, as one of the appliances, is used in large 
quantities in lighting fixtures. In general, to meet the industry 
requirements in regards to power quality, an electronic ballasts has to 
meet two fundamental requirements: (i) draw power from the power line with 
power factor (PF) of at least 0.9, (ii)draw current from the power line 
with total harmonic distortion (THD) of less than 20 percent. 
The electronic ballast has to meet other requirements related to 
compatibility with a lamp-load. It shall provide 1amp current crest factor 
of less than 1.7, where the "crest factor" is equal to a peak magnitude of 
the lamp current divided by its effective (RMS) value. This is related to 
maximum allowable modulation of the lamp current magnitude, which is 
responsible for light flicker and poor lamp efficacy expressed in lumens 
of light produced from each watt of power consumed. It is desirable to 
have constant power to be delivered to the lamp load over the entire cycle 
of the voltage supplied by the power line. 
In order to convert the low frequency power line alternating voltage 
(120V/60 Hz or 220V/50 Hz) to high frequency (typically from 10 kHz to 100 
kHz) alternating voltage or current source, one has to rectify the signal 
from the power line to a DC voltage which later is converted, by switching 
transistors, to the high frequency source. 
Conventional off-line rectifiers have a capacitive smoothing filter located 
beyond a diode rectifier circuit. This smoothing capacitor causes harmonic 
distortion of the current waveforms during periods in which the rectified 
output is higher than the voltage over the smoothing capacitor, and during 
which time the capacitor charges up. This charging time, or conduction 
angle, is very small if large capacitor is used, and all the required 
charge has to be loaded into the capacitor in a short period of time. This 
results in a large current output from the rectified power line source. 
These current spikes increase the harmonic content of the power supply, 
and when large number of ballasts are operated from the power line, this 
increased harmonic distortion causes a poor power factor in the supply. 
This situation is not accepted upon by electricity supply authorities and 
causing interference with other electrical equipment. 
Techniques for improving power factor include passive waveform shaping 
methods. One of them is described in U.S. Pat. No. 5,150,013 issued to 
BOBEL. This method requires an inductor to operate in resonant mode with a 
capacitor, and the resonant frequency is approximately 180 Hz when power 
line frequency is 60 Hz. Is is inexpensive and reliable method. However, 
the inductor must be large in size. 
It is known to use a storage conversion principle, whereby an inductor is 
controlled at high frequency in order to allow charging of the smoothing 
capacitor over wide conduction angle. The system, however, requires a 
control circuit for the storage converter, known also as "boost 
converter", in order to regulate the discharge of energy from the storage 
inductor. Such use of the storage conversion principle requires additional 
noise filtering, because large amount of noise is being generated by 
switching devices. The circuit is very complex and expensive to produce. 
Furthermore, the second stage converter is necessary to convert the DC 
voltage source to the high frequency alternating voltage or current 
source. This type circuit is described in U.S. Pat. No. 5,049,790 issued 
to Herfurth. 
It is highly desirable to have simple and low cost single stage electronic 
energy converter. Such a circuit shall have low parts count and cost, it 
shall be adaptable to all power line voltages and lamps kinds, it shall be 
easy manufacturable in large quantities with great repeatability as 
required by industry quality standards, it shall meet the power quality 
standards and draw power from the power line with near-sinusoidal current 
waveform and provide near-constant power to the lamp over the entire cycle 
of power line voltage waveform. 
SUMMARY OF THE INVENTION 
In accordance with the invention there is provided an energy conversion 
device having a DC pulsating voltage at DC input terminals and adapted to 
deliver a high frequency signal to a load, the device comprising: 
rectifier means receiving a source voltage from an AC power source and 
providing at first DC output terminals a first pulsating DC voltage; 
boosting rectifier means having a boost input terminal and providing a 
second pulsating voltage at second DC output terminals wherein said first 
and second DC output terminals are suitably oriented, connected in 
circuit, and coupled to the DC input terminals, and provide the DC 
pulsating voltage equal to the sum of the first DC pulsating voltage and 
the second DC pulsating voltage; 
capacitor means coupled to the DC input terminals and receiving said DC 
pulsating voltage; 
semiconductor switching means coupled to the capacitor means; 
resonant oscillator means operable to draw a pulsating current from the DC 
input terminals and operable to develop the second DC pulsating voltage, 
and said oscillator circuit comprises: (i) a resonant load circuit coupled 
to the DC input terminals and to the semiconductor switching means, and 
having an inductor and a first capacitor connected in series, and having 
the load connected effectively in parallel to said first capacitor, (ii) a 
resonant boost circuit having the inductor connected in series with a 
second resonant capacitor and coupled to the boost input terminal and to 
the semiconductor switching means, and (iii) a switching feedback loop 
coupled to the semiconductor means and responsive to instantaneous 
magnitude of the pulsating current and operable to deliver to the 
semiconductor switching means a switching signal modulated in proportion 
to the modulation of instantaneous magnitude of the second DC pulsating 
voltage. 
The device further comprising the rectifier means as unidirectional devices 
connected in the form of a ordinary bridge circuit and having positive and 
negative first DC output terminals, respectively, and the rectifier means 
having each of the unidirectional devices exhibit a switching action 
characterized by an ON-time period when conducting electrical current, and 
characterized by OFF-time period when not conducting electrical current. 
The device further comprising the boosting rectifier means as two 
unidirectional devices connected in series via boost input terminal. 
The device further comprising the capacitor means as polarized electrolytic 
capacitor. 
The device further comprising the semiconductor switching means as a pair 
of npn bipolar transistors connected in a half-bridge configuration for 
alternating operation. 
The device further comprising the resonant oscillator means having the 
switching feedback loop equipped with a non-saturable current transformer. 
The device further comprising the resonant oscillator means which has the 
switching feedback loop equipped with a saturable current transformer. 
The device further comprising the saturable current transformer made with a 
toriodal ferrite core having an initial permability of 5000 or more and 
size of 6 millimeters in diameter and 3 millimeters in height. 
The device further comprising the resonant oscillator means which has the 
saturable current transformer equipped with one turn primary winding and 
few turns each secondary windings. 
The device further comprising the resonant oscillator means which has the 
switching feedback loop equipped with a control circuit. 
The device of present invention operates with the instantaneous frequency 
of oscillation of the resonant oscillator means modulated in proportion to 
the modulation of instantaneous magnitude of the second DC pulsating 
voltage. 
The device of present invention has the semiconductor switching means which 
exhibit an instantaneous switching duty cycle modulated in proportion to 
the modulation of instantaneous magnitude of the second DC pulsating 
voltage. 
In such a device the instantaneous magnitude of input current is 
proportional to the instantaneous magnitude of the power line voltage, and 
the total harmonic distortion of the current is below 20%. In result, 
power is drawn from the power line with power factor of 99%, lamp current 
crest factor is below 1.7. 
Other objects and advantages of the present invention shall be made clear 
in following description of the invention detailed with reference to 
various embodiments of the invention as shown in accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 schematically illustrates the main preferred embodiment of the 
invention in the form of an electrical circuit diagram. 
In FIG. 1 a voltage source 101 represents an ordinary 120Volt/60 Hz 
electric utility power line and is connected through a RFI/EMI filter 102 
to AC input terminals P1 and P2 of a full wave rectifier bridge 103. The 
bridge 103 is made of four rectifier diodes and has a pair of DC output 
terminals P+,P- where the terminal P+ is a positive and the terminal P- is 
a negative. Two diodes D5,D6 are connected in series via boost input 
terminal A. A cathode electrode of the diode D5 is connected to the 
terminal P- and an anode electrode of the diode D6 is connected to a DC 
input terminal V-. The terminal P+ of the bridge 103 is connected to 
another DC input terminal V+. 
A diode 104 is connected with its anode electrode to the terminal V+ and 
with its cathode electrode to a node VDC. A storage capacitor 108 is 
connected between the node VDC and the terminal V-. 
A half-bridge switching transistor inverter 106 has a bipolar transistor 
(of the type MJE 13005) connected at its collector electrode to the node 
VDC. The transistor 105 has its emitter electrode connected to a node C. A 
further npn transistor 107 (like the transistor 105, of the type MJE 
13005) of the inverter has its collector electrode connected to the node 
C. The transistor 107 has its emitter electrode connected to the terminal 
V-. 
A resonant oscillator circuit consisting of two integrated and coupled 
resonant circuits. The first resonant circuit has a DC blocking capacitor 
BC (having value of approximately 0.1 uF), and first resonant capacitor 
114 (having value of approximately 18 nF), and resonant inductor 110 
(having value of approximately 1 mH), and a primary winding W1 of a 
feedback transformer 109, all connected in series between terminal V+ and 
the node C, via filaments 116,115 of a gas discharge lamp 113. Thereby, 
the gas discharge lamp (of the type Dulux E 26W by Osram) is effectively 
connected across the resonant capacitor 114 via two pairs of lamp 
terminals a-b,c-d. The second resonant circuit has the same resonant 
inductor 110, and second resonant capacitor 112, and the primary winding 
W1 of the feedback transformer, all connected in series between node C and 
the boost input terminal A. The feedback transformer 109 is equipped with 
two secondary windings W2,W3 connected across base-emitter junctions of 
the switching transistors 105,107, respectively. A junction F is a common 
terminal of both resonant circuits equipped with one common inductor 110 
and two resonant capacitors 114 and 112. This device can be made 
operational with either saturable core or non-saturable core used in 
design of the feedback transformer. The saturable core used is made by 
Magnetics, Inc. of Butler, Pa., model No. OW40603-TC. The non-saturable 
core feedback transformer may be designed with core made by Magnetics, 
Inc., model No. J-42510-EC. 
FIG. 2 illustrates a second embodiment of the invention in combination of 
the invention described and claimed in the parent application Ser. No. 
08/005,817 of the present inventor. The secondary winding N22 of the 
resonant inductor 210 is connected to a pair of AC input terminals F1,F2 
of a bridge 206. This embodiment has also two resonant circuits comprised 
of two resonant capacitors 214,212 and one common resonant inductor 210. 
Two gas discharge lamps 215,216 connected in series are implemented and 
having three pairs of filament terminals a-b, c-d, and e-f connected to 
respected filament windings of the resonant inductor 210. 
FIG. 3 illustrates yet another embodiment of the present invention wherein 
two boost capacitors 306 and 311 are connected in series via boost input 
terminal A, and connected between DC input terminals V+,V-. In this 
circuit, as is in circuit of FIG. 1, two resonant circuits are implemented 
having first and second resonant capacitors 314,312 and one common 
resonant inductor 310. The second resonant capacitor 312 is connected to 
the boost input terminal A. 
FIG. 4 illustrates an alternative version of the present invention 
described in FIG. 1. The resonant oscillator is equipped with a Control 
Circuit which has at least four terminals as follows: signal input 
terminal SIT, ground terminal GT, and two gate terminals G1,G2, 
respectively. 
FIG. 5 illustrates an alternative version of the present invention wherein 
resonant oscillator circuit comprising two resonant circuits. The first 
resonant circuit has a DC blocking capacitor BC connected in series with a 
primary winding N15 of a resonant inductor 510, and with a primary winding 
of a feedback transformer 509, all connected between the terminal V+ and 
the node C. A first resonant capacitor is connected in parallel with the 
primary winding N15 of the resonant inductor 510. A second resonant 
circuit has serially connected winding W1 of the feedback transformer, the 
primary winding N15 of the same resonant inductor 510 and a second 
resonant capacitor 512, all connected between the node C and boost input 
terminal A. The resonant inductor 510 is equipped also with a secondary 
winding N25 and has a gas discharge load 513 connected to that winding via 
current limiting capacitor 517. 
FIG. 6 illustrates yet another alternative version of present invention 
wherein the feedback transformer is eliminated and switching feedback 
signal is provided to the switching transistors by means of secondary 
windings W16,W26 magnetically coupled to the resonant inductor 610. 
It is obvious that more alternative versions or different combinations may 
be possible to create by those skilled in the art, for example, 
improvements and resonant oscillator of FIG. 6 can be used in combination 
of boost input terminal A and diodes D5,D6 of FIG. 1. 
DETAILS OF OPERATION 
In order to clearly describe the operation of the device of FIG. 1. the 
second resonant capacitor 112 will be not connected to the boost input 
terminal A. 
FIGS. 7(a)-7(d) indicate various current and voltage waveforms illustrative 
of the operation of the device of FIG. 1 with the capacitor 112 not 
connected to the terminal A. With reference to the waveforms of FIGS. 
7(a)-7(d) the operation of the device of FIG. 1 is very similar to the 
device explained in U.S. Pat. No. 3,084,283 issued to Grunwaldt. The 
differences are objects of this invention accomplished by providing the 
rectifier bridge 103 connected in series with diodes D5 and D6, and diode 
104 connected in series with storage capacitor 108. By implementing such 
improvements, new behavior of the device was discovered. A DC input 
voltage developed across DC input terminals V+,V-, as per FIG. 7(a) is a 
result of commonly known rectification of voltage delivered by AC voltage 
source 101 and filtering by capacitor 108. 
The device starts oscillation by triggering provided with a commonly known 
diac circuit (not shown). The converter is delivering a constant magnitude 
voltage and constant magnitude current into the lamp load 113. The 
frequency of the switching inverter 106 is equal to resonant oscillation 
frequency of the series resonant tank circuit which includes load 113 
connected in parallel to resonant capacitor 110 and in series with the 
resonant inductor 110. 
The device draws a pulsating current from the energy storing capacitor 108 
and from the power line via bridge 103. The pulsating current flows 
periodically through diodes D6 and D5. Whenever diodes D5 and D6 are 
conducting the pulsating current, the DC input terminal V- is in effect 
connected to the terminal P- of the bridge 103. Therefore, the diodes 
exhibiting a switching ON/OFF action due to flow of the pulsating current. 
The peak magnitude of the DC input voltage between terminals V+,V- is equal 
to peak magnitude of the rectified AC voltage source 101. 
The waveform of the voltage across terminals P+,P- of the bridge 103 is 
presented in FIG. 7(b). A waveform of the voltage developed between 
terminals P-,V- (both diodes D5,D6) is presented in FIG. 7(c). At any 
moment during operation of the device, the instantaneous magnitude of the 
DC input voltage (as per FIG. 7(a)) is equal to a sum of instantaneous 
magnitude of the rectified AC voltage source (as per FIG. 7(b)) and 
instantaneous magnitude of the voltage developed across both diodes D5,D6 
(as per FIG. 7(c)). The waveform of the input current is presented in FIG. 
7(d). 
The oscillation frequency (fo) of such series resonant circuit can be 
expressed by the following formula: 
##EQU1## 
where: =2 fo .omega.=2.pi.fo 
L=inductance of the resonant inductor 110; 
C=capacitance of the resonant capacitor 114; 
R=resistance of the load; 
A feedback signals obtained by the switching feedback windings W2,W3 of the 
feedback transformer 109 for the self-oscillation of the converter is in 
phase with an output current delivered at the output terminals I,F. Thus, 
the frequency obtained always adjusts itself--in proportion to 
instantaneous magnitude of the DC input voltage at the terminals V+,V- and 
according to changes of the load 113 connected across first resonant 
capacitor 114. Under these conditions, it can be proved that, if the 
resonant inductor 110 and resonant capacitor are free of losses, the 
current supplied to the load 114 is dependent of the resistance of the 
load thereof. This current depends only upon the DC input voltage at the 
terminals V+,V- and upon the quotient 
##EQU2## 
Furthermore, the output voltage magnitude is relatively constant as this 
is a characteristic of a gas discharge load. Thus, the voltage magnitude 
across the resonant inductor is relatively constant, as this is a 
characteristic of the series resonant circuit, where voltage magnitude 
across the resonant capacitor is directly proportional to voltage 
magnitude across the resonant inductor. This series resonant circuit is 
high-Q type with ability to produce across it resonant components 110,114 
voltages of much higher magnitudes than DC input voltage magnitude. And 
the voltages across the resonant components 114,110 can be easily 
modulated by providing modulation of instantaneous value of either: the 
load 113, the inductor 110, or the capacitor 114. The same can be 
accomplished by limiting and modulation of magnitude of the voltage across 
one of the resonant components. 
The operation of the device of FIG. 1 when the connection of the second 
resonant capacitor 112 is provided at the boost input terminal A will be 
referenced to waveforms of FIGS. 8(a)-8(d). 
Whenever the capacitor 112 connection is provided at the terminal A, the 
interaction of input and output of the device begins. Such an interaction 
is an effect of development of resonant boost circuit having ability to 
store and release energy. The diode D6 is acting as a switching device of 
the boost circuit and is ON when the transistor 107 is conducting and said 
diode is OFF when the transistor 105 is conducting. Both transistor 
conduct current periodically and alternately as is in any commonly known 
two transistor inverter. The diode D5, however, is acting as boost diode 
of a commonly known boost circuit. Whenever the instantaneous voltage 
developed between terminals A and V- is higher than instantaneous voltage 
v(t) present across the storage capacitor 108, diode D5, and diodes of the 
bridge 103, and diode 104, all will conduct capacitor charging current iCH 
for as long until said voltages become equal. It may be that at the end of 
the particular oscillatory period, when the transistors reverse its 
states, current will continue to flow from terminal A, but this time to 
the load 113 via capacitor BC. Whenever the transistor 107 conducts 
current the second resonant circuit stores energy which is released in the 
period when the transistor 105 conducts current. Both resonant circuits 
are integrated by having common resonant inductor 110. The first resonant 
circuit is series resonant with load 114 connected in parallel to the 
resonant capacitor. The second resonant circuit, however, is series 
resonant with a boost load connected in series with both resonant 
capacitor and resonant inductor. The boost load is a complex load 
represented by impedance of the storage capacitor, as equivalent series 
resistance, and losses of all active and passive circuit components, and 
the load 113, all connected in arrangements as per circuit of FIG. 1. Such 
variable and complex load arrangement which is changing in very dynamic 
way effects modulation of the resonant circuit gain, accordingly. 
Therefore, the impedance character (less or more inductive) of the entire 
resonant oscillator is changing also in proportion to the changes 
mentioned above. The instantaneous magnitude of the voltage developed 
across switching diode D6 and boost diode D5 is in effect transformed to 
an instantaneous magnitude of a boost load connected in series with the 
second resonant circuit. However, despite such modulations, the magnitude 
of the pulsating current i1 which flows through the resonant inductor, and 
magnitude of the load current are being kept relatively constant due to 
instantaneous self-adjustment of the switching frequency of the resonant 
oscillator by the feedback transformer 109, so the impedance effective 
value associated with the first series resonant circuit is being kept 
relatively constant. The voltage magnitude between terminals P-,V- (as per 
FIG. 8(c)) is equal again to a difference of instantaneous magnitude of 
the DC input voltage developed across terminals V+,V- and instantaneous 
magnitude of rectified, not filtered voltage between terminals P+ and P-, 
the later being provided by rectified AC voltage source and is shown in 
FIG. 8(b). 
The peak magnitude of the DC input voltage is equal or higher than peak 
magnitude of the rectified AC voltage source. The parameters of 
determining the magnitude of that voltage, as per FIG. 8(a), are: 
instantaneous and effective load value and Q-factors of the first and 
second series resonant circuits. The above parameters are most important 
factors in obtaining the device stability and proper operation. 
It will be appreciated that due to the implementation of the second 
resonant circuit as resonant boost circuit the voltage magnitude to which 
the capacitor 108 is charged, being partially provided by AC voltage 
source and partially provided by the resonant boost action. Thus, a 
charging current iCH of the capacitor 108 is partially provided by AC 
voltage source, and partially by the resonant boost circuit. Therefore, 
the input current waveform (as per FIG. 8(d)) taken from the AC voltage 
source is substantially proportional to the voltage waveform of the AC 
voltage source. The power is drawn from the power source with power factor 
of 99%, and current delivered to the device from the source is having 
total harmonic distortion below 20%. 
It will be appreciated that due to implementation of the resonant boost 
circuit integrated with the resonant circuit which operates the load, 
according to the present invention, the modulation of frequency dependent 
impedance characters of these circuits in proportion to the modulation of 
instantaneous magnitude of the voltage equal to a difference between 
instantaneous magnitude of the DC input voltage and instantaneous 
magnitude of the rectified AC voltage source is developed. Accordingly, it 
will be appreciated that due to implementation of the resonant boost 
circuit integrated with other resonant circuit which operates the load, 
the frequency of oscillation of the resonant oscillator made with said 
circuits is modulated in proportion to the modulation of instantaneous 
magnitude of the voltage equal to a difference between instantaneous 
magnitude of the DC input voltage and instantaneous magnitude of the 
rectified AC voltage source. In result, the instantaneous magnitude of the 
current drawn from the AC voltage source is substantially proportional to 
the instantaneous magnitude of the voltage provided by said AC voltage 
source, and the amplitudes of the voltage and current delivered to the 
load, are relatively constant. 
In regards to device of FIG. 2 which is a second embodiment of the present 
invention the feedback winding N22 of the resonant inductor 210 is 
provided in combination with the resonant boost circuit as in device of 
FIG. 1. Operation of the circuit is similar to the one described in FIG. 
1. with addition of the feedback winding coupled to the resonant inductor 
and connected to the AC terminals of the bridge 206, the effective 
inductance value of the resonant inductor is modulated here in proportion 
to the modulation of the voltage present at terminals F+,F-. In effect 
this device operates providing the same results as device of FIG. 1. It 
may be selected as a design choice when improvement of the energy feedback 
is necessary to provide proper input and output parameters of the device. 
In regards to device of FIG. 3 which is another embodiment of the present 
invention the diodes of the rectifying bridge 303 perform boost switching 
and rectifying functions. The boost capacitors 306,311 are being 
periodically charged by the resonant boost circuit via capacitor 312, and 
discharged periodically whenever the voltage across storage capacitor is 
lower than voltage across DC input terminals V+,V-. This embodiment is 
used when the device is required to operate the variety of different lamps 
types in regards to its power ratings and sizes. Two integrated resonant 
circuits having one common resonant inductor interact in such a way that 
input and output parameters within large range of output power are being 
kept within desired specifications. 
The device of FIG. 4 is an alternative version of the device of FIG. 1 
wherein the Control Circuit perform the function of the feedback 
transformer of the device of FIG. 1. The Control Circuit senses the 
instantaneous magnitude of the voltage across terminals P-,V- and provides 
to the transistors Q1, Q2 switching signals in proportion to said 
magnitude. Thus, the switching frequency of the oscillator circuit is 
modulated in proportion to the modulation of the amplitude of the voltage 
between terminals P- and V-. All other aspects of the operation of this 
device are identical to the operation of the device of FIG. 1. 
The device of FIG. 5 is an alternative version of device of FIG. 4 which 
has implemented the parallel resonant circuit as the first resonant 
circuit, and series resonant circuit as the resonant boost circuit. The 
parallel resonant circuit comprises a capacitor 514 which is operates in 
parallel resonant with the inductance of the primary winding N15. The 
boost resonant circuit, however, operates as the series resonant circuit 
wherein the same inductor interacts with the capacitor 512. The coupling 
and integration of these resonant circuits results in development of 
resonant oscillator circuit wherein the switching signal is provided to 
the transistors by the feedback transformer 509. In this embodiment, like 
in the described embodiment of FIG. 3, the energy stored in the boosting 
resonant circuit which includes boosting capacitors 506 and 511, is 
naturally released and provided as additional voltage to the rectified AC 
voltage source. 
FIG. 6, attached hereto represents the alternative version of the device of 
FIG. 5. The circuit shown here is identical in operation to the one of 
FIG. 5, with the exception that the switching feedback is accomplished 
with use of secondary windings W16,W26 operable to provide switching 
signal proportional to the pulsating voltage which is developed across 
both resonant elements 614, N61 of the parallel resonant circuit. 
It will thus be appreciated that the devices, as described herein will 
provide for substantial stability of its critical parameters (input power, 
power factor, total harmonic distortion, load current crest factor) 
despite: large variations of nominal AC voltage source, b) application of 
other than nominal load type, c) subjecting the devices to low and high 
temperatures. 
It will be appreciated that device as described herein, will be very 
simple--with very low parts count, easily adaptable to all power line 
voltages and load types, repeatable in manufacturing process, and 
inexpensive. 
It will be also appreciated that various other modifications or 
alternatives to the above described embodiments will be apparent to the 
person skilled in the art without departing from the inventive concept 
described herein.