Methods and configurations of LC combined transformers and effective utilizations of cores therein

• US 9,257,225 B2
• Filed: 07/02/2008
• Issued: 02/09/2016
• Est. Priority Date: 07/02/2008
• Status: Active Grant

• Current Assignee: Chun Li, Jason Li, Ran Ran Li
• Original Assignee: Chun Li, Jason Li, Ran Ran Li
• Inventors: Li, Chun, Li, Jason (Jian Hao), Li, Ran Ran
• Primary Examiner(s): Lian, Mangtin
• Application Number:
  US12/166,322
• Publication Number:
  US 20100001822A1
• Time in Patent Office: 2,778 Days
• Field of Search: 336/105, 336/212, 336/145, 336/146, 336/182, 336/170
• US Class Current: 1/1
• CPC Class Codes: H01F 27/385 for reducing harmonics
• CPC Class Codes: H01F 3/12 Magnetic shunt paths
• CPC Class Codes: H01F 38/16 Cascade transformers, e.g. for use with extra high tension

Abstract

The LC combined transformer is a combination of capacitors, inductors and an electrically-isolated mutual inductor, i.e. conventional transformer; which in principle is a unity-coupled mutual capacitor or a cascade connection of an ideal transformer and unity-coupled mutual capacitor(s). To improve the imperfections of widely-used transformers, by employing the simplest passive-circuit design to attain a perfectly-functional match between mutual capacitors and the mutual inductor, this invention achieves optimal features of current or/and voltage transformation, and introduces a new function of waveform conversion from square to quasi-sine. The ideal current transformer herein is suitable for sinusoidal current measurements, the ideal voltage transformer herein suitable for sinusoidal voltage measurements, and they also could be upgraded to ideal transformers for both current and voltage transformations. This transformer can be designed as power transferable as well as waveform convertible, applicable in power systems or power electronics. Herein also states the design approach of integrated inductor and mutual inductor, and the use of push-pull inductor, materials being fully utilized and sizes decreased.

Claims

1. A species of electric transformer, termed LC combined transformer, used for transferring electric signal or energy of periodic sine wave, and proportionally altering the amplitude(s)/magnitude(s) of current or/and voltage of the periodic sine wave between input and output ports when neglecting power loss,

being a current type unity-coupled mutual capacitor characterized as current transformation, or a voltage type unity-coupled mutual capacitor characterized as voltage transformation, or a circuit of LC combined transformer in cascade connection of an ideal transformer plus one current type unity-coupled mutual capacitor or two voltage type unity-coupled mutual capacitors, comprising

said current type unity-coupled mutual capacitor consisting of three linear capacitances in delta (Δ

) configuration with a sum of the reciprocals of said three capacitances being zero;

said voltage type unity-coupled mutual capacitor consisting of three linear capacitances in wye (Y) configuration with a sum of said three capacitances being zero;

either of said unity-coupled mutual capacitors including negative capacitance(s) which may be realized through negative impedance converter(s) (NIC) or by employing linear inductor(s) when operating at a constant frequency;

said circuit of LC combined transformer comprising current transformation-A type LC combined transformer consisting of a mutual inductor (Tr), an inductor (Lb) and a capacitor (Cm), if designating the primary winding terminals of said mutual inductor (Tr) as the input port of said current transformation-A type LC combined transformer, said mutual inductor (Tr)'"'"'s secondary winding and said inductor (Lb) and said capacitor (Cm) being connected in series to form a closed loop before designating the two terminals of said capacitor (Cm) as the output port;

said current transformation-A type LC combined transformer presenting a ratio of current transformation between ports as

2. The electric transformer according to claim 1,

wherein the inductor (Lb) and the mutual inductor (Tr) may be linearly integrated into an integrated inductor and mutual inductor, comprising:

the core magnetic circuit (F1) of said mutual inductor (Tr), the core magnetic circuit (F2) of said inductor (Lb), the first winding (N1) of said mutual inductor (Tr), the two-in-one common coil (N2) serving both as the second winding of said mutual inductor (Tr) and also as the winding of said inductor (Lb), and the auxiliary winding (Δ

N) (set when needed) of (Lb),

being structurally built as that said first winding (N1) is just wound around said core magnetic circuit (F1) with its terminals designated as one port of said integrated inductor and mutual inductor, said two-in-one common coil (N2) wound around the paralleled and adjacent-to-each-other portions of both said core magnetic circuits (F1) and (F2), said auxiliary winding (Δ

N) just wound around said core magnetic circuit (F2), plus said two-in-one common coil (N2) and said auxiliary winding (Δ

N) connected in series-aiding with their terminals after series designated as the other port,

with a result that the turns ratio (n), the coupling coefficient (k), the self-inductances (L₁) and (L₂) respectively of said windings (N1) and (N2), and relationships of currents and powers of said mutual inductor (Tr) will all remain unchanged as those of its original mutual inductor without being integrated, the inductance (L_b) of said inductor (L_b) will be determined by said core magnetic circuit (F2) and said winding (N2+Δ

N) as that of a normal inductor, except that the total inductance of said other port of this integrated inductor and mutual inductor will be the sum of said inductances (L₂) and (L_b) when both said core magnetic circuits are linear.

3. The electric transformer according to claim 1,

wherein the inductor (La) may be a center-tapped inductor, thus being termed a use of push-pull inductor, including:

{circle around (1)} the center-tapped inductor, two electrically-symmetric switching devices such as power bipolar junction transistors (BJTs) - - - each with a diode connected in series-aiding or in reverse-parallel for a purpose of protection, and two electrically-symmetric auxiliary switching devices such as diodes;

{circle around (2)} being constructed as that the center-tap of said inductor is electrically connected to a high potential, one end of said inductor connected to collector of the first BJT and also to anode of the first diode, the other end of said inductor connected to collector of the second BJT as well as to anode of the second diode, emitters of both BJTs connected together to the reference potential, cathodes of both diodes connected together to another appropriate high potential, and bases of both BJTs respectively connected to corresponding control-and-drive signals;

{circle around (3)} and employing a technique of bi-periodically time-shared driving to drive the push-pull inductor.

4. The use of push-pull inductor according to claim 3,

wherein the technique of bi-periodically time-shared driving is described as:

a pulse-width modulation (PWM) control and drive with two switching periods being a cycle of a sequence, stated as follows;

for the first period the second switching device keeping OFF while the first switching device being ON no longer than T/2 before being turned off;

for the second period the first switching device keeping OFF while the second switching device being ON no longer than T/2 before being turned off, with the end of the second period as the end of a cycle of the bi-periodically time-shared driving;

where T is the time interval of switching period of the circuit.