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VARIABLE IMPEDANCE TANK CIRCUIT

IP.com Disclosure Number: IPCOM000242726D
Publication Date: 2015-Aug-07
Document File: 3 page(s) / 77K

Publishing Venue

The IP.com Prior Art Database

Abstract

A variable impedance tank circuit is disclosed. The variable impedance tank circuit dynamically adjusts gain characteristics for a high voltage pulse generation system. The variable impedance tank circuit includes a resistor Rr, a capacitor Cr and inductors Lr1, Lr2, a sub-resonant tank, a control, a drive module and a zero crossing detection. The inductors Lr1, Lr2 are coupled with an active switch to exhibit controllable inductor characteristics. The sub-resonant tank is connected in parallel with a secondary-side of the inductor Lr2. The sub-resonant tank may also increase a resonant tank gain with enhanced gain characteristics. During a rising cycle of kilovolts (kV), the inductor Lr2 is short-circuited, while the inductor Lr1 exhibits the controllable inductor characteristics. After the kV rises to about 70%~80% of a rated voltage (Vo), the secondary side of the inductor Lr2 is open.

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VARIABLE IMPEDANCE TANK CIRCUIT

BACKGROUND

The present invention relates generally to power circuits, and more particularly to a variable impedance tank circuit.

One continuous challenge during medical examination is minimizing radiation exposure of patients and doctors.  For this purpose an x-ray generator is required to possess a fast kilovolts (kV) rise time and fall time.  Conventional systems use a fixed resonant tank circuit and the fixed resonant tank circuit provides a constant gain. 

The fixed resonant tank circuit used in conventional systems is unable to maintain a balance between a steady-state circuit performance and a large surge primary current to achieve the fast Kv rise time.  Further, the fixed resonant tank circuit changes switching frequency to modify a tank voltage division ratio to manipulate the kV rise time.  As a result, the conventional techniques are unable to dynamically adjust gain characteristics to achieve the fast kV rise time. 

 

It would be desirable to have a variable impedance tank circuit for dynamically adjusting gain characteristics.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 depicts a variable impedance tank for dynamic adjustment of gain characteristics in medical examination systems.

DETAILED DESCRIPTION

This disclosure proposes a variable impedance tank circuit for medical examination systems.  The variable impedance tank circuit dynamically adjusts gain characteristics for a high voltage pulse generation system. Figure 1 depicts the variable impedance tank circuit.   

Figure 1

The variable impedance tank circuit is shown in the red dotted box in Figure 1.  The variable impedance tank circuit includes a resistor Rr, a capacitor Cr and inductors Lr1, Lr2, a sub-resonant tank, a control, a drive module and a zero crossing detection.  The inductors Lr1, Lr2 are coupled with an active switch to exhibit controllable inductor characteristics.  In an embodiment, the controllable inductor characteristics are within order of nanosecond (ns)...