2-Wire Intercom Power Inductance Circuit for High DC and Stable AC Impedance
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Solution Overview
Problem
Conventional electronic inductance circuits for 2-wire video intercom systems face limitations in providing sufficient direct current power supply while maintaining stable alternating current impedance, especially when dealing with large-scale systems, as the resistance component's size and value are constrained by the need for both low voltage drop and high impedance, leading to insufficient performance at low frequencies.
Innovation Solution
The proposed electronic inductance circuit incorporates a main circuit path with an inductor and FET, a resistor, and a freewheeling diode in parallel, along with a secondary circuit path including a capacitor and another resistor, allowing for a coil inductor with an auxiliary resistor and freewheeling diode as AC feedback components, which enables larger direct current supply with stable alternating current impedance that does not depend on direct current changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coil inductor is used as the inductance component, then the audio signal impedance is sufficient, but the size of the inductor becomes very large
Solution Approach 1:
The patent replaces the mechanical coil inductor with an electronic inductance circuit consisting of FETs, resistors, and capacitors. This substitution eliminates the need for large magnetic components while achieving the required inductance effect through electronic means, specifically using the gate-drain capacitance of the FETs in conjunction with feedback resistors to create the inductive impedance characteristic needed for audio signal suppression.
Solution Approach 2:
The patent changes the operating parameters of the FETs, particularly utilizing the gate-drain capacitance (Cgd) which varies with the drain-source voltage (UDS). By operating the FETs in a specific region where Cgd provides the necessary reactance at audio frequencies, the circuit achieves inductive behavior without requiring physical inductors. The parameter optimization includes selecting appropriate feedback resistor values (R1, R2) and capacitor values (C1, C2) to tune the inductance and Q-factor.
2Reliability
If the resistance component value is increased to achieve high impedance, then the alternating current impedance is sufficient, but the voltage drop increases and direct current power supply capability is reduced
Solution Approach 1:
The patent employs dynamic operation of FETs Q1 and Q2 where the gate-drain capacitance (Cgd) varies with the drain-source voltage (UDS). As the DC current changes, the FET operating point shifts, automatically adjusting the effective inductance and impedance characteristics. This dynamic behavior allows the circuit to maintain high AC impedance across varying DC current conditions without requiring a fixed high resistance value that would cause excessive voltage drop.
Solution Approach 2:
The patent implements feedback mechanisms through resistors R1 and R2 connected from the drain to gate of each FET. This feedback stabilizes the FET operating point and ensures that the gate-drain capacitance maintains the required reactance value. The feedback also compensates for variations in FET parameters and ensures consistent inductance behavior across different operating conditions, allowing the circuit to achieve high impedance without excessive voltage drop.
3Power
If the resistance component value is decreased to reduce voltage drop, then the direct current power supply capability is improved, but the alternating current impedance becomes insufficient
Solution Approach 1:
The patent utilizes the dynamic characteristics of FET gate-drain capacitance which automatically adjusts with operating conditions. When DC current increases, the FET operating point shifts, and the gate-drain capacitance value changes to maintain the required reactance. This dynamic adjustment allows the use of lower resistance values (reducing voltage drop) while still achieving sufficient AC impedance through the capacitive reactance of the FET gates.
4Device complexity
If conventional electronic inductance circuit configuration is used, then the circuit complexity is reduced, but the direct current power supply capability and alternating current impedance are limited
Solution Approach 1:
The patent divides the inductance function into two separate FET-based branches (Q1 and Q2) operating in parallel. Each FET with its associated resistors and capacitors forms an independent inductance simulation unit. This segmentation allows each branch to be optimized for specific operating conditions, and together they provide enhanced DC power supply capability while maintaining high AC impedance. The segmented architecture also improves current distribution and reduces the burden on individual components.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for a larger direct current power supply with stable and sufficient alternating current impedance, ensuring fast response and reduced power consumption, enabling larger 2-wire intercom systems with improved performance across a range of frequencies.
Implementation Method 1
utilizing the gate-drain capacitance, generated by the Miller effect, of the FETs
Implementation Method 2
the power supply circuits of the system power supply and devices thereof have to comprise an inductance component connected to the common bus in series, which allows the direct current passing whilst also suppresses the alternating current signal
Data Source
AI summary
The present invention discloses an electronic inductance circuit for the power supply of a 2-wire bus intercom system and a device thereof. The electronic inductance circuit comprises a main circuit path along an inductor and a source terminal and a drain terminal of a FET between the input terminal and the output terminal of said electronic inductance circuit, in which said inductor is connected to said source terminal of said FET; a resistor and a freewheeling diode individually connected to said inductor in parallel; and a secondary circuit path along a capacitor connected with a second resistor in series between said input terminal and said output terminal, which is connected to said main circuit path in parallel. The solutions of the present invention achieve larger direct current power supply for the 2-wire intercom system and stable alternating current impedance with fast response to the DC power supply.