PIN Diode Switching Circuit With Inductor-Assisted Fast Blocking
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Solution Overview
Problem
Current magnetic resonance systems are limited by the switching time of PIN diodes in transmission/reception diplexers, which restricts the minimum achievable echo time, preventing the full exploitation of Ultra Short Echo Time (UTE) technology for imaging tissues with short relaxation times.
Innovation Solution
A circuit incorporating a PIN diode, an inductor, and multiple switch settings allows for faster switching by using the inductor as a temporary current source to discharge the PIN diode, enabling quicker transition from a conductive to a blocking state, potentially mimicking a blocking voltage effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the PIN diode is switched from conductive to blocking state using conventional methods, then the switching speed is limited by charge carrier recombination time, but the circuit structure remains simple
Solution Approach 1:
An inductor is introduced as an intermediary component to enable faster switching. The inductor stores energy during the conductive state and releases it as a discharge current in the blocking direction during the transition to the blocking state, actively removing charge carriers from the PIN diode much faster than natural recombination alone.
Solution Approach 2:
The inductor is pre-charged with current while the PIN diode is in the conductive state. This preliminary energy storage in the inductor prepares the discharge current that will be released when switching to the blocking state is required, enabling rapid transition without waiting for natural charge carrier recombination.
2Reliability
If the inductor is continuously supplied with current in the first switch setting, then the PIN diode remains in conductive state, but power loss increases
Solution Approach 1:
Instead of continuous current supply, the inductor is supplied with current periodically or in pulses. The switch setting transitions between conducting and non-conducting states, allowing the inductor to be charged only when needed and then used to drive the discharge current, reducing continuous power loss while maintaining reliable switching capability.
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 approach significantly accelerates the PIN diode's switching into a radio-frequency blocking state, enabling shorter echo times and enhancing the capability to image tissues with short relaxation times using UTE sequences.
Implementation Method 1
the inductor in this current loop consequently acts as a (temporary) direct current source that allows a discharge current to flow through the PIN diode
Data Source
AI summary
A circuit for switching a PIN diode has a PIN diode and an inductor (in particular a coil) as well as a direct voltage source and a group of switches, wherein in a first switch setting of the group of switches the PIN diode can be fed with current from the direct voltage source in its admission direction; and in a further switch setting the PIN diode and the inductor are separated from the direct voltage source and are arranged in a closed current loop such that the inductor can generate a discharge current upon transitioning to the further switch setting, which discharge current is directed to the PIN diode opposite to the current generated by the direct voltage source (DC).