Switching Circuit for Fast Turn-On Ideal Diode Approximation
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Solution Overview
Problem
Existing switching circuits with semiconductor switches have long turn ON times and significant forward voltage drops, making them unsuitable for applications requiring fast response and low power dissipation, as they fail to approximate the characteristics of an ideal diode.
Innovation Solution
A switching circuit that includes a voltage multiplier circuit, a reservoir capacitor, and a semiconductor switching element, where the charge stored in the capacitor is redistributed to the control terminal of the switching element, providing a substantially constant drive voltage for immediate turn ON, and a comparator circuit to manage the switching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a semiconductor switch is used to reduce forward voltage drop, then power dissipation is reduced, but turn ON time increases significantly
Solution Approach 1:
The charge pump circuit pre-charges a reservoir capacitor to a voltage higher than the switch threshold voltage before the switching event. When the switch needs to turn on, the pre-charged capacitor immediately discharges through the switch gate, providing the necessary gate drive current instantaneously. This preliminary charging action eliminates the delay that would otherwise occur while charging the gate capacitance during switch turn-on.
Solution Approach 2:
The reservoir capacitor acts as an intermediary energy storage device between the charge pump circuit and the semiconductor switch. It stores electrical energy in its electric field and releases it rapidly when needed to drive the switch gate. This intermediary component decouples the slow charge pump operation from the fast switching requirement, allowing the switch to turn on immediately without waiting for the charge pump to build up sufficient voltage.
2Speed
If a charge pump circuit is used to drive the switch gate, then turn ON time is reduced, but the low output current causes slow turn ON
Solution Approach 1:
The charge pump circuit continuously or periodically charges the reservoir capacitor to a predetermined voltage level before the switch needs to turn on. This preliminary charging ensures that when the switching signal arrives, the capacitor is already charged and ready to immediately discharge high current through the switch gate, achieving fast turn-on despite the charge pump's limited output current capability.
Solution Approach 2:
The circuit dynamically switches between two operational modes: during the charging phase, the charge pump slowly charges the reservoir capacitor; during the switching phase, the pre-charged capacitor rapidly discharges to provide high peak current. This dynamic behavior allows the system to achieve both energy efficiency (slow charging) and fast response (rapid discharging) in different time intervals.
3Power
If a boost regulator is used for gate drive, then sufficient drive current is provided, but board area increases and noise is generated
Solution Approach 1:
The invention extracts and removes the inductor component from the gate drive circuitry by using a charge pump-based voltage multiplier instead of a traditional boost regulator. The charge pump uses only capacitors and switches to achieve voltage multiplication, eliminating the need for magnetic components. This extraction of the inductor reduces board area significantly and removes the source of switching noise and gate node chatter that plagues inductor-based solutions.
Solution Approach 2:
The invention replaces the electromagnetic mechanism of the inductor-based boost regulator with an electrostatic mechanism using capacitors and electronic switches. Instead of using magnetic field energy storage and conversion, the charge pump uses electric field energy storage in capacitors to achieve voltage multiplication. This substitution eliminates the mechanical/magnetic components that occupy board space and generate noise, while maintaining the ability to provide sufficient gate drive current.
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
The solution achieves turn ON times under 5 microseconds, closely approximating the switching characteristics of an ideal diode, with reduced power dissipation and improved load regulation, suitable for various applications including power supplies and telecommunications systems.
Implementation Method 1
a voltage multiplier circuit such as a charge pump having an input and output
Implementation Method 2
a charge storage device such as a reservoir capacitor coupled to the output of the voltage multiplier circuit
Data Source
AI summary
A switching circuit approximating the fast switching characteristics and small forward voltage drop of an ideal diode is provided. The switching circuit may include a voltage multiplier circuit, a reservoir capacitor and a pull up switch configured to be coupled to the control terminal of a semiconductor switch.