Gate Voltage Switching for Capacitive Load Inrush Suppression
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Solution Overview
Problem
Existing methods to suppress inrush current in capacitive loads require additional transistors for each discharge path, leading to increased costs.
Innovation Solution
A discharge control circuit with a first and second gate voltage output circuit and a switching control circuit to manage the gate voltage of a transistor, using a voltage supply and current supply to maintain a constant discharge current and switch to a constant voltage after initial discharge, reducing the need for multiple transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a first discharge path including a current limiting resistor and a second discharge path not including a current limiting resistor are provided with transistors to switch connection/disconnection with the capacitive load, then inrush current can be suppressed during pre-discharge period and power can be supplied efficiently during subsequent discharge period, but the transistor count increases leading to higher cost
Solution Approach 1:
The patent merges the pre-discharge and main discharge functions into a single transistor by utilizing the body diode of the transistor as the current limiting element during pre-discharge. This eliminates the need for a separate transistor in the first discharge path, reducing the total transistor count from two to one while maintaining both inrush current suppression and efficient power supply capabilities.
Solution Approach 2:
The transistor's body diode is utilized to provide the current limiting function during pre-discharge without requiring an additional component. The body diode naturally limits current during the pre-discharge period, and the transistor itself handles the main discharge phase, making the system self-sufficient with fewer external components.
2Ease of operation
If a transistor is provided between the capacitive load and power supply to control power supply, then power can be controlled, but an excessive inrush current flows when the transistor is switched from off state to on state
Solution Approach 1:
The patent implements preliminary discharge action by utilizing the body diode to discharge the capacitive load before the transistor is fully turned on. This pre-discharge phase limits the inrush current that would otherwise occur when the transistor switches from off to on state, allowing safe power control without excessive current spikes.
Data Source
AI summary
A discharge control circuit includes: a first gate voltage output circuit that outputs a first gate voltage supplied to a transistor connected to a capacitive load; a second gate voltage output circuit that outputs a second gate voltage supplied to the transistor; and a switching control circuit that switches supply of the first gate voltage and the second gate voltage to the transistor. The first gate voltage output circuit includes: a voltage supply circuit that supplies a voltage to a gate of the transistor until the transistor changes from an off state to an on state; and a current supply circuit that supplies a current to the gate of the transistor. The second gate voltage output circuit outputs a voltage at a constant level as the second gate voltage. The switching control circuit performs control to supply the second gate voltage after supplying the first gate voltage to the transistor.