Load Switch IC Discharge Control to Block Reverse Current
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Solution Overview
Problem
Conventional load switch ICs lack a discharge circuit to rapidly lower power to the load when turned off, leading to potential malfunctions or destruction, and they allow reverse current flow when switching to a backup power supply.
Innovation Solution
A semiconductor integrated circuit device with a switching transistor, discharging transistor, and control circuit that rapidly discharges output terminal charge and prevents reverse current flow by controlling the transistors based on logic levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a discharge circuit is provided to rapidly lower power to the load when the load switch is turned off, then the power drop speed is improved, but current from the backup power supply flows through the discharge circuit to the ground point
Solution Approach 1:
The patent applies dynamics by making the discharge circuit dynamically controllable through a control signal. The discharge transistor is turned on or off based on the logic level of the control signal, allowing the circuit to adapt its behavior: when the control signal is at a second logic level, the discharge circuit actively lowers power to the load; when at a first logic level, it prevents current flow to the ground point. This dynamic control resolves the contradiction between rapid power drop and prevention of harmful current flow.
2Reliability
If a discharge circuit is simply provided at the output terminal, then electric charge is released from the output terminal, but current from the backup power supply flows through the discharge circuit to the ground point upon switching to backup power supply
Solution Approach 1:
The patent implements feedback control where the state of the discharge circuit is controlled based on the logic level of an external control signal. The control circuit monitors the control signal and adjusts the discharge transistor accordingly: when the control signal indicates backup power supply mode (first logic level), the discharge circuit is disabled to prevent current leakage; when it indicates normal operation mode (second logic level), the discharge circuit is enabled to release charge. This feedback mechanism ensures the discharge circuit functions reliably without causing harmful current flow.
3Productivity
If the load switch is turned off to interrupt power to the load, then power interruption is achieved, but it takes time for the power supply output to drop
Solution Approach 1:
The patent applies preliminary action by providing a discharge circuit that is activated simultaneously with or immediately after the load switch turns off. The discharge circuit proactively releases stored electric charge from the output terminal through a controlled path to the ground point, accelerating the voltage drop process. This preliminary discharge action ensures rapid power interruption without excessive delay, resolving the contradiction between achieving power interruption and minimizing voltage drop time.
Data Source
AI summary
Disclosed is a semiconductor integrated circuit device including: a switching transistor connected between a voltage input terminal where DC voltage is input and a voltage output terminal; a discharging transistor connected between the voltage output terminal and a ground point; an external terminal where a control signal of an external device is input; and a control circuit including a logic circuit and controlling and turning on or off the switching transistor and the discharging transistor based on the control signal. Upon the control signal input to the external terminal being at a first logic level, the logic circuit generates a signal that turns on the switching transistor and turns off the discharging transistor. Upon the control signal being at a second logic level, the logic circuit generates a signal that turns off the switching transistor and turns on the discharging transistor.