Power Supply Control Device Using Merged Switches
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Solution Overview
Problem
Existing power supply control devices that use two FETs between a battery and each load are inefficient due to their large size and high manufacturing costs, as they require twice the number of FETs needed for the number of loads.
Innovation Solution
A power supply control device that uses a minimal number of semiconductor switches, including a controller to switch on and off a first semiconductor switch and multiple second semiconductor switches, with parasitic diodes connected between the switches to control power supply, allowing power to be managed efficiently with fewer components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two FETs are connected between the battery and each load, then reliable power control is achieved, but the device size and manufacturing cost increase significantly
Solution Approach 1:
The patent merges the power control function for multiple loads into a single P-channel FET (first semiconductor switch) that controls the positive power line, while each N-channel FET (second semiconductor switch) independently controls its respective load's ground connection. This consolidation reduces the total number of FETs from twice the number of loads to just one P-channel FET plus one N-channel FET per load, directly resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The P-channel FET serves as a universal power control switch for all loads simultaneously, controlling the common positive power supply line. This multi-functional approach allows a single device to perform what previously required multiple individual FETs, reducing overall component count while maintaining reliable power control across all loads.
2Ease of manufacture
If two FETs are connected between the battery and each load, then power control is achieved, but the manufacturing cost increases
Solution Approach 1:
By combining the positive power control function for all loads into a single P-channel FET, the patent reduces the total semiconductor switch count from 2N to N+1 (where N is the number of loads). This merging strategy directly lowers manufacturing costs by reducing component quantity, assembly steps, and bill of materials complexity.
3Object-generated harmful factors
If the cathodes of parasitic diodes are connected together, then current flow is prevented when FETs are off, but current may flow through parasitic diodes in incorrect battery connections
Solution Approach 1:
The patent creates an asymmetric parasitic diode configuration where the P-channel FET's parasitic diode points in the opposite direction relative to the N-channel FET's parasitic diode. Specifically, the P-channel FET's source is connected to the positive terminal while its drain connects to the N-channel FET's drain, creating a parasitic diode that blocks current in the reverse direction. This asymmetric arrangement ensures that even if battery polarity is reversed, the parasitic diodes block harmful current flow, simultaneously achieving both current control and connection protection.
Data Source
AI summary
A power supply control device that includes a controller configured to switch on and off a first semiconductor switch and a plurality of second semiconductor switches whose current input terminals are connected to a current output terminal of the first semiconductor switch, the controller being configured to control supply of power via the plurality of second semiconductor switches by switching; a first parasitic diode connected between a current input terminal and the current output terminal of the first semiconductor switch; and a plurality of second parasitic diodes that are respectively connected between the current input terminals and current output terminals of the plurality of second semiconductor switches.