Power Supply Control Device Switching Loss Reduction
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Solution Overview
Problem
Existing power supply control devices with two N-channel FETs and a single drive circuit suffer from high switching loss due to the time-consuming process of switching on and off each FET, which is costly and inefficient.
Innovation Solution
A power supply control device with a switching unit that controls a first and second semiconductor switch, utilizing a resistor and diode configuration to adjust the voltage at the control terminal, allowing for rapid switching with minimal switching loss by supplying current only to parasitic capacitances when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If two N-channel FETs are controlled by a single drive circuit, then manufacturing cost is reduced, but switching time increases and switching loss increases
Solution Approach 1:
The drive circuit is segmented into a first drive circuit for controlling the first FET and a second drive circuit for controlling the second FET. This segmentation allows independent optimization of switching timing for each FET, reducing overlapping conduction time and minimizing switching loss while maintaining cost-effectiveness compared to completely separate control systems.
Solution Approach 2:
The switching control is designed to turn off the first FET before turning on the second FET, and turn on the first FET after turning off the second FET. This preliminary action sequence prevents simultaneous conduction of both FETs, eliminating short-circuit current and reducing switching loss while maintaining simple circuit architecture.
2Device complexity
If two N-channel FETs are controlled by a single drive circuit, then device complexity is reduced, but switching speed decreases
Solution Approach 1:
The control system is divided into separate drive circuits for each FET, allowing independent voltage application and faster switching response. The first drive circuit can rapidly charge/discharge the gate of the first FET, and the second drive circuit does the same for the second FET, achieving high switching speed without requiring a complex unified control system.
Solution Approach 2:
The drive circuits are designed to dynamically control the gate voltage of each FET independently, enabling rapid transitions between on and off states. This dynamic control approach allows each FET to switch quickly by directly manipulating its gate voltage without being constrained by a shared control mechanism.
3Reliability
If FETs are switched off to prevent current flow, then battery connection errors are detected, but current may still flow through parasitic diode
Solution Approach 1:
The circuit design accepts the presence of parasitic diodes but converts their potential harm into a beneficial feature. The body diodes of the FETs are utilized to provide a safe current path during switching transitions and to indicate connection status. By properly timing the FET switching, the parasitic diodes become part of the protection mechanism rather than a source of errors.
Solution Approach 2:
The FETs are switched off in advance before any potential reverse current could flow through parasitic diodes. The control system proactively disables the FETs when battery connection errors are detected, preventing harmful current flow before it can occur. This preliminary action ensures that even if parasitic diodes are present, they cannot conduct harmful reverse 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 enables quick switching on and off of semiconductor switches with reduced switching loss, maintaining low manufacturing costs while preventing current flow to the load during incorrect battery connections.
Implementation Method 1
a diode whose cathode is connected to the control terminal of the first semiconductor switch and whose anode is connected to the control terminal of the second semiconductor switch
Implementation Method 2
a resistor that is connected between a current input terminal and the control terminal of the first semiconductor switch
Data Source
AI summary
A power supply control device includes a first semiconductor switch and a second semiconductor switch, which are switched on if the voltage at the gate is at least an ON-threshold, and they are switched off if the voltage at the gate is less than an OFF-threshold. A resistor is connected between the source and the gate of the first semiconductor switch. A diode is connected between gates of the first semiconductor switch and the second semiconductor switch. A driving unit adjusts the voltage at the gate of the second semiconductor switch, switches on and off the first semiconductor switch and the second semiconductor switch, and controls the supply of power via the second semiconductor switch.