Floating Head Switch NMOS Topology for DC-DC Converter Loss Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional DC-DC converters face inefficiencies due to high thermal losses in floating switches, particularly when using both PMOS and NMOS transistors, which increase ohmic and switching losses as application voltage approaches supply voltage, and leakage currents are significant in low power applications.
Innovation Solution
Implementing a floating head switch with an NMOS transistor and a flying capacitor configuration, where the gate-to-source voltage remains constant regardless of application voltage, and using body biasing to control leakage currents by adjusting the body bias voltage based on power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If both PMOS and NMOS transistors are used in floating switches, then switching capability is improved, but ohmic and switching losses increase as application voltage approaches supply voltage
Solution Approach 1:
The patent extracts the PMOS transistor from the floating switch configuration, using only an NMOS transistor for the floating head switch. This eliminates the body effect issues and high losses associated with PMOS transistors in floating configurations, while maintaining switching capability through proper gate voltage control using the flying capacitor.
Solution Approach 2:
The patent changes the operating parameters by maintaining a constant gate-to-source voltage (Vgs) for the NMOS transistor regardless of application voltage changes. This is achieved through the flying capacitor configuration that couples the gate driver output to the gate terminal, ensuring optimal switching performance across different voltage conditions without the losses inherent in dual-transistor configurations.
2Productivity
If conventional floating switches are used, then voltage conversion is achieved, but thermal losses are high
Solution Approach 1:
The patent removes the problematic PMOS transistor from the conventional floating switch design, retaining only the NMOS transistor. This extraction eliminates the body effect and associated thermal losses that occur in PMOS devices when operated in floating configurations, while preserving the essential voltage conversion function through the modified single-transistor topology.
Solution Approach 2:
The patent substitutes the conventional dual-transistor mechanical/electrical switching mechanism with a single NMOS transistor controlled by a flying capacitor-based gate driver. This substitution reduces the number of active components and eliminates the body effect mechanism that causes thermal losses, achieving efficient voltage conversion with reduced thermal dissipation.
3Loss of energy
If body biasing is applied to control leakage currents, then leakage is reduced, but device complexity increases
Solution Approach 1:
The patent implements self-service body biasing where the body of the NMOS transistor is automatically biased through the existing power management circuitry. The body bias voltage is generated as a byproduct of the normal operation of the voltage converter, eliminating the need for separate bias generation circuits and reducing overall device complexity while effectively controlling leakage currents.
Solution Approach 2:
The patent makes the power management circuitry multi-functional by having it perform both voltage conversion and body bias generation simultaneously. The same circuit elements that control the main switching operation also provide the necessary body bias voltage, eliminating dedicated bias circuits and reducing device complexity while maintaining effective leakage control.
Data Source
AI summary
Devices, methods and systems provide improved performance for voltage converters and enable more efficient operations by reducing energy loss in a head switch of the voltage converter. These improvements are achieved in-part by reducing one or both of an ohmic conduction loss and a switching loss of the head switch. One example floating head switch includes an n-type metal oxide semiconductor (NMOS) transistor, a capacitor, one or more drivers and an active low switch. The capacitor ends are connected to the supply voltages of the drivers and the active low switch is coupled to, and controlled by, the output of the one or more drivers and turns on or off in response to a change in the input voltage.