Boost DC Regulator Back-Gate Control for Low-Voltage Startup
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Solution Overview
Problem
Conventional DC-DC converters require multiple main switching transistors to operate efficiently at low input voltages, leading to complex and larger circuits.
Innovation Solution
A step-up type DC-DC converter using an N-type main switching transistor with a comparator and back-gate control unit to adjust the back-gate voltage based on output voltage levels, allowing a single transistor to handle both startup and steady-state operations, reducing circuit size and preventing leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple main switching transistors are used to enable low-voltage startup and high-efficiency operation, then the DC-DC converter can operate at low input voltages with high efficiency, but the circuit complexity and size increase
Solution Approach 1:
The patent makes a single N-type main switching transistor perform multiple functions by dynamically changing its threshold voltage. During startup, the transistor operates with a lowered threshold voltage to enable operation at low input voltages. During steady-state operation, the threshold voltage is raised to reduce leakage current and improve efficiency. This multi-functional operation eliminates the need for separate switching transistors for startup and steady-state operation, thereby reducing circuit complexity while maintaining high operating efficiency
Solution Approach 2:
The patent changes the threshold voltage parameter of the main switching transistor dynamically based on operating conditions. A back-gate voltage control unit adjusts the threshold voltage: lowering it during startup to enable low-voltage operation, and raising it during steady-state operation to minimize leakage current. This parameter change allows a single transistor to adapt to different operational requirements, resolving the contradiction between enabling low-voltage startup and maintaining high efficiency without increasing circuit complexity
2Use of energy by moving object
If multiple main switching transistors are used to enable low-voltage startup and high-efficiency operation, then the DC-DC converter can operate at low input voltages with high efficiency, but the circuit size increases
Solution Approach 1:
The patent makes a single N-type main switching transistor serve dual purposes: enabling low-voltage startup and ensuring high-efficiency steady-state operation. By dynamically adjusting the transistor's threshold voltage through back-gate control, one transistor replaces what would traditionally require multiple transistors, thereby reducing the overall circuit area while maintaining high operating efficiency across different operational phases
3Reliability
If the threshold voltage of the main switching transistor is kept low to enable low-voltage startup, then the DC-DC converter can start up at low input voltages, but leakage current increases during steady-state operation
Solution Approach 1:
The patent applies dynamic control to the threshold voltage of the main switching transistor through back-gate voltage adjustment. During startup, the threshold voltage is kept low to ensure reliable operation at low input voltages. During steady-state operation, the threshold voltage is dynamically raised to minimize leakage current and improve efficiency. This dynamic adaptation allows the system to optimize performance for each operational phase, resolving the contradiction between startup capability and leakage current reduction
Solution Approach 2:
The patent changes the threshold voltage parameter of the main switching transistor based on operational phase. A back-gate voltage control unit monitors the operating condition and adjusts the threshold voltage: maintaining a low value during startup to ensure reliability, and increasing it during steady-state operation to reduce leakage current. This parameter change strategy enables the single transistor to achieve both reliable low-voltage startup and low leakage current operation
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
Enables efficient startup at low input voltages with reduced circuit size and minimized leakage current by dynamically adjusting the threshold voltage of the main switching transistor.
Implementation Method 1
a back-gate control unit that, in accordance with a comparison result obtained from the comparator, sets a back-gate voltage of the main switching transistor at a first back-gate voltage during the first period, and sets the back-gate voltage thereof at a second back-gate voltage lower than the first back-gate voltage during the second period
Data Source
AI summary
The invention provides a DC-DC converter capable of being started up in a state in which an input voltage is low and capable of being structured without increasing a circuit size. A back-gate voltage (Vsb) is outputted from a back-gate voltage generating circuit (VBGN), and is inputted to a back gate of a transistor (FET1). During a period during which an output voltage (Vout) is lower than a reference voltage (e0), an oscillation signal (OS1) is inputted to a gate of the transistor (FET1), and the back-gate voltage (Vsb) is set at a grounded voltage. Therefore, the transistor (FET1) has a reference threshold voltage (Vto). On the other hand, during a period during which the output voltage (Vout) is higher than the reference voltage (e0), a pulse signal (PS) is inputted to the gate of the transistor (FET1), and the back-gate voltage (Vsb) is set at an output voltage of a charge pump portion (5). Therefore, the transistor (FET1) has a threshold voltage higher than the reference threshold voltage (Vto).