Power Regulator Bias Control for Low-Leakage Power Amplifiers
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Solution Overview
Problem
Power regulators in mobile communication devices face challenges in reducing leakage current when in the OFF state, as MOS transistors with low threshold voltage exhibit higher leakage, and increasing channel length has a weak effect while reducing efficiency.
Innovation Solution
A switching arrangement is implemented to bias the regulator transistor differently between ON and OFF states, using a leakage current reduction voltage to control the sub-threshold biasing voltage, and a voltage generator to generate complementary waveforms and rectify them, limiting the rectified voltage to a controllable value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If MOS transistors with low threshold voltage are used in the regulator, then the on-resistance is decreased and power efficiency is improved in the ON state, but the leakage current from source to drain increases in the OFF state
Solution Approach 1:
The patent applies dynamics by making the biasing voltage of the regulator transistor time-varying and state-dependent. During the ON state, the transistor is biased with a voltage that maintains low on-resistance for efficient power transfer. During the OFF state, the biasing voltage is dynamically adjusted to a level that minimizes subthreshold leakage current. This dynamic adaptation of the operating point allows the transistor to optimize its electrical characteristics for each operational state, resolving the contradiction between low on-resistance and low leakage current.
Solution Approach 2:
The patent employs parameter changes by modifying the gate-to-source voltage (Vgs) of the regulator transistor based on the operational state. In the ON state, Vgs is set to a value that ensures low on-resistance for minimal power loss. In the OFF state, Vgs is changed to a specific biasing voltage that reduces the subthreshold leakage current by controlling the electric field distribution in the channel. This parameter adjustment strategy enables the transistor to achieve both low power loss and low leakage current at different times.
2Object-generated harmful factors
If the channel length of the regulator transistor is increased to reduce leakage current, then the leakage current is reduced, but the on-resistance increases and efficiency decreases
Solution Approach 1:
Instead of changing the physical dimension (channel length) of the transistor, the patent changes the electrical parameter (biasing voltage) to control leakage current. By adjusting the gate-to-source voltage to an optimal biasing level during the OFF state, the patent reduces subthreshold leakage without affecting the physical channel length. This approach maintains the low on-resistance characteristic that would be degraded by increasing the channel length, while still achieving the goal of reducing leakage current.
Solution Approach 2:
The patent uses dynamic biasing control to achieve leakage reduction without structural modification. The biasing voltage is dynamically adjusted based on the operational state, allowing the transistor to exhibit low leakage characteristics during the OFF state while maintaining its original channel length and consequently low on-resistance during the ON state. This dynamic control approach avoids the static compromise that would result from increasing the channel length.
Data Source
AI summary
A regulator with decreased leakage and low loss for a power amplifier is described. Switching circuitry is used to connect the regulator input bias to a bias control voltage when the power amplifier is to be operated in an on condition or to a voltage generator when the power amplifier is to be operated in an off condition.