Low-Voltage Startup Circuit With Rectifier Voltage Doubling
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Solution Overview
Problem
The reduction of coil inductance in wireless charging systems leads to a decrease in coupling voltage, which fails to satisfy the normal startup voltage requirement of chips, limiting the power and charging area.
Innovation Solution
A low-voltage startup circuit is introduced to control the rectifier SR to operate in a voltage-doubler rectification mode under low-voltage conditions, utilizing a Vmax power supply selection control module, power-on reset module, band-gap reference circuit, and rectifier voltage-doubler logic control to double the input voltage to the MCU.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the coil inductance is reduced to lower impedance and increase current capability, then the power loss of the coil is reduced and current capability is improved, but the coupling voltage decreases and cannot satisfy the normal startup voltage requirement of the chip
Solution Approach 1:
The patent changes the operating parameters of the rectifier circuit by introducing a voltage-doubler mode. When the coupling voltage is low (below 1.4V), the rectifier switches to voltage-doubler mode which doubles the output voltage, thereby compensating for the reduced coupling voltage caused by lower coil inductance and ensuring the chip can still start up normally.
2Productivity
If the coil inductance is reduced to improve current capability and power, then the impedance of the coil is reduced, but the charging area and couple voltage are reduced
Solution Approach 1:
The patent introduces dynamic operation modes for the rectifier circuit. The rectifier can dynamically switch between normal rectification mode and voltage-doubler mode based on the detected coupling voltage level. This dynamic adaptation allows the system to maintain high current capability with low inductance coils while compensating for the reduced charging area through intelligent mode switching.
3Loss of energy
If the coil inductance is reduced to lower impedance, then the power loss is reduced, but the coupling voltage drops below the threshold required for chip startup
Solution Approach 1:
The patent introduces an intermediary voltage-doubler circuit as a mediator between the low-voltage rectifier output and the chip startup requirement. This intermediary circuit doubles the voltage when needed, bridging the gap between the reduced coupling voltage from low-inductance coils and the minimum startup voltage required by the chip.
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 circuit ensures the MCU can start up normally by doubling the input voltage to 1.4V, overcoming the low-voltage limitation and enabling efficient operation of the low-inductance wireless charging system.
Implementation Method 1
a low-voltage band-gap reference circuit lv_bgr
Implementation Method 2
control the rectifier SR to enter the voltage-double rectification mode
Data Source
AI summary
A low-voltage startup circuit for a low-inductance wireless charging system includes a voltage input port Vrect, a common grounding port VSS, a PMOS driver signal control module pgate_ctrl_logic, a NMOS MN1 and a PMOS MP1, a Vmax power supply selection control module vmax_sel, a power-on reset module por, a low-voltage band-gap reference circuit lv_bgr, a rectifier logic control module boost_logic, a rectifier SR and a rectifier output under_voltage protection control module vrect_uvlo. The low-voltage startup circuit can normally start the MCU at the Vrect voltage under a low-voltage condition (1.4V).