CMOS Bridge Rectifier Circuit for Medical Implants
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Solution Overview
Problem
Existing CMOS bridge circuits for rectification in medical implants face challenges with diode voltage drops and space constraints when converting AC to DC voltage, especially in low-power applications like retinal implants, where additional components like capacitors and diodes are impractical due to size limitations.
Innovation Solution
A CMOS bridge rectifier circuit that uses a rectangular wave input signal to provide a rectified DC output voltage without a discrete smoothing capacitor or diodes, utilizing a substantially resistive load with only parasitic capacitances, integrated on a single chip for medical implants like retinal or cochlear implants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components like capacitors and diodes are added to the CMOS bridge circuit for proper rectification, then the rectification performance is improved, but the device size increases and power consumption increases
Solution Approach 1:
The invention extracts and eliminates the discrete smoothing capacitor and output diode from the traditional CMOS bridge circuit. By removing these additional components and relying solely on the inherent parasitic capacitances of the CMOS switches, the circuit achieves proper full-wave rectification with significantly reduced device size and lower power consumption, while maintaining reliable operation in medical implant applications
Solution Approach 2:
The invention enables the CMOS bridge circuit to self-regulate and perform smoothing functions using its own internal parasitic capacitances rather than requiring external capacitors. The parasitic capacitances inherent in the CMOS switches automatically provide the necessary charge storage and voltage smoothing, making the circuit self-sufficient and eliminating the need for additional discrete components
2Reliability
If output diode is connected in series with load resistor and output capacitor, then the capacitor discharge issue is resolved, but power loss increases due to diode voltage drop
Solution Approach 1:
The invention removes the output diode from the circuit configuration. By eliminating the series diode, the circuit avoids the voltage drop and associated power loss that would occur during capacitor discharge, while still maintaining proper control of capacitor discharge through the inherent switching behavior of the CMOS bridge circuit
Solution Approach 2:
The invention utilizes the inherently present but previously underutilized parasitic capacitances of the CMOS switches as the primary charge storage element. These parasitic capacitances, though small individually, collectively provide sufficient smoothing capability, replacing the need for large discrete capacitors and reducing overall energy loss in the system
3Reliability
If smoothing capacitor and diode are added to the bridge circuit, then constant DC voltage is achieved, but space availability is reduced
Solution Approach 1:
The invention merges the rectification and smoothing functions into a single integrated CMOS bridge circuit. By combining these functions and utilizing the parasitic capacitances inherent in the CMOS switches, the circuit achieves constant DC voltage output without requiring separate discrete smoothing capacitors and diodes, thereby maximizing space availability for medical implant applications
Solution Approach 2:
The CMOS bridge circuit is designed to perform multiple functions simultaneously: rectification, voltage regulation, and smoothing. The same CMOS switches that perform rectification also provide smoothing through their parasitic capacitances, making the circuit universal and eliminating the need for additional dedicated components for each function
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 conversion of AC to DC voltage without diode voltage drops and reduces component size, suitable for low-power medical implants by using a resistive load and parasitic capacitances, ensuring stable operation and minimizing space requirements.
Implementation Method 1
the CMOS bridge circuit 100 can be used in such a rectifier... the CMOS-bridge 100 of Fig. 1 represents a full-wave rectifier
Implementation Method 2
For u1(t) ≥ uTHR, PMOS1 and NMOS2 are switched on (low impedance), whereas transistor PMOS2 and NMOS1 are switched off (high impedance)
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
A signal processing circuit includes an input inverter and an output inverter. Each inverter has a signal input for receiving an input rectangular signal, a signal output for providing an inverted output rectangular signal, and a pair of voltage outputs for developing a rectified dc output voltage. A first circuit input terminal is connected to the output of the input inverter and the input of the output inverter. A second circuit input terminal is connected to the input of the input inverter and the output of the output inverter, wherein the signal input terminals receive an input signal having a data component. A pair of supply voltage output terminals is connected to the voltage output terminals of the inverters for providing a rectified dc supply voltage output. A first circuit output terminal is connected to one of the supply voltage output terminals, and a second circuit output terminal connected to the second circuit input terminal, wherein the circuit output terminals provide an output signal including the data component.