Switching Regulator Supply Voltage Circuit Design
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Solution Overview
Problem
Integrated circuits, such as those used in pulse width modulation controllers, face challenges with power dissipation in high voltage components like MOSFETs when used as internal power supplies, leading to increased costs due to higher on-resistance or larger package sizes.
Innovation Solution
A circuit design incorporating a first and second switch, a capacitor, and control logic to generate an output voltage by charging the capacitor without additional power dissipation from the source, utilizing a transformer's primary inductance and controlling switch states to minimize power loss and electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high voltage MOSFET is used for power generation within the integrated circuit, then the internal power supply can be provided, but the power dissipation increases due to the high voltage drop across the MOSFET
Solution Approach 1:
The power generation function is segmented into two parts: the high voltage switch (Q1) that handles the high voltage current sourcing, and the low voltage MOSFET (Q2) that handles only the voltage conversion to generate VCC. This segmentation allows the high voltage component to operate at lower power dissipation while the low voltage MOSFET handles the voltage conversion efficiently.
Solution Approach 2:
A capacitor (C1) is introduced as an intermediary energy storage element between the high voltage switch and the low voltage MOSFET. The capacitor charges during the switch on-time and discharges to provide the VCC voltage, acting as a buffer that decouples the high voltage power source from the low voltage circuit requirements, thereby reducing power dissipation in the MOSFET.
2Loss of energy
If the on resistance of the MOSFET is reduced to decrease power dissipation, then the power loss decreases, but the cost of the integrated circuit increases
Solution Approach 1:
The circuit changes the operating parameters of the MOSFET by using it in a switched mode rather than as a linear regulator. The MOSFET operates as a switch with near-zero on-resistance losses, and the voltage conversion is achieved through the switching action combined with the capacitor, rather than through continuous conduction with high resistive losses.
3Loss of energy
If a larger integrated circuit package with low thermal resistance is used, then the power dissipation is reduced, but the cost of the integrated circuit increases
Solution Approach 1:
The power dissipation problem is extracted from the integrated circuit by using an external high voltage switch (Q1) and capacitor (C1). The integrated circuit only contains the low voltage MOSFET (Q2) and control logic, which generate minimal heat. This extraction allows the use of a smaller, lower-cost package while maintaining low power dissipation.
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 solution effectively reduces power dissipation and electromagnetic interference, providing an efficient internal power supply for integrated circuits without additional power loss from the source voltage, thus improving the circuit's efficiency and cost-effectiveness.
Implementation Method 1
A capacitor C1 is connected between the node N1 and a ground. The capacitor C1 charges during the switch off-time.
Implementation Method 2
The switch Q1 sources a current through a primary inductance of a transformer T1.
Data Source
AI summary
Circuits and methods for converting a current to an output voltage are disclosed herein. An embodiment of the circuit includes a first switch connected between a source of current and a first node and a second switch connected between the first node and a common voltage. The circuit also includes a first controller for controlling the state of the first switch and a second controller for controlling the state of the second switch. A capacitor is coupled to the first node; the voltage on the capacitor is the output voltage. When the second switch is open, the capacitor charges, and when the second switch is closed, the capacitor does not charge. The current flows through the primary inductance of a transformer.