Adaptive Constant On-Time Buck-Boost Hold-Up Circuit
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Solution Overview
Problem
Conventional hold-up circuits for electronic systems are inefficient due to large capacitance requirements, increasing cost and size, and often require complex boost mode control schemes, which complicates the implementation and stability of power supply during sudden power losses.
Innovation Solution
A last gasp hold-up circuit using a buck-boost control circuit with constant on-time control, employing only two power switches to operate in both buck and boost modes, simplifying the compensation and reducing silicon area, and utilizing an inductor and energy storage capacitor to provide a regulated voltage during power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a large capacitor bank is used to store energy for hold-up circuits, then the energy storage capacity is improved, but the size and cost of the circuit increase
Solution Approach 1:
The patent transforms the hold-up circuit from a simple energy storage function to a voltage transformation function by using a buck-boost converter. The circuit now converts voltage from one level to another, allowing energy to be stored in a smaller capacitor at a higher voltage and then converted to the required output voltage, thereby reducing the physical size of the capacitor bank while maintaining the same energy storage capacity.
Solution Approach 2:
The buck-boost converter serves multiple functions: it acts as both a voltage transformation device and an energy storage device. The same inductor and switching circuitry used for voltage conversion also perform the energy storage function, eliminating the need for a separate large capacitor bank and reducing overall circuit complexity and size.
2Quantity of substance
If conventional hold-up circuits use large capacitance values, then the energy storage is improved, but the manufacturing cost increases
Solution Approach 1:
The patent changes the operating voltage parameter of the energy storage capacitor, storing energy at a higher voltage level. This allows the use of smaller capacitance values to achieve the same energy storage capacity, thereby reducing component cost and making the circuit more economical to manufacture while maintaining the required hold-up time.
3Stability of the object's composition
If complex boost mode control schemes are used, then the power supply stability is improved, but the device complexity increases
Solution Approach 1:
The patent inverts the conventional control approach by using constant off-time control instead of constant on-time control for the buck-boost converter. This inversion simplifies the control scheme while maintaining stability, as the fixed off-time provides natural frequency compensation and reduces the complexity of the compensation network required in conventional constant on-time control schemes.
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 ensures a stable and efficient power supply during primary power loss events by charging a capacitor and redirecting stored energy, reducing complexity and silicon area while maintaining a regulated voltage, thus enabling graceful shutdown of non-volatile memory systems.
Implementation Method 1
an inductor coupled between the first node and a second node
Implementation Method 2
an energy storage capacitor coupled between the second current handling terminal of the high-side switch and the ground potential
Data Source
AI summary
A hold-up circuit coupled to a first node to receive an input voltage and to provide a hold-up voltage includes an inductor, a constant on-time buck-boost control circuit configured to drive a high-side power switch and a low-side power switch to operate in a buck mode and a boost mode of operation, and an energy storage capacitor. When the input voltage is greater than a predetermined threshold, the buck-boost control circuit is configured to drive the power switches in the boost mode to charge the capacitor to a capacitor voltage greater than the input voltage. When the input voltage is less than the predetermined threshold, the buck-boost control circuit is configured to drive the power switches in the buck mode to supply the energy stored on the capacitor to the inductor to provide a regulated voltage less than the capacitor voltage as the hold-up voltage to the first node.