High-Voltage Flying Capacitor Generator with the Microchip HV2705FG-G

High-voltage (HV) DC generation is a critical requirement in numerous modern applications, including piezoelectric actuators, medical imaging systems, industrial sensors, and scientific instrumentation. Traditional inductive boost converters often face limitations in achieving very high voltages efficiently while managing size and electromagnetic interference (EMI). An alternative and highly effective topology is the flying capacitor multiplier charge pump, which utilizes capacitors and switches to step up voltage without a magnetic component. The Microchip HV2705FG-G is a monolithic integrated circuit specifically engineered to excel in this role, serving as the core of a compact and efficient high-voltage generator.

The fundamental principle behind this generator is the charge pump voltage multiplier architecture. Unlike a boost converter, which stores energy in an inductor’s magnetic field, a charge pump transfers energy directly using capacitors. The "flying capacitor" is repeatedly switched between an input source and an output stack. During one phase, it charges to the input voltage. In the next phase, it disconnects from the input and connects in series with both the input source and the output capacitor, thereby "pumping" its charge and adding its voltage to the source to achieve a higher output. By cascading multiple stages, significant voltage multiplication can be achieved.

The HV2705FG-G is a sophisticated controller that optimizes this process. It integrates eight high-voltage DMOS switches, an internal oscillator, and all necessary logic and level-shifting circuitry. Its key advantage is its ability to generate voltages up to 300V from a single low-voltage supply (e.g., 5V), all within a single IC. The device can be configured in various multiplier modes (e.g., doubling, tripling) by simply connecting external capacitors to its switch pins. This flexibility allows designers to tailor the output voltage and current capability to their specific needs without a complex discrete design.

A significant benefit of using the HV2705FG-G is its inherent efficiency and low noise operation. By eliminating the inductor, the design sidesteps issues related to core losses, radiated EMI from magnetic fields, and potential saturation. The integrated switches are highly efficient, minimizing resistive losses. Furthermore, the IC features a shutdown pin, enabling a low quiescent current standby mode, which is crucial for battery-powered portable equipment where power conservation is paramount.

In a typical application circuit, a few small external ceramic capacitors are all that is required alongside the HV2705FG-G to form a complete HV generator. The output voltage is clean and stable for low-current loads, making it ideal for biasing applications. For instance, it is perfectly suited to supply the high bias voltage for piezoelectric transducers in ultrasonic devices or for photomultiplier tubes (PMTs), where minimal noise and small form factor are critical design constraints.

In conclusion, the flying capacitor generator topology, empowered by the Microchip HV2705FG-G, offers a superior solution for generating moderate-current high-voltage rails. Its magnetic-free design, simplicity, and high level of integration make it an excellent choice for space-constrained and noise-sensitive applications.

ICGOODFIND: The Microchip HV2705FG-G provides a compact, efficient, and inductor-less solution for high-voltage generation, simplifying design and reducing EMI in advanced electronic systems.

Keywords:

Charge Pump

High-Voltage Generation

Flying Capacitor

Microchip HV2705FG-G

Voltage Multiplier