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Power Supply For Gate Driver In Switched-Capacitor Circuit

Patent No. US12212232 (titled "Power Supply For Gate Driver In Switched-Capacitor Circuit") was filed by Psemi Corp on Dec 19, 2023.

What is this patent about?

’232 is related to the field of switched capacitor converters , specifically focusing on improving the efficiency of gate drivers within these converters. Switched capacitor converters generate output voltages by dynamically reconfiguring capacitors using a network of switches. As conversion gain increases, so does the number of capacitors and switches, leading to increased complexity in driving these switches. Efficiently driving these switches, typically implemented as MOSFETs, is crucial for overall converter efficiency.

The underlying idea behind ’232 is to power the gate drivers of the switches in a switched capacitor converter directly from the capacitors within the converter's charge transfer path. This approach leverages the fact that the voltage across these capacitors is a fraction of the overall output voltage, enabling the use of lower-voltage transistors for switching and reducing the power required to drive the gates. By tapping into the existing capacitor network, the invention avoids the need for separate power supplies for the gate drivers, improving efficiency and reducing complexity.

The claims of ’232 focus on an integrated circuit comprising a charge pump circuit with first and second phases , each having power switches and flying capacitors. The key aspect is that the gate driver circuits for these switches are powered by the flying capacitors themselves. Specifically, a gate driver is connected to the positive and negative terminals of a flying capacitor, receiving voltage from the negative terminal to drive a switch. This configuration is implemented in both phases of the charge pump.

In practice, the invention utilizes a multi-phase approach where charge transfer paths are shifted in time. This allows one phase to derive energy from an alternate phase to power circuitry, further enhancing efficiency. The gate drivers are designed to maintain desired limits on the gate-to-source voltages of the transistors, ensuring reliable operation. A pre-charge circuit initializes the capacitor voltages during startup, preventing voltage stresses on the transistors and providing immediate power to the gate drivers.

This design differs from prior approaches that typically rely on separate power supplies for gate drivers, leading to increased power consumption and complexity. By integrating the power supply for the gate drivers into the existing switched capacitor network, ’232 achieves a more efficient and compact solution. The use of cascaded switches and tapered gate drivers further optimizes the design, allowing for higher voltage operation without requiring high-voltage transistors. The multi-phase architecture ensures a continuous charge transfer path, improving overall performance.

How does this patent fit in bigger picture?

Technical landscape at the time

In the early 2010s when ’232 was filed, switched capacitor converters were commonly used to generate different voltage levels by switching capacitors using MOSFETs. At a time when gate drivers were essential for controlling these switches, providing sufficient charge to the gate terminal of a MOSFET was typically implemented using a power supply. The number of capacitors and switches generally increased with the desired conversion gain.

Novelty and Inventive Step

The examiner allowed the claims because the prior art failed to disclose specific configurations of gate driver circuits connected to flying capacitors. Specifically, the prior art did not teach a first gate driver circuit connected to positive and negative terminals of a first flying capacitor configured to receive a voltage at its negative terminal and drive a first power switch. Similarly, the prior art did not teach a second gate driver circuit connected to a second flying capacitor configured to receive a voltage at its negative terminal and drive a second power switch. Furthermore, the prior art failed to disclose a first switch driven by a first gate driver and connected to a first terminal of a first flying capacitor, a second switch driven by a second gate driver and connected between the first terminal of the first flying capacitor and an output terminal, a third switch driven by a third gate driver and connected to the output terminal and a second terminal of the first flying capacitor, and so on, with specific supply terminal connections and additional switches.

Claims

This patent contains 30 claims, with independent claims 1 and 22. The independent claims are directed to integrated circuits comprising power switches and gate drivers configured to form a charge pump circuit. The dependent claims generally elaborate on specific configurations, components, and operational aspects of the integrated circuit and its constituent switches and gate drivers.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)Support for SpecificationInterpretation
Activated state
(Claim 1)		“The switches in such converters must be driven to open and close at opportune times. In those cases in which the switch is implemented as a MOSFET, driving a switch requires causing charge to flow into a gate terminal so as to cause an electric field. In an enhancement mode MOSFET, this electric field causes an inversion layer that permits charge to flow between source and drain.”A state in which a power switch is turned on, allowing current to flow.
Charge pump circuit
(Claim 1)		“A switch-mode power converter produces an output voltage by switching reactive elements into different topologies using a switching network. In those cases in which the reactive elements are capacitors, the resulting power converter is referred to as a switched-capacitor power converter. In a typical switched-capacitor converter, the number of capacitors and switches increases as the conversion gain increases.”A circuit that uses capacitors to store and transfer electrical charge to increase or decrease voltage.
Deactivated state
(Claim 1)		“The switches in such converters must be driven to open and close at opportune times. In those cases in which the switch is implemented as a MOSFET, driving a switch requires causing charge to flow into a gate terminal so as to cause an electric field. In an enhancement mode MOSFET, this electric field causes an inversion layer that permits charge to flow between source and drain.”A state in which a power switch is turned off, preventing current flow.
Flying capacitors
(Claim 1, Claim 22)		“FIGS. 1-2 show cascade multipliers that receive an input voltage VI from a voltage source 16 and provide an output voltage VO to a load 18. Consistent with conventional circuit representations, a capacitor's anode is shown as a straight line and its cathode is shown as a curved line.”Capacitors used in a charge pump circuit to store and transfer charge.
Gate driver circuits
(Claim 1, Claim 22)		“The switches in such converters must be driven to open and close at opportune times. In those cases in which the switch is implemented as a MOSFET, driving a switch requires causing charge to flow into a gate terminal so as to cause an electric field. A circuit that causes charge to flow into a transistor's gate terminal is often called a “gate driver.””Circuits that provide the necessary voltage or current to the gate terminal of a switch (e.g., a MOSFET) to turn it on or off.

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US12212232

PSEMI CORP
Application Number
US18544466
Filing Date
Dec 19, 2023
Status
Granted
Expiry Date
Mar 15, 2033
External Links
Slate, USPTO, Google Patents