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Compact gate drivers for switched capacitor converters using charge pump

IP.com Disclosure Number: IPCOM000249333D
Publication Date: 2017-Feb-16
Document File: 9 page(s) / 622K

Publishing Venue

The IP.com Prior Art Database

Abstract

A half-bridge circuit is a circuit topology that comprises two switches, e.g., MOSFETs,

connected in a cascode arrangement. Each switch is driven by complementary and non- overlapping square-wave voltages. The half-bridge circuit has numerous applications in power

electronics, e.g., DC level converters of switched-capacitor or resonant type. The

complementary square-wave voltages that drive the gates of the MOSFETs are generated by a

gate-driver circuit which is typically powered by dedicated and isolated power supplies. The

presence of dedicated power supplies leads to higher cost, complexity and bulk of the DC level

converter. This disclosure describes techniques to utilize existing components of a DC level

converter, e.g., flying capacitors, to form a charge pump circuit that powers the gate-driver

circuit. Per techniques described herein, at least a few dedicated power supplies to the gate

driver are eliminated. The techniques provide a compact and low-cost half-bridge gate driver

that lends itself to easy and dense integration.

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Compact gate drivers for switched capacitor converters using charge pump

ABSTRACT

A half-bridge circuit is a circuit topology that comprises two switches, e.g., MOSFETs,

connected in a cascode arrangement. Each switch is driven by complementary and non-

overlapping square-wave voltages. The half-bridge circuit has numerous applications in power

electronics, e.g., DC level converters of switched-capacitor or resonant type. The

complementary square-wave voltages that drive the gates of the MOSFETs are generated by a

gate-driver circuit which is typically powered by dedicated and isolated power supplies. The

presence of dedicated power supplies leads to higher cost, complexity and bulk of the DC level

converter. This disclosure describes techniques to utilize existing components of a DC level

converter, e.g., flying capacitors, to form a charge pump circuit that powers the gate-driver

circuit. Per techniques described herein, at least a few dedicated power supplies to the gate

driver are eliminated. The techniques provide a compact and low-cost half-bridge gate driver

that lends itself to easy and dense integration.

KEYWORDS

● Voltage level converter

● Switched capacitor converter

● Half-bridge circuit

● Gate driver

BACKGROUND

Fig. 1: DC-DC level converter using a switched tank topology

Fig. 1 illustrates an example DC-DC level converter (102) using a switched tank

topology. A DC voltage level Vin is translated to a DC voltage level Vout, delivered to load

(104). The example level translator of Fig. 1 uses MOSFETs Q1 through Q16, capacitors C1

through C5, and inductors L1 through L3 interconnected as shown. The capacitor Cout

connected across the load smoothens any residual ripples in the voltage Vout. The section of the

circuit comprising MOSFETs Q1 through Q6, capacitors C1 through C5, and inductors L1

through L3 is referred to as the “high side” (102H) of the level translator. The section of the

circuit comprising MOSFETs Q7 through Q16 is referred to as the “low side” (102L) of the

level translator.

In a typical configuration, MOSFETs Q1 through Q6 of the high side are driven by

half-bridge gate drivers, as shown in the example of Fig. 2 below.

Fig. 2: Half-bridge gate drivers supplying complementary square-wave voltage waveforms to the

gates of MOSFETs comprising a switched-tank circuit

Half-bridge gate-drivers 202-206 supply complementary square-wave voltage

waveforms to high side MOSFETs Q1 through Q6. The coordinated switching (on/off) of

MOSFETs Q1 through Q6 resulting from the square-wave voltage waveforms enables the

voltage translation function. Half-bridge drivers 202 through 206 require their own dedicated

isolated power supply that adds to the cost and bulk of the converter.

DESCRIPTION

Techniques of this disclosure generate the power supply for high side gate drivers from

components that are part of a switched capacitor or tank circuit, e.g., low-side gate-drivers and

capacitors. The components are configured to act as a charge p...