Biasing system and method for low voltage DC-DC converters with built-in N-FETs

• US 20030193364A1
• Filed: 04/16/2003
• Published: 10/16/2003
• Est. Priority Date: 04/16/2002
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Arques Technology Inc (ON Semiconductor Corporation)
• Inventors: Negru, Sorin L., Liu, Kwang H.
• Granted Patent: US 6,903,535 B2
• Time in Patent Office: Days
• US Class Current: 327/536
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H03K 17/063 in field-effect transistor switches
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A gate drive supply circuit generating a high-level supply voltage and a low-level supply voltage for driving N-type high-side and low-side power MOSFETs in a multiple-output, low-voltage DC-DC converter integrated circuit. The gate drive supply circuit includes a boost regulator for generating the low-level supply voltage and a charge pump doubler for generating the high-level supply voltage. Both the high-level supply voltage and the low-level supply voltage are distributed to one or more regulators, including but not limited to buck or boost type regulators.

Claims

1. A system for driving a first and second n-channel power switching transistors, the system comprising:

a power conversion circuit for generating a first regulated voltage from an input voltage and including a reference voltage generator for generating a reference voltage, and an up-converter that receives the input voltage and the reference voltage and generates the first regulated voltage;

a charge pump circuit for generating a second regulated voltage from the first regulated voltage;

a first voltage driver having an input for receiving a pulse stream and an output for driving the gate of the first power switching transistor, and operating from a supply voltage connected to the first regulated voltage such that the first voltage driver is capable of driving the gate of the first power switching transistor substantially close to the first regulated voltage; and

a second voltage driver having an input for receiving a pulse stream and an output for driving the gate of the second power switching transistor, and operating from a supply voltage connected to the second regulated voltage such that the second voltage driver is capable of driving the gate of the second power switching transistor substantially close to the second regulated voltage.

2. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the up-converter is a boost regulator.

3. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the reference voltage generator is a bandgap reference device.

4. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the second regulated voltage is approximately twice the first regulated voltage.

5. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the input voltage has a range of about 2 to 5½

volts and the first regulated voltage has a range of about 4 to 5 volts.

6. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the input voltage has a range of about 2 to 5½

volts and the second regulated voltage has a range of about 8 to 10 volts.

7. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the first regulated voltage is approximately 5 volts and the second regulated voltage is approximately 10 volts.

8. A system for driving a first and second n-channel power switching transistors, as recited in claim 1, wherein the output of the first voltage driver provides a gate voltage such that the gate-to-source voltage of the n-channel power switching transistors is in the range of approximately 4 to 6 volts.

9. A power system as recited in claim 1, wherein the up-converter includes:

an inductor having first and second nodes, the first node for receiving a positive voltage from an external power source;

a rectifying diode having a positive and negative node, the positive node of the rectifying diode being connected to the second node of the inductor;

a filter capacitor having a first node connected to the negative node of the rectifying diode, and a second node being connected to a return voltage of the external power source;

a voltage sensing circuit for sensing a voltage on the first node of the filter capacitor and providing an output giving an indication of the value of the voltage on the first node of the filter capacitor;

an amplifier having a first input connected to the voltage sensing circuit and a second input connected to the reference voltage, an output of the amplifier providing an amplified difference between the voltage sensing circuit output and the reference voltage;

a comparator having a positive input node connected to receive-a ramp waveform and a negative input node connected to the amplifier output, the comparator operative to compare the output of the amplifier and the ramp waveform and to generate on an output node a voltage indicative of the comparison;

a pulse generator having an input that receives the comparator output and operative to generate at an output a voltage pulse when the comparator output indicates that the output of the voltage sensing circuit is different from the reference voltage;

a switching transistor having a gate, source and drain, a channel being definable between the source and drain, the gate of the switching transistor being connected to the output of the pulse generator, the channel of the switching transistor being connected between the second node of the inductor and the return voltage, such that during the voltage pulse the channel of the switching transistor connects the second node of the inductor to the return voltage to store in the inductor current from the external power source, and when the voltage pulse is not present the inductor charges the filter capacitor with stored current.

10. A power system as recited in claim 8, wherein the voltage sensing circuit is a voltage divider.