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Method and apparatus for controlling the charge of a bootstrap capacitor for non-synchronous type DC-DC converter

A DC-DC and capacitor technology, applied in the field of asynchronous dc-dc converters, can solve problems such as reducing the efficiency of DC-DC converters

Inactive Publication Date: 2007-01-31
PANASONIC CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

But this approach will reduce the efficiency of the DC-DC converter for all conditions

Method used

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  • Method and apparatus for controlling the charge of a bootstrap capacitor for non-synchronous type DC-DC converter
  • Method and apparatus for controlling the charge of a bootstrap capacitor for non-synchronous type DC-DC converter
  • Method and apparatus for controlling the charge of a bootstrap capacitor for non-synchronous type DC-DC converter

Examples

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no. 1 example

[0046] refer to image 3 , shows a first embodiment of an asynchronous DC-DC converter according to the invention.

[0047] The DC-DC converter has an error amplifier 2, an oscillator 6, a pulse width modulation (PWM) circuit 4, a driver stage 1, a power transistor 3, a linear regulator 17, a diode 9, a bootstrap capacitor 7, a diode 5 , inductor 11, capacitor 13, and control circuit 30. The load control circuit 30 has a BS (bootstrap) voltage detector 21 , a small load detector 19 , an on-time control 23 , and a second switch 25 formed of a transistor 25 . The second switch 25 can be formed by a plurality of transistors.

[0048] Here, a bipolar power transistor 3 is used, but it could also be of any other type, such as an NMOS transistor or an N-type DMOS transistor. The bootstrap capacitor 7 is connected between the cathode of the diode 9 and the switching node LX. Here, LX is also used as the voltage level at node LX. A voltage regulator 17 is connected to the anode of ...

no. 2 example

[0055] refer to Figure 6 , shows a second embodiment of an asynchronous DC-DC converter with a maximum duty limit according to the invention.

[0056] Figure 6 The second embodiment shown in the image 3 The difference of the first embodiment is that the second embodiment does not have the small load detector 19. Figure 6 components in the image 3 Components used in have the same reference numbers and have the same image 3 elements in the same function. The turn-on time of the second transistor 25 is determined by the period during which the maximum voltage is higher than the ramp signal, or by using the same method as described in FIG. 5 .

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Abstract

A method of controlling the charge of the bootstrap capacitor during light load or no load conditions for a non-synchronous type of DC-DC converter consists of bootstrap capacitor voltage detector, light load detector and secondary switch controller. By turning on the secondary switch during the off-time of the power transistor when the bootstrap voltage is lower than the required value under light load condition, the bootstrap capacitor voltage will be able to charge back to the required value, yet minimizing the minimum current requirement for the DC-DC converter.

Description

technical field [0001] The present invention relates to an asynchronous dc-dc converter with a bootstrap capacitor and a control circuit, more particularly, to a method for controlling the charging of a bootstrap capacitor of an asynchronous DC-DC converter, and also to An apparatus for controlling the charging of a bootstrap capacitor of a non-synchronous type DC-DC converter. Background technique [0002] In an integrated step-down dc-dc converter system, typically, the power supply device is an NPN transistor in bipolar technology, NMOS in CMOS technology, or N-type DMOS in BCD technology. To reduce losses in the top power transistor, a bootstrap is typically used to boost the driver voltage above the power rail. P-type transistors are generally not used due to the need for a relatively large area about 2-3 times larger than N-type transistors. [0003] For non-synchronous DC-DC converters, in normal operation, when the load current is large enough, the voltage regulato...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M3/07H02M3/10H02M3/155
CPCY02B70/1466Y02B70/16H02M3/1588H02M2001/0032H02M1/0032Y02B70/10
Inventor 黄夏秀于国磊
Owner PANASONIC CORP