Power-up and no-load/light load protective mechanisms for DC:DC converters

• US 6,529,354 B1
• Filed: 03/03/2000
• Issued: 03/04/2003
• Est. Priority Date: 03/03/2000
• Status: Expired due to Fees

• Current Assignee: MMC Bidding, Inc.
• Original Assignee: Switch Power Inc.
• Inventors: Goder, Dimitry, Shteynberg, Anatoly
• Primary Examiner(s): Jackson, Stephen W.
• Application Number:
  US09/517,941
• Time in Patent Office: 1,096 Days
• Field of Search: 361/18, 361/90, 361/100, 361/58
• US Class Current: 361/18
• CPC Class Codes: H02M 1/0029 Circuits or arrangements for limiting the slope of switching signals, e.g. slew rate
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/0045 Converters combining the concepts of switch-mode regulation and linear regulation, e.g. linear pre-regulator to switching converter, linear and switching converter in parallel, same converter or same transistor operating either in linear or switching mode
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H03K 17/163 Soft switching
• CPC Class Codes: H03K 17/166 Soft switching
• 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

Switching circuits including DC:DC converters of various topologies are provided with a soft-start mechanism that ensures safe start-up operation. The mechanism causes the converter switches to be driven such that on-impedance is increased during at least a portion of the time the switches are turned on. Increased on-impedance condition is invoked during power-up, and/or no-load or light-load condition. The increased on-impedance temporarily reduces output voltage and/or drive current provided by the converter.

Claims

1. For use with a switching circuit that receives an operating voltage Vin and outputs a signal Vo, said switching circuit defineable as having switch circuit-on times and switch circuit-off times but where magnitude of said Vo need not be controllable by a duty cycle ratio of said switch circuit-on times/switch circuit-off times, a method to control at least one parameter describing said signal Vo, comprising:

coupling a switch to said operating voltage Vin so as to conduct current through said switch as a function of impedance of said switch such that magnitude of said Vo is controlled by impedance of said switch; and

said switch having a switch impedance that is varied continuously during circuit switch-on times between a low switch-on impedance and a higher switch-off impedance during at least one of Vo power-up for said switching circuit and low load coupled to said switching circuit.

2. The method of claim 1, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state;

further including

determining duration of said time period tss by monitoring at least one parameter associated with said signal Vo.

3. The method of claim 2, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state; and

magnitude of said switch impedance is increased during time t<

tss.

4. The method of claim 1, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state operation; and

said switch is a solid state device coupled to receive a drive signal that during time t<

tss is insufficent in magnitude to turn said switch completely on;

wherein said time period tss is determined by components defining a time constant of tss.

5. The method of claim 1, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring current through said switch.

6. The method of claim 1, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring current output by said DC;

DC converter.

7. The method of claim 1, wherein:

said switching circuit is part of a DC;

DC converter that requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring magnitude of said signal Vo.

8. The method of claim 1, wherein said circuit includes a DC:

DC converter having at least one characteristic selected from a group consisting of (a) said DC;

DC converter has an isolating topology, (b) said DC;

DC converter has a non-isolating topology, and (c) said DC;

DC converter has a push-pull topology.

9. A method of safely operating a DC:

DC switching converter coupled between Vin operating potential and ground, and outputting at least one output signal Vo whose magnitude need not be controllable by varying switching duty cycle, the DC;

DC converter having an inductor with a inductor node coupleable to said operating Vin potential, and having a semiconductor switch coupled to said inductor so as to conduct current responsive to a switch drive signal;

the method comprising the following steps;

(A) detecting at least one DC;

DC switching converter event selected from a group consisting of (i) start-up operation, (ii) no-load operation, and (iii) too-light load operation; and

(B) during at least detection of an event detected at step (a), continuously varying impedance of said semiconductor switch during DC;

DC switching converter on-times between a low switch-on impedance and a higher switch-off impedance;

wherein current conducted through said switch varies as a function of impedance of said switch so as to vary magnitude of said output signal Vo.

10. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state;

further including

duration of said time period tss is determined by monitoring at least one parameter associated with said output signal Vo.

11. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state; and

magnitude of said semiconductor switch impedance is increased during time t<

tss.

12. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state operation; and

during time t<

tss said solid state switch receives a drive signal insufficient in magnitude to turn said solid state switch completely on;

wherein said time period tss is determined by components defining a time constant of tss.

13. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring current through said solid state switch.

14. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring current output by said DC;

DC switching converter.

15. The method of claim 9, wherein:

said DC;

DC switching converter requires a time period tss to achieve steady-state operation; and

duration of said time period tss is determined by monitoring magnitude of said output signal Vo.

16. The method of claim 9, wherein said DC:

DC switching converter has at least one characteristic selected from a group consisting of (a) said DC;

DC converter has an isolating topology, (b) said DC;

DC converter has a non-isolating topology, and (c) said DC;

DC converter has a push-pull topology.