Switching power converter with gated oscillator controller

Details Switching power converter with gated oscillator controller Switching power converter with gated oscillator controller

2000-06-02

2001-08-14

Sterrett, Jeffrey (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C323S222000, C363S016000

Reexamination Certificate

active

06275018

ABSTRACT:

FIELD OF THE INVENTION
This invention pertains generally to the field of power conversion and more particularly to a switching power supply with gated oscillator control.
RELATED APPLICATION DATA
This application is related to U.S. Ser. No. 09/444,032, filed Nov. 19, 1999 and U.S. Ser. No. 09/540,058, filed Mar. 31, 2000, the contents of both of which are hereby incorporated by reference.
BACKGROUND
Compact and efficient power supplies are an increasing concern to users and manufacturers of electronics. Pulse width modulated (PWM) switching power supplies offer both compactness and efficiency in a number of different topologies in two main categories: direct-coupled switching power supplies and transformer-coupled switching power supplies. In a direct-coupled switching power supply, such as a buck or boost switching power supply, the power output is not isolated from the power input. In contrast, the power output is isolated from the power input through a transformer in transformer-coupled power supplies such as a flyback converter.
In either type of power converter, however, a pulse-width-modulator controls the duty cycle of the power switch(es) within the converter. Consider, for example, a boost switching power supply
6
of FIG.
1
. The boost converter
6
comprises a power switch Q
1
(typically a field effect transistor (FET)) coupled to a boost inductor
8
, a steering diode
10
, and a storage capacitor
12
. A pulse-width modulator
14
adjusts a duty cycle of the power switch Q
1
in response to sensing an output voltage, V
out
. The relationship between the input voltage, V
in
, and V
out
may be approximated as
V
out
=V
in
*(
T/t
off
)
where T is the switching period and t
off
is the off time of the power switch Q
1
.
In this boost converter
6
, the off time, t
off
(and hence also the on time, t
on
) of the power switch Q
1
defines a power cycle, or power pulse, which is reflected in the value of V
out
through the above equation. The power pulse is thus a regulated power pulse because its characteristics have a direct relationship on the output voltage. This relationship between the characteristics of a single power cycle or pulse and the output voltage is generic to prior art PWM switching power supplies, regardless of whether the PWM switching power supply is direct coupled or transformer coupled. Thus, a single power cycle or pulse in these prior art PWM switching power supplies may be denoted as an “intelligent” power cycle or pulse because of its effect on the output voltage. There is, however, a limit to the amount of pulse-width modulation these PWM switching power supplies can apply to a given power pulse. Thus, maximum efficiency for such power supplies is usually achieved at a fairly high power level and drops off quickly for load conditions above or below this power level. To aid efficiency, a “sleep mode” may be implemented such as described in U.S. Pat. No. 5,912,552 during a low load state wherein the power switch is kept in the OFF state for the duration of the “sleep” period.
Thus, there is a need in the art for improved switching power converters that maintain high efficiencies over a broad range of load conditions.
SUMMARY OF THE INVENTION
The invention provides in one aspect a switching power supply having a power switch wherein an ON and OFF cycle of the power switch produces an pulse of power at an output of the switching power supply. A controller controls the number of pulses of power appearing at the output over time.
Other aspects and advantages of the present invention are disclosed by the following description and figures.


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Micrel, Inc., Product Brochure, MIC 2141 Micropower Boost Converter, Preliminary Information, Jun. 2000.
TNY253/254/255, TinySwitch™Family, Energy Efficient, Low Power Off-line Switchers, Power Integrations, Inc., Feb. 1999, pp. 1-16.

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