Power supply device and method for limiting an output current of a power supply device

Patent metadata

Field	Value
Publication number	US-9941782-B2
Application number	US-201415033041-A
Country	US
Kind code	B2
Filing date	Nov 18, 2014
Priority date	Dec 6, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A switched-mode power supply system and method for converting an input voltage into an output voltage, including at least one switching stage controlled by a pulse-width modulation circuit in a clocked manner, and a control circuit that influences a pulse-width modulation circuit to vary the level of the output voltage, characterized by the provision of a current limiting circuit which, after a threshold voltage has been exceeded, limits the power supply output current first to an elevated maximum current for a first period of time, and thereafter to a regular maximum current. The control circuit is such that the first period of time for which the output current is limited to the elevated maximum current is dependent on the level of the output current.

First claim

What is claimed is:

1. A switched-mode power supply for converting an input voltage to an output voltage, comprising:
(a) a transformer having primary and secondary windings:
(b) at least one switching stage circuit which supplies said input voltage to said transformer primary winding; thereby causing said secondary winding to produce an output current and an output voltage, said switching stage circuit including a switching element:
(c) a pulse-width modulation circuit connected with said switching stage switching element to control in a clocked manner the operation of said switching stage circuit: and
(d) a control circuit which controls the operation of said pulse-width modulation circuit to vary the level of the output voltage, said control circuit including a current limiting circuit for establishing a current threshold level and operable when said current threshold level has been exceeded by a voltage signal that is a function of the output current to limit for a first period of time the output current to an elevated maximum current, and thereafter to limit the output current to a regular maximum current, said first period of time being dependent on the level of said output current, said current limiting circuit including
(1) a first comparison circuit for comparing a first voltage signal with a first reference voltage, thereby to produce an output voltage signal that controls the operation of said pulse-width modulation circuit, and thereby control the level of said output voltage;
(2) an integrator circuit for filtering said first voltage signal to produce a second voltage signal; and
(3) a second comparison circuit for comparing said second voltage signal with a second reference voltage corresponding with said regular maximum current, thereby to produce a third voltage signal that is supplied as an input to said first comparison circuit to influence the operation of said first comparison circuit.

2. A switched-mode power supply as defined in claim 1 , wherein the longer said first period of time exists, the smaller is the difference between said first voltage signal and said first threshold value during said first period of time.

3. A switched-mode power supply as defined in claim 1 , wherein said integrator circuit comprises a low-pass filter including at least one charging/discharging resistor and a capacitor.

4. A switched-mode power supply as defined in claim 1 , wherein said integrator circuit includes a first branch including a charging resistor connected in series with a first diode having a first polarity, and a second branch connected in parallel with said first branch, said second branch including a discharging resistor connected in series with a second diode of the opposite polarity.

5. A switched-mode power supply arrangement as defined in claim 4 , and further including a temperature-dependent resistor connected in series in said second branch.

6. A switched-mode power supply as defined in claim 1 , wherein said input voltage has a range of from between about 10 volts to about 800 volts.

7. A switched-mode power supply as defined in claim 1 , wherein said input voltage has a range of from about 15 volts to about 265 volts.

8. A switched-node power supply as defined in claim 1 , wherein said input, voltage is an alternating-current voltage, and said output voltage is a direct-current voltage.

9. A switched-mode power supply as defined in claim 1 , wherein said output current normally has a nominal current value, and further wherein said elevated maximum current is between 5 to 10 times said nominal current value, and said regular maximum current is between 1.1 and 1.5 times said nominal current.

10. A switched-mode power supply for converting an input voltage to an output voltage, comprising:
(a) a transformer having primary and secondary windings;
(b) at least one switching stage circuit for supplying said input voltage to said transformer primary winding, thereby causing said transformer secondary winding to produce an output current and an output voltage, said switching stage circuit containing a switching element;
(c) a pulse-width modulation circuit connected with said switching stage switching element for controlling in a clocked manner the operation of said switching stage circuit; and
(d) a control circuit controlling the operation of said pulse-width modulation circuit to vary the level of the output voltage, said control circuit including:
(1) a first comparison stage including:
(a) a first operational amplifier having an output terminal connected with said pulse-width modulation circuit, and a pair of input terminals; and
(b) a first reference voltage connected with a first one of said first operational amplifier input terminals;

(2) a sensor which applies a first voltage signal that is a function of the output current to a second input terminal of said first operational amplifier, whereby upon the occurrence of an overload, an elevated maximum current is permitted;
(3) an integrator circuit for generating from said first voltage signal a time-integrated second voltage signal;

(4) a second comparison stage including:
(a) a second operational amplifier having an output terminal connected with said first operational amplifier first input terminal, and a pair of input terminals; and
(b) a second reference voltage connected with a first input terminal of said second operational amplifier, the second input of said second operational amplifier being connected with said integrator circuit to receive said time-integrated second voltage signal, thereby to produce a third voltage signal at the output terminal of said second operational amplifier that influences the operation of said first operational amplifier;
(5) said control circuit being operable when the threshold level established by said second reference voltage has been exceeded to limit for a first period of time the output current at the elevated maximum current, and thereafter to limit the output current to a regular maximum current, said first period of time being dependent on the level of said output current.

Assignees

• Weidmueller Interface Gmbh & Co Kg
• Weidmueller Interface Gmbh & Co Kg

Inventors

• Schuermann Klaus
• Buschkamp Michael

Classifications

• H02M3/33507

  with automatic control of the output voltage or current, e.g. flyback converters (H02M3/33561, H02M3/33569 take precedence) · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02H9/02

  responsive to excess current {(current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025)} · CPC title