Switching power supply operating at little or no load
First Claim
1. A switching power supply with an output, said power supply comprising:
- voltage transformation means with an output;
electrical load means for providing an electrical load;
a low-pass filter coupled to said output of said voltage transformation means, said low-pass filter having an output;
comparison means coupled to said output of said low-pass filter for generating a first voltage if said output of said low-pass filter is below a pre-determined voltage; and
first switching means coupled to said comparison means for electrically connecting said electrical load means across said output of said power supply if said comparison means generates said first voltage.
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Accused Products
Abstract
A switching power supply contains a transformer. Connected on the secondary side of the transformer is a dummy load circuit. The dummy load circuit rectifies, voltage divides and low-pass filters the signal on the secondary side of the transformer. If the output of the low-pass filter is below a predetermined value, it is recognized that an insufficient load (which might be no load at all) is connected to the output of the switching power supply. In that case, the dummy load circuit activates a transistor which switches a dummy load resistor across the output of the power supply to assure at least a predetermined minimum electrical load on the output. If the electrical loads on the output of the switching power supply include a voltage source such as a battery, a relay is connected in series with the dummy load resistor within the switching power supply. The relay opens when the switching power supply is turned off, to prevent inadvertent leakage current from the voltage source through the transistor which switches the dummy load resistor.
44 Citations
15 Claims
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1. A switching power supply with an output, said power supply comprising:
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voltage transformation means with an output; electrical load means for providing an electrical load; a low-pass filter coupled to said output of said voltage transformation means, said low-pass filter having an output; comparison means coupled to said output of said low-pass filter for generating a first voltage if said output of said low-pass filter is below a pre-determined voltage; and first switching means coupled to said comparison means for electrically connecting said electrical load means across said output of said power supply if said comparison means generates said first voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A switching power supply with an output, said power supply comprising:
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a transformer with a secondary winding; a dummy electrical load; a rectifier coupled to said secondary winding; a low-pass filter coupled to said rectifier, said low-pass filter having an output; a comparator with an input and an output, said input coupled to said output of said low-pass filter; and a switching device with a control input and a switched output responsive to said control input, said control input coupled to said output of said comparator and said switched output coupled to said load resistor; wherein said comparator and said transistor are configured such that said transistor conducts current through said dummy electrical load if said output of said low-pass filter is below a predetermined voltage. - View Dependent Claims (10, 11, 12, 13)
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14. A method for coupling an electrical load to a switching power supply having an output and having a transformer with a secondary winding, said method comprising the steps of:
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providing an electrical load; low-pass filtering an output signal from said secondary winding to generate a low-pass filtered signal; comparing said low-pass filtered signal to a predetermined value; and coupling said electrical load across said output of said switching power supply if said low-pass filtered signal has a voltage less than said predetermined value. - View Dependent Claims (15)
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Specification