Voltage converter
First Claim
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1. A voltage converter circuit comprising:
- an input;
an output; and
a current control arrangement for controlling an output current of said converter circuit, said current control arrangement comprising a first mode when a voltage output by said converter circuit is above a threshold voltage and the output current of said converter circuit is substantially constant and a second mode in which the voltage output by said converter circuit is below said threshold voltage, said first and second modes being controlled by the same current control arrangement, said current control arrangement comprising comparing means, arranged to receive a reference voltage, comprising a voltage offset associated with at least one of a plurality of inputs of the comparing means;
whereby when the voltage output by said converter circuit is in a short circuit condition, the comparing means provides a predetermined non zero output.
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Abstract
A voltage converter comprises an input, an output and a current control arrangement for controlling the output current of the voltage converter circuit. The current control arrangement comprises a first mode, when the voltage output by the converter circuit is above a threshold voltage, and a second mode in which the voltage output by the circuit is below the threshold voltage. The first and second modes are controlled by the same current control arrangement. The current control arrangement comprises comparing means arranged to receive a reference voltage wherein the reference voltage is a voltage offset associated with at least one of the inputs of the comparing means.
35 Citations
31 Claims
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1. A voltage converter circuit comprising:
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an input;
an output; and
a current control arrangement for controlling an output current of said converter circuit, said current control arrangement comprising a first mode when a voltage output by said converter circuit is above a threshold voltage and the output current of said converter circuit is substantially constant and a second mode in which the voltage output by said converter circuit is below said threshold voltage, said first and second modes being controlled by the same current control arrangement, said current control arrangement comprising comparing means, arranged to receive a reference voltage, comprising a voltage offset associated with at least one of a plurality of inputs of the comparing means;
wherebywhen the voltage output by said converter circuit is in a short circuit condition, the comparing means provides a predetermined non zero output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A voltage converter to provide an output voltage to a load, the voltage converter comprising:
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an input adapted to receive an input voltage;
an output to provide the output voltage to the load;
a voltage control loop, connected to the output, to control a value of the output voltage provided to the load; and
a current control loop, connected to the output, to control a value of a current provided to the load, the current control loop having a first mode in which the value of the output voltage is above a threshold value and the value of the current provided to the load has a first and substantially constant value, and a second mode in which the value of the output voltage is at or below the threshold value and the value of the current provided to the load varies between the first value and a second and non-zero value that is below the first value, wherein when the value of the output voltage is below the threshold value and a short circuit condition exists, the value of the current provided to the load is limited to the second value. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31)
a transistor having a fist main terminal coupled to the input of the voltage converter, a second main terminal, and a control terminal;
an inductor having a first terminal that is coupled to the second main terminal of the transistor and a second terminal;
a first resistor coupled to the second terminal of the inductor and the output of the voltage converter; and
a capacitor coupled between the second terminal of the inductor and in parallel with the load;
wherein the current control loop includes a comparator having a first input that is coupled through a second resistor to the second terminal of the inductor and a second input that is coupled through a voltage offset to the output of the voltage converter, an output of the comparator being coupled to the control terminal of the transistor, the comparator comparing a first voltage drop across the first resistor to a second voltage drop across the second resistor to provide a control signal that controls the value of the current provided to the load in the second mode, wherein when the first voltage drop is greater that the second voltage drop and the short circuit condition exists, the control signal limits the value of the current provided to the load to the second value.
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25. The voltage converter of claim 24, wherein the second value of the current provided to the load is limited to a value of the voltage offset divided by a resistance of the first resistor.
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26. The voltage converter of claim 25, wherein when the second drop is greater than the first voltage drop and the value of the output voltage is above the threshold value, the control signal fixed the value of the current provided to the load in the first mode of the first value.
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27. The voltage converter of claim 26, wherein the first value of the current provided to the load is approximately equal to a value of the first voltage drop divided by the resistance of the first resistor.
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28. The voltage converter of claim 24, wherein the comparator is a first comparator and the control signal is a first control signal, and wherein the voltage control loop includes:
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a voltage divider coupled to the output converter, the voltage divider having an output;
a second comparator having a first input that is coupled to the output of the voltage divider and a second input that is coupled to a reference voltage, an output of the second comparator being coupled to the control terminal of the transistor, the second comparator comparing the output of the voltage divider to the reference voltage to provide a second control signal that regulates the value of the voltage provided to the load.
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29. The voltage converter of claim 28, further comprising:
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an OR circuit, coupled to the output of the first and second comparators, the OR circuit selecting one of the first and second control signals to provide as an output of the OR circuit based upon which of the first and second control signals is larger; and
a third comparator having a first input coupled to the output of the OR circuit and a second input that is coupled to an output of a saw tooth generator, an output of the third comparator being coupled to the control terminal of the transistor to provide a modulated output signal that controls the transistor.
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30. The voltage converter of claim 24, wherein when the second voltage drop is greater that the first voltage drop and the value of the output voltage is above the threshold value, the control signal fixes the value of the current provided to the load in the first mode to the first value.
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31. The voltage converter of claim 24, wherein the first value of the current provided to the load is approximately equal to a value of the first voltage drop divided by the resistance of the first resistor.
Specification