Startup circuit for converter with pre-biased load
First Claim
1. A startup circuit for a DC—
- DC power converter, the power converter including an error amplifier which provides a compensation signal to a pulse width modulation (PWM) circuit that uses the compensation signal and a triangular PWM waveform to develop a PWM signal to control a switching circuit which converts an input voltage to an output voltage relative to a common power reference voltage, the switching circuit including an enable input, said startup circuit comprising;
a first circuit that establishes a minimum peak voltage and a maximum peak voltage for the triangular PWM waveform;
a second circuit that establishes a reference voltage having a linear relationship with the output voltage, wherein said reference voltage ranges from said minimum to maximum peak voltages while the output voltage ranges from the common power reference voltage to the level of the input voltage; and
a comparator having a first input for receiving the compensation signal, a second input receiving said reference voltage, and an output providing an enable signal which is for providing to the enable input of the switching circuit.
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Accused Products
Abstract
A method of starting a DC—DC converter into a precharged output voltage including generating a reference voltage having a linear relationship with the output voltage such that the reference voltage ranges between a minimum and maximum voltage level of a PWM triangular waveform as the output voltage ranges between zero and an input voltage level, and enabling output switching of the DC—DC converter when the reference voltage is approximately equal to a compensation signal generated by an error amplifier comparing the reference voltage with a feedback signal representative of the output voltage. Generating a reference voltage may include applying a first current based on the input voltage through two resistors to develop the minimum and maximum voltage levels, applying the first current in one direction through a third resistor, and applying a second current based on the output voltage through the third resistor in the opposite direction.
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Citations
18 Claims
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1. A startup circuit for a DC—
- DC power converter, the power converter including an error amplifier which provides a compensation signal to a pulse width modulation (PWM) circuit that uses the compensation signal and a triangular PWM waveform to develop a PWM signal to control a switching circuit which converts an input voltage to an output voltage relative to a common power reference voltage, the switching circuit including an enable input, said startup circuit comprising;
a first circuit that establishes a minimum peak voltage and a maximum peak voltage for the triangular PWM waveform; a second circuit that establishes a reference voltage having a linear relationship with the output voltage, wherein said reference voltage ranges from said minimum to maximum peak voltages while the output voltage ranges from the common power reference voltage to the level of the input voltage; and a comparator having a first input for receiving the compensation signal, a second input receiving said reference voltage, and an output providing an enable signal which is for providing to the enable input of the switching circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- DC power converter, the power converter including an error amplifier which provides a compensation signal to a pulse width modulation (PWM) circuit that uses the compensation signal and a triangular PWM waveform to develop a PWM signal to control a switching circuit which converts an input voltage to an output voltage relative to a common power reference voltage, the switching circuit including an enable input, said startup circuit comprising;
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8. A DC—
- DC converter, comprising;
an output switching circuit, having an enable input for receiving an enable signal, that, when enabled, switchably applies an input voltage to an output inductor to develop an output voltage based on a PWM signal; an error amplifier that generates a compensation voltage based on an output voltage feedback signal compared with a reference voltage; PWM logic that generates said PWM signal based on said compensation voltage and a ramp signal ranging between minimum and maximum ramp voltages; and a startup circuit, comprising; a reference circuit that generates said reference voltage to vary in a linear manner relative to said output voltage between said minimum ramp voltage if said output voltage is zero and said maximum ramp voltage if said output voltage is at the same voltage as said input voltage; and a comparator that compares said compensation voltage with said reference voltage and that provides said enable signal. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
- DC converter, comprising;
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16. A method of starting a DC—
- DC converter into a precharged output voltage, comprising;
generating a reference voltage having a linear relationship with the output voltage, wherein the reference voltage ranges between a minimum and maximum voltage level of a PWM triangular waveform as the output voltage ranges between zero and an input voltage level; and enabling output switching of the DC—
DC converter when the reference voltage is approximately equal to a compensation signal generated by an error amplifier comparing the reference voltage with a feedback signal representative of the output voltage. - View Dependent Claims (17, 18)
- DC converter into a precharged output voltage, comprising;
Specification