Pulse width modulator control circuit
First Claim
1. A circuit which generates control signals used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtooth signal oscillating between a maximum voltage level and a minimum voltage level, the circuit comprising:
- sawtooth signal generating means, for generating the sawtooth signal; and
,square wave signal generating means, coupled to the sawtooth signal generating means, for receiving the sawtooth signal, for comparing the voltage level of the sawtooth signal with a first voltage slightly above the minimum voltage level and with a second voltage slightly below the maximum voltage level, and for generating a square wave with a rising edge that occurs only when voltage of the sawtooth signal is increasing and reaches the first voltage and with a falling edge that occurs only when voltage of the sawtooth signal is increasing and reaches the second voltage.
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Abstract
A circuit generates control signals used in pulse width modulation. A square wave signal generator generates a square wave signal based on the value of a sawtooth signal. The sawtooth signal has a maximum voltage level and a minimum voltage level. The voltage level of the sawtooth signal is compared with a first voltage slightly above the minimum voltage level. When voltage of the sawtooth signal is increasing and reaches the first voltage, a rising edge of the square wave is generated. The voltage level of the sawtooth signal is also compared with a second voltage slightly below the maximum voltage level. When voltage of the sawtooth signal is increasing and reaches the second voltage, a falling edge of the square wave signal is generated.
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Citations
12 Claims
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1. A circuit which generates control signals used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtooth signal oscillating between a maximum voltage level and a minimum voltage level, the circuit comprising:
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sawtooth signal generating means, for generating the sawtooth signal; and
,square wave signal generating means, coupled to the sawtooth signal generating means, for receiving the sawtooth signal, for comparing the voltage level of the sawtooth signal with a first voltage slightly above the minimum voltage level and with a second voltage slightly below the maximum voltage level, and for generating a square wave with a rising edge that occurs only when voltage of the sawtooth signal is increasing and reaches the first voltage and with a falling edge that occurs only when voltage of the sawtooth signal is increasing and reaches the second voltage.
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2. A circuit which generates control signal used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtooth signal having a maximum voltage level and a minimum voltage level, the circuit comprising:
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sawtooth signal generating means, for generating the sawtooth signal; and square wave signal generating means, coupled to the sawtooth signal generating means, for receiving the sawtooth signal, for comparing the voltage level of the sawtooth signal with a first voltage slightly above the minimum voltage level and with a second voltage slightly below the maximum voltage level, and for generating a square wave with a rising edge that occurs when voltage of the sawtooth signal is increasing and reaches the first voltage and with a falling edge that occurs when the voltage of the sawtooth signal is increasing and reaches the second voltage, wherein the square wave signal generating means includes; a first voltage source for generating the first voltage; a second voltage source for generating the second voltage; a switch, coupled to the first voltage source and the second voltage source, for selecting, based on a voltage of the square wave, one of the first voltage and the second voltage to place on a switch output; a comparator, coupled to the switch output and to the sawtooth signal generating means, for comparing voltage of the sawtooth signal with voltage at the switch output to produce a comparator output; a one shot pulse generator means, coupled to the comparator, for generating a pulse at a rising edge of the comparator output; and flip-flop means, coupled to the one shot pulse generator means, for toggling voltage of the square wave signal upon receiving a pulse from the one shot pulse generating means. - View Dependent Claims (3)
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4. A circuit which generates control signals used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtooth signal having a maximum voltage level and a minimum voltage level, the circuit comprising:
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sawtooth signal generating means, for generating the sawtooth signal; and
,square wave signal generating means, coupled to the sawtooth signal generating means, for receiving the sawtooth signal, for comparing the voltage level of the sawtooth signal with a first voltage slightly above the minimum voltage level and with a second voltage slightly below the maximum voltage level, and for generating a square wave with a rising edge that occurs when voltage of the sawtooth signal is increasing and reaches the first voltage and with a falling edge that occurs when voltage of the sawtooth signal is increasing and reaches the second voltage, wherein the square wave signal generating means includes; a first voltage source for generating the first voltage; a second voltage source for generating the second voltage; a first comparator, coupled to the first voltage source and to the sawtooth signal generating means, for comparing voltage of the sawtooth signal with the first voltage to produce a first comparator output; a second comparator, coupled to the second voltage source and to the sawtooth signal generating means, for comparing voltage of the sawtooth signal with the second voltage to produce a second comparator output; first one shot pulse generator means, coupled to the first comparator, for generating a pulse at a rising edge of the first comparator output; and second one shot pulse generator means, coupled to the second comparator, for generating a pulse at a rising edge of the second comparator output; and flip-flop means, coupled to the first one shot pulse generator means and to the second one shot pulse generator means, for toggling voltage of the square wave signal upon receiving a pulse from the first one shot pulse generating means and for toggling voltage of the square wave signal upon receiving a pulse from the second one shot pulse generating means. - View Dependent Claims (5)
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6. In a circuit which generates control signals used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtooth signal having a maximum voltage level and a minimum voltage level, a method comprising the steps of:
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(a) generating the sawtooth signal so that the sawtooth signal oscillates between the maximum voltage level and the minimum voltage level; (b) comparing voltage level of the sawtooth signal with a first voltage slightly above the minimum voltage level; (c) generating a rising edge of the square wave only when voltage of the sawtooth signal is increasing and reaches the first voltage; (d) comparing voltage level of the sawtooth signal with a second voltage slightly below the maximum voltage level; and
,(e) generating a falling edge of the square wave signal only when voltage of the sawtooth signal is increasing and reaches the second voltage.
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7. A circuit which generates control signals used in pulse width modulation, the control signals including a square wave signal and a sawtooth signal, the sawtoth signal having a first voltage level and a second voltage level, the circuit comprising:
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sawtooth signal generating means, for generating the sawtooth signal which oscillates between the first voltage level and the second voltage level; and
,square wave signal generating means, coupled to the sawtooth signal generating means, for receiving the sawtooth signal, for comparing the voltage level of the sawtooth signal with a third voltage level between the first voltage level and the second voltage level and with a fourth voltage level between the first voltage level and the third voltage level, and for generating a square wave with a rising edge that occurs only when voltage of the sawtooth signal is oscillating from the second voltage level to the first voltage level and reaches the third voltage level and with a falling edge that occurs only when voltage of the sawtooth signal is oscillating from the second voltage level to the first voltage level and reaches the fourth voltage level. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification