Method and apparatus for pulse width modulation
AssigneePower Integrations, Inc.
InventorZhao-Jun Wang
Life of this patent
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Abstract
An apparatus and method of providing a pulse width modulated signal that is responsive to a current are disclosed. A circuit according to aspects of the present invention includes a capacitor to convert a first current to a first voltage on the capacitor during a first time duration and to discharge a second current from the capacitor to change the first voltage to a second voltage during a second time duration. A comparator is also included and is coupled to an output of the capacitor to compare a voltage on the capacitor to a reference voltage during the second time duration to change a pulse width of a periodic output signal in response to an input current.
Claims19
An integrated control circuit, comprising:
- a capacitor coupled to develop a first voltage during a first time duration in response to a charge current received by the capacitor and to develop a second voltage during a second time duration in response to a discharge current provided by the capacitor and wherein the charge current is generated in response to a control signal;
- a comparator coupled to the capacitor to generate an output indicating when the capacitor reaches the second voltage;
- and
- a control logic that is coupled to output a periodic output signal, wherein the control logic sets a duty ratio of the periodic output signal in response to a time that it takes the capacitor to discharge from the first voltage to the second voltage, wherein the duty ratio of the periodic output signal is substantially independent of the value of the capacitor.
An integrated control circuit, comprising:
- a capacitor coupled to develop a first voltage during a first time duration in response to a charge current received by the capacitor and to develop a second voltage during a second time duration in response to a discharge current provided by the capacitor and wherein the charge current is generated in response to a control signal;
- a comparator coupled to the capacitor to generate an output indicating when the capacitor reaches the second voltage;
- and
- a control logic that is coupled to output a periodic output signal, wherein the control logic sets a duty ratio of the periodic output signal in response to a time that it takes the capacitor to discharge from the first voltage to the second voltage, wherein a change in capacitor voltage terminates when the voltage on the capacitor reaches the second voltage during the second time duration.
An integrated control circuit, comprising:
- a capacitor coupled to develop a first voltage during a first time duration in response to a charge current received by the capacitor and to develop a second voltage during a second time duration in response to a discharge current provided by the capacitor and wherein the charge current is generated in response to a control signal;
- a comparator coupled to the capacitor to generate an output indicating when the capacitor reaches the second voltage;
- a control logic that is coupled to output a periodic output signal, wherein the control logic sets a duty ratio of the periodic output signal in response to a time that it takes the capacitor to discharge from the first voltage to the second voltage;
- and
- an oscillator coupled to provide a timing signal to the control logic, wherein a period of the periodic output signal is a period of the timing signal, wherein the timing signal received from the oscillator determines a maximum on-time of the periodic output signal.
Dependencies are inferred from the claim text.