Switching regulator
A switching regulator includes a switching element to generate an output voltage, a reference voltage source to generate a reference voltage, a soft-start circuit to set the reference voltage increasing gradually within a range, an error amplifier circuit to generate an error difference voltage indicating an error difference between the reference voltage and feedback voltage of the output voltage of the switching regulator, a switching circuit to generate a switching signal to control the switching element in response to the error difference voltage, and a current limiting circuit to generate a limiting signal indicating a comparison result between an current into the switching element and a limit being set to increase within a range, wherein the switching circuit controls a duty cycle of the switching signal so that the current through the switching element does not exceed the limit in response to the limiting signal.
1. A switching regulator comprising:
a switching element to generate an output voltage of the switching regulator;
a reference voltage source to generate a reference voltage;
a soft-start circuit to set the reference voltage increasing gradually from a first value to a second value;
an error amplifier to generate an error difference voltage indicating an error difference between the reference voltage and a feedback voltage of the output voltage of the switching regulator;
a current limiting circuit to generate a limiting signal indicating a comparison result between a current flowing through the switching element and a current limit value having been set to increase gradually from a third value to a fourth value; and
a switching control circuit to generate a switching signal to control the switching element to regulate a duty cycle of the switching element, based on the error difference voltage and the limiting signal,
wherein the switching control circuit controls the duty cycle of the switching signal in response to the limiting signal so that the current flowing through the switching element does not exceed the current limit value; and
a control circuit to control the soft-start circuit and the error amplifier circuit,
wherein the control circuit selectively switches between a first state in which the soft-start circuit sets the reference voltage to the first value and the error amplifier circuit is set with a predetermined offset voltage, and a second state in which the reference voltage is set to increase gradually from the first value to the second value by the soft-start circuit to release the offset voltage in the error amplifier circuit, and
wherein the control circuit, when the switching regulator receives an enable signal as input, sets the soft-start circuit and the error amplifier circuit in the first state, and, when the feedback voltage becomes greater than a predetermined threshold voltage, sets the soft-start circuit and the error amplifier in the second state.
2. The switching regulator as claimed in claim 1 , further comprising:
a PWM signal converting circuit to control the reference voltage input to the soft-start circuit in response to a predetermined PWM signal.
3. The switching regulator as claimed in claim 1 , wherein the switching control circuit controls the duty cycle of the switching signal by prioritizing the limiting signal over the error difference voltage so that the current flowing through the switching element does not exceed the current limit value.
4. A switching regulator comprising:
a switching element to generate an output voltage of the switching regulator;
a reference voltage source to generate a reference voltage;
a soft-start circuit to set the reference voltage increasing gradually from a first value to a second value;
an error amplifier to generate an error difference voltage indicating an error difference between the reference voltage and a feedback voltage of the output voltage of the switching regulator;
a current limiting circuit to generate a limiting signal indicating a comparison result between a current flowing through the switching element and a current limit value having been set to increase gradually from a third value to a fourth value; and
a switching control circuit to generate a switching signal to control the switching element to regulate a duty cycle of the switching element, based on the error difference voltage and the limiting signal,
wherein the switching control circuit controls the duty cycle of the switching signal in response to the limiting signal so that the current flowing through the switching element does not exceed the current limit value; and
a control circuit to control the soft-start circuit and the error amplifier circuit,
wherein the control circuit selectively switches between a first state in which the soft-start circuit sets the reference voltage to the first value and the error amplifier circuit is set with a predetermined offset voltage, and a second state in which the reference voltage is set to increase gradually from the first value to the second value by the soft-start circuit to release the offset voltage in the error amplifier circuit, and
wherein the control circuit, when the switching regulator receives an enable signal as input, sets the soft-start circuit and the error amplifier circuit in the first state, and, when a predetermined time has passed after receiving the enable signal, sets the soft-start circuit and the error amplifier in the second state.
5. The switching regulator as claimed in claim 4 , further comprising:
a PWM signal converting circuit to control the reference voltage input to the soft-start circuit in response to a predetermined PWM signal.
6. A switching regulator comprising:
a switching element to generate an output voltage of the switching regulator;
a reference voltage source to generate a reference voltage;
a soft-start circuit to set the reference voltage increasing gradually from a first value to a second value;
an error amplifier to generate an error difference voltage indicating an error difference between the reference voltage and a feedback voltage of the output voltage of the switching regulator;
a current limiting circuit to generate a limiting signal indicating a comparison result between a current flowing through the switching element and a current limit value having been set to increase gradually from a third value to a fourth value; and
a switching control circuit to generate a switching signal to control the switching element to regulate a duty cycle of the switching element, based on the error difference voltage and the limiting signal,
wherein the switching control circuit controls the duty cycle of the switching signal in response to the limiting signal so that the current flowing through the switching element does not exceed the current limit value; and
a control circuit to control the soft-start circuit and the error amplifier circuit,
wherein the control circuit selectively switches between a first state in which the soft-start circuit sets the reference voltage to the first value and the error amplifier circuit is set with a predetermined offset voltage, and a second state in which the reference voltage is set to increase gradually from the first value to the second value by the soft-start circuit to release the offset voltage in the error amplifier circuit, and
wherein the control circuit, when the switching regulator receives an enable signal as input, sets the soft-start circuit and the error amplifier circuit in the first state, and, when the current flowing through the switching element becomes greater than the current limit value, sets the soft-start circuit and the error amplifier in the second state.
7. The switching regulator as claimed in claim 6 , further comprising:
a PWM signal converting circuit to control the reference voltage input to the soft-start circuit in response to a predetermined PWM signal.