Switching regulator with over-current protection
A switching regulator with over-current protection is disclosed. The invention comprises an error amplifier, a pulse width modulator, an over-current protection unit, a gate driver, a tank circuit and a load. According to the invention, the variation of the output current outside a chip is detected and controlled by monitoring the voltage level of the error signal for over-current protection, thus reducing power dissipation caused by an additive resistor and raising efficiency of voltage conversion.
1. A switching regulator with over-current protection, comprising:
a tank circuit for receiving and converting a driving signal into an output voltage and an output current;
a first comparator for comparing a reference level voltage and the output voltage, and then generating an error signal;
a second comparator for comparing the error signal and a periodic signal and then generating a pulse signal;
an over-current protection unit counting a number of times that the voltage of the error signal rises above a predetermined voltage, and enabling a control signal if the number of times is greater than a predetermined value; and
a gate driver for generating the driving signal in accordance with the pulse signal and the control signal.
2. The switching regulator as claimed in claim 1 , wherein the over-current protection unit comprises:
a third comparator for comparing the error signal and the predetermined voltage, and then generating a comparison signal; and
a first counting logic circuit for receiving the comparison signal to count the number of times that the voltage of the error signal rises above the predetermined voltage within a predetermined time period, and then enabling the control signal while the number of times is greater than a first threshold value.
3. The switching regulator as claimed in claim 2 , wherein the over-current protection unit further comprises:
a second counting logic circuit for receiving the comparison signal to count a time period that the voltage of the error signal stays above the predetermined voltage, and then enabling the control signal while the time period is greater than a second threshold value.
4. The switching regulator as claimed in claim 2 , wherein the over-current protection unit further comprises:
a third counting logic circuit for counting the predetermined time period, and then generating a reset signal to reset the first counting logic circuit if the counting is completed.
5. The switching regulator as claimed in claim 1 , wherein the tank circuit comprises:
a switching unit, comprising a plurality of transistors, for generating the output voltage and the output current in accordance with the driving signal;
an inductor connected to the plurality of transistors; and
a capacitor connected to the inductor.
6. The switching regulator as claimed in claim 1 , wherein the first comparator, the second comparator, the over-current protection unit, the gate driver and the switching unit are embedded on a control chip.
7. The switching regulator as claimed in claim 1 , wherein the first comparator, the second comparator, the over-current protection unit and the gate driver are embedded on a control chip.
8. A regulating method of generating an output voltage with over-current protection, comprising the steps of:
comparing the output voltage and a reference level voltage to generate an error signal;
comparing the error signal and a periodic signal to generate a pulse signal;
generating a control signal by counting a number of times that the voltage of the error signal rises above the predetermined voltage within a predetermined time period, and then enabling the control signal while the number of times is greater than a first threshold value;
generating a driving signal in accordance with the pulse signal and the control signal; and
generating the output signal in accordance with the driving signal.
9. The switching method as claimed in claim 8 , wherein the step of generating the control signal further comprises the step of:
counting a time period that the voltage of the error signal stays above the predetermined voltage, and then enabling the control signal if the time period is greater than a second threshold value.