Constant on-time buck converter with improved transient response
View Patent ↗A COT (constant on-time) buck converter includes a first transistor, a second transistor, a driver circuit, an inductor, a first resistor, a second resistor, a capacitor, a load, and a feedback loop circuit. The feedback loop circuit includes a first switch, a second switch, an error amplifier, a comparator, a frequency locked loop circuit, an inverter and a COT logic circuit. The COT buck converter is able to improve DC (direct-current) regulation efficiency and transient response time.
1. A COT (constant on-time) buck converter comprising:
a first transistor comprising:
a first terminal for receiving an input voltage;
a second terminal coupled to a switch node; and
a control terminal;
a second transistor comprising:
a first terminal coupled to the switch node;
a second terminal couple to a voltage ground; and
a control terminal;
a driver circuit coupled to the control terminal of the first transistor and the control terminal of the second transistor, and configured to control the first transistor and the second transistor;
an inductor comprising:
a first end coupled to the switch node; and
a second end coupled to an output node;
a first resistor comprising:
a first end coupled to the output node; and
a second end coupled to a feedback node;
a second resistor comprising:
a first end coupled to the feedback node; and
a second end coupled to the voltage ground;
a capacitor comprising:
a first end coupled to the output node; and
a second end coupled to the voltage ground;
a load comprising:
a first end coupled to the output node; and
a second end coupled to the voltage ground; and
a feedback control circuit comprising:
a first switch comprising:
a first terminal coupled to the feedback node;
a second terminal; and
a control terminal;
a second switch comprising:
a first terminal coupled to the second terminal of the first switch;
a second terminal; and
a control terminal;
an error amplifier comprising:
a negative input terminal coupled to the second terminal of the first switch;
a positive input terminal for receiving a reference voltage; and
an output terminal coupled to the second terminal of the second switch for outputting an error signal;
a comparator configured to compare the error signal and a feedback voltage at the feedback node and to output a comparison signal;
a frequency locked loop circuit configured to generate a frequency signal;
an inverter comprising:
an input end coupled to the frequency locked loop circuit and the control terminal of the second switch; and
an output end coupled to the control terminal of the first switch; and
a COT logic circuit configured to receive the frequency signal and the comparison signal and generate a COT signal to the driver circuit.
2. The COT buck converter of claim 1 , wherein the first switch and the second switch are metal-oxide-semiconductor field-effect transistors (MOSFET).
3. The COT buck converter of claim 1 , wherein the first switch and the second switch are bipolar junction transistors (BJT).
4. The COT buck converter of claim 1 , wherein the first transistor is a P-type transistor.
5. The COT buck converter of claim 1 , wherein the second transistor is an N-type transistor.