CONSTANT ON-TIME (COT) CONTROL IN ISOLATED CONVERTER

摘要

The present invention discloses a constant on-time isolated converter comprising a transformer with a primary side and a secondary side. The primary side is connected to an electronic switch and secondary-side is connected to a load and a processor. The processor is connected to a driver on primary side through at least one coupling element and to the electronic switch. The processor receives an output voltage or an output current across the load generating a control signal accordingly. The driver receives the control signal through the coupling element and accordingly changes the ON/OFF state of the electronic switch, regulating the output voltage and the output current via the transformer, where the duration of the ON/OFF state of the electronic switch is determined between the moment control signal changes from negative to positive and the moment it changes from positive to negative to achieve a high-speed load transient response.

主权项

1. A constant on-time (COT) isolated converter connected to an input terminal for receiving an input voltage, the constant on-time isolated converter comprises:
a transformer including a primary side and secondary side, wherein the primary side is connected to the input terminal and the secondary side is connected to a load; a driver connected to the input terminal receiving the input voltage, thereby generating a first pulse signal; a first electronic switch connected to the primary side of the transformer and the driver, the first electronic switch receives the first pulse signal and accordingly changes its ON/OFF state to control the transformer receiving the input voltage from the input terminal thus generating an output voltage and an output current applied onto the load, and to control the transformer generating a sample voltage containing the input voltage at the secondary side of the transformer; a processor connected between the secondary side of the transformer and the load is provided with a first preset reference voltage, the processor receives either the output voltage or the output current, and the sampling voltage, and captures a corresponding detection voltage from either the output voltage or the output current, wherein when the detection voltage is less than the first preset reference voltage, the processor generates a second pulse signal according to the input voltage; and at least one coupling element connected to the processor and the driver between the primary side and the secondary side of the transformer, the coupling element transmits the second pulse signal to the driver at the primary side to control the driver stop generating the first pulse signal, the driver amplifies the second pulse signal to produce a first digital signal transmitted to the first electronic switch, wherein the first electronic switch changes the ON/OFF state accordingly to control the transformer receiving the input voltage from the input terminal, thus regulating the output voltage and the output current.