buck constant voltage control circuit

Abstract

The invention relates to a BUCK constant voltage control circuit, which is characterized in that it includes a rectifier diode D2, a control chip, a filter capacitor C1, a sampling resistor R1, a sampling resistor R2, an inductor L1, a freewheeling diode D1 and a capacitor C3; the rectifier diode The cathode of D2 is connected to one end of the input capacitor C2 and the drain end of the control chip, the anode of the rectifier diode D2 and the other end of the input capacitor C2 are connected to the input voltage VINac, and the other end of the input capacitor C2 is connected to the circuit ground; the control chip The source terminal is internally connected to the sampling terminal and externally connected to one end of the sampling resistor R1 and one end of the sampling resistor R2, the other end of the sampling resistor R2 is connected to one end of the inductor L1, the cathode of the freewheeling diode D1 and the chip ground, and the other end of the sampling resistor R1 is connected to the inductor L1 The other end of the capacitor C3 and the other end of the capacitor C3, the other end of the capacitor C3 and the anode of the freewheeling diode D1 are connected to the line ground. The off time of the chip of the present invention is controlled by an internal control signal and is not affected by external conditions, thereby improving the load regulation rate.

Description

technical field [0001] The invention relates to a BUCK constant voltage control circuit, in particular to a BUCK constant voltage control circuit, which belongs to the technical field of circuits. Background technique [0002] The traditional BUCK constant voltage circuit, such as figure 1 As shown, the voltage value of Va is stabilized to the value of the output voltage Vout through the diode D1 and the capacitor C4 (such as figure 2 As shown), when the FB terminal voltage of the detection chip 100 is higher than the threshold of the internal comparator, the chip 100 stops the switching action, and when it is lower than the internal comparison threshold, the switch tube is turned on. The disadvantage of this is that there will be an extra diode and capacitor in the application, and the cost of the solution is high. Second, the off-time of the chip is completely determined by the discharge speed of the peripheral capacitor C4 through the resistors R1 and R2. If the capacit...

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Problems solved by technology

The disadvantage of this is that there will be an extra diode and capacitor in the application, and the cost of the solution is high. Second, the off-time of the chip is completely determined by the discharge speed of the peripheral capacitor C4 through the resistors R1 and R2. If the capacitor and resistor values ​​are not obtained properly, It will lead to poor load regulation of the chip, and the output voltage difference between light load and heavy load is relatively large

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