CN-121983906-A - Self-adaptive adjustable current overcurrent protection circuit

Abstract

The invention discloses a self-adaptive adjustable current overcurrent circuit, and belongs to the field of integrated circuits and switching power supplies. The circuit comprises a power level circuit and a control loop, wherein the power level circuit is of a BUCK framework, the control loop samples current flowing through a high-side power tube through a current sampling circuit, a voltage comparator compares sampling voltage with reference voltage, a signal is output to a bidirectional counter, and the counter controls a resistor array to dynamically adjust the reference voltage. The invention can accurately detect the current flowing through the high-side power tube, and timely turn off the high-side power tube, thereby avoiding overlarge current and improving the safety performance of the converter during working.

Inventors

• ZHANG JIAN

Assignees

• 西安电子科技大学
• 张健

Dates

Publication Date

20260505

Application Date

20260210

Claims (5)

1. 1. The self-adaptive adjustable current overcurrent detection circuit is characterized by comprising a power level circuit and a control loop, wherein the power level circuit adopts a BUCK framework, the control loop comprises a resistor string R, a voltage source V, a reference voltage Vref, a sampling circuit Isense, a voltage comparator Comp, a bidirectional Counter and a resistor Array R_array, the voltage comparator Comp compares the SW point voltage in the power level circuit with the reference voltage Vref and outputs a signal to the bidirectional Counter, and the bidirectional Counter outputs an equivalent resistance value of the control resistor Array R_array so as to dynamically adjust the reference voltage Vref.
2. 2. The adaptive adjustable current foldback circuit of claim 1, wherein the resistor Array R_array is composed of a plurality of resistors R_1 to R_32 and a plurality of switching transistors counter_1 to counter_32, the switching transistors being controlled by an output signal of a up-down Counter.
3. 3. The self-adaptive adjustable current overcurrent protection circuit according to claim 2, wherein resistors in the resistor Array R_array are connected in series, switching tubes are connected in parallel at two ends of the resistors, and the equivalent resistance is changed by switching on and off of the switching tubes.
4. 4. The adaptive adjustable current foldback circuit of claim 1, wherein the Counter is a 5Bit Counter, and the initial state is set to an intermediate value, and is capable of counting up or down according to an input signal.
5. 5. The adaptively adjustable current foldback circuit of claim 1, wherein said circuit is adapted for a synchronous rectification buck DC-DC converter for detecting and turning off a current flowing through the high-side power transistor M1.

Description

Self-adaptive adjustable current overcurrent protection circuit Technical Field The invention belongs to the field of integrated circuits and the field of switching power supplies, and relates to a self-adaptive overcurrent protection circuit which can realize current detection. Background Synchronous rectification buck DC-DC converters are widely used in a variety of electronic devices because of their high efficiency and simplicity. In the step-down DC-DC converter, when the current in the DC-DC converter exceeds the maximum rated current value, the device is easily damaged, affecting the normal operation of the DC-DC converter chip. Therefore, an overcurrent protection circuit is generally arranged in the DC-DC converter chip, and when the current is detected to exceed the maximum rated current value, the overcurrent protection current can timely influence the driving module, so that the power tube enters a cut-off state, the chip enters an operation suspension state, and the chip is prevented from being burnt out due to overlarge output current. However, the conventional overcurrent protection circuit is difficult to accurately detect due to the influence of the process, the temperature and the offset elegance of the comparator. Disclosure of Invention Aiming at the defects of the traditional overcurrent protection circuit, the invention provides the self-adaptive adjustable current overcurrent protection circuit which can accurately sample current, can effectively detect current when the DC-DC converter works and solves the problem of insufficient sampling precision of the traditional overcurrent protection circuit. The technical scheme of the invention is as follows: An adaptive adjustable resistance overcurrent protection circuit comprises a power stage circuit and a control loop. Specifically, the power stage circuit comprises a driving module Driver, an input voltage VIN, a high-side power tube M1, a low-side power tube M2, an inductor L, an output capacitor Cout and a load resistor RL, and the control loop comprises a resistor string R, a voltage source V, a current sampling circuit Isense, a reference voltage Vref, a voltage comparator Comp, a bidirectional Counter and a resistor Array R_array. The power class circuit forms a BUCK architecture. The control loop is used for modulating the overcurrent protection reference voltage Vref so that the overcurrent protection reference voltage Vref can be accurately compared with the sampling voltage Vsense. One end of the current sampling circuit Isense is connected with the input voltage VIN and the high-side power tube M1, and the other end of the current sampling circuit Isense is connected with the high-side power tube M1, the low-side power tube M2 and the inductor L, and the current sampling circuit Isense outputs a Vsense signal. One end of the voltage comparator Comp is connected with the high-side power tube M1, the low-side power tube M2 and the inductor L, and the other end of the voltage comparator Comp is connected with the resistor R and the resistor Array R_array, and the output end of the voltage comparator Comp outputs an UP/DOWN signal. One end of the voltage source V is grounded, and the other end of the voltage source V is connected with the resistor string R. The UP/DOWN signal is input to the Counter, and the counter_out signal is output to control the resistor Array r_array. The resistor Array R_array is formed by interconnecting 32 resistors R_ <1-32>, and 32 switching tubes counter_ <1-32 >. Taking the connection relationship between R_1 and counter_1 as an example, one end of R_1 is connected with a resistor R, the other end of R_1 is connected with a resistor R_2, one end of counter_1 is connected with resistors R_1 and R, and the other end of counter_1 is connected with R_1 and R_2. The gate of the switching tube counter_ <1-32> is connected to counter_out. In the scheme of the invention, whether the time for closing the low-side power tube M2 is proper or not is judged by comparing the sampling voltage Vsense with the reference voltage Vref. The time advance and the time delay correspond to the larger and smaller output of the comparator COMP respectively, and the calibration of the comparison voltage Vref is completed through the Counter and the resistor Array r_array. The calibration process is smooth, real-time modulation can be carried out under the normal working condition of the DC-DC converter, and the method can effectively adapt to the change of external conditions such as temperature, voltage, current and the like in the working process of the converter. The self-adaptive adjustable current overcurrent protection circuit has the beneficial effects that for the BUCK type DC-DC converter, sampling voltage is obtained by sampling current flowing through the power tube, a comparison result is obtained by comparing the sampling voltage with the reference voltage, the current is judged to be too large or too small accordi