Module power supply high-end current detection amplification circuit

Abstract

The invention provides a module power supply high-end current detection amplification circuit. The module power supply high-end current detection amplification circuit comprises a sampling resistor R1, triodes Q1, Q2 and Q3, resistors R2, R3, R4, R5, R6 and R7 and a capacitor C1; one end of the sampling resistor R1 is connected with one end of the R2 and an input positive end, the other end of the sampling resistor R1 is connected with one end of the R3, the other end of the R2 is connected with the E pole of the Q1 and the E pole of the Q3, and the other end of the R3 is connected with the E pole of the Q2; the C pole of the Q1 is connected with one end of the R4, the C pole of the Q2 is connected with one end of the R5, the C pole of the Q3 is connected with one end of the R6 and one end of the R7, the other ends of the R4, the R5 and the R6 are connected with the input negative end, the B pole and the C pole of the Q1 are connected with the B pole of the Q2, the B pole of the Q3 is connected with the C pole of the Q2, the other end of the R7 is connected with one end of the capacitor C1, and the other end of the capacitor C1 is connected with the input negative end; the resistance value of the R2 is equal to the resistance value of the R3, and the resistance value of the R4 is equal to the resistance value of the R5; one end of the R7 is a sampling point used for sampling for current detection. The circuit can realize high-end detection, can synchronously amplify current signals, has few devices, and reduces the size and cost of the circuit.

Description

technical field [0001] The invention relates to the technical field of power supplies, in particular to a high-end current detection amplifying circuit of a module power supply. Background technique [0002] Current detection circuits are basically used in current switching power supplies, most of which are used for loop control to improve the stability and dynamic response of switching power supplies, and some are used to detect overcurrent or output short circuit to protect switching power supplies. At present, the commonly used detection methods include transformer detection, resistance sampling, and special detection chips. Among them, the detection of transformers must ensure magnetic reset, so it cannot be used in occasions with a relatively large duty cycle. The cost of dedicated detection chips is high, and isolation The chip also needs isolated power supply, which increases the complexity of the circuit, and is mostly used in high-power switching power supply applic...

AI Technical Summary

Problems solved by technology

At present, the commonly used detection methods include transformer detection, resistance sampling, and special detection chips. Among them, the detection of transformers must ensure magnetic reset, so it cannot be used in occasions with a relatively large duty cycle. The cost of dedicated detection chips is high, and isolation The chip also needs isolated power supply, which increases the complexity of the circuit, and is mostly used in high-power switching power supply applications. The resistance detection circuit is simple, low in cost, and small in size, which is the most commonly used solution for module power supply current detection.

[0003] Resistance detection current is divided into high-end current detection (the sampling resistor is placed on the positive terminal) and low-side current detection (the sampling resistor is placed on the negative terminal). The advantage of low-side current sampling is that the common-mode voltage is low, and low-cost ordinary operational amplifiers can be used , the disadvantage is that the current-sensing resistor introduces ground level interference, the greater the current, the more obvious the ground potential interference, and sometimes even affects the load

The advantage of high-end current detection is that it can detect and distinguish whether the load is short-circuited or not, and there is no ground level interference. The disadvantage is that the common-mode voltage is high. If an operational amplifier is used to realize this function, the selected operational amplifier is required to have a higher common-mode input voltage. The price of this kind of operational amplifier is generally extremely expensive, and it accounts for a relatively high proportion of the cost of the entire power supply.

The biggest defect of resistance detection is that the signal detected by a small resistance is relatively small, which is not conducive to participating in control or realizing reliable protection logic. A large detection signal value requires a large resistance resistor, and the power consumption and volume of a large resistance resistance also increase with the increase, which is not conducive to reducing the size of the module

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