Current detection circuit of switch power supply and switch power supply

Abstract

The invention discloses a current detection circuit of a switch power supply and a switch power supply, relating to the current detection technology field. The current detection circuit of the switch power supply comprises a first current mutual inductor, a second current mutual inductor, a sampling resistor and a control system; the second current mutual inductor converts second current which is transmitted from the secondary of a transformer TX1 to an upper side diode to small current which is then supplied to a sampling resistor; the second current mutual inductor converts second current which is transmitted from the secondary of a transformer to an upper side diode to small current which is then supplied to the sampling resistor; and the control system obtain voltage on two ends of the sampling resistor which is converted to corresponding current. Through the clever choice of the current detection point, the current mutual inductor can be used to participate in current detection, the current mutual inductor can convert big current to the small current, and the small current can be supplied to the sampling resistor, which greatly reduce the loss of the sampling resistor, reduces the cost, and improves the precision and design difficulty. Besides, the switch power supply can realize the detection of the charging current, which can benefit the control of the charging current.

Description

technical field [0001] The invention relates to the technical field of current detection, in particular to a current detection circuit of a switching power supply and a switching power supply. Background technique [0002] In new energy vehicles, batteries are often used. After the energy of the batteries is exhausted, a charger needs to be used to charge the batteries. Current chargers often use a switching power supply as an energy conversion device, and the input is taken from the AC power grid, which is converted into DC power after isolation by a high-frequency transformer. In order to realize the control of the charging current, it is necessary to detect the output current of the charger. Since the output current is DC, current sampling resistors are often used to sample the current, such as figure 1 As shown, the switching power supply includes a transformer TX1, a diode D1 (called the upper side rectifier diode), a diode D2 (called the lower side rectifier diode), ...

AI Technical Summary

Problems solved by technology

[0003] The cost of the current sampling method using the sampling resistor R1 is relatively low, but the detection accuracy is poor, especially when detecting large currents, not only the accuracy is poor, but the loss is also large

On the other hand, due to the use of resistance sampling, in order to select the voltage reference, the ground of the control system needs to share the ground with the secondary ground of the power system, which increases the difficulty of system design

The use of Hall sensors can improve accuracy, but the cost is high and cannot be used in low-cost solutions

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