Startup and shutdown circuit of low-voltage system

Abstract

The invention discloses a startup and shutdown circuit of a low-voltage system, which comprises interfaces J1 and J2, a fuse F1, a thermistor T1, an isolated Hall detection chip U1, an MOS transistorQ1, an MOS transistor Q2, an MOS transistor Q3, triodes Q4, Q5, Q6, Q7, Q8, Q9, Q10, Q11, diodes D1, D2, D3 and D4, capacitors C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, and resistors R1,R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, R19, R20, R21, R22, R23 and R24. The beneficial effects are that the service life of devices and the reliability of circuits are improved.

Description

technical field [0001] The invention relates to the technical field of switching machine circuits, in particular to a switching machine circuit of a low-voltage system. Background technique [0002] At present, the existing switch circuit such as figure 2 and 3 As shown, in the switch circuit, the switch button is directly connected to the power supply terminal, and the button is closed to charge C56 through D15, R76, and R81. When the base point of Q14 reaches 0.7V, the triode Q14 is turned on, and the MOS tube Q12 is turned on. After the circuit is powered on and the switch button is closed, the capacitor C57 is charged through D14 and R72, and the base voltage of Q13 gradually increases. When the base voltage of Q13 is higher than the emitter voltage, Q13 is turned on, and Q11 is turned on. C59 is charged, when the voltage of C59 reaches 0.7V, the triode Q15 is turned on, the base voltage of Q14 is pulled down to about 0.2V, the MOS tube Q12 is turned off, the whole cir...

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Problems solved by technology

[0003]However, the switch circuit has the following defects:

[0004]1. The switching circuit has a certain impedance after shutdown, which will cause a small battery loss, which is not conducive to storage;

[0005]2. The current detection circuit is built by ordinary operational amplifiers, and its nonlinear range is large, resulting in low accuracy of current detection;

[0006]3. There is no slow start circuit, the surge current is large when starting up, and the reliability is reduced;

[0008]5. The main circuit is a P-channel MOS transistor D12 as a switch. Due to the existence of the body diode of the MOS, the drain to the source is a unidirectional conduction characteristic when it is not powered on. Therefore, when the rear stage of the circuit has an inductive load, the reverse current in the load will flow back to the source through the drain after shutdown, resulting in malfunction of the circuit

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