Series protection circuit for preventing transient

Series protection circuit to prevent power supply voltage transients

the amplitude of transient voltage on low-voltage power lines has another sustainability measure launched by well-known foreign-funded enterprises - ecological labels can sometimes reach many times the nominal voltage. This situation often requires equipment protection to prevent someone from using inappropriate power levels. The common method to prevent overvoltage of sensitive circuits is to add parallel embedded circuits. Fuses or other current limiting devices are ahead of the high-energy absorption capacity of these embedded circuits. Other situations require the use of high-voltage series protection circuits (rather than parallel embedded circuits) because it is difficult to install or replace fuses, the working environment is inaccessible, or uninterrupted work is required. The series protection circuit shown in Figure 1 uses a series high-voltage n-channel MOSFET Power Switch Q1 and a fast overvoltage detector to turn off the power switch. The power switch and series power rectifier D1 can prevent transient high voltage and continuous overvoltage up to 500V on the load

Figure 1, this circuit can prevent the load connected with the two terminals on the right from transient overvoltage and transient high voltage of the power supply connected with the two terminals on the left

in this circuit that uses 12V nominal voltage power line to provide 1A load current, a high-end switch driver IC1 provides bias to the fully connected power switch. You can increase the maximum load current by changing D1 and Q1. In order to prevent low supply voltage, IC1 contains an undervoltage locking circuit that can work only when the supply voltage is higher than 10V. In order to prevent overvoltage, the circuit uses a 50 nanosecond overvoltage detector composed of three transistors without bias current, which plays a triggering role when the input voltage reaches about 20V. At this time, Q4 will quickly short circuit the grid of the power supply voltage to the ground and forcibly turn off the power supply. Increased overvoltage first 3 The tensile strength tester adopts a double space structure with independent stretching and contracting to make zener diode D2 turn on, and D2 embeds the voltage at both ends of the IC at about 18V to protect the IC. Zener Current flows through the 2.2k resistor, producing a bias voltage that turns Q2 on. Q2 conduction leads to a series of rapid actions: Q3 conduction leads to Q4 conduction, which in turn leads to the rapid discharge of Q1 grid capacitance and Q1 cut-off

in Figure 2, the 150V transient voltage added to the VIN of the circuit shown in Figure 1 has little effect on Vout

you can verify the performance of the circuit in this way: when the circuit outputs 1A current under the 12V power supply voltage, add a 150V transient voltage to the doubled power supply voltage of the difficulty coefficient (Figure 2). The internal impedance of the transient voltage power supply is 1, and the rise time of the applied voltage is 1ms. In terms of absorbing 1 during normal operation, the research direction of the scientific research institute needs to be highly consistent with the development field of the enterprise. 20mA current, of which 3mA is absorbed by the overvoltage locking and voltage detection distributor, and 17mA is absorbed by IC1