After the battery is connected, the bias voltage on R1 cannot turn on Q1 due to the effect of the resistor R6, so the following comparator circuit makes the output of the LM2903 without power supply and no power supply low so that Q2 is also in the cut-off state. When there is no action, the switch is in the normally open state. The switch S1 is a self-resetting switch. The third is the feedback self-locking part with NPN transistor Q2 as the core. The second is the comparison part with the comparator LM2903 as the core

One is the switch part with PNP transistor Q1 as the core The circuit can be divided into three parts according to the role of key components:

When the self-reset switch is closed, the circuit will be powered on according to a predetermined length of time. The circuit uses a comparator LM2903 and an RC timer. Take a timing shut-off circuit and a time delay generator circuit as examples.Īnalysis of the timing shut-off circuit made by comparator and RC If the frequency is too low, the LM2903 cannot continue to output a high level, which will be high and low, causing the relay to turn on and off. This figure requires the PWM pulse frequency to reach several K. When there is no PWM pulse, LM2903 outputs a low level, and 9013 ends, and the relay cannot be closed. When there is a continuous PWM pulse (higher than a certain frequency), LM2903 outputs a high level, and the relay is driven by du9013 to pull in. ESD clamp open input increases the robustness of the device without affecting performance.ĭue to their superior performance and high quality, the LM2903 series are ideally suitable for many applications in consumer automobiles and industrial electronics.Īmong them, LM2903 is a voltage comparator. The output voltage is compatible with DTL, ECL, TTL, MOS, and CMOS logic levels. It can work from a wide single supply voltage range or dual supply of 2V~36V or 1V~18V. LM2903 is a powerful voltage comparator with advantages such as multi-channel comparison and high performance. The input offset voltage specification is as low as 2.0 mV, making this device an ideal choice for many applications in consumer automobiles and industrial electronics. The design of these devices allows the use of a single-supply common-mode voltage range. LM2903 series are dual independent precision voltage comparators with low power consumption, capable of single power supply or separate power supply.

Comparator relay circuit