Under-voltage warning circuit
An under-voltage warning circuit includes a Zener diode, a transistor, an annunciator, and a thyristor. When the power source is within a certain range, the annunciator does not work. When the voltage level of the power source V_in is lower than the predetermined value, the annunciator works to denote that the power source is under-voltage.
1. An under-voltage warning circuit for detecting a power source, comprising:
a Zener diode, wherein a cathode of the Zener diode is connected to the power source;
a transistor, wherein a collector of the transistor is connected to the power source via a pull-up resistor, a base of the transistor is connected to an anode of the Zener diode via a first resistor, an emitter of the transistor is grounded;
an annunciator; and
a thyristor, wherein an anode of the thyristor is connected to the power source via the annunciator and a second resistor, a control terminal of the thyristor is connected to the collector of the transistor via a third resistor, a cathode of the thyristor is grounded.
2. The under-voltage warning circuit of claim 1 , wherein the base of the transistor is grounded via a fourth resistor.
3. The under-voltage warning circuit of claim 1 , wherein the annunciator is a light emitting diode.
4. The under-voltage warning circuit of claim 1 , wherein the annunciator is a buzzer.