Patent ID: 8344714

Claim:
A linear voltage regulator circuit comprising: a first voltage input terminal to receive a first external voltage; a second voltage input terminal to receive a second external voltage which is greater than the first external voltage; a voltage output terminal; a voltage switch unit connected to the first and second voltage input terminals, wherein the voltage switch unit comprises a relay and a thyristor; the relay comprises a coil and a single-pole double-throw switch having a pole, a first throw, and a second throw; the first throw of the switch is connected to the first voltage input terminal, the second throw of the switch is connected to the second voltage input terminal, the pole of the switch is connected to an anode of the thyristor via the coil, a cathode of the thyristor is grounded; a voltage regulator unit connected to the pole of the switch of the relay of the voltage switch unit, to selectively receive the first or second external voltage from the voltage switch unit, and output the selected one of the first and second external voltages through the voltage output terminal; and a voltage detecting unit to detect an output voltage of the voltage output terminal and connected to a control terminal of the thyristor of the voltage switch unit, wherein the voltage detecting unit outputs a first control signal to the control terminal of the thyristor for controlling the voltage switch unit to output the first external voltage to the voltage regulator unit, in response to the output voltage being less than or equal to a predetermined value, wherein the voltage detecting unit outputs a second control signal to the control terminal of the thyristor for controlling the voltage switch unit to output the second external voltage to the voltage regulator unit, in response to the output voltage being greater than the predetermined value.