Direct voltage/direct voltage converter

A direct voltage/direct voltage converter, comprising:

• a switch-shaping circuit for receiving an input voltage by turning on a switch and then shaping and filtering the input voltage to produce an output voltage;
• a voltage-sensing device for measuring the input voltage and outputting a sensing signal;
• and
• a control device coupled to the voltage-sensing device and the switch-shaping circuit, wherein the control device provides a plurality of running modes such that the control device chooses one among the running modes to serve as a current operating mode according to the sensing signal, and according to the current operating mode, the control device outputs a switching signal for controlling the switch-shaping circuit;
• wherein the running modes include a lock-in made and a non-lock-in mode and, according to the sensing signal, the control device acts the operating mode of the converter to the lock-in mode when the output voltage is between an upper voltage limit and a lower voltage limit and sets the operating mode of the converter to the non-lock-in mode otherwise;
• and
• wherein the panel of sensing signals includes an out-of-target voltage signal, an exceed-upper-voltage-limit signal, a below-lower-voltage-limit signal and a lock-in voltage range signal, and the control device furthermore comprises:
• an up/down counter coupled to the voltage-sensing device for counting in one direction on receiving the exceed-upper-voltage-limit signal and counting in another direction on receiving the below-lower-voltage-limit signal;
• a counter for receiving a clocking signal and performing a cyclic counting procedure;
• a digital comparator coupled to the up/down counter and the counter for monitoring the output value of both the up/down counter and the counter and outputting an equivalent signal when the output value from the up/down counter and the counter are identical;
• and
• a switch-controlling device coupled to the digital comparator, the logic gate of the lock-in voltage comparator and the third comparator of the output voltage monitoring device such that the switch-controlling device outputs a switch signal to cut off the switching device when the switch-controlling device picks up an equivalent signal and the switch-controlling device outputs a switch signal to turn on the switching device when the switch-controlling device picks up a lock-in voltage range signal and an out-of-target voltage signal at the same time.