Drive circuit with an external mode-adjusting pin

A drive circuit with an external mode-adjusting pin, for driving a driven circuit and selecting an operational mode to control the driven circuit, the driven circuit including a first switch energized by a power source, at least one operational element and an inductor electrically bridging the first switch and the at least one operational element, the inductor generating an induced current as the first switch is turned on, the drive circuit comprising:

• an operational mode control circuit, further comprising:
• a current mirror circuit, having a first output port and a second output port;
• a power circuit, coupling the first output port, having a voltage input port with an input voltage;
• a resistor, coupling the voltage input port of the power circuit;
• a capacitor, coupling the second output port of the current mirror circuit;
• and
• a control comparator, having a first comparator input port, a second comparator input port and a comparator output port, the first comparator input port being to receive a first reference voltage, the second comparator input port being coupled with the second output port and the capacitor, the input voltage energizing the resistor to produce a resistor current for the current mirror circuit to generate a charge current for charging the capacitor, the comparator output port of the control comparator outputting a trigger signal as another charge voltage at the second comparator input port reaches the first reference voltage after a delay time;
• and
• a drive processing circuit, electrically connected with the comparator output port and the first switch, for receiving the trigger signal and turning on the first switch according to the trigger signal, so as to determine the operational mode of the driven circuit by controlling the induced current of the inductor;
• wherein the external mode-adjusting pin is defined as one of the voltage input port and the second comparator input port for selecting one of a resistance of the resistor and a capacitance of the capacitor, respectively, to determine the operational mode of the driven circuit;
• and
• wherein the power circuit includes a control calculator and a transistor, the control calculator having a calculator input port, the voltage input port and an operational output port, the calculator input port being to receive a second reference voltage equal to the input voltage, the voltage input port being coupled to one end of the resistor while another thereof is grounded, the operational output port being coupled with a gate of the transistor while a source of the transistor is coupled to the voltage input port and a drain thereof is coupled to the first output port.