Drain pump driving apparatus and laundry treatment machine including the same

A laundry treatment machine comprising:

• a washing tub;
• a driving unit to drive the washing tub;
• a drain pump;
• and
• a drain pump driving apparatus to drive the drain pump,
• wherein the drain pump driving apparatus comprises:
• a motor configured to drive the drain pump for drainage;
• an inverter to convert a direct current (DC) power to an alternating current (AC) power by a switching operation, and output the converted AC power to the motor;
• a DC terminal capacitor disposed at a DC terminal and configured to store the DC power;
• an output current detector configured to detect an output current flowing to the motor;
• and
• a controller configured to control the inverter, wherein the drain pump is connected to a drain pipe,
• wherein the controller is further configured to:
• control the motor to rotate at a first speed,
• when speed of the motor is a second speed after rotating the motor at the first speed, calculate a lift as a first level based on the second speed, control the motor to rotate at a third speed based on the first level of the lift, wherein the lift is a difference between a water level of a water introduction part through which water flows into the drain pump and a water level of a water discharge part for discharging water from the drain pump,
• when the speed of the motor is a fourth speed lower than the second speed after rotating the motor at the first speed, calculate the lift as a second level less than the first level based on the third speed, control the motor to rotate at a fifth speed lower than the third speed based on the second level of the lift,
• wherein a first timing for stopping the motor when the drainage is completed based on the first level of the lift is faster than a second timing for stopping the motor when the drainage is completed without being based on the first level of the lift,
• wherein the controller is configured to calculate a level of the lift based on the speed of the motor without a sensing data from a water pressure sensor or a water level sensor,
• wherein the output current detector is disposed between the DC terminal capacitor and the inverter, and the output current detector is configured to detect a current which corresponds to the output current flowing to the motor in time division manner when one lower switching device, from among a plurality of upper switching devices and a plurality of lower switching devices of the inverter, is turned on,
• wherein the controller is configured to control the inverter based on the detected current.