Method and apparatus for dynamically adjusting a dead time of brushless direct current motor during a phase change

A method for dynamically adjusting a dead time of a brushless direct-current motor during a phase change, wherein the brushless direct-current motor is connected between two output terminals of an H-bridge circuit that is established by a first upper-side switch, a first lower-side switch, a second upper-side switch, and a second lower-side switch, the method comprising:

• A.) during the dead time, turning on the second lower-side switch while turning off the other switches, or turning on the first and the second lower-side switches while turning off the other switches, for consuming a winding current of the brushless direct-current motor;
• B.) detecting the winding current during the dead time;
• and
• C.) terminating the dead time once the winding current is detected equal to or smaller than a zero-current threshold;
• wherein the step B comprises temporarily turning off the second lower-side switch at regular time intervals for the winding current to be detected.

An apparatus for dynamically adjusting a dead time of a brushless direct-current motor during a phase change, wherein the brushless direct-current motor is connected between two output terminals of an H-bridge circuit that is established by a first upper-side switch, a first lower-side switch, a second upper-side switch, and a second lower-side switch, the apparatus comprising:

• a PWM controller connected to the H-bridge circuit, operative to control the switches such that during the dead time, the second lower-side switch is turned on while the other switches are turned off, or the first and the second lower-side switches are turned on while the other switches are turned off, for consuming a winding current of the brushless direct-current motor;
• and
• a current detector connected to the H-bridge circuit and the PWM controller, detecting the winding current during the dead time for signaling the PWM controller to terminate the dead time once the winding current is detected to be equal to or smaller than a zero-current threshold;
• wherein the PWM controller, during the dead time, applies a short pulse to a control terminal of the second lower-side switch for temporarily turning off the second lower-side switch, thereby allowing the current detector to detect the winding current.

An apparatus for dynamically adjusting a dead time of a brushless direct-current motor during a phase change, wherein the brushless direct-current motor is connected between two output terminals of an H-bridge circuit that is established by a first upper-side switch, a first lower-side switch, a second upper-side switch, and a second lower-side switch, the apparatus comprising:

• a PWM controller connected to the H-bridge circuit, operative to control the switches such that during the dead time, the second lower-side switch is turned on while the other switches are turned off, or the first and the second lower-side switches are turned on while the other switches are turned off, for consuming a winding current of the brushless direct-current motor;
• and
• a current detector connected to the H-bridge circuit and the PWM controller, detecting the winding current during the dead time for signaling the PWM controller to terminate the dead time once the winding current is detected to be equal to or smaller than a zero-current threshold;
• wherein the PWM controller, during the dead time, applies a short pulse to a control terminal of the second upper-side switch and to a control terminal of the second lower-side switch, for temporarily turning the second lower-side switch off and the second upper-side switch on, thereby allowing the current detector to detect the winding current.

An apparatus for dynamically adjusting a dead time of a brushless direct-current motor during a phase change, wherein the brushless direct-current motor is connected between two output terminals of an H-bridge circuit that is established by a first upper-side switch, a first lower-side switch, a second upper-side switch, and a second lower-side switch, the apparatus comprising:

• a PWM controller connected to the H-bridge circuit, operative to control the switches such that during the dead time, the second lower-side switch is turned on while the other switches are turned off, or the first and the second lower-side switches are turned on while the other switches are turned off, for consuming a winding current of the brushless direct-current motor;
• and
• a current detector connected to the H-bridge circuit and the PWM controller, detecting the winding current during the dead time for signaling the PWM controller to terminate the dead time once the winding current is detected to be equal to or smaller than a zero-current threshold;
• wherein the PWM controller, during the dead time, applies a short pulse to a control terminal of the second lower-side switch at regular time intervals for temporarily turning off the second lower-side switch, thereby allowing the current detector to detect the winding current.

An apparatus for dynamically adjusting a dead time of a brushless direct-current motor during a phase change, wherein the brushless direct-current motor is connected between two output terminals of an H-bridge circuit that is established by a first upper-side switch, a first lower-side switch, a second upper-side switch, and a second lower-side switch, the apparatus comprising:

• a PWM controller connected to the H-bridge circuit, operative to control the switches such that during the dead time, the second lower-side switch is turned on while the other switches are turned off, or the first and the second lower-side switches are turned on while the other switches are turned off, for consuming a winding current of the brushless direct-current motor;
• and
• a current detector connected to the H-bridge circuit and the PWM controller, detecting the winding current during the dead time for signaling the PWM controller to terminate the dead time once the winding current is detected to be equal to or smaller than a zero-current threshold;
• wherein the PWM controller, during the dead time, applies a short pulse to a control terminal of the second upper-side switch and to a control terminal of the second lower-side switch at regular time intervals, for temporarily turning the second lower-side switch off and the second upper-side switch on, thereby allowing the current detector to detect the winding current.