Inverter and air conditioner controlled by normal and defrost energization patterns

An inverter comprising:

• a) a switching circuit including a plurality of switching elements sequentially energizing windings of a plurality of phases of a brushless motor driving a compressor of a heat pump;
• b) a pulse width modulation circuit for obtaining a pulse width modulated signal;
• c) position detecting means for detecting a rotational position of a rotor of the brushless motor by comparing a terminal voltage of each winding with a reference voltage, thereby generating a position detection signal;
• d) energization signal forming means determining a commutation time on the basis of the position detection signal generated by the position detecting means and forming an energization signal corresponding to the determined commutation time, the energization signal forming means having a normal energization signal forming pattern and a loss increasing energization signal forming pattern wherein an efficiency of the brushless motor is lower than in the normal energization signal forming pattern, the energization signal forming means switching from the normal signal forming pattern to the loss increasing energization signal forming pattern in a predetermined period during drive of the brushless motor;
• and
• e) a drive circuit synthesizing the energization signal and the pulse width modulated signal, thereby obtaining a signal for driving each switching element.