Various electronic devices, electric propulsion vehicles, and the like include DC-DC converters (also referred to as DC converter circuits or DC to DC power supplies) that convert a direct current power to another direct current power. For example, DC-DC converters are utilized for generating a constant output voltage or a plurality of output voltages with different values on the basis of voltage with large fluctuation.
As an example of the configuration of a DC-DC converter, Patent Document 1 discloses a non-isolated DC-DC converter including a coil, a diode, and a transistor.
There are various kinds of non-isolated DC-DC converters such as a step-up DC-DC converter, a step-down DC-DC converter, an inverting DC-DC converter, and a step-up and step-down DC-DC converter.
Step-up DC-DC converters convert an inputted direct-current voltage into a direct-current voltage higher than the inputted direct-current voltage and output the higher direct-current voltage. Step-down DC-DC converters convert an inputted direct-current voltage into a direct-current voltage lower than the inputted direct-current voltage and output the lower direct-current voltage. Inverting DC-DC converters have a configuration in which a coil and a diode of a step-up DC-DC converter interchange with each other. The inverting DC-DC converters convert an inputted direct-current voltage into a direct-current voltage with polarity opposite to that of the inputted direct-current voltage and output the direct-current voltage with the opposite polarity.
Patent Document 2 discloses a step-up DC-DC converter, a step-down DC-DC converter, and an inverting DC-DC converter as non-isolated DC-DC converters.
Patent Document 3 discloses an example of the configuration of an inverting DC-DC converter. FIG. 6 illustrates a converter controller 610 and a switching element 606 that are included in an inverting DC-DC converter in Patent Document 3.
In FIG. 6, the converter controller 610 includes a negative-to-positive voltage conversion circuit 601, an error amplifier 603, a pulse width modulation comparator 604, and a buffer transistor 605.
From a feedback voltage output terminal of an inverting DC-DC converter, a feedback voltage (VFB) which is a negative voltage is supplied to a feedback voltage input terminal 607 of the converter controller 610 without any change. In the converter controller 610, the negative-to-positive voltage conversion circuit 601 converts the supplied feedback voltage (VFB) which is a negative voltage into a positive voltage, and an output of the negative-to-positive voltage conversion circuit 601 is input to the error amplifier 603. The error amplifier 603 compares the output of the negative-to-positive voltage conversion circuit 601 to a reference voltage Vref.