A high-voltage power source includes a high-voltage power source unit configured to apply high voltage obtained by superposing a high alternating-current voltage on a high direct-current voltage to a charging member, an output unit configured to output a first direct-current voltage having a first voltage value according to an externally input pulse-width modulation signal, a direct-current voltage conversion unit configured to convert the first direct-current voltage into a second direct-current voltage, a generation unit configured to boost the second direct-current voltage to generate a high direct-current voltage, a peak value detection unit configured to detect a positive peak value and a negative peak value from an alternating-current component of the high direct-current voltage, and a voltage difference output unit configured to output a third direct-current voltage having a third voltage value to the direct-current voltage conversion unit.
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