| 摘要 |
PROBLEM TO BE SOLVED: To enable a noise measure in a switching power supply, even if a transmission EMI standard is expanded to a low frequency region.SOLUTION: A jitter control circuit, which is configured to supply a jitter (frequency spread) to a switching frequency to drive a switching element to thereby reduce the occurrence of a transmission EMI noise, receives a feedback voltage (FB voltage) indicative of the magnitude of a load, to expand a switching frequency diffusion width step-by-step, as a shift from a maximum oscillation frequency (65 kHz) fixation frequency region to a frequency reduction region and a minimum oscillation frequency (25 kHz) fixation frequency region. This enables the acquisition of a sufficient EMI noise reduction effect, even if the measurement frequency range of the EMI noise is expanded to a lower region side.SELECTED DRAWING: Figure 1 |
