Power supply, head light device using the power supply, and vehicle using the headlight device

摘要

A control circuit is configured to compare an input voltage measured through an input voltage detection circuit with a first threshold which is lower than a rated voltage of an external DC power supply and with a second threshold which is lower than the first threshold. The control circuit is configured, when detecting that a duration time in which the input voltage is kept lower than the first threshold reaches a predetermined holding period, to stop operating a switching device. The control circuit is configured, after detecting that the input voltage is lower than the second threshold, to more shorten a maximum ON time than that during a normal operation or lengthen an OFF time of the switching device than a maximum OFF time during the normal operation.

主权项

1. A power supply comprising:
a DC-DC converter, comprising a switching device, an inductor in which energy is accumulated by an electric power from an external DC power supply when the switching device is turned on, and a capacitor configured to be charged by a regeneration current from the inductor when the switching device is turned off; and a control circuit configured to control switching operation of the switching device, wherein the control circuit is configured, in a normal operation,
to turn off the switching device when a primary current flowing through the switching device reaches a primary current instruction value or when an ON-time of the switching device reaches an ON-time threshold, andto turn on the switching device when a predetermined delay time elapses from a time when the regeneration current stops or when an OFF-time of the switching device reaches an OFF-time threshold, the control circuit comprises an input voltage detection circuit configured to measure an input voltage from the DC power supply to the DC-DC converter, and the control circuit is configured:
to compare the input voltage measured through the input voltage detection circuit with a first threshold which is lower than a rated voltage of the DC power supply and with a second threshold which is lower than the first threshold;when detecting that a duration time in which the input voltage is kept lower than the first threshold reaches a predetermined holding period, to stop operating the switching device; andafter detecting that the input voltage is lower than the second threshold, to employ a different ON-time threshold which is shorter than the ON-time threshold defined for the normal operation and to turn on the switching device when the delay time elapses from a time when the regeneration current stops or when the OFF-time of the switching device reaches the different OFF-time threshold.