CPC H03K 17/0828 (2013.01) [B60R 16/03 (2013.01); G01K 7/01 (2013.01); G01K 7/16 (2013.01); H02H 3/08 (2013.01); H02H 5/04 (2013.01); H02H 6/00 (2013.01); H02M 3/156 (2013.01); H03K 17/168 (2013.01)] | 11 Claims |
1. A switch device comprising:
a switching element configured to connect/disconnect a current path from a power supply terminal to a ground terminal via a load;
an overcurrent protection circuit configured to limit output current flowing in the switching element to be an overcurrent limit value or less; and
a duty control unit, wherein
when an output short circuit of the load is detected, the overcurrent protection circuit decreases the overcurrent limit value to be smaller as a power supply voltage is higher,
wherein the overcurrent protection circuit includes:
a reference current generation portion configured to generate a reference current, and
a comparison portion configured to compare a threshold value voltage corresponding to the reference current with a sense voltage corresponding to the output current so as to generate a first overcurrent protection signal for controlling a conduction degree of the switching element, and
when an output short circuit of the load is detected, the reference current generation portion decreases the reference current to be smaller as the power supply voltage is higher, and
wherein the reference current generation portion includes:
a differential amplifier portion,
an upper side current generation portion configured to generate an upper side current,
a lower side current generation portion configured to generate a lower side current, and
a difference current generation portion configured to output a difference current based on the lower side current and the upper side current, as the reference current,
wherein the duty control unit is configured to turn off the switching element for a predetermined off-period when a current limiting operation by the over current protection circuit continues for a predetermined on-period,
wherein the over current protection circuit is configured to generate a status notification signal for notifying the duty control unit that the over current protection circuit currently limits the output current,
wherein the duty control unit is configured to receive the status notification signal so as to generate a second overcurrent protection signal for turning off the switching element for the predetermined off-period when the current limiting operation by the over current protection circuit continues for the predetermined on-period.
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