US 9,812,983 B2
Synchronous rectifier circuit
Naoki Inoue, Kyoto (JP)
Assigned to ROHM CO., LLTD., Ukyo-Ku, Kyoto (JP)
Filed by ROHM CO., LTD., Ukyo-Ku, Kyoto (JP)
Filed on May 13, 2016, as Appl. No. 15/153,932.
Claims priority of application No. 2015-101298 (JP), filed on May 18, 2015.
Prior Publication US 2016/0344302 A1, Nov. 24, 2016
Int. Cl. H02M 7/219 (2006.01); H02M 1/00 (2006.01)
CPC H02M 7/219 (2013.01) [H02M 2001/0009 (2013.01); H02M 2001/0025 (2013.01); H02M 2001/0048 (2013.01); H02M 2007/2195 (2013.01); Y02B 70/1408 (2013.01); Y02B 70/1491 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A control circuit structured to form a synchronous rectifier circuit together with a bridge circuit, wherein the bridge circuit comprises:
a first transistor arranged between a first input node and a rectification node;
a second transistor arranged between a second input node and the rectification node;
a third transistor arranged between the first input node and a reference node; and
a fourth transistor arranged between the second input node and the reference node,
and wherein the control circuit comprises:
a first variable voltage source structured to generate a first threshold voltage which is variable;
a first zero current detection comparator structured to compare a first voltage at the first input node with the first threshold voltage, and to generate a first detection signal having a first level when the first voltage is higher than the first threshold voltage, and having a second level when the first voltage is lower than the first threshold voltage;
a first adjustment comparator structured to compare the first voltage with a first reference voltage;
a first adjustment unit structured to adjust the first threshold voltage generated by the first variable voltage source, based on an output of the first adjustment comparator; and
a control logic structured to switch a state of the bridge circuit according to the first detection signal,
and wherein the first adjustment unit comprises an up/down counter structured to select one from among a count up operation and a count down operation, according to an output of the first adjustment comparator,
and wherein the first adjustment voltage is set according to a count value of the up/down counter,
and wherein the first threshold voltage is variable in the vicinity of zero,
wherein the first reference voltage is configured as a negative voltage,
wherein the control logic is structured to instruct the bridge circuit to transit from a first state to a second state when the first detection signal becomes the first level,
wherein a pair of the first transistor and the fourth transistor are turned off and a pair of the second transistor and the third transistor are turned on in the first state, and the first transistor through the fourth transistor are turned off in second state.