| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce semiconductor loss with large current, and to reduce a relative ripple value with small current. <P>SOLUTION: The present invention includes: a first coil winding to which current to be measured flows to form a magnetic field; a second coil winding to which compensation current flows to generate a magnetic field for compensating the first winding; a magnetic core with a gap; a terminal resistor which is serially connected to the second winding; sensor means which is exposed to a synthetic magnetic field of the first and second windings; and a booster circuit which is connected to a downstream of the sensor means. The sensor means supplies the compensation current to the second winding via the terminal resistor. The booster circuit has a switching type amplification part with a pulse width and density modulation part which generates a pulse width and density modulation voltage signal. The modulation part changes the compensation current into pulse width and density modulation current by using a switching frequency. The switching frequency of the modulation part is a function of the compensation current in the meaning that the switching frequency is high in small current, and the switching frequency is low in large current. <P>COPYRIGHT: (C)2013,JPO&INPIT |
