| 摘要 |
Current measurement apparatus (100) and methods are disclosed to measure load DC output current on the secondary side of a high frequency transformer (104) in a switched power supply (102). Current in the primary side (106) of the transformer (104) is detected with a current transformer (118), which produces a voltage across a resistance (Rs) proportional to the primary current in the high frequency transformer (104). Averaging of the voltage across the resistance (Rs) is performed during periods of power transfer in the high frequency transformer (104) and held by a capacitor (138) until the next period of power transfer. The held voltage is used to determine the true load DC output current on the secondary side of the high frequency transformer (104) by the turns ratio relationship of the secondary current to the primary current of the high frecuency transformer (104). By averaging the voltage only over the periods of power transfer in the transformer, the effects of magnetizing current in the high frequency transformer (104) are negated, thereby affording a more accurate measurement of DC ouput current. |
