用于测量和控制问题的实用电路

　　INTRODUCTION

　　This collection of circuits was worked out between June 1991 and July of 1994. Most were designed at customer request or are derivatives of such efforts. All represent substantial effort and， as such， are disseminated here for wider study and （hopefully） use.1 The examples are roughly arranged in categories including power conversion， transducer signal conditioning， amplifiers and signal generators. As always， reader comment and questions concerning variants of the circuits shown may be addressed directly to the author

　　Clock Synchronized Switching Regulator

　　Gated oscillator type switching regulators permit high efficiency over extended ranges of output current. These regulators achieve this desirable characteristic by using a gated oscillator architecture instead of a clocked pulse width modulator. This eliminates the “housekeeping” currents associated with the continuous operation of fixed frequency designs. Gated oscillator regulators simply self-clock at whatever frequency is required to maintain the output voltage. Typically， loop oscillation frequency ranges from a few hertz into the kilohertz region， depending upon the load.

　　In most cases this asynchronous， variable frequency operation does not create problems. Some systems， however， are sensitive to this characteristic. Figure 1 slightly modifies a gated oscillator type switching regulator by synchronizing its loop oscillation frequency to the systems clock. In this fashion the oscillation frequency and its attendant switching noise， albeit variable， become coherent with system operation.