Digital controlled power supply

#The present invention relates to a digital controlled power supply for turning a switching element on/off in response to a Pulse Width Modulation (PWM) signal to obtain an output voltage required for a load from an input voltage inputted thereto.

#Due to the recent development of the semiconductor fine machining technology, there have appeared highly functional microprocessors having higher performance. Also, due to reduction in the operation voltage and the increase in the clock frequency, the current consumed in the processor and the change rate per unitary time thereof become larger. The tendency toward a lower voltage and a larger current causes a serious problem when supplying power to the processor. To cope with the problem, a Point-of-Load (POL) converter is used in ordinary cases.

#The POL converter is a very small power source and is disposed at a position in the vicinity of the load to minimize line impedance between the power supply and the load of the microprocessor. To design and to install the POL converter, it is required to sufficiently give consideration to changes in various parameters caused by, for example, variations in the environmental temperature and the load. As such parameter variation, there has been well known a direct-current (DC) bias characteristic of a choke coil. This is a phenomenon in which when a direct current flows through the choke coil, inductance thereof lowers. Due to reduction in the inductance, the current further flows and an output ripple voltage becomes greater, leading to deterioration in stableness of the circuit operation and reduction in the circuit performance. It is likely in the worst situation that constituent components such as an output capacitor or condenser and IC circuits are destroyed.

#FIG. 1 is a block diagram showing a first embodiment of a digital controlled power supply.

#FIG. 2 is a graph showing a DC bias characteristic of a choke coil.

#FIG. 3 is a graph to explain an operation of the first embodiment.

#Referring now to the drawings, description will be given of an embodiment of the present invention.

#FIG. 1 shows a first embodiment of the digital controlled power supply according to the present invention.

#The power supply includes a power source circuit 100, a digital controller 111, and amplifiers 109 and 110. The power source circuit 100 receives an input voltage 101 as an input thereto and converts the voltage 101 into a voltage necessary for a load device 102 to output the converted voltage thereto. The circuit 100 includes a high-side Metal Oxide Semiconductor Field Effect Transistor (MOSFET) 103, a low-side MOSFET 104, a choke coil 105, a smoothing capacitor 106, and a current detector circuit 107 to obtain a current detection value of the choke coil 105. The constituent components 105 to 107 forms a smoothing circuit or a ripple filter circuit. As the current detector circuit 107, a hole device or a shunt resistor is available.