Various types of static DC to DC converters are known. Some of these have output rectifiers including phase controlled SCRs. The present invention eliminates the need for controlled output SCRs by pulse width modulation of switching elements in a control circuit controlling the converter circuitry itself. This results in the elimination of some switching devices, higher reliability and higher-efficiency, A unijunction oscillator drives a one-shot multivibrator and a flip flop. The unijunction oscillator, one-shot multivibrator and flip flop feed two AND gates which are alternately enabled to allow pulses of current to flow from a DC source through opposite halves of a primary winding of a transformer. The output of the secondary winding is rectified and filtered to provide the converter output. Voltage regulation is accomplished by controlling the one-shot multivibrator. In one embodiment, paralleling of a number of converters is enabled by providing for frequency and pulse width synchronization.
A source for providing a voltage or current which is (remotely) controlled by a digital signal includes a digital-to-analogue converter (30) which supplies a proportion of a reference voltage (V.sub.R) in accordance with the digital signal. The gain of an amplifier (48, 50) receiving an oscillatory signal is controlled by an error integrator (32) in dependence upon the difference between the converter output and a feedback signal derived via a precision rectifier (62) from a secondary winding (60) on a transformer (56), the primary (54) of which is coupled to the amplifier output, so the feedback signal tracks the converter output. Another (isolated) secondary winding (66) and precision rectifier (70) provide an output voltage equal to the feedback signal; the output voltage can be used to control a voltage-controlled current source (74). Although the output voltage or current is d.c. isolated, it tracks the reference voltage, so the source (14) can be coupled to the (floating) input circuitry (22a) of a digital voltmeter (22) and at the same time track the reference voltage in the separately-earthed analogue-to-digital converter (22b) of the voltmeter.
A plurality of conventional, parallel a.c. to d.c. to a.c. to d.c. converters are driven by a common a.c. source supply current to a common load. Each of the converters includes a controller for a pulse width modulated chopper; the controller determines the amplitude of d.c. current at the output terminals of the particular converter. Input terminals of each controller are responsive to the output voltage of the particular converter with which the controller is associated. A common controller for the controllers of the individual converters is responsive to the load voltage. The common controller varies the impedance of a single variable impedance connected in parallel to remote sense input terminals of the controller of each of the converters.
A device package that receives a voltage from a power supply on a motherboard and that includes provisions for a voltage control element that controls the power supply voltage. The provisions for the voltage control element are such that the voltage from the power supply has a first voltage if the voltage control element is installed and a second voltage if the voltage control element is missing. Such a device is useful in (computer) systems having wiring boards with power supplies that produce output voltages that depend on adjust voltages on adjust inputs. The provisions of the device package can then set the adjust voltage such that the power supply has a first voltage if the voltage control element is installed and a second voltage if the voltage control element is missing.
A power supply employing a clock-driven D.C.-A.C.-D.C. converter having a current transformer in the A.C. section to develop a trapezoidal current feedback pulse train which is then converted to a trapezoidal voltage pulse train. A comparator compares the trapezoidal voltage pulse train to a voltage reference level set such that it is normally crossed by the ramp portion of each trapezoidal voltage pulse. Upon occurrence of a ramp crossing, which varies with the level of the output current, a control pulse is produced by the comparator and supplied to gating logic which develops driving pulse trains for the D.C.-A.C.-D.C. converter and cuts off each driving pulse upon occurrence of a control pulse. The resulting power supply constitutes a voltage-controlled constant current power supply which may be connected with an arbitrary number of other such supplies to a power bus and to a common feedback-controlled voltage reference source.
A high-voltage power source apparatus has a step-up transformer for producing a high-voltage output, a rectifier/smoothing circuit for rectifying and smoothing the high-voltage output from the transformer, and a control section including a constant current or voltage control circuit for changing the output magnitude at a predetermined frequency and for obtaining a constant load current or voltage.
