A DC-DC converter includes a regeneration preventing circuit to bring a synchronous rectifying switching element to an OFF-state when an output of an error amplifier is lower than a lower-limit potential of a triangular-wave signal, that is, when the output of the error amplifier deviates from a voltage range of the triangular-wave signal in a side (direction), which would cause a smaller ON duty ratio of a main switching element. This configuration prevents a rise of voltage in an input side du...

An inductive electric energy transmission circuit includes: an oscillating circuit; a push-pull circuit including a first switching transistor and a second switching transistor that are configured to alternate a current flow through the oscillating circuit. The circuit arrangement also includes, a control circuit including first and second control transistors configured to control the first and second switching transistors; and a frequency generator configured to generate an output signal, where...

There is provided a high-efficiency DC-DC converter which comprises a voltage resonance circuit to which electric power from a low-voltage direct-current power supply, including a household fuel cell and a solar cell, is input and performs DC-AC conversion by zero-voltage switching, an insulating high-frequency transformer which transmits the converted power, a current resonance circuit which is provided on the secondary side of the transformer and performs zero-current switching, a rectifier ci...

A resonant switching power system operates with two resonant frequencies. A first frequency depends on the secondary leakage inductance of an output transformer and capacitor. The first frequency varies with changes in the load because load changes alter the leakage inductance. A second resonant frequency depends on the gate source capacitance of two MOSFET power devices in the circuit and the leakage inductance of the circuit's driving transformer. Power is thereby supplied that is always in ph...

A power supply for inductively powering a remote device has an inverter operating at an operating frequency and a primary coil. A phase comparator compares the phase of the voltage or current delivered by the power supply. If the phase relationship detected by the comparator is unacceptable, the inverter is disabled. After a period of time, the inverter is re-enabled, and the phase relationship is again determined.

A control circuit 8 of a switching power source comprises a voltage detector 31 for detecting a voltage V.sub.DC of a DC power supply 1 to produce a detection voltage V.sub.DT; a comparator 41 for producing an output signal V.sub.CP when detection voltage V.sub.DT from voltage detector 31 exceeds a reference voltage V.sub.R2; a bottom voltage detector 51 for detecting a bottom point of voltage V.sub.DS across a MOS-FET 3 after energy has been discharged from transformer 2; and a switching contro...

An object of this power supply device is to enable an overheat protection level and an overvoltage protection level to be set accurately. This power supply device includes a Schottky barrier diode (D52), which is placed as a temperature detection element at a region where a temperature is measured, to which a reverse voltage is applied, and through which a reverse leakage current flows; a comparator (Z51) which sets a potential of an output terminal thereof to a low level when a voltage correspo...

A synchronous commutation DC-DC converter comprises a current detection transformer (51) for detecting currents (I.sub.Q1, I.sub.Q2) flowing through the primary circuit, first and second DC bias power sources (53, 54) generating bias voltages (V.sub.BS1, V.sub.BS2) larger than the voltage corresponding to the exciting current of a transformer (4), and first and second comparators (55, 57) for driving first and second commutation MOS-FETs (7, 8) when the detection voltage (V.sub.DT) of a current ...

System and method for protecting a power converter. The system includes a compensation system configured to receive an input signal and generate a control signal, a cycle threshold generator configured to receive the control signal and generate a cycle threshold, and a comparator configured to receive the cycle threshold and a feedback signal and generate a comparison signal. Additionally, the system includes a pulse-width-modulation generator configured to receive the comparison signal and gene...

A voltage-waveform detector produces a voltage-feedback signal and a discharge-time signal by multi-sampling a voltage signal of a transformer. The discharge-time signal represents a discharge time of a secondary-side switching current. A voltage-loop error amplifier amplifies the voltage-feedback signal and generates a control signal. An off-time modulator correspondingly generates a discharge-current signal and a standby signal in response to the control signal and an under-voltage signal. The...