Smk Corporation

Toshihiro Amei

Katsuhiko Okitsu

Kenji Hatano

Yoshitaka Kimura

In a DC-DC converter, a voltage at a connecting point where a switching transistor is connected to an inductor is compared with a threshold voltage set within a variation range of the voltage at the connecting point during switching operation of the switching transistor. When a polarity in which the voltage at the connecting point and the threshold voltage are compared does not vary in a detection time longer than the predetermined period of a driving circuit, the switching transistor is determined to be operating in an active state with a risk of heat generation.

DC-DC converter

In a DC-DC converter, a voltage at a connection point on the side of connection with a primary winding of a switching transistor is compared to a threshold voltage set within a variation range of the voltage at the connection point while the switching transistor is performing a switching operation, and, when the polarity by which the voltage was compared to the threshold voltage does not change during a detection period longer than the predetermined period of the drive signal for bringing the switching transistor under switching control, the switching transistor is determined as being operating in an active state with a danger of heat generation.

An object of the present disclosure is to provide a DC-to-DC converter with a simple circuit configuration that continues the supply of direct current power to a load without providing a redundant power supply circuit even if a switching transistor operates abnormally in the active state. A protection circuit unit that converts an input voltage of a direct current input power supply to a different direct current voltage obtained by stepping down the input voltage, as in a direct current voltage conversion circuit unit including a first switching transistor, is connected between the direct current voltage conversion circuit unit and the direct current input power supply and, if the first switching transistor operates in an active state, direct current power of the direct current voltage converted by the protection circuit unit is supplied to a load causing the first switching transistor to maintain operating in the active state.

DC-to-DC converter

Provided is a contact contacting structure that reliably prevents the development of arc discharge in a simple configuration regardless of the magnitude of electric energy accumulated between a pair of contacts that are connected and disconnected. An intermediate contact body disposed continuously with a first contact along a movement path of a second contact is formed from material with higher electric resistivity than the first contact in a shape such that the cross sectional area of a transverse section perpendicular to the movement path is gradually decreased in a separating direction along the movement path.

Contact contacting structure

There is provided a self-excited switching power supply circuit. A cycle control capacitor is charged with a flyback voltage generated in a feedback winding of a transformer during OFF operation period in which an exciting current does not flow in a primary winding of the transformer. An OFF control capacitor the charging speed of which changes ON operation period is charged with the charging voltage of the cycle control capacitor during the ON operation period in which an exciting current flows in the primary winding. The charging voltage of the cycle control capacitor is changed with a periodic cycle Tc sufficiently longer than an oscillation cycle To to make the oscillation cycle To of continuous oscillating operation variable based on the periodic cycle Tc. As a result, the frequency of a harmonic is distributed.

Self-excited switching power supply circuit

There is provided a self-excited switching power supply circuit which shifts to continuous oscillating operation immediately after the self-excited switching power supply circuit is connected to an AC power supply and started and which does not cause start-up failure while using a start-up resistor of a high resistance value to maintain standby power consumption at a low level. A bypass charging circuit connected in series to a start-up resistor is connected between a high-voltage side terminal of a DC input power supply and the gate of an oscillation field effect transistor. A charging current flowing in the start-up resistor, and additionally, a charging current to charge a start-up capacitor through the bypass charging circuit flow in a transitional period during which the voltage of the DC input power supply increases.

In a synchronous rectification switching power supply circuit, a primary winding of a transformer and a main switching device are serially connected to a direct current input power supply. A secondary winding and a synchronous rectification device on the secondary side are serially connected between output terminals. A power supply apparatus has a capacitor charged with a voltage across the winding on the secondary side of the transformer by turning the main switching device on and off. An electronic instrument, to which the power supply apparatus is connected, has a control IC which sends a control signal to the gate terminal of the synchronous rectification device. When the synchronous rectification device is turned on, the output capacitor is charged and the direct current input power supply recovers power from the output capacitor through the transformer, thereby supplying output electric power set by the control IC to the electronic instrument.

Synchronous rectifying switching power source circuit

The present invention provides a constant voltage output control method and a constant voltage output control device for a switching power supply circuit that allow accurate execution of a constant voltage control of an output voltage, even if there is variation in a utilized circuit element or an integrated circuit. A set voltage Vis obtained based on equation (1),&#x2003;&#x2003;(1) where, Vrepresents an output voltage of a secondary output winding that is subject to the constant voltage control, Np represents a number of turns of a primary winding, and Ns represents a number of turns of the secondary output winding; and the set voltage Vis compared with a flyback voltage Vof the primary winding.

Constant voltage output control method and constant voltage output control device for switching power supply circuit

A self-excited switching power supply circuit is provided which reduces a discharge current generated when an oscillating field effect transistor () is turned on, whereby it is possible to reduce energy loss and generation of noise when switching is executed. A time constant of an ON-control circuit () is set such that when a polarity of a voltage of a feedback winding () has reversed, a gate voltage of the oscillating field effect transistor () exceeds a threshold voltage V. Accordingly, after a voltage of a primary winding () has become equal to or less than a power supply voltage, the oscillating field effect transistor () is turned on, and electrical charge stored in stray capacitance between the windings of the primary winding () and in parasitic capacitance of the oscillating field effect transistor () is discharged gradually.

A constant current output control method and device for a switching power supply circuit for constant current output control of an output current Iof a rectifying smoothing. An OFF adjustment time Tis:&#xd7;(&#xf7;2&#x2212;1)&#x2212;&#x2003;&#x2003;(1)

Constant current output control method and constant current output control device for switching power supply circuit

An intermittent switching power supply circuit prevents excessive output power on a secondary side of a circuit. An intermittent oscillator is alternately switched on and off to maintain output voltage and/or current roughly constant. An output power monitoring circuit monitors output power from a rectifying/smoothing circuit. A control circuit outputs a stop control signal to an control terminal of the intermittent oscillator when the output power monitoring circuit determines that the output voltage and/or current exceeds a reference value. The protection circuit and a photocoupler receiver element are connected in parallel with the control circuit. Where a circuit error occurs and the photocoupler receiver element fails to cycle the intermittent oscillator between active and inactive conditions for a predetermined time, the protection circuit provides a backup which outputs a stop control signal to stop oscillation of the intermittent oscillator element.

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Tokyo, Japan

Toshihiro Amei