Fuji Electric Co., Ltd.

Fuji Electric Systems Co. Ltd.

Fuji Electronic Co., Ltd.

Jian Chen

Jun Yabuzaki

Koji Sonobe

Masayuki Yamadaya

Tsuyoshi Yoshizawa

YoshinorI Kobayashi

Kiminori Tanaka

Koji Murata

A detection circuit including a temperature voltage generator circuit and an output circuit. The temperature voltage generator circuit generates a detection voltage corresponding to a temperature of the detection circuit based on a predetermined constant current, when a pulse signal received by the detection circuit is at a first level, and stop generating the detection voltage when the pulse signal is at a second level. The output circuit outputs a detection signal indicating whether the temperature is higher than a predetermined temperature based on the detection voltage, during a period of time between a first time that is a predetermined time period after the pulse signal reaches the first level and a second time at which the pulse signal switches from the first level to the second level, the pulse signal remaining in the first level in the period of time.

Detection circuit, switching control circuit, and power supply circuit

A switching control circuit for controlling a power supply circuit having a transformer and a transistor. The switching control circuit is configured to operate based on a power supply voltage that corresponds to a voltage from an auxiliary coil of the transformer. The switching control circuit includes a drive signal output circuit that outputs a drive signal that corresponds to an operation mode of the power supply circuit, the operation mode including a burst mode, a drive circuit that performs switching of the transistor based on the drive signal outputted by the drive signal output circuit, and a control circuit that outputs, to the drive signal output circuit, a control signal for operating the power supply circuit in the burst mode, when a first transition condition or a second transition condition is satisfied, the first transition condition including time as a condition, and the second transition condition not including time as a condition.

Switching control circuit and power supply circuit

A switching period in a burst cycle includes three pulses, that is to say, a start pulse that turns on a low-side switching element, a main pulse that turns on a high-side switching element, and an end pulse that turns on the low-side switching element. A burst stop period corresponding to the magnitude of a load is set during a switching stop period. When the burst cycle approaches a cycle corresponding to a frequency close to the upper limit of the audible frequencies, a second off-threshold voltage of the main pulse is made equal to a first off-threshold voltage of the start pulse to narrow the on-width of the main pulse. By doing so, energy transmitted to the secondary side of a transformer is reduced and the burst cycle is shortened.

Burst controller and burst control method of resonance converter

A control apparatus of a current resonance type switching power supply that has a switching element and generates an output voltage. The control apparatus includes a drive circuit configured to generate a drive signal to drive the switching element of the switching power supply, and a soft-start control circuit connected to the drive circuit, the soft-start control circuit being configured to send a signal to the drive circuit to cause the drive circuit to increment an on-width of the drive signal by a prescribed step per prescribed switching number, to thereby reduce an overshoot of the output voltage when the switching power supply is started.

Control apparatus of switching power supply for generating drive signal of incremental on-width

A switching power supply includes a current resonance-type DC-DC converter that has an auxiliary winding provided on the primary side of a transformer, divides a voltage, which has been generated in the auxiliary winding by a current resonance operation, using a voltage divider circuit formed of resistors, and supplies, to a control IC, the divided voltage as a detection voltage for the resonant voltage for setting a timing for turning off a switching element. A phase correcting capacitor is provided between the auxiliary winding and the voltage divider circuit and corrects a delay in switching timing by setting the phase of the voltage of the voltage divider circuit ahead of the voltage of the auxiliary winding.

Switching power supply

A switching power supply controller, including a high-side drive circuit, a low-side drive circuit, a control circuit which supplies a high-side drive signal to the high-side drive circuit, and which supplies a low-side drive signal to the low-side drive circuit, an oscillation circuit which generates an on-trigger signal and an off-trigger signal at a switching frequency corresponding to a voltage signal, and which supplies the on-trigger signal and the off-trigger signal to the control circuit, and a precharge circuit which receives from the control circuit a burst operation signal, indicative of a burst operation in a standby mode, and which supplies for a second period a precharge signal that causes the control circuit to output the low-side drive signal upon detecting that a switching stop period, during which the first voltage signal falls below a threshold voltage, exceeds a first period.

Switching power supply controller

An apparatus for controlling a switching power supply during burst control that includes a switching period and a no switching period. The switching power supply includes first and second switching elements and a resonance circuit. The control apparatus includes a load detecting circuit that shunts and averages a resonance current of the resonance circuit, an off signal generating circuit that generates off signals for turning off the first and second switching elements during the switching period, an on signal generating circuit that obtains a number of resonance cycles of the ringing voltage in the no switching period and generates a first pulse on signal for turning on the second switching element to restart the switching period, and a control circuit that receives the off signals and the first pulse on signal, and generates first and second control signals for alternating on-off control of the first and second switching elements.

Control apparatus for controlling switching power supply

First, it is assumed that a low-side switching element is turned off. At this time a resonance current before-inversion time is counted. When a resonance current is inverted, a count value is held and the counting operation of a resonance current after-inversion time is begun. Next, a target value of the resonance current after-inversion time at which a high-side switching element is to be turned off is calculated based on a feedback signal and the counting operation of the resonance current after-inversion time is continued. When a count value reaches the target value, the counting operation of the resonance current after-inversion time is ended and the high-side switching element is turned off. After a high-side half cycle is controlled, a low-side half cycle is controlled in the same way. Responsiveness to a sudden change in load is improved by exercising control every half cycle.

Switching power supply apparatus control method and control circuit of switching power supply apparatus

A control apparatus for a resonant converter that receives a direct current (DC) voltage of a bulk capacitor. The control apparatus includes a forced turn-off control circuit that receives a resonance current detection signal, which has been produced by shunting a resonance current flowing through the resonant converter and converting the shunted resonance current to a voltage, outputs a forced turn-off signal in response to the resonance current detection signal falling between a first variable threshold and a second variable threshold that is smaller than the first variable threshold, and varies the first variable threshold and the second variable threshold in accordance with an input voltage inputted to the forced turn-off control circuit by dividing the DC voltage of the bulk capacitor.

Control apparatus for resonant converter

A switching power supply device includes a control unit alternately turning a first switching device and a second switching device ON/OFF so as to drive a primary side of a transformer, wherein the control unit includes: a peak power limiting circuit that monitors input power to the primary side of the transformer and outputs a forced turn OFF signal every time the input power becomes higher than a prescribed value; and a switching cycle counter circuit that estimates an output voltage on a secondary side of the transformer by counting a number of times the forced turn OFF signal is outputted by the peak power limiting circuit, and outputs a switching stop signal that causes the alternating turning ON/OFF of the first and second switching devices to stop when the estimated output voltage reaches an overvoltage protection detection voltage.

Switching power supply with output power estimation

A switching power supply apparatus, including a power converting device body configured to switch DC input power through a first switching element to thereby store the DC input power in an inductor, and to transfer the stored power to an output capacitor through a second switching element by use of resonance of the inductor, a control circuit configured to drive the first and second switching elements to alternately turn ON or OFF the two switching elements, to thereby resonate the inductor, and an overload detecting circuit configured to detect a load state of the power converting device body based on a peak value or an effective value of a resonance voltage generated from the resonance of the inductor, to thereby control operation of the control circuit.

Switching power supply apparatus

A switching power supply apparatus, including serially-connected first and second switching elements, a series circuit of a resonant inductance and a resonant capacitor connected in parallel to the first or second switching element, first and second capacitors respectively connected in parallel to the first and second switching elements, and a switching control circuit that alternately turns on the first and second switching elements. The switching control circuit includes a load detection circuit detecting a load state, a burst control circuit that switches to a burst control mode when the load detection circuit detects a light load, and a detection circuit that detects a timing at which a high-side reference voltage at a connection point between the first and second switching elements has a lowest value. The burst control circuit switches from switching stop to switching operation of the first and second switching elements at the detected timing.

Current-resonant type switching power supply apparatus with burst control

A control IC includes a VS voltage detection circuit that indirectly detects input voltage, by utilizing a fact that a voltage of a VS terminal of a reference potential of a high side drive circuit changes to a voltage equivalent to the input voltage when a high side drive signal is output from a control circuit to cause the high side drive circuit to turn on a high side switching element. The VS voltage detection circuit determines the level of the input voltage by sampling the VS terminal voltage at a time point that is delayed by a predetermined time from a rising edge of the high side drive signal, and supplies the determined level to the control circuit.

Switching power supply with input voltage detection at the switching node

A switching power supply device includes an energy storage element which is charged with a voltage generated in an auxiliary winding of a transformer; a switching control circuit to which the terminal voltage of the energy storage element is given as a power supply voltage and which controls the switching operation of a switching element; an initial operation control circuit which, when it is detected that the power supply voltage is lower than a first voltage, causes a current supply circuit to stop the switching operation until the power supply voltage rises to a second voltage; and a switching suppression circuit which, when it is detected that the power supply voltage is lower than a third voltage which is higher than the first voltage and lower than the second voltage, causes the current supply circuit to stop the switching operation for a predetermined period.

Switching power supply device

In a standby signal generation circuit, a first comparator compares a FB voltage fed back from a secondary side with a first reference voltage, and a second comparator compares a signal indicative of the magnitude of a load with a second reference voltage. When the FB voltage falls under the first reference voltage, the first comparator sets an RS flip-flop via a first delay circuit. At this time, if the signal is lower than the second reference voltage and a reset signal is not inputted to the RS flip-flop, it is determined, based on a standby control signal from the load, that an output voltage of a switching power supply apparatus has fallen. Accordingly, a standby signal indicative of standby mode is outputted via a second delay circuit. If the signal transiently exceeds the second reference voltage, the standby signal is set to normal mode.

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Matsumoto, Japan

Jian Chen