33results about How to "Improve EMI" patented technology

The invention discloses a non-complementary flyback active clamp converter. The non-complementary flyback active clamp converter comprises a transformer, a main switching tube, a clamp switching tube, a clamp capacitor and a drive module. The drive module outputs main drive signals to the drive end of the main switching tube, and the driving signals are used for controlling the main switching tube to be alternately switched on and switched off. The drive module outputs clamp drive signals to the drive end of the clamp switching tube. The clamp drive signals and the main drive signals have the same period. Each period comprises a first pulse signal which is generated when the switching-on state of the main switching tube is converted to the switching-off state, a second pulse signal which is generated when the main switching tube is in the switching-off state, and a signal which is generated at the remaining time and used for controlling the switching-on and the switching-off of the clamp switching tube, wherein the first pulse signal and the second pulse signal are independent of each other and both used for controlling the switching-on and the switching-off of the clamp switching tube. By the adoption of the non-complementary flyback active clamp converter, it is guaranteed that a high-frequency current generated when the clamp capacitor is charged fully flows through the clamp switching tube and avoids a backward diode of the clamp switching tube.

A switching controller having switching frequency hopping for a power converter includes an oscillator generating a pulse signal for determining a switching frequency of a switching signal, a maximum duty-cycle circuit generating a maximum duty-cycle signal in response to the switching signal for determining the switching frequency of the switching signal, a pattern generator generating a digital pattern code in response to a clock signal, a programmable capacitor coupled to the pattern generator and the oscillator for modulating the switching frequency of the switching signal in response to the digital pattern code, and a PWM circuit coupled to the oscillator and the maximum duty-cycle circuit for generating the switching signal in accordance with the pulse signal and the maximum duty-cycle signal. A maximum on-time of the switching signal is limited by the maximum duty-cycle signal. The switching signal is utilized to switch a transformer of the power converter.

The invention discloses an LED (Light Emitting Diode) constant-current driving circuit. The LED constant-current driving circuit comprises a voltage reference unit which is used for generating the reference voltage, a peak current detection keeping unit, an error amplifier unit, a current comparator unit, a demagnetization detection unit and a self-adaptive unit. According to the LED constant-current driving circuit disclosed by the invention, the LED constant-current control can be realized, the service life of an LED can be prolonged, the problem of CTR (Current Transmission Rate) attenuation of an optical coupler is overcome as the circuit is free from an optical coupler device, the stability of the circuit is increased, the EMI (Electro Magnetic Interference) and the harmonic distortion can be greatly improved as the switching frequency of a power switching tube of the circuit is a variable frequency, an external circuit can be greatly simplified by adopting the circuit, and the using cost can be greatly reduced.

The invention discloses a quasi-resonant mode switching power supply controller and a control method thereof. The controller comprises a zero-crossing detection circuit which samples zero-crossing points and generates zero-crossing signals; a valley bottom conduction logic circuit which receives the zero-crossing signal and the maximum frequency signal, generates the valley bottom opening signal,and decides whether to select a new valley bottom for latching according to the preset judgment logic; a PWM logic control circuit which receives a valley bottom opening signal and a minimum frequencysignal, thereby controlling the PWM signal to be turned on, and controlling the PWM signal to be turned off according to the FB voltage signal and the CS voltage signal; and a time setting circuit which receives the PWM signal and the FB voltage signal, generates a maximum frequency signal and a minimum frequency signal, and thereby controlling the maximum frequency and the minimum frequency of the PWM operation. The invention not only can eliminate the audio noise caused by the continuous switching of adjacent valleys when the quasi-resonant mode operates, but also can improve the EMI, and has high use and popularization value.

The invention belongs to the technical field of power management chips, and particularly relates to a high-precision oscillator circuit with jitter frequency and slope compensation applied to a switching power supply. A zero temperature coefficient current source generated by a reference current source is adopted to charge and discharge a capacitor, and a three-bit digital frequency modulation technology is utilized to change the frequency of an output oscillator by changing a charging mirror current; the total capacitance is changed by using the jitter frequency capacitance to improve EMI; and the slope compensation module is formed by adopting source negative feedback and can adjust the slope. On the basis of the high-precision output frequency of a traditional oscillator, the output frequency can be linearly switched within a wide range, slope-adjustable slope compensation current triangular wave signals are provided for a modulation circuit, the output of the oscillator can be trimmed within a certain range, and the output frequency of the oscillator can be adjusted within a certain range. And the requirements on the stability and high precision of the clock signal in a power management chip circuit are met.

The invention provides a lens drive device which comprises a fixed part, a movable part and a drive part for driving the movable part to move relative to the fixed part. The drive part comprises a plurality of magnets, wherein the magnets are fixed on the fixed part or the movable part, arranged along the circumferential direction of a lens and polarized along the radial direction of the lens; each magnet is divided into a plurality of layers along the axial direction of the lens, and the polarization directions of every two adjacent layers are opposite, thereby leading the magnets to form a magnetic loop in an axial plane of the parallel lenses; and the polarization directions of the corresponding layers of at least two adjacent magnets are opposite, thereby leading the two adjacent magnets to form the magnetic loop together. The drive part also comprises at least two coils fixed in the fixed part or the movable part, wherein each coil comprises the two adjacent layers respectively towards the corresponding magnets along the axial direction of the lens. Each coil is simultaneously positioned in a plurality of magnetic loops, thereby greatly reinforcing the intensity of a magneticfield in which the coils are positioned, reducing magnetic flux leakage, improving EMI and increasing the utilization ratio of the magnetic field.

The invention provides a switching power supply. The switching power supply includes an inductor and a main switch which is controlled for conduction or turn-off so as to enable the switching power supply to output the output voltage. The switching power supply also includes a first branch circuit which is in parallel connection with the inductor, a detection module, and a logic module, wherein the first branch circuit includes a first switch and a ringing inhibition resistor which are connected in series; the connection node between the inductor and the main switch is marked as a switching node; an input terminal of the detection module is directly or indirectly coupled with the switching node, and the detection module is suitable for detecting whether the reduction amplitude of the voltage of the switching node in the preset time exceeds the threshold-voltage, and an output terminal of the detection module outputs the detection result; and a first input terminal of the logic module is coupled with the output terminal of the detection module, and a second input terminal of the logic module is coupled with a control terminal of the main switch, so that when the main switch is controlled to be turned off and the detection result indicates that the reduction amplitude of the voltage of the switching node in the preset time exceeds the threshold-voltage, the logic module controls the first switch to be conducted until the main switch is controlled to be conducted, or the logic module controls the first switch to be turned off. The switching power supply can inhibit ringing, and is low in cost and high in stability.

The invention discloses a double-output DC-DC oscillator circuit. When reference voltage VR1 and an enable signal EN are added, an internal oscillation circuit generates square signals V1 and V2 which are fixed and identical in frequency and opposite in phase, two channels of narrow-pulse signals V3 and V4 with the phase difference of 180 degrees are generated by the aid of two pulse generating circuits, the two channels of narrow-pulse signals can be directly used as output signals of the circuit to trigger switching on of a switching tube, two channels of sawtooth signals V5 and V6 with the phase difference of 180 degrees are generated by the aid of a sawtooth wave generating circuit under the action of input voltage VIN, reference voltage VR2 and the enable signal EN respectively to be used as the other kind of output signals of the circuit, the RMS current of double channels of DC-DC input is effectively decreased, and the interference between two channels of output is eliminated. A ramp voltage signal is provided by a sawtooth wave generating unit of the oscillator circuit, and the ramp voltage signal capable of realizing ramp low-level control and input voltage feed-forward control enhances the stability of a voltage-mode loop.

The invention discloses a cascade circuit and a control method thereof, the cascade circuit comprises a pre-stage buck-boost circuit and a post-stage isolation switch power supply circuit, the buck-boost circuit comprises switch tubes Q1 to Q4, an inductor L and a capacitor C1; one end of the switching tube Q1 serves as the positive input of the buck-boost circuit, the other end of the switching tube Q1 is connected with one end of the switching tube Q2 and one end of the inductor L, the other end of the inductor L, one end of the switching tube Q4 and one end of the capacitor C1 are connected together to serve as the positive output of the buck-boost circuit, and the other end of the capacitor C1 is connected with one end of the switching tube Q3. And the other end of the switching tube Q2, the other end of the switching tube Q4 and the other end of the switching tube Q3 are connected together to form an input power ground of the buck-boost circuit. According to the invention, the switching tube Q4 and the active clamping circuit formed by the switching tube Q3 and the capacitor C1 are combined with a buck-boost control method, so that the device type selection, EMI and efficiency of the switching tube are greatly optimized, and the cost and the size are reduced.

The invention discloses an EMI-ameliorated transformer, comprising a winding frame, primary windings, secondary windings and an auxiliary winding, wherein the primary windings are wound on the winding frame and coupled to an input circuit, the secondary windings are wound on the winding frame and coupled to an output circuit, and the auxiliary winding is wound on the winding frame, is sandwiched between the secondary windings and is coupled to the input circuit. The EMI-ameliorated transformer has the beneficial effect that the auxiliary winding is arranged between the secondary windings so that a good flying capacitor effect can be formed between the primary windings and the secondary windings and thus EMI is ameliorated.

The invention belongs to the technical field of integrated circuits and discloses a gate driving circuit. The device comprises a power tube conduction circuit, a power tube turn-off circuit and at least one light load marking circuit; the input ends of the power tube conduction circuit, the power tube turn-off circuit and the light load marking circuits can be connected with a main control chip; the output ends of the power tube conduction circuit, the power tube turn-off circuit and the light load marking circuits can be connected with the grid driving end of a power switch tube; each light load marking circuit is connected with the power tube turn-off circuit; and each light load marking circuit generates a second power tube turn-off signal when the current working state of a switching power source circuit is a light load state, wherein the second power tube turn-off signal and first a power tube turn-off signal can jointly control the turn-off of the power switch tube. The inventionalso discloses a switching power source circuit. With the gate driving circuit provided by the invention adopted, full-load EMI and light-load standby power consumption can be well balanced.

The invention relates to a cloth filling anti-stripping method, and belongs to the field of optical systems and electronics precision mechanical structures. In order to solve the problem that an existing sealing method uses a self-adhesive tape for sealing, and is poor in reliability, particularly to applications to aerospace engineering, a conductive adhesive tape has a precipitation phenomenon of a gum after high and low temperature bonding. The cloth filling anti-stripping method comprises the following steps that 1, long strip-shaped cloth is selected, and flanging sewing on two long sidesof the cloth is conducted by using a line to form a concave long cloth strip; and 2, a gap is filled with the long cloth strip formed in the step 1, and during filling, after the gap is filled, a non-concave part of the concave long cloth strip needs to keep outside the gap with the thickness larger than the width of the gap. The cloth used for sewing is made of conductive fabric, cotton cloth and the like. The sealing method does not use adhesives, and relies on a physical structure of the cloth to fill the gap. The gap may be an irregular geometry. If special requirements exist, the cloth may adopt the conductive fabric.

The invention belongs to the technical field of power semiconductors, and relates to a super-junction VDMOS. According to the super-junction VDMOS capable of improving EMI provided by the invention, asecond conductive type semiconductor voltage-withstanding columns with different lengths are introduced into a drift region, so that the longitudinal broadening of a depletion layer between the gateand the drain of a super-junction device is relieved, and the Cgd capacitance value is increased when Vds is smaller, so that a Cgd-Vds curve is flatter. Effective alleviation of voltage and current overshoot is realized. Therefore, the problem of electromagnetic interference of the device can be relieved on the basis of ensuring the original basic electrical properties of the super-junction VDMOS.

The invention discloses a voltage absorption circuit comprising an input circuit, an absorption circuit and a control circuit, wherein the absorption circuit comprises a resonance circuit and a rectification circuit that are connected with each other in parallel. An input end of the input circuit is used for receiving input voltage; an output end of the input circuit is connected with an input end of the resonance circuit, an input end of the rectification circuit and a control end of the control circuit; the input circuit is used for providing input voltage for the voltage absorption circuit, the resonance circuit is used for absorbing peak voltage which is generated by the rectification circuit when the control circuit is switched from an off state to an on state, and the resonance circuit is also used for absorbing peak voltage which is generated when the control circuit is switched from the on state to the off state. Via adoption of the voltage absorption circuit, the peak voltage can be absorbed in a lossless manner, and energy conversion efficiency can be improved.

The invention discloses a cloth-filling anti-detaching method, belongs to the field of optical system and electronics precise mechanical structure, and aims to solve the problems that the existing sealing method is to use an adhesive tape to seal, is poor in reliability, and particularly, when the adhesive tape is applied to the aerospace engineering, the spliced gum of the electric conducting adhesive tape after high and low temperature can be separated out. The cloth-filling anti-detaching method comprises the following steps: step 1, selecting strip-shaped cloth, utilizing a thread to carry out edge sewing on the two long sides of the cloth to form a concave long strip; step 2, utilizing the long strip formed in the step 1 to fill a gap, during the filling process, enabling the non-concave part of the concave long strip to be kept on the outer side of the gap after the gap is filled, and keeping the thickness greater than the width of the gap. The cloth adopted for sewing is selected from a conductive fabric, cotton cloth and the like. The sealing method disclosed by the invention avoids the use of glue, and the gap is filled with cloth by virtue of the physical structure of the cloth; the gap can be in irregularly geometric shape; if the special requirement is required, the conductive fabric can be used as the cloth.