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.

Embodiments of the present application provide a bilateral feedback control method and a bilateral feedback device. The bilateral feedback control method is applied to a bilateral feedback architecture. The method includes: judging the timing stage of the circuit according to the voltage change on the transformer winding. When the feedback signal of the primary circuit is received, the primary controller controls the main switching tube according to the current timing stage when the feedback signal is detected and the voltage change signal of the secondary circuit fed back. This application adopts the logic control method of bilateral feedback to the bilateral feedback architecture, which can reduce the secondary output ripple, improve the dynamic response and no-load power consumption, reduce the power consumption of the main switch when it is turned on, and improve EMI; it can also realize variable voltage output etc.

The invention discloses a control method of a flyback converter. By adding clamping diodes, auxiliary capacitors and auxiliary clamping tubes to the clamping circuit of the flyback converter, and using the main switch drive signal, the main clamp drive signal and the The auxiliary clamp driving signal respectively drives the main switching tube, the main clamping tube and the auxiliary clamping tube, and in the first period, the setting of the main clamping driving signal is gradually increased from low level to high level, so that the flyback conversion The transformer works intermittently according to the alternating cycle of working time and non-working time. During the working time, the three switching tubes are in the intermittent working mode, and all of them can realize zero-voltage switching; moreover, the clamping diode can be used to clamp the transformer , to eliminate oscillation during the second and seventh periods of working time and non-working hours; and, the present invention can prevent the drain-source voltage of the main switching tube from changing abruptly in the first period, avoiding the main switching tube in the prior art. There is a problem with a large current spike when entering the active phase.

The present invention proposes a quasi-resonance device for a switching power supply, including: a sampling module for sampling the secondary degaussing time Tds of the transformer according to the feedback signal Vsen output by the switching power supply voltage after the switch tube of the quasi-resonance module in the switching power supply is turned off; The valley sampling module is used to sample the resonance valley signal of the quasi-resonance module according to Vsen; the fixed ratio time generation module is connected with the sampling module, and is used to generate time T with a preset ratio by processing Tds; the logic processing module, the logic processing module They are respectively connected to the valley bottom sampling module and the fixed-proportion time generation module, and are used to obtain the first valley bottom signal as a switch signal after time T to turn on the switch tube. The device can improve efficiency, improve electromagnetic interference, reduce cost, and avoid switching loss and noise. The invention also provides a quasi-resonance system for switching power supply and a quasi-resonance control method for switching power supply.

The invention provides a lens driving device, which comprises a fixed part, a moving part and a driving part; the fixed part comprises an iron case; the moving part comprises a lens bracket; the driviThe invention provides a lens driving device, which comprises a fixed part, a moving part and a driving part; the fixed part comprises an iron case; the moving part comprises a lens bracket; the driving part comprises a plurality of magnetic irons which are fixed on one of the iron case and the lens bracket; the plurality of magnetic irons are divided into at least two layers along the axial direcng part comprises a plurality of magnetic irons which are fixed on one of the iron case and the lens bracket; the plurality of magnetic irons are divided into at least two layers along the axial direction of the lens, and divided into a plurality of groups along the circumferential direction of the lens; each magnetic iron is polarized along the radial direction of the lens; the magnetic irons oftion of the lens, and divided into a plurality of groups along the circumferential direction of the lens; each magnetic iron is polarized along the radial direction of the lens; the magnetic irons ofeach layer form 2N magnetic poles, a plurality of magnetic loops are formed on a plane which is vertical to the axial direction of the lens, and N is an integral number which is not less than 1; the peach layer form 2N magnetic poles, a plurality of magnetic loops are formed on a plane which is vertical to the axial direction of the lens, and N is an integral number which is not less than 1; the polarities of two adjacent magnetic irons in one group are opposite, thus forming a magnetic loop on the plane which is parallel to the axial direction of the lens; and the driving part also comprisesolarities of two adjacent magnetic irons in one group are opposite, thus forming a magnetic loop on the plane which is parallel to the axial direction of the lens; and the driving part also comprisesat least two coils which correspond to the plurality of magnetic irons and are fixed on one of the iron case and the lens bracket. As each coil is positioned in a plurality of magnetic loops, the magnat least two coils which correspond to the plurality of magnetic irons and are fixed on one of the iron case and the lens bracket. As each coil is positioned in a plurality of magnetic loops, the magnetic density where the coils are positioned is greatly strengthened, the magnetic leakage is reduced, the EMI is improved and the magnetic field utilization ratio is increased.etic density where the coils are positioned is greatly strengthened, the magnetic leakage is reduced, the EMI is improved and the magnetic field utilization ratio is increased.

The invention discloses a clamp circuit of an active clamp flyback converter and a control method thereof. By connecting a switch unit with good reverse recovery characteristics in series in a clamp capacitor discharge circuit, when the main switch tube is turned off, when the main switch tube is turned off, After the resonant current is reduced to zero, the resonant current only generates a negative current and the switch unit can be turned off, so as to prevent the energy stored in the clamping capacitor from being accidentally released during the turn-off of the main switch. It can improve the efficiency of the flyback converter and improve the EMI of the flyback converter by solving the problem of the resonant period change caused by the recovery.

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 lens driving device, which comprises a fixed part, a moving part and a driving part used for driving the moving part to move relative to the fixed part; the fixed part comprises an iron case; the moving part comprises a lens bracket used for holding the lens; the driving part comprises a plurality of magnetic groups which are arranged along the circumferential direction ofthe lens; the magnetic groups are fixed on one of the iron case and the lens bracket; each magnetic group comprises at least two magnetic irons which are superposed along the axial direction of the lens; each magnetic iron is polarized along the radial direction of the lens; the polarities of two adjacent magnetic irons in one group are opposite; the driving part also comprises at least one coilwhich is fixed on one of the iron case and the lens bracket and faces to the magnetic groups; and the winding center of the coil is vertical to the axial direction of the lens. As adjacent magnetic irons in one group form a magnetic loop and pass through the coil, and each magnetic loop is short and has smaller magnetic resistance, the magnetic density where the coil is positioned is greatly strengthened, the magnetic leakage is reduced, the EMI is improved and the magnetic field utilization ratio is increased.

The invention discloses a flyback converter and a control method thereof. By adding a clamping diode, an auxiliary capacitor and an auxiliary clamping tube in the clamping circuit, and using the main switch drive signal, the main clamp drive signal and the auxiliary clamp drive The signals are driven separately, so that the flyback converter works intermittently according to the alternating cycle of working time and non-working time. During the working time, the three switching tubes are in the intermittent working mode, and all can realize zero-voltage switching; and, in the working time In the sixth period of time, the leakage inductance energy of the transformer can be recovered to improve the efficiency of the flyback converter; moreover, the clamp diode can be used to clamp the transformer, so that the second and seventh periods of the working time and the non-working time Eliminate oscillation; therefore, the present invention improves the efficiency of the flyback converter and reduces the frequency of the flyback converter on the premise that each switching tube in the flyback converter can realize zero-voltage switching during the whole working process. Oscillation during work, optimized for EMI.

The invention discloses an active clamp flyback converter and a control method thereof, comprising a main power circuit, a main clamp circuit, an auxiliary clamp circuit and an output rectifying and filtering circuit; wherein, the main power circuit consists of a transformer and a main switching tube The main clamping circuit is formed by connecting the main clamping switch tube and the main clamping capacitor; the auxiliary clamping circuit is formed by connecting the auxiliary clamping switch tube, auxiliary clamping capacitor and auxiliary clamping diode; the output rectification filter The circuit is formed by connecting the output rectifier diode and the output capacitor; in the continuous working state, the driving mode is: the main clamping switch tube and the main switching tube are complementary driven, and the auxiliary clamping switch tube is not driven; in the intermittent working state, the driving mode is The mode is: the main clamp switch tube and the main switch tube are driven non-complementarily, and the auxiliary clamp switch tube and the main switch tube are driven complementary. Compared with the prior art, the invention has a wide input voltage range, realizes zero-voltage turn-on of all switch tubes, improves circuit working efficiency, and improves circuit EMI.

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.