Abstract: A method for improving the conversion efficiency of a CCM mode of a flyback resonant switch power supply, comprising: presetting a critical value Tset, calculating a time interval Ttap between adjacent zero points in the current connection time, outputting a shutdown signal at the zero points, and comparing the time interval Ttap with the preset critical value Tset; when Ttap>Tset, controlling the current shutdown time to be less than the shutdown time of the preceding cycle and outputting a start signal; when Ttap=0, controlling the current shutdown time to be greater than the shutdown time of the preceding cycle and outputting a start signal; and when 0<Ttap<=Tset, controlling the current shutdown time to be the same as the shutdown time of the preceding switch cycle and outputting a start signal.

Abstract: A power semiconductor device includes a substrate; drain metal; a drift region; a base region; a gate structure; a first conductive type doped region contacting the base region on the side of the base region distant from the gate structure; a source region provided in the base region and between the first conductive type doped region and the gate structure; contact metal that is provided on the first conductive type doped region and forms a contact barrier having rectifying characteristics together with the first conductive type doped region below; and source metal wrapping the contact metal and contacting the source region.

Abstract: A flyback converter and an output voltage acquisition method therefor and apparatus thereof, wherein the output voltage acquisition method comprises the following steps: acquiring the reference output voltage of a flyback converter; sampling the current output voltage of the flyback converter within a reset time of each switching period among M continuous switching periods of the flyback converter, wherein M is a positive integer; and according to the reference output voltage and the current output voltage, sampling a dichotomy to successively approximate the current output voltage until the M switching periods are finished, and acquiring the output voltage of the flyback converter.

Abstract: A heterojunction semiconductor device with a low on-resistance includes a metal drain electrode, a substrate, and a buffer layer. A current blocking layer arranged in the buffer layer, a gate structure is arranged on the buffer layer, and the gate structure comprises a metal gate electrode, GaN pillars and AlGaN layers, wherein a metal source electrode is arranged above the metal gate electrode; and the current blocking layer comprises multiple levels of current blocking layers, the centers of symmetry of the layers are collinear, and annular inner openings of the current blocking layers at all levels gradually become smaller from top to bottom. The AlGaN layers and the GaN pillars are distributed in a honeycomb above the buffer layer.

Abstract: Disclosed are a system and method for controlling an active clamp flyback (ACF) converter. The system includes: a drive module configured to control turning-on or turning-off of a main switching transistor SL and a clamp switching transistor SH; a main switching transistor voltage sampling circuit configured to sample a voltage drop between an input terminal and an output terminal of the main switching transistor SL; a first comparator connected to the main switching transistor voltage sampling circuit and configured to determine whether a sampled first sampling voltage is a positive voltage or a negative voltage; and a dead time calculation module configured to adjust, according to an output of the first comparator and a main switching transistor control signal DUTYL of a current cycle, a clamp switching transistor control signal DUTYH of next cycle outputted by the drive module.

Abstract: A synchronous rectification control system and method for a quasi-resonant flyback converter are provided. The control system includes a switching transistor voltage sampling circuit configured to sample an output terminal voltage of the switching transistor to obtain a sampled voltage of the switching transistor; a sampling calculation module configured to obtain a dead-time based on the sampled voltage of the switching transistor and a preset relationship, the preset relationship being a correspondence between the duration of the sampled voltage of the switching transistor being below a first preset value and the dead-time during an on-time of a switching cycle of the switching transistor, the dead-time being a time from when the switching transistor is turned off to when the synchronous rectification transistor is turned on; and a control module configured to receive the dead-time and control switching of the synchronous rectification transistor based on the dead-time.

Abstract: The invention provides a graphene channel silicon carbide power semiconductor transistor, and its cellular structure thereof. Characterized in that, a graphene strip serving as a channel is embedded in a surface of the P-type body region and two ends of the graphene strip are respectively contacted with a boundary between the N+-type source region and the P-type body region and a boundary between the P-type body region and the N-type drift region, and the graphene strip is distributed in a cellular manner in a gate width direction, a conducting channel of a device is still made of graphene; in the case of maintaining basically invariable on-resistance and current transmission capacity, the P-type body regions are separated by the graphene strip, thus enhancing a function of assisting depletion, which further reduces an overall off-state leakage current of the device, and improves a breakdown voltage.

Abstract: The invention provides a graphene channel silicon carbide power semiconductor transistor, and its cellular structure thereof. Characterized in that, a graphene strip serving as a channel is embedded in a surface of the P-type body region and two ends of the graphene strip are respectively contacted with a boundary between the N+-type source region and the P-type body region and a boundary between the P-type body region and the N-type drift region, and the graphene strip is distributed in a cellular manner in a gate width direction, a conducting channel of a device is still made of graphene; in the case of maintaining basically invariable on-resistance and current transmission capacity, the P-type body regions are separated by the graphene strip, thus enhancing a function of assisting depletion, which further reduces an overall off-state leakage current of the device, and improves a breakdown voltage.

Abstract: The present invention discloses a gate drive circuit for reducing a reverse recovery current of a power device, and belongs to the field of basic electronic circuit technologies. The gate drive circuit includes a high-voltage LDMOS transistor, a diode forming a freewheeling path when the diode is turned on or a low-voltage MOS transistor in anti-parallel connection with a body diode, and a voltage detection circuit.

Abstract: The invention discloses a self-adaptive synchronous rectification control system and a self-adaptive synchronous rectification control method of an active clamp flyback converter. The control system comprises a sampling and signal processing circuit, a control circuit with a microcontroller as a core and a gate driver. According to the control method, a switching-on state, an early switching-off state, a late switching-off state and an exact switching-off state of a secondary synchronous rectifier of the active clamp flyback converter can be directly detected, and the synchronous rectifier and a switching-on time of the synchronous rectifier in next cycle can be controlled according to a detection result. After several cycles of self-adaptive control, the synchronous rectifier enters the exact switching-on state, thus avoiding oscillation of an output waveform of the active clamp flyback converter.

Abstract: A heterojunction semiconductor device comprises a substrate; a second barrier layer is disposed on the second channel layer and a second channel is formed; a trench gate structure is disposed in the second barrier layer; the trench gate structure is embedded into the second barrier layer and is composed of a gate medium and a gate metal located in the gate medium; an isolation layer is disposed in the second channel layer and separates the second channel layer into an upper layer and a lower layer; a first barrier layer is disposed between the lower layer of the second channel layer and the first channel layer and a first channel is formed; a bottom of the metal drain is flush with a bottom of the first barrier layer; and a first metal source is disposed between the second metal source and the first channel layer.

Abstract: The present invention discloses a gate drive circuit for reducing a reverse recovery current of a power device, and belongs to the field of basic electronic circuit technologies. The gate drive circuit includes a high-voltage LDMOS transistor, a diode forming a freewheeling path when the diode is turned on or a low-voltage MOS transistor in anti-parallel connection with a body diode, and a voltage detection circuit.

Abstract: The invention discloses a self-adaptive synchronous rectification control system and a self-adaptive synchronous rectification control method of an active clamp flyback converter. The control system comprises a sampling and signal processing circuit, a control circuit with a microcontroller as a core and a gate driver. According to the control method, a switching-on state, an early switching-off state, a late switching-off state and an exact switching-off state of a secondary synchronous rectifier of the active clamp flyback converter can be directly detected, and the synchronous rectifier and a switching-on time of the synchronous rectifier in next cycle can be controlled according to a detection result. After several cycles of self-adaptive control, the synchronous rectifier enters the exact switching-on state, thus avoiding oscillation of an output waveform of the active clamp flyback converter.

Abstract: A method and an apparatus for reducing noise of a switched reluctance motor, includes: supplying a PWM signal as a driving signal to a driving circuit of a switched reluctance motor; and varying a carrier frequency of the PWM signal as an operation period of the switched reluctance motor varies; if the switched reluctance motor changes phase, determining that the operation period of the switched reluctance motor varies.

Abstract: An automatic dead zone time optimization system in a primary-side regulation flyback power supply CCM mode, comprising a closed loop formed by a control system, consisting of a single output DAC midpoint sampling module, a digital control module, a current detection module, a dead zone time calculation module and a PWM driving module, and a controlled synchronous rectification primary-side regulation flyback converter. By means of a DAC Sampling mechanism, a primary-side current is sampled to calculate a secondary-side average current, so as to obtain a primary-side average current Imid_p and a secondary-side average current Is(tmid) in the case of CCM; a secondary-side current is input into the dead zone time calculation module to obtain a reasonable dead zone time td; and finally, the PWM driving module is jointly controlled by a primary-side regulation loop and the obtained dead zone time td.

Abstract: A method for improving the conversion efficiency of a CCM mode of a flyback resonant switch power supply, comprising: presetting a threshold value Tset, calculating a time interval Ttap between adjacent zero points during a present conducting time, outputting a switch-off signal at zero points, and comparing the time interval Ttap with the preset threshold value Tset; when Ttap>Tset, he present switch-off time to be less than a switch-off time of a previous cycle, outputting a switch-on signal; when Ttap=0, controlling the present switch-off time to be greater than a switch-off time of the previous cycle, outputting a switch-on signal; and when 0<Ttap<=Tset, controlling the present switch-off time to be the same as the switch-off time of the previous switch cycle, outputting a switch-on signal.

Abstract: Provided is a dynamic control method that turns off a primary-side switching transistor when an output voltage exceeds an upper limit, and control the switching of a secondary-side synchronous rectification transistor with a fixed cycle and a fixed duty cycle. During the time that the synchronous rectification transistor is turned on, the energy of a load capacitor at the output end is extracted to the primary side, which causes the output voltage to drop rapidly and the overshoot voltage to decrease greatly.

Abstract: Parasitic high-voltage diodes implemented by integration technology in a high-voltage level shift circuit are used for charging a bootstrap capacitor CB, wherein a power supply end of the high voltage level shift circuit is a high-side floating power supply VB, and a reference ground is a floating voltage PGD that is controlled by a bootstrap control circuit. A first parasitic diode DB1 and a second parasitic diode DB2 are provided between the VB and the PGD. The bootstrap control circuit is controlled by a high-side signal and a low-side signal.

Abstract: A control method for improving dynamic response of switch power is based on a closed-loop control system comprising a sampling module, a dynamic control module, an error calculation module, a PID module, a mode control module, and a PWM module. The sampling module samples an output voltage Vo, and the dynamic control module compares the output voltage Vo with a set maximum voltage Vomax, a set minimum voltage Vomin, and a reference voltage Vref, so as to determine whether to adopt a dynamic mode. In the dynamic mode, when the output voltage Vo changes greatly, the output voltage Vo is rapidly restored to a stable voltage by inputting large power or small power.

Abstract: Parasitic high-voltage diodes implemented by integration technology in a high-voltage level shift circuit are used for charging a bootstrap capacitor CB, wherein a power supply end of the high voltage level shift circuit is a high-side floating power supply VB, and a reference ground is a floating voltage PGD that is controlled by a bootstrap control circuit. A first parasitic diode DB1 and a second parasitic diode DB2 are provided between the VB and the PGD. The bootstrap control circuit is controlled by a high-side signal and a low-side signal.