Abstract: The present invention relates to the technical field of protein engineering, and, in particular, to a xylanase mutant with improved heat tolerance. The present invention artificially introduces two or three unnatural disulfide bridges into xylanase by site-directed mutagenesis and obtains the mutants XynA1 and XynA2 with improved heat tolerance, especially the mutant XynA2 into which three disulfide bridges are introduced, achieving residual enzyme activity of 75% after treatment at 80° C. for 5 min, 72% higher than the residual enzyme activity of the mutant XynA1. The present invention further obtains, by screening, three mutation sites Q51N, H143K, and Q161F that can significantly increase the heat tolerance of mutants, and introduction of the mutation sites into the XynA1 and XynA2 xylanases, whether at a single point or a combination of two points or a combination of three points, can effectively improve the heat tolerance of the mutants.

Abstract: The present invention relates to the technical field of protein engineering, and, in particular, to a xylanase mutant with improved heat tolerance. The present invention artificially introduces two or three unnatural disulfide bridges into xylanase by site-directed mutagenesis and obtains the mutants XynA1 and XynA2 with improved heat tolerance, especially the mutant XynA2 into which three disulfide bridges are introduced, achieving residual enzyme activity of 75% after treatment at 80° C. for 5 min, 72% higher than the residual enzyme activity of the mutant XynA1. The present invention further obtains, by screening, three mutation sites Q51N, H143K, and Q161F that can significantly increase the heat tolerance of mutants, and introduction of the mutation sites into the XynA1 and XynA2 xylanases, whether at a single point or a combination of two points or a combination of three points, can effectively improve the heat tolerance of the mutants.

Abstract: The present invention relates to the field of genetic engineering, in particular, the present invention relates to a method for producing a phytase variant with an improved thermal stability, and a phytase variant and the use thereof. The phytase variant contains at least one proline modification, compared to the phytase from Escherichia coli and other mutants thereof. The phytase variants with the modification have preferably improved properties, such as the thermal stability, optimal reaction temperature, pH property, specific activity, protease resistance and performance in animal feeds.

Abstract: A zero-crossing voltage detection circuit for detecting a phase voltage of a converter includes a comparator, a first transistor and a second transistor. The first transistor has a first base, a first collector and a first emitter. The first base couples with the first collector. The first emitter receives the phase voltage. The first collector provides a first voltage to a first terminal of the comparator. The second transistor has a second base, a second collector and a second emitter. The second base couples with the first base. The second base couples with the second collector. The second emitter receives a ground voltage. The second collector provides a second voltage to a second terminal of the comparator. The comparator compares the first voltage with the second voltage to generate a zero-crossing voltage signal.

Abstract: The present invention relates to the field of genetic engineering, in particular, the present invention relates to a method for producing a phytase variant with an improved thermal stability, and a phytase variant and the use thereof. The phytase variant contains at least one proline modification, compared to the phytase from Escherichia coli and other mutants thereof. The phytase variants with the modification have preferably improved properties, such as the thermal stability, optimal reaction temperature, pH property, specific activity, protease resistance and performance in animal feeds.

Abstract: The present invention provides a constant on time controller packaged in one single package for controlling a buck converting circuit to convert an input voltage into an output voltage. The constant on time controller includes an input voltage detecting circuit, an on-time determining circuit and a driving circuit. The input voltage detecting circuit receives a bootstrap voltage to generate an input voltage detecting signal indicative of the input voltage. The on-time determining circuit receives the input voltage detecting signal and generates an on-time signal in response to the input voltage detecting signal and the output voltage. The driving circuit controls the buck converting circuit according to the n-time signal.

Abstract: A delay circuit includes a current circuit, a first current mirror circuit, a second current mirror circuit, a self-compensation circuit, and a delay capacitor. A fixed ratio is between the first current and the second current provided by the current circuit. The first current mirror circuit generates a first mirror current in response to the first current. A partial current of the second current flowing through the second current mirror circuit is a base current, and the second current mirror circuit generates a second mirror current in response to the base current. The self-compensation circuit generates a feedback current in response to the second mirror current. The delay capacitor generates a delay signal. The charging current is equal to the second current subtracting the base current. The first mirror current is the sum of the base current, the second mirror current, and the feedback current.

Abstract: A DC-DC converter, adapted to control a converting circuit to convert an input voltage into an output voltage, is disclosed. The converting circuit comprises a switch module and an LC filter, the switch module is coupled to the input voltage, and the LC filter is coupled to the switch module and provides the output voltage. The DC-DC converter comprises a system control circuit, a driver circuit, and an output voltage adjusting circuit. The system control circuit generates a switch control signal according to a reference voltage and a state of the LC filter. The driver circuit controls the switch module according to the switch control signal for adjusting the output voltage in response to the reference voltage. The output voltage adjusting circuit determines whether adjusting the output voltage toward a predetermined adjusting voltage according to an adjusting reference voltage and a detecting voltage indicative of the output voltage.

Abstract: A buck converting controller, adapted to control a DC-DC buck converting circuit to convert an input voltage into an output voltage, is disclosed. The buck converting controller comprises a feedback control circuit, an off-time determination circuit and a load control circuit. The feedback control circuit turns on and off a high-side transistor and a low-side transistor of the DC-DC buck converting circuit in response to a feedback signal indicative of the output voltage. The off-time determination circuit determines a preset off-time period according to the input voltage and the output voltage and generates an off notice signal according to the preset off-time period. The load control circuit is coupled to the DC-DC buck converting circuit and determines whether to release an electronic energy stored in the DC-DC buck converting circuit according to the off notice signal.

Abstract: A multiphase converter controller with current balance, configured to control a plural converting circuit to commonly supply an output voltage, is disclosed. The multiphase converter controller comprises a feedback circuit, a fixed on-time circuit, and a multiphase logical circuit. The feedback circuit detects the output voltage to generate a feedback control signal. The fixed on-time circuit generates an on-time signal according to the feedback control signal, and a pulse width of the on-time signal is determined according to a single timer. The multiphase logical circuit chooses a corresponding converting circuit, generates a phase signal according to a sequence of the feedback control signal and controls the corresponding converting circuit according to the on-time signal. Wherein, the fixed on-time circuit determines a correction value according to currents of the plural converting circuit and the phase signal, so as to correct the pulse width of the on-time signal.

Abstract: A level shift circuit and a DC-DC buck converter controller for using the same are disclosed. The level shift circuit is capable of detecting a state of a converting circuit, and avoids a current leakage when determining that the converting circuit is operating under a light-load. Therefore, the level shift circuit and the DC-DC converting controller provided by the present invention can reduce power consumption under the light-load and have power-saving advantage.

Abstract: A zero-crossing voltage detection circuit for detecting a phase voltage of a converter includes a comparator, a first transistor and a second transistor. The first transistor has a first base, a first collector and a first emitter. The first base couples with the first collector. The first emitter receives the phase voltage. The first collector provides a first voltage to a first terminal of the comparator. The second transistor has a second base, a second collector and a second emitter. The second base couples with the first base. The second base couples with the second collector. The second emitter receives a ground voltage. The second collector provides a second voltage to a second terminal of the comparator. The comparator compares the first voltage with the second voltage to generate a zero-crossing voltage signal.

Abstract: A programmable on-time period of a DC to DC buck converting controller is adjusted according to a level of a preset output voltage or a reference signal. Therefore, the DC to DC buck converting controller of the present invention is suitable for any applications with different requests of output voltages or different operating mode.

Abstract: A constant on time control circuit, configured to control a converting circuit to transform an input voltage into a stable output voltage, is disclosed. The constant on time control circuit comprises a comparing circuit and a logic circuit. The comparing circuit compares a reference signal and a voltage signal indicative of the output voltage and accordingly outputs a compared result signal. The logic circuit periodically controls the converting circuit to perform voltage transformation and makes a time period of a duty cycle in every cycle being substantially constant. A start point in time of every cycle is determined according to the compared result signal. The comparing circuit comprises a differential pair, a base current source and an extra current source. The base current source provides a bias current to the differential pair. The extra current source provides a substantial ramp current to one channel in the differential pair.

Abstract: A delay circuit includes a current circuit, a first current mirror circuit, a second current mirror circuit, a self-compensation circuit, and a delay capacitor. A fixed ratio is between the first current and the second current provided by the current circuit. The first current mirror circuit generates a first mirror current in response to the first current. A partial current of the second current flowing through the second current mirror circuit is a base current, and the second current mirror circuit generates a second mirror current in response to the base current. The self-compensation circuit generates a feedback current in response to the second mirror current. The delay capacitor generates a delay signal. The charging current is equal to the second current subtracting the base current. The first mirror current is the sum of the base current, the second mirror current, and the feedback current.

Abstract: A buck converting controller, adapted to control a DC-DC buck converting circuit to convert an input voltage into an output voltage, is disclosed. The buck converting controller comprises a feedback control circuit, an off-time determination circuit and a load control circuit. The feedback control circuit turns on and off a high-side transistor and a low-side transistor of the DC-DC buck converting circuit in response to a feedback signal indicative of the output voltage. The off-time determination circuit determines a preset off-time period according to the input voltage and the output voltage and generates an off notice signal according to the preset off-time period. The load control circuit is coupled to the DC-DC buck converting circuit and determines whether to release an electronic energy stored in the DC-DC buck converting circuit according to the off notice signal.

Abstract: The present invention provides a constant on time controller packaged in one single package for controlling a buck converting circuit to convert an input voltage into an output voltage. The constant on time controller includes an input voltage detecting circuit, an on-time determining circuit and a driving circuit. The input voltage detecting circuit receives a bootstrap voltage to generate an input voltage detecting signal indicative of the input voltage. The on-time determining circuit receives the input voltage detecting signal and generates an on-time signal in response to the input voltage detecting signal and the output voltage. The driving circuit controls the buck converting circuit according to the n-time signal.

Abstract: A level shift circuit and a DC-DC buck converter controller for using the same are disclosed. The level shift circuit is capable of detecting a state of a converting circuit, and avoids a current leakage when determining that the converting circuit is operating under a light-load. Therefore, the level shift circuit and the DC-DC converting controller provided by the present invention can reduce power consumption under the light-load and have power-saving advantage.

Abstract: In a DC-DC converter controller of the present invention, a ramp voltage for compensating a reference voltage is designed to have the same valley value or peak value irrespective of an input voltage and an output voltage of a controlled converting circuit when the controlled converting circuit operates in the steady state. Hence, the DC-DC converter controller of the present invention is capable of controlling the controlled converting circuit to accurately output the output voltage in different applications.

Abstract: A constant on-time controller, comprising a ripple generator, a comparing circuit and a logic control circuit, is provided. The ripple generator generates a ripple signal, which is injected into one of a voltage reference signal and a voltage detection signal to form a ripple modulated signal with ripple information. The comparing circuit compares the ripple modulated signal with the other of the voltage reference signal and the voltage detection signal and accordingly generates a comparison result signal. The logic control circuit generates a control signal with a fixed pulse width according to the comparison result signal. The ripple generator has a level modulation circuit for modulating an amplitude of the ripple modulated signal to make the amplitude within an preset range under different applications.