TWI410031B - Apparatus and method for changing operation mode according to load - Google Patents

Abstract

Apparatus and method for changing operation mode according to load are disclosed. In which the apparatus and method are applicable to a power conversion unit which has a switch component. The apparatus includes a driving control unit and a switch conduction unit, wherein the switch conduction unit has a trough switch unit and a cut-off time restriction unit. The trough switch conduction unit provides trough switch mechanism to the power conversion unit when the load is slight, in order to reduce the switching loss. Additionally, the cut-off time restriction unit is for restricting the cut-off time of the switch. When the cut-off time increases to an upper limit according to the raising load, the cut-off time restriction unit then makes the switch component conducting. So that the power conversion unit can work in continuous conduction mode when the load is heavy, in order to reduce the conduction loss.

Description

Device and method for changing operation mode with load

A device and method for changing the mode of operation, and more particularly to a device and method for changing the mode of operation with load.

Currently, Switched Mode Power Supply (SMPS) is widely used in various electronic products, regardless of the type of power converter. In terms of circuit design and the use of various electronic components, Take into account the loss of energy.

Generally, there are losses caused by switching elements (that is, transistors) in a power converter, mainly switching loss and conduction loss, and with the power converter load (load) The weight and the proportion of switching loss and conduction loss will also be different. In simple terms, when the power converter is in the case of light load, the power consumption of the switching component is mainly focused on switching loss; while the power converter is in the case of low voltage heavy load, the switching component power The focus of the consumption considerations is conduction loss.

Traditional power converters operate in a mode that is generally Discontinuous Conduction Mode (DCM). In the case of light load, since the switching loss is the main consideration, the switching loss is reduced by switching the transistor from off to on at the voltage waveform trough between the drain and the source of the transistor. In the case of heavy load, the conduction loss is the key point, but the power converter in the discontinuous conduction mode operates with a high peak current, so the value of the conduction loss is large, resulting in waste of energy.

In view of the above, the technical problem to be solved by the present invention is to provide a mechanism for the power converter to operate in a discontinuous conduction mode at a light load and a continuous conduction mode at a low voltage and heavy load to reduce the low voltage and heavy load. The conduction loss of the switching elements in the power converter improves the operating efficiency.

In order to achieve the above object, according to an aspect of the present invention, an apparatus for changing an operation mode with a load is provided, which is applied to a power conversion unit including a drive control unit and a switch conduction unit. The power conversion unit has a switching component, which may be a transistor or the like, and the driving control unit is coupled to the power conversion unit for driving the switching element to be turned on or off.

The switch conducting unit is coupled to the power conversion unit and the driving control unit for extracting a detection signal from the power conversion unit, determining the load status of the power conversion unit according to the detection signal, and generating a communication number to control the switch. The conduction of the components enables the power conversion unit to switch modes of operation.

The switch conducting unit includes a cutoff time fixing unit and a valley switching unit. The valley switching unit is configured to capture the voltage across the switching element, and generate a conduction number according to the voltage across the switch, so that the switching element can switch at a valley of the voltage across the voltage waveform, so that the power conversion unit operates at light load. In the discontinuous conduction mode (DCM), it can have lower switching losses.

The cut-off time fixed unit is used to limit the cut-off time of the switching element, and the power conversion unit enters the Continuous Conduction Mode (CCM) to reduce the conduction loss when it is heavily loaded. The detection signal captured by the switching element is the cut-off time length of the switching element, because under the mechanism of the valley switching of the discontinuous conduction mode, when the load is heavier and heavier, the switching element cut-off period is lengthened, so the detection switch The length of the component's cut-off time can be known about the weight of the load. When the cut-off time length of the switching element exceeds the upper limit value set by the cut-off time fixing unit (indicating that the load has been increased to a certain value), the cut-off time fixing unit outputs a communication number to force the switching element to be turned on, so that the power conversion unit Enter the continuous conduction mode to reduce conduction losses.

According to another aspect of the present invention, a method for changing an operation mode with a load is provided, which is applied to a power conversion unit, and the method includes: using a switch conduction unit to extract a detection signal from a power conversion unit to determine a load of the power conversion unit, and then The switch conducting unit generates a communication signal to the driving control unit according to the detecting signal, so that the driving control unit can control whether the switching element of the power converting unit is turned on or not according to the guiding communication number.

The switch conducting unit includes a valley switching unit and a cutoff time fixing unit. The valley switching unit extracts the voltage across the switching elements to control the switching of the switching elements, and when the power conversion unit is in light load and operates in the discontinuous conduction mode, it can provide a valley switching mechanism to reduce switching losses. The cut-off time fixed unit is the length of the cut-off time of the switching component, to determine the severity of the current load. If the cut-off time is greater than a certain value (representing the load increase), the cut-off time fixed unit outputs the communication number. The switching element is forcibly turned on, causing the power conversion unit to enter a continuous conduction mode to reduce conduction loss.

By detecting the load state, the power conversion unit can operate in discontinuous conduction mode and provide valley switching mechanism at light load to reduce switching loss and operate in continuous conduction mode during heavy load to reduce conduction loss. To improve the operational efficiency of the overall power conversion unit.

The above summary and the following examples are intended to be illustrative of the invention and the embodiments of the invention.

Referring to the first figure, a block diagram of an embodiment of a device for changing an operational mode with a load includes a power conversion unit 11, a drive control unit 13, and a switch conduction unit 15. The power conversion unit 11 can be an AC to DC converter or a DC to DC converter, etc., and has at least one switching element. The drive control unit 13 is coupled to the power conversion unit 11, and may be a PWM drive controller for controlling the on and off of the switching element and adjusting its duty cycle.

The switch conducting unit 15 includes a valley switching unit 151 and a cutoff time fixing unit 153. The valley switching unit 151 further includes a comparing unit 1511 and a conductive signal generating unit 1513. The comparing unit 1511 and the conductive signal generating unit 1513 are coupled to each other for operating in the discontinuous conduction mode in the light load power conversion unit 11 (Discontinuous). In the Conduction Mode (DCM), a detection signal is taken from the power conversion unit 11 as a basis for controlling the valley switching to reduce the switching loss in the discontinuous conduction mode.

The detection signal captured by the valley switching unit 151 from the power conversion unit 11 may be a switching voltage or an inductor current of a switching element (such as a transistor) in the power conversion unit 11. The comparing unit 1511 in the valley switching unit 151 receives the switch voltage or the inductor current, and compares it with a reference value. The comparison signal is generated and sent to the pilot signal generating unit 1513. The pilot signal generating unit 1513 determines whether the switch voltage or the inductor current is in the valley of the harmonic oscillation according to the comparison signal. If the determination result is yes, then A pilot communication number is transmitted to the drive control unit 13, and the drive control unit 13 is turned on to the switching element of the power conversion unit 11, and the control of the valley switching is completed.

That is to say, the valley switching unit 151 sets the reference value to a value slightly larger than the valley voltage of the switching voltage or the inductor current harmonic oscillation by the value of the fine adjustment reference value, so that the comparison unit 1511 has not oscillated at the switching voltage or the inductor current. When the valley is reached, the comparison signal generated is a low-level signal, and a high-level comparison signal is generated at the moment when the switch voltage or inductor current oscillates to the valley. After receiving the comparison signal of the high level, the communication number generating unit 1513 outputs the communication number to make the switching element turn on, and achieves the effect of switching the switching element at the valley of the harmonic oscillation to minimize the switching loss.

Referring to the first figure, the switch-on unit 15 further includes a cut-off time fixing unit 153, because when the load is getting heavier, the cut-off time length of the switching elements in the power-conversion unit 11 is longer, so the cut-off time fixing unit The length of the off time of the switching elements in the power conversion unit 11 is 153, and the weight of the current load can be known. On the other hand, if the cut-off time length of the switching element is increased to be the same as the upper limit value set by the cut-off time fixing unit 153 (representing that the load has reached a certain value), the cut-off time fixing unit 153 generates a communication number to the drive control unit 13, forcing The switching element is turned on to allow the power conversion unit 11 to enter a Continuous Conduction Mode (CCM) to reduce conduction loss.

In other words, the cut-off time fixing unit 153 is used to set the upper limit value of the switching element cut-off time. When the cut-off time length of the switching element is less than the upper limit value of the cut-off time (that is, the state where the load is light), the cut-off time fixing unit The 153 does not operate. At this time, the power conversion unit 11 is in a discontinuous conduction mode, and the valley switching unit 151 provides a mechanism for the valley switching of the power conversion unit 11 to reduce the switching loss. When the cut-off time length of the switching element gradually increases with the load size until the upper limit value of the cut-off time is exceeded, the cut-off time control unit 153 starts to operate, forcibly fixing the cut-off time length which should be greater than the upper limit value to the The upper limit of the cutoff time causes the power conversion unit 11 to operate in a continuous conduction mode to reduce conduction loss.

Referring to the second figure, a flowchart of a method for changing an operation mode with a load, with reference to the first figure, the method is applied to the power conversion unit 11, and the step includes using the switch conduction unit 15 to retrieve the power from the power converter 11. The test signal (S201), and then the switch-on unit 15 generates the communication number according to the detection signal and transmits it to the drive control unit 13 (S203). Finally, the drive control unit 13 controls whether the switch element is turned on or not according to the guide signal number. (S205), to provide a mechanism for valley switching when the power conversion unit 11 is in the light load discontinuous conduction mode, or to switch the power conversion unit 11 from the discontinuous conduction mode to the continuous conduction mode at the time of heavy load.

Referring to the third figure, a circuit diagram of an embodiment of a device for changing an operation mode with a load, the power conversion unit 11, the drive control unit 13, the valley switching unit 151, and the cutoff time fixing unit 153 are shown, and the valley switching is performed. The unit 151 further includes a comparing unit 1511 and a pilot number generating unit 1513. In this embodiment, the power conversion unit 11 is a standard DC to DC fly-back converter that receives a DC input voltage Vi and is processed to generate an output voltage of a desired level. Vo. The drive control unit 13 is a PWM drive controller that extracts the output voltage Vo and the feedback voltage Vfb of the power conversion unit 11, and modulates the duty cycle of the switching element Q1 through the wafer Ub1.

When the load is light, the power conversion unit 11 is in the discontinuous conduction mode, and the comparison unit 1511 of the valley switching unit 151 extracts the switching voltage signal of the switching element Q1 from the auxiliary winding Aux of the transformer T of the power conversion unit 11 to Refer to the values for comparison. The magnitude of the reference value is adjusted by changing the impedance values of the resistors R2 and R3, and is adjusted to a value slightly larger than the valley of the switching voltage across the switching element Q1.

Referring to FIG. 4A, and referring to the third figure, when the voltage across the switching element Q1 has not oscillated to the valley bottom (between time points t0 and t1), the level of the output of the operational amplifier OP is a low level, and When the switching of the switching element Q1 is oscillated to the valley (time t1), the operational amplifier OP instantaneously outputs a high-level comparison voltage to the pilot signal generating unit 1513. When receiving the comparison signal of the high level, the transistor Q2 of the conduction voltage generating unit 1513 will be turned on instantaneously and connect the pin ZCD of the wafer Ub1 in the driving control unit 13 to the ground point GND, and then the wafer Ub1 will be The switching element Q1 is turned on, the voltage across the switching element Q1 is reduced to zero, and the switching element Q1 starts to flow current (between the time points t1 and t2) to achieve the purpose of valley switching, so as to reduce the switch at light load. loss. Finally, by the PWM drive control of the drive control unit 13, at time t2, the switching element Q1 is turned off again and enters the next duty cycle.

Referring to FIG. 4B, and referring to the third figure, the cut-off time fixing unit 153 sets the cut-off time upper limit value by adjusting the capacitance of the capacitor C1 and the magnitude of the resistance of the resistor R1. When the load is getting larger, the cut-off time of the switching element Q1 will be longer and longer, if the cut-off time of the switching element Q1 is increased to the upper limit of the cut-off time (such as the time between the time points t3 and t4 in the fourth B-picture) In the case of length, since the time is sufficient for the discharge C1 of the cut-off time fixing unit 153 to be completely discharged, at the time point t4, the cut-off time fixing unit 153 pulls the pin ZCD of the wafer Ub1 to ground, and the drive control unit 13 is forcibly turned on. The switching element Q1 causes the off time of the switching element Q1 not to exceed the set upper limit value of the off time, causing the power conversion unit 11 to enter the continuous conduction mode to reduce the conduction loss at the time of heavy load. Finally, according to the PWM drive control of the drive control unit 13, the switching element Q1 is turned off at the time point t4 to enter the next duty cycle.

It is worth mentioning that, in reference to the third figure, the valley switching unit 151 further includes a diode D, which captures the signal of the pin GD of the chip Ub1, and functions when the heavy-duty cut-off time fixing unit 153 is in operation. It is ensured that the valley switching unit 151 does not malfunction, and the stability of the circuit is improved.

Referring to FIG. 5, a circuit diagram of another embodiment for changing the operation mode with load, which is an AC to DC Power Factor Correction circuit, including a power conversion unit 11', and a driving The control unit 13', the valley switching unit 151', and the cutoff time fixing unit 153', and the valley switching unit 151' further includes a comparing unit 1511' and a pilot number generating unit 1513'. The power conversion unit 11' receives the AC input voltage Vi' and undergoes rectification and voltage transformation to generate a DC output voltage Vo'.

Referring back to the fifth diagram, in a preferred embodiment, the power conversion unit 11' operates at a light load boundary state between the discontinuous conduction mode and the continuous conduction mode, that is, the transient mode. The comparing unit 1511' of the valley switching unit 151' draws the inductor current of the inductor L, and sets the reference value through the resistance values of the trimming resistors R2' and R3' to compare with the inductor current, so that the operational amplifier OP' of the comparing unit 1511' is When the inductor current is just zero, a high level comparison signal is instantaneously generated and transmitted to the pilot signal generating unit 1513'. When the transistor Q2' in the pilot signal generating unit 1513' receives the comparison signal of the high level, it will be turned on instantaneously so that the fifth pin of the wafer Ub1' is pulled, and then the wafer Ub1' will switch the element Q1'. Turn on, let the inductor current waveform as shown in Figure 6A, to achieve the purpose of operating in transient mode at light load to reduce switching losses.

Similarly, when the load is heavy, the upper limit value of the cutoff time is set by the capacitor C1' and the resistor R1' in the cutoff time fixing unit 153', so that the cutoff time length of the switching element Q1' does not exceed the upper limit of the cutoff time. After the load is increased to a certain extent, the power conversion unit 11' can enter a continuous conduction mode to reduce conduction loss. A schematic diagram of the inductor current waveform of the inductance L of the power conversion unit 11' in the continuous conduction mode is as shown in the sixth B. The circuit operation flow of the deadline fixing unit 153' has been described above and will not be repeated here.

In particular, referring to FIG. 5, the valley switching unit 151' further includes a diode D', which picks up the pin signal of the chip Ub1', and functions when the heavy-duty cut-off time fixing unit 153' is in operation. It is ensured that the valley switching unit 151' does not malfunction, and the stability of the circuit is improved.

In summary, the power conversion unit can operate in a discontinuous conduction mode at a light load and provide a valley switching mechanism to reduce switching loss; and can operate in a continuous conduction mode at a heavy load to reduce conduction loss. To improve the operational efficiency of the overall power conversion unit.

The above description of the embodiments of the present invention and the drawings are intended to be within the scope of the following claims, and any one skilled in the art of the present invention can easily Any changes or modifications may be covered by the patents defined in this case.

11, 11'‧‧‧Power Conversion Unit

13, 13'‧‧‧ drive control unit

15‧‧‧Switch conduction unit

151, 151'‧‧ trough switching unit

1511, 1511'‧‧‧ comparison unit

1513, 1513' ‧‧ ‧ communication number generation unit

153, 153’ ‧ ‧ deadline fixed unit

S201~S205‧‧‧ Flowchart Step Description

The first figure is a block diagram of an embodiment of an apparatus for changing an operation mode with a load according to the present invention; the second figure is a flowchart of a method for changing an operation mode with a load according to the present invention; Circuit diagram of an embodiment of the apparatus; FIG. 4A and FIG. 4B are waveform diagrams related to the circuit diagram of the third diagram; FIG. 5 is a circuit diagram of another embodiment of the apparatus for changing the operation mode with load according to the present invention; The six A diagram and the sixth B diagram are waveform diagrams related to the circuit diagram of the fifth diagram.

11. . . Power conversion unit

13. . . Drive control unit

15. . . Switch conduction unit

151. . . Valley switching unit

1511. . . Comparison unit

1513. . . Communication number generation unit

153. . . Deadline fixed unit

Claims (18)

A device for changing an operation mode according to a load is applied to a power conversion unit, wherein the power conversion unit has a switching component, including: a switch conducting unit, including a cutoff time fixing unit and a valley switching unit, the cutoff time fixing unit and the The wave switching unit is coupled to the power conversion unit, and receives a detection signal from the power conversion unit to determine the current weight of the power conversion unit load, and generates a communication number according to the detection signal; and a driving control The unit is coupled to the power conversion unit and the switch conducting unit to receive the communication number transmitted by the switch conducting unit, and control whether the switching element is turned on or not according to the guiding communication number. The apparatus for changing the operation mode according to the load in the first aspect of the patent application, wherein the detection signal captured by the cut-off time fixing unit is a cut-off time length of the switching element. The apparatus for changing the operation mode according to the load according to Item 2 of the patent application, wherein the cut-off time fixing unit sets an off-time upper limit value, and when the cut-off time length of the switching element is greater than the cut-off time upper limit value When the communication number is output to the drive control unit. The apparatus for changing an operation mode according to the load according to Item 3 of the patent application, wherein the cut-off time fixing unit sets the cut-off time upper limit value by using a capacitor and a resistor. The apparatus for changing the operation mode according to the load in the first aspect of the patent application, wherein the detection signal captured by the valley switching unit is a switching voltage or an inductor current of the power conversion unit. As described in the first paragraph of the patent application, the load operation mode is changed according to the load. The trough switching unit includes a comparison unit and a pilot communication number generating unit, and the comparing unit and the communication signal generating unit are coupled to each other. The device of claim 4, wherein the comparing unit receives the detection signal to compare with a reference value and outputs a comparison signal to the conduction. Signal generation unit. The device for changing the operation mode according to the load in the seventh aspect of the patent application, wherein the communication number generating unit generates the communication number to the driving control unit according to the comparison signal. A device for changing an operation mode with a load as described in claim 1, wherein the drive control unit is a PWM drive controller. A method for changing an operation mode according to a load is applied to a power conversion unit, comprising: a switch conduction unit that extracts a detection signal from the power conversion unit, wherein the switch conduction unit includes a cutoff time fixing unit and a valley switching unit The switch conducting unit determines the load of the power conversion unit according to the detection signal, and outputs a communication number to a driving control unit; and the driving control unit controls a switching element of the power conversion unit according to the guiding communication number. Turn on or not. The method for changing an operation mode with a load according to claim 10, wherein the switch conducting unit extracts the detection signal from the power conversion unit, and the cut-off time fixing unit extracts the switch from the power conversion unit. The length of a cutoff time of the component. As stated in the application scope of claim 11, the mode of operation change with load The method, wherein the cut-off time fixing unit is configured to have an off-time upper limit value, and when the cut-off time length is greater than the cut-off time upper limit value, the cut-off time fixing unit outputs the guide communication number to the drive control unit. The method for changing an operation mode according to a load according to claim 12, wherein the cut-off fixed unit sets the cut-off upper limit value by using a capacitor and a resistor. The method for changing an operation mode with a load according to claim 10, wherein the switch conduction unit extracts the detection signal from the power conversion unit, and the valley switching unit captures a switch cross from the power conversion unit. Voltage or an inductor current. The method for changing an operation mode with a load according to claim 10, wherein the valley switching unit comprises a comparison unit and a conduction number generation unit, and the comparison unit and the communication number generation unit are coupled to each other. The method for changing an operation mode with a load according to claim 15, wherein the comparison unit of the valley switching unit receives the detection signal to compare with a reference value, and outputs a comparison signal to the conduction. Signal generation unit. The method for changing an operation mode according to a load according to claim 16 , wherein the communication number generating unit generates a communication number to the driving control unit according to the comparison signal. A method for changing an operation mode with a load as described in claim 10, wherein the drive control unit is a PWM drive controller.