CN102263398B - Control method, power supply control method, and power supply controller - Google Patents

Abstract

A power control method and a power supply suitable for the method are provided. The power supply includes an inductive element. According to a compensation signal, a load state of the power supply is determined. When the load state is a heavy load, the switch is operated at a high working frequency; when the load state is light load or no load, the switch is operated at a low working frequency. When the compensation signal exceeds a critical value, the load state is judged to be an overload state, and the switch is closed after the overload state lasts for a permissible time. The allowable time is determined by an external capacitor, and is independent of the high and low operating frequencies of the switch operation.

Description

Control method, power supply control method, and power supply controller

technical field

The invention relates to an overload protection of a switch mode power supply (SMPS).

Background technique

A power supply is a power management device used to convert power to provide power to electronic devices or components. For example, FIG. 1 shows a known power supply 60 with a flyback topology. The bridge rectifier 62 rectifies the AC power V _AC to provide the input power V _IN to the transformer 64 . When the switch 72 is turned on (close), the primary winding L _P of the transformer 64 stores energy; when it is closed (open), the secondary winding L _S of the transformer 64 releases energy to the load capacitor (load capacitor) 69 through the rectifier 66 to establish an output power supply V _OUT . The error amplifier (erroramplifier) EA compares the voltage of the output power V _OUT with the target voltage V _Target and generates a compensation signal V _COM . The controller 74 controls the switch 72 with the control signal V _GATE according to the compensation signal V _COM and the current detection signal V _CS . The current detection signal V _CS reflects the inductor current flowing through the primary winding L _P.

It is known that the power supply in FIG. 1 has various protections, such as overvoltage protection (OVP), overtemperature protection (OTP), overload protection (OLP) and so on. Among them, OLP generally refers to the protection measures that the power supply will take when the output load is too large and exceeds the rated output power of the power supply.

OLP has many practices. For example, one is to limit the output current, and the other is to limit the inductor current flowing through the primary winding L _P. The main idea is to prevent the power supply from delivering more power than a certain level.

Contents of the invention

An embodiment of the present invention provides a control method suitable for a power supply, which includes a switch and an inductance element. The method includes: detecting the inductor current flowing through the inductor element; making the power supply operate in a normal load state or an overload state according to a feedback signal; in the normal load state, making the inductor current flowing through the inductor element A current peak value is not greater than a certain value, and the operating frequency of the switch is a first frequency; in the overload state, a current peak value flowing through the inductive element is about the fixed value, and the operating frequency of the switch is is a second frequency, and the second frequency is higher than the first frequency; calculate the duration of the power supply in the overload state; when the duration exceeds an allowable time, stop the inductor current; wherein, the allowable time Unaffected by this change in operating frequency.

An embodiment of the present invention provides a power supply. A controller controls the inductor current flowing through an inductor element. The controller includes a working clock generator, a current limiter, and an overload protector. The working clock generator is used to generate a working frequency. The current limiter can make a current peak value flowing through the inductance element approximately a certain value. When the current limiter makes the current peak value approximately the fixed value, the working frequency is not lower than a first frequency. In the overload protector, an overload identifier can identify whether the power supply should enter an overload state according to a feedback signal. When the power supply operates in the overload state, the operating frequency is a second frequency higher than the first frequency. A current supplier provides an external capacitor charging and discharging current, which can be used to calculate the duration of the power supply in the overload state. When the duration exceeds an allowable time, the controller stops the inductor current, and the allowable time is not affected by the change of the working frequency.

An embodiment of the present invention provides a power supply, which is suitable for a power supply. The power supply has an inductance element and a switch. The power controller includes a first comparator, a working clock generator, and an overload protector. The first comparator receives a compensation signal and a current detection signal to control the switch. The current detection signal corresponds to an inductor current flowing through the inductor element. The compensation signal corresponds to a load state of the power supply. The first comparator is used for approximately determining the current peak value of the inductor current according to the compensation signal. The working clock generator is used for roughly providing a working frequency of the switch according to the compensation signal. When the load state corresponding to the compensation signal is heavy load, the operating frequency is a high-frequency operating frequency; when the load state corresponding to the compensation signal is light load or no load, the operating frequency is a low-frequency operation frequency. The overload protector has a charge-discharge device coupled to an external capacitor for detecting the compensation signal to determine whether an overload event occurs, and outputs an overload protection signal to close the switch after a allowable time after the overload event occurs. The external capacitor and the charge-discharge device form a clock oscillator for determining the allowable time, and the allowable time is not affected by the working clock generator.

An embodiment of the present invention provides a power control method, which is suitable for a power supply, and the power supply includes an inductance element. The method includes: judging a load state of the power supply according to a compensation signal, making the switch operate at a high operating frequency when the load state is heavy load, and making the switch operate at a high operating frequency when the load state is light load or no load, making the switch operate at a low operating frequency; and, when the compensation signal exceeds a critical value, judging that the load state is an overload state, and closing the switch after the overload state lasts for a permissible time. The allowable time is determined by an external capacitor and has nothing to do with the high and low operating frequencies of the switching operation.

An embodiment of the present invention provides a power control method suitable for a power supply. The power supply includes an inductance element controlled by a switch to store or release energy to generate an output power. The method includes: providing an operating clock generator to roughly provide an operating frequency of the switch; detecting a load state of the power supply; adjusting the operating frequency according to the load state, wherein the load state is a heavy load , the operating frequency is a first frequency; when the load state is overload, within an allowable time, the operating frequency is approximately a second frequency, the second frequency is higher than the first frequency; and, and After the allowable time is over, the operation of the switch is stopped. The allowable time is not affected by the working clock generator.

Description of drawings

FIG. 1 is a known power supply.

FIG. 2 is a power supply implemented according to the present invention.

FIG. 3 illustrates some circuits and external capacitors in the controller.

FIG. 4 shows the relationship between the operating frequency of the operating clock generator and the compensation signal V _COM .

[Description of main component labels]

60, 90 Power Supplier 62 bridge rectifier 64 transformer 66 rectifier 69 load capacitance 72 switch 73,74 controller 75 external capacitor 82, 84, 88, 94 Comparators 85 current supply 86 logic control unit 92 counter 96 working clock generator

CT Pin EA error amplifier f _HEAVY reload frequency f _OverLoad Overload frequency L _P primary side winding L _S secondary side winding V _AC AC power V _COM compensation signal V _CS Current detection signal V _GATE control signal V _OLP OLP threshold _VOUT output power V _Target target voltage

detailed description

FIG. 2 shows a power supply 90 according to the present invention. The same reference numerals in FIG. 2 and FIG. 1 represent the same or similar components, devices, or signals, which are known technologies and will not be repeated here. FIG. 2 is only an embodiment, and it is not necessary to use the same or similar elements, devices, or signals in FIG. 1 to implement the present invention. The scope of rights of the present invention should be interpreted as limited by the scope of the patent application.

In one embodiment, the controller 73 in FIG. 2 is implemented with a single integrated circuit; in another embodiment, the controller 73 and the switch 72 are implemented with a single integrated circuit. Different from the controller 74 in FIG. 1 , the controller 73 in FIG. 2 has an additional pin (pin) CT connected to an external capacitor 75 , and its function will be described briefly.

FIG. 3 illustrates part of the circuits and the external capacitor 75 in the controller 73 . The comparator 82 provides over _- current protection (OCP), and is also a peak _limiter , which controls the peak voltage of the current detection signal V _CS in FIG. The current peak value (peakcurrent) is not greater than I _CS-LIMIT (=V _CS-LIMIT /R _CS ), where R _CS is the resistance value of the resistor CS. The comparator 84 roughly determines the peak current of the primary winding _LP according to the compensation signal V _COM , and the voltage value of the compensation signal V _COM can be regarded as the corresponding power required to maintain the current output voltage, or corresponding to the output load state . The compensation signal V _COM not only approximately determines the peak current of the primary winding _LP , but also determines the operating frequency output by the operating clock generator 96 , that is, the operating frequency of the switch 72 in FIG. 2 . For example, when the voltage value of the compensation signal V _COM is low, it is light load/no load, and the output operating frequency is about 20 kHz; when the voltage value of the compensation signal V _COM is high, it is heavy load, and the output operating frequency is about 20 kHz. 65kHz. Whether it is heavy load or light load/no load, it is regarded as a normal load state.

The current supplier 85 provides charging and discharging current to the external capacitor 75 through the pin CT. The current supplier 85 and the external capacitor 75 can be regarded as a clock oscillator in a timer. When the compensation signal V _COM is higher than an OLP critical value V _OLP , it is determined that an output overload situation has occurred at the moment, and the operation is started in the overload state, and the comparator 88 makes the counter (counter) 92 start counting according to the clock signal output by the clock oscillator . Once the comparator 94 judges that the output of the counter 92 reaches a certain preset condition, that is, the overload situation continues for more than a certain period of time, the comparator 94 outputs an overload protection signal to trigger the OLP, and the logic control unit 86 continues to close the switch 72 to stop the conversion of electric energy with pass. If the compensation signal V _COM returns below the OLP critical value V _OLP before the allowable time is up, it means that the power supply 90 is out of the overload state, the counter 92 is reset to zero, and the switch 72 is still operating according to the operating clock generator 96 The operating frequency of the output continues to operate. The current provider 85, the comparator 88, the counter 92, and the comparator 94 can be regarded as an overload protector. In another embodiment, the comparator 94 can be omitted, and the logic "1" or "0" of an output bit (output bit) of the counter 92 is directly used as the trigger judgment of the OLP.

It can be seen from the above circuit that the allowable time refers to the duration of the allowable power supply 90 in an overload state, which is set by the frequency generated by the clock oscillator composed of the current supply 85 and the external capacitor 75 and the comparator 94. determined by predetermined conditions. This allowable time is not affected by changes in the operating frequency of the operating clock generator 96 . For example, in terms of design, the preset condition of the comparator 94 is built in the integrated circuit without being changed by the value of the external components, and the frequency of the OLP oscillator can be determined by the capacitance value of the external capacitor 75 . Therefore, in terms of system design, the allowable time can be conveniently determined by selecting an appropriate capacitance value of the external capacitor 75 .

In one embodiment, after the OLP is triggered, when the compensation signal V _COM returns to be lower than the OLP critical value V _OLP , the OLP is released, and the power conversion and transmission are restarted; in another embodiment, only the controller 73 The AC power removed and re-powered start (restart) to release the OLP.

FIG. 4 shows the relationship between the operating frequency of the operating clock generator 96 and the compensation signal V _COM . When the voltage value of the compensation signal V _COM corresponds to V _cs-LIMIT , it can be regarded as heavy load, and the operating frequency of the working clock generator 96, for example, is a heavy load frequency f _HEAVY (such as 65Khz); when the compensation signal V When the voltage of _COM corresponds to the OLP critical value V _OLP , it can be regarded as an overload state, and the operating frequency of the working clock generator 96 is an overload frequency f _OverLoad (for example, 130Khz). Figure 4 also shows that when the peak current of the primary winding L _P is approximately I _cs-LIMIT , the operating frequency is at least the heavy-duty frequency f _HEAVY . During the allowable time, that is, when the compensation signal V _COM is higher than the OLP critical value V _OLP , the peak current flowing through the primary winding L _P will be approximately fixed at I _cs-LIMIT due to the limitation of the comparator 82, but the operating frequency But it is no longer the overload frequency f _HEAVY , but a higher overload frequency f _OverLoad . For example, the overload frequency f _OverLoad may be double or triple the overload frequency f _HEAVY .

The above embodiment can get two benefits:

1. Avoid transformer 64 from being saturated: _Ics-LIMIT can select the maximum current that makes transformer 64 unsaturated (saturate), so that when transformer 64 is not saturated, only the operating frequency of the controller 73 can be increased to overload frequency f _OverLoad to temporarily increase the output power.

2. The allowable time can be adjusted externally: as mentioned above, the allowable time has nothing to do with the operating frequency, and is determined by the clock oscillator formed by the current supplier 85 and the external capacitor 75 . Therefore, the allowable time can be determined by properly selecting the capacitance value of the external capacitor 75 . The external capacitor 75 has another benefit. If the allowable time is as high as several seconds, the corresponding clock oscillator constructed entirely in integrated circuits will require a staggering area cost. However, the realization of the external capacitor 75 can properly save the cost, so that the part of the integrated circuit is relatively very small.

Although the present invention takes a flyback-type SMPS as an example, the present invention can also be applied to similar SMPSs such as buck power converters and boost power converters.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (12)

1. A control method, suitable for a power supply, which includes a switch and an inductance element, the method includes: detecting the inductive current flowing through the inductive element; making the power supply operate in a normal load state or an overload state according to a feedback signal; In the normal load state, the peak value of the current flowing through the inductance element is not greater than a certain value, and the operating frequency of the switch is a first frequency; In the overload state, make a peak value of the current flowing through the inductance element approximately the constant value, and make the operating frequency of the switch be a second frequency, and the second frequency is higher than the first frequency; calculating the duration that the power supply is in the overload state; and When the duration exceeds an allowable time, stopping the inductor current; Wherein, the allowable time is not affected by the change of the operating frequency, and when the power supply enters the overload state from the normal load state, the operating frequency of the switch increases linearly from the first frequency. 2. The control method according to claim 1, further comprising: According to the feedback signal, the working frequency is changed. 3. The control method according to claim 1, further comprising: When the power supply is out of the overload state, a counter is reset to recalculate the duration. 4. The control method according to claim 1, further comprising: providing an operating clock generator to generate the operating frequency; Wherein, the operating frequency does not affect the allowable time. 5. A power controller, suitable for a power supply, the power supply has an inductance element, and a switch, the power controller includes: A first comparator, receiving a compensation signal and a current detection signal to control the switch, wherein the current detection signal corresponds to an inductor current flowing through the inductance element, and the compensation signal corresponds to the power supply a load state, the first comparator is used to determine the current peak value of the inductor current according to the compensation signal; An operating clock generator, used to provide an operating frequency of the switch according to the compensation signal, wherein when the load state corresponding to the compensation signal is heavy load, the operating frequency is a high-frequency operating frequency, and when the When the load state corresponding to the compensation signal is light load or no load, make the operating frequency a low operating frequency; and An overload protector, having a charge-discharge device coupled to an external capacitor, is used to detect the compensation signal to determine whether an overload event occurs, and output an overload protection signal to turn off the overload event after an allowable time has occurred switch; The external capacitor and the charge-discharge device form a clock oscillator to determine the allowable time, and the allowable time is not affected by the working clock generator, and when the power supply enters an overload state from a normal load state, the The operating frequency of the switch increases linearly from the low operating frequency, and the normal load state includes heavy load, the light load and the no-load state. 6. The power controller according to claim 5, wherein the overload protector further comprises: a second comparator for comparing the compensation signal with a critical signal, and when the compensation signal is greater than the critical signal, an overload protection signal is sent to indicate that the overload event occurs; and a counter, coupled to the second comparator, for receiving a clock signal, the counter starts counting after the second comparator sends out the overload protection signal; Wherein, the overload protection signal is output after the output of the counter meets a condition. 7. The power controller according to claim 5, wherein within the allowable time after the overload event occurs, the working clock generator makes the working frequency an overload frequency, wherein the overload frequency is greater than the high frequency working frequency. 8. The power controller according to claim 5, wherein the power controller further comprises: A peak limiter is used to detect the current detection signal and send out a peak limit signal to control the switch, and limit the current peak value of the inductor current flowing through the inductance element to a limited peak value. 9. A power control method, suitable for a power supply, the power supply includes an inductance element and a switch, the method comprising: According to a compensation signal, a load state of the power supply is judged, when the load state is heavy load, the switch is operated at a high operating frequency, and when the load state is light load or no load, the switch is operated at a low operating frequency; and When the compensation signal exceeds a critical value, judging that the load state is an overload state, and closing the switch after the overload state lasts for a permissible time; Wherein the allowable time is determined by an external capacitor and has nothing to do with the high and low operating frequencies of the switch operation, and when the power supply enters the overload state from the normal load state, the operating frequency of the switch increases linearly from the low operating frequency, The normal load state includes heavy load, the light load and the no load state. 10. The power control method according to claim 9, wherein when the load state is the overload state, the switch is operated at an overload frequency within the allowable time, and the overload frequency is greater than the high operating frequency. 11. The power control method according to claim 9, comprising; detecting an inductive current flowing through the inductive element to generate a current detection signal; and The current peak value of the inductor current is determined according to the compensation signal and the current detection signal. 12. A power control method, suitable for a power supply, the power supply has an inductance element and a switch, the method comprising: providing an operating clock generator to provide an operating frequency of the switch; detecting a load state of the power supply; adjusting the operating frequency according to the load state, wherein when the load state is a heavy load, the operating frequency is a first frequency; When the load state is overload, within an allowable time, make the operating frequency a second frequency, the second frequency being higher than the first frequency; and And after the end of the allowable time, stop the operation of the switch; Wherein, the allowable time is not affected by the working frequency, and when the load state changes from heavy load to overload, the working frequency increases linearly from the first frequency to the second frequency.