TWI559278B - Switching Regulator and Control Circuit and Control Method Thereof - Google Patents

Description

Switching power supply and control circuit and control method thereof

The invention relates to a switching power supply device and a control circuit and control method thereof, in particular to a switching power supply device with a function of adaptively adjusting an overcurrent protection threshold value, a control circuit thereof and a control method thereof.

FIG. 1A shows a schematic diagram of a prior art switched power supply 100. As shown in FIG. 1A, the switched power supply 100 is used to receive power to drive the display panel 10. The switched power supply 100 includes a power stage circuit 101, a control circuit 102, and a display drive circuit 103. As shown, the power stage circuit 101 receives the input voltage Vin and operates the power switch based on the operation signal generated by the control circuit 102 to generate an output voltage Vout. Display driver circuit 103 receives the output voltage for driving display panel 10.

One of the problems of the prior art described above is that the switching power supply 100 can receive a plurality of circuits, including wires, etc. from the receiving power source to the driving display panel 10, and the sum of the resistance values can be regarded as the line as shown in the figure. Resistance, with impedance R. Since the line resistance has the impedance R, when the input current Iin flows through the power stage circuit 101, a voltage drop of the input current Iin multiplied by the impedance R is generated. When the display panel 10 is refreshed on the screen, there is a period in which the liquid crystal is reversed, which is called a blanking interval. During this blanking period, the control circuit 102 is required to increase the input current Iin and increase the duty ratio of the operation signal, thereby generating a relatively high voltage drop, resulting in an input voltage. Vin fell. Fig. 1B is a diagram showing signal waveforms of the input voltage Vin, the output voltage Vout, and the input current Iin during normal operation. As shown in FIG. 1B, during the blanking period, the input current Iin rises, the input voltage Vin decreases, and the output voltage Vout rises. During this blanking period, the input voltage Vin may be lower than the under voltage lock out (UVLO) level due to the drop of the input voltage Vin, causing the entire system to shut down.

Figure 2 shows a schematic diagram that uses the reduced undervoltage lockout level to avoid system shutdown. As shown in Figure 2, reducing the undervoltage lockout level from UVLO to UVLO' does prevent the system from shutting down during the blanking period due to the input voltage Vin being too low. However, this increases the operational risk of the switched power supply 100, and the undervoltage lockout level needs to be set to a higher level in many applications, making this not feasible.

U.S. Patent No. 6,445,144 shows a solution to the above problems. It uses the detected input current to feedback the control switch to limit the upper and lower limits of the input current. However, as a result, many power switches and circuits are required to increase the power consumption and manufacturing cost.

In view of this, the present invention is directed to the deficiencies of the prior art described above, and provides a switched power supply and a control circuit and control method thereof. The invention adaptively adjusts the overcurrent protection threshold according to the input voltage or the input current, can not only reduce the input current when necessary, and avoids the input voltage being lower than the undervoltage lock level without adjusting the undervoltage lock level; There is no need to add additional power circuits to control manufacturing costs and power consumption.

In one aspect, the present invention provides a switched power supply for converting an input voltage into an output voltage, the switched power supply comprising: a power stage circuit that switches according to an operation signal At least one power switch to convert the input voltage to the output voltage; and a control circuit coupled to the power stage circuit for generating the operation signal, The control circuit includes a threshold adjustment circuit for generating and adaptively adjusting an overcurrent protection threshold according to the input voltage or an input current; wherein the input current flows through the power stage circuit; wherein the overcurrent The protection threshold is used to limit the input current; wherein the control circuit does not turn on the power switch when the input current exceeds the overcurrent protection threshold.

In a preferred embodiment, the threshold adjustment circuit adaptively lowers the overcurrent protection threshold when the input voltage drops, and drops the input voltage to no higher than a predetermined first input voltage. The overcurrent protection threshold is maintained at an overcurrent protection threshold; and when the input voltage rises, the overcurrent protection threshold is adaptively increased, and the input voltage rises to no less than one When the second input voltage is set, the overcurrent protection threshold is maintained at an overcurrent protection maximum threshold; wherein the preset first input voltage is lower than the preset second input voltage, and the overcurrent protection is minimally critical The value is below the maximum threshold for the overcurrent protection.

In a preferred embodiment, the threshold adjustment circuit adaptively reduces the overcurrent protection threshold when the input current rises, and when the input current rises to a predetermined first input current, The overcurrent protection threshold is maintained at a minimum threshold of overcurrent protection, and the input current is maintained at the preset first input current; and when the input current decreases, the overcurrent protection threshold is adaptively adjusted, and And maintaining the overcurrent protection threshold at an overcurrent protection maximum threshold when the input current drops to not higher than a preset second input current; wherein the preset first input current is higher than the preset Two input currents, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold.

In a preferred embodiment, the threshold adjustment circuit adaptively adjusts the overcurrent protection threshold such that the input voltage is not lower than a predetermined under voltage lockout due to the input current being too high. UVLO) level.

In a preferred embodiment, the output voltage is used to supply a display panel, and during a blanking interval, the threshold adjustment circuit is based on the input voltage or the The input current is adaptively adjusted to the overcurrent protection threshold; and outside the blanking period, the threshold adjustment circuit maintains the overcurrent protection threshold at a fixed preset overcurrent protection threshold.

In a preferred embodiment, the threshold adjustment circuit includes: a voltage-current conversion circuit for converting the input voltage or its associated signal into a first current; a first current modulation circuit, And the voltage current conversion circuit is coupled to convert the first current into a first amplification current proportional thereto, and generate a second current according to a difference between an overcurrent protection upper limit current and the first amplification current a second current modulation circuit coupled to the first current modulation circuit for converting the second current into a second amplification current proportional thereto, and protecting the lower limit current according to an overcurrent a difference between the second amplification currents to generate a third current; a third current modulation circuit coupled to the second current modulation circuit for converting the third current into a third ratio Amplifying the current and protecting the minimum threshold current and the third current according to an overcurrent to generate a modulation current; and a current voltage conversion circuit coupled to the third current modulation circuit for adjusting the current Current conversion to this Current protection threshold.

In the foregoing embodiment, the second current modulation circuit preferably further includes a uniform energy switch circuit for determining whether to generate the second amplification current according to the uniform energy signal.

In the foregoing embodiment, the enabling signal preferably determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not to generate the second amplifying current; wherein the output is The voltage is used to supply a display panel, and the blanking period is related to the period from the end of the front screen scanning of one of the display panels to the start of the scanning of the subsequent screen.

In a preferred embodiment, the threshold adjustment circuit includes: an input current sensing circuit for sensing the input current to generate a current sensing signal; and a voltage current conversion circuit for The current sensing signal is converted into a first current; a first current modulation circuit is coupled to the voltage current conversion circuit for converting the first current into a first amplification current proportional thereto, and according to a difference between the first amplified current and an overcurrent protection lower limit current a second current modulation circuit coupled to the first current modulation circuit for converting the second current into a second amplification current proportional thereto, and according to an overcurrent protection a difference between the upper limit current and the second amplified current to generate a third current; a third current amplifying circuit coupled to the second current modulation circuit for converting the third current into a proportional ratio thereof a third current-amplifying circuit coupled to the second current-modulating circuit for converting the third current into a third amplifying current proportional thereto, and protecting according to an overcurrent a minimum threshold current and the third current generate a modulation current; and a current voltage conversion circuit coupled to the third current modulation circuit for converting the modulation current into the overcurrent protection threshold .

In the foregoing embodiment, the second current modulation circuit preferably further includes a uniform energy switch circuit for determining whether to generate the second amplification current according to the uniform energy signal.

In the foregoing embodiment, the enabling signal preferably determines to generate the third current during a blanking period; and outside the blanking period, determining not to generate the third current; wherein the output voltage is used A display panel is provided, and the blanking period is related to a period in which the front screen scan ends one of the display panels to the start of the scan.

In another aspect, the present invention provides a switching power supply control method, wherein the switching power supply is configured to convert an input voltage into an output voltage, and the switching power supply control method includes Actuating at least one power switch of a power stage circuit to convert the input voltage to the output voltage according to an operation signal; and generating and adaptively adjusting an overcurrent protection threshold according to the input voltage or an input current; The input current is limited by the overcurrent protection threshold; and the power switch is not turned on when the input current exceeds the overcurrent protection threshold; wherein the input current flows through the power stage circuit.

In a preferred embodiment, the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current comprises: adaptively reducing the overcurrent protection when the input voltage drops Threshold value, and the input voltage drops to no more than one pre- When the first input voltage is set, the overcurrent protection threshold is maintained at an overcurrent protection minimum threshold; and when the input voltage rises, the overcurrent protection threshold is adaptively adjusted, and the input voltage rises to When the preset second input voltage is not lower than a preset second input voltage, the overcurrent protection threshold is maintained at an overcurrent protection maximum threshold; wherein the preset first input voltage is lower than the preset second input voltage, and the preset The overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold.

In a preferred embodiment, the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current comprises: adaptively reducing the overcurrent protection when the input current rises a threshold value, and when the input current rises to a predetermined first input current, the overcurrent protection threshold is maintained at an overcurrent protection minimum threshold, and the input current is maintained at the preset first input current; And adaptively raising the overcurrent protection threshold when the input current decreases, and maintaining the overcurrent protection threshold at an overcurrent when the input current drops to not higher than a predetermined second input current The maximum critical value is protected; wherein the preset first input current is higher than the preset second input current, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold.

In a preferred embodiment, the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current further comprises: preventing the input voltage from being too low due to the input current being too high. A preset under voltage lockout (UVLO) level.

In a preferred embodiment, the output voltage is used to supply a display panel, and the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current includes: blanking During the period, the overcurrent protection threshold is adaptively adjusted according to the input voltage or the input current; and the overcurrent protection threshold is maintained at a fixed preset overcurrent protection threshold outside the blanking period.

In a preferred embodiment, the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage comprises: converting the input voltage or its related signal into a first current; a current is converted into a first amplification current proportional thereto, and a second current is generated according to a difference between an overcurrent protection upper limit current and the first amplification current; the second current is converted into a proportional ratio to the second Amplifying the current, and generating a third current according to a difference between the current protection lower limit current and the second amplification current; converting the third current to a third amplification current proportional thereto, and minimizing the protection according to an overcurrent The threshold current and the third current generate a modulation current; and convert the modulation current into the overcurrent protection threshold.

In the foregoing embodiment, the step of converting the second current into a second amplification current proportional thereto and generating a third current according to a difference between an overcurrent protection lower limit current and the second amplification current The good ground further includes: determining whether to generate the second amplification current according to the consistent energy signal.

In the foregoing embodiment, the enabling signal preferably determines to generate the third current during a blanking period; and outside the blanking period, determining not to generate the third current; wherein the output voltage is used A display panel is provided, and the blanking period is related to a period in which the front screen scan ends one of the display panels to the start of the scan.

In a preferred embodiment, the step of generating and adaptively adjusting the overcurrent protection threshold according to the input current comprises: sensing the input current to generate a current sensing signal; and sensing the current The signal is converted into a first current; the first current is converted into a first amplification current proportional thereto, and a second current is generated according to a difference between the first amplification current and an overcurrent protection lower limit current; The second current is converted into a second amplification current proportional thereto, and a third current is generated according to a difference between an overcurrent protection upper limit current and the second amplification current; and the third current is converted into a proportional ratio thereof a third amplification current; converting the third amplification current into Comparing with a fourth amplification current, and according to an overcurrent protection minimum threshold current and the fourth amplification current, generating a modulation current; and converting the modulation current into the overcurrent protection threshold.

In the foregoing embodiment, the step of converting the second current into a proportional second amplification current preferably further comprises: determining whether to generate the second amplification current according to the uniform energy signal.

In the foregoing embodiment, the enabling signal preferably determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not to generate the second amplifying current; wherein the output is The voltage is used to supply a display panel, and the blanking period is related to the period from the end of the front screen scanning of one of the display panels to the start of the scanning of the subsequent screen.

In another aspect, the present invention provides a control circuit in a switched power supply for generating an operation signal, switching at least one power switch in the switched power supply, and converting an input voltage into an output. a voltage, wherein the control circuit includes a threshold adjustment circuit for generating and adaptively adjusting an overcurrent protection threshold according to the input voltage to limit the input current, wherein the threshold adjustment circuit comprises: a voltage current a conversion circuit for converting the input voltage or its associated signal into a first current; a first current modulation circuit coupled to the voltage current conversion circuit for converting the first current to be proportional thereto a first amplifying current, and generating a second current according to a difference between an overcurrent protection upper limit current and the first amplifying current; a second current modulating circuit coupled to the first current modulating circuit Connected to convert the second current to a second amplification current proportional thereto, and according to an difference between an overcurrent protection lower limit current and the second amplification current, Generating a third current; a third current modulation circuit coupled to the second current modulation circuit for converting the third current into a third amplification current proportional thereto, and according to an overcurrent Protecting the minimum threshold current and the third current to generate a modulation current; and a current voltage conversion circuit coupled to the third current modulation circuit for converting the modulated current into the overcurrent protection threshold Value; The overcurrent protection threshold is used to limit the input current; wherein the control circuit does not turn on the power switch when the input current exceeds the overcurrent protection threshold

In a preferred embodiment, when the input voltage drops, the overcurrent protection threshold is adaptively lowered, and the overcurrent is caused when the input voltage falls below a predetermined first input voltage. The protection threshold is maintained at a minimum threshold of overcurrent protection; and when the input voltage rises, the overcurrent protection threshold is adaptively adjusted, and when the input voltage rises to not lower than a preset second input voltage The overcurrent protection threshold is maintained at an overcurrent protection maximum threshold.

In another aspect, the present invention provides a control circuit in a switched power supply for generating an operation signal, switching at least one power switch in the switched power supply, and converting an input voltage into an output. a voltage, wherein the control circuit includes a threshold adjustment circuit for generating and adaptively adjusting an overcurrent protection threshold according to the input current to limit the input current, wherein the threshold adjustment circuit comprises: an input current a sensing circuit for sensing the input current to generate a current sensing signal; a voltage current converting circuit for converting the current sensing signal into a first current; and a first current modulation circuit And the voltage current conversion circuit is coupled to convert the first current into a first amplification current proportional thereto, and generate a second according to a difference between the first amplification current and an overcurrent protection lower limit current. a second current modulation circuit coupled to the first current modulation circuit for converting the second current into a second amplification And generating a third current according to a difference between the current protection upper limit current and the second amplification current; a third current amplifying circuit coupled to the second current modulation circuit for using the third The current is converted into a third amplification current proportional thereto; a fourth current modulation circuit is coupled to the third current amplification circuit for converting the third amplification current into a fourth amplification current proportional thereto And generating a modulation current according to an overcurrent protection minimum threshold current and the fourth amplification current; and a current voltage The conversion circuit is coupled to the third current modulation circuit for converting the modulation current into the overcurrent protection threshold.

In a preferred embodiment, the threshold adjustment circuit adaptively reduces the overcurrent protection threshold when the input current rises, and when the input current rises to a predetermined first input current, The overcurrent protection threshold is maintained at a minimum threshold of overcurrent protection, and the input current is maintained at the preset first input current; and when the input current decreases, the overcurrent protection threshold is adaptively adjusted, and And maintaining the overcurrent protection threshold at an overcurrent protection maximum threshold when the input current drops to not higher than a preset second input current; wherein the preset first input current is higher than the preset Two input currents, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold.

In one preferred embodiment, the control circuit adaptively adjusts the overcurrent protection threshold such that the input voltage is not below a predetermined under voltage lockout (UVLO) level.

In a preferred embodiment, the output voltage is used to supply a display panel, and during a blanking period, the control circuit adaptively adjusts the overcurrent protection threshold according to the input voltage or the input current; Outside of the blanking period, the control circuit maintains the overcurrent protection threshold at a fixed predetermined overcurrent protection threshold.

The purpose, technical content, features and effects achieved by the present invention will be more readily understood by the detailed description of the embodiments.

10‧‧‧Display panel

100,200‧‧‧Switching power supply

101,201‧‧‧Power level circuit

102,202‧‧‧Control circuit

103,203‧‧‧Display driver circuit

2021‧‧‧critical value adjustment circuit

2022, 3022‧‧‧Voltage current conversion circuit

2023, 3023‧‧‧First current modulation circuit

2024, 3024‧‧‧Second current modulation circuit

2025‧‧‧ Third current modulation circuit

2026, 3026‧‧‧ Current and voltage conversion circuit

3021‧‧‧Input current sensing circuit

3025‧‧‧third current amplifier circuit

3027‧‧‧fourth current modulation circuit

EN‧‧‧Enable signal

I1, Ic1‧‧‧ first current

I1’, Ic1’‧‧‧ first amplified current

I2, Ic2‧‧‧second current

I2’, Ic2’‧‧‧second amplification current

I3, Ic3‧‧‧ third current

I3’, Ic3’‧‧‧ third amplified current

Ic4‧‧‧ fourth amplification current

Iin‧‧‧ input current

Iin1‧‧‧Preset first input current

Iin2‧‧‧Preset second input

Ilol, Ilo‧‧‧Overcurrent protection lower limit current

Imin‧‧‧Overcurrent protection minimum threshold current

Imod‧‧‧ modulated current

Iup1, Iup‧‧‧Overcurrent protection upper limit current

OCP‧‧‧Overcurrent protection threshold

OCPmax‧‧‧Overcurrent protection maximum critical value

OCPmin‧‧‧Over-current protection minimum threshold

R‧‧‧ impedance

R1, R2, Rsen‧‧‧ resistance

SW‧‧‧Enable Switching Circuit

UVLO, UVLO’‧‧‧ Undervoltage lock level

Vin‧‧‧Input voltage

Vin1‧‧‧Preset first input voltage

Vin2‧‧‧Preset second input voltage

Vout‧‧‧ output voltage

FIG. 1A shows a schematic diagram of a prior art switched power supply 100.

Fig. 1B is a diagram showing signal waveforms of the input voltage Vin, the output voltage Vout, and the input current Iin during normal operation.

Figure 2 shows a schematic diagram that uses the reduced undervoltage lockout level to avoid system shutdown.

Figure 3 shows a first embodiment of the invention.

Figure 4A-4K shows a synchronous or asynchronous step-down, step-up, back-pressure, buck-boost, step-up, or flyback power stage circuit.

Figure 5 is a graph showing the relationship between the overcurrent protection threshold OCP and the input voltage Vin, in accordance with one embodiment of the present invention.

Figure 6 shows a second embodiment of the invention.

Fig. 7 shows a third embodiment of the present invention.

Figure 8 is a diagram showing waveforms of input voltage and input current signals in accordance with the present invention.

Figure 9 is a graph showing the relationship between the overcurrent protection threshold OCP and the input current Iin in accordance with one embodiment of the present invention.

Fig. 10 shows a fourth embodiment of the present invention.

Figure 11 shows a fifth embodiment of the present invention.

The drawings in the present invention are schematic, mainly intended to indicate the coupling relationship between the circuits, and the relationship between the signal waveforms, and the circuit, signal waveform and frequency are not drawn to scale.

Figure 3 shows a first embodiment of the invention. As shown in FIG. 3, the switching power supply 200 is configured to convert the input voltage Vin into an output voltage Vout, and is driven by the display driving circuit 203. The display panel 10 is moved. The switched power supply 200 includes a power stage circuit 201, a control circuit 202, and a display drive circuit 203. The power stage circuit 201 switches at least one of the power switches to convert the input voltage Vin into an output voltage Vout according to the operation signal. The power stage circuit 201 includes at least one power switch, which can be a synchronous or non-synchronous step-down, step-up, back-pressure type, buck-boost type, step-up type, or flyback type power stage circuit, such as 4A -4K picture shown. The display driver circuit 203 drives the display panel 10 to receive the output voltage Vout, which is not the focus of the present invention and will not be described herein.

The control circuit 202 is coupled to the power stage circuit 201 for generating an operation signal. The control circuit 202 includes a threshold adjustment circuit 2021 for generating and adaptively adjusting the overcurrent protection threshold OCP according to the input voltage Vin or the input current Iin. The input current Iin flows through the power stage circuit 201. Among them, the overcurrent protection threshold OCP is used to limit the input current Iin. The control circuit 202 does not turn on the power switch when the input current Iin exceeds the overcurrent protection threshold OCP. The control circuit 202 uses this mechanism to feedback the control input current Iin so that the input current Iin is not too high, so that the input voltage Vin is not lower than the preset under voltage lockout (UVLO) level. The so-called input current Iin is too high or not too high, mainly due to the voltage drop caused by the input current Iin multiplied by the impedance R of the line group, causing the drop of the input voltage Vin, and making the input voltage Vin lower than the preset ow When the under voltage lockout (UVLO) level is used, the input current Iin is too high; if the input voltage Vin is kept higher than the preset undervoltage lock level, the input current Iin is not too high.

In the present embodiment, the threshold value adjustment circuit 2021 includes, for example, a voltage current conversion circuit 2022, a first current modulation circuit 2023, a second current modulation circuit 2024, a third current modulation circuit 2025, and current and voltage conversion. Circuit 2026. For example, as shown in FIG. 5, the threshold adjustment circuit 2021 adaptively adjusts the overcurrent protection threshold OCP when the input voltage Vin falls, and the input voltage Vin is not higher than the preset first input voltage Vin1. The overcurrent protection threshold OCP is maintained at the overcurrent protection minimum threshold OCPmin; and when the input voltage rises, the overcurrent protection threshold OCP is adaptively adjusted, and the input voltage Vin is not lower than the preset second input. When the voltage Vin2 is made The overcurrent protection threshold OCP is maintained at the overcurrent protection maximum threshold OCPmax; wherein the preset first input voltage Vin1 is lower than the preset second input voltage Vin2, and the overcurrent protection minimum threshold OCPmin is lower than the overcurrent protection maximum critical The value OCPmax.

Figure 6 shows a second embodiment of the invention. This embodiment shows a more specific embodiment of the threshold adjustment circuit 2021. As shown in FIG. 6, the threshold value adjustment circuit 2021 includes, for example, a voltage current conversion circuit 2022, a first current modulation circuit 2023, a second current modulation circuit 2024, a third current modulation circuit 2025, and a current voltage. Conversion circuit 2026. The voltage/current conversion circuit 2022 is configured to convert the input voltage Vin or its related signal into the first current I1. It should be noted that the related signal of the input voltage Vin refers to the signal related to the input voltage Vin. Due to various factors, the voltage current conversion circuit 2022 does not have to directly receive the input voltage Vin, but can receive and input the voltage Vin. Other signals having a proportional or linear function relationship, which are proportional to the input voltage Vin or have a linear function relationship, are related signals of the input voltage Vin. As shown, the voltage-current conversion circuit 2022 receives, for example, an input voltage Vin and, via a low-dropout regulator (LDO) as shown, including a resistor R1 to convert the input voltage Vin into a first A current I1.

The first current modulation circuit 2023 is coupled to the voltage current conversion circuit 2022 for converting the first current I1 into a ratio of 1:M1, for example, to a first amplification current I1′ proportional thereto, and protecting the upper limit current according to the overcurrent. The difference between Iup1 and the first amplification current I1' produces a second current I2. In this embodiment, the first current modulation circuit 2023 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the first current I1 into a first amplification current I1′ proportional thereto. The current protection upper limit current Iup1 is provided, for example, by a fixed current source; wherein the relationship between the second current I2, the first amplification current I1', and the overcurrent protection upper limit current Iup1 is: I2=Iup1-I1'.

The second current modulation circuit 2024 is coupled to the first current modulation circuit 2023 for converting the second current I2 into a ratio of 1:M2, for example, to a second amplification current I2' proportional thereto, and according to A difference between the current protection lower limit current Ilol and the second amplification current I2' produces a third current I3. In this embodiment, the second current modulation circuit 2024 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the second current I2 into a second amplification current I2' proportional thereto. The current protection lower limit current Ilol is provided, for example, by a fixed current source; wherein, the relationship between the third current I3, the second amplification current I2', and the overcurrent protection lower limit current Ilol is: I3=Ilol-I2'.

The third current modulation circuit 2025 is coupled to the second current modulation circuit 2024 for converting the third current I3 into a ratio of 1:M3, for example, to a third amplification current I3' proportional thereto, and according to the overcurrent The minimum threshold current Imin and the third amplification current I3' are protected to generate a modulation current Imod. In this embodiment, the third current modulation circuit 2025 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the third current I3 into a third amplification current I3′ proportional thereto. The current protection minimum threshold current Imin is provided, for example, by a fixed current source; wherein, the relationship between the modulation current Imod, the third amplification current I3', and the overcurrent protection minimum threshold current Imin is: Imod=I3'+Imin.

The current-to-voltage conversion circuit 2026 is coupled to the third current modulation circuit 2025 for converting the modulation current Imod into an overcurrent protection threshold OCP. The current-voltage conversion circuit 2026 includes, for example, a resistor R2 to adjust the voltage difference generated by the current Imod flowing through the resistor R2 as the overcurrent protection threshold OCP.

In the present embodiment, the value of the overcurrent protection minimum threshold OCPmin is: OCPmin=Imin×R2 and the value of the overcurrent protection maximum threshold OCPmax is: OCPmax=(Imin+Ilol×M3)×R2 according to the embodiment, The preset first input voltage Vin1 is: The preset second input voltage Vin2 is: And in FIG. 5, between the preset first input voltage Vin1 and the preset second input voltage Vin2, the slope slop of the overcurrent protection threshold OCP rise is: That is to say, the user can appropriately select the resistor R1, the resistor R2, the overcurrent protection upper limit current Iup1, the overcurrent protection lower limit current Ilol, the overcurrent protection minimum threshold current Imin, and the current mirror amplification ratio M1, M2, as needed. M3, to obtain an overcurrent protection minimum threshold OCPmin, an overcurrent protection maximum threshold OCPmax, a first input voltage Vin1, a preset second input voltage Vin2, and a slope slop that rises from the overcurrent protection threshold OCP.

Fig. 7 shows a third embodiment of the present invention. The difference between the present embodiment and the second embodiment is that in the embodiment, the second current modulation circuit 2024 further includes an enable switch circuit SW for determining whether to generate the second amplified current I2 according to the enable signal EN. '. In this embodiment, the enable signal EN can determine to generate the second amplification current I2' during the blanking period; and outside the blanking period, it is determined that the second amplification current I2' is not generated, and outside the blanking period. The threshold adjustment circuit 2021 maintains the overcurrent protection threshold OCP at a fixed preset overcurrent protection threshold, that is, a fixed value related to the overcurrent protection lower limit current Ilol, the overcurrent protection minimum threshold current Imin, and the resistor R2. The output voltage Vout is used to supply the display panel 10, and the blanking period is related to the period from the end of the screen scanning before the display panel 10 to the start of the scanning of the screen.

Figure 8 is a diagram showing the waveforms of the input voltage Vin and the input current Iin according to the present invention. Compared with the prior art, the present invention adjusts the over-voltage according to the change of the input voltage Vin or the input current Iin, especially during the aforementioned blanking period, the drop of the input voltage Vin and the rise of the input current. The current protection threshold OCP uses the mechanism of overcurrent protection to limit the input current Iin to avoid the input voltage Vin being below the preset under voltage lockout (UVLO) level (especially during blanking). The thick solid line portion in the figure represents a signal waveform diagram of the input voltage Vin and the input current Iin according to the present invention, and the thick broken line portion represents a signal waveform diagram of the prior art input voltage Vin and the input current Iin.

Figure 9 is a graph showing the relationship between the overcurrent protection threshold OCP and the input current Iin in accordance with one embodiment of the present invention. The present invention can be used to adjust the overcurrent protection threshold OCP when the input current Iin rises by using the threshold adjustment circuit 2021. and to make the overcurrent protection threshold when the input current Iin rises to reach the preset first input current Iin1. The OCP maintains the minimum current value OCPmin of the overcurrent protection, and maintains the input current Iin at the preset first input current Iin1; and when the input current Iin falls, adaptively raises the overcurrent protection threshold OCP, and does not input the current Iin. When the preset second input current Iin2 is higher than the preset second input current Iin2, the overcurrent protection threshold OCP is maintained at the overcurrent protection maximum threshold OCPmax; wherein the preset first input current Iin1 is higher than the preset second input current Iin2, and the overcurrent is The protection minimum threshold OCPmin is lower than the overcurrent protection maximum threshold OCPmax.

Fig. 10 shows a fourth embodiment of the present invention. This embodiment shows another more specific embodiment of the threshold adjustment circuit 2021. As shown in FIG. 10, the threshold adjustment circuit 2021 includes, for example, an input current sensing circuit 3021, a voltage current conversion circuit 3022, a first current modulation circuit 3023, a second current modulation circuit 3024, and a third current amplification circuit. 3025, a fourth current modulation circuit 3027, and a current voltage conversion circuit 3026. The input current sensing circuit 3021 is configured to sense the input current Iin to generate a current sensing signal, which is connected in series with the power stage circuit 101 by using a resistor Rsen, for example, to obtain a voltage across the resistor Rsen as a current sensing signal. The voltage-current conversion circuit 3022 is configured to convert the current sensing signal into the first current Ic1. As shown, the voltage-current conversion circuit 3022 includes, for example, an error amplifier circuit and a low-dropout regulator (LDO) to convert the current sense signal into a first current Ic1.

The first current modulation circuit 3023 is coupled to the voltage current conversion circuit 2022 for converting the first current Ic1 into a ratio of 1:M1, for example, to a first amplification current Ic1′ proportional thereto, and according to the first amplification current Ic1. 'The difference from the overcurrent protection lower limit current Ilo produces a second current Ic2. In this embodiment, the first current modulation circuit 3023 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the first current Ic1 into a first amplification current Ic1' proportional thereto. The current protection lower limit current Ilo is provided, for example, by a fixed current source; wherein, the relationship between the second current Ic2, the first amplification current Ic1', and the overcurrent protection lower limit current Ilo is: Ic2=Ic1'-Ilo.

The second current modulation circuit 3024 is coupled to the first current modulation circuit 3023 for converting the second current Ic2 into a ratio of 1:M2, for example, to a second amplification current Ic2' proportional thereto, and according to the overcurrent The difference between the upper limit current Iup and the second amplified current Ic2' is generated to generate a third current Ic3. In this embodiment, the second current modulation circuit 3024 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the second current Ic2 into a second amplification current Ic2' proportional thereto. The current protection upper limit current Iup is provided, for example, by a fixed current source; wherein, the relationship between the third current Ic3, the second amplification current Ic2', and the overcurrent protection upper limit current Iup is: Ic3=Iup-Ic2'.

The third current amplifying circuit 3025 is coupled to the second current modulating circuit 3024 for converting the third current Ic3 to a third amplifying current Ic3' proportional thereto, for example, at a ratio of 1:M3. In the present embodiment, the third current amplifying circuit 3025 includes, for example but not limited to, a current mirror circuit.

The fourth current modulation circuit 3027 is coupled to the third current amplification circuit 3025 for converting the third amplification current Ic3′ to the fourth amplification current Ic4 proportional thereto, and protecting the minimum threshold current Imin according to the overcurrent protection The four amplification current Ic4 generates a modulation current Imod. In this embodiment, the fourth current modulation circuit 3027 includes, for example but not limited to, a current mirror circuit and a fixed current source, and the current mirror circuit converts the third amplification current Ic3′ to a fourth amplification current Ic4 proportional thereto. The overcurrent protection minimum threshold current Imin is provided, for example, by a fixed current source; wherein the modulation current Imod, fourth The relationship between the amplification current Ic4 and the overcurrent protection minimum threshold current Imin is: Imod=Ic4+Imin.

The current-to-voltage conversion circuit 3026 is coupled to the fourth current modulation circuit 3027 for converting the modulation current Imod into an overcurrent protection threshold OCP. The current-voltage conversion circuit 3026 includes, for example, a resistor R2 to regulate the voltage difference generated by the current Imod flowing through the resistor R2 as the overcurrent protection threshold OCP.

Figure 11 shows a fifth embodiment of the present invention. The present embodiment differs from the fourth embodiment in that, in the embodiment, the second current modulation circuit 3024 further includes an enable switch circuit SW for determining whether to generate the second amplification current Ic2 according to the enable signal EN. '. In this embodiment, the enable signal EN can determine to generate the second amplification current Ic2' during the blanking period; and outside the blanking period, it is determined that the second amplification current Ic2' is not generated, and outside the blanking period. The threshold adjustment circuit 2021 maintains the overcurrent protection threshold OCP at a fixed preset overcurrent protection threshold, that is, a fixed value related to the overcurrent protection upper limit current Iup, the overcurrent protection minimum threshold current Imin, and the resistor R2. The output voltage Vout is used to supply the display panel 10, and the blanking period is related to the period from the end of the screen scanning before the display panel 10 to the start of the scanning of the screen.

The present invention has been described with reference to the preferred embodiments thereof, and the present invention is not intended to limit the scope of the present invention. In the same spirit of the invention, various equivalent changes can be conceived by those skilled in the art. For example, in the embodiments, the two circuits or components that are directly connected may be interposed with other circuits or components that do not affect the main function. Therefore, "coupling" should be considered as including direct and indirect connections. For example, the current is amplified in a symptom-prone manner, and is not limited to the current mirror circuit, and can be extended to other circuits having the same amplification effect; for example, the positive and negative terminals of the amplifier circuit and the comparator circuit can be interchanged, and only the relevant circuit or the corresponding circuit needs to be modified. It is the meaning of the level of the signal. All such modifications may be made in accordance with the teachings of the present invention, and the scope of the present invention should be construed to cover the above and other equivalents.

10‧‧‧Display panel

200‧‧‧Switching power supply

201‧‧‧Power level circuit

202‧‧‧Control circuit

203‧‧‧Display driver circuit

2021‧‧‧critical value adjustment circuit

2022‧‧‧Voltage current conversion circuit

2023‧‧‧First current modulation circuit

2024‧‧‧Second current modulation circuit

2025‧‧‧ Third current modulation circuit

2026‧‧‧current voltage conversion circuit

Iin‧‧‧ input current

Vin‧‧‧Input voltage

Vout‧‧‧ output voltage

Claims (28)

A switching power supply for converting an input voltage into an output voltage, the switching power supply comprising: a power stage circuit, switching at least one of the power switches to convert the input voltage according to an operation signal And the control circuit is coupled to the power stage circuit for generating the operation signal, and the control circuit includes a threshold adjustment circuit for generating and adapting according to the input voltage or an input current. Adjusting an overcurrent protection threshold; wherein the input current flows through the power stage circuit; wherein the overcurrent protection threshold is used to limit the input current; wherein the control circuit exceeds the overcurrent protection At the critical value, the power switch is not turned on. The switching power supply device of claim 1, wherein the threshold adjustment circuit adaptively reduces the overcurrent protection threshold when the input voltage drops, and drops the input voltage to no higher than When a first input voltage is preset, the overcurrent protection threshold is maintained at an overcurrent protection minimum threshold; and when the input voltage rises, the overcurrent protection threshold is adaptively adjusted, and the input voltage is applied to the input voltage When the voltage rises to a preset second input voltage, the overcurrent protection threshold is maintained at an overcurrent protection maximum threshold; wherein the preset first input voltage is lower than the preset second input voltage, And the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold. The switching power supply device of claim 1, wherein the threshold adjustment circuit adaptively lowers the overcurrent protection threshold when the input current rises, and reaches a preset when the input current rises During the first input current, the overcurrent protection threshold is maintained at a minimum threshold of overcurrent protection, and the input current is maintained at the preset first input current; and when the input current decreases, the adaptive adjustment is performed. An overcurrent protection threshold value, and maintaining the overcurrent protection threshold value at an overcurrent protection maximum critical value when the input current drops to not higher than a predetermined second input current; wherein the preset first input The current is higher than the preset second input current, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold. The switching power supply device of claim 1, wherein the threshold adjustment circuit adaptively adjusts the overcurrent protection threshold so that the input voltage is not caused by the input current being too high and lower than a predetermined ow Under voltage lockout (UVLO) level. The switching power supply of claim 1, wherein the output voltage is used to supply a display panel, and during a blanking interval, the threshold adjusting circuit is based on the input voltage or the input The current, adaptively adjusts the overcurrent protection threshold; and outside the blanking period, the threshold adjustment circuit maintains the overcurrent protection threshold at a fixed preset overcurrent protection threshold. The switching power supply device of claim 1, wherein the threshold value adjustment circuit comprises: a voltage current conversion circuit for converting the input voltage or its related signal into a first current; a current modulation circuit coupled to the voltage current conversion circuit for converting the first current into a first amplification current proportional thereto, and protecting the difference between the upper limit current and the first amplification current according to an overcurrent a second current modulation circuit coupled to the first current modulation circuit for converting the second current into a second amplification current proportional thereto, and according to a a difference between the current protection lower limit current and the second amplification current to generate a third current; a third current modulation circuit coupled to the second current modulation circuit for converting the third current Comparing with the third amplification current, and according to an overcurrent protection minimum threshold current and the third amplification current, generating a modulation current; and a current voltage conversion circuit coupled to the third current modulation circuit For converting the modulation current threshold for overcurrent protection. The switching power supply device of claim 6, wherein the second current modulation circuit further comprises a uniform energy switching circuit for determining whether to generate the second amplification current according to the uniform energy signal. The switching power supply device of claim 7, wherein the enabling signal determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not to generate the first And amplifying the current; wherein the output voltage is used to supply a display panel, and the blanking period is related to a period from the end of the front screen scanning of the display panel to the beginning of the scanning of the screen. The switching power supply device of claim 1, wherein the threshold value adjusting circuit comprises: an input current sensing circuit for sensing the input current to generate a current sensing signal; a voltage current a conversion circuit for converting the current sensing signal into a first current; a first current modulation circuit coupled to the voltage current conversion circuit for converting the first current into a proportional ratio thereof a first amplification current, and generating a second current according to the difference between the first amplification current and an overcurrent protection lower limit current; a second current modulation circuit coupled to the first current modulation circuit, The second current is converted into a second amplification current proportional thereto, and a third current is generated according to a difference between an overcurrent protection upper limit current and the second amplification current; a third current amplifying circuit, and The second current modulation circuit is coupled to convert the third current into a third amplification current proportional thereto; a fourth current modulation circuit coupled to the third current amplification circuit for The third Converting the current into a fourth amplification current proportional thereto, and protecting a minimum threshold current and the fourth amplification current according to an overcurrent, generating a modulation current; and a current voltage conversion circuit, and the fourth current modulation The circuit is coupled to convert the modulated current to the overcurrent protection threshold. The switching power supply device of claim 9, wherein the second current modulation circuit further comprises a uniform energy switching circuit for determining whether to generate the second amplification current according to the uniform energy signal. The switching power supply device of claim 10, wherein the enabling signal determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not to generate the first And amplifying the current; wherein the output voltage is used to supply a display panel, and the blanking period is related to a period from the end of the front screen scanning of the display panel to the beginning of the scanning of the screen. A switching power supply control method, wherein the switching power supply is configured to convert an input voltage into an output voltage, and the switching power supply control method comprises: operating a power level according to an operation signal At least one power switch in the circuit to convert the input voltage into the output voltage; and generating and adaptively adjusting an overcurrent protection threshold according to the input voltage or an input current; and limiting the threshold by the overcurrent protection threshold Input current; and when the input current exceeds the overcurrent protection threshold, the power switch is not turned on; wherein the input current flows through the power stage circuit. The method for controlling a switching power supply according to claim 12, wherein the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current comprises: dropping the input voltage Adjusting the overcurrent protection threshold value adaptively, and maintaining the overcurrent protection threshold value at a minimum value of an overcurrent protection threshold when the input voltage drops to not higher than a predetermined first input voltage; When the input voltage rises, the overcurrent protection threshold is adaptively adjusted, and the overcurrent protection threshold is maintained at an overcurrent protection when the input voltage rises to not lower than a predetermined second input voltage. a maximum threshold; wherein the preset first input voltage is lower than the preset second input voltage, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold. The method for controlling a switching power supply according to claim 12, wherein the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current comprises: increasing the input current Adjusting the overcurrent protection threshold value adaptively, and maintaining the overcurrent protection threshold value at an overcurrent protection threshold value and maintaining the input when the input current rises to a predetermined first input current Current is at the preset first input current; and when the input current is decreased, adaptively raising the overcurrent protection threshold, and when the input current drops to not higher than a predetermined second input current, The overcurrent protection threshold is maintained at an overcurrent protection maximum threshold; wherein the preset first input current is higher than the preset second input current, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum critical value. The control method of the switching power supply device of claim 12, wherein the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current further comprises: making the input voltage It is not caused by the input current being too high and below a preset under voltage lockout (UVLO) level. The control method of the switching power supply device of claim 12, wherein the output voltage is used to supply a display panel, and the overcurrent protection is generated and adaptively adjusted according to the input voltage or the input current. The threshold value step includes: adaptively adjusting the overcurrent protection threshold according to the input voltage or the input current during a blanking period; and maintaining the overcurrent protection threshold value at a fixed time outside the blanking period The preset overcurrent protection threshold. The method for controlling a switching power supply according to claim 12, wherein the step of generating and adaptively adjusting the overcurrent protection threshold according to the input voltage comprises: the input voltage or a related signal thereof, Converting to a first current; converting the first current to a first amplification current proportional thereto, and generating a second current according to a difference between an overcurrent protection upper limit current and the first amplification current; The second current is converted into a second amplification current proportional thereto, and a third current is generated according to a difference between an overcurrent protection lower limit current and the second amplification current; the third current is converted into a third ratio proportional thereto Amplifying the current and protecting the minimum threshold current and the third current according to an overcurrent to generate a modulated current; and converting the modulated current to the overcurrent protection threshold. The control method of the switching power supply device of claim 17, wherein the second current is converted into a second amplification current proportional thereto, and the current is limited according to an overcurrent protection current and the second amplification The step of generating a third current by the difference of the currents further includes: determining whether to generate the second amplified current according to the consistent energy signal. The control method of the switching power supply device of claim 18, wherein the enabling signal determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not The second amplifying current is generated; wherein the output voltage is used to supply a display panel, and the blanking period is related to a period from the end of the front screen scanning of the display panel to the beginning of the scanning of the screen. The method for controlling a switching power supply according to claim 12, wherein the step of generating and adaptively adjusting the overcurrent protection threshold according to the input current comprises: sensing the input current to generate a a current sensing signal, converting the current sensing signal into a first current; converting the first current into a first amplification current proportional thereto, and according to the first amplification current and an overcurrent protection lower limit current a second current is generated by converting the second current into a second amplifying current proportional thereto, and generating a third current according to a difference between an overcurrent protection upper limit current and the second amplifying current; The third current is converted into a third amplification current proportional thereto; the third amplification current is converted into a fourth amplification current proportional thereto, and the minimum threshold current and the fourth amplification current are generated according to an overcurrent protection a modulated current; and converting the modulated current to the overcurrent protection threshold. The method for controlling a switching power supply according to claim 20, wherein the converting the second current into a step of proportional to the second amplifying current further comprises: determining whether to generate the The second amplified current. The control method of the switching power supply device of claim 21, wherein the enabling signal determines to generate the second amplifying current during a blanking period; and outside the blanking period, determining not The second amplifying current is generated; wherein the output voltage is used to supply a display panel, and the blanking period is related to a period from the end of the front screen scanning of the display panel to the beginning of the scanning of the screen. A control circuit in a switching power supply for generating an operation signal, switching at least one power switch in the switching power supply, and converting an input voltage into an output voltage, wherein the control circuit includes a threshold a value adjustment circuit for generating and adaptively adjusting an overcurrent protection threshold according to the input voltage to limit the input current, wherein the threshold adjustment circuit comprises: a voltage current conversion circuit for using the input voltage or The related signal is converted into a first current; a first current modulation circuit is coupled to the voltage current conversion circuit for converting the first current into a first amplification current proportional thereto, and according to the first a difference between the current protection upper limit current and the first amplification current to generate a second current; a second current modulation circuit coupled to the first current modulation circuit for converting the second current Comparing with a second amplification current, and generating a third current according to a difference between an overcurrent protection lower limit current and the second amplification current; a third current The modulation circuit is coupled to the second current modulation circuit for converting the third current into a third amplification current proportional thereto, and protecting the minimum threshold current and the third current according to an overcurrent And generating a modulation current; and a current-voltage conversion circuit coupled to the third current modulation circuit for converting the modulation current into the overcurrent protection threshold; wherein the overcurrent protection threshold, The method is configured to limit the input current; wherein the control circuit does not turn on the power switch when the input current exceeds the overcurrent protection threshold. The control circuit in the switching power supply device of claim 23, wherein when the input voltage drops, the overcurrent protection threshold is adaptively lowered, and the input voltage drops to no higher than one When the first input voltage is set, the overcurrent protection threshold is maintained at an overcurrent protection minimum threshold; and when the input voltage rises, the overcurrent protection threshold is adaptively increased, and the input voltage rises to When the voltage is not lower than a preset second input voltage, the overcurrent protection threshold is maintained at an overcurrent protection maximum threshold. A control circuit in a switching power supply for generating an operation signal, switching at least one power switch in the switching power supply, and converting an input voltage into an output voltage, wherein the control circuit includes a threshold a value adjustment circuit for generating and adaptively adjusting an overcurrent protection threshold according to the input current to limit the input current, wherein the threshold adjustment circuit comprises: an input current sensing circuit for sensing the input a current is generated to generate a current sensing signal; a voltage current conversion circuit for converting the current sensing signal into a first current; a first current modulation circuit coupled to the voltage current conversion circuit, The first current is converted into a first amplification current proportional thereto, and a second current is generated according to a difference between the first amplification current and an overcurrent protection lower limit current; and a second current modulation circuit And the first current modulation circuit is coupled to convert the second current into a second amplification current proportional thereto, and according to an overcurrent protection upper limit a difference between the current and the second amplification current to generate a third current; a third current amplification circuit coupled to the second current modulation circuit for converting the third current into a proportional ratio a third current modulating circuit coupled to the third current amplifying circuit for converting the third amplifying current into a fourth amplifying current proportional thereto, and minimizing the criticality according to an overcurrent protection The value current and the fourth amplification current generate a modulation current; and a current voltage conversion circuit coupled to the fourth current modulation circuit for converting the modulation current into the overcurrent protection threshold. The control circuit in the switching power supply device of claim 25, wherein the threshold value adjusting circuit adaptively lowers the overcurrent protection threshold when the input current rises, and rises in the input current When a predetermined first input current is reached, the overcurrent protection threshold is maintained at a minimum threshold of overcurrent protection, and the input current is maintained at the preset first input current; and when the input current decreases, adapting Adjusting the overcurrent protection threshold value, and maintaining the overcurrent protection threshold value at an overcurrent protection threshold value when the input current drops to not higher than a preset second input current; wherein the pre The first input current is higher than the preset second input current, and the overcurrent protection minimum threshold is lower than the overcurrent protection maximum threshold. The control circuit in the switching power supply device of claim 23 or 25, adapted to adjust the overcurrent protection threshold so that the input voltage is not lower than a preset undervoltage lockout (under voltage lockout, UVLO) level. The control circuit of the switching power supply according to claim 23 or 25, wherein the output voltage is used to supply a display panel, and the control circuit is based on the input voltage or the input during a blanking period. The current, adaptively adjusts the overcurrent protection threshold; and outside the blanking period, the control circuit maintains the overcurrent protection threshold at a fixed preset overcurrent protection threshold.