Controller and control method for power converter

Abstract

The present invention relates to a controller of a power converter, which includes a current sampling circuit, an overcurrent protection circuit, a compensation circuit and a pulse width modulation signal generating circuit. The overcurrent protection circuit receives a current detection signal provided by the current sampling circuit in response to an output current exceeding a preset value to generate an overcurrent protection signal. The compensation circuit receives a reference voltage, an output voltage and the overcurrent protection signal to generate a compensation signal. The pulse width modulation signal generating circuit receives the overcurrent protection signal and the compensation signal to generate a control signal. The compensation circuit includes a voltage adjusting circuit and an error amplifier circuit. The voltage adjusting circuit receives the reference voltage, the output voltage and the overcurrent protection signal, and is controlled by the overcurrent protection signal to generate an adjusted reference voltage. The error amplifier circuit receives the adjusted reference voltage and the output voltage to generate the compensation signal to the pulse width modulation signal generating circuit. The controller of the power converter of the present invention can effectively avoid the output voltage of the power converter from having a severe overshoot phenomenon under a load removal condition.

Description

Technical Field

[0001] This invention relates to power converters, and more particularly to a controller and control method for a power converter. Background Technology

[0002] When a traditional multiphase power converter encounters an overcurrent event, its pulse width modulation signal generator is limited by the overcurrent protection signal, which changes the pulse width modulation signal it generates, thereby limiting the total output current of the multiphase power converter.

[0003] For example, such as Figure 1 As shown, at the first time T1, the power converter starts generating the overcurrent protection signal TOCL, causing the output voltage VOUT to begin to decrease. At time T2, the instant the load is removed, the power converter stops generating the overcurrent protection signal TOCL, causing the output voltage VOUT to begin to rise and exceed the reference voltage VREF. However, once the output voltage VOUT continues to rise and the difference between it and the reference voltage VREF becomes too large, the power converter then fully activates, causing a severe overshoot phenomenon in the output voltage VOUT (as shown by the dashed circle), which requires further resolution. Summary of the Invention

[0004] In view of this, the present invention proposes a controller and control method for a power converter to effectively solve the above-mentioned problems encountered in the prior art.

[0005] According to a specific embodiment of the present invention, a controller for a power converter is provided. In this embodiment, the controller provides control signals to cause the power converter to generate output current and output voltage. The controller includes a current sampling circuit, an overcurrent protection circuit, a compensation circuit, and a pulse width modulation signal generation circuit. The current sampling circuit senses the output current to provide a current detection signal. The overcurrent protection circuit is coupled to the current sampling circuit and receives the current detection signal to generate an overcurrent protection signal in response to the output current exceeding a preset value. The compensation circuit is coupled to the overcurrent protection circuit and receives a reference voltage, an output voltage, and the overcurrent protection signal to generate a compensation signal. The pulse width modulation signal generation circuit is coupled to the overcurrent protection circuit and the compensation circuit and receives the overcurrent protection signal and the compensation signal to generate a control signal. The compensation circuit includes a reference voltage adjustment circuit and an error amplification circuit. The reference voltage adjustment circuit is coupled to the overcurrent protection circuit and receives the reference voltage, the output voltage, and the overcurrent protection signal, and is controlled by the overcurrent protection signal to generate an adjusted reference voltage. The error amplifier circuit is coupled to the reference voltage adjustment circuit and the pulse width modulation signal generation circuit to receive the adjusted reference voltage and output voltage to generate a compensation signal to the pulse width modulation signal generation circuit.

[0006] According to another specific embodiment of the present invention, a control method for a power converter is provided. In this embodiment, the control method provides a control signal to cause the power converter to generate an output current and an output voltage. The control method includes the following steps: sensing the output current to provide a current detection signal; generating an overcurrent protection signal in response to the output current exceeding a preset value; generating a compensation signal based on a reference voltage, the output voltage, and the overcurrent protection signal; and generating a control signal based on the overcurrent protection signal and the compensation signal. The step of generating the compensation signal includes: controlling the overcurrent protection signal to generate an adjusted reference voltage based on the reference voltage and the output voltage; and generating the compensation signal based on the adjusted reference voltage and the output voltage.

[0007] Compared to prior art, the power converter controller and control method proposed in this invention utilize an overcurrent protection signal generated when the output current exceeds a preset value to change the reference voltage input to the error amplifier circuit, thereby changing the compensation signal output from the error amplifier circuit to the pulse width modulation signal generation circuit, so as to effectively avoid severe overshoot phenomenon of the power converter output voltage when the load is removed.

[0008] The advantages and spirit of the present invention can be further understood from the following detailed description of the invention and the accompanying drawings. Attached Figure Description

[0009] The accompanying drawings of this invention are described below:

[0010] Figure 1 The waveform of the output voltage of a conventional multiphase power converter exhibiting severe overshoot when the load is removed is shown.

[0011] Figure 2 A schematic diagram illustrating the controller of a power converter in a specific embodiment of the present invention is shown.

[0012] Figure 3 and Figure 4 Different embodiments of the reference voltage adjustment circuit in the compensation circuit are illustrated.

[0013] Figure 5 The diagram illustrates the waveform of the power converter controller of the present invention generating a compensation signal based on an adjusted reference voltage to prevent overshoot of its output voltage when the load is removed.

[0014] Figure 6 A flowchart illustrating a control method for a power converter according to another specific embodiment of the present invention is shown.

[0015] Figure 7 Draw Figure 6 Step S14 also includes flowcharts of sub-steps S140 and S142. Detailed Implementation

[0016] Reference will now be made in detail to exemplary embodiments of the invention, and examples of these exemplary embodiments will be illustrated in the drawings. Elements / components using the same or similar reference numerals in the drawings and embodiments are used to represent the same or similar parts.

[0017] The main component symbols of this invention are explained below:

[0018] T1…First Time

[0019] T2…Second Time

[0020] T3…Third Time

[0021] PC…Power Converter

[0022] 1…Controller

[0023] OS…output level

[0024] L…output inductor

[0025] C…capacitor

[0026] R…resistance

[0027] LD…load

[0028] VIN…Input voltage

[0029] IOUT…output current

[0030] VOUT…output voltage

[0031] M1…First Switch

[0032] M2…Second Switch

[0033] 10… Current sampling circuit

[0034] 12…Overcurrent Protection Circuit

[0035] 14…compensation circuit

[0036] 140…Reference Voltage Adjustment Circuit

[0037] 142…Error Amplifier Circuit

[0038] 16…Pulse Width Modulation Signal Generation Circuit

[0039] CS… Current detection signal

[0040] TOCL…Overcurrent protection signal

[0041] VREF…reference voltage

[0042] VC… Adjusted reference voltage

[0043] EA… Error Amplifier

[0044] RC…Resistor-Capacitor Compensation Unit

[0045] K…output terminal

[0046] VCOMP…compensation signal

[0047] P1~P2… control signals

[0048] VDD…Operating voltage

[0049] ICH…charging current

[0050] BF…buffer

[0051] N1…First node

[0052] N2…Second node

[0053] VREF2…Second reference voltage

[0054] SC… switching circuit

[0055] SW1…First Switching Unit

[0056] SW2…Second Switching Unit

[0057] SE… Current Source

[0058] SW…Switching element

[0059] Steps S10~S16…

[0060] S140~S142… Sub-steps

[0061] According to a specific embodiment of the present invention, a controller for a power converter is provided. In this embodiment, the power converter may be a multiphase power converter, and its controller is used to provide control signals to generate output current and output voltage, but is not limited thereto.

[0062] Please refer to Figure 2 , Figure 2 A schematic diagram illustrating the controller of the power converter in this embodiment is shown. (As shown) Figure 2 As shown, the power converter PC includes a controller 1, an output stage OS, an output inductor L, a capacitor C, a resistor R, and a load LD. The output stage OS includes a first switch M1 and a second switch M2 connected in series between the input voltage VIN and ground. The controller 1 is coupled to the control terminals of the first switch M1 and the second switch M2 in the output stage OS, as well as to both ends of the output inductor L. One end of the output inductor L is coupled between the first switch M1 and the second switch M2. The capacitor C and the resistor R are connected in series between the other end of the output inductor L and ground. The load LD is coupled between the other end of the output inductor L and ground.

[0063] The controller 1 includes a current sampling circuit 10, an overcurrent protection circuit 12, a compensation circuit 14, and a pulse width modulation signal generation circuit 16. The current sampling circuit 10 is coupled to both ends of the output inductor L and the overcurrent protection circuit 12. The overcurrent protection circuit 12 is coupled to the current sampling circuit 10, the compensation circuit 14, and the pulse width modulation signal generation circuit 16. The compensation circuit 14 is coupled to the overcurrent protection circuit 12 and the pulse width modulation signal generation circuit 16. The pulse width modulation signal generation circuit 16 is coupled to the control terminals of the overcurrent protection circuit 12, the compensation circuit 14, and the first switch M1 and the second switch M2 in the output stage OS.

[0064] The current sampling circuit 10 senses the output current IOUT flowing through the output inductor L to provide a current detection signal CS to the overcurrent protection circuit 12. The overcurrent protection circuit 12 receives the current detection signal CS and determines whether the output current IOUT exceeds a preset value. If the determination result is yes, the overcurrent protection circuit 12 generates an overcurrent protection signal TOCL in response to the output current IOUT exceeding the preset value, which is sent to the compensation circuit 14 and the pulse width modulation signal generation circuit 16. The compensation circuit 14 receives the reference voltage VREF, the output voltage VOUT, and the overcurrent protection signal TOCL, and generates a compensation signal VCOMP to the pulse width modulation signal generation circuit 16. The pulse width modulation signal generation circuit 16 receives the overcurrent protection signal TOCL and the compensation signal VCOMP, and generates control signals P1 to P2 to the control terminals of the first switch M1 and the second switch M2 in the output stage OS to control the opening or closing of the first switch M1 and the second switch M2.

[0065] In this embodiment, the compensation circuit 14 includes a reference voltage adjustment circuit 140 and an error amplifier circuit 142. The error amplifier circuit 142 includes an error amplifier EA and a resistor-capacitor compensation unit RC. The error amplifier circuit 142 has a first input terminal (e.g., a positive input terminal +), a second input terminal (e.g., a negative input terminal -), and an output terminal. The reference voltage adjustment circuit 140 is coupled to both the overcurrent protection circuit 12 and the positive input terminal + of the error amplifier EA in the error amplifier circuit 142. The error amplifier circuit 142 is coupled to a pulse width modulation signal generation circuit 16; more specifically, the output terminal K of the error amplifier EA is coupled to the pulse width modulation signal generation circuit 16. The resistor-capacitor compensation unit RC is coupled between the output terminal K of the error amplifier EA and ground. In one embodiment, the error amplifier EA may be constructed from a transconductance amplifier.

[0066] The reference voltage adjustment circuit 140 receives the reference voltage VREF, the output voltage VOUT, and the overcurrent protection signal TOCL, and is controlled by the overcurrent protection signal TOCL to generate an adjusted reference voltage VC to the positive input terminal + of the error amplifier EA. The positive input terminal + and the negative input terminal - of the error amplifier EA in the error amplifier circuit 142 receive the adjusted reference voltage VC and the output voltage VOUT, respectively, and outputs a compensation signal VCOMP from the output terminal K to the pulse width modulation signal generation circuit 16.

[0067] In one embodiment, such as Figure 3 As shown, the reference voltage adjustment circuit 140 includes a resistor R, a capacitor C, a buffer BF, and a switching circuit SC. The resistor R and capacitor C are connected in series between the operating voltage VDD and ground. The charging current ICH flows through the resistor R. The buffer BF is coupled to the first node N1 between the resistor R and the capacitor C. The switching circuit SC is coupled to the first node N1 and the positive input terminal + of the error amplifier EA in the error amplifier circuit 142. The buffer BF receives the output voltage VOUT and the overcurrent protection signal TOCL and is controlled by the overcurrent protection signal TOCL to output a second reference voltage VREF2 to the first node N1. The output waveform of the second reference voltage VREF2 follows the output voltage VOUT. The switching circuit SC includes a first switching unit SW1 and a second switching unit SW2. The first switching unit SW1 is coupled between the reference voltage VREF and the positive input terminal + of the error amplifier EA. The second switching unit SW2 is coupled between the first node N1 and the positive input terminal + of the error amplifier EA.

[0068] It should be noted that the switching circuit SC determines whether the adjusted reference voltage VC output from the reference voltage adjustment circuit 140 to the positive input terminal + of the error amplifier EA in the error amplifier circuit 142 is the original reference voltage VREF, or the second reference voltage VREF2 following the output voltage VOUT, by turning on the first switching unit SW1 or the second switching unit SW2.

[0069] When an overcurrent event occurs in the power converter PC, the overcurrent protection signal TOCL generated by the overcurrent protection circuit 12 triggers the output of the buffer BF in the reference voltage adjustment circuit 140 to follow the second reference voltage VREF2 of the output voltage VOUT to the first node N1. At this time, the first switching unit SW1 of the switching circuit SC is turned off and the second switching unit SW2 is turned on, so that the adjusted reference voltage VC received at the positive input terminal + of the error amplifier EA is approximately the second reference voltage VREF2 of the output voltage VOUT, and both the positive input terminal + and the negative input terminal - of the error amplifier EA have signals approximately the output voltage VOUT.

[0070] When the load is removed, the overcurrent protection circuit 12 stops generating the overcurrent protection signal TOCL, and the buffer BF stops outputting the second reference voltage VREF2, which is approximately the output voltage VOUT, to the first node N1. At this time, the first switching unit SW1 of the switching circuit SC is still off, and the second switching unit SW2 is still on, so that the positive input terminal + of the error amplifier EA is also connected to the original second reference voltage VREF2.

[0071] At this time, the output voltage VOUT received at the negative input terminal of error amplifier EA will start to rise and exceed the adjusted reference voltage VC received at the positive input terminal of error amplifier EA. This causes the compensation signal VCOMP output by error amplifier EA to pulse width modulation signal generation circuit 16 to fall, thereby controlling pulse width modulation signal generation circuit 16 to stop outputting control signals P1 to P2 to output stage OS. Therefore, it can effectively limit the output voltage VOUT of power converter PC from continuing to rise, thereby avoiding serious overshoot.

[0072] In another embodiment, such as Figure 4 As shown, the reference voltage adjustment circuit 140 includes a current source SE, a capacitor C, a switching element SW, and a switching circuit SC. The current source SE and capacitor C are connected in series between the operating voltage VDD and ground. The current source SE provides the charging current ICH. The switching element SW is coupled to a second node N2 between the current source SE and capacitor C. The switching circuit SC is coupled to the second node N2 and the positive input terminal + of the error amplifier EA in the error amplifier circuit 142. The switching element SW is controlled to be turned on or off by the overcurrent protection signal TOCL. The switching circuit SC includes a first switching unit SW1 and a second switching unit SW2. The first switching unit SW1 is coupled between the reference voltage VREF and the positive input terminal + of the error amplifier EA. The second switching unit SW2 is coupled between the second node N2 and the positive input terminal + of the error amplifier EA.

[0073] When an overcurrent event occurs in the power converter PC, the overcurrent protection signal TOCL generated by the overcurrent protection circuit 12 will turn on the switching element SW in the reference voltage adjustment circuit 140, causing the switching element SW to output a second reference voltage VREF2, approximately equal to the output voltage VOUT, to the second node N2. At this time, the first switching unit SW1 of the switching circuit SC is turned off and the second switching unit SW2 is turned on, so that the adjusted reference voltage VC received at the positive input terminal + of the error amplifier EA is the second reference voltage VREF2, approximately equal to the output voltage VOUT, and both the positive input terminal + and the negative input terminal - of the error amplifier EA have signals approximately equal to the output voltage VOUT.

[0074] When the load is removed, because the switching element SW2 remains on, a second reference voltage VREF2, approximately the same as the output voltage VOUT, continues to be output to the second node N2. At this time, the positive input terminal + of the error amplifier EA still receives the original second reference voltage VREF2.

[0075] At this time, the output voltage VOUT received at the negative input terminal of error amplifier EA will start to rise and exceed the adjusted reference voltage VC received at the positive input terminal of error amplifier EA. This causes the compensation signal VCOMP output by error amplifier EA to pulse width modulation signal generation circuit 16 to fall, thereby controlling pulse width modulation signal generation circuit 16 to stop outputting control signals P1 to P2 to output stage OS. Therefore, it can effectively limit the output voltage VOUT of power converter PC from continuing to rise, thereby avoiding serious overshoot.

[0076] Please refer to Figure 5 , Figure 5 The diagram illustrates the waveform of the power converter controller of the present invention generating a compensation signal based on an adjusted reference voltage to prevent overshoot of its output voltage when the load is removed.

[0077] like Figure 5 As shown, at the first time T1, the output current IOUT is deloaded, causing an overcurrent event. The overcurrent protection circuit 12 starts to generate the overcurrent protection signal TOCL. The first switching unit SW1 of the switching circuit SC is disconnected and the second switching unit SW2 is turned on, so that the positive input terminal of the error amplifier EA + the received adjusted reference voltage VC is approximately the second reference voltage VREF2 of the output voltage VOUT.

[0078] At the second time T2, the output current IOUT is unloaded, but the overcurrent protection circuit 12 continues to generate the overcurrent protection signal TOCL. The first switching unit SW1 of the switching circuit SC remains off and the second switching unit SW2 remains on, so that the positive input terminal of the error amplifier EA still receives the original second reference voltage VREF2.

[0079] Subsequently, the output voltage VOUT received at the negative input terminal of error amplifier EA will begin to rise and exceed the adjusted reference voltage VC received at the positive input terminal of error amplifier EA. This causes the compensation signal VCOMP output by error amplifier EA to pulse width modulation signal generation circuit 16 to decrease, thereby controlling pulse width modulation signal generation circuit 16 to stop outputting control signals P1 to P2 to output stage OS. After the third time T3, the output voltage VOUT of power converter PC is suppressed from continuing to rise, thus avoiding serious overshoot.

[0080] According to another specific embodiment of the present invention, there is a control method for a power converter. In this embodiment, the control method is used to provide control signals to cause the power converter to generate output current and output voltage.

[0081] Please refer to Figure 6 , Figure 6 A flowchart illustrating the control method of the power converter in this embodiment is shown.

[0082] like Figure 6 As shown, the control method for the power converter includes the following steps:

[0083] Step S10: Sensing the output current to provide a current detection signal;

[0084] Step S12: Generate an overcurrent protection signal in response to the current detection signal exceeding a preset value;

[0085] Step S14: Generate a compensation signal based on the reference voltage, output voltage, and overcurrent protection signal; and

[0086] Step S16: Generate a control signal based on the overcurrent protection signal and the compensation signal.

[0087] In one embodiment, such as Figure 7 As shown, step S14 further includes the following sub-steps:

[0088] Step S140: Controlled by the overcurrent protection signal, an adjusted reference voltage is generated based on the reference voltage and the output voltage; and

[0089] Step S142: Generate a compensation signal based on the adjusted reference voltage and output voltage.

[0090] In practical applications, step S142 involves performing error amplification (i.e., differential amplification) on the reference voltage, the adjusted reference voltage, and the output voltage to generate a compensation signal, but this is not the only limitation.

[0091] Compared to prior art, the power converter controller and control method proposed in this invention utilize an overcurrent protection signal generated when the output current exceeds a preset value to change the reference voltage input to the error amplifier circuit, thereby changing the compensation signal output from the error amplifier circuit to the pulse width modulation signal generation circuit, so as to effectively avoid severe overshoot phenomenon of the power converter output voltage when the load is removed.

Claims

1. A controller for a power converter, configured to provide control signals to cause the power converter to generate output current and output voltage, the controller comprising: A current sampling circuit senses the output current to provide a current detection signal; An overcurrent protection circuit, coupled to the current sampling circuit, is used to receive the current detection signal and generate an overcurrent protection signal in response to the output current exceeding a preset value. A compensation circuit, coupled to the overcurrent protection circuit, is used to receive a reference voltage, the output voltage, and the overcurrent protection signal to generate a compensation signal. as well as A pulse width modulation signal generation circuit, coupled to the overcurrent protection circuit and the compensation circuit, is used to receive the overcurrent protection signal and the compensation signal to generate the control signal; The compensation circuit includes: A reference voltage adjustment circuit, coupled to the overcurrent protection circuit, is used to receive the reference voltage, the output voltage, and the overcurrent protection signal, and is controlled by the overcurrent protection signal to generate the adjusted reference voltage; and An error amplifier circuit, coupled to the reference voltage adjustment circuit and the pulse width modulation signal generation circuit, is used to receive the adjusted reference voltage and the output voltage to generate the compensation signal to the pulse width modulation signal generation circuit.

2. The controller according to claim 1, wherein the error amplification circuit comprises: An error amplifier has a first input terminal, a second input terminal, and an output terminal. The first input terminal receives the adjusted reference voltage, and the second input terminal receives the output voltage. The output terminal outputs the compensation signal. as well as A resistor-capacitor compensation unit is coupled between the output terminal and the ground terminal of the error amplifier.

3. The controller according to claim 1, wherein the reference voltage adjustment circuit comprises: The resistor through which the charging current flows; A capacitor is connected in series with the resistor at the first node; A buffer, coupled to the first node, is used to receive the output voltage and the overcurrent protection signal and is controlled by the overcurrent protection signal to generate a second reference voltage at the first node; as well as The switching circuit includes a first switching unit and a second switching unit. The first switching unit is coupled between the reference voltage and the positive input terminal of the error amplifier, and the second switching unit is coupled between the first node and the positive input terminal of the error amplifier.

4. The controller according to claim 3, wherein the error amplification circuit comprises: An error amplifier has a first input terminal, a second input terminal, and an output terminal. The first input terminal is used to receive the reference voltage or the adjusted reference voltage, and the second input terminal receives the output voltage. The output terminal outputs the compensation signal. as well as A resistor-capacitor compensation unit is coupled between the output terminal and the ground terminal of the error amplifier.

5. The controller according to claim 1, wherein the reference voltage adjustment circuit comprises: A current source, used to provide charging current; A capacitor is connected in series with the current source at the second node; as well as A switching element, coupled to the second node, is used to receive the output voltage and the overcurrent protection signal and is controlled by the overcurrent protection signal to generate a second reference voltage at the second node.

6. The controller according to claim 5, wherein the error amplification circuit comprises: An error amplifier has a first input terminal, a second input terminal, and an output terminal. The first input terminal receives the reference voltage and the adjusted reference voltage, and the second input terminal receives the output voltage. The output terminal outputs the compensation signal. as well as A resistor-capacitor compensation unit is coupled between the output terminal and the ground terminal of the error amplifier.

7. A control method for a power converter, used to provide control signals to cause the power converter to generate output current and output voltage, the control method comprising the following steps: The output current is sensed to provide a current detection signal; An overcurrent protection signal is generated in response to the current detection signal exceeding a preset value; A compensation signal is generated based on the reference voltage, the output voltage, and the overcurrent protection signal. as well as The control signal is generated based on the overcurrent protection signal and the compensation signal; The step of generating the compensation signal includes: Controlled by the overcurrent protection signal, the adjusted reference voltage is generated based on the reference voltage and the output voltage; and The compensation signal is generated based on the adjusted reference voltage and the output voltage.

8. The control method according to claim 7, wherein the compensation signal is generated by differential amplification of the reference voltage, the adjusted reference voltage and the output voltage.

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