System and method for a power conversion system

Abstract

A method for operating a power supply system, the method comprising: Operating a power converter (100) with a first output power, wherein the power converter is controlled according to a first switching pattern; Monitoring a first input voltage at an input port (155) of the power converter and when it is detected that the first input voltage falls below a first predetermined voltage threshold, Reducing the first output power of the power converter (100) to a second output power which is lower than the first output power, wherein reducing the first output power of the power converter (100) comprises modifying the switching pattern of the power converter (100) so that the power converter is controlled with a second switching pattern modified compared to the first switching pattern, and Suspending the operation of the power converter (100) after reducing the first output power of the power converter (100).

Description

TECHNICAL FIELD

[0001] The present application relates generally to an electronic device and, more particularly, to a system and method for a power conversion system (current and / or voltage conversion). BACKGROUND

[0002] Switching networks, including switching power converters and motor controllers, are widely used in power conversion systems in many electronic applications, from computers to automobiles. Generally, voltages in a switching power conversion system are generated by performing DC-to-DC, DC-to-AC, and / or AC-to-DC conversion by operating a switch coupled to an inductor or transformer. Switching power supplies are typically more efficient than other types of power conversion systems because power conversion is performed by controlled charging and discharging of a low-loss component, such as an inductor or transformer, thus reducing the energy lost due to power dissipation across resistive voltage drops.Similarly, switching motor controllers can be used to commutate brushless DC motors with low losses in the driver circuit.

[0003] During operation of a power conversion system, the input voltage supplied to the power conversion system may fluctuate and temporarily fall below a certain voltage threshold, causing a brownout condition. To protect the power conversion system from the adverse effects caused by the brownout condition, appropriate monitoring, control, and operating procedures are required. Providing capabilities for this is a challenge.

[0004] A power converter is known from US 2009 / 0 103 338 A1. In a variant referred to as conventional in this document, switching of the power converter is stopped when the input voltage falls below an input threshold by applying a logical 1 as a stop signal to a NOR gate whose output is connected to a control input of a switching transistor. In a figure of this document, this logical 1 then briefly drops to 0 several times due to ripples in the input voltage. In a power converter circuit based on this, switching is then terminated with a delay after the voltage falls below a threshold by applying the logical 1 to the NOR gate.

[0005] Another power converter is known from US 2013 / 0 063 990 A1. BRIEF PRESENTATION

[0006] A method according to claim 1 or 12 and a system according to claim 18 are provided. The subclaims define further embodiments. The system can be configured to carry out the methods.

[0007] According to one embodiment, a method for operating a power system includes operating a power converter at a first output power and monitoring a first input voltage at an input port of the power converter. The method further includes, when the first input voltage is detected to fall below a first predetermined voltage threshold, reducing the first output power of the power converter to a second output power lower than the first output power, and discontinuing (suspending, terminating) operation of the power converter after the first output power of the power converter is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a more complete understanding of the present invention and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings: Fig. 1 illustrates a power conversion system using a switching power converter according to some embodiments; Fig. 2 illustrates a waveform diagram showing an ideal rectified AC voltage and an output voltage of a rectifier of a switching power supply before and after switching is stopped; Fig. 3 illustrates a waveform diagram showing an ideal rectified AC voltage and a rectifier output voltage of an embodiment of a switching power supply in which switching is stopped after the output power is reduced; The Fig. 4A and Fig. 4B illustrate waveform diagrams showing ideal rectified AC voltages and rectifier output voltages for other embodiments of the switching power supply system; The Fig. 5A and Fig. 5B illustrate circuits used to operate a power system according to some embodiments; Fig. 6 illustrates the ideal rectified AC voltage and the output voltage of the rectifier circuit according to various embodiments of methods for operating a power system; Fig. 7 illustrates an execution diagram of a controller of a power conversion system; Fig. 8 illustrates a flowchart of a method for operating a power system according to some embodiments, and Fig. 9 illustrates a flowchart of a method of operating a power converter according to some embodiments.

[0009] Corresponding numbers and symbols in different figures generally refer to corresponding parts unless otherwise noted. The figures are drawn to clearly illustrate the relevant aspects of the preferred embodiments and are not necessarily drawn to scale. To more clearly illustrate certain embodiments, a letter illustrating variations of the same structure, material, or process step may follow a figure number. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0010] The making and using of presently preferred embodiments are discussed in detail below. It should be understood, however, that the present invention provides many applicable inventive concepts that can be practiced in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways of making and using the invention and do not limit the scope of the invention.

[0011] The present invention will be described with respect to the preferred embodiments in a specific context, a system, and a method for a power conversion system with a flyback converter. Those skilled in the art will appreciate that embodiments of the present invention may also be applied to various power conversion systems using other types of power converters, such as boost converters, buck converters, or other suitable types of power converters.

[0012] Embodiments of the present invention are directed to measuring the AC line voltage of a power conversion system to detect a voltage drop condition and / or a voltage drop condition. In a power conversion system, the amplitude of the AC input voltage may fluctuate during normal operation (e.g., when the power converter is switching). When the AC input voltage drops below a low voltage threshold, a voltage drop condition occurs. Voltage drop conditions can have many adverse effects on the power system. For example, for a switching power supply with a regulated output, current consumption increases as the input voltage drops to maintain the same output, which can stress the power supply and affect its reliability.A voltage drop condition can also cause unexpected behavior in digital systems, as reduced voltages can bring signal levels below the threshold at which logic circuits can reliably detect the conditions represented by the signal levels. To avoid the adverse effects due to the voltage drop condition and protect the system, various embodiments of the system can detect the voltage drop condition and respond by stopping or ceasing switching of the power converter. When the input AC voltage recovers from the voltage drop and rises above a predetermined high voltage threshold, a voltage drop condition occurs. The various embodiments of the system can detect the voltage drop condition and respond by resuming switching of the power converter.

[0013] In conventional systems that determine the AC line voltage by monitoring the rectified AC voltage at the input of the switching power converter, some errors can be introduced due to coupled switching noise and ringing due to inductances in the power supply. If a measurement of the AC line voltage is performed during such a transient condition, the measurement can lead to an overestimation of the AC line voltage. For example, in a power system with an AC input voltage with a nominal peak amplitude of 110 V, a voltage drop condition voltage threshold is set at 80 V and a voltage rise condition voltage threshold is set at 85 V. If the AC input voltage falls below the voltage drop condition threshold (e.g.However, if the voltage drops below 79 V, a measured value of the rectified AC voltage could exceed the voltage increase threshold (e.g., at 86 V) due to switching noise and ringing. The falsely high measurement of 86 V could cause the power conversion system to make an erroneous decision regarding subsequent voltage increase detection.

[0014] In various embodiments of the present invention, the switching pattern of the switching power converter is modified when a voltage drop condition is detected so that the effect of the transient condition on the input voltage of the switching power converter is reduced or eliminated. For example, in one embodiment, the current output of the switching power converter is reduced for a period of time after the voltage drop condition is detected so that the effect of the transient condition on the input voltage of the switching power converter is reduced. In another embodiment, the switch of the switching power converter is toggled after the power converter has been stopped to remove an erroneous sampled voltage on the input capacitor of the switching power converter and enable correct detection of a subsequent voltage increase condition.

[0015] Fig. 1 illustrates an exemplary power conversion system 100 in which an AC input voltage is applied to input ports 101 and 103 of the power conversion system 100. In some embodiments, the AC input ports 101 and 103 are coupled to a rectifier circuit via an optional line filter 107. As shown in Fig. 1, the rectifier circuit may be a bridge rectifier including diodes 111, 113, 115, and 117. The rectifier circuit converts the input AC voltage into a rectified AC voltage (e.g., a time-varying DC voltage) between a first output port 120 and a second output port 122 of the rectifier circuit. In some embodiments, the second output port 122 of the rectifier circuit is coupled to a reference voltage level, e.g., a ground level. Therefore, the following description may refer only to the first output port 120 as an output port of the rectifier circuit, with the understanding that the second output port 122 is at a reference level, e.g., ground level. Additional components, such as input capacitors 105 and 109, may be used to suppress high-frequency noise in the circuit, as in Fig. 1 illustrates.

[0016] With reference to Fig. 1, a capacitor 119 is coupled between output ports 120 and 122 of the rectifier circuit. One skilled in the art will readily recognize that the circuit to the right of capacitor 119 is Fig. 1 includes a switching power converter and in particular a flyback converter, the details of which are described in more detail below. Although Fig. 1 shows a flyback converter as an example, any other suitable converters, e.g. a buck converter or a boost converter, could be used in the Fig. 1 (e.g., replacing the flyback converter). Therefore, the following discussion may refer to the flyback converter in Fig. 1 as a power converter or a switching power converter. The voltage V across the terminals of capacitor 119 is thus equivalent to the input voltage of the switching power converter according to some embodiments. Input port 155 of the switching power converter is coupled to terminal 124 of capacitor 119 in various embodiments.

[0017] As in Fig. As illustrated in Figure 1, the switching power converter includes a controller 200, which may be implemented using a power control integrated circuit (IC), a microcontroller, a processor, a digital signal processor (DSP), or any other suitable controller. The controller 200 monitors the status of the power conversion system 100, e.g., the input and / or output voltages of the switching power converter, and controls the operation of the switching power converter by, e.g., stopping or continuing switching of the switching power converter.

[0018] A detection pin of the controller 200, in Fig. 1 as HV, is coupled to a first terminal 124 of capacitor 119 through a resistor 121, wherein the first terminal 124 of capacitor 119 is coupled to the output port 120 of the rectifier circuit in some embodiments. By measuring the signal at sense pin HV, controller 200 can monitor the input voltage of the switching power converter. An output pin of controller 200, in Fig. 1 as GD, is coupled to a control terminal of a switch 123 of the switching power converter according to some embodiments. The switch 123 may be, for example, a pass gate, an NMOS transistor, a PMOS transistor, or any other suitable switch. In the example of Fig. 1, the switch 123 is an N-type transistor, and the control terminal of the switch 123 is the gate electrode of the transistor 123. According to some embodiments, the controller 200 generates a pulse sequence at the output pin GD, the pulse sequence turning the switch 123 on and off according to a switching pattern of the pulse sequence, thereby controlling the switching of the switching power converter.

[0019] As in Fig. 1, a first terminal 151 (e.g., the drain electrode 151 of transistor 123) of switch 123 is coupled to a first terminal of the primary winding 133 of transformer 130, which transformer also has a secondary winding 135 that, in some embodiments, is electromagnetically coupled to the primary winding 133. A second terminal of the primary winding 133 is coupled to the terminal 124 of the capacitor 119. In some embodiments, the switching power converter further includes a resistor 139, a capacitor 137, and a diode 141 forming a resistor-capacitor-diode (RCD) snubber circuit, as shown in Fig. 1. A diode 143 is coupled between a first terminal of the secondary winding 135 and the output port 147 of the power conversion system 100 in some embodiments. Additionally, a capacitor 145 is coupled between the output ports 147 and 149 of the power conversion system 100 in some embodiments.

[0020] Furthermore, with reference to Fig. 1, in some embodiments, a second terminal 153 of switch 123 (e.g., the source electrode 153 of transistor 123) is coupled to a reference level, e.g., a ground level, via a resistor 127. In addition, the second terminal 153 of the switch 123 may be further coupled to an input pin of the controller 200, e.g., pin CS of the controller 200, which input pin may be used by the controller 200 for current measurement. In some embodiments, the controller 200 includes a further sense pin, e.g., pin ZCD, coupled to an auxiliary winding 131 via resistor 125 and to a reference level (e.g., a ground level) via resistor 129. According to some embodiments, the auxiliary winding 131 is electromagnetically coupled to the primary winding 133.Accordingly, a voltage proportional to the input voltage of the switching power converter is available at sense pin ZCD while the switching power converter is switching, and the voltage at pin ZCD may be measured by controller 200 to monitor the input voltage of the switching power converter in accordance with some embodiments.

[0021] To detect a voltage drop condition, the input AC voltage can be monitored by measuring the rectified AC voltage at the input of the power converter (e.g., measuring the voltage across capacitor 119). However, errors may be introduced into the measured values ​​of the rectified AC voltage due to coupled switching noise and ringing. In some embodiments, the ringing arises due to a resonant circuit formed by the inductance of the input filter (e.g., line filter 107) and the one or more input capacitors.According to some embodiments, switching of the power converter results in a transient in the input current, and the transient in the input current causes a voltage across an inductive component, such as the line filter 107, which voltage is added to the input AC voltage at the input of the rectifier circuit and causes a high frequency time-varying voltage component at the output of the rectifier circuit, as described below with reference to FIG. Fig. 2 is discussed.

[0022] Fig. Figure 2 illustrates a waveform diagram representing an ideal rectified AC voltage 210 and an output voltage 220 of a rectifier of a switching power supply before and after switching is stopped. The voltage 220 may, for example, correspond to the voltage across the Fig. 1. The initial part of the curve 220 (e.g. the part between time t=0 and t=t prot) illustrates the rectified AC voltage measured across capacitor 119 when the power converter switches. For reference, Fig. 2 also shows a curve 210, which represents an ideal rectified AC voltage, where “ideal” means that the curve 210 does not exhibit the effects of switching noise and oscillation. As in Fig. 2, curve 210 represents four cycles, or periods, of an ideal rectified AC voltage having a low frequency related to the frequency of the input AC voltage. In contrast, in various embodiments, curve 220 includes a high-frequency time-varying voltage component caused by power converter switching and / or ringing. To simplify the following description, this high-frequency time-varying voltage component may be referred to as an induction-induced voltage or a switching-induced voltage. In some embodiments, when the power converter is switching, curve 220 is substantially equivalent to a corresponding portion of curve 210 with the switching-induced voltage added.

[0023] The power conversion system 100 monitors the rectified AC voltage (e.g., the voltage across capacitor 119) and detects a brownout condition by processing measured values ​​of the rectified AC voltage using signal processing techniques in some embodiments. The controller 200 may process current and previously measured values ​​of the rectified AC voltage using signal processing techniques such as averaging, prediction, curve fitting, and filtering (e.g., low-pass filtering) to obtain an estimate of the rectified AC voltage and compare the estimated AC voltage to the brownout condition voltage threshold. In response to detecting a brownout condition, the controller 200 changes the operating state of the power converter in various embodiments.A simplified method for operating the power conversion system is to stop switching the power converter when the voltage drop condition is detected and to resume switching at a later time after a voltage increase condition is subsequently detected. However, such a simplified method may result in false voltage increase condition detection, as discussed below with reference to FIG. Fig. 2, understanding the limitation of this simplified method leads to understanding the various embodiments of the present application.

[0024] In the Fig. 2 example, at t=t prota voltage drop condition is detected and switching is stopped when the voltage drop condition is detected. In some embodiments, the switching is stopped by opening the switch 123 of the power converter (e.g., forming a high impedance between the first terminal 151 and the second terminal 153 in Fig. 1). Temporarily, Fig. 1. When switch 123 is in the open state (e.g., high impedance), the rectifier circuit and capacitor 119 form a peak detector that holds the maximum voltage applied across capacitor 119, according to some embodiments. For example, if a new voltage V2 at the output port 120 of the rectifier circuit is greater than a previously held maximum voltage V1, the new voltage V2 charges capacitor 119, and voltage V2 is held by capacitor 119 as the new maximum voltage; conversely, if the voltage at the output port 120 of the rectifier circuit falls below a previously held maximum voltage V1, capacitor 119 may not be discharged (e.g., due to diodes 111 and 115 in the rectifier circuit being reverse biased), causing capacitor 119 to continue holding voltage V1.

[0025] Again with reference to Fig. 2 the voltage value V s the rectified alternating voltage at time t prot held by the capacitor 119 after switching is stopped after a voltage drop condition at t=t prot was detected. Due to the switching-induced voltage, the voltage V s have a falsely large value, although the ideal rectified AC voltage (e.g., curve 210) is below the voltage drop condition voltage threshold. This falsely large voltage V s is held by the capacitor 119 (see the part of the curve 220 after t=t prot ), since the capacitor 119 and the rectifier circuit act as a peak detector. The controller 200 of the power conversion system 100 monitors the voltage across the capacitor 119 to detect a voltage increase condition in some embodiments. Since the voltage V s, which is held by the capacitor 119, but is greater than the voltage increase detection threshold, the controller 200 may erroneously determine that a voltage increase has occurred. As an example, assume a case where the voltage drop state and the voltage increase state have a voltage threshold of 80 V and 85 V, respectively. Suppose that switching is stopped once the voltage drop state at t = t prot is detected and the capacitor 119 has a voltage V sof 86 V due to the switching-induced voltage. Although the input AC voltage (indicated by the ideal rectified AC voltage curve 210) is below 85 V, the measured voltage value across capacitor 119 is 86 V, thus the power conversion system controller 200 could erroneously determine the presence of a voltage increase condition. After the power conversion system continues switching based on the false detection of the voltage increase condition, capacitor 119 is able to discharge, and the voltage across capacitor 119 follows curve 210 (in Fig. 2 (not shown), and the controller 200 may determine that the AC input voltage is still low and may again detect a voltage drop condition. This may cause the power conversion system to cycle between voltage drop detection and voltage increase detection, disrupting proper operation of the power conversion system.

[0026] An embodiment of a method for operating a power conversion system is described with reference to Fig. 3 described. In Fig. 3, curve 310 represents the ideal rectified AC voltage similar to curve 210 in Fig. 2. Curve 320 represents the rectified AC voltage applied between the terminals of capacitor 119 of Fig. 1 is measured. In the example of Fig. 3 switches the power conversion system initially. To detect a voltage drop condition while the power converter is switching, the controller 200 may form an estimate of the input AC voltage by, for example, processing the current and previously measured values ​​of the rectified AC voltage (e.g., the voltage across capacitor 119). As previously described with reference to Fig. 1, in some embodiments, the rectified AC voltage is obtained directly by measuring the signal at a first sense pin (e.g., the HV pin). In other embodiments, the rectified AC voltage is obtained indirectly by measuring the signal at a second sense pin (e.g., the ZCD pin) coupled to an auxiliary winding 131, where the auxiliary winding is electromagnetically coupled to a primary winding 133 of the power converter. In various embodiments, current and previously measured values ​​of the rectified AC voltage during the one or more past cycles may be processed using suitable signal processing techniques to obtain an estimate of the input AC voltage. Examples of suitable signal processing techniques include, but are not limited to, averaging, prediction, curve fitting, and filtering (e.g., low-pass filtering).The estimated input voltage is compared to a predetermined low voltage threshold to detect a brownout condition. In some embodiments, the predetermined low voltage threshold is adjusted for a voltage measured at different sense pins. For example, depending on factors such as the turns ratio between primary winding 133 and auxiliary winding 131 and the resistance of resistors 125 and 129, the measured voltage value at the second sense pin (e.g., the ZCD pin) is proportional to the input voltage of the switching power converter, so the low voltage threshold of the brownout condition may need to be adjusted accordingly.

[0027] With reference to Fig. 3, switching is not immediate at t prot stopped when a voltage drop condition occurs at time t=t protis detected; instead, the switching lasts for a certain period of time (e.g. from t prot are stop ), while gradually reducing the output power of the switching converter, and switching is discontinued after the output power is reduced to a predetermined level. The output power of the switching power converter is reduced by gradually reducing the peak current of the power converter, for example, when the controller 200 uses peak current control according to some embodiments.

[0028] In other embodiments, the controller 200 controls a pulse width modulation (PWM) generator 218 of the controller 200 (see Fig. 7) to change the switching pattern of the power converter so that the output power of the power converter is reduced, where the switching pattern includes parameters such as switching frequency, duty cycle, on-time, and off-time. The maximum duty cycle of the switching pattern can, for example, be reduced from almost 100% to a lower duty cycle, e.g., between about 20% and about 30%. For power converters such as flyback converters, the output power is quadratically proportional to the on-time. Thus, reducing the duty cycle can effectively reduce the output power under some conditions. In other embodiments, the off-time of the switching pattern is extended so that the output power of the power converter is reduced. The reduction in output power takes place gradually over a certain period of time, e.g.,less than one cycle or more than one cycle, depending on factors such as the original output power and the reduced output power according to some embodiments.

[0029] As the output power of the power converter is gradually reduced, the input current and the transient in the input current are reduced, resulting in a smaller induction-induced voltage. As shown in Fig. 3, the curve 320 is plotted from time t prot until time t stop due to the decreasing induction-induced voltage gradually becomes smoother and the curve 320 approaches the ideal rectified AC voltage curve 310 at time t stop very close. At time t stopthe switching of the power converter is discontinued. After the switching is discontinued, the induction-induced voltage is substantially attenuated and / or no longer exists. The combination of the capacitor 119 with the rectifier circuit can be considered a peak detector in some embodiments. For example, the curve 320 in Fig. 3 a voltage V B which is generated by the capacitor 119 after the time t stop is held until a higher voltage V B It should be noted that the voltage V Bdoes not have a falsely large value because the switching-induced voltage has been significantly reduced. The controller 200 monitors the voltage across the capacitor 119 (e.g., the voltage shown in curve 320) and compares the voltage to the voltage increase condition voltage threshold, and if it detects a voltage increase condition (e.g., the input voltage rises above the voltage increase condition voltage threshold), it continues switching the power converter according to some embodiments. In the example of Fig. 3 is the time t stop for adjusting the switching of the power converter at a peak value of the curve 310. The time t stop However, it is not limited to the peak value and could be in a cycle elsewhere once the power converter output has been sufficiently reduced.

[0030] The Fig. 4A and Fig. 4B illustrate waveform diagrams corresponding to another embodiment of a voltage drop detection method. Curve 410 represents the ideal rectified AC voltage similar to curve 210 in Fig. 2 and the curve 420 represents the rectified alternating voltage applied between the terminals of the capacitor 119 of Fig. 1. In one embodiment of the present invention, the controller 200 stops switching the power converter at a predetermined time in a cycle after detecting the voltage drop condition, instead of reducing the output power of the power converter. In the examples of Fig. 4A and Fig. 4B voltage drop states at time t=t prot detected. With reference to Fig. 4A, the predetermined time may be time t zeroin a cycle when the ideal rectified AC voltage 410 is low, e.g., at or near zero. Since the ideal rectified AC voltage at time t zero is at or near zero, the voltage across capacitor 119 at time t zero is also kept small (e.g., less than the voltage increase state voltage threshold) when switching of the power converter is stopped. After switching is stopped, the voltage across capacitor 119, shown in curve 420, tracks the maximum input voltage, as indicated by the behavior of curve 420 after time t zero in various embodiments. Alternatively, with reference to Fig. 4B, the predetermined time for setting the switching may be a time in a range, e.g., between the time t L and t R in Fig. 4B, where t L and t Rbe chosen so that a large difference between the ideal rectified AC voltage 410 and the voltage increase state voltage threshold in the range between t L and t R is present, so that the voltage held by capacitor 119 is below the voltage increase condition voltage threshold when switching of the power converter is set. In some embodiments, after setting the switching at the preferred time, controller 200 monitors the output voltage of the peak detector across capacitor 119 (e.g., curve 420) and detects the voltage increase condition. The voltage curve described above with reference to Fig. 4A and Fig. 4B use knowledge of the rectifier circuit output, e.g., phases of the rectifier circuit output voltage, so that the controller 200 can stop switching at the predetermined time.

[0031] In yet another embodiment of the method, a resistor 751 is connected in parallel with the capacitor 119, as in Fig. 5A. Resistor 751 allows capacitor 119 to discharge after the switching of the power converter has ceased; therefore, no peak detector is formed, and the voltage V across capacitor 119 follows the rectifier output voltage (e.g., the ideal rectified AC voltage plus the switching-induced voltage). Consequently, controller 200 could cease switching when a voltage drop condition is detected. The voltage increase condition can be detected by processing measured values ​​of the rectified AC voltage using signal processing techniques similar to the process for voltage drop condition detection. However, resistor 751 can cause a loss of efficiency. Another method is described in Fig. 5B illustrates a switch 753 connected between resistor 751 and capacitor 119. Switch 753 is in the open position (e.g., high impedance) during normal operation (e.g., the power converter is switching). After a voltage drop condition is detected, controller 200 stops switching the power converter and closes switch 753, allowing the voltage across capacitor 119 to track the rectifier output voltage, thus enabling proper detection of a voltage increase condition. Alternatively, controller 200 could stop switching the power converter, close switch 753 for a short period to discharge capacitor 119, and then reopen switch 753.In some embodiments, the voltage across capacitor 119 is discharged to a voltage below a voltage increase condition voltage threshold, thus avoiding maintaining a falsely large voltage across capacitor 119. This allows controller 200, in various embodiments, to correctly detect a subsequent voltage increase condition without false detection.

[0032] Fig. Figure 6 illustrates waveform diagrams corresponding to another embodiment of the method for operating a power system. Curve 610 represents the ideal rectified AC voltage, and curve 620 represents the voltage across capacitor 119 according to the present embodiment. As shown in Fig. As illustrated in Figure 6, the power converter switches from time t=0 to time t=t stop, as shown with respect to curve 620, which represents the corresponding voltage across capacitor 119. At time t=t stop a voltage drop condition is detected and the switching of the power converter is discontinued according to some embodiments. After the switching is discontinued, the rectifier circuit and capacitor 119 act as a peak detector, as indicated by the behavior of curve 620 after t = t stop is shown. In the Fig. In the example shown in Figure 6, the capacitor 119 holds a falsely large voltage V A when switching is set. Then, after a predetermined period of time (e.g., a fraction of a cycle, one cycle, or more than one cycle), the switch 123 (see Fig. 1) in different embodiments at time t=t Dclosed for a predetermined period of time (e.g., short circuit) to discharge capacitor 119. Switch 123 may be closed by a pulse generated by controller 200 and applied to a control terminal of switch 123. The duration of the pulse, or pulse width, may be determined by factors such as the capacitance of capacitor 119, the inductance of line filter 107, and the system input voltage. For example, for a 100 nF capacitor 119 and an input voltage in the range of 80 V to 100 V, a pulse width of about 2 µs to about 5 µs may be used, although other pulse widths are also possible and within the scope of the present application.

[0033] According to some embodiments, the capacitor 119 is discharged such that a voltage across the capacitor 119 is below the voltage increase state voltage threshold. As in the example of Fig. 6, the voltage across capacitor 119 drops at time t D due to the discharge, and when the discharge is complete, the voltage across capacitor 119 tracks the peak of the rectifier output voltage (e.g., curve 610). In some embodiments, controller 200 monitors the voltage across capacitor 119 and processes the measured voltage values ​​for voltage increase condition detection; when the voltage increase condition is detected, controller 200 continues switching the power converter. Although Fig. 6 shows that switching after detection of the voltage drop condition at t stop is set, a person skilled in the art will appreciate that switching at a time between t stop and t D could be discontinued without departing from the spirit of the present application.

[0034] Fig. 7 illustrates an execution diagram of a controller 200. As in Fig. 7, the controller 200 includes a first measurement circuit 216 (e.g., the HV measurement circuit), a second measurement circuit 240 (e.g., the ZCD measurement circuit), a pulse width modulation (PWM) generator 218, and a signal processing circuit 230. The first measurement circuit 216 is coupled to a first input pin 211 (e.g., the HV pin) and measures a signal at the first input pin 211 to provide, in some embodiments, a measured value (e.g., a measured voltage value) of the first signal at the first input pin 211. The second measurement circuit 240 is coupled to a second input pin 241 (e.g., the ZCD pin) and measures a signal at the second input pin 241 to provide, in some embodiments, a measured value (e.g., a measured voltage value) of the second signal at the second input pin 241. As described above with reference to Fig. 1, the first measuring circuit 216 may directly measure the input voltage of the switching power converter by measuring the voltage V across the capacitor 119. Alternatively, the second measuring circuit 240 may indirectly measure the input voltage of the switching power converter by measuring the signal at the second input 241 coupled to the auxiliary winding 131 while the power converter is switching.

[0035] The PWM generator 218 generates a pulse sequence with a specific switching pattern at an output pin 221 (e.g., the GD pin), where the switching pattern includes parameters such as switching frequency, duty cycle, on-time, and off-time of the pulses. In some embodiments, the output of the PWM generator 218 is connected to the control terminal of the switch 123 (see Fig. 1). The measured signal values ​​from the first measurement circuit 216 and / or the second measurement circuit 240 are sent to the signal processing circuit 230, which monitors the signals at the first input pin 211 and / or the second input pin 241, e.g., by checking the measured signal values ​​in some embodiments.

[0036] Based on the measured signal values, controller 200 detects and determines the status of power conversion system 100 and sends control signals to PWM generator 218 to modify the switching pattern of the pulse sequence, which in turn controls switch 123, thus, in some embodiments, changing the status of power conversion system 100. For example, controller 200 may instruct PWM generator 218 to generate a voltage level (e.g., a high or low voltage) to open switch 123, thereby stopping or ceasing switching of the power converter; or controller 200 may instruct PWM generator 218 to generate a single pulse so that switch 123 is closed for a specific period of time and then open switch 123, e.g., to discharge capacitor 119.As another example, the controller 200 may instruct the PWM generator 218 to change the switching pattern to change the output power of the switching power converter.

[0037] Fig. 8 illustrates a flowchart of a method of operating a power system according to some embodiments. Fig. 9 illustrates a flowchart of a method for operating a power converter according to other embodiments. It should be understood that the Fig. 8 and Fig. 9 are two examples of many possible embodiments of the method. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, various embodiments as shown in the Fig. 8 and Fig. 9 illustrated steps can be added, removed, replaced, rearranged and repeated.

[0038] As in Fig. 8, in step 1010, a power converter is operated at a first output power. In step 1020, a first input voltage at an input port of the power converter is monitored. In step 1030, if the first input voltage is detected to fall below a first predetermined voltage threshold, the output power of the power converter is reduced to a second output power that is less than the first output power. In step 1040, after reducing the output power of the power converter, operation of the power converter is discontinued.

[0039] With reference to Fig. 9, a power converter is switched at a first switching frequency so that a rectified AC voltage is converted into a DC voltage in step 2010. In step 2020, a voltage drop condition is detected. In step 2030, the switching of the power converter is stopped for a first predetermined period of time after the voltage drop condition is detected. In step 2040, after the first predetermined period of time, a switch of the power converter is closed for a second predetermined period of time so that a capacitor coupled to an input port of the power converter is discharged. In step 2050, after the second predetermined period of time, the switch is opened. In step 2060, a voltage increase condition is detected after the switch is opened.

[0040] According to some embodiments, circuits or systems may be configured to perform certain operations or actions using software, firmware, hardware, or a combination thereof installed in the system that, when operated, causes the system to perform those actions. One general aspect includes a method of operating a power system, the method including operating a power converter at a first output power, monitoring a first input voltage at an input port of the power converter, and upon detecting that the first input voltage falls below a first predetermined voltage threshold, reducing the first output power of the power converter to a second output power lower than the first output power, and ceasing operation of the power converter after reducing the first output power of the power converter.Other embodiments of this aspect include corresponding circuits and systems configured to perform the various actions of the methods.

[0041] Implementations may include one or more of the following features. The method further includes, after adjusting, continuing operation of the power converter when it is detected that the first input voltage rises above a second predetermined voltage threshold. In some embodiments, detecting that the first input voltage rises above the second predetermined voltage threshold includes measuring an output of a peak detector while operation of the power converter is adjusted, wherein the peak detector includes a capacitor connected in parallel with a rectifier circuit. The method further includes rectifying an AC voltage to produce the first input voltage. In some embodiments, operating the power converter includes switching the power converter at a first switching frequency with a first duty cycle.In one embodiment, monitoring the first input voltage includes measuring a voltage across a capacitor coupled to the input port of the power converter while the power converter is switching. In various embodiments, monitoring the first input voltage includes measuring a second voltage at the output of a transformer electromagnetically coupled to the power converter while the power converter is switching.

[0042] According to some embodiments, reducing the first output power of the power converter includes reducing a peak current of the power converter. In other embodiments, reducing the first output power of the power converter includes modifying a switching pattern of the power converter. In one embodiment, modifying the switching pattern includes reducing a duty cycle of the switching pattern of the power converter. In another embodiment, modifying the switching pattern includes increasing an off-time of the switching pattern of the power converter. In various embodiments, adjusting operation of the power converter includes opening a switch of the power converter.

[0043] Another general aspect includes a method of operating a power conversion system by switching a power converter at a first switching frequency such that a rectified AC voltage is converted to a DC voltage, detecting a voltage drop condition, and stopping the switching of the power converter for a first predetermined period of time when the voltage drop condition is detected. The method also includes, after the first predetermined period of time, closing a switch of the power converter for a second predetermined period of time such that a capacitor coupled to an input port of the power converter is discharged. The method further includes, after the second predetermined period of time, opening the switch and detecting a voltage increase condition after the switch opening.

[0044] Implementations may include one or more of the following features. The method may further include continuing to switch the power converter after the voltage increase condition is detected. In some embodiments, detecting the voltage drop condition includes measuring a first voltage between terminals of the capacitor and comparing the first voltage to a predetermined low voltage threshold. In other embodiments, detecting the voltage drop condition includes measuring a second voltage at an output of a transformer coupled to the power converter and comparing the second voltage to a predetermined low voltage threshold. In some embodiments, closing the switch of the power converter discharges the capacitor such that a voltage across the capacitor is lower than a predetermined high voltage threshold.Detecting the voltage increase condition may include measuring a first voltage between terminals of the capacitor and comparing the first voltage to a predetermined high voltage threshold.

[0045] Another general aspect includes a power conversion system including a controller, the controller including a pulse generation circuit configured to generate pulses having a first pulse pattern at a first output terminal of the controller, the first output terminal configured to be coupled to a switch of the power conversion system. The controller also includes a first measurement circuit configured to measure a first signal at a first sense pin of the controller and provide a first measured value of the first signal at the first sense pin, and a signal processing circuit having a first input coupled to the first measurement circuit and a first output coupled to the pulse generation circuit.The signal processing circuit is configured to compare the first measured value of the first signal with a predetermined low voltage threshold to detect a voltage drop condition while the power conversion system is switching, to change the first pulse pattern of the pulse generation circuit after detecting the voltage drop condition so that an output power of the power conversion system is reduced, and to discontinue switching of the power conversion system after the output power is reduced.

[0046] Implementations may include one or more of the following features. The power conversion system may further include a switch, wherein a control terminal of the switch is coupled to the first output terminal of the controller. The power conversion system may further include a rectifier circuit, wherein an output port of the rectifier circuit is coupled to the first sense pin of the controller. The power conversion system may further include a transformer, wherein a first terminal of the transformer is coupled to a first terminal of the switch and a second terminal of the transformer is coupled to the output port of the rectifier circuit.The power conversion system may further include a first resistor coupled between the first sense pin of the controller and a first terminal of a capacitor coupled to the output port of the rectifier circuit, wherein the signal processing circuit is further configured to compare the first measured value of the first signal to a predetermined high voltage threshold to detect a voltage increase condition while switching of the power conversion system is suspended, and to resume switching of the power conversion system when the voltage increase condition is detected. The power conversion system may further include a second resistor coupled between the first sense pin of the controller and a first terminal of an auxiliary winding, wherein the auxiliary winding is electromagnetically coupled to a primary winding of the transformer.The controller of the power conversion system may further include a second measurement circuit configured to measure a second signal at a second sense pin of the controller and provide a second measured value of the second signal. The power conversion system may further include a third resistor coupled between the second sense pin of the controller and a first terminal of a capacitor coupled to the output port of the rectifier circuit, wherein the signal processing circuit is further configured to compare the second measured value of the second signal to a predetermined high voltage value to detect a voltage increase condition while switching of the power conversion system is suspended, and to resume switching of the power conversion system after the voltage increase condition is detected.

[0047] In some embodiments, the signal processing circuit of the power conversion system is configured to reduce a duty cycle of the first pulse pattern of the pulse generation circuit, thereby reducing an output power of the power conversion system. In other embodiments, the signal processing circuit of the power conversion system is configured to increase an off-time of the first pulse pattern of the pulse generation circuit, thereby reducing an output power of the power conversion system. In yet another embodiment, the signal processing circuit of the power conversion system is configured to reduce a peak current of the power conversion system, thereby reducing an output power of the power conversion system.

[0048] Advantages of embodiments of the systems and methods include the ability to reliably detect voltage increase conditions while avoiding false voltage increase detection. For example, with respect to the Fig. In the embodiment of the method illustrated in Figure 3, the power converter adjusts the switching of the power converter in a controlled manner, for example, by gradually reducing the output power of the power converter before adjusting the switching. By reducing the output power, the switching-induced voltage is reduced, and the voltage held by capacitor 119 after adjusting the switching correctly tracks the voltage peak of the rectifier circuit output, thereby avoiding false voltage increase condition detection. Fig.In the embodiment of the method illustrated in Figure 6, the power supply discharges capacitor 119 before a voltage increase condition is detected. Since the voltage across capacitor 119 is discharged to a voltage lower than the voltage increase condition threshold, false voltage increase condition detection is also avoided.

Claims

[1] A method of operating a power supply system, the method comprising: Operating a power converter (100) with a first output power, wherein the power converter is controlled according to a first switching pattern; Monitoring a first input voltage at an input port (155) of the power converter and when it is detected that the first input voltage falls below a first predetermined voltage threshold, Reducing the first output power of the power converter (100) to a second output power which is lower than the first output power, wherein reducing the first output power of the power converter (100) comprises modifying the switching pattern of the power converter (100) so that the power converter is controlled with a second switching pattern modified compared to the first switching pattern, and Suspending the operation of the power converter (100) after reducing the first output power of the power converter (100). [2] The method of claim 1, further comprising: after the suspension, resuming operation of the power converter (100) when it is detected that the first input voltage rises above a second predetermined voltage threshold. [3] The method of claim 2, wherein detecting that the first input voltage rises above the second predetermined voltage threshold comprises: Measuring an output of a peak detector while operation of the power converter (100) is suspended, the peak detector comprising a capacitor (119) connected in parallel with a rectifier circuit (111-117). [4] The method of any of claims 1-3, further comprising rectifying an AC voltage to generate the first input voltage. [5] The method of any of claims 1-4, wherein operating the power converter comprises switching the power converter (100) at a first switching frequency with a first duty cycle according to the first switching pattern. [6] The method of any of claims 1-5, wherein monitoring the first input voltage comprises measuring a voltage across a capacitor (119) coupled to the input port (155) of the power converter (100) while the power converter (100) is switching. [7] The method of any of claims 1-6, wherein monitoring the first input voltage comprises measuring a second voltage at an output of a transformer (130) of the power converter (100) while the power converter (100) is switching. [8] The method of any of claims 1-7, wherein reducing the first output power of the power converter (100) comprises reducing a peak current of the power converter (100). [9] The method of any of claims 1-8, wherein modifying the switching pattern comprises reducing a duty cycle of the switching pattern of the power converter (100). [10] The method of any of claims 1-9, wherein modifying the switching pattern comprises increasing an off-time of the switching pattern of the power converter (100). [11] The method of any of claims 1-10, wherein suspending operation of the power converter (100) comprises opening a switch (123) of the power converter. [12] A method of operating a power conversion system, the method comprising: Switching a power converter (100) at a first switching frequency so that a rectified AC voltage is converted to a DC voltage; Detecting a voltage drop condition; stopping the switching of the power converter (100) for a first predetermined period of time after the voltage drop condition is detected; after the first predetermined period of time, closing a switch (753) of the power converter for a second predetermined period of time such that a capacitor (119) coupled to an input port (155) of the power converter is discharged; after the second predetermined period of time, opening the switch (753) and Detecting a voltage increase condition after opening the switch (753). [13] The method of claim 12, further comprising continuing to switch the power converter (100) after the voltage increase condition is detected. [14] The method of claim 12 or 13, wherein detecting the voltage drop condition comprises: Measuring a first voltage between terminals of the capacitor (119) and Comparing the first voltage with a predetermined low voltage threshold. [15] A method according to any one of claims 12-14, wherein detecting the voltage drop condition comprises: Measuring a second voltage at an output of a transformer (130) of the power converter; and Comparing the second voltage with a predetermined low voltage threshold. [16] The method of any of claims 12-15, wherein closing the switch (753) of the power converter discharges the capacitor (119) such that a voltage across the capacitor (119) is lower than a predetermined high voltage threshold. [17] A method according to any one of claims 12-16, wherein detecting the voltage increase condition comprises: Measuring a first voltage between terminals of the capacitor (119), and Comparing the first voltage with a predetermined high voltage threshold. [18] Power conversion system comprising: a controller (200), the controller comprising: a pulse generation circuit (218) configured to generate pulses having a first switching pattern at a first output terminal (221) of the controller, wherein the first output terminal (221) is configured to be coupled to a switch (123) of the power conversion system; a first measurement circuit (216) configured to measure a first signal at a first detection pin (211) of the controller (200) and to provide a first measured value of the first signal at the first detection pin (211); a signal processing circuit (230) having a first input coupled to the first measuring circuit (216) and a first output coupled to the pulse generation circuit (218), wherein the signal processing circuit (230) is configured comparing the first measured value of the first signal with a predetermined low voltage threshold to detect a voltage drop condition while the power conversion system is switching, after the voltage drop condition has been detected, modifying the first switching pattern of the pulse generating circuit (218) to a second switching pattern so that an output power of the power conversion system is reduced, and to suspend the switching of the power conversion system after the output power has been reduced. [19] The power conversion system of claim 18, further comprising the switch (123), wherein a control terminal of the switch (123) is coupled to the first output terminal (221) of the controller. [20] The power conversion system of claim 18 or 19, further comprising a rectifier circuit (111-117), wherein an output port (120) of the rectifier circuit (111-117) is coupled to the first sense pin (211) of the controller (200). [21] The power conversion system of claim 20, further comprising a transformer (130), wherein a first terminal of the transformer (130) is coupled to a first terminal of the switch (123) and a second terminal of the transformer (130) is coupled to the output port (120) of the rectifier circuit (111-117). [22] The power conversion system of claim 21, further comprising a first resistor (121) coupled between the first sense pin (211) of the controller and a first terminal of a capacitor (119) coupled to the output port (120) of the rectifier circuit, wherein the signal processing circuit (230) is further configured to comparing the first measured value of the first signal with a predetermined high voltage threshold to detect a voltage increase condition while switching of the power conversion system is set, and to continue switching the power conversion system when the voltage increase condition is detected. [23] The power conversion system of claim 21 or 22, further comprising a second resistor coupled between the first sense pin of the controller and a first terminal of an auxiliary winding (131), the auxiliary winding (131) being electromagnetically coupled to a primary winding (133) of the transformer. [24] The power conversion system of claim 23, wherein the controller further comprises a second measurement circuit configured to measure a second signal at a second sense pin of the controller (200) and provide a second measured value of the second signal. [25] The power conversion system of claim 24, further comprising a third resistor coupled between the second sense pin of the controller (200) and a first terminal of a capacitor (119) coupled to the output port of the rectifier circuit (111-117), wherein the signal processing circuit (230) is further configured to comparing the second measured value of the second signal with a predetermined high voltage value to detect a voltage increase condition while switching of the power conversion system is suspended, and to continue switching the power conversion system when the voltage increase condition is detected. [26] The power conversion system according to any one of claims 18-25, wherein the signal processing circuit (230) is configured to reduce a duty cycle of the first switching pattern of the pulse generating circuit to generate the second switching pattern, so that an output power of the power conversion system is reduced. [27] The power conversion system according to any one of claims 18-26, wherein the signal processing circuit (230) is configured to increase an off-time of the first switching pattern of the pulse generating circuit to generate the second switching pattern, so that an output power of the power conversion system is reduced. [28] The power conversion system of any of claims 18-27, wherein the signal processing circuit (230) is configured to reduce a peak current of the power conversion system so that an output power of the power conversion system is reduced.

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