TWI406486B - Systems and methods of primary-side sensing and regulation for flyback power converter with high stability - Google Patents

Abstract

The present invention discloses a system and methods to adjust the output voltage of power conversion system that comprises an error amplifier coupled with a capacitor. The error amplifier is allocated to get a reference voltage, a first voltage and the regulation current as well as cooperated with the capacitor to generate a compensation voltage. The first voltage is related to the feedback voltage. The system comprises: a current generator allocated to get the compensation voltage and generate the regulation current and a first current; a signal generator allocated to get a first and a second current .The signal generator is also allocated to get the sensor voltage and generate the modulation signal. In addition, the system also includes a gate driver that is directly/indirectly coupled with the signal generator and is allocated based on the least information related to the modulation signal to generate a driving signal.

Description

System and method for primary side sensing and adjustment of a flyback power converter

The present invention relates to an integrated circuit. More specifically, the present invention provides systems and methods for primary side sensing and adjustment. Merely by way of example, the invention has been applied to flyback power converters. However, it will be appreciated that the invention has a wide range of applications.

Primary side sensing and adjustment is widely used in flyback power converters for small power applications such as chargers. A flyback power converter typically includes a primary winding and a secondary winding associated with the output voltage of the converter. For primary side sensing and adjustment, the output voltage is typically sensed by detecting the voltage of the auxiliary winding that is tightly coupled to the secondary winding. Since the voltage of the auxiliary winding reflects the output voltage associated with the secondary winding, the voltage sensed in the auxiliary winding can be used to adjust the secondary side output voltage.

1 is a simplified diagram showing a conventional switch mode flyback power conversion system with primary side sensing and adjustment. The flyback power conversion system 100 includes a transformer 110, a power switch 120, a sense resistor 130, a cable resistor 140 representing an equivalent resistance of the output cable, a sample and hold element 180, an error amplifier 182, a loop compensation network 184, A PWM/PFM signal generator 186, a logic control element 188, and a gate driver 190. Additionally, transformer 110 includes a primary winding 112, a secondary winding 114, and an auxiliary winding 116. In addition, the flyback power conversion system 100 includes resistors 170 and 172, diodes 160 and 168, and capacitors 196 and 198. For example, loop compensation network 184 is also referred to as a compensation network. In another example, loop compensation network 184 includes a loop filter.

As shown in FIG. 1, power conversion system 100 produces an output voltage 142 at an output terminal that is received by output load 150. In order to adjust the output voltage 142 within the desired range, information related to the output voltage 142 and the output load 150 needs to be extracted for control purposes. Such information can be extracted using the auxiliary winding 116 in a discontinuous conduction mode (DCM).

Specifically, when the power switch 120 is turned "on", energy is stored in the transformer 110. Then, when the power switch 120 is off, the stored energy is delivered to the output terminal, and the output voltage 142 can be mapped by the auxiliary voltage 118 of the auxiliary winding 116. For example, the auxiliary voltage 118 and the output voltage 142 have the following relationship:

V _aux = n ×( V _o + V _F + I _o × R _eq ) (Equation 1)

Where V _aux represents the auxiliary voltage 118, V _o represents the output voltage 142, and V _F represents the forward voltage of the diode 160. In addition, I _o represents an output current corresponding to the output voltage 142. The output current is also called the load current. Further, _Req represents the resistance of the output cable resistor 140. Moreover, n represents the turns ratio between the auxiliary winding 116 and the secondary winding 114, and n is equal to N _aux /N _sec . N _aux represents the number of turns of the auxiliary winding 116, and N _sec represents the number of turns of the secondary winding 114.

As shown in FIG. 1, the auxiliary voltage 118 is received by a voltage divider including resistors 170 and 172 that convert the auxiliary voltage 118 to a feedback voltage 174.

V _FB = k × V _aux = k × n × ( V _o + V _F + I _o × R _eq ) (Equation 2-1)

k = R ₂ /( R ₁ + R ₂ ) (Equation 2-2)

Where V _FB represents the feedback voltage 174 and k represents the feedback coefficient. In addition, R ₁ and R ₂ represent the resistances of the resistors 170 and 172, respectively.

2 is a simplified diagram showing a conventional waveform of a feedback voltage 174 and a secondary current flowing through the secondary winding 114. As shown in FIG. 2, V _FB and I _sec represent the feedback voltage 174 and the secondary current, respectively. In addition, t _on represents a period of time when the power switch 120 is turned on, and t _off represents a period of time when the power switch 120 is turned off. In addition, t _Demag represents the time period of the demagnetization process.

Referring to Figures 1 and 2, the feedback voltage V _FB is received by the sample and hold element 180. At the end of the near demagnetization process, the secondary current flowing through the secondary winding 114 becomes close to zero. At this time, the feedback voltage V _FB is sampled, for example, at point A in FIG. 2 . The sampled voltage V _{A is} then held by element 180 until the next sample.

The sampled voltage V _A is received by an error amplifier 182 that compares the sampled voltage V _A with a reference voltage V _ref and also amplifies the difference between V _A and V _ref . Error amplifier 182, along with compensation network 184, transmits one or more output signals 185 to PWM/PFM signal generator 186. For example, compensation network 184 includes a capacitor. In another example, PWM/PFM signal generator 186 also receives sense voltage 132 from sense resistor 130, which converts the primary current flowing through primary winding 112 into a sense voltage. In response, PWM/PFM signal generator 186 outputs modulated signal 187 to logic control element 188, which sends control signal 189 to gate driver 190. In response, gate driver 190 transmits drive signal 192 to power switch 120.

Thus, as shown in FIG. 1, the output signal 185 is used to control the pulse width or switching frequency of the drive signal 192, and thus the output voltage 142. For example, one of the output signals 185 is associated with a compensation voltage _Vcomp . In another example, FIG. 3 is a drawing showing the output current I _o (also referred to as a load current) compensation voltage V _comp simplified diagram of the function.

Specifically, the negative feedback loop is used to adjust the output voltage V _o by adjusting the sampled voltage V _A such that V _A becomes equal to the reference voltage V _ref . therefore,

V _ref = k × n × ( V _o + V _F + I _o × R _eq ) (Equation 3)

therefore,

Since the output voltage _Vo is adjusted by the negative feedback loop, it is often important that the loop remains stable for all load conditions at all input voltages. In addition, the feedback loop usually needs to exhibit good dynamics.

As shown in FIG. 1, for the power conversion system 100, the feedback loop includes at least a control stage and a power stage. For example, the control stage includes at least a portion of error amplifier 182, loop compensation network 184, and PWM/PFM signal generator 186. In another example, the power stage comprising at least a logic control unit 188, a gate driver 190 and a gate driver 190 between certain elements of the output terminal voltage and an output V _o.

The overall transfer function of the forward path is determined by the transfer function of the control stage and the transfer function of the power stage. For the power conversion system 100, the transfer function of the power stage is:

Where R _o represents the output resistance, C _o represents the output capacitance, and R _esr represents the resistance in series with the output capacitance. In addition, s is equal to jω, and ω is an angular frequency, which is usually simply referred to as frequency. Further, D represents the duty cycle of the modulation signal 187.

Based on Equation 5, the pole position of the power stage in the frequency domain is:

Thus, for a given C _o , the frequency of the pole position changes with the output resistance. In addition, the zero position of the power stage in the frequency domain is:

Usually R _{esr is} very small, so ω _z1 is usually much larger than ω _p1 .

4 and 5 each show a simplified conventional Bode diagram of the power stage of the flyback power conversion system 100.

As discussed above, the power stage and control stage are part of the forward path of the feedback loop. The feedback loop can be characterized by stability and dynamics, both of which are often important for primary side sensing and adjustment of the flyback power conversion system.

It is therefore highly desirable to improve the techniques of primary side sensing and adjustment.

The present invention relates to an integrated circuit. More specifically, the present invention provides systems and methods for primary side sensing and adjustment. Merely by way of example, the invention has been applied to flyback power converters. However, it will be appreciated that the invention has a wide range of applications.

According to one embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier coupled to a capacitor. The error amplifier is configured to receive a reference voltage, a first voltage, and a regulated current and to generate a compensation voltage with the capacitor. The first voltage is associated with a feedback voltage. Additionally, the system includes a current generator configured to receive the compensation voltage and generate the regulated current and the first current, and a signal generator configured to receive the first current and the second current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Additionally, the system includes: a gate driver coupled directly or indirectly to the signal generator and configured to generate a drive signal based at least on information associated with the modulated signal; and a switch configured to receive the drive signal and affect flow through The primary current of the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system, and the power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage depends at least on the primary current. The error amplifier is characterized by at least a transconductance and is further configured to vary the transconductance based at least on information associated with the regulated current, and the transconductance decreases as the output current of the power conversion system decreases. For example, the transconductance also increases as the output current of the power conversion system increases.

In accordance with another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage, a first voltage, and an adjustment current by an error amplifier. The first voltage is associated with a feedback voltage. Additionally, the method includes: processing information associated with a reference voltage, a first voltage, and a regulated current; generating a compensation voltage by an error amplifier coupled to the capacitor; receiving a compensation voltage; and generating an adjustment based on at least information associated with the compensation voltage Current and first current. Moreover, the method includes receiving a first current, a second current, and a sensing voltage; generating a modulated signal based on at least information associated with the first current, the second current, and the sensing voltage; processing is associated with the modulated signal Information; and generating a drive signal based at least on information associated with the modulated signal. The method also includes receiving a drive signal and affecting the primary current based at least on information associated with the drive signal. The primary current flows through a primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The error amplifier is characterized by at least one transconductance. The step of processing information associated with the reference voltage, the first voltage, and the regulated current includes changing the transconductance based at least on information associated with the regulated current. The transconductance decreases as the output current of the power conversion system decreases. For example, the transconductance also increases as the output current of the power conversion system increases.

In accordance with yet another embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier that is indirectly coupled to a capacitor through a first switch. The error amplifier is configured to receive the reference voltage and the first voltage and to generate a compensation voltage with the capacitor if the first switch is turned "on". The first voltage is associated with a feedback voltage. Additionally, the system includes a first switch coupled to at least the error amplifier and the capacitor, and a signal generator configured to receive the compensation voltage and the first current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Additionally, the system further includes: a logic control element configured to receive the modulated signal and generate a control signal based on at least information associated with the modulated signal; a gate driver configured to receive the control signal and configured to be based at least on the control signal The associated information generates a drive signal; and a second switch configured to receive the drive signal and affect a primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system, and the power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a pulse width and a switching frequency. The first switch configuration is controlled by a control signal. Furthermore, if the control signal is at a logic high level, the first switch is turned "on" and if the control signal is at a logic low level, the first switch is turned "off".

In accordance with yet another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage and a first voltage by an error amplifier. The first voltage is associated with a feedback voltage and the error amplifier is indirectly coupled to the capacitor through the first switch. Additionally, the method includes: processing information associated with the reference voltage and the first voltage; if the first switch is turned on, generating a compensation voltage with the capacitor by the error amplifier; receiving the compensation voltage, the first current, and the sensing voltage; The modulated signal is generated based at least on information associated with the compensation voltage, the first current, and the sense voltage. Additionally, the method includes: processing information associated with the modulated signal; generating a control signal based on at least information associated with the modulated signal; processing information associated with the control signal; based at least on information associated with the control signal Generating a drive signal; and affecting the primary current based at least on information associated with the drive signal. The primary current flows through a primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a pulse width and a switching frequency. The step of processing information associated with the control signal includes turning the first switch on if the control signal is at a logic high level, and turning off the first switch if the control signal is at a logic low level.

In accordance with yet another embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier that is indirectly coupled to a capacitor through a first switch. The error amplifier is configured to receive the reference voltage and the first voltage and to generate a compensation voltage with the capacitor if the first switch is turned "on". The first voltage is associated with a feedback voltage. Additionally, the system includes a first switch coupled to at least the error amplifier and the capacitor, and a signal generator configured to receive the compensation voltage and the first current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Moreover, the system includes a logic control element configured to receive the modulated signal and generate a control signal based at least on information associated with the modulated signal. Additionally, the system includes a one-shot generator configured to receive a control signal and to send a click signal to the first switch, a gate driver configured to receive the control signal and configured to be based at least on the control signal The information generates a drive signal; and a second switch configured to receive the drive signal and affect a primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a first pulse width and a first switching frequency. The click signal is characterized by at least a second pulse width and a second switching frequency. The second pulse width is a constant determined by the click generator, and the second switching frequency is equal to the first switching frequency. The first switch configuration is controlled by a click signal. If the click signal is at a logic high level, the first switch is turned "on" and if the click signal is at a logic low level, the first switch is turned off.

In accordance with yet another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage and a first voltage by an error amplifier. The first voltage is associated with a feedback voltage and the error amplifier is indirectly coupled to the capacitor through the first switch. Additionally, the method includes: processing information associated with the reference voltage and the first voltage; if the first switch is turned on, generating a compensation voltage with the capacitor by the error amplifier; receiving the compensation voltage, the first current, and the sensing voltage; A modulated signal is generated based at least on information associated with the compensation voltage, the first current, and the sense voltage. Additionally, the method includes: processing information associated with the modulated signal; generating a control signal based on at least information associated with the modulated signal; processing information associated with the control signal; and generating at least information based on the control signal Click on the signal and drive signal. Moreover, the method includes adjusting a first switch based on information associated with the click signal; and affecting the primary current based on at least information associated with the drive signal, the primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a first pulse width and a first switching frequency, and the click signal is characterized by at least a second pulse width and a second switching frequency. The second pulse width is a constant determined by the click generator, and the second switching frequency is equal to the first switching frequency. The step of adjusting the first switch based on information associated with the click signal includes turning on the first switch if the click signal is at a logic high level, and disconnecting if the click signal is at a logic low level The first switch.

Many benefits are obtained by the present invention compared to conventional techniques. Certain embodiments of the present invention provide an error amplifier having a transconductance that decreases as the output current of the power conversion system decreases and increases as the output current of the power conversion system increases. For example, the power conversion system includes a feedback loop that includes at least a control stage and a power stage. The zero position of the control stage is lower in frequency than the pole position of the power stage. In another example, the gain curve of the combination of the control stage and the power stage has a slope of -20 dB/dec at a position where the gain is equal to 0 dB. In yet another example, the power conversion system has sufficient phase margin at a location where the gain is equal to 0 dB, thereby ensuring stability of the feedback loop from full load conditions to no load conditions. Some embodiments of the present invention provide good dynamics and stability for the feedback loop under all load conditions.

One or more of these benefits may be obtained depending on the embodiment. These and other additional objects, features and advantages of the present invention will be fully understood from the description and appended claims.

The present invention relates to an integrated circuit. More specifically, the present invention provides systems and methods for primary side sensing and adjustment. Merely by way of example, the invention has been applied to flyback power converters. However, it will be appreciated that the invention has a much broader range of applications.

6 is a simplified diagram showing a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with an embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

According to one embodiment, system 600 for primary side sensing and adjustment includes a feedback loop having at least a power stage 650. For example, power stage 650 has a transfer function Z _power (s) as described in Equation 5. In another example, power stage 650 has a pole position ω _{p in the} frequency domain and a zero position ω _{z in the} frequency domain, as described by Equation 6 and Equation 7, respectively.

According to another embodiment, system 600 further includes at least a control stage including transconductance elements 620, 622, and 624, a capacitive element 630, and an addition element 640. For example, transconductance element 620 and subtraction element 610 are part of an error amplifier belonging to system 600. In another example, the transport stage has the following transfer function:

Therefore, the zero position of the transmission stage in the frequency domain is:

Figures 7(a), (b) and (c) are simplified Bode plots showing the combined transfer function of the power and control stages with constant _gm1 under different load conditions. Specifically, FIGS. 7(a), (b), and (c) correspond to light load, medium load, and heavy load, respectively. For example, light load, medium load, and heavy load are represented by small output current I _o , medium output current I _{o ,} and large output current I _o , respectively. In another example, the combined transfer function is equal to the transfer function of the power stage multiplied by the transfer function of the control stage.

As shown in Fig. 7(c), for a heavy load, the pole position ω _{p1 is} higher than the zero position ω _z2 at the frequency. In addition, gain curve 710 intersects the horizontal axis at point A1 with a slope of -20 dB/dec at 0 dB. Point A1 corresponds to point J1 on phase curve 712. Therefore, the point J1 has a phase of more than -90° from -180°. Therefore, the feedback loop is stable.

As shown in Fig. 7(b), for a medium load, the pole position ω _{p1 is} lower than the zero position ω _z2 at the frequency. In addition, gain curve 720 intersects the horizontal axis at point B1 with a slope of -40 dB/dec at 0 dB. Point B1 corresponds to point K1 on phase curve 722. Therefore, the point K1 has a phase of less than 90° from -180°. Therefore, the feedback loop is unstable.

Similarly, as shown in Fig. 7(a), for a light load, the pole position ω _{p1 is} lower than the zero position ω _z2 at the frequency. In addition, gain curve 730 intersects the horizontal axis at point E1 with a slope of -40 dB/dec at 0 dB. Point E1 corresponds to point L1 on phase curve 732. Therefore, the point L1 has a phase of less than 90° from -180°. Therefore, the feedback loop is unstable.

According to one embodiment, one way to increase the stability of the feedback loop is to increase the compensation capacitance C. Thus, gain curves 710, 720, and 730 intersect the horizontal axis at 0 dB, such as at very low frequencies, which keeps all load conditions at a sufficient phase margin from -180°. However, a large compensation capacitor C may result in a low loop bandwidth and thus a poor dynamics.

According to another embodiment, in order to stabilize the feedback loop, the frequency ω _{z2 of the} zero point position should be varied with the load condition, because according to Equation 6, the frequency ω _p1 of the pole position changes with the load condition. For example, as described in Equation 9, the frequency of the zero position ω _z2 is reduced by decreasing g _m1 as the load is lowered. In another example, the frequency of the pole position ω _p1 remains above the zero position ω _z2 under all load conditions. According to yet another embodiment, the gain also decreases as the _gm1 is lowered.

8(a), (b) and (c) are simplified Bode plots showing a combined transfer function of a power stage and a control stage having _gm1 reduced as the load decreases, in accordance with an embodiment of the present invention. Specifically, FIGS. 8(a), (b), and (c) correspond to light load, medium load, and heavy load, respectively. For example, light load, medium load, and heavy load are represented by small output current I _o , medium output current I _{o ,} and large output current I _o , respectively. In another example, the combined transfer function is equal to the transfer function of the power stage multiplied by the transfer function of the control stage.

As shown in Fig. 8(c), for a heavy load, the pole position ω _{p1 is} higher than the zero position ω _z2 at the frequency. Furthermore, the gain curve 810 intersects the horizontal axis at point A2, for example with a slope of -20 dB/dec at 0 dB. Point A2 corresponds to point J2 on phase curve 812. According to one embodiment, point J2 has a phase greater than -180° from greater than 90°. Thus, for example, the feedback loop is stable to heavy loads.

Similarly, as shown in Fig. 8(b), for a medium load, the pole position ω _p1 is also higher than the zero position ω _z2 at the frequency. Gain curve 820 intersects the horizontal axis at point B2, for example with a slope of -40 dB/dec at 0 dB. Point B2 corresponds to point K2 on phase curve 822. According to another embodiment, point K2 has a phase greater than -180° from greater than 90°. Thus, for example, the feedback loop is stable to moderate loads.

Similarly, as shown in Fig. 8(a), for a light load, the pole position ω _p1 is also higher than the zero position ω _z2 at the frequency. Gain curve 830 intersects the horizontal axis at point E2, for example having a slope of -40 dB/dec at 0 dB. Point E2 corresponds to point L2 on phase curve 832. According to another embodiment, point L2 has a phase greater than -180° from greater than 90°. Thus, for example, the feedback loop is stable to light loads.

9 is a simplified diagram showing a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

In one embodiment, the flyback power conversion system 900 includes a power switch 920, a sense resistor 930, a sample and hold component 980, an error amplifier 982, a PWM/PFM signal generator 986, a logic control component 988, a gate driver 990, Capacitor 954, current generator 952, and feed forward element 962. For example, power switch 920, sense resistor 930, sample and hold element 980, logic control element 988, and gate driver 990 are coupled to power switch 120, sense resistor 130, sample and hold element 180, logic control element 188, and gate driver 190, respectively. the same. In another example, PWM/PFM signal generator 986 is identical to PWM/PFM signal generator 186.

In another embodiment, the flyback power conversion system 900 further includes a transformer 110, a cable resistor 140, resistors 170 and 172, diodes 160 and 168, capacitors 196 and 198, both of which are shown in FIG. . For example, transformer 110 includes a primary winding 112, a secondary winding 114, and an auxiliary winding 116.

As shown in FIGS. 6 and 9, error amplifier 982 includes a subtraction element 610 and a transconductance element 620, according to one embodiment. In another embodiment, the forward feed element 962 corresponds to the transconductance element 622. In yet another embodiment, capacitor 954 corresponds to capacitive element 630 and current generator 952 corresponds to transconductance element 624. In yet another embodiment, the node 964 for summing the currents I ₁ and I ₂ corresponds to the summing element 640.

In one embodiment, the feedback voltage V _FB is received by the sample and hold element 980. For example, at the end of the near demagnetization process, when the secondary current becomes near zero, the feedback voltage V _FB is sampled, and the sampled voltage V _{A is} then held by element 980 until the next sample. In another example, the sampled voltage V _A is received by an error amplifier 982 that compares the sampled voltage V _A with a reference voltage V _ref and also amplifies the difference between V _A and V _ref .

In another embodiment, error amplifier 982, along with capacitor 954, sends a compensation voltage 984 to current generator 952. In response, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows into or out of error amplifier 982. In another example, current I ₁ flows into node 964 and is applied to current I ₂ , and the sum of the two currents flows into PWM/PFM signal generator 986.

In yet another embodiment, current I ₂ is generated by forward feed element 962, which receives and processes sampled voltage V _A and reference voltage V _ref . For example, currents I ₁ and I ₂ have different phases. In yet another example, PWM/PFM signal generator 986 also receives sense voltage 932 from sense resistor 930, which converts the primary current flowing through primary winding 112 into a sense voltage.

As shown in FIG. 9, in accordance with an embodiment, error amplifier 982 changes its transconductance _gm1 in response to current I _EA . For example, the compensation voltage reflects the load conditions, as shown in Figure 3. In another example, the compensation voltage is used to control the transconductance _{gm1 of the} error amplifier 982 via the current I _EA .

According to one embodiment, the zero position ω _{z2 of} system 900 is reduced in frequency by decreasing g _m1 with reduced load, as described in Equation 9. For example, the gain also decreases as _gm1 decreases. In another example, the pole position ω _p1 remains above the zero position ω _z2 at all frequencies under load conditions.

As shown in FIG. 9, PWM/PFM signal generator 986 outputs modulated signal 987 to logic control component 988, which sends control signal 989 to gate driver 990. In response, gate driver 990 sends drive signal 992 to power switch 920, in response.

10(a) is a simplified diagram showing an error amplifier 982, a capacitor 954, and a current generator 952 for a switched mode flyback power conversion system 900, in accordance with one embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

As shown in FIG. 10(a), error amplifier 982, along with capacitor 954, transmits compensation voltage 984 to current generator 952. In response, in accordance with an embodiment, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows out of error amplifier 982. In another example, current I ₁ flows out of error amplifier 982.

According to one embodiment, I ₁ decreases as V _comp increases, and I ₁ increases as V _comp decreases. According to another embodiment, the error amplifier 982 changes its transconductance _gm1 in response to the current I _EA . For example, the compensation voltage 984 decreases the output current I _o is reduced. In another example, current I _EA increases as compensation voltage 984 decreases. In yet another example, as shown in FIG. 10(a),

Where I _bias represents a constant current generated by a current source, and n _a is a constant determined by the characteristics of certain elements of the error amplifier 982. According to one embodiment of the present invention, based on Equation 10, g _m1 982 of the error amplifier with a current I _EA and thus increases as the output current I _o (also referred to as a load current) decreases. For example, the current I _EA increases as the output current decreases and decreases as the output current increases, so the g _m1 of the error amplifier 982 changes with the output load condition, thereby making the zero point under all load conditions. The position ω _z2 remains below the pole position ω _p1 .

10(b) is a simplified diagram showing an error amplifier 982, a capacitor 954, and a current generator 952 for a switch mode flyback power conversion system 900 in accordance with another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

As shown in FIG. 10(b), error amplifier 982, along with capacitor 954, transmits compensation voltage 984 to current generator 952. In response, in accordance with an embodiment, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows into error amplifier 982. In yet another example, current I ₁ flows out of error amplifier 982.

According to one embodiment, I ₁ decreases as V _comp increases, and I ₁ increases as V _comp decreases. According to another embodiment, the compensation voltage 984 decreases the output current I _o is reduced. For example, current I _EA increases as the compensation voltage 984 decreases. In another example, as shown in FIG. 10(b),

Wherein, I _bias represents the constant current generated by the current source, and n _b is determined by the characteristics of some of the elements of the error amplifier 982 constant. According to another embodiment of the present invention, based on Equation 11, g _m1 982 of the error amplifier with a current I _EA and thus increases as the output current I _o (also referred to as a load current) decreases. For example, the current I _EA increases as the output current decreases and decreases as the output current increases, so the g _m1 of the error amplifier 982 changes with the output load condition, thereby making the zero point under all load conditions. The position ω _z2 remains below the pole position ω _p1 .

10(c) is a simplified diagram showing an error amplifier 982, a capacitor 954, and a current generator 952 for a switched mode flyback power conversion system 900 in accordance with yet another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

As shown in FIG. 10(c), error amplifier 982, along with capacitor 954, transmits compensation voltage 984 to current generator 952. In response, in accordance with an embodiment, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows into error amplifier 982. In yet another example, current I ₁ flows out of error amplifier 982.

According to one embodiment, I ₁ decreases as V _comp increases, and I ₁ increases as V _comp decreases. According to another embodiment, the compensation voltage 984 decreases the output current I _o is reduced. For example, current I _EA decreases as the compensation voltage 984 decreases. In another example, as shown in FIG. 10(c),

Wherein, I _bias represents the constant current generated by the current source, and n _c is determined by the characteristics of some of the elements of the error amplifier 982 constant. According to still another embodiment is reduced to reduce the embodiment of the present invention, based on Equation 12, g _m1 982 of the error amplifier decreases and thus the current I _EA as the output current I _o (also referred to as a load current). For example, the current I _EA decreases as the output current decreases and increases as the output current increases, so the g _m1 of the error amplifier 982 changes with the output load condition, thereby making the zero point under all load conditions. The position ω _z2 remains below the pole position ω _p1 .

10(d) is a simplified diagram showing an error amplifier 982, a capacitor 954, and a current generator 952 for a switched mode flyback power conversion system 900 in accordance with yet another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

As shown in FIG. 10(d), error amplifier 982, along with capacitor 954, transmits compensation voltage 984 to current generator 952. In response, in accordance with an embodiment, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows out of error amplifier 982. In yet another example, current I ₁ flows out of error amplifier 982.

According to one embodiment, I ₁ decreases as V _comp increases, and I ₁ increases as V _comp decreases. According to another embodiment, the compensation voltage 984 decreases the output current I _o is reduced. For example, current I _EA decreases as the compensation voltage 984 decreases. In another example, as shown in Figure 10(d),

Wherein, I _bias represents the constant current generated by the current source, and n _c is determined by the characteristics of some of the elements of the error amplifier 982 constant. According to still another embodiment is reduced to reduce the embodiment of the present invention, based on equation 13, g _m1 982 of the error amplifier decreases and thus the current I _EA as the output current I _o (also referred to as a load current). For example, the current I _EA decreases as the output current decreases and increases as the output current increases, so the g _m1 of the error amplifier 982 changes with the output load condition, thereby making the zero point under all load conditions. The position ω _z2 remains below the pole position ω _p1 .

11 is a simplified diagram showing an error amplifier 982, a capacitor 954, and a current generator 952 for a switched mode flyback power conversion system 900 in accordance with yet another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

As shown in FIG. 11, error amplifier 982, along with capacitor 954, sends a compensation voltage 984 to current generator 952. In response, in accordance with an embodiment, current generator 952 produces currents I _EA and I ₁ . For example, current I _EA flows out of error amplifier 982. In yet another example, current I ₁ flows out of error amplifier 982. In yet another example, error amplifier 982 includes one or more NMOS transistors.

According to one embodiment, I ₁ decreases as V _comp increases, and I ₁ increases as V _comp decreases. According to another embodiment, the compensation voltage 984 decreases the output current I _o is reduced. For example, _gm1 of error amplifier 982 decreases as compensation voltage 984 decreases. In another example, g _m1 with the output current I _o (also referred to as a load current) decreases.

12 is a simplified diagram showing a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

In one embodiment, flyback power conversion system 1200 includes power switch 1220, sense resistor 1230, sample and hold component 1280, error amplifier 1282, PWM/PFM signal generator 1286, logic control component 1288, gate driver 1290, Capacitor 1254, forward feed element 1262, and switch 1264. For example, power switch 1220, sense resistor 1230, sample and hold element 1280, logic control element 1288, and gate driver 1290, respectively, and power switch 120, sense resistor 130, sample and hold element 180, logic control element 188, and gate driver 190 the same. In another example, PWM/PFM signal generator 1286 is substantially identical to PWM/PFM signal generator 186. In yet another example, error amplifier 1282 is the same as error amplifier 182.

In another embodiment, the flyback power conversion system 1200 further includes a transformer 110, a cable resistor 140, resistors 170 and 172, diodes 160 and 168, capacitors 196 and 198, all of which are shown in FIG. . For example, transformer 110 includes a primary winding 112, a secondary winding 114, and an auxiliary winding 116.

According to one embodiment, the feedback voltage V _FB is received by the sample and hold element 1280. For example, at the end of the near demagnetization process, when the secondary current becomes near zero, the feedback voltage V _FB is sampled, and the sampled voltage V _{A is} then held by element 1280 until the next sample. In another example, the sampled voltage V _A is received by an error amplification 1282 that compares the sampled voltage V _A with a reference voltage V _ref and also amplifies the difference between V _A and V _ref .

According to another embodiment, if switch 1264 is turned on, error amplifier 1282, along with capacitor 1254, sends compensation voltage 1284 to PWM/PFM signal generator 1286. For example, the PWM/PFM signal generator 1286 also receives the current I ₂ generated by the forward feed element 1262. In another example, forward feed element 1262 receives and processes sampled voltage V _A and reference voltage V _ref . In yet another example, the compensation voltage 1284 and the current I ₂ have different phases.

According to yet another embodiment, the PWM/PFM signal generator 1286 also receives a sense voltage 1232 from the sense resistor 1230, which transforms the primary current flowing through the primary winding 112 into a sense voltage. For example, the PWM/PFM converts the compensation voltage 1284 into a load compensation current and adds the compensation current to the current I ₂ .

As shown in FIG. 12, PWM/PFM signal generator 1286 outputs modulated signal 1287 to logic control element 1288, which sends control signal 1289 to both switch 1264 and gate driver 1290. In response, in response, gate driver 1290 sends drive signal 1292 to power switch 1220. According to another embodiment, switch 1264 is turned "on" when control signal 1289 is at a logic high level and is turned off when control signal 1289 is at a logic low level.

For example, the switching frequency of the control signal 1289 changes with the load in the PFM mode, the light load produces a low switching frequency, while the large load produces a high frequency. In another example, the pulse width of control signal 1289 changes with the load in the PWM mode, with a light load producing a narrow pulse width and a large load producing a wide pulse width. Thus, according to one embodiment, the effective transconductance of error amplifier 1282 changes with load conditions.

According to another embodiment,

g _{m 1_ eff} = g _{m 1} × T _on × f _sw (Equation 14)

Where g _{m1_eff} represents the effective transconductance of error amplifier 1282 and g _m1 represents the inherent transconductance of error amplifier 1282. In addition, T _on represents the pulse width of the control signal 1289, and f _sw represents the switching frequency of the control signal 1289.

For example, the effective transconductance changes with output load conditions, thereby keeping the zero position in the frequency domain below the pole position. In another example, the effective transconductance error amplifier 1282 as the load becomes lighter (e.g., as the smaller the output current I _o) becomes small. In yet another example, the frequency of the zero position ω _z2 of the system 1200 is reduced by decreasing g _{m1 — eff} as the load decreases. In one embodiment, the gain also decreases as _{gm1_eff} decreases. In another example, the pole position ω _p1 remains above the zero position ω _z2 at all frequencies under load conditions.

13 is a simplified diagram showing a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention. This illustration is only an example and should not unduly limit the scope of the claimed patent. Those skilled in the art will recognize many variations, substitutions and modifications.

In one embodiment, flyback power conversion system 1300 includes power switch 1320, sense resistor 1330, sample and hold component 1380, error amplifier 1382, PWM/PFM signal generator 1386, logic control component 1388, gate driver 1390, A capacitor 1354, a forward feed element 1362, a switch 1364, and a click generator 1352. For example, power switch 1320, sense resistor 1330, sample and hold element 1380, logic control element 1388, and gate driver 1390 are coupled to power switch 120, sense resistor 130, sample and hold element 180, logic control element 188, and gate driver 190, respectively. the same. In another example, PWM/PFM signal generator 1386 is substantially identical to PWM/PFM signal generator 186. In yet another example, error amplifier 1382 is the same as error amplifier 182.

In another embodiment, the flyback power conversion system 1300 further includes a transformer 110, a cable resistor 140, resistors 170 and 172, diodes 160 and 168, capacitors 196 and 198, all of which are shown in FIG. . For example, transformer 110 includes a primary winding 112, a secondary winding 114, and an auxiliary winding 116.

According to one embodiment, the feedback voltage V _FB is received by the sample and hold element 1380. For example, at the end of the near demagnetization process, when the secondary current becomes near zero, the feedback voltage V _FB is sampled, and the sampled voltage V _{A is} then held by element 1380 until the next sample. In another example, the sampled voltage V _A is received by an error amplifier 1382 that compares the sampled voltage V _A with a reference voltage V _ref and also amplifies the difference between V _A and V _ref .

According to another embodiment, if switch 1364 is turned "on", error amplifier 1382, along with capacitor 1354, sends a compensation voltage 1384 to PWM/PFM signal generator 1386. For example, the PWM/PFM signal generator 1386 also receives the current I ₂ generated by the forward feed element 1362. In another example, forward feed element 1362 receives and processes sampled voltage V _A and reference voltage V _ref . In yet another example, the compensation voltage 1384 and the current I ₂ have different phases.

According to yet another embodiment, the PWM/PFM signal generator 1386 also receives a sense voltage 1332 from the sense resistor 1330, which transforms the primary current flowing through the primary winding 112 into a sense voltage. For example, the PWM/PFM converts the compensation voltage 1384 into a compensation current and adds the compensation current to the current I ₂ .

As shown in FIG. 13, PWM/PFM signal generator 1386 outputs modulated signal 1387 to logic control element 1388, which sends control signal 1389 to both click generator 1352 and gate driver 1390. In response, gate driver 1390 sends drive signal 1392 to power switch 1320, in response.

According to another embodiment, click generator 1352 generates a pulse having a constant width as part of signal 1353 in response to a pulse of control signal 1389. According to yet another embodiment, the switch 1364 is turned "on" when the control signal 1389 is at a logic high level and is turned off when the control signal 1389 is at a logic low level.

For example, the switching frequency of control signal 1389 changes with load, a light load produces a low switching frequency, and a large load produces a high frequency. Thus, according to one embodiment, the effective transconductance of error amplifier 1382 changes with load conditions.

According to another embodiment,

g _{m 1_ eff} = g _{m 1} × T _{on _ const} × f _sw (Equation 15)

Where g _{m1_eff} represents the effective transconductance of error amplifier 1382, and g _m1 represents the inherent transconductance of error amplifier 1382. _Further, T on_const represents a constant pulse width signal 1353, f _sw 1389 represents the switching frequency control signal. For example, the switching frequency of the control signal 1389 is the same as the switching frequency of the signal 1353.

In another example, the effective transconductance changes with output load conditions, thereby causing the zero point position to remain below the pole position in the frequency domain. In yet another example, the effective transconductance error amplifier 1382 as the load becomes lighter (e.g., as the smaller the output current I _o) becomes small. In yet another example, the frequency of the zero position ω _z2 of the system 1300 is reduced by decreasing g _{m1 — eff} as the load decreases. In one embodiment, the gain also decreases as _{gm1_eff} decreases. In another example, the pole position ω _p1 remains above the zero position ω _z2 at all frequencies under load conditions.

In accordance with another embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier coupled to a capacitor. The error amplifier is configured to receive a reference voltage, a first voltage, and a regulated current and to generate a compensation voltage with the capacitor. The first voltage is associated with a feedback voltage. Additionally, the system includes a current generator configured to receive the compensation voltage and generate the regulated current and the first current, and a signal generator configured to receive the first current and the second current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Additionally, the system includes: a gate driver coupled directly or indirectly to the signal generator and configured to generate a drive signal based at least on information associated with the modulated signal; and a switch configured to receive the drive signal and affect flow through The primary current of the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system, and the power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The error amplifier is characterized by at least a transconductance and is further configured to vary the transconductance based at least on information associated with the regulated current, and the transconductance decreases as the output current of the power conversion system decreases. For example, the transconductance also increases as the output current of the power conversion system increases. In another example, the system is implemented in accordance with Figures 6, 9, 10(a), 10(b), 10(c), 10(d), and/or Figure 11.

In yet another example, the system further includes a forward feed element configured to receive the reference voltage and the first voltage and generate a second current. The second current and the first current are associated with different phases. In yet another example, the system further includes a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and output the maintained voltage as the first voltage . In yet another example, the system further includes a logic control element coupled to the signal generator and the gate driver. The logic control element is configured to receive the modulation signal and output the control signal to the gate driver based at least on the information associated with the modulation signal. In yet another example, the error amplifier includes a constant current source configured to generate a constant current, regulate current flow into or out of the error amplifier, and the transconductance of the error amplifier depends at least on the constant current and the regulated current. In yet another example, the power conversion system includes a feedback loop that includes at least a control stage and a power stage. The power stage includes at least a gate driver and one or more components between the gate driver and an output terminal for output voltage and output current, and the control stage includes at least a portion of the error amplifier and the signal generator. In yet another example, the control stage is characterized by at least a first transfer function having at least a zero position in the frequency domain, and the power stage is characterized by at least a second transfer function having at least a pole position in the frequency domain. The feedback loop is characterized by at least a combination of a first transfer function and a second transfer function. In yet another example, the zero position is lower in frequency than the pole position regardless of the output current. In yet another example, the combination of the first transfer function and the second transfer function is associated with a gain as a function of the first frequency and a phase as a function of the second frequency. In yet another example, regardless of the output current, if the gain is equal to 0 dB, the first frequency function has a slope of 20 dB/dec. In yet another example, regardless of the output current, if the gain is equal to 0 dB, the phase is at least 90° from -180°.

In accordance with yet another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage, a first voltage, and an adjustment current by an error amplifier. The first voltage is associated with a feedback voltage. Additionally, the method includes: processing information associated with a reference voltage, a first voltage, and a regulated current; generating a compensation voltage by an error amplifier coupled to the capacitor; receiving a compensation voltage; and generating an adjustment based on at least information associated with the compensation voltage Current and first current. Moreover, the method includes receiving a first current, a second current, and a sensing voltage; generating a modulated signal based on at least information associated with the first current, the second current, and the sensing voltage; processing is associated with the modulated signal Information; and generating a drive signal based at least on information associated with the modulated signal. The method also includes receiving a drive signal and affecting the primary current based at least on information associated with the drive signal. The primary current flows through a primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The error amplifier is characterized by at least one transconductance. The step of processing information associated with the reference voltage, the first voltage, and the regulated current includes changing the transconductance based at least on information associated with the regulated current. The transconductance decreases as the output current of the power conversion system decreases. For example, the transconductance also increases as the output current of the power conversion system increases. In another example, the method is implemented in accordance with FIGS. 6, 9, 10(a), 10(b), 10(c), 10(d), and/or FIG. In yet another example, the method further includes receiving the reference voltage and the first voltage by the forward feed element and generating the second current based on at least information associated with the reference voltage and the first voltage. The first current and the second current have at least different phases.

In accordance with yet another embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier that is indirectly coupled to a capacitor through a first switch. The error amplifier is configured to receive the reference voltage and the first voltage and to generate a compensation voltage with the capacitor if the first switch is turned "on". The first voltage is associated with a feedback voltage. Additionally, the system includes a first switch coupled to at least the error amplifier and the capacitor, and a signal generator configured to receive the compensation voltage and the first current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Additionally, the system further includes: a logic control element configured to receive the modulated signal and generate a control signal based on at least information associated with the modulated signal; a gate driver configured to receive the control signal and configured to be based at least on the control signal The associated information generates a drive signal; and a second switch configured to receive the drive signal and affect a primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system, and the power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a pulse width and a switching frequency. The first switch configuration is controlled by a control signal. Furthermore, if the control signal is at a logic high level, the first switch is turned "on" and if the control signal is at a logic low level, the first switch is turned "off". For example, the system is implemented in accordance with FIG.

In another example, the system further includes a forward feed element configured to receive the reference voltage and the first voltage and generate the first current. The first current and the compensation voltage are associated with different phases. In yet another example, the system further includes a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and output the maintained voltage as the first voltage . In yet another example, at least the combination of the error amplifier and the first switch is characterized by at least an effective transconductance. The effective transconductance depends at least on the pulse width and the switching frequency. In yet another example, the effective transconductance decreases as the output current of the power conversion system decreases and increases as the output current of the power conversion system increases.

In accordance with yet another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage and a first voltage by an error amplifier. The first voltage is associated with a feedback voltage and the error amplifier is indirectly coupled to the capacitor through the first switch. Additionally, the method includes: processing information associated with the reference voltage and the first voltage; if the first switch is on, generating a compensation voltage by the error amplifier together with the capacitor; receiving the compensation voltage, the first current, and the sensing voltage; And generating a modulated signal based at least on information associated with the compensation voltage, the first current, and the sensed voltage. Additionally, the method includes: processing information associated with the modulated signal; generating a control signal based on at least information associated with the modulated signal; processing information associated with the control signal; based at least on information associated with the control signal Generating a drive signal; and affecting the primary current based at least on information associated with the drive signal. The primary current flows through a primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a pulse width and a switching frequency. The step of processing information associated with the control signal includes turning the first switch on if the control signal is at a logic high level, and turning off the first switch if the control signal is at a logic low level. For example, the method is implemented in accordance with FIG. In another example, the method includes receiving a reference voltage and a first voltage by a forward feed element, and generating a first current based on at least information associated with the reference voltage and the first voltage. The first current and the compensation voltage have at least different phases.

In accordance with yet another embodiment, a system for adjusting an output voltage of a power conversion system includes an error amplifier that is indirectly coupled to a capacitor through a first switch. The error amplifier is configured to receive the reference voltage and the first voltage and to generate a compensation voltage with the capacitor if the first switch is turned "on". The first voltage is associated with the feedback voltage. Additionally, the system includes a first switch coupled to at least the error amplifier and the capacitor, and a signal generator configured to receive the compensation voltage and the first current. The signal generator is also configured to receive the sense voltage and generate a modulated signal. Moreover, the system includes a logic control element configured to receive the modulated signal and generate a control signal based at least on information associated with the modulated signal. Additionally, the system includes: a click generator configured to receive a control signal and to send a click signal to the first switch; a gate driver configured to receive the control signal and configured to generate a drive signal based on at least information associated with the control signal; And a second switch configured to receive the drive signal and affect a primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The power conversion system includes at least a primary winding and a secondary winding. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a first pulse width and a first switching frequency. The click signal is characterized by at least a second pulse width and a second switching frequency. The second pulse width is a constant determined by the click generator, and the second switching frequency is equal to the first switching frequency. The first switch configuration is controlled by a click signal. If the click signal is at a logic high level, the first switch is turned "on" and if the click signal is at a logic low level, the first switch is turned off. For example, the system is implemented in accordance with FIG.

In another example, the system further includes a forward feed element configured to receive the reference voltage and the first voltage and generate the first current. The first current and the compensation voltage are associated with different phases. In yet another example, the system further includes a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and output the maintained voltage as the first voltage . In yet another example, at least the combination of the error amplifier and the first switch is characterized by at least an effective transconductance. The effective transconductance depends at least on the first switching frequency. In yet another example, the effective transconductance decreases as the output current of the power conversion system decreases, and increases as the output current of the power conversion system increases.

In accordance with yet another embodiment, a method for adjusting an output voltage of a power conversion system includes receiving a reference voltage and a first voltage by an error amplifier. The first voltage is associated with a feedback voltage and the error amplifier is indirectly coupled to the capacitor through the first switch. Additionally, the method includes: processing information associated with the reference voltage and the first voltage; if the first switch is turned on, generating a compensation voltage by the error amplifier together with the capacitor; receiving the compensation voltage, the first current, and the sensing voltage; A modulated signal is generated based on information associated with the compensation voltage, the first current, and the sense voltage. Additionally, the method includes: processing information associated with the modulated signal; generating a control signal based on at least information associated with the modulated signal; processing information associated with the control signal; and generating at least information based on the control signal Click on the signal and drive signal. Moreover, the method includes adjusting a first switch based on information associated with the click signal; and affecting the primary current based at least on information associated with the drive signal, the primary current flowing through the primary winding coupled to the secondary winding. The secondary winding is associated with an output voltage and an output current of the power conversion system. The feedback voltage depends at least on the output voltage and the output current, and the sense voltage is at least dependent on the primary current. The control signal is characterized by at least a first pulse width and a first switching frequency, and the click signal is characterized by at least a second pulse width and a second switching frequency. The second pulse width is a constant determined by the click generator, and the second switching frequency is equal to the first switching frequency. The step of adjusting the first switch based on information associated with the click signal includes turning on the first switch if the click signal is at a logic high level, and disconnecting if the click signal is at a logic low level The first switch. For example, the method is implemented in accordance with FIG. In another example, the method includes receiving a reference voltage and a first voltage by a forward feed element, and generating a first current based on at least information associated with the reference voltage and the first voltage. The first current and the compensation voltage have at least different phases.

Although specific embodiments of the invention have been described, it will be understood by those skilled in the art that Therefore, it is understood that the invention is not limited to the particular embodiments shown, but only by the scope of the claims.

100. . . Flyback power conversion system

110. . . transformer

112. . . Primary winding

114. . . Secondary winding

116. . . Auxiliary winding

118. . . Auxiliary voltage

120. . . switch

130. . . Sense resistor

132. . . Sense voltage

140. . . Cable resistor

142. . . The output voltage

150. . . Output load

160,168. . . Dipole

170, 172. . . Resistor

174. . . Feedback voltage

180. . . Sample and hold component

182. . . Error amplifier

184. . . Loop compensation network

185. . . output signal

186. . . PWM/PFM signal generator

187. . . Modulated signal

188. . . Logic control element

190. . . Gate driver

192. . . Drive signal

196, 198. . . Capacitor

600. . . system

610. . . Subtraction component

620, 622, 624. . . Transconductance component

630. . . Capacitive component

640. . . Additive component

650. . . Power stage

710, 720, 730. . . Gain curve

712, 722, 732. . . Phase curve

810, 820, 830. . . Gain curve

812, 822, 832. . . Phase curve

900. . . Flyback power conversion system

920. . . switch

930. . . Sense resistor

932. . . Sense voltage

952. . . Current generator

954. . . Capacitor

962. . . Forward feed element

964. . . node

980. . . Sample and hold component

982. . . Error amplifier

984. . . Compensation voltage

986. . . PWM/PFM signal generator

987. . . Modulated signal

988. . . Logic control element

989. . . control signal

990. . . Gate driver

992. . . Drive signal

1200. . . Flyback power conversion system

1220. . . switch

1230. . . Sense resistor

1232. . . Sense voltage

1254. . . Capacitor

1262. . . Forward feed element

1264. . . switch

1280. . . Sample and hold component

1282. . . Error amplifier

1284. . . Compensation voltage

1286. . . PWM/PFM signal generator

1287. . . Modulated signal

1288. . . Logic control element

1289. . . control signal

1290. . . Gate driver

1292. . . Drive signal

1300. . . Flyback power conversion system

1320. . . switch

1330. . . Sense resistor

1332. . . Sense voltage

1352. . . Click generator

1353. . . signal

1354. . . Capacitor

1362. . . Forward feed element

1364. . . switch

1380. . . Sample and hold component

1382. . . Error amplifier

1384. . . Compensation voltage

1386. . . PWM/PFM signal generator

1387. . . Modulated signal

1388. . . Logic control element

1389. . . control signal

1390. . . Gate driver

1392. . . Drive signal

1 is a simplified diagram illustrating a conventional switch mode flyback power conversion system with primary side sensing and adjustment;

2 is a simplified diagram illustrating a conventional waveform of a feedback voltage 174 and a secondary current flowing through the secondary winding 114;

3 is a simplified diagram illustrating a compensation voltage as a function of output current (also referred to as load current);

4 and 5 each illustrate a simplified conventional Bode diagram of a power stage of a flyback power conversion system;

6 is a simplified diagram illustrating a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with an embodiment of the present invention;

7(a), (b) and (c) are simplified Bode diagrams illustrating combined transfer functions of a power supply stage and a control stage having a constant _gm1 under different load conditions;

8(a), (b) and (c) are simplified Bode diagrams illustrating a combined transfer function of a power stage and a control stage having _gm1 reduced as the load decreases, in accordance with an embodiment of the present invention;

9 is a simplified diagram illustrating a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention;

10(a), (b), (c) and (d) are simplified diagrams illustrating error amplifiers, capacitors and current generators for a switched mode flyback power conversion system in accordance with one embodiment of the present invention;

11 is a simplified diagram illustrating an error amplifier, a capacitor, and a current generator for a switch mode flyback power conversion system in accordance with yet another embodiment of the present invention;

12 is a simplified diagram illustrating a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention;

13 is a simplified diagram illustrating a primary side sensing and adjustment system for a switch mode flyback power conversion system in accordance with another embodiment of the present invention.

600. . . system

610. . . Subtraction component

620, 622, 624. . . Transconductance component

630. . . Capacitive component

640. . . Additive component

650. . . Power stage

Claims (27)

A system for adjusting an output voltage of a power conversion system, the system comprising: an error amplifier coupled to a capacitor, the error amplifier configured to receive a reference voltage, a first voltage, and a regulation current and generate the same with the capacitor a compensation voltage, the first voltage being associated with a feedback voltage; a current generator configured to receive the compensation voltage and generating the regulated current and a first current; a signal generator configured to receive the first current and a second current, the signal generator further configured to receive a sense voltage and generate a modulated signal; a gate driver coupled directly or indirectly to the signal generator and configured to be based at least on the modulation The signal associated information generates a drive signal; a switch configured to receive the drive signal and affect a primary current flowing through a primary winding coupled to the primary winding; wherein: the secondary winding is coupled to a power conversion system An output voltage is associated with an output current, the power conversion system including at least the primary winding and the time a winding; the feedback voltage is dependent at least on the output voltage and the output current; the sense voltage is dependent at least on the primary current; wherein: the error amplifier is characterized by at least a transconductance and is further configured to be based at least on the regulated current The information is coupled to change the transconductance; the transconductance decreases as the output current of the power conversion system decreases. The system of claim 1, further comprising a forward feed element configured to receive the reference voltage and the first voltage and generate the second current, the second current and the first A current is associated with a different phase. The system of claim 1, further comprising a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and The held voltage output is taken as the first voltage. The system of claim 1, further comprising a logic control element coupled to the signal generator and the gate driver, the logic control element configured to receive the modulated signal and based at least on The information associated with the modulated signal outputs a control signal to the gate driver. A system as claimed in claim 1 wherein: the error amplifier comprises a constant current source configured to generate a constant current; the regulated current flows into or out of the error amplifier; the transconductance of the error amplifier depends at least The constant current and the regulated current. The system of claim 1, wherein: the power conversion system comprises a feedback loop, the feedback loop includes at least a control stage and a power stage; the power stage includes at least the gate driver and the gate driver One or more components between the output voltage and an output terminal of the output current; the control stage includes at least a portion of the error amplifier and the signal generator. The system of claim 6 wherein: the control stage is characterized by at least a first transfer function having a zero position in a frequency domain; the power stage being at least at least in the frequency domain Characterized by a second transfer function having a pole position; the feedback loop is characterized by at least a combination of the first transfer function and the second transfer function. The system of claim 7, wherein the zero position is lower in frequency than the pole position regardless of the output current. The system of claim 8 wherein the combination of the first transfer function and the second transfer function is associated with a gain as a first frequency function and a phase as a second frequency function. The system of claim 9, wherein the first frequency function has a slope of -20 dB/dec if the gain is equal to 0 dB regardless of the output current. The system of claim 10, wherein regardless of the output current, if the gain is equal to 0 dB, the phase is at least 90° from -180°. A method for adjusting an output voltage of a power conversion system, the method comprising: receiving, by an error amplifier, a reference voltage, a first voltage, and an adjustment current, the first voltage being associated with a feedback voltage; processing and the reference a voltage, the first voltage, and the adjustment current associated with the information; generating, by the error amplifier coupled to a capacitor, a compensation voltage; receiving the compensation voltage; generating the regulated current and based at least on information associated with the compensation voltage a first current; receiving the first current, a second current, and a sensing voltage; generating a modulation signal based on at least information associated with the first current, the second current, and the sensing voltage; processing Information associated with the modulated signal; generating a drive signal based on at least information associated with the modulated signal; receiving the drive signal; affecting a primary current based on at least information associated with the drive signal, the primary Current flows through a primary winding coupled to the primary winding; wherein: an output voltage of the secondary winding and a power conversion system An output current is associated; the feedback voltage is dependent at least on the output voltage and the output current; the sense voltage is dependent at least on the primary current; wherein: the error amplifier is characterized by at least a transconductance; for processing and the reference The step of voltage, the first voltage, and the information associated with the regulated current includes: changing the transconductance based at least on information associated with the regulated current; the transconductance decreases with the output current of the power conversion system And decrease. The method of claim 12, the method comprising: receiving the reference voltage and the first voltage by a forward feed element; generating the at least based on information associated with the reference voltage and the first voltage a second current; wherein the first current and the second current have at least different phases. A system for adjusting an output voltage of a power conversion system, the system comprising: an error amplifier coupled indirectly to a capacitor through a first switch, the error amplifier configured to receive a reference voltage and a first voltage And if the first switch is turned on, generating a compensation voltage with the capacitor, the first voltage being associated with a feedback voltage; the first switch being coupled to at least the error amplifier and the capacitor; a signal generator, Configuring to receive the compensation voltage and a first current, the signal generator is further configured to receive a sense voltage and generate a modulated signal; a logic control element configured to receive the modulated signal and based at least on the modulation Signal-related information to generate a control signal; a gate driver configured to receive the control signal and configured to generate a drive signal based on at least information associated with the control signal; a second switch configured to receive the drive signal And affecting a primary current flowing through a primary winding coupled to the primary winding; The secondary winding is associated with an output voltage and an output current of a power conversion system including at least the primary winding and the secondary winding; the feedback voltage is dependent at least on the output voltage and the output current; The sense voltage is at least dependent on the primary current; wherein: the control signal is characterized by at least a pulse width and a switching frequency; the first switch configuration is controlled by the control signal; if the control signal is a logic high level, The first switch is turned on; if the control signal is at a logic low level, the first switch is turned off. The system of claim 14, further comprising a forward feed element configured to receive the reference voltage and the first voltage and to generate the first current, the first current and the compensation The voltage is associated with a different phase. The system of claim 14, further comprising a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and The held voltage output is taken as the first voltage. The system of claim 14, wherein: at least the combination of the error amplifier and the first switch is characterized by at least one effective transconductance; the effective transconductance depends at least on the pulse width and the switching frequency. The system of claim 17 wherein the effective transconductance decreases as the output current of the power conversion system decreases. A method for adjusting an output voltage of a power conversion system, the method comprising: receiving, by an error amplifier, a reference voltage and a first voltage, the first voltage being associated with a feedback voltage, the error amplifier passing through a first switch Interposed to a capacitor; processing information associated with the reference voltage and the first voltage; if the first switch is turned on, generating a compensation voltage with the capacitor by the error amplifier; receiving the compensation voltage, a first current and a sensing voltage; generating a modulation signal based on at least information associated with the compensation voltage, the first current, and the sensing voltage; processing information associated with the modulated signal; based at least on Information associated with the modulated signal to generate a control signal; processing information associated with the control signal; generating a drive signal based at least on information associated with the control signal; based at least on an associated signal associated with the drive signal Information affecting a primary current flowing through a primary winding coupled to the primary winding; wherein: the secondary The group is associated with an output voltage and an output current of a power conversion system; the feedback voltage is dependent at least on the output voltage and the output current; the sensing voltage is dependent at least on the primary current; wherein: the control signal is at least one Characterizing the pulse width and a switching frequency; the step of processing information associated with the control signal includes turning the first switch on if the control signal is at a logic high level, and if the control signal is logic low At the level, the first switch is turned off. The method of claim 19, the method comprising: receiving the reference voltage and the first voltage by a forward feed element; generating the at least based on information associated with the reference voltage and the first voltage a first current; wherein the first current and the compensation voltage have at least different phases. A system for adjusting an output voltage of a power conversion system, the system comprising: an error amplifier coupled indirectly to a capacitor through a first switch, the error amplifier configured to receive a reference voltage and a first voltage And if the first switch is turned on, generating a compensation voltage with the capacitor, the first voltage being associated with a feedback voltage; the first switch being coupled to at least the error amplifier and the capacitor; a signal generator, Configuring to receive the compensation voltage and a first current, the signal generator is further configured to receive a sense voltage and generate a modulated signal; a logic control element configured to receive the modulated signal and based at least on the modulation Signal-associated information to generate a control signal; a click generator configured to receive the control signal and to send a click signal to the first switch; a gate driver configured to receive the control signal and configured to be based at least on The information associated with the control signal generates a drive signal; a second switch configured to receive the drive And affecting a primary current flowing through a primary winding coupled to the primary winding; wherein: the secondary winding is associated with an output voltage and an output current of a power conversion system, the power conversion system including at least the primary a winding and the secondary winding; the feedback voltage is dependent at least on the output voltage and the output current; the sensing voltage is dependent at least on the primary current; wherein: the control signal is at least a first pulse width and a first switching frequency Characterizing; the click signal is characterized by at least a second pulse width and a second switching frequency; the second pulse width is a constant determined by the click generator; the second switching frequency is equal to the first switching Frequency; the first switch is configured to be controlled by the click signal; if the click signal is a logic high level, the first switch is turned on; if the click signal is a logic low level, the first The switch is open. The system of claim 21, further comprising a forward feed element configured to receive the reference voltage and the first voltage and generate the first current, the first current and the compensation The voltage is associated with a different phase. The system of claim 21, further comprising a sample and hold element configured to receive the feedback voltage, sample the feedback voltage at a predetermined time, maintain the sampled voltage, and The held voltage output is taken as the first voltage. The system of claim 21, wherein: at least the combination of the error amplifier and the first switch is characterized by at least one effective transconductance; the effective transconductance being dependent at least on the first switching frequency. The system of claim 24, wherein the effective transconductance decreases as the output current of the power conversion system decreases. A method for adjusting an output voltage of a power conversion system, the method comprising: receiving, by an error amplifier, a reference voltage and a first voltage, the first voltage being associated with a feedback voltage, the error amplifier passing through a first switch Interposed to a capacitor; processing information associated with the reference voltage and the first voltage; if the first switch is turned on, generating a compensation voltage with the capacitor by the error amplifier; receiving the compensation voltage, a first current and a sensing voltage; generating a modulation signal based on at least information associated with the compensation voltage, the first current, and the sensing voltage; processing information associated with the modulated signal; at least based on The information associated with the modulated signal generates a control signal; processing information associated with the control signal; generating a click signal and a drive signal based on at least information associated with the control signal; based on the click signal The associated information adjusts the first switch; affecting a primary current based on at least information associated with the drive signal, the primary current Flowing through a primary winding coupled to the primary winding; wherein: the secondary winding is associated with an output voltage and an output current of a power conversion system; the feedback voltage is dependent at least on the output voltage and the output current; The sensing voltage is at least dependent on the primary current; wherein: the control signal is characterized by at least a first pulse width and a first switching frequency; the click signal is characterized by at least a second pulse width and a second switching frequency The second pulse width is a constant determined by a click generator; the second switching frequency is equal to the first switching frequency; and the step of adjusting the first switch based on information associated with the click signal includes : If the click signal is a logic high level, the first switch is turned on, and if the click signal is a logic low level, the first switch is turned off. The method of claim 26, the method comprising: receiving the reference voltage and the first voltage by a forward feed element; generating the first based on at least information associated with the reference voltage and the first voltage a current; wherein the first current and the compensation voltage have at least different phases.