Patent Application
20240313659
This invention relates to power conversion, particularly to a controller and an operating method for an asymmetrical half-bridge converter.
Power converters convert input voltages to output voltages to provide power suitable for various circuits. Asymmetric half-bridge (AHB) converters are a type of asymmetric converters with a transformer. They use two switches in a half-bridge configuration on the primary side. Asymmetric half-bridge converters are named because the two switches are driven by different pulse-width modulation (PWM) signals. They are characterized by their simple structure, low switching losses, and low electromagnetic interference (EMI).
One way to reduce switching losses in medium-loading or light-loading power converters is to increase the switching period duration, which means reducing the switching frequency. Patent application number CN101882875A in China and several other patent applications cited in its background technology teach various power supply devices that can adjust the switching frequency according to the load status. Thus, the power supply device can use appropriate modulation methods to reduce the switching frequency under light-loading and no-load conditions, increasing the switching period duration, reducing switching losses, and improving the output efficiency of the power supply.
In relevant technology, asymmetric half-bridge converters are too complicate to control and cannot provide high energy transfer efficiency and zero-voltage switching in both heavy-loading and light-loading conditions.
An embodiment of the invention provides a controller for an asymmetrical half-bridge converter with an auxiliary winding formed on a primary side of the asymmetrical half-bridge converter. The auxiliary winding generates a feedback voltage. The controller comprises a first switch driver, a second switch driver, and a control logic. The first switch driver is configured to drive a first switch of the asymmetrical half-bridge converter. The second switch driver is configured to drive a second switch of the asymmetrical half-bridge converter. The control logic is coupled to the first switch driver and the second switch driver. During a first switching period and a second switching period, the control logic is configured to control the first switch driver to turn on the first switch for a first ON duration; control the first switch driver and the second switch driver to turn off the first switch and the second switch for a first OFF duration after the first ON duration; control the second switch driver to turn on the second switch for a second ON duration after the first OFF duration; control the first switch driver and the second switch driver to turn off the first switch and the second switch for a second OFF duration after the second ON duration; control the second switch driver to turn on the second switch for a third ON duration after the second OFF duration; and control the first switch driver and the second switch driver to turn off the first switch and the second switch for a third OFF duration after the third ON duration. During the first switching period, the control logic determines a discharge period according to the feedback voltage. During the second switching period, the control logic adjusts a length of the second ON duration to a fixed ratio of the discharge period, the fixed ratio is less than 1.
Another embodiment of the invention further provides a controller for an asymmetrical half-bridge converter. The asymmetrical half-bridge converter comprises an auxiliary winding formed on a primary side of the asymmetrical half-bridge converter. The auxiliary winding generates a feedback voltage. The controller comprises a first switch driver, a second switch driver, and a control logic. The first switch driver is configured to drive a first switch of the asymmetrical half-bridge converter. The second switch driver is configured to drive a second switch of the asymmetrical half-bridge converter. The control logic is coupled to the first switch driver and the second switch driver. During a first switching period and a second switching period and when the asymmetrical half-bridge converter is in a light-loading mode, the control logic is configured to control the first switch driver to turn on the first switch for a first ON duration; control the first switch driver and the second switch driver to turn off the first switch and the second switch for a first OFF duration after the first ON duration; control the second switch driver to turn on the second switch for a second ON duration after the first OFF duration; control the first switch driver and the second switch driver to turn off the first switch and the second switch for a second OFF duration after the second ON duration; control the second switch driver to turn on the second switch for a third ON duration after the second OFF duration; and control the first switch driver and the second switch driver to turn off the first switch and the second switch for a third OFF duration after the third ON duration. The control logic is configured to terminate the second OFF duration and start the third ON duration when the feedback voltage approaches one of resonant peaks after an end the second ON duration.
Another embodiment of the invention further provides a method of operating an asymmetrical half-bridge converter. The asymmetrical half-bridge converter has an auxiliary winding formed on a primary side of the asymmetrical half-bridge converter. The auxiliary winding generates a feedback voltage. A first switch driver drives a first switch of the asymmetrical half-bridge converter, and a second switch driver drives a second switch of the asymmetrical half-bridge converter. The method comprises: during a first switching period and a second switching period, a control logic controlling the first switch driver to turn on the first switch for a first ON duration; controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a first OFF duration after the first ON duration; controlling the second switch driver to turn on the second switch for a second ON duration after the first OFF duration; controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a second OFF duration after the second ON duration; controlling the second switch driver to turn on the second switch for a third ON duration after the second OFF duration; and controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a third OFF duration after the third ON duration. The method further comprises determining a discharge period according to the feedback voltage during the first switching period; and adjusting a length of the second ON duration to a fixed ratio of the discharge period during the second switching period to make the duration of the second ON duration shorter than a duration of the discharge period.
Another embodiment of the invention further provides a method of operating a controller for an asymmetrical half-bridge converter. The asymmetrical half-bridge converter has an auxiliary winding formed on a primary side of the asymmetrical half-bridge converter. The auxiliary winding generates a feedback voltage. A first switch driver drives a first switch of the asymmetrical half-bridge converter, and a second switch driver drives a second switch of the asymmetrical half-bridge converter. The method comprises during a first switching period and a second ON duration during a second switching period and when the asymmetrical half-bridge converter is in a light-loading mode, controlling the first switch driver to turn on the first switch for a first ON duration; controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a first OFF duration after the first ON duration; controlling the second switch driver to turn on the second switch for a second ON duration after the first OFF duration; controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a second OFF duration after the second ON duration; controlling the second switch driver to turn on the second switch for a third ON duration after the first OFF duration; and controlling the first switch driver and the second switch driver to turn off the first switch and the second switch for a third OFF duration after the third ON duration. The method further comprises terminating the second OFF duration and starting the third ON duration when the feedback voltage approaches one of resonant peaks after the second ON duration.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
The AHB converter 12 may comprise a main switch 120, a resonant zero-voltage switch 122, a primary winding W1, a secondary winding W2, an auxiliary winding Waux, a resonant capacitor Cr, a shunt resistor Rshunt, resistors R1 and R2, a diode Dout, and an output capacitor Cout. The main switch 120 has a control end, a first end, and a second end. The first end of the main switch 120 is coupled to an input end IN to receive the input voltage Vin. The resonant zero-voltage switch 122 has a control end, a first end, and a second end. The first end of the resonant zero-voltage switch 122 is coupled to the second end of the main switch 12. The primary winding W1 and the secondary winding W2 may form a transformer and have opposite polarities. The primary winding W1 and the auxiliary winding Waux may have opposite polarities. The primary winding W1 has a first end and a second end. The first end of the primary winding W1 is coupled to the second end of the main switch 120. The resonant capacitor Cr has a first end and a second end. The first end of the resonant capacitor Cr is coupled to the second end of the secondary winding W1. The shunt resistor Rshunt has a first end and a second end, which are respectively coupled to the second end of the resonant capacitor Cr and a ground end GND1. The auxiliary winding Waux may be formed on the primary side of the AHB converter 12 and have a first end and a second end. The second end of the auxiliary winding Waux is coupled to the ground end GND1. The resistor R1 has a first end and a second end, which are respectively coupled to the first end of the auxiliary winding Waux and a first end of the resistor R2. The resistor R2 has a first end and a second end, which are respectively coupled to the second end of the resistor R1 and the ground end GND1. A voltage divider formed by the resistor R1 and the resistor R2 is used to provide a feedback voltage Vfb. The secondary winding W2 has a first end and a second end. The first end of the secondary winding W2 is used to provide a voltage Vs. The diode Dout has an anode and a cathode. The anode of the diode Dout is coupled to the first end of the secondary winding W2. The output capacitor Cout has a first end and a second end, which are respectively coupled to the cathode of the diode Dout and a ground end GND2. The ground ends GND1 and GND2 may be isolated from each other and may provide a ground voltage, for example, 0V. The main switch 120 and the resonant zero-voltage switch 122 may be N-type metal-oxide-semiconductor field-effect transistors (MOSFETs). In some embodiments, the main switch 120 and the resonant zero-voltage switch 122 may also be other types of transistors. The diode Dout may also be replaced by a synchronous rectification switch and associated control circuitry.
Although in the embodiment of
The voltage at a coupling node where the second end of the main switch 120, the first end of the resonant zero-voltage switch 122, and the first end of the primary winding W1 are mutually coupled is called a voltage Vhb. The current flowing through the primary winding W1 is called a current Ihb, and the current flowing through the primary winding W1 and related to the magnetic flux of the transformer is called a magnetizing current. The current Ihb is positive if the current Ihb flows from the coupling node to the primary winding W1; and the current Ihb is negative if the current Ihb flows from the primary winding W1 to the coupling node.
The main switch 120 and the resonant zero-voltage switch 122 are cascaded between the input end IN and the ground end GND1, forming a half-bridge circuit. In some embodiments, the main switch 120 may be coupled to a rectifier, which may receive an alternating current (AC) voltage and convert the AC voltage to the input voltage Vin. The main switch 120 and the resonant zero-voltage switch 122 will not be turned on at the same time. When the main switch 120 is turned on and the resonant zero-voltage switch 122 is turned off, the primary winding W1 may store energy due to the input voltage Vin. When the main switch 120 is turned off and the resonant zero-voltage switch 122 is turned on, the energy stored in the primary winding W1 and the resonant energy generated by a resonant circuit, which is formed by the primary winding W1 and the resonant capacitor Cr, will be transferred from the primary winding W1 to the secondary winding W2. The resistors R1 and R2 may form a voltage divider to divide the voltage at the first end of the auxiliary winding Waux to generate the feedback voltage Vfb. For example, if the resistances of the resistors R1 and R2 are equal, and the voltage at the first end of the auxiliary winding Waux is 20V, the feedback voltage Vfb may be 10V. The output capacitor Cout may act as a filter to stabilize the output voltage Vout.
The controller 10 may comprise a main switch driver 100, a resonant zero-voltage switch driver 102, and a control logic 104. The main switch driver 100 is coupled to the control end of the main switch 120 to output a control signal Vhs to drive the main switch 120. The resonant zero-voltage switch driver 102 is coupled to the control end of the resonant zero-voltage switch 122 to output a control signal Vls to drive the resonant zero-voltage switch 122. The control logic 104 is coupled to the main switch driver 100 and the resonant zero-voltage switch driver 102. In each switching period of the AHB converter system 1, the control logic 104 may: (1) control the main switch driver 100 to output a control signal Vhs having one main pulse, so as to store energy in the primary winding W1 and regulate the output voltage Vout to a fixed level (e.g., 12V) or a fixed range (e.g., 12V±10%), and (2) control the resonant zero-voltage switch driver 102 in two ways: (2a) in a light-loading condition, to output a control signal Vls having both a first pulse and a second pulse, and (2b) in a heavy-loading condition, to output a control signal Vls having at least the first pulse, so as to facilitate resonant energy transfer and zero-voltage switching in both the light-loading condition and the heavy-loading condition.
In light-loading conditions, the AHB converter system 1 can provide less power to the load L, the operating frequency is lower, and the corresponding switching period duration is longer. In a heavy-loading condition, the AHB converter system 1 can provide more power to the load L, the operating frequency is higher, and the corresponding switching period duration is shorter. The embodiments of
Step S200: The control logic 104 controls the main switch driver 100 to turn on the main switch 120 for a first ON duration;
Step S202: After the first ON duration, the control logic 104 controls the main switch driver 100 and the resonant zero-voltage switch driver 102 to turn off the main switch 120 and the resonant zero-voltage switch 122 for a first OFF duration Td1. The first OFF duration Td1 helps to avoid the risk of the main switch 120 and the resonant zero-voltage switch 122 being turned on accidentally at the same time, which may lead to an explosion due to the near short circuit between the input end IN and the ground end GND1;
Step S204: After the first OFF duration Td1, the control logic 104 controls the resonant zero-voltage switch driver 102 to turn on the resonant zero-voltage switch 122 for a second ON duration. The control logic 104 may determine the length of the second ON duration of the current switching period based on a discharge period Tdis period in the previous switching period. For example, the length of the second ON duration in the current switching period is a fixed proportion of 0.8 of the discharge period Tdis in the previous switching period. The second ON duration is started when the resonant zero-voltage switch 122 is turned on, and the resonant zero-voltage switch 122 is turned off. A second OFF duration Td2 is started when the second ON duration reaches the length determined by the control logic 104;
Step S206: After the second ON duration, the control logic 104 controls the main switch driver 100 and the resonant zero-voltage switch driver 102 to turn off the main switch 120 and the resonant zero-voltage switch 122 for the second OFF duration Td2. The second OFF duration Td2 ends at the time point of a resonant peak of the feedback voltage Vfb following an end of a switching period duration Fmax;
Step S208: After the second OFF duration Td2, the control logic 104 controls the resonant zero-voltage switch driver 102 to turn on the resonant zero-voltage switch 122 for a third ON duration;
Step S210: After the third ON duration, the control logic 104 controls the main switch driver 100 and the resonant zero-voltage switch driver 102 to turn off the main switch 120 and the resonant zero-voltage switch 122 for a third OFF duration Td3; then return to step S200.
In step S200, the first ON duration may be equal to the pulse width of the main pulse, such as the pulse width Wh31 of the main pulse Ph31 in
In step S204, the second ON duration can be equal to the pulse width of the first pulse, such as the pulse width Wl31 of a first pulse Pl31 in
In some embodiments, the control logic 104 may set an initial second ON duration. During the first switching period, the control logic 104 may control the main switch driver 100 and the resonant zero-voltage switch driver 102 to turn off the main switch 120 and the resonant zero-voltage switch 122 after the initial second ON duration, and determine the discharge period of the first switching period based on the knee point of the feedback voltage Vfb. As shown in
In step S206, the control logic 104 adjusts the second OFF duration Td2 based on at least the feedback voltage Vfb. In some embodiments, the secondary side provides a compensation signal based on the load 16 or the output voltage Vout. After receiving the compensation signal, the control logic 104 may determine the operating frequency for switching the main switch 120 and the resonant zero-voltage switch 122 or determine the corresponding switching period duration Fmax (which is approximately equal to the inverse of the operating frequency), so that the output voltage Vout approaches the target voltage value. The control logic 104 may also count the peaks of the feedback voltage Vfb during the first switching period to generate a count value. In the second switching period, the control logic 104 selects one of resonant peaks of the feedback voltage Vfb according to the count value, the discharge period, and the operating frequency. The control logic 104 terminates the second OFF duration Td2 and starts the third ON duration at the time point when the selected resonant peak occurs. The selected resonant peak is corresponding to the operating frequency. In some embodiments, the selected resonant peak may be the resonant peak following the end of the switching period duration Fmax within the switching period Tsw. For example, as shown in
In Taiwan patent application No. TW202135442A, a modulation control method for active clamped flyback (ACF) power converters is disclosed. This method may determine when to generate a second active clamp switch signal QH2 to assist in ZVS switching according to the peak count value in a previous period, an equivalent secondary side current discharge period, and an operating frequency signal. Another possible implementation of step S206 of the control method in
In step S208, the second ON duration may be equal to the pulse width of the second pulse, such as the pulse width Wl32 of the second pulse Pl32 in
Taiwan patent application No. TW202135452A discloses a modulation control method for active clamped flyback (ACF) power converters. This method discloses a control method that may automatically adjust a turn-on time TONH of an active clamp switch QQH to assist the power converter to perform ZVS when a main switch QQL is turned on again. For step S208 of the method in
In step S210, during the third OFF duration Td3, the negative current Ihb may raise the voltage Vhb of the coupling node close to the input voltage Vin. This helps to reduce the voltage difference between the two ends of the main switch 120, which in turn helps the main switch 120 to achieve zero-voltage switching when it is turned on again. After the third OFF duration Td3 ends, the method returns to step S200.
The Taiwan patent application No. TW202135452A not only discloses the modulation control method for active clamped flyback power converters, but also discloses a control method that may automatically adjust a dead time TDEAD between the turn-on times of the active clamp switch QQH and the main switch QQL. This helps the main switch QQL to perform ZVS when it is turned on again. For step S210 of the method in
In the embodiment, the control logic 104 (1) determines the pulse width Wh31 of the main pulse Ph31 according to the ratio of the required output voltage Vout to the current input voltage Vin, (2) determines the pulse width Wl31 of the first pulse Pl31 according to the discharge period in the previous switching period, (3) starts to generate the second pulse when the next resonant peak of the feedback voltage Vfb appears after the end of the switching period duration Fmax, (4) determines the third ON duration (Pl32) according to two sampling values of the auxiliary winding current, and (5) determines the third OFF duration Td3 according to two other sampling values of the auxiliary winding current. Therefore, the start times and widths of the main pulse, the first pulse, and the second pulse are all independently controlled, and the control mechanism is simple. Under light-loading conditions, most of the resonant energy is transferred and the main switch 120 undergoes zero-voltage switching, improving energy transfer efficiency.
Before time point t1, due to the pulse with W132 occurred in the third ON duration of the previous switching period, the voltage Vhb rises to approach the input voltage Vin, the feedback voltage Vfb drops to approach the ground voltage, and the output current Io is 0 A. At time point t1, the main pulse Ph31 and the switching period duration Fmax start. At time point t2, the main pulse Ph31 ends. The period between time points t1 and t2 can be referred to as the first ON duration. Between time points t1 and t2, the current Ihb and the magnetization current Im linearly increase to store energy in the primary winding W1, the voltage Vhb is kept at the input voltage Vin, the feedback voltage Vfb is kept at the ground voltage, and the output current Io stays at 0 A.
Between time points t2 and t3, the voltage Vhb drops to approach the ground voltage, and the feedback voltage Vfb rises to approach the platform voltage Vp. At time point t3, the first pulse Pl31 starts, and at time point t4, the first pulse Pl31 ends. The period between time points t2 and t3 can be referred to as the first OFF duration. The period between time points t3 and t4 can be referred to as the second ON duration. Between time points t3 and t4, the current Ihb resonates, the magnetization current Im linearly decreases to transfer energy to the secondary side, the voltage Vhb is kept at the ground voltage, the feedback voltage Vfb is kept at the platform voltage Vp, and the output current Io starts to resonate and exceeds 0 A. At time point t4, the first pulse Pl31 ends, causing the resonant zero-voltage switch 122 to turn off, the current Ihb returns to 0 A, the output current Io returns to 0 A, the feedback voltage Vfb briefly falls from the platform voltage Vp, thus causing the first knee point of the feedback voltage Vfb.
Between time points t4 and t5, the current Ihb remains at 0 A, but the magnetization current Im is still greater than 0 A, so the feedback voltage Vfb rises back to the platform voltage Vp. At time point t5, the magnetization current Im continues decreasing linearly, the second knee point of the feedback voltage Vfb occurs, and the discharge period Tdis ends. The period between time points t3 and t5 can be referred to as the discharge period Tdis.
In the embodiment, a first peak of the feedback voltage Vfb occurs at time point t6. The switching period duration Fmax ends at time point t7. A second peak of the feedback voltage Vfb occurs at time point t8. The period between time points t1 and t7 can be referred to as the switching period duration Fmax of the first switching period Tsw. At time point t8 when the next peak appears after the end of the switching period duration Fmax, the second OFF duration Td2 ends and the third ON duration starts, that is, the start of the second pulse Pl32 is triggered.
At time point t8, the voltage Vhb drops to the ground voltage, and the feedback voltage Vfb rises to the platform voltage Vp. The second pulse Pl32 starts at time point t8. The period between time points t4 and t8 can be referred to as the second OFF duration Td2. The period between time points t8 and t9 can be referred to as the third ON duration. Between time points t8 and t9, the current Ihb and the magnetization current Im decrease from 0 A to negative values, the voltage Vhb is kept at the ground voltage, and the feedback voltage Vfb is kept at the platform voltage Vp.
The period between time points t9 and t10 can be referred to as the third OFF duration Td3. Between time points t9 and t10, the negative current Ihb and the magnetization current Im pull the voltage Vhb up, approaching the input voltage Vin. This facilitates zero-voltage switching of the main switch 120 when it turns on again at time point t10. The main pulse Ph32 starts at time point t10, once again storing energy in the primary winding W1.
Steps S400 to S404 and S410 are similar to steps S200 to S204 and S210, respectively. Therefore, they are not repeated here.
If the control logic 104 detects that the current load has changed from light-loading to heavy-loading, and wants to switch from the light-loading mode flow (i.e., the operation method 200) as illustrated in
For example, if the AHB converter 12 was in the light-loading condition in the previous switching period (i.e, the first switching period) and the operation method 200 was being executed, as shown on the left side of
In the embodiment, due to the independent control of the main pulse, the first pulse, and the second pulse, the control mechanism is simple, and most of the resonant energy transfer and zero-voltage switching of the main switch 120 are achieved in the heavy-loading condition, which improves the energy transfer efficiency.
Before time point t1, due to the pulse with W132 occurred in the third ON duration of the previous switching period, the voltage Vhb rises to approach the input voltage Vin, the feedback voltage Vfb drops to approach the ground voltage, and the output current Io is 0 A. At time point t1, the main pulse Ph31 of the first switching period Tsw starts, and the switching period duration Fmax starts. At time point t2, the main pulse Ph31 ends. The period between time points t1 and t2 can be called the first ON duration. Between time points t1 and t2, the current Ihb and the magnetization current Im rise linearly to store energy in the primary winding W1, the voltage Vhb is kept at the input voltage Vin, the feedback voltage Vfb is kept at the ground voltage, and the output current Io stays at 0 A.
Between time points t2 and t3, the voltage Vhb drops to approach the ground voltage, and the feedback voltage Vfb rises to approach the platform voltage Vp. At time point t3, the first pulse Pl31 of the first switching period Tsw starts. At time point t4, the switching period duration Fmax of the first switching period Tsw ends. At time point t5, the first pulse Pl31 ends. The period between time points t2 and t3 may be called the first OFF duration Td1. The period between time points t3 and t5 may be called the second ON duration. The period between time points t1 and t4 may be called the switching period duration Fmax of the first switching period Tsw. Between time points t3 and t5, the current Ihb resonates, the magnetization current Im decreases linearly to transfer energy to the secondary side, the voltage Vhb is kept at ground voltage, the feedback voltage Vfb is kept at the platform voltage Vp, and the output current Io starts to resonate and exceeds 0 A. At time point t5, the first pulse Pl31 ends, causing the resonant zero-voltage switch 122 to turn off, the current Ihb and the output current Io return to 0 A, the feedback voltage Vfb falls from the platform voltage Vp, and the first knee point of the feedback voltage Vfb occurs. However, the magnetization current Im has not yet dropped to 0, so the feedback voltage Vfb will soon recover to the platform voltage Vp.
At time point t6, the magnetization current Im decreases to 0, the discharge period Tdis ends, and the feedback voltage Vfb again falls from the platform voltage Vp, resulting in the second knee point of the feedback voltage Vfb. Since the switching period duration Fmax ended before the end of the discharge period Tdis, the control logic 104 executes the operation method 400 for the heavy-loading condition in the later second switching period Tsw, but still executes step S206 in the current first switching period Tsw. Therefore, the control logic 104 controls the second pulse Pl32 of the first switching period Tsw to start at time point t8 when the first peak of the feedback voltage Vfb occurs. The period between time points t5 and t8 may be called the second OFF duration Td2. At time point t9, the second pulse Pl32 ends. The period between time points t8 and t9 may be called the third ON duration.
Between time points t9 and t10, the voltage Vhb rises to approach the input voltage Vin, and the feedback voltage Vfb drops to approach the ground voltage. At time point t10, the main pulse Ph51 of the second switching period Tsw starts, and the switching period duration Fmax starts. At time point t11, the main pulse Ph51 ends. The period between time points t9 and t10 may be called the third OFF duration Td3. The period between time points t10 and t11 may be called the fourth ON duration. Between time points t10 and t11, the current Ihb and the magnetization current Im increase linearly to store energy in the primary winding W1, the voltage Vhb is kept at the input voltage Vin, the feedback voltage Vfb is kept at ground voltage, and the output current Io stays at 0 A.
Between time points t11 and t12, the voltage Vhb drops to approach the ground voltage, and the feedback voltage Vfb rises to approach the platform voltage Vp. At time point t12, the first pulse Pl51 of the second switching period Tsw starts. At time point t13, the switching period duration Fmax ends. At time point t14, the first pulse Pl51 ends. The period between time points t11 and t12 may be called the fourth OFF duration Td4. The period between time points t12 and t14 may be called the fifth ON duration. The period between time points t10 and t13 may be called the switching period duration Fmax of the second switching period Tsw. Between time points t12 and t14, the current Ihb resonates, the magnetization current Im linearly decreases to transfer energy to the secondary side, the voltage Vhb is kept at ground voltage, the feedback voltage Vfb is kept at the platform voltage Vp, and the output current Io starts to resonate and exceeds 0 A. At time point t14, the first pulse Pl51 ends, causing the resonant zero-voltage switch 122 to turn off, the current Ihb returns to 0 A, the feedback voltage Vfb falls from the platform voltage Vp, and the first knee point of the feedback voltage Vfb occurs. However, the magnetization current Im has not yet decreased to 0, so the feedback voltage Vfb will soon recover to the platform voltage Vp.
At time point t15, the magnetization current Im decreases to 0, the discharge period Tdis ends, causing the second knee point of the feedback voltage Vfb. The period between time points t12 and t15 may be called the discharge period Tdis. The period between time points t14 and t15 may be called the fifth OFF duration Td5. The control logic 104, based on the detection results of the previous switching period, starts the second pulse Pl52 at time point t15, which corresponds to the second knee point at the end of the discharge period Tdis in the second switching period.
Additionally, because the switching period duration Fmax has already ended before time point t15 (when the discharge period Tdis of the second switching period ends and the second knee point occurs), the control logic 104 executes the operation method 400 for the heavy-loading condition in a subsequent third switching period Tsw shown in
At time point t16, the second pulse Pl52 ends. The period between time points t15 and t16 may be called the sixth ON duration. Between time points t15 and t16, the current Ihb and magnetization current Im decrease from 0 A to negative values, the voltage Vhb rises from the ground voltage and then drops back to the ground voltage, and the feedback voltage Vfb drops from the platform voltage Vp and then rises back to the platform voltage Vp. Between time points t16 and t17, the voltage Vhb rises to approach the input voltage Vin, and the feedback voltage Vfb drops to approach the ground voltage.
At time point t17, the main pulse Ph52 starts, again storing energy in the primary winding W1. The period between time points t16 and t17 may be called the sixth OFF duration Td6. Between time points t16 and t17, the negative current Ihb and the magnetization current Im will pull up the voltage Vhb to approach the input voltage Vin, which will help the main switch 120 to achieve zero-voltage switching when it is turned on again at time point t17.
In the aforementioned embodiment, if the AHB converter system 1 operates in the light-loading mode shown in
In another embodiment, when a timing circuit within the control logic 104 operates at a faster calculation speed and can adjust the duration-related parameters in real-time based on the detection result, it can also immediately trigger the AHB converter system 1 to switch from the light-loading mode in
Step S600: The control logic 104 controls the main switch driver 100 to turn on the main switch 120 for a fourth ON duration;
Steps S600, S602, and S606 are similar to steps S200, S202, and S210, respectively, and are not further elaborated here.
In step S604, the fifth duration may be equal to a sum of the discharge period Tdis and the third duration under the light-loading condition. In the case of a heavy load (for example, in the previous switching period, the switching period duration Fmax has ended before the second knee point corresponding to the end of the discharge period Tdis occurs), the length of the fifth ON duration is extended to the sum of the discharge period Tdis and the pulse width Wl32 under the light-loading condition. This means that the resonant zero-voltage switch 122 is only turned on and off once in the next switching period, shortening the total time required for the entire switching period, allowing the AHB converter system 1 to switch at a higher frequency. Therefore, the fifth ON duration of the operation method 600 can be equal to the sum of the discharge period Tdis and the third duration under the light-loading condition, in order to achieve resonant energy transfer and generate the negative current required for zero-voltage switching during the fifth ON duration.
In the embodiment, due to the independent control of the main pulse and the first pulse, the control mechanism is simple, and most of the resonant energy transfer and zero-voltage switching of the main switch 120 are achieved in the heavy-loading condition, which improves the energy transfer efficiency.
At time point t6, the magnetization current Im drops to 0, the discharge period Tdis ends, and the feedback voltage Vfb falls from the platform voltage Vp again, thus the second knee point occurs of the feedback voltage Vfb. Since the switching period duration Fmax ends before the end of the discharge period Tdis in the previous switching period, the control logic 104 executes the operation method 400 for the heavy-loading condition in the later second switching period Tsw, but still executes step S206 in the current first switching period Tsw. Therefore, the control logic 104 controls the second pulse Pl32 of the first switching period Tsw to start at time point t8 when the first peak of the feedback voltage Vfb occurs.
Between time points t9 and t10, the voltage Vhb rises to approach the input voltage Vin, and the feedback voltage Vfb drops to approach the ground voltage. At time point t10, the main pulse Ph71 of the first switching period starts, and the switching period duration Fmax starts. The main pulse Ph71 ends at time point t11. The period between time points t10 and t11 can be called the fourth ON duration. Between time points t10 and t11, the current Ihb and the magnetization current Im linearly increase to store energy in the primary winding W1, the voltage Vhb is kept at the input voltage Vin, the feedback voltage Vfb is kept at the ground voltage, and the output current Io stays at 0 A.
Between time points t11 and t12, the voltage Vhb drops to approach the ground voltage, and the feedback voltage Vfb rises to approach the platform voltage Vp. Based on the detection results of the previous switching period, the control logic 104 sets the pulse width Wl71 of the first pulse Pl71 in the second switching period to be equal to the sum of the discharge period Tdis of the first switching period and the pulse width Wl32 of the second pulse Pl32. During the period corresponding to the first pulse Pl71 (between time points t12 and t15), the current Ihb undergoes a complete resonance and the magnetization current Im linearly decreases to transfer energy to the secondary side, the voltage Vhb is kept at the ground voltage, the feedback voltage Vfb is kept at the platform voltage Vp, and the output current Io undergoes a complete resonance. Between time points t14 and t15, the current Ihb and the magnetization current Im decrease from 0 A to negative values, the voltage Vhb rises from the ground voltage and then drops back to the ground voltage, the feedback voltage Vfb drops from the platform voltage Vp and then rises back to the platform voltage Vp, and the output current Io remains at 0 A.
Because the end time point t13 of the switching period duration Fmax of the second switching period Tsw is earlier than the occurrence time point t15 corresponding to the second knee point at the end of the discharge period Tdis, the control logic 104 continues executing the operation method 600 shown in
At time point t16, the main pulse Ph72 starts, once again storing energy in the primary winding W1. The period between time points t15 and t16 can be called the fifth OFF duration Td5. Between time points t15 and t16, the negative current Ihb and the magnetization current Im pull the voltage Vhb up, approaching the input voltage Vin. This facilitates zero-voltage switching of the main switch 120 when it turns on again at time point t16.
In the embodiment, due to the independent control of the main switch 120 and the resonant zero-voltage switch 122, the control mechanism is simple, and most of the resonant energy transfer and zero-voltage switching of the main switch 120 are achieved in the heavy-loading condition, which improves the energy transfer efficiency.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202310260695.6 | Mar 2023 | CN | national |
