TWI839624B - Synchronous Rectification Controller - Google Patents

Abstract

The present invention proposes a synchronous rectification controller, which is applicable to a power conversion circuit. The synchronous rectification controller includes: a first end, a second end, and a switch detection unit. The first end is used to couple to the primary side of the power conversion circuit. The second end is used to couple to the secondary side of the power conversion circuit. The switch detection unit is coupled to the first end to detect the switching of the primary side of the power conversion circuit. When the switch detection unit detects a trigger signal, the second end is driven to send a synchronization signal, thereby controlling the secondary side of the power conversion circuit.

Description

Synchronous rectification controller

The present invention relates to a power conversion circuit technology, and more particularly to a synchronous rectification controller for a power conversion circuit.

In known power conversion circuits, such as DC-to-DC switching power conversion circuits, an analog signal is usually fed back to the primary side of the power conversion circuit through the secondary side of the power conversion circuit as a basis for adjustment. However, the above-mentioned method of feeding back analog signals from the secondary side of the power conversion circuit and the circuit architecture make it difficult to directly synchronize the primary and secondary sides of the power conversion circuit, so it is also difficult to achieve precise control of the operation of synchronous rectification on the secondary side of the power conversion circuit.

Therefore, the synchronous rectification control technology of the known power conversion circuit still needs to be improved.

One purpose of the present invention is to provide a synchronous rectification controller for a power conversion circuit. The synchronous rectification controller can detect the trigger signal of the primary side or the secondary side of the power conversion circuit, and send a synchronous control signal to the secondary side of the power conversion circuit accordingly, so that the primary side and the secondary side of the power conversion circuit are directly synchronized and precisely controlled.

To achieve at least the above-mentioned purpose, the present invention proposes a synchronous rectification controller, which is applicable to a power conversion circuit. The synchronous rectification controller includes: a first end, a second end, and a switch detection unit. The first end is used to couple to the primary side of the power conversion circuit. The second end is used to couple to the secondary side of the power conversion circuit. The switch detection unit is coupled to the first end to detect the switching of the primary side of the power conversion circuit. When the switch detection unit detects a trigger signal, the second end is driven to send a synchronization signal, thereby controlling the secondary side of the power conversion circuit.

In some embodiments, the synchronous rectification controller further includes: a voltage detection unit and a logic unit. The voltage detection unit is used to detect a detection signal on the secondary side of the power conversion circuit. The two input ends of the logic unit are respectively coupled to the output end of the switch detection unit and the voltage detection unit, the output end of the logic unit is coupled to the second end, and the logic unit is used to generate the synchronization signal.

In some embodiments, the synchronous rectification controller further includes: a coupling unit, wherein the output end of the switch detection unit is coupled to the logic unit through the coupling unit, wherein the coupling unit is one of an optical coupling unit, a magnetic coupling unit and a capacitive coupling unit.

In some embodiments, the synchronous rectification controller further includes: a comparison unit, the two input terminals of the comparison unit are respectively used to receive a reference signal and a detection signal of the secondary side of the power conversion circuit, the first end of the comparison unit is coupled to the output terminal of the switch detection unit, the output terminal of the comparison unit is coupled to the second end, and the comparison unit is used to compare the reference signal and the detection signal to generate the synchronization signal.

In some embodiments, the synchronous rectification controller further includes: a coupling unit, wherein the output end of the switch detection unit is coupled to the comparison unit through the coupling unit, wherein the coupling unit is one of an optical coupling unit, a magnetic coupling unit, and a capacitive coupling unit.

In some embodiments, the auxiliary winding of the power conversion circuit is disposed on the primary side or the secondary side of the power conversion circuit.

In some embodiments, the synchronous rectification controller is an integrated circuit.

As described above, multiple embodiments of a synchronous rectification controller for a power conversion circuit are proposed. Thus, the synchronous rectification controller can be implemented to detect the trigger signal of the primary side or the secondary side of the power conversion circuit, and send a synchronous control signal to the secondary side of the power conversion circuit accordingly, so that the primary side and the secondary side of the power conversion circuit are directly synchronized and precise control is achieved.

1. 1A-1F: Synchronous rectification controller

11, 11A, 11B, 11C, 11D: First end

12, 12A, 12B, 12C, 12D: Second end

9, 9A, 9B: Power conversion circuit

91: primary side

92: Secondary side

93A, 93B: Auxiliary winding

120: Coupling unit

130: Switch detection unit

150: Voltage detection unit

160:Logic unit

170: Comparison unit

V _IN : Input voltage

V _OUT : Output voltage

S _SYNC : Synchronous signal

Figure 1 is a schematic block diagram of the architecture of an implementation of a synchronous rectification controller.

FIG2 is a schematic block diagram of an embodiment of a synchronous rectification controller based on FIG1.

FIG3 is a schematic block diagram of another embodiment of the synchronous rectification controller based on FIG1.

FIG4 is a schematic block diagram of another embodiment of the synchronous rectification controller based on FIG1.

FIG5 is a schematic block diagram of another embodiment of the synchronous rectification controller based on FIG1.

FIG6A is a schematic block diagram of an embodiment of a synchronous rectification controller based on FIG1 applied to a power conversion circuit.

FIG6B is a schematic block diagram of another embodiment of the synchronous rectification controller of FIG1 applied to a power conversion circuit.

FIG7 is a schematic block diagram of an embodiment of a switch detection unit detecting a trigger signal.

FIG8 is a schematic block diagram of an embodiment of a switch detection unit.

In order to fully understand the purpose, features and effects of the present invention, the present invention is described in detail through the following specific embodiments and in conjunction with the attached drawings, as follows: Please refer to Figure 1, which is a schematic block diagram of the architecture of an implementation method of a synchronous rectification controller 1. As shown in Figure 1, the synchronous rectification controller 1 is suitable for a power conversion circuit 9, and the synchronous rectification controller 1 includes: a first end 11, a second end 12 and a switch detection unit 130. The first end 11 is used to couple to the primary side 91 of the power conversion circuit 9. The second end 12 is used to couple to the secondary side 92 of the power conversion circuit 9. The switch detection unit 130 is coupled to the first end 11 to detect the switching of the primary side 91 of the power conversion circuit 9. When the switch detection unit 130 detects a trigger signal, the second terminal 12 is driven to send a synchronization signal S _SYNC , thereby controlling the secondary side 92 of the power conversion circuit 9 .

For example, as shown in FIG. 1 , the power conversion circuit 9 includes a primary side 91 and a secondary side 92. The power conversion circuit 9 receives an input voltage V _IN through the primary side 91 and outputs an output voltage V _OUT after power conversion through the secondary side 92. For example, the power conversion circuit 9 is a DC-to-DC switching power conversion circuit. The primary side 91 and the secondary side 92 are respectively switched by switches implemented by transistors controlled by signals to perform power conversion. In addition, in the overall circuit of the power conversion circuit 9, there is a main transformer. The transformer has a magnetic core, and there are a primary winding (as represented by 91 in FIG. 1 ), a secondary winding (as represented by 92 in FIG. 1 ) and at least one auxiliary winding on the magnetic core. The auxiliary winding can be arranged on the primary side 91 (as shown in FIG. 1 and FIG. 6A); in another example, the auxiliary winding can also be arranged on the secondary side 92 (please refer to FIG. 6B). In order to enable the primary side 91 and the secondary side 92 of the power conversion circuit 9 to achieve the effect of real-time and precise control, a synchronous rectification controller 1 is used outside the power conversion circuit 9 to control the synchronous rectification. For example, the synchronous rectification controller 1 can be implemented as an integrated circuit for easy use. In this way, the synchronous rectification controller 1 can be provided with a plurality of connection terminals with different functions, as shown in the embodiments of the synchronous rectification controller 1 in the following FIGS. 2 to 5, so as to implement synchronous rectification controllers with different circuit configurations according to the type and needs of the power conversion circuit 9, so as to facilitate circuit design and use during implementation.

The internal circuit of the synchronous rectification controller 1 has a switch detection unit 130. The switch detection unit 130 can be implemented as a circuit using a comparator (such as the example of FIG. 8 ) and electrically coupled to the primary side 91 of the power conversion circuit 9 to detect a trigger signal. The trigger signal is, for example, a waveform of a voltage drop as shown in FIG. 7 . When the switch detection unit 130 detects a trigger signal, the second end 12 is driven to send a synchronization signal S _SYNC , thereby controlling the secondary side 92 of the power conversion circuit 9 for synchronous operation.

In some embodiments, the synchronous rectification controller 1 can generate the synchronization signal S _SYNC in a variety of ways, such as directly based on or indirectly triggering a signal, or further in conjunction with other conditions. Other conditions include, for example, a signal on the primary side 91 of the power conversion circuit 9, such as a control signal of a control switch (such as a transistor) on the primary side 91 of the power conversion circuit 9; and/or a signal on the secondary side 92 of the power conversion circuit 9, such as a detection signal on the secondary side 92 of the power conversion circuit 9, such as a signal on the non-control end of a switch (such as a transistor) (such as the voltage level of the source or drain). Therefore, various embodiments under the architecture of the synchronous rectification controller 1 are described below by way of example.

Please refer to FIG. 2, which is a schematic block diagram of an embodiment of the synchronous rectification controller based on FIG. 1. As shown in FIG. 2, the synchronous rectification controller 1A is an embodiment based on the synchronous rectification controller 1, and has a first terminal 11A, a second terminal 12A, and a switch detection unit 130. Compared with the synchronous rectification controller 1, the synchronous rectification controller 1A further includes: a coupling unit 120, which has a coupling input terminal and a coupling output terminal, wherein the coupling input terminal is coupled to the switch detection unit 130, and the coupling output terminal is electrically coupled to the second terminal 12A.

The synchronous rectification controller 1A in FIG2 utilizes the coupling unit 120 to obtain electrical isolation between the coupling input terminal and the coupling output terminal (as represented by the dotted line in FIG2 ), thereby reducing the signal interference on the primary side and the secondary side.

For example, the synchronous rectification controller 1A can be implemented as an integrated circuit for easy use. The synchronous rectification controller 1A can be provided with a plurality of connection terminals with different functions, such as SWIN (such as representing the switching signal input terminal; such as the first terminal 11A), SYNC (such as representing the synchronization signal output terminal; such as the second terminal 12A) respectively used to connect the primary side 91 and the secondary side 92 of the power conversion circuit 9 to detect the trigger signal and output the synchronization signal S _SYNC ; such as Vccp and Vccs respectively used to connect the power supply (such as Vcc, etc.) of the primary side 91 and the secondary side 92 of the power conversion circuit 9 for use by the internal circuit of the synchronous rectification controller 1A; such as GNDP and GNDS respectively used to connect the ground terminal of the primary side 91 and the secondary side 92 of the power conversion circuit 9 for use by the internal circuit of the synchronous rectification controller 1A. In the following embodiments of FIG. 3 to FIG. 5 , the same symbols represent the same connection terminals, and thus will not be described in detail.

In some embodiments, the coupling unit 120 can be implemented as an optical coupling unit. In other embodiments, the coupling unit 120 can also be implemented as a magnetic coupling unit. In other embodiments, the coupling unit 120 can also be implemented as a capacitive coupling unit.

Please refer to Figure 3, which is a schematic block diagram of another embodiment of the synchronous rectification controller based on Figure 1. As shown in Figure 3, the synchronous rectification controller 1B is an embodiment based on the synchronous rectification controller 1, having a first end 11B, a second end 12B, and a switch detection unit 130. The switch detection unit 130 is used to detect the switching of the primary side 91 of the power conversion circuit 9, for example, receiving the control signal of the switching switch (such as a transistor) of the primary side 91 of the power conversion circuit 9. The synchronous rectification controller 1B further includes: a voltage detection unit 150 and a logic unit 160. The voltage detection unit 150 is used to detect a detection signal of the secondary side 92 of the power conversion circuit 9. The two input terminals of the logic unit 160 are respectively coupled to the switch detection unit 130 and the voltage detection unit 150 , and the output terminal of the logic unit 160 is coupled to the second terminal 12B. The logic unit 160 is used to generate the synchronization signal S _SYNC . In the embodiment of FIG. 3 , the switch detection unit 130 is coupled to the logic unit 160 via the coupling unit 120 .

In addition, general synchronous rectification refers to replacing the diode with a switching element in the charging loop on the secondary side of the power conversion circuit. The switching element is, for example, a field effect transistor (FET), and the switching element still has some impedance in the on state (for example, 200 milliohms, depending on the operating current). The aforementioned voltage detection unit detects when the current drops to almost zero (the feedback reaction current drops to zero approximately linearly) by detecting the voltage caused by the reaction current on the secondary side of the power conversion circuit passing through the switching element.

For example, the logic unit 160 performs a logic AND operation. Further, through the voltage detection unit 150 and the logic unit 160, the synchronous rectification controller 1B can further use more complex and precise conditions as the basis for the synchronous rectification controller to generate the synchronization signal S _SYNC , thereby facilitating more direct, instant, and precise synchronization control. For example, the detection signal is a detection signal from the secondary side 92 of the power conversion circuit 9, such as a signal of a non-control end of a switching switch (such as a transistor) (such as the voltage of the source or drain), such as S _FB in FIG. 6A or FIG. 6B.

For example, the synchronous rectification controller 1B can be implemented as an integrated circuit for easy use. The synchronous rectification controller 1B can be provided with multiple connection terminals with different functions. In addition to the connection terminals mentioned above, it also includes Vdrain for connecting the signal of the secondary side 92 of the power conversion circuit 9 (such as the voltage of the drain) for use by the circuit inside the synchronous rectification controller 1B. Please also refer to FIG. 6A or FIG. 6B. In the embodiments of the following FIG. 4 to FIG. 5, the same symbols represent the same connection terminals, so they will not be repeated.

In other embodiments, another logic unit may be connected after the switch detection unit 130 to perform logic operations or act as a buffer, and the synchronous rectifier controller 1B may further utilize more complex conditions as the basis for the synchronous rectifier controller to generate the synchronization signal S _SYNC , thereby facilitating more direct, instant, and precise synchronization control. For example, the circuits on the first end of the synchronous rectifier controller in FIG3 , FIG4 , and FIG5 all use the same architecture, and the corresponding circuits on the second end may be implemented using different architectures for customization, or to meet the needs of synchronization control of the power conversion circuit to be applied to the individual design of the synchronous rectifier controller.

Please refer to FIG. 4 , which is a schematic block diagram of another embodiment of the synchronous rectification controller based on FIG. 1 . As shown in FIG. 4 , the synchronous rectification controller 1C is an embodiment based on the synchronous rectification controller 1, and has a first terminal 11C, a second terminal 12C, and a switch detection unit 130. Compared with the synchronous rectification controller 1B, the synchronous rectification controller 1C further includes: a comparison unit 170. The two input terminals of the comparison unit 170 are respectively used to receive a reference signal (such as Vref) and a detection signal (such as the aforementioned S _FB ) of the secondary side 92 of the power conversion circuit 9; an enable terminal EN of the comparison unit 170 is coupled to the switch detection unit 130 (such as through the coupling unit 120); and the output terminal of the comparison unit 170 is coupled to the second terminal 12C. The comparison unit 170 is used to compare the reference signal (such as Vref) and the detection signal (such as the aforementioned S _FB ) to generate the synchronization signal S _SYNC , wherein the comparison unit 170 determines whether to output the synchronization signal S _SYNC through the output terminal of the comparison unit 170 according to the signal of the enable terminal EN. The switch detection unit 130 controls whether the comparison unit 170 is allowed to output the synchronization signal S _SYNC through the coupled output terminal and the enable terminal EN.

Please refer to FIG5, which is a schematic block diagram of another embodiment of the synchronous rectification controller based on FIG1. As shown in FIG5, the synchronous rectification controller 1D is an embodiment based on the synchronous rectification controller 1C, and has a first terminal 11D, a second terminal 12D, a switch detection unit 130, and a comparison unit 170. Compared with the synchronous rectification controller 1C, the synchronous rectification controller 1D does not use the coupling unit 120. The two input terminals of the comparison unit 170 are respectively used to receive a reference signal (such as Vref) and a detection signal (such as the aforementioned S _FB ) of the secondary side 9 of the power conversion circuit 9; an enable terminal EN of the comparison unit 170 is coupled to the output terminal of the switch detection unit 130; and the output terminal of the comparison unit 170 is coupled to the second terminal 12C. The comparison unit 170 is used to compare the reference signal (such as Vref) and the detection signal (such as the aforementioned S _FB ) to generate the synchronization signal S _SYNC , wherein the comparison unit 170 determines whether to output the synchronization signal S _SYNC through the output terminal of the comparison unit 170 according to the signal of the enable terminal EN. The switch detection unit 130 controls the comparison unit 170 through the enable terminal EN to determine whether to allow the output of the synchronization signal S _SYNC . In FIG. 5 , the synchronous rectification controller 1D does not use the coupling unit 120 and can be regarded as a simplified implementation of the synchronous rectification controller 1C.

Please refer to FIG6A, which is a schematic block diagram of an embodiment of a synchronous rectification controller 1E based on FIG1 applied to a power conversion circuit 9A, wherein an auxiliary winding 93A of the power conversion circuit 9A is arranged on the primary side of the power conversion circuit 9A. Please refer to FIG6B, which is a schematic block diagram of another embodiment of a synchronous rectification controller 1F based on FIG1 applied to a power conversion circuit 9B, wherein an auxiliary winding 93B of the power conversion circuit 9B is arranged on the secondary side of the power conversion circuit 9B. As shown in FIG6A or FIG6B, the synchronous rectification controller 1E or 1F schematically represents an embodiment of the synchronous rectification controller in the aforementioned FIG2 to FIG5. For example, the power conversion circuit 9A or 9B is a flyback power converter; the switches on the primary side and the secondary side of the power conversion circuit are implemented by transistors Q1 and Q2 respectively, the control signal (switching signal) of transistor Q1 is PGate, and the synchronization signal of transistor Q2 is S _SYNC , wherein PGND and SGND represent the ground terminals of the primary side and the secondary side respectively. In other embodiments, the embodiments of the synchronous rectification controller can also be appropriately modified and applied to other suitable power converters, so it is not limited to the above examples.

In other embodiments, the switch on the primary side of the power conversion circuit is directly controlled by the secondary side of the power conversion circuit. In this case, the switch detection unit can be configured to be coupled to the secondary side of the power conversion circuit for detection. In addition, in some embodiments, an auxiliary winding is provided on the secondary side of the power conversion circuit (as shown in FIG. 6B ), so the coil signal processing unit can also be configured to be coupled to the auxiliary winding on the secondary side of the power conversion circuit for detection. In the application scenario where the auxiliary coil of FIG. 6B is placed on the secondary side of the power conversion circuit, for example, the architecture of FIG. 5 is used to implement a synchronous rectification controller.

In addition, in the embodiments of FIG. 2 to FIG. 4 above, the coupling unit 120 is optional, and whether the coupling unit needs to be used in the synchronous rectification controller can be selected based on, for example, whether the auxiliary coil is placed on the primary side or the secondary side of the power conversion circuit.

The following are some examples of conditions applicable to judging synchronous control, which can be appropriately adjusted to implement the embodiments shown in Figures 2 to 5.

In some examples, the necessary conditions (such as logical AND (AND) operation on the conditions) for the switching switch (such as transistor Q2) on the secondary side of the power conversion circuit (such as 9A or 9B) controlled by the synchronous rectification controller to start (maintain) conduction are: (1) when the primary side main switch (such as transistor Q1) is turned off, one of the primary side switches sends a signal to the secondary side, for example, using an optically coupled output terminal to send a signal; and (2) the coil signal processing unit detects a positive voltage, the source of which is the electromotive force (emf) generated by the magnetic core energy, which is an indicator of signal lag, and the electromotive force corresponding to the release of magnetic field energy can also be used to enable the synchronous rectification switch. In addition, further conditions may be added, such as (3) the drain of the transistor on the secondary side detects a negative voltage, wherein the secondary side detects a negative voltage (such as using the voltage detection unit 150), and an amplifier (such as the comparison unit 170) may be used to respond to output a synchronization signal.

In some examples, sufficient conditions (such as a logical OR operation to operate on the conditions) for closing the switching switch (such as transistor Q2) on the secondary side of the power conversion circuit (such as 9A or 9B) controlled by the synchronous rectification controller are: (1) the primary side main switch is turned on (ON) (such as the power conversion circuit is a flyback type), and when the primary is about to be turned on, a signal is sent first, such as using an optical coupling unit to force the output of a low-level signal; (2) the coil signal processing unit detects a sudden drop in voltage, and when the energy of the magnetic core is about to be exhausted, the electromotive force (emf) drops significantly, and a signal is sent immediately; (3) the drain of the secondary side transistor cannot maintain a negative voltage, and for example, the current drop gate (set to maintain at -40mV) is set to be maintained at -40mV. (4) Secondary side lock, in which the drain voltage turns negative and cannot restart conduction to avoid noise or vibration. The unlocking of the lock requires changes on the primary side (such as the light-emitting diode (LED) of the optical coupling unit turning from off to on).

Please refer to FIG8 , which is a schematic block diagram of an embodiment of the switch detection unit 130 . As shown above, the switch detection unit 130 in the above embodiment can be implemented using a comparator circuit. As shown in FIG8 , an embodiment of the switch detection unit 130 can include a comparator, a resistor, and a capacitor to implement, wherein a negative input terminal of the comparator is used to receive a reference signal V _ref2 , and a positive input terminal of the comparator is used to receive a signal from the primary side 91 of the power conversion circuit 9 through a loop including a resistor and a capacitor, such as through SWIN (such as representing a switching signal input terminal; such as the first terminal 11A). The output of the comparator provides positive feedback to the positive input terminal, which is a way of implementing a Schmitt trigger.

As described above, multiple embodiments of a synchronous rectification controller for a power conversion circuit are proposed. Thus, the synchronous rectification controller can be implemented to detect the trigger signal of the primary side or the secondary side of the power conversion circuit, and send a synchronous control signal to the secondary side of the power conversion circuit accordingly, so that the primary side and the secondary side of the power conversion circuit are directly synchronized and precisely controlled.

The present invention has been disclosed in the above text with preferred embodiments, but those familiar with the present technology should understand that the embodiments are only used to describe the present invention and should not be interpreted as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to the embodiments should be included in the scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the patent application.

1: Synchronous rectification controller

11: First end

12: Second end

9: Power conversion circuit

91: primary side

92: Secondary side

130: Switch detection unit

V _IN : Input voltage

V _OUT : Output voltage

S _SYNC : Synchronous signal

Claims (3)

A synchronous rectification controller is applicable to a power conversion circuit. The synchronous rectification controller comprises: a first end, coupled to the primary side of the power conversion circuit; a second end, coupled to the secondary side of the power conversion circuit; a switch detection unit, coupled to the first end, for detecting the switching of the primary side of the power conversion circuit; a voltage detection unit, for detecting a detection signal of the secondary side of the power conversion circuit; a logic unit, two input ends of the logic unit are respectively coupled to the switch detection unit. The output end of the switch detection unit and the voltage detection unit, the output end of the logic unit is coupled to the second end, and the logic unit is used to generate a synchronization signal; and a coupling unit, wherein the output end of the switch detection unit is coupled to the logic unit through the coupling unit, wherein the coupling unit is one of an optical coupling unit, a magnetic coupling unit and a capacitive coupling unit; wherein when the switch detection unit detects a trigger signal, the second end is driven to send the synchronization signal, thereby controlling the secondary side of the power conversion circuit. A synchronous rectification controller as described in claim 1, wherein the auxiliary winding of the power conversion circuit is arranged on the primary side or the secondary side of the power conversion circuit. A synchronous rectifier controller as described in claim 1, wherein the synchronous rectifier controller is an integrated circuit.

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