Synchronous rectification controller and related control method

Abstract

The embodiment of the invention provides a synchronous rectification controller and a related control method, which are used for controlling a synchronous rectification switch. The synchronous rectification switch is provided with a control end and a detection end. The synchronous rectification controller comprises a starting time recorder and a differential driver. The turn-on time recorder is used for recording the previous turn-on time of the synchronous rectification switch according to a detection signal on the detection end and determining a first regulation and control time period and a second regulation and control time period. The first regulation and control period occurs before the second regulation and control period. According to the detection signal, the differential driver drives the control end to regulate the detection signal at a first target voltage and a second target voltage respectively in the first regulation time period and the second regulation time period. The first target voltage is different from the second target voltage.

Description

Technical Field

[0001] This invention relates generally to synchronous rectification control of LLC converters, and more particularly to signal control of synchronous rectification switches during synchronous rectification. Background Technology

[0002] LLC converters are a type of resonant converter, which typically offers a smooth output waveform, high conversion efficiency, and high output power. Generally, a resonant converter converts a DC input power supply into a sinusoidal signal. This conversion is achieved through a switch network architecture, providing a square-wave voltage to a resonant tank. After filtering by the resonant tank, the fundamental frequency of the square-wave voltage is roughly retained, thus approximating a sinusoidal input current. Due to the inductive effect, an alternating current is generated on the secondary side of the LLC converter, which, after rectification, can be used to establish the output power supply.

[0003] LLC converters are generally used for high-current output. To improve conversion efficiency, synchronous rectification can be used on the secondary side of the LLC converter. This involves replacing the traditional rectifier diode with a synchronous rectifier switch and a synchronous rectifier controller. This reduces or eliminates the high power consumption caused by the rectifier diode's approximately fixed forward bias when conducting high currents.

[0004] While synchronous rectification may increase conversion efficiency, it can also introduce other problems that require special attention. Especially in LLC converters, large current variations can easily exacerbate the effects of parasitic inductance, leading to errors in synchronous rectification control. Summary of the Invention

[0005] This invention provides a synchronous rectification controller for controlling a synchronous rectification switch. The synchronous rectification switch has a control terminal and a detection terminal. The synchronous rectification controller includes an on-time recorder and a differential driver. The on-time recorder records a previous on-time of the synchronous rectification switch based on a detection signal on the detection terminal, and determines a first control period and a second control period. The first control period occurs before the second control period. Based on the detection signal, the differential driver drives the control terminal to adjust the detection signal to a first and a second target voltage during the first and second control periods, respectively. The first target voltage is different from the second target voltage.

[0006] This invention provides a control method for controlling a synchronous rectifier switch, applicable to a synchronous rectifier controller. The synchronous rectifier switch has a control terminal and a detection terminal. The control method includes: recording a previous on-time of the synchronous rectifier switch based on a detection signal on the detection terminal, and determining a first control period and a second control period, the first control period occurring before the second control period; and driving the control terminal based on the detection signal to adjust the detection signal to a first and a second target voltage during the first and second control periods, respectively, wherein the first target voltage is different from the second target voltage, and both the first and second control periods are related to the previous on-time. Attached Figure Description

[0007] Figure 1 Display an LLC converter.

[0008] Figure 2 A controller according to the present invention.

[0009] Figure 3 This shows when the target voltage V REG1 With V REG2 Some signal logic and waveforms at -0.18V and -0.24V respectively.

[0010] Figure 4 This shows when the target voltage V REG1 With V REG2 Some signal logic and waveforms when all are -0.18V.

[0011] Figure 5 The parasitic inductance in a synchronous rectifier switch is shown.

[0012] Figure 6 and 7 Remade separately Figure 3 and 4 Inductor current I LS1 With detection signal V DT1 The waveform, the ON signal, and the control signal V G1 The waveform is the same, but with the added effect of parasitic inductance.

[0013] [Symbol Explanation]

[0014] 100 LLC converter

[0015] 102 load

[0016] 104 Synchronous Rectifier Controller

[0017] 120 transducer

[0018] 122 Fully Open Drive

[0019] 124. Start the time recorder

[0020] 126 Target Voltage Generator

[0021] 128 Shut down the drive

[0022] 130 drive

[0023] 132 Differential drive

[0024] BVD1 and BVD2 controllers

[0025] CI Input Capacitor

[0026] CO output capacitor

[0027] CR resonant capacitor

[0028] DT1 and DT2 detection terminals

[0029] G1, G2 control terminals

[0030] GNDI input ground wire

[0031] GNDO output ground wire

[0032] HI Upper Arm Control Signal

[0033] HS upper arm switch

[0034] I LS1 I LS2 Inductor current

[0035] IN Input power line

[0036] I R Alternating current

[0037] LL1 Parasitic Inductance

[0038] LO lower arm control signal

[0039] LP primary winding

[0040] LR resonant inductor

[0041] LS lower arm switch

[0042] LS1 and LS2 secondary windings

[0043] NM1 N-type metal-oxide-semiconductor transistor

[0044] ON signal

[0045] OUT output power line

[0046] PL1, PL2 pulses

[0047] RT1 and RT2 resistors

[0048] SR1 and SR2 synchronous rectifier switches

[0049] SW input endpoint

[0050] Time points t10, t11, t12, t13, t20, t21, t22, t23, t30, t31, t32, t33, t40, t41, t42

[0051] Intersection of t1C, t2C, and t3C

[0052] t3S and t4S switching points

[0053] T0 Full Opening Period

[0054] T1 and T2 control periods

[0055] TF Transformer

[0056] TNK LLC resonant circuit

[0057] TON current opening time

[0058] TON_pre previous opening time

[0059] V CC Operating power supply

[0060] V det_OFF Reference voltage

[0061] V DT1 V DT2 Detection signal

[0062] V G1 V G2 control signals

[0063] V IN Input power

[0064] V OUT Output power

[0065] V REG Target signal

[0066] V REG1 V REG2 Target voltage

[0067] V SW Square wave voltage Detailed Implementation

[0068] In this specification, some identical symbols are used to represent elements having the same or similar structure, function, or principle, which can be inferred by those skilled in the art based on the teachings of this specification. For the sake of brevity, elements with the same symbols will not be repeated.

[0069] Figure 1 To illustrate the LLC converter 100, it is used to convert the input power supply V located on the primary side. IN Converted to output power V located on the secondary side OUT The LLC converter 100 employs synchronous rectification, using two synchronous rectifier switches SR1 and SR2 to rectify the inductor current I output from the two secondary windings LS1 and LS2, respectively. LS1 with I LS2 .

[0070] On the primary side, the upper arm switch HS and the lower arm switch LS are connected in series between the input power line IN and the input ground line GNDI via the input terminal SW, forming a half-bridge structure, which can be regarded as a square wave generator. The input capacitor CI acts as a filter capacitor, connected between the input power line IN and the input ground line GNDI, which can stabilize the input power supply V. IN The voltage. The upper arm switch HS and the lower arm switch LS are controlled by the upper arm control signal HI and the lower arm control signal LO, respectively.

[0071] The resonant inductor LR, the primary winding LP of the transformer TF, and the resonant capacitor CR are connected in series between the input terminal SW and the input ground line GNDI, forming an LLC resonant tank TNK. In one embodiment, the resonant inductor LR may not be an independent component, but rather a leakage inductance in the primary winding LP that is not inductively coupled to the secondary windings LS1 and LS2.

[0072] The upper arm switch HS and the lower arm switch LS are turned on alternately, providing a square wave voltage V. SW By applying force to the input terminal SW of the resonant circuit, the LLC resonant circuit TNK resonates. An alternating current I is generated across the resonant inductor LR. R Through the inductive coupling of transformer TF, corresponding inductive currents I will also be generated in the secondary windings LS1 and LS2. LS1 with I LS2 The secondary-side synchronous rectifier switches SR1 and SR2 provide full-wave rectification. Synchronous rectifier switch SR1 is connected between the output ground line GNDO and the sensing terminal DT1, while synchronous rectifier switch SR2 is connected between the output ground line GNDO and the sensing terminal DT2. The output capacitor CO provides low-pass filtering, generating the output power V across the output power line OUT and the output ground line GNDO. OUTThis is used to power load 102. Figure 1 In the middle, the output power supply V OUT It also serves as the operating power supply V for the synchronous rectifier controller 104. CC It supplies the electrical energy required for the operation of the synchronous rectifier controller 104.

[0073] The synchronous rectifier controller 104 is connected to the detection terminals DT1 and DT2 via resistors RT1 and RT2, respectively. Based on the detection signals V on the detection terminals DT1 and DT2... DT1 With V DT2 The synchronous rectification controller 104 drives the control terminals G1 and G2 of the synchronous rectification switches SR1 and SR2 respectively. For example, the controller BVD1 in the synchronous rectification controller 104 determines the control terminal G1 and G2 based on the detection signal V. DT1 To generate a control signal V with an appropriate voltage. G1 This is used to control the synchronous rectifier switch SR1.

[0074] Figure 2 show Figure 1 The controller BVD1 is described above. The controller BVD2 can be deduced from the description of controller BVD1, and will not be repeated here. Controller BVD1 includes an on-time recorder 124, a target voltage generator 126, and a driver 130, as... Figure 2 As shown. The power-on time recorder 124 records the previous power-on time TON_pre, which will be explained later. The target voltage generator 126 provides the target voltage V. REG1 With V REG2 The differential drive 132 is supplied with a control signal V at the control terminal G1. G1 .

[0075] Please see Figure 2 and Figure 3 . Figure 3 This shows the inductor current I flowing through the synchronous rectifier switch SR1. LS1 The detection signal V of the detection terminal DT1 DT1 Waveforms, some in Figure 2 The signal logic and waveforms, and the control signal V on the control terminal G1. G1 The waveform.

[0076] exist Figure 3 Before time point t10, the synchronous rectifier switch SR1 is in the closed state, and the control signal V G1 The voltage is 0V. Detection signal V DT1 Greater than 0V, but inductor current I LS1 The current is 0A, and there is no leakage current or reverse current.

[0077] From time point t10 to time point t13, because the LLC resonant circuit TNK resonates, the inductor current I... LS1 If positive, the detection signal V DT1 The value is negative. Between time point t10 and time point t13, that is, within the current on-time TON, the synchronous rectifier switch SR1 should be turned on, exhibiting a conducting state, to reduce the inductor current I. LS1 The impedance flowing through the synchronous rectifier switch SR1.

[0078] Figure 2 The start-up time recorder 124 can be based on the detection signal V DT1 This is used to determine the start and end of the current activation time TON. For example, the activation time recorder 124 compares and detects the signal V. DT1 With reference voltage V det_OFF (Taking -0.1V as an example). When the detection signal V DT1 Dropped below reference voltage V det_OFF The ON signal changes to a logical "1", indicating the start of the current on time TON, as... Figure 3 As shown at time point t01. When the detection signal V DT1 Higher than the reference voltage V det_OFF The time indicates the end of the current ON time, as shown at time point t13.

[0079] The time recorder 124 records the previous start time TON_pre, which represents the length of the previous current start time TON. In other words, at time t13, when the current start time ON ends, the length of the current start time TON can be used to update the previous start time TON_pre.

[0080] The time recorder 124, based on the previous on-time TON_pre, divides the current on-time ON into a full-on period T0, a control period T1, and T2, corresponding to pulses PRD0, PRD1, and PRD2 respectively, as shown in the diagram. Figure 3 As shown. In Figure 3 In this embodiment, the activation time recorder 124 starts the full-on period T0 simultaneously with the current activation time ON, but the length of the full-on period T0 is equal to 0.5 times the previous activation time TON_pre (a preset ratio), as shown at time points t10 to t11. The control period T1 follows the end of the full-on period T0, and its length is equal to 0.3 times the previous activation time TON_pre (a first preset ratio), as shown at time points t11 to t12. The control period T2 follows the end of the control period T1 until the current activation time ON ends, as shown at time points t12 to t13. Figure 3In this embodiment, in steady state, the length of the control period T2 is approximately equal to 0.2 times the previous on-time TON_pre (the second preset ratio). The control periods T1 and T2 can be considered related to the previous on-time TON_pre. As... Figure 3 For example, the control period T1 begins approximately 0.5 times the previous opening time TON_pre after the current opening time ON, while the control period T2 begins approximately 0.8 times the previous opening time TON_pre after the current opening time ON.

[0081] Figure 2 The driver 130 drives the control terminal G1 in different ways during the fully open period T0, the control period T1, and T2. Figure 2 The driver 130 includes a shut-off driver 128, a fully open driver 122, and a differential driver 132. Outside of the current ON time, the shut-off driver 128 causes the control signal V to... G1 The voltage is 0V, so the synchronous rectifier switch SR1 is turned off to prevent reverse current. During the fully open period T0 (represented by pulse PRD0), the fully open driver 122 attempts to push the control signal V... G1 The voltage is pulled up to a fixed voltage, which can be the highest voltage that the synchronous rectifier switch SR1 can withstand, such as the operating power supply V. CC The operating voltage is adjusted to reduce the impedance of the synchronous rectifier switch SR1. During the control period T1, the transconductor 120 is enabled, and the detection signal V is compared. DT1 With target voltage V REG1 The impedance of the synchronous rectifier switch SR1 is controlled to regulate the detection signal V. DT1 At the target voltage V REG1 During the control period T2, transconductor 120 is enabled, and the detection signal V is compared. DT1 With target voltage V REG2 To regulate the detection signal V DT1 At the target voltage V REG2 .exist Figure 3 In the embodiment, the target voltage V REG1 With V REG2 The values ​​are -0.18V and -0.24V respectively, so the target signal V at one input terminal of transducer 120 is... REG During the control periods T1 and T2, the values ​​were -0.18V and -0.24V, respectively.

[0082] Figure 3 The control signal V is displayed during the fully open period T0. G1 Pulled to operating power supply V CCThe operating voltage. During the control period T1, the control signal V... G1 Still maintained at operating power V CC The operating voltage, because of the detection signal V DT1 Continuously below -0.18V (target voltage V) REG1 Therefore, transducer 120 still transmits the control signal V. G1 Fixed on the operating power supply V CC The operating voltage is generally the maximum permissible voltage. At the crossover point t1C within the control period T2, the detection signal V... DT1 It starts to be higher than -0.24V (target voltage V). REG2 Transducer 120 starts pulling the control signal V low. G1 We hope to make the detection signal V DT1 It remained at -0.24V until time point t13, as... Figure 3 As shown.

[0083] Figure 2 In the middle, the target voltage generator 126 can be based on the detection signal V DT1 To provide the target voltage V REG1 With V REG2 In one embodiment, the target voltage generator 126 is based on the detection signal V DT1 The period or frequency determines the target voltage V. REG1 With V REG2 In another embodiment, when the current on-time TON_pre is a preset length, the target voltage V... REG1 With V REG2 The values ​​are -0.18V and -0.24V respectively; when the current on-time TON_pre is another shorter preset length, the target voltage V REG1 With V REG2 These are -0.14V and -0.20V, respectively. In other embodiments, the target voltage generator 126 can be based on the detection signal V. DT1 The lowest value or output power V OUT The target voltage V is determined by the voltage. REG1 With V REG2 .

[0084] exist Figure 3 In the middle, the target voltage V REG1 With V REG2 The values ​​are -0.18V and -0.24V respectively. Figure 4 and Figure 3 Similarly, they all display the same signal waveform or logic, but... Figure 4 In the embodiment, the target voltage V REG1 With V REG2 Both are -0.18V. Figure 4 and Figure 3 Similarities or resemblances can be found through previous... Figure 3 As explained above, it will not be repeated here. Figure 4 In the middle, after the crossover point t2C in the control period T2, the detection signal V DT1 When the voltage rises above -0.18V, transducer 120 begins to pull the control signal V low. G1 We hope to make the detection signal V DT1 It remained at -0.18V until time point t23, as... Figure 4 As shown.

[0085] When the inductor current I LS1 When the voltage is high, the parasitic inductance generated by the package pins of the synchronous rectifier switch SR1 can have a significant impact. Figure 5 The synchronous rectifier switch SR1 and its associated circuitry are shown. Figure 5 In the circuit, the synchronous rectifier switch SR1 includes an N-type metal-oxide-semiconductor transistor NM1 connected in series and a parasitic inductance LL1. The parasitic inductance LL1 can be represented by the inductance of the package wires connecting the source and drain of the N-type metal-oxide-semiconductor transistor NM1. When the upper arm switch HS and the lower arm switch LS on the primary side switch, the detection signal V may be affected. DT1 Rapid changes.

[0086] Figure 6 and 7 Remade separately Figure 3 and 4 Inductor current I LS1 With detection signal V DT1 The waveform, the ON signal, and the control signal V G1 The waveform, but with an additional... Figure 5 The potential impact of parasitic inductance LL1. Figure 6 The switching point t3S in the middle and Figure 7 The switching point t4S occurs approximately at the same time point during the current ON time, at which point one of the primary side upper arm switch HS and lower arm switch LS switches from the ON state to the OFF state. Therefore, at switching points t3S and t4S, Figure 6 and Figure 7 The detection signal V in DT1 Very short pulses PL1 and PL2 were generated, with the heights of the two upward pulses being approximately the same.

[0087] exist Figure 6 In the middle, pulse PL1 did not touch the reference voltage V. det_OFF Therefore, the current start time TON will continue until time point t33 ends, and... Figure 3 Same. Figure 6 and Figure 3 The current opening time is the same as TON.

[0088] exist Figure 7 In the middle, pulse PL2 touches the reference voltage V det_OFF Therefore, the ON signal immediately becomes logically "0", and the on-time TON immediately ends at the switching point t4S, just like... Figure 7 As shown. Compared to Figure 4 , Figure 7 The current activation time (TON) is significantly shorter. Furthermore, in... Figure 7 At the switching point t4S, the inductor current I LS1 The value is still quite large, and turning off the synchronous rectifier switch SR1 at this point would cause many unnecessary conduction losses.

[0089] Compare Figure 6 and Figure 7 It can be seen that, due to Figure 6 Control signal V in G1 At the crossover point t3C, the signal is pulled low, therefore the detection signal V... DT1 At the switching point t3S, compared to the detection signal V DT1 At the switching point t4S, there is a relatively low value. Therefore, at Figure 6 In the middle, pulse PL1 did not touch the reference voltage V. det_OFF In contrast, Figure 7 In the middle, pulse PL2, which is about the same height as pulse PL1, hits the reference voltage V. det_OFF This leads to unnecessary conduction loss.

[0090] In short, the detection signal V is adjusted during the control period T1 and the control period T2 respectively. DT1 At -0.18V and -0.24V, this can be avoided. Figure 7 The conduction loss due to premature shutdown of synchronous rectification.

[0091] In some embodiments, the full-on period T0 can be omitted, with only the control periods T1 and T2. In some embodiments, the current on time ON has sequentially connected control periods T1, T2, T3, ... TN, which are used to control the detection signal V. DT1 At the target voltage V REG1 V REG2 V REG3 ...V REGN , where N is an integer. All target voltages V REG1 V REG2 V REG3 ...V REGN All are negative numbers, with the one used earlier being greater than the one used later.

[0092] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be within the scope of the present invention.

Claims

1. A synchronous rectification controller for controlling a synchronous rectification switch, the synchronous rectification switch having a control terminal and a detection terminal, comprising: The time recorder is activated to record the previous activation time of the synchronous rectifier switch based on the detection signal at the detection terminal, and to determine a first control period and a second control period, wherein the first control period occurs before the second control period; and The differential driver drives the control terminal based on the detection signal, and the architecture is configured to adjust the detection signal to a first target voltage and a second target voltage respectively during the first control period and the second control period, wherein the first target voltage is different from the second target voltage; in, Both the first and second control periods are related to the previous start time.

2. The synchronous rectification controller as described in claim 1, wherein, The synchronous rectifier switch has a ground terminal connected to a ground power line. Both the first target voltage and the second target voltage are lower than the ground voltage of the ground power line, and the second target voltage is lower than the first target voltage.

3. The synchronous rectification controller as described in claim 1, wherein, The turn-on time recorder determines the full-on period, which occurs before the first control period. The synchronous rectifier controller also includes a full-on driver to give the control terminal a fixed voltage.

4. The synchronous rectification controller as described in claim 3, wherein, The full-open period is a preset proportion of the previous open time, and the first control period begins at the end of the full-open period.

5. The synchronous rectification controller as described in claim 1, wherein, The first control period is a first preset ratio of the previous opening time, and the second control period begins at the end of the first control period.

6. The synchronous rectification controller as described in claim 1, wherein, The differential driver compares the detection signal with the target signal to drive the control terminal, and during the first and second control periods, the target signal is the first and second target voltage, respectively.

7. The synchronous rectification controller as described in claim 1, wherein, The start-up time recorder determines the start and end times of the current start-up time of the synchronous rectifier switch based on the detection signal, and updates the previous start-up time accordingly.

8. A control method for controlling a synchronous rectifier switch, applicable to a synchronous rectifier controller, wherein, The synchronous rectifier switch has a control terminal and a detection terminal, and the control method includes: Based on the detection signal on the detection terminal, the previous turn-on time of the synchronous rectifier switch is recorded, and a first control period and a second control period are determined. The first control period occurs before the second control period. as well as Based on the detection signal, the control terminal is driven to adjust the detection signal to the first and second target voltages during the first and second control periods, respectively. The first target voltage is different from the second target voltage, and both the first and second control periods are related to the previous turn-on time.

9. The control method as described in claim 8, wherein, The synchronous rectifier switch has a ground terminal connected to a ground power line. Both the first target voltage and the second target voltage are lower than the ground voltage of the ground power line, and the second target voltage is lower than the first target voltage.

10. The control method as described in claim 1, wherein, The first control period is a first preset ratio of the previous opening time, and the second control period begins at the end of the first control period.

11. The control method as described in claim 1, further comprising: Based on the detection signal, the period of full operation is determined; and During this fully open period, the control terminal is given a fixed voltage; in, The full opening period is a preset proportion of the previous opening time.

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