Compensation circuit and current compensation asymmetric half-bridge input voltage detection circuit

Abstract

An embodiment of the present invention relates to a compensation circuit and a current-compensated asymmetric half-bridge input voltage detection circuit, wherein the current-compensated asymmetric half-bridge input voltage detection circuit comprises: a detection circuit, a compensation switch signal generating circuit and a current compensation circuit; the detection circuit comprises a transformer having a main winding, an auxiliary winding and a secondary winding, wherein the auxiliary winding side circuit is used to detect the input voltage of the asymmetric half-bridge control circuit; the compensation switch signal generating circuit determines whether to output a first compensation switch signal for turning on current compensation or a second compensation switch signal for turning off current compensation based on whether the output voltage of the asymmetric half-bridge control circuit is higher than a threshold voltage for starting compensation; the current compensation circuit performs current compensation on the detection circuit based on the received first compensation switch signal, or the current compensation circuit does not perform current compensation on the detection circuit based on the received second compensation switch signal.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a compensation circuit and a current-compensated asymmetric half-bridge input voltage detection circuit. Background Art

[0002] With the iterative upgrade of electronic products, they have placed high demands on battery life. Due to the limitation of battery capacity, fast charging speed has become one of the best solutions. To reduce charging time and increase charging speed, fast charging uses a handshake protocol to change the output voltage, realizing power supply for different loads. The output voltage ranges from 5V, 9V, 15V, and 20V. In 2021, the USB-IF Association released the latest USB PD3.1 fast charging standard, which increases the charging power from the original 100W to 240W and supports a maximum voltage output of 48V, meeting the needs of modern people's fast-paced lifestyles.

[0003] The asymmetrical half-bridge (AHB) circuit achieves efficient power conversion by achieving zero voltage switch-on (ZVS) of the primary power transistor and zero current shutdown (ZCS) of the secondary power transistor. Thanks to soft switching, the power supply can operate at a higher switching frequency, significantly improving power density. Therefore, the AHB circuit is widely used for its high efficiency and power density. However, current technologies have some drawbacks in input voltage detection, especially when using the transformer auxiliary winding Na to detect the input voltage.

[0004] In an asymmetric half-bridge control circuit, input voltage detection is performed for input undervoltage protection, typically using the transformer's auxiliary winding Na. However, because the resonant capacitor Cr participates in the resonance process, its voltage varies with the circuit's operating state. Consequently, the influence of the resonant capacitor voltage on the resonant capacitor Cr in the asymmetric half-bridge circuit can lead to inaccurate input voltage detection by the auxiliary winding Na. In particular, when the output voltage is high, the voltage across the resonant capacitor also increases, which can severely prevent the power supply system from starting.

[0005] Furthermore, when a Power Delivery (PD) power supply is in standby mode, the output voltage is typically kept low. To further reduce standby power consumption, the compensation circuit also needs to be synchronously turned on and off according to the output voltage to achieve low power consumption. Summary of the Invention

[0006] The purpose of the present invention is to provide a current compensation circuit and a current compensated asymmetric half-bridge input voltage detection circuit. When the output voltage is large, current compensation is started, and compensation for the detection current is provided by the compensation circuit, so that the detection current remains basically unchanged, which can greatly reduce the influence of the resonant capacitor on the input voltage detection, ensure the stable operation of the power supply system, and meet the low power consumption requirements.

[0007] To achieve the above object, in one aspect, the present invention provides a current-compensated asymmetric half-bridge input voltage detection circuit, the current-compensated asymmetric half-bridge input voltage detection circuit comprising: a detection circuit, a compensation switch signal generation circuit, and a current compensation circuit;

[0008] The detection circuit includes a transformer having a main winding, an auxiliary winding and a secondary winding, wherein the auxiliary winding side circuit is used to detect the input voltage of the asymmetric half-bridge control circuit;

[0009] The compensation switch signal generating circuit determines to output a first compensation switch signal for turning on current compensation or a second compensation switch signal for turning off current compensation according to whether the output voltage of the asymmetric half-bridge control circuit is higher than a threshold voltage for starting compensation;

[0010] The current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, or the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal.

[0011] Preferably, the same-named ends of the main winding are opposite to the same-named ends of the auxiliary winding, and opposite to the same-named ends of the secondary winding.

[0012] Preferably, in the detection circuit, the main winding side circuit includes: a first switching tube, a second switching tube and a resonant capacitor; the first switching tube and the second switching tube are connected in series between the voltage input terminal and the ground; the two ends of the resonant capacitor are respectively connected to the same-name end of the main winding and the reference node between the first switching tube and the second switching tube;

[0013] The auxiliary winding side circuit includes a first resistor, a second resistor and a diode. One end of the first resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the second resistor at a voltage divider node. The other end of the second resistor is grounded; the positive electrode of the diode is grounded, and the negative electrode is connected to the voltage divider node.

[0014] Further preferably, the compensation switch signal generating circuit includes: a fifth voltage-dividing resistor, a fourth voltage-dividing resistor and a third switch tube;

[0015] One end of the fifth voltage-dividing resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the fourth voltage-dividing resistor at the first control node, and the other end of the fourth voltage-dividing resistor is grounded; the control end of the third switching transistor is connected to the first control node, the input end of the third switching transistor is connected to the same-name terminal of the auxiliary winding, and the output end of the third switching transistor is connected to the control end of the current compensation circuit;

[0016] The current compensation circuit includes: a seventh voltage-dividing resistor, a sixth voltage-dividing resistor, a fourth switch tube and a third resistor;

[0017] One end of the seventh voltage-dividing resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the sixth voltage-dividing resistor at the second control node, and the other end of the sixth voltage-dividing resistor is grounded; the second control node is connected to the control end of the fourth switch tube;

[0018] One end of the third resistor is connected to the voltage dividing node, and the other end is connected to the current input end of the fourth switch tube. The current output end of the fourth switch tube is connected to the same-name end of the auxiliary winding.

[0019] Further preferably, the compensation switch signal generating circuit includes: a fifth voltage-dividing resistor, a fourth voltage-dividing resistor and an operational amplifier with a built-in reference;

[0020] One end of the fifth voltage-dividing resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the fourth voltage-dividing resistor at the first control node, and the other end of the fourth voltage-dividing resistor is grounded; the anode of the operational amplifier is connected to the same-name terminal of the auxiliary winding, the cathode is connected to the control terminal of the current compensation circuit, and the reference terminal is connected to the first control node;

[0021] The current compensation circuit includes: a voltage-stabilizing tube, a sixth voltage-dividing resistor, a third switching tube and a third resistor;

[0022] One end of the sixth voltage-dividing resistor is connected to the cathode of the operational amplifier, and the other end is grounded; the cathode of the voltage-regulating diode is connected to the cathode of the operational amplifier, and the anode of the voltage-regulating diode is connected to the control end of the third switching tube; one end of the third resistor is connected to the voltage-dividing node, and the other end is connected to the current input end of the third switching tube, and the current output end of the third switching tube is connected to the same-name end of the auxiliary winding.

[0023] Further preferably, when the third switch tube is turned on, the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal, and the fourth switch tube is turned off; the detection current I det For: I det ≈(V in -nV O1 )×N a / N p / R1;

[0024] When the third switch tube is turned off, the current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, and the fourth switch tube is turned on; the detection current I det For: I det ≈[(V in -nV O2 )×N a / N p ] / [R1×R3 / (R1+R3)];

[0025] Among them, V in is the input voltage, N a is the number of turns of the transformer auxiliary winding, N p is the number of turns of the transformer main winding, R1 is the resistance of the first resistor, and R3 is the resistance of the third resistor; V O1 <Start compensation threshold voltage ≤ V O2 .

[0026] Further preferably, when the current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, the compensation current I provided by the current compensation circuit comp for:

[0027] I comp =[(V in -nV O2 )×N a / N p ] / R3.

[0028] Further preferably, Vcr≈nV o ; Among them, V Cr is the voltage of the resonant capacitor, n is the primary-to-secondary turns ratio of the transformer, V o is the output voltage.

[0029] Preferably, the threshold voltage for starting compensation is a function related to the conduction voltage drop of the third switch tube, the primary-to-secondary turns ratio of the transformer, and the resistance ratio of the fourth voltage-dividing resistor to the fifth voltage-dividing resistor.

[0030] In another aspect, the present invention provides a compensation circuit for the current-compensated asymmetric half-bridge input voltage detection circuit described in the first aspect, comprising:

[0031] a compensation switch signal generating circuit, configured to determine, based on whether the output voltage of the asymmetric half-bridge control circuit is higher than a threshold voltage for starting compensation, whether to output a first compensation switch signal for controlling the start of current compensation or a second compensation switch signal for controlling the stop of current compensation;

[0032] The current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, or does not perform current compensation on the detection circuit according to the received second compensation switch signal.

[0033] The current-compensated asymmetric half-bridge input voltage detection circuit provided in an embodiment of the present invention introduces a compensation circuit so that when the output voltage is large, current compensation is started. The compensation circuit provides compensation for the detection current, so that the detection current can be basically maintained unchanged regardless of high or low voltage output. This can greatly reduce the impact of the resonant capacitor on input voltage detection, ensuring the stable operation of the power supply system. At the same time, the automatic opening and closing control based on the output voltage compensation enables the circuit to meet low power consumption requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A circuit diagram of a current-compensated asymmetric half-bridge input voltage detection circuit provided by an embodiment of the present invention;

[0035] Figure 2 Another circuit diagram of the current-compensated asymmetric half-bridge input voltage detection circuit provided by an embodiment of the present invention;

[0036] Figure 3 A circuit diagram of an asymmetric half-bridge input voltage detection circuit without current compensation;

[0037] Figure 4 This is a specific waveform diagram of the current compensation asymmetric half-bridge input voltage detection circuit when no current compensation is performed;

[0038] Figure 5 This is a specific waveform diagram of the current compensation of the current compensated asymmetric half-bridge input voltage detection circuit. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0040] An embodiment of the present invention provides a current-compensated asymmetric half-bridge input voltage detection circuit, which can be used to automatically adapt the power supply to perform or not perform current compensation on the detection current under high voltage load and low voltage load applications, so that the detection current can accurately reflect the input voltage, thereby realizing accurate detection of the input voltage.

[0041] Based on the above ideas, the current-compensated asymmetric half-bridge input voltage detection circuit provided by the present invention includes: a detection circuit, a compensation switch signal generation circuit and a current compensation circuit.

[0042] The detection circuit includes a transformer T1 having a main winding Np, an auxiliary winding Na and a secondary winding Ns, wherein the auxiliary winding side circuit is used to detect the input voltage of the asymmetric half-bridge control circuit;

[0043] The compensation switch signal generating circuit is based on the output voltage V of the asymmetric half-bridge control circuit. o Whether the voltage is higher than the threshold voltage for starting compensation, determining to output a first compensation switch signal for controlling to start current compensation or output a second compensation switch signal for controlling to shut down current compensation;

[0044] The current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, or the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal.

[0045] In a specific circuit implementation, such as Figure 1 shown. Figure 1 A circuit diagram of a current compensation asymmetric half-bridge input voltage detection circuit provided by an embodiment of the present invention is shown below in conjunction with Figure 1 , the current-compensated asymmetric half-bridge input voltage detection circuit provided by the present invention is described.

[0046] In the detection circuit, the main winding side circuit includes: a first switching tube Q1, a second switching tube Q2 and a resonant capacitor Cr; the first switching tube Q1 and the second switching tube Q2 are connected in series between the voltage input terminal and ground; the two ends of the resonant capacitor Cr are respectively connected to the same-name terminal of the main winding and the reference node HB between the first switching tube Q1 and the second switching tube Q2.

[0047] The auxiliary winding-side circuit includes a first resistor R1, a second resistor R2, and a diode D2. One end of the first resistor R1 is connected to the same-name terminal of the auxiliary winding Na, and the other end is connected to one end of the second resistor R2 at a voltage divider node A. The other end of the second resistor R2 is grounded. The positive electrode of the diode D2 is grounded, and the negative electrode is connected to the voltage divider node A.

[0048] The compensation switch signal generation circuit includes a fifth voltage-dividing resistor R5, a fourth voltage-dividing resistor R4, and a third switching transistor, which is a transistor Q3 as shown. One end of the fifth voltage-dividing resistor R5 is connected to the same-name terminal of the auxiliary winding Na, and the other end is connected to one end of the fourth voltage-dividing resistor R4 at the first control node B. The other end of the fourth voltage-dividing resistor R4 is grounded. The control end of the third switching transistor Q3 is connected to the first control node B, the input end of the third switching transistor Q3 is connected to the same-name terminal of the auxiliary winding Na, and the output end is connected to the control end of the current compensation circuit.

[0049] The current compensation circuit includes: a seventh voltage-dividing resistor R7, a sixth voltage-dividing resistor R6, a fourth switch tube Q4 and a third resistor R3;

[0050] One end of the seventh voltage-dividing resistor R7 is connected to the same-name terminal of the auxiliary winding Na, and the other end is connected to one end of the sixth voltage-dividing resistor R6 at the second control node C. The other end of the sixth voltage-dividing resistor R6 is grounded. The second control node C is connected to the control end of the current compensation circuit.

[0051] One end of the third resistor R3 is connected to the voltage dividing node A, and the other end is connected to the current input end of the fourth switch tube Q4. The current output end of the fourth switch tube Q4 is connected to the same-name terminal of the auxiliary winding Na.

[0052] The detection current in the above detection circuit is I det shown in the figure.

[0053] The present invention provides Figure 1 In the circuit shown, in order to make the compensation more effective, it is important to reasonably set the resistance relationship between the fourth voltage-dividing resistor R4 and the fifth voltage-dividing resistor R5, the resistance relationship between the sixth voltage-dividing resistor and the seventh voltage-dividing resistor, and the resistance relationship between the third resistor R3 and the first resistor R1.

[0054] Preferably, the resistance ratio of the fourth voltage-dividing resistor to the fifth voltage-dividing resistor is set to R4:R5=50:1-60:1; the resistance ratio of the sixth voltage-dividing resistor to the seventh voltage-dividing resistor is set to R6:R7=4:1-5:1; and the resistance ratio of the first resistor to the third resistor is set to R1:R3=3:1-4:1.

[0055] When applying this technology, those skilled in the art can configure the above-mentioned resistance groups based on the specific parameters of the actual circuit to be applied. Under the premise of knowing the technical solution of the present invention, the specific configuration of the parameters does not require creative work for those skilled in the art.

[0056] In a specific circuit implementation, such as Figure 2 shown.

[0057] Detection circuit part and Figure 1 The implementation schemes shown are the same and will not be repeated here.

[0058] The compensation switch signal generation circuit includes a fifth voltage-divider resistor R5, a fourth voltage-divider resistor R4, and an op amp U1 with a built-in reference TL431. One end of the fifth voltage-divider resistor R5 is connected to the same-name terminal of the auxiliary winding Na, and the other end is connected to one end of the fourth voltage-divider resistor R4 at the first control node B. The other end of the fourth voltage-divider resistor R4 is grounded. The op amp TL431's A pin (anode) is connected to the same-name terminal of the auxiliary winding Na, its K pin (cathode) is connected to the control terminal of the current compensation circuit, and its R pin (reference) is connected to the first control node B. The current compensation circuit includes a voltage-stabilizing diode ZD1, a sixth voltage-divider resistor R6, a third switching diode Q3, and a third resistor R3. One end of the sixth voltage-divider resistor R6 is connected to the K pin of U1 and the other end is grounded. The cathode of the voltage-divider diode ZD1 is connected to the K pin of the op amp, and the anode is connected to the control terminal of the third switching diode Q3. One end of the third resistor R3 is connected to the voltage-divider node A, and the other end is connected to the current input terminal of the third switching diode Q3. The current output terminal of the third switching diode Q3 is connected to the same-name terminal of the auxiliary winding Na.

[0059] Preferably, the resistance ratio of the fourth voltage-dividing resistor R4 to the fifth voltage-dividing resistor R5 is set to 20:1-30:1; the resistance ratio of the third resistor R3 to the first voltage-dividing resistor R1 is set to 1:1-5:1.

[0060] In order to explain the working principle of the circuit more clearly, Figure 3 The circuit shown in the figure is used as an example for comparison. Figure 1 and Figure 2 The working principle of the circuit shown is similar. Figure 1 The circuit shown is compared and explained. Figure 3 The circuit shown is Figure 1 and Figure 2 The detection circuit part in the present invention can reflect the working principle of the asymmetric half-bridge input voltage detection circuit without a compensation circuit in the prior art.

[0061] First, as Figure 3 Circuit shown.

[0062] In this circuit, when the power is turned on, the voltage across the resonant capacitor Cr increases from 0V. When the output voltage stabilizes to Vo, the voltage across the resonant capacitor V Cr ≈nV o ; Transformer main winding voltage V Np =V in -V Cr .

[0063] When the first switch tube Q1 is turned off and the second switch tube Q2 is turned on, the voltage V across the auxiliary winding Na of the transformer is Na =(V in -V Cr )×N a / N p, the detection current I det is directly connected to the voltage V of the auxiliary winding Na Na Calculated: I det ≈(V in -V Cr )×N a / N p / R1; where V Na is the auxiliary winding voltage, V Cr is the voltage of the resonant capacitor, V o is the output voltage, n is the turns ratio of the transformer primary winding Np and secondary winding Ns, Vcr≈nV o ; V in is the input voltage, N a is the number of turns of the transformer auxiliary winding, N p is the number of turns of the transformer main winding.

[0064] It can be seen that when the detection current I det is detected, the input voltage V in But because V Cr The presence of input voltage V in The detection is greatly affected, especially when the output voltage V o When it is higher, due to V Cr ≈nV o , so V Cr It will also be high, thus affecting the accuracy of I det detection.

[0065] exist Figure 1 In the current-compensated asymmetric half-bridge input voltage detection circuit shown, a compensation switch signal generation circuit and a current compensation circuit are added.

[0066] exist Figure 1 In the circuit shown, the output voltage V o For low voltage (for easy distinction, use V o1 Indicates that it is applied to low-voltage load charging). When the current compensation circuit activation condition is not met, the current compensation circuit is not activated.

[0067] The voltage of R5 is V R5 =[(V in -nV O1 )×Na / Np] / [R5 / (R5+R4)]; R7 voltage is V R7 =[(V in -nV O1 )×Na / Np] / [R7 / (R7+R6)]. At this time, the third switch tube Q3 is turned on, making the fourth switch tube Q4 non-conductive. The detection current I det For: I det ≈(V in -nVO1 )×N a / N p / R1.

[0068] The output voltage V o For high voltage (for easy distinction, use V o2 Indicates the application of high voltage load charging), when the current compensation circuit is turned on, the current compensation circuit is turned on. At this time, the third switch tube Q3 is turned off and the fourth switch tube Q4 is turned on. At this time, the compensation current I provided by the current compensation circuit is comp For: I comp =[(V in -nV O2 )×N a / N p ] / R3.

[0069] The detection current I in the detection circuit det For: I det ≈[(V in -nV O2 )×N a / N p ] / [R1×R3 / (R1+R3)].

[0070] It can be seen that due to the compensation current I comp The existence of the detection current I det is effectively compensated, so that the detection current Idet can more accurately reflect the input voltage V in , thereby reducing the output voltage V o When the V Cr The larger error caused by the higher input voltage makes the input voltage detection more accurate and reliable.

[0071] exist Figure 2 In the asymmetric half-bridge input voltage detection circuit shown, a compensation circuit consisting of a third resistor R3, a fourth voltage-dividing resistor R4, a fifth voltage-dividing resistor R5, a sixth resistor R6, an operational amplifier TL431 U1 with a built-in reference, and a voltage regulator diode ZD1 is added.

[0072] exist Figure 2 In the circuit shown, when the output voltage is not established, transistor Q3 is not conducting. At this time, the detection current Idet is the same as before the circuit improvement and is directly affected by V Cr impact.

[0073] When the output voltage is not established, V R5 =[(V in -V cr )×N a / N p ]×R5 / (R4+R5); at this time, V R5When the voltage is greater than the internal reference voltage of U1 (2.5V), the voltage of the K pin of U1 is low, the third switch Q3 is not turned on, and the compensation circuit does not work.

[0074] When the output is high voltage, V R5 When the voltage is less than the reference 2.5V, the voltage of the K pin of U1 is high level, the voltage regulator tube ZD1 breaks down, the third switch tube Q3 is turned on, the compensation circuit works, and the parallel shunt effect of the third resistor R3 and the first voltage divider resistor R1 makes the detection current I det Becomes: I det ≈[(V in -Vcr)×N a / N p ] / [R1×R3 / (R1+R3)].

[0075] Therefore, the detection current Idet can more accurately reflect the input voltage V in , thus reducing the output voltage Vo when V Cr The larger error caused by the higher input voltage makes the input voltage detection more accurate and reliable.

[0076] The embodiment of the present invention also Figure 1 The circuit shown in the figure is used to conduct a set of actual tests on the current-compensated asymmetric half-bridge input voltage detection circuit proposed in the present invention under two conditions: low-voltage load charging (without current compensation) and high-voltage load charging (with current compensation). The test conditions and parameters are the same. Figure 4 It is a specific waveform diagram when no current compensation is performed; Figure 5 This is a specific waveform diagram when current compensation is performed.

[0077] By comparison, we can see that Figure 4 In the low output voltage V O1 When , I comp is 12uA, which basically has no compensation effect. Figure 5 When the output voltage is high, Icomp is approximately 420uA. Due to the presence of the compensation current, even if the output voltage increases, resulting in an increase in Vcr, Idet is compensated. It can be seen that with the current-compensated asymmetric half-bridge input voltage detection circuit provided by the present invention, Idet remains essentially unchanged at approximately 1mA regardless of whether the output voltage is high or low. This demonstrates that compensation is effective, resulting in more accurate Idet detection.

[0078] The current-compensated asymmetric half-bridge input voltage detection circuit provided in an embodiment of the present invention does not start current compensation when the output voltage is large; when the output voltage is large, current compensation is started, and compensation for the detection current is provided by the compensation circuit, which can greatly reduce the influence of the resonant capacitor on the input voltage detection, ensure the stable operation of the power supply system, and meet the low power consumption requirements.

[0079] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A current-compensated asymmetric half-bridge input voltage detection circuit, characterized in that: The current-compensated asymmetric half-bridge input voltage detection circuit comprises: a detection circuit, a compensation switch signal generation circuit and a current compensation circuit; The detection circuit includes a transformer having a main winding, an auxiliary winding and a secondary winding, wherein the auxiliary winding side circuit is used to detect the input voltage of the asymmetric half-bridge control circuit; The compensation switch signal generating circuit determines to output a first compensation switch signal for turning on current compensation or a second compensation switch signal for turning off current compensation according to whether the output voltage of the asymmetric half-bridge control circuit is higher than a threshold voltage for starting compensation; The current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, or the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal; The same-named end of the main winding is opposite to the same-named end of the auxiliary winding and opposite to the same-named end of the secondary winding; In the detection circuit, the main winding side circuit includes: a first switching tube, a second switching tube and a resonant capacitor; the first switching tube and the second switching tube are connected in series between the voltage input terminal and the ground; the two ends of the resonant capacitor are respectively connected to the same-name end of the main winding and the reference node between the first switching tube and the second switching tube; the opposite-name end of the main winding is connected to the voltage input terminal; The auxiliary winding side circuit includes a first resistor, a second resistor, and a diode. One end of the first resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the second resistor at a voltage divider node. The other end of the second resistor is grounded. The positive electrode of the diode is grounded, and the negative electrode is connected to the voltage divider node. The opposite-name terminal of the auxiliary winding is grounded. The compensation switch signal generating circuit includes: a fifth voltage-dividing resistor, a fourth voltage-dividing resistor and a third switch tube; the current compensation circuit includes: a seventh voltage-dividing resistor, a sixth voltage-dividing resistor, a fourth switch tube and a third resistor; One end of the fifth voltage-dividing resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the fourth voltage-dividing resistor at the first control node, and the other end of the fourth voltage-dividing resistor is grounded; the control end of the third switching transistor is connected to the first control node, the input end of the third switching transistor is connected to the same-name terminal of the auxiliary winding, and the output end of the third switching transistor is connected to the control end of the fourth switching transistor; One end of the seventh voltage-dividing resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the sixth voltage-dividing resistor at the second control node, and the other end of the sixth voltage-dividing resistor is grounded; the second control node is connected to the control end of the fourth switch tube; One end of the third resistor is connected to the voltage dividing node, and the other end is connected to the current input end of the fourth switch tube. The current output end of the fourth switch tube is connected to the same-name end of the auxiliary winding.

2. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 1, characterized in that: When the third switch tube is turned on, the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal, and the fourth switch tube is turned off; the detection current I det For: I det ≈(V in -nV O1 )×N a / N p / R1; When the third switch tube is turned off, the current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, and the fourth switch tube is turned on; the detection current I det For: I det ≈[(V in -nV O2 )×N a / N p ] / [R1×R3 / (R1+R3)]; Among them, V in is the input voltage, N a is the number of turns of the transformer auxiliary winding, N p is the number of turns of the transformer main winding, R1 is the resistance of the first resistor, and R3 is the resistance of the third resistor; V O1 <Start compensation threshold voltage ≤ V O2 ; n is the primary-to-secondary turns ratio of the transformer.

3. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 2, characterized in that: When the current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, the compensation current I provided by the current compensation circuit comp for: I comp =[(V in -nV O2 )×N a / N p ] / R3。 4. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 1, characterized in that: In cr ≈nV o ; Among them, V Cr is the voltage of the resonant capacitor, n is the primary-to-secondary turns ratio of the transformer, V o is the output voltage.

5. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 1, characterized in that: The threshold voltage for starting compensation is a function related to the conduction voltage drop of the third switch tube, the primary-to-secondary turns ratio of the transformer, and the resistance ratio of the fourth voltage-dividing resistor to the fifth voltage-dividing resistor.

6. A current-compensated asymmetric half-bridge input voltage detection circuit, characterized in that: The current-compensated asymmetric half-bridge input voltage detection circuit comprises: a detection circuit, a compensation switch signal generation circuit and a current compensation circuit; The detection circuit includes a transformer having a main winding, an auxiliary winding and a secondary winding, wherein the auxiliary winding side circuit is used to detect the input voltage of the asymmetric half-bridge control circuit; The compensation switch signal generating circuit determines to output a first compensation switch signal for turning on current compensation or a second compensation switch signal for turning off current compensation according to whether the output voltage of the asymmetric half-bridge control circuit is higher than a threshold voltage for starting compensation; The current compensation circuit performs current compensation on the detection circuit according to the received first compensation switch signal, or the current compensation circuit does not perform current compensation on the detection circuit according to the received second compensation switch signal; The same-named end of the main winding is opposite to the same-named end of the auxiliary winding and opposite to the same-named end of the secondary winding; In the detection circuit, the main winding side circuit includes: a first switching tube, a second switching tube and a resonant capacitor; the first switching tube and the second switching tube are connected in series between the voltage input terminal and the ground; the two ends of the resonant capacitor are respectively connected to the same-name end of the main winding and the reference node between the first switching tube and the second switching tube; the opposite-name end of the main winding is connected to the voltage input terminal; The auxiliary winding side circuit includes a first resistor, a second resistor, and a diode. One end of the first resistor is connected to the same-name terminal of the auxiliary winding, and the other end is connected to one end of the second resistor at a voltage divider node. The other end of the second resistor is grounded. The positive electrode of the diode is grounded, and the negative electrode is connected to the voltage divider node. The opposite-name terminal of the auxiliary winding is grounded. The compensation switch signal generating circuit includes: a fifth voltage-dividing resistor, a fourth voltage-dividing resistor and an operational amplifier with a built-in reference; One end of the fifth voltage-dividing resistor is connected to the same-name end of the auxiliary winding, and the other end is connected to one end of the fourth voltage-dividing resistor at the first control node, and the other end of the fourth voltage-dividing resistor is grounded; the anode of the operational amplifier is connected to the same-name end of the auxiliary winding, and the reference end is connected to the first control node; The current compensation circuit includes: a voltage-stabilizing tube, a sixth voltage-dividing resistor, a third switching tube and a third resistor; One end of the sixth voltage-dividing resistor is connected to the cathode of the operational amplifier, and the other end is grounded; the cathode of the voltage-regulating diode is connected to the cathode of the operational amplifier, and the anode of the voltage-regulating diode is connected to the control end of the third switching tube; one end of the third resistor is connected to the voltage-dividing node, and the other end is connected to the current input end of the third switching tube, and the current output end of the third switching tube is connected to the same-name end of the auxiliary winding.

7. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 6, characterized in that: In cr ≈nV o ; Among them, V Cr is the voltage of the resonant capacitor, n is the primary-to-secondary turns ratio of the transformer, V o is the output voltage.

8. The current-compensated asymmetric half-bridge input voltage detection circuit according to claim 6, characterized in that: The threshold voltage for starting compensation is a function related to the conduction voltage drop of the third switch tube, the primary-to-secondary turns ratio of the transformer, and the resistance ratio of the fourth voltage-dividing resistor to the fifth voltage-dividing resistor.

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