A flyback power supply circuit and control method thereof

Abstract

The invention discloses a flyback power supply circuit and a control method thereof. The flyback power supply circuit comprises an input circuit, an output circuit, a transformer, a primary side control chip, a secondary side control chip, a primary side switch tube, a secondary side switch tube and an isolation communication module; the output end of the input circuit is connected to the same-name end of the primary side of the transformer; the opposite-name end of the primary side of the transformer is connected to the output end of the primary side control chip through the primary side switch tube; the input end of the primary side control chip is connected to the output end of the secondary side control chip through the isolation communication module; the input end of the secondary side control chip is respectively connected to the same-name end of the secondary side of the transformer and one end of the output circuit through the secondary side switch tube; the other end of the output circuit is connected to the opposite-name end of the secondary side of the transformer; the primary side control chip controls the conduction of the primary side switch tube by detecting the rising edge of the output of the secondary side control chip; not only can the risk of flyback power supply direct conduction be reduced, but also the power consumption of signal transmission is reduced.

Description

Technical Field

[0001] The present invention relates to the field of flyback power supplies, and in particular to a flyback power supply circuit and a control method thereof. Background Art

[0002] Most existing flyback power supplies use primary control mode when controlling, and the primary control mode is prone to the situation where the primary power switch tube and the secondary power switch tube are turned on at the same time during synchronous rectification. In addition, most existing controls use duty cycle mode for control, and the duty cycle control mode consumes more power during signal transmission. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a flyback power supply circuit and a control method thereof, which can reduce the risk of flyback power supply shoot-through while reducing the power consumption of signal transmission.

[0004] In order to solve the above technical problems, a technical solution adopted by the present invention is:

[0005] A flyback power supply circuit includes an input circuit, an output circuit, a transformer, a primary side control chip, a secondary side control chip, a primary side switch tube, a secondary side switch tube and an isolation communication module;

[0006] The output end of the input circuit is connected to the same-name end of the primary side of the transformer;

[0007] The opposite-name end of the primary side of the transformer is connected to the output end of the primary side control chip through the primary side switch tube;

[0008] The input end of the primary side control chip is connected to the output end of the secondary side control chip through the isolation communication module;

[0009] The input end of the secondary side control chip is connected to the same-name end of the secondary side of the transformer and one end of the output circuit respectively through the secondary side switch tube;

[0010] The other end of the output circuit is connected to the opposite end of the secondary side of the transformer;

[0011] The primary-side control chip controls the conduction of the primary-side switch tube by detecting the rising edge of the output of the secondary-side control chip.

[0012] Further, the input circuit includes a rectifier bridge;

[0013] The input end of the rectifier bridge is used to be connected to an AC input source, and the output end of the rectifier bridge is connected to the same-name end of the primary side of the transformer.

[0014] Further, it also includes an input filter capacitor;

[0015] The input filter capacitor is connected in parallel with the rectifier bridge.

[0016] Further, the output circuit includes an output filter capacitor;

[0017] One end of the output filter capacitor is connected to the opposite-name end of the secondary side of the transformer, and the other end is connected to the secondary-side switch tube.

[0018] Further, the isolated communication module includes a millimeter wave transmitting module and a millimeter wave receiving module;

[0019] The output end of the secondary-side control chip is connected to the input end of the millimeter-wave transmitting module;

[0020] The output end of the millimeter wave transmitting module and the input end of the millimeter wave receiving module realize wireless communication through millimeter waves;

[0021] The output end of the millimeter wave receiving module is connected to the input end of the primary side control chip.

[0022] Further, the primary side control chip includes a primary handshake unit, a startup unit, an opening module, a first AND operator, a first OR operator, a second OR operator, an SR trigger, a pulse driving module, a comparator, a CS comparison reference generation module, a first resistor and a second resistor;

[0023] The output end of the isolation communication module is connected to the first input end of the first AND operator and the input end of the primary handshake unit respectively;

[0024] The output of the primary handshake unit is connected to the input end of the start unit and the second input end of the first AND operator respectively;

[0025] The first output terminal of the start-up unit is connected to the first input terminal of the first OR operator;

[0026] The second output terminal of the startup unit is connected to the positive input terminal of the comparator;

[0027] The output terminal of the AND operator is connected to the second input terminal of the first OR operator;

[0028] The output terminal of the first OR operator is connected to the S terminal of the SR trigger;

[0029] The Q end of the SR trigger is connected to the input end of the pulse driving module and the input end of the CS comparison reference generating module respectively;

[0030] The output end of the pulse driving module is connected to the base of the primary side switch tube;

[0031] The collector of the primary-side switch tube is connected to the opposite-name end of the primary side of the transformer;

[0032] The emitter of the primary-side switch tube is connected to one end of the first resistor and one end of the second resistor respectively, and the other end of the first resistor is connected to the positive input end of the comparator;

[0033] The other end of the second resistor is grounded;

[0034] The output terminal of the CS comparison reference generation module is connected to the inverting input terminal of the comparator;

[0035] The output terminal of the comparator is connected to the first input terminal of the second OR operator;

[0036] The output end of the opening module is connected to the second input end of the second OR operator;

[0037] The output terminal of the second OR operator is connected to the R terminal of the SR trigger.

[0038] Further, the secondary side control chip includes a synchronous rectification detection module, a synchronous rectification control module, a CV / CC detection module, a CV / CC control module and a second AND operator;

[0039] The same-name end of the secondary side of the transformer is respectively connected to the first input end of the second AND operator, the input end of the synchronous rectification detection module and the collector of the secondary-side switch tube;

[0040] The output end of the synchronous rectification detection module is connected to the input end of the synchronous rectification control module;

[0041] The output end of the synchronous rectification control module is connected to the base of the secondary side switch tube;

[0042] The emitter of the secondary side switch tube is connected to the output circuit;

[0043] The opposite-name terminal of the secondary side of the transformer is connected to the input terminal of the CV / CC detection module;

[0044] The output end of the CV / CC detection module is connected to the input end of the CV / CC control module;

[0045] The output end of the CV / CC control module is connected to the second input end of the second AND operator;

[0046] The output end of the second AND operator is connected to the input end of the isolation communication module.

[0047] In order to solve the above technical problems, another technical solution adopted by the present invention is:

[0048] A control method for the above-mentioned flyback power supply circuit comprises the steps of:

[0049] Powering on the primary-side control chip, so that the primary-side control chip controls the on and off of the primary-side switch tube;

[0050] When the primary-side switch tube is turned off, the secondary-side switch tube is turned on through the transformer, and the output circuit is charged;

[0051] When the output circuit reaches a preset power value, the secondary side control chip sends a handshake signal to the primary side control chip;

[0052] Determine whether the handshake is successful, and if so, stop powering on the primary-side control chip, and control the on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip;

[0053] If not, return to the step of powering on the primary-side control chip.

[0054] Further, the controlling the turning on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip includes:

[0055] The secondary side control chip sends a pulse signal of a preset width to the primary side control chip through the isolation communication module;

[0056] When the primary-side control chip receives the pulse signal and detects a rising edge, the primary-side switch tube is turned on.

[0057] Furthermore, the method further comprises the steps of:

[0058] If the output power does not reach the preset power value, the process returns to the step of powering on the primary-side control chip.

[0059] The beneficial effect of the present invention is that in a flyback power supply circuit, a secondary control method is used to control whether the primary side switch tube is turned on or not, thereby avoiding the situation that the primary side switch tube and the secondary side switch tube are turned on at the same time during synchronous rectification. At the same time, a rising edge control method is used to control whether the primary side switch tube is turned on or not. Only a very narrow pulse is needed to achieve control. Compared with the existing duty cycle control method, the power consumption of signal transmission is greatly reduced. Therefore, by adopting a secondary control method based on the rising edge, not only the risk of the flyback power supply being directly connected can be reduced, but also the power consumption of signal transmission can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1A schematic diagram of the circuit structure of a flyback power supply circuit according to an embodiment of the present invention;

[0061] Figure 2 It is a schematic diagram of the internal control structure of the primary-side control chip and the secondary-side control chip in a flyback power supply circuit according to an embodiment of the present invention;

[0062] Figure 3 A control timing diagram of the primary side in a flyback power supply circuit according to an embodiment of the present invention;

[0063] Figure 4 A control timing diagram of the secondary side of a flyback power supply circuit according to an embodiment of the present invention;

[0064] Figure 5 The present invention is a flowchart of a control method for a flyback power supply circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0065] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0066] The above-mentioned flyback power supply circuit and control method of the present application can be applied to any scenario where the flyback power supply needs to be controlled, and the following is an explanation through specific implementation methods:

[0067] In an optional embodiment, if Figure 1 As shown, a flyback power supply circuit includes an input circuit, an output circuit, a transformer T1, a primary side control chip P1, a secondary side control chip P2, a primary side switch tube Q1, a secondary side switch tube Q2 and an isolation communication module;

[0068] The output end of the input circuit is connected to the same-name end of the primary side of the transformer T1;

[0069] The opposite-name end of the primary side of the transformer T1 is connected to the output end of the primary side control chip P1 through the primary side switch tube Q1;

[0070] The input end of the primary side control chip P1 is connected to the output end of the secondary side control chip P2 through the isolation communication module;

[0071] The input end of the secondary side control chip P2 is connected to the same-name end of the secondary side of the transformer T1 and one end of the output circuit respectively through the secondary side switch tube Q2;

[0072] The other end of the output circuit is connected to the opposite end of the secondary side of the transformer T1;

[0073] The primary-side control chip P1 controls the conduction of the primary-side switch tube Q1 by detecting the rising edge of the output of the secondary-side control chip P2.

[0074] In another optional embodiment, the input circuit includes a rectifier bridge;

[0075] The input end of the rectifier bridge is used to be connected to an AC input source, and the output end of the rectifier bridge is connected to the same-name end of the primary side of the transformer T1.

[0076] In another optional embodiment, it also includes an input filter capacitor Cin;

[0077] The input filter capacitor Cin is connected in parallel with the rectifier bridge;

[0078] The output circuit includes an output filter capacitor Cout;

[0079] One end of the output filter capacitor Cout is connected to the opposite-name end of the secondary side of the transformer T1 , and the other end is connected to the secondary-side switch tube Q2 . The output filter capacitor Cout is connected in parallel with the output load RL.

[0080] In another optional embodiment, the isolated communication module includes a millimeter wave transmitting module and a millimeter wave receiving module;

[0081] The output end of the secondary side control chip P2 is connected to the input end of the millimeter wave transmitting module;

[0082] The output end of the millimeter wave transmitting module and the input end of the millimeter wave receiving module realize wireless communication through millimeter waves;

[0083] The output end of the millimeter wave receiving module is connected to the input end of the primary side control chip.

[0084] When implementing it specifically, Figure 1 As shown, the input part consists of an AC input source and a rectifier bridge, Cin is an input filter capacitor, T1 is a transformer that transfers energy from the primary side to the secondary side, Cout is an output filter capacitor, RL is an output load, Q2 is an output synchronous rectifier MOS tube, P2 is a secondary side control chip, TX is a millimeter wave transmitting signal module, RX is a millimeter wave receiving signal module, P1 is a primary side control chip, and Q1 is a primary side switch MOS tube;

[0085] The AC power input energy charges the inductor on the primary side of transformer T1 through the opening of switch tube Q1. When switch tube Q1 is turned off, the energy stored in the primary side of transformer T1 is transmitted to the output end, and the output voltage is stabilized through the chip control on the secondary side.

[0086] In another optional embodiment, Figure 2 As shown, the primary side control chip includes a primary handshake unit, a startup unit, an opening module, a first AND operator, a first OR operator, a second OR operator, an SR trigger, a pulse driving module DRV, a comparator, a CS comparison reference generation module, a first resistor and a second resistor;

[0087] Among them, the opening module is a PWM opening module, which starts timing when the primary side switch MOS tube is turned on, and turns off the primary side switch MOS tube when the maximum Ton time is reached, regardless of whether the shutdown signal of the primary side switch MOS tube arrives;

[0088] The output end of the isolation communication module is connected to the first input end of the first AND operator and the input end of the primary handshake unit respectively;

[0089] The output of the primary handshake unit is connected to the input end of the start unit and the second input end of the first AND operator respectively;

[0090] The first output terminal of the start-up unit is connected to the first input terminal of the first OR operator;

[0091] The second output terminal of the startup unit is connected to the positive input terminal of the comparator;

[0092] The output terminal of the AND operator is connected to the second input terminal of the first OR operator;

[0093] The output terminal of the first OR operator is connected to the S terminal of the SR trigger;

[0094] The Q end of the SR trigger is connected to the input end of the pulse driving module and the input end of the CS comparison reference generating module respectively;

[0095] The output end of the pulse driving module is connected to the base of the primary side switch tube;

[0096] The collector of the primary-side switch tube is connected to the opposite-name end of the primary side of the transformer;

[0097] The emitter of the primary-side switch tube is connected to one end of the first resistor and one end of the second resistor respectively, and the other end of the first resistor is connected to the positive input end of the comparator;

[0098] The other end of the second resistor is grounded;

[0099] The output terminal of the CS comparison reference generation module is connected to the inverting input terminal of the comparator;

[0100] The output terminal of the comparator is connected to the first input terminal of the second OR operator;

[0101] The output end of the opening module is connected to the second input end of the second OR operator;

[0102] The output terminal of the second OR operator is connected to the R terminal of the SR trigger.

[0103] In another optional embodiment, Figure 2 As shown, the secondary side control chip includes a synchronous rectification detection module, a synchronous rectification control module, a CV / CC (constant current / constant voltage) detection module, a CV / CC control module and a second AND operator;

[0104] The same-name end of the secondary side of the transformer is respectively connected to the first input end of the second AND operator, the input end of the synchronous rectification detection module and the collector of the secondary-side switch tube;

[0105] The output end of the synchronous rectification detection module is connected to the input end of the synchronous rectification control module;

[0106] The output end of the synchronous rectification control module is connected to the base of the secondary side switch tube;

[0107] The emitter of the secondary side switch tube is connected to the output circuit;

[0108] The opposite-name terminal of the secondary side of the transformer is connected to the input terminal of the CV / CC detection module;

[0109] The output end of the CV / CC detection module is connected to the input end of the CV / CC control module;

[0110] The output end of the CV / CC control module is connected to the second input end of the second AND operator;

[0111] The output end of the second AND operator is connected to the input end of the isolation communication module.

[0112] In another optional embodiment, a control method of the flyback power supply circuit described in any of the above embodiments comprises the steps of:

[0113] Powering on the primary-side control chip, so that the primary-side control chip controls the on and off of the primary-side switch tube;

[0114] When the primary-side switch tube is turned off, the secondary-side switch tube is turned on through the transformer, and the output circuit is charged;

[0115] When determining whether the output circuit reaches a preset power value, if so, the secondary side control chip sends a handshake signal to the primary side control chip, and if not, returns to execute the step of powering on the primary side control chip;

[0116] Determine whether the handshake is successful, and if so, stop powering on the primary-side control chip, and control the on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip;

[0117] If not, return to the step of powering on the primary-side control chip.

[0118] Wherein, controlling the turning on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip includes:

[0119] The secondary side control chip sends a pulse signal of a preset width to the primary side control chip through the isolation communication module;

[0120] When the primary-side control chip receives the pulse signal and detects a rising edge, the primary-side switch tube is turned on.

[0121] When implementing it specifically, Figure 3 As shown, when the primary is powered on, the primary startup unit will send out a soft-start CLK, which has a pulse width of 10ns. The frequency increases from 25K to 500K over time, and after reaching 500K, it maintains for 512us and then changes to 400K. The CLK signal controls the on and off of the primary power switch Q1. When the primary power switch Q1 is on, the input AC power supply AC provides current to the primary inductor of the transformer T1. The current of the primary inductor will continue to increase, and the voltage on the second resistor Rsense will increase with the increase of the current on the primary side. When the voltage on the second resistor Rsense increases to the REF threshold, the primary side will turn off Q1. At this time, the energy in the transformer T1 will transfer energy to the secondary output through magnetic energy. The secondary forms a current loop to charge the output capacitor Cout through the conduction of the body diode of Q2. When the next CLK arrives, Q1 will be turned on again. This cycle will continue until the output voltage Vout reaches 90% of the output voltage target value. The secondary will send a pulse with a width of 20ns to the primary to send a handshake signal to the primary. After the handshake is successful, the opening of the primary switch Q1 is controlled by the pulse sent by the secondary, and the primary CLK signal will be disabled. After the handshake is successful, the turn-off of the primary switch Q1 is still controlled by the voltage sampled by the second resistor;

[0122] Figure 4The figure shows the secondary control timing diagram. When the secondary detects that the output voltage is reduced, it sends a 20ns pulse to TX. After receiving the pulse, TX sends the pulse to RX through millimeter wave. After receiving the pulse, RX passes the signal to the primary control chip. After receiving the pulse, the primary control chip turns on Q1. That is, this implementation only needs a signal with a pulse width of 20ns to realize the control of the primary side switch tube.

[0123] Figure 5 The figure shows the handshake flow chart between the primary side and the secondary side. The primary side starts to power on, and then the secondary side starts to power on. If the secondary side completes power-on within tAR (82ms), the secondary side will send a pulse handshake signal to the primary side, otherwise it will enter the automatic restart mode. After the primary side receives the handshake signal from the secondary side, it will perform a handshake. If the handshake is successful, the control right will be handed over to the secondary side, and the handshake will end, and it will enter the secondary control mode. If the handshake is unsuccessful, the primary side will continue to control the switch and switch to the automatic restart mode until the handshake is successful.

[0124] In summary, the present invention provides a flyback power supply circuit and a control method thereof. In the flyback power supply circuit, a secondary control method is adopted to control the conduction of the primary side switch power tube, and the control is achieved by a rising edge control method. Only a very narrow pulse (20ns) is required to achieve control, which can not only reduce the risk of flyback power supply direct conduction, but also greatly reduce the power consumption of signal transmission.

[0125] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A flyback power supply circuit, characterized in that: It includes an input circuit, an output circuit, a transformer, a primary side control chip, a secondary side control chip, a primary side switch tube, a secondary side switch tube and an isolation communication module; The output end of the input circuit is connected to the same-name end of the primary side of the transformer; The opposite-name end of the primary side of the transformer is connected to the output end of the primary side control chip through the primary side switch tube; The input end of the primary side control chip is connected to the output end of the secondary side control chip through the isolation communication module; The input end of the secondary side control chip is connected to the same-name end of the secondary side of the transformer and one end of the output circuit respectively through the secondary side switch tube; The other end of the output circuit is connected to the opposite end of the secondary side of the transformer; The primary side control chip controls the conduction of the primary side switch tube by detecting the rising edge of the output of the secondary side control chip; The primary side control chip includes a primary handshake unit, a startup unit, an opening module, a first AND operator, a first OR operator, a second OR operator, an SR trigger, a pulse driving module, a comparator, a CS comparison reference generation module, a first resistor and a second resistor; The output end of the isolation communication module is connected to the first input end of the first AND operator and the input end of the primary handshake unit respectively; The output of the primary handshake unit is connected to the input end of the start unit and the second input end of the first AND operator respectively; The first output terminal of the start-up unit is connected to the first input terminal of the first OR operator; The second output terminal of the startup unit is connected to the positive input terminal of the comparator; The output terminal of the AND operator is connected to the second input terminal of the first OR operator; The output terminal of the first OR operator is connected to the S terminal of the SR trigger; The Q end of the SR trigger is connected to the input end of the pulse driving module and the input end of the CS comparison reference generating module respectively; The output end of the pulse driving module is connected to the base of the primary side switch tube; The collector of the primary-side switch tube is connected to the opposite-name end of the primary side of the transformer; The emitter of the primary-side switch tube is connected to one end of the first resistor and one end of the second resistor respectively, and the other end of the first resistor is connected to the positive input end of the comparator; The other end of the second resistor is grounded; The output terminal of the CS comparison reference generation module is connected to the inverting input terminal of the comparator; The output terminal of the comparator is connected to the first input terminal of the second OR operator; The output end of the opening module is connected to the second input end of the second OR operator; The output terminal of the second OR operator is connected to the R terminal of the SR trigger.

2. A flyback power supply circuit according to claim 1, characterized in that: The input circuit includes a rectifier bridge; The input end of the rectifier bridge is used to be connected to an AC input source, and the output end of the rectifier bridge is connected to the same-name end of the primary side of the transformer.

3. A flyback power supply circuit according to claim 2, characterized in that: It also includes input filter capacitors; The input filter capacitor is connected in parallel with the rectifier bridge.

4. A flyback power supply circuit according to claim 1, characterized in that: The output circuit includes an output filter capacitor; One end of the output filter capacitor is connected to the opposite-name end of the secondary side of the transformer, and the other end is connected to the secondary-side switch tube.

5. A flyback power supply circuit according to claim 1, characterized in that: The isolated communication module includes a millimeter wave transmitting module and a millimeter wave receiving module; The output end of the secondary-side control chip is connected to the input end of the millimeter-wave transmitting module; The output end of the millimeter wave transmitting module and the input end of the millimeter wave receiving module realize wireless communication through millimeter waves; The output end of the millimeter wave receiving module is connected to the input end of the primary side control chip.

6. A flyback power supply circuit according to any one of claims 1 to 5, characterized in that: The secondary side control chip includes a synchronous rectification detection module, a synchronous rectification control module, a CV / CC detection module, a CV / CC control module and a second AND operator; The same-name end of the secondary side of the transformer is respectively connected to the first input end of the second AND operator, the input end of the synchronous rectification detection module and the collector of the secondary-side switch tube; The output end of the synchronous rectification detection module is connected to the input end of the synchronous rectification control module; The output end of the synchronous rectification control module is connected to the base of the secondary side switch tube; The emitter of the secondary side switch tube is connected to the output circuit; The opposite-name terminal of the secondary side of the transformer is connected to the input terminal of the CV / CC detection module; The output end of the CV / CC detection module is connected to the input end of the CV / CC control module; The output end of the CV / CC control module is connected to the second input end of the second AND operator; The output end of the second AND operator is connected to the input end of the isolation communication module.

7. A control method for a flyback power supply circuit according to any one of claims 1 to 6, characterized in that: Includes steps: Powering on the primary-side control chip, so that the primary-side control chip controls the on and off of the primary-side switch tube; When the primary-side switch tube is turned off, the secondary-side switch tube is turned on through the transformer, and the output circuit is charged; When the output circuit reaches a preset power value, the secondary side control chip sends a handshake signal to the primary side control chip; Determine whether the handshake is successful, and if so, stop powering on the primary-side control chip, and control the on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip; If not, return to the step of powering on the primary-side control chip.

8. The control method of a flyback power supply circuit according to claim 7, characterized in that: The controlling the turning on and off of the primary-side switch tube according to the rising edge of the pulse signal sent by the secondary-side control chip comprises: The secondary side control chip sends a pulse signal of a preset width to the primary side control chip through the isolation communication module; When the primary-side control chip receives the pulse signal and detects a rising edge, the primary-side switch tube is turned on.

9. The control method of a flyback power supply circuit according to claim 7, characterized in that: Also includes the steps: If the output power does not reach the preset power value, the process returns to the step of powering on the primary-side control chip.

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