Power conversion device

Abstract

The utility model provides a power conversion device. The protocol circuit adjusts the feedback voltage output by the optical coupler, so that the control circuit reduces the output voltage of the transformer circuit, and the optical coupler is closed when the output voltage of the transformer circuit is lower than a first set voltage, so that the feedback voltage is increased. The control circuit performs a power limiting operation when the output voltage of the transformer circuit is lower than a first set voltage and the feedback voltage is higher than a second set voltage. Therefore, the power supply conversion device provided by the utility model can conform to the power-limited power supply standard, save the circuit space and reduce the cost at the same time.

Description

Technical Field

[0001] The utility model relates to an electronic device, in particular to a power conversion device. Background Art

[0002] For safety reasons, the design of power supplies that meet the Limited Power Source (LPS) standard must meet the maximum allowable output voltage, output current and output power standards. The advantage that LPS power supplies bring to customers is that system installers only need to comply with relatively loose requirements when wiring and installing loads powered by LPS power supplies on site. Since the output current and voltage delivered to the load are limited, a qualified LPS power supply is not likely to cause electric shock or fire.

[0003] Generally speaking, power conversion circuits on the market usually require two sets of optical coupling components to communicate for power limiting protection, which results in space waste and additional cost. Utility Model Content

[0004] The utility model provides a power conversion device which can save circuit space and reduce costs while meeting the power-limited power supply standard.

[0005] The power conversion device of the utility model includes a transformer circuit, a power switch, a control circuit, a reference coil, an optical coupler and a protocol circuit. The transformer circuit includes a primary coil and a secondary coil, receives an input voltage and outputs an output voltage. The power switch is coupled between the primary coil and the ground. The control circuit is coupled to the power switch, and controls the power switch to switch between an on state and an off state to control the output of the transformer circuit. The reference coil is coupled to the control circuit, and senses the current of the primary coil to generate an induced voltage. The optical coupler is coupled to the control circuit. The protocol circuit is coupled to the secondary coil and the optical coupler, and controls the optical coupler to provide a feedback voltage to the control circuit according to the output of the transformer circuit. When the induced voltage indicates that the output voltage is lower than the first set voltage and the feedback voltage is higher than the second set voltage, the control circuit performs a power limiting operation.

[0006] In one embodiment of the present invention, the above-mentioned protocol circuit determines whether the output voltage is greater than the default voltage in the power limited power protection mode, and responds that the output voltage is greater than the default voltage, controls the optical coupler to adjust the feedback voltage, and causes the control circuit to reduce the output voltage according to the feedback voltage.

[0007] In an embodiment of the present invention, the control circuit reduces the duty cycle of the pulse width modulation control signal provided to the power switch to reduce the output voltage.

[0008] In an embodiment of the present invention, the protocol circuit determines whether the output voltage is lower than the first set voltage, and responds to the output voltage being lower than the first set voltage by turning off the optical coupler to increase the feedback voltage.

[0009] In one embodiment of the present invention, the optical coupler comprises a light emitting diode and an optical coupling transistor. The light emitting diode is coupled to the protocol circuit and is controlled by the protocol circuit to generate an optical signal. The optical coupling transistor is coupled to the control circuit and receives the optical signal to generate a feedback voltage.

[0010] In an embodiment of the present invention, the protocol circuit controls the light emitting diode to stop generating the optical signal, so as to turn off the optical coupler.

[0011] In an embodiment of the present invention, the power limiting operation includes controlling the power switch to be in an off state.

[0012] In an embodiment of the present invention, the control circuit is an analog-to-digital conversion chip.

[0013] In an embodiment of the present invention, the protocol circuit is a power delivery chip.

[0014] In an embodiment of the present invention, the power conversion device further includes a full-wave rectifier circuit coupled to the transformer circuit for performing full-wave rectification on the AC input voltage to generate an input voltage.

[0015] Based on the above, the control circuit of the embodiment of the utility model can perform a power limiting operation according to the induced voltage provided by the reference coil and the feedback voltage provided by the optocoupler. For example, the power limiting operation is performed when the induced voltage indicates that the output voltage of the transformer circuit is lower than the first set voltage and the feedback voltage is higher than the second set voltage. In this way, the power conversion device can comply with the power-limited power supply standard without using two optocouplers, thereby effectively saving circuit space and reducing costs.

[0016] In order to make the above features and advantages of the present invention more obvious and easy to understand, embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram of a power conversion device according to the utility model;

[0018] Figure 2 is a schematic diagram of a power conversion device according to another embodiment of the utility model;

[0019] Figure 3 It is a timing diagram of the operation of a power conversion device according to the utility model. DETAILED DESCRIPTION

[0020] Figure 1 1 is a schematic diagram of a power conversion device according to the present invention. The power conversion device may include a transformer circuit T, a power switch Mp, a control circuit 102, a protocol circuit 104, an optical coupler 106, and a reference coil Na. The transformer circuit T includes a primary coil Np and a secondary coil Ns. The first end of the primary coil Np receives an input voltage VIN. The power switch Mp is coupled between the second end of the primary coil Np and the ground. The control end of the power switch Mp is coupled to the control circuit 102. In this embodiment, the power switch Mp is implemented by a transistor, but is not limited thereto. The protocol circuit 104 is coupled to the secondary coil Ns. The protocol circuit 104 may be implemented, for example, by a power delivery IC. The optocoupler 106 is coupled to the control circuit 102 and the protocol circuit 104, and the reference coil Na is coupled to the control circuit 102, wherein the optocoupler 106 is controlled by the protocol circuit 104 to provide a feedback voltage VFB to the control circuit 102, and the reference coil Na can sense the current of the primary side coil Ns to generate an induced voltage VS, and the induced voltage VS can be used to indicate the voltage size of the output voltage VOUT of the transformer circuit T.

[0021] The transformer circuit T can receive an input voltage VIN and convert the input voltage VIN into an output voltage VOUT. The control circuit 102 can output a pulse width modulation control signal PWM to a control terminal of the power switch Mp to control the power switch Mp to switch between an on state and an off state, thereby controlling the output voltage VOUT of the transformer circuit T.

[0022] When the protocol circuit 104 determines in the power-limited power supply protection mode that the output current or output power of the transformer circuit T is close to the current value or power value specified by the power-limited power supply standard, the blocking transistor (blocking MOS) inside the protocol circuit 104 is turned off, so that the output of the power conversion device meets the current value or power value specified by the power-limited power supply standard. When the blocking transistor inside the protocol circuit 104 is turned off, and the protocol circuit 104 still detects the current of the blocking transistor, it means that the blocking transistor has been short-circuited. At this time, the protocol circuit 104 can determine whether the output voltage VOUT is greater than the default voltage. When it is determined that the output voltage VOUT is greater than the default voltage, the protocol circuit 104 controls the optical coupler 106 to adjust the feedback voltage VFB provided to the control circuit 102, so that the control circuit 102 reduces the duty ratio of the pulse width modulation control signal PWM provided to the power switch Mp according to the feedback voltage VFB, thereby reducing the output voltage VOUT output by the transformer circuit T.

[0023] After the protocol circuit 104 detects that the output voltage VOUT decreases to a first set voltage (where the first set voltage is less than a default voltage), the optical coupler 106 may be turned off to pull up the feedback voltage VFB so that the feedback voltage VFB is higher than a second set voltage. The control circuit 102 may obtain the output voltage VOUT of the transformer circuit T by referring to the induced voltage VS generated by the reference coil Na, and perform a power limiting operation when the induced voltage VS indicates that the output voltage VOUT of the transformer circuit T is lower than the first set voltage and the feedback voltage VFB is higher than the second set voltage, so as to meet the requirements of the power-limited power supply standard for the output voltage VOUT. The power limiting operation may be, for example, controlling the power switch Mp to be in an off state, but is not limited thereto.

[0024] As described above, the protocol circuit 104 of the present embodiment can adjust the feedback voltage VFB output by the optocoupler 106 to enable the control circuit 102 to reduce the output voltage VOUT, and turn off the optocoupler 106 when the output voltage VOUT is lower than the first set voltage to increase the feedback voltage VFB. The control circuit 102 can perform a power limiting operation when the output voltage VOUT of the transformer circuit T is lower than the first set voltage and the feedback voltage VFB is higher than the second set voltage. In this way, the output of the power conversion device can meet the power-limited power supply standard without using two optocouplers, thereby effectively saving circuit space and reducing costs.

[0025] Furthermore, the implementation of the power conversion device can be as follows: Figure 2 As shown. Figure 2 In an embodiment, the power conversion device may include an electromagnetic interference filter 202 and a full-bridge rectifier circuit 204 in addition to the transformer circuit T, the control circuit 102, the protocol circuit 104, the optical coupler 106 and the reference coil Na, wherein the electromagnetic interference filter 202 is coupled to the full-bridge rectifier circuit 204, and the full-bridge rectifier circuit 204 is coupled to the primary side coil Np.

[0026] In addition, the control circuit 102 is implemented by an analog-to-digital (AC / DC) conversion chip, and the optical coupler 106 includes a light-emitting diode D1 and an optical coupling transistor M1. The light-emitting diode D1 is coupled to the protocol circuit 104, and the optical coupling transistor M1 is coupled to the control circuit 102. The analog-to-digital conversion chip may include six pins, namely, VCC, AC / EXOT, FB, GATE, CS / DEM, and GND. Among them, the reference coil Na is coupled to the pin CS / DEM through a diode and a resistor, the control end of the power switch Mp is coupled to the pin GATE, and the optical coupling transistor M1 is coupled to the pin FB.

[0027] The electromagnetic interference filter 202 can filter the AC input voltage to remove electromagnetic interference. The full-bridge rectifier circuit 204 can perform full-wave rectification on the AC input voltage filtered by the electromagnetic interference filter 202 to generate an input voltage VIN. The operation timing of the power conversion device can be as follows: Figure 2 As shown, during period P1, the protocol circuit 104 determines that the output voltage VOUT is greater than the default voltage, and controls the optical coupler 106 to start reducing the feedback voltage VFB provided to the control circuit 102. During period P2, the control circuit 102 detects that the feedback voltage VFB received by the pin FB is reduced, so the duty ratio of the pulse width modulation control signal PWM provided to the power switch Mp is reduced to reduce the output voltage VOUT output by the transformer circuit T. At this time, the voltage VDEM received by the pin CS / DEM of the control circuit 102 also decreases as the output voltage VOUT decreases. During period P3, the protocol circuit 104 detects that the output voltage VOUT has decreased to below the first set voltage VOUT_LPS, so it stops providing the driving current to the light emitting diode D1 to stop it from providing the optical signal. The optical coupling transistor M1 enters the off state because the light emitting diode D1 stops providing the optical signal, so that the pull-up resistor coupled to the pin FB in the control circuit 102 pulls the voltage on the pin FB (i.e., the feedback voltage VFB) higher than the second set voltage FBOLP_LPS. During period P4, the control circuit 102 determines that the output voltage VOUT is lower than the first set voltage VOUT_LPS based on the induced voltage VS provided by the reference coil Na (i.e., based on the voltage VDEM on the pin CS / DEM), and that the feedback voltage VFB is higher than the second set voltage FBOLP_LPS based on the pin FB. Therefore, it is determined that the power conversion device enters the limited power supply (LPS) protection, and the pulse width modulation control signal PWM is controlled to be maintained at a low voltage, so that the power switch Mp is in the off state, thereby making the output voltage VOUT meet the requirements of the limited power supply standard.

[0028] In summary, the control circuit of the embodiment of the utility model can perform a power limiting operation according to the induced voltage provided by the reference coil and the feedback voltage provided by the optocoupler. For example, the power limiting operation is performed when the induced voltage indicates that the output voltage of the transformer circuit is lower than the first set voltage and the feedback voltage is higher than the second set voltage. In this way, the power conversion device can comply with the power-limited power supply standard without using two optocouplers, thereby effectively saving circuit space and reducing costs.

[0029] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the claims.

Claims

1. A power conversion device, characterized in that: include: A transformer circuit, including a primary coil and a secondary coil, receives an input voltage and outputs an output voltage; A power switch coupled between the primary coil and ground; A control circuit coupled to the power switch to control the power switch to switch between an on state and an off state to control the output of the transformer circuit; A reference coil, coupled to the control circuit, inducing the current of the primary coil to generate an induced voltage; an optical coupler coupled to the control circuit; as well as A protocol circuit is coupled to the secondary coil and the optical coupler, and controls the optical coupler to provide a feedback voltage to the control circuit according to the output of the transformer circuit. The control circuit performs a power limiting operation when the induced voltage indicates that the output voltage is lower than a first set voltage and the feedback voltage is higher than a second set voltage.

2. The power conversion device according to claim 1, characterized in that: The protocol circuit determines whether the output voltage is greater than a default voltage in the power-limited power protection mode, and responds that the output voltage is greater than the default voltage, controls the optical coupler to adjust the feedback voltage, and causes the control circuit to reduce the output voltage according to the feedback voltage.

3. The power conversion device according to claim 2, characterized in that: The control circuit reduces the duty cycle of the pulse width modulation control signal provided to the power switch to reduce the output voltage.

4. The power conversion device according to claim 2, characterized in that: The protocol circuit determines whether the output voltage is lower than the first set voltage, and in response to the output voltage being lower than the first set voltage, turns off the optical coupler to increase the feedback voltage.

5. The power conversion device according to claim 4, characterized in that: The optical coupler comprises: a light emitting diode, coupled to the protocol circuit and controlled by the protocol circuit to generate an optical signal; and The optical coupling transistor is coupled to the control circuit and receives the optical signal to generate the feedback voltage.

6. The power conversion device according to claim 5, characterized in that: The protocol circuit controls the light emitting diode to stop generating the optical signal so as to turn off the optical coupler.

7. The power conversion device according to claim 1, characterized in that: The power limiting operation includes controlling the power switch to be in an off state.

8. The power conversion device according to claim 1, characterized in that: The control circuit is an analog-to-digital conversion chip.

9. The power conversion device according to claim 1, characterized in that: The protocol circuit is a power delivery chip.

10. The power conversion device according to claim 1, characterized in that: Also includes: The full-wave rectifier circuit is coupled to the transformer circuit and performs full-wave rectification on the AC input voltage to generate the input voltage.

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