TW202024841A - Power adaptor - Google Patents

Abstract

A power adaptor is provided. The power adaptor includes a transformer, a power switch, a control circuit and a current sensing circuit. The transformer includes a primary winding, a secondary winding and an auxiliary winding. The transformer is utilized for converting an input voltage to an output voltage. A first terminal of the power switch is coupled to the primary winding. The control circuit is coupled to a second terminal of the power switch for generating a control signal to control the operation of the power switch. The current sensing circuit is coupled to a third terminal of the power switch for sensing a current sensing voltage provided to the control circuit according to a first voltage associated with the auxiliary winding and a reference voltage.

Description

Power Adapter

The present invention refers to a power adapter, especially a power adapter that can effectively increase the overall output power

With the development of technology, the types of electronic products are increasing, such as mobile communication devices, notebook computers, personal assistants, multimedia players, etc. These electronic products all need to use power adapters (adaptor) to connect high-voltage AC power or DC The power source is converted into a stable DC power source that meets the requirements and used as a power source for charging or normal operation. Furthermore, in order to achieve power supply for various different electrical devices, the Universal Serial Bus Power Delivery (USB PD) standard specification proposes specifications for different output voltages. For example, the power adapter can provide at least 5 volts, 9 volts, 15 volts, and 20 volts.

In order to ensure the normal and stable operation of the power adapter, an automatic protection mechanism is usually used to stop the operation of the power adapter when conditions such as over current, over voltage, over power, overload, short circuit, etc. occur, so as to prevent internal components or related equipment from suffering damage. For example, please refer to Figure 1. Figure 1 is a schematic diagram of a conventional power adapter 1. The power adapter 1 includes a transformer 10, a control circuit 12, a power switch SW1, and a resistor R1. The transformer 10 can convert an input voltage VI into an output voltage VO. The transformer 10 includes a primary winding NP, a secondary winding NS, and an auxiliary winding NA. The control circuit 12 senses the current detection voltage generated by the current of the primary winding NP flowing through the resistor R1 to perform over current protection. When the current detection voltage reaches a certain value, turn off the power switch SW1 or the power adapter to prevent excessive current at the output terminal from causing damage. However, from another point of view, the over-current protection mechanism will limit the maximum power output of the power adapter and cannot maximize the output energy. Therefore, it is necessary to improve the conventional technology.

Therefore, the main purpose of the present invention is to provide a power adapter that can effectively increase the overall output power.

The present invention discloses a power adapter including: a transformer including a primary winding, a secondary winding, and an auxiliary winding for converting an input voltage into an output voltage; a power switch, one of the power switches One end is coupled to the primary winding; a control circuit, coupled to a second end of the power switch, used to generate a switch control signal to control the operation of the power switch; and a current detection circuit, coupled Connected to a third terminal of the power switch for sensing a current detection voltage according to a first voltage and a reference voltage related to the auxiliary winding to provide it to the control circuit.

In the specification and subsequent patent applications, certain words are used to refer to specific elements. Those with general knowledge in the field should understand that hardware manufacturers may use different terms to refer to the same component. The scope of this specification and subsequent patent applications does not use differences in names as a way of distinguishing components, but uses differences in functions of components as a criterion. The "include" mentioned in the entire specification and the subsequent patent application scope is an open term, so it should be interpreted as "include but not limited to". In addition, the term "coupling" here includes any direct and indirect electrical connection means. Therefore, if it is described that a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connecting means.

Please refer to Fig. 2, which is a schematic diagram of a power adapter 2 according to an embodiment of the present invention. The power adapter 2 is used to provide an output voltage VO to a load Load. Among them, Load can be any electronic product that requires power, and the output voltage VO can be used as a power source for electronic product charging or normal operation. The power supply device 2 includes a transformer 20, a control circuit 22, a current detection circuit 24, a voltage stabilizing circuit 26, a power switch SW1, a capacitor CO, and a diode DO. The transformer 20 can convert an input voltage VI into an output voltage VO. The transformer 20 includes a primary winding NP, a secondary winding NS, and an auxiliary winding NA. The first terminal of the primary winding NP receives the input voltage VI, and the second terminal of the primary winding NP is coupled to the power switch SW1. The first end of the secondary winding NS is coupled to the diode DO, and the second end of the secondary winding NS is coupled to a second ground GND2. The first end of the auxiliary winding NA is coupled to the voltage stabilizing circuit 26, and the second end of the auxiliary winding NA is coupled to the first ground GND1. The anode of the diode DO is coupled to the first end of the secondary winding, and the cathode of the diode DO is coupled to the capacitor CO and the load Load. A first end of the capacitor CO is coupled to the cathode of the diode DO and the load Load, and a second end of the capacitor CO is coupled to a second ground GND2.

The first end of the power switch SW1 is coupled to the second end of the primary winding NP. The second end of the power switch SW1 is coupled to the control circuit 22 for receiving a control signal S1. The third terminal of the power switch SW1 is coupled to the current detection circuit 24. The power switch SW1 can control the signal transmission path between the first terminal and the third terminal according to the potential of the control signal S1 to present a conductive state (short circuit) or a non-conductive state (open circuit). The power switch SW1 can be a power transistor. For example, the power switch SW1 can be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), a bipolar Junction Transistor (BJT) or other components with similar functions, but not Limit this. When the power switch SW1 is turned on, the primary winding current ICS flows through the primary winding NP and the power switch SW1, and the primary winding NP stores energy. At this time, the output voltage VO is generated by the capacitor CO to supply power to the load Load. When the power switch SW1 is not turned on, the energy stored in the primary winding NP will be transferred to the secondary winding NS to supply power to the capacitor CO.

The control circuit 22 is coupled to the power switch SW1, the current detection circuit 24 and the voltage stabilizing circuit 26. The control circuit 22 includes pins GD, CS, Vcc, and GND. The control circuit 22 can receive a power supply voltage VCC through the pin Vcc and perform related operations accordingly. The control circuit 22 is used to generate a switch control signal S1 to control the operation of the power switch SW1. For example, the control circuit 22 can generate the switch control signal S1 according to a current detection voltage VCS to control the operation of the power switch SW1. In one embodiment, when the current detection voltage VCS is greater than a first threshold, the control circuit 22 can generate the switch control signal S1 according to the current detection voltage VCS to control the power switch SW1 to switch to a non-conducting state. In another embodiment, when the current detection voltage VCS is greater than a second threshold, the control circuit 22 can control the power adapter 2 to shut down according to the current detection voltage VCS.

The current detection circuit 24 is coupled to the third terminal of the power switch SW1 and the control circuit 22. The current detection circuit 24 can sense the current detection voltage VCS according to a first voltage related to the auxiliary winding NA and a reference voltage VR. In detail, the current detection circuit 24 includes a comparator 242, a driver 244, an auxiliary switch SW2, and resistors R1 and R2. The first end of the resistor R1 is coupled to the third end of the power switch SW1, and the second end of the resistor R1 is coupled to the first ground GND1. The first end of the resistor R2 is coupled to the third end of the power switch SW1, and the second end of the resistor R2 is coupled to the first end of the auxiliary switch SW2. The comparator 242 includes a first input terminal, a second input terminal, and an output terminal. The comparator 242 of the current detection circuit 24 can compare the signals received by the first input terminal and the second input terminal to generate a comparison signal. The comparison signal can be a voltage signal or a current signal, but is not limited to this. The first input terminal of the comparator 242 is used to receive a first voltage related to the auxiliary winding NA. In one embodiment, as shown in FIG. 2, the first input terminal of the comparator 242 is coupled to the voltage stabilizing circuit 26 for receiving a capacitor voltage VC1 related to the auxiliary winding NA. In this case, the aforementioned first voltage related to the auxiliary winding NA is the capacitor voltage VC1. In another embodiment, the first input terminal of the comparator 242 can receive the auxiliary winding voltage VNA of the auxiliary winding NA or other voltage signals related to the auxiliary winding NA, that is to say, the aforementioned first voltage related to the auxiliary winding NA It can also be the auxiliary winding voltage VNA of the auxiliary winding NA or other voltage signals related to the auxiliary winding NA. Further, the second input terminal of the comparator 242 is used to receive a reference voltage VR, and the output terminal of the comparator 242 is used to output a comparison signal. The driver 244 is coupled to the output terminal of the comparator 242 for receiving the comparison signal and generating a driving signal S2 to the auxiliary switch SW2 accordingly. The first end of the auxiliary switch SW2 is coupled to the second end of the resistor R2, and the second end of the auxiliary switch SW2 is coupled to the driver 244 for receiving the driving signal S2. The third terminal of the auxiliary switch SW2 is coupled to the first ground GND1.

When the voltage of the first input terminal (non-inverting terminal) of the comparator 242 (that is, the first voltage related to the auxiliary winding NA) is less than or equal to the voltage of the second input terminal (that is, the reference voltage VR), the comparator 242 generates a comparison signal to the driver 244. The driver 244 generates a driving signal S2 to the auxiliary switch SW2 according to the comparison signal. In this case, in response to the driving signal S2, the auxiliary switch SW2 is in a non-conductive state. In other words, when the first voltage related to the auxiliary winding NA is less than or equal to the reference voltage VR, the comparator 242 outputs the corresponding comparison signal to the driver 244, so that the driver 244 generates the corresponding driving signal S2 to the auxiliary switch SW2 to control The auxiliary switch SW2 is in a non-conductive state. In this case, since the auxiliary switch SW2 is in a non-conductive state, the resistor R2 is in an open state. Therefore, the total resistance value of the load resistance coupled between the switch SW1 and the first ground GND1 is the resistance value of the resistance R1.

When the voltage of the first input terminal (non-inverting terminal) of the comparator 242 (ie the first voltage related to the auxiliary winding NA) is greater than the voltage of the second input terminal (ie the reference voltage VR), the comparator 242 generates and outputs Compare the signal to the driver 244. The driver 244 generates the driving signal S2 to the auxiliary switch SW2 according to the comparison signal. In this case, in response to the driving signal S2, the auxiliary switch SW2 is turned on. In other words, when the first voltage related to the auxiliary winding NA is greater than the reference voltage VR, the comparator 242 outputs a corresponding comparison signal to the driver 244, so that the driver 244 generates a corresponding driving signal S2 to the auxiliary switch SW2 to control the auxiliary switch SW2 is in the conducting state. In this case, since the auxiliary switch SW2 is in an on state, the resistor R2 is in a short-circuit state. Therefore, the total resistance value of the load resistance coupled between the switch SW1 and the first ground GND1 is the parallel resistance value of the resistance R1 and the resistance R2 in parallel. Since the equivalent resistance of the resistors in parallel will be smaller than the resistance of the respective resistances, as a result, the total resistance of the load resistance coupled between the switch SW1 and the first ground GND1 will change compared to the resistance of the resistance R1. Small (resistor R1 and resistor R2 in parallel resistance value <resistance R1 resistance value), so that a larger primary winding current ICS will be allowed to reach the overcurrent protection trigger voltage, which can effectively improve the power adapter 2. The overall power output energy.

The voltage stabilizing circuit 26 is coupled to the auxiliary winding NA and the control circuit 22 for generating a power supply voltage VCC to the control circuit 22 and a capacitor voltage VC1 to the current detection circuit 24 according to an auxiliary winding voltage VNA of the auxiliary winding NA. As shown in Fig. 2, the voltage stabilizing circuit 26 includes diodes D1 and D2, capacitors C1 and C2, Zener diode ZD, transistor Q1, and resistor R3. The anode of the diode D1 is coupled to the first end of the auxiliary winding NA, and the cathode of the diode D1 is coupled to the capacitor C1, the transistor Q1, the resistor R3, and the first input end of the comparator 242. The first terminal of the capacitor C1 is coupled to the cathode of the diode D1 and the first input terminal of the comparator 242, and the second terminal of the capacitor C1 is coupled to the first ground GND1, wherein the capacitor voltage VC1 is a cross-section of the capacitor C1 The capacitor voltage VC1 is related to the auxiliary winding voltage VNA, one of the auxiliary windings NA. The first end of the resistor R3 is coupled to the cathode of the diode D1, the first end of the capacitor C1 and the first input end of the comparator 242, and the second end of the resistor R3 is coupled to the Zener diode ZD. The cathode of the Zener diode ZD is coupled to the second end of the resistor R3 and the transistor Q1, and the anode of the Zener diode ZD is coupled to the first ground GND1. The first end of transistor Q1 is coupled to the anode of diode D2, the second end of transistor Q1 is coupled to the cathode of Zener diode ZD and the second end of resistor R3, and the third end of transistor Q1 It is coupled to the cathode of the diode D1, the first terminal of the resistor R3 and the first input terminal of the comparator 242. The anode of the diode D2 is coupled to the first end of the transistor Q1, and the cathode of the diode D2 is coupled to the pin Vcc of the control circuit 22. The first end of the capacitor C2 is coupled to the cathode of the diode D2 and the pin Vcc of the control circuit 22 to output the power supply voltage VCC to the control circuit 22, and the second end of the capacitor C2 is coupled to the first ground GND1.

In one embodiment, the comparator 242 compares the capacitor voltage VC1 received at the first input terminal with the reference voltage VR received at the second input terminal to determine whether the auxiliary switch SW2 is on or off. Assume that the turns ratio of the primary winding NP, the secondary winding NS, and the auxiliary winding NA is 35:5:15. The maximum power supply voltage that the control circuit 22 can withstand is 40 volts. The second input terminal of the comparator 242 is coupled to a certain voltage source to receive a reference voltage VR, where the reference voltage VR is 40 volts. When the output voltage VO is 5V or 9V, the auxiliary winding voltage VNA of the auxiliary winding NA is between 15V and 27V and the capacitor voltage VC1 is between 15V and 27V. At this time, the Zener diode ZD has not collapsed, and the maximum value of the capacitor voltage VC2 of the capacitor C2 is equal to the maximum value of the power supply voltage VCC. The maximum value of the capacitor voltage VC2 of the capacitor C2 and the maximum power supply voltage VCC can be based on the following formula And get: VC2=VCC=27 volts-forward bias of diode D1-forward bias of transistor Q1 VBE-forward bias of diode D2 = 27 volts-0.7 volts-0.7 volts-0.7 Volts = 24.9 Volts (1)

It can be seen from formula (1) that the maximum value of the power supply voltage VCC is 24.9 volts and does not exceed the power supply voltage value that the control circuit 22 can withstand. In other words, the voltage stabilizing circuit 26 does achieve the purpose of voltage stabilization. Furthermore, since the capacitor voltage VC1 is between 15V and 27V and the reference voltage VR is 40V, the voltage at the first input terminal (15V to 27V) of the comparator 242 is smaller than the voltage at the second input terminal at this time (40V), the comparator 242 generates and outputs a low-voltage comparison signal to the driver 244. The driver 244 generates a low-level driving signal S2 to the auxiliary switch SW2 according to the low-level comparison signal. In this case, in response to the low-level driving signal S2, the auxiliary switch SW2 is in a non-conductive state. In this case, since the auxiliary switch SW2 is in a non-conductive state, the resistor R2 is in an open state. Therefore, the total resistance value of the load resistance coupled between the switch SW1 and the first ground GND1 is the resistance value of the resistance R1.

When the output voltage VO is 15V or 20V, the auxiliary winding voltage VNA of the auxiliary winding NA is between 45V and 60V, and the capacitor voltage VC1 is between 45V and 60V. At this time, the Zener diode ZD collapses and conducts and the voltage of the Zener diode ZD is maintained at 30 volts. In this case, the maximum value of the capacitor voltage VC2 of the capacitor C2 is equal to the maximum value of the power supply voltage VCC. The maximum value of the capacitor voltage VC2 of the capacitor C2 and the maximum power supply voltage VCC can be obtained according to the following formula: VC2=VCC= 30 volts-forward bias voltage of transistor Q1 VBE-forward bias voltage of diode D2 = 30 volts-0.7 volts-0.7 volts = 28.6 volts

It can be seen from formula (2) that the maximum value of the power supply voltage VCC is 28.6 volts and does not exceed the power supply voltage value that the control circuit 22 can withstand. Therefore, the voltage stabilizing circuit 26 does achieve the purpose of voltage stabilization. Furthermore, since the capacitor voltage VC1 is between 45 volts and 60 volts and the reference voltage VR is 40 volts, the voltage (45 volts to 60 volts) of the first input terminal (non-inverting terminal) of the comparator 242 at this time is greater than With the voltage (40 volts) of the second input terminal (inverting terminal), the comparator 242 generates and outputs a high-voltage comparison signal to the driver 244. The driver 244 generates a high-level driving signal S2 to the auxiliary switch SW2 according to the high-voltage level comparison signal. In this case, the auxiliary switch SW2 is turned on in response to the high-level driving signal S2. Since the auxiliary switch SW2 is in the on state and the resistor R2 is in a short-circuit state, the total resistance of the load resistor coupled between the switch SW1 and the first ground GND1 is the parallel resistance value of the resistor R1 and the resistor R2 in parallel. Since the equivalent resistance of the resistors in parallel will be smaller than the resistance of the individual resistors, the primary winding current ICS will allow a larger primary winding current ICS to reach the overcurrent protection trigger voltage and be effective Increase the overall output energy of the power adapter 2.

In summary, the embodiments of the present invention can dynamically adjust the sensing current tolerance value in response to different output voltages without affecting the over-current protection, thereby effectively increasing the overall output power of the power supply. The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

1, 2: Power adapter 10, 20: Transformer 12, 22: control circuit 24: Current detection circuit 242: Comparator 244: Drive 26: voltage regulator circuit C1, C2, CO: Capacitor CS, GD, GND, Vcc: pins D1, D2, DO: Diode GND1: first ground GND2: second ground ICS: primary winding current Load: load NA: auxiliary winding NP: Primary winding NS: Secondary winding Q1: Transistor R1, R2, R3: resistance S1: Control signal S2: Drive signal SW1: Power switch SW2: auxiliary switch VC1, VC2: capacitor voltage VCC: power supply voltage VCS: Current detection voltage VI: Input voltage VO: output voltage VNA: auxiliary winding voltage VR: Reference voltage ZD: Zener diode

Figure 1 is a schematic diagram of a traditional power adapter. Figure 2 is a schematic diagram of a power adapter according to an embodiment of the invention.

2: power adapter

20: Transformer

22: Control circuit

24: Current detection circuit

242: Comparator

244: Drive

26: voltage regulator circuit

C1, C2, CO: Capacitor

CS, GD, GND, Vcc: pins

D1, D2, DO: Diode

GND1: first ground

GND2: second ground

ICS: primary winding current

Load: load

NA: auxiliary winding

NP: Primary winding

NS: Secondary winding

Q1: Transistor

R1, R2, R3: resistance

S1: Control signal

S2: Drive signal

SW1: Power switch

SW2: auxiliary switch

VC1, VC2: capacitor voltage

VCC: power supply voltage

VCS: Current detection voltage

VI: Input voltage

VO: output voltage

VNA: auxiliary winding voltage

VR: Reference voltage

ZD: Zener diode

Claims (8)

A power adapter includes: a transformer including a primary winding, a secondary winding and an auxiliary winding for converting an input voltage into an output voltage; a power switch, one of the first terminals of the power switch is coupled Connected to the primary winding; a control circuit coupled to a second end of the power switch for generating a switch control signal to control the operation of the power switch; and a current detection circuit coupled to the A third terminal of the power switch is used for sensing a current detection voltage according to a first voltage and a reference voltage related to the auxiliary winding to provide to the control circuit. The power adapter described in claim 1, wherein the current detection circuit includes: a first resistor, a first end of the first resistor is coupled to the third end of the power switch, and the A second end of the first resistor is coupled to a first ground; a second resistor, a first end of the second resistor is coupled to the third end of the power switch; an auxiliary switch, the auxiliary switch A first terminal is coupled to a second terminal of the second resistor, a second terminal of the auxiliary switch is used to receive a driving signal, and a third terminal of the auxiliary switch is coupled to the first ground; a comparison The device includes a first input terminal, a second input terminal, and an output terminal for comparing the signals received by the first input terminal and the second input terminal to generate a comparison signal, wherein the first input terminal is used To receive the first voltage related to the auxiliary winding, the second input terminal is used to receive the reference voltage, and the output terminal is used to output the comparison signal; and a driver coupled to the output terminal of the comparator , Used to generate the driving signal according to the comparison signal. For the power adapter described in item 2 of the scope of patent application, when the first voltage related to the auxiliary winding is less than the reference voltage, the comparator generates and outputs the comparison signal, and the driver generates the driving signal to The auxiliary switch and the auxiliary switch are in a non-conductive state due to the driving signal. For the power adapter described in item 2 of the scope of patent application, when the first voltage related to the auxiliary winding is greater than the reference voltage, the comparator generates and outputs the comparison signal, and the driver generates the driving signal to The auxiliary switch and the auxiliary switch are turned on due to the driving signal. The power adapter described in item 1 of the scope of patent application, wherein the first voltage related to the auxiliary winding is an auxiliary winding voltage of the auxiliary winding. For example, the power adapter described in item 1 of the scope of patent application further includes: a voltage stabilizing circuit coupled to the auxiliary winding and the control circuit for generating a power supply voltage to the auxiliary winding voltage of the auxiliary winding The control circuit generates the first voltage related to the auxiliary winding to the current detection circuit. The power adapter described in item 6 of the scope of patent application, wherein the voltage stabilizing circuit includes: a first diode, an anode of the first diode is coupled to a first end of the auxiliary winding, and A cathode of the first diode is coupled to the current detection circuit; a first capacitor, a first end of the first capacitor is coupled to the cathode of the first diode and the current detection circuit , And a second end of the first capacitor is coupled to the first ground, wherein the first voltage related to the auxiliary winding is a cross voltage of the first capacitor; a third resistor, the third resistor A first end is coupled to the cathode of the first diode; a Zener diode, a cathode of the Zener diode is coupled to a second end of the third resistor, and the Zener two An anode of the pole body is coupled to the first ground; a transistor including a first end, a second end and a third end, and the second end of the transistor is coupled to the Zener diode The cathode, the third end of the transistor is coupled to the cathode of the first diode; a second diode, an anode of the second diode is coupled to the first diode of the transistor One end, and a cathode of the second diode is coupled to the control circuit; and a second capacitor, a first end of the second capacitor is coupled to the cathode of the second diode and the control Circuit, and a second end of the second capacitor is coupled to the first ground. The power adapter described in claim 1 of the scope of patent application further includes: a third diode, an anode of the third diode is coupled to the secondary winding; and a third capacitor, the A first end of the third capacitor is coupled to a cathode of the third diode, and a second end of the third capacitor is coupled to a second ground.

Images