CN101145738A - Power adapter and power supply system using same - Google Patents

Abstract

The invention relates to a power supply adapter capable of simultaneously providing low-level direct current voltage and high-level direct current voltage. The voltage commutator comprises a transformer having a primary side winding for storing energy when a main switch connected thereto is turned on and transferring the stored energy to a secondary side of the transformer when the main switch is turned off. The transformer includes a first secondary side winding and a second secondary side winding connected in series with each other. The first rectifying and filtering circuit is connected to the first secondary side winding and used for rectifying and filtering the energy received by the first secondary side winding to generate a low-level direct-current voltage. The second rectifying and filtering circuit is connected across the first secondary side winding and the second secondary side winding and is used for rectifying and filtering the energy received by the first secondary side winding and the second secondary side winding to generate high-level direct-current voltage. The invention can greatly reduce the power loss of the DC-AC converter and greatly improve the conversion efficiency of the DC-AC converter.

Description

Power adapter and power supply system using the power adapter

technical field

The present invention relates to a power adapter, and more specifically, the present invention relates to a power adapter capable of simultaneously outputting low-level DC voltage and high-level DC voltage to power converters of different specifications for power conversion.

Background technique

FIG. 1 is a system block diagram of a prior art power supply system for a flat panel display. As shown in FIG. 1 , the power adapter (power adapter) 100 is configured to receive an input AC voltage Vin and convert the input AC voltage Vin into an output DC voltage Vo, and the output DC voltage Vo is provided to a DC-AC converter 101 respectively. (or called an inverter) and a DC-DC converter 102 . The DC-DC converter 102 is configured to convert the output DC voltage Vo into a DC voltage with a lower voltage level for powering a control circuit (not shown) inside the flat panel display. The DC-AC converter 101 is configured to convert the output DC voltage Vo into a high frequency high-level AC voltage for lighting a discharge lamp (not shown) as a backlight source of a flat panel display.

A typical power adapter for a flat panel display receives an input AC voltage of 110V or 220V and provides an output DC voltage of 12V. Therefore, the output DC voltage Vo provided by the power adapter 100 shown in FIG. 1 is generally a low-level DC voltage with a voltage value of about 12V. The voltage value of the output DC voltage generally can be 1.5V, 2.5V, 3V, 3.3V, 4.5V, 5V, 6V, 7.5V, 9V, 12V. However, generally speaking, the DC-AC converter 101 needs to output a high-frequency AC voltage to meet the power required for lighting the discharge lamp inside the flat panel display. Therefore, the DC-AC converter 101 must convert the output DC voltage Vo of about 12V provided by the power adapter 100 into a high-frequency AC voltage.

The DC-AC converter 101 is configured to convert a low-level DC voltage into a high-level AC voltage via switching of an internal transistor switch (not shown) and voltage boosting operation of a high-voltage transformer (not shown). In this situation, the voltage transformation ratio of the DC-AC converter 101 becomes quite large. Therefore, the DC-AC converter 101 will generate a considerable power loss, which further reduces the conversion efficiency of the DC-AC converter 101 . If the power adapter 100 can provide an output DC voltage with a higher voltage level to the DC-AC converter 101 for power conversion, the power loss generated by the DC-AC converter 101 can be reduced, and the DC - The conversion efficiency of the AC converter 101 is improved.

FIG. 2 shows a schematic circuit diagram of the power adapter 100 in FIG. 1 . As shown in FIG. 2, the power adapter 100 includes a bridge rectifier (bridge rectifier) 201, which is configured to rectify the input AC voltage Vin into a full-wave rectified DC voltage, and a transformer T21, which has a primary winding (primary winding ) Np21 and the secondary winding (secondary winding) Ns21, wherein the primary winding Np21 is set to store the energy received from the input AC voltage Vin when the main switch S21 connected in series with the primary winding Np21 is turned on, and the main switch S21 When turned off, the stored energy is transmitted to the secondary side winding Ns21. Switching of the main switch S21 is controlled by a pulse-width modulator (PWM) 202 . The power adapter 100 further includes a rectification filter circuit, which is composed of a rectification diode D21 and a filter capacitor C21 and is coupled to the secondary winding Ns21. The rectification and filtering circuit ( D21 , C21 ) is set to rectify and filter the energy received by the secondary winding Ns21 to generate a desired output DC voltage Vo. The power adapter 100 also includes a feedback control circuit (feedback control circuit) 203, which is set to detect the change of the output DC voltage Vo, and sends a feedback signal (feedback signal) to the pulse width modulator 202 according to the detection result to start The pulse width modulator 202 is used to stabilize the output DC voltage Vo at a predetermined value.

As mentioned above, the output DC voltage Vo of the conventional power adapter 100 is a low-level DC voltage. If this low-level output DC voltage Vo is provided to the DC-AC converter 101 shown in FIG. The conversion efficiency is low. Here, if a power adapter capable of simultaneously outputting low-level DC voltage and high-level DC voltage is developed, it is an ideal solution to solve the above-mentioned defects. The present invention fulfills this need.

Contents of the invention

The object of the present invention is to provide a power adapter, which can provide a low-level DC voltage to a DC-DC converter for power conversion, and provide a high-level DC voltage to a DC-AC converter for power conversion.

According to a preferred embodiment of the present invention, the power adapter includes a rectifier for rectifying an input AC voltage into a rectified DC voltage, and a transformer having a primary winding connected in series with a main switch. The primary side winding is set to store energy when the main switch is on and to transfer the stored energy to the secondary side of the transformer when the main switch is off. The transformer also includes a first secondary winding and a second secondary winding, wherein the first secondary winding and the second secondary winding are connected in series. The power adapter also includes a first rectifying and filtering circuit coupled to the first secondary winding for rectifying and filtering the energy received by the first secondary winding to generate a low-level DC voltage, and The second rectification and filtering circuit is connected across the first secondary winding and the second secondary winding, and is used for rectifying and synchronizing the energy received by the first secondary winding and the second secondary winding. filtering to produce a high-level DC voltage.

According to the idea of the present invention, the present application provides a power supply system, which includes: a power adapter for simultaneously converting the input AC voltage into a low-level output DC voltage and a high-level output DC voltage; DC-DC conversion A device, coupled to the power adapter, is used to receive the low-level output DC voltage provided by the power adapter and convert it into a DC voltage output; and a DC-AC converter, coupled to the power adapter The adapter is used to receive the high-level output DC voltage provided by the power adapter and convert it into an AC voltage output. Wherein, the power adapter includes: a switch; and a transformer having a primary side winding, a first secondary side winding and a second secondary side winding, wherein the primary side winding is connected in series with the switch and the first secondary side winding The second secondary winding is connected in series with each other, and it is set to store energy in the primary winding when the switch is turned on, and transfer the energy stored in the primary winding to the first winding when the switch is turned off. The secondary side winding and the second secondary side winding; the first rectification and filtering circuit, coupled to the first secondary side winding, used to rectify and filter the energy received by the first secondary side winding to generate the low-level output DC voltage; and a second rectification and filtering circuit connected across the first secondary winding and the second secondary winding for connecting the first secondary winding to the second secondary The energy received by the side winding is rectified and filtered to generate the high-level output DC voltage.

According to the power adapter of the present invention, the rectifier is a bridge rectifier.

According to the power adapter of the present invention, further comprising a pulse width modulator for controlling switching of the switch.

The power adapter according to the present invention further includes a feedback control circuit, which is used to detect the change of the low-level output DC voltage and the change of the high-level output DC voltage, and send a feedback signal to the The pulse width modulator is used to activate the pulse width modulator to stabilize the low-level output DC voltage at a predetermined value and stabilize the high-level output DC voltage at a predetermined value.

According to the power adapter of the present invention, the first rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor.

According to the power adapter of the present invention, the second rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor.

Since the voltage value of the input voltage of the DC-AC converter is greatly increased, the voltage conversion ratio of the DC-AC converter is reduced, thereby greatly reducing the power loss of the DC-AC converter and greatly improving the conversion efficiency of the DC-AC converter .

The advantages and features of the present invention can be better understood through the detailed description of the following embodiments in conjunction with the following drawings.

Description of drawings

FIG. 1 shows a system block diagram of a prior art power supply system for a flat panel display.

FIG. 2 shows a schematic circuit diagram of the power adapter of FIG. 1 .

FIG. 3 shows a system block diagram of the power adapter of the present invention applied to a power supply system of a flat panel display.

FIG. 4 shows a schematic circuit diagram of a preferred embodiment of the power adapter of the present invention.

Wherein, the reference signs are explained as follows:

100: power adapter

101: DC-AC Converter

102: DC-DC Converter

Vin: input AC voltage

Vo: output DC voltage

201: Bridge Rectifier

T21: Transformer

Np21: Primary side winding of transformer T21

Ns21: Secondary side winding of transformer T21

S21: main switch

202: Pulse Width Modulator

D21: rectifier diode

C21: filter capacitor

203: Feedback control circuit

300: power adapter

301: DC-AC Converter

302: DC-DC Converter

Vo1: output DC voltage

Vo2: output DC voltage

401: Bridge Rectifier

T41: Transformer

Np41: Primary side winding of transformer T41

Ns41: the first secondary side winding of transformer T41

Ns42: Secondary side winding of transformer T41

S41: main switch

402: Pulse Width Modulator

D41: rectifier diode

C41: filter capacitor

D42: rectifier diode

C42: filter capacitor

403: Feedback control circuit

Detailed ways

Preferred embodiments embodying the features and advantages of the present invention will be described in detail in the ensuing description. It should be understood that the invention is capable of various changes in different embodiments, all without departing from the scope of the invention, and that the description and reference numerals therein are illustrative in nature and not limiting. this invention.

FIG. 3 shows a system block diagram of the power adapter of the present invention applied to a power supply system of a flat panel display. As shown in FIG. 3 , the power adapter 300 is set to provide a low-level output DC voltage Vol to the DC-DC converter 302 for power conversion, and at the same time provide a high-level output DC voltage Vo2 to DC - AC converter 301 for power conversion. Since the DC-AC converter 301 input power is a high-level DC voltage, its voltage conversion ratio can be reduced, so that the power loss generated by the DC-AC converter 301 can be reduced and the conversion efficiency of the DC-AC converter 301 can be reduced. be improved.

A schematic circuit diagram of a preferred embodiment of the power adapter of the present invention is shown in FIG. 4 . As shown in FIG. 4, the power adapter 300 includes a bridge rectifier 401, which is configured to rectify the input AC voltage Vin into a full-wave rectified DC voltage, and a transformer T41, which has a primary side winding Np41, a first secondary side The winding Ns41 and the second secondary side winding Ns42, wherein the primary side winding Np41 is set to store the energy received from the input AC voltage Vin when the main switch S41 connected in series with the primary side winding Np41 is turned on, and when the main switch S41 is turned off , and transmit the stored energy to the first and second secondary side windings Ns41, Ns42. Switching of the main switch S41 is controlled by a pulse width modulator 402 . The power adapter 300 also includes a first rectification filter circuit and a second rectification filter circuit, wherein the first rectification filter circuit is composed of a rectifier diode D41 and a filter capacitor C41 and is coupled to the secondary side winding Ns41, and the second rectification filter circuit The circuit is composed of a rectifier diode D42 and a filter capacitor C42 and is connected across the first and second secondary side windings Ns41 and Ns42. The first rectifying and filtering circuit (D41, C41) is set to rectify and filter the energy received by the first secondary side winding Ns41 to generate the desired low-level output DC voltage Vo1, while the second rectifying and filtering circuit ( D42, C42) are set to rectify and filter the energy received by the first and second secondary windings Ns41 and Ns42 to generate the desired high-level output DC voltage Vo2. The power adapter 300 also includes a feedback control circuit 403, which is configured to detect changes in the output DC voltages Vo1 and Vo2, and send a feedback signal to the pulse width modulator 402 according to the detection result, so as to activate the pulse width modulator 402 to respectively The output DC voltages Vo1 and Vo2 are stabilized at a predetermined value.

As we all know, the voltage value of the output voltage of the power adapter 300 depends on the turn ratio of the transformer. In order for the power adapter 300 to provide a higher level of output DC voltage to the DC-AC converter 301 shown in FIG. 3 for power conversion, it is necessary to add an additional secondary winding on the secondary side of the transformer T41. To be connected in series with the intrinsic secondary side winding of the transformer, and an additional rectification and filtering circuit is added to connect across the secondary side of the transformer T41, so that the transformer turns ratio faced by this additional rectification and filtering circuit is the largest. As shown in FIG. 4, the power adapter 300 according to the present invention adds an additional second secondary winding Ns42, which is connected in series with the inherent first secondary winding Ns41 of the transformer T41, and the power adapter 300 increases A second rectifying and filtering circuit (D42, C42) is provided across the first and second secondary side windings Ns41 and Ns42. The voltage value of the input voltage of the second rectification filter circuit ( D42 , C42 ) will depend on the turns ratio between the first and second secondary side windings Ns41 and Ns42 and the primary side winding Np41 . In this case, the voltage level of the output DC voltage Vo2 provided by the second rectifying and filtering circuit (D42, C42) will be higher than the voltage level of the output DC voltage Vo1 provided by the first rectifying and filtering circuit (D41, C41). To come high.

It should be noted that the circuit structures of the above-mentioned first rectifying and filtering circuit and the second rectifying and filtering circuit are not limited to the types disclosed herein, but can be completed by any other rectifying and filtering components. For example, the rectifier diodes and filter capacitors in the first rectification and filter circuit or the second rectification and filter circuit can be replaced by a power factor correction boost converter (PFC boost converter).

Based on the above, the power adapter of the present invention is set to output low-level DC voltage and high-level DC voltage at the same time, and provide them to DC-DC converter and DC-AC converter respectively for power conversion . In order to allow the power adapter to output low-level DC voltage and high-level DC voltage at the same time, an additional second secondary winding is added on the secondary side of the transformer, which is connected in series with the inherent first secondary winding of the transformer , and an additional rectification and filtering circuit is added, which is connected across the inherent first secondary side winding of the transformer and the additional second secondary side winding, so that the transformer turns ratio faced by the additional rectification and filtering circuit is the largest. Therefore, the additional rectification and filtering circuit can generate an output DC voltage with a voltage level higher than that generated by the inherent rectification and filtering circuit of the power adapter. This high-level output DC voltage is then provided to a DC-AC converter for power conversion. Since the voltage value of the input voltage of the DC-AC converter is greatly increased, the voltage conversion ratio of the DC-AC converter is reduced, thereby greatly reducing the power loss of the DC-AC converter and greatly improving the conversion efficiency of the DC-AC converter .

The application can be modified by a person skilled in the art, without however departing from the scope of protection of the appended claims.

Claims (14)

1. A power adapter for simultaneously converting an input AC voltage into a low-level output DC voltage and a high-level output DC voltage, comprising: switch; a transformer having a primary winding and a first secondary winding and a second secondary winding, wherein the primary winding is in series with the switch and the first secondary winding and the second secondary winding are in series with each other, It is set to store energy in the primary side winding when the switch is turned on, and transfer the energy stored in the primary side winding to the first secondary side winding and the second secondary side winding when the switch is off ; a first rectification and filtering circuit, coupled to the first secondary winding, for rectifying and filtering the energy received by the first secondary winding to generate the low-level output direct current voltage; and The second rectification and filtering circuit is connected across the first secondary winding and the second secondary winding, and is used for rectifying and synchronizing the energy received by the first secondary winding and the second secondary winding. filtering to generate the high level output DC voltage. 2. The power adapter as claimed in claim 1, further comprising a rectifier for rectifying the input AC voltage into a full-wave rectified DC voltage. 3. The power adapter as claimed in claim 2, wherein the rectifier is a bridge rectifier. 4. The power adapter as claimed in claim 1, further comprising a pulse width modulator for controlling switching of the switch. 5. The power adapter according to claim 4, further comprising a feedback control circuit for detecting the change of the low-level output DC voltage and the change of the high-level output DC voltage, and sending feedback according to the detection result signal to the pulse width modulator to activate the pulse width modulator to stabilize the low-level output DC voltage at a predetermined value and stabilize the high-level output DC voltage at a predetermined value. 6. The power adapter as claimed in claim 1, wherein the first rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor. 7. The power adapter as claimed in claim 1, wherein the second rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor. 8. A power supply system comprising: The power adapter is used to simultaneously convert the input AC voltage into a low-level output DC voltage and a high-level output DC voltage. The power adapter includes: switch; and a transformer having a primary winding and a first secondary winding and a second secondary winding, wherein the primary winding is in series with the switch and the first secondary winding and the second secondary winding are in series with each other, It is set to store energy in the primary side winding when the switch is turned on, and transfer the energy stored in the primary side winding to the first secondary side winding and the second secondary side winding when the switch is off ; a first rectification and filtering circuit, coupled to the first secondary winding, for rectifying and filtering the energy received by the first secondary winding to generate the low-level output direct current voltage; and The second rectification and filtering circuit is connected across the first secondary winding and the second secondary winding, and is used for rectifying and synchronizing the energy received by the first secondary winding and the second secondary winding. filtering to generate the high-level output DC voltage; a DC-DC converter, coupled to the power adapter, for receiving the low-level output DC voltage provided by the power adapter and converting it into a DC voltage output; and The DC-AC converter is coupled to the power adapter for receiving the high-level output DC voltage provided by the power adapter and converting it into an AC voltage output. 9. The power supply system as claimed in claim 8, wherein the power adapter further comprises a rectifier for rectifying the input AC voltage into a full-wave rectified DC voltage. 10. The power supply system as claimed in claim 9, wherein the rectifier is a bridge rectifier. 11. The power supply system as claimed in claim 8, wherein the power adapter further comprises a pulse width modulator for controlling switching of the switch. 12. The power supply system as claimed in claim 11, wherein the power adapter further comprises a feedback control circuit for detecting the change of the low-level output DC voltage and the change of the high-level output DC voltage, and according to The detection result sends a feedback signal to the pulse width modulator to start the pulse width modulator to stabilize the low-level output DC voltage at a predetermined value and stabilize the high-level output DC voltage at a predetermined value. 13. The power supply system as claimed in claim 8, wherein the first rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor. 14. The power supply system as claimed in claim 8, wherein the second rectifying and filtering circuit is composed of a rectifying diode and a filtering capacitor.

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