CN108809070B

CN108809070B - Power conversion device, slow start circuit and power control chip

Info

Publication number: CN108809070B
Application number: CN201710281300.5A
Authority: CN
Inventors: 何峻徹; 陈曜洲; 李一惟
Original assignee: Richtek Technology Corp
Current assignee: Richtek Technology Corp
Priority date: 2017-04-26
Filing date: 2017-04-26
Publication date: 2020-05-01
Anticipated expiration: 2037-04-26
Also published as: CN108809070A

Abstract

A power conversion device, a slow start circuit and a power control chip are provided, wherein the power conversion device comprises: the voltage conversion circuit is provided with a first side and a second side, the first side receives a rectified voltage to generate an output voltage on the second side, and the first side is provided with a first side switch; the switch control circuit is provided with a starting state and a normal working state and provides a control signal to the control end of the first side switch; the starting circuit provides current to the control end when the switch control circuit is in a starting state so as to lead the first side switch to be at least partially conducted; and a slow start circuit, when the switch control circuit is in the start state and the level of the output voltage does not reach a predetermined level within a first predetermined time, the slow start circuit reduces the total amount of current provided to the control terminal within a second predetermined time after the first predetermined time.

Description

Power conversion device, slow start circuit and power control chip

Technical Field

The present invention relates to a power conversion device, and more particularly, to a power conversion device having a slow start circuit for preventing problems caused by short circuit at the output terminal in the start state.

Background

Fig. 1 shows a prior art power conversion apparatus 10, which includes a voltage conversion circuit 11, and a switch control circuit 12 and a start-up circuit for controlling the voltage conversion circuit 11, wherein the start-up circuit includes a resistor R and a start-up control circuit 13. The voltage converting circuit 11 includes a transformer having a first side and a second side, the first side receives a rectified voltage Vin to generate an output voltage Vo at the second side, and the voltage converting circuit 11 includes a first side switch M (having a control terminal G) at the first side for controlling the current conduction at the first side. Referring to fig. 2, when the power conversion apparatus 10 is started, the switch control circuit 12 is still in the start state and has not yet entered the normal operation state, so that it is not yet able to generate the correct control signal to control the first side switch M. Therefore, the power conversion device 10 provides the control terminal G with the charge (the start current Is) through the resistor R in the start circuit, and the charge Is accumulated to make the first side switch M in the partially conducting state. The start control circuit 13 detects the first side current Ip to periodically discharge the charges accumulated in the control terminal G, thereby generating a repeated start voltage waveform between the peak level and the valley level. When the voltage converting circuit 11 is started and the secondary side voltage Vo of the voltage converting circuit 11 reaches a threshold, the whole circuit enters a normal working state, and the switch control circuit 12 controls the first side switch M. However, the load coupled to the secondary-side voltage Vo may be damaged or short-circuited due to environmental factors, so that the secondary-side voltage Vo may not reach the threshold continuously. The secondary side voltage Vo continuously fails to reach the threshold value, which causes the start control circuit 13 to control the first side switch M to be continuously in a partial conducting state. When the first side switch M is in a partially conducting state, its on-resistance is high, and if the first side switch M is continuously in this state, a high temperature is generated, which may damage the circuit.

It is therefore important to provide adequate protection during the start-up phase.

Disclosure of Invention

The present invention is directed to overcome the disadvantages and drawbacks of the prior art, and provides a power conversion device, a slow start circuit and a power control chip, which can provide proper protection measures during a start-up phase.

To achieve the above object, in one aspect, the present invention provides a power conversion apparatus, including: a voltage conversion circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch to control a current conduction state through the first side; the switch control circuit is provided with a starting state and a normal working state and provides a control signal to the control end of the first side switch so as to control the conducting state of the first side switch in the normal working state; a starting circuit, when the switch control circuit is in a starting state, providing current to the control end to make the first side switch at least partially conducted; and a slow start circuit, when the switch control circuit is in the start state, adjusting the control signal, wherein when the switch control circuit is in the start state and the level of the output voltage does not reach a predetermined level within a first predetermined time, the slow start circuit reduces the total amount of current provided to the control terminal within a second predetermined time after the first predetermined time.

In one embodiment, the slow start circuit does not decrease the total amount of current supplied to the control terminal within a third predetermined time after the second predetermined time.

In one embodiment, when the switch control circuit is in the active state, the active circuit enables the control signal to have a plurality of repeated active voltage waveforms between a peak level and a valley level, and the slow start circuit reduces the total amount of current supplied to the control terminal within the second predetermined time after the first predetermined time by one or more of: the slow start circuit prolongs the time for each start voltage waveform to reach the peak level within the second preset time; the slow start circuit reduces the frequency of the start voltage waveforms reaching the peak level within the second predetermined time; or the slow start circuit prolongs the time of staying at the valley level within the second predetermined time.

In one embodiment, the slow start circuit comprises: at least one current bleeder circuit, coupled between the control end of the first side switch and the ground; and a control unit for controlling the conduction state of the at least one current bleeder circuit, when the switch control circuit is in the start state and the level of the output voltage does not reach the predetermined level within the first predetermined time, the control signal has a plurality of repeated start voltage waveforms between a peak level and a valley level, and the control unit conducts the at least one current bleeder circuit within the second predetermined time to prolong the time that each of the start voltage waveforms reaches the peak level within the second predetermined time. In one embodiment, the control signal has a first start voltage waveform that reaches a peak level, and the slow start circuit starts timing for a first predetermined time from when the first start voltage waveform reaches the peak level, wherein the slow start circuit starts decreasing the total amount of current of the control signal for a second predetermined time when the level of the output voltage does not reach a predetermined level within the first predetermined time.

In one embodiment, each of the current leakage circuits includes a current switch and a current source connected in series, and the current switch and the current source are coupled between the control terminal of the first side switch and ground, wherein when the current switch is in a conducting state, the current source is conducted between the control terminal of the first side switch and ground to reduce the total amount of current of the control signal in the second predetermined time.

In one embodiment, the slow start circuit includes a plurality of the current bleeding circuits, and when the switch control circuit is in the start state and the level of the output voltage does not reach the predetermined level within the first predetermined time, the control unit gradually increases the number of the current bleeding circuits within the second predetermined time to reduce the total amount of current of the control signal within the second predetermined time.

In one embodiment, after the control unit turns on the current bleeding circuits for more than the second predetermined time, the control unit turns off the current bleeding circuits to re-determine whether the level of the output voltage reaches the predetermined level within a third predetermined time after the second predetermined time.

In one embodiment, when the level of the output voltage reaches the predetermined level, a Power on reset (Power on reset) signal is generated, wherein the switch control circuit switches from the active state to the normal operating state according to the Power on reset signal.

In one embodiment, the slow start circuit stops adjusting the control signal according to the electrical reset signal.

In one embodiment, the enable circuit enables the control signal to have a plurality of repeated enable voltage waveforms between a peak level and a valley level when the switch control circuit is in the enable state, and wherein the enable circuit comprises: a resistor coupled between the rectified voltage and the control terminal of the first side switch; a grounding switch coupled between the control end of the first side switch and the ground; and a pulse generator for intermittently generating a pulse to turn on the grounding switch.

In one embodiment, the slow start circuit is coupled between the pulse generator and the ground switch for prolonging the time duration of the pulse, wherein when the switch control circuit is in the start state and the slow start circuit receives the pulse, the slow start circuit prolongs the turn-on time of the ground switch to prolong the time of staying at the valley level within the second predetermined time.

In one embodiment, the power conversion apparatus further includes a power supply circuit coupled between the control terminals of the first side switches for providing power to the start circuit and the slow start circuit.

To achieve the above object, from one aspect, the present invention provides a slow start circuit for controlling a voltage converting circuit, the voltage converting circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch, wherein the voltage converting circuit includes a switch control circuit and a start circuit, the switch control circuit having a start state and a normal operation state, the switch control circuit providing a control signal to a control terminal of the first side switch in the normal operation state, the start circuit providing a current to the control terminal when the switch control circuit is in the start state to make the first side switch at least partially conductive, the slow start circuit comprising: at least one current bleeder circuit, coupled between the control end of the first side switch and the ground; and a control unit for controlling the conduction state of the at least one current leakage circuit, wherein when the switch control circuit is in the starting state and the level of the output voltage does not reach a predetermined level within a first predetermined time, the control unit conducts the at least one current leakage circuit within a second predetermined time after the first predetermined time so as to reduce the total amount of current provided to the control terminal.

In one embodiment, when the level of the output voltage reaches the predetermined level, an electrical reset signal is generated, and the slow start circuit stops reducing the total amount of current provided to the control terminal according to the electrical reset signal.

In one embodiment, after the control unit turns on the current bleeding circuits for more than the second predetermined time, the control unit does not turn on the current bleeding circuits, and re-determines whether the level of the output voltage reaches the predetermined level within a third predetermined time after the second predetermined time.

To achieve the above objective and in one aspect, the present invention provides a power control chip for controlling a voltage converting circuit, the voltage converting circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch, a control terminal of the first side switch receiving a start current from the rectified voltage, the power control chip having a start state and a normal operating state, the power control chip comprising: the switch control circuit provides a control signal to the control end of the first side switch in the normal working state; a start-up control circuit comprising: a grounding switch coupled between the control end of the first side switch and the ground; and a pulse generator for generating a pulse for conducting the control terminal of the first side switch to ground according to a comparison result of the current passing through the first side and a reference value in the start state, so that the control terminal of the first side switch has a plurality of repeated start voltage waveforms between a peak level and a valley level; and a slow start circuit, coupled between the pulse generator and the grounding switch, for prolonging the time that the start voltage waveform stays at the valley level according to the pulse within a second predetermined time after a first predetermined time when the level of the output voltage does not reach a predetermined level within the first predetermined time in the start state.

Drawings

FIG. 1 shows a schematic diagram of a power conversion device according to the prior art;

FIG. 2 is a diagram illustrating control signals according to the prior art;

FIG. 3 is a schematic diagram of a power conversion apparatus according to an embodiment of the invention;

FIG. 4 is a schematic diagram showing the control signals of the present invention when the normal start is not possible and when the normal start is possible;

FIG. 5 is a schematic diagram of control signals according to an embodiment of the invention;

FIG. 6 shows a schematic diagram of a slow start circuit according to an embodiment of the invention;

FIG. 7 is a schematic diagram of control signals according to an embodiment of the invention;

FIG. 8 is a schematic diagram of a start-up control circuit according to an embodiment of the invention;

FIG. 9 is a schematic diagram of a start-up control circuit and a slow start-up circuit according to an embodiment of the invention;

FIGS. 10, 11, and 12 are schematic diagrams illustrating control signals according to various embodiments of the present invention;

FIG. 13 is a schematic diagram of a power conversion device according to an embodiment of the invention;

FIG. 14 is a schematic diagram of a power supply circuit according to an embodiment of the invention.

Description of the symbols in the drawings

10. 20, 30, 40 power supply conversion device

11 voltage conversion circuit

12 switch control circuit

13 start control circuit

131 ground switch

132 pulse generator

14 slow start circuit

141 current bleeder circuit

1411 Current Source

1412 current switch

142 control unit

15 supply circuit

G control terminal

Ip first side current

Is starting current

M first side switch

R, R1 resistor

T1, T2, T3, T4, T1, T2, T3 times

Vdd1, Vdd2 power supplies

Vin rectified voltage

Vo output voltage

Vref reference value

Detailed Description

The foregoing and other aspects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment, as illustrated in the accompanying drawings. Directional terms as referred to in the following examples, for example: up, down, left, right, front or rear, etc., are referred to only in the direction of the attached drawings. The drawings are schematic and are intended to show functional relationships between devices and elements, and the shapes, thicknesses and widths are not drawn to scale.

Referring to fig. 3, a power conversion apparatus 20 according to an embodiment of the invention is shown. The power conversion device 20 includes: a voltage conversion circuit 11 having a first side and a second side, the first side receiving a rectified voltage Vin to generate an output voltage Vo at the second side, the first side having a first side switch M for controlling a conducting state of a first side current Ip passing through the first side; a switch control circuit 12 having a start state and a normal operation state, the switch control circuit 12 providing a control signal to the control terminal G of the first side switch M to control the conducting state of the first side switch M in the normal operation state; a start circuit (including a resistor R and a start control circuit 13) for providing current to the control terminal G when the switch control circuit 12 is in a start state, so as to turn on the first side switch M at least partially; and a slow start circuit 14, which adjusts the control signal when the switch control circuit 12 is in the on state, wherein when the switch control circuit 12 is in the on state and the level of the output voltage Vo does not reach a predetermined level within a first predetermined time, the slow start circuit 14 reduces the total amount of current provided to the control terminal within a second predetermined time (fig. 4, 5, 7, 10-12) after the first predetermined time.

FIG. 4 is a schematic diagram showing the control signals of the present invention when the normal start is not possible and the normal start is possible. Referring to fig. 3 and 4, when the switch control circuit 12 is in the active state, the control signal is generated by the active control circuit 13, and the control signal has a plurality of repeated active voltage waveforms between a peak level and a valley level. When the switch control circuit 12 is in a normal operation state, the control signal is generated by the switch control circuit 12. When the switch control circuit 12 is in the active state (i.e. the power conversion device 20 is in the active state) for a first predetermined time and still fails to start normally, the slow start circuit 14 reduces the total amount of current supplied to the control terminal within a second predetermined time after the first predetermined time. Fig. 4 illustrates one of the ways of "reducing the total amount of current supplied to the control terminal", but the present invention is not limited thereto, and other ways will be illustrated hereinafter. On the other hand, when the power conversion apparatus 20 is normally started within the first predetermined time, the switch control circuit 12 enters a normal operation state, and the control signal is generated by the switch control circuit 12.

Whether the power conversion device 20 is normally activated can be determined according to the level of the output voltage Vo in one embodiment. When the level of the output voltage Vo reaches the predetermined level, which represents that the power conversion device 20 is normally activated, the switch control circuit 12 switches from the activated state to the normal operating state, and starts to generate the control signal to the control terminal G. After the normal working state is switched, the start-up control circuit 13 and the slow start-up circuit 14 can be both closed (disabled); for example, the slow start circuit 14 may stop decreasing the total amount of current of the control signal, and the start control circuit 13 may stop discharging the charges accumulated at the control terminal G.

The level of the output voltage Vo reaches a predetermined level, and the determination method can be determined as required. For example, normally, when the Power conversion apparatus 20 is started, an electrical reset (Power on reset) signal is generated inside or outside the Power conversion apparatus, and the Power conversion apparatus can be switched to a normal operation state according to the electrical reset (Power on reset) signal. Alternatively, the output voltage Vo may be sensed by a voltage sensing circuit, and when the sensed output voltage Vo reaches a predetermined level, the switch control circuit 12 is switched from the on state to the normal operating state to start generating the control signal to the control terminal G. The electrical reset signal shown in fig. 3 is only an example, and as mentioned above, other methods may be used to determine whether the output voltage Vo reaches the predetermined level.

According to the present invention, when the power conversion device 20 or the switch control circuit 12 still fails to start normally after the first predetermined time is reached, the total amount of current supplied to the control terminal G is reduced. The total amount of current supplied to the control terminal G is reduced, which means that the integral conduction time and the conduction degree of the first side switch M are reduced, and the heat generation of the first side switch M can be reduced. Referring to fig. 5, the total amount of current supplied to the control terminal G is reduced by, for example, extending the time for the level of the start voltage waveform to reach the peak level from the valley level (the slope of the start voltage waveform after extension is lower, and the time T2 is longer than the time T1). Since time T2 is longer than time T1, the frequency of the startup voltage waveform drops. In other words, the embodiment of fig. 5 shows: the total amount of current supplied to the control terminal G may be reduced by increasing the time for each start voltage waveform to reach the peak level, or by reducing the frequency at which the start voltage waveform reaches the peak level, or by both, within the second predetermined time.

In addition to the manner of the embodiment shown in fig. 5, in another embodiment, the slow start circuit 14 may extend the time between the previous start waveform and the next start waveform to stay at the valley level within the second predetermined time, which will be described later.

FIG. 6 shows an embodiment of the present invention, in which the slow start circuit 14 includes: at least one current leakage circuit 141 coupled between the control terminal G of the first side switch M and ground; and a control unit 142 for controlling the conducting state of the current bleeding circuit 141. The control unit 142 may calculate the first predetermined time in any manner, such as but not limited to, according to an internal timer, or according to the number of times the start waveform reaches the peak level, or according to the number of times the first side current Ip reaches a current reference value, etc. After the first predetermined time, the control unit 142 turns on the at least one current bleeding circuit 141.

When the current bleeder circuit 141 conducts the control terminal G to ground, a portion of the start-up current Is provided to the control terminal G through the resistor R Is conducted to ground through the current bleeder circuit 141. As the number of current bleeding circuits 141 that are turned on increases, the proportion of the inrush current Is that Is conducted to ground through the current bleeding circuits 141 increases. In this embodiment, the slow start circuit 14 can control the number of the conducting current bleeding circuits 141 to prolong the time for each start voltage waveform to reach the peak level. Referring to fig. 5 and 7 for the second predetermined time portion, when the number of the turned-on current bleeder circuits 141 is small (or the current passing through the current source 1411 is low), the time for each start-up voltage waveform to reach the peak level is short, i.e., the slope of the start-up voltage waveform is high. When the number of the current bleeder circuits 141 that are turned on is large (or the current through the current source 1411 is high), the time for each start-up voltage waveform to reach the peak level is long, i.e., the slope of the start-up voltage waveform is low. Thus, by controlling the current bleeding circuit 141, the total amount of current supplied to the control terminal G can be reduced in the second predetermined time.

The current bleeding circuit 141 can be designed according to the aforementioned operation characteristics, and fig. 6 shows only one embodiment thereof. According to fig. 6, each current draining circuit 141 includes a current switch 1412 and a current source 1411 connected in series, and the current switch 1412 and the current source 1411 are coupled between the control terminal G of the first side switch M and ground. When the current switch 1412 is in the conducting state, the current source 1411 is conducted between the control terminal G of the first side switch M and the ground to reduce the total amount of current supplied to the control terminal G within the second predetermined time. According to the present invention, the slow-start circuit 14 may include only a single current bleeder circuit 141, or may include a plurality of current bleeder circuits 141, and the current bleeder circuit 141 may also be in other forms (e.g., including a variable current source, etc.), and is not limited to the embodiment of fig. 6.

Referring to fig. 7, in an embodiment, the slow-start circuit 14 includes a plurality of current bleeder circuits 141, and when the switch control circuit 12 is in the start state and the output voltage Vo does not reach the predetermined level within the first predetermined time, the control unit 142 gradually turns on the plurality of current bleeder circuits 141 within the second predetermined time to gradually increase the total amount of current decreased within the second predetermined time (fig. 7, time T1< T2< T3< T4). In addition, the number of the on-current draining circuits 141 may be determined according to other determination factors, for example, when the operating temperature of the first side switch M is higher, the number of the on-current draining circuits 141 is increased, and when the operating temperature of the first side switch M is lower, the number of the on-current draining circuits 141 is decreased.

When the control unit 142 turns on the plurality of current bleeding circuits 141 for more than the second predetermined time and the level of the output voltage Vo does not reach the predetermined level within the second predetermined time, the control unit 142 may turn off all or a portion of the current bleeding circuits 141 within a third predetermined time after the second predetermined time, or turn off the current bleeding circuits 141 one by one, to re-determine whether the level of the output voltage Vo reaches the predetermined level within the third predetermined time. Fig. 7 shows all or the current bleeder circuits 141 turned off for a third predetermined time, so that the time from the valley level to the peak level is restored to T1, but may be progressively restored to T3 from T4, to T2, to T1, or other arrangements. As with the first predetermined time, the control unit 142 may calculate the second predetermined time in any manner.

When the output voltage Vo reaches the predetermined level within the third predetermined time, the slow start circuit 14 stops controlling the total amount of current of the control terminal G, and the switch control circuit controls the control terminal G. When the level of the output voltage Vo does not reach the predetermined level within the third predetermined time, the start circuit and the slow start circuit 14 can continue to control the total amount of current provided to the control terminal. In addition, after the third predetermined time, if the output voltage Vo still does not reach the predetermined level, the arrangement manner similar to the second predetermined time can be returned again.

Referring to fig. 8, in an embodiment, the start-up control circuit 13 includes: a ground switch 131 coupled between the control end G of the first side switch M and ground; and a pulse generator 132 for intermittently generating a pulse to turn on the grounding switch 131. In one embodiment, the pulse generator 132 intermittently generates pulses, for example, by: determining whether to turn on the grounding switch 131 according to the comparison result between the first side current Ip and a reference value Vref (in an embodiment, according to the comparison between the voltage difference of the current Ip passing through the resistor R1 and the reference value Vref); thus, the control signal has a plurality of repeated start voltage waveforms between a peak level and ground.

Fig. 9 shows a power conversion apparatus 30 according to another embodiment of the invention, in which a slow start circuit 14 is coupled between a pulse generator 312 and a ground switch 131 for prolonging the duration of a pulse. When the switch control circuit 12 is in the start state and the slow start circuit 14 receives the pulse, the slow start circuit 14 extends the on-time of the ground switch to extend the valley level time from the previous start voltage waveform to the next start voltage waveform within the second predetermined time; the increased valley level time may be fixed or incremented during the second predetermined time (fig. 10, 0< t1< t 2). The slow start circuit 14 of fig. 9 and 10 reduces the amount of current supplied to the control terminal G by directly coupling the control terminal G to ground. Although the slow start circuit 14 in fig. 9 and 10 is different from the slow start circuit 14 in fig. 6 in that the current source 1411 is disposed between the control terminal of the first side switch and the ground, both embodiments have the effect of reducing the total amount of current supplied to the control terminal G. Further, the two embodiments can be combined to enhance the effect of reducing the total amount of current provided to the control terminal G, and the generated control signal, see fig. 11, has the effect of reducing the slope of the start waveform and prolonging the valley level time. For example, the slow start circuit 14 may generate a rising edge according to the rising edge of the output pulse of the pulse generator 312, but delay the falling edge of the output pulse of the pulse generator 312 may extend the time length of the pulse.

Fig. 12 shows an embodiment of the present invention, in which the slow-start circuit 14 of fig. 9 extends the grounding time between start waveforms, and after a second predetermined time is exceeded, the slow-start circuit 14 may restore the original time length of the pulse (may immediately restore the pulse shown in fig. 12, or gradually restore from t2 to t1 and then restore to close to 0), so as to re-determine whether the output voltage Vo reaches the predetermined level within a third predetermined time after the second predetermined time.

Similar to the previous embodiment, the valley level time does not have to be gradually increased or gradually decreased, and may be arranged as follows: when the operation temperature of the first side switch M is higher, the valley level time is increased, and when the operation temperature of the first side switch M is lower, the valley level time is decreased.

Fig. 13 shows a power conversion apparatus 40 according to another embodiment of the invention, which includes a switch control circuit 12, a start-up control circuit 13, a slow start-up circuit 14, and a power supply circuit 15. This embodiment also additionally shows that the resistor R can be equivalently connected at the position of the icon. The power supply circuit 15 is coupled to the control terminal G of the first side switch M to provide power (Vdd1, Vdd2, wherein Vdd1 and Vdd2 may be the same or different) for the start-up control circuit 13 and the slow start circuit 14. Since the start control circuit 13 and the slow start circuit 14 operate when the output voltage Vo does not reach the predetermined level, the power source thereof needs to be other than the output voltage Vo. FIG. 14 shows a power supply circuit 15 according to one embodiment, which includes a capacitor for providing power Vdd1 and Vdd2 to the slow start circuit 14 and the start control circuit 13. If the power supply required by the start-up control circuit 13 is different from that of the slow start-up circuit 14, a voltage divider circuit can be used to generate different voltages.

In one embodiment, the switch control circuit 12, the start control circuit 13 and the slow start circuit 14 can be fabricated in a single integrated circuit or integrated in the same power control chip.

The present invention has been described in terms of the preferred embodiments, and the above description is only for the purpose of making the content of the present invention easy to understand for those skilled in the art, and is not intended to limit the scope of the present invention. Those skilled in the art will recognize a variety of equivalent variations that are within the spirit of the invention. In each embodiment, the two circuits or elements directly connected to the icon may be inserted with other circuits or elements that do not affect the main function, and only the meaning of the relevant circuit or signal needs to be modified correspondingly. These and other equivalent variations are intended to be encompassed by the present invention, as these teachings are followed. The above embodiments are not limited to be used alone, but can also be used in combination, for example, but not limited to, the two embodiments are used together, or a local circuit of one embodiment is used to replace a corresponding circuit of the other embodiment.

Claims

1. A power conversion device, comprising:

a voltage conversion circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch to control a current conduction state through the first side;

the switch control circuit is provided with a starting state and a normal working state and provides a control signal to the control end of the first side switch so as to control the conducting state of the first side switch in the normal working state;

a starting circuit, when the switch control circuit is in a starting state, providing current to the control end to make the first side switch at least partially conducted; and

and the slow start circuit adjusts the control signal when the switch control circuit is in a start state, wherein when the switch control circuit is in the start state and the level of the output voltage does not reach a predetermined level within a first predetermined time, the slow start circuit reduces the total amount of current provided for the control end within a second predetermined time after the first predetermined time.

2. The power conversion device of claim 1, wherein the slow start circuit does not reduce the total amount of current supplied to the control terminal for a third predetermined time after the second predetermined time.

3. The power conversion device of claim 1, wherein when the switch control circuit is in the active state, the enable circuit enables the control signal to have a plurality of repeated enable voltage waveforms between a peak level and a valley level, and the slow start circuit reduces the total amount of current provided to the control terminal within the second predetermined time after the first predetermined time by one or more of: the slow start circuit prolongs the time for each start voltage waveform to reach the peak level within the second preset time; the slow start circuit reduces the frequency of the start voltage waveform reaching the peak level within the second predetermined time; or the slow start circuit prolongs the time of staying at the valley level within the second predetermined time.

4. The power conversion device of claim 1, wherein the slow start circuit comprises:

at least one current bleeder circuit, coupled between the control end of the first side switch and the ground; and

the control unit is used for controlling the conducting state of the at least one current bleeder circuit, when the switch control circuit is in the starting state and the level of the output voltage does not reach the predetermined level within the first predetermined time, the control signal has a plurality of repeated starting voltage waveforms between a peak level and a valley level, and the control unit conducts the at least one current bleeder circuit within the second predetermined time so as to prolong the time for each starting voltage waveform to reach the peak level within the second predetermined time.

5. The power conversion device of claim 4, wherein each of the current leakage circuits comprises a current switch and a current source connected in series, the current switch and the current source being coupled between the control terminal of the first side switch and ground, wherein when the current switch is turned on, the current source is turned on between the control terminal of the first side switch and ground to reduce the total amount of current of the control signal within the second predetermined time.

6. The power conversion device of claim 4, wherein the slow start circuit comprises a plurality of current bleeding circuits, and when the switch control circuit is in the start state and the level of the output voltage does not reach the predetermined level within the first predetermined time, the control unit gradually increases the number of the current bleeding circuits during the second predetermined time to reduce the total amount of current of the control signal during the second predetermined time.

7. The power conversion device of claim 6, wherein when the control unit turns on the current-bleeding circuit for more than the second predetermined time, the control unit turns off the current-bleeding circuit to re-determine whether the level of the output voltage reaches the predetermined level within a third predetermined time after the second predetermined time.

8. The power conversion device of claim 1, wherein when the level of the output voltage reaches the predetermined level, an electrical reset signal is generated, and wherein the switch control circuit switches from the activated state to the normal operation state according to the electrical reset signal.

9. The power conversion device of claim 8, wherein the slow start circuit stops adjusting the control signal according to the electrical reset signal.

10. The power conversion device of claim 1, wherein the enable circuit causes the control signal to have a plurality of repeated enable voltage waveforms between a peak level and a valley level when the switch control circuit is in the enable state, and wherein the enable circuit comprises:

a resistor coupled between the rectified voltage and the control terminal of the first side switch;

a grounding switch coupled between the control end of the first side switch and the ground; and

a pulse generator for intermittently generating a pulse to turn on the grounding switch.

11. The power conversion device of claim 10, wherein the slow start circuit is coupled between the pulse generator and the ground switch for prolonging the duration of the pulse, wherein when the switch control circuit is in the start state and the slow start circuit receives the pulse, the slow start circuit prolongs the on-time of the ground switch for prolonging the time staying at the valley level within the second predetermined time.

12. The power conversion device of claim 1, further comprising a power supply circuit coupled to the control terminal of the first side switch for providing power to the start-up circuit and the slow start-up circuit.

13. A slow start circuit for controlling a voltage converting circuit, the voltage converting circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch, wherein the voltage converting circuit includes a switch control circuit and a start circuit, the switch control circuit having a start state and a normal operating state, the switch control circuit providing a control signal to a control terminal of the first side switch when in the normal operating state, the start circuit providing a current to the control terminal when the switch control circuit is in the start state to turn on the first side switch at least partially, the slow start circuit comprising:

and the control unit is used for controlling the conducting state of the at least one current leakage circuit, wherein when the switch control circuit is in the starting state and the level of the output voltage does not reach a predetermined level within a first predetermined time, the control unit conducts the at least one current leakage circuit within a second predetermined time after the first predetermined time so as to reduce the total amount of current provided for the control end.

14. The slow start circuit of claim 13, wherein the slow start circuit does not reduce the total amount of current supplied to the control terminal for a third predetermined time after the second predetermined time.

15. The slow start circuit of claim 13, wherein when the level of the output voltage reaches the predetermined level, a reset signal is generated, and the slow start circuit stops decreasing the amount of current supplied to the control terminal according to the reset signal.

16. The slow-start circuit of claim 13, wherein the slow-start circuit comprises a plurality of current-bleeding circuits, and when the switch control circuit is in the start state and the level of the output voltage does not reach the predetermined level within the first predetermined time, the control unit gradually turns on the number of the current-bleeding circuits within the second predetermined time to reduce the total amount of current of the control signal within the second predetermined time.

17. The slow start circuit of claim 13, wherein the control unit does not turn on the current bleeding circuit after the control unit turns on the current bleeding circuit for more than the second predetermined time, and re-determines whether the level of the output voltage reaches the predetermined level within a third predetermined time after the second predetermined time.

18. A power control chip for controlling a voltage conversion circuit, the voltage conversion circuit having a first side and a second side, the first side receiving a rectified voltage to generate an output voltage at the second side, the first side having a first side switch, a control terminal of the first side switch receiving a start current from the rectified voltage, the power control chip having a start state and a normal operation state, the power control chip comprising:

the switch control circuit provides a control signal to the control end of the first side switch in the normal working state;

a start-up control circuit comprising:

a pulse generator for generating a pulse for conducting the control terminal of the first side switch to ground according to a comparison result of the current passing through the first side and a reference value in the start state, so that the control terminal of the first side switch has a plurality of repeated start voltage waveforms between a peak level and a valley level; and

and the slow starting circuit is coupled between the pulse generator and the grounding switch and used for prolonging the time that the starting voltage waveform stays at the valley level according to the pulse within a second preset time after a first preset time when the level of the output voltage does not reach a preset level within the starting state and the first preset time.