BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to power conversion; in particular, to a power conversion circuit and a simulation current signal generation circuit thereof.

2. Description of the Prior Art

Conventionally, in power converter applications with high voltage-converting ratio (the input voltage VIN/the output voltage VOUT) or high-speed switching, since the on-time (TON) of the first power switch in its output stage is very short, it is very difficult to sense current when the first power switch is turned on.

Currently, different methods can be used to obtain the complete output current waveform, such as error amplifier (EA) sensing method, sample-and-hold sensing method, direct current resistance (DCR) sensing method, etc. However, since the EA sensing method determines the current by sensing the voltage difference across the resistor and the sample-and-hold sensing method alternately switches the first power switch (the upper bridge switch) and the second power switch (the lower bridge switch) of the output stage at high speed, they both fail to obtain the real-time output current waveform, and they are not suitable for power converters with high voltage-converting ratio and very short on-time; although the DCR sensing method can sense the real-time output current waveform, it requires additional components and pins, resulting in a complicated circuit and increased cost.

SUMMARY OF THE INVENTION

Therefore, the invention provides a power conversion circuit and a simulation current signal generation circuit thereof to effectively solve the above-mentioned problems in the prior art.

An embodiment of the invention is a simulation current signal generation circuit applied to a power conversion circuit. In this embodiment, the power conversion circuit has an output terminal and includes an output stage, a pulse-width modulation (PWM) circuit and an impedance component. One terminal of the impedance component is coupled to the output terminal. The simulation current signal generation circuit includes a first current signal circuit, a second current signal circuit and a switching circuit. The first current signal circuit is coupled to the other terminal of the impedance component and configured to provide a first current signal. The second current signal circuit is coupled to the output stage and configured to sense a current of a power switch in the output stage to provide a second current signal. The switching circuit is coupled to the first current signal circuit, the second current signal circuit and the PWM circuit respectively and configured to selectively output the first current signal or the second current signal according to a PWM signal provided by the PWM circuit.

In an embodiment of the invention, the simulation current signal generation circuit further includes an output inductor. The output inductor is coupled between the output stage and the output terminal and matches the impedance component.

In an embodiment of the invention, another power switch of the output stage and the power switch are coupled in series between an input voltage and a ground terminal and controlled by a switch control signal related to the PWM signal to be turned on alternately.

In an embodiment of the invention, when the power switch is turned on, the switching circuit outputs the second current signal; when the another power switch is turned on, the switching circuit outputs the first current signal.

In an embodiment of the invention, the first current signal circuit includes a voltage follower and a current mirror circuit and is configured to generate the first current signal with current-type to the switching circuit according to an input voltage and an output voltage of the output terminal.

In an embodiment of the invention, the first current signal circuit includes a voltage follower and is configured to generate the first current signal with voltage-type to the switching circuit according to an input voltage and an output voltage of the output terminal.

Another embodiment of the invention is a power conversion circuit. In this embodiment, the power conversion circuit has an output terminal. The power conversion circuit includes an output stage, a PWM circuit, an impedance component and a simulation current signal generation circuit. One terminal of the impedance component is coupled to the output terminal. The simulation current signal generation circuit includes a first current signal circuit, a second current signal circuit and a switching circuit. The first current signal circuit is coupled to the other terminal of the impedance component and configured to provide a first current signal. The second current signal circuit is coupled to the output stage and configured to sense a current of a power switch in the output stage to provide a second current signal. The switching circuit is coupled to the first current signal circuit, the second current signal circuit and the PWM circuit respectively and configured to selectively output the first current signal or the second current signal according to a PWM signal provided by the PWM circuit.

Compared to the prior art, the power conversion circuit of the invention selects an impedance component matching the output inductance and connects it in series between the output terminal and the simulation current signal generation circuit. The output current (the inductor current) when one of the power switches (such as the upper bridge switch in the buck power converter) in the output stage is turned on can be simulated according to the difference between the input voltage and the output voltage, and it can be combined with the sense current when the other power switch (such as the lower bridge switch in the buck power converter) in the output stage is turned on to output a complete output current (the inductor current) waveform. There is no disadvantage that the real-time output current waveform cannot be obtained when switching at high speed alternately, and no additional components and pins are required, which can reduce circuit complexity and cost.

The advantage and spirit of the invention may be understood by the following detailed descriptions together with the appended drawings.

