Detection circuit to detect input voltage of transformer and detecting method for the same
A circuit and a method for detecting a voltage of a transformer are provided. The circuit includes a current output circuit coupled to a winding of a transformer to generate a current signal. A current-to-voltage circuit is coupled to the current output circuit to generate a voltage signal in response to the current signal. A sample-and-hold circuit generates an output signal by sampling the voltage signal. An input voltage is applied to the transformer. The output signal is correlated to the input voltage of the transformer.
1. A voltage detection circuit, adaptive to detecting an input voltage being applied to a transformer, the voltage detection circuit comprising:
a current output circuit, coupled to an auxiliary winding of the transformer, to generate a current signal;
a current-to-voltage circuit, coupled to the current output circuit, to generate a voltage signal in response to the current signal; and
a sample-and-hold circuit, coupled to the current-to-voltage circuit, to generate an output signal in response to the voltage signal,
wherein when the input voltage is applied to the transformer, the output signal is correlated to the input voltage applied to the transformer, wherein the current output circuit is coupled to the auxiliary winding of the transformer through a resistor.
2. The voltage detection circuit as claimed in claim 1 , further comprising a pulse generator coupled to the sample-and-hold circuit to provide a pulse signal for the sample-and-hold circuit in response to the switching of the transformer.
3. The voltage detection circuit as claimed in claim 1 , further comprising a bias circuit coupled to the current output circuit to provide a bias voltage to the current output circuit.
4. A method for detecting an input voltage being applied to a transformer, the method comprising:
generating a bias voltage in response to a constant current source to generate a current signal;
generating the current signal in response to the input voltage being applied to the transformer by coupling a current output circuit to an auxiliary winding of the transformer;
generating a voltage signal in response to the current signal; and
generating an output signal in response to the voltage signal and a switching signal, wherein the output signal is used to indicate the switching of the transformer and is correlated to the input voltage applied to the transformer.
5. The method as claimed in claim 4 , further comprising generating a pulse signal to start to sampling and holding the voltage signal in order to generating the output signal in response to the switching signal.
6. The method as claimed in claim 4 , further comprising generating a drive signal in response to the switching signal to switch the transformer.
7. A power converter, comprising a transformer and a control circuit, wherein the control circuit comprises a voltage detection circuit, adaptive to detecting an input voltage being applied to the transformer, wherein the voltage detection circuit comprising:
a current output circuit, coupled to an auxiliary winding of the transformer, to generate a current signal;
a current-to-voltage circuit, coupled to the current output circuit, to generate a voltage signal in response to the current signal; and
a sample-and-hold circuit, coupled to the current-to-voltage circuit, to generate an output signal in response to the voltage signal,
wherein when the input voltage is applied to the transformer, the output signal is correlated to the input voltage applied to the transformer, wherein the current output circuit is coupled to the auxiliary winding of the transformer through a resistor.
8. A method for detecting an input voltage being applied to a transformer, the method comprising:
generating a bias voltage in response to a constant current source to generate a current signal;
generating the current signal in response to the input voltage being applied to the transformer by coupling a current output circuit to an auxiliary winding of the transformer;
generating an output signal in response to the current signal and a switching signal, wherein the output signal is used to indicate the switching of the transformer and is correlated to the input voltage applied to the transformer.
9. The method as claimed in claim 8 , further comprising generating a pulse signal to generate the output signal in response to the switching signal.
10. The method as claimed in claim 8 , further comprising generating a drive signal in response to the switching signal to switch the transformer.