Power converter output voltage clamp and supply terminal
A secondary control circuit includes a voltage regulator circuit coupled to an output of the power converter to provide a regulated power supply. One or more switched loads are coupled between a first terminal and an output ground terminal. The first terminal is coupled to the output of the power converter. Each switched load is coupled to draw a respective current from a load current to clamp the output of a power converter. One or more comparator circuits are coupled to a second terminal. The second terminal is coupled to receive an output sense signal. Each comparator circuit is coupled to receive a reference signal that is a scaled representation of a first reference signal. Each switched load is switched in response to a respective comparator circuit to draw a respective current from the load current of the power converter to clamp the output of the power converter.
1. A secondary control circuit for use in a power converter, comprising:
a voltage regulator circuit to be coupled to an output of the power converter coupled to provide power to an output load coupled to the output of the power converter, the voltage regulator circuit coupled to provide a regulated power supply of the secondary control circuit;
one or more switched loads coupled between a first terminal and an output ground terminal of the power converter, wherein the first terminal is to be coupled to the output of the power converter, wherein each one of the one or more switched loads is coupled to draw a respective current from a load current to clamp the output of a power converter; and
one or more comparator circuits coupled to a second terminal, the second terminal coupled to receive an output sense signal representative of an output of the power converter, wherein each one of the one or more comparator circuits is coupled to receive a respective one of one or more reference signals, wherein each respective one of the one or more reference signals is a scaled representation of a first one of the one or more reference signals, and wherein each one of the one or more switched loads is coupled to be switched in response to an output of a respective one of the one or more comparator circuits to draw the respective current from the load current of the power converter to clamp the output of the power converter.
2. The secondary control circuit of claim 1 wherein the voltage regulator circuit is coupled to the first terminal.
3. The secondary control circuit of claim 1 wherein a first one of the one or more comparator circuits is coupled to receive the first one of the one or more reference signals, wherein an output of the first one of the one or more comparator circuits is coupled to a feedback signal generator circuit to output a feedback signal representative of the output of the power converter.
4. The secondary control circuit of claim 3 wherein a primary control circuit of the power converter is coupled to control switching of a power switch of the power converter in response to the feedback signal representative of the output of the power converter to regulate the output of the power converter.
5. The secondary control circuit of claim 1 further comprising a reference signal generator circuit coupled the voltage regulator circuit to generate the one or more reference signals.
6. The secondary control circuit of claim 5 wherein the reference signal generator circuit comprises a resistor divider circuit coupled to a variable current source, wherein each one of the one or more reference signals is generated from a corresponding one of one or more resistors of the resistor divider circuit.
7. The secondary control circuit of claim 6 wherein the variable current source is coupled to vary a reference current through the resistor divider circuit in response to a reference control signal.
8. The secondary control circuit of claim 1 wherein each one of the one or more switched loads comprises a current source and a switch coupled between the first terminal and the output ground terminal of the power converter, wherein the switch is coupled to be switched in response to the output of the respective one of the one or more comparator circuits.
9. The secondary control circuit of claim 1 wherein each one of the one or more switched loads comprises a load resistance and a switch coupled between the first terminal and the output ground terminal of the power converter, wherein the switch is coupled to be switched in response to the output of the respective one of the one or more comparator circuits.
10. The secondary control circuit of claim 1 wherein the one or more comparator circuits includes hysteretic comparators.
11. The secondary control circuit of claim 1 wherein the output sense signal is coupled to be received from an output sense circuit coupled to the output of the power converter.
12. The secondary control circuit of claim 11 wherein the output sense circuit coupled to the output of the power converter includes an output resistor divider coupled to generate the output sense signal.