Startup/brownout active clamping for capacitor-drop power supply
AssigneeTexas Instruments Incorporated
InventorBoQiang Xiao
Life of this patent
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Abstract
A circuit includes a rectifier, a charge pump, and a clamp control circuit. The rectifier has an input configured to be coupled to an alternating current (AC) power source. The rectifier rectifies an AC signal from the AC power source to produce a rectified voltage on a first voltage node. The rectifier includes a first transistor coupled to a ground node and to the input. The first switch has a first control input. The charge pump is coupled to the first voltage node. The charge pump is configured to generate a second voltage on a second voltage node. The voltage regulator is coupled to the second voltage node. The clamp control circuit is coupled to the first and second voltage nodes and has an output node coupled to the first control input.
Claims21
A system, comprising:
- a capacitor-drop power supply including:
- a rectifier having an input configured to be coupled to an alternating current (AC) power source, the rectifier configured to rectify an AC signal from the AC power source to produce a rectified voltage on a first voltage node, the rectifier including a first transistor coupled to a ground node and to the input;
- an N:1 converter coupled to the first voltage node, the N:1 converter configured to generate a second voltage on a second voltage node;
- a voltage regulator coupled to the second voltage node, the voltage regulator having an output voltage node;
- and
- a clamp control circuit coupled to the first and second voltage nodes, the clamp control circuit configured to:
- when at least one of the rectified voltage is less than a first threshold voltage, or the second voltage is less than a second threshold, control the on/off state of the first transistor based on both the rectified and second voltages;
- and
- a load coupled to the output voltage node.
A circuit, comprising:
- a first transistor having a first control input and first and second current terminals;
- a second transistor having a second control input and third and fourth current terminals, the third current terminal coupled to the second current terminal;
- a first logic gate having an output coupled to the first control input;
- a second logic gate having an output coupled to the second control input;
- and
- a bridge clamp monitor having an enable input, a power supply input, and a clamp output, the clamp output coupled to the second and third current terminals, and the power supply input coupled to a first supply voltage node;
- wherein, responsive to a voltage on the first supply voltage node being less than a first threshold, the enable input receives a signal to disable the bridge clamp monitor, and the first and second gates control the first and second control inputs, respectively, based on a first power-on reset signal indicative of whether the voltage on the first supply voltage node is less than the first threshold, and based on a second power-on reset signal indicative of whether a voltage on a second voltage node is less than a second threshold.
A system, comprising:
- a rectifier having an input configured to be coupled to an alternating current (AC) power source, the rectifier configured to rectify an AC signal from the AC power source to produce a rectified voltage on a first voltage node, the rectifier including a first transistor coupled to a ground node and to the input;
- an N:1 converter coupled to the first voltage node, the N:1 converter configured to generate a second voltage on a second voltage node;
- and
- a clamp control circuit coupled to the first and second voltage nodes, the clamp control circuit configured to, when at least one of the rectified voltage is less than a first threshold voltage, or the second voltage is less than a second threshold, control the on/off state of the first transistor based on both the rectified and second voltages.
Dependencies are inferred from the claim text.