Semiconductor Switching Power Supply Control with Shared Timer Circuit
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Solution Overview
Problem
Existing semiconductor devices for switching power supply control face challenges in accurately detecting brownout and plug removal states while minimizing chip size and noise, especially when both functions share a high voltage input starting terminal, leading to increased chip size and noise generation due to separate timer circuits.
Innovation Solution
A semiconductor device with a high voltage input starting terminal, a discharger, and an input state detection circuit that includes a voltage divider, peak hold circuit, comparators for brownout and plug removal detection, and a shared timer circuit to measure delay times for both functions, allowing accurate detection and reducing chip size and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate timer circuits are provided for brownout detection and plug removal detection functions, then the detection accuracy is improved, but the chip size increases and noise generation occurs
Solution Approach 1:
The patent merges the timer circuits for brownout detection and plug removal detection into a single shared timer circuit. The timer circuit is configured to measure different time periods based on detection signals: measuring a first time period from brownout detection signal edges for brownout detection, and measuring a second time period from plug removal detection signal edges for plug removal detection. This consolidation eliminates the need for separate timer circuits, thereby reducing chip size and suppressing noise while maintaining accurate detection capabilities for both functions.
2Ease of operation
If a resistor for discharging is connected in parallel with the X capacitor, then the discharge function is provided, but the standby power consumption increases
Solution Approach 1:
The patent implements periodic discharge action by controlling the discharge switch to operate only when needed. The discharge switch is turned on based on detection of plug removal or brownout conditions, causing the X capacitor to discharge periodically rather than continuously. When the plug is removed or brownout occurs, the discharge switch is activated to rapidly discharge the X capacitor through the resistor. This periodic operation eliminates continuous power consumption while maintaining the necessary discharge function, thereby reducing standby power consumption.
Data Source
AI summary
Disclosed is a semiconductor device for switching power supply control including: a high voltage input starting terminal; a discharger; and an input state detection circuit that includes: a voltage divider; a peak hold circuit; a first comparator which detects generation of a plug removal state; a second comparator which detects generation of a brownout state; a timer circuit; and a control signal generation circuit which generates a signal to turn on the discharger or a signal to stop outputting of a switching control signal, Td1, Td2 and Td3 are set to have a relationship of Td1<Td2<Td3, Td1 being a delay time until the capacitor is discharged, Td2 being a delay time for determining the plug removal state, and Td3 being a delay time for determining the brownout state, and at least the delay time Td2 and the delay time Td3 are measured by a common timer circuit.